Preparation of small CNTs@Fe₃O₄ and alignment in carbon fabrics/epoxy composites to improve mechanical and tribological properties

The CNTs@Fe₃O₄ hybrids were synthesized via a modified co-precipitation method and aligned along the through-thickness of carbon fabrics-reinforced epoxy composites (CFRPCs) by applying a weak magnetic field. The effects of the length, orientation and concentration of CNTs@Fe₃O₄ on the mechanical and tribological properties of CFRPCs were investigated. The results showed that the modified co-precipitation method decreased the size of Fe₃O₄ nanoparticles (approximately 10 nm in diameter), promoting the dispersion of CNTs@Fe₃O₄ in epoxy resin. The alignment of CNTs@Fe₃O₄ hybrids significantly increased the interlaminar shear strength (ILSS) and hardness of CFRPCs. The long CNTs@Fe₃O₄ can more effectively improve the ILSS of CFRPCs compared to short CNTs@Fe₃O₄. Besides, the addition of aligned CNTs@Fe₃O₄ hybrids significant improves the tribological properties of CFRPCs. Compared to long CNTs@Fe₃O₄-reinforced CFRPCs, the short CNTs@Fe₃O₄-reinforced CFRPCs show the best tribological properties. The properties anisotropy of CNTs@Fe₃O₄ and high CNTs@Fe₃O₄ concentration in near surface of CFRPCs are the main reason for the improvement in tribological properties of CFRPCs.