Fatigue Mechanisms in Graphite/SiC Composites at Room and High Temperature

Some deductions have been made from fractographic evidence about mechanisms of low‐cycle mechanical fatigue in plain woven graphite/SiC composites at room and high temperature in vacuum. At both room temperature and 830°C, fatigue appears to be confined to the crack wake, where attrition reduces the...

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Bibliographic Details
Published in:Journal of the American Ceramic Society 1994-03, Vol.77 (3), p.792-800
Main Authors: Morris, Winfred L., Cox, Brian N., Marshall, David B., Inman, Richard V., James, Michael R.
Format: Article
Language:English
Subjects:
360603 - Materials- Properties
Applied sciences
Building materials. Ceramics. Glasses
CARBIDES
CARBON
CARBON COMPOUNDS
Ceramic industries
Chemical industry and chemicals
COMPOSITE MATERIALS
CRACK PROPAGATION
ELEMENTAL MINERALS
ELEMENTS
Exact sciences and technology
FATIGUE
Fatigue of materials
Grain boundaries
GRAPHITE
High temperature effects
MATERIALS
MATERIALS SCIENCE
MECHANICAL PROPERTIES
MINERALS
Miscellaneous
Morphology
NONMETALS
Residual stresses
Silicon carbide
SILICON CARBIDES
SILICON COMPOUNDS
Technical ceramics
TEMPERATURE DEPENDENCE
Vacuum applications
Wear of materials
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Summary:Some deductions have been made from fractographic evidence about mechanisms of low‐cycle mechanical fatigue in plain woven graphite/SiC composites at room and high temperature in vacuum. At both room temperature and 830°C, fatigue appears to be confined to the crack wake, where attrition reduces the efficacy of bridging fibers. It is inferred that the crack tip advances at some critical value of the crack tip stress intensity factor, as in monotonic growth, rather than by any intrinsic fatigue mechanism in the matrix. However, the manifestations of attrition are very different at room and high temperatures. At high temperature, wear is greatly accelerated by the action of SiC debris within the crack. This distinction is rationalized in terms of the temperature dependence expected in the opening displacement of a bridged crack. This argument leads in turn to plausible explanations of trends in loadlife curves and the morphology of cracks as the temperature rises.
ISSN:0002-7820
1551-2916
DOI:10.1111/j.1151-2916.1994.tb05367.x