Computer Simulation Of Thin Film Wrinkling On Elastic Substrate

A rigid film bound to a strained soft substrate shows a complex wrinkling response during the elastic substrate restores,wrinkling mechanism has potential applications in flexible electronics,optical device,micro/nano fabrication,film metrology etc.But so far,research on wrinkling dynamics is rare.In this work,we develop a novel coarse-grained model based on molecular dynamic framework and simulate the wrinkling process of two-layer compound system,and our research is focused on the uniaxial tensile wrinkling.The wrinkling model includes two parts: the rigid film and the elastic substrate,the rigid film is a single-layered,the interaction between the film and the substrate is the Lennard-Jones 6-12 potential energy.By tuning the bonding and nonbonding parameters,the modulus and Poisson’s ratio of the material can changed,and the binding strength of the interfacial interaction can be tuned by the well depth of the LJ potential energy.In this paper we establish two substrates with different Poisson’s ratio,and the dynamics of wrinkling depending on the film modulus,the elongation ratio,substrate thickness and binding strength are systematically studied.Three stages for the wrinkling process are found: incubation period,rapid growth period and balanced period.In incubation period,the length of the system decreases slowly,the average amplitude increases slowly with the exponent 0.25,at this stage no obvious wrinkles emerge;in rapid growth period,a rapid drop of system length results in the formation of wrinkles and the amplitude increases sharply with the exponent 1;in balanced period,the wrinkling optimizes,the amplitude and length of the system approach their equilibrium values.It is found that the system doesn’t retract to the initial size and the final length increase with the increase of the film modulus.Delamination from the substrate will happen in the cases of softer upper film,high elongation ratio or weaker binding interaction.At the same time,we compare the simulation results with the existing theoretical results and obtain a good agreement.