Enhancing the interfacial strength of carbon fiber/epoxy composites by introducing “rigid-flexible” structure onto carbon fiber surface via π–π interaction

The "rigid-flexible" multi-scale gradient modulus interlayer was constructed by establishing the π-bridges between CF and CNTs with the assistance of pyrene compounds and chemically grafting polyetheramine (PEA) on the CF surface, and the effect of the gradient modulus interlayer on the interfacial properties of CF composites was studied. The construction of the "rigid-flexible" structure significantly increased the roughness and activity of CF surface, resulting in improving the mechanical interlocking and chemical bonding between fibers and the resin. The interfacial shear strength (IFSS), interlaminar shear strength (ILSS), transverse fiber bundle (TFB) strength and flexural strength of CF composites increased by 71.1%, 58.3%, 89.7% and 45.7%, respectively. The interfacial failure behaviors and strengthening mechanisms of the composites were also investigated. This scheme of establishing rigid-flexible gradient modulus interfacial layer with simple operation and nondestructive to fibers would provide a valuable reference for obtaining high performance CF composites.