The acousto-ultrasonic technique has many potential applications in the NDE of composite materials. However, problems of poor reproducibility and of the sensitivity of the results to precise instrument settings have restricted its application in industry The waves employed in acousto-ultrasonics are chiefly Lamb waves which propagate in the plane of the laminate. In this paper, Lamb wave propagation in composite laminates both with and without defects is investigated both numerically and experimentally. Acousto-ultrasonic parameters based on both predicted and measured responses are calculated, and tests are carried out using a commercially available instrument. The factors which lead to the poor reproducibility of acousto-ultrasonic results are discussed and possible improvements to the technique are proposed.
- Lamb waves