Flores-Johnson, E. A., Rupert, T. J., Hemker, K. J., Gianola, D. S., & Gan, Y. (2015). Modelling wrinkling interactions produced by patterned defects in metal thin films. Extreme Mechanics Letters. In press.
Wrinkling patterns in freestanding metal thin films under tensile loading are investigated through finite-element simulations with experimental validation. Numerical simulations of the tensile testing of a thin film specimen with different arrays of holes were conducted. Good agreement between experiments and simulations was found for not only the spatial wrinkling pattern distributions, but also the pattern evolution over the different loading stages. The numerical results show that plasticity plays an important role in the evolution of wrinkling patterns and their associated interactions in Al thin films. It was found that the spacing between defects and defect size control the level of interaction between wrinkle branches generated by the defects. Strong interactions resulted in the merging of different wrinkle branches into one single wrinkle with a large displacement amplitude and a well-defined profile in the out-of-plane direction. The simulations proved to be robust in their descriptions of the experimentally observed wrinkling phenomenon and could be used to predict wrinkling in other hole-patterned thin film configurations. The interaction and merging of wrinkle branches from multiple holes indicate that the resulting wrinkle patterns can be manipulated by using different defect configurations to achieve a desired wrinkled “microstructure”.