SiO ₂ -Based Janus Nanosheet-Modified Carbon Fibers for Carbon Fiber/Epoxy (CF/EP) Composites

High-performance carbon fiber/epoxy resin (CF/EP) composites are widely applied in engineering and technology, where the interfacial bonding between the CF surface and the epoxy matrix is crucial to composite performance. To achieve enhanced interfacial performance, a dual-surface heterofunctional structure was proposed. SiO2-based Janus nanosheets with inner amino groups and outer epoxy groups were synthesized via a sol–gel self-assembly method. These two-dimensional rigid materials were then introduced onto the surface of CFs through electrochemical grafting. The experimental results indicated that the SiO2-based Janus nanosheets were uniformly grafted onto the CF surface via chemical bonding. The proposed Janus nanosheets increased the interfacial shear strength (IFSS) by 38.3% due to enhanced mechanical interlocking between the carbon fibers (CFs) and the resin. This study presents a strategy to improve interfacial adhesion in CF composites with two-dimensional Janus nanosheets, thereby creating a dual-chemical-bonding interfacial layer.