Designing multifunctional integrated interfaces on carbon fibers via self-assembly toward high-strength, tough, and fire-Resistant CFRPs

The practical application of carbon fiber-reinforced epoxy resin composites (CFRPs) is hindered by weak fiber-matrix interfacial adhesion and the inherent flammability of epoxy resins. In this study, a multifunctional integrated interface was innovatively constructed on the carbon fiber surface via electrostatic self-assembly of polyhedral oligomeric silsesquioxane based nanocomponents (PPI) and MXene nanosheets. This mild modification strategy preserves the intrinsic tensile strength of the fibers while significantly enhancing surface wettability and surface energy. The resulting PPI-MXene hybrid interface substantially improves interfacial adhesion, achieving a 43.9% increase in interfacial shear strength compared to unmodified CFRPs. The optimal composite, 5-MPCF/EP, exhibits outstanding mechanical performance, with interlaminar shear strength, flexural strength, and unnotched impact strength increased by 30.9%, 30.1%, and 50.6%, respectively. Moreover, the integrated interface endows the composites with exceptional flame retardancy, achieving a UL-94 V-0 rating and a limiting oxygen index of 35.4%. Cone calorimetry tests reveal significant reductions in peak heat release rate (53.4%), total heat release (33.2%), and carbon monoxide production (76.9%). The synergistic flame-retardant mechanism involves physical barrier formation, radical scavenging, catalytic carbonization, and thermal reflection. This work overcomes the longstanding trade-off between flame retardancy and mechanical properties in CFRPs, offering a promising strategy for developing high-performance, fire-safe composites.