Viscoelastic Materials (VEMs) are in widespread use for vibration damping and isolation. Magnetorheological (MR) fluid devices are also increasingly used for vibration control. MR fluids are suspensions of metal particles in various carrier fluids that have properties controllable by imposition of a magnetic field, using mechanisms that suggest analogous manipulation of properties in more solid carrier or base materials. This paper describes a research effort that studied the properties of composite or compound materials that we call MR-VEM. Compared to traditional VEM, the material offers the opportunity to change properties — at a minimum, the stiffness, and to a lesser extent material damping — by application of magnetic fields. Properties can be manipulated with a DC or AC field. Magnetic design studies for MR-VEM compounds are described. The paper focuses on the experimental characterization of dynamic performance of MR-VEM devices for use in vibration isolation systems. Two properties were used as the basis for distinguishing samples: particle fill factor, that is the volume ratio of MR particles to the base VEM, and the magnitude of magnetic field applied while curing the MR-VEM elements. Applied magnetic field was also varied during testing. The compound material performance is studied through a range of experiments. Test data showing a factor of five stiffness adjustability are presented. Limitations imposed by the size of required magnetic components and by material heating are quantified and discussed. Overall, the material shows promise for applications requiring adjustability in effective stiffness. The paper concludes by considering actuation with the materials.
Characterization of viscoelastic materials used to control underwater sound
