Investigation On Shear Properties And Magnetic Driving Properties Of Magnetorheological Elastomers With Inclined Chain Structures

Magnetorheological elastomer(MRE)is a kind of material in which the magnetic particles are embedded in the non-magnetic elastic matrix.As a typical smart material,MRE can respond to external magnetic fields and produce rapid and reversible changes in material properties,has a wide range of application prospects in fields such as vibration damping and soft robotics.There are many factors that affect the characteristics of MRE materials,including the matrix material,filler particle material,etc.Among these factors,the orientation of the particle-formed chain structures affects both the shear properties of MRE and its static equilibrium orientation under homogenous magnetic fields.Based on this,MRE samples with different chain angles have been fabricated and tested for investigating the effect of the chain angle on shear properties and static magneticdriven properties.On the basis of the experimental results,the effects of the chain angle on shear properties of MRE materials have been analyzed based on the dipoleinteraction theory.And then,an operator-based model has been established to describe the asymmetrical hysteresis loop between the input(strain)and output(stress)of the MRE samples with different chain angles in shear test.On the other hand,the effects of the chain angle on static equilibrium orientation of MRE under homogenous magnetic fields have been tested based on the designed experimental setup.And then,a model has been established to describe the static relationship between input(magnetic field)and output(rotation angle)of MRE materials.Finally,a MRE deformation programming methodology has been presented based on the principle that the equilibrium orientation of the MRE is related to chain angle.The main content of the paper is summarized below:1.The effects of the chain angle on shear properties of the MRE have been investigated by experiments and modeling.The shear properties of MRE samples with different chain angles have been tested under different shear amplitudes and excitation frequencies.Based on the experimental results,the effects of strain amplitude,excitation frequency and iron particle fraction on shear properties of MRE samples with inclined chains have been characterized.Moreover,based on the dipole interaction principle,a model has been established to analyze the effects of the chain angle on shear properties of MRE.2.An operator-based hysteresis model was developed to describe the input-output relationship of the MRE for the effects of the chain angle on the hysteresis loop in shear tests.The experimental results illustrate that MRE samples with inclined chain structures have asymmetrical hysteresis loops in their input(strain)– output(stress)relationship.To describe the asymmetrical hysteresis loops of MRE materials,a generalized Prandtl-Ishlinskii(PI)model was developed based on the classic stop operator based PI model.The experimental results show that the established generalized PI model can describe the asymmetrical hysteresis loop of MRE in shear test under different excitation amplitudes and different magnetic fields.3.The effects of the chain angle and the iron particle fraction on the static magnetic driving properties of MRE materials have been investigated by experiments and modeling.The equilibrium orientation of MRE samples with different chain angles and iron particle fractions has been tested under quasi-static homogenous magnetic fields.Based on the experimental results,the effects of the chain angle and the iron particle fraction on the equilibrium orientation of MRE samples driven by homogenous magnetic fields have been analyzed,and then a model has been established to describe the static relationship between the input(magnetic field)and the output(rotation angle)of MRE samples under homogenous magnetic fields.4.A MRE deformation programming methodology has been presented on the basis of the magnetic driving properties of MRE.Based on the principle that the equilibrium orientation of MRE materials can be affected by chain angle,MRE composites were fabricated by combining MRE elements with different chain angles to catch specific curvatures.By utilizing this methodology,MRE composites have been fabricated to mimic typical biomimetic morphologies(the peeking-up posture of snakes and the flying posture of birds).