Fatigue Crack Growth Mitigation by In Situ Healing in Thermoset CFRP Composite

Delamination due to fatigue loading in laminated composites is difficult to detect and, therefore, could lead to catastrophic failure if left undetected. Hence, it is important to be able to detect and quantify the delamination crack growth behavior due to fatigue loading and explore methods to heal the delamination in situ, without the need for mechanical fasteners. To this end, double cantilever beam specimens of carbon-fiber-reinforced polymer composite containing thermoplastic healants were manufactured, and mode I fatigue delamination experiments were carried out for the virgin and healed cases for oven healing, and in situ macro fiber composite healing cases. The primary purpose of using thermoplastic healants (polycaprolactone and shape memory polymer) was to heal the cracks formed during fatigue loading and regain the load-carrying capacity of the composite structure. The in situ healing was carried out by activating the macro fiber composite actuators attached to the double cantilever beam specimen after 5000 cycles of loading to generate heat. After in situ healing, significant reduction in crack growth compared to the virgin cycle was observed, and healing was repetitive. We envision that these findings will be immensely helpful in extending the service life of composites and may also result in significant repair cost savings.