Constitutive Models Of Mechanical-magnetic Properties For Magnetorheological Elastomers

Magnetorheological elastomers(MREs)are a kind of intelligent composite materials formed by dispersing micron-sized ferromagnetic particles into polymers.The physical properties such as modulus,stiffness and damping of MREs can be changed quickly and reversibly with the change of external magnetic field,this unique character makes it has a wide range of applications in the sensor,vibration control,biomedicine,intelligent devices and so on.According to the internal microstructure,MREs can be divided into two categories:one is the isotropic magnetorheological elastomer,ferromagnetic particles in the matrix randomly distributed;the other is anisotropic magnetorheological elastomer,the ferromagnetic particles arrange chain-like structures in the matrix after curing.As an intelligent material,magnetorheological elastomers are very different from traditional materials.At present,the study of magnetorheological elastomers is not yet fully mature.On the one hand,the experimental test method is still relatively simple;on the other hand,the theoretical research is not enough depth,the application of the theoretical model has great limitations.In this paper,the mechanical properties of magnetorheological elastomers are studied from three aspects:experiment,theoretical analysis and numerical simulation.Main research contents and results are as follows:Magnetrorheological elastomers were prepared and the test platform was constructed.The mechanical properties of compression and shear of magnetorheological elastomers were tested.Two kinds of MREs,isotropic and anisotropic silicone rubber-based magnetorheological elastomers were prepared.The preparation method was optimized and the efficiency was improved.Combined with the traditional MTS,a mechanical-magnetic coupling test platform was built by adding a magnetic field generation module.The platform can achieve continuous changes in magnetic field from 110mT to 800mT,and can test the quasi-static and low strain rate compression performance of magnetorheological elastomers.The compressive properties of the magnetorheological elastomers were tested,and the macroscopic mechanical properties of the materials were explained from the microscopic point of view.The shear properties of magnetorheological elastomers were tested,and the effects of ferromagnetic particle content on the shear strength and maximum shear strain were analyzed.Based on the magnetic dipole interaction theory,a theoretical model was proposed to describe the mechanical-magnetic coupling behaviors of magnetorheological elastomers with the principle of minimum potential energy.In this model,the fully coupled interaction among all particles and chains was considered according to the micro-structure of magnetorheological elastomers.The energy equations of magnetic interaction and the elastic potential energy equations based on Mooney-Rivlin model were derived respectively.Then a theoretical model was developeded to describe the stress-strain relationship of magnetorheological elastomers under uniaxial load.This model agrees well with existing experimental data and can be used to explain the micro-mechanism of magneto-induced stress.Studies have shown that the mechanism of magneto-induced stress is tightly related to the inner micro-structure,and the nonlinear property of magneto-induced stress mainly results from the interaction among both particles and chains.By using the mesoscopic modeling method,a finite element model was established which is closer to the real material,and the magneto-magnetic coupling calculation of magnetorheological elastomers was realized.Based on the microscopic statistical parameters of the material,the isotropic and anisotropic finite element model of magnetorheological elastomers were established.Compared with the previous work,the model can be closer to the real microstructure of the material.By analyzing the magnetic interaction between the ferromagnetic particles in the matrix,the magnetic interaction force was transformed into time and position-dependent variables in each calculation step.By using the secondary development program based on MATLAB and COMSOL Multiphysics platform,the coupling calculation was realized.The tensile and shear mechanical properties of magnetorheological elastomers with different fraction of particles under different magnetic fields were calculated.The results show that the microstructure of the magnetorheological elastomers is the main factor affecting the mechanical properties of the materials.