Materials Technology
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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. |
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. |
Sindirac, Can; Akkurt, Sedat Formation of La1-xSrxCo1-yFeyO3-delta cathode materials from precursor salts by heating in contact with CGO electrolyte Journal Article INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, 41 (40), pp. 18157-18165, 2016, ISSN: 0360-3199. @article{ISI:000384852200041, title = {Formation of La1-xSrxCo1-yFeyO3-delta cathode materials from precursor salts by heating in contact with CGO electrolyte}, author = {Can Sindirac and Sedat Akkurt}, doi = {10.1016/j.ijhydene.2016.07.143}, issn = {0360-3199}, year = {2016}, date = {2016-10-01}, journal = {INTERNATIONAL JOURNAL OF HYDROGEN ENERGY}, volume = {41}, number = {40}, pages = {18157-18165}, abstract = {The purpose of this study is to determine the solid state reactions leading to the formation of La0.6Sr0.4Co0.8Fe0.2O3 and La0.6Sr0.4Co0.2Fe0.8O3 which are widely used as cathode material in solid oxide fuel cells (SOFC) from precursor salts. Interactions between the cathode and the electrolyte layers are also investigated while the cathode layer formed upon heating in contact with the surface of cerium -gadolinium oxide (CGO) electrolyte substrates. Almost all combinations of precursor salt mixtures were tested to see if all solid state reactions are completed and what phases eventually formed. Most of the transformation was complete after 1050 degrees C heat treatment to yield different mixed oxides. The cathode layer was usually in porous form but was found to spread well over the substrate. Uneven diffusion of La, Sr, Co or Fe into the substrate influenced the stoichiometry of the resulting cathode layer in varying degrees. Fe was found to diffuse into the substrate. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The purpose of this study is to determine the solid state reactions leading to the formation of La0.6Sr0.4Co0.8Fe0.2O3 and La0.6Sr0.4Co0.2Fe0.8O3 which are widely used as cathode material in solid oxide fuel cells (SOFC) from precursor salts. Interactions between the cathode and the electrolyte layers are also investigated while the cathode layer formed upon heating in contact with the surface of cerium -gadolinium oxide (CGO) electrolyte substrates. Almost all combinations of precursor salt mixtures were tested to see if all solid state reactions are completed and what phases eventually formed. Most of the transformation was complete after 1050 degrees C heat treatment to yield different mixed oxides. The cathode layer was usually in porous form but was found to spread well over the substrate. Uneven diffusion of La, Sr, Co or Fe into the substrate influenced the stoichiometry of the resulting cathode layer in varying degrees. Fe was found to diffuse into the substrate. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. |
Turkan, Ugur; Guden, Mustafa; Sudagidan, Mert Staphylococcus epidermidis adhesion on surface-treated open-cell Ti6Al4V foams Journal Article BIOMEDICAL ENGINEERING-BIOMEDIZINISCHE TECHNIK, 61 (3), pp. 299-307, 2016, ISSN: 0013-5585. @article{ISI:000377547000006, title = {Staphylococcus epidermidis adhesion on surface-treated open-cell Ti6Al4V foams}, author = {Ugur Turkan and Mustafa Guden and Mert Sudagidan}, doi = {10.1515/bmt-2015-0007}, issn = {0013-5585}, year = {2016}, date = {2016-06-01}, journal = {BIOMEDICAL ENGINEERING-BIOMEDIZINISCHE TECHNIK}, volume = {61}, number = {3}, pages = {299-307}, abstract = {The effect of alkali and nitric acid surface treatments on the adhesion of Staphylococcus epidermidis to the surface of 60% porous open-cell Ti6Al4V foam was investigated. The resultant surface roughness of foam particles was determined from the ground flat surfaces of thin foam specimens. Alkali treatment formed a porous, rough Na2Ti5O11 surface layer on Ti6Al4V particles, while nitric acid treatment increased the number of undulations on foam flat and particle surfaces, leading to the development of finer surface topographical features. Both surface treatments increased the nanometric-scale surface roughness of particles and the number of bacteria adhering to the surface, while the adhesion was found to be significantly higher in alkali-treated foam sample. The significant increase in the number of bacterial attachment on the alkali-treated sample was attributed to the formation of a highly porous and nanorough Na2Ti5O11 surface layer.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The effect of alkali and nitric acid surface treatments on the adhesion of Staphylococcus epidermidis to the surface of 60% porous open-cell Ti6Al4V foam was investigated. The resultant surface roughness of foam particles was determined from the ground flat surfaces of thin foam specimens. Alkali treatment formed a porous, rough Na2Ti5O11 surface layer on Ti6Al4V particles, while nitric acid treatment increased the number of undulations on foam flat and particle surfaces, leading to the development of finer surface topographical features. Both surface treatments increased the nanometric-scale surface roughness of particles and the number of bacteria adhering to the surface, while the adhesion was found to be significantly higher in alkali-treated foam sample. The significant increase in the number of bacterial attachment on the alkali-treated sample was attributed to the formation of a highly porous and nanorough Na2Ti5O11 surface layer. |
Merter, Emrah N; Baser, Gulnur; Tanoglu, Metin JOURNAL OF COMPOSITE MATERIALS, 50 (12, SI), pp. 1697-1706, 2016, ISSN: 0021-9983. @article{ISI:000374328300014, title = {Effects of hybrid yarn preparation technique and fiber sizing on the mechanical properties of continuous glass fiber-reinforced polypropylene composites}, author = {Emrah N Merter and Gulnur Baser and Metin Tanoglu}, doi = {10.1177/0021998315595710}, issn = {0021-9983}, year = {2016}, date = {2016-05-01}, journal = {JOURNAL OF COMPOSITE MATERIALS}, volume = {50}, number = {12, SI}, pages = {1697-1706}, abstract = {In this study, hybrid yarns were developed by commingling the continuous polypropylene and glass fibers using air jet and direct twist preparation techniques. The non-crimp fabrics were obtained with +/- 45 degrees fiber orientation from these hybrid yarns. The fabrics were prepared with fiber sizings that are compatible and incompatible with polypropylene matrix to investigate the effect of interfacial adhesion on the properties of the thermoplastic composites. Composite panels were produced from the developed fabrics by hot press compression method and microstructural and mechanical properties of the composites were investigated. It was found that type of the hybrid yarn preparation technique and glass fiber sizing applied on the glass fibers have some important role on the properties of the composites. Composites made of fabrics produced by air jet hybrid yarn preparation technique exhibited better results than those produced by direct twist covering (single or double) hybrid yarn preparation techniques. The highest flexural properties (99.1MPa flexural strength and 9.55 GPa flexural modulus) were obtained from the composites manufactured from fabric containing compatible sizing, due to better adhesion at the interface of glass fibers and polypropylene matrix. The composite fabricated from fabric with polypropylene compatible sizing also exhibited the highest peel resistance (interlaminar peel strength value of 5.87N/mm). On the other hand, it was found that hybrid yarn preparation technique and type of the glass fiber sizing have insignificant effect on the impact properties of the glass fiber/polypropylene composites.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, hybrid yarns were developed by commingling the continuous polypropylene and glass fibers using air jet and direct twist preparation techniques. The non-crimp fabrics were obtained with +/- 45 degrees fiber orientation from these hybrid yarns. The fabrics were prepared with fiber sizings that are compatible and incompatible with polypropylene matrix to investigate the effect of interfacial adhesion on the properties of the thermoplastic composites. Composite panels were produced from the developed fabrics by hot press compression method and microstructural and mechanical properties of the composites were investigated. It was found that type of the hybrid yarn preparation technique and glass fiber sizing applied on the glass fibers have some important role on the properties of the composites. Composites made of fabrics produced by air jet hybrid yarn preparation technique exhibited better results than those produced by direct twist covering (single or double) hybrid yarn preparation techniques. The highest flexural properties (99.1MPa flexural strength and 9.55 GPa flexural modulus) were obtained from the composites manufactured from fabric containing compatible sizing, due to better adhesion at the interface of glass fibers and polypropylene matrix. The composite fabricated from fabric with polypropylene compatible sizing also exhibited the highest peel resistance (interlaminar peel strength value of 5.87N/mm). On the other hand, it was found that hybrid yarn preparation technique and type of the glass fiber sizing have insignificant effect on the impact properties of the glass fiber/polypropylene composites. |
Basturk, S B; Tanoglu, M; Cankaya, M A; Egilmez, O O Dynamic behavior predictions of fiber-metal laminate/aluminum foam sandwiches under various explosive weights Journal Article JOURNAL OF SANDWICH STRUCTURES & MATERIALS, 18 (3), pp. 321-342, 2016, ISSN: 1099-6362. @article{ISI:000375128600003b, title = {Dynamic behavior predictions of fiber-metal laminate/aluminum foam sandwiches under various explosive weights}, author = {S B Basturk and M Tanoglu and M A Cankaya and O O Egilmez}, doi = {10.1177/1099636215603036}, issn = {1099-6362}, year = {2016}, date = {2016-05-01}, journal = {JOURNAL OF SANDWICH STRUCTURES & MATERIALS}, volume = {18}, number = {3}, pages = {321-342}, abstract = {Application of blast tests causes some problems to characterize the performance of panels due to the drastic conditions of explosive medium. Real test has high safety concerns and is not easily accessible because of its extra budget. Some approaches are needed for the preliminary predictions of dynamic characteristics of panels under blast loading conditions. In this study, the response of sandwiches under blast effect was evaluated by combining quasi-static experiments and computational blast test data. The primary aim is to relate the quasi-static panel analysis to dynamic blast load. Based on this idea, lightweight sandwich composites were subjected to quasi-static compression loading with a special test apparatus and the samples were assumed as single degree-of-freedom mass-spring systems to include dynamic effect. This approach provides a simpler way to simulate the blast loading over the surface of the panels and reveals the possible failure mechanisms without applying any explosives. Therefore the design of the panels can be revised by considering quasi-static test results. In this work, the peak deflections and survivabilities of sandwiches for various explosive weights were predicted based on the formulations reported in the literature. Major failure types were also identified and evaluated with respect to their thicknesses.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Application of blast tests causes some problems to characterize the performance of panels due to the drastic conditions of explosive medium. Real test has high safety concerns and is not easily accessible because of its extra budget. Some approaches are needed for the preliminary predictions of dynamic characteristics of panels under blast loading conditions. In this study, the response of sandwiches under blast effect was evaluated by combining quasi-static experiments and computational blast test data. The primary aim is to relate the quasi-static panel analysis to dynamic blast load. Based on this idea, lightweight sandwich composites were subjected to quasi-static compression loading with a special test apparatus and the samples were assumed as single degree-of-freedom mass-spring systems to include dynamic effect. This approach provides a simpler way to simulate the blast loading over the surface of the panels and reveals the possible failure mechanisms without applying any explosives. Therefore the design of the panels can be revised by considering quasi-static test results. In this work, the peak deflections and survivabilities of sandwiches for various explosive weights were predicted based on the formulations reported in the literature. Major failure types were also identified and evaluated with respect to their thicknesses. |
Tasdemirci, Alper; Kara, Ali; Turan, Kivanc; Sahin, Selim; Guden, Mustafa Effect of heat treatment on the blast loading response of combined geometry shell core sandwich structures Journal Article THIN-WALLED STRUCTURES, 100 , pp. 180-191, 2016, ISSN: 0263-8231. @article{ISI:000369463600016, title = {Effect of heat treatment on the blast loading response of combined geometry shell core sandwich structures}, author = {Alper Tasdemirci and Ali Kara and Kivanc Turan and Selim Sahin and Mustafa Guden}, doi = {10.1016/j.tws.2015.12.012}, issn = {0263-8231}, year = {2016}, date = {2016-03-01}, journal = {THIN-WALLED STRUCTURES}, volume = {100}, pages = {180-191}, abstract = {The effect of heat treatment on the dynamic crushing and energy absorption behavior of combined geometry shell cores (hemisphere and cylinder) of sandwich structures were investigated both experimentally and numerically. The applied heat treatment on the combined geometry shell cores relieved the stress caused by deep drawing, diminishing the peak transmitted forces. The verified numerical models of the as-received and heat-treated combined geometry shells were used to model blast loading of various sandwich configurations and the additional sandwich configurations of reversing the cylindrical side of the cores to the impacted side. Both the applied heat-treatment and the reversing process decreased the magnitude of the force transmitted to the protected structure. The applied heat treatment increased the arrival time of blast force wave to the protected structure, while the reversing resulted in opposite. (C) 2015 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The effect of heat treatment on the dynamic crushing and energy absorption behavior of combined geometry shell cores (hemisphere and cylinder) of sandwich structures were investigated both experimentally and numerically. The applied heat treatment on the combined geometry shell cores relieved the stress caused by deep drawing, diminishing the peak transmitted forces. The verified numerical models of the as-received and heat-treated combined geometry shells were used to model blast loading of various sandwich configurations and the additional sandwich configurations of reversing the cylindrical side of the cores to the impacted side. Both the applied heat-treatment and the reversing process decreased the magnitude of the force transmitted to the protected structure. The applied heat treatment increased the arrival time of blast force wave to the protected structure, while the reversing resulted in opposite. (C) 2015 Elsevier Ltd. All rights reserved. |
2014 |
