Calibration of nonlocal models for tensile fracture in quasi-brittle heterogeneous materials

A new calibration strategy for integral-type nonlocal damage models for quasi-brittle materials is proposed. It is based on the assumption that in the fracture process zone in quasi-brittle materials the large majority of energy is dissipated in a localised rough crack. Measuring the roughness of the fracture surface allows for calibrating the interaction radius of nonlocal models by matching experimental and numerical standard deviations of spatial distributions of dissipated energy densities. Firstly, fracture analyses with a lattice model with random fields for strength and fracture energy are used to support the assumptions of the calibration process. Then, the calibration strategy is applied to an integral-type nonlocal damage model for the case of a fracture surface of a three-point bending test.