Magnetic field-induced dynamic viscoelastic properties of isotropic and pre-structured magnetorheological elastomers having non-spherical shaped iron particles: Impact of particle–particle and particle–matrix interactions

The magnetorheological elastomers (MRE) are smart materials with magnetic particles embedded in a rubber matrix. When exposed to an external magnetic field, the MRE undergoes rapid phase transitions, generating magnetic field-induced stress, and quickly reverts to its original state once the field is removed. The tuneable properties of MRE have received tremendous application potential because of its ease of use in many devices. The filler (magnetic particles) and matrix structure significantly influence MRE's magneto-rheological (MR) properties. The arrangement and interaction of filler particles within the matrix are pivotal in shaping the overall rheological behaviour of MRE. Different configurations can alter how stresses and strains are distributed within the material, consequently affecting its properties. Previously, spherical and non-spherical particles were used to enhance the MR properties. Pre-structured particles (anisotropic MRE) tend to align preferentially within the matrix rather than being randomly dispersed (isotropic MRE). This alignment creates directional pathways for stress transmission, thereby modifying the material's magnetic response. The improvement in MR properties in pre-structured spherical particles-based MREs was explained based on the magnetic dipole–dipole interactions. This study introduces the pivotal role of particle–matrix and particle–particle interaction on the MR properties of isotropic and pre-structured MRE having non-spherical shaped iron particles as fillers. The variations in magnetic field-induced rheological properties were explained based on the particle–particle and particle–matrix interactions. A universal curve, independent of particle alignments and rheological modes, is proposed to explain the reduced yield stress variation with the reduced magnetic field.