Demir, Mustafa M; Horzum, Nesrin; Tasdemirci, Alper; Turan, Kivanc; Guden, Mustafa Mechanical Interlocking between Porous Electrospun Polystyrene Fibers and an Epoxy Matrix Journal Article ACS APPLIED MATERIALS & INTERFACES, 6 (24), pp. 21901-21905, 2014, ISSN: 1944-8244. @article{ISI:000347139400018, title = {Mechanical Interlocking between Porous Electrospun Polystyrene Fibers and an Epoxy Matrix}, author = {Mustafa M Demir and Nesrin Horzum and Alper Tasdemirci and Kivanc Turan and Mustafa Guden}, doi = {10.1021/am507029c}, issn = {1944-8244}, year = {2014}, date = {2014-12-01}, journal = {ACS APPLIED MATERIALS & INTERFACES}, volume = {6}, number = {24}, pages = {21901-21905}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Kandemir, Sinan; Atkinson, Helen V; Weston, David P; Hainsworth, Sarah V METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, 45A (12), pp. 5782-5798, 2014, ISSN: 1073-5623. @article{ISI:000342443200049, title = {Thixoforming of A356/SiC and A356/TiB2 Nanocomposites Fabricated by a Combination of Green Compact Nanoparticle Incorporation and Ultrasonic Treatment of the Melted Compact}, author = {Sinan Kandemir and Helen V Atkinson and David P Weston and Sarah V Hainsworth}, doi = {10.1007/s11661-014-2501-0}, issn = {1073-5623}, year = {2014}, date = {2014-11-01}, journal = {METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE}, volume = {45A}, number = {12}, pages = {5782-5798}, abstract = {Thixoforming is a type of semi-solid processing which is based on forming metals in the semi-solid state rather than fully liquid or solid state. There have been no reports of the thixoforming of nanocomposites in the literature. The incorporation of ceramic nanoparticles into liquid metals is a challenging task for the fabrication of metal matrix nanocomposites due to their large surface-to-volume ratio and poor wettability. Previous research work by a number of workers has highlighted the challenges with the incorporation of nanoparticles into liquid aluminum alloy. In the present study, SiC and TiB2 nanoparticles with an average diameter between 20 and 30 nm were firstly incorporated into green compacts by a powder forming route, and then the compacts were melted and treated ultrasonically. The microstructural studies reveal that the engulfment and relatively effective distribution of the nanoparticles into the melt were achieved. The hardness was considerably improved with only 0.8 wt pct addition of the nanoparticles. The nanocomposites were successfully thixoformed at a solid fraction between 0.65 and 0.70. The microstructures, hardness, and tensile mechanical properties of the thixoformed nanocomposites were investigated and compared with those of the as-received A356 and thixoformed A356 alloys. The tensile properties of the thixoformed nanocomposites were significantly enhanced compared to thixoformed A356 alloy without reinforcement, indicating the strengthening effects of the nanoparticles.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Thixoforming is a type of semi-solid processing which is based on forming metals in the semi-solid state rather than fully liquid or solid state. There have been no reports of the thixoforming of nanocomposites in the literature. The incorporation of ceramic nanoparticles into liquid metals is a challenging task for the fabrication of metal matrix nanocomposites due to their large surface-to-volume ratio and poor wettability. Previous research work by a number of workers has highlighted the challenges with the incorporation of nanoparticles into liquid aluminum alloy. In the present study, SiC and TiB2 nanoparticles with an average diameter between 20 and 30 nm were firstly incorporated into green compacts by a powder forming route, and then the compacts were melted and treated ultrasonically. The microstructural studies reveal that the engulfment and relatively effective distribution of the nanoparticles into the melt were achieved. The hardness was considerably improved with only 0.8 wt pct addition of the nanoparticles. The nanocomposites were successfully thixoformed at a solid fraction between 0.65 and 0.70. The microstructures, hardness, and tensile mechanical properties of the thixoformed nanocomposites were investigated and compared with those of the as-received A356 and thixoformed A356 alloys. The tensile properties of the thixoformed nanocomposites were significantly enhanced compared to thixoformed A356 alloy without reinforcement, indicating the strengthening effects of the nanoparticles. |
Kilicaslan, C; Odaci, I K; Tasdemirci, A; Guden, M STRAIN, 50 (3), pp. 236-249, 2014, ISSN: 1475-1305. @article{ISI:000336487800004, title = {Experimental Testing and Full and Homogenized Numerical Models of the Low Velocity and Dynamic Deformation of the Trapezoidal Aluminium Corrugated Core Sandwich}, author = {C Kilicaslan and I K Odaci and A Tasdemirci and M Guden}, doi = {10.1111/str.12085}, issn = {1475-1305}, year = {2014}, date = {2014-06-01}, journal = {STRAIN}, volume = {50}, number = {3}, pages = {236-249}, abstract = {The simulations of the low velocity and dynamic deformation of a multi-layer 1050-H14 Al trapezoidal zig-zag corrugated core sandwich were investigated using the homogenized models (solid models) of a single core layer (without face sheets). In the first part of the study, the LS-DYNA MAT-26 material model parameters of a single core layer were developed through experimental and numerical compression tests on the single core layer. In the second part, the fidelities of the developed numerical models were checked by the split-Hopkinson pressure bar direct impact, low velocity compression and indentation and projectile impact tests. The results indicated that the element size had a significant effect on the initial peak and post-peak stresses of the homogenized models of the direct impact testing of the single-layer corrugated sandwich. This was attributed to the lack of the inertial effects in the homogenized models, which resulted in reduced initial peak stresses as compared with the full model and experiment. However, the homogenized models based on the experimental stress-strain curve of the single core layer predicted the low velocity compression and indentation and projectile impact tests of the multi-layer corrugated sandwich with an acceptable accuracy and reduced the computational time of the models significantly.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The simulations of the low velocity and dynamic deformation of a multi-layer 1050-H14 Al trapezoidal zig-zag corrugated core sandwich were investigated using the homogenized models (solid models) of a single core layer (without face sheets). In the first part of the study, the LS-DYNA MAT-26 material model parameters of a single core layer were developed through experimental and numerical compression tests on the single core layer. In the second part, the fidelities of the developed numerical models were checked by the split-Hopkinson pressure bar direct impact, low velocity compression and indentation and projectile impact tests. The results indicated that the element size had a significant effect on the initial peak and post-peak stresses of the homogenized models of the direct impact testing of the single-layer corrugated sandwich. This was attributed to the lack of the inertial effects in the homogenized models, which resulted in reduced initial peak stresses as compared with the full model and experiment. However, the homogenized models based on the experimental stress-strain curve of the single core layer predicted the low velocity compression and indentation and projectile impact tests of the multi-layer corrugated sandwich with an acceptable accuracy and reduced the computational time of the models significantly. |
Sutcu, Mucahit; del Diaz, Juan Jose Coz; Rabanal, Felipe Pedro Alvarez; Gencel, Osman; Akkurt, Sedat Thermal performance optimization of hollow clay bricks made up of paper waste Journal Article ENERGY AND BUILDINGS, 75 , pp. 96-108, 2014, ISSN: 0378-7788. @article{ISI:000337013200010, title = {Thermal performance optimization of hollow clay bricks made up of paper waste}, author = {Mucahit Sutcu and Juan Jose del Coz Diaz and Felipe Pedro Alvarez Rabanal and Osman Gencel and Sedat Akkurt}, doi = {10.1016/j.enbuild.2014.02.006}, issn = {0378-7788}, year = {2014}, date = {2014-06-01}, journal = {ENERGY AND BUILDINGS}, volume = {75}, pages = {96-108}, abstract = {In this paper, the thermal behavior of hollow clay bricks made up of paper waste has been studied and their thermal performance has been optimized. On the one hand, both strength and thermal properties of different paper waste concentrations have been obtained by means of laboratory tests. Thermal conductivity of the microporous brick materials with additives produced in this study reduced from 0.68 W/m K to 0.39 W/m K compared with that of the sample without additives. On the other hand, the finite element method (FEM) has been applied to the nonlinear numerical thermal analysis of three different hollow bricks, including radiation and convection phenomena inside holes. Next, using the design of experiments (DOE) over the FEM models, several parameters such as the material conductivity, the convection and radiation properties and the mean brick temperature have been studied. In general, the thermal resistance is a nonlinear function that depends on the geometry of the recesses, the material properties and the temperature distribution. In all analyzed cases, minimizing the material thermal conductivity of bricks and decreasing the recesses surface radiation emissivity caused a lower thermal transmittance in the brick. Finally, the most important conclusions and the main findings of this research are exposed. (C) 2014 Elsevier B.V. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this paper, the thermal behavior of hollow clay bricks made up of paper waste has been studied and their thermal performance has been optimized. On the one hand, both strength and thermal properties of different paper waste concentrations have been obtained by means of laboratory tests. Thermal conductivity of the microporous brick materials with additives produced in this study reduced from 0.68 W/m K to 0.39 W/m K compared with that of the sample without additives. On the other hand, the finite element method (FEM) has been applied to the nonlinear numerical thermal analysis of three different hollow bricks, including radiation and convection phenomena inside holes. Next, using the design of experiments (DOE) over the FEM models, several parameters such as the material conductivity, the convection and radiation properties and the mean brick temperature have been studied. In general, the thermal resistance is a nonlinear function that depends on the geometry of the recesses, the material properties and the temperature distribution. In all analyzed cases, minimizing the material thermal conductivity of bricks and decreasing the recesses surface radiation emissivity caused a lower thermal transmittance in the brick. Finally, the most important conclusions and the main findings of this research are exposed. (C) 2014 Elsevier B.V. All rights reserved. |
Ozyildiz, Figen; Uzel, Atac; Hazar, Ayse Serpil; Guden, Mustafa; Olmez, Sultan; Aras, Isil; Karaboz, Ismail Photocatalytic antimicrobial effect of TiO2 anatase thin-film-coated orthodontic arch wires on 3 oral pathogens Journal Article TURKISH JOURNAL OF BIOLOGY, 38 (2), pp. 289-295, 2014, ISSN: 1300-0152. @article{ISI:000332944300015, title = {Photocatalytic antimicrobial effect of TiO2 anatase thin-film-coated orthodontic arch wires on 3 oral pathogens}, author = {Figen Ozyildiz and Atac Uzel and Ayse Serpil Hazar and Mustafa Guden and Sultan Olmez and Isil Aras and Ismail Karaboz}, doi = {10.3906/biy-1308-43}, issn = {1300-0152}, year = {2014}, date = {2014-01-01}, journal = {TURKISH JOURNAL OF BIOLOGY}, volume = {38}, number = {2}, pages = {289-295}, abstract = {The aim of this study was to introduce antimicrobial activity to stainless steel orthodontic arch wires by coating them with TiO2 in anatase form. Stainless steel (0.016 x 0.022 inch), D-rect (0.016 x 0.022 inch), and multistranded hammered retainer wires (0.014 x 0.018 inch) were coated with TiO2 anatase by the sol-gel dip coating method. The wires were assessed for their photocatalytic antimicrobial activity against Streptococcus mutans, Candida albicans, and Enterococcus faecalis. After illumination under UVA (315400 nm) at 1.0 mW/cm(2) for 1 h, the reduction efficiencies of the anatase-coated arch wires were calculated by using colony-forming unit counts. All anatase-coated arch wires showed remarkable inhibitor effects against the test microorganisms under UVA. The most efficient wire on S. mutans was the stainless steel wire, with a 99.99% reduction in growth, but multistranded hammered retainer wire was the most active against both C. albicans and E. faecalis, with 98.0% and 91.68% reduction rates, respectively. TiO2-coated arch wires exposed to UVA illumination showed significant antimicrobial activity when compared with uncoated samples and coated, but not UVA-exposed, samples. Our results suggest that the antimicrobial effect of TiO2-coated arch wires in long-lasting orthodontic treatments would be beneficial for the prophylaxis of caries.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The aim of this study was to introduce antimicrobial activity to stainless steel orthodontic arch wires by coating them with TiO2 in anatase form. Stainless steel (0.016 x 0.022 inch), D-rect (0.016 x 0.022 inch), and multistranded hammered retainer wires (0.014 x 0.018 inch) were coated with TiO2 anatase by the sol-gel dip coating method. The wires were assessed for their photocatalytic antimicrobial activity against Streptococcus mutans, Candida albicans, and Enterococcus faecalis. After illumination under UVA (315400 nm) at 1.0 mW/cm(2) for 1 h, the reduction efficiencies of the anatase-coated arch wires were calculated by using colony-forming unit counts. All anatase-coated arch wires showed remarkable inhibitor effects against the test microorganisms under UVA. The most efficient wire on S. mutans was the stainless steel wire, with a 99.99% reduction in growth, but multistranded hammered retainer wire was the most active against both C. albicans and E. faecalis, with 98.0% and 91.68% reduction rates, respectively. TiO2-coated arch wires exposed to UVA illumination showed significant antimicrobial activity when compared with uncoated samples and coated, but not UVA-exposed, samples. Our results suggest that the antimicrobial effect of TiO2-coated arch wires in long-lasting orthodontic treatments would be beneficial for the prophylaxis of caries. |
2013 |
Attila, Yigit; Guden, Mustafa; Tasdemirci, Alper Foam glass processing using a polishing glass powder residue Journal Article CERAMICS INTERNATIONAL, 39 (5), pp. 5869-5877, 2013, ISSN: 0272-8842. @article{ISI:000318577600141, title = {Foam glass processing using a polishing glass powder residue}, author = {Yigit Attila and Mustafa Guden and Alper Tasdemirci}, doi = {10.1016/j.ceramint.2012.12.104}, issn = {0272-8842}, year = {2013}, date = {2013-07-01}, journal = {CERAMICS INTERNATIONAL}, volume = {39}, number = {5}, pages = {5869-5877}, abstract = {The foaming behavior of a powder residue/waste of a soda-lime window glass polishing facility was investigated at the temperatures between 700 and 950 degrees C. The results showed that the foaming of the glass powder started at a characteristic temperature between 670 and 680 degrees C. The maximum volume expansions of the glass powder and the density of the foams varied between 600% and 750% and 0.206 and 0.378 g cm(-3), respectively. The expansion of the studied glass powder residue resulted from the decomposition of the organic compounds on the surfaces of the glass powder particles, derived from an oil-based coolant used in the polishing. The collapse stress of the foams ranged between similar to 1 and 4 MPa and the thermal conductivity between 0.048 and 0.079 W K-1 m(-1). Both the collapse stress and thermal conductivity increased with increasing the foam density. The foams showed the characteristics of the compression deformation of the open cell brittle foams, which was attributed to the relatively thick cell edges. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The foaming behavior of a powder residue/waste of a soda-lime window glass polishing facility was investigated at the temperatures between 700 and 950 degrees C. The results showed that the foaming of the glass powder started at a characteristic temperature between 670 and 680 degrees C. The maximum volume expansions of the glass powder and the density of the foams varied between 600% and 750% and 0.206 and 0.378 g cm(-3), respectively. The expansion of the studied glass powder residue resulted from the decomposition of the organic compounds on the surfaces of the glass powder particles, derived from an oil-based coolant used in the polishing. The collapse stress of the foams ranged between similar to 1 and 4 MPa and the thermal conductivity between 0.048 and 0.079 W K-1 m(-1). Both the collapse stress and thermal conductivity increased with increasing the foam density. The foams showed the characteristics of the compression deformation of the open cell brittle foams, which was attributed to the relatively thick cell edges. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved. |
