Understanding the Impact of Active-to-Passive Area Ratio on Deformation in One-Dimensional Dielectric Elastomer Actuators with Uniaxial Strain State

Abstract

There is increasing interest in the use of novel elastomers with inherent or modified advanced dielectric and mechanical properties, as components of dielectric elastomer actuators (DEA). This requires corresponding techniques to assess their electro-mechanical performance. A common way to test dielectric materials is the fabrication of actuators with pre-stretch fixed by a stiff frame. This results in the problem that the electrode size has an influence on the achievable actuator displacement and strain, which is detrimental to the comparability of experiments. This paper presents an in-depth study of the active-to-passive ratio with the aim of investigating the influence of the coverage ratio on uniaxial actuator displacement and strain. To model the effect, a simple lumped-parameter model is proposed. The model shows that the coverage ratio for maximal displacement is 50%. To validate the model results, experiments are carried out. For this, a rectangular, fiber-reinforced DEA is used to assess the relation of the coverage ratio and deformation. Due to the stiffness of the fibers, highly anisotropic mechanical properties are achieved, leading to the uniaxial strain behavior of the actuator, which allows the validation of the one-dimensional model. To consider the influence of the simplifications in the lumped-parameter model, the results are compared to a hyperelastic model. In summary, it is shown that the ratio of the active-to-passive area has a significant influence on the actuator deformation. Both the model and experiments confirm that an active-to-passive ratio of 50% is particularly advantageous in most cases.

Influence of Active-to-Passive Ratio on the Deformation in Circular Dielectric Elastomer Actuators

“…The lumped parameter model is derived by modeling a slice of the circular actuator with a network based on a mechanical structure for one-dimensional DEAs with a uniaxial strain state [ 21 , 22 ]. As shown in Figure 5 , the active and the passive areas are described by their respective spring compliances and with velocity v and radial displacement .…”

Highly anisotropic carbon fiber electrodes for DEAs and their dynamic non-monotonic conductive properties

“…Various options exist for anisotropic reinforcement fibers, including polyamide, polyethylene, glass, or carbon fibers. [10][11][12][13] Carbon fibers are especially advantageous due to their high stiffness, extreme anisotropy, and electrical conductivity, therefore, making them suitable for the use as an electrode material as well. 11,14 While carbon fibers posses superb mechanical stiffness under tension, their stiffness in compressive loading scenarios is limited due to buckling of the slender fibers.…”