Investigations of High Performance Fiberglass Impact Using a Combustionless Two-stage Light-gas Gun

Two types of high performance fiberglass panels were investigated at normal impact conditions of around 1 km/s (2200 mph). Thin phenolic laminates of plain-weave glass cloth impregnated with synthetic thermosetting resins, one melamine and the other epoxy, were impacted by a 1.6 mm diameter nylon sphere using a combustionless two-stage light-gas gun. The resulting impact and ejecta was captured using high-speed imaging, and the perforation characteristics and damage zone were examined post-mortem using optical microscopy. Both composites had a fiber volume fraction of an estimated 56% and identical fiber weave so that the role of the matrix on impact performance could be comparatively investigated. The epoxy fiberglass resulted in full perforation of the target, whereas the melamine fiberglass resulted in deformation, but not full perforation. The overall damage zone of melamine fiberglass was twice the size on the rear surface than the epoxy fiberglass. In addition, the melamine fiberglass rear damage zone was 5 times the impactor diameter and exhibited ductile debonding and delamination as the main failure mechanisms. In contrast, the epoxy matrix rear damage was 3 times the impactor diameter and exhibited brittle failure mechanisms of fiber breakage and pullout. These experimental results suggest that the matrix material is a driving factor in the impact damage and perforation characteristics, and is discussed in context of the compressive and tensile strength at break of the materials.