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: 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: 27Citation - Scopus: 28Split Hopkinson Pressure Bar Multiple Reloading and Modeling of a 316 L Stainless Steel Metallic Hollow Sphere Structure(Elsevier Ltd., 2010) Taşdemirci, Alper; Ergönenç, Çağrı; Güden, MustafaThe 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 μm) 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 × 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.Article Citation - WoS: 24Citation - Scopus: 26Split Hopkinson Pressure Bar Compression Testing of an Aluminum Alloy: Effect of Lubricant Type(Chapman & Hall, 2003) Hall, Ian W.; Güden, MustafaThe Split Hopkinson Pressure Bar (SHPB), or Kolsky Bar, is widely used for studying the dynamic mechanical properties of metals and other materials. A cylindrical specimen is sandwiched between the incident and transmitter bars, Fig. 1, and a constant amplitude elastic wave is generated by the striker bar. Strain gages mounted on the incident and transmitter bars allow the compressive stress-strain response of the specimen to be established using uniaxial elastic wave theory [1]. A more detailed overview of SHPB testing is found in [2]. Lubricant is usually applied to the interfaces because the presence of any frictional effect on the specimen surfaces forms a multiaxial stress-state and invalidates one of the most important assumptions of the SHPB analysis, namely, a uniaxial stress state. This paper quantifies the effect for an aluminum alloy.Article Citation - WoS: 32Citation - Scopus: 37Modeling Quasi-Static and High Strain Rate Deformation and Failure Behavior of a (±45) Symmetric E-glass/Polyester Composite Under Compressive Loading(Elsevier Ltd., 2013) Kara, Ali; Taşdemirci, Alper; Güden, MustafaQuasi-static (1 × 10−3–1 × 10−2 s−1) and high strain rate (∼1000 s−1) compressive mechanical response and fracture/failure of a (±45) symmetric E-glass/polyester composite along three perpendicular directions were determined experimentally and numerically. A numerical model in LS-DYNA 971 using material model MAT_162 was developed to investigate the compression deformation and fracture of the composite at quasi-static and high strain rates. The compressive stress–strain behaviors of the composite along three directions were found strain rate sensitive. The modulus and maximum stress of the composite increased with increasing strain rate, while the strain rate sensitivity in in-plane direction was higher than that in through-thickness direction. The damage progression determined by high speed camera in the specimens well agreed with that of numerical model. The numerical model successfully predicted the damage initiation and progression as well as the failure modes of the composite.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: 37High Strain-Rate Compression Testing of a Short-Fiber Reinforced Aluminum Composite(Elsevier Ltd., 1997) Güden, Mustafa; Hall, Ian W.Compression behavior of 15–26 Vf% Saffil™ short-fiber reinforced Al-1.17wt.%Cu alloy metal matrix composites has been determined over a strain-rate range of approximately 10−4 to 2×103 s−1. The strain-rate sensitivity of composite samples at 4% strain, tested parallel and normal to the plane of reinforcement, was found to be higher than that of unreinforced alloy in the strain-rate range studied. Quantitative analysis of fiber fragment lengths from samples tested to different strain levels showed that, at small strains, high strain-rate testing induced a relatively shorter fiber fragment length distribution in the composite compared to quasi-static testing. At quasi-static strain rates, the fiber strengthening effect was found to increase with increasing Vf% and was higher in samples tested parallel to the planar random array. The observed anisotropy of the composite at quasi-static strain rates was also observed to continue into the high strain-rate regime. Microscopic observations on composite samples tested quasi-statically and dynamically to a range of strains showed that the major damage process involved during compression testing was fiber breakage followed by the microcracking of the matrix at relatively large strains. Fiber breakage modes were found to be mostly shearing and buckling.Article Citation - WoS: 5Citation - Scopus: 7High Strain Rate Testing of a Unidirectionally Reinforced Graphite Epoxy Composite(Chapman & Hall, 2001) Hall, Ian W.; Güden, MustafaSince accurate, reproducible methods of testing polymer composites are not very well developed or standardized, this research forms part of a program to gain a better understanding of the mechanical properties and failure mechanisms of polymer composites at high strain rates. Since failure modes differ markedly depending on fiber architecture, orientation, fiber/matrix combination and so forth, these initial tests were carried out using a simple unidirectionally reinforced composite. Beginning with testing in the longitudinal and transverse directions, reported here, future experiments are being carried out to determine how the high strain rate properties vary with angle of testing, and then move on to other simple fiber lay-ups, ±90◦, ±45◦, etc.Article Citation - WoS: 4Citation - Scopus: 5High Strain Rate Properties of an Sicw/2124-t6 Aluminum Composite at Elevated Temperatures(Elsevier Ltd., 1998) Güden, Mustafa; Hall, Ian W.Metal matrix composites, (MMC’s) provide several important advantages over unreinforced metals and alloys. Among these, higher moduli and yield stresses and enhanced thermo-mechanical properties are normally considered important in structural applications of MMC’s. It is also possible that MMC’s may be exposed to loading conditions involving high strain rates during service, for example, components of a car in collision with another or turbine blades hit by ingestion of foreign objects. In such situations of rapidly increasing loading conditions, the material property response may be considerably different from that which applies during slow loading of normal quasi-static testing and, consequently, dynamic mechanical properties are of increasing interest and importance.Article Citation - WoS: 25Citation - Scopus: 28High Strain Rate Deformation Behavior of a Continuous Fiber Reinforced Aluminum Metal Matrix Composite(Elsevier Ltd., 2000) Güden, Mustafa; Hall, Ian W.An aluminum metal matrix composite reinforced with continuous unidirectional α-Al2O3 fibers has been compression tested at quasi-static and dynamic strain rates. In the transverse direction, the composite showed increased flow stress and maximum stress within the studied strain rate regime, 10−3 to 3500 s−1. The strain rate sensitivity of the flow stress in this direction was found to be similar to that of a similar, but unreinforced, alloy determined from previous work. In the longitudinal direction, the maximum stress of the composite increased with increasing strain rate within the range 10−5 to 700 s−1. The strain rate dependent maximum stress in this direction was described by the strain rate dependent fiber buckling stress.Article Citation - WoS: 10High Strain Rate Behavior of a Sic Particulate Reinforced Al2o3 Ceramic Matrix Composite(Elsevier Ltd., 1998) Hall, Ian W.; Güden, MustafaThe high strain rate deformation behavior of composite materials is important for several reasons. First, knowledge of the mechanical properties of composites at high strain rates is needed for designing with these materials in applications where sudden changes in loading rates are likely to occur. Second, knowledge of both the dynamic and quasi-static mechanical responses can be used to establish the constitutive equations which are necessary to increase the confidence limits of these materials, particularly if they are to be used in critical structural applications. Moreover, dynamic studies and the knowledge gained form them are essential for the further development of new material systems for impact applications. In this study, the high strain rate compressive deformation behavior of a ceramic matrix composite (CMC) consisting of SiC particles and an Al{sub 2}O{sub 3} matrix was studied and compared with its quasi-static behavior. Microscopic observations were conducted to investigate the deformation and fracture mechanism of the composite.