Hierarchical Interfacial Construction by Grafting Cellulose Nanocrystals onto Carbon Fiber for Improving the Mechanical Performance of Epoxy Composites

Carbon fiber-reinforced composites have been widely used in the aerospace industry because of their superior comprehensive performance, including high strength, low density, fatigue resistance, long service life, etc. The interface between the fiber reinforcement and the matrix is one of the key factors that determines the performance of the composites. The construction of covalent bonding connections between the components has proven to be an effective strategy for improving the interfacial bonding strength but always reduces the toughness. In this work, dual silane coupling agents are applied to covalently connect cellulose nanocrystals (CNCs) onto carbon fibers, constructing hierarchical interfacial connections between the fibers and the epoxy matrix and significantly improving the interfacial bonding strength. As a result, the tensile strength of the epoxy composites increased from 519 MPa to nearly 900 MPa, which provides a potential approach for significantly improving the mechanical performance of composites.