Ballistic Limit of Sandwich Plates With a Metal Foam Core

Abstract

The ballistic perforation of sandwich plates comprising two identical/unidentical aluminum alloy face sheets and an aluminum foam core is investigated to gain insights into the factors governing the penetration processes. The impact velocities of projectiles with conical, flat, and hemispherical noses range from 60 ms−1 to 220 ms−1 in the experiments. Against conical-ended projectiles, petalling failure is found to be an active failure mode at the rear face sheet. Against projectiles with flat and hemispherical noses, both petalling failure and petalling-flipped-cover failure are observed. Finite element simulations considering the effect of foam meso-structure on the ballistic limit of sandwich plates are performed and validated against the experimental results. It is shown that the local bending and fracture of the cell walls significantly dissipate the kinetic energy of the projectile and restrain the occurrence of the high stress regions. Characteristic double-peak and single-peak modes of contact force time histories are observed for projectiles with various nose shapes. It is also found that a sandwich plate with thicker front face sheet has higher ballistic resistance, which may facilitate the instructional arrangement of face sheets with regard to mass distribution to achieve higher ballistic resistance. Finally, a three-stage theoretical model based on energy balance principle is developed for each type of projectile to predict the residual velocities after perforation of sandwich plate.