Multiscale MOFs/PDA-enhanced carbon fiber/phenolic composites with rigid–flexible structure.

Paper‐based friction materials with phenolic resin as the matrix are prone to thermal damage under harsh working conditions easily leading to materials failure. To satisfy the requirements of high speed and heavy load service situations, paper‐based friction materials with different polyimide resin content were prepared by wet forming technology to reveal the effect of polyimide resin on the properties of composites. And a paper‐based composite with phenolic resin was used for comparison. Results show that compared with the phenolic composite, tensile strength, and shear strength of the polyimide composite were increased by 50.5% and 36.4%, respectively. Due to the strong hydrogen bond in the imide ring of polyimide, the temperature of the polyimide composite at 2% weight loss was 292.7°C, which was 106.3°C higher than that of the phenolic composite. Moreover, the wear rate was reduced by 30.3% because the friction transfer film was produced during friction. To sum up, polyimide resin has the potential to replace phenolic resin under the condition of high speed and heavy load. Besides, the composite with polyimide resin content of 40.0 wt% demonstrated the best wear resistance and considerable strength attributed to the best interface combination. This research lays a theoretical foundation for the application of polyimide resin to paper‐based friction materials.

Under the heavy-loading harsh condition, achieving prominent mechanical and tribological performances of paper-based friction materials are an extreme demand for meeting their application in the braking of vehicles. In this study, modifying carbon fiber with epoxy groups and designing silicone@SiO 2 core-shell structure as efficient and feasible strategies, were employed to boost the mechanical and tribological properties of friction materials. The above core-shell hybrid, acted as an effective interfacial linker, contributed to forming strong mechanical interlocks and increasing chemical cross-linking density at the interphase. The tensile and interlaminar shear strength of silicone@SiO 2 -modified sample were improved by 28.6% and 12.9%, respectively. Meanwhile, the toughness of silicone@SiO 2 -modified sample showed a 102.82% increase. Moreover, compared with pristine sample, the dynamic friction coefficient of silicone@SiO 2 -modified sample increased from 0.1020 to 0.1202, while the wear rate decreased from 0.617 Â 10 À8 cm 3 J À1 to 0.432 Â 10 À8 cm 3 J À1 .