Browsing by Author "Bayhan, Mesut"

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Advanced Material Characterization and Modeling the Foreign Body Impact Damage Initiation and Progression of a Laminated Carbon Composite
(01. Izmir Institute of Technology, 2023-07) Bayhan, Mesut; Taşdemirci, Alper; Güden, Mustafa; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
The coupon level composite sample tests and the accompanying numerical models were carried out to predict the response of woven carbon fiber composite structures against impact. The numerical models of the coupon-level tests were implemented in LSDYNA software using the MAT_162 and MAT_58 composite material models. The results obtained by both quasi-static and dynamic tests were used to determine their constants. In addition to the tests that were used for the determination and calibration of the material model parameters, separate tests and their models were performed for the validation, including punch shear tests and low-velocity impact tests. It could be said that the material models examined were considered comprehensive and precise as the experimental results were well predicted by the numerical models. Also, the rate sensitivity of the woven carbon composite in the in-plane and thickness directions was investigated experimentally and numerically. In the tests, the DIC method was employed in the determination of the displacement and strain of the specimen. Based on the results obtained, it was concluded that the in-plane tensile properties are rate insensitive. Besides, the simulations of the component level tests, such as bird strike and drone impact, were established to investigate the damage initiation and propagation within the composite. It was found that the drone impact results in more severe damage compared to the bird impact. It is worth noting that the development of such precise composite material models to simulate dynamic loadings will definitely shorten the time between the beginning of designing and the component testing.
Residual Strength Analysis of an E Glass/Polyester Composite Subjected To Impact
(Izmir Institute of Technology, 2018-12) Bayhan, Mesut; Taşdemirci, Alper; Güden, Mustafa; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
In this thesis, residual strength analysis of an E-Glass/polyester laminate was carried out for multiple impact loading. MAT_162 material model in LS-DYNA finite element code was used to model the constitutive behavior of the composite and material model parameters were determined using the results of the mechanical characterization. Experimental and numerical multiple loading were performed for two cases, namely Split Hopkinson Pressure Bar (SHPB) and projectile impact testing device. Numerical models were simulated DYNAIN file method strategy in which a composite laminate was impacted multiple times, which was very close to the actual case. A numerical ballistic test model using conventional strategy (in the same simulation all the loads applied sequentially) was employed to check the accuracy of that using the proposed new methodology. After the first hit the SHPB results revealed that delamination occurred at the interface between the first and second layers. Following the second hit, delamination propagated along the inside layers of the composite and occurred at the interface between the eighth and ninth layer. As far as the bar responses concerned, the reflected pulse increased from zero to a maximum value then gradually decreased at the first impact. However, a sharp rise was seen in the reflected pulse of the second impact due to failure corresponding to catastrophic failure. In projectile impact tests, delamination was also found to be increased with the increasing number of hits at both front and back surfaces. Similar results were obtained for both DYNAIN and conventional strategies. It was concluded that simulations showed well agreement with experimental results.
Citation - WoS: 25
Citation - Scopus: 30
The Strain Rate Sensitive Flow Stresses and Constitutive Equations of a Selective-Laser and an Annealed-Rolled 316l Stainless Steel: a Comparative Study
(Elsevier, 2022-03-24) Güden, Mustafa; Enser, Samed; Bayhan, Mesut; Taşdemirci, Alper; Yavaş, Hakan; 03.10. Department of Mechanical Engineering; 01. Izmir Institute of Technology; 03. Faculty of Engineering
The strain rate dependent compressive flow stresses of a Selective-Laser-Melt 316L (SLM-316L) alloy and a commercial (annealed-extruded) 316L (C-316L) alloy were determined, for comparison, between 1x10-4 and ∼2500 s-1 and between 1x10-4 and ∼2800 s-1, respectively. The Johnson and Cook flow stress material model parameters of both alloys were also determined. The microstructural examinations of the deformed cross-sections of tested specimens (interrupted tests) showed a twinning-induced-plasticity in SLM-316L alloy and a martensitic transformation-induced-plasticity in C-316L alloy. Twin and martensite formations were detected microscopically higher in the dynamically tested specimens until about 0.22 strain, while the twin and martensite formations decreased at increasing strains due to adiabatic heating. The rate sensitivity of SLM-316L was determined slightly higher than that of C-316L within the quasi-static strain rate range (1x10-4 and 1x10-2 s-1), while the rate sensitivities of both alloys were similar in the quasi-static-high strain rate range (1x10-4 and ∼2500-2800 s-1) at low strains. A more rapid decrease in the rate sensitivity of C-316L at increasing strains was found in the quasi-static-high strain rate range. The similar activation volumes of both alloys, corresponding to the dislocation intersections, indicated a similar thermally activated deformation process involvement in both alloys.