Measurement and alalysis of micro-stress distribution in all oxide composite with structural change of matrix

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Micro-stress distribution near fiber-matrix interface of Al_2O_3 fiber-reinforced Al_2O_3 matrix composite has been measured by a high-speed scanning type fluorescence microscope. Two-dimensional stress mapping near the interface of the composite was successfully obtained. The stress distribution indicated that the stress field was expressed as superimpose of (i) stress by thermal mismatch between fiber and matrix, (ii) stress by anisotropy of Al_2O_3 and (iii) stress by applied stress. In situ measurement of micro-stress distribution in fracture test of Al_2O_3/Al_2O_3 composites with different grain sizes was performed. The interfacial stress and the initiation stress for the crack propagation depended on the grain size of the Al_2O_3 matrix. The guide for optimizing matrix structure (particularly grain size) to maximize the fracture resistance was obtained for a given material system.