Crack impinging on a curved weak interface: Penetration or deflection?

Abstract

Curved weak interfaces present promising advantages to be implemented as crack arrestors in structures designed under the damage tolerant-design principles. Among other advantages, they neither add extra weight nor significantly affect the global stiffness of the structural element, in contrast with alternative crack arrestors concepts. To be employed as a crack arrestor, it is key that the interface is able to deviate the crack. If the crack penetrates across the interface, the effect of the weak interface as a crack arrestor is canceled. In view of this, this work studies how to set the interface parameters to promote crack deviation along the interface. In particular, following the dimensional analysis of the problem, the effect of three significant dimensionless parameters is studied: interface to bulk fracture toughness, interface to bulk tensile strength, and the interface curvature radius normalized with the material characteristic length. The corresponding analysis is carried out using three approaches widely applied for the prediction of cracking events: Linear Elastic Fracture Mechanics, Finite Fracture Mechanics, and a combination of Phase field and Cohesive Zone Model. The results present a clear effect of some parameters, such as the ratio of the interface to bulk fracture toughness, for which the three approaches agree. However, the results are moderately diverse in which correspond to the effect of the ratio of the interface to bulk tensile strength and quite divergent in what respect to the effect of the radius. The results are interpreted and explained as a consequence of the main assumptions behind the approaches studied.