The micro‐nano construction of metal‐free nacre‐like interface for polyimide/carbon fiber composite via multi‐molecular grafting method

Abstract The multi‐molecular grafting interface becomes significant for the perfect structure construction of carbon fiber reinforced composite (CFRC), being built in this study between the epoxy‐sized carbon fibers (CFs) and polyimide (PI) matrix via the multi‐molecular coupling reactions among the epoxy sizing layer, hydroxyl‐rich silicide nanomaterial (SiO₂OH), and disulfide catalyst. They not only endowed the composite with multiple coupling interactions at the PI/CF interface but also promoted the surface‐initiated radical curing reactions on both the sizing layer and the surface of SiO₂OH. As a result, the SiO₂OH nanofiller within the PI/CF composite constituted the composite interface with a nacre‐like structure, exhibiting superior interfacial shear stability and excellent mechanical properties. The interfacial shear strength (IFSS) of the PI/CF composite reached 1.93 times the original thermally cured ones (value of 144.23 MPa), keeping higher flexural strength and modulus of 2000.1 MPa and 191.0 GPa. The nanofilling effect of SiO₂OH components endowed the CFRC with structural integrity and mechanical failure mechanism based on the whole fracture of the composite rather than the delamination failure among the CF/matrix multilayers.