Compression vs. Tension-Induced Wrinkle Formation on Thin Film Structures: Three-Dimensional Numerical Simulations

The development of surface wrinkles on thin films bonded to compliant substrates is recognized as a form of mechanical instability. While this wrinkling behavior is widely studied when the thin film is under direct compression, much less attention has been devoted to the prediction of wrinkle formation caused by tension and cyclic compression-tension deformations. This work focuses on compression vs. tension-induced wrinkles using a relatively stiff polymeric film on an elastomeric substrate as the model system. Experimental observations show that parallel wrinkles formed during unidirectional compression gradually disappear under reverse loading. When the thin film structure is pulled into tension, a new set of parallel wrinkles in the perpendicular direction would develop. The tension-induced wrinkles are caused by Poisson’s ratio mismatch between the film and substrate, which generates lateral compression in the film. By way of the embedded imperfection technique in three-dimensional (3D) finite element modeling, we illustrate that this type of wrinkle transition can be simulated in a seamless manner. With the linear elastic assumption, the overall load-displacement response and evolution of wrinkles are shown to be reversible. The tension-after-compression and direct tension loading conditions lead to exactly the same material response, including the deformation instability. Further analyses on the effects of film modulus and Poisson’s ratio are performed, with the differences in wrinkling behavior under compressive and tensile loading contrasted.