Cakircali, Metin; Kilicaslan, Cenk; Guden, Mustafa; Kiranli, Engin; Shchukin, Valery Y; Petronko, Vladimir V Cross wedge rolling of a Ti6Al4V (ELI) alloy: the experimental studies and the finite element simulation of the deformation and failure Journal Article INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY, 65 (9-12), pp. 1273-1287, 2013, ISSN: 0268-3768. @article{ISI:000316364000007, title = {Cross wedge rolling of a Ti6Al4V (ELI) alloy: the experimental studies and the finite element simulation of the deformation and failure}, author = {Metin Cakircali and Cenk Kilicaslan and Mustafa Guden and Engin Kiranli and Valery Y Shchukin and Vladimir V Petronko}, doi = {10.1007/s00170-012-4256-3}, issn = {0268-3768}, year = {2013}, date = {2013-04-01}, journal = {INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY}, volume = {65}, number = {9-12}, pages = {1273-1287}, abstract = {The cross wedge rolling (CWR) deformation and fracture of a Ti6Al4Al (ELI) alloy were investigated experimentally and numerically using a coupled thermo-mechanical finite element model analysis. The experimentally determined flow stress and damage model parameters were verified by tension split Hopkinson pressure bar testing of notched samples. The simulation and experimental CWR forces showed well agreements except near the end of the stretching zone. The model analysis showed that the temperature distribution in the work piece was non-uniform during the CWR. When the initial temperature of the work piece was relatively low, the work piece temperature increased, a heating effect of the plastic deformation, while relatively high initial work piece temperatures resulted in cooling the work piece, caused by the work piece contact with the tools. The cracks were shown numerically to initiate in the midsections of the work piece during the guiding action and elongated in a direction normal to the maximum tensile stress triaxiality, resulting in cruciform-shaped crack formation, which was well agreed with the previously observed crack shape.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The cross wedge rolling (CWR) deformation and fracture of a Ti6Al4Al (ELI) alloy were investigated experimentally and numerically using a coupled thermo-mechanical finite element model analysis. The experimentally determined flow stress and damage model parameters were verified by tension split Hopkinson pressure bar testing of notched samples. The simulation and experimental CWR forces showed well agreements except near the end of the stretching zone. The model analysis showed that the temperature distribution in the work piece was non-uniform during the CWR. When the initial temperature of the work piece was relatively low, the work piece temperature increased, a heating effect of the plastic deformation, while relatively high initial work piece temperatures resulted in cooling the work piece, caused by the work piece contact with the tools. The cracks were shown numerically to initiate in the midsections of the work piece during the guiding action and elongated in a direction normal to the maximum tensile stress triaxiality, resulting in cruciform-shaped crack formation, which was well agreed with the previously observed crack shape. |
Kesici, Kutsal; Tuney, Inci; Zeren, Dogus; Guden, Mustafa; Sukatar, Atakan Morphological and molecular identification of pennate diatoms isolated from Urla, Izmir, coast of the Aegean Sea Journal Article TURKISH JOURNAL OF BIOLOGY, 37 (5), pp. 530-537, 2013, ISSN: 1300-0152. @article{ISI:000325300500004, title = {Morphological and molecular identification of pennate diatoms isolated from Urla, Izmir, coast of the Aegean Sea}, author = {Kutsal Kesici and Inci Tuney and Dogus Zeren and Mustafa Guden and Atakan Sukatar}, doi = {10.3906/biy-1205-40}, issn = {1300-0152}, year = {2013}, date = {2013-01-01}, journal = {TURKISH JOURNAL OF BIOLOGY}, volume = {37}, number = {5}, pages = {530-537}, abstract = {Diatoms represent an important class of aquatic phototrophs. They are not only one of the major contributors to global carbon fixation, but they also play a key role in the biogeochemical cycling of silica. Molecular identification methods based on conserved DNA sequences, such as internal transcribed spacer (ITS) have revolutionized our knowledge and understanding of conventional taxonomy. In this study, we aimed to compare the conventional identification methods with molecular identification methods. To do so, we isolated 4 diatom samples from the coast at Urla and characterized them Using light microscopy (LM) and scanning electron microscopy (SEM) according to morphological features. Then we amplified ITS regions using a conventional polymerase chain reaction (PCR), sequenced the PCR products, and analyzed the sequences using bioinformatic tools. Bioinformatic analysis indicated that the isolated species had high sequence similarity to Pseudo-nitzschia delicatissima, Achnanthes taeniata, Amphora coffeaeformis, and Cylindrotheca closterium. We think that molecular identification methods enable rapid and more reliable identification of diatom species and are crucial for monitoring harmful algal blooms.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Diatoms represent an important class of aquatic phototrophs. They are not only one of the major contributors to global carbon fixation, but they also play a key role in the biogeochemical cycling of silica. Molecular identification methods based on conserved DNA sequences, such as internal transcribed spacer (ITS) have revolutionized our knowledge and understanding of conventional taxonomy. In this study, we aimed to compare the conventional identification methods with molecular identification methods. To do so, we isolated 4 diatom samples from the coast at Urla and characterized them Using light microscopy (LM) and scanning electron microscopy (SEM) according to morphological features. Then we amplified ITS regions using a conventional polymerase chain reaction (PCR), sequenced the PCR products, and analyzed the sequences using bioinformatic tools. Bioinformatic analysis indicated that the isolated species had high sequence similarity to Pseudo-nitzschia delicatissima, Achnanthes taeniata, Amphora coffeaeformis, and Cylindrotheca closterium. We think that molecular identification methods enable rapid and more reliable identification of diatom species and are crucial for monitoring harmful algal blooms. |
Kesici, Kutsal; Tuney, Inci; Zeren, Dogus; Guden, Mustafa; Sukatar, Atakan Morphological and molecular identification of pennate diatoms isolated from Urla, Izmir, coast of the Aegean Sea Journal Article TURKISH JOURNAL OF BIOLOGY, 37 (5), pp. 530-537, 2013, ISSN: 1300-0152. @article{ISI:000325300500004b, title = {Morphological and molecular identification of pennate diatoms isolated from Urla, Izmir, coast of the Aegean Sea}, author = {Kutsal Kesici and Inci Tuney and Dogus Zeren and Mustafa Guden and Atakan Sukatar}, doi = {10.3906/biy-1205-40}, issn = {1300-0152}, year = {2013}, date = {2013-01-01}, journal = {TURKISH JOURNAL OF BIOLOGY}, volume = {37}, number = {5}, pages = {530-537}, abstract = {Diatoms represent an important class of aquatic phototrophs. They are not only one of the major contributors to global carbon fixation, but they also play a key role in the biogeochemical cycling of silica. Molecular identification methods based on conserved DNA sequences, such as internal transcribed spacer (ITS) have revolutionized our knowledge and understanding of conventional taxonomy. In this study, we aimed to compare the conventional identification methods with molecular identification methods. To do so, we isolated 4 diatom samples from the coast at Urla and characterized them Using light microscopy (LM) and scanning electron microscopy (SEM) according to morphological features. Then we amplified ITS regions using a conventional polymerase chain reaction (PCR), sequenced the PCR products, and analyzed the sequences using bioinformatic tools. Bioinformatic analysis indicated that the isolated species had high sequence similarity to Pseudo-nitzschia delicatissima, Achnanthes taeniata, Amphora coffeaeformis, and Cylindrotheca closterium. We think that molecular identification methods enable rapid and more reliable identification of diatom species and are crucial for monitoring harmful algal blooms.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Diatoms represent an important class of aquatic phototrophs. They are not only one of the major contributors to global carbon fixation, but they also play a key role in the biogeochemical cycling of silica. Molecular identification methods based on conserved DNA sequences, such as internal transcribed spacer (ITS) have revolutionized our knowledge and understanding of conventional taxonomy. In this study, we aimed to compare the conventional identification methods with molecular identification methods. To do so, we isolated 4 diatom samples from the coast at Urla and characterized them Using light microscopy (LM) and scanning electron microscopy (SEM) according to morphological features. Then we amplified ITS regions using a conventional polymerase chain reaction (PCR), sequenced the PCR products, and analyzed the sequences using bioinformatic tools. Bioinformatic analysis indicated that the isolated species had high sequence similarity to Pseudo-nitzschia delicatissima, Achnanthes taeniata, Amphora coffeaeformis, and Cylindrotheca closterium. We think that molecular identification methods enable rapid and more reliable identification of diatom species and are crucial for monitoring harmful algal blooms. |
Gulturk, E A; Guden, M; Tasdemirci, A Calcined and natural frustules filled epoxy matrices: The effect of volume fraction on the tensile and compression behavior Journal Article COMPOSITES PART B-ENGINEERING, 44 (1), pp. 491-500, 2013, ISSN: 1359-8368. @article{ISI:000313854200059, title = {Calcined and natural frustules filled epoxy matrices: The effect of volume fraction on the tensile and compression behavior}, author = {E A Gulturk and M Guden and A Tasdemirci}, doi = {10.1016/j.compositesb.2012.03.022}, issn = {1359-8368}, year = {2013}, date = {2013-01-01}, journal = {COMPOSITES PART B-ENGINEERING}, volume = {44}, number = {1}, pages = {491-500}, abstract = {The effects of calcined diatom (CD) and natural diatom (ND) frustules filling (0-12 vol.%) on the quasi-static tensile and quasi-static and high strain rate compression behavior of an epoxy matrix were investigated experimentally. The high strain rate testing of frustules-filled and neat epoxy samples was performed in a compression Split Hopkinson Pressure Bar set-up. The frustules filling increased the stress values at a constant strain and decreased the tensile failure strains of the epoxy matrix. Compression tests results showed that frustules filling of epoxy increased both elastic modulus and yield strength values at quasi-static and high strain rates. While, a higher strengthening effect and strain rate sensitivity were found with ND frustules filling. Microscopic observations revealed two main compression deformation modes at quasi-static strain rates: the debonding of the frustules from the epoxy and/or crushing of the frustules. However, the failure of the filled composites at high strain rates was dominated by the fracture of epoxy matrix. (C) 2012 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The effects of calcined diatom (CD) and natural diatom (ND) frustules filling (0-12 vol.%) on the quasi-static tensile and quasi-static and high strain rate compression behavior of an epoxy matrix were investigated experimentally. The high strain rate testing of frustules-filled and neat epoxy samples was performed in a compression Split Hopkinson Pressure Bar set-up. The frustules filling increased the stress values at a constant strain and decreased the tensile failure strains of the epoxy matrix. Compression tests results showed that frustules filling of epoxy increased both elastic modulus and yield strength values at quasi-static and high strain rates. While, a higher strengthening effect and strain rate sensitivity were found with ND frustules filling. Microscopic observations revealed two main compression deformation modes at quasi-static strain rates: the debonding of the frustules from the epoxy and/or crushing of the frustules. However, the failure of the filled composites at high strain rates was dominated by the fracture of epoxy matrix. (C) 2012 Elsevier Ltd. All rights reserved. |
2012 |
Tasdemirci, A; Turan, A K; Guden, M The effect of strain rate on the mechanical behavior of Teflon foam Journal Article POLYMER TESTING, 31 (6), pp. 723-727, 2012, ISSN: 0142-9418. @article{ISI:000307614000002, title = {The effect of strain rate on the mechanical behavior of Teflon foam}, author = {A Tasdemirci and A K Turan and M Guden}, doi = {10.1016/j.polymertesting.2012.05.004}, issn = {0142-9418}, year = {2012}, date = {2012-09-01}, journal = {POLYMER TESTING}, volume = {31}, number = {6}, pages = {723-727}, abstract = {The quasi-static (1 x 10(-3), 1 x 10(-2) and 1 x 10(-1) s(-1)) and high strain rate (7200 and 9500 s(-1)) experimental and high strain rate numerical compression deformation of a Gore Polarchip (TM) CP7003 heat insulating Teflon foam was investigated. High strain rate tests were conducted with the insertion of quartz crystal piezoelectric transducers at the end of the transmitter bar of a compression Split Hopkinson Pressure Bar (SHPB) set-up in order to measure the force at the back face of the specimen. A fully developed numerical model of the SHPB test on Teflon was also implemented using LS-DYNA. The simulation stresses showed close correlations with the experimentally measured stresses on the bars. The developed model successfully simulated the high strain rate loading. The damage initiation and progression of experimental high strain rate tests were further recorded using a high speed camera and found to be very similar to those of the simulation high strain rate tests. (C) 2012 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The quasi-static (1 x 10(-3), 1 x 10(-2) and 1 x 10(-1) s(-1)) and high strain rate (7200 and 9500 s(-1)) experimental and high strain rate numerical compression deformation of a Gore Polarchip (TM) CP7003 heat insulating Teflon foam was investigated. High strain rate tests were conducted with the insertion of quartz crystal piezoelectric transducers at the end of the transmitter bar of a compression Split Hopkinson Pressure Bar (SHPB) set-up in order to measure the force at the back face of the specimen. A fully developed numerical model of the SHPB test on Teflon was also implemented using LS-DYNA. The simulation stresses showed close correlations with the experimentally measured stresses on the bars. The developed model successfully simulated the high strain rate loading. The damage initiation and progression of experimental high strain rate tests were further recorded using a high speed camera and found to be very similar to those of the simulation high strain rate tests. (C) 2012 Elsevier Ltd. All rights reserved. |
