Accession Number:

ADA224494

Title:

Matrix Density Effects on the Mechanical Properties of SiC/RBSN composites

Descriptive Note:

Technical memo.

Corporate Author:

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER

Report Date:

1990-01-01

Pagination or Media Count:

17.0

Abstract:

The room temperature mechanical properties were measured for SiC fiber-reinforced reaction-bonded silicon nitride composites SiCRBSN of different densities. The composites consisted of approx. 30 vol uniaxially aligned 142 um diameter SiC fibers Textron SCS-6 in a reaction-bonded Si3N4 matrix. The composite density was varied by changing the consolidation pressure during RBSN processing and by hot isostatically pressing the SiCRBSN composites. Results indicate that as the consolidation pressure during RBSN processing and by hot isostatically pressing the SiCRBSN composites. Results indicate that as the consolidation pressure was increased from 27 to 138 MPa, the average pore size of the nitrided composites decreased from 0.04 to 0.02 microns and the composite density increased from 2.07 to 2.45 gmcc. Nonetheless, these improvements resulted in only small increases in the first matrix cracking stress, primary elastic modulus, and ultimate tensile strength values of the composites. In contrast, HIP consolidation of SiCRBSN resulted in a fully dense material whose first matrix cracking stress and elastic modulus values were approx. 15 and approx. 50 percent higher, respectively, the ultimate tensile strength values were approx. 40 percent lower than those for unHIPed SiCRBSN composites. The modulus behavior for all specimens can be explained by simple rule-of-mixture theory. Also, the loss in ultimate strength for the HIP temperature. SDW

Subject Categories:

  • Metallurgy and Metallography
  • Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE