Extrinsic fatigue-life extension in structural composite materials by impregnated microcapsules

The investigation of the crack propagation behavior and fatigue-life extension was conducted by using a tapered double cantilever beam (TDCB) specimen consisting of neat epoxy with diethylene triamine (DETA) as a curing agent, epoxy-DETA with 15% dicyclopentadiene (DCPD) and Grubb’s catalyst, and epoxy-DETA with 15% ethyl phenyl acetate (EPA) microcapsules. Both the epoxy-DETA with EPA microcapsules and epoxy-DETA with DCPD and Grubb’s catalyst demonstrated a significant fatigue life extension. The healing efficiency was found to be about 3500% for TDCB specimen with epoxy-EPA microcapsules and about 410% for a TDCB specimen with DCPD/catalyst microcapsule system, which is about 9 times for epoxy-EPA relative to DCPD/catalyst system. Two healing mechanisms contributed to the fatigue life extension: the reaction between the matrix material and the healing agent and the capillary effect of the liquid healing agent.