单向C/C复合材料高温氧化环境力学性能试验

为研究高温氧化环境单向C/C复合材料力学特性,对C/C复合材料单向板开展了700 ℃和900 ℃的氧化试验以及室温、700 ℃和900 ℃的拉伸试验。结果表明:无涂层单向C/C复合材料在相同温度下,失重率随着氧化时间的增加而增大,在相同氧化时间内,温度越高,氧化失重率越大;无涂层单向C/C复合材料在700 ℃氧化4 h后失重率为83.78%,有涂层单向C/C复合材料700 ℃氧化4 h后的氧化失重率为1.17%;有涂层单向C/C复合材料在700 ℃的力学性能高于室温,室温和700 ℃的应力应变曲线均呈线性;氧化后的试验件的应力/应变曲线呈明显非线性;相同温度下,材料的力学性能随着氧化时间的增加而降低;相同时间内,温度越高,材料的拉伸强度退化的越剧烈。建立了一种考虑氧化速率的C/C复合材料高温氧化环境力学性能退化模型,拟合得到了无涂层单向C/C复合材料700 ℃和900 ℃拉伸强度随氧化时间的变化曲线,并外推计算得到了无氧化时的单向C/C复合材料700 ℃的拉伸强度,得到了良好的预测效果。 

Experiment on mechanical property of unidirectional C/C composites under high temperature and oxidation environment

In order to investigate the mechanical properties of unidirectional C/C composites under high temperature oxidation environment, the oxidation experiment of C/C composite unidirectional laminates was carried out at 700 ℃ and 900 ℃, meanwhile, the tensile experiment of C/C composite unidirectional laminate was carried out at room temperature, 700 ℃ and 900 ℃. Results showed that the weight loss rate increased with the increase of oxidation time at the same temperature, and the higher the temperature, the higher the oxidation loss rate in the same oxidation time. The weight loss rate of unidirectional C/C composites was 83.78% in case of thermal retardation 4 h at 700 ℃. But the weight loss rate was only 1.17% only after 4 h thermal retardation for the specimens with anti-oxidation coating. The mechanical properties of C/C composite unidirectional laminates were strengthened when temperature rose from room temperature to 700 ℃. The stress/strain curves of C/C composite unidirectional laminates were linear at room temperature and 700 ℃. Tensile stress/strain curves of specimens were obviously nonlinear. At the same temperature, the mechanical properties of the materials decreased with the increasing oxidation time. The higher temperature, the more tensile strength degradation of unidirectional C/C composites. A kind of mechanical properties degradation model for C/C composites about the oxidation rate was established. The tensile strength degradation curves were got by fitting the experiment data of unidirectional C/C composites at 700 ℃ and 900 ℃. Extrapolation was made to calculate the tensile strength of non-oxidation of unidirectional C/C composites at 700 ℃.