Abstract

Permanently magnetizable (hard) NdFeB particle-filled magnetorheological elastomers (hMREs) find application in soft robotic manipulators, sensors, etc. The hMREs are essentially two phase composites, having hard magnetic inclusions in a mechanically soft matrix. Energy dissipates in these composites mainly due to the ferromagnetic hysteresis loss in the underlying particles. In this context, we propose a thermodynamically-consistent, macroscopic effective model for the isotropic hMREs in terms of the energetic and dissipation potentials. The proposed model has strong foundations on its microstructure evolution under applied magnetic and mechanical loads. Moreover, our microstructurally-guided model is developed considering a single calibration parameter, which is computed subsequently with the aid of full-field numerical homogenization computations.

The model outputs show excellent agreement with the experimental observations for the deflection of a pre-magnetized soft cantilever beam. Moreover, the model predictions find a critical difference between the uniformly and non-uniformly pre-magnetized hMRE beams. Several propositions for the architectured materials with a combined non-magnetic and pre-magnetized members are made. These materials show extreme positive and negative swelling under very low actuating fields ~ 40 mT.