WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
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Article Citation - WoS: 2Citation - Scopus: 2A Comprehensive Study on the Effectiveness of the Stress and Damage Model Parameters in Predicting the Compression Fracture Behavior of Selective Laser Melted AlSi10Mg BCC Lattices(Elsevier B.V., 2025) Guden, Mustafa; Erten, Hacer Irem; Gorguluarslan, Recep M.; Gulletutan, Umut Can; Dagkolu, Akin; Gokdag, Istemihan; Namazov, SubhanThe Johnson and Cook (JC) stress and damage model parameters determined from the machined bulk cylindrical specimens and as-built struts through tension and compression tests were used to model quasi-static compression behavior of selective laser melt-fabricated AlSi10Mg alloy lattices. The lattices had the same cell size (10 mm) and strut diameter (1 mm), but different number of cells (2 x 2 x 2, 10 x 10 x 2 and 5 x 5 x 5) and geometries (sandwich and cubic). Four different sets of JC damage model parameters (brittle and ductile notch-insensitive and compression and tension notch-sensitive) were further implemented in the lattice compression numerical models. The brittle damage model parameters and smaller mesh sizes resulted in cracking the face-sheet corner strut nodes before the occurrence of a bending-dominated initial peak stress. The notch-sensitive damage model parameters exhibited no bent-strut fracture in the middle layers of the lattices and increased the crack initiation strains as compared with the notch-insensitive damage model parameters. Despite significant variations in the initial peak stresses of the tested 2 x 2 x 2 and 10 x 10 x 2 lattices, the implication of the strut micro-tension stress model together with the compression notch-sensitive damage model parameters using 0.25 mm mesh size conservatively approximated the experimental deformation stresses while the machined bulk specimen tensionstress model over predicted the experimental stresses. On the other side, the strut stress model with 0.15 mm mesh size accurately predicted the experimental diagonal shear/fracture mode of struts with a slightly higher numerical initial peak stress. The compression tests on the strut specimens extracted from the as-built lattices yielded similar stress model parameters with the micro-tension tests. The differences between the initial peak stresses of the investigated sandwich and cubic lattices were further explained by the differences in the lattice boundary conditions.Article Citation - WoS: 23Citation - Scopus: 24Determination of the Material Model and Damage Parameters of a Carbon Fiber Reinforced Laminated Epoxy Composite for High Strain Rate Planar Compression(Elsevier Ltd., 2021) Shi, C.; Guo, B.; Sarıkaya, Mustafa; Çelik, Muhammet; Chen, P.; Güden, MustafaThe progressive failure of a 0°/90° laminated carbon fiber reinforced epoxy composite was modeled in LS-DYNA using the MAT_162 material model, including the strain rate, damage progression and anisotropy effects. In addition to conventional standard and non-standard tests, double-shear and Brazilian tests were applied to determine the through-thickness shear modulus and the through-thickness tensile strength of the composite, respectively. The modulus reduction and strain softening for shear and delamination parameters were calibrated by low velocity drop-weight impact tests. The rate sensitivities of the modulus and strength of in-plane and through-thickness direction were determined by the compression tests at quasi-static and high strain rates. The fidelity of the determined model parameters was finally verified in the in-plane and through-thickness direction by the 3D numerical models of the Split Hopkinson Pressure Bar compression tests. The numerical bar stresses and damage progressions modes showed acceptable correlations with those of the experiments in both directions. The composite failed both numerically and experimentally by the fiber buckling induced fiber-matrix axial splitting in the in-plane and the matrix shear fracture in the through-thickness direction. © 2020Article Citation - WoS: 9Citation - Scopus: 9Quasi-Static and High Strain Rate Properties of a Cross-Ply Metal Matrix Composite(Elsevier Ltd., 2009) Hall, Ian W.; Taşdemirci, Alper; Derrick, J.A series of compression tests has been carried out at quasi-static and high strain rates on cylindrical samples of an alumina fiber/Al-6061 metal matrix composite. The composite plates