The mechanical model obtained by a non-traditional approach to the basic components of the traditional viscoelastic models—spring and damper—elucidates the back-relaxation of ionic electroactive polymer actuators. The corresponding PDE characterizes the curvature or bending moment of the actuators throughout stimulated bending forward followed by relaxation back towards the initial shape. Combining series of short entities containing the lumped electrical circuit, and the transient bending moment generated according to the PDE, results in a new model of the ionic electroactive polymer actuators. This model takes into account the back-relaxation of the actuators as well as the superposition principle. The experiments carried out with three actuators of different ionic electroactive polymer materials show excellent accordance with the model.
A large-scale effort was carried out to test the performance of seven types of ionic electroactive polymer (IEAP) actuators in space-hazardous environmental factors in laboratory conditions. The results substantiate that the IEAP materials are tolerant to long-term freezing and vacuum environments as well as ionizing Gamma-, X-ray, and UV radiation at the levels corresponding to low Earth orbit (LEO) conditions. The main aim of this material behaviour investigation is to understand and predict device service time for prolonged exposure to space environment.
We have developed a technique to determine the bending strain of ionic electroactive polymer actuators without the use of the macroscopic bending geometry. In situ comparisons of the scanning electron microscope micrographs from a bending ionic electroactive polymer actuator, using a digital image correction methodology, identify its bi-directional deformation field. The developed technique allows verification of the factual axial and thickness strains of any notional layer of the actuator, including the outer surfaces of the electrodes. Thus, calculation of the bending and thickness strains of the ionic electroactive polymer laminate becomes possible. Moreover, the technique allows the determination of the position of the neutral layer of bending that is an important requirement for the calculation of the second area and bending moments of the beam. The four examples presented demonstrate the potential variations of the bending schemes, in cases where the neutral layer is at the centroid and shifted away from the centroid.
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