Reduction of detrimental torsion in ionic polymer-metal composite actuators through coupled electrochemical-mechanical simulation

Authors

1 Department of Mechanical and Aerospace Engineering, SR.C., Islamic Azad University, Tehran, Iran.

2 Modern Automotive Research Center, Department of Mechanical and Aerospace Engineering, SR.C., Islamic Azad University, Tehran, Iran.

3 Department of Mechanical Engineering, Ab.C., Islamic Azad University, Abhar, Iran.

10.22044/jsfm.2026.16539.3998

Abstract

In this paper, a multiphysics framework is proposed for the analysis and mitigation of torsion in ionic polymer–metal composite (IPMC) actuators, where both viscoelastic and electroactive effects of the material are considered simultaneously. The governing equations were first derived based on Euler–Bernoulli beam theory and the principle of minimum energy, and then coupled with the Nernst–Planck–Poisson electrochemical relations to obtain the torsional moment induced by ion migration under an electric field. To account for material softening, the mechanical moduli were formulated as combined models dependent on both time and electric field. Numerical simulations reveal that, under an applied voltage of 5 V and a thickness of 1 mm, the shear modulus decreases by nearly 85% within about 10 seconds; however, by introducing transverse stiff layers and symmetric longitudinal excitation, the torsional moment drops to less than 5% of its initial value and the torsional angle is effectively eliminated. A stability analysis was performed through the definition of a specific index that simultaneously captures the influence of time, electric field intensity, and boundary constraints. The numerical results demonstrate that while modulus reduction over time and with higher voltages decreases the shear and bending stiffness and increases viscous energy, the imposition of boundary conditions at the edges suppresses torsion even under severe softening. Geometrical sensitivity analysis further indicated that variations in length and width have only a limited effect on viscous energy, whereas boundary conditions play a decisive role in torsion control.

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Journal of Solid and Fluid Mechanics
Volume 15, Issue 6
January and February 2026
Pages 491-507

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