A 3D Cohesive interface for the delamination analysis of a stiff film on a soft elastic substrate and the wrinkling/buckling deformation modes

Abstract

The paper proposes a finite element systematic study of a mechanical system composed by a soft elastic substrate, subjected to a uniform state of compression, covered by a stiff thin film. This kind of problem is rather common for coating systems where layered materials with severe mismatch of elastic and thermal properties are largely employed. The specific mechanical problem stands on the concomitant competition between elastic wrinkling surface deformation and the nonlinear delamination that can develop at the interface between the thin film and the substrate. Both mechanical phenomena have their source in the nonlinear elastic buckling of the thin stiff film, which can be viewed as a thin bending plate on a soft elastic foundation. Beside the elastic instability which produce wrinkling a further material nonlinear phenomena may develop, which is the delamination of the thin film in a buckled configuration with respect to substrate. Because of the relevance in the new small scale technologies, this problem has been intensively analyzed in recent years either by analytic approaches or by numerical analysis. In this contribution the problem is faced by numerical approach and a recently proposed cohesive interface model in large displacement regime is extended to 3D problems and therefore applied for a complete finite element nonlinear analysis. The numerical simulations are performed exploringthe post elastic buckling conditions, the formation and the subsequent interface crack propagation, which in turns produces surface bubbles. For 3D problems in which the interface is a plane surface the wrinkling and the bubble surface can assume very complex patterns.