Influence of interfacial shear strength on the mechanical properties of SiC fiber-reinforced reaction-bonded silicon nitride matrix composites. Technical memo
The influence of fiber/matrix interface microstructure and interfacial shear strength on the mechanical properties of a fiber-reinforced ceramic composite has been evaluated. The composite consisted of about 30 vol % uniaxially aligned 142 micron diameter SiC fibers (Textron SCS-6) in a reaction-bonded Si3N4 matrix (SiC/RBSN). The interface microstructure was varied by controlling the composite fabrication conditions and by heat treating the composite in an oxidizing environment. Interfacial shear strength was determined by the matrix crack spacing method. The results of microstructural examination indicate that the carbon-rich coating provided with the as-produced SiC fibers was stable in composites fabricated at 1200 C in a nitrogen or in a nitrogen plus 4 percent hydrogen mixture for 40 hr. However this coating degraded in composites fabricated at 1350 C in N2 + 4%H2 for 40 and 72 hr and also in composites heat treated in an oxidizing environment at 600 C for 100 hr after fabrication at 1200 C in a nitrogen. It was determined that degradation occurred by carbon removal which in turn had a strong influence on interfacial shear strength and other mechanical properties. Specifically, as the carbon coating was removed, the composite interfacial shear strength, primary elastic modulus, first matrix cracking stress, and ultimate tensile strength decreased, but the first matrix cracking strain remained nearly the same.
- Research Organization:
- National Aeronautics and Space Administration, Cleveland, OH (USA). Lewis Research Center
- OSTI ID:
- 6483683
- Report Number(s):
- AD-A-224968/8/XAB; NASA-E-5250
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SILICON CARBIDES
MECHANICAL PROPERTIES
SILICON NITRIDES
CARBON
CERAMICS
COATINGS
COMPOSITE MATERIALS
CRACKS
ELASTICITY
ENVIRONMENT
FIBERS
FRACTURE PROPERTIES
HYDROGEN
INTERFACES
MATRIX MATERIALS
MICROSTRUCTURE
MIXTURES
NITROGEN
OXIDATION
REINFORCED MATERIALS
SHEAR PROPERTIES
STRESSES
TENSILE PROPERTIES
CARBIDES
CARBON COMPOUNDS
CHEMICAL REACTIONS
CRYSTAL STRUCTURE
DISPERSIONS
ELEMENTS
MATERIALS
NITRIDES
NITROGEN COMPOUNDS
NONMETALS
PNICTIDES
SILICON COMPOUNDS
360203* - Ceramics
Cermets
& Refractories- Mechanical Properties