Impact perforation of aluminium Cymat foam

The perforation behaviour of Cymat(C) aluminium foam at various impact loading rates was studied both experimentally and numerically. Perforation tests were performed with an inverse perforation setup using a split Hopkinson pressure bar (SHPB) system at speeds up to 40 m/s. Compared with a quasi-static test using the same specimen and clamping system, a significantly enhanced piercing force was found under impact loading. Numerical simulations of the perforation test were carried out using LS-DYNA code, and the material models available in this code were benchmarked. Good agreement was found between the experimental and simulated force/displacement curves when using the honeycomb material model with an appropriate failure criterion. The simulation revealed that a strain discontinuity front propagated ahead of the perforator when the impact velocity of the perforator exceeded 20 m/s. The significance of this numerical model is that it demonstrates that the main feature (average perforation force) can be reproduced with a rather simple pre-implemented material law for a homogeneous specimen. An analytical model using the concept of a shock front with a power law densification assumption is proposed to describe the enhancement in the impact piercing force.