A study of the effect of mechanical preloads on hysteresis loop of magnetorheological elastomers

In this work, an investigation of the effect of mechanical preloads on the hysteresis loop of composite soft magnetorheological elastomer (MRE) was carried out. MRE is a “smart” composite material that consists of magnetically permeable particles in a non-magnetic polymeric elastomer. When subjected to an external magnetic field, a large deformational change occurs in the mechanical properties of these materials. Due to their coupled magnetomechanical response, these materials have been found suitable for various engineering applications. Inspired by experimental work, we present a model of the effect of mechanical preloads on the magnetization response of MRE based on a general continuum formulation. Using the Jiles - Atherton (JA) model parameters derived from the fitting of experimental measurement, the hysteresis loop of isotropic MRE was numerically resolved, which was then coupled to mechanical fields based on an energetically constitutive model valid for finitely strained MREs. Simulation analysis is performed for uniaxial stresses parallel to the direction of the applied magnetic field. For the applied tensile and compressive stresses, only a small change is observed in the hysteresis loop of these materials. Additionally, microscale modeling of the magnetization behavior of the isotropic MRE based on experimental results was performed. Considering the interaction between the magnetic particles, the magnetic and mechanical fields are resolved explicitly inside the composite material. A computational homogenization scheme was utilized to relate the microscopic behavior to the effective macroscopic properties of the MRE. In principle, the predicted effective magnetization behavior is observed to agree with the measured hysteresis loop of MRE materials.