Coordination-interlocked brick-and-mortar interphase for simultaneously strengthening, toughening, and EMI shielding of CFRPs

Resolving the intrinsic trade-off between interfacial strength and toughness in carbon fiber reinforced polymer composites (CFRPs) remains a central challenge for achieving reliable structural performance. Inspired by the hierarchical brick-and-mortar architecture of nacre, we engineer a coordination-interlocked hybrid coating on carbon fiber surfaces through a layer-by-layer assembly strategy, integrating rigid reduced graphene oxide (rGO) nanosheets as “bricks” with flexible metal-phenolic networks (MPNs) as “mortar.” This bioinspired interphase simultaneously reconstructs the interfacial chemistry and mechanical architecture, establishing a graded modulus transition that facilitates efficient stress transfer. Meanwhile, it activates multiscale energy-dissipation mechanisms, including crack deflection, as well as possible Fe-O bond breakage and interlayer sliding and friction. Consequently, the interfacial shear strength and interfacial fracture toughness increase by 122.3% and 376.1%, respectively, relative to untreated composites. Systematic component substitution demonstrates that only the coordination-interlocked configuration that synergistically couples rigid nanofillers with flexible MPNs achieves concurrent strengthening and toughening, underscoring the critical role of mechanical complementarity and structural confinement within the interphase. Beyond mechanical enhancement, the conductive hybrid architecture reconstructs surface impedance and polarization-active interfaces, enhancing conduction loss and interfacial polarization relaxation to deliver an electromagnetic interference shielding effectiveness of 26.3 dB in the X-band. This work establishes a biomimetic and multifunctional interfacial engineering strategy for structure–function integrated CFRPs.