Savaci, Umut; Yilmaz, Sinan; Guden, Mustafa Open cell lead foams: processing, microstructure, and mechanical properties Journal Article JOURNAL OF MATERIALS SCIENCE, 47 (15), pp. 5646-5654, 2012, ISSN: 0022-2461. @article{ISI:000304110400004, title = {Open cell lead foams: processing, microstructure, and mechanical properties}, author = {Umut Savaci and Sinan Yilmaz and Mustafa Guden}, doi = {10.1007/s10853-012-6496-x}, issn = {0022-2461}, year = {2012}, date = {2012-08-01}, journal = {JOURNAL OF MATERIALS SCIENCE}, volume = {47}, number = {15}, pages = {5646-5654}, abstract = {Open cell lead foams with the porosities between 48 and 74 % were prepared by means of powder metallurgical and casting routes, using ammonium bicarbonate particles, silica beads, and sodium chloride salt particles as space holder. The resulting foam samples structure closely resembled open cell foam structure: each cell had few interconnections with neighboring cells. Small-sized lead (II) fluoride precipitates were microscopically observed in the interior of cells in the foam samples prepared using silica beads as space holder, resulting from the reaction between silica and hydrofluoric acid in the space holder dissolution step. The compression stress-strain curve of foam samples prepared by powder metallurgical route showed brittle deformation behavior following the initial elastic deformation region, while the foam samples prepared by casting route showed characteristic foam deformation behavior: cell edge crushing on the bent cell walls, and cell wall tearing. The collapse stresses, densification strains, and elastic moduli of the prepared foams were further fitted with scaling relations.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Open cell lead foams with the porosities between 48 and 74 % were prepared by means of powder metallurgical and casting routes, using ammonium bicarbonate particles, silica beads, and sodium chloride salt particles as space holder. The resulting foam samples structure closely resembled open cell foam structure: each cell had few interconnections with neighboring cells. Small-sized lead (II) fluoride precipitates were microscopically observed in the interior of cells in the foam samples prepared using silica beads as space holder, resulting from the reaction between silica and hydrofluoric acid in the space holder dissolution step. The compression stress-strain curve of foam samples prepared by powder metallurgical route showed brittle deformation behavior following the initial elastic deformation region, while the foam samples prepared by casting route showed characteristic foam deformation behavior: cell edge crushing on the bent cell walls, and cell wall tearing. The collapse stresses, densification strains, and elastic moduli of the prepared foams were further fitted with scaling relations. |
Tasdemirci, A; Tunusoglu, G; Guden, M The effect of the interlayer on the ballistic performance of ceramic/composite armors: Experimental and numerical study Journal Article INTERNATIONAL JOURNAL OF IMPACT ENGINEERING, 44 , pp. 1-9, 2012, ISSN: 0734-743X. @article{ISI:000301473600001, title = {The effect of the interlayer on the ballistic performance of ceramic/composite armors: Experimental and numerical study}, author = {A Tasdemirci and G Tunusoglu and M Guden}, doi = {10.1016/j.ijimpeng.2011.12.005}, issn = {0734-743X}, year = {2012}, date = {2012-06-01}, journal = {INTERNATIONAL JOURNAL OF IMPACT ENGINEERING}, volume = {44}, pages = {1-9}, abstract = {The effect of rubber, Teflon and aluminum foam interlayer material on the ballistic performance of composite armor was investigated both experimentally and numerically. Although, rubber interlayer did not cause any significant delay in the initial stress build-up in the composite layer, Teflon and aluminum foam interlayer caused a significant delay and reduction in the magnitude of the stress transmitted to the composite backing plate. Damage in the ceramic layer was found to be highly localized around the projectile impact zone for the configuration without interlayer and rubber interlayer while aluminum foam and Teflon interlayer spread the damage zone in the radial direction. Relatively large pieces of the ceramic around the impact axis in the rubber interlayer configuration were observed while the ceramic layer was efficiently fragmented in aluminum foam and Teflon interlayer configuration. (C) 2011 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The effect of rubber, Teflon and aluminum foam interlayer material on the ballistic performance of composite armor was investigated both experimentally and numerically. Although, rubber interlayer did not cause any significant delay in the initial stress build-up in the composite layer, Teflon and aluminum foam interlayer caused a significant delay and reduction in the magnitude of the stress transmitted to the composite backing plate. Damage in the ceramic layer was found to be highly localized around the projectile impact zone for the configuration without interlayer and rubber interlayer while aluminum foam and Teflon interlayer spread the damage zone in the radial direction. Relatively large pieces of the ceramic around the impact axis in the rubber interlayer configuration were observed while the ceramic layer was efficiently fragmented in aluminum foam and Teflon interlayer configuration. (C) 2011 Elsevier Ltd. All rights reserved. |
Sutcu, Mucahit; Akkurt, Sedat; Bayram, Alican; Uluca, Uluc Production of anorthite refractory insulating firebrick from mixtures of clay and recycled paper waste with sawdust addition Journal Article CERAMICS INTERNATIONAL, 38 (2), pp. 1033-1041, 2012, ISSN: 0272-8842. @article{ISI:000300472500020, title = {Production of anorthite refractory insulating firebrick from mixtures of clay and recycled paper waste with sawdust addition}, author = {Mucahit Sutcu and Sedat Akkurt and Alican Bayram and Uluc Uluca}, doi = {10.1016/j.ceramint.2011.08.027}, issn = {0272-8842}, year = {2012}, date = {2012-03-01}, journal = {CERAMICS INTERNATIONAL}, volume = {38}, number = {2}, pages = {1033-1041}, abstract = {Production of porous anorthite refractory insulating firebricks from mixtures of two different clays (K244 clay and fireclay), recycled paper processing waste and sawdust addition are investigated. Suitability of alkali-containing-clay, low-alkali fireclay, pore-making paper waste and sawdust in the products was evaluated. Prepared slurry mixtures were shaped, dried and fired. Highly porous anorthite ceramics from the mixtures with up to 30% sawdust addition were successfully produced. Physical properties such as bulk density, apparent porosity, percent linear change were investigated as well as the mechanical strengths and thermal conductivity values of the samples. Thermal conductivities of the samples produced from fireclay and recycled paper waste decreased from 0.25 W/mK (1.12 g/cm(3)) to 0.13 W/mK (0.64 g/cm(3)) with decreasing density. Samples were stable at high temperatures up to 1100 degrees C, and their cold strength was sufficiently high. The porous anorthite ceramics produced in this study can be used for insulation in high temperature applications. (C) 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Production of porous anorthite refractory insulating firebricks from mixtures of two different clays (K244 clay and fireclay), recycled paper processing waste and sawdust addition are investigated. Suitability of alkali-containing-clay, low-alkali fireclay, pore-making paper waste and sawdust in the products was evaluated. Prepared slurry mixtures were shaped, dried and fired. Highly porous anorthite ceramics from the mixtures with up to 30% sawdust addition were successfully produced. Physical properties such as bulk density, apparent porosity, percent linear change were investigated as well as the mechanical strengths and thermal conductivity values of the samples. Thermal conductivities of the samples produced from fireclay and recycled paper waste decreased from 0.25 W/mK (1.12 g/cm(3)) to 0.13 W/mK (0.64 g/cm(3)) with decreasing density. Samples were stable at high temperatures up to 1100 degrees C, and their cold strength was sufficiently high. The porous anorthite ceramics produced in this study can be used for insulation in high temperature applications. (C) 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved. |
Odaci, Ismet Kutlay; Kilicaslan, Cenk; Tasdemirci, Alper; Guden, Mustafa INTERNATIONAL JOURNAL OF CRASHWORTHINESS, 17 (5), pp. 508-518, 2012, ISSN: 1358-8265. @article{ISI:000308991800004, title = {Projectile impact testing of glass fiber-reinforced composite and layered corrugated aluminium and aluminium foam core sandwich panels: a comparative study}, author = {Ismet Kutlay Odaci and Cenk Kilicaslan and Alper Tasdemirci and Mustafa Guden}, doi = {10.1080/13588265.2012.690215}, issn = {1358-8265}, year = {2012}, date = {2012-01-01}, journal = {INTERNATIONAL JOURNAL OF CRASHWORTHINESS}, volume = {17}, number = {5}, pages = {508-518}, abstract = {E-glass/polyester composite and layered corrugated aluminium and aluminium foam core sandwich panels were projectile impact tested between 127 m/s and 190 m/s using a hardened steel sphere projectile. The corrugated aluminium cores, constructed from aluminium fin layers and aluminium interlayers and face sheets, exhibited relatively lower-plateau stresses and higher stress oscillations in the plateau region than aluminium foam cores. The applied brazing process resulted in reductions in the plateau stresses of the corrugated aluminium cores. The sandwich panels with 2- and 3-mm-thick composite face sheets and the epoxy-bonded corrugated aluminium sheet cores were perforated, while the sandwich panels with 5-mm-thick composite face sheets were penetrated in the projectile impact tests. On the other hand, the sandwich panels with aluminium foam cores were only penetrated. A simple comparison between the ballistic limits of the sandwich panels as a function of total weight revealed significant increases in the ballistic limits of the cores with the inclusion of composite face sheets. The determined higher impact resistance of the foam core sandwich panels was attributed to the relatively higher strength of the foam cores investigated and the ability to distribute the incident impulse to a relatively large area of the backing composite plate.}, keywords = {}, pubstate = {published}, tppubtype = {article} } E-glass/polyester composite and layered corrugated aluminium and aluminium foam core sandwich panels were projectile impact tested between 127 m/s and 190 m/s using a hardened steel sphere projectile. The corrugated aluminium cores, constructed from aluminium fin layers and aluminium interlayers and face sheets, exhibited relatively lower-plateau stresses and higher stress oscillations in the plateau region than aluminium foam cores. The applied brazing process resulted in reductions in the plateau stresses of the corrugated aluminium cores. The sandwich panels with 2- and 3-mm-thick composite face sheets and the epoxy-bonded corrugated aluminium sheet cores were perforated, while the sandwich panels with 5-mm-thick composite face sheets were penetrated in the projectile impact tests. On the other hand, the sandwich panels with aluminium foam cores were only penetrated. A simple comparison between the ballistic limits of the sandwich panels as a function of total weight revealed significant increases in the ballistic limits of the cores with the inclusion of composite face sheets. The determined higher impact resistance of the foam core sandwich panels was attributed to the relatively higher strength of the foam cores investigated and the ability to distribute the incident impulse to a relatively large area of the backing composite plate. |
Odaci, Ismet Kutlay; Kilicaslan, Cenk; Tasdemirci, Alper; Guden, Mustafa INTERNATIONAL JOURNAL OF CRASHWORTHINESS, 17 (5), pp. 508-518, 2012, ISSN: 1358-8265. @article{ISI:000308991800004b, title = {Projectile impact testing of glass fiber-reinforced composite and layered corrugated aluminium and aluminium foam core sandwich panels: a comparative study}, author = {Ismet Kutlay Odaci and Cenk Kilicaslan and Alper Tasdemirci and Mustafa Guden}, doi = {10.1080/13588265.2012.690215}, issn = {1358-8265}, year = {2012}, date = {2012-01-01}, journal = {INTERNATIONAL JOURNAL OF CRASHWORTHINESS}, volume = {17}, number = {5}, pages = {508-518}, abstract = {E-glass/polyester composite and layered corrugated aluminium and aluminium foam core sandwich panels were projectile impact tested between 127 m/s and 190 m/s using a hardened steel sphere projectile. The corrugated aluminium cores, constructed from aluminium fin layers and aluminium interlayers and face sheets, exhibited relatively lower-plateau stresses and higher stress oscillations in the plateau region than aluminium foam cores. The applied brazing process resulted in reductions in the plateau stresses of the corrugated aluminium cores. The sandwich panels with 2- and 3-mm-thick composite face sheets and the epoxy-bonded corrugated aluminium sheet cores were perforated, while the sandwich panels with 5-mm-thick composite face sheets were penetrated in the projectile impact tests. On the other hand, the sandwich panels with aluminium foam cores were only penetrated. A simple comparison between the ballistic limits of the sandwich panels as a function of total weight revealed significant increases in the ballistic limits of the cores with the inclusion of composite face sheets. The determined higher impact resistance of the foam core sandwich panels was attributed to the relatively higher strength of the foam cores investigated and the ability to distribute the incident impulse to a relatively large area of the backing composite plate.}, keywords = {}, pubstate = {published}, tppubtype = {article} } E-glass/polyester composite and layered corrugated aluminium and aluminium foam core sandwich panels were projectile impact tested between 127 m/s and 190 m/s using a hardened steel sphere projectile. The corrugated aluminium cores, constructed from aluminium fin layers and aluminium interlayers and face sheets, exhibited relatively lower-plateau stresses and higher stress oscillations in the plateau region than aluminium foam cores. The applied brazing process resulted in reductions in the plateau stresses of the corrugated aluminium cores. The sandwich panels with 2- and 3-mm-thick composite face sheets and the epoxy-bonded corrugated aluminium sheet cores were perforated, while the sandwich panels with 5-mm-thick composite face sheets were penetrated in the projectile impact tests. On the other hand, the sandwich panels with aluminium foam cores were only penetrated. A simple comparison between the ballistic limits of the sandwich panels as a function of total weight revealed significant increases in the ballistic limits of the cores with the inclusion of composite face sheets. The determined higher impact resistance of the foam core sandwich panels was attributed to the relatively higher strength of the foam cores investigated and the ability to distribute the incident impulse to a relatively large area of the backing composite plate. |
