| This work is focused on the fundamental understanding of the dynamic behavior of thick magnetorheological elastomers (MREs). Experimental and theoretical studies are conducted to investigate the dynamic shear properties of MREs which are affected by increasing the thickness, as well as the percentage of iron particles contained in these materials.;In the experimental study MREs are made with various thicknesses and different amounts of iron particles. These include thicknesses of 25.40mm, 19.05mm, 12.7mm, 6.25mm and 3.05mm with iron particle percentages of 30%, 50%, 60% and 70% by weight. A double shear test setup is designed and built to test the MRE samples. All samples are analyzed over a range of frequencies from 200Hz to 800Hz. Experiments are performed at peak accelerations of 0.25g, 0.5g, and 0.75g. The 25.40mm samples are also tested under preloads of 1% and 2% strains. Since all tests are performed at constant peak accelerations, the strain amplitude varies as a function of frequency. The results demonstrated that the thickness of MRE significantly affects the material properties in the "off" state, that is, when no magnetic field is applied. This is believed to be related to the strain amplitude; a phenomenon known as the Payne Effect. However, in the "on" state, when the material is activated by a magnetic field, the thickness of the sample does not show a significant effect on the change in storage modulus. This change remains constant for all samples with different thicknesses under the same magnetic field.;The theoretical analysis includes a macro-mechanical model describing the storage and loss moduli of MREs as a function of sample thickness, volume percentage of iron particles, and applied magnetic field. This model is based on fractional derivatives and is applicable to input vibration acceleration of 0.25g with no preloading.;Comparisons between the theoretical and experimental results show that the model accurately presents the dynamic behavior of thick MREs. |
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