The elastic and damping properties of magnetorheological elastomers: Dissertation

Magnetorheological elastomers (MREs) belong to the group of so-called smart materials, which respond to an external stimulus by changing their viscoelastic properties. Magnetorheological (MR) material can be fluid, gel or solid material. The mechanical properties of the MR materials change when subjected to an external magnetic field. The MREs are interesting candidates especially for the active stiffness and vibration control of structural systems. The aim of this study was to increase the knowledge on the mechanical and viscoelastic properties of isotropic and aligned MREs. The focus was to clarify the changes in the elastic and vibration damping properties of both studied types of MREs when subjected to magnetic field. Isotropic and aligned MREs were prepared from silicone elastomer matrix with varying carbonyl iron content. The MREs were tested in bending and compression modes with sinusoidal dynamic loading. The 3-point bending experiments were carried out using a dynamic mechanical analyzer (DMA) in resonance for both isotropic and aligned MREs where the filler content varied from 0 to 30 vol.%. For characterizing the materials in compression with applied magnetic field, a special coil device was designed. Isotropic and aligned MREs with 30 vol.% of Fe were also characterized in dynamic compression with varying frequencies and strain amplitudes. The spring constant, elastic/shear modulus and damping ratio/loss factor values were calculated on the basis of the measured data with and without applied magnetic field. The results show, that the stiffness and damping properties of both isotropic and aligned MREs can be modified by applying external magnetic field. The damping and stiffness properties of the MREs depend significantly on the mutual directions of load, magnetic field and the particle alignment in the composite.