Failure Mechanisms of Edge Delamination of Composites

The mechanisms controlling edge delamination in [± 30°/ ± 30°/90°/90°] s composites have been studied. Edge delamination strength and fracture toughness were strongly dependent on the resin matrices. For the same resin matrix, however, these prop erties drastically and consistently varied with the fibers studied, suggesting a fiber/matrix interface-controlled mechanism. Failure analyses using microscopy techniques revealed corresponding variations of fiber/matrix adhesion and crack paths. As the fiber/matrix adhesion decreased, the dominant crack paths in the laminates changed from straight —30°/90° interply failure to zig-zag 90° intraply failure. The critical role of fiber/matrix adhesion on edge delamination was demonstrated.