Size scaling of strength in thin film delamination

TL;DR

This study uses numerical simulations to analyze how the size of thin elastic films affects their shear delamination strength, revealing different behaviors based on crack shape and size, with implications for material failure prediction.

Contribution

It provides new insights into the size dependence of delamination strength in thin films, highlighting the role of crack shape and size through numerical modeling.

Findings

Circular cracks show a crossover from size-independent to size-dependent strength regimes.

Cracks spanning the system width exhibit a logarithmic size dependence.

Results are explained using extreme value statistics.

Abstract

We investigate by numerical simulation the system size dependence of the shear delamination strength of thin elastic films. The films are connected to a rigid substrate by a disordered interface containing a pre-existing crack. The size dependence of the strength of this system is found to depend crucially on the crack shape. For circular cracks, we observe a crossover between a size-independent regime at large crack radii which is controlled by propagation of the pre-existing crack, and a size-dependent regime at small radii which is dominated by nucleation of new cracks in other locations. For cracks of finite width that span the system transversally, we observe for all values of the crack length a logarithmic system size dependence of the failure stress. The results are interpreted in terms of extreme value statistics.