Mechanical behavior and failure mechanism of three-dimensional braided composites at different temperatures

This investigation explored the effect of temperature on the compressive behaviors and failure mechanism of three dimensional (3D) carbon/epoxy five-directional braided composite laminates. The compression tests of 3D braided composite laminates were performed at six different temperatures, which are 20 degrees C (room temperature), 50 degrees C, 70 degrees C, 90 degrees C, 110 degrees C and 130 degrees C, respectively. Then the effect of temperature on the failure mechanism, stress-strain curves, compressive modulus and strength of the composite laminates were analyzed and compared to that at room temperature. The results have shown that the temperature had a significant effect on the compressive properties and failure mechanism of 3D braided composite laminates. At 20 degrees C and 50 degrees C, the 3D braided composite laminates failed by shear fracture, and the stress-strain curves exhibited obvious linear elasticity and a brittle failure feature. While, at higher temperatures (70 degrees C, 90 degrees C, 110 degrees C and 130 degrees C), it was found that the specimens exhibited obvious plastic kinking, and the stress-strain curves exhibited obvious non-linear trend and a plastic failure feature due to the epoxy resin matrix becoming softened and plastic. The compressive modulus and strength decreased as temperature increased. The compressive modulus and strength decreased by 92.3 % and 93.8% when the temperature increased from 20 degrees C to 130 degrees C.