Insight into the enhanced interfacial adhesion of carbon fiber reinforced composites: A facile ferric ion and tannic acid self-assembly strategy

Applications of carbon fiber reinforced polymer composites are subjected the poor interfacial adhesion due to the smooth and chemically inert of CF surface. In this work, we proposed an effective and simple approach to improve the interfacial properties between CF and matrix by self-assembling the ferric ion (Fe³⁺) and tannic acid (TA) on the carbon fiber surface within minutes. TA can rapidly coordinate with Fe³⁺ ions into three-dimensional Fe³⁺-TA complex networks, the morphologies of which were controlled by Fe³⁺/TA molar ratio and deposition cycles, which played a key role in the interfacial performance. As Fe³⁺/TA molar ratio is optimized to 4, Fe³⁺-TA complex aggregated to nano-sized bulges on the fiber surface, affording numerous mechanical interlocking points which can promote the stress transfer from matrix to fiber and induce the deflection of cracks. Moreover, breaking metal–ligand coordination bonds of Fe³⁺-TA complex as cracks propagate can dissipate lots of fracture energy, leading to the interfacial shear strength of Fe³⁺-TA complex modified CF/epoxy vinyl resin composites being improved by ∼ 80 % as compared with the pristine sample. This strategy is facile, mild, and eco-friendly, which opens a feasible avenue for enhancing the interfacial adhesion of CFRPs.