Construction of Soft/Hard Structures Hybrid Polyacrylic Acid/Metal–Organic Frameworks on Carbon Fiber Surfaces for Reinforcement of Epoxy Nanocomposites

ABSTRACT A new hybrid PAA/UiO‐66‐NH ₂ reinforced carbon fiber with a “soft/hard” structure was prepared through in situ electrochemical polymerization followed by in situ growth, as confirmed by FTIR, XRD, XPS, and SEM. This novel hybrid structure exhibited a synergistic effect of the soft PAA layer and the hard UiO‐66‐NH ₂ layer, leading to an effective enhancement. The modified fiber composites showed remarkable improvements in interlaminar shear strength (80.2 MPa) and tensile strength (937.1 MPa), corresponding to increases of 50.7% and 25.4%, respectively. This enhancement was attributed to the improved interfacial bonding strength, which facilitated effective energy absorption and load transfer. Abundant carboxyl groups of PAA provided more active sites on carbon fibers, thereby regulating the concentration of metal precursors of metal–organic frameworks to control nucleation and ensure uniform formation of metal–organic frameworks. The facile and effective method will provide a new interface design strategy for developing carbon fiber composites.