Multifunctional nickel-coated carbon fiber veil for improving both fracture toughness and electrical performance of carbon fiber/epoxy composite laminates

The poor lightning strike resistance limits the application of carbon fiber-reinforced polymer (CFRP) composites in aircraft. Multifunctional fiber composites can reduce lightning strike damage by improving interlaminar mechanical properties and electrical conductivity. In this study, nickel-coated carbon fiber (NiCF) veil was explored as a functional interleaf of CFRP composites to simultaneously improve the interlaminar fracture toughness (G(IC) by 74.75% and G(IIC) by 36.22%) and through-thickness electrical conductivity (by 220.49%). The toughening mechanisms of NiCF veils mainly include the pull-out, debonding, and breakage of NiCFs, as well as peeling and splitting of nickel coating. The improvement of conductivity is mainly attributed to the increase of conductive paths. Furthermore, the NiCF veil-interleaved laminates still maintained relatively high-electrical conductivity after delamination, which was formulated as a structure-function relationship expression. The interesting finding is beneficial to lightning protection, especially for damaged composites. The NiCF veil is a potential interleaf for structure-function integration of composites, and has the potential to suppress lightning damage to aerostructures.