采用应力比为0.1, 频率为3Hz的正弦波分别在室温和1300℃水氧环境对2D C/SiC复合材料进行了拉-拉疲劳试验．结果表明, 若取循环基数为105, 室温和高温水氧环境下的疲劳极限分别为244.8MPa和93.3MPa, 高温下的水氧腐蚀是材料失效的主要原因．根据疲劳断口特征分析得出以下结论: 在高温水氧环境下, 足够大的外载荷将会显著削弱SiO2层的封填裂纹效果, 导致氧化性气氛通过外力拉开的微裂纹扩散进入材料内部．外载荷越大, 气体在材料内部的扩散越快, 复合材料的疲劳寿命越短．
Tension-tension fatigue experiments were conducted at room temperature and in water vapor containing environment at 1300℃, using a stress ratio of 0.1 at sinusoidal frequency of 3Hz. The results show that the fatigue limit (based on 105 cycles) in the above two environments are 244.8MPa and 90.8MPa, respectively. Oxidation is the dominant damage mechanism. Based on the microstructure observation of the fracture surfaces, it is concluded that in water-vapor containing environment at 1300℃, sufficiently high stress remarkably weakens the sealing effect of SiO2, which enables the oxidizing species to diffuse through the coating cracks caused by the applied stress. The higher the applied stress, the higher the gaseous diffusivity, the shorter the composite fatigue life.
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