Harnessing mussel-inspired phenolic-iron complexes for strengthening carbon fiber reinforced polymer composite interfaces

Carbon fiber reinforced polymer composites (CFRPs) offer exceptional specific strength and lightweight characteristics due to the high-performance nature of carbon fiber. However, carbon fiber's chemical inertness results in weak interactions with the polymer matrix, which hinders the overall performance of the composites. Improving the interfacial properties has been a longstanding challenge in CFRPs development. Introducing nanomaterials along with chemical agents at the interface can enhance both physical and chemical interactions, facilitating better load transfer and more uniform stress distribution. Despite this, surface modification remains a complex process, and the lack of anchor bonds limits the effectiveness of chemical interactions. In this work, inspired by the crack-resistance mechanism of byssal cuticle through metal coordination bonds, we introduce a metal-phenolic network comprising ferric iron (Fe³⁺) and tannic acid (TA) onto the carbon fiber surface using a simple one-pot deposition method. This approach significantly enhances the interfacial properties of the composite. The Fe³⁺-TA complex forms nano-sized aggregates on the fiber surface, with their morphology controllable by adjusting the precursor concentration and pH. The multiple reactive groups on TA allow for the incorporation of a silane coupling agent, effectively creating a chemical bridge between the carbon fiber and the matrix, further improving interfacial properties through synergistic chemical and physical interactions. This metal-phenolic network not only simultaneously strengthens and toughens the interface by promoting mechanical interlocking but also provides multiple chemical anchor sites to bridge the two components, offering new insights into strategies for interfacial strengthening and regulation.