Transversely isotropic magnetoactive elastomers: theory and experiments (original) (raw)
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Finite deformation analysis of isotropic magnetoactive elastomers
Continuum Mechanics and Thermodynamics, 2020
In this study, the large deformation analysis of the magnetoactive elastomers based on continuum mechanics approach has been conducted. First, the governing differential equations for the spatial configuration are presented. Stored energy density function defined with respect to the invariants of the right or left Cauchy-Green deformation tensor and the magnetic field induction vector is adopted to develop a material model for finite deformation of isotropic magnetoactive elastomers (MAEs). An isotropic magnetoactive sample with 15% iron particle volume fraction is then fabricated, and a test setup has been designed to measure its magnetic permeability. Using an advanced magnetorheometer, quasi-static tests are then carried out on MAE circular cylindrical samples to find their torque-twist response under various magnetic fields. The experimental results are then effectively utilized to identify the unknown parameters in the proposed material model. The accuracy of the proposed constitutive model in predicting the response behavior of the MAE is then demonstrated through comparison of theoretical results with those obtained experimentally.
Journal of Magnetism and Magnetic Materials
The storage modulus variation of anisotropic magnetorheological elastomers (MREs) induced by an external magnetic field was modelled in the frequency domain. This involves synthesising five anisotropic MREs with different particle content and measuring its dynamic and magnetic properties. Dynamic properties were measured using a rheometer equipped with a magnetorheological cell and the magnetic permeability of each sample was measured with a vibrating sample magnetometer. Scanning Electron Microscope images were used to determine particle distribution. A four parameter fractional derivative model was used to describe MRE viscoelasticity in the absence of magnetic field and the fitting error was not larger than 1%. Magneto-induced modulus was also studied and two different models were analysed, the one of Jolly et al. (Smart Mater Struct;5:607 (1999)) and the other one of López-López et al. (J Rheol. 56:1209 (2012)). The first model underestimated the influence of the magnetic field for low particle contents while at high ones it overestimated the magnetic field effect, up to 13%. However, in the second model magnetic permeability values were used, and the error between the model prediction and experimental data did not exceed 7%. Hence, a new linear magneto-viscoelastic model was proposed in frequency domain for anisotropic MREs based on López-López et al. model, which predicts the effect of magnetic field on the dynamic shear modulus in function of particle content and frequency.
Development of a small-deformation material model for an isotropic magneto-active elastomer
Acta Mechanica, 2020
In the present work, a continuum-based material model has been developed for an isotropic magnetoactive elastomer (MAE) to investigate its behavior under small deformations. Firstly, the governing magnetomechanical equations are formulated for the flexible magneto-active medium. Subsequently, a linearization scheme is used to construct constitutive equations for the small-deformation analysis of MAEs by expressing the magnetic parameters by two constituents involving the rigid-body and perturbation states. The material constants of the constitutive model are estimated from the experiments performed on a right cylindrical sample of a magneto-active material comprising the elastic matrix with 15% volume fraction of carbonyl iron particles.
Magnetorheological Elastomers: Experiments and Modeling
HAL (Le Centre pour la Communication Scientifique Directe), 2011
-Magnetorheological elastomers (MREs) are ferromagnetic particle impregnated elastomers whose mechanical properties are altered by the application of external magnetic fields. Due to their magnetoelastic coupling response MREs are finding an increasing number of engineering applications. The objective of this work is : (a) the experimental study of transversely isotropic MREs (i.e., the particles form chains along a certain direction) that are subjected to prestressing and arbitrary magnetic fields and (b), the phenomenological modeling of these materials using transversely isotropic energy functions. Mots clés-magneto-mechanics, multi-physics, elastomers.
Journal of Industrial and Engineering Chemistry, 2012
This paper deals with the process of achievement of anisotropic magnetorheological elastomers (MREs), based on silicone rubber and iron nanoparticles. Plane capacitors are manufactured with MREs. The capacity C of the plane capacitors is measured as function of the intensity H of the magnetic field. By using the approximation of the dipolar magnetic moment and the ideal elastic body model, respectively, the tensions and deformations field and respectively the elasticity module of MREs function of H have been determined, for magnetic field values of up to 1000 kA/m. The obtained results are presented and discussed.
