SINGLE-SIDED INSPECTION OF COMPOSITE-MATERIALS USING AIR COUPLED ULTRASOUND

A single sided, air coupled ultrasonic NDT system based on the generat ion and reception of the a(0) Lamb mode is described. 1-3 composite ul trasonic transducers are employed, transmitting and receiving transduc ers being oriented at the appropriate coincidence angle for the genera tion and detection of the mode; they are placed close together and sca nned over the surface of the plate to produce a 'C-scan' image. Tests have been carried out on carbon fiber composite plates with delaminati on 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.