单向碳/碳复合材料高温疲劳试验研究

Experiment on Fatigue of Unidirectional Carbon/Carbon Composites at Elevated Temperature

为了研究单向碳/碳的高温疲劳特性,从疲劳损伤力学出发,提出了考虑温度、氧化速率的碳/碳复合材料剩余刚度、剩余强度模型,并开展了碳/碳复合材料[0]16单向板试验件在室温、有涂层700℃和无涂层700℃的拉/拉疲劳试验和剩余强度试验。试验结果表明:单向碳/碳复合材料的剩余刚度曲线呈倒"S"形,材料的刚度退化存在三个阶段;单向碳/碳复合材料在室温和有抗氧化涂层700℃的疲劳加载初期和末期存在刚度突降,中期的刚度无明显退化;单向碳/碳复合材料在室温的疲劳刚度退化小于10%,而有抗氧化涂层单向碳/碳复合材料700℃的刚度退化超过30%;无抗氧化涂层单向碳/碳复合材料在疲劳中期存在明显刚度退化,末期无刚度突降。模型的拟合结果表明:复合材料高温剩余刚度、剩余强度模型能够很好地预测单向碳/碳复合材料在室温和700℃的剩余刚度、剩余强度变化。

In order to study high temperature fatigue characteristic of unidirectional carbon/carbon composites,the residual stiffness model and residual strength model of carbon/carbon composites considering temperature and oxidation rate were proposed from fatigue damage mechanics. Tensile/tensile fatigue experiment and residual strength experiment of[0]16 unidirectional carbon/carbon composite laminates specimens with and without anti-oxidation coating also were carried out at room temperature and 700℃. The experiment results show that residual stiffness curves of unidirectional carbon/carbon composites have three stages and present lying'S'. The stiffness of unidirectional carbon/carbon composites with anti-oxidation coating decline sharply in initial stage and last stage of fatigue at room temperature and 700℃,but the stiffness have no obvious degradation in middle stage of fatigue. The stiffness degradation of unidirectional carbon/carbon composites is less than 10% at room temperature. However,the stiffness degradation of unidirectional carbon/carbon composites with anti-oxidation coating become more than 30% at 700℃. The unidirectional carbon/carbon composites without anti-oxidation coating exist stiffness degradation obviously,and there is no stiffness sudden drop when material access fatigue life. The fitting results of the model show that the high temperature residual stiffness model and residual strength model of composites can predict well on residual stiffness and residual strength changes of unidirectional carbon/carbon composites at room temperature and 700℃.