Executive Summary : | Membrane structures made of soft active materials like dielectric and magnetorheological elastomers, are capable of undergoing large deformations in response to applied external electric or magnetic fields. They have several potential applications in the field of soft/bio-inspired robotics. However, these structures exhibit a highly nonlinear response and are prone to snap-through and wrinkling instabilities. Developing computationally efficient nonlinear finite deformation models, that can predict the coupled response in these materials, are necessary to aid device design. Thus, in this proposed work, the PI intends to develop large deformation 2D membrane models in coupled electro-magneto-elastic materials and study the onset of instabilities in these soft structures. Starting from the 3D potential energy expression for an electroelastic/magnetoelastic continuum, a 2D membrane model will be derived using asymptotic expansion. The resulting system of equations are highly nonlinear and prone to convergence issues, especially once the membrane becomes unstable. Under pressure loading, the membrane deformation may experience a snap-through instability, i.e., a sudden increase in deformation for a small change in voltage or pressure loading, or start to form wrinkles due to the presence of compressive stresses. Thus, the system of differential equations obtained from the membrane model will be solved using both finite difference and finite element schemes and the convergence aspect will be studied and compared for both the cases. The modelling framework will be supplemented with experimental analysis of a soft dielectric elastomer based circular membrane actuator. The dielectric elastomer undergoes large deformations under applied electric field. The deformation and onset of snap-through and wrinkling instabilities will be studied through experiments as well as modelling, and the results will be compared to validate the model. Further, parametric studies will be performed to improve the design of the actuator by controlling/reversing the instability effects in the device operation. While instability in soft hyperelastic membranes has been a topic of great interest to the mechanics and soft materials communities, these effects have not been studied in great detail for soft smart/active materials like magnetorheological elastomers and dielectric elastomers. Through the proposed research, the PI intends to address this gap and enable their utilization in soft robotic applications. Overall, the proposed work will potentially improve the design of soft actuators and sensors using smart materials. |