Tough and recyclable carbon-fiber composites with ultrastrong interfacial adhesion enabled by tailored vitrimer and carbon fiber

Carbon-fiber-reinforced polymers (CFRPs) play a major role in enabling highly efficient energy usage in various applications ranging from aerospace to automobiles and sporting goods, because of their lightweight and robust mechanical properties. However, most of the CFRPs are not easily recyclable, leaving a significant carbon footprint, and they exhibit poor fiber-matrix interfacial adhesion, leading to delamination between fibers and polymer matrices. This invention unveils tough, strong fiber-matrix interfacial adhesion through a interface of carbon fiber, that enables very strong, recyclable carbon fiber-reinforced vitrimer (CFRV) composites with closed-loop circularity. The bonding in vitrimer resin and fiber interface enables tough mechanical properties, strong fiber-matrix interfacial adhesion, and efficient closed loop-recycling of both fiber and resin. The interface between the fiber and matrix was measured by Raman mapping, which indicates strong interfacial between the carbon fiber and vitrimer matrix. For instance, the CF containing CFRV showed 38% higher interfacial adhesion than that of pristine CF containing CFRP. Moreover, the vitrimer composites with carbon fiber exhibit ~ 731 MPa tensile strength, which is 26% and 49% higher than those of the unmodified CFRV composites and conventional epoxy CFRP composites respectively, demonstrating the greater reinforcement effect of fiber modification. In addition, the improvement of interfacial shear strength of the CF composites resulted in a 45% increase compared to the pristine CF composite, reinforcing the vital role of the functionalization of the fibers. Importantly, the CFRV composites can undergo closed-loop recyclability and recovered CF can maintain their mechanical integrity over multiple cycles without deteriorating the mechanical performance. The CFRV composite also exhibit repairability, fast thermoformability, and self-adhesives when hot-pressed at 200 °C for 10 minutes.

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