Chapter 35. Mechanical Properties and Microstructure of Oxidized SiC/SiC Composites

  1. John B. Wachtman Jr.
  1. Ö. Ünal1,
  2. A. J. Eckel2 and
  3. F. C. Laabs1

Published Online: 28 MAR 2008

DOI: 10.1002/9780470314876.ch35

Proceedings of the 20th Annual Conference on Composites, Advanced Ceramics, Materials, and Structures - B: Ceramic Engineering and Science Proceedings, Volume 17, Issue 4

Proceedings of the 20th Annual Conference on Composites, Advanced Ceramics, Materials, and Structures - B: Ceramic Engineering and Science Proceedings, Volume 17, Issue 4

How to Cite

Ünal, Ö., Eckel, A. J. and Laabs, F. C. (1996) Mechanical Properties and Microstructure of Oxidized SiC/SiC Composites, in Proceedings of the 20th Annual Conference on Composites, Advanced Ceramics, Materials, and Structures - B: Ceramic Engineering and Science Proceedings, Volume 17, Issue 4 (ed J. B. Wachtman), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470314876.ch35

Author Information

  1. 1

    Ames Laboratory, Metallurgy and Ceramics Div., Ames, IA 50010

  2. 2

    NASA Lewis Research Center, Ceramics Div., Cleveland, OH 44135

Publication History

  1. Published Online: 28 MAR 2008
  2. Published Print: 1 JAN 1996

ISBN Information

Print ISBN: 9780470375433

Online ISBN: 9780470314876

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Keywords:

  • oxidation heat-treatment;
  • primary oxidation product;
  • sealed smallsurface pores;
  • oxidizing environments;
  • boron-nitride as interface coating

Summary

The mechanical properties and microstructure of oxidized CVI-SiC/SiC composites were studied at room temperature. Oxidation heat-treatment, which was carried out between 950 and 1400°C in flowing dry-oxygen for 50 hours, led to weight loss and degradation in mechanical properties. The largest impact, however, was seen at 950°C. The SiO2 phase, which was the primary oxidation product, sealed small surface pores between 950 and 1400°C. The loss of interfacial carbon by oxidation, the formation of SiO2 inside the composite, and the degradation of fibers particularly at elevated temperatures were responsible for the brittle fracture, low strength, low toughness and inferior fatigue life seen in these composites.