18. Tensile Properties of Nextel ™720-Based Tows and Minicomposites Subjected to High-Temperature Soaking

  1. Edgar Lara-Curzio and
  2. Michael J. Readey
  1. D. M. Pai1,
  2. S. Yarmolenko1,
  3. B. Kailasshankar1,
  4. C. Murphy1,
  5. J. Sankar1 and
  6. L. P. Zawada2

Published Online: 26 MAR 2008

DOI: 10.1002/9780470291191.ch18

28th International Conference on Advanced Ceramics and Composites B: Ceramic Engineering and Science Proceedings, Volume 25, Issue 4

28th International Conference on Advanced Ceramics and Composites B: Ceramic Engineering and Science Proceedings, Volume 25, Issue 4

How to Cite

Pai, D. M., Yarmolenko, S., Kailasshankar, B., Murphy, C., Sankar, J. and Zawada, L. P. (2004) Tensile Properties of Nextel ™720-Based Tows and Minicomposites Subjected to High-Temperature Soaking, in 28th International Conference on Advanced Ceramics and Composites B: Ceramic Engineering and Science Proceedings, Volume 25, Issue 4 (eds E. Lara-Curzio and M. J. Readey), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470291191.ch18

Author Information

  1. 1

    Center for Advanced Materials and Smart Structures Department of Mechanical and Chemical Engineering North Carolina A&T State University Greensboro, NC 27411

  2. 2

    U. S. Air Force Research Laboratory Wright-Patterson AFB, OH 45433

Publication History

  1. Published Online: 26 MAR 2008
  2. Published Print: 1 JAN 2004

ISBN Information

Print ISBN: 9780470051528

Online ISBN: 9780470291191

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Keywords:

  • coated minicomposites;
  • room temperature;
  • alumina grains;
  • phosphorus;
  • tensile properties

Summary

The tensile strengths of fiber tows and minicomposites based on Nextel ™720 fiber were investigated at room temperature (RT) and at 1200°C (HT). Uncoated and monazite coated fibers were used, and the minicomposites were made with an alumina matrix. As-received (‘unsoaked’) and thermally soaked tows and minicomposites were used. It was found that uncoated fiber tows tested at RT have the highest strength and linear stress-strain curves with clearly-defined fracture. This was unlike coated fiber tows, which exhibit residual load-carrying capability beyond the maximum load point, because the fibers are not loaded equally during the tension test. Soaked uncoated and coated tows tested at RT retained 30% and 73% of their corresponding unsoaked RT strengths. The protective effect of the coating on contact-related damage of tows appears to dominate over the damage caused by soaking at HT. On the other hand, uncoated, unsoaked tows tested at HT retained 32% of the RT average tensile strength of 544 MPa. Coated, unsoaked tows tested at HT retained 100% of their RT average strength of 312 MPa. Strength degradation of tows appears to originate from contact between fibers in a tow during testing. The beneficial effect of the coatings in reducing contact-related damage of tows during RT and HT testing can explain the identical results for RT and HT strengths of coated tows. Degradation of the monazite coating was observed after thermal soaking of minicomposites.