Layer by layer self-assembly of metal-phenolic networks on carbon fibers for enhancement in interfacial adhesion of epoxy composites

Currently, various studies have been conducted on the surface treatment of carbon fibers (CF), but most methods suffer from various shortcomings such as environmental pollution, high costs, complex processes, and damage to the fibers themselves. This paper aims to improve the interface bonding between CF and epoxy resin , and proposes a low-cost, environmentally friendly, and mild strategy for treating CF without strength reduction. Tannic acid (TA) and iron ions (Fe 3+ ) were deposited on CF through layer-by-layer self-assembly method to form metal-polyphenol networks (MPN) coating. The effects of deposition cycles on the surface morphology , chemical properties and interfacial bonding properties of CF/epoxy composites were studied. The introduction of MPN can increase the roughness of CF and improve the wettability of resin. As the number of self-assembly cycles was 1, the modified CF composites held the best interfacial properties , and the interlaminar shear strength (ILSS), flexural strength , transverse fiber bundle tensile (TFBT) and interfacial shear strength (IFSS) were increased by 36.7 %, 47.7 %, 46.3 % and 42.6 %, respectively. MPN can firmly bond CF and resin together, forming an interphase region with continuous modulus transition, allowing stress to propagate continuously between the matrix and the reinforcement. The protrusions formed by MPN can mechanically engage with the resin, thereby deflecting cracks, extending the propagation path of cracks, and consuming more energy during the failure process of composites. This work proposes a novel and promising strategy for the preparation of high-performance CF composites from the perspective of green environmental protection and high efficiency. • Metal-polyphenol networks firstly layer-by-layer self-assembly on CF. • The effect of self-assembly cycles on the interfacial properties was studied. • The mechanism of MPN reinforced composites was proposed.