Oxidation of Continuous Carbon Fibers within a Silicon Carbide Matrix under Stressed and Unstressed Conditions

Carbon fiber reinforced silicon carbide matrix composites (C/SiC) are a ceramic matrix composite (CMC) material that offers benefits for use in a wide range of high temperature structural applications. However the susceptibility of the carbon fibers to degradation in oxidizing environments has hinde...

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Bibliographic Details
Main Authors: Halbig, Michael C, Eckel, Andrew J
Format: Report
Language:English
Subjects:
523-61-13-00
CARBON FIBERS
CERAMIC MATRIX COMPOSITES
Ceramics, Refractories and Glass
CRACKS
CREEP
DEGRADATION
FIBER REINFORCED COMPOSITES
HIGH TEMPERATURE
OXIDATION RESISTANCE
PE61102A
REACTION KINETICS
RUPTURE
SILICON CARBIDES
STRESS TESTING
STRUCTURAL PROPERTIES
THERMOGRAVIMETRIC ANALYSIS
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Summary:Carbon fiber reinforced silicon carbide matrix composites (C/SiC) are a ceramic matrix composite (CMC) material that offers benefits for use in a wide range of high temperature structural applications. However the susceptibility of the carbon fibers to degradation in oxidizing environments has hindered the material's use in certain applications requiring long lives under oxidizing conditions. The susceptibility of carbon fibers to oxidation will be discussed as well as the enhancement (improvement in oxidation resistance) of C/SiC materials. Thermogravimetric analysis of carbon fibers shows susceptibility to oxidation in two distinct kinetic regimes. However, in the thermogravimetric (wt. loss) analysis of unstressed, unenhanced, seal coated C/SiC coupons, the two regimes were not observed due to crack closure and matrix effects, which inhibited the oxidation process. Stressed oxidation (creep rupture) tests put the material under a stress, which is a more realistic condition for many applications. In stressed oxidation tests, the two oxidation kinetics regimes were observed. These tests can provide better insight into how the material will perform in applications involving stress. Stressed oxidation of enhanced materials containing oxidation inhibitors showed significantly improved lives at the specific test conditions considered, although there was susceptibility to oxidation at intermediate temperatures. Prepared for the 24th Annual Conference on Composites, Advanced Ceramics, Materials, and Structures sponsored by the American Ceramic Society, Cocoa Beach, Florida, January 23-28, 2000.