Kandemir, Sinan; Yalamanchili, Anurag; Atkinson, Helen V Production of Aluminium Matrix Nanocomposite Feedstock for Thixoforming by an Ultrasonic Method Inproceedings {Merklein, M; Hagenah, H} (Ed.): MATERIAL FORMING - ESAFORM 2012, PTS 1 & 2, pp. 339-344, DynaMore GmbH; GOM mbh; Hirschvogel Holding GmbH; International Journal of Material Forming; QuantorForm Ltd; Simufact Engineering GmbH; Zwick GmbH & Co KG; Friedrich Alexander Univ, Erlangen Nurnberg 2012, ISSN: 1013-9826, (15th Conference of the European Scientific Association on Material Forming, (ESAFORM 2012), Erlangen, GERMANY, MAR 14-16, 2012). @inproceedings{ISI:000309335500055, title = {Production of Aluminium Matrix Nanocomposite Feedstock for Thixoforming by an Ultrasonic Method}, author = {Sinan Kandemir and Anurag Yalamanchili and Helen V Atkinson}, editor = {M {Merklein and H} Hagenah}, doi = {10.4028/www.scientific.net/KEM.504-506.339}, issn = {1013-9826}, year = {2012}, date = {2012-01-01}, booktitle = {MATERIAL FORMING - ESAFORM 2012, PTS 1 & 2}, volume = {504-506}, pages = {339-344}, organization = {DynaMore GmbH; GOM mbh; Hirschvogel Holding GmbH; International Journal of Material Forming; QuantorForm Ltd; Simufact Engineering GmbH; Zwick GmbH & Co KG; Friedrich Alexander Univ, Erlangen Nurnberg}, series = {Key Engineering Materials}, abstract = {Metal matrix nanocomposites (MMNCs) could be strong candidates for use in the automotive and aerospace industry, where the mechanical performance is a crucial factor. This study aims to determine the feasibility of Al/SiC nanocomposite fabrication by the ultrasonic technique for the production of thixoforming feedstock material. Aluminium (A356) matrix composites were fabricated with the addition of 0.2 wt.% SiC nanoparticles using an ultrasonic method. Two different particle feeding mechanisms; the Al foil double capsulate method and the crucible placement approach, were employed. Better results were obtained for the double capsulate method. Also, Ti and Nb probe tips were tried to provide ultrasonic vibration in the melt. It has been shown that Nb is a promising ultrasonic probe tip material to produce MMNCs above 650 degrees C as it is thermodynamically stable in comparison with Ti.}, note = {15th Conference of the European Scientific Association on Material Forming, (ESAFORM 2012), Erlangen, GERMANY, MAR 14-16, 2012}, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } Metal matrix nanocomposites (MMNCs) could be strong candidates for use in the automotive and aerospace industry, where the mechanical performance is a crucial factor. This study aims to determine the feasibility of Al/SiC nanocomposite fabrication by the ultrasonic technique for the production of thixoforming feedstock material. Aluminium (A356) matrix composites were fabricated with the addition of 0.2 wt.% SiC nanoparticles using an ultrasonic method. Two different particle feeding mechanisms; the Al foil double capsulate method and the crucible placement approach, were employed. Better results were obtained for the double capsulate method. Also, Ti and Nb probe tips were tried to provide ultrasonic vibration in the melt. It has been shown that Nb is a promising ultrasonic probe tip material to produce MMNCs above 650 degrees C as it is thermodynamically stable in comparison with Ti. |
2011 |
Basturk, Bahar S; Tanoglu, Metin Mechanical and energy absorption behaviors of metal/polymer layered sandwich structures Journal Article JOURNAL OF REINFORCED PLASTICS AND COMPOSITES, 30 (18), pp. 1539-1547, 2011, ISSN: 0731-6844. @article{ISI:000297764900003, title = {Mechanical and energy absorption behaviors of metal/polymer layered sandwich structures}, author = {Bahar S Basturk and Metin Tanoglu}, doi = {10.1177/0731684411421844}, issn = {0731-6844}, year = {2011}, date = {2011-09-01}, journal = {JOURNAL OF REINFORCED PLASTICS AND COMPOSITES}, volume = {30}, number = {18}, pages = {1539-1547}, abstract = {This article considers the sandwich structures with aluminium (Al) foams of various thicknesses in conjunction with skins composed of fibre-metal laminates (FML). The FMLs with Al sheet and glass fiber reinforced polypropylene (GFPP) composites were integrated with Al foam for composing the sandwich panels. The FML-foam sandwich systems were manufactured by hot pressing in a mold at 200 degrees C under 1.5 MPa pressure. The bonding between the components of the sandwich was achieved by various surface modification techniques, i.e., silane surface treatment, PP adhesive film additition, and their combination. The Al sheet/Al foam sandwiches were also prepared by bonding the components with an epoxy adhesive for comparing the effect of GFPP on the mechanical performance of the sandwich structures. The energy absorption capacities together with compressive mechanical behavior of both Al foams and FML-foam sandwich systems were evaluated by flatwise compression tests. Experiments were performed on samples of varying foam thicknesses.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This article considers the sandwich structures with aluminium (Al) foams of various thicknesses in conjunction with skins composed of fibre-metal laminates (FML). The FMLs with Al sheet and glass fiber reinforced polypropylene (GFPP) composites were integrated with Al foam for composing the sandwich panels. The FML-foam sandwich systems were manufactured by hot pressing in a mold at 200 degrees C under 1.5 MPa pressure. The bonding between the components of the sandwich was achieved by various surface modification techniques, i.e., silane surface treatment, PP adhesive film additition, and their combination. The Al sheet/Al foam sandwiches were also prepared by bonding the components with an epoxy adhesive for comparing the effect of GFPP on the mechanical performance of the sandwich structures. The energy absorption capacities together with compressive mechanical behavior of both Al foams and FML-foam sandwich systems were evaluated by flatwise compression tests. Experiments were performed on samples of varying foam thicknesses. |
Yalamac, Emre; Carry, Claude; Akkurt, Sedat Microstructural development of interface layers between co-sintered alumina and spinel compacts Journal Article JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 31 (9), pp. 1649-1659, 2011, ISSN: 0955-2219. @article{ISI:000291143400015, title = {Microstructural development of interface layers between co-sintered alumina and spinel compacts}, author = {Emre Yalamac and Claude Carry and Sedat Akkurt}, doi = {10.1016/j.jeurceramsoc.2011.03.020}, issn = {0955-2219}, year = {2011}, date = {2011-08-01}, journal = {JOURNAL OF THE EUROPEAN CERAMIC SOCIETY}, volume = {31}, number = {9}, pages = {1649-1659}, abstract = {Tests were performed to investigate the microstructure of the interface between alumina and spinel materials after high temperature thermal treatment (1500 degrees C). The first test involved co-sintering of co-pressed alumina and spinel compacts. Microstructures were investigated by SEM, EDS, WDS and EBSD. A microstructurally distinct layer with columnar grains of up to 40 mu m length and 5 mu m width was observed after 16 h at 1500 degrees C. Growth rate of the columnar spinel grains from parent spinet towards alumina follows parabolic kinetics, controlled by a mixed process of O(2-) ion diffusion and interface reaction. Diffusion couples of spinel and alumina were investigated. Same columnar spinel grains were observed at the interface which grew into alumina during thermal treatment with the same kinetics as in co-sintering experiments. The shape of the phase boundaries between spinel and alumina can be a further indication of the direction of their growth. (C) 2011 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Tests were performed to investigate the microstructure of the interface between alumina and spinel materials after high temperature thermal treatment (1500 degrees C). The first test involved co-sintering of co-pressed alumina and spinel compacts. Microstructures were investigated by SEM, EDS, WDS and EBSD. A microstructurally distinct layer with columnar grains of up to 40 mu m length and 5 mu m width was observed after 16 h at 1500 degrees C. Growth rate of the columnar spinel grains from parent spinet towards alumina follows parabolic kinetics, controlled by a mixed process of O(2-) ion diffusion and interface reaction. Diffusion couples of spinel and alumina were investigated. Same columnar spinel grains were observed at the interface which grew into alumina during thermal treatment with the same kinetics as in co-sintering experiments. The shape of the phase boundaries between spinel and alumina can be a further indication of the direction of their growth. (C) 2011 Elsevier Ltd. All rights reserved. |
Turkan, Ugur; Guden, Mustafa The effect of surface treatment on CaP deposition of Ti6Al4V open cell foams in SBF solution (vol 39, pg 1805, 2010) Journal Article CERAMICS INTERNATIONAL, 37 (2), pp. 693, 2011, ISSN: 0272-8842. @article{ISI:000286957900040, title = {The effect of surface treatment on CaP deposition of Ti6Al4V open cell foams in SBF solution (vol 39, pg 1805, 2010)}, author = {Ugur Turkan and Mustafa Guden}, doi = {10.1016/j.ceramint.2010.07.002}, issn = {0272-8842}, year = {2011}, date = {2011-03-01}, journal = {CERAMICS INTERNATIONAL}, volume = {37}, number = {2}, pages = {693}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Durmus, A; Guden, M; Gulcimen, B; Ulku, S; Musa, E Experimental investigations on the ballistic impact performances of cold rolled sheet metals Journal Article MATERIALS & DESIGN, 32 (3), pp. 1356-1366, 2011, ISSN: 0261-3069. @article{ISI:000286904200033, title = {Experimental investigations on the ballistic impact performances of cold rolled sheet metals}, author = {A Durmus and M Guden and B Gulcimen and S Ulku and E Musa}, doi = {10.1016/j.matdes.2010.09.016}, issn = {0261-3069}, year = {2011}, date = {2011-03-01}, journal = {MATERIALS & DESIGN}, volume = {32}, number = {3}, pages = {1356-1366}, abstract = {This study focuses on the ballistic performances of 1 and 2 mm-thick and 2 x 1 mm-thick cold rolled sheet metal plates against 9 mm standard NATO projectile. The velocity of the projectile before and after perforation, the diameter of the front face deformation, the depth of the crater and the diameter of the hole were measured. The fracture surfaces of the plates near the ballistic limit were also microscopically analyzed. The highest ballistic limit was found in 2 mm-thick plate (332 m s(-1)) and the lowest in 1 mm-thick plate (97 m s(-1)). While, the ballistic limit of 2 x 1 mm-thick plate decreased to 306 m s(-1). Typical failure mechanism of the projectile was the flattening and mushrooming at relatively low velocities and the separation from the jacket at relatively high velocities. In accord with the ballistic limits, 2 mm-thick target plate exhibited the highest hardness value. Microscopic investigations showed the significant reductions in the grain size of the targets after the test. (C) 2010 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This study focuses on the ballistic performances of 1 and 2 mm-thick and 2 x 1 mm-thick cold rolled sheet metal plates against 9 mm standard NATO projectile. The velocity of the projectile before and after perforation, the diameter of the front face deformation, the depth of the crater and the diameter of the hole were measured. The fracture surfaces of the plates near the ballistic limit were also microscopically analyzed. The highest ballistic limit was found in 2 mm-thick plate (332 m s(-1)) and the lowest in 1 mm-thick plate (97 m s(-1)). While, the ballistic limit of 2 x 1 mm-thick plate decreased to 306 m s(-1). Typical failure mechanism of the projectile was the flattening and mushrooming at relatively low velocities and the separation from the jacket at relatively high velocities. In accord with the ballistic limits, 2 mm-thick target plate exhibited the highest hardness value. Microscopic investigations showed the significant reductions in the grain size of the targets after the test. (C) 2010 Elsevier Ltd. All rights reserved. |
Depboylu, Can O; Yilmaz, Selahattin; Akkurt, Sedat Effects of Catalyst Precursor Type and Preparation Conditions, and Solvent Type on Activity and Selectivity of Pt/SiO2 Catalyst in Citral Hydrogenation Journal Article INTERNATIONAL JOURNAL OF CHEMICAL REACTOR ENGINEERING, 9 , 2011, ISSN: 1542-6580. @article{ISI:000289118100001, title = {Effects of Catalyst Precursor Type and Preparation Conditions, and Solvent Type on Activity and Selectivity of Pt/SiO2 Catalyst in Citral Hydrogenation}, author = {Can O Depboylu and Selahattin Yilmaz and Sedat Akkurt}, issn = {1542-6580}, year = {2011}, date = {2011-01-01}, journal = {INTERNATIONAL JOURNAL OF CHEMICAL REACTOR ENGINEERING}, volume = {9}, abstract = {In this study, citral hydrogenation reaction in liquid phase over silica gel supported Pt catalysts was investigated. It was desired to hydrogenate carbonyl group selectively to produce valuable unsaturated alcohols, namely geraniol and nerol. Pt/SiO2 catalysts were prepared by impregnation method. The effects of parameters investigated in the present study included Pt precursor type (hexachloroplatinic acid (HCLPA), platinum II acetylacetonate (PAA)), catalyst activation temperature (350 degrees C and 450 degrees C), catalyst activation without calcination, catalyst washing with 0.1 M NaOH and solvent type (ethanol, 2-pentanol). The catalysts activities and selectivities were affected by the type of precursor and activation temperature. The maximum citral conversion (89.50 percent) was achieved at lower activation temperature (350 degrees C) with PAA precursor based catalyst. It was observed that higher activation temperature provided lower citral conversion but higher selectivity to unsaturated alcohols; increasing the activation temperature to 450 degrees C decreased citral conversion to 26.10 percent. But selectivity to unsaturated alcohols, geraniol and nerol, increased from 7.06 to 54.60 percent. Catalyst washing and 2-pentanol prevented acetal formation. Catalyst activation without calcination gave lower citral conversion (20.84 percent) and selectivity to unsaturated alcohols (30.00 percent).}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, citral hydrogenation reaction in liquid phase over silica gel supported Pt catalysts was investigated. It was desired to hydrogenate carbonyl group selectively to produce valuable unsaturated alcohols, namely geraniol and nerol. Pt/SiO2 catalysts were prepared by impregnation method. The effects of parameters investigated in the present study included Pt precursor type (hexachloroplatinic acid (HCLPA), platinum II acetylacetonate (PAA)), catalyst activation temperature (350 degrees C and 450 degrees C), catalyst activation without calcination, catalyst washing with 0.1 M NaOH and solvent type (ethanol, 2-pentanol). The catalysts activities and selectivities were affected by the type of precursor and activation temperature. The maximum citral conversion (89.50 percent) was achieved at lower activation temperature (350 degrees C) with PAA precursor based catalyst. It was observed that higher activation temperature provided lower citral conversion but higher selectivity to unsaturated alcohols; increasing the activation temperature to 450 degrees C decreased citral conversion to 26.10 percent. But selectivity to unsaturated alcohols, geraniol and nerol, increased from 7.06 to 54.60 percent. Catalyst washing and 2-pentanol prevented acetal formation. Catalyst activation without calcination gave lower citral conversion (20.84 percent) and selectivity to unsaturated alcohols (30.00 percent). |
