Piezoelectric transducer arrangement for the inspection of large composite structures

The aim of the present work is to develop a system of smart devices that could be permanently attached on the surface of the composite structure and monitor the interaction of low-frequency Lamb waves with defects. A linear array of transmitters would generate a relatively uniform wavefront allowing the inspection of large areas with a limited number of sensors. The asymmetric A₀ Lamb mode is generated in carbon fibre reinforced plastic (CFRP) quasi-isotropic laminates using an array of thin piezoceramic transmitters operating in-phase. In this paper, the effect of damage size on the propagation of Lamb waves is presented. Experimental verification is also presented in multidirectional CFRP composite panels. Critical size impact damage is detected. Finally, the technique is applied to a stiffened panel. Damage on the skin or flange is detectable while damage on the web or cap is not detected with the current experimental set up.