Mechanical and Tribological Enhancement of Carbon Fiber/Poly(Hexahydrotriazine) Composites via Modulus Gradient Zinc Oxide@Zeolitic Imidazolate Framework-8 Array Interphase

Carbon fiber–reinforced polymers (CFRPs) inherently experience stress concentration due to the significant modulus differences between carbon fiber (CF) and the resin. In this work, the zinc oxide nanorods synthesized on the surface of CF cloth were employed as the zinc source to construct a zinc oxide@zeolitic imidazolate framework-8 (ZnO@ZIF-8) interfacial transition layer, which effectively narrowed the modulus gap between CF and poly(hexahydrotriazine) cross-linked polyimide (PI-PHT), thereby facilitating stress transfer and frictional heat dissipation. Compared to unmodified composite, CF@ZnO@ZIF-8/PI-PHT exhibited a 45% increase in tensile strength and a 54% reduction in wear rate. Furthermore, closed-loop recycling of CF@ZnO@ZIF-8 and its composite was achieved while retaining superior mechanical and tribological performance. This work provides a new strategy for developing environmentally sustainable, recyclable, and wear-resistant CFRPs. Highlights Modulus gradient design effectively reduced stress concentration. Interface was reinforced by mechanical interlocking and chemical bonding. Interphase significantly enhanced the tribological properties of composites. Closed-loop recycling was achieved through the degradability of resin. Recycled composites still maintain high performance.