Chapter 80. The Effect of Static and Cyclic Tensile Stress and Temperature on Fatlure for Precracked Hi-Nicalon/BN/CVD Sic Minicomposites in Air

  1. J. P. Singh
  1. Gregory N. Morscher

Published Online: 26 MAR 2008

DOI: 10.1002/9780470294437.ch80

Proceedings of the 21st Annual Conference on Composites, Advanced Ceramics, Materials, and Structures: A: Ceramic Engineering and Science Proceedings, Volume 18, Issue 3

Proceedings of the 21st Annual Conference on Composites, Advanced Ceramics, Materials, and Structures: A: Ceramic Engineering and Science Proceedings, Volume 18, Issue 3

How to Cite

Morscher, G. N. (1997) The Effect of Static and Cyclic Tensile Stress and Temperature on Fatlure for Precracked Hi-Nicalon/BN/CVD Sic Minicomposites in Air, in Proceedings of the 21st Annual Conference on Composites, Advanced Ceramics, Materials, and Structures: A: Ceramic Engineering and Science Proceedings, Volume 18, Issue 3 (ed J. P. Singh), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470294437.ch80

Author Information

  1. Case Western Reserve University, Cleveland, OH

Publication History

  1. Published Online: 26 MAR 2008
  2. Published Print: 1 JAN 1997

ISBN Information

Print ISBN: 9780470375495

Online ISBN: 9780470294437

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Keywords:

  • matrix minicomposites;
  • cyclic fatigue;
  • degradation;
  • precracked minicomposites;
  • intermediate temperature tests

Summary

Single tow Hi-Nicalon, BN-interphase, CVI SiC matrix minicomposites were tested in tension for a variety of stress/temperature conditions. These included, stressrupture, thermal fatigue, and cyclic fatigue in air for precracked minicomposites. The time-dependent mechanical properties were compared to the time-dependent mechanical properties expected for the fibers alone. The intermediate temperature range of∼ 900 to 1100°C was found to result in the most severe degradation judged relative to the fiber mechanical properties for the same test conditions. Cyclic stress was found to be the most severe loading condition for these intermediate temperature tests. The proposed mechanisms for intermediate temperature degradation were fiber degradation combined with stress concentrations placed on the fibers. Fiber degredation was considered to be caused by the formation of a liquid in the interphase region which reacts with the fiber. The stress concentrations result from a strong bonding glass formed in the interphase region due to solidification of the originally low viscosity B2O3-SiO2 liquid as the B-content of the liquid decreased due to hydrolysis and Si-content of the liquid increased due to reaction with the fiber and matrix. For higher temperature and lower stress conditions, the fiber creep-rupture properties dominated.