Fracture resistance of SiC-fiber-reinforced Si{sub 3}N{sub 4} composites at ambient and elevated temperatures
- National Inst. of Standards and Technology, Gaithersburg, MD (United States)
- Univ. of Maryland, College Park, MD (United States). Materials and Nuclear Engineering
The crack growth behavior in unidirectional SiC-fiber-reinforced Si{sub 3}N{sub 4}-matrix composites fabricated in their laboratories was investigated as a function of fiber volume fraction an temperature. Both the stress-intensity factor and an energy approach were adopted in the characterization of the crack growth behavior. Crack resistance increased with crack extension (R-curve or T-curve) as a result of bridging effects associated with the intact fibers. Large-scale bridging was observed, and was considered in the determination of the R-curves. Temperature and fiber volume fraction affected the crack propagation behavior. At room temperature a single crack was initiated at the notch tip; it then branched and delaminated upon further loading. In contrast, at 1,200 C, little crack branching was observed. Increasing fiber volume fraction increased the degree of crack branching. Temperature and fiber volume fraction also affected the R-curve behavior. Raising the temperature to 1,200 C did not significantly degrade the room-temperature R-curve effect. Increasing the fiber volume fraction from 14% to 29% substantially enhanced the toughening effect and the R-curve behavior.
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 79783
- Journal Information:
- Journal of the American Ceramic Society, Journal Name: Journal of the American Ceramic Society Journal Issue: 3 Vol. 78; ISSN 0002-7820; ISSN JACTAW
- Country of Publication:
- United States
- Language:
- English
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