Abstract:
In this method the sample is compressed, and a dual-beam laser Doppler vibrometer is used to measure the resulting strain. The sample is suspended in air by thin threads. A transient acoustic signal is used to compress the sample, where the wavelength of the acoustic signal in air is significantly greater than the sample dimensions. A rigid reflector is placed behind the sample to double the acoustic pressure. Data are presented for a rubber--air composite material. Extension of the above method to measurements as a function of temperature and pressure is described. The frequency range for this method is ~100--3000 Hz.