Chapter 41. Effects of Fiber Coating Composition on Mechanical Behavior of Silicon Carbide Fiber-Reinforced Celsian Composites

  1. Ersan Ustundag and
  2. Gary Fischman
  1. Narottam P. Bansal and
  2. Jeffrey L Eidridge

Published Online: 26 MAR 2008

DOI: 10.1002/9780470294567.ch41

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

Bansal, N. P. and Eidridge, J. L. (1999) Effects of Fiber Coating Composition on Mechanical Behavior of Silicon Carbide Fiber-Reinforced Celsian Composites, 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.ch41

Author Information

  1. Materials Division, NASA Lewis Research Center, Cleveland, OH 44135

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:

  • composite;
  • microstucture;
  • elastic modulus;
  • celsian matrix;
  • therrmal stresses

Summary

Celsian matrix composites reinforced with Hi-Nicalon fibers, pie-coated with a dual layer of BN/SiC by chemical vapor deposition in two separate batches, were fabricated. Mechanical properties of the composites were measured in three-point flexure. Despite supposedly identical processing, the composite panels fabricated with fibers coated in two batches exhibited substantially different mechanical behavior. The first matrix cracking stresses (σmc) of the composites reinforced with fibers coated in batch 1 and batch 2 were 436 and 122 MPa, respectively. This large difference in σmo, was attributed to differences in fiber sliding stresses (τfriction), 121.2 ± 48.7 and 10.4 ±3.1 MPa, respectively, for the two composites as determined by the fiber push-in method. Such a large difference in values of τfriction for the two composites was found to be due to the difference in the compositions of the interface coatings. Scanning Auger microprobe analysis revealed the presence of carbon layers between the fiber and BN, and also between the BN and SiC coatings in the composite showing lower τfriction. This resulted in lower σmc, in agreement with the ACK theory. The ultimate strengths of the two composites, 904 and 7S9 MPa, depended mainly on the fiber volume fraction and were not significantly effected by τfriction values, as expected. The poor reproducibility of the fiber coating composition between the two batches was judged to be the primary source of the large differences in performance of the two composites.