Buckling of thin films: Lateral growth and kinetic evolution of telephone cords

We conduct a thorough investigation of the lateral growth and kinetic evolution of telephone cord buckles within thin films, employing both experimental and numerical techniques. Our exploration begins with in-situ experiments conducted on annealed silicon nitride films, aimed at capturing empirical data on the formation and evolution of these distinctive patterns. These experiments yield valuable insights into the morphological changes of telephone cords, such as wave flipping and merging, which lead to the enlargement of buckles at double wavelengths and widths. Subsequently, we employ a combined approach of geometrically nonlinear plate modeling and surface-based cohesive interface framework within a finite element numerical model to analyze the interplay between buckling-induced delamination and growth triggered by mode mixity-dependent interfacial toughness. Through this integrated approach, we effectively capture the mutual evolution of buckling and delamination occurrences, thus highlighting their inherently dynamic nature. Our numerical simulations show that the width and wavelength of telephone cords are doubled, consistent with experimental findings.