On anisotropic mechanical properties of heterogeneous magnetic polymeric composites

Abstract

This study is devoted to the magneto-mechanical characterization of heterogeneous magnetoactive elastomers based on an elastic polydimethylsiloxane matrix with embedded spherical magnetic soft microparticles and magnetic hard microparticles of irregular shape. An issue of the anisotropic mechanical properties of these smart composites is considered. Non-magnetized and pre-magnetized specimens are characterized using a planar shear and axial loading in an externally applied homogeneous magnetic field. The field direction differs relative to the direction of the field used for the specimens pre-magnetization. Results of the different methods allow comparison of the tensile shear moduli for the samples with an initially identical composition. Obtained results demonstrate a strong correlation between the composite behaviour and orientation of the magnetic field used for the pre-magnetization of the sample relative to the external field applied to a sample during the test. Composites pre-magnetized in the direction parallel to an applied mechanical force and external magnetic field show higher magnetorheological response than composites pre-magnetized transversally to the force and the field. Application of the external field directed opposite to the direction of the pre-magnetization reduces the observed stiffening. Moreover, in this situation a softening of the material can be observed, depending on the magnitude of the external field and the field used for pre-magnetization. This article is part of the theme issue ‘Heterogeneous materials: metastable and non-ergodic internal structures’.

Heterogeneous materials: metastable and non-ergodic internal structures

“…The last two papers shed light on the internal structures in highly concentrated magnetic composites with liquid and mechanically soft matrices as well as on macroscopical properties of these systems. Experiments (see, for example, papers [3,4] as well as paper [17] in this issue) show that nonergodic long-lived structures appear in magnetic gels and suspensions under the action of an applied magnetic field. These structures determine the macroscopic properties and behaviour of these composite systems.…”

“…In part, one can control, in a wide range, the mechanical characteristics and behaviour of the composites by using an external magnetic field. Anisotropic structures in the magnetic polymers with a high concentration of magnetic particles, the effect of these structures, as well as the effect of external magnetic field on the mechanical properties of the composites are studied in the work reported by Dmitry Borin, Gennady Stepanov and Eike Dohmen [17]. The last two papers shed light on the internal structures in highly concentrated magnetic composites with liquid and mechanically soft matrices as well as on macroscopical properties of these systems.…”

Reversible and non-reversible motion of NdFeB-particles in magnetorheological elastomers

“…Besides that, interest for different applications of those materials arouse, for example, as a sensor element presented by Becker et al (2018). Furthermore Borin et al considered a mixture of magnetically soft and hard particles in recent studies regarding spherical powder (2019a) and powder particles of irregular geometry (2019b). Several recent works are devoted to theoretical and experimental studies of macroscopic magnetic properties of magnetorheological elastomers containing magnetically hard particles.…”

Coupled Anisotropic Magneto-Mechanical Material Model for Structured Magnetoactive Materials

“…Due to their adaptability, this material group is of high interest for numerous technical applications. However, since many of these applications involve complex magnetic fields with strongly position-dependent field strengths and field orientations, MA materials will be affected by the field, resulting in locally varying material behavior and locally varying deformations [ 1 , 2 , 3 , 4 , 5 , 6 , 7 ], which in turn influence the magnetic field. Therefore, for an efficient utilization of MA materials, advanced material models are necessary, capable of describing the dependency of rheological or mechanical properties on field strength, temperature, load type, load direction, and field orientation.…”