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| Prof. Dr. Mustafa Güden | Res. Assist. Senagül Tunca Taşkıran | |||
| Assoc. Prof. Dr. Sinan Kandemir | ||||
| Prof. Dr. Metin Tanoğlu | ||||
| Assist. Prof. Dr. M. Fatih Toksoy | ||||
Composite Materials Laboratory
Responsible Faculty Member
- Mechanical Engineering Building (147)
- +90 232 750 6747
Composite Research Laboratory
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- Mechanical Engineering Building (Z36)
- +90 232 750 6704
Material Chracterization Laboratory
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- Mechanical Engineering Building (150)
- +90 232 750 6750
Metal Processing Laboratory
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- Mechanical Engineering Building (153)
- +90 232 750 6782
Metallography Laboratory
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- Mechanical Engineering Building (148)
- +90 232 750 6747
Powder Metallurgy Laboratory
Responsible Faculty Member
- Mechanical Engineering Building (145)
- +90 232 750 6745
2023 |
Enser, Samed; Guden, Mustafa; Tasdemirci, Alper; Davut, Kemal The strain rate history effect in a selective-laser-melt 316L stainless steel Journal Article MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, 862 , 2023. @article{WOS:000905147200003, title = {The strain rate history effect in a selective-laser-melt 316L stainless steel}, author = {Samed Enser and Mustafa Guden and Alper Tasdemirci and Kemal Davut}, doi = {10.1016/j.msea.2022.144439}, year = {2023}, date = {2023-01-01}, journal = {MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, volume = {862}, abstract = {The strain rate history effect in a selective laser melt 316L (SLM-316L) alloy was investigated through quasi -static (10-3 s- 1) and high strain rate (1600-3200 s-1) interrupted and reloading compression tests. The speci-mens pre-tested until about prescribed strains at quasi-static and high strain rates were reloaded dynamically and quasi-statically, respectively. The results revealed that the flow stress depended on strain and strain rate as well as strain-rate history. Quasi-static reloading the dynamically pre-tested specimens until about prescribed strains induced a higher flow stress than the specimens tested quasi-statically. The strengthening was-70 MPa at 0.11 pre-strain and decreased as the dynamic test pre-strain was increased due to adiabatic heating. On the other side, reloading the quasi-statically pre-tested specimens dynamically at 0.11 pre-strain resulted in-60 MPa lower flow stress than the specimens tested dynamically. The grains of the quasi-statically tested specimens until 0.11 strain were shown to have a lower Taylor factor for twinning and geometrically necessary dislocation density, indicating more potential for twinning than dynamically tested specimen. Although, quasi-statically and dynamically tested specimens were deformed predominantly by the twinning induced plasticity, a higher frac-tion of twin boundaries was shown microscopically in the dynamically pre-tested specimens until 0.11 pre-strain. This phenomenon of boundary strengthening could be used as a tool of strengthening of SLM-316L alloy at low strains.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The strain rate history effect in a selective laser melt 316L (SLM-316L) alloy was investigated through quasi -static (10-3 s- 1) and high strain rate (1600-3200 s-1) interrupted and reloading compression tests. The speci-mens pre-tested until about prescribed strains at quasi-static and high strain rates were reloaded dynamically and quasi-statically, respectively. The results revealed that the flow stress depended on strain and strain rate as well as strain-rate history. Quasi-static reloading the dynamically pre-tested specimens until about prescribed strains induced a higher flow stress than the specimens tested quasi-statically. The strengthening was-70 MPa at 0.11 pre-strain and decreased as the dynamic test pre-strain was increased due to adiabatic heating. On the other side, reloading the quasi-statically pre-tested specimens dynamically at 0.11 pre-strain resulted in-60 MPa lower flow stress than the specimens tested dynamically. The grains of the quasi-statically tested specimens until 0.11 strain were shown to have a lower Taylor factor for twinning and geometrically necessary dislocation density, indicating more potential for twinning than dynamically tested specimen. Although, quasi-statically and dynamically tested specimens were deformed predominantly by the twinning induced plasticity, a higher frac-tion of twin boundaries was shown microscopically in the dynamically pre-tested specimens until 0.11 pre-strain. This phenomenon of boundary strengthening could be used as a tool of strengthening of SLM-316L alloy at low strains. |
Tuncer, C; Güden, M; Orhan, M; Sarıkaya, M K; Taşdemirci, A Quasi-static and dynamic Brazilian testing and failure analysis of a deer antler in the transverse to the osteon growth direction Journal Article Journal of the Mechanical Behavior of Biomedical Materials, 138 , 2023. @article{Tuncer2023, title = {Quasi-static and dynamic Brazilian testing and failure analysis of a deer antler in the transverse to the osteon growth direction}, author = {C Tuncer and M Güden and M Orhan and M K Sarıkaya and A Taşdemirci}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85145658319&doi=10.1016%2fj.jmbbm.2023.105648&partnerID=40&md5=f2b3c0121aa41d2857249a24554f05da}, doi = {10.1016/j.jmbbm.2023.105648}, year = {2023}, date = {2023-01-01}, journal = {Journal of the Mechanical Behavior of Biomedical Materials}, volume = {138}, abstract = {The transverse tensile strength of a naturally fallen red deer antler (Cervus Elaphus) was determined through indirect Brazilian tests using dry disc-shape specimens at quasi-static and high strain rates. Dynamic Brazilian tests were performed in a compression Split-Hopkinson Pressure Bar. Quasi-static tensile and indirect Brazilian tests were also performed along the osteon growth direction for comparison. The quasi-static transverse tensile strength ranged 31.5–44.5 MPa. The strength increased to 83 MPa on the average in the dynamic Brazilian tests, proving a rate sensitive transverse strength. The quasi-static tensile strength in the osteon growth direction was however found comparably higher, 192 MPa. A Weibull analysis indicated a higher tensile ductility in the osteon growth direction than in the transverse to the osteon growth direction. The microscopic analysis of the quasi-static Brazilian test specimens (tensile strain along the osteon growth direction) revealed a micro-cracking mechanism operating by the crack deflection/twisting at the lacunae in the concentric lamellae region and at the interface between concentric lamellae and interstitial lamellae. On the other side, the specimens in the transverse direction fractured in a more brittle manner by the separation/delamination of the concentric lamellae and pulling of the interstitial lamellae. The detected increase in the transverse strength in the high strain rate tests was further ascribed to the pull and fracture of the visco-plastic collagen fibers in the interstitial lamellae. This was also confirmed microscopically; the dynamically tested specimens exhibited flatter fracture surfaces. © 2023 Elsevier Ltd}, keywords = {}, pubstate = {published}, tppubtype = {article} } The transverse tensile strength of a naturally fallen red deer antler (Cervus Elaphus) was determined through indirect Brazilian tests using dry disc-shape specimens at quasi-static and high strain rates. Dynamic Brazilian tests were performed in a compression Split-Hopkinson Pressure Bar. Quasi-static tensile and indirect Brazilian tests were also performed along the osteon growth direction for comparison. The quasi-static transverse tensile strength ranged 31.5–44.5 MPa. The strength increased to 83 MPa on the average in the dynamic Brazilian tests, proving a rate sensitive transverse strength. The quasi-static tensile strength in the osteon growth direction was however found comparably higher, 192 MPa. A Weibull analysis indicated a higher tensile ductility in the osteon growth direction than in the transverse to the osteon growth direction. The microscopic analysis of the quasi-static Brazilian test specimens (tensile strain along the osteon growth direction) revealed a micro-cracking mechanism operating by the crack deflection/twisting at the lacunae in the concentric lamellae region and at the interface between concentric lamellae and interstitial lamellae. On the other side, the specimens in the transverse direction fractured in a more brittle manner by the separation/delamination of the concentric lamellae and pulling of the interstitial lamellae. The detected increase in the transverse strength in the high strain rate tests was further ascribed to the pull and fracture of the visco-plastic collagen fibers in the interstitial lamellae. This was also confirmed microscopically; the dynamically tested specimens exhibited flatter fracture surfaces. © 2023 Elsevier Ltd |
Enser, S; Güden, M; Taşdemirci, A; Davut, K The strain rate history effect in a selective-laser-melt 316L stainless steel Journal Article Materials Science and Engineering A, 862 , 2023. @article{Enser2023, title = {The strain rate history effect in a selective-laser-melt 316L stainless steel}, author = {S Enser and M Güden and A Taşdemirci and K Davut}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85143677799&doi=10.1016%2fj.msea.2022.144439&partnerID=40&md5=d3e4693f86b0e95c1ee6eb89a46551aa}, doi = {10.1016/j.msea.2022.144439}, year = {2023}, date = {2023-01-01}, journal = {Materials Science and Engineering A}, volume = {862}, abstract = {The strain rate history effect in a selective laser melt 316L (SLM-316L) alloy was investigated through quasi-static (10−3 s−1) and high strain rate (1600-3200 s−1) interrupted and reloading compression tests. The specimens pre-tested until about prescribed strains at quasi-static and high strain rates were reloaded dynamically and quasi-statically, respectively. The results revealed that the flow stress depended on strain and strain rate as well as strain-rate history. Quasi-static reloading the dynamically pre-tested specimens until about prescribed strains induced a higher flow stress than the specimens tested quasi-statically. The strengthening was ∼70 MPa at 0.11 pre-strain and decreased as the dynamic test pre-strain was increased due to adiabatic heating. On the other side, reloading the quasi-statically pre-tested specimens dynamically at 0.11 pre-strain resulted in ∼60 MPa lower flow stress than the specimens tested dynamically. The grains of the quasi-statically tested specimens until 0.11 strain were shown to have a lower Taylor factor for twinning and geometrically necessary dislocation density, indicating more potential for twinning than dynamically tested specimen. Although, quasi-statically and dynamically tested specimens were deformed predominantly by the twinning induced plasticity, a higher fraction of twin boundaries was shown microscopically in the dynamically pre-tested specimens until 0.11 pre-strain. This phenomenon of boundary strengthening could be used as a tool of strengthening of SLM-316L alloy at low strains. © 2022 Elsevier B.V.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The strain rate history effect in a selective laser melt 316L (SLM-316L) alloy was investigated through quasi-static (10−3 s−1) and high strain rate (1600-3200 s−1) interrupted and reloading compression tests. The specimens pre-tested until about prescribed strains at quasi-static and high strain rates were reloaded dynamically and quasi-statically, respectively. The results revealed that the flow stress depended on strain and strain rate as well as strain-rate history. Quasi-static reloading the dynamically pre-tested specimens until about prescribed strains induced a higher flow stress than the specimens tested quasi-statically. The strengthening was ∼70 MPa at 0.11 pre-strain and decreased as the dynamic test pre-strain was increased due to adiabatic heating. On the other side, reloading the quasi-statically pre-tested specimens dynamically at 0.11 pre-strain resulted in ∼60 MPa lower flow stress than the specimens tested dynamically. The grains of the quasi-statically tested specimens until 0.11 strain were shown to have a lower Taylor factor for twinning and geometrically necessary dislocation density, indicating more potential for twinning than dynamically tested specimen. Although, quasi-statically and dynamically tested specimens were deformed predominantly by the twinning induced plasticity, a higher fraction of twin boundaries was shown microscopically in the dynamically pre-tested specimens until 0.11 pre-strain. This phenomenon of boundary strengthening could be used as a tool of strengthening of SLM-316L alloy at low strains. © 2022 Elsevier B.V. |
Zeybek, M K; Güden, M; Taşdemirci, A Journal of Materials Engineering and Performance, 2023. @article{Zeybek2023, title = {The Effect of Strain Rate on the Compression Behavior of Additively Manufactured Short Carbon Fiber-Reinforced Polyamide Composites with Different Layer Heights, Infill Patterns, and Built Angles}, author = {M K Zeybek and M Güden and A Taşdemirci}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85147762551&doi=10.1007%2fs11665-023-07918-1&partnerID=40&md5=e7bbc8949f442fcf22b8812d43a6fa1e}, doi = {10.1007/s11665-023-07918-1}, year = {2023}, date = {2023-01-01}, journal = {Journal of Materials Engineering and Performance}, abstract = {Previous studies on the fused deposition modelling (FDM) processed short carbon fiber/Polyamide 6 (PA6) matrix composites and neat PA6 have mostly concentrated on the quasi-static mechanical properties. Present study focused on the strain rate-dependent deformation behavior of a short carbon fiber-reinforced PA6 (Onyx) and neat PA6, produced in different layer heights, infill patterns and built angles. As compared with PA6, Onyx showed a higher compression stress at all strain rates investigated. A layer height of 0.2 mm in PA6 specimens promoted a better bonding between [0/90°] infill layers; hence, a higher flow stress than 0.2 mm layer height specimens, while 0.2 mm layer height induced a higher porosity in Onyx specimens, leading to a lower flow stress. The porosities in Onyx [0/90°] infill specimens were due to the constraining effect of 0/90° fiber layers. Changing infill pattern from a [0/90°] to a concentric one decreased porosity at the same layer height and hence increased the compressive flow stress. The highest compressive strength was found in the specimens with the loading axis 90 and 0° to [0/90°] infill plane. The lowest strength was, however, determined in the specimens with the loading axis 30 and 60o to [0/90°] infill plane in quasi-static loading. However, the specimens with the loading axis of 60, 45, 30 and 0° exhibited a brittle behavior in high strain rate loading (1500 s−1). The specimens with the loading axis of 45° had the lowest fracture stress and strain in the high strain rate loading. This signified the importance of loading angle at high strain rates. Finally, the rate sensitivities of PA6 and Onyx specimens were shown to be similar, showing a matrix dominated deformation. However, the strain rate jump tests indicated a slightly higher rate sensitivity of Onyx specimens at quasi-static strain rates (10−3-10−1 s−1). © 2023, ASM International.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Previous studies on the fused deposition modelling (FDM) processed short carbon fiber/Polyamide 6 (PA6) matrix composites and neat PA6 have mostly concentrated on the quasi-static mechanical properties. Present study focused on the strain rate-dependent deformation behavior of a short carbon fiber-reinforced PA6 (Onyx) and neat PA6, produced in different layer heights, infill patterns and built angles. As compared with PA6, Onyx showed a higher compression stress at all strain rates investigated. A layer height of 0.2 mm in PA6 specimens promoted a better bonding between [0/90°] infill layers; hence, a higher flow stress than 0.2 mm layer height specimens, while 0.2 mm layer height induced a higher porosity in Onyx specimens, leading to a lower flow stress. The porosities in Onyx [0/90°] infill specimens were due to the constraining effect of 0/90° fiber layers. Changing infill pattern from a [0/90°] to a concentric one decreased porosity at the same layer height and hence increased the compressive flow stress. The highest compressive strength was found in the specimens with the loading axis 90 and 0° to [0/90°] infill plane. The lowest strength was, however, determined in the specimens with the loading axis 30 and 60o to [0/90°] infill plane in quasi-static loading. However, the specimens with the loading axis of 60, 45, 30 and 0° exhibited a brittle behavior in high strain rate loading (1500 s−1). The specimens with the loading axis of 45° had the lowest fracture stress and strain in the high strain rate loading. This signified the importance of loading angle at high strain rates. Finally, the rate sensitivities of PA6 and Onyx specimens were shown to be similar, showing a matrix dominated deformation. However, the strain rate jump tests indicated a slightly higher rate sensitivity of Onyx specimens at quasi-static strain rates (10−3-10−1 s−1). © 2023, ASM International. |
Turan, A K; Tasdemirci, A; Kara, A; Sahin, S; Guden, M Thin-Walled Structures, 182 , 2023. @article{Turan2023, title = {Investigation of penetration behavior of combined geometry shells at quasi-static and intermediate strain rates: An experimental and numerical study}, author = {A K Turan and A Tasdemirci and A Kara and S Sahin and M Guden}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85140804922&doi=10.1016%2fj.tws.2022.110261&partnerID=40&md5=a68187ac67baf30b83898f98789e157e}, doi = {10.1016/j.tws.2022.110261}, year = {2023}, date = {2023-01-01}, journal = {Thin-Walled Structures}, volume = {182}, abstract = {In this study, the penetration/perforation behavior of a core material with previously determined static and dynamic crushing characteristics was investigated both experimentally and numerically. Penetration/perforation problems occur due to shrapnel effect when sandwich structures containing energy-absorbing core materials by crushing are exposed to blast loads. The penetration behavior of combined geometry shells consisting of a hemispherical cap and a cylindrical segment was investigated experimentally using blunt, conical and hemispherical penetrator tips. The quasi-static penetration tests were performed in a universal test machine, and the intermediate strain rate penetration tests were performed in a drop weight test device. The numerical models of penetration tests were implemented in LS-DYNA at the test strain rates as well as at the higher strain rates. Results showed that different penetrator geometries induced damage forms of symmetrical tearing, petaling, plugging and inversely formed hemispherical domed cone. The increase in the thickness of core geometry resulted in a decent increase in force–displacement curves, as average of force levels increased around 140%, 200% and 220% for blunt, conical and hemispherical tip penetrators, respectively. Numerical results indicated very good correlation with experimental work and enabled to investigate effect of strain rate and micro-inertia over numerical models at elevated penetrator velocities. Penetration behavior was found to be affected from micro-inertia effects up to a threshold displacement of 4 mm for thicker and 5 mm for thinner core units and strain rate effects were found to be dominant beyond that point. © 2022 Elsevier Ltd}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, the penetration/perforation behavior of a core material with previously determined static and dynamic crushing characteristics was investigated both experimentally and numerically. Penetration/perforation problems occur due to shrapnel effect when sandwich structures containing energy-absorbing core materials by crushing are exposed to blast loads. The penetration behavior of combined geometry shells consisting of a hemispherical cap and a cylindrical segment was investigated experimentally using blunt, conical and hemispherical penetrator tips. The quasi-static penetration tests were performed in a universal test machine, and the intermediate strain rate penetration tests were performed in a drop weight test device. The numerical models of penetration tests were implemented in LS-DYNA at the test strain rates as well as at the higher strain rates. Results showed that different penetrator geometries induced damage forms of symmetrical tearing, petaling, plugging and inversely formed hemispherical domed cone. The increase in the thickness of core geometry resulted in a decent increase in force–displacement curves, as average of force levels increased around 140%, 200% and 220% for blunt, conical and hemispherical tip penetrators, respectively. Numerical results indicated very good correlation with experimental work and enabled to investigate effect of strain rate and micro-inertia over numerical models at elevated penetrator velocities. Penetration behavior was found to be affected from micro-inertia effects up to a threshold displacement of 4 mm for thicker and 5 mm for thinner core units and strain rate effects were found to be dominant beyond that point. © 2022 Elsevier Ltd |
