Interfacial characterization and reinforcing mechanism of novel carbon nanotube – carbon fibre hybrid composites

Carbon nanotube (CNT) deposition onto carbon fibre resulting in hybrid surface structures with various morphologies were successfully carried out using electrospray technique. In terms of tensile testing and Weibull analysis this process did not degrade fibre mechanical properties. When incorporated into composites, the interfacial shear strength (IFSS), as measured by single fibre fragmentation testing, increased by up to 124%. Experimental work was carried out to develop a deeper understanding of the interfacial reinforcing mechanism. Contact angle measurements demonstrated that the CNT deposition resulted in good wettability by the resin. Significant increases in roughness, friction and surface area were also found after CNT deposition, especially for the sample prepared using the parameter of 20 kV/10 cm at 100 °C. Surface energy analysis revealed that an increase in the dispersive surface energy due to the CNTs likely contributed to the improvement of interaction between fibre and matrix. Fractographic analysis revealed that the length of fibre pull-out and the size of cracks between the fibre and matrix were markedly decreased in the hybrid CNT surface structure, indicating that the stress transfer and interfacial shear strength have been improved. Finally, the potential for further improvement in interfacial composite properties by this approach was assessed.