[SY-M1] Modelling and Experimental Verified Coupled Visco hyper electro-elastic Behaviour of Dielectric Elastomer Circular Actuator
Soft dielectric elastomers, with very low stiffness and high permittivity and electric breakdown strength, hold promise as candidate materials for a variety of applications including, in energy harvesting, as actuators and biological muscles. As actuators in particular, a number of applications have emerged where, utilising coupled electro-hyperelasticity under very high electric fields in thin, membrane-like structures, large actuation has been achieved. Moreover, the theoretical framework for electro-hyperelasticity of these materials has also been established. But long time durability of these devices, is still a matter of concern. The concern arises primarily from the fact that these soft elastomers not only physically age with time, but are also highly rate dependent. We have used an equi-biaxially pre-stretched circular dielectric elastomer membrane attached to a rigid frame with a load hung at the centre to demonstrate the effects of viscoelasticity. The membrane is then loaded with oscillating voltage and the motion of the center of the membrane is tracked with a laser displacement sensor, over many time periods. As the membrane is taken through a large number of cycles,the response slowly drifts. For a very soft elastomer like VHB, the drift can be sometimes discerned in as few as 20-30 cycles of operation. To model the deformation and the drift with time, a coupled electrostatic, visco-hyperelastic large deformation model for the elastomer has been incorporated into an explicit Finite Element framework. We have been able to reproduce the experimental response of the VHB membrane fixed to a rigid frame very accurately. Though the modelling has been verified for VHB only, the framework is general enough to be used to assess the effectiveness of any dielectric elastomeric material, used as a membrane under any three dimensional electro-mechanically loaded configuration.