Session: 01-09: Magnetic Materials

Paper Number: 110855

110855 - Magnetostrictive Properties of Magnetoactive Elastomeric Cylinders 

Magnetoactive elastomers (MAEs) are promising materials for magnetically controlled soft actuators, e.g., for soft robotics applications. The change in the dimensions of a material in a uniform magnetic field is commonly defined as magnetostriction. The main origin of these magnetic field-induced deformations in MAEs is the form effect (strain dependence of demagnetizing energy) and not the spin-orbital coupling as in conventional crystalline ferromagnets. As a result, mechanically soft MAEs exhibit “giant” magnetostrictive strains of the order of magnitude of 10^-1 in moderate magnetic fields (≈400 kA/m) [1]. Hitherto, magnetostriction is a less explored feature of MAEs than the magnetorheological effect.

We report systematic investigations of thirty-six cylindrical MAE samples with a diameter of 15 mm, where a soft polydimethylsiloxane (PDMS) matrix was filled with micrometer-sized carbonyl iron particles. The stoichiometry ratio of the polymerization reaction (ratio of molar concentrations of hydride and vinyl reactive groups) was close to unity. Longitudinal and transversal strains of MAE cylinders in uniform quasi-static magnetic fields were measured using image processing. MAEs cylinders differed in weight percent of iron filler, aspect ratio and the presence of structural anisotropy (vulcanization either in the presence or in the absence of a magnetic field). Longitudinal and transversal deformations of MAE cylinders in uniform quasi-static magnetic fields were measured using image processing. Cylinders exhibited a “giant” change in height (up to 35%, which is the highest reported value hitherto) as well as significant lateral contraction. In a magnetic field, a concave dent was formed on the free, circular base, which was characterized experimentally. From these measurements, the volume of MAE bodies was calculated for the first time, and the volumetric strain was significant (up to 10%). We believe that we observed a “colossal” non-Joulean magnetostriction due to the form effect. Finally, transient behaviour in deformative response of MAE cylinders to time varying magnetic fields was investigated.

References:

1. Saveliev, D.V.; Belyaeva, I.A.; Chashin, D.V.; Fetisov, L.Y.; Romeis, D.; Kettl, W.; Kramarenko, E.Y.; Saphiannikova, M.; Stepanov, G.V.; Shamonin, M. Giant Extensional Strain of Magnetoactive Elastomeric Cylinders in Uniform Magnetic Fields. Materials 2020, 13, 3297, doi:10.3390/ma13153297.

Presenting Author: Mikhail Shamonin Ostbayerische Technische Hochschule Regensburg

Presenting Author Biography: Mikhail Shamonin is since 2002 Professor of Sensor Technology in the Faculty of Electrical Engineering and Information Technology at Ostbayerische Technische Hochschule Regensburg in Germany.