Hybrid ZnO Nanorod Grafted Carbon Fiber Reinforced Polymer Composites; Randomly versus Radially Aligned Long ZnO Nanorods Growth.

Integrating nano-sized reinforcing materials into carbon fiber polymer composites (CFRPs) could enhance several aspects of their mechanical performance; e.g., interfacial strength, delamination resistance and vibrations attenuation. In this study, ZnO nanorods were grown on the surface of carbon fibers to create hybrid reinforcements. The hydrothermal synthesis of ZnO nanorods was tuned such that relatively long (>2.0 μm) nanorods can be grown. This synthesis technique requires pre-deposition of a thin seeding layer of ZnO particulates on the carbon fibers to initiate the ZnO nanorods growth. Depending on the method by which the seeding layer is deposited, the grown ZnO nanorods could display different morphologies. In this study, two different techniques were utilized to pre-deposit the ZnO seeding layer on the carbon fibers; ZnO nanoparticles/solution mixture airbrush spraying, and magnetron sputtering. The carbon fibers pre-coated with the airbrush spraying method yielded forests of randomly oriented ZnO nanorods, while the fibers pre-coated via the sputtering technique exhibited radially aligned ZnO nanorods forests. Hybrid CFRPs were fabricated based on the aforementioned carbon fiber fabrics and tested via 3-point bending dynamic mechanical analysis (DMA) and quasi-static tension tests. The loss tangent of the CFRPs, which delineates the damping capability, increased by 28% and 19% via radially and randomly grown ZnO nanorods, respectively. The in-plane tensile strength of the hybrid CFRPs were improved by 18% for the composites based on randomly oriented ZnO nanorods over the carbon fibers. The fractographs of the tension samples were also captured to reveal the role of the long ZnO nanorods in the in-plane performance of the hybrid CFRPs.