Dynamic response of a cellular block with varying cross-section

In this paper, the plastic crushing response is studied for an aluminum foam block of varying cross-section under impact. The influence of the gradient on the cross-section is investigated. Based on the one-dimensional shock theory, an analytical model is proposed to investigate an impact scenario, in which a foam block with a gradient in its cross-section together with a rigid mass impinges onto a rigid target. Because of the change in the cross-sectional area along the length, two possible deformation modes may appear, namely the double shock mode and the single shock mode. When the largest cross-section is impinged, two compaction zones in the foam block are found, while only one compaction zone appears from the impinged end when the smallest cross-section is impinged. Of particular interests are the absorbed energy and the force transmitted to the target. The analysis reveals that the energy absorption capacity is weakened with a negative gradient while positive gradient has no influence on the energy absorption capacity of the graded foam. An experiment was then designed to investigate the behavior of the graded foam block under impact. The rigid mass together with the foam block was fired from a gas gun barrel, and its speed was measured before it collided onto the rigid target. The deformation history of the specimen was recorded by a high-speed video camera. Image analysis was employed to obtain the velocity of the impinging mass during the process. Observation of the deformation profile demonstrates the two basic deformation modes described in the analytical modeling.