Delamination detection in composite laminates from variations of their modal characteristics

As a first step in developing a health monitoring system, the effect of delamination on the modal frequencies of laminated composite beams has been investigated. A piezoceramic patch driven with a linear rapid frequency sweep was used to induce vibrations on the structure and its response registered via piezoelectric film sensors. Modal frequencies were obtained by applying concepts of a novel method known as resonant ultrasound spectroscopy. Changes of the modal frequencies after delamination initiation, compared to those of a non-delaminated specimen, gave a good indication of the degree of damage, demonstrating the feasibility of using measured changes in the vibration characteristics to detect damage.