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.