Research On Electrical Properties Of Magnetorheologica Materials

Magnetorheological materials are a kind of magnetically controlled intelligent composite polymer materials,generally composed of iron magnetic particles and non-conductive polymer matrix.The magnetorheological effect occurs and chain structures are formed under the action of an applied magnetic field.The magnetorheological materials have not only excellent mechanical properties but also conductive characteristics,similar to the conductivity of ordinary conductive polymer composites,which can be widely used in various kinds of sensors,bionic skin and other fields.So that the conductive characteristics of magnetorheological materials have high value of utility.In view of these characteristics,the following studies were carried out.Firstly,the preparation process of Magnetorheological Fluids(MRF)and the Magnetorheological Elastomer(MRE)were studied,and the particle pre-treatment process was established,including the investigation of particle coating process and microscopic analysis of particle structure.Through the microscopic observation of the internal particle structure,it is seen that under the action of magnetic field the particles gradually form a single chain independent of each other,with the increase of magnetic field intensity,the particle chain intersects and eventually forms a mesh structure.According to its structural characteristics,the conductive mould was designed and the capacitance elements of MRF and MRE were prepared.Based on the study of the conductivity mechanism of Magnetorheological Material,and the capacitance model under high frequency AC environment is established from macroscopic and microscopic aspects.Through simulation analysis and logarithmic fitting,the capacitance between particles decreases with the increase of particle spacing,and the capacitance between particles under the action of magnetic field is larger than that under zero fields(no field applied).Equivalent capacitance model was established and a sinusoidal AC experimental platform was developed,the conductive characteristics of MRF and MRE were studied respectively,Inlluencing factors include applied magnetic field,particle volume ratio,sample height,carbon black additive,external pressure,etc.Based on the above theory and simulation analysis,the conductive characteristics of MRF were tested.Appropriate experimental equipment was selected,and design of the experimental circuit.The experimental results were analyzed,and the following conclusions were drawn:the MRF increases initially and then decreases with the increase of frequency under the applied magnetic field,exhibiting obvious capacitance characteristics,with the increase of magnetic field,the capacitance increases and the conductivity is enhanced.Under the same magnetic field conditions,the MRF conductivity of different particle volume ratio increases first and then decreases with the change in frequency,the smaller the particle volume ratio,the greater the current,and the better the conductivity.The effect of carbon black additive on the conductivity of MRF is positively correlated,with the increase of conductive filler in MRF,the higher the current,and the stronger the conductivity.By increasing the height of the sample element,the current and capacitance values are increased,which makes the conductivity of the MRF enhanced.A study on the conductivity of MRE with different particle volume ratios under external excitation(external pressure,applied magnetic field)was carried out.Due to the structure of particles,and the dipole model based on the action of adjacent particles,the conductive properties of MRE under external excitation are analyzed theoretically.The conductivity of MRE is dependent on the change of the applied pressure,with the increase of the pressure,the distance between particles decreases,the contact surface of the particles increases,the resulting conductive channel increases,and the conductivity of the sample increases.Based on the influence of the applied magnetic field on the internal structure of MRE,the MRE capacitance of different particle volume ratio varies with the trend of magnetic field,with the increase of magnetic field,the capacitance increases and the conductivity is enhanced.