Toksoy, A K; Guden, M The optimisation of the energy absorption of partially Al foam-filled commercial 1050H14 and 6061T4 Al crash boxes Journal Article INTERNATIONAL JOURNAL OF CRASHWORTHINESS, 16 (1), pp. 97-109, 2011, ISSN: 1358-8265. @article{ISI:000288960900009, title = {The optimisation of the energy absorption of partially Al foam-filled commercial 1050H14 and 6061T4 Al crash boxes}, author = {A K Toksoy and M Guden}, doi = {10.1080/13588265.2010.514774}, issn = {1358-8265}, year = {2011}, date = {2011-01-01}, journal = {INTERNATIONAL JOURNAL OF CRASHWORTHINESS}, volume = {16}, number = {1}, pages = {97-109}, abstract = {Partially Alulight and Hydro Al closed-cell foam-filled commercial 1050H14 Al and 6061T4 Al crash boxes were optimised using the response surface methodology in order to maximise specific energy absorption (SEA). The quasi-static crushing of empty and filled crash boxes was simulated using LS-DYNA, and the results were further confirmed with experimental quasi-static crushing testing of empty and Alulight foam-filled commercial 1050H14 Al crash boxes. Results showed that partial foam filling of commercial crash boxes increased both SEA and mean load because of foam filler axial and lateral deformation in between the progressing folds of the crash box. Within the studied constraint range of box mean load, box wall thickness and foam filler density, the optimised Alulight and Hydro foam-filled 1050H14 and 6061T4 crash boxes resulted in 26%-40% increase in total energy absorption as compared with empty crash boxes. Considering the same weight basis, the use of a higher yield strength box wall material and higher plateau stresses of Al foam filler resulted in higher energy absorptions in partial foam-filled boxes at relatively low displacements.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Partially Alulight and Hydro Al closed-cell foam-filled commercial 1050H14 Al and 6061T4 Al crash boxes were optimised using the response surface methodology in order to maximise specific energy absorption (SEA). The quasi-static crushing of empty and filled crash boxes was simulated using LS-DYNA, and the results were further confirmed with experimental quasi-static crushing testing of empty and Alulight foam-filled commercial 1050H14 Al crash boxes. Results showed that partial foam filling of commercial crash boxes increased both SEA and mean load because of foam filler axial and lateral deformation in between the progressing folds of the crash box. Within the studied constraint range of box mean load, box wall thickness and foam filler density, the optimised Alulight and Hydro foam-filled 1050H14 and 6061T4 crash boxes resulted in 26%-40% increase in total energy absorption as compared with empty crash boxes. Considering the same weight basis, the use of a higher yield strength box wall material and higher plateau stresses of Al foam filler resulted in higher energy absorptions in partial foam-filled boxes at relatively low displacements. |
2010 |
Turkan, U; Guden, M The effect of nitric acid surface treatment on CaP deposition of Ti6Al4V open-cell foams in SBF solution Journal Article SURFACE & COATINGS TECHNOLOGY, 205 (7), pp. 1904-1916, 2010, ISSN: 0257-8972. @article{ISI:000286343100017, title = {The effect of nitric acid surface treatment on CaP deposition of Ti6Al4V open-cell foams in SBF solution}, author = {U Turkan and M Guden}, doi = {10.1016/j.surfcoat.2010.08.071}, issn = {0257-8972}, year = {2010}, date = {2010-12-01}, journal = {SURFACE & COATINGS TECHNOLOGY}, volume = {205}, number = {7}, pages = {1904-1916}, abstract = {The effect of nitric acid surface treatment on CaP deposition of an open-cell Ti6Al4V foam (60% porous and 300-500 m in pore size), prepared by means of the space holder method using 94 and 66 mu m average particle size powders, was investigated in a simulated body fluid (SBF) solution up to 14 days. Although, nitric acid surface treatment did not change the foam flat surface roughness values significantly, it increased surface area difference greatly by introducing nano scale undulations on the surface. The increased surface area difference was found to be more pronounced in smaller particle size foam samples. A continuous relatively thin CaP coating layer formed after 5 and 14 days of SBF immersion in nitric acid surface treated small and larger average particle size foam specimens, respectively. Whereas, the cells of untreated foam specimen were observed to be filled with CaP precipitates and a continuous CaP layer development was found after 14 days of SBF immersion. These results were also confirmed with the grazing incidence XRD and FTIR analysis of SBF immersed specimens. (C) 2010 Elsevier B.V. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The effect of nitric acid surface treatment on CaP deposition of an open-cell Ti6Al4V foam (60% porous and 300-500 m in pore size), prepared by means of the space holder method using 94 and 66 mu m average particle size powders, was investigated in a simulated body fluid (SBF) solution up to 14 days. Although, nitric acid surface treatment did not change the foam flat surface roughness values significantly, it increased surface area difference greatly by introducing nano scale undulations on the surface. The increased surface area difference was found to be more pronounced in smaller particle size foam samples. A continuous relatively thin CaP coating layer formed after 5 and 14 days of SBF immersion in nitric acid surface treated small and larger average particle size foam specimens, respectively. Whereas, the cells of untreated foam specimen were observed to be filled with CaP precipitates and a continuous CaP layer development was found after 14 days of SBF immersion. These results were also confirmed with the grazing incidence XRD and FTIR analysis of SBF immersed specimens. (C) 2010 Elsevier B.V. All rights reserved. |
Yurdakul, Hilmi; Seyhan, Tugrul A; Turan, Servet; Tanoglu, Metin; Bauhofer, Wolfgang; Schulte, Karl Electric field effects on CNTs/vinyl ester suspensions and the resulting electrical and thermal composite properties Journal Article COMPOSITES SCIENCE AND TECHNOLOGY, 70 (14), pp. 2102-2110, 2010, ISSN: 0266-3538. @article{ISI:000283759400010, title = {Electric field effects on CNTs/vinyl ester suspensions and the resulting electrical and thermal composite properties}, author = {Hilmi Yurdakul and Tugrul A Seyhan and Servet Turan and Metin Tanoglu and Wolfgang Bauhofer and Karl Schulte}, doi = {10.1016/j.compscitech.2010.08.007}, issn = {0266-3538}, year = {2010}, date = {2010-11-01}, journal = {COMPOSITES SCIENCE AND TECHNOLOGY}, volume = {70}, number = {14}, pages = {2102-2110}, abstract = {In this study, electrical conductivity of a vinyl ester based composite containing low content (0.05, 0.1 and 0.3 wt.%) of double and multi-walled carbon nanotubes with and without amine functional groups (DWCNTs, MWCNTs, DWCNT-NH2 and MWCNT-NH2) was investigated. The composite with pristine MWCNTs was found to exhibit the highest electrical conductivity. Experiments aimed to induce an aligned conductive network with application of an alternating current (AC) electric field during cure were carried out on the resin suspensions with MWCNTs. Formation of electric anisotropy within the composite was verified. Light microscopy (LM), scanning electron (SEM) and transmission electron microscopy (TEM) were conducted to visualize dispersion state and the extent of alignment of MWCNTs within the polymer cured with and without application of the electric field. To gain a better understanding of electric field induced effects, glass transition temperature (T-g) of the composites was measured via Differential Scanning Calorimetry (DSC). It was determined that at 0.05 wt.% loading rate of MWCNTs, the composites, cured with application of the AC electric field, possessed a higher T-g than the composites cured without application of the AC electric field. (C) 2010 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, electrical conductivity of a vinyl ester based composite containing low content (0.05, 0.1 and 0.3 wt.%) of double and multi-walled carbon nanotubes with and without amine functional groups (DWCNTs, MWCNTs, DWCNT-NH2 and MWCNT-NH2) was investigated. The composite with pristine MWCNTs was found to exhibit the highest electrical conductivity. Experiments aimed to induce an aligned conductive network with application of an alternating current (AC) electric field during cure were carried out on the resin suspensions with MWCNTs. Formation of electric anisotropy within the composite was verified. Light microscopy (LM), scanning electron (SEM) and transmission electron microscopy (TEM) were conducted to visualize dispersion state and the extent of alignment of MWCNTs within the polymer cured with and without application of the electric field. To gain a better understanding of electric field induced effects, glass transition temperature (T-g) of the composites was measured via Differential Scanning Calorimetry (DSC). It was determined that at 0.05 wt.% loading rate of MWCNTs, the composites, cured with application of the AC electric field, possessed a higher T-g than the composites cured without application of the AC electric field. (C) 2010 Elsevier Ltd. All rights reserved. |
Turkan, Ugur; Guden, Mustafa The effect of surface treatment on CaP deposition of Ti6Al4V open cell foams in SBF solution Journal Article CERAMICS INTERNATIONAL, 36 (6), pp. 1805-1816, 2010, ISSN: 0272-8842. @article{ISI:000280027800008, title = {The effect of surface treatment on CaP deposition of Ti6Al4V open cell foams in SBF solution}, author = {Ugur Turkan and Mustafa Guden}, doi = {10.1016/j.ceramint.2010.03.030}, issn = {0272-8842}, year = {2010}, date = {2010-08-01}, journal = {CERAMICS INTERNATIONAL}, volume = {36}, number = {6}, pages = {1805-1816}, abstract = {The effects of alkali and nitric acid surface treatment and acid etching on the CaP deposition of an open cell Ti6Al4V foam (60% porous and 300-500 mu m in pore size) developed for biomedical applications were investigated in a simulated body fluid (SBF) solution for 14-day. The surface roughness of the foam specimens ground flat surfaces was measured in nano-metric scale before and after SBF immersion using an atomic force microscope (AFM). A significant increase in the surface roughness of alkali treated foam specimen after SBF immersion indicated a smaller crystal size CaP deposition, which was also confirmed by the AFM micrographs. The microscopic evaluation clearly showed that alkali treatment and nitric acid treatment induced a continuous, uniform CaP deposition on the cell wall surfaces of the foam (interior of cells). While in untreated foam specimen the cells are filled with CaP precipitates and acid etching did not produce a continuous coating layer on particles interior of the cells. The coating layer thickness was similar to 3 mu m in alkali treated foam specimens after 14-day of SBF immersion, while nitric acid treatment induced relatively thinner coating layer, 0.6 mu m. (C) 2010 Elsevier Ltd and Techna Group S.r.l. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The effects of alkali and nitric acid surface treatment and acid etching on the CaP deposition of an open cell Ti6Al4V foam (60% porous and 300-500 mu m in pore size) developed for biomedical applications were investigated in a simulated body fluid (SBF) solution for 14-day. The surface roughness of the foam specimens ground flat surfaces was measured in nano-metric scale before and after SBF immersion using an atomic force microscope (AFM). A significant increase in the surface roughness of alkali treated foam specimen after SBF immersion indicated a smaller crystal size CaP deposition, which was also confirmed by the AFM micrographs. The microscopic evaluation clearly showed that alkali treatment and nitric acid treatment induced a continuous, uniform CaP deposition on the cell wall surfaces of the foam (interior of cells). While in untreated foam specimen the cells are filled with CaP precipitates and acid etching did not produce a continuous coating layer on particles interior of the cells. The coating layer thickness was similar to 3 mu m in alkali treated foam specimens after 14-day of SBF immersion, while nitric acid treatment induced relatively thinner coating layer, 0.6 mu m. (C) 2010 Elsevier Ltd and Techna Group S.r.l. All rights reserved. |
Budak, Meral; Akkurt, Sedat; Boeke, Hasan Evaluation of heat treated clay for potential use in intervention mortars Journal Article APPLIED CLAY SCIENCE, 49 (4, SI), pp. 414-419, 2010, ISSN: 0169-1317. @article{ISI:000281425700010, title = {Evaluation of heat treated clay for potential use in intervention mortars}, author = {Meral Budak and Sedat Akkurt and Hasan Boeke}, doi = {10.1016/j.clay.2009.11.031}, issn = {0169-1317}, year = {2010}, date = {2010-08-01}, journal = {APPLIED CLAY SCIENCE}, volume = {49}, number = {4, SI}, pages = {414-419}, abstract = {In this study, raw material compositions, basic physical, mineralogical, microstructural and hydraulic properties of lime mortars used in two selected historic buildings were determined by XRD, SEM-EDS and TGA analyses. The results showed that the mortars were hydraulic due to the use of pozzolanic aggregates. Taking into account the hydraulic characteristics of mortars due to the use of pozzolanic aggregates, the possibility of obtaining hydraulic mortars by using pozzolanic aggregates produced from heated commercial clays was investigated. For this purpose, four clay samples used in the ceramic industry in Turkey were heated at varying temperatures of 400, 450, 500, 550, 600, 800, and 1200 degrees C with a heating rate of 10 degrees C/min. Pozzolanic properties of heated clay samples were determined. The results showed that commercial clays studied are well suited for use as pozzolanic aggregates when they are heated between 500 and 700 degrees C. This is also confirmed by testing the compressive strengths of the three month aged laboratory-produced mortars that contained thermally treated clay (at 600 degrees C) as pozzolanic aggregates. Compressive strength of this mortar was around 5 MPa which is satisfactorily high. (C) 2009 Elsevier B.V. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, raw material compositions, basic physical, mineralogical, microstructural and hydraulic properties of lime mortars used in two selected historic buildings were determined by XRD, SEM-EDS and TGA analyses. The results showed that the mortars were hydraulic due to the use of pozzolanic aggregates. Taking into account the hydraulic characteristics of mortars due to the use of pozzolanic aggregates, the possibility of obtaining hydraulic mortars by using pozzolanic aggregates produced from heated commercial clays was investigated. For this purpose, four clay samples used in the ceramic industry in Turkey were heated at varying temperatures of 400, 450, 500, 550, 600, 800, and 1200 degrees C with a heating rate of 10 degrees C/min. Pozzolanic properties of heated clay samples were determined. The results showed that commercial clays studied are well suited for use as pozzolanic aggregates when they are heated between 500 and 700 degrees C. This is also confirmed by testing the compressive strengths of the three month aged laboratory-produced mortars that contained thermally treated clay (at 600 degrees C) as pozzolanic aggregates. Compressive strength of this mortar was around 5 MPa which is satisfactorily high. (C) 2009 Elsevier B.V. All rights reserved. |
