Chapter 15. Formation and Removal of Crack-Interface Bridges in Ferrites

  1. John B. Wachtman Jr.
  1. E. K. Beauchamp and
  2. S. L. Monroe

Published Online: 26 MAR 2008

DOI: 10.1002/9780470310557.ch15

A Collection of Papers Presented at the 13th Annual Conference on Composites and Advanced Ceramic Materials, Part 1 of 2: Ceramic Engineering and Science Proceedings, Volume 10, Issue 7/8

A Collection of Papers Presented at the 13th Annual Conference on Composites and Advanced Ceramic Materials, Part 1 of 2: Ceramic Engineering and Science Proceedings, Volume 10, Issue 7/8

How to Cite

Beauchamp, E. K. and Monroe, S. L. (2008) Formation and Removal of Crack-Interface Bridges in Ferrites, in A Collection of Papers Presented at the 13th Annual Conference on Composites and Advanced Ceramic Materials, Part 1 of 2: Ceramic Engineering and Science Proceedings, Volume 10, Issue 7/8 (ed J. B. Wachtman), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470310557.ch15

Author Information

  1. Sandia National Laboratories Albuquerque, NM

Publication History

  1. Published Online: 26 MAR 2008
  2. Published Print: 1 JAN 1989

ISBN Information

Print ISBN: 9780470374863

Online ISBN: 9780470310557

SEARCH

Keywords:

  • chemical vapor deposition;
  • fiber-reinforced ceramic composites;
  • chemical vapor infiltration;
  • high fracture toughness;
  • carbon-carbon composites

Summary

Swanson et al. showed that crack-interface bridges formed during crack passage reduce K1 at the crack tip (K1(tip)) and increase the fracture toughness in alumina ceramics. From crack velocity measurements on the double cantilever beam, we found that bridges also play a key role in subcritical crack growth in MnZn ferrites, suppressing K1(tip) so cracks remain subcritical for applied K1 significantly greater that K1c(transgranular). The bridge concentration increases with K1, leading to intermittent crack growth and history dependence for crack velocity. The K1 dependence of bridge formation permitted us to insert a narrow band of bridges, then continue to grow the crack at K1 values where no new bridges were being formed. By measuring instantaneous velocity, we were able to infer K1(tip) and observe that it decreased as the crack grew. Bridge removal was monitored by measuring acoustic emission. Rate of removal depended on relative humidity and was limited by subcritical crack growth at the bridge.