Dynamic properties of isotropic natural rubber-based magnetorheological elastomers

Magnetorheological elastomers (MRE) are one of smart materials comprised of micron-sized iron particles in the elastomeric matrix, which exhibit variable dynamic properties in a changeable manner under the application of an external magnetic field. This paper presents experimental characterisations of static and dynamic properties of natural rubber-based on isotropic MRE with 30 and 60 wt% of carbonyl iron particles (CIPs) using the procedure outlined in the related standards. The static properties of these materials were measured as a function of the magnetic flux density using a servo-hydraulic machine in shear mode. The MRE with the highest magnetorheological (MR) effect was selected for the following dynamic properties with a range of shear strain amplitudes (2.5 to 20%), frequencies (1 to 50 Hz), and magnetic flux densities (0 to 240 mT). The storage modulus and loss modulus were found to increase with increasing frequency and decrease with increasing strain amplitude. Further investigation revealed that the relative MR effect reached its peak at 5% shear strain amplitude and 1 Hz with a value of 14.11%. Therefore, low strain levels must be considered in designing vibration applications using natural rubber (NR)-based MRE. The measured dynamic properties results were used to develop MRE test specifications for automotive products in Malaysia, as well as a possible smart material for vibration and noise control in various engineering applications.