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A “soft‐stiff” structure is equipped onto carbon fiber (CF) surface by hydrothermal and self‐assembly methods, in which MnO2 nanosheets and natural polysaccharide chitosan (CS) act as “stiff” phase and “soft” phase, respectively, leading to strong interfacial phase in CF/epoxy composite. The roughness, polar functional group content, and wettability of the CF surface are significantly promoted by this protocol. Moreover, the unique structure also serves as a buffer area to relieve stress concentration and change the direction of crack propagation, thus enhancing the interfacial properties of the composites. The strengthening effect of the “soft‐stiff” structure is verified by interlaminar shear strength (ILSS) and flexural strength tests, which are improved by 47.4% and 48.2%, respectively compared with pristine CF/epoxy composites. This work provides a potential reinforcement strategy to access high‐performance CF composites.

The carbon fiber/hydroxyapatite (CF/HA) reinforcement with a three-dimensional flower-like structure was rapidly fabricated with the biomimetic mineralization method to strengthen the interfacial performance and bioactivity of carbon fiber/polyether ether ketone (CF/PEEK) composites. Silk fibroin (SF), which can construct a robust interphase between CF and PEEK, supported an organic template to regulate the growth of inorganic HA. The interfacial properties were markedly enhanced through mechanical interlocking and interface adhesion induced by increasing roughness and surface energy of CF. Besides, the mineralization time was significantly reduced after the addition of cetyltrimethylammonium bromide to the simulated body fluid, and the prepared CF/HA possessed good bioactivity. In this study, the interlaminar shear strength (ILSS) and flexural strength of CF-HA/45/PEEK composites demonstrated an enhancement of 45.9% and 51.2%, respectively, compared to the untreated CF/PEEK composites. It is predicted that this strategy could provide a rapid and convenient route to ameliorate the interfacial performance and bioactivity of CF/PEEK composites simultaneously.