Facial functionalization carbon fiber with <scp>MnO₂</scp> nanosheets for high‐performance epoxy composites with excellent flame retardancy and mechanical properties

Abstract The carbon fiber (CF) reinforced epoxy composites possess exceptional and distinctive properties as advanced composite materials. However, the flammability of epoxy resin and inadequate interfacial bonding between the resin and CF often impose limitations on their broader application. Herein, in order to enhance the flame retardancy of EP composites effectively, a hierarchical reinforcement was developed by facilely growing MnO 2 nanosheets onto CF surface through an in situ process. Owing to their synergistic effects of physical barrier and chemical catalytic behavior, the presence of MnO 2 nanosheets can effectively retard the combustion process by facilitating charring formation and suppressing heat and smoke release. Specifically, compared to the Untreated CF, the modified fiber reinforced composites exhibited significantly improved fire safety with reduction of 76.23%, 51.5% and 23.1% in peak heat release rate, total heat release and peak smoke production rate, respectively. Additionally, incorporating MnO 2 nanosheets significantly enhanced mechanical properties of the composites, leading to remarkable enhancements of 41.8% in flexural strength and 28.14% in interlaminar shear strength. This study proposes an effective strategy for achieving outstanding flame retardancy and mechanical performance, thereby introducing an innovative concept for the production of high‐performance CF reinforced polymer composites. Highlights Growth of MnO 2 nanoparticles enhanced the mechanical properties of the CF/EP composites. The CF‐MnO 2 /EP composites showed excellent flame retardancy. The flame retardant mechanism of CF‐MnO 2 /EP composites were analyzed. Highlight the potential application of MnO 2 in the field of flame retardancy.