Enhanced delamination resistance and through-thickness thermal conductivity of carbon fiber epoxy resin composites by in situ generation of interconnected thick oriented matrix-carbon nanotube layer

Conventional carbon fiber/epoxy resin-based composites are widely used due to their high specific strength. However, typical laminated composites have poor delamination resistance as well as through-thickness thermal conductivity due to poor interfacial bonding between the polymer matrix and carbon fibers, two-dimensional structure without interlayer load-bearing phases, lack of continuous interlayer thermal conductive path. In this work, the carbon fiber cloth was firstly surface-treated with in-situ growth carbon nanotube on its surface by chemical vapor deposition, then the treated cloth was combined with the synthesized liquid crystal epoxy resin. An interconnected intrinsic thick orientation layer around the carbon fiber was formed by the orientation of liquid crystal epoxy resin molecules along the direction of the carbon nanotube layers grown on the carbon fiber surface, and was observed by X-ray diffraction as well as polarized light microscopy. The interlayer strength as well as the through-thickness thermal conductivity are enhanced by the generation of high-strength oriented layers and continuous thermal conductivity paths, resulting in an increase of 56.4 % in ILSS and 70.6 % in through-thickness thermal conductivity, a “brittle to ductile” transition in the failure mode of the interlayer matrix is also observed in the region of overlapping oriented layers. The ultra-thickness of such oriented layers and their in-situ generation during the curing process allows them to overlap each other to form a continuous reinforcing/toughening structure as well as a continuous thermally conductive network to provide the enhancement capabilities described above.