A Biomedically Inspired Interface Design Strategy of Carbon Fiber Composites by Growing Mg( <scp>OH</scp> ) ₂ ‐Polydopamine Three‐Dimensional Structure on Carbon Fiber

ABSTRACT The comparatively sleek surface and chemical inactivity of carbon fibers (CF) give rise to inferior interfacial performance in their composites, limiting practical applications. Constructing a three‐dimensional (3D) structural interface layer on CF surfaces is an effective strategy to improve their chemical inertness. However, the firm attachment and uniform dispersion of introduced two‐dimensional nanoreinforcements on CF surfaces remain key challenges. This study first employs in situ polymerization to coat polydopamine (PDA) onto CF surfaces. By leveraging the catechol groups in PDA and weakly electrophilic Mg 2+ , Mg(OH) 2 nanosheets are then innovatively grown in situ on PDA‐modified CF through coordination bond interactions. The successful construction of an inorganic–organic 3D structural interface layer at the CF‐resin interphase is attributed to physical and chemical entanglements, which enable the strong adhesion and uniform distribution of Mg(OH) 2 . Compared with CF/EP, the Mg(OH) 2 ‐PDA‐CF/EP composite exhibits increases of 46.4% in interlaminar shear strength, 52.0% in flexural strength, and 121.5% in interfacial shear strength. The entire modification process is simple, eco‐friendly, and cost‐effective, requiring no toxic solvents and enabling easy mass production of high‐performance CFRPs in industrial settings.