Analytical solutions for dynamic deformation of foam materials during the Taylor cylinder-Hopkinson bar impact experiment were obtained. It was shown that shock wave of foam collapse appears during the fast impact. The results of this experiment can be used in estimating the average material properties of the foam under dynamic loading conditions. Results show that the undeformed and change in length of foam specimens are in good agreement between theory and experiment, as well as numerical analysis.

a b s t r a c tThe effect of rubber, Teflon and aluminum foam interlayer material on the ballistic performance of composite armor was investigated both experimentally and numerically. Although, rubber interlayer did not cause any significant delay in the initial stress build-up in the composite layer, Teflon and aluminum foam interlayer caused a significant delay and reduction in the magnitude of the stress transmitted to the composite backing plate. Damage in the ceramic layer was found to be highly localized around the projectile impact zone for the configuration without interlayer and rubber interlayer while aluminum foam and Teflon interlayer spread the damage zone in the radial direction. Relatively large pieces of the ceramic around the impact axis in the rubber interlayer configuration were observed while the ceramic layer was efficiently fragmented in aluminum foam and Teflon interlayer configuration.

The energy absorption in a foam-filled thin-walled circular Al tube was investigated based on the experimentally determined strengthening coefficient of filling using Al and polystyrene closed-cell foams with three different densities. Foam filling was found to change the deformation mode of tube from diamond (empty tube) into concertina, regardless the foam type and density used. Although foam filling resulted in higher energy absorption than the sum of the energy absorptions of the tube alone and foam alone, it was not effective in increasing the specific energy than simply thickening the tube wall. It was shown that for efficient foam filling an appropriate foam-tube combination must be selected by taking into account the magnitude of strengthening coefficient of foam filling and the foam filler plateau load.

The main objective of this study was to measure the fracture toughness of the human teeth enamel using the microindentation technique and to compare the results calculated from the equations developed for Palmqvist and radial-median cracks. Vickers microhardness measurements of dental ceramic (alumina) and human teeth were performed using indentation fracture method. The fracture toughness of enamel was calculated using different equations reported in the literature. Vickers microhardness of the sintered alumina specimen (98.8% theoretical density) was measured to be 14.92 GPa under 9.8N indentation load. Three equations based on the radial-median cracks were found to be applicable for the fracture toughness determination of the enamel. Results show that indentation fracture method is adequate to measure microhardness and fracture toughness of dental materials. However the calculation of fracture toughness depended on the nature of the cracks and also on the location of the indentation. Therefore, it is necessary to identify the crack profile and to select the appropriate equation for accurate fracture toughness values.

The experimental and numerical quasi-static crushing responses of extruded closed cell polystyrene foam-filled thin-walled aluminum tubes were investigated. The numerical crash analysis of empty and foam-filled tubes was performed using the explicit finite element code PAM-CRASHe. Satisfactory agreements were generally achieved between the finite element model and experimental deformed shapes, load-displacements, fold lengths and specific energy absorptions. The model and experiments have also highlighted the several effects of foam filling on the crushing of thin-walled tubes. The energy absorptions in foam-filled tubes were further shown to be higher than the sum of the energy absorptions of empty tube (alone) and filler (alone).