TY - JOUR A1 - Sorokin, Vladislav V. A1 - Stepanov, Gennady V. A1 - Shamonin (Chamonine), Mikhail A1 - Monkman, Gareth J. A1 - Khokhlov, Alexei R. A1 - Kramarenko, Elena Yu T1 - Hysteresis of the viscoelastic properties and the normal force in magnetically and mechanically soft magnetoactive elastomers: Effects of filler composition, strain amplitude and magnetic field JF - Polymer N2 - Hysteresis in dynamic modulus, loss factor and normal forces of magnetoactive elastomers (MAEs) comprising various proportions of small (3-5 mu m) and large (50-60 mu m) ferromagnetic particles are experimentally studied using dynamic torsion performed at a fixed oscillation frequency in varying DC magnetic fields. It is shown that hysteresis is a characteristic feature of MAEs observed both under increasing/decreasing magnetic field strength and increasing/decreasing strain amplitude. This hysteresis is attributed to the specific rearrangement of the magnetic filler network under simultaneously applied magnetic field and shear deformation. Rheological properties of the magnetic filler network formed in the magnetic field and, therefore, the rheological properties of MAEs depend strongly on the filler composition and the magnetic field magnitude. Larger magnetic particles and higher magnetic fields provide stronger magnetic networks. Both factors result in the extension of the linear viscoelastic regime to larger strain amplitudes and lead to higher values of shear storage and loss moduli. It is found that the hysteresis width maximises at an intermediate magnetic field where it is attributed to the balance between elastic and magnetic particle interactions. This is apparently where the most significant restructuring of the magnetic network occurs. The hysteresis width decreases with increasing fraction of large particles in the magnetic filler. The loss factor grows significantly when the magnetic network is physically broken by large strains gamma > 1%. A huge (more than one order of magnitude) increase of normal force at maximum magnetic field strengths is observed. It is predicted that any physical quantity depending on the internal structuring of the magnetic filler should demonstrate hysteresis either with a changing magnetic field and constant deformation amplitude or under variable deformation in a constant magnetic field. (C) 2015 Elsevier Ltd. All rights reserved. KW - BEHAVIOR KW - COMPRESSION KW - Dynamic modulus KW - GELS KW - hysteresis KW - Magnetorheological elastomers KW - magnetostriction KW - MODULUS KW - PARTICLES KW - POLYMER COMPOSITES KW - shear Y1 - 2015 U6 - https://doi.org/10.1016/j.polymer.2015.08.040 VL - 76 SP - 191 EP - 202 PB - Elsevier ER - TY - JOUR A1 - Sorokin, Vladislav V. A1 - Ecker, Eva A1 - Stepanov, Gennady V. A1 - Shamonin (Chamonine), Mikhail A1 - Monkman, Gareth J. A1 - Kramarenko, Elena Yu A1 - Khokhlov, Alexei R. T1 - Experimental study of the magnetic field enhanced Payne effect in magnetorheological elastomers JF - Soft Matter N2 - The dynamic modulus and the loss factor of magnetorheological elastomers (MREs) of various compositions and anisotropies are studied by dynamic torsion oscillations performed in the absence and in the presence of an external magnetic field. The emphasis is on the Payne effect, i.e. the dependence of the elastomer magnetorheological characteristics on the strain amplitude and their evolution with cyclically increasing and decreasing strain amplitudes. MREs are based on two silicone matrices differing in storage modulus (soft, G' similar to 10(3) Pa, and hard, G' similar to 10(4) Pa, matrices). For each matrix, the concentration of carbonyl iron particles with diameters of 3-5 mu m was equal to 70 and 82 mass% (22 and 35 vol%, respectively) in the composite material. Samples for each filler content, isotropic and aligned-particles, are investigated. It is found that the Payne effect significantly increases in the presence of an external magnetic field and varies with the cyclical loading which reaches saturation after several cycles. The results are interpreted as the processes of formation-destruction-reformation of the internal filler structure under the simultaneously applied mechanical force and magnetic field. Impacts of matrix elasticity and magnetic interactions on the filler alignment are elucidated. KW - BEHAVIOR KW - CARRAGEENAN KW - DAMPERS KW - MODEL KW - SEALS KW - SENSITIVE ELASTOMERS KW - Shear modulus KW - VISCOELASTIC PROPERTIES KW - WIDE-RANGE MODULATION Y1 - 2014 U6 - https://doi.org/10.1039/c4sm01738b VL - 10 IS - 43 SP - 8765 EP - 8776 PB - ROYAL Society of CHEMISTRY ER -