Multi-Trigger Thermo-Electro-Mechanical Soft Actuators under Large Deformations

Abstract

Dielectric actuators (DEAs), because of their exceptional properties, are well-suited for soft actuators (or robotics) applications. This article studies a multi-stimuli thermo-dielectric-based soft actuator under large bending conditions. In order to determine the stress components and induced moment (or stretches), a nominal Helmholtz free energy density function with two types of hyperelastic models are employed. Non-linear electro-elasticity theory is adopted to derive the governing equations of the actuator. Total deformation gradient tensor is multiplicatively decomposed into electro-mechanical and thermal parts. The problem is solved using the second-order Runge-Kutta method. Then, the numerical results under thermo-mechanical loadings are validated against the finite element method (FEM) outcomes by developing a user-defined subroutine, UHYPER in a commercial FEM software. The effect of electric field and thermal stimulus are investigated on the mean radius of curvature and stresses distribution of the actuator. Results reveal that in the presence of electric field, the required moment to actuate the actuator is smaller. Finally, due to simplicity and accuracy of the present boundary problem, the proposed thermally-electrically actuator is expected to be used in future studies and 4D printing of artificial thermo-dielectric-based beam muscles.

Constitutive Modeling of multi-stimuli-responsive shape memory polymers with multi-functional capabilities

“…Here, to consider the electro-magnetic response of thermo-visco-hyperelastic materials, similar to recently proposed models [26,28], we assume that the equilibrium part includes fibrous electro-magneto-hyperelastic behavior. Therefore, Eq.…”

“…The second approach that considers the deformation dependency on the electric permittivity and the magnetic permeability, is an alternative and reliable method in electromagneto-elasticity theory, in particular, at large strains [46][47][48][49]. In this way, many researchers have used different types of nominal Helmholtz free energy density functions such as Kumar and Sarangi [48,49], Yarali et al [28], and Dorfmann and Ogden [50,53]. In this study, a nominal Helmholtz free energy density function in terms of deformation gradient tensor, electric field vector, and magnetic field vector introduced by Kumar and Sarangi [49] is adopted as:…”

“…Here, by adopting the Neo-Hookean model for the purely mechanical hyperelastic property of the material, and based on the research works done in [28,48,50,53,54], a version of the nominal Helmholtz free energy density function for transversely isotropic electro-magneto-hyperelastic materials by ignoring the matric-fiber interaction is considered as: (23) in which 𝐶 1 , 𝐶 3 , 𝐶 4 , 𝐶 6 and 𝐶 7 are materials constants. q is a positive non-dimensional parameter that measures the rapidly increasing stiffness of the fibers with increasing stretch [55], and 𝐸 ̅ is a positive material modulus that measures the degree of anisotropy.…”

“…Adding electro-active particles such as carbon nanotubes and magneto-active particles such as Fe 3 O 4 or carbonyl iron to elastomers makes the matrix multi-trigger EMREs. Thanks to their unique properties, they have found great potential in many engineering applications such as multi-trigger soft actuators [28]. Electric and magnetic fields are used to activate SMPs and EMREs in two different ways.…”

Corrigendum to “Magnetorheological elastomer composites: Modeling and dynamic finite element analysis” [Compos. Struct. 254 (2020) 112881]

“…The advanced composite materials can be fabricated from smart materials such as shape memory alloys (SMAs), shape memory polymers (SMPs), piezoelectrics, magneto-electro-elastics (MEE), electrorheological (ER) and magnetorheological (MR) materials. Using these materials can provide additional functionalities to the composites, such as shape memory effect, reversible cyclic behavior, and mag-netic or electric dependent behavior [8][9][10][11][12][13][14]67]. Among these smart materials, MR elastomers (MREs), which are polymers reinforced by ferromagnetic particles [15], have recently gained a great deal of attention due to their sensitivity to the magnetic fields [16].…”