Constructing “nunchaku-like” multi-stage gradient interface via covalently grafting rigid-flexible-rigid structures onto carbon fibers: An effect strategy to improve interfacial properties of composites

A multi-scale “nunchaku-like” rigid-flexible-rigid structure was constructed on the CF surface using carbon nanotubes (CNTs) and polyether amines (PEA) to improve the interfacial properties of carbon fiber (CF) reinforced polymer composites. The multi-scale rigid-flexible-rigid structure not only enhanced the chemical bonding, mechanical engagement and wettability, but also balanced the modulus of the fibers and resin to achieve best match for less stress concentration. As a consequence, IFSS, ILSS and TFBT strength increased by 73.4%, 65.4% and 137.0% compared to the original composites. In addition, the composites failure behavior and the interfacial strengthening mechanism were investigated in detail. This work proposed a novel and promising strategy for the preparation of high-performance CF composite from the perspective of interfacial structure design.