A NOVEL TECHNIQUE FOR PENETRATOR VELOCITY-MEASUREMENT AND DAMAGE IDENTIFICATION IN BALLISTIC PENETRATION EXPERIMENTS

A novel experimental configuration that can simultaneously record proj ectile velocity histories and target back surface out-of-plane motion in penetration experiments has been developed. The technique: was used to investigate failure mechanisms during ballistic impact of an S-2 g lass fiber woven composite with 60% fiber volume fraction. Microscopy studies performed on recovered samples clearly show interply delaminat ion, fiber breakage, ply inelasticity, and fiber kinking as the major failure modes in these composites. Recorded penetrator velocity histor ies indicate the failure process is rate dependent. Three well defined regions with different failure zones are observed in the laminate. In a region at the rear of the target plate, Region A, extensive delamin ation between plies is seen leading to bulge formation. Damage is obse rved in front of the penetrator with substantial fiber shearing. In a middle region, Region B, tensile fiber failure and large fiber deflect ion, to accommodate the lateral expansion generated by the steel penet rator, are observed. At the projectile entrance, Region C, fiber micro fracture followed by fiber tensile failure is believed to be the failu re mode in this region. Noticeable delamination is also produced in pl ies close to the front specimen surface. Two major fiber failure modes are observed in the micrographs, fiber kinking and cracking. Well def ined kink bands are seen in Regions B and C on plies with fibers orien ted perpendicular to the penetration direction. The formation of kink bands appears to be the result of compressive failure due to lateral m otion of the plies away from the advancing steel penetrator.