İplikçi, Hande; Barisik, Murat; Türkdoğan, Ceren; Martin, Seçkin; Yeke, Melisa; Nuhoğlu, Kaan; Esenoğlu, Gözde; Tanoğlu, Metin; Aktaş, Engin; Dehneliler, Serkan; İriş, Mehmet Erdem Effects of nanosecond laser ablation parameters on surface modification of carbon fiber reinforced polymer composites Journal Article Journal of Composite Materials, 57 (18), pp. 2843 – 2855, 2023. @article{İplikçi20232843, title = {Effects of nanosecond laser ablation parameters on surface modification of carbon fiber reinforced polymer composites}, author = {Hande İplikçi and Murat Barisik and Ceren Türkdoğan and Seçkin Martin and Melisa Yeke and Kaan Nuhoğlu and Gözde Esenoğlu and Metin Tanoğlu and Engin Aktaş and Serkan Dehneliler and Mehmet Erdem İriş}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85162945413&doi=10.1177%2f00219983231178892&partnerID=40&md5=1e698a002a7d62e7f42a2444aafff1d5}, doi = {10.1177/00219983231178892}, year = {2023}, date = {2023-01-01}, journal = {Journal of Composite Materials}, volume = {57}, number = {18}, pages = {2843 – 2855}, abstract = {Removal of contaminants and top polymer layer from the surface of carbon-fiber-reinforced polymer (CFRP) composites is critical for high-quality adhesive-joining with direct bonding to the reinforcing fiber constituents. Surface treatment with a laser beam provides selective removal of the polymer matrix without damaging the fibers and increasing the wettability. However, inhomogeneous thermal properties of CFRP make control of laser ablation difficult as the laser energy absorbed by the carbon fibers is converted into heat and transmitted through the fiber structures during the laser operation. In this study, the effect of scanning speed and laser power on nanosecond laser surface treatment was characterized by scanning electron microscope images and wetting angle measurements. Low scanning speeds allowed laser energy to be conducted as thermal energy through the fibers, which resulted in less epoxy matrix removal and substantial thermal damage. Low laser power partially degraded the epoxy the surface while the high power damaged the carbon fibers. For the studied CFRP specimens consisting of unidirectional [45/0/−45/90]2s stacking of carbon/epoxy prepregs (HexPly®-M91), 100 mJ/mm2 generated by 10 m/s scanning speed and 30 W power appeared as optimum processing parameters for the complete removal of epoxy matrix from the top surface with mostly undamaged carbon fibers and super hydrophilic surface condition. © The Author(s) 2023.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Removal of contaminants and top polymer layer from the surface of carbon-fiber-reinforced polymer (CFRP) composites is critical for high-quality adhesive-joining with direct bonding to the reinforcing fiber constituents. Surface treatment with a laser beam provides selective removal of the polymer matrix without damaging the fibers and increasing the wettability. However, inhomogeneous thermal properties of CFRP make control of laser ablation difficult as the laser energy absorbed by the carbon fibers is converted into heat and transmitted through the fiber structures during the laser operation. In this study, the effect of scanning speed and laser power on nanosecond laser surface treatment was characterized by scanning electron microscope images and wetting angle measurements. Low scanning speeds allowed laser energy to be conducted as thermal energy through the fibers, which resulted in less epoxy matrix removal and substantial thermal damage. Low laser power partially degraded the epoxy the surface while the high power damaged the carbon fibers. For the studied CFRP specimens consisting of unidirectional [45/0/−45/90]2s stacking of carbon/epoxy prepregs (HexPly®-M91), 100 mJ/mm2 generated by 10 m/s scanning speed and 30 W power appeared as optimum processing parameters for the complete removal of epoxy matrix from the top surface with mostly undamaged carbon fibers and super hydrophilic surface condition. © The Author(s) 2023. |
2022 |
Ulker, Sevkan; Guden, Mustafa MATERIALS EXPRESS, 12 (8), pp. 1094-1107, 2022. @article{WOS:000897716200001, title = {The effect of the temperature of heat treatment process and the concentration and duration of acid leaching on the size and crystallinity of nano-silica powders formed by the dissociation of natural diatom frustule}, author = {Sevkan Ulker and Mustafa Guden}, doi = {10.1166/mex.2022.2251}, year = {2022}, date = {2022-08-01}, journal = {MATERIALS EXPRESS}, volume = {12}, number = {8}, pages = {1094-1107}, abstract = {The present study focused on the processing of nano-silica powders in varying sizes and crystallinities through IP: 846247.10 On: Wed, 14 Dec 2022 07:29:25 heat treatment (900-1200 degrees C), hydrofluoric acid leaching (1-7 N), and ball milling (1 h, 500 rpm) of natural Copyright American Scentfic P blishers diatom frustules. The starting natural frustules were determined to be composed of amorphous silica (88%) Delivered by Ingenta and quartz. The partially ordered crystalline low-quartz and or precursor to low-cristobalite started to form at-900 degrees C. As the heat treatment temperature increased, the crystallinity of the frustules increased from 9.3% at 25 degrees C to 46% at 1200 degrees C. Applying a ball milling reduced the mean particle sizes of the as-received and heat-treated frustules from 15.6-13.7 mu m to 7.2-6.7 mu m, respectively. Acid leaching of the as-received and heat-treated frustules resulted in a further increase in the crystallinity. Furthermore, a ball milling applied after an acid leaching was very effective in reducing the particle size of the as-received and heat-treated frustules. The mean particle size of the acid-leached frustules decreased to 774-547 nm with a crystallinity varying between 12 and 48% after ball milling. A partially dissolved amorphous phase was observed in between crystalline silica grains after acid leaching, which resulted in a rapid fracture/separation of the frustules in ball milling.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The present study focused on the processing of nano-silica powders in varying sizes and crystallinities through IP: 846247.10 On: Wed, 14 Dec 2022 07:29:25 heat treatment (900-1200 degrees C), hydrofluoric acid leaching (1-7 N), and ball milling (1 h, 500 rpm) of natural Copyright American Scentfic P blishers diatom frustules. The starting natural frustules were determined to be composed of amorphous silica (88%) Delivered by Ingenta and quartz. The partially ordered crystalline low-quartz and or precursor to low-cristobalite started to form at-900 degrees C. As the heat treatment temperature increased, the crystallinity of the frustules increased from 9.3% at 25 degrees C to 46% at 1200 degrees C. Applying a ball milling reduced the mean particle sizes of the as-received and heat-treated frustules from 15.6-13.7 mu m to 7.2-6.7 mu m, respectively. Acid leaching of the as-received and heat-treated frustules resulted in a further increase in the crystallinity. Furthermore, a ball milling applied after an acid leaching was very effective in reducing the particle size of the as-received and heat-treated frustules. The mean particle size of the acid-leached frustules decreased to 774-547 nm with a crystallinity varying between 12 and 48% after ball milling. A partially dissolved amorphous phase was observed in between crystalline silica grains after acid leaching, which resulted in a rapid fracture/separation of the frustules in ball milling. |
Esenoğlu, G; Barisik, M; Tanoğlu, M; Yeke, M; Türkdoğan, C; İplikçi, H; Martin, S; Nuhoğlu, K; Aktaş, E; Dehneliler, S; İriş, M E Improving adhesive behavior of fiber reinforced composites by incorporating electrospun Polyamide-6,6 nanofibers in joining region Journal Article Journal of Composite Materials, 56 (29), pp. 4449-4459, 2022. @article{Esenoğlu20224449, title = {Improving adhesive behavior of fiber reinforced composites by incorporating electrospun Polyamide-6,6 nanofibers in joining region}, author = {G Esenoğlu and M Barisik and M Tanoğlu and M Yeke and C Türkdoğan and H İplikçi and S Martin and K Nuhoğlu and E Aktaş and S Dehneliler and M E İriş}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85139985112&doi=10.1177%2f00219983221133478&partnerID=40&md5=699a47f9c6bc7948245cdc6f370c483e}, doi = {10.1177/00219983221133478}, year = {2022}, date = {2022-01-01}, journal = {Journal of Composite Materials}, volume = {56}, number = {29}, pages = {4449-4459}, abstract = {Adhesive joining of fiber reinforced polymer (CFRP) composite components is demanded in various industrial applications. However, the joining locations frequently suffer from adhesive bond failure between adhesive and adherent. The aim of the present study is improving bonding behavior of adhesive joints by electrospun nanofiber coatings on the prepreg surfaces that have been used for composite manufacturing. Secondary bonding of woven and unidirectional CFRP parts was selected since this configuration is preferred commonly in aerospace practices. The optimum nanofiber coating with a low average fiber diameter and areal weight density is succeed by studying various solution concentrations and spinning durations of the polyamide-6.6 (PA 66) electrospinning. We obtained homogeneous and beadles nanofiber productions. As a result, an average diameter of 36.50 ± 12 nm electrospun nanofibers were obtained and coated onto the prepreg surfaces. Prepreg systems with/without PA 66 nanofibers were hot pressed to fabricate the CFRP composite laminates. The single-lap shear test coupons were prepared from the fabricated laminates to examine the effects of PA 66 nanofibers on the mechanical properties of the joint region of the composites. The single-lap shear test results showed that the bonding strength is improved by about 40% with minimal adhesive use due to the presence of the electrospun nanofibers within the joint region. The optical and SEM images of fractured surfaces showed that nanofiber-coated joints exhibited a coherent failure while the bare surfaces underwent adhesive failure. The PA66 nanofibers created better coupling between the adhesive and the composite surface by increasing the surface area and roughness. As a result, electrospun nanofibers turned adhesive failure into cohesive and enhanced the adhesion performance composite joints substantially. © The Author(s) 2022.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Adhesive joining of fiber reinforced polymer (CFRP) composite components is demanded in various industrial applications. However, the joining locations frequently suffer from adhesive bond failure between adhesive and adherent. The aim of the present study is improving bonding behavior of adhesive joints by electrospun nanofiber coatings on the prepreg surfaces that have been used for composite manufacturing. Secondary bonding of woven and unidirectional CFRP parts was selected since this configuration is preferred commonly in aerospace practices. The optimum nanofiber coating with a low average fiber diameter and areal weight density is succeed by studying various solution concentrations and spinning durations of the polyamide-6.6 (PA 66) electrospinning. We obtained homogeneous and beadles nanofiber productions. As a result, an average diameter of 36.50 ± 12 nm electrospun nanofibers were obtained and coated onto the prepreg surfaces. Prepreg systems with/without PA 66 nanofibers were hot pressed to fabricate the CFRP composite laminates. The single-lap shear test coupons were prepared from the fabricated laminates to examine the effects of PA 66 nanofibers on the mechanical properties of the joint region of the composites. The single-lap shear test results showed that the bonding strength is improved by about 40% with minimal adhesive use due to the presence of the electrospun nanofibers within the joint region. The optical and SEM images of fractured surfaces showed that nanofiber-coated joints exhibited a coherent failure while the bare surfaces underwent adhesive failure. The PA66 nanofibers created better coupling between the adhesive and the composite surface by increasing the surface area and roughness. As a result, electrospun nanofibers turned adhesive failure into cohesive and enhanced the adhesion performance composite joints substantially. © The Author(s) 2022. |
Güneş, M D; Karabaş, İmamoğlu N; Deveci, H A; Tanoğlu, G; Tanoğlu, M Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 236 (19), pp. 10290-10303, 2022. @article{Güneş202210290, title = {Fatigue life prediction and optimization of GFRP composites based on Failure Tensor Polynomial in Fatigue model with exponential fitting approach}, author = {M D Güneş and N İmamoğlu Karabaş and H A Deveci and G Tanoğlu and M Tanoğlu}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85130983288&doi=10.1177%2f09544062221101462&partnerID=40&md5=144a189eaf81ed03065a753253307cad}, doi = {10.1177/09544062221101462}, year = {2022}, date = {2022-01-01}, journal = {Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science}, volume = {236}, number = {19}, pages = {10290-10303}, abstract = {In this study, a new fatigue life prediction and optimization strategy utilizing the Failure Tensor Polynomial in Fatigue (FTPF) model with exponential fitting and numerical bisection method for fiber reinforced polymer composites has been proposed. Within the experimental stage, glass/epoxy composite laminates with (Formula presented.), (Formula presented.), and (Formula presented.) lay-up configurations were fabricated, quasi-static and fatigue mechanical behavior of GFRP composites was characterized to be used in the FTPF model. The prediction capability of the FTPF model was tested based on the experimental data obtained for multidirectional laminates of various composite materials. Fatigue life prediction results of the glass/epoxy laminates were found to be better as compared to those for the linear fitting predictions. The results also indicated that the approach with exponential fitting provides better fatigue life predictions as compared to those obtained by linear fitting, especially for glass/epoxy laminates. Moreover, an optimization study using the proposed methodology for fatigue life advancement of the glass/epoxy laminates was performed by a powerful hybrid algorithm, PSA/GPSA. So, two optimization scenarios including various loading configurations were considered. The optimization results exhibited that the optimized stacking sequences having maximized fatigue life can be obtained in various loading cases. It was also revealed that the tension-compression loading and the loadings involving shear loads are critical for fatigue, and further improvement in fatigue life may be achieved by designing only symmetric lay-ups instead of symmetric-balanced and diversification of fiber angles to be used in the optimization. © IMechE 2022.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, a new fatigue life prediction and optimization strategy utilizing the Failure Tensor Polynomial in Fatigue (FTPF) model with exponential fitting and numerical bisection method for fiber reinforced polymer composites has been proposed. Within the experimental stage, glass/epoxy composite laminates with (Formula presented.), (Formula presented.), and (Formula presented.) lay-up configurations were fabricated, quasi-static and fatigue mechanical behavior of GFRP composites was characterized to be used in the FTPF model. The prediction capability of the FTPF model was tested based on the experimental data obtained for multidirectional laminates of various composite materials. Fatigue life prediction results of the glass/epoxy laminates were found to be better as compared to those for the linear fitting predictions. The results also indicated that the approach with exponential fitting provides better fatigue life predictions as compared to those obtained by linear fitting, especially for glass/epoxy laminates. Moreover, an optimization study using the proposed methodology for fatigue life advancement of the glass/epoxy laminates was performed by a powerful hybrid algorithm, PSA/GPSA. So, two optimization scenarios including various loading configurations were considered. The optimization results exhibited that the optimized stacking sequences having maximized fatigue life can be obtained in various loading cases. It was also revealed that the tension-compression loading and the loadings involving shear loads are critical for fatigue, and further improvement in fatigue life may be achieved by designing only symmetric lay-ups instead of symmetric-balanced and diversification of fiber angles to be used in the optimization. © IMechE 2022. |
Üstün, Sinan H; Toksoy, Kaan A; Tanoğlu, M Investigation of hybridization effect on ballistic performance of multi-layered fiber reinforced composite structures Journal Article Journal of Composite Materials, 56 (15), pp. 2411-2431, 2022. @article{SinanÜstün20222411, title = {Investigation of hybridization effect on ballistic performance of multi-layered fiber reinforced composite structures}, author = {H Sinan Üstün and A Kaan Toksoy and M Tanoğlu}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85130035790&doi=10.1177%2f00219983221090018&partnerID=40&md5=c04588512f22392bf8cac3ef9d118408}, doi = {10.1177/00219983221090018}, year = {2022}, date = {2022-01-01}, journal = {Journal of Composite Materials}, volume = {56}, number = {15}, pages = {2411-2431}, abstract = {The aim of this study is enhancing the ballistic performance of multi-layered fiber reinforced composite structures by hybridization approach against fragment simulating projectile (FSP). For manufacturing of homogeneous and hybrid composite structures, 170 g/m2 twill weave aramid and 280 g/m2 plain weave E-Glass fibers were used with epoxy resin systems and two different thickness values for each composite panel were fabricated and tested to obtain a relationship between areal density and V50 parameters. Tensile, 3-point bending, and short beam strength tests of composite panels were performed, and ballistic performance of composite structures were measured by V50 test method with 1.1 g FSP threat. Ballistic performance of hybrid composite structures was compared with high-performance composite ballistic panel test results reported in literature. As a result, it was found that E-Glass fabric layers together with aramid fabrics increased the energy absorbing capability of hybrid composite panels and ballistic performance was enhanced to be similar or higher than ballistic fiber reinforced composites. Hence, hybridization was found to be an effective way to enhance ballistic performance of fiber reinforced composite structures. © The Author(s) 2022.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The aim of this study is enhancing the ballistic performance of multi-layered fiber reinforced composite structures by hybridization approach against fragment simulating projectile (FSP). For manufacturing of homogeneous and hybrid composite structures, 170 g/m2 twill weave aramid and 280 g/m2 plain weave E-Glass fibers were used with epoxy resin systems and two different thickness values for each composite panel were fabricated and tested to obtain a relationship between areal density and V50 parameters. Tensile, 3-point bending, and short beam strength tests of composite panels were performed, and ballistic performance of composite structures were measured by V50 test method with 1.1 g FSP threat. Ballistic performance of hybrid composite structures was compared with high-performance composite ballistic panel test results reported in literature. As a result, it was found that E-Glass fabric layers together with aramid fabrics increased the energy absorbing capability of hybrid composite panels and ballistic performance was enhanced to be similar or higher than ballistic fiber reinforced composites. Hence, hybridization was found to be an effective way to enhance ballistic performance of fiber reinforced composite structures. © The Author(s) 2022. |
Uz, Y C; Tanoğlu, M Determination of activation energy for carbon/epoxy prepregs containing carbon nanotubes by differential scanning calorimetry Journal Article High Performance Polymers, 2022. @article{Uz2022, title = {Determination of activation energy for carbon/epoxy prepregs containing carbon nanotubes by differential scanning calorimetry}, author = {Y C Uz and M Tanoğlu}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85135891731&doi=10.1177%2f09540083221115987&partnerID=40&md5=4b3d7c567d57a6b645d854737e03917d}, doi = {10.1177/09540083221115987}, year = {2022}, date = {2022-01-01}, journal = {High Performance Polymers}, abstract = {The aim of the present study is the thermal characterization of laboratory-scale carbon fiber/epoxy-based prepregs by incorporating single-wall carbon nanotubes (SWCNTs). Investigation of the cure behavior of a prepreg system is crucial for the characterization and optimization of the fiber reinforced polymeric (FRP) composite. To affect dispersion characteristics, SWCNTs were functionalized by oxidizing their surface with carboxyl (-COOH) group using an acid treatment. The modified resin system contained 0.05, 0.1, and 0.2 wt. % functionalized SWCNTs (F-SWCNTs). Carbon fiber (CF) reinforced prepregs containing various amount of F-SWCNTs were prepared using drum-type winding technique. FTIR was performed to identify new bonding groups formed after the functionalization of SWCNTs. Cure kinetics of prepregs prepared with/without F-SWCNTs were investigated using isoconversional methods. © The Author(s) 2022.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The aim of the present study is the thermal characterization of laboratory-scale carbon fiber/epoxy-based prepregs by incorporating single-wall carbon nanotubes (SWCNTs). Investigation of the cure behavior of a prepreg system is crucial for the characterization and optimization of the fiber reinforced polymeric (FRP) composite. To affect dispersion characteristics, SWCNTs were functionalized by oxidizing their surface with carboxyl (-COOH) group using an acid treatment. The modified resin system contained 0.05, 0.1, and 0.2 wt. % functionalized SWCNTs (F-SWCNTs). Carbon fiber (CF) reinforced prepregs containing various amount of F-SWCNTs were prepared using drum-type winding technique. FTIR was performed to identify new bonding groups formed after the functionalization of SWCNTs. Cure kinetics of prepregs prepared with/without F-SWCNTs were investigated using isoconversional methods. © The Author(s) 2022. |
