A FEM ANALYSIS OF CRACK-GROWTH IN MICROCRACKING BRITTLE SOLIDS

In this study large scale microcracking ahead of the growing main crack in brittle solids was studied numerically. The random nucleation, orientation and size effects of discrete microcracks and resulting interactions are fully accounted for in a hybrid element model. The results obtained were compared with the available continuum solutions. The continuum description of microcracking can provide a reasonable estimation of shielding resulting from pre-nucleated and continuous nucleation of microcracks ahead of the growing main crack. However, it fails to distinguish the effects of microcrack zone length and the role of the wake region during the crack extension. The knowledge of the magnitude of shielding is not sufficient to predict the development of the R-curve behavior. It is essential to know the inherent fracture toughness of the material undergoing microcracking, since not every shielding event during the course of crack extension corresponds to an increase in the R-curve. It will also be shown that crack branching and crack kinking can readily develop as a result of microcracking.