Modelling visco-hyperelastic response of Silicone based elastomers for soft robotics and foldable structure applications

Silicone elastomers play a critical role in the construction of soft robotics and foldable devices, owing to their exceptional versatility and mobility. This necessitates the development of innovative approaches in constitutive modeling to accurately simulate their behavior and optimize the design of such devices. Samples from five elastomers namely Smooth Sil 936, Clearflex 30, Dragon Skin 10 SLOW, Dragon Skin FX-Pro, Ecoflex 00–30, were subjected to both monotonic tensile tests and cyclic tests following the ASTM D412 standard. Smooth Sil 936 exhibited the highest stiffness and was selected for viscoelastic experimental characterization. To comprehend the time-dependent and quasi-static stress response of Smooth Sil 936, a series of tensile tests were conducted at various deformation rates, along with single-step relaxation tests. A database of material parameters for finite element analysis was established by performing hyperelastic modelling with and without Mullin's effect for all elastomers. A visco-hyperelastic model was proposed for elastomeric materials, effectively capturing their time-dependent hyperelastic stress response and accounting for Mullin's effect during cyclic loading. This model was calibrated using specific parameters for Smooth Sil 936, and the simulation results demonstrated good agreement with experimental data.