Surface Wrinkling versus Global Buckling Instabilities in Thin Film‐Substrate Systems under Biaxial Loading: Direct 3D Numerical Simulations

Abstract

When a thin film bonded to a compliant substrate is subject to in‐plane compressive loading, wrinkles on the thin film may form as a consequence of deformation instability. The specimen geometry may also favor global buckling. In this study, a recently developed computational approach is employed to directly simulate 3D wrinkling and buckling from pre‐instability to post‐instability in a straightforward manner, covering a wide biaxial loading spectrum. The finite element models contain an embedded imperfection with perturbed material properties at the film‐substrate interface. This approach is capable of activating the first and subsequent bifurcation modes, along with the deformation patterns in between. It is demonstrated that, in addition to the temporal evolution of wrinkle patterns, surface wrinkling and global buckling can form simultaneously as the substrate becomes thinner. Wrinkles and buckle can either co‐develop, or the buckling‐induced curvature may help facilitate wrinkle formation depending on the specimen thickness and loading biaxiality. Different wrinkle patterns, such as parallel waveform and checkerboard, can even coexist on the same buckled structure. The state of biaxiality can influence the deformation instability significantly, and each bifurcation point can be traced back to certain abrupt changes in the overall load–displacement response.

Evolution of Thin-Film Wrinkle Patterns on a Soft Substrate: Direct Simulations and the Effects of the Deformation History

“…The embedded imperfection, while underneath the interface in the substrate domain, was assigned the material properties of the film layer. This approach has been systematically tested and proven to be a reliable way to trigger deformation instabilities in our earlier studies [38,39,41]. Numerical simulations were performed using the finite element software ABAQUS (Version 2017, Dassault Systems Simulia Corp., Johnston, RI, USA).…”

Analysis of Experimental Biaxial Surface Wrinkling Pattern Based on Direct 3D Numerical Simulation

“…To overcome the drawbacks of the geometrical imperfection methods, a direct FEM simulation method that uses embedded imperfections with perturbed material properties at the film-substrate interface has been recently proposed. The direct simulation can successfully perform the pre/post-buckling simulations in only one analysis step with any common finite element code and analysis platform [21][22][23]. The direct FEM model can provide the wrinkling wavelength of a surface wrinkling as a function of material properties, and thus the extraction of material properties such as Young's modulus has been achieved [24].…”

FEM Analysis of Buckled Dielectric Thin-Film Packaging Based on 3D Direct Numerical Simulation

“…In addition, it can be implemented with any common finite element code and analysis platform. A direct and easy numerical simulation has been reported to overcome the drawbacks of the geometrical imperfection methods and, thus, it is applied to extract material properties extraction based on commercial scotch-tape surface wrinkling [ 26 ]. The reported literature has presented modeling methods of the basic structure and an elastic thin film on a polymeric substrate under uniaxial and biaxial loading conditions, and the resultant wrinkling patterns have been successfully created complying with theoretical patterns.…”