Novel Sandwich Structures with High Energy Absorption

This paper presents several novel sandwich structures based on plain foam core or core with embedded composite pins or pipes and composite or metal skins. Those sandwich structures are either subjected to projectile impact or impulsive blast loading. The corresponding deformation and failure modes are obtained to evaluate the structures in terms energy absorption against variation of core density, diameter of composite rod and pipe. For some sandwich structures subjected to projectile impact and blast, load-displacement traces are obtained to work out the energy absorption. It is found that PVC foam core with embedded carbon fibre tubes can have specific absorb energy approaching to 150 kJ/kg'. Finite element models are also developed to simulate impact and blast response of pure core structures and/or sandwich structures. Here, the PVC foam is modeled as crushable foam with strain hardening and ductile failure. Composite skins and Kevlar stitches are modeled as an anisotropic linear elastic material up to onset of the failure, followed by damage evolution controlled by fracture energy. The aluminium alloy skins are simulated as elasto-plastic material following Johnson Cook plastic behavior and damage evolution. In addition, various contact conditions are set between different materials to simulate the related interaction. The numerical deformation and failure modes, as well as load-displacement traces are compared with the corresponding experimental results, with reasonably good correlation. Using validated models, parametric studies are also carried out to investigate sandwich structures under more loading conditions.