Microcracking in Ceramic/Ceramic Composites

Abstract

A technique was developed to detect the onset, size, evolution, and anisotropy of surface microcracks in ceramic composite materials as a function of applied stress. The method is based on measuring the electrical resistance changes of a thin gold film sputtered on the surface of the composite as a function of stress. The technique was applied to the tensile surfaces of a 90/0/90, single crossply, 50 vol% SiC-LAS composite bars subjected to three-point bending. The resistance changes during the first loading cycle were found to be a strong function of the surface condition prior to testing. The onset of microcracking varied between 70 and 160 MPa. The anisotropy in the resistance changes in two orthogonal directions demonstrated that, for a given stress, the damage resulting from axial cracks was comparable to that of matrix cracks and occurred simultaneously. Furthermore, the matrix cracks were found to close more readily than the axial ones. The resistance changes were converted to crack lengths assuming that one large crack extended normal to the applied stress. The presence of such cracks was confirmed by SEM. How this method can be used nondestructively to assess the integrity of a finished surface is also discussed.

Cite this paper

@article{barsoum1988microcracking,
  title = {{Microcracking in Ceramic/Ceramic Composites}},
  author = {Barsoum, Michel W. and Zhou, Otto},
  journal = {Advanced Ceramic Materials},
  volume = {3},
  number = {4},
  pages = {361--368},
  year = {1988},
  doi = {10.1111/j.1551-2916.1988.tb00235.x}
}

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