Failure modes of SiC-fiber/Si{sub 3}N{sub 4}-matrix composites at elevated temperatures

Journal Article · Wed Feb 01 04:00:00 EST 1995 · Journal of the American Ceramic Society

DOI:https://doi.org/10.1111/j.1151-2916.1995.tb08812.x· OSTI ID:566566

Xu, H H.K.; Braun, L M; Ostertag, C P; Krause, Jr, R F ^[1]; Lloyd, I K ^[2]

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1. National Inst. of Standards and Technology, Gaithersburg, MD (United States)
2. Univ. of Maryland, College Park, MD (United States). Dept. of Materials and Nuclear Engineering

An investigation of composite failure modes as a function of temperature and fiber-volume fraction was carried out in SiC-fiber-reinforced Si{sub 3}N{sub 4}-matrix composites. Mechanical testing was carried out at temperatures from 25 to 1,500 C. Matrix-cracking stress and ultimate strength of the composites were measured from load-displacement curves. They were both found to decrease with increasing temperature, but their temperature sensitivity decreased with increasing fiber-volume fraction. The tendency for noncatastrophic failure increased with fiber-volume fraction, while the tendency for catastrophic failure increased with temperature. The failure mode was demonstrated experimentally to be determined by the fiber bundle strength, S{sub fb}, and the matrix cracking stress, {sigma}{sub c}. These two parameters, in turn, were shown to be controlled by the fiber-volume fraction, f, and the temperature. Failure at various temperatures was noncatastrophic when S{sub fb} > {sigma}{sub c}, and catastrophic when S{sub fb} < {sigma}{sub c}. Transition in composite failure mode between noncatastrophic and catastrophic failure was controlled via the variation of fiber-volume fraction and testing temperature. Catastrophic failure at high temperatures was found to be mainly a result of fiber strength loss.

• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 566566
• Journal Information: Journal of the American Ceramic Society, Journal Name: Journal of the American Ceramic Society Journal Issue: 2 Vol. 78; ISSN 0002-7820; ISSN JACTAW
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
COMPOSITE MATERIALS
CRACK PROPAGATION
EXPERIMENTAL DATA
FAILURES
FRACTURE PROPERTIES
SILICON CARBIDES
SILICON NITRIDES
TEMPERATURE DEPENDENCE
ULTIMATE STRENGTH