Modeling the transition of microcracks into macrocracks in heterogeneous viscoelastic media using a two-way coupled multiscale model

Fracture in heterogeneous media is still an open topic in the research community. One of the main reasons is the fact that cracks may occur in widely different length scales. While microcracks can be satisfactorily modeled by a loss in the tangent moduli tensor without considering the microcracks explicitly, such as in continuum damage models, macrocracks cannot be accurately modeled unless a discontinuity is explicitly considered. This is especially true in wave problems, since reflection or transmission of the waves is greatly affected by the presence of a discontinuity. Furthermore, the (scale) transition of microcracks into macrocracks is a key mechanism that must be considered in order to accurately model fracture in heterogeneous materials. This paper presents a two-way coupled multiscale approach for modeling fracture in heterogeneous viscoelastic media and proposes a scheme to account for the transition of microcracks into macrocracks. The model has been implemented into a finite element code and numerical results are shown for demonstration purposes.