In this paper, we introduce the analytical framework of the modeling dynamic characteristics of a soft artificial muscle actuator for aquatic propulsor applications. The artificial muscle used for this underwater application is an ionic polymer-metal composite (IPMC) which can generate bending motion in aquatic environments. The inputs of the model are the voltages applied to multiple IPMCs, and the output can be either the shape of the actuators or the thrust force generated from the interaction between dynamic actuator motions and surrounding water. In order to determine the relationship between the input voltages and the bending moments, the simplified RC model is used, and the mechanical beam theory is used for the bending motion of IPMC actuators. Also, the hydrodynamic forces exerted on an actuator as it moves relative to the surrounding medium or water are added to the equations of motion to study the effect of actuator bending on the thrust force generation. The proposed method can be used for modeling the general bending type artificial muscle actuator in a single or segmented form operating in the water. The segmented design has more flexibility in controlling the shape of the actuator when compared with the single form, especially in generating undulatory waves. Considering an inherent nature of large deformations in the IPMC actuator, a large deflection beam model has been developed and integrated with the electrical RC model and hydrodynamic forces to develop the state space model of the actuator system. The model was validated against existing experimental data.

Silicone elastomer and multi-walled carbon nanotubes (MWCNTs) composites, applicable as actuators and controllable dampers, were studied. Dynamic mechanical analysis (DMA) and vibrating sample magnetometry (VSM) were used to investigate the mechanical and magnetic properties of silicone elastomers and MWCNTs composites. Also, measurement of their dielectric property was conducted. The addition of MWCNT was able to tailor the damping and dielectric properties of the silicone elastomer. In this study, a 0.7 wt% of MWCNT composite demonstrated an attractive condition for the damping and the dielectric property. Exceedingly, the modulus increased with the application of a magnetic field. The good filler effect with the small addition of the MWCNTs content is caused by their unique structure, catalytic effect, and magnetic property.

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The numerous possible applications of ionic polymer-metal composites (IPMCs) as an underwater propulsor have led to the investigation of IPMC behaviour in an aqueous environment. This study compares the performance of an IPMC subjected to fluid drag forces to its performance without such forces. Both the form (i.e. pressure) drag and the viscous (i.e. skin friction) drag forces experienced by the IPMC due to the surrounding liquid are modelled. These forces are incorporated into a two-dimensional (2D) analytical model of a segmented IPMC. The model is based on small deflection and can be conveniently used. The maximum IPMC deflection for aqueous and non-aqueous environments is compared, both analytically and experimentally. Using video-capturing techniques, the deflection of the IPMC, both in air and in water, is investigated. The experimental results are used in order to better understand the performance of an IPMC in water. A large-deflection model for the segmented IPMC is also proposed.