Tensile stress rupture of SiC{sub f}/SiC{sub m} minicomposites with carbon and boron nitride interphases at elevated temperatures in air

Journal Article · Fri Aug 01 04:00:00 EDT 1997 · Journal of the American Ceramic Society

OSTI ID:532936

Morscher, G N ^[1]

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1. Case Western Reserve Univ., Cleveland, OH (United States)

The stress-rupture properties of precracked minicomposites were determined in air at temperatures in the range of 700--1,200 C. The minicomposite systems consisted of a single tow of Nicalon or Hi-Nicalon fibers with carbon or boron nitride (BN) interphases and a chemical-vapor-infiltrated silicon carbide (CVI-SiC) matrix. The stress-rupture results were compared to single-fiber stress-rupture data and composite data in the literature. Severe embrittlement occurred for carbon interphase minicomposites. However, BN interphase minicomposites showed only mild degradation in the rupture properties. This was true even though the BN interphase reacted and vaporized because of water vapor in the atmosphere at intermediate temperatures (700--950 C) and glass formation occurred at higher temperatures (950--1,200 C). The severe degradation in rupture properties that occurred for carbon interphase composites at intermediate temperatures was due to degradation of the Nicalon-fiber properties from the environment. The rupture properties of the BN-interphase minicomposites were controlled by the fiber rupture properties at temperatures of less than {approximately}900 C and greater than {approximately}1,100 C. In the range of {approximately}900--1,100 C, most fibers fused to the matrix because of a glass layer that formed between the fiber and matrix, resulting in fiber stress concentrations that led to the mild embrittlement of the BN-interphase minicomposites.

• Sponsoring Organization: National Aeronautics and Space Administration, Washington, DC (United States)
• OSTI ID: 532936
• Journal Information: Journal of the American Ceramic Society, Journal Name: Journal of the American Ceramic Society Journal Issue: 8 Vol. 80; ISSN 0002-7820; ISSN JACTAW
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BORON NITRIDES
CARBON
COMPOSITE MATERIALS
EMBRITTLEMENT
FIBERS
INTERFACES
SILICON CARBIDES
STRESSES
TEMPERATURE RANGE 1000-4000 K
TENSILE PROPERTIES