Propagation des fronts de fissure plane dans les matériaux fragiles hétérogènes de dimensions finies

Our approach consists in testing the classical crack-pinning models for controlled toughness patterns and realistic sample geometries, i.e. of finite size. We model the effect of sample thickness on the stress intensity factor at the crack tip. The predictions of the theoretical model developed in [L. Legrand, S. Patinet, J.-B. Leblond, J. Frelat, V. Lazarus, D. Vandembroucq, Coplanar perturbation of a crack lying on the mid-plane of a plate, Int. J. Frac.] are validated by finite-element calculations. These calculations converge as a function of the crack front perturbation frequency towards two asymptotic regimes: semi-infinite medium and thin plate. In the case of a crack interacting with a single defect, we compare our calculations with an experimental crack configuration. We show a remarkable improvement of elastic line model predictions when the sample thickness is taken into account.