Microstructure and mechanical properties of polymer-derived Si{sub 3}N{sub 4}/SiC fabric composite

Conference · Sat Dec 31 04:00:00 EST 1994

OSTI ID:96529

Pan, Y -M; Davidson, D L; Schwab, S T ^[1]

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1. Southwest Research Institute, San Antonio, TX (United States)

SiC fiber-reinforced Si{sub 3}N{sub 4} matrix composites were fabricated through the utilization of preceramic polysilizanes and polymer infiltration/pyrolysis processing techniques. Microstructures and mechanical properties (modulus of rupture, compressive strength, and fracture toughness) were characterized. The K{sub IC} and work of fracture, measured by the chevron notch method, were 15.6 MPa M{sup 1/2} and 11.8 KJ/m{sup 2}, which compare favorably to those of hot-pressed, SCS-6 reinforced Si{sub 3}N{sub 4}. The toughening of these polymer-derived Si{sub 3}N{sub 4} composites is associated with the substantial nonlinear behavior illustrated in the dimensionless load vs. load-point displacement plot. This is consistent with the rising R-curve behavior. The compressive strength of approximately 500 MPa was found to be independent of temperature up to 800{degrees}C; however, the linearity of the {sigma}-{epsilon} does reflect the test temperature. Micromechanics experiments suggest that the high level of fracture toughness may be attributed to pseudo-plastic strain response of the composite material near the crack tip.

• OSTI ID: 96529
• Report Number(s): CONF-940416--
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CERAMICS
COMPRESSION STRENGTH
CRACKS
FLEXURAL STRENGTH
FRACTURE PROPERTIES
INTERFACES
MANUFACTURING
MECHANICAL PROPERTIES
MICROSTRUCTURE
MORPHOLOGY
SILICON CARBIDES
SILICON NITRIDES
TEMPERATURE DEPENDENCE