Ballistic impact behavior of foam core sandwich structures:\ud Formulation

An analytical method based on the energy balance and wave propagation approach was developed for a sandwich panel\ud subjected to a ballistic impact. Possible energy absorbing mechanisms in the complete perforation of a sandwich panel\ud involve tensile fiber stretching and damage, matrix delamination and fracture, core compression and crushing, plugging, delamination between the core and bottom face sheet and friction. The complete perforation of the sandwich panel was modeled as 3-stage process that describes perforation of the top face sheet, complete densification of foam core, and perforation of the bottom face sheet sequentially. An experimental study was carried out to compare ballistic impact performance of foam core sandwich panel with composite face sheets to a plain composite laminate having same areal density.\u