Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 1Citation - Scopus: 1Epoxy Matrix Nano Composites: Modulus, Strength and Ductility Enhancement Through Auxeticity of Α-Cristobalite Filler(Elsevier, 2023) Güden, Mustafa; Ülker, Sevkan; Movahedi, NimaThe negative Poisson's ratio (NPR) nano-size ?-Cristobalite particle/epoxy composites were prepared and tensile tested. The elastic modulus and strength of the composites were improved as the particle volume fraction increased from 0 to 0.02. Unlike the conventional particle reinforced composites, the fracture strain increased with the nano ?-Cristobalite addition, an effect which was ascribed to the intrinsic NPR behavior of the filler. © 2023 Elsevier B.V.Article Citation - WoS: 15Citation - Scopus: 15The Effect of Strain Rate on the Compression Behavior of Additively Manufactured Short Carbon Fiber-Reinforced Polyamide Composites With Different Layer Heights, Infill Patterns, and Built Angles(Springer, 2023) Zeybek, Mehmet Kaan; Güden, Mustafa; Taşdemirci, AlperPrevious studies on the fused deposition modelling (FDM) processed short carbon fiber/Polyamide 6 (PA6) matrix composites and neat PA6 have mostly concentrated on the quasi-static mechanical properties. Present study focused on the strain rate-dependent deformation behavior of a short carbon fiber-reinforced PA6 (Onyx) and neat PA6, produced in different layer heights, infill patterns and built angles. As compared with PA6, Onyx showed a higher compression stress at all strain rates investigated. A layer height of 0.2 mm in PA6 specimens promoted a better bonding between [0/90°] infill layers; hence, a higher flow stress than 0.2 mm layer height specimens, while 0.2 mm layer height induced a higher porosity in Onyx specimens, leading to a lower flow stress. The porosities in Onyx [0/90°] infill specimens were due to the constraining effect of 0/90° fiber layers. Changing infill pattern from a [0/90°] to a concentric one decreased porosity at the same layer height and hence increased the compressive flow stress. The highest compressive strength was found in the specimens with the loading axis 90 and 0° to [0/90°] infill plane. The lowest strength was, however, determined in the specimens with the loading axis 30 and 60o to [0/90°] infill plane in quasi-static loading. However, the specimens with the loading axis of 60, 45, 30 and 0° exhibited a brittle behavior in high strain rate loading (1500 s−1). The specimens with the loading axis of 45° had the lowest fracture stress and strain in the high strain rate loading. This signified the importance of loading angle at high strain rates. Finally, the rate sensitivities of PA6 and Onyx specimens were shown to be similar, showing a matrix dominated deformation. However, the strain rate jump tests indicated a slightly higher rate sensitivity of Onyx specimens at quasi-static strain rates (10−3-10−1 s−1).Article Citation - WoS: 13Citation - Scopus: 14The Quasi-Static Crush Response of Electron-Beam Ti6al4v Body-Centred Lattices: The Effect of the Number of Cells, Strut Diameter and Face Sheet(Wiley, 2022) Güden, Mustafa; Alpkaya, Alican Tuncay; Arslan Hamat, Burcu; Hızlı, Burak; Taşdemirci, Alper; Tanrıkulu, A. Alptuğ; Yavaş, HakanThe effect of the number of cells, strut diameter and face sheet on the compression of electron-beam-melt (EBM) Ti6Al4V (Ti64) body-centred-cubic (BCC) lattices was investigated experimentally and numerically. The lattices with the same relative density (~0.182) were fabricated with and without 2-mm-thick face sheets in 10 and 5 mm cell size, 8–125 unit cell (two to five cells/edge) and 2 and 1 mm strut diameter. The experimental compression tests were further numerically simulated in the LS-DYNA. Experimentally two bending-dominated crushing modes, namely, lateral and diagonal layer crushing, were determined. The numerical models however exhibited merely a bending-dominated lateral layer crushing mode when the erosion strain was 0.4 and without face-sheet models showed a diagonal layer crushing mode when the erosion strain was 0.3. Lower erosion strains promoted a diagonal layer crushing mode by introducing geometrical inhomogeneity to the lattice, leading to strain localisation as similar to the face sheets which introduced extensive strut bending in the layers adjacent to the face sheets. The face-sheet model showed a higher but decreasing collapse strength at an increasing number of cells, just as opposite to the without face-sheet model, and the collapse strength of both models converged when the number of cells was higher than five-cell/edge. The decrease/increase of the collapse strengths of lattices before the