Solak, Ay Z; Kartav, O; Tanoglu, M Enhancement of filament wound glass fiber/epoxy-based cylindrical composites by toughening with single-walled carbon nanotubes Journal Article Polymers and Polymer Composites, 30 , 2022. @article{AySolak2022, title = {Enhancement of filament wound glass fiber/epoxy-based cylindrical composites by toughening with single-walled carbon nanotubes}, author = {Z Ay Solak and O Kartav and M Tanoglu}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85131795670&doi=10.1177%2f09673911221086718&partnerID=40&md5=ee2274734defe29b42d80148622b6359}, doi = {10.1177/09673911221086718}, year = {2022}, date = {2022-01-01}, journal = {Polymers and Polymer Composites}, volume = {30}, abstract = {In this study, the effect of incorporating nano-sized fillers (noncovalently functionalized with ethoxylated alcohol chemical-vapor-deposition-grown SWCNTs) within an epoxy resin on the performance of filament wound glass fiber (GF)-based cylindrical composites (GFCCs) was investigated. For this purpose, SWCNTs were dispersed with the concentration of 0.05 and 0.1 weight percent (wt.%) within an epoxy resin using mechanical stirring and calendaring (3-roll-milling) techniques. The rheological behavior of the SWCNT incorporated epoxy mixture was characterized to determine the suitability of blends for the filament winding process. It was revealed that the viscosity value of the resin was not significantly affected by the addition of SWCNTs in given concentrations. Moreover, contact angle measurements were also performed on the SWCNT/epoxy blends dropped on the GF for the evaluation of the wettability behavior of the GF in the presence of the SWCNTs in relevant concentrations. Eventually, it was observed that the wettability behavior of GF was not reasonably affected by the presence of the SWCNTs. The double cantilever beam (DCB), flexural, and short beam shear (SBS) tests were performed on the reference and SWCNT-modified GFCC specimens to evaluate the effects of the SWCNT presence on the interlaminar fracture toughness and out-of-plane properties of GFCCs. The fractured surfaces after the DCB and SBS tests were analyzed under the scanning electron microscopy to reveal the toughening mechanisms and the filler morphologies. Consequently, although SWCNT incorporation was on the outermost layer of GFCCs, it was found that the interlaminar shear strength (ILSS) values and Mode I interlaminar fracture toughness values of the curved composite samples were improved up to 22 and 216%, respectively, due to the presence of the SWCNTs. © The Author(s) 2022.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, the effect of incorporating nano-sized fillers (noncovalently functionalized with ethoxylated alcohol chemical-vapor-deposition-grown SWCNTs) within an epoxy resin on the performance of filament wound glass fiber (GF)-based cylindrical composites (GFCCs) was investigated. For this purpose, SWCNTs were dispersed with the concentration of 0.05 and 0.1 weight percent (wt.%) within an epoxy resin using mechanical stirring and calendaring (3-roll-milling) techniques. The rheological behavior of the SWCNT incorporated epoxy mixture was characterized to determine the suitability of blends for the filament winding process. It was revealed that the viscosity value of the resin was not significantly affected by the addition of SWCNTs in given concentrations. Moreover, contact angle measurements were also performed on the SWCNT/epoxy blends dropped on the GF for the evaluation of the wettability behavior of the GF in the presence of the SWCNTs in relevant concentrations. Eventually, it was observed that the wettability behavior of GF was not reasonably affected by the presence of the SWCNTs. The double cantilever beam (DCB), flexural, and short beam shear (SBS) tests were performed on the reference and SWCNT-modified GFCC specimens to evaluate the effects of the SWCNT presence on the interlaminar fracture toughness and out-of-plane properties of GFCCs. The fractured surfaces after the DCB and SBS tests were analyzed under the scanning electron microscopy to reveal the toughening mechanisms and the filler morphologies. Consequently, although SWCNT incorporation was on the outermost layer of GFCCs, it was found that the interlaminar shear strength (ILSS) values and Mode I interlaminar fracture toughness values of the curved composite samples were improved up to 22 and 216%, respectively, due to the presence of the SWCNTs. © The Author(s) 2022. |
Tuzgel, F; Akbulut, E F; Guzel, E; Yucesoy, A; Sahin, S; Tasdemirci, A; Guden, M Testing and modeling blast loading of a sandwich structure cored with a bio-inspired (balanus) core Journal Article Thin-Walled Structures, 175 , 2022. @article{Tuzgel2022, title = {Testing and modeling blast loading of a sandwich structure cored with a bio-inspired (balanus) core}, author = {F Tuzgel and E F Akbulut and E Guzel and A Yucesoy and S Sahin and A Tasdemirci and M Guden}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85127099692&doi=10.1016%2fj.tws.2022.109185&partnerID=40&md5=598aa9ba4baa82852c1ddd0b8676727c}, doi = {10.1016/j.tws.2022.109185}, year = {2022}, date = {2022-01-01}, journal = {Thin-Walled Structures}, volume = {175}, abstract = {The blast loading response of a sandwich structure consisted of bio-inspired (balanus) cores/units was investigated experimentally and numerically. A Direct Pressure Pulse (DPP) set-up was used to impose a blast-like loading. The equivalent blast conditions corresponding to the used impact velocities were implemented in the models. A benchmark study was performed by using three different methods namely pure Lagrangian, Arbitrary Lagrangian Eulerian, and hybrid. Dynamic crushing behavior was analyzed and exhibited a higher specific energy absorption capacity than its constituents (core and shell). Among the core configurations, all-front configuration was found the most efficient configuration regarding the specific energy absorption. © 2022 Elsevier Ltd}, keywords = {}, pubstate = {published}, tppubtype = {article} } The blast loading response of a sandwich structure consisted of bio-inspired (balanus) cores/units was investigated experimentally and numerically. A Direct Pressure Pulse (DPP) set-up was used to impose a blast-like loading. The equivalent blast conditions corresponding to the used impact velocities were implemented in the models. A benchmark study was performed by using three different methods namely pure Lagrangian, Arbitrary Lagrangian Eulerian, and hybrid. Dynamic crushing behavior was analyzed and exhibited a higher specific energy absorption capacity than its constituents (core and shell). Among the core configurations, all-front configuration was found the most efficient configuration regarding the specific energy absorption. © 2022 Elsevier Ltd |
Güden, M; Alpkaya, A T; Hamat, B A; Hızlı, B; Taşdemirci, A; Tanrıkulu, A A; Yavaş, H Strain, 58 (3), 2022. @article{Güden2022, title = {The quasi-static crush response of electron-beam-melt Ti6Al4V body-centred-cubic lattices: The effect of the number of cells, strut diameter and face sheet}, author = {M Güden and A T Alpkaya and B A Hamat and B Hızlı and A Taşdemirci and A A Tanrıkulu and H Yavaş}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85125105289&doi=10.1111%2fstr.12411&partnerID=40&md5=e6515c23c4247096157d4bec2da4a9f3}, doi = {10.1111/str.12411}, year = {2022}, date = {2022-01-01}, journal = {Strain}, volume = {58}, number = {3}, abstract = {The effect of the number of cells, strut diameter and face sheet on the compression of electron-beam-melt (EBM) Ti6Al4V (Ti64) body-centred-cubic (BCC) lattices was investigated experimentally and numerically. The lattices with the same relative density (~0.182) were fabricated with and without 2-mm-thick face sheets in 10 and 5 mm cell size, 8–125 unit cell (two to five cells/edge) and 2 and 1 mm strut diameter. The experimental compression tests were further numerically simulated in the LS-DYNA. Experimentally two bending-dominated crushing modes, namely, lateral and diagonal layer crushing, were determined. The numerical models however exhibited merely a bending-dominated lateral layer crushing mode when the erosion strain was 0.4 and without face-sheet models showed a diagonal layer crushing mode when the erosion strain was 0.3. Lower erosion strains promoted a diagonal layer crushing mode by introducing geometrical inhomogeneity to the lattice, leading to strain localisation as similar to the face sheets which introduced extensive strut bending in the layers adjacent to the face sheets. The face-sheet model showed a higher but decreasing collapse strength at an increasing number of cells, just as opposite to the without face-sheet model, and the collapse strength of both models converged when the number of cells was higher than five-cell/edge. The decrease/increase of the collapse strengths of lattices before the critical number of cells was claimed mainly due to the size-imposed lattice boundary condition, rather than the specimen volume. The difference in the experimental collapse strengths between the 5- and the 10-mm cell-size lattices was ascribed to the variations in the microstructures—hence the material model parameters between the small-diameter and the large-diameter EBM-Ti64 strut lattices. © 2022 John Wiley & Sons Ltd.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The effect of the number of cells, strut diameter and face sheet on the compression of electron-beam-melt (EBM) Ti6Al4V (Ti64) body-centred-cubic (BCC) lattices was investigated experimentally and numerically. The lattices with the same relative density (~0.182) were fabricated with and without 2-mm-thick face sheets in 10 and 5 mm cell size, 8–125 unit cell (two to five cells/edge) and 2 and 1 mm strut diameter. The experimental compression tests were further numerically simulated in the LS-DYNA. Experimentally two bending-dominated crushing modes, namely, lateral and diagonal layer crushing, were determined. The numerical models however exhibited merely a bending-dominated lateral layer crushing mode when the erosion strain was 0.4 and without face-sheet models showed a diagonal layer crushing mode when the erosion strain was 0.3. Lower erosion strains promoted a diagonal layer crushing mode by introducing geometrical inhomogeneity to the lattice, leading to strain localisation as similar to the face sheets which introduced extensive strut bending in the layers adjacent to the face sheets. The face-sheet model showed a higher but decreasing collapse strength at an increasing number of cells, just as opposite to the without face-sheet model, and the collapse strength of both models converged when the number of cells was higher than five-cell/edge. The decrease/increase of the collapse strengths of lattices before the critical number of cells was claimed mainly due to the size-imposed lattice boundary condition, rather than the specimen volume. The difference in the experimental collapse strengths between the 5- and the 10-mm cell-size lattices was ascribed to the variations in the microstructures—hence the material model parameters between the small-diameter and the large-diameter EBM-Ti64 strut lattices. © 2022 John Wiley & Sons Ltd. |
Movahedi, N; Fiedler, T; Taşdemirci, A; Murch, G E; Belova, I V; Güden, M Impact loading of functionally graded metal syntactic foams Journal Article Materials Science and Engineering A, 839 , 2022. @article{Movahedi2022, title = {Impact loading of functionally graded metal syntactic foams}, author = {N Movahedi and T Fiedler and A Taşdemirci and G E Murch and I V Belova and M Güden}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85124878036&doi=10.1016%2fj.msea.2022.142831&partnerID=40&md5=7c2f5ff50091f5c640df480605838c8c}, doi = {10.1016/j.msea.2022.142831}, year = {2022}, date = {2022-01-01}, journal = {Materials Science and Engineering A}, volume = {839}, abstract = {The present study addresses the impact loading of functionally graded metal syntactic foams (FG-MSF). For comparison, samples of the same material were also compression loaded at quasi-static velocities. Samples of A356 aluminium FG-MSF were produced using counter-gravity infiltration casting with combination of equal-sized layers of expanded perlite (EP) and activated carbon (AC) particles. A modified Split Hopkinson Pressure Bar test set-up was used to impact the FG-MSFs from their EP or AC layers at 55 m/s or 175 m/s impact velocities. A high-speed camera captured the deformation of the samples during testing. It was shown that increasing the loading velocity enhanced both the compressive proof strength and energy absorption of the impacted FG-MSF from both layers, confirming a dynamic strengthening effect of the foam. The samples impacted from both layers at 55 and 175 m/s showed a transition and a shock mode of deformation, respectively. The impacted samples at 55 m/s experienced lower final average strain values compared to 175 m/s. © 2022 Elsevier B.V.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The present study addresses the impact loading of functionally graded metal syntactic foams (FG-MSF). For comparison, samples of the same material were also compression loaded at quasi-static velocities. Samples of A356 aluminium FG-MSF were produced using counter-gravity infiltration casting with combination of equal-sized layers of expanded perlite (EP) and activated carbon (AC) particles. A modified Split Hopkinson Pressure Bar test set-up was used to impact the FG-MSFs from their EP or AC layers at 55 m/s or 175 m/s impact velocities. A high-speed camera captured the deformation of the samples during testing. It was shown that increasing the loading velocity enhanced both the compressive proof strength and energy absorption of the impacted FG-MSF from both layers, confirming a dynamic strengthening effect of the foam. The samples impacted from both layers at 55 and 175 m/s showed a transition and a shock mode of deformation, respectively. The impacted samples at 55 m/s experienced lower final average strain values compared to 175 m/s. © 2022 Elsevier B.V. |
Güden, M; Enser, S; Bayhan, M; Taşdemirci, A; Yavaş, H Materials Science and Engineering A, 838 , 2022. @article{Güden2022b, title = {The strain rate sensitive flow stresses and constitutive equations of a selective-laser-melt and an annealed-rolled 316L stainless steel: A comparative study}, author = {M Güden and S Enser and M Bayhan and A Taşdemirci and H Yavaş}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85124262590&doi=10.1016%2fj.msea.2022.142743&partnerID=40&md5=c9a9ea5a5d2240e3b1fb245fdb7f8e27}, doi = {10.1016/j.msea.2022.142743}, year = {2022}, date = {2022-01-01}, journal = {Materials Science and Engineering A}, volume = {838}, abstract = {The strain rate dependent compressive flow stresses of a Selective-Laser-Melt 316L (SLM-316L) alloy and a commercial (annealed-extruded) 316L (C-316L) alloy were determined, for comparison, between 1x10-4 and ∼2500 s-1 and between 1x10-4 and ∼2800 s-1, respectively. The Johnson and Cook flow stress material model parameters of both alloys were also determined. The microstructural examinations of the deformed cross-sections of tested specimens (interrupted tests) showed a twinning-induced-plasticity in SLM-316L alloy and a martensitic transformation-induced-plasticity in C-316L alloy. Twin and martensite formations were detected microscopically higher in the dynamically tested specimens until about 0.22 strain, while the twin and martensite formations decreased at increasing strains due to adiabatic heating. The rate sensitivity of SLM-316L was determined slightly higher than that of C-316L within the quasi-static strain rate range (1x10-4 and 1x10-2 s-1), while the rate sensitivities of both alloys were similar in the quasi-static-high strain rate range (1x10-4 and ∼2500-2800 s-1) at low strains. A more rapid decrease in the rate sensitivity of C-316L at increasing strains was found in the quasi-static-high strain rate range. The similar activation volumes of both alloys, corresponding to the dislocation intersections, indicated a similar thermally activated deformation process involvement in both alloys. © 2022 Elsevier B.V.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The strain rate dependent compressive flow stresses of a Selective-Laser-Melt 316L (SLM-316L) alloy and a commercial (annealed-extruded) 316L (C-316L) alloy were determined, for comparison, between 1x10-4 and ∼2500 s-1 and between 1x10-4 and ∼2800 s-1, respectively. The Johnson and Cook flow stress material model parameters of both alloys were also determined. The microstructural examinations of the deformed cross-sections of tested specimens (interrupted tests) showed a twinning-induced-plasticity in SLM-316L alloy and a martensitic transformation-induced-plasticity in C-316L alloy. Twin and martensite formations were detected microscopically higher in the dynamically tested specimens until about 0.22 strain, while the twin and martensite formations decreased at increasing strains due to adiabatic heating. The rate sensitivity of SLM-316L was determined slightly higher than that of C-316L within the quasi-static strain rate range (1x10-4 and 1x10-2 s-1), while the rate sensitivities of both alloys were similar in the quasi-static-high strain rate range (1x10-4 and ∼2500-2800 s-1) at low strains. A more rapid decrease in the rate sensitivity of C-316L at increasing strains was found in the quasi-static-high strain rate range. The similar activation volumes of both alloys, corresponding to the dislocation intersections, indicated a similar thermally activated deformation process involvement in both alloys. © 2022 Elsevier B.V. |
2021 |
Aydin, Murat; Bulut, Tugrul; Guden, Mustafa; Erel, Nuri Transdiscal screw fixation in L5-S1 spondylolysis: A biomechanical study Transdiscal screw fixation in L5-51 spondylolysis Journal Article ANNALS OF CLINICAL AND ANALYTICAL MEDICINE, 12 (9), pp. 1055-1057, 2021. @article{WOS:000732457800019, title = {Transdiscal screw fixation in L5-S1 spondylolysis: A biomechanical study Transdiscal screw fixation in L5-51 spondylolysis}, author = {Murat Aydin and Tugrul Bulut and Mustafa Guden and Nuri Erel}, doi = {10.4328/ACAM.20586}, year = {2021}, date = {2021-09-01}, journal = {ANNALS OF CLINICAL AND ANALYTICAL MEDICINE}, volume = {12}, number = {9}, pages = {1055-1057}, abstract = {Aim: This study aimed to investigate whether the L5-S1 transdiscal screw fixation is biomechanically sufficient against axial loads and the resulting shear forces. Material and Methods: Eighteen fresh calf spines under 1 year of age were used in this study. Two randomly selected spines were used as test materials. The inferior facet and ligamentum flavum were removed in 7 randomly selected spines. In these spines (transdiscal screw group), two transdiscal screws were placed bilaterally between 15 and S1. Tests were performed on the remaining 9 spines, while the spines were initially intact (intact group) and after creating a listhesis model (injury group). The extent of displacement occurring as a result of axial loading was noted in all groups in order to calculate the load-displacement curves. Results: The mean displacement as a result of successive axial loadings of 5000 N was as follows: 3 mm (range: 2.4 - 4 mm) in the intact group, 3.5 mm (range: 3 - 4.5 mm) in the transdiscal screw group and 4.5 mm (range: 3.9 - 5 mm) In the group with injury. The difference was statistically significant (p<0.05). None of the samples exhibited broken screws, screw deformation or dislocation, even in failure tests, in the transdiscal screw group. Discussion: These findings have shown that transdiscal screw fixation can be biomechanically sufficient against the shear forces occurring as a result of axial loading. We believe that this technique can be a good alternative as a fixation method for the L5-S1 spondylolisthesis.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Aim: This study aimed to investigate whether the L5-S1 transdiscal screw fixation is biomechanically sufficient against axial loads and the resulting shear forces. Material and Methods: Eighteen fresh calf spines under 1 year of age were used in this study. Two randomly selected spines were used as test materials. The inferior facet and ligamentum flavum were removed in 7 randomly selected spines. In these spines (transdiscal screw group), two transdiscal screws were placed bilaterally between 15 and S1. Tests were performed on the remaining 9 spines, while the spines were initially intact (intact group) and after creating a listhesis model (injury group). The extent of displacement occurring as a result of axial loading was noted in all groups in order to calculate the load-displacement curves. Results: The mean displacement as a result of successive axial loadings of 5000 N was as follows: 3 mm (range: 2.4 - 4 mm) in the intact group, 3.5 mm (range: 3 - 4.5 mm) in the transdiscal screw group and 4.5 mm (range: 3.9 - 5 mm) In the group with injury. The difference was statistically significant (p<0.05). None of the samples exhibited broken screws, screw deformation or dislocation, even in failure tests, in the transdiscal screw group. Discussion: These findings have shown that transdiscal screw fixation can be biomechanically sufficient against the shear forces occurring as a result of axial loading. We believe that this technique can be a good alternative as a fixation method for the L5-S1 spondylolisthesis. |
Kangal, Serkan; Say, Harun A; Ayakda, Ozan; Kartav, Osman; Aydin, Levent; Artem, Secil H; Aktas, Engin; Yuceturk, Kutay; Tanoglu, Metin; Kandemir, Sinan; Beylergil, Bertan A Comprehensive Study on Burst Pressure Performance of Aluminum Liner for Hydrogen Storage Vessels Journal Article JOURNAL OF PRESSURE VESSEL TECHNOLOGY-TRANSACTIONS OF THE ASME, 143 (4), 2021. @article{WOS:000669955100012, title = {A Comprehensive Study on Burst Pressure Performance of Aluminum Liner for Hydrogen Storage Vessels}, author = {Serkan Kangal and Harun A Say and Ozan Ayakda and Osman Kartav and Levent Aydin and Secil H Artem and Engin Aktas and Kutay Yuceturk and Metin Tanoglu and Sinan Kandemir and Bertan Beylergil}, doi = {10.1115/1.4049644}, year = {2021}, date = {2021-08-01}, journal = {JOURNAL OF PRESSURE VESSEL TECHNOLOGY-TRANSACTIONS OF THE ASME}, volume = {143}, number = {4}, abstract = {This paper presents a comparative study on the burst pressure performance of aluminum (Al) liner for type-III composite overwrapped pressure vessels (COPVs). In the analysis, the vessels were loaded with increasing internal pressure up to the burst pressure level. In the analytical part of the study, the burst pressure of the cylindrical part was predicted based on the modified von Mises, Tresca, and average shear stress criterion (ASSC). In the numerical analysis, a finite element (FE) model was established in order to predict the behavior of the vessel as a function of increasing internal pressure and determine the final burst. The Al pressure vessels made of Al-6061-T6 alloy with a capacity of 5 L were designed. The manufacturing of the metallic vessels was purchased from a metal forming company. The experimental study was conducted by pressurizing the Al vessels until the burst failure occurred. The radial and axial strain behaviors were monitored at various locations on the vessels during loading. The results obtained through analytical, numerical, and experimental work were compared. The average experimental burst pressure of the vessels was found to be 279 bar. The experimental strain data were compared with the results of the FE analysis. The results indicated that the FE analysis and ASSC-based elastoplastic analytical approaches yielded the best predictions which are within 2.2% of the experimental burst failure values. It was also found that the elastic analysis underestimated the burst failure results; however, it was effective for determining the critical regions over the vessel structure. The strain behavior of the vessels obtained through experimental investigations was well correlated with those predicted through FE analysis.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This paper presents a comparative study on the burst pressure performance of aluminum (Al) liner for type-III composite overwrapped pressure vessels (COPVs). In the analysis, the vessels were loaded with increasing internal pressure up to the burst pressure level. In the analytical part of the study, the burst pressure of the cylindrical part was predicted based on the modified von Mises, Tresca, and average shear stress criterion (ASSC). In the numerical analysis, a finite element (FE) model was established in order to predict the behavior of the vessel as a function of increasing internal pressure and determine the final burst. The Al pressure vessels made of Al-6061-T6 alloy with a capacity of 5 L were designed. The manufacturing of the metallic vessels was purchased from a metal forming company. The experimental study was conducted by pressurizing the Al vessels until the burst failure occurred. The radial and axial strain behaviors were monitored at various locations on the vessels during loading. The results obtained through analytical, numerical, and experimental work were compared. The average experimental burst pressure of the vessels was found to be 279 bar. The experimental strain data were compared with the results of the FE analysis. The results indicated that the FE analysis and ASSC-based elastoplastic analytical approaches yielded the best predictions which are within 2.2% of the experimental burst failure values. It was also found that the elastic analysis underestimated the burst failure results; however, it was effective for determining the critical regions over the vessel structure. The strain behavior of the vessels obtained through experimental investigations was well correlated with those predicted through FE analysis. |
