Interfacial layer in high-performance CFRP composites cured out-of-autoclave: Influence of the carbon fiber surface and its graphite-like properties

This contribution addresses the challenging investigation of the chemical mechanisms occurring at the carbon fiber-matrix interface of carbon fiber-reinforced polymer (CFRP) composite materials cured out-of-autoclave. A high energy radiation curing method (electron-beam) was used to initiate free radical polymerization of acrylate-based matrices. Comparison with state-of-the-art thermally cured composites reveals the lower transverse mechanical properties of the radiation-cured CFRP composites. To improve the interfacial layer, several points related to the polymerization at the interphase have been investigated. Notably, the influence on the polymerization of acrylate matrices of the chemical functional groups present at the carbon fiber surface and its graphite-like properties are discussed using representative molecules. It is shown that these additives exhibit strong inhibiting effects, whereas thiol groups efficiently sensitize the initiation mechanisms and undergo transfer reactions. Moreover, it is discussed that graphite-like molecules affect the matrix polymerization and the mechanical properties of the composites. An adapted solution is proposed.