were prepared with fibers in the 0°, 0/90° and ±45° orientations. It was found that the mechanical properties were strongly dependent upon the imposed strain rate, with fracture stress increases of >50% being noted for several orientations at high strain rates: these increases are not believed to be related to strain rate sensitivity of either the matrix or fibers but to arise from the inertia of fragments which remain in place after fracture and continue to bear load. Also, and in contradiction to behavior anticipated from the rule of mixtures, it was found that 0/90° samples exhibited properties superior to those of 0° unidirectional samples. High-speed photography was used to confirm the sequence of deformation and fracture events at high strain rate. © 2008 Elsevier B.V. All rights reserved.Article Citation - WoS: 51Citation - Scopus: 58Effect of Additives on Flexible Pvc Foam Formation(Elsevier Ltd., 2008) Demir, Hasan; Sipahioğlu, Muzaffer; Balköse, Devrim; Ülkü, SemraIn this study, effects of Ca/Zn stearate and organotin heat stabilizers and zeolite, CaCO3, cellulose and luffa flours fillers, and their concentrations (2.5, 5, 10 and 20% by weight) on production of flexible PVC foams by chemical blowing agent, azodicarbonamide were investigated. Foam morphology, foam density, compressive mechanical properties and water uptake capacities of samples were determined. Morphology of the sample without any filler showed that employment of Ca stearate and Zn stearate heat stabilizers instead of organotin stabilizers increases foam formation and decreases pore sizes and regularity in pore size distribution. Foams having organotin stabilizer were more resistant to heat than the ones with Ca/Zn stearate for long heating periods. Foams, including organotin-based heat stabilizers, have compact structure. It was observed that, samples containing zeolite, CaCO3, cellulose or luffa flour had lower pore volume but higher Young's modulus and stress values compared to unfilled samples.Article Citation - WoS: 22Citation - Scopus: 28Mechanical Interlocking Between Porous Electrospun Polystyrene Fibers and an Epoxy Matrix(American Chemical Society, 2014) Demir, Mustafa Muammer; Horzum, Nesrin; Taşdemirci, Alper; Turan, Ali Kıvanç; Güden, MustafaAn epoxy matrix filled with nonwoven mats of porous polystyrene (PS) fibers processed by an electrospinning was compression tested at quasi-static (1 × 10–3 s–1) and high strain (315 s–1) rates. The electrospun PS fibers with a diameter between 6 and 9 μm, accommodated spherical pores on the surface with the sizes ranging from 0.1 to 0.2 μm. The filling epoxy matrix with 0.2 wt % PS fibers increased the compressive elastic modulus and compressive strength over those of neat epoxy resin. The microscopic observations indicated that the surface pores facilitated the resin intrusions into the fiber, enhancing the interlocking between resin and fibers, and increased the deformation energy expenditure of the polymer matrix.Article Citation - WoS: 19Citation - Scopus: 19Experimental Investigation of Interaction Effects in Foam-Filled Thin-Walled Aluminum Tubes(Springer Verlag, 2006) Güden, Mustafa; Toksoy, Ahmet Kaan; Kavi, HalitThe interaction coefficients of polystyrene foam filling of thin-walled aluminum cylindrical tubes were investigated experimentally through compression testing of partially foam-filled tubes with and without adhesive. The experimental load-displacement curves and observation of the crushed sections of filled tubes have shown that partial foam filling reduced the fold length and hence increased the average crushing loads of tubes, proving the interaction effect between tube wall and filler. The interaction coefficients for the partial foam filling were further calculated to be in the level and/or higher than that of the foam plateau load of transverse direction.Article Citation - WoS: 19Citation - Scopus: 21Effect of Strain Rate on the Compressive Mechanical Behavior of a Continuous Alumina Fiber Reinforced Ze41a Magnesium Alloy Based Composite(Elsevier Ltd., 2006) Güden, Mustafa; Akil, Övünç; Taşdemirci, Alper; Çiftçioğlu, Muhsin; Hall, Ian W.The compressive mechanical response of an FP™ continuous fiber (35 vol.