Interface strengthening and high-value recycling of epoxy resin/carbon fiber fabric composites

Thermoset epoxy resin/carbon fiber fabric (EP/CF) composites are used increasingly in the fields of automotive, aerospace, and wind power, but the large difficulty in interfacial strengthening and high-value recycling of CF hinders their wide applications in advanced sustainable materials. Here, thiol-terminated hyperbranched polyimides (DSPI-n) were synthesized by a newly designed imide monomer and then were covalently grafted onto the surface of pristine carbon fiber fabric (PCF) by a thiol-ene click reaction to produce thiol-functionalized carbon fiber fabric (TCF). Then, the degradable imide skeleton hyperbranched epoxy resin (DIHE-n) was synthesized from DSPI-n by a click reaction to prepare the DIHE-n/TCF composites. Compared with the DIHE-n/PCF composites, the tensile strength, interlaminar shear strength, and interfacial shear strength of the DIHE-n/TCF composites were distinctly increased, explained by an interfacial strengthening mechanism, being attributed to a synergistic effect of the wide interface layer, strong load transfer capacity of the deformable hyperbranched topological structure, and mechanical interlock of double crosslinked structure. Moreover, the prepared composites can be completely degraded under mild conditions and the carbon fiber fabric can be intactly recycled. This study offers a new approach for the preparation of recyclable and high-performance EP/CF composites.