High temperature compressive behavior of three-dimensional five-directional braided composites

An experimental study was performed to investigate the high temperature compressive properties and failure mechanism of three-dimensional (3D) five-directional braided composites. The compression tests of 3D braided composites were conducted at six different temperatures. The failure modes, stress-strain curves, compressive modulus and strength at high temperature were analyzed and compared with those at room temperature. The results showed that temperature has a visible impact on these parameters. The 3D braided composites failed due to shear fracture, and the stress-strain curves exhibited obvious linear elasticity and a brittle failure feature at 20 and 50 degrees C, while the failure was characterized by fiber/matrix interface debonding, fiber bundles loosening and by outward expansion, and the stress-strain curves exhibited an obvious non-linear trend and a plastic failure feature at 70, 90, 110 and 130 degrees C. The compressive modulus and strength decreased as temperature increased. The compressive modulus and strength decreased by 92.9% and 94.1 % as the temperature increased from 20 degrees C to 130 degrees C, which was mainly due to the degradation of the matrix properties and fiber/matrix interface properties at high temperature.