Improving Interface and Mechanical Properties of CFRPs by Surface Modification of Carbon Fibers Using Tannic Acid-Fe³⁺- (3-Aminopropyl)triethoxysilane Complexes

Inspired by mussel adhesion, researchers have explored polydopamine (PDA)-based sizing solutions to enhance the surface chemistry and texture of carbon fibers. However, PDA-based solutions face challenges associated with high costs, longer fiber treatment times, and scalability concerns for industrial adoption. Recently, tannic acid, an abundant natural polyphenol, has emerged as an alternative capable of forming similar chemical interactions, such as Michael addition, Schiff-base reactions, and coordination complexes with metal ions, and so forth, as in PDA. In this work, tannic acid-Fe³⁺- (3-aminopropyl)triethoxysilane complexes were deposited on the CF surface by a facile self-assembly process in 15 min. The deposited nano-sized aggregates increased reactive surface functional groups on the fiber and enhanced its surface roughness. As a result, the interlaminar shear strength, flexural strength, and modulus of unidirectional CFRPs, reinforced with treated fibers, increased by 35%, 30%, and 12.4%, respectively, compared to those with as-received CF. The impact load-bearing capacity of CFRPs with a modified interface also increased by 19.8% and their residual compressive strength after impact increased by 20.8%. This approach to improving the surface characteristics of CF can offer a cost-effective solution to enhance the performance of CFRPs.