Chapter 69. Ultrasonic Assessment of Thermal Oxidation Damage in SiC/Si3N4 Composites

  1. John B. Wachtman Jr.
  1. S. I. Rokhlin1,
  2. Y. C. Chu1,
  3. G. Y. Baaklini2 and
  4. R. T. Bhatt2

Published Online: 28 MAR 2008

DOI: 10.1002/9780470314180.ch69

Proceedings of the 17th Annual Conference on Composites and Advanced Ceramic Materials, Part 1 of 2: Ceramic Engineering and Science Proceedings, Volume 14, Issue 7/8

Proceedings of the 17th Annual Conference on Composites and Advanced Ceramic Materials, Part 1 of 2: Ceramic Engineering and Science Proceedings, Volume 14, Issue 7/8

How to Cite

Rokhlin, S. I., Chu, Y. C., Baaklini, G. Y. and Bhatt, R. T. (1993) Ultrasonic Assessment of Thermal Oxidation Damage in SiC/Si3N4 Composites, in Proceedings of the 17th Annual Conference on Composites and Advanced Ceramic Materials, Part 1 of 2: Ceramic Engineering and Science Proceedings, Volume 14, Issue 7/8 (ed J. B. Wachtman), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470314180.ch69

Author Information

  1. 1

    The Ohio State University Department of Welding Engineering Columbus, Ohio 43210

  2. 2

    NASA Lewis Research Center Cleveland, Ohio 44135

Publication History

  1. Published Online: 28 MAR 2008
  2. Published Print: 1 JAN 1993

ISBN Information

Print ISBN: 9780470375266

Online ISBN: 9780470314180

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Keywords:

  • oxidation;
  • nondestructively;
  • significantly;
  • ultrasonic;
  • interphasial modulus

Summary

In this paper an ultrasonic method for oxidation damage characterization in ceramic matrix composites is proposed. In this approach the elastic constants of the composite are determined nondestructively by measuring the angular dependence of both longitudinal and transverse wave velocities. Unidirectional SiC/Si3N4 composites with different fiber fraction and matrix porosity were used in these experiments. The samples were exposed in a flowing oxygen environment for 1, 10 and 100 hours at temperatures 600, 900, 1200 and 1400 °C to investigate the effect of exposure time and temperature on oxidation damage in SiC/Si3N4 composites. For each exposure time and temperature, multiple samples were investigated and their averaged results were used in the analysis. In the fiber direction, the Young's modulus obtained from ultrasonic measurements decreases significantly for heating at 600 and 900 °C but retains its original value at temperatures 1200 and 1400 °C. The composite transverse moduli obtained from ultrasonic measurements decrease continually up to 1400 °C. The shear stiffnesses show behavior similar to the transverse moduli. To investigate the change of constituent properties due to oxidation, a multi-phase micromechanical model for composites with anisotropic constituents is used to analyze the experimental data. Using this model we determine the elastic moduli of the fiber-matrix interphases in as-received and oxidized composite samples and suggest using the degree of the interphasial modulus reduction as a quantitative measure of interphase degradation due to oxidation.