Improved wettability and interfacial adhesion in carbon fibre/epoxy composites via an aqueous epoxy sizing agent

In this paper, a modified epoxy emulsifier (MEE) was synthesised for preparing an aqueous epoxy sizing agent, which was used to reinforce interfacial adhesion of carbon fibre (CF)/epoxy composites. The sizing agent was evenly wrapped on the fibre surface with tiny particles, as well as increased the surface roughness of fibres; meanwhile, the activated carbon atoms on the surface of sized CF were further increased, as confirmed via SEM, AFM and XPS. The contact angle (CA) of fibres was observed via drop-on-fibre system. The results showed that the wettability of CF was significantly improved and the CA of CF was reduced by approximately 23°. According to the single-fibre fragmentation test, the interfacial shear strength of sized CF/EP composites increased by 70%-76%. The improvement of interfacial adhesion could be mainly attributed to the generation of chemical interaction bonds and the interface mechanical interlock of CF and the epoxy matrix.