Field-Induced Transversely Isotropic Shear Response of Ellipsoidal Magnetoactive Elastomers

Abstract

Magnetoactive elastomers (MAEs) claim a vital place in the class of field-controllable materials due to their tunable stiffness and the ability to change their macroscopic shape in the presence of an external magnetic field. In the present work, three principal geometries of shear deformation were investigated with respect to the applied magnetic field. The physical model that considers dipole-dipole interactions between magnetized particles was used to study the stress-strain behavior of ellipsoidal MAEs. The magneto-rheological effect for different shapes of the MAE sample ranging from disc-like (highly oblate) to rod-like (highly prolate) samples was investigated along and transverse to the field direction. The rotation of the MAE during the shear deformation leads to a non-symmetric Cauchy stress tensor due to a field-induced magnetic torque. We show that the external magnetic field induces a mechanical anisotropy along the field direction by determining the distinct magneto-mechanical behavior of MAEs with respect to the orientation of the magnetic field to shear deformation.

Magneto-Mechanical Enhancement of Elastic Moduli in Magnetoactive Elastomers with Anisotropic Microstructures

“…Thus, from Equations ( 15) and ( 21), we have ψ el = ψ iso . Therefore, the present formalism is fully consistent with the previous studies of isotropic MAEs [31,37,38,53].…”

“…The magneto-rheological effect (MR) is defined as the change in the elastic moduli of the MAE in the presence of an external magnetic field [37]. The initial shape of an MAE sample affects the MR effect significantly, as already shown in our previous works [37,38]. Here, along with the initial shape, we also study the effect of different microstructures (SCs and SDs).…”

“…where [38]. The total free energy density of anisotropic MAEs is now a combination of three contributions: ψ iso , ψ aniso , and ψ mag .…”

“…Recently, anisotropic MAEs are also synthesized using novel 3D-printing techniques [32][33][34]. The mechanical properties of MAEs are highly sensitive to the initial shape of a sample [35][36][37][38] as well as to the particle microstructure [39][40][41]. MAEs possess the ability to change their elastic moduli in the presence of an external magnetic field [42][43][44][45].…”

“…The dimensionless parameters related to the stretch of anisotropic microstructures are estimated using the rule of mixtures. Following our previous works [37,38], an ellipsoidal MAE sample of two equal semiaxes and one distinct semi-axis is considered, as shown in Figure 2. We study the effect of different particle microstructures and the initial shape of an MAE sample on its mechanical properties.…”