ANALYSIS OF TRANSFORMATION TOUGHENING BY ZRO2 PARTICLES IN ANISOTROPIC COMPOSITE

In order to estimate the effect of transformation toughening (Delta K) in an anisotropic composite, the stress analysis approach for Delta K proposed by McMeeking et al., which is applicable only to isotropic m aterials, has been extended to anisotropic analysis. Numerical calcula tion is carried out for SiC whisker (SiCW) and ZrO2 reinforced glass m atrix composites by considering the anisotropy induced by whisker alig nment. Bueckner's weight function method is applied to this analysis. Though the weight function can originally be applied only to the isotr opic case, it is extended to the anisotropic case in this study. Eshel by's equivalent inclusion method is used for calculating elastic const ants and transformation strain of the ZrO2 composite. From calculation s on a triple phase composite, consisting of SiCW, ZrO2 and glass matr ix, it is found that the whisker enhances the transformation toughenin g. It is also expected that the transformation toughening acts almost independently with other toughening mechanisms, such as whisker bridgi ng. The effect of anisotropy on toughening is also estimated for align ed SiCW in the triple phase composite. The results show that the perpe ndicular SiCW alignment with respect to the crack plane brings larger enhancement of the toughening effect than the parallel alignment, but the difference between them is not so large.