Designing “soft-rigid” hybrid layer for CF/Epoxy composites towards outstanding interfacial and tribological properties

[Display omitted] •A unique “soft-rigid” hybrid layer was synthesized onto the CF surface.•The hybrid layer could improve interfacial interaction between CF and epoxy.•The stress could be transferred uniformly and gradually in the hybrid layer.•Modified composite with “soft-rigid” hybrid layer showed improved IFSS. To enhance interfacial and tribological performances of carbon fiber (CF)/Epoxy composites, a unique “soft-rigid” hybrid layer was synthesized onto CF surface. Polydopamine (PDA), 3-aminopropyl triethoxysilane (APTES), and modified MXene (MXene-PEI) nanosheets reacted to form the hybrid layer. PDA and APTES were the components of the soft part, formed by self-polymerization, hydrogen bond and van der Waals Force. The stiff portion, on the other hand, was composed of MXene-PEI nanosheets that were grafted with polyethyleneimine (PEI) and 3-glycidoxypropyltriethoxysilane (GPTES). The results showed that when the “soft-rigid” hybrid layer was prepared, the CF’s surface roughness, surface energy, and wettability significantly were increased. The CF-(PDA + APTES + MXene-PEI) (abbreviated as CF-PAM)/Epoxy composites with “soft-rigid” hybrid layer showed improved IFSS (35.7 MPa) of 63.8 %, in comparison to unsized CF/Epoxy composites. Furthermore, The tribological performance of CF-PAM/Epoxy composite exhibited superior tribological performance, and its wear rate decreased to 1.46*10-4 mm3 N-1m−1 from that of Epoxy (7.86*10-4 mm3 N-1m−1). The “soft-rigid” hybrid layer could form a buffer zone inside the hybrid layer, in addition to improving the interfacial interaction between CF and epoxy. Moreover, the stress could be transferred uniformly and gradually in the “soft-rigid” hybrid layer, leading to a complicated and long crack path and excellent wear resistance.