Permeability of Various Hybrid Composites Subjected to Extreme Thermal Cycling and Low-velocity Impacts

This experimental exploratory study investigates the effects of embedding a ‘barrier’ layer within a graphite/epoxy composite during manufacture on reducing the permeability after thermal cycling and low velocity impact events. The baseline composite material was an eight ply graphite/epoxy system. Barrier layer candidates include aluminized Mylar®, aluminum foil, and two β-Ti 15-3 films. Cryogenic thermal cycling was performed on the hybrid composites and control composites to determine if the interleaved composites exhibited reduced permeability after thermal cycling as compared to the controls. Drop-weight impact tests were performed on the hybrids and controls to determine the effect of interleaving on the critical impact energy of the graphite/epoxy composites. The results of this research suggest that the addition of an embedded barrier layer can increase a graphite/epoxy composite’s resistance to low-velocity impacts, which cause permeation. This research indicates that hybrid composites are promising materials for applications where extreme temperatures and moderate impact loads are experienced.