Modeling of Shock Propagation in Aluminum Foam Under Impact
Stavros Gaitanaros (Univeristy of Texas at Austin), Stelios Kyriakides (University of Texas at Austin)
Instability in Solids and Structures
Mon 2:40 - 4:00
Barus-Holley 190
It has long been known that many lightweight cellular materials when impacted at a high enough velocity crush by the propagation of shocks. The formation of shocks in a class of metallic open cell foams has been confirmed and quantified in the accompanying experimental study. The present work uses micromechanically accurate models of random foams to first reproduce and subsequently study parametrically the dynamics of such shocks. Such a model starts as soap froth generated using the Surface Evolver software. It is converted into a solid by assigning non-uniform material distribution along its straight ligaments in accordance with measurements made on Al open-cell foams. Finite size cylindrical models are subsequently discretized with finite elements within the explicit code LS-DYNA, while the Al-alloy is modeled as a finitely deforming elastic-plastic material. Utilization of the beam-to-beam contact algorithm of the code is an essential component of the simulation of crushing. The models are first used to simulate impact experiments where they are shown to faithfully reproduce the formation and evolution of shocks including the force acting at the two ends, the shock front velocity, and energy absorbed. Numerical models are subsequently used to establish all features of the phenomenon, elucidate and reinforce experimental observations, and examine the validity of the use of 1D shock theory for this problem.