A magneto-rheological elastomer vibration isolator for lightweight structures

Magneto-rheological elastomers (MRE), consisting of elastomeric matrix containing ferromagnetic particles, are a kind of smart material, whose mechanical properties are controllable via applied magnetic fields. In this paper, the possibility of adopting these materials to realize vibration isolators for lightweight structures is evaluated. Such isolators must be stiff enough in the vertical direction, to support the structure weight, while they must have a low horizontal stiffness to isolate ground vibrations originated by different sources. To meet these requirements, an isolation system, constituted by MRE pads and ball transfer units (BTU), is proposed. The BTUs support the structure weight allowing it to move in any horizontal direction, while the MRE pads provide a controllable horizontal restoring force. Therefore, the pad stiffness may be chosen considering only the horizontal isolation characteristics, regardless of the vertical ones. The paper describes the isolator layout, the criteria followed to make up a set of MRE specimens and the experimental set-up adopted to characterize them. The dynamic behaviour of the isolated structure and the isolator performances are described by means of numerical simulations. The analytical description of the isolator restoring force was deduced adopting a generalized Maxwell model in parallel with a Bouc–Wen element whose coefficients were identified from the experimental test results.