Self-healing of fatigue crack in epoxy materials with epoxy/mercaptan system

Successful retardation or arrest of fatigue crack is observed in self-healing epoxy composite containing dual encapsulated healant, i.e. two types of microcapsules that respectively include expoxy prepolymer and mercaptan/tertiary amine hardener. Fast curing of the released healing agent from the broken capsules leads to rapid development of its bonding strength and fracture toughness at room temperature. It is found that the effects of microcapsules induced-toughening, hydrodynamic pressure crack tip shielding, polymeric wedge and adhesive bonding of the healing agent are responsible for the extension of fatigue life. Depending on the applied stress intensity range, Delta K-I, and the competition between polymerization kinetics of the healing agent and crack growth rate, the above mechanisms exert different influences on crack retardation. The results might serve as a reference for further improving the performance of the healant system under fatigue circumstances.