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

Conference · Mon Jan 01 00:00:00 EST 1990

OSTI ID:6597207

Bhatt, R T

The influence of fiber/matrix interface microstructure and interfacial shear strength on the mechanical properties of a fiber-reinforced ceramic composite was evaluated. The composite consisted of approximately 30 vol percent uniaxially aligned 142 microns diameter SiC fibers (Textron SCS-6) in a reaction-bonded Si{sub 3}N{sub 4} 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 percent 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: 6597207
• Report Number(s): N-90-24382; NASA-TM-102462; E-5250; NAS-1.15:102462; AVSCOM-TR-90-C-003; CONF-900221-
• Resource Relation: Conference: International symposium on interfacial reactions in metal or ceramics matrix composites, Anaheim, CA (USA), 19-22 Feb 1990
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
MATRIX MATERIALS
MECHANICAL PROPERTIES
CARBON
CRACKS
FABRICATION
FIBERS
HEAT TREATMENTS
HYDROGEN
MICROSTRUCTURE
NITROGEN
OXIDATION
SHEAR PROPERTIES
SILICON CARBIDES
SILICON NITRIDES
CARBIDES
CARBON COMPOUNDS
CHEMICAL REACTIONS
CRYSTAL STRUCTURE
ELEMENTS
MATERIALS
NITRIDES
NITROGEN COMPOUNDS
NONMETALS
PNICTIDES
SILICON COMPOUNDS
360603* - Materials- Properties