Preparation of highly electrically conductive carbon-fiber composites with high interlaminar fracture toughness by using silver-plated interleaves

Abstract Structural carbon-fiber composites with high electrical conductivity and high interlaminar toughness are important for the next generation of aircraft. Highly electrically conductive and simultaneously high toughness carbon fiber reinforced epoxy composites were hence developed by interleaving silver-plated veils. Two electrically conductive veils of nylon and Kevlar fibers were prepared by electroless silver plating, respectively. The effect of the veil structure and silver-plating on the conductivity and interlaminar fracture toughness was studied. It was found that the in-plane electrical conductivity perpendicular to the fiber direction (RY) and the through-thickness conductivity (RZ) increases from about 0.21 S/cm to 333 S/cm and 0.122 S/m to over 3.45 S/cm for the both samples interleaved with the nylon and Kevlar veils, respectively. The improvement is attributed to the electrical contact of the highly conductive veils in the interlayer's, forming an electrical network throughout the media. At the same time, the Mode I and Mode II interlaminar fracture toughness were also increased for the both composites, and it was more effective for the nylon-interleaved samples than for the Kevlar interleaved ones. Mechanism study showed that the interlaminar fracture mechanism can be controlled by the structural design of the veils. The failure mechanism of the nylon-interleaved composites was dominantly affected by the restraint of the fusion-bonded dots and pre-cracking which may compensate the negative effect of Ag-plating on the toughening, whereas the weak interfaces were responsible for the relatively lower toughness performance of the system interleaved with the Kevlar veils.