Brittle failure by transgranular and intergranular mechanisms is commonly addressed by probabilistic methods based on the weakest-link concept. For homogeneous materials this approach is straightforward and well established. Different methods have been proposed in the past to incorporate the presence of heterogeneities, e.g. due to welding or segregated zones. A key issue in this context is the length that characterizes variations in the heterogeneous microstructure in relation to a representative size of the zone where brittle fracture typically has been observed to occure, i.e., fracture process zone (FPZ). Here, a new approach for weakest-link modelling of heterogeneous materials is proposed that accounts for the interplay between the different scales.
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