%) Mg composite has been determined in the transverse and longitudinal directions at quasi-static and high strain rates. It was found that the composite in the transverse direction exhibited strain rate sensitivity of the flow stress and maximum stress within the studied strain-rate range of 1.3 × 10−4 to 1550 s−1. The failure strain in this direction, however, decreased with increasing strain rate. Microscopic observations on the failed samples have shown that the composite failed by shear banding along the diagonal axis, 45° to the loading axis. Twinning was observed in the deformed cross-sections of the samples particularly in and near the shear band region. The strain rate sensitivity of the fracture stress of the composite in transverse direction is attributed to the matrix strain rate sensitivity. In the longitudinal direction, the composite failed by kink formation at quasi-static strain rates, while kinking and splitting were observed at the high strain rates. The maximum stress in the longitudinal direction was, however, found to be strain rate insensitive within the strain rate regime of 1.3 × 10−4 to 500 s−1. In this direction, similar to transverse direction, twinning was observed in the highly deformed kink region. Several different reasons are proposed for the strain rate insensitive compressive strength in this direction.Article Citation - WoS: 25Citation - Scopus: 36Effect of Strain Rate on the Compression Behaviour of a Woven Fabric S2-Glass Fiber Reinforced Vinyl Ester Composite(Elsevier, 2003) Akil, Övünç; Yıldırım, Uygar; Güden, Mustafa; Hall, Ian W.Quasi-static (~10−3s−1) and high strain rate (>500 s−1) compression behavior of an S2-glass woven fabric/vinyl ester composite plate was determined in the in-plane and through-thickness directions. In both directions, modulus and failure strength increased with increasing strain rate. A higher strain rate sensitive modulus was found in the through-thickness direction while a higher strain rate sensitive failure strength was found in the in-plane direction. In the in-plane direction, the failure mode was observed to change from splitting followed by “kink banding” (localized fiber buckling) to predominantly splitting at increasing strain rates, while it remained the same in the through-thickness direction.Article Citation - WoS: 26Citation - Scopus: 40Effect of Strain Rate on the Compression Behaviour of a Woven Glass Fiber/Sc-15 Composite(Elsevier Ltd., 2004) Güden, Mustafa; Yıldırım, Uygar; Hall, Ian W.Strain rate dependent compression behavior of a plain-weave S-2 glass fabric SC-15 epoxy (rubber toughened resin) composite plate, currently studied as the backing plate for composite armor applications, was determined in the through-thickness direction (normal to the fiber plane) in the strain rate regime of 1×10−4 to 1.1×103 s−1. In the studied strain rate regime, the modulus and failure strength of the composite were found to be rate sensitive and increased with increasing strain rate. Microscopic observations showed that the composite failed by ductile failure, involving matrix cracks and, later, cracking through and between the fiber layers. Crack deflections at rubber particle/matrix interface and particle pull-out were observed in the failed samples, contributing to the toughness of the composite.Article Citation - WoS: 24Citation - Scopus: 26Diatom Frustule-Filled Epoxy: Experimental and Numerical Study of the Quasi-Static and High Strain Rate Compression Behavior(Elsevier Ltd., 2008) Taşdemirci, Alper; Yüksel, Sinan; Karsu, Deniz; Gültürk, Elif; Hall, Ian W.; Güden, MustafaIn this study, centric type diatom frustules obtained from a diatomaceous earth filter material were used as filler in an epoxy resin with a weight percentage of 15% in order to assess the possible effects on the compressive behavior at quasi-static and high strain rates. The high strain rate testing of frustule-filled and neat epoxy samples was performed in a split-Hopkinson pressure bar (SHPB) set-up and modeled using the commercial explicit finite element code LS-DYNA 970. Result has shown that 15% frustule filling of epoxy increased both modulus and yield strength values at quasi-static and high strain rates without significantly reducing the failure strain. Microscopic observations revealed two main deformation modes: the debonding of the frustules from the epoxy and crushing/fracture of the frustules. The modeling results have further confirmed the attainment of stress equilibrium in the samples in SHPB testing following the initial elastic region and showed good agreement with the experimental stress–time response and deformation sequence of the samples in high strain rate testing.