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Intermediate temperature strength degradation in SiC/SiC composites

Woven silicon carbide fibre-reinforced, silicon carbide matrix composites are leading candidate materials for an advanced jet engine combustor liner application. Although the operating temperature in the hot region for this application is expected to exceed 1200 C, a potential life-limiting concern...

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Bibliographic Details
Published in:Journal of the European Ceramic Society 2002, Vol.22 (14-15), p.2777-2787
Main Authors: MORSCHER, G. N, CAWLEY, J. D
Format: Article
Language:English
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Summary:Woven silicon carbide fibre-reinforced, silicon carbide matrix composites are leading candidate materials for an advanced jet engine combustor liner application. Although the operating temperature in the hot region for this application is expected to exceed 1200 C, a potential life-limiting concern for this composite system exists at intermediate temperatures (800 plus or minus 200 C), where significant time-dependent strength degradation has been observed under stress rupture loading. A number of factors control the degree of stress rupture strength degradation, the major factor being the nature of the interphase separating the fibre and the matrix. BN interphases are superior to carbon interphases due to the slower oxidation kinetics of BN. A model for the intermediate temperature stress rupture of SiC/BN/SiC composites is presented based on the observed mechanistic process that leads to strength degradation for the simple case of through-thickness matrix cracks. The approach taken has much in common with that used by Curtin and coworkers, for two different composite systems. The predictions of the model are in good agreement with the data for stress rupture of both precracked and as-produced composites. Also, three approaches that dramatically improve the intermediate temperature stress rupture properties are described: Si-doped BN, fibre spreading, and "outside debonding". 32 refs.
ISSN:0955-2219
1873-619X
DOI:10.1016/S0955-2219(02)00144-9