Bistable structures with controllable wrinkled surface

The deformation of a tri-layer composite rubber from a mono-stable saddle, a monostable state with wrinkles, a bistable cylinder, to a bistable state with wrinkles was investigated in this work. Among these forms, the wrinkled bi-stability was a unique shape that combined two different deformations into one structure and was primarily studied. The dependence of the rubber shape on the geometric and mechanical parameters was investigated. The phase diagram for the rubber transformation provides accurate pre-strain values and width of structure that correspond to various states. Finite element analysis could reproduce these deformation states well considering the above influencing factors. For the bistable surface, the inner layer was wrinkled, while the outer layer remained flat at the same pre-strain. The morphological differences could be related to the constraints in a manner that is analogous to unidirectional strain. Furthermore, the pre-strain field of the top and bottom layers could be simplified to one layer using Poisson’s ratio. The investigated deformation processes have potential applications for the precise control of flexible machines and robots.