Bend properties and failure mechanism of a carbon/carbon composite with a 3D needle-punched preform at room and high temperatures

A 3D needle-punched C/C composite with a high density was fabricated and its bend properties were investigated at room and high temperatures. Macro-fracture and SEM micrographs were examined to understand the deformation and failure mechanism. Results show that the load-deflection curves below 400℃ exhibit a linear elastic and brittle fracture failure, while the curves at temperatures above 500℃ show an obvious tough and plastic failure. The bend strength and modulus decrease significantly with increasing temperature due to severe carbon oxidation. Below 500℃, the main damage to the composite is in the form of matrix cracking, 90° fiber/matrix debonding, local twisting and fracture of the 0° fibers. Above 500℃, the oxidation of the composite is significant and the interfacial adhesion between fibers and matrix is decreased significantly.