Zinc Oxide Nanowire Interphase for Enhanced Interfacial Strength in Lightweight Polymer Fiber Composites

A novel functionalization method for aramid fibers is developed to enhance the bonding of a ZnO nanowire interphase grown on the fiber surface for interfacial strength enhancement. The nanowire interphase functionally grades the typically discrete interface and reduces the stress concentration between the fiber and matrix. The functionalization process is developed to improve the bonding between the ZnO nanowires and the aramid fiber and is validated through Fourier transform IR and X-ray photoelectron spectroscopy studies. Mechanical testing shows significant improvement in the interfacial shear strength with no decrease in the base fiber strength. This is the only technique found in the literature for the growth of a nanowire interphase on polymer fibers for structural enhancement without degrading the in-plane properties of the bulk composite. Furthermore, it is firmly shown that the functionalization process is a necessary condition for enhanced interfacial strength, demonstrating that ZnO nanowires strongly interact with carboxylic acid functional groups.