Enhanced inter-laminar and high-velocity impact resistance of CF/epoxy composites via carboxylated CNTs

Improving the inter-laminar and high-speed impact performance of carbon fiber (CF) epoxy matrix composites is of vital importance to the aero-engine containment casing. Carbon nanotubes (CNT) with three lengths and four carboxyl group contents were added into the CF epoxy prepreg to process the CNT/CF epoxy composites. Inter-laminar shear and high-speed impact tests were conducted to obtain Inter-laminar shear strength ( ILSS ) and ballistic limit ( BL ). The characterization methods of C-C bonds volume density and CNT length were proposed. The effect of the C-C bonds volume density and CNT length on ILSS and BL were given by the experimental results. Then, the high-speed impact process, strain and displacement field were analyzed. At last, the inter-laminar and high-speed impact performance strengthening mechanism were given, and a convenient optimization scheme of ILSS and BL for CNT/CF epoxy composites was proposed. The results show that ILSS and BL increase dramatically by 58% and 48%, when the CNT length is 20 μm and carboxyl group content is 5.4%, where the interfacial failure mode is on the conversion from the CNT pullout to CNT fracture. The results show great potential for enhancing impact resistance performance of the aero-engine containment casing.