Finite size effects on crack front pinning at heterogeneous planar interfaces: Experimental, finite elements and perturbation approaches

摘要

Understanding the role played by the microstructure of materials on theirmacroscopic failure properties is an important challenge in solid mechanics.Indeed, when a crack propagates at a heterogeneous brittle interface, the frontis trapped by tougher regions and deforms. This pinning induces non-linearitiesin the crack propagation problem, even within Linear Elastic Fracture Mechanicstheory, and modifies the overall failure properties of the material. Forexample crack front pinning by tougher places could increase the fractureresistance of multilayer structures, with interesting technologicalapplications. Analytical perturbation approaches, based on Bueckner-Riceelastic line models, focus on the crack front perturbations, hence allow for adescription of these phenomena. Here, they are applied to experimentsinvestigating the propagation of a purely interfacial crack in a simpletoughness pattern: a single defect strip surrounded by homogeneous interface.We show that by taking into account the finite size of the body, quantitativeagreement with experimental and finite elements results is achieved. Inparticular this method allows to predict the toughness contrast, i.e. thetoughness difference between the single defect strip and its homogeneoussurrounding medium. This opens the way to a more accurate use of theperturbation method to study more disordered heterogeneous materials, where thefinite elements method is less adequate. From our results, we also propose asimple method to determine the adhesion energy of tough interfaces by measuringthe crack front deformation induced by known interface patterns.