critical number of cells was claimed mainly due to the size-imposed lattice boundary condition, rather than the specimen volume. The difference in the experimental collapse strengths between the 5- and the 10-mm cell-size lattices was ascribed to the variations in the microstructures—hence the material model parameters between the small-diameter and the large-diameter EBM-Ti64 strut lattices.Article Citation - WoS: 8Citation - Scopus: 8Comparing Compression Deformation and Rate Sensitivity of Additively Manufactured and Extruded-Annealed 316l Alloys(Springer, 2021) Enser, Samed; Yavaş, Hakan; Arslan Hamat, Burcu; Aydın, Hüseyin; Kafadar, Gülten; Tanrıkulu, A. Alptuğ; Zeytin Kazdal, Havva; Öztürk, Fahrettin; Güden, MustafaThe deformation behavior of a selective-laser-melt-processed 316-L alloy (SLM-316L) under compression was determined together with a commercial annealed-extruded 316L alloy bar (C-316L) for comparison. Strain rate jump tests and hardness tests on the untested and compression tested samples were also performed. Extensive microscopic observations on the deformed and undeformed samples showed a twinning-dominated deformation in SLM-316L, similar to twinning-induced-plasticity steels, while a martensitic transformation-dominated deformation in C-316L alloy, similar to transformation-induced-plasticity steels. Within the studied quasi-static strain rate regime, the measured higher strain rate sensitivity of SLM-316L was ascribed to the lower distances between the nano-twins, in the level of 100 nm, than the distances between martensite plates, in the level of 1000 nm. A higher hardness increase in the martensite transformation region as compared with the twinned region proved the higher work hardening of C-316L. The hardness tests in the micron and sub-micron levels further confirmed the previously determined relatively low resistances of the dislocation cell walls (sub-grain) to the dislocation motion in SLM-316L alloy.Article Citation - WoS: 3Citation - Scopus: 4Impact Loading and Modelling a Multilayer Aluminium Corrugated/Fin Core: the Effect of the Insertion of Imperfect Fin Layers(John Wiley and Sons Inc., 2019) Sarıkaya, Mustafa; Taşdemirci, Alper; Güden, MustafaThe quasi-static compression (0.0048 m/s) and Taylor-like impact (135, 150, and 200 m/s) loading of a multilayer 1050 H14 aluminium corrugated core were investigated both experimentally and numerically in LS-DYNA using the perfect and imperfect sample models. In the imperfect sample models, one or two layers of corrugated fin structure were replaced by the fin layers made of bent-type cell walls. The localised deformation in the quasi-static imperfect models of cylindrical sample started at the imperfect layers, the same as the tests, and the layers were compressed until about the densification strain in a step-wise fashion. The localised deformation in the perfect models, however, started at the layers at and near the top and bottom of the test sample. In the shock mode, the sample crushed sequentially starting at the impact end layer regardless the perfect or imperfect sample models were used. Furthermore, the perfect and imperfect models resulted in nearly the same initial crushing stresses in the shock mode. The layer strain histories revealed a velocity-dependent layer densification strain. Both model types, the imperfect and perfect, well approximated the stress-time histories and layer deformations of the shock mode. The rigid perfectly plastic locking model based on the numerically determined densification strains also showed well agreements with the experimental and numerical plateau stresses of the shock mode.Article Citation - WoS: 4Citation - Scopus: 4The Effect of Cell Wall Material Strain and Strain-Rate Hardening Behaviour on the Dynamic Crush Response of an Aluminium Multi-Layered Corrugated Core(Taylor and Francis Ltd., 2021) Güden, Mustafa; Canbaz, İlkerThe effect of the parameters of the Johnson and Cook material model on the direct impact crushing behaviour of a layered 1050 H14 aluminium corrugated structure was investigated numerically in LS-DYNA at quasi-static (0.0048 m s(-1)) and dynamic (20, 60, 150 and 250 m s(-1)) velocities. Numerical and experimental direct impact tests were performed by lunching a striker bar onto corrugated samples attached to the end of the incident bar of a Split Hopkinson Pressure Bar set-up. The numerical impact-end stress-time and velocity-time curves were further compared with those of rigid-perfectly-plastic-locking (r-p-p-l) model. Numerical and r-p-p-l model impact-end stress analysis revealed a shock mode at 150 and 250 m s(-1), transition mode at 60 m s(-1) and