MEASUREMENT OF ELASTIC-CONSTANTS IN COMPOSITE-MATERIALS USING AIR-COUPLED ULTRASONIC BULK WAVES

This paper presents numerical simulations and experimental measurement s of longitudinal and shear bulk waves in composite materials, generat ed and detected with an air-coupled ultrasonic system. The transfer fu nction of an anisotropic absorbing layered plate immersed in air is co mputed with the transfer matrix method, and the waveforms produced by transmission through a plate are simulated from the convolution of. re ference waveform and the impulse response of the plate. The calculated waveforms compare well to those recorded experimentally, confirming t hat the waveforms recorded experimentally have the correct characteris tics. It is demonstrated that it is possible to identify longitudinal and shear modes. Results are presented showing how this data may be us ed to recover the stiffness matrix of composite materials, using the a ngular variation of velocity of both modes. (C) 1996 Acoustical Societ y of America