Interface Engineering of CF / PEEK Composites via a Chalcone‐Containing Fluorinated Poly(Aryl Ether Ketone) Sizing Agent

Carbon fiber (CF) exhibits inherent chemical inertness and a non‐polar surface, resulting in poor interfacial compatibility with polyether ether ketone (PEEK) matrix and limited mechanical performance of CF/PEEK composites. Herein, a fluorinated poly(aryl ether ketone) containing chalcone moieties (ChF‐PAEK), previously reported as a fluorinated polymer structure, was employed as a structurally compatible sizing agent for CF/PEEK interface modification. The influence of ChF‐PAEK concentration on the interfacial properties is systematically investigated. Results indicate that the ChF‐PAEK sizing at an appropriate concentration forms a uniform and PEEK‐compatible interphase, enhancing interfacial compatibility through multiple proposed interactions, including π – π interactions, van der Waals forces, and macromolecular entanglement with the PEEK matrix. The composite 0.5 wt% ChF‐PAEK shows the best mechanical properties with interlaminar shear strength (ILSS) of 103.5 MPa and flexural strength of 286.1 MPa. The ILSS is improved by 66.4% compared with that of desized CF/PEEK composite. Thermal behavior, crystallization analysis, mechanical testing, and fracture morphology reveal that the ChF‐PAEK sizing agent improves interfacial compatibility, accelerates resin infiltration, and promotes stress transfer. This work provides a facile and effective molecular‐design strategy to improve the interfacial compatibility of CF/PEEK and other carbon fiber–reinforced thermoplastic composites.