Switched-state Control of a Vibration Isolation Mount using Ionomeric Materials

摘要

Materials that exhibit controllable modulus variations will enable new developments in applications in vibration suppression and shape change. In this paper we analyze a class of materials that exhibits reversible modulus variations due to solvent incorporation or removal. These materials, known as ionomeric polymers, have been shown previously to exhibit 20X changes in modulus depending on the hydration state of the material. A test fixture that allows a ionomeric polymer sample to be placed in a hydration controlled environment is developed. The Young's modulus of unplated materials and materials plated with metal is measured as a function of hydration level. A change of 2.56 and 3.89 times in modulus is obtained for the unplated and plated material, respectively. Experiments are performed to determine the ability to increase the stiffening rate of the polymer using applied electrical energy. Square input signals are applied to increase the elastic modulus of these materials. The rate of modulus change is higher or lower depending on the voltage amplitude and the forcing frequency of the input signal. Different kinds of solvents are used to control the modulus of the ionomer plated with platinum. Glycerol is the solvent with the highest modulus reduction (88.87%) and water is the smallest (67.71%). In addition, a test fixture consisting of a mass on a plate is built and modeled as moving-base. The change in stiffness is explored as a method to reduce unwanted vibration. The displacement transmissibility versus frequency is measured for water and acetonitrile solvents. The stiffness of Nafion 117 is computed when the solvents are applied and after they dry. The steady state response of the system is measured by applying a sinusoidal input signal. A forcing frequency of 94 Hz near the natural frequency is selected to produce a high amplitude. The displacement amplitude is reduced 5 times in 10 seconds after the application of the acetonitrile to the ionomeric polymer. These results demonstrate the basic feasibility of controlling the modulus in real time and quantify the time constants associated with hydration and dehydration of the material.