Mode-I and mode-II interlaminar fracture properties of high strength polyacrylonitrile-based carbon fiber reinforced disulfide-based epoxy-covalent adaptable network polymer composite

Advances have focused on disulfide-based epoxy-covalent adaptable network (CAN) polymer systems, which leverage reversible disulfide exchange reactions. The evolution from conventional carbon fiber reinforced thermosetting composites (CFRPs) to disulfide-based epoxy-CAN polymer composites represents a paradigm shift toward sustainable, high-performance materials. Recently, Teijin Ltd. has developed disulfide-based epoxy-CAN CFRP (carbon fiber: IMS65; resin: DGEBA/4-APD/PES5003P (disulfide-based epoxy-CAN polymer)). In this study, the mode-I and mode-II interlaminar fracture properties of the disulfide-based epoxy-CAN CFRP were investigated. The mode-I and mode-II interlaminar fracture tests were conducted under static loading using a double cantilever beam and end notched flexure specimens. The values of the mode-I and mode-II interlaminar fracture toughness of the disulfide-based epoxy-CAN CFRP were 0.293 and 1.054 kN/m, which were higher than those of conventional epoxy CFRP. The fracture surfaces of the disulfide-based epoxy-CAN CFRP were rougher than those of conventional epoxy CFRP. These improvements are attributed to enhanced fiber bridging, plastic deformation, and the dynamic disulfide exchange mechanism, which promote energy dissipation and interfacial adhesion. Compared to conventional epoxy CFRPs, the novel composite exhibits superior delamination resistance, recyclability, and potential for self-healing.