Bio-inspired interfacial crosslinking reinforcement strategy to construct “soft-hard” structure for improving the interfacial properties of carbon fiber composites

Inspired by organic–inorganic soft and hard components found in mollusk shells, this study utilized phytic acid (PA) and MXene (Ti3C2) to create "soft-hard" structure on the surface of carbon fiber (CF) through the bio-interfacial cross-linking reinforcement (BICR) strategy. This strategy not only increased the chemical reaction activity on the fibre surface, but also enlarged the interphase area of the fibres, which facilitated the formation of a strong physical riveting interaction among the fibres and substrate. Compared with the untreated CF composites, the flexural strength, flexural modulus, interlaminar shear strength (ILSS), tensile strength and interfacial shear strength (IFSS) of the CF/PEI/PA/MXene composites were increased by 51.4%, 62.5%, 63.0%, 74.9%, and 45.8%, respectively. These positive results were attributed to the large number of reactive functional groups on the PA myo-inositol ring, which increased the chemical reactivity of the fiber surface. Additionally, the MXene assembled on the fibre surface enhanced the adhesion and mechanical interlocking between the fibre and resin. This work provides an advanced route to fabricate CF composites with excellent mechanical properties.