Polyo‐Phenylenediamine/Graphene Oxide Multi‐Scale Reinforcement Structures for Enhanced Interfacial Properties of <scp>CF</scp> / <scp>PPESK</scp> Composites

ABSTRACT The development of advanced carbon fiber‐reinforced high‐performance thermoplastic resin (CFRHTP) composites is heavily reliant on the quality of the interface bonding between CFs and the matrix. This article presented a novel surface modification strategy for CFs that utilized electrochemical polymerization and chemical grafting. Polyo‐phenylenediamine (PoPD)/graphene oxide (GO) organic/inorganic hybrid multi‐scale structures were successfully constructed on the surface of the CFs, which significantly enhanced the fiber's surface roughness, and the introduction of nitrogen‐containing active groups improved fiber wettability and absorption efficiency for the PPESK matrix. The tensile strength of single CF monofilaments increased from 3.34 to 3.63 GPa. Due to the enhanced interface bonding and the formation of an interface phase with modulus transition characteristics, the interlaminar shear strength (ILSS), flexural strength, and tensile strength of the CF/PPESK composite reached 85.1, 1573, and 2535 MPa, respectively, representing increases of 35.7%, 55.4%, and 40.6%, respectively. Furthermore, the failure mode of the composite transitioned from interface debonding to plastic deformation and GO slippage within the resin matrix. In conclusion, this study provides a promising interface modification strategy that can significantly enhance the performance of advanced CFRHTPs.