Synthesis of a Fully Bio-based Tannic Acid/Chitosan/Ferric Ions Double Cross-Linked Coating: a Green and Sustainable Strategy to Enhance the Carbon Fiber/Epoxy Composites

This study presents an eco-friendly surface modification strategy to enhance the interfacial properties of carbon fiber-reinforced polymer (CFRP) composites through a double cross-linked coating of tannic acid (TA), chitosan (CS), and ferric ions (Fe3+). The coating is formed through Schiff base-mediated covalent cross-linking and metal coordination, resulting in a stable and durable network on the fiber surface. The results demonstrate that this modification significantly improves the interfacial adhesion of composites, with the interlaminar shear strength (ILSS) and interfacial shear strength (IFSS) increase by 39.2 and 66.2%, respectively, compared to untreated fibers. Atomic force microscopy (AFM) analysis of the interfacial modulus distribution shows a notable enhancement in interface thickness and stress transfer efficiency postmodification. This sustainable, nontoxic approach offers an effective, environmentally conscious solution for improving interfacial properties and lays the groundwork for the development of high-performance, eco-friendly CFRP composites.