Enser, S; Yavas, H; Hamat, B A; Aydın, H; Kafadar, G; Tanrıkulu, A A; Kazdal, H Z; Ozturk, F; Güden, M Comparing Compression Deformation and Rate Sensitivity of Additively Manufactured and Extruded-Annealed 316L Alloys Journal Article Journal of Materials Engineering and Performance, 30 (12), pp. 8831-8840, 2021. @article{Enser20218831, title = {Comparing Compression Deformation and Rate Sensitivity of Additively Manufactured and Extruded-Annealed 316L Alloys}, author = {S Enser and H Yavas and B A Hamat and H Aydın and G Kafadar and A A Tanrıkulu and H Z Kazdal and F Ozturk and M Güden}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85118462128&doi=10.1007%2fs11665-021-06340-9&partnerID=40&md5=d25a9a6e9c2f3be728f463e1a9b2e3a0}, doi = {10.1007/s11665-021-06340-9}, year = {2021}, date = {2021-01-01}, journal = {Journal of Materials Engineering and Performance}, volume = {30}, number = {12}, pages = {8831-8840}, abstract = {The deformation behavior of a selective-laser-melt-processed 316-L alloy (SLM-316L) under compression was determined together with a commercial annealed-extruded 316L alloy bar (C-316L) for comparison. Strain rate jump tests and hardness tests on the untested and compression tested samples were also performed. Extensive microscopic observations on the deformed and undeformed samples showed a twinning-dominated deformation in SLM-316L, similar to twinning-induced-plasticity steels, while a martensitic transformation-dominated deformation in C-316L alloy, similar to transformation-induced-plasticity steels. Within the studied quasi-static strain rate regime, the measured higher strain rate sensitivity of SLM-316L was ascribed to the lower distances between the nano-twins, in the level of 100 nm, than the distances between martensite plates, in the level of 1000 nm. A higher hardness increase in the martensite transformation region as compared with the twinned region proved the higher work hardening of C-316L. The hardness tests in the micron and sub-micron levels further confirmed the previously determined relatively low resistances of the dislocation cell walls (sub-grain) to the dislocation motion in SLM-316L alloy. © 2021, ASM International.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The deformation behavior of a selective-laser-melt-processed 316-L alloy (SLM-316L) under compression was determined together with a commercial annealed-extruded 316L alloy bar (C-316L) for comparison. Strain rate jump tests and hardness tests on the untested and compression tested samples were also performed. Extensive microscopic observations on the deformed and undeformed samples showed a twinning-dominated deformation in SLM-316L, similar to twinning-induced-plasticity steels, while a martensitic transformation-dominated deformation in C-316L alloy, similar to transformation-induced-plasticity steels. Within the studied quasi-static strain rate regime, the measured higher strain rate sensitivity of SLM-316L was ascribed to the lower distances between the nano-twins, in the level of 100 nm, than the distances between martensite plates, in the level of 1000 nm. A higher hardness increase in the martensite transformation region as compared with the twinned region proved the higher work hardening of C-316L. The hardness tests in the micron and sub-micron levels further confirmed the previously determined relatively low resistances of the dislocation cell walls (sub-grain) to the dislocation motion in SLM-316L alloy. © 2021, ASM International. |
Polat, D; Güden, M Processing and characterization of geopolymer and sintered geopolymer foams of waste glass powders Journal Article Construction and Building Materials, 300 , 2021. @article{Polat2021, title = {Processing and characterization of geopolymer and sintered geopolymer foams of waste glass powders}, author = {D Polat and M Güden}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85110473118&doi=10.1016%2fj.conbuildmat.2021.124259&partnerID=40&md5=0d7a948bc247b782e77d4b5908d062f3}, doi = {10.1016/j.conbuildmat.2021.124259}, year = {2021}, date = {2021-01-01}, journal = {Construction and Building Materials}, volume = {300}, abstract = {Geopolymer foams of fine and coarse waste glass (WG) powders were prepared using an activation solution of NaOH (8 M) and Na2SiO3. The effects of WG powder particle size, solid/liquid ratio (S/L = 1, 1.5, and 2) and Al foaming agent content (2–20 wt%) on the expansion and temperature behavior of the slurries were determined in-situ using a laser sensor and a thermocouple, respectively. The geopolymer foams processed using a coarse WG powder slurry, S/L = 2, and 2 wt% Al, were further sintered at 600, 700, 725, and 750 °C. The compression strengths and thermal conductivities of the geopolymer and sintered geopolymer foams were also determined. The slurry expansions continued until about a maximum, and the temperatures of the slurries increased to a maximum, 85–88 °C. At the maximum temperature, the slurry evaporation and the resultant increase in the S/L ratio limited the slurry expansion. Increasing the Al content decreased the final density of the foams (238–555 kg m−3), while the coarse powder slurries resulted in lower densities than the fine powder slurries. Three crystal phases, muscovite, sodium aluminum silicate hydrate, and thermonitrite, were determined in the geopolymer foams. The muscovite formation was noted to be favored at high S/L ratios. During sintering, the partial melting of glass particles started after about 700 °C, while sintering above this temperature decreased the final density of the foams. The reduced density above 700 °C was ascribed to the release of CO2 due to the decomposition of thermonitrite. Both the compressive strength and thermal conductivity of the geopolymer and sintered geopolymer foams increased with increasing foam density. The highest increase in the compressive strength and reduction in the density were seen in the geopolymer foams sintered at 750 °C. © 2021 Elsevier Ltd}, keywords = {}, pubstate = {published}, tppubtype = {article} } Geopolymer foams of fine and coarse waste glass (WG) powders were prepared using an activation solution of NaOH (8 M) and Na2SiO3. The effects of WG powder particle size, solid/liquid ratio (S/L = 1, 1.5, and 2) and Al foaming agent content (2–20 wt%) on the expansion and temperature behavior of the slurries were determined in-situ using a laser sensor and a thermocouple, respectively. The geopolymer foams processed using a coarse WG powder slurry, S/L = 2, and 2 wt% Al, were further sintered at 600, 700, 725, and 750 °C. The compression strengths and thermal conductivities of the geopolymer and sintered geopolymer foams were also determined. The slurry expansions continued until about a maximum, and the temperatures of the slurries increased to a maximum, 85–88 °C. At the maximum temperature, the slurry evaporation and the resultant increase in the S/L ratio limited the slurry expansion. Increasing the Al content decreased the final density of the foams (238–555 kg m−3), while the coarse powder slurries resulted in lower densities than the fine powder slurries. Three crystal phases, muscovite, sodium aluminum silicate hydrate, and thermonitrite, were determined in the geopolymer foams. The muscovite formation was noted to be favored at high S/L ratios. During sintering, the partial melting of glass particles started after about 700 °C, while sintering above this temperature decreased the final density of the foams. The reduced density above 700 °C was ascribed to the release of CO2 due to the decomposition of thermonitrite. Both the compressive strength and thermal conductivity of the geopolymer and sintered geopolymer foams increased with increasing foam density. The highest increase in the compressive strength and reduction in the density were seen in the geopolymer foams sintered at 750 °C. © 2021 Elsevier Ltd |
Shi, C; Guo, B; Sarıkaya, M; Çelik, M; Chen, P; Güden, M International Journal of Impact Engineering, 149 , 2021. @article{Shi2021, title = {Determination of the material model and damage parameters of a carbon fiber reinforced laminated epoxy composite for high strain rate planar compression}, author = {C Shi and B Guo and M Sarıkaya and M Çelik and P Chen and M Güden}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85097220985&doi=10.1016%2fj.ijimpeng.2020.103771&partnerID=40&md5=eecdd1023b76f40453f6cd5e379c9ec8}, doi = {10.1016/j.ijimpeng.2020.103771}, year = {2021}, date = {2021-01-01}, journal = {International Journal of Impact Engineering}, volume = {149}, abstract = {The progressive failure of a 0°/90° laminated carbon fiber reinforced epoxy composite was modeled in LS-DYNA using the MAT_162 material model, including the strain rate, damage progression and anisotropy effects. In addition to conventional standard and non-standard tests, double-shear and Brazilian tests were applied to determine the through-thickness shear modulus and the through-thickness tensile strength of the composite, respectively. The modulus reduction and strain softening for shear and delamination parameters were calibrated by low velocity drop-weight impact tests. The rate sensitivities of the modulus and strength of in-plane and through-thickness direction were determined by the compression tests at quasi-static and high strain rates. The fidelity of the determined model parameters was finally verified in the in-plane and through-thickness direction by the 3D numerical models of the Split Hopkinson Pressure Bar compression tests. The numerical bar stresses and damage progressions modes showed acceptable correlations with those of the experiments in both directions. The composite failed both numerically and experimentally by the fiber buckling induced fiber-matrix axial splitting in the in-plane and the matrix shear fracture in the through-thickness direction. © 2020}, keywords = {}, pubstate = {published}, tppubtype = {article} } The progressive failure of a 0°/90° laminated carbon fiber reinforced epoxy composite was modeled in LS-DYNA using the MAT_162 material model, including the strain rate, damage progression and anisotropy effects. In addition to conventional standard and non-standard tests, double-shear and Brazilian tests were applied to determine the through-thickness shear modulus and the through-thickness tensile strength of the composite, respectively. The modulus reduction and strain softening for shear and delamination parameters were calibrated by low velocity drop-weight impact tests. The rate sensitivities of the modulus and strength of in-plane and through-thickness direction were determined by the compression tests at quasi-static and high strain rates. The fidelity of the determined model parameters was finally verified in the in-plane and through-thickness direction by the 3D numerical models of the Split Hopkinson Pressure Bar compression tests. The numerical bar stresses and damage progressions modes showed acceptable correlations with those of the experiments in both directions. The composite failed both numerically and experimentally by the fiber buckling induced fiber-matrix axial splitting in the in-plane and the matrix shear fracture in the through-thickness direction. © 2020 |
Güden, M; Canbaz, İ International Journal of Crashworthiness, 26 (1), pp. 38-52, 2021. @article{Güden202138, title = {The effect of cell wall material strain and strain-rate hardening behaviour on the dynamic crush response of an aluminium multi-layered corrugated core}, author = {M Güden and İ Canbaz}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074867388&doi=10.1080%2f13588265.2019.1682351&partnerID=40&md5=4c12613ac0ed4e34ef1ed09c892300c6}, doi = {10.1080/13588265.2019.1682351}, year = {2021}, date = {2021-01-01}, journal = {International Journal of Crashworthiness}, volume = {26}, number = {1}, pages = {38-52}, abstract = {The effect of the parameters of the Johnson and Cook material model on the direct impact crushing behaviour of a layered 1050 H14 aluminium corrugated structure was investigated numerically in LS-DYNA at quasi-static (0.0048 m s−1) and dynamic (20, 60, 150 and 250 m s−1) velocities. Numerical and experimental direct impact tests were performed by lunching a striker bar onto corrugated samples attached to the end of the incident bar of a Split Hopkinson Pressure Bar set-up. The numerical impact-end stress-time and velocity-time curves were further compared with those of rigid-perfectly-plastic-locking (r-p-p-l) model. Numerical and r-p-p-l model impact-end stress analysis revealed a shock mode at 150 and 250 m s−1, transition mode at 60 m s−1 and quasi-static homogenous mode at 20 m s−1. The increase of velocity from quasi-static to 20 m s−1 increased the numerical distal-end initial peak-stress, while it almost stayed constant between 20 and 250 m s−1 for all material models. The increased distal-end initial peak-stress of strain rate insensitive models from quasi-static to 20 m s−1 confirmed the effect of micro-inertia. The numerical models further indicated a negligible effect of used material models on the impact-end stress of investigated structure. Finally, the contribution of strain rate to the distal-end initial peak-stress of cellular structures made of low strain rate sensitive Al alloys was shown to be relatively low as compared with that of strain hardening and micro-inertia, but it might be substantial for the structures constructed using relatively high strain rate sensitive alloys. © 2019 Informa UK Limited, trading as Taylor & Francis Group.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The effect of the parameters of the Johnson and Cook material model on the direct impact crushing behaviour of a layered 1050 H14 aluminium corrugated structure was investigated numerically in LS-DYNA at quasi-static (0.0048 m s−1) and dynamic (20, 60, 150 and 250 m s−1) velocities. Numerical and experimental direct impact tests were performed by lunching a striker bar onto corrugated samples attached to the end of the incident bar of a Split Hopkinson Pressure Bar set-up. The numerical impact-end stress-time and velocity-time curves were further compared with those of rigid-perfectly-plastic-locking (r-p-p-l) model. Numerical and r-p-p-l model impact-end stress analysis revealed a shock mode at 150 and 250 m s−1, transition mode at 60 m s−1 and quasi-static homogenous mode at 20 m s−1. The increase of velocity from quasi-static to 20 m s−1 increased the numerical distal-end initial peak-stress, while it almost stayed constant between 20 and 250 m s−1 for all material models. The increased distal-end initial peak-stress of strain rate insensitive models from quasi-static to 20 m s−1 confirmed the effect of micro-inertia. The numerical models further indicated a negligible effect of used material models on the impact-end stress of investigated structure. Finally, the contribution of strain rate to the distal-end initial peak-stress of cellular structures made of low strain rate sensitive Al alloys was shown to be relatively low as compared with that of strain hardening and micro-inertia, but it might be substantial for the structures constructed using relatively high strain rate sensitive alloys. © 2019 Informa UK Limited, trading as Taylor & Francis Group. |
Kandemir, S; Gavras, S; Dieringa, H Journal of Magnesium and Alloys, 9 (5), pp. 1753-1767, 2021. @article{Kandemir20211753, title = {High temperature tensile, compression and creep behavior of recycled short carbon fibre reinforced AZ91 magnesium alloy fabricated by a high shearing dispersion technique}, author = {S Kandemir and S Gavras and H Dieringa}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85106274015&doi=10.1016%2fj.jma.2021.03.029&partnerID=40&md5=33482583e6489310dc991aed7c7b0793}, doi = {10.1016/j.jma.2021.03.029}, year = {2021}, date = {2021-01-01}, journal = {Journal of Magnesium and Alloys}, volume = {9}, number = {5}, pages = {1753-1767}, abstract = {The present study seeks the feasibility of using short carbon fibres recycled from polymer matrix composites as alternative to virgin carbon fibres in the reinforcement of magnesium alloys. The microstructures, high temperature mechanical and creep properties of AZ91 alloy and its composites with various recycled carbon fibre contents (2.5 and 5 wt.%) and lengths (100 and 500 μm) were investigated in the temperature range of 25–200 °C. The microstructural characterization showed that the high shear dispersion technique provided the cast composites with finer grains and relatively homogenous distribution of fibres. The materials tested displayed different behaviour depending on the type of loading. In general, while enhancements in the mechanical properties of composites is attributed to the load bearing and grain refinement effects of fibres, the fluctuations in the properties were discussed on the basis of porosity formation, relatively high reinforcement content leading to fibre clustering and interlayer found between the matrix and reinforcement compared to those of AZ91 alloy. The compressive creep tests revealed similar or higher minimum creep rates in the recycled carbon fibre reinforced AZ91 in comparison to the unreinforced AZ91. © 2021}, keywords = {}, pubstate = {published}, tppubtype = {article} } The present study seeks the feasibility of using short carbon fibres recycled from polymer matrix composites as alternative to virgin carbon fibres in the reinforcement of magnesium alloys. The microstructures, high temperature mechanical and creep properties of AZ91 alloy and its composites with various recycled carbon fibre contents (2.5 and 5 wt.%) and lengths (100 and 500 μm) were investigated in the temperature range of 25–200 °C. The microstructural characterization showed that the high shear dispersion technique provided the cast composites with finer grains and relatively homogenous distribution of fibres. The materials tested displayed different behaviour depending on the type of loading. In general, while enhancements in the mechanical properties of composites is attributed to the load bearing and grain refinement effects of fibres, the fluctuations in the properties were discussed on the basis of porosity formation, relatively high reinforcement content leading to fibre clustering and interlayer found between the matrix and reinforcement compared to those of AZ91 alloy. The compressive creep tests revealed similar or higher minimum creep rates in the recycled carbon fibre reinforced AZ91 in comparison to the unreinforced AZ91. © 2021 |
Martin, S; Kandemir, S; Antonov, M Investigation of the high temperature dry sliding wear behavior of graphene nanoplatelets reinforced aluminum matrix composites Journal Article Journal of Composite Materials, 55 (13), pp. 1769-1782, 2021. @article{Martin20211769, title = {Investigation of the high temperature dry sliding wear behavior of graphene nanoplatelets reinforced aluminum matrix composites}, author = {S Martin and S Kandemir and M Antonov}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85097279024&doi=10.1177%2f0021998320979037&partnerID=40&md5=554c5ed3fcc37de88e360d033402ed4b}, doi = {10.1177/0021998320979037}, year = {2021}, date = {2021-01-01}, journal = {Journal of Composite Materials}, volume = {55}, number = {13}, pages = {1769-1782}, abstract = {In this study, graphene nanoplatelets (GNPs) with a thickness of 50-100 nm have been utilized to improve the mechanical and tribological properties of A360 alloy due to their extraordinary mechanical properties and solid lubricant nature. For the investigation of tribological properties, ball-on disc tests were carried out at various temperatures including room temperature (RT), 150 °C, and 300 °C. According to the hardness and ball-on-disc test results, the nanocomposite samples reinforced with GNPs exhibited improved hardness and wear resistance. The improvement in the wear behavior of nanocomposites was referred to the temporarily formed solid lubricant film of harder GNPs during the wear, and hence coefficient of friction (COF) and volume loss were considerably reduced. Abrasive-adhesive, oxidative, and mild-to-severe were found to be main wear mechanisms at RT, 150 °C, and 300 °C, respectively. Overall, the results show that the nanocomposites fabricated by casting method combined with mechanical stirring and ultrasonication have promising wear performance, especially at elevated temperatures. This may suggest that these developed materials could be potential candidates to be used in the engineering applications requiring high temperature wear performance. © The Author(s) 2020.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, graphene nanoplatelets (GNPs) with a thickness of 50-100 nm have been utilized to improve the mechanical and tribological properties of A360 alloy due to their extraordinary mechanical properties and solid lubricant nature. For the investigation of tribological properties, ball-on disc tests were carried out at various temperatures including room temperature (RT), 150 °C, and 300 °C. According to the hardness and ball-on-disc test results, the nanocomposite samples reinforced with GNPs exhibited improved hardness and wear resistance. The improvement in the wear behavior of nanocomposites was referred to the temporarily formed solid lubricant film of harder GNPs during the wear, and hence coefficient of friction (COF) and volume loss were considerably reduced. Abrasive-adhesive, oxidative, and mild-to-severe were found to be main wear mechanisms at RT, 150 °C, and 300 °C, respectively. Overall, the results show that the nanocomposites fabricated by casting method combined with mechanical stirring and ultrasonication have promising wear performance, especially at elevated temperatures. This may suggest that these developed materials could be potential candidates to be used in the engineering applications requiring high temperature wear performance. © The Author(s) 2020. |
