Stress/Life Behavior of C/SiC Composites in a Low Partial Pressure of Oxygen Environment Part II: Stress Rupture Life and Residual Strength Relationship

摘要

Stress-rupture lives and residual strength measurements were obtained for carbon fiber-reinforced silicon carbide (C/SiC) composite specimens. Two types of tests were performed for this study. The first set consisting of several creep-rupture tests all performed under a constant stress of 207 MPa was used to determine the mean rupture life of the C/SiC composite. A second set of creep-rupture tests performed under the same constant stress of 207 MPa were interrupted at a fixed fraction of the mean rupture life and residual strength measurements were taken. All testing was performed at 1200 °C in an environment of 1000 ppm O_2/Ar. The low oxygen partial pressure environment was used to retard carbon fiber oxidation and thereby extend rupture life and improve the data spread over a high range of stress. All specimens were machined from a single processing lot of material. A statistical comparison of the test results reveals a relationship between residual strength and creep-life for the C/SiC material. The results also support the development of a Probabilistic Residual Strength (PRS) life model.