A study of the effect of target thickness on the ballistic perforation of glass-fibre-reinforced plastic composites

Ballistic tests were conducted using hard-steel cylinders of two diameters and three nose shapes against glass-fibre-reinforced plastic (GRP) composite plates of various thicknesses. The data when plotted as energy to penetrate as a function of target thickness exhibit simple bi-linear relationships. This is also found to be the case for a broad range of reported composite ballistic impact data. A simple model is developed to explain the bi-linear behaviour and to provide the basis for geometrical scaling of composite ballistic perforation data, and also to help with the interpretation of material parameter and bond strength influences on ballistic resistance. The study also shows that energy absorption in thin GRP targets is largely independent of projectile nose geometry and that thin GRP and Kevlar targets respond similarly on a thickness basis to impact by fragment simulating projectiles. Measurements on geometric damage parameters in the perforated composites are presented.