Photo‐Triggered Frontal Polymerization for the Preparation of Carbon Fiber‐Reinforced Epoxy Resin Composites

ABSTRACT Conventional thermal curing of carbon fiber‐reinforced epoxy resin composites is plagued by high energy consumption, while photo curing is constrained by the poor penetration of ultraviolet light and the challenge of curing dark‐colored systems, creating an urgent demand for advanced curing technologies. This study systematically investigates the curing behavior and properties of epoxy resins and their carbon fiber‐reinforced composites prepared via photo‐triggered radical‐induced cationic frontal polymerization (RICFP). Driven by practical application needs, the work addresses two key challenges in conventional curing processes: high energy consumption associated with thermal curing and limited ultraviolet (UV) light penetration in optically opaque carbon fiber systems. By optimizing the contents of cationic photoinitiator, free‐radical thermal initiator, and resin monomer, a stable frontal polymerization process was successfully achieved. Results demonstrate that when the contents of initiators are both 1.5 wt% and the monomer content is 40 wt%, frontal polymerization proceeds smoothly and rapidly. The cured resin exhibits a tensile strength of 68.0 MPa and a flexural strength of 117.3 MPa. RICFP enables high conversion efficiency and uniform curing of epoxy resins; curing kinetics reveal that monomer addition significantly lowers the activation energy. Carbon fiber‐reinforced composites cured via RICFP achieve properties comparable to those of traditional thermally cured, featuring a tensile strength of 361.9 MPa and a flexural strength of 503.3 MPa. This work provides an efficient and energy‐saving strategy for the preparation of high‐performance carbon fiber/epoxy composites.