Kartav, O; Kangal, S; Yücetürk, K; Tanoğlu, M; Aktaş, E; Artem, H S Development and analysis of composite overwrapped pressure vessels for hydrogen storage Journal Article Journal of Composite Materials, 55 (28), pp. 4141-4155, 2021. @article{Kartav20214141, title = {Development and analysis of composite overwrapped pressure vessels for hydrogen storage}, author = {O Kartav and S Kangal and K Yücetürk and M Tanoğlu and E Aktaş and H S Artem}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85110939454&doi=10.1177%2f00219983211033568&partnerID=40&md5=c31db8e0f0de63135bf2da9bf634900d}, doi = {10.1177/00219983211033568}, year = {2021}, date = {2021-01-01}, journal = {Journal of Composite Materials}, volume = {55}, number = {28}, pages = {4141-4155}, abstract = {In this study, composite overwrapped pressure vessels (COPVs) for high-pressure hydrogen storage were designed, modeled by finite element (FE) method, manufactured by filament winding technique and tested for burst pressure. Aluminum 6061-T6 was selected as a metallic liner material. Epoxy impregnated carbon filaments were overwrapped over the liner with a winding angle of ±14° to obtain fully overwrapped composite reinforced vessels with non-identical front and back dome layers. The COPVs were loaded with increasing internal pressure up to the burst pressure level. During loading, deformation of the vessels was measured locally with strain gauges. The mechanical performances of COPVs designed with various number of helical, hoop and doily layers were investigated by both experimental and numerical methods. In numerical method, FE analysis containing a simple progressive damage model available in ANSYS software package for the composite section was performed. The results revealed that the FE model provides a good correlation as compared to experimental strain results for the developed COPVs. The burst pressure test results showed that integration of doily layers to the filament winding process resulted with an improvement of the COPVs performance. © The Author(s) 2021.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, composite overwrapped pressure vessels (COPVs) for high-pressure hydrogen storage were designed, modeled by finite element (FE) method, manufactured by filament winding technique and tested for burst pressure. Aluminum 6061-T6 was selected as a metallic liner material. Epoxy impregnated carbon filaments were overwrapped over the liner with a winding angle of ±14° to obtain fully overwrapped composite reinforced vessels with non-identical front and back dome layers. The COPVs were loaded with increasing internal pressure up to the burst pressure level. During loading, deformation of the vessels was measured locally with strain gauges. The mechanical performances of COPVs designed with various number of helical, hoop and doily layers were investigated by both experimental and numerical methods. In numerical method, FE analysis containing a simple progressive damage model available in ANSYS software package for the composite section was performed. The results revealed that the FE model provides a good correlation as compared to experimental strain results for the developed COPVs. The burst pressure test results showed that integration of doily layers to the filament winding process resulted with an improvement of the COPVs performance. © The Author(s) 2021. |
Güden, M; Yavaş, H; Tanrıkulu, A A; Taşdemirci, A; Akın, B; Enser, S; Karakuş, A; Hamat, B A Orientation dependent tensile properties of a selective-laser-melt 316L stainless steel Journal Article Materials Science and Engineering A, 824 , 2021. @article{Güden2021b, title = {Orientation dependent tensile properties of a selective-laser-melt 316L stainless steel}, author = {M Güden and H Yavaş and A A Tanrıkulu and A Taşdemirci and B Akın and S Enser and A Karakuş and B A Hamat}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85111194339&doi=10.1016%2fj.msea.2021.141808&partnerID=40&md5=d838bade5a0604998ddd4cb8ecce7457}, doi = {10.1016/j.msea.2021.141808}, year = {2021}, date = {2021-01-01}, journal = {Materials Science and Engineering A}, volume = {824}, abstract = {The effect of specimen inclination angle with respect to building direction on the tensile properties of a selective laser melt 316L alloy was investigated. Tensile test specimens were fabricated with the angles between 0° to 90° at 15° intervals using a rotation scanning. In addition, 316L alloy test specimens were generated in the ANSYS 2020R1 additive module and tensile tested in LS-DYNA in order to determine the effect of residual stresses on the tensile strengths. The microscopic analysis revealed a strong ⟨110⟩ fiber texture orientation along the building direction (the loading axis of 0° inclined specimens) and a weak <111> texture or nearly random distribution of directions in the normal to the building direction (tensile loading axis of 90° inclined specimens). The yield and tensile strength increased and ductility decreased with increasing inclination angle. The strength variation with the inclination angle was shown well-fitted with the Tsai-Hill failure criterion. Although, the used numerical models indicated an inclination-dependent residual stress, the difference in the residual stresses was much lower than the difference in the strengths between 0° and 90° inclined specimens. Predictions showed a lower twinning stress in 0° inclined specimens due to ⟨110⟩ fiber texture orientation in the tensile axis. The fiber texture resulted in extensive twinning; hence, higher ductility and tension-compression asymmetry in 0° inclined specimens. Based on these results, the variations in the strength and ductility of tested SLM-316L specimens with the inclination angle was ascribed to the variations in the angle between the fiber texture orientation and loading axis. © 2021 Elsevier B.V.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The effect of specimen inclination angle with respect to building direction on the tensile properties of a selective laser melt 316L alloy was investigated. Tensile test specimens were fabricated with the angles between 0° to 90° at 15° intervals using a rotation scanning. In addition, 316L alloy test specimens were generated in the ANSYS 2020R1 additive module and tensile tested in LS-DYNA in order to determine the effect of residual stresses on the tensile strengths. The microscopic analysis revealed a strong ⟨110⟩ fiber texture orientation along the building direction (the loading axis of 0° inclined specimens) and a weak <111> texture or nearly random distribution of directions in the normal to the building direction (tensile loading axis of 90° inclined specimens). The yield and tensile strength increased and ductility decreased with increasing inclination angle. The strength variation with the inclination angle was shown well-fitted with the Tsai-Hill failure criterion. Although, the used numerical models indicated an inclination-dependent residual stress, the difference in the residual stresses was much lower than the difference in the strengths between 0° and 90° inclined specimens. Predictions showed a lower twinning stress in 0° inclined specimens due to ⟨110⟩ fiber texture orientation in the tensile axis. The fiber texture resulted in extensive twinning; hence, higher ductility and tension-compression asymmetry in 0° inclined specimens. Based on these results, the variations in the strength and ductility of tested SLM-316L specimens with the inclination angle was ascribed to the variations in the angle between the fiber texture orientation and loading axis. © 2021 Elsevier B.V. |
Seven, S B; Çankaya, M A; Uysal, Ç; Tasdemirci, A; Saatçi, S; Güden, M Constitutive equation determination and dynamic numerical modelling of the compression deformation of concrete Journal Article Strain, 57 (2), 2021. @article{Seven2021, title = {Constitutive equation determination and dynamic numerical modelling of the compression deformation of concrete}, author = {S B Seven and M A Çankaya and Ç Uysal and A Tasdemirci and S Saatçi and M Güden}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85099175099&doi=10.1111%2fstr.12377&partnerID=40&md5=4651c623ee9ea5323e2e6b03771b2c5f}, doi = {10.1111/str.12377}, year = {2021}, date = {2021-01-01}, journal = {Strain}, volume = {57}, number = {2}, abstract = {The dynamic compression deformation of an in-house cast concrete (average aggregate size of 2–2.5 mm) was modelled using the finite element (FE), element-free Galerkin (EFG) and smooth particle Galerkin (SPG) methods to determine their capabilities of capturing the dynamic deformation. The numerical results were validated with those of the experimental split Hopkinson pressure bar tests. Both EFG and FE methods overestimated the failure stress and strain values, while the SPG method underestimated the peak stress. SPG showed similar load capacity profile with the experiment. At initial stages of the loading, all methods present similar behaviour. Nonetheless, as the loading continues, the SPG method predicts closer agreement of deformation profile and force histories. The increase in strength at high strain rate was due to both the rate sensitivity and lateral inertia caused by the confinement effect. The inertia effect of the material especially is effective at lower strain values and the strain rate sensitivity of the concrete becomes significant at higher strain values. © 2021 John Wiley & Sons Ltd}, keywords = {}, pubstate = {published}, tppubtype = {article} } The dynamic compression deformation of an in-house cast concrete (average aggregate size of 2–2.5 mm) was modelled using the finite element (FE), element-free Galerkin (EFG) and smooth particle Galerkin (SPG) methods to determine their capabilities of capturing the dynamic deformation. The numerical results were validated with those of the experimental split Hopkinson pressure bar tests. Both EFG and FE methods overestimated the failure stress and strain values, while the SPG method underestimated the peak stress. SPG showed similar load capacity profile with the experiment. At initial stages of the loading, all methods present similar behaviour. Nonetheless, as the loading continues, the SPG method predicts closer agreement of deformation profile and force histories. The increase in strength at high strain rate was due to both the rate sensitivity and lateral inertia caused by the confinement effect. The inertia effect of the material especially is effective at lower strain values and the strain rate sensitivity of the concrete becomes significant at higher strain values. © 2021 John Wiley & Sons Ltd |
2020 |
Beylergil, Bertan; Tanoglu, Metin; Aktas, Engin Experimental and statistical analysis of carbon fiber/epoxy composites interleaved with nylon 6,6 nonwoven fabric interlayers Journal Article JOURNAL OF COMPOSITE MATERIALS, 54 (27), pp. 4173-4184, 2020, ISSN: 0021-9983. @article{ISI:000535519800001, title = {Experimental and statistical analysis of carbon fiber/epoxy composites interleaved with nylon 6,6 nonwoven fabric interlayers}, author = {Bertan Beylergil and Metin Tanoglu and Engin Aktas}, doi = {10.1177/0021998320927740, Early Access Date = MAY 2020}, issn = {0021-9983}, year = {2020}, date = {2020-11-01}, journal = {JOURNAL OF COMPOSITE MATERIALS}, volume = {54}, number = {27}, pages = {4173-4184}, abstract = {Thermoplastic interleaving is a promising technique to improve delamination resistance of laminated composites. In this study, plain-weave carbon fiber/epoxy composites were interleaved with nylon 6,6 nonwoven fabrics with an areal weight density of 17 gsm. The carbon fiber/epoxy composite laminates with/without nylon 6,6 nonwoven fabric interlayers were manufactured by VARTM technique. Double cantilever beam fracture toughness tests were carried out on the prepared composite test specimens in accordance with ASTM 5528 standard. The experimental test data were statistically analyzed by two-parameter Weibull distribution. The results showed that the initiation and propagation fracture toughness Mode-I fracture toughness of carbon fiber/epoxy composites could be improved by about 34 and 156% (corresponding to a reliability level of 0.50) with the incorporation of nylon 6,6 interlayers in the interlaminar region, respectively. The results also revealed that the percent increase in the propagation fracture toughness value was 67 and 41% at reliability levels of 0.90 and 0.95, respectively.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Thermoplastic interleaving is a promising technique to improve delamination resistance of laminated composites. In this study, plain-weave carbon fiber/epoxy composites were interleaved with nylon 6,6 nonwoven fabrics with an areal weight density of 17 gsm. The carbon fiber/epoxy composite laminates with/without nylon 6,6 nonwoven fabric interlayers were manufactured by VARTM technique. Double cantilever beam fracture toughness tests were carried out on the prepared composite test specimens in accordance with ASTM 5528 standard. The experimental test data were statistically analyzed by two-parameter Weibull distribution. The results showed that the initiation and propagation fracture toughness Mode-I fracture toughness of carbon fiber/epoxy composites could be improved by about 34 and 156% (corresponding to a reliability level of 0.50) with the incorporation of nylon 6,6 interlayers in the interlaminar region, respectively. The results also revealed that the percent increase in the propagation fracture toughness value was 67 and 41% at reliability levels of 0.90 and 0.95, respectively. |
Ay, Z; Tanoglu, M The Effect of Single-Walled Carbon Nanotube (SWCNT) Concentration on the Mechanical and Rheological Behavior of Epoxy Matrix Journal Article MECHANICS OF COMPOSITE MATERIALS, 56 (4), pp. 523-532, 2020, ISSN: 0191-5665. @article{ISI:000567735300002, title = {The Effect of Single-Walled Carbon Nanotube (SWCNT) Concentration on the Mechanical and Rheological Behavior of Epoxy Matrix}, author = {Z Ay and M Tanoglu}, doi = {10.1007/s11029-020-09900-7, Early Access Date = SEP 2020}, issn = {0191-5665}, year = {2020}, date = {2020-09-01}, journal = {MECHANICS OF COMPOSITE MATERIALS}, volume = {56}, number = {4}, pages = {523-532}, abstract = {The improvement of Mode I fracture toughness of epoxy by the addition of single-walled carbon nanotubes (SWCNTs) is considered. To prepare nanocomposites, chemical-vapor-deposition-grown SWCNTs noncovalently functionalized with an ethoxylated alcohol was used as the additive and a diglycidyl ether of bisphenol-A-based epoxy as the matrix material. The SWCNTs were dispersed in the epoxy matrix via a mechanical stirrer and a 3-roll mill. The effect of their concentration (0.0125, 0.025, 0.05, 0.1, 0.3, and 0.5 wt.%) on the mechanical properties of the nanocomposites was investigated, and the optimum concentration was determined. Mode I fracture toughness (single-edge-notch 3-point bending) and tensile tests were carried out on neat epoxy and SWCNT-reinforced epoxy nanocomposites. The fractured surfaces of fracture toughness and tensile test specimens were examined by the SEM to reveal the effect of SWCNTs on their failure modes.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The improvement of Mode I fracture toughness of epoxy by the addition of single-walled carbon nanotubes (SWCNTs) is considered. To prepare nanocomposites, chemical-vapor-deposition-grown SWCNTs noncovalently functionalized with an ethoxylated alcohol was used as the additive and a diglycidyl ether of bisphenol-A-based epoxy as the matrix material. The SWCNTs were dispersed in the epoxy matrix via a mechanical stirrer and a 3-roll mill. The effect of their concentration (0.0125, 0.025, 0.05, 0.1, 0.3, and 0.5 wt.%) on the mechanical properties of the nanocomposites was investigated, and the optimum concentration was determined. Mode I fracture toughness (single-edge-notch 3-point bending) and tensile tests were carried out on neat epoxy and SWCNT-reinforced epoxy nanocomposites. The fractured surfaces of fracture toughness and tensile test specimens were examined by the SEM to reveal the effect of SWCNTs on their failure modes. |
Zeren, Dogus; Senturk, Ufuk; Guden, Mustafa The expansion behavior of slurries containing recycled glass powder carboxymethyl cellulose, lime and aluminum powder Journal Article CONSTRUCTION AND BUILDING MATERIALS, 240 , 2020, ISSN: 0950-0618. @article{ISI:000527362400021, title = {The expansion behavior of slurries containing recycled glass powder carboxymethyl cellulose, lime and aluminum powder}, author = {Dogus Zeren and Ufuk Senturk and Mustafa Guden}, doi = {10.1016/j.conbuildmat.2019.117898}, issn = {0950-0618}, year = {2020}, date = {2020-04-01}, journal = {CONSTRUCTION AND BUILDING MATERIALS}, volume = {240}, abstract = {The rheology and foaming/expansion of the slurries of a waste/recycled glass powder with 50, 55 and 60 wt% of solid (glass powder) were experimentally investigated. The glass powder slurries were foamed using aluminum powder as foaming agent (0.75 wt%) and calcium hydroxide as activator (1 wt%). Sodium carboxymethyl cellulose (CMC) was added to the slurries as a binder with the amounts between 0 and 4 wt%. The expansions of the slurries were measured in-situ using a laser sensor and reported as percent volume expansion. The CMC-addition increased the viscosities of the slurries, particularly the fine size powder slurries. The slurries with the relatively low-viscosity exhibited lower initial expansion rates compared to the slurries with the relatively high-viscosity. The maximum expansions of the slurries increased from 300 to 350%, when the viscosity increased to 5 Pa s and reached a steady value around 400% between 5 and 50 Pa s. The expansions of the slurries could not be achieved above 50 Pa s since they became too thick to be foamed. The foam samples made from the slurries with 55 and 60 wt% of solid and sintered at 700 and 750 degrees C for 30 min had the average densities between 355 and 530 kg m(-3) and the average compressive strengths between 0.2 and 0.5 MPa. Increasing sintering time to 60 min at 750 degrees C increased the average compressive strength from 0.5 to 1.5 MPa for the foam samples made from the slurry with 60 wt% of solid. These proved that both sintering temperature and time were effective in increasing the compressive strengths of the foamed structures. The thermal conductivities of the sintered foam samples with the densities of 355 and 504 kg m(-3) were measured 0.042 and 0.057 W m(-1) K-1, respectively. (C) 2019 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The rheology and foaming/expansion of the slurries of a waste/recycled glass powder with 50, 55 and 60 wt% of solid (glass powder) were experimentally investigated. The glass powder slurries were foamed using aluminum powder as foaming agent (0.75 wt%) and calcium hydroxide as activator (1 wt%). Sodium carboxymethyl cellulose (CMC) was added to the slurries as a binder with the amounts between 0 and 4 wt%. The expansions of the slurries were measured in-situ using a laser sensor and reported as percent volume expansion. The CMC-addition increased the viscosities of the slurries, particularly the fine size powder slurries. The slurries with the relatively low-viscosity exhibited lower initial expansion rates compared to the slurries with the relatively high-viscosity. The maximum expansions of the slurries increased from 300 to 350%, when the viscosity increased to 5 Pa s and reached a steady value around 400% between 5 and 50 Pa s. The expansions of the slurries could not be achieved above 50 Pa s since they became too thick to be foamed. The foam samples made from the slurries with 55 and 60 wt% of solid and sintered at 700 and 750 degrees C for 30 min had the average densities between 355 and 530 kg m(-3) and the average compressive strengths between 0.2 and 0.5 MPa. Increasing sintering time to 60 min at 750 degrees C increased the average compressive strength from 0.5 to 1.5 MPa for the foam samples made from the slurry with 60 wt% of solid. These proved that both sintering temperature and time were effective in increasing the compressive strengths of the foamed structures. The thermal conductivities of the sintered foam samples with the densities of 355 and 504 kg m(-3) were measured 0.042 and 0.057 W m(-1) K-1, respectively. (C) 2019 Elsevier Ltd. All rights reserved. |
