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The primary aim of this research was to optimise the design of magnetorheological elastomers (MREs), composite materials consisting of magnetic particles in an elastomer matrix. In doing so, the understanding of their dynamic behaviour when subjected to stress would be furthered. Plenty of uses have been suggested for these materials which adapt to their environments and can be tuned to suit operating conditions, but very few of these have actually been realised. Characterising their dynamic behaviour is crucial if they are to gain wider use in commercial applications. The first objective of the research was to investigate the factors affecting the magnetorheological (MR) performance of MREs and to optimise this performance. The objective was achieved by rheometric experiments to measure the increase in shear storage modulus of the materials. Secondary objectives were the analyses of mechanical properties such as strength, fatigue behaviour and expected lifetime. Following experimentation, it was concluded that the MR performance of an MRE, which is greatly affected by the microstructure of the composite, can be maximised by improving particle orientation during curing. This was achieved by optimising recipes and vulcanisation procedures to accommodate alignment of the magnetic particles. This work refutes the assertion that MREs must always possess very low moduli in order to produce significant improvements in physical properties, a constraint that would severely limit their potential applications. Uniaxial testing and crack propagation tests show the incorporation of magnetic particles into a rubber matrix itself is not a contributing factor to any reduction in tensile properties or resistance to crack growth, rather that the addition of magnetic particles replaces a portion of other fillers, such as carbon black in rubber vulcanisates.
Mcintyre, J. (2013) Characterisation and Optimisation of Magnetorheological Elastomers. Doctoral Thesis, Dublin Institute of Technology. doi:10.21427/D7Z32P