In designing materials to resist impact and penetrations, numerical simulation offers effective means to ascertain impact mechanism close to practical experimental procedures. This work presents penetration characteristics of water as an inter-layer between ultra-high strength steel sandwich structure. Residual velocities for both monolithic and sandwiched structures have been investigated. In the case of the monolithic structure, good agreement was found between experimental and simulation results in reducing projectile initial velocity of 854 m/s to obtained residual velocities of 487 m/s and 460 m/s respectively. Energy dissipation capability of water as an interlayer has also been investigated. Water, proving very effective in decreasing projectile velocity of 390 m/s to zero in a 2 mm steel-2 mm water – 2 mm steel sandwich system. Numerical simulation has been carried out using Ansys Explicit / Autodyn – a commercial software based on finite element method which is very effective in solving non-linear problems. Lagrange elements were used in the discretization of both the water and steel media.

This review reports on the current trends in steel-based sandwich structures subjected under high velocity impact. The review begins with a brief introduction on sandwich structures in general. It then delves into detail on some structural configuration parameters that affect sandwich performance. Light has been thrown on the energy absorption mechanisms of sandwich panels. The current global demand on energy necessitates the design of lightweight structures. Therefore, the review also elucidates on sandwich design optimization techniques mostly employed by researchers in meeting design constraints and objectives at the minimum weight and cost. Among these optimization techniques are the artificial neural network, fuzzy logic, Taguchi based method, response surface method, particle swarm optimization, genetic algorithm among others. The promising potential of auxetic materials with their negative Poisson's ratio in resisting impact penetration has been discussed. A comprehensive explanation on failure mechanisms that are encountered during projectile penetration has also been elaborated upon. Parameters such as projectile geometry, core design, core material and thickness of facesheets noted to have enormous influence on penetration resistance have also been addressed.