ANALYSIS OF SHEAR-STRESS DISTRIBUTION IN PUSHOUT PROCESS OF FIBER-REINFORCED CERAMICS

The interfacial shear stress distribution of a thin specimen of SiC fi ber-reinforced glass matrix composite (fiber volume fraction of 0.1, 0 .5, and 0.7) during a fiber pushout process was subjected to finite el ement analysis using a three concentric axisymmetrical model which con sisted of fiber, matrix, and composite. A stress criterion was used to determine interface debonding. Effects of thermally-induced stress an d a post debond sliding process at the interface were also included in the analysis. The analytical result showed that shear stress near the specimen surface was introduced during the specimen preparation proce ss. Before the interfacial debonding, the distribution of shear stress during the pushout test was affected by the existence of thermally-in duced stress in the specimen. The interfacial shear debonding initiate d similar to 30 mu m below the pushing surface and the sliding at the debonded interface proceeded in the direction of both the pushing surf ace and back surface from the peak shear position; the debonding from the back surface initiated just before the complete debonding of the i nterface. The pushout load-displacement curve near the origin was stra ight, however, after the existence of interface sliding at the debonde d interface, the curve exhibited non-linearity with the increase in ap plied load up to the complete debonding at the interface. This debondi ng process was essentially independent of the fiber volume fraction. T he results indicate that the total of thermally-induced stress in the specimen and shear stress distribution generated by applied load are i mportant for the initiation of debonding and the frictional sliding pr ocess of the thin specimen pushout test.