Sutcu, Mucahit; Akkurt, Sedat; Okur, Salih A microstructural study of surface hydration on a magnesia refractory Journal Article CERAMICS INTERNATIONAL, 36 (5), pp. 1731-1735, 2010, ISSN: 0272-8842. @article{ISI:000278432800035, title = {A microstructural study of surface hydration on a magnesia refractory}, author = {Mucahit Sutcu and Sedat Akkurt and Salih Okur}, doi = {10.1016/j.ceramint.2010.02.043}, issn = {0272-8842}, year = {2010}, date = {2010-07-01}, journal = {CERAMICS INTERNATIONAL}, volume = {36}, number = {5}, pages = {1731-1735}, abstract = {Hydration of the surface of a periclase refractory was studied in a controlled humidity atmosphere (92% relative humidity) at 26 degrees C for up to 92 h. The effect of humidity on the specimens was examined using a scanning probe microscope (SPM) and a scanning electron microscope (SEM), which showed that the degree of hydration was noticeably less in the intergranular bond phase compared to the periclase crystallites. The SPM study indicated significant growth of hydrates on the refractory grain surface. Growth rate of the hydrate layer was least on (0 0 1) orientation, higher for the (1 0 3) orientation, and highest for the (1 0 1) oriented grain. The rate of loss of refractory phases by hydration on a (1 0 1) oriented grain was 4.53 nm/h. This material loss may be insignificant for a bulk brick, but is a serious threat for a magnesia castable consisting of fine magnesia powder due to large surface area exposed to humidity or water itself. (C) 2010 Elsevier Ltd and Techna Group S.r.l. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Hydration of the surface of a periclase refractory was studied in a controlled humidity atmosphere (92% relative humidity) at 26 degrees C for up to 92 h. The effect of humidity on the specimens was examined using a scanning probe microscope (SPM) and a scanning electron microscope (SEM), which showed that the degree of hydration was noticeably less in the intergranular bond phase compared to the periclase crystallites. The SPM study indicated significant growth of hydrates on the refractory grain surface. Growth rate of the hydrate layer was least on (0 0 1) orientation, higher for the (1 0 3) orientation, and highest for the (1 0 1) oriented grain. The rate of loss of refractory phases by hydration on a (1 0 1) oriented grain was 4.53 nm/h. This material loss may be insignificant for a bulk brick, but is a serious threat for a magnesia castable consisting of fine magnesia powder due to large surface area exposed to humidity or water itself. (C) 2010 Elsevier Ltd and Techna Group S.r.l. All rights reserved. |
Ozyildiz, E; Guden, M; Uzel, A; Karaboz, I; Akil, O; Bulut, H Antimicrobial Activity of TiO2-coated Orthodontic Ceramic Brackets against Streptococcus mutans and Candida albicans Journal Article BIOTECHNOLOGY AND BIOPROCESS ENGINEERING, 15 (4), pp. 680-685, 2010, ISSN: 1226-8372. @article{ISI:000281514400022, title = {Antimicrobial Activity of TiO2-coated Orthodontic Ceramic Brackets against Streptococcus mutans and Candida albicans}, author = {E Ozyildiz and M Guden and A Uzel and I Karaboz and O Akil and H Bulut}, doi = {10.1007/s12257-009-3005-4}, issn = {1226-8372}, year = {2010}, date = {2010-07-01}, journal = {BIOTECHNOLOGY AND BIOPROCESS ENGINEERING}, volume = {15}, number = {4}, pages = {680-685}, abstract = {Polycrystalline alumina ceramic orthodontic brackets were coated with anatase TiO2 film via a sol-gel dip-coating method. The surface structure morphology and composition of the films were evaluated via scanning electron microscopy, atomic force microscopy, and X-ray diffraction. The antimicrobial activity of the ceramic brackets was assessed against two oral pathogens, S. mutans and C. albicans. The results demonstrated that TiO2-coated brackets exposed to low energy UV-A illumination efficiently reduced the populations of test microorganisms relative to the uncoated brackets. The reduction efficiencies were 98% for S. mutans ATCC 10449 and 93% for C. albicans ATCC 60193.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Polycrystalline alumina ceramic orthodontic brackets were coated with anatase TiO2 film via a sol-gel dip-coating method. The surface structure morphology and composition of the films were evaluated via scanning electron microscopy, atomic force microscopy, and X-ray diffraction. The antimicrobial activity of the ceramic brackets was assessed against two oral pathogens, S. mutans and C. albicans. The results demonstrated that TiO2-coated brackets exposed to low energy UV-A illumination efficiently reduced the populations of test microorganisms relative to the uncoated brackets. The reduction efficiencies were 98% for S. mutans ATCC 10449 and 93% for C. albicans ATCC 60193. |
Toksoy, A K; Guden, M Partial Al foam filling of commercial 1050H14 Al crash boxes: The effect of box column thickness and foam relative density on energy absorption Journal Article THIN-WALLED STRUCTURES, 48 (7), pp. 482-494, 2010, ISSN: 0263-8231. @article{ISI:000278670400002, title = {Partial Al foam filling of commercial 1050H14 Al crash boxes: The effect of box column thickness and foam relative density on energy absorption}, author = {A K Toksoy and M Guden}, doi = {10.1016/j.tws.2010.02.002}, issn = {0263-8231}, year = {2010}, date = {2010-07-01}, journal = {THIN-WALLED STRUCTURES}, volume = {48}, number = {7}, pages = {482-494}, abstract = {The crushing behavior of partially Al closed-cell foam filled commercial 1050H14 Al crash boxes was determined at quasi-static and dynamic deformation velocities. The quasi-static and dynamic crushing of the boxes were simulated using the LS-DYNA. The results showed that partial foam filling tended to change the deformation mode of empty boxes from a non-sequential to a sequential folding mode. In general, the experimental and simulation results showed similar mean load values and deformation modes. The SEA values of empty, partially and fully foam filled boxes were predicted as function of box wall thickness between 1 and 3 mm and foam filler relative density between 0 and 0.2, using the analytical equations developed for the mean crushing loads. The analysis indicated that both fully and partially foam filled boxes were energetically more efficient than empty boxes above a critical foam filler relative density. Partial foam filling, however, decreases the critical foam filler density at increasing box wall thicknesses. (C) 2010 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The crushing behavior of partially Al closed-cell foam filled commercial 1050H14 Al crash boxes was determined at quasi-static and dynamic deformation velocities. The quasi-static and dynamic crushing of the boxes were simulated using the LS-DYNA. The results showed that partial foam filling tended to change the deformation mode of empty boxes from a non-sequential to a sequential folding mode. In general, the experimental and simulation results showed similar mean load values and deformation modes. The SEA values of empty, partially and fully foam filled boxes were predicted as function of box wall thickness between 1 and 3 mm and foam filler relative density between 0 and 0.2, using the analytical equations developed for the mean crushing loads. The analysis indicated that both fully and partially foam filled boxes were energetically more efficient than empty boxes above a critical foam filler relative density. Partial foam filling, however, decreases the critical foam filler density at increasing box wall thicknesses. (C) 2010 Elsevier Ltd. All rights reserved. |
Sutcu, Mucahit; Akkurt, Sedat Utilization of recycled paper processing residues and clay of different sources for the production of porous anorthite ceramics Journal Article JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 30 (8), pp. 1785-1793, 2010, ISSN: 0955-2219. @article{ISI:000276563600003, title = {Utilization of recycled paper processing residues and clay of different sources for the production of porous anorthite ceramics}, author = {Mucahit Sutcu and Sedat Akkurt}, doi = {10.1016/j.jeurceramsoc.2010.01.038}, issn = {0955-2219}, year = {2010}, date = {2010-06-01}, journal = {JOURNAL OF THE EUROPEAN CERAMIC SOCIETY}, volume = {30}, number = {8}, pages = {1785-1793}, abstract = {Production of porous anorthite ceramics from mixtures of paper processing residues and three different clays are investigated. Suitability of three different clays such as enriched clay, commercial clay and fireclay for manufacturing of anorthite based lightweight refractory bricks was studied. Porous character to the ceramic was provided by addition of paper processing residues (PPR). Samples with 30-40 wt% PPR fired at 1200-1400 degrees C contained anorthite (CaO center dot Al2O3 center dot 2SiO(2)) as major phase and some minor secondary phases such as mullite (3Al(2)O(3)center dot 2SiO(2)) or gehlenite (2CaO center dot Al2O3 center dot SiO2), depending on the calcite to clay ratio. Anorthite formation for all clay types was quite successful in samples with 30-40 wt% of paper residues fired at 1300 degrees C. A higher firing temperature of 1400 degrees C was needed for the fireclay added samples to produce a well sintered product with large pores. Gehlenite phase occurred mostly at lower temperatures and in samples containing higher amount of calcium (50 wt% PPR). Compressive strength of compacted and fired pellets consisting of mainly anorthite ranged from 8 to 43 MPa. (C) 2010 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Production of porous anorthite ceramics from mixtures of paper processing residues and three different clays are investigated. Suitability of three different clays such as enriched clay, commercial clay and fireclay for manufacturing of anorthite based lightweight refractory bricks was studied. Porous character to the ceramic was provided by addition of paper processing residues (PPR). Samples with 30-40 wt% PPR fired at 1200-1400 degrees C contained anorthite (CaO center dot Al2O3 center dot 2SiO(2)) as major phase and some minor secondary phases such as mullite (3Al(2)O(3)center dot 2SiO(2)) or gehlenite (2CaO center dot Al2O3 center dot SiO2), depending on the calcite to clay ratio. Anorthite formation for all clay types was quite successful in samples with 30-40 wt% of paper residues fired at 1300 degrees C. A higher firing temperature of 1400 degrees C was needed for the fireclay added samples to produce a well sintered product with large pores. Gehlenite phase occurred mostly at lower temperatures and in samples containing higher amount of calcium (50 wt% PPR). Compressive strength of compacted and fired pellets consisting of mainly anorthite ranged from 8 to 43 MPa. (C) 2010 Elsevier Ltd. All rights reserved. |
Sezgin, F E; Tanoglu, M; Egilmez, O O; Donmez, C Mechanical Behavior of Polypropylene-based Honeycomb-Core Composite Sandwich Structures Journal Article JOURNAL OF REINFORCED PLASTICS AND COMPOSITES, 29 (10), pp. 1569-1579, 2010, ISSN: 0731-6844. @article{ISI:000278117500013, title = {Mechanical Behavior of Polypropylene-based Honeycomb-Core Composite Sandwich Structures}, author = {F E Sezgin and M Tanoglu and O O Egilmez and C Donmez}, doi = {10.1177/0731684409341674}, issn = {0731-6844}, year = {2010}, date = {2010-05-01}, journal = {JOURNAL OF REINFORCED PLASTICS AND COMPOSITES}, volume = {29}, number = {10}, pages = {1569-1579}, abstract = {This article presents results from an experimental study, investigating the effects of core thickness on the mechanical properties of composite sandwich structures with polypropylene( PP)-based honeycomb core and glass fiber-reinforced polymer (GFRP) face-sheets fabricated by hand lay-up technique. Epoxy matrix and non-crimp glass fibers were used for the production of GFRP laminates. Flatwise compression (FC), edgewise compression (EC), three-point bending (3PB) and double cantilever beam (DCB) tests were performed to evaluate the mechanical behavior of the composite sandwich structures (CSSs). Based on the FC tests, an increase in the compressive modulus and strength was observed with an increase in the core thickness. For EC tests, peak loads up to crush of the sandwich panel is discussed using core thickness. According to the 3PB tests, a decrease in core shear stress and facesheet bending stress was observed as the core thickness increases.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This article presents results from an experimental study, investigating the effects of core thickness on the mechanical properties of composite sandwich structures with polypropylene( PP)-based honeycomb core and glass fiber-reinforced polymer (GFRP) face-sheets fabricated by hand lay-up technique. Epoxy matrix and non-crimp glass fibers were used for the production of GFRP laminates. Flatwise compression (FC), edgewise compression (EC), three-point bending (3PB) and double cantilever beam (DCB) tests were performed to evaluate the mechanical behavior of the composite sandwich structures (CSSs). Based on the FC tests, an increase in the compressive modulus and strength was observed with an increase in the core thickness. For EC tests, peak loads up to crush of the sandwich panel is discussed using core thickness. According to the 3PB tests, a decrease in core shear stress and facesheet bending stress was observed as the core thickness increases. |
Coskun, Selim; Ovecoglu, Lutfi M; Ozkal, Burak; Tanoglu, Metin Characterization investigations during mechanical alloying and sintering of W-20 vol% SiC composites Journal Article JOURNAL OF ALLOYS AND COMPOUNDS, 492 (1-2), pp. 576-584, 2010, ISSN: 0925-8388. @article{ISI:000276018900125, title = {Characterization investigations during mechanical alloying and sintering of W-20 vol% SiC composites}, author = {Selim Coskun and Lutfi M Ovecoglu and Burak Ozkal and Metin Tanoglu}, doi = {10.1016/j.jallcom.2009.11.185}, issn = {0925-8388}, year = {2010}, date = {2010-03-01}, journal = {JOURNAL OF ALLOYS AND COMPOUNDS}, volume = {492}, number = {1-2}, pages = {576-584}, abstract = {The effect of mechanical alloying and the sintering regime on the microstructural and the physical properties of W-SiC composites were investigated. Powder mixtures of W-20 vol.% SiC were mechanically alloyed (MA'd) using a Spex mill for 3 h, 6 h and 24 h. MA'd powders were characterized by Laser Diffraction Particle Size Analyzer, SEM and XRD investigations. MA'd W-20 vol.% SiC powder composites were sintered under inert Ar and reducing H(2) gas conditions at 1680 degrees C and 1770 degrees C for 1 h. The microstructural and mechanical characterizations of the sintered samples were carried out by scanning electron microscope (SEM) and X-ray diffraction (XRD) and Vickers Hardness analyses. The addition of SiC remarkably increases the hardness of the composites. Hardness is also increased with decreasing grain size and increasing amount of MA. (C) 2009 Elsevier B.V. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The effect of mechanical alloying and the sintering regime on the microstructural and the physical properties of W-SiC composites were investigated. Powder mixtures of W-20 vol.% SiC were mechanically alloyed (MA'd) using a Spex mill for 3 h, 6 h and 24 h. MA'd powders were characterized by Laser Diffraction Particle Size Analyzer, SEM and XRD investigations. MA'd W-20 vol.% SiC powder composites were sintered under inert Ar and reducing H(2) gas conditions at 1680 degrees C and 1770 degrees C for 1 h. The microstructural and mechanical characterizations of the sintered samples were carried out by scanning electron microscope (SEM) and X-ray diffraction (XRD) and Vickers Hardness analyses. The addition of SiC remarkably increases the hardness of the composites. Hardness is also increased with decreasing grain size and increasing amount of MA. (C) 2009 Elsevier B.V. All rights reserved. |
