Development and Evaluation of Damping characteristics and Shear properties of Magnetorheological elastomers

Abstract

Elastomers are widely used to reduce vibrations and noise in structures, machines, and instruments. The passive nature of elastomers inhibits its use over a wider range of frequencies. Incorporating ferromagnetic ingredients in the non-magnetic elastomer matrix makes these structures smart when exposed to a magnetic field. These elastomers are better than conventional elastomers and can be applied in a wide frequency range. They belong to a class of smart material called Magnetorheological materials whose rheological properties can be reversibly controlled by a magnetic field. This research is focused on preparation and damping characterization isotropic magnetorheological elastomers using different matrices by varying the volume percentage of carbonyl iron powder. Natural rubber, Nitrile rubber, RTV and HTV silicone and a new type of MRE by mixing RTV silicone and polyurethane was prepared and tested at various magnetic fields and input conditions. Experimental studies were conducted to understand the influence of matrix material, percentage concentration of carbonyl iron powder and magnetic field on the mechanical properties of the MREs i.e. shear modulus (G) and dynamic damping (loss factor η). Force vibration tests were performed to understand the enhancement of damping property of MRE samples. Experimentally it was proved that nitrile rubber and silicone-polyurethane hybrid MREs showed better damping performance than other matrix materials. The performance was also dependent upon the input strain rate and weakly on the operating frequency. The influence of size of the particle ingredient was investigated on a small scale. The inherent damping property of the matrix plays a major role in the respective MRE sample. Magnetic field and percentage particle content was found to be the dominating parameters influencing the damping properties. The dimension of the test sample, input strain and frequency also influence the damping on a lesser scale. Linear viscoelastic model was fitted to the experimental data using the MATLAB optimization tools which closely matched with the experimental values. The application of MRE as damping material was investigated by following ASTM E756-05 standard in sandwich beam configuration. The loss factor and shear modulus modifications were investigated under non-homogeneous magnetic field by subjecting it to impulse excitation.