Effects and mechanisms of hBN/PEI composite sizing agent on the interfacial properties of carbon fiber reinforced polyetheretherketone composites

Carbon fiber-reinforced poly (ether ether ketone) (CF/PEEK) composites exhibit excellent comprehensive properties, but their performance is often restricted by weak interfacial bonding between chemically inert carbon fibers and the PEEK matrix, which limits efficient load transfer. To overcome this limitation, a hexagonal boron nitride/polyetherimide (hBN/PEI) composite sizing agent was developed to modify the carbon fiber surface and regulate the CF/PEEK interface. The uniformly decorated hBN/PEI sizing layer increased the surface roughness of carbon fibers and improved interfacial adhesion with the PEEK matrix. As a result, the interlaminar shear strength (ILSS) of the sized CF/PEEK composites increased by up to 45.07%. To elucidate the underlying reinforcement mechanism, molecular dynamics (MD) simulations were conducted to investigate molecular-scale interfacial interactions. The simulation results showed that the hBN/PEI sizing interlayer strengthened the interactions between carbon fibers and PEEK. This enhancement was mainly attributed to intensified mechanical interlocking, which changed the interfacial failure mode and enabled more effective load transfer. This study provides an effective interfacial regulation strategy for CF/PEEK composites and offers theoretical guidance for designing high-performance thermoplastic composites.