Tasdemirci, A; Ergonenc, C; Guden, M Split Hopkinson pressure bar multiple reloading and modeling of a 316 L stainless steel metallic hollow sphere structure Journal Article INTERNATIONAL JOURNAL OF IMPACT ENGINEERING, 37 (3), pp. 250-259, 2010, ISSN: 0734-743X. @article{ISI:000273106000003, title = {Split Hopkinson pressure bar multiple reloading and modeling of a 316 L stainless steel metallic hollow sphere structure}, author = {A Tasdemirci and C Ergonenc and M Guden}, doi = {10.1016/j.ijimpeng.2009.06.010}, issn = {0734-743X}, year = {2010}, date = {2010-03-01}, journal = {INTERNATIONAL JOURNAL OF IMPACT ENGINEERING}, volume = {37}, number = {3}, pages = {250-259}, abstract = {The high strain rate (600 s(-1)) compression deformation of a 316 L metallic hollow sphere (MHS) structure (density: 500 kg m(-3): average outer hollow sphere diameter: 2 mm and wall thickness: 45 mu m) was determined both numerically and experimentally. The experimental compressive stress-strain behavior at high strain rates until about large strains was obtained with multiple reloading tests using a large-diameter compression type aluminum Split Hopkinson Pressure Bar (SHPB) test apparatus. The multiple reloading of MHS samples in SHPB was analyzed with a 3D finite element model using the commercial explicit finite element code LS-DYNA. The tested MHS samples showed increased crushing stress values, when the strain rate increased from quasi-static (0.8 x 10(-4) s(-1)) to high strain rate (600 s(-1)). Experimentally and numerically deformed sections of MHS samples tested showed very similar crushing characteristics; plastic hinge formation, the indentation of the spheres at the contact regions and sphere wall buckling at intermediate strains. The extent of micro-inertial effects was further predicted with the strain rate insensitive cell wall material model and with the strain rate sensitive behavior of MHS structure similar to that of the cell wall material. Based on the predictions, the strain rate sensitivity of the studied 316 L MHS sample was attributed to the strain rate sensitivity of the cell wall material and the micro-inertia. (C) 2009 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The high strain rate (600 s(-1)) compression deformation of a 316 L metallic hollow sphere (MHS) structure (density: 500 kg m(-3): average outer hollow sphere diameter: 2 mm and wall thickness: 45 mu m) was determined both numerically and experimentally. The experimental compressive stress-strain behavior at high strain rates until about large strains was obtained with multiple reloading tests using a large-diameter compression type aluminum Split Hopkinson Pressure Bar (SHPB) test apparatus. The multiple reloading of MHS samples in SHPB was analyzed with a 3D finite element model using the commercial explicit finite element code LS-DYNA. The tested MHS samples showed increased crushing stress values, when the strain rate increased from quasi-static (0.8 x 10(-4) s(-1)) to high strain rate (600 s(-1)). Experimentally and numerically deformed sections of MHS samples tested showed very similar crushing characteristics; plastic hinge formation, the indentation of the spheres at the contact regions and sphere wall buckling at intermediate strains. The extent of micro-inertial effects was further predicted with the strain rate insensitive cell wall material model and with the strain rate sensitive behavior of MHS structure similar to that of the cell wall material. Based on the predictions, the strain rate sensitivity of the studied 316 L MHS sample was attributed to the strain rate sensitivity of the cell wall material and the micro-inertia. (C) 2009 Elsevier Ltd. All rights reserved. |
2009 |
Balikoglu, Fatih; Akkurt, Sedat Isothermal corrosion testing of frit furnace refractories Journal Article CERAMICS INTERNATIONAL, 35 (8), pp. 3411-3419, 2009, ISSN: 0272-8842. @article{ISI:000271368100062, title = {Isothermal corrosion testing of frit furnace refractories}, author = {Fatih Balikoglu and Sedat Akkurt}, doi = {10.1016/j.ceramint.2009.06.002}, issn = {0272-8842}, year = {2009}, date = {2009-12-01}, journal = {CERAMICS INTERNATIONAL}, volume = {35}, number = {8}, pages = {3411-3419}, abstract = {In this paper, the corrosion behaviour of aluminosilicate type refractories in frit melts is studied in an isothermal corrosion test setup. A refractory brick of largely andalusite and sillimanite composition was compared to another refractory brick of mullite and sillimanite composition, both of which were made by different manufacturers for use in different frit furnaces. The industrial frit used for corrosion tests was a commercial product used in a wall tile glaze formulation. Corrosion tests conducted under isothermal conditions provide quantitative and reproducible data about the corrosion performance of refractories. In this study, tests were performed by partially immersing a 15 mm x 15 mm x 115 mm refractory specimen into a frit melt at temperatures between 1404 and 1504 degrees C. The effects of temperature, duration of exposure and the refractory brick type were investigated using a statistically designed set of experiments. The ANOVA (analysis of variance) table indicated that temperature and test duration were the most important factor effects, as expected. Increasing both temperature and exposure duration led to an increased amount of corrosion as measured by the cross-sectional area loss of the corroded refractory specimen. Postmortem microstructural analysis was also done on the specimens, with extensive amount of ZnO center dot Al2O3 precipitation observed along the frit-refractory interface, where crystals of mullite and alumina were also found to precipitate. Increasing the amount of exposure time and temperature produced more ZnO center dot Al2O3 precipitation. As identified by SEM-EDS analysis, mullite crystals were in the needle-like morphology, while alumina crystals were generally cubic. Additional experiments were conducted by rotating the specimens in the melt at 50 rpm of rotational speed. Due to the reduction of boundary layer thickness, more dissolution was observed from the rotated specimens. In all specimens, corrosion was more pronounced in the bond phase than through the large filler grains of mullite and andalusite. (c) 2009 Elsevier Ltd and Techna Group S.r.l. All fights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this paper, the corrosion behaviour of aluminosilicate type refractories in frit melts is studied in an isothermal corrosion test setup. A refractory brick of largely andalusite and sillimanite composition was compared to another refractory brick of mullite and sillimanite composition, both of which were made by different manufacturers for use in different frit furnaces. The industrial frit used for corrosion tests was a commercial product used in a wall tile glaze formulation. Corrosion tests conducted under isothermal conditions provide quantitative and reproducible data about the corrosion performance of refractories. In this study, tests were performed by partially immersing a 15 mm x 15 mm x 115 mm refractory specimen into a frit melt at temperatures between 1404 and 1504 degrees C. The effects of temperature, duration of exposure and the refractory brick type were investigated using a statistically designed set of experiments. The ANOVA (analysis of variance) table indicated that temperature and test duration were the most important factor effects, as expected. Increasing both temperature and exposure duration led to an increased amount of corrosion as measured by the cross-sectional area loss of the corroded refractory specimen. Postmortem microstructural analysis was also done on the specimens, with extensive amount of ZnO center dot Al2O3 precipitation observed along the frit-refractory interface, where crystals of mullite and alumina were also found to precipitate. Increasing the amount of exposure time and temperature produced more ZnO center dot Al2O3 precipitation. As identified by SEM-EDS analysis, mullite crystals were in the needle-like morphology, while alumina crystals were generally cubic. Additional experiments were conducted by rotating the specimens in the melt at 50 rpm of rotational speed. Due to the reduction of boundary layer thickness, more dissolution was observed from the rotated specimens. In all specimens, corrosion was more pronounced in the bond phase than through the large filler grains of mullite and andalusite. (c) 2009 Elsevier Ltd and Techna Group S.r.l. All fights reserved. |
Seyhan, A T; Sun, Z; Deitzel, J; Tanoglu, M; Heider, D Cure kinetics of vapor grown carbon nanofiber (VGCNF) modified epoxy resin suspensions and fracture toughness of their resulting nanocomposites Journal Article MATERIALS CHEMISTRY AND PHYSICS, 118 (1), pp. 234-242, 2009, ISSN: 0254-0584. @article{ISI:000271556000042, title = {Cure kinetics of vapor grown carbon nanofiber (VGCNF) modified epoxy resin suspensions and fracture toughness of their resulting nanocomposites}, author = {A T Seyhan and Z Sun and J Deitzel and M Tanoglu and D Heider}, doi = {10.1016/j.matchemphys.2009.07.045}, issn = {0254-0584}, year = {2009}, date = {2009-11-01}, journal = {MATERIALS CHEMISTRY AND PHYSICS}, volume = {118}, number = {1}, pages = {234-242}, abstract = {In this study, the cure kinetics of Cycom 977-20. an aerospace grade toughened epoxy resin, and its suspensions containing various amounts (1, 3 and 5 wt.%) of vapor grown carbon nanofibers (VGCNFs) with and without chemical treatment were monitored via dynamic and isothermal dynamic scanning calorimetry (DSC) measurements. For this purpose, VGCNFs were first oxidized in nitric acid and then functionalized with 3-glycidoxypropyltrimethoxy silane (GPTMS) coupling agent. Fourier transform infrared (FTIR) spectroscopy was subsequently used to verify the chemical functional groups grafted onto the surfaces of VGCNFs. Sonication technique was conducted to facilitate proper dispersion of as-received, acid treated and silanized VGCNFs within epoxy resin. Dynamic DSC measurements showed that silanized VGCNF modified resin suspensions exhibited higher heat of cure compared to those with as-received VGCNFs. Experimentally obtained isothermal DSC data was then con elated with Kamal phenomenological model. Based on the model predictions, it was found that silanized VGCNFs; maximized the cure reaction rates at the very initial stage of the reaction. Accordingly, an optimized curing cycle was applied to harden resin suspensions. Fracture testing was then carried out on the cured samples in order to relate the curing behavior of VGCNF modified resin suspensions to mechanical response of their resulting nanocomposites With addition of 1 wt % of silanized VGCNFs, the fracture toughness value of neat epoxy was found to be improved by 12%. SEM was further employed to examine the fracture surfaces of the samples. (C) 2009 Elsevier B V. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this study, the cure kinetics of Cycom 977-20. an aerospace grade toughened epoxy resin, and its suspensions containing various amounts (1, 3 and 5 wt.%) of vapor grown carbon nanofibers (VGCNFs) with and without chemical treatment were monitored via dynamic and isothermal dynamic scanning calorimetry (DSC) measurements. For this purpose, VGCNFs were first oxidized in nitric acid and then functionalized with 3-glycidoxypropyltrimethoxy silane (GPTMS) coupling agent. Fourier transform infrared (FTIR) spectroscopy was subsequently used to verify the chemical functional groups grafted onto the surfaces of VGCNFs. Sonication technique was conducted to facilitate proper dispersion of as-received, acid treated and silanized VGCNFs within epoxy resin. Dynamic DSC measurements showed that silanized VGCNF modified resin suspensions exhibited higher heat of cure compared to those with as-received VGCNFs. Experimentally obtained isothermal DSC data was then con elated with Kamal phenomenological model. Based on the model predictions, it was found that silanized VGCNFs; maximized the cure reaction rates at the very initial stage of the reaction. Accordingly, an optimized curing cycle was applied to harden resin suspensions. Fracture testing was then carried out on the cured samples in order to relate the curing behavior of VGCNF modified resin suspensions to mechanical response of their resulting nanocomposites With addition of 1 wt % of silanized VGCNFs, the fracture toughness value of neat epoxy was found to be improved by 12%. SEM was further employed to examine the fracture surfaces of the samples. (C) 2009 Elsevier B V. All rights reserved. |
Seyhan, Tugrul A; Tanoglu, Metin; Schulte, Karl MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, 523 (1-2), pp. 85-92, 2009, ISSN: 0921-5093. @article{ISI:000270632900014, title = {Tensile mechanical behavior and fracture toughness of MWCNT and DWCNT modified vinyl-ester/polyester hybrid nanocomposites produced by 3-roll milling}, author = {Tugrul A Seyhan and Metin Tanoglu and Karl Schulte}, doi = {10.1016/j.msea.2009.05.035}, issn = {0921-5093}, year = {2009}, date = {2009-10-01}, journal = {MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, volume = {523}, number = {1-2}, pages = {85-92}, abstract = {This study aims to investigate the tensile mechanical behavior and fracture toughness of vinyl-ester/polyester hybrid nanocomposites containing various types of nanofillers, including multi- and double-walled carbon nanotubes with and without amine functional groups (MWCNTs, DWCNTs, MWCNT-NH2 and DWCNT-NH2). To prepare the resin suspensions, very low contents (0.05, 0.1 and 0.3 wt.%) of carbon nanotubes (CNTs) were dispersed within a specially synthesized styrene-free polyester resin, conducting 3-roll milling technique. The collected resin stuff was subsequently blended with vinyl-ester via mechanical stirring to achieve final suspensions prior to polymerization. Nanocomposites containing MWCNTs and MWCNT-NH2 were found to exhibit higher tensile strength and modulus as well as larger fracture toughness and fracture energy compared to neat hybrid polymer. However, incorporation of similar contents of DWCNTs and DWCNT-NH2 into the hybrid resin did not reflect the same improvement in the corresponding mechanical properties. Furthermore, experimentally measured elastic moduli of the nanocomposites containing DWCNTs, DWCNT-NH2, MWCNTs and MWCNT-NH2 were fitted to Halphin-Tsai model. Regardless of amine functional groups or content of carbon nanotubes, MWCNT modified nanocomposites exhibited better agreement between the predicted and the measured elastic moduli values compared to nanocomposites with DWCNTs. Furthermore, Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) were used to reveal dispersion state of the carbon nanotubes within the hybrid polymer and to examine the CNT induced failure modes that occurred under mechanical loading, respectively. Based on the experimental findings obtained, it was emphasized that the types of CNTs and presence of amine functional groups on the surface of CNTs affects substantially the chemical interactions at the interface, thus tuning the ultimate mechanical performance of the resulting nanocomposites. (C) 2009 Elsevier B.V. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This study aims to investigate the tensile mechanical behavior and fracture toughness of vinyl-ester/polyester hybrid nanocomposites containing various types of nanofillers, including multi- and double-walled carbon nanotubes with and without amine functional groups (MWCNTs, DWCNTs, MWCNT-NH2 and DWCNT-NH2). To prepare the resin suspensions, very low contents (0.05, 0.1 and 0.3 wt.%) of carbon nanotubes (CNTs) were dispersed within a specially synthesized styrene-free polyester resin, conducting 3-roll milling technique. The collected resin stuff was subsequently blended with vinyl-ester via mechanical stirring to achieve final suspensions prior to polymerization. Nanocomposites containing MWCNTs and MWCNT-NH2 were found to exhibit higher tensile strength and modulus as well as larger fracture toughness and fracture energy compared to neat hybrid polymer. However, incorporation of similar contents of DWCNTs and DWCNT-NH2 into the hybrid resin did not reflect the same improvement in the corresponding mechanical properties. Furthermore, experimentally measured elastic moduli of the nanocomposites containing DWCNTs, DWCNT-NH2, MWCNTs and MWCNT-NH2 were fitted to Halphin-Tsai model. Regardless of amine functional groups or content of carbon nanotubes, MWCNT modified nanocomposites exhibited better agreement between the predicted and the measured elastic moduli values compared to nanocomposites with DWCNTs. Furthermore, Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) were used to reveal dispersion state of the carbon nanotubes within the hybrid polymer and to examine the CNT induced failure modes that occurred under mechanical loading, respectively. Based on the experimental findings obtained, it was emphasized that the types of CNTs and presence of amine functional groups on the surface of CNTs affects substantially the chemical interactions at the interface, thus tuning the ultimate mechanical performance of the resulting nanocomposites. (C) 2009 Elsevier B.V. All rights reserved. |
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 |
| 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 |