Chapter 53. Damping Characteristics of Cast Graphite-Magnesium Composites

  1. John B. Wachtman Jr.
  1. S. P. Rawal,
  2. J. H. Armstrong and
  3. M. S. Misra

Published Online: 28 MAR 2008

DOI: 10.1002/9780470310496.ch53

Proceedings of the 12th Annual Conference on Composites and Advanced Ceramic Materials, Part 1 of 2: Ceramic Engineering and Science Proceedings, Volume 9, Issue 7/8

Proceedings of the 12th Annual Conference on Composites and Advanced Ceramic Materials, Part 1 of 2: Ceramic Engineering and Science Proceedings, Volume 9, Issue 7/8

How to Cite

Rawal, S. P., Armstrong, J. H. and Misra, M. S. (1988) Damping Characteristics of Cast Graphite-Magnesium Composites, in Proceedings of the 12th Annual Conference on Composites and Advanced Ceramic Materials, Part 1 of 2: Ceramic Engineering and Science Proceedings, Volume 9, Issue 7/8 (ed J. B. Wachtman), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470310496.ch53

Author Information

  1. Martin Marietta Astronautics Group Denver, CO 80201

Publication History

  1. Published Online: 28 MAR 2008
  2. Published Print: 1 JAN 1988

ISBN Information

Print ISBN: 9780470374801

Online ISBN: 9780470310496

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Keywords:

  • propagation;
  • diagonal;
  • microstructural;
  • indentation;
  • reliability

Summary

During cyclic loading, energy dissipation characteristics of fiber, matrix, and interfaces influence the dynamic response of metal matrix composites. Damping measurements of pitch 55 graphite fibers reinforced with high damping Mg-0.6% Zr and Mg-1% Mn alloys exhibit a transition at strain level 10-6 from strain amplitude independent to dependent damping response. Comparison of predicted and measured composite damping capacity at low strain amplitudes yields an in situ matrix damping contribution of 9%, which is substantially lower than the damping capacity of cast Mg alloys. Low in situ matrix damping in the composite can be attributed to the fine grain structure near the fiber-matrix interface. The strain amplitude dependent response can be explained in terms of the Granato-Lucke (G-L) model, suggesting that dislocation damping is the likely energy dissipation mechanism. Also, mobile dislocation densities predicted by G-L theory are consistent with the average dislocation density values obtained from various transmission electron micrographs near the fiber-matrix interface.