New technique for dynamic moduli and loss factor measurements

A new resonance technique capable of providing rapid and accurate dynamic modulus and loss factor measurements on a wide range of materials (soft and rigid) over a wide range of frequency and temperature has been developed. Miniature accelerometers are placed on the ends of a small strip of material and one end is driven by a noise source. The output from the two accelerometers is analyzed by a fast Fourier transform (FFT) spectrum analyzer. At certain frequencies, the amplitude of the acceleration ratio goes through peaks due to resonances. At these resonances, or more properly when the phase difference is 90 degrees, the equations of motion are easily solved. The amplitude and phase of the acceleration ratio are measured continuously over a frequency range of five decades (0.2 to 25000 Hz) and the computerized data analyzed to provide a family of Young's modulus and loss factor curves. The data is presented in two ways: (a) a frequency plot showing the relaxational nature of the material, and (b) a temp...