Kangal, S; Kartav, O; Tanoğlu, M; Aktaş, E; Artem, H S Journal of Composite Materials, 54 (7), pp. 961-980, 2020. @article{Kangal2020961, title = {Investigation of interlayer hybridization effect on burst pressure performance of composite overwrapped pressure vessels with load-sharing metallic liner}, author = {S Kangal and O Kartav and M Tanoğlu and E Aktaş and H S Artem}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85071956589&doi=10.1177%2f0021998319870588&partnerID=40&md5=90d8ba513531b1cd09c963d447aebf4a}, doi = {10.1177/0021998319870588}, year = {2020}, date = {2020-01-01}, journal = {Journal of Composite Materials}, volume = {54}, number = {7}, pages = {961-980}, abstract = {In this study, multi-layered composite overwrapped pressure vessels for high-pressure gaseous storage were designed, modeled by finite element method and manufactured by filament winding technique. 34CrMo4 steel was selected as a load-sharing metallic liner. Glass and carbon filaments were overwrapped on the liner with a winding angle of [±11°/90°2]3 to obtain fully overwrapped composite reinforced vessel with non-identical front and back dome endings. The vessels were loaded with increasing internal pressure up to the burst pressure level. The mechanical performances of pressure vessels, (i) fully overwrapped with glass fibers and (ii) with additional two carbon hoop layers on the cylindrical section, were investigated by both experimental and numerical approaches. In numerical approaches, finite element analysis was performed featuring a simple progressive damage model available in ANSYS software package for the composite section. The metal liner was modeled as elastic–plastic material. The results reveal that the finite element model provides a good correlation between experimental and numerical strain results for the vessels, together with the indication of the positive effect on radial deformation of the COPVs due to the composite interlayer hybridization. The constructed model was also able to predict experimental burst pressures within a range of 8%. However, the experimental and finite element analysis results showed that hybridization of hoop layers did not have any significant impact on the burst pressure performance of the vessels. This finding was attributed to the change of load-sharing capacity of composite layers due to the stiffness difference of carbon and glass fibers. © The Author(s) 2019.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, multi-layered composite overwrapped pressure vessels for high-pressure gaseous storage were designed, modeled by finite element method and manufactured by filament winding technique. 34CrMo4 steel was selected as a load-sharing metallic liner. Glass and carbon filaments were overwrapped on the liner with a winding angle of [±11°/90°2]3 to obtain fully overwrapped composite reinforced vessel with non-identical front and back dome endings. The vessels were loaded with increasing internal pressure up to the burst pressure level. The mechanical performances of pressure vessels, (i) fully overwrapped with glass fibers and (ii) with additional two carbon hoop layers on the cylindrical section, were investigated by both experimental and numerical approaches. In numerical approaches, finite element analysis was performed featuring a simple progressive damage model available in ANSYS software package for the composite section. The metal liner was modeled as elastic–plastic material. The results reveal that the finite element model provides a good correlation between experimental and numerical strain results for the vessels, together with the indication of the positive effect on radial deformation of the COPVs due to the composite interlayer hybridization. The constructed model was also able to predict experimental burst pressures within a range of 8%. However, the experimental and finite element analysis results showed that hybridization of hoop layers did not have any significant impact on the burst pressure performance of the vessels. This finding was attributed to the change of load-sharing capacity of composite layers due to the stiffness difference of carbon and glass fibers. © The Author(s) 2019. |
Yardimci, Atike Ince; Tanoglu, Metin; Yilmaz, Selahattin; Selamet, Yusuf Effect of CNT incorporation on PAN/PPy nanofibers synthesized by electrospinning method Journal Article TURKISH JOURNAL OF CHEMISTRY, 44 (4), pp. 1002-1015, 2020, ISSN: 1300-0527. @article{ISI:000560919000010, title = {Effect of CNT incorporation on PAN/PPy nanofibers synthesized by electrospinning method}, author = {Atike Ince Yardimci and Metin Tanoglu and Selahattin Yilmaz and Yusuf Selamet}, doi = {10.3906/kim-1911-49}, issn = {1300-0527}, year = {2020}, date = {2020-01-01}, journal = {TURKISH JOURNAL OF CHEMISTRY}, volume = {44}, number = {4}, pages = {1002-1015}, abstract = {In this study, carbon nanotubes (CNTs) added polyacrylonitrile/polypyrrole (PAN/PPy) electrospun nanofibers were produced. Average diameters of the nanofibers were measured as 268 and 153 nm for 10 and 25 wt% of PPy contents, respectively. A relatively higher strain to failure values (23.3%) were observed for the low PPy content. When as-grown CNTs (1 and 4 wt%) were added into the PAN/PPy blends, disordered nanofibers were observed to form within the microstructure. To improve the interfacial properties of CNTs/PAN/PPy composites, CNTs were functionalized with H2SO4/HNO3/HCl solution. The functionalized CNTs were well dispersed within the nanofibers and aligned along the direction of nanofibers. Therefore, beads formation on nanofibers decreased. The impedance of the nanofibers was found to decrease with the PPy content and CNT addition. These nanofibers had a great potential to be used as an electrochemical actuator or a tissue engineering scaffold.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, carbon nanotubes (CNTs) added polyacrylonitrile/polypyrrole (PAN/PPy) electrospun nanofibers were produced. Average diameters of the nanofibers were measured as 268 and 153 nm for 10 and 25 wt% of PPy contents, respectively. A relatively higher strain to failure values (23.3%) were observed for the low PPy content. When as-grown CNTs (1 and 4 wt%) were added into the PAN/PPy blends, disordered nanofibers were observed to form within the microstructure. To improve the interfacial properties of CNTs/PAN/PPy composites, CNTs were functionalized with H2SO4/HNO3/HCl solution. The functionalized CNTs were well dispersed within the nanofibers and aligned along the direction of nanofibers. Therefore, beads formation on nanofibers decreased. The impedance of the nanofibers was found to decrease with the PPy content and CNT addition. These nanofibers had a great potential to be used as an electrochemical actuator or a tissue engineering scaffold. |
Kilicaslan, Cenk; Guden, Mustafa The effect of core height on energy absorbing capacity in aluminum corrugated sandwich panels Journal Article JOURNAL OF THE FACULTY OF ENGINEERING AND ARCHITECTURE OF GAZI UNIVERSITY, 35 (1), pp. 17-26, 2020, ISSN: 1300-1884. @article{ISI:000520598100002, title = {The effect of core height on energy absorbing capacity in aluminum corrugated sandwich panels}, author = {Cenk Kilicaslan and Mustafa Guden}, doi = {10.17341/gazimmfd.639834}, issn = {1300-1884}, year = {2020}, date = {2020-01-01}, journal = {JOURNAL OF THE FACULTY OF ENGINEERING AND ARCHITECTURE OF GAZI UNIVERSITY}, volume = {35}, number = {1}, pages = {17-26}, abstract = {In this study, energy absorbing capacity of brazed and polyurethane adhesively bonded corrugated aluminum sandwich panels were investigated. In sandwich panels, Al 1050 H14 trapezoidal zig-zag corrugated cores and face and interlayer sheets were used. Each sandwich panel has core orientation of 0 degrees/0 degrees or 0 degrees/90 degrees. The cores used in these panels were smaller, core height is about 3 mm, in contrast to conventional sandwich cores. Impact tests were conducted at 3 and 6 m/s with spherical projectors. Adhesively bonded sandwich panels were also tested at 6 m/s with flat and conical projectors. Numerical models were prepared in LSDYNA to investigated the deformation behavior of cores. Panels tested with flat and conical projectors experienced complete perforation and absorbed more energy at configuration of 0 degrees/0 degrees core orientation. However, panels tested with spherical projectors were not perforated and they absorbed more energy at configuration of 0 degrees/90 degrees core orientation. Energy absorbing capacity of the panels were also compared to the panels having 9 mm height corrugated cores. The results showed that effective collapsing length was seen to increase due to increase in core height and impact energy distributed the whole panel surface more homogenous manner.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, energy absorbing capacity of brazed and polyurethane adhesively bonded corrugated aluminum sandwich panels were investigated. In sandwich panels, Al 1050 H14 trapezoidal zig-zag corrugated cores and face and interlayer sheets were used. Each sandwich panel has core orientation of 0 degrees/0 degrees or 0 degrees/90 degrees. The cores used in these panels were smaller, core height is about 3 mm, in contrast to conventional sandwich cores. Impact tests were conducted at 3 and 6 m/s with spherical projectors. Adhesively bonded sandwich panels were also tested at 6 m/s with flat and conical projectors. Numerical models were prepared in LSDYNA to investigated the deformation behavior of cores. Panels tested with flat and conical projectors experienced complete perforation and absorbed more energy at configuration of 0 degrees/0 degrees core orientation. However, panels tested with spherical projectors were not perforated and they absorbed more energy at configuration of 0 degrees/90 degrees core orientation. Energy absorbing capacity of the panels were also compared to the panels having 9 mm height corrugated cores. The results showed that effective collapsing length was seen to increase due to increase in core height and impact energy distributed the whole panel surface more homogenous manner. |
Seven, Semih Berk; Cankaya, Alper M; Uysal, Cetin; Tasdemirci, Alper; Saatci, Selcuk; Guden, Mustafa Constitutive equation determination and dynamic numerical modelling of the compression deformation of concrete Journal Article STRAIN, 2020, ISSN: 0039-2103. @article{ISI:000605351700001, title = {Constitutive equation determination and dynamic numerical modelling of the compression deformation of concrete}, author = {Semih Berk Seven and Alper M Cankaya and Cetin Uysal and Alper Tasdemirci and Selcuk Saatci and Mustafa Guden}, doi = {10.1111/str.12377, Early Access Date = JAN 2021}, issn = {0039-2103}, year = {2020}, date = {2020-00-00}, journal = {STRAIN}, abstract = {The dynamic compression deformation of an in-house cast concrete (average aggregate size of 2-2.5 mm) was modelled using the finite element (FE), element-free Galerkin (EFG) and smooth particle Galerkin (SPG) methods to determine their capabilities of capturing the dynamic deformation. The numerical results were validated with those of the experimental split Hopkinson pressure bar tests. Both EFG and FE methods overestimated the failure stress and strain values, while the SPG method underestimated the peak stress. SPG showed similar load capacity profile with the experiment. At initial stages of the loading, all methods present similar behaviour. Nonetheless, as the loading continues, the SPG method predicts closer agreement of deformation profile and force histories. The increase in strength at high strain rate was due to both the rate sensitivity and lateral inertia caused by the confinement effect. The inertia effect of the material especially is effective at lower strain values and the strain rate sensitivity of the concrete becomes significant at higher strain values.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The dynamic compression deformation of an in-house cast concrete (average aggregate size of 2-2.5 mm) was modelled using the finite element (FE), element-free Galerkin (EFG) and smooth particle Galerkin (SPG) methods to determine their capabilities of capturing the dynamic deformation. The numerical results were validated with those of the experimental split Hopkinson pressure bar tests. Both EFG and FE methods overestimated the failure stress and strain values, while the SPG method underestimated the peak stress. SPG showed similar load capacity profile with the experiment. At initial stages of the loading, all methods present similar behaviour. Nonetheless, as the loading continues, the SPG method predicts closer agreement of deformation profile and force histories. The increase in strength at high strain rate was due to both the rate sensitivity and lateral inertia caused by the confinement effect. The inertia effect of the material especially is effective at lower strain values and the strain rate sensitivity of the concrete becomes significant at higher strain values. |
2019 |
Beylergil, B; Tanoǧlu, M; Aktaş, E Mode-I fracture toughness of carbon fiber/epoxy composites interleaved by aramid nonwoven veils Journal Article Steel and Composite Structures, 31 (2), pp. 113-123, 2019. @article{Beylergil2019113, title = {Mode-I fracture toughness of carbon fiber/epoxy composites interleaved by aramid nonwoven veils}, author = {B Beylergil and M Tanoǧlu and E Aktaş}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85065238224&doi=10.12989%2fscs.2019.31.2.113&partnerID=40&md5=c8783b96f972924d7754bb7820373a14}, doi = {10.12989/scs.2019.31.2.113}, year = {2019}, date = {2019-01-01}, journal = {Steel and Composite Structures}, volume = {31}, number = {2}, pages = {113-123}, abstract = {In this study, carbon fiber/epoxy (CF/EP) composites were interleaved with aramid nonwoven veils with an areal weight density of 8.5 g/m 2 to improve their Mode-I fracture toughness. The control and aramid interleaved CF/EP composite laminates were manufactured by VARTM in a [0]4 configuration. Tensile, three-point bending, compression, interlaminar shear, Charpy impact and Mode-I (DCB) fracture toughness values were determined to evaluate the effects of aramid nonwoven fabrics on the mechanical performance of the CF/EP composites. Thermomechanical behavior of the specimens was investigated by Dynamic Mechanical Analysis (DMA). The results showed that the propagation Mode-I fracture toughness values of CF/EP composites can be significantly improved (by about 72%) using aramid nonwoven fabrics. It was found that the main extrinsic toughening mechanism is aramid microfiber bridging acting behind the crack-tip. The incorporation of these nonwovens also increased interlaminar shear and Charpy impact strength by 10 and 16.5%, respectively. Moreover, it was revealed that the damping ability of the composites increased with the incorporation of aramid nonwoven fabrics in the interlaminar region of composites. On the other hand, they caused a reduction in in-plane mechanical properties due to the reduced carbon fiber volume fraction, increased thickness and void formation in the composites. Copyright © 2019 Techno-Press, Ltd.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, carbon fiber/epoxy (CF/EP) composites were interleaved with aramid nonwoven veils with an areal weight density of 8.5 g/m 2 to improve their Mode-I fracture toughness. The control and aramid interleaved CF/EP composite laminates were manufactured by VARTM in a [0]4 configuration. Tensile, three-point bending, compression, interlaminar shear, Charpy impact and Mode-I (DCB) fracture toughness values were determined to evaluate the effects of aramid nonwoven fabrics on the mechanical performance of the CF/EP composites. Thermomechanical behavior of the specimens was investigated by Dynamic Mechanical Analysis (DMA). The results showed that the propagation Mode-I fracture toughness values of CF/EP composites can be significantly improved (by about 72%) using aramid nonwoven fabrics. It was found that the main extrinsic toughening mechanism is aramid microfiber bridging acting behind the crack-tip. The incorporation of these nonwovens also increased interlaminar shear and Charpy impact strength by 10 and 16.5%, respectively. Moreover, it was revealed that the damping ability of the composites increased with the incorporation of aramid nonwoven fabrics in the interlaminar region of composites. On the other hand, they caused a reduction in in-plane mechanical properties due to the reduced carbon fiber volume fraction, increased thickness and void formation in the composites. Copyright © 2019 Techno-Press, Ltd. |
2018 |
Oztoprak, N; Gunes, M D; Tanoglu, M; Aktas, E; Egilmez, O O; Senocak, C; Kulac, G Developing polymer composite-based leaf spring systems for automotive industry Journal Article Science and Engineering of Composite Materials, 25 (6), pp. 1167-1176, 2018. @article{Oztoprak20181167, title = {Developing polymer composite-based leaf spring systems for automotive industry}, author = {N Oztoprak and M D Gunes and M Tanoglu and E Aktas and O O Egilmez and C Senocak and G Kulac}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85056594508&doi=10.1515%2fsecm-2016-0335&partnerID=40&md5=f8692f0ca38d12eec3006c474b120b21}, doi = {10.1515/secm-2016-0335}, year = {2018}, date = {2018-01-01}, journal = {Science and Engineering of Composite Materials}, volume = {25}, number = {6}, pages = {1167-1176}, abstract = {Composite-based mono-leaf spring systems were designed and manufactured to replace existing mono-leaf metal leaf spring in a light commercial vehicle. In this study, experimentally obtained mechanical properties of different fiber-reinforced polymer materials are presented first, followed by the description of the finite element analytical model created in Abaqus 6.12-1 (Dassault Systemes Simulia Corp., RI, US) using the obtained properties. The results from the finite element analysis are presented next and compared with actual size experimental tests conducted on manufactured prototypes. The results demonstrated that the reinforcement type and orientation dramatically influenced the spring rate. The prototypes showed significant weight reduction of about 80% with improved mechanical properties. The hybrid composite systems can be utilized for composite-based leaf springs with considerable mechanical performance. © 2018 Walter de Gruyter GmbH, Berlin/Boston.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Composite-based mono-leaf spring systems were designed and manufactured to replace existing mono-leaf metal leaf spring in a light commercial vehicle. In this study, experimentally obtained mechanical properties of different fiber-reinforced polymer materials are presented first, followed by the description of the finite element analytical model created in Abaqus 6.12-1 (Dassault Systemes Simulia Corp., RI, US) using the obtained properties. The results from the finite element analysis are presented next and compared with actual size experimental tests conducted on manufactured prototypes. The results demonstrated that the reinforcement type and orientation dramatically influenced the spring rate. The prototypes showed significant weight reduction of about 80% with improved mechanical properties. The hybrid composite systems can be utilized for composite-based leaf springs with considerable mechanical performance. © 2018 Walter de Gruyter GmbH, Berlin/Boston. |
Beylergil, B; Tanoğlu, M; Aktaş, E Effect of polyamide-6,6 (PA 66) nonwoven veils on the mechanical performance of carbon fiber/epoxy composites Journal Article Composite Structures, 194 , pp. 21-35, 2018. @article{Beylergil201821, title = {Effect of polyamide-6,6 (PA 66) nonwoven veils on the mechanical performance of carbon fiber/epoxy composites}, author = {B Beylergil and M Tanoğlu and E Aktaş}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85044992271&doi=10.1016%2fj.compstruct.2018.03.097&partnerID=40&md5=5a48cd887d9aa73061331019a3e6b047}, doi = {10.1016/j.compstruct.2018.03.097}, year = {2018}, date = {2018-01-01}, journal = {Composite Structures}, volume = {194}, pages = {21-35}, abstract = {In this study, carbon fiber/epoxy (CF/EP) composites were interleaved with polyamide-6,6 (PA 66) nonwoven veils at two different areal weight densities (17 and 50 gsm) to improve their delamination resistance against Mode-I loading. Mode-I fracture toughness (DCB), tensile, open hole tensile (OHT), flexural, compression, short beam shear (ILSS) and Charpy-impact tests were performed on the reference and PA 66 interleaved composite specimens. The DCB test results showed that the initiation and propagation Mode-I fracture toughness values of the composites were significantly improved by 84 and 171% using PA 66-17 gsm veils respectively, as compared to reference laminates. The use of denser PA 66-50 gsm veils in the interlaminar region led to higher improvement in fracture toughness values (349% for initiation and 718% for propagation) due to the higher amount of veil fibers involved in fiber bridging toughening mechanism. The incorporation of PA 66-50 gsm nonwoven veils also increased the ILSS and Charpy impact strength of the composites by 25 and 15%, respectively. On the other hand, the PA 66 veils reduced in-plane mechanical properties of CF/EP composites due to lower carbon fiber volume fraction and increased thickness. © 2018}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, carbon fiber/epoxy (CF/EP) composites were interleaved with polyamide-6,6 (PA 66) nonwoven veils at two different areal weight densities (17 and 50 gsm) to improve their delamination resistance against Mode-I loading. Mode-I fracture toughness (DCB), tensile, open hole tensile (OHT), flexural, compression, short beam shear (ILSS) and Charpy-impact tests were performed on the reference and PA 66 interleaved composite specimens. The DCB test results showed that the initiation and propagation Mode-I fracture toughness values of the composites were significantly improved by 84 and 171% using PA 66-17 gsm veils respectively, as compared to reference laminates. The use of denser PA 66-50 gsm veils in the interlaminar region led to higher improvement in fracture toughness values (349% for initiation and 718% for propagation) due to the higher amount of veil fibers involved in fiber bridging toughening mechanism. The incorporation of PA 66-50 gsm nonwoven veils also increased the ILSS and Charpy impact strength of the composites by 25 and 15%, respectively. On the other hand, the PA 66 veils reduced in-plane mechanical properties of CF/EP composites due to lower carbon fiber volume fraction and increased thickness. © 2018 |
