Oxidation Effects on the Mechanical Properties of SiC Fiber-Reinforced Reaction-Bonded Silicon Nitride Matrix Composites
Abstract
The room temperature mechanical properties of Silicon Carbide fiber- reinforced reaction-bonded silicon nitride composites (SiC/RBSN) were measured after 100 hr exposure at temperatures to 1400 C in flowing nitrogen and in oxygen environments. The results indicate that composites heat-treated in a nitrogen environment at temperatures to 1400 C showed deformation and fracture behavior equivalent to that of the as-fabricated composites. The composites heat-treated in an oxidizing environment beyond 400 C yielded significantly lower ultimate tensile strength values. In the temperature range from 600 to 1000 C, composites retained approx. 40 percent of their as-fabricated strength, and those heat-treated in the temperature range from 1200 to 1400 C retained approx. 70 percent. For all oxygen heat treatment conditions, composite specimens displayed strain capability beyond the matrix fracture stress; a typical behavior of a tough composite. For the oxygen treated composites, the variation of the primary elastic modulus, the first matrix cracking stress, and the interfacial shear strength with heat treating temperature showed trends similar to that of the ultimate tensile strength. The oxygen effects were influenced by oxidation of the carbon-rich fiber surface coating and oxidation of the RBSN matrix. Keywords: Ceramic composites.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1989
- Accession Number
- ADA217852
Entities
People
- Ramakrishna T. Bhatt
Organizations
- National Aeronautics and Space Administration