Chapter 23. Mechanical and Microstructural Properties of Nextel™ 720 Relating to its Suitability for High Temperature Application in CMCs

  1. Ersan Ustundag and
  2. Gary Fischman
  1. C. Milz,
  2. J. Goering and
  3. H. Schneider

Published Online: 26 MAR 2008

DOI: 10.1002/9780470294567.ch23

23rd Annual Conference on Composites, Advanced Ceramics, Materials, and Structures : A: Ceramic Engineering and Science Proceedings, Volume 20, Issue 3

23rd Annual Conference on Composites, Advanced Ceramics, Materials, and Structures : A: Ceramic Engineering and Science Proceedings, Volume 20, Issue 3

How to Cite

Milz, C., Goering, J. and Schneider, H. (1999) Mechanical and Microstructural Properties of Nextel™ 720 Relating to its Suitability for High Temperature Application in CMCs, in 23rd Annual Conference on Composites, Advanced Ceramics, Materials, and Structures : A: Ceramic Engineering and Science Proceedings, Volume 20, Issue 3 (eds E. Ustundag and G. Fischman), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470294567.ch23

Author Information

  1. German Aerospace Center Cologne (DLR) Institute for Materials Research D-51147 Köln, Germany

Publication History

  1. Published Online: 26 MAR 2008
  2. Published Print: 1 JAN 1999

ISBN Information

Print ISBN: 9780470375631

Online ISBN: 9780470294567

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Keywords:

  • tensile;
  • thermal stability;
  • dynamic fatigue method;
  • ceramic;
  • poly-crystalline

Summary

Nextel™ 720 fibers and their suitability for high-temperature (HT) applications in CMCs were analyzed at temperatures ranging from 900° to 1300°C. The thermal stability of the Nextel™ 720 fibers was characterized by single-fiber tensile tests at various temperatures after heat treatments up to 1300°C. In addition to bulk fiber grain growth resulting from heat treatment at T > 1200°C, a locally-catastrophic degradation of the fiber material occurred during heat treatment at 1300°C. This degradation was caused by locally enriched impurities and had a mean spacing of 135mm [1]. The subcritical crack growth (SCG) was determined using the dynamic fatigue method. At 900°C no SCG could be detected while at 1000°C (N=18) and at 1100°C (N=9.4) intensive SCG was found. Nevertheless the locally catastrophic degradation as well as the intense SCG has only a minor influence on the use of Nextel™ 720 fibers in a ceramic composite; this due to low values (between 0.34 and 15.2 mm) of the fiber length relevant to composite failure.