Hybrid polyurethane and silane sized carbon fibre/epoxy composites with enhanced impact resistance

A hybrid sizing agent of polyurethane and silane is synthesized and used on carbon fibre surfaces with different sizing rates to enhance the interfacial bonding between carbon fibre and epoxy matrix in the composites. The proposed sizing mechanism is studied. With successful and suitable rate of sizing on the carbon fibre surface, both the tensile strength and wear resistance of carbon fibre bundles significantly increase. Meanwhile, the wettability of the carbon fibre with epoxy is improved with a suitable amount of hybrid sizing on the fibre surfaces, which can directly enhance the impregnation process during fabrication of the composite. The inter-laminar shear strength and impact resistance of the composites are enhanced by the sized carbon fibres. B scan and C scan images of the composites after impaction show that the damage areas in the thickness direction and within the plane decrease significantly when carbon fibres with an optimised sizing rate are used in the composites. The impact stress can be effectively transferred to the resin in the composite due to the hybrid sizing on the fibre surfaces enhancing the bonding strength between fibres and matrix, providing a feasible way to enhance the impact resistivity of the composites.