Magnetic anisotropy in magnetoactive elastomers, enabled by matrix elasticity
Polymer, 2019
Polydimethylsiloxane based magnetoactive elastomers demonstrate above the melting transition range (e.g. at room temperature) an induced uniaxial magnetic anisotropy, which grows with increasing magnetic field. By freezing a material down to 150 K, displaced iron microparticles are immobilized, so that the magnetic anisotropy can be measured. Magnetic anisotropy "constant" is a consequence of particle displacements and a characteristic of the energy of internal deformations in the polymer matrix. The maximum anisotropy constant of the filling is at least one order of magnitude larger than the shear modulus of the pure elastomer (matrix). In a magnetic field, the gain in the rigidity of the composite material is attributed to the magnetomechanical coupling, which is in turn a source of anisotropy. The concept of effective magnetic field felt by the magnetization allows one to explain the magnetization curve at room temperature from low-temperature measurements. The results can be useful for developing vibration absorbers and isolators.
Modeling and identification of the constitutive behaviour of magneto-rheological elastomers
2018
In this thesis, we study a class of “active materials” called Magnetorheological elastomers (MRE) which are ferromagnetic impregnated rubbers whose mechanical properties are altered by the application of external magnetic fields. With the purpose of characterizing the behavior of MREs up to large strains and high magnetic fields, this work brings a completely novel experimental, theoretical and numerical approach.The first part of this study focuses on an experimental investigation of MRE where multiple microstructures (isotropic and transversely isotropic materials) and multiple particles’ volume fraction are tested. A special sample geometry is designed in order to increase the uniformity of internal magnetic and mechanical fields measured during coupled-field experiments. The interfacial adhesion between the iron fillers and the silicone matrix is investigated and we show that when specimens are subjected to external magnetic fields, a silane primer treatment of the particles is ...
Response Analysis of Isotropic and Anisotropic Magnetorheological Elastomer
The purpose of this paper is to research the response of isotropic and anisotropic Magnetorheological Elastomer (MRE) with 15 and 30 percent of iron particles comprising in matrix of MRE with respect to transmissibility and percentage of vibration absorption. Fabrication and experimental investigation were carried out to study the response of MREs with respect to transmissibility and percentage of vibration absorption by using fast fourier transform (FFT). To ensure the validation of experimental result different readings were taken to compare characteristics in different loading conditions. Result obtained from the experimental analysis of samples of isotropic and anisotropic MREs with with 15 and 30 percent of iron particles were compared. Result show that best performance of vibration control and transmissibility were obtained with fabrication of anisotropic and isotropic MRE with 30 gm iron particle behind that anisotropic and isotropic MRE with 15 gm iron particle have good results of vibration control.
Magnetic Field-Induced Deformation of Isotropic Magnetorheological Elastomers
Magnetochemistry
In our research, the magnetic field-induced deformation of isotropic magnetorheological elastomer (MRE) discs loaded with two types of magnetite and an iron powder were examined. A measurement system using a microscope camera was assembled, and the magnitude of the deformation was determined from the optical contour obtained with digital image processing. We found that the MRE discs with a height-to-width aspect ratio of 1:2 underwent expansion in the direction of the external field in all cases. The magnitude of the dilatation increased with the magnetic field strength in cases of all filler materials, but the exact trend depended on the type and concentration of the filler. An inhibition of the polymerization of the matrix was observed in the case of one of the magnetite fillers, which resulted in a decreased zero-field elastic modulus at higher particle loadings. A correlation was found between the reduced elastic modulus and the increased magnitude of the deformation.
Effect of a homogeneous magnetic field on the viscoelastic behavior of magnetic elastomers
Polymer, 2007
Viscoelastic behavior of highly elastic magnetic elastomers has been studied by three different experimental techniques: elongation, static and dynamic shears. It has been shown that the elastic modulus of the materials increases considerably in an external homogeneous magnetic field of up to 0.3 T (100-fold increase of the tangential modulus has been observed at small 1e4% deformations). The appearance of the new effect of pseudo-plasticity induced by the magnetic field has been observed leading to a considerable (up to 100-fold) increase in the shear loss modulus of the composites.