Creep in vacuum of woven Sylramic-iBN melt-infiltrated composites

In order to better understand the effect of stressed-oxidation, the performance of woven Sylramic-iBN fiber-reinforced slurry cast melt-infiltrated (MI) composites were tested in creep and fatigue under non-oxidizing conditions. Initially creep and fatigue tests were performed at 1204 °C in an argon atmosphere; however, it was observed that sufficient oxidizing species existed in the environment to degrade the composites in a manner similar to air environments. Therefore, creep and fatigue tests were performed at 1204 °C in a vacuum environment which showed no evidence of oxidation and superior properties to composites subjected to stressed-oxidation conditions. The mechanical results and microscopy of the vacuum and argon are compared to the behavior of these composites tested in air. It was found that the stress-rupture properties of the vacuum-tested composites could be predicted from single fiber creep rupture data assuming reasonable values for the Weibull modulus.