Failure mechanisms and behavior of ceramic matrix composites under transverse loading
- Northwestern Univ., Evanston, IL (United States)
- European Center of Advanced Technologies, Athens (Greece)
Transverse tensile loading of brittle matrix composites is the most severe type of loading because of the low tensile strength of the matrix material and the high stress concentration at the fiber matrix interface. Failure initiation in the form of short cracks usually takes place in the interphase region. The location and orientation of these cracks depend on the relative elastic and ultimate properties of the constituents, i.e., fiber, matrix and interphase, and on the fiber packing and volume ratio. Failure mechanisms under transverse tensile loading were observed under the microscope in real time. The first microcracks originated at the fiber-matrix interface and were nearly normal to it. When the fibers are closely packed, usually in a near hexagonal array, radial cracks initiate at approximately 45{degrees} from the loading axis. When fibers are further apart and are surrounded by a relatively large volume of matrix, radial cracks occur at approximately 90{degrees} from the loading axis. As the load increases isolated interface cracks develop and they eventually coalesce with the radial microcracks to form a catastrophic macrocrack. The effects of the various failure mechanisms on the stiffness and the overall stress-strain behavior were studied. The type and location of failure initiation was used in conjunction with an elastic analysis of a three-phase material and a maximum stress criterion for the matrix to determine the effective stiffness of the interphase.
- OSTI ID:
- 175374
- Report Number(s):
- CONF-950686--
- Country of Publication:
- United States
- Language:
- English
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