Phd Degree / Doktora
Permanent URI for this collectionhttps://hdl.handle.net/11147/2869
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Doctoral Thesis Experimental and Numerical Evaluation of the Blast-Like Loading of Fiber Reinforced Polymer Composites and Aluminum Corrugated Core Composite Sandwiches Through Projectile Impact Testing Using Aluminum Corrugated Projectiles(Izmir Institute of Technology, 2015) Odacı, İsmet Kutlay; Güden, Mustafa; Taşdemirci, AlperThis thesis develops and validates a laboratory scale blast-like testing method that can simulate explosive blast tests in air and under water without using explosives. The study has mainly focused on the shock loading potential of 1050 H14 trapezoidal corrugated core aluminium sandwich structures on E-glass/polyester composite plates and corrugated core composite sandwich structures experimentally, numerically and analytically. The composite plates were modelled using MAT_162 material model in LS-DYNA finite element code. Quasi-static and high strain rate tests were performed to determine the material model parameters of composite and corrugated structure. The resultant parameters were calibrated and validated by comparing the numerical results with the experimental results. The planar shock wave formation and propagation in corrugated core sandwich structures were shown experimentally using a direct impact Split Hopkinson Pressure Bar test set-up. Rigid-perfectly-plastic-locking material model and Hugoniot jump relations revealed the shock loading potential of the tested corrugated core sandwich structures. The shock loading response of composite plates and sandwich structures were investigated by firing the corrugated sandwich projectiles on the targets. These impact tests were also simulated numerically and an analytic model was used to predict the plate deflections. The experimentally, numerically and analytically determined back face deflections were compared with the deflections of the Conwep blast simulations in LS-DYNA. The results have shown that the corrugated core sandwich structures can generate shock loading as in the explosive blast tests and can be used to produce shock loads in laboratory scale experiments.Doctoral Thesis Experimental and Numerical Investigation of the Quasi-Static and High Strain Rate Crushing Behavior of Single and Multi-Layer Zig-Zag 1050 H14 Al Trapezoidal Corrugated Core Sandwich Structures(Izmir Institute of Technology, 2014) Kılıçaslan, Cenk; Güden, Mustafa; Taşdemirci, Alper; Güden, Mustafa; Taşdemirci, AlperThe quasi-static and dynamic crushing behavior of single, double and multi-layer zig-zag 1050 H14 Al trapezoidal corrugated core sandwich structures in 0°/0° and 0°/90° core orientations and with and without interlayer sheets were investigated both experimentally and numerically at varying impact velocities. The numerical simulations were conducted using the finite element code of LS-DYNA. The effect of fin wall imperfection was assessed through the fin wall bending and bulging. The numerical homogenization of the single layer corrugated structure was performed using MAT26 honeycomb material model. The buckling stress of single- and double-layer corrugated sandwich structures increased when the strain rate increased. The increased buckling stresses were ascribed to the micro inertial effects. The initial buckling stress at quasi-static and high strain rate was numerically shown to be imperfection sensitive. Increasing the number of core layers decreased the buckling stress and increased the densification strain. The panels tested with spherical and flat striker tips were not penetrated and experienced slightly higher deformation forces and energy absorptions in 0°/90° corrugated layer orientation than in 0°/0° orientation. However, the panels tested using a conical striker tip were penetrated/perforated and showed comparably smaller deformation forces and energy absorptions, especially in 0°/90° layer orientation. The homogenized models predicted the low velocity compression /indentation and projectile impact tests of the multi-layer corrugated sandwich with an acceptable accuracy with reduced computational time.