DYNAMIC BUCKLING OF IMPULSIVELY LOADED PRISMATIC CORES

When sandwich panels with prismatic cores are impulsively loaded, the stresses imposed by the core on the front face, as well as those transmitted through the core govern the response metrics, especially the center displacement, resistance to tearing, and loads transmitted to the supports. This article presents a basic study of the dynamic response with emphasis on the I-core. A prior assessment revealed bucklewaves induced because of inertial phenomena accompanying the rapid compression of the members. The development of these waves is an integral aspect of the dynamic response. One objective of this investigation is to ascertain the characteristics governing such waves in I-core configurations through a combined experimental and numerical study. A particular emphasis is on the influence of manufacturing imperfections in the core members on the formation and propagation of the buckles. A second goal is to examine the stresses associated with the dynamic compression of the core, again through a combined experimental and numerical investigation. The investigation is conducted for stainless steel I-core panels supported at the back face and subjected to a constant velocity at the front. Imperfections to be included in the numerical study have been ascertained by comparing buckle patterns with those found experimentally over the relevant velocity range. The simulations reveal that the stresses induced differ on the front and back faces. On the front they are higher and velocity dependent. On the rear they are velocity invariant and scale with the relative density and material yield strength. The duration of the stress pulses, which is essentially the same on both faces, scales linearly with the core height. It correlates with the time needed for bucklewaves to propagate through the core to the back face. After the pulse terminates, the core continues to compress at a stress level about an order of magnitude smaller.