Manufacturing and mechanical characterisation of polyurethane resin based sandwich composites for three-dimensional fabric reinforcement

Three-dimensional (3D) sandwich composites are an excellent material, boasting light weight, high strength, and high specific stiffness. For materials comprising this structure, a new type of sandwich composite, made with a 3D fabric reinforcement structure, was independently developed. A sandwich composite is a lightweight composite with practical mechanical properties, manufactured using compression moulding techniques. The 3D fabrics were produced by sewing jute yarns having configurable structures using Kevlar fibre threads, while an epoxy resin was impregnated into the 3D fabrics, achieving a more uniform resin and voids distribution and thus a better polyurethane resin impregnation for the sandwich composite. Jute composite panels were used to form the upper and lower skins during the compression moulding process. The composites had been subjected to compression, flexural and impact tests, and their fracture surfaces had been characterised by scanning electron microscopy (SEM). Mechanical tests showed that the compression and flexural strengths of the composites markedly increased, reaching 21.4 and 18.5 MPa respectively, which was approximately 7.7 and 3.8 times higher than similar properties of the blank composites without 3D fabrics. SEM micrographs of the composites showed the presence of jute fibre pull-outs in the 3D fabrics and the existence of voids in the composite.