Nonlinear finite element analysis and size effect study in a metal-reinforced ceramics-composite

Enhancing the toughness of advanced ceramics most often results in the development of a so-called fracture process zone (FPZ) along the crack tip. Computationally, this has mostly been addressed through a linear model based on Dugdale's model. Concrete, on the other hand, also exhibits a FPZ, however, linear elastic based models have long been rejected in favor of nonlinear ones based on cohesive stress-crack opening displacements (Hillerborg's model). Following a brief review of similarities and dissimilarities between those two materials, we report on the nonlinear finite element analysis of fracture tests conducted on alumina/20% Mo. It will be shown that such an analysis, routinely performed in concrete but seldom in ceramics, yields very good correlation with experimental results. Finally, a size effect investigation is numerically performed and the range of crack sizes for which linear elastic fracture mechanics, nonlinear fracture mechanics or plasticity-based models are applicable, is tentatively presented.