Acoustic Properties of Selected High Strength Thermosetting Plastic Composites at Ultrasonic Frequencies

High strength thermosetting plastic composites provide static strengths comparable to some metals while having densities slightly greater than water and an acoustic impedance comparable to aluminum. To evaluate their use as ultrasonic resonators measurements were made of their density, extensional sound velocity and elastic constant. To determine their utility and limitations as ultrasonic horns operating at substantial displacements and stress their Q was also measured at stress levels in the range of 50 MPa (7300 psi) at 20 kHz. It was found that one of these materials, although more costly than metals, may serve well as a replacement for metal horns for output displacements in the range of 75 microns (3 mils), peak-peak at 20 kHz, particularly in applications where low weight and long length is desired.