Tannic Acid-Fe ³⁺ Assisted Graphene/Graphene Oxide Coatings for Bioinspired Interfacial Enhancement of Carbon Fiber/Epoxy Composites

assisted by graphene (GR) and graphene oxide (GO). Owing to π-π interactions, the MPN-GR and MPN-GO hybrid coatings were well distributed onto the fiber surface, introducing abundant oxygen-containing functional groups and a multiscale roughened architecture without compromising the intrinsic tensile strength of the fibers. Compared with pristine composites, the interfacial and mechanical properties were markedly improved, particularly for the CF-MPN/GO system, which exhibited a maximum increase of 95.7% in interlaminar shear strength and 117.6% in flexural strength. Fracture morphology analysis revealed a transition from interfacial debonding to matrix-dominated failure, indicating significantly improved load transfer and interfacial toughness. The superior performance of the MPN/GO interphase is attributed to the synergistic effects of metal-ligand coordination, π-π stacking, hydrogen bonding, and enhanced mechanical interlocking. This study provides a facile and environmentally friendly strategy for constructing well-defined hybrid interphases in carbon fiber reinforced polymer composites.