1. Ultrasonic wave propagation testing

Ultrasound is well known to engineers for non-destructive testing . The application of ultrasonic waves to the stiffness and damping properties of composite materials is less well known. The advantages over other types of testing are manifold: like vibration testing, these are non-destructive tests that can be used to determine virtually all the moduli of elasticity and a large proportion of the damping coefficients of a composite material on a single sample, thus avoiding dispersion problems and simplifying implementation.

These ultrasonic techniques are based on measuring the phase velocity of a plane volume wave propagating through the material. The wave, which carries eight pieces of information (direction of propagation: 2; polarization: 2; amplitude: 1; number of waves: 1; frequency: 1; attenuation, if the material is damping: 1) gives the...