Influence of interfacial shear strength on the mechanical properties of SiC fiber-reinforced reaction-bonded silicon nitride matrix composites. Technical memo

Technical Report · Mon Jan 01 04:00:00 EST 1990

OSTI ID:6483683

Bhatt, R T

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

Related Subjects

36 MATERIALS SCIENCE
360203* -- Ceramics
Cermets
& Refractories-- Mechanical Properties
CARBIDES
CARBON
CARBON COMPOUNDS
CERAMICS
CHEMICAL REACTIONS
COATINGS
COMPOSITE MATERIALS
CRACKS
CRYSTAL STRUCTURE
DISPERSIONS
ELASTICITY
ELEMENTS
ENVIRONMENT
FIBERS
FRACTURE PROPERTIES
HYDROGEN
INTERFACES
MATERIALS
MATRIX MATERIALS
MECHANICAL PROPERTIES
MICROSTRUCTURE
MIXTURES
NITRIDES
NITROGEN
NITROGEN COMPOUNDS
NONMETALS
OXIDATION
PNICTIDES
REINFORCED MATERIALS
SHEAR PROPERTIES
SILICON CARBIDES
SILICON COMPOUNDS
SILICON NITRIDES
STRESSES
TENSILE PROPERTIES