Abstract

Dielectric elastomers (DE) belong to a very performant and efficient class of functional materials for actuators, while being compliant, low-weight and silent, they offer high energy efficiencies and large deformations under an applied electric field. In this work, a comparison of different approaches to derive expressions for the electrically induced stress states in dielectric materials is given. In particular, the focus is on three different ways to analytically describe stress states in planar actuator setups and to show how they are connected to each other regarding their resulting deformations. This is the basis to evaluate the suitability of these approaches for cylindrical actuator geometries together with exemplary calculations for concrete use cases. As an outcome, conclusions on the suitability of the different approaches for certain actuator setups are drawn. In particular cylindrical actuator geometries are taken into account and a recommendation on which approach is useful to describe a certain actuator effect is given.

Highlights

  • IntroductionElectroactive polymers (EAP) and the related dielectric elastomer actuators (DEAs) are offering great potential for soft robotic applications and unconventional actuator setups

  • Cylindrical Dielectric ElastomerElectroactive polymers (EAP) and the related dielectric elastomer actuators (DEAs) are offering great potential for soft robotic applications and unconventional actuator setups.Current developments are generating an impressive innovative momentum with ongoing improvements in the field of soft robotics and drive concepts.For methodical descriptions of actuator effects in general it is necessary to formulate a suitable analytical description of their actuation impact

  • For the most simple case of a planar actuator setup, consisting of a dielectric film, sandwiched between two compliant electrodes, the directly resulting stress state from the attraction of the electrodes towards each other is in thickness direction of the dielectric film

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Summary

Introduction

Electroactive polymers (EAP) and the related dielectric elastomer actuators (DEAs) are offering great potential for soft robotic applications and unconventional actuator setups. In the case of DEAs this is the electrically induced stress state in a dielectric material, leading to a deformation in a certain spatial direction. From an engineering point of view that stress component will not sufficiently describe a desired actuation effect in the planar spatial directions and needs certain additional considerations. Alongside with some established approaches, a method to describe the electrically induced stress state in dielectric materials, depending only on electric field variables is proposed. We point out how to describe electrically induced stress states in DEAs. In the first part the focus is on the well-described planar setups and how different derived stress states are linked to each other as a review. The material can be modeled to be uniformly deformed under an applied electric field in thickness direction. Some of the approaches even can not be used to analytically describe the behavior of the macroscopic geometry

Model Approaches
Stored Energy Approach
Energy Balance Approach
Maxwell Stress Tensor Approach
Resulting Deformations and Equivalent Stress States
Planar Actuator Geometries
Cylindrical Actuator Geometries
Validity Comparison for Cylindrical Geometries
Findings
Comparison of Approaches and Conclusions
Full Text
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