Kandemir, S Development of Graphene Nanoplatelet-Reinforced AZ91 Magnesium Alloy by Solidification Processing Journal Article Journal of Materials Engineering and Performance, 27 (6), pp. 3014-3023, 2018. @article{Kandemir20183014, title = {Development of Graphene Nanoplatelet-Reinforced AZ91 Magnesium Alloy by Solidification Processing}, author = {S Kandemir}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85046038152&doi=10.1007%2fs11665-018-3391-x&partnerID=40&md5=1915050ebdd364d0e0e99a6144a89c16}, doi = {10.1007/s11665-018-3391-x}, year = {2018}, date = {2018-01-01}, journal = {Journal of Materials Engineering and Performance}, volume = {27}, number = {6}, pages = {3014-3023}, abstract = {It is a challenging task to effectively incorporate graphene nanoplatelets (GNPs) which have recently emerged as potential reinforcement for strengthening metals into magnesium-based matrices by conventional solidification processes due to their large surface areas and poor wettability. A solidification processing which combines mechanical stirring and ultrasonic dispersion of reinforcements in liquid matrix was employed to develop AZ91 magnesium alloy matrix composites reinforced with 0.25 and 0.5 wt.% GNPs. The microstructural studies conducted with scanning and transmission electron microscopes revealed that fairly uniform distribution and dispersion of GNPs through the matrix were achieved due to effective combination of mechanical and ultrasonic stirring. The GNPs embedded into the magnesium matrix led to significant enhancement in the hardness, tensile strength and ductility of the composites compared to those of unreinforced AZ91 alloy. The strength enhancement was predominantly attributed to the grain refinement by the GNP addition and dislocation generation strengthening due to the coefficient of thermal expansion mismatch between the matrix and reinforcement. The improved ductility was attributed to the refinement of β eutectics by transforming from lamellar to the divorced eutectics due to the GNP additions. In addition, the strengthening efficiency of the composite with 0.25 wt.% GNP was found to be higher than those of the composite with 0.5 wt.% GNP as the agglomeration tendency of GNPs is increased with increasing GNP content. These results were compared with those of the GNP-reinforced magnesium composites reported in the literature, indicating the potential of the process introduced in this study in terms of fabricating light and high-performance metal matrix composites. © 2018, ASM International.}, keywords = {}, pubstate = {published}, tppubtype = {article} } It is a challenging task to effectively incorporate graphene nanoplatelets (GNPs) which have recently emerged as potential reinforcement for strengthening metals into magnesium-based matrices by conventional solidification processes due to their large surface areas and poor wettability. A solidification processing which combines mechanical stirring and ultrasonic dispersion of reinforcements in liquid matrix was employed to develop AZ91 magnesium alloy matrix composites reinforced with 0.25 and 0.5 wt.% GNPs. The microstructural studies conducted with scanning and transmission electron microscopes revealed that fairly uniform distribution and dispersion of GNPs through the matrix were achieved due to effective combination of mechanical and ultrasonic stirring. The GNPs embedded into the magnesium matrix led to significant enhancement in the hardness, tensile strength and ductility of the composites compared to those of unreinforced AZ91 alloy. The strength enhancement was predominantly attributed to the grain refinement by the GNP addition and dislocation generation strengthening due to the coefficient of thermal expansion mismatch between the matrix and reinforcement. The improved ductility was attributed to the refinement of β eutectics by transforming from lamellar to the divorced eutectics due to the GNP additions. In addition, the strengthening efficiency of the composite with 0.25 wt.% GNP was found to be higher than those of the composite with 0.5 wt.% GNP as the agglomeration tendency of GNPs is increased with increasing GNP content. These results were compared with those of the GNP-reinforced magnesium composites reported in the literature, indicating the potential of the process introduced in this study in terms of fabricating light and high-performance metal matrix composites. © 2018, ASM International. |
Kandemir, S Development of Graphene Nanoplatelet-Reinforced AZ91 Magnesium Alloy by Solidification Processing Journal Article Journal of Materials Engineering and Performance, 27 (6), pp. 3014-3023, 2018. @article{Kandemir20183014b, title = {Development of Graphene Nanoplatelet-Reinforced AZ91 Magnesium Alloy by Solidification Processing}, author = {S Kandemir}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85046038152&doi=10.1007%2fs11665-018-3391-x&partnerID=40&md5=1915050ebdd364d0e0e99a6144a89c16}, doi = {10.1007/s11665-018-3391-x}, year = {2018}, date = {2018-01-01}, journal = {Journal of Materials Engineering and Performance}, volume = {27}, number = {6}, pages = {3014-3023}, abstract = {It is a challenging task to effectively incorporate graphene nanoplatelets (GNPs) which have recently emerged as potential reinforcement for strengthening metals into magnesium-based matrices by conventional solidification processes due to their large surface areas and poor wettability. A solidification processing which combines mechanical stirring and ultrasonic dispersion of reinforcements in liquid matrix was employed to develop AZ91 magnesium alloy matrix composites reinforced with 0.25 and 0.5 wt.% GNPs. The microstructural studies conducted with scanning and transmission electron microscopes revealed that fairly uniform distribution and dispersion of GNPs through the matrix were achieved due to effective combination of mechanical and ultrasonic stirring. The GNPs embedded into the magnesium matrix led to significant enhancement in the hardness, tensile strength and ductility of the composites compared to those of unreinforced AZ91 alloy. The strength enhancement was predominantly attributed to the grain refinement by the GNP addition and dislocation generation strengthening due to the coefficient of thermal expansion mismatch between the matrix and reinforcement. The improved ductility was attributed to the refinement of β eutectics by transforming from lamellar to the divorced eutectics due to the GNP additions. In addition, the strengthening efficiency of the composite with 0.25 wt.% GNP was found to be higher than those of the composite with 0.5 wt.% GNP as the agglomeration tendency of GNPs is increased with increasing GNP content. These results were compared with those of the GNP-reinforced magnesium composites reported in the literature, indicating the potential of the process introduced in this study in terms of fabricating light and high-performance metal matrix composites. © 2018, ASM International.}, keywords = {}, pubstate = {published}, tppubtype = {article} } It is a challenging task to effectively incorporate graphene nanoplatelets (GNPs) which have recently emerged as potential reinforcement for strengthening metals into magnesium-based matrices by conventional solidification processes due to their large surface areas and poor wettability. A solidification processing which combines mechanical stirring and ultrasonic dispersion of reinforcements in liquid matrix was employed to develop AZ91 magnesium alloy matrix composites reinforced with 0.25 and 0.5 wt.% GNPs. The microstructural studies conducted with scanning and transmission electron microscopes revealed that fairly uniform distribution and dispersion of GNPs through the matrix were achieved due to effective combination of mechanical and ultrasonic stirring. The GNPs embedded into the magnesium matrix led to significant enhancement in the hardness, tensile strength and ductility of the composites compared to those of unreinforced AZ91 alloy. The strength enhancement was predominantly attributed to the grain refinement by the GNP addition and dislocation generation strengthening due to the coefficient of thermal expansion mismatch between the matrix and reinforcement. The improved ductility was attributed to the refinement of β eutectics by transforming from lamellar to the divorced eutectics due to the GNP additions. In addition, the strengthening efficiency of the composite with 0.25 wt.% GNP was found to be higher than those of the composite with 0.5 wt.% GNP as the agglomeration tendency of GNPs is increased with increasing GNP content. These results were compared with those of the GNP-reinforced magnesium composites reported in the literature, indicating the potential of the process introduced in this study in terms of fabricating light and high-performance metal matrix composites. © 2018, ASM International. |
2017 |
Ma, Luoning; Xie, Kelvin Y; Toksoy, Muhammet F; Kuwelkar, Kanak; Haber, Richard A; Hemker, Kevin J The effect of Si on the microstructure and mechanical properties of spark plasma sintered boron carbide Journal Article MATERIALS CHARACTERIZATION, 134 , pp. 274-278, 2017, ISSN: 1044-5803. @article{ISI:000419416400031, title = {The effect of Si on the microstructure and mechanical properties of spark plasma sintered boron carbide}, author = {Luoning Ma and Kelvin Y Xie and Muhammet F Toksoy and Kanak Kuwelkar and Richard A Haber and Kevin J Hemker}, doi = {10.1016/j.matchar.2017.11.010}, issn = {1044-5803}, year = {2017}, date = {2017-12-01}, journal = {MATERIALS CHARACTERIZATION}, volume = {134}, pages = {274-278}, abstract = {Fully dense boron carbide discs were achieved by spark plasma sintering boron carbide powders with 10 wt% silicon. The silicon did not diffuse into boron carbide grains to produce a solid solution of Si-doped boron carbide; instead the silicon reacted with impurities in the starting powder to form beta-SiC and borosilicate glass. The resultant new phases facilitated densification of the multiphase ceramic through liquid phase-assisted sintering. The resultant material exhibits improved hardness (34.3 GPa Vikers hardness under 1 kg load) with toughness comparable to both Si-free and commercially available boron carbide.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Fully dense boron carbide discs were achieved by spark plasma sintering boron carbide powders with 10 wt% silicon. The silicon did not diffuse into boron carbide grains to produce a solid solution of Si-doped boron carbide; instead the silicon reacted with impurities in the starting powder to form beta-SiC and borosilicate glass. The resultant new phases facilitated densification of the multiphase ceramic through liquid phase-assisted sintering. The resultant material exhibits improved hardness (34.3 GPa Vikers hardness under 1 kg load) with toughness comparable to both Si-free and commercially available boron carbide. |
Kandemir, Sinan Effects of TiB2 nanoparticle content on the microstructure and mechanical properties of aluminum matrix nanocomposites Journal Article MATERIALS TESTING, 59 (10), pp. 844-852, 2017, ISSN: 0025-5300. @article{ISI:000415695400003, title = {Effects of TiB2 nanoparticle content on the microstructure and mechanical properties of aluminum matrix nanocomposites}, author = {Sinan Kandemir}, doi = {10.3139/120.111079}, issn = {0025-5300}, year = {2017}, date = {2017-10-01}, journal = {MATERIALS TESTING}, volume = {59}, number = {10}, pages = {844-852}, abstract = {The present work reports the fabrication of A357 alloy matrix nanocomposites reinforced with 0.5, 1.0 and 2.0 wt.-% TiB2 nanoparticles (20-30 nm) by a novel method which is the combination of semi-solid mechanical mixing and ultrasonic dispersion of nanoparticles in liquid state. The microstructural and mechanical properties of the fabricated nanocomposites were investigated. The microstructural studies conducted with optical and advanced electron microscopes indicated that reasonably effective deagglomeration and uniform distribution of TiB2 nanoparticles into the matrix were achieved. Transmission electron microscopy studies also confirmed that the nanoparticles were embedded into the matrix and a good bonding was obtained between the matrix and the reinforcement. Increasing nanoparticle content led to grain refinement and significant enhancement in the mechanical properties of nanocomposites. The addition of 0.5, 1.0, and 2.0 wt.-% TiB2 nanoparticles increased the 0.2 % proof stress of matrix alloy by approximately 31, 48 and 61 %, respectively. The contribution of different mechanisms to the strength enhancement is discussed. It is proposed that the strengthening is mainly due to Orowan mechanism and dislocation generation effect by the coefficient of thermal expansion mismatch between the TiB2 nanoparticles and the matrix.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The present work reports the fabrication of A357 alloy matrix nanocomposites reinforced with 0.5, 1.0 and 2.0 wt.-% TiB2 nanoparticles (20-30 nm) by a novel method which is the combination of semi-solid mechanical mixing and ultrasonic dispersion of nanoparticles in liquid state. The microstructural and mechanical properties of the fabricated nanocomposites were investigated. The microstructural studies conducted with optical and advanced electron microscopes indicated that reasonably effective deagglomeration and uniform distribution of TiB2 nanoparticles into the matrix were achieved. Transmission electron microscopy studies also confirmed that the nanoparticles were embedded into the matrix and a good bonding was obtained between the matrix and the reinforcement. Increasing nanoparticle content led to grain refinement and significant enhancement in the mechanical properties of nanocomposites. The addition of 0.5, 1.0, and 2.0 wt.-% TiB2 nanoparticles increased the 0.2 % proof stress of matrix alloy by approximately 31, 48 and 61 %, respectively. The contribution of different mechanisms to the strength enhancement is discussed. It is proposed that the strengthening is mainly due to Orowan mechanism and dislocation generation effect by the coefficient of thermal expansion mismatch between the TiB2 nanoparticles and the matrix. |
Beylergil, Bertan; Tanoglu, Metin; Aktas, Engin Enhancement of interlaminar fracture toughness of carbon fiber-epoxy composites using polyamide-6,6 electrospun nanofibers Journal Article JOURNAL OF APPLIED POLYMER SCIENCE, 134 (35), 2017, ISSN: 0021-8995. @article{ISI:000403346000012, title = {Enhancement of interlaminar fracture toughness of carbon fiber-epoxy composites using polyamide-6,6 electrospun nanofibers}, author = {Bertan Beylergil and Metin Tanoglu and Engin Aktas}, doi = {10.1002/app.45244}, issn = {0021-8995}, year = {2017}, date = {2017-09-01}, journal = {JOURNAL OF APPLIED POLYMER SCIENCE}, volume = {134}, number = {35}, abstract = {In this study, carbon fiber-epoxy composites are interleaved with electrospun polyamide-6,6 (PA 66) nanofibers to improve their Mode-I fracture toughness. These nanofibers are directly deposited onto carbon fabrics before composite manufacturing via vacuum infusion. Three-point bending, tensile, compression, interlaminar shear strength, Charpy impact, and double cantilever beam tests are performed on the reference and PA 66 interleaved specimens to evaluate the effects of PA 66 nanofibers on the mechanical properties of composites. To investigate the effect of nanofiber areal weight density (AWD), nanointerlayers with various AWD are prepared by changing the electrospinning duration. It is found that the electrospun PA 66 nanofibers are very effective in improving Mode-I toughness and impact resistance, compressive strength, flexural modulus, and strength of the composites. However, these nanofibers cause a decrease in the tensile strength of the composites. The glass-transition temperature of the composites is not affected by the addition of PA 66 nanofibers. (c) 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45244.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, carbon fiber-epoxy composites are interleaved with electrospun polyamide-6,6 (PA 66) nanofibers to improve their Mode-I fracture toughness. These nanofibers are directly deposited onto carbon fabrics before composite manufacturing via vacuum infusion. Three-point bending, tensile, compression, interlaminar shear strength, Charpy impact, and double cantilever beam tests are performed on the reference and PA 66 interleaved specimens to evaluate the effects of PA 66 nanofibers on the mechanical properties of composites. To investigate the effect of nanofiber areal weight density (AWD), nanointerlayers with various AWD are prepared by changing the electrospinning duration. It is found that the electrospun PA 66 nanofibers are very effective in improving Mode-I toughness and impact resistance, compressive strength, flexural modulus, and strength of the composites. However, these nanofibers cause a decrease in the tensile strength of the composites. The glass-transition temperature of the composites is not affected by the addition of PA 66 nanofibers. (c) 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45244. |
Toksoy, Muhammet Fatih; Rafaniello, William; Xie, Kelvin Yu; Ma, Luoning; Hemker, Kevin Jude; Haber, Richard Alan Densification and characterization of rapid carbothermal synthesized boron carbide Journal Article INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, 14 (3), pp. 443-453, 2017, ISSN: 1546-542X. @article{ISI:000404259000018, title = {Densification and characterization of rapid carbothermal synthesized boron carbide}, author = {Muhammet Fatih Toksoy and William Rafaniello and Kelvin Yu Xie and Luoning Ma and Kevin Jude Hemker and Richard Alan Haber}, doi = {10.1111/ijac.12654}, issn = {1546-542X}, year = {2017}, date = {2017-05-01}, journal = {INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY}, volume = {14}, number = {3}, pages = {443-453}, abstract = {Submicrometer boron carbide powders were synthesized using rapid carbothermal reduction (RCR) method. Synthesized boron carbide powders had smaller particle size, lower free carbon, and high density of twins compared to commercial samples. Powders were sintered using spark plasma sintering at different temperatures and dwell times to compare sintering behavior. Synthesized boron carbide powders reached >99% TD at lower temperature and shorter dwell times compared to commercial powders. Improved microhardness observed in the densified RCR samples was likely caused by the combination of higher purity, better stoichiometry control, finer grain size, and a higher density of twin boundaries.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Submicrometer boron carbide powders were synthesized using rapid carbothermal reduction (RCR) method. Synthesized boron carbide powders had smaller particle size, lower free carbon, and high density of twins compared to commercial samples. Powders were sintered using spark plasma sintering at different temperatures and dwell times to compare sintering behavior. Synthesized boron carbide powders reached >99% TD at lower temperature and shorter dwell times compared to commercial powders. Improved microhardness observed in the densified RCR samples was likely caused by the combination of higher purity, better stoichiometry control, finer grain size, and a higher density of twin boundaries. |
Odac, Ismet Kutlay; Guden, Mustafa; Klcaslan, Cenk; Tasdemirci, Alper The varying densification strain in a multi-layer aluminum corrugate structure: Direct impact testing and layer-wise numerical modelling Journal Article INTERNATIONAL JOURNAL OF IMPACT ENGINEERING, 103 , pp. 64-75, 2017, ISSN: 0734-743X. @article{ISI:000395844400006, title = {The varying densification strain in a multi-layer aluminum corrugate structure: Direct impact testing and layer-wise numerical modelling}, author = {Ismet Kutlay Odac and Mustafa Guden and Cenk Klcaslan and Alper Tasdemirci}, doi = {10.1016/j.ijimpeng.2016.10.014}, issn = {0734-743X}, year = {2017}, date = {2017-05-01}, journal = {INTERNATIONAL JOURNAL OF IMPACT ENGINEERING}, volume = {103}, pages = {64-75}, abstract = {An aluminum (1050 H14) multi-layer corrugated structure composed of brazed 16 trapezoidal zig-zig fin layers was direct impact tested above the critical velocities for shock formation using a modified Split Hopkinson Pressure Bar. The experimentally measured stress-time histories of the cylindrical test samples in the direct impact tests were verified with the simulations implemented in the explicit finite element code of LS-DYNA. The quasi-static experimental and simulation deformation of the corrugated samples proceeded with the discrete, non-contiguous bands of crushed fin layers, while the dynamic crushing started from the proximal impact end and proceeded with a sequential and in-planar manner, showing shock type deformation characteristic. The experimental and numerical crushing stresses and the numerically determined densification strains of the fin layers increased with increasing impact velocity above the critical velocities. When the numerically determined densification strain at a specific velocity above the critical velocities was incorporated, the rigid-perfectly-plastic-locking idealized model resulted in peak stresses similar to the experimental and simulation mean crushing stresses. However, the model underestimated the experimental and simulation peak stresses below 200 m s(-1). It was proposed, while the micro inertial effects were responsible for the increase of the crushing stresses at and below subcritical velocities, the shock deformation became dominant above the critical velocities. (C) 2016 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } An aluminum (1050 H14) multi-layer corrugated structure composed of brazed 16 trapezoidal zig-zig fin layers was direct impact tested above the critical velocities for shock formation using a modified Split Hopkinson Pressure Bar. The experimentally measured stress-time histories of the cylindrical test samples in the direct impact tests were verified with the simulations implemented in the explicit finite element code of LS-DYNA. The quasi-static experimental and simulation deformation of the corrugated samples proceeded with the discrete, non-contiguous bands of crushed fin layers, while the dynamic crushing started from the proximal impact end and proceeded with a sequential and in-planar manner, showing shock type deformation characteristic. The experimental and numerical crushing stresses and the numerically determined densification strains of the fin layers increased with increasing impact velocity above the critical velocities. When the numerically determined densification strain at a specific velocity above the critical velocities was incorporated, the rigid-perfectly-plastic-locking idealized model resulted in peak stresses similar to the experimental and simulation mean crushing stresses. However, the model underestimated the experimental and simulation peak stresses below 200 m s(-1). It was proposed, while the micro inertial effects were responsible for the increase of the crushing stresses at and below subcritical velocities, the shock deformation became dominant above the critical velocities. (C) 2016 Elsevier Ltd. All rights reserved. |
