Reconfigurable mesostructures with prestressing, reverse stiffness and shape memory effects

Abstract Most thermally triggered reconfigurable mesostructures with shape memory polymers (SMPs) require direct mechanical training at high temperatures. In this work, we suggest a method to generate reconfiguration of mesostructures using preload and reverse stiffness combined with shape memory effects, producing programmable deformations at high temperatures. We analyze the transformation mechanism of the reconfigurable structures, providing a design guideline on the thermomechanical deformation for preloading and geometric conditions of multi-materials. Applying preload to a mechanical assembly, we demonstrate a temperature-triggered shape-change of mesostructures using a reverse stiffness effect at a temperature above its glass transition, followed by recovery with a shape memory effect. Using an analytical model verified by experiments and finite element (FE)-based simulations, we demonstrate the unconventional thermal transformation with recovery for three patterns: circle-triangle, circle-square, and circle-hexagon. This work shows that the strain energy conversion by reverse stiffness of two materials, which are designed with prestressing and triggered by temperature, can open a new field of the design of reconfigurable metamaterials.