ENERGY-TRANSFER IN BALLISTIC PERFORATION OF FIBER-REINFORCED COMPOSITES

High speed cine techniques have been used to examine the perforation o f thin targets constructed of glass fibre reinforced plastic (GRP), Sp ectra (Allied Signal) and Kevlar (Du Pont) composites as well as nylon and Kevlar fabrics. From the film record the kinetic, strain and (for the composites only) delamination/surface energy terms were evaluated for the rear layer of material. Simple models for the deformation of the panels were used to compare these energies, summed for all layers, with the projectile energy loss. All the energy terms are shown to be significant. The Kevlar fabric does not fit the pattern of the other materials, in that for this material nearly all the projectile energy appeared as tensile strain energy in only the rear layer of the target . This result was a consequence of the high apparent strain observed i n the fabric, and is not simply explained. Energy terms not evaluated, but which may be significant, are crushing and ejection of fibres for GRP composites and spalling of matrix phase with the Spectra composit es. The work highlights many of the features which need to be accounte d for in modelling ballistic perforation of fabric and fibre reinforce d composite materials. (C) 1998 Chapman & Hall.