Enhanced viscoelastic magneto-mechanical properties for off-axis anisotropic magnetorheological elastomers: Experiment and modelling

In this study, the microstructure of tilt angle magnetic chains is adopted to construct off-axis anisotropic magnetorheological elastomers (MREs) for tailoring viscoelastic magneto-mechanical properties. The magneto-rheological behaviour of anisotropic MREs is investigated using magneto-controlled smart devices to achieve dynamic mechanical response. The viscoelastic behaviour is modelled by fractional derivative (FDM) and extended Kelvin-Voigt model (EKVM), the viscoelastic properties of anisotropic MREs are characterized by experimental and theoretical methods. Meanwhile, a magneto-induced mechanical model is established to reveal the influence of the tilt angle of the magnetic chain, the prestrain, the mass fraction of carbonyl iron particles (CIPs), and the magnetic flux on the magneto-induced mechanical properties. First, the complex moduli of anisotropic MREs with 25% and 40% mass fractions containing 0 degrees, 15 degrees, and 25 degrees magnetic chains were experimentally characterized under shear mode using excitation frequency (1-100 Hz) and flux densities (300mT). The nonlinear robustness method is used to identify the parameters of the storage modulus and loss modulus functions from the experimental results in the viscoelastic theoretical models. The error analysis of anisotropic MREs for complex moduli between the theoretical and experimental solutions is evaluated at different tilt angles and CIPs contents. Finally, magnetorheological tests on anisotropic MREs verified the theoretical results on the magneto-induced elastic modulus influenced by tilt angle, magnetic particle content and flux density. The description of the storage modulus in EKVM, with an error of less than 3%, is superior to that in FDM, with an error of less than 8.1% in the frequency domain. The loss modulus of anisotropic MREs in FDM for different tilt angles and mass fractions, was accurately evaluated at low frequency compared to the EKVM solution.