Field-induced interactions in magneto-active elastomers - A comparison of experiments and simulations

Abstract

In this contribution, field-induced interactions of magnetizable particles embedded into a soft elastomer matrix are analyzed with regard to the resulting mechanical deformations. By comparing experiments for two-, three- and four-particle systems with the results of finite element simulations, a fully coupled continuum model for magneto-active elastomers is validated with the help of real data for the first time. The model under consideration permits the investigation of magneto-active elastomers with arbitrary particle distances, shapes and volume fractions as well as magnetic and mechanical properties of the individual constituents. It thus represents a basis for future studies on more complex, realistic systems. Our results show a very good agreement between experiments and numerical simulations—the deformation behavior of all systems is captured by the model qualitatively as well as quantitatively. Within a sensitivity analysis, the influence of the initial particle positions on the systems’ response is examined. Furthermore, a comparison of the full three-dimensional model with the often used, simplified two-dimensional approach shows the typical overestimation of resulting interactions in magneto-active elastomers.

Magneto-Mechanical Coupling in Magneto-Active Elastomers

“…The comparison of the experimental and numerical results for the best fit in Figure 3 b shows a very good qualitative and quantitative agreement: for all inter-particle distances , the sample behavior is captured by the presented micro-continuum approach which demonstrates that it represents an adequate framework to describe microstructural interactions in MAEs. Variations of the particles initial positions that were also performed in [ 62 ], indicate a sensitivity of the simulations with regard to the sample geometry. To this end, the systematic error for and the small deviations for the distance of particles 1 and 2 can be eliminated by incorporating data from micro-tomography measurements [ 65 ] for the generation of more accurate simulation models.…”

“…For the magnetic contribution of the Helmholtz free energy, holds within the matrix material, while the experimentally observed magnetization curves of carbonyl iron powder and nickel particles as described in [ 61 , 62 ] are applied to capture the nonlinear magnetization behavior of the particles. Thus, is given by with and being sets of associated saturation magnetizations and scaling parameters that are used in the examples.…”

“…To this end, a proper validation of the micro-continuum model can only be performed with well-defined, simplified MAE samples under controlled loading scenarios. In a previous study, this procedure was applied for systems with only few magnetizable particles [ 62 ]. It allows for a detailed analysis of the sample behavior with a limited number of influencing factors.…”

“…A schematic illustration of the system under consideration is shown in Figure 3 a: three magnetizable nickel particles with diameters of approximately were placed into the center of a Polydimethylsiloxane (PDMS) matrix with a quadratic cross section of length and a thickness of , see [ 62 ] for further information on the sample generation. During the experiment, a magnetic field with norm was applied.…”

Coupled Anisotropic Magneto-Mechanical Material Model for Structured Magnetoactive Materials

“…Theoretical description and simulation of MA materials was performed by many work groups with different goals [ 16 , 17 , 18 , 19 , 20 , 21 ]. However, to simulate complex assemblies and get a deeper understanding of experimentally observed effects, it is necessary to find an appropriate theoretical description for such magneto-mechanical coupled anisotropic MA materials, where a distinction between material’s anisotropic preferential direction and field direction is possible.…”