Bruce Hartmann Gilbert F. Lee John D. Lee
Polymer Sci. Group, Naval Surface Warfare Ctr., Silver Spring, MD 20903-5640
A resonance apparatus for the characterization of viscoelastic materials will be described. Measurements have been made of modulus values as low as 0.1 MPa and as high as 70 GPa and loss factors from 0.003 to 2.5. Material properties are determined as exact (numerical) solutions of the wave equation with no simplifying assumptions. In particular, the loss factor is not calculated from the half-power point and is valid for large values of loss factor. By bonding the sample to the driver, clamping errors common with other instruments are eliminated. For any given measurement temperature, the frequency range of the measurements is about 1.5 decades centered at about 1 kHz. Depending on the sample length and modulus, data can be obtained from 100 Hz to 25 kHz. Once measurements have been made as a function of temperature, the data are shifted to form a master curve and fitted to an analytical model. Illustrative data will be presented for a high-loss and a low-loss polyurethane. [This work was sponsored by the Independent Research Program of the Naval Surface Warfare Center.]