Damage resistance and damage tolerance of hybrid carbon-glass laminates

This paper explores the influence of impact energy and stacking sequence on the damage resistance and damage tolerance of hybrid Carbon Fiber Reinforced Plastic (CFRP) and Glass Fibre Reinforced Plastic (GFRP) hybrid laminates in order to establish their suitability as an alternative to CFRP laminates for use in aircraft structures. Compression after impact tests demonstrate that CFRP/GFRP hybrid laminates display increases in failure stress of up to 32% in comparison to laminates constructed entirely from CFRP. Laminates displaying the highest stresses at failure are those that exploit stacking sequence and GFRP content to prevent delamination from occurring close to the outer surface of the laminate during impact. This eliminates local sublaminate buckling and hence rules out failures due to delamination propagation. A switch to an anti-symmetric buckling mode is noted at low levels of stress in the CFRP baseline laminates subject to higher energy impacts. This mode switch did not occur in the hybrid designs. A previously developed analytical model for assessing damage tolerance of laminates that fail following local buckling induced delamination propagation is shown to be applicable to hybrid laminates.