Single sided inspection of composite materials using air coupled ultrasound

A single sided, air coupled ultrasonic NDT system based on the generation and reception of the a(0) Lamb mode is described. 1-3 composite ultrasonic transducers are employed, transmitting and receiving transducers being oriented at the appropriate coincidence angle for the generation and detection of the mode; they are placed close together and scanned over the surface of the plate to produce a 'C-scan' image. Tests have been carried out on carbon fiber composite plates with delamination defects, the damaged areas being readily detected. The measurements have also been compared with numerical predictions based on a finite element model, good agreement being obtained.