Environmental effects on creep and stress-rupture properties of advanced SiC fibers
- Cleveland State Univ., OH (United States)
- NASA Lewis Research Center, Cleveland, OH (United States)
Small diameter polycrystalline SiC fibers are of high technical interest for reinforcement of ceramic matrix composites. These fibers have high room temperature stiffness and strength, and the potential for retaining these properties in oxidizing environments up to 1400{degrees}C. However, with current SiC fibers, it has been observed that the influence of environment on the high temperature creep and rupture behavior of individual fibers can be very complex. For example, Bodet et al. reported better creep resistance of ceramic grade Nicalon fiber in a controlled CO environment than in argon. Yun et al. reported better rupture resistance of Nicalon and Hi-Nicalon in air than in vacuum. Rugg reported better rupture resistance of the Carborundum fiber in nitrogen than in air. In general, in comparison to inert conditions, testing in oxygen can increase or decrease fiber creep resistance, while having similar or opposite effects on rupture resistance. These effects can vary significantly with stress, temperature, and the SiC fiber grain boundary structure, second phase and impurity compositions, stoichiometry, as well as open porosity. As an initial step to better understand these factors, the objectives of this study were (1) to measure the effects of air and argon environments on the creep and rupture behavior of various advanced SiC fibers, (2) to determine whether these effects can be correlated among the fiber types, and (3) to suggest probable sources for these effects based on microstructural mechanisms.
- OSTI ID:
- 134944
- Report Number(s):
- CONF-9508127--
- Country of Publication:
- United States
- Language:
- English
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