Mullite fiber reinforced reaction bonded Si{sub 3}N{sub 4} composites
- Massachusetts Institute of Technology, Cambridge, MA (United States)
- NASA Lewis Research Center, Cleveland, OH (United States)
Fracture toughnesses of brittle ceramic materials have been improved by introducing reinforcements and carefully tailored interface layers. Silicon carbide and Si{sub 3}N{sub 4} have been emphasized as matrices of structural composites intended for high temperature service because they combine excellent mechanical, chemical, thermal and physical properties. Both matrices have been successfully toughened with SiC fibers, whiskers and particles for ceramic matrix composite (CMC) parts made by sintering, hot pressing or reaction forming processes. These SiC reinforced CMCs have exhibited significantly improved toughnesses at low and intermediate temperature levels, as well as retention of properties at high temperatures for selected exposures; however, they are vulnerable to attack from elevated temperature dry and wet oxidizing atmospheres after the matrix has cracked. Property degradation results from oxidation of interface layers and/or reinforcements. The problem is particularly acute for small diameter ({approximately}20 {mu}m) polymer derived SiC fibers used for weavable toes. This research explored opportunities for reinforcing Si{sub 3}N{sub 4} matrices with fibers having improved environmental stability; the finding should also be applicable to SiC matrix CMCs.
- OSTI ID:
- 567474
- Report Number(s):
- CONF-960106--; CNN: Contract N00014-94-1-0425
- Country of Publication:
- United States
- Language:
- English
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