Material Modeling and Microstructural Optimization of Dielectric Elastomer Actuators

The modeling and 3D numerical implementation of dielectric elastomer actuators are discussed in this work. The electromechanical coupling for the actuator is realized via the Maxwell stress in the mechanical balance. In this nonlinear numerical problem the consistent tangent matrix, which is used for the Newton iterations, is described in detail. The operational curve of a homogeneous capacitor structure is compared to analytical solutions by implementing the Neo-Hooke and the Yeoh material model in the numerical simulations respectively. In this simulations the instability aspects of this type of structure is discussed. Furthermore the optimization of the operational curve is analyzed for both material models through the consideration of inclusion materials in the elastomer structure. Piezoceramic and a soft material inclusions with a fiber and a spherical geometry are considered. The results show the capability of improving the operational curves of the actuator with these inhomogeneities

A comparison of Finite Elements for Nonlinear Beams: The absolute nodal coordinate and geometrically exact formulations

Two of the most popular finite element formulations for solving nonlinear beams are the absolute nodal coordinate and the geometrically exact approaches. Both can be applied to problems with very large deformations and strains, but they differ substantially at the continuous and the discrete levels. In addition, implementation and run-time computational costs also vary significantly. In the current work, we summarize the main features of the two formulations, highlighting their differences and similarities, and perform numerical benchmarks to assess their accuracy and robustness. The article concludes with recommendations for the choice of one formulation over the other