Triple Dynamic Network-Enabled Vitrimer for Repairable and Recyclable Carbon Fiber-Reinforced Composites

Abstract

Conventional thermosets such as epoxies offer superior mechanical properties but lack recyclability, posing environmental challenges and sustainability concerns. In this context, vitrimer, which offers “thermoset-like” mechanical properties and “thermoplastic-like” flow behavior, emerges as a promising alternative. Herein, a triple dynamic covalent adaptable network (CAN) was installed in the epoxy system to offer recyclability without compromising the mechanical properties. This “epoxy vitrimer” was used to design a carbon fiber-reinforced vitrimer epoxy (CFRVE) laminate. Fourier transform infrared (FTIR) was used to confirm the formation of cross-links with epoxide groups. The tensile strength for these systems is in the range of 43–53 MPa depending on the number of preinstalled CANs, which compares well with the conventional epoxies. Thermal and mechanical analyses of the vitrimer epoxy systems reveal exceptional properties, including degradation temperatures above 250 °C and an activation energy of 56 kJ/mol for stress relaxation. CFRVE laminates, fabricated via vacuum-assisted resin transfer molding (VARTM), exhibit 38 MPa interlaminar shear strength (ILSS) and 520 MPa flexural strength (FS), which are comparable to those of conventional carbon fiber-reinforced epoxy (CFRE) laminates. The CFRVE laminate exhibits a remarkable self-healing efficiency of 56% in ILSS. Furthermore, the vitrimer matrix enables nondestructive recovery of carbon fibers (CFs) and reusable degradation products, offering a closed-loop recycling solution for CFRVE composites.