Covalent Interface Design in SiC Nanofiber/BMI–Urea Nanocomposites with Enhanced Rain Erosion Resistance and Recyclable Properties

Abstract To address the challenges of insufficient toughness and limited recyclability in high-performance thermosetting composites, this study develops a SiC nanofiber-reinforced BMI–urea resin nanocomposite through a DFT-guided interfacial engineering strategy. DFT calculations reveal strong interactions between BMI and the SiC surface, with a binding energy of 155 kJ·mol–1, identifying BMI as an effective interfacial modifier. Mechanochemical surface functionalization was employed to improve the compatibility between SiC nanofibers and the polymer matrix. With only 0.05 wt % SiC nanofibers, the nanocomposites exhibited significant enhancements in mechanical properties, with tensile strength, elongation at break, and impact strength increasing by 37.2%, 40.1%, and 24.8%, respectively, together with a 10 °C increase in thermal decomposition temperature. Microscopic characterization revealed improved interfacial continuity and nanoscale structural uniformity, facilitating stress transfer. High-pressure rain erosion tests demonstrated enhanced resistance to repeated liquid-droplet impact, indicating potential for protective coating applications. Furthermore, an alkaline hydrothermal treatment enabled effective recovery of SiC nanofibers from the BMI–urea network while maintaining their fibrous morphology. Although further validation of the purification and reuse performance is required, this work presents a DFT-guided interface design strategy for enhancing the mechanical performance and recycling potential of high-performance thermosetting nanocomposites.