Magnetoelastic properties in isotropic magnetic elastomers

Purpose. To investigate the influence of magnetic field on the elastic characteristics of isotropic magnetic elastomer.

Methods. The behavior of magnetic particles in the sample was studied based on the idea of a hierarchical model of chain formation combined with a lattice model of particle arrangement. When studying systems with chain aggregates, a statistical distribution function was introduced for the number of particles in a chain, which made it possible to calculate the number of chains in a composite with a given particle concentration. The nonlinear magnetization of particles in the sample was modeled in the form of the semi-empirical Frohlich-Kaenely law, which made it possible to calculate the magnetization of materials with good accuracy, both in weak and strong magnetic fields.

Results. The paper presents a model describing the elastic properties of an isotropic magnetic elastomer synthesized without the effect of a magnetic field. The elastomer consists of particles with a volume concentration of 28.6%, capable of magnetization, the size of which is 10 microns. These particles are embedded in a polymer matrix. Under the action of a magnetic field, chains of magnetic particles are formed in the polymer. It is assumed that the length of such chains is less than the size of the sample in the direction of the field. The dependences of the shear modulus of the composite on the external magnetic field are determined.

Conclusion. A physical model is proposed that successfully predicts the magnetorheological effect in the studied composite material with a soft matrix and randomly distributed particles synthesized without a magnetic field. The research is based on an improved lattice theory that takes into account the probabilistic distribution of particles due to the polymerization process of the composite. A hierarchical principle of forming particle chains is proposed, where their number doubles at each stage. It has been established that chains of such length make the main contribution to the macroscopic shear modulus of the composite. The agreement between theoretical results and experimental data confirms the adequacy of the proposed model for describing the behavior of a magnetic elastomer in an external magnetic field.

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