Electrothermally Self-Healing Delamination Cracks in Carbon/Epoxy Composites Using Sandwich and Tough Carbon Nanotube/Copolymer Interleaves

Herein, two sandwich and porous interleaves composed of carbon nanotube (CNT) and poly(ethylene-co-methacrylic acid) (EMAA) are proposed, which can simultaneously toughen and self-heal the interlaminar interface of a carbon fiber-reinforced plastic (CFRP) by in situ electrical heating of the CNTs. The critical strain energy release rate modes I (G(IC)) and II (G(IIC)) are measured to evaluate the toughening and self-healing efficiencies of the interleaves. The results show that compared to the baseline CFRP, the CNT-EMAA-CNT interleaf could increase the G(IC) by 24.0% and the G(IIC) by 15.2%, respectively, and their respective self-healing efficiencies could reach 109.7–123.5% and 90.6–91.2%; meanwhile, the EMAA-CNT-EMAA interleaf can improve the G(IC) and G(IIC) by 66.9% and 16.7%, respectively, and the corresponding self-healing efficiencies of the G(IC) and G(IIC) are 122.7–125.9% and 93.1–94.7%. Thus, both the interleaves show good toughening and self-healing efficiencies on the interlaminar fracture toughness. Specifically, the EMAA-CNT-EMAA interleaf possesses better multi-functionality, i.e., moderate toughening ability but notable self-healing efficiency via electrical heating, which is better than the traditional neat EMAA interleaf and oven-based heating healing method.