Interaction of ZnO Nanowires with Carbon Fibers for Hierarchical Composites with High Interfacial Strength

Abstract

When grown on the surface of carbon fiber, vertically aligned arrays of ZnO nanowires have been shown to increase the interfacial shear strength without decreasing the in-plane properties of the composite. Analysis of the failure surface indicates that the ZnO debonds from the carbon fiber which combined with the higher interfacial shear strength, indicates that the ZnO more strongly adheres to the carbon surface than epoxy adheres to the carbon surface. Previous work was unable to identify the specific chemical interaction that enhanced the ZnO — carbon fiber interface, however it hypothesized that the presence carboxylic acid groups on the fiber were responsible. In this study an aramid fiber is used to elucidate the surface interaction since it can be produced with no carboxylic acid or with these groups through functionalization. The model fiber demonstrates that only fibers with carboxylic acid groups experience increased interfacial strength from the ZnO nanowires. The interaction between ZnO and carboxylic acid groups is verified to be critical to the enhancement of the interfacial strength in carbon fiber — ZnO nanowire — epoxy composites.