Laminate behavior for SiC fiber-reinforced reaction-bonded silicon nitride matrix composites
- Propulsion Laboratory, Cleveland, OH (USA) BP America, Warrensville, OH (USA)
The room temperature mechanical properties of SiC fiber reinforced reaction-bonded silicon nitride matrix composite laminates (SiC/RBSN) have been measured. The laminates contained approx 30 volume fraction of aligned 142-micron diameter SiC fiber in a porous RBSN matrix. Three types of laminate studied were unidirectional: (1) (0) sub 8, (2) (10) sub 8, and (3) (45) sub 8, and (90) sub 8; cross plied laminates (0 sub 2/90 sub 2); and angle plied laminates: (+45 sub 2/-45 sub 2). Each laminate contained eight fiber plies. Results of the unidirectionally reinforced composites tested at various angles to the reinforcement direction indicate large anisotropy in in-plane properties. In addition, strength properties of these composites along the fiber direction were independent of specimen gage length and were unaffected by notches normal to the fiber direction. Splitting parallel to the fiber at the notch tip appears to be the dominant crack blunting mechanism responsible for notch insensitive behavior of these composites. In-plane properties of the composites can be improved by 2-D laminate construction. Mechanical property results for (0 sub 2/90 sub 2) sub s and (+45/-45 sub 2) sub s laminates showed that their matrix failure strains were similar to that for (0) sub 8 laminates, but their primary elastic moduli, matrix cracking strengths, and ultimate composite strengths were lower. The elastic properties of unidirectional, cross-ply, and angle-ply composites can be predicted from modified constitutive equations and laminate theory. Further improvements in laminate properties may be achieved by reducing the matrix porosity and by optimizing the bond strength between the SiC fiber and RBSN matrix. 14 refs.
- OSTI ID:
- 6818877
- Journal Information:
- Journal of Composites Technology and Research; (USA), Journal Name: Journal of Composites Technology and Research; (USA) Vol. 12; ISSN 0885-6804; ISSN JCTRE
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360203* -- Ceramics
Cermets
& Refractories-- Mechanical Properties
AMBIENT TEMPERATURE
BONDING
CARBIDES
CARBON COMPOUNDS
CERAMICS
COMPOSITE MATERIALS
ELASTICITY
FABRICATION
FIBERS
JOINING
MATERIALS
MECHANICAL PROPERTIES
NITRIDES
NITROGEN COMPOUNDS
PNICTIDES
REINFORCED MATERIALS
SILICON CARBIDES
SILICON COMPOUNDS
SILICON NITRIDES
TENSILE PROPERTIES