quasi-static homogenous mode at 20 m s(-1). The increase of velocity from quasi-static to 20 m s(-1) increased the numerical distal-end initial peak-stress, while it almost stayed constant between 20 and 250 m s(-1) for all material models. The increased distal-end initial peak-stress of strain rate insensitive models from quasi-static to 20 m s(-1) confirmed the effect of micro-inertia. The numerical models further indicated a negligible effect of used material models on the impact-end stress of investigated structure. Finally, the contribution of strain rate to the distal-end initial peak-stress of cellular structures made of low strain rate sensitive Al alloys was shown to be relatively low as compared with that of strain hardening and micro-inertia, but it might be substantial for the structures constructed using relatively high strain rate sensitive alloys.Article Citation - WoS: 8Citation - Scopus: 9The Increased Compression Strength of an Epoxy Resin With the Addition of Heat-Treated Natural Nano-Structured Diatom Frustules(SAGE Publications Inc., 2017) Zeren, Doğuş; Güden, MustafaNatural diatom frustules composing nanometer size silica particles were heat-treated at temperatures between 600 and 1200℃ for 2 h and used as filler/reinforcing agent (15 wt%) in an epoxy resin. The opal structure of as-received natural diatom frustules was transformed into cristobalite after the heat-treatment above 900℃. 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 7 × 10−3 s−1. The results showed that the inclusion of the frustules heat-treated at 1000℃ increased the compressive yield strength of the resin by 50%, while the addition of the diatom frustules heat-treated above and below 1000℃ and the as-received frustules increased the strength by ∼25% and 16%, respectively. The heat treatment above 1000℃ decreased the surface area of the frustules from 8.23 m2 g−1 to 3.46 m2 g−1. The cristobalite grains of the frustules heat-treated at 1000℃ was smaller than 100 nm, while the grain size increased to ∼500 nm at 1200℃. The increased compressive stresses of the resin at the specific heat treatment temperature (1000℃) were ascribed to nano size crystalline cristobalite grains. The relatively lower compressive stresses of the epoxy resin filled with frustules heat-treated above 1000℃ 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.Article Citation - WoS: 29Citation - Scopus: 32The Optimisation of the Energy Absorption of Partially Al Foam-Filled Commercial 1050h14 and 6061t4 Al Crash Boxes(Taylor and Francis Ltd., 2011) Toksoy, Ahmet Kaan; Güden, MustafaPartially 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.Article Citation - WoS: 41Citation - Scopus: 38Simulation of the Strain Rate Sensitive Flow Behavior of Sic-Particulate Reinforced Aluminum Metal Matrix Composites(Elsevier Ltd., 2008) Tirtom, İsmail; Güden, Mustafa; Yıldız, HasanStrain rate dependent compression mechanical behavior of an SiC-particulate reinforced Al (2024-O) metal matrix composite (MMC) with different particle volume fractions was numerically investigated at various strain rates. Calculations were performed using axisymmetric finite element unit cell model, in which an elastic SiC particle was embedded inside a strain rate sensitive viscoplastic Al matrix. Stress–strain curves of Al matrix material were derived from Split Hopkinson Pressure Bar experiments at various strain rates and used as inputs in the FEM model. Numerically computed stress–strain curves and strain rate sensitivity were compared with those of experiments for a 15% SiC-particulate reinforced MMC. Computed strain rate sensitivity of the MMC was found to be higher than that of the matrix alloy and increased with increasing strain contrary to the strain independent matrix strain rate sensitivity. The strain rate sensitivity of the MMC was also found to increase with increasing particle volume fraction at the same particle size. Finally, several possible reasons including assumptions used in the model, adiabatic heating, microstructural variations between the composite matrix and matrix alloy, particle shape and distribution and damage accumulation for the small discrepancy found between computed and experimental stress–strain curves and strain rate sensitivity of the composite were discussed.Article Citation - WoS: 14Citation - Scopus: 18Projectile Impact Testing of Glass Fiber-Reinforced Composite and Layered Corrugated Aluminium and Aluminium Foam Core Sandwich Panels: a Comparative Study(Taylor and Francis Ltd., 2012) Odacı, İsmet Kutlay; Kılıçaslan, Cenk; Taşdemirci, Alper; Güden, MustafaE-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.