Effect of temperature and loading mode on flexural properties and failure mechanisms of fine weave punctured C/C composites over 2000 °C

Abstract

Fine weave punctured C/C composites are extensively utilized in aerospace applications owing to their superior mechanical properties. The effects of temperature over 2000 °C and loading mode on the flexural properties and failure mechanism were reported. It was found that the load-displacement curves of Y-direction flexure showed linear characteristics, but those of Z-direction flexure showed nonlinear characteristics because of interlayer failure. The flexural performances in the Z-direction were significantly higher than in the Y-direction. Both Y- and Z-directions flexural strengths increased dramatically, but flexural moduli initially climbed and subsequently declined with increasing temperature. In contrast with room temperature, the Y- and Z-direction flexural strengths increased by 55.6 % and 188.5 % at 2000 °C, while their corresponding flexural moduli increased by 14.3 % and 40.4 % at 1200 °C. Flexural failure in the Y direction was primarily distributed along the rows of Z-yarns. Due to narrower slits and tighter composite connections, failure gradually spreads over the Z-yarns at higher temperatures. While, the failure cracks of Z-direction flexural specimens were mainly distributed in the interlayer. As the temperature rose, the carbon fiber monofilaments of the pulled Z-direction yarns became harder linked, with neater breaks.