On the out-of-plane ballistic performances of hexagonal, reentrant, square, triangular and circular honeycomb panels

Abstract Ballistic penetration is a serious threat to military vehicles. Honeycomb structure is one of the most focused solution to improve the ballistic performance due to its great lightweight design and high resistant against impact. There are lots of honeycomb structure topologies. However, no comprehensive comparison on out-of-plane ballistic performance between common honeycomb types had been conducted to our knowledge. Therefore, hexagonal, reentrant, square, triangle and two circular (CS and CH types) honeycomb structures with identical mass and thickness are developed and modelled in this paper. Their relative densities are firstly calculated. Their numerical models and the Lambert-Jonas ballistic model are established. The ballistic performances of these six cases impacted by a blunt nose cylinder projectile from out-of-plane direction are detailed compared through numerical method. Their dynamic response, elastic and plastic deformation, failure mechanism and energy absorption capability are researched. Relations between initial velocity and residual velocity of projectile and the ballistic limit velocities of all cases are also compared. The results indicated that reentrant, square and triangular cases perform worse than hexagonal honeycomb. The fascinating deformation mechanism of CS and CH cases results in a long elastic deformation time and high strength after elastic deformation, which leads to a large decrease in residual velocity. Compared with hexagonal honeycomb, ballistic limit velocities of CS and CH type are improved by 15.2 % and 25.0 %, respectively. This comparison research provides a useful reference for sandwich honeycomb core design.