A NUMERICAL-ANALYSIS OF CRACK-PROPAGATION IN MICROCRACKING CERAMIC AND CERAMIC COMPOSITES

In this study, a set of numerical analyses of crack growth performed t o elucidate the mechanism of microcracking on the observed fracture be haviour of brittle solids and composites is described. The random nucl eation, orientation and size effects of discrete microcracks and resul ting interactions are fully accounted for in a hybrid finite-element m odel. The results indicate that the energy expenditure due to microcra ck nucleation seems not to contribute significantly to the resistance to crack growth. The main controlling parameter appears to be elastic interaction of the microcracks with the main crack in the absence of a reinforcing phase; therefore, the microcrack density plays an importa nt role. In the case of composites, the interaction of the main crack with the stress fields of the reinforcing phase, rather than interacti on of microcracks, is the controlling parameter for the resistance to crack growth even in the presence of a large population of microcracks . It is also shown that crack branching and crack kinking can readily develop as a result of microcracking.