Zeren, Dogus; Guden, Mustafa The increased compression strength of an epoxy resin with the addition of heat-treated natural nano-structured diatom frustules Journal Article JOURNAL OF COMPOSITE MATERIALS, 51 (12), pp. 1681-1691, 2017, ISSN: 0021-9983. @article{ISI:000401035100002, title = {The increased compression strength of an epoxy resin with the addition of heat-treated natural nano-structured diatom frustules}, author = {Dogus Zeren and Mustafa Guden}, doi = {10.1177/0021998316669855}, issn = {0021-9983}, year = {2017}, date = {2017-05-01}, journal = {JOURNAL OF COMPOSITE MATERIALS}, volume = {51}, number = {12}, pages = {1681-1691}, abstract = {Natural diatom frustules composing nanometer size silica particles were heat-treated at temperatures between 600 and 1200 degrees C for 2h and used as filler/reinforcing agent (15wt%) in an epoxy resin. The opal structure of as-received natural diatom frustules was transformed into cristobalite after the heat-treatment above 900 degrees C The epoxy resin test samples reinforced with heat-treated and as-received frustules and neat epoxy test samples were compression tested at the quasi-static strain rate of 7x10(-3)s(-1). The results showed that the inclusion of the frustules heat-treated at 1000 degrees C increased the compressive yield strength of the resin by 50%, while the addition of the diatom frustules heat-treated above and below 1000 degrees C and the as-received frustules increased the strength by similar to 25% and 16%, respectively. The heat treatment above 1000 degrees C decreased the surface area of the frustules from 8.23m(2)g(-1) to 3.46m(2)g(-1). The cristobalite grains of the frustules heat-treated at 1000 degrees C was smaller than 100nm, while the grain size increased to similar to 500nm at 1200 degrees C. The increased compressive stresses of the resin at the specific heat treatment temperature (1000 degrees C) were ascribed to nano size crystalline cristobalite grains. The relatively lower compressive stresses of the epoxy resin filled with frustules heat-treated above 1000 degrees C were attributed to the micro-cracking of the frustules that might be resulted from higher density of the cristobalite than that of the opal and accompanying reduction of the surface area and the surface pore sizes that might impair the resin-frustule interlocking and intrusion.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Natural diatom frustules composing nanometer size silica particles were heat-treated at temperatures between 600 and 1200 degrees C for 2h and used as filler/reinforcing agent (15wt%) in an epoxy resin. The opal structure of as-received natural diatom frustules was transformed into cristobalite after the heat-treatment above 900 degrees C The epoxy resin test samples reinforced with heat-treated and as-received frustules and neat epoxy test samples were compression tested at the quasi-static strain rate of 7x10(-3)s(-1). The results showed that the inclusion of the frustules heat-treated at 1000 degrees C increased the compressive yield strength of the resin by 50%, while the addition of the diatom frustules heat-treated above and below 1000 degrees C and the as-received frustules increased the strength by similar to 25% and 16%, respectively. The heat treatment above 1000 degrees C decreased the surface area of the frustules from 8.23m(2)g(-1) to 3.46m(2)g(-1). The cristobalite grains of the frustules heat-treated at 1000 degrees C was smaller than 100nm, while the grain size increased to similar to 500nm at 1200 degrees C. The increased compressive stresses of the resin at the specific heat treatment temperature (1000 degrees C) were ascribed to nano size crystalline cristobalite grains. The relatively lower compressive stresses of the epoxy resin filled with frustules heat-treated above 1000 degrees C were attributed to the micro-cracking of the frustules that might be resulted from higher density of the cristobalite than that of the opal and accompanying reduction of the surface area and the surface pore sizes that might impair the resin-frustule interlocking and intrusion. |
Kandemir, Sinan JOURNAL OF COMPOSITE MATERIALS, 51 (3), pp. 395-404, 2017, ISSN: 0021-9983. @article{ISI:000394801300009, title = {Microstructure and mechanical properties of A357/SiC nanocomposites fabricated by ultrasonic cavitation-based dispersion of ball-milled nanoparticles}, author = {Sinan Kandemir}, doi = {10.1177/0021998316644850}, issn = {0021-9983}, year = {2017}, date = {2017-02-01}, journal = {JOURNAL OF COMPOSITE MATERIALS}, volume = {51}, number = {3}, pages = {395-404}, abstract = {In this work, A357/0.5wt.% SiC nanocomposites were fabricated with a combination of ultrasonic processing and a nanoparticle feeding mechanism that involves the introduction of a closed end aluminium tube filled with the ball-milled SiC nanoparticles (20-30nm) and aluminium powders (<75 mu m) into the melt for complete deagglomeration and uniform dispersion of nanoparticles through the matrix. The microstructural and mechanical properties of the fabricated nanocomposites were investigated. The microstructural studies conducted with optical and advanced electron microscopes indicate that relatively effective deagglomeration and uniform dispersion of SiC nanoparticles into the molten alloy were achieved. The hardness and tensile properties of the nanocomposites were notably improved compared to those of the ultrasonically processed A357 alloy without reinforcement, showing the strengthening potency of nanoparticles and the good bonding obtained at the particle-reinforcement interface.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this work, A357/0.5wt.% SiC nanocomposites were fabricated with a combination of ultrasonic processing and a nanoparticle feeding mechanism that involves the introduction of a closed end aluminium tube filled with the ball-milled SiC nanoparticles (20-30nm) and aluminium powders (<75 mu m) into the melt for complete deagglomeration and uniform dispersion of nanoparticles through the matrix. The microstructural and mechanical properties of the fabricated nanocomposites were investigated. The microstructural studies conducted with optical and advanced electron microscopes indicate that relatively effective deagglomeration and uniform dispersion of SiC nanoparticles into the molten alloy were achieved. The hardness and tensile properties of the nanocomposites were notably improved compared to those of the ultrasonically processed A357 alloy without reinforcement, showing the strengthening potency of nanoparticles and the good bonding obtained at the particle-reinforcement interface. |
Beylergil, B; Tanoğlu, M; Aktaş, E Enhancement of interlaminar fracture toughness of carbon fiber–epoxy composites using polyamide-6,6 electrospun nanofibers Journal Article Journal of Applied Polymer Science, 134 (35), 2017. @article{Beylergil2017, title = {Enhancement of interlaminar fracture toughness of carbon fiber–epoxy composites using polyamide-6,6 electrospun nanofibers}, author = {B Beylergil and M Tanoğlu and E Aktaş}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85019089440&doi=10.1002%2fapp.45244&partnerID=40&md5=ef8bdba44c46b9b1bc9aaedfbbbde061}, doi = {10.1002/app.45244}, year = {2017}, date = {2017-01-01}, journal = {Journal of Applied Polymer Science}, volume = {134}, number = {35}, abstract = {In this study, carbon fiber–epoxy composites are interleaved with electrospun polyamide-6,6 (PA 66) nanofibers to improve their Mode-I fracture toughness. These nanofibers are directly deposited onto carbon fabrics before composite manufacturing via vacuum infusion. Three-point bending, tensile, compression, interlaminar shear strength, Charpy impact, and double cantilever beam tests are performed on the reference and PA 66 interleaved specimens to evaluate the effects of PA 66 nanofibers on the mechanical properties of composites. To investigate the effect of nanofiber areal weight density (AWD), nanointerlayers with various AWD are prepared by changing the electrospinning duration. It is found that the electrospun PA 66 nanofibers are very effective in improving Mode-I toughness and impact resistance, compressive strength, flexural modulus, and strength of the composites. However, these nanofibers cause a decrease in the tensile strength of the composites. The glass-transition temperature of the composites is not affected by the addition of PA 66 nanofibers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45244. © 2017 Wiley Periodicals, Inc.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, carbon fiber–epoxy composites are interleaved with electrospun polyamide-6,6 (PA 66) nanofibers to improve their Mode-I fracture toughness. These nanofibers are directly deposited onto carbon fabrics before composite manufacturing via vacuum infusion. Three-point bending, tensile, compression, interlaminar shear strength, Charpy impact, and double cantilever beam tests are performed on the reference and PA 66 interleaved specimens to evaluate the effects of PA 66 nanofibers on the mechanical properties of composites. To investigate the effect of nanofiber areal weight density (AWD), nanointerlayers with various AWD are prepared by changing the electrospinning duration. It is found that the electrospun PA 66 nanofibers are very effective in improving Mode-I toughness and impact resistance, compressive strength, flexural modulus, and strength of the composites. However, these nanofibers cause a decrease in the tensile strength of the composites. The glass-transition temperature of the composites is not affected by the addition of PA 66 nanofibers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45244. © 2017 Wiley Periodicals, Inc. |
Kandemir, S Journal of Composite Materials, 51 (3), pp. 395-404, 2017. @article{Kandemir2017395, title = {Microstructure and mechanical properties of A357/SiC nanocomposites fabricated by ultrasonic cavitation-based dispersion of ball-milled nanoparticles}, author = {S Kandemir}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85011573357&doi=10.1177%2f0021998316644850&partnerID=40&md5=1c26ba4dde5d58581fb0feb8fa56d880}, doi = {10.1177/0021998316644850}, year = {2017}, date = {2017-01-01}, journal = {Journal of Composite Materials}, volume = {51}, number = {3}, pages = {395-404}, abstract = {In this work, A357/0.5 wt.% SiC nanocomposites were fabricated with a combination of ultrasonic processing and a nanoparticle feeding mechanism that involves the introduction of a closed end aluminium tube filled with the ball-milled SiC nanoparticles (20-30 nm) and aluminium powders (<75 μm) into the melt for complete deagglomeration and uniform dispersion of nanoparticles through the matrix. The microstructural and mechanical properties of the fabricated nanocomposites were investigated. The microstructural studies conducted with optical and advanced electron microscopes indicate that relatively effective deagglomeration and uniform dispersion of SiC nanoparticles into the molten alloy were achieved. The hardness and tensile properties of the nanocomposites were notably improved compared to those of the ultrasonically processed A357 alloy without reinforcement, showing the strengthening potency of nanoparticles and the good bonding obtained at the particle-reinforcement interface. © The Author(s) 2016.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this work, A357/0.5 wt.% SiC nanocomposites were fabricated with a combination of ultrasonic processing and a nanoparticle feeding mechanism that involves the introduction of a closed end aluminium tube filled with the ball-milled SiC nanoparticles (20-30 nm) and aluminium powders (<75 μm) into the melt for complete deagglomeration and uniform dispersion of nanoparticles through the matrix. The microstructural and mechanical properties of the fabricated nanocomposites were investigated. The microstructural studies conducted with optical and advanced electron microscopes indicate that relatively effective deagglomeration and uniform dispersion of SiC nanoparticles into the molten alloy were achieved. The hardness and tensile properties of the nanocomposites were notably improved compared to those of the ultrasonically processed A357 alloy without reinforcement, showing the strengthening potency of nanoparticles and the good bonding obtained at the particle-reinforcement interface. © The Author(s) 2016. |
Kandemir, S Journal of Composite Materials, 51 (3), pp. 395-404, 2017. @article{Kandemir2017395b, title = {Microstructure and mechanical properties of A357/SiC nanocomposites fabricated by ultrasonic cavitation-based dispersion of ball-milled nanoparticles}, author = {S Kandemir}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85011573357&doi=10.1177%2f0021998316644850&partnerID=40&md5=1c26ba4dde5d58581fb0feb8fa56d880}, doi = {10.1177/0021998316644850}, year = {2017}, date = {2017-01-01}, journal = {Journal of Composite Materials}, volume = {51}, number = {3}, pages = {395-404}, abstract = {In this work, A357/0.5 wt.% SiC nanocomposites were fabricated with a combination of ultrasonic processing and a nanoparticle feeding mechanism that involves the introduction of a closed end aluminium tube filled with the ball-milled SiC nanoparticles (20-30 nm) and aluminium powders (<75 μm) into the melt for complete deagglomeration and uniform dispersion of nanoparticles through the matrix. The microstructural and mechanical properties of the fabricated nanocomposites were investigated. The microstructural studies conducted with optical and advanced electron microscopes indicate that relatively effective deagglomeration and uniform dispersion of SiC nanoparticles into the molten alloy were achieved. The hardness and tensile properties of the nanocomposites were notably improved compared to those of the ultrasonically processed A357 alloy without reinforcement, showing the strengthening potency of nanoparticles and the good bonding obtained at the particle-reinforcement interface. © The Author(s) 2016.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this work, A357/0.5 wt.% SiC nanocomposites were fabricated with a combination of ultrasonic processing and a nanoparticle feeding mechanism that involves the introduction of a closed end aluminium tube filled with the ball-milled SiC nanoparticles (20-30 nm) and aluminium powders (<75 μm) into the melt for complete deagglomeration and uniform dispersion of nanoparticles through the matrix. The microstructural and mechanical properties of the fabricated nanocomposites were investigated. The microstructural studies conducted with optical and advanced electron microscopes indicate that relatively effective deagglomeration and uniform dispersion of SiC nanoparticles into the molten alloy were achieved. The hardness and tensile properties of the nanocomposites were notably improved compared to those of the ultrasonically processed A357 alloy without reinforcement, showing the strengthening potency of nanoparticles and the good bonding obtained at the particle-reinforcement interface. © The Author(s) 2016. |
2016 |
An, Qi; III, William Goddard A; Xie, Kelvin Y; Sim, Gi-dong; Hemker, Kevin J; Munhollon, Tyler; Toksoy, Fatih M; Haber, Richard A Superstrength through Nanotwinning Journal Article NANO LETTERS, 16 (12), pp. 7573-7579, 2016, ISSN: 1530-6984. @article{ISI:000389963200038, title = {Superstrength through Nanotwinning}, author = {Qi An and William A Goddard III and Kelvin Y Xie and Gi-dong Sim and Kevin J Hemker and Tyler Munhollon and Fatih M Toksoy and Richard A Haber}, doi = {10.1021/acs.nanolett.6b03414}, issn = {1530-6984}, year = {2016}, date = {2016-12-01}, journal = {NANO LETTERS}, volume = {16}, number = {12}, pages = {7573-7579}, abstract = {The theoretical strength of a material is the minimum stress to deform or fracture the perfect single crystal material that has no defects. This theoretical strength is considered as an upper bound on the attainable strength for a real crystal. In contradiction to this expectation, we use quantum mechanics (QM) simulations to show that for the boron carbide (B4C) hard ceramic, this theoretical shear strength can be exceeded by 11% by imposing nanoscale twins. We also predict from QM that the indentation strength of nanotwinned B4C is 12% higher than that of the perfect crystal. Further, we validate this effect experimentally, showing that nanotwinned samples are harder by 2.3% than the twin-free counterpart of B4C. The origin of this strengthening mechanism is suppression of twin boundary (TB) slip within the nanotwins due to the directional nature of covalent bonds at the TB.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The theoretical strength of a material is the minimum stress to deform or fracture the perfect single crystal material that has no defects. This theoretical strength is considered as an upper bound on the attainable strength for a real crystal. In contradiction to this expectation, we use quantum mechanics (QM) simulations to show that for the boron carbide (B4C) hard ceramic, this theoretical shear strength can be exceeded by 11% by imposing nanoscale twins. We also predict from QM that the indentation strength of nanotwinned B4C is 12% higher than that of the perfect crystal. Further, we validate this effect experimentally, showing that nanotwinned samples are harder by 2.3% than the twin-free counterpart of B4C. The origin of this strengthening mechanism is suppression of twin boundary (TB) slip within the nanotwins due to the directional nature of covalent bonds at the TB. |
Project Title | Director of the Project | Start Date | Funds |
| Karbon Nanotüp (CNT) / Poliester Nanokompozitlerin Geliştirilmesi | Prof. Dr. Metin Tanoğlu | 2004 | JÜLICH, Almanya - TÜBİTAK |
| Tenzorezistörlerin Düşük Termohassasiyet Termal Katsayısı İle Geliştirilmesi | Prof. Dr. Metin Tanoğlu | 2002 | NATO |
| Havacılık uygulamaları için yapısal kompozit parçaların yenilikçi yaklaşımlar ile birleştirilme yöntemlerinin geliştirilmesi, çevresel etkilere dayanım ve mekanik performansının karakterize edilmesi | Prof. Dr. Metin Tanoğlu | 2019 | TÜBİTAK |
| Alüminyum Köpük Metal Dolu Alüminyum ve Kompozit Tüplerin Ezilme Davranışları | Prof. Dr. Mustafa Güden | 2004 | TÜBİTAK |
| Çapraz-kama haddeleme prosesinin teknik özelliklerinin Türk ve Belarus Endüstrileri için detaylandırılması | Prof. Dr. Mustafa Güden | 2010 | TÜBİTAK |
| Çok Katmanlı Malzemelerde Dalga Geçişi | Prof. Dr. Mustafa Güden | 2003 | NSF - TÜBİTAK |
| Frit Fırını Refrakterlerinin İzotermal Korozyon Testi | Prof.Dr.Sedat Akkurt | 2005 | TÜBİTAK |
| Grafen Nanolevha Takviyeli Metal Matrisli Nanokompozitlerin Geliştirilmesi | Yrd. Doç. Dr. Sinan Kandemir | 2015 | TÜBİTAK |
| Kil /EPDM Esaslı Nanokompozitlerin Geliştirilmesi | Prof. Dr. Metin Tanoğlu | 2006 | ARÇELİK A.Ş. - TÜBİTAK |
| Kompozit Malzemelerin Örgüsüz Cam / Termoplastik Hibrid Elyaflardan Geliştirilmesi | Prof. Dr. Metin Tanoğlu | 2010 | TÜBİTAK |
| Nanokompozit Malzemelerin Polimer ve Tabakalı Kil Yapılardan Geliştirilmesi ve Karakterizasyonu | Prof. Dr. Metin Tanoğlu | 2005 | TÜBİTAK |
| Patlama Etkisine Karşı Koruyucu Zırh Geliştirmesi | Prof. Dr. Metin Tanoğlu | 2008 | Milli Savunma Bakanlığı ve TÜBİTAK |
| Seramik Matriks Kompozitlerin Düşük Sıcaklıklarda Polimer Pyroliz Yöntemi İle Üretimi ve Karakterizasyonu | Prof. Dr. Metin Tanoğlu | 2002 | TÜBİTAK |
| Sic-Parçacık Takviyeli Alüminyum Köpük Metal Üretimi ve Karakterizasyonu | Prof. Dr. Mustafa Güden | 1998 | TÜBİTAK |
| Sic-Vıskırlı Aluminium Köpüklerin Hazırlanması | Prof. Dr. Mustafa Güden | 2003 | TÜBİTAK |
| Antibakteriyel Kompoze Taş Üretimi | Prof. Dr. Metin Tanoğlu | 2014 | SANTEZ |
| Gelişmiş Kemik Entegrasyonu Sağlayan Yeni Gözenekli ve Köpük Ti6Al4V Spinal Kafes İmplatların Tasarımı ve İmalatı | Prof. Dr. Mustafa Güden | 2009 | SANTEZ |
| Otomotiv Sektörüne Yönelik Kompozit Malzeme Esaslı Yaprak Yay Sistemlerinin Tasarımı ve Üretim Tekniklerinin Geliştirilmesi | Prof. Dr. Metin Tanoğlu | 2014 | SANTEZ |
| Ege Bölgesi Beylikler Dönemi Tarihi Yapılarındaki Özgün Harçların Karakterizasyonu ve Restorasyonlarda Kullanılacak Onarım Harçlarının Laboratuvarda Hazırlanması | Prof.Dr.Sedat Akkurt | 2003 | DPT |
| Fonksiyonel Dereceli Sic-Parçacık Takviyeli Alüminyum Matris Kompozit Malzemelerin Toz Metalürjisi Yöntemi İle Hazırlanması ve Statik ve Dinamik Özelliklerinin Mekanik ve Ultrasonik Yöntemlerle Ölçülmesi | Prof. Dr. Mustafa Güden | 2003 | DPT |
| Kompozit Zırh Malzemelerinin Geliştirilmesi | Prof. Dr. Metin Tanoğlu | 2003 | DPT |
| Akma ile Kalınlaşan Sıvı Zırh Sistemlerinin Geliştirilmesi | Prof. Dr. Metin Tanoğlu | 2014 | Savunma Sanayi Müsteşarlığı Projesi |
| İmplant Uygulamaları Için Ti Köpük Malzemelerin Hazırlanması | Prof. Dr. Mustafa Güden | 2003 | HİPOKRAT |
| Seramik Vitrifiye Ürünlerin Yüksek Basınçlı Dökümü Için Gözenekli Malzemelerin Geliştirilmesi ve Karakterizasyonu | Prof. Dr. Metin Tanoğlu | 2001 | EGE VİTRİFİYE A.Ş |
| Çoklu Alüminyum Kapalı Hücreli Köpük Dolu Alüminyum ve Polimerik Kompozit Tüplerin Ezilme Davranışlarının Belirlenmesi | Prof. Dr. Mustafa Güden | 2003 | İYTE-BAP |
| FP Aluminium Uzun Fiber Takviyeli Magnesium Kompozitlerin Deformasyon Hızına Bağlı Mekanik Davranışları | Prof. Dr. Mustafa Güden | 2003 | İYTE-BAP |
| Hafif, Düşük Maliyetli Polimer Esaslı Kompozit Malzemelerin Üretim Teknolojilerinin Yerleştirilmesi ve Savunma Sanayi Ne Yönelik Kompozit Zırh Malzemelerin Geliştirilmesi | Prof. Dr. Metin Tanoğlu | 2001 | İYTE-BAP |
| Jeotermal Uygulamalar İçin Polimerik Kompozit Boru Malzeme Mikroyapısısnın Malzeme Dayanım, Mekanik ve Termal Özelliklerine Etkisi | Prof. Dr. Metin Tanoğlu | 2002 | İYTE-BAP |
| Kölemanit Ilkavesiyle Kaolen Ve Kalsitten Anortit Seramikleri Sentezlenmesi ve Sinterlenmesi | Prof.Dr.Sedat Akkurt | 2004 | İYTE-BAP |
| Korozyona Uğramış Manyezit-Bazlı Çimento Fırını Refrakterlerin Mikroyapısal Karakterizasyon | Prof.Dr.Sedat Akkurt | 2001 | İYTE-BAP |
| Krom Manyezit Çimento Fırını Refrakterlerinde Bulunan Demirce Zengin Halkaların İncelenmesi | Prof.Dr.Sedat Akkurt | 2002 | İYTE-BAP |
| Nanokompozit malzemelerin geliştirilmesi ve karakterizasyonu | Prof. Dr. Metin Tanoğlu | 2003 | İYTE-BAP |
| Sinterlenmiş Yüksek Saflıktaki Alüminanın Bof Curuflarıyla Korozyonunun Laboratuvar İncelemesi | Prof.Dr.Sedat Akkurt | 2001 | İYTE-BAP |
| Spinel ve Alüminanın Düşük Sıcaklıkta Üretiminde Mekanokimyasal Sentezin Kullanılması | Prof.Dr.Sedat Akkurt | 2002 | İYTE-BAP |
| Titanyum Esaslı Açık Hücreli Köpük Metal Üretim Proses Parametrelerinin ve Mekanik Özelliklerinin Belirlenmesi | Prof. Dr. Mustafa Güden | 2004 | İYTE-BAP |
| Yüksek Balistik Dayanımlı Kompozit Hafif Zırh Malzemelerinin Geliştirilmesi | Prof. Dr. Metin Tanoğlu | 2002 | İYTE-BAP |
