Ultrasonic defect evaluation using DGS-diagrams modified for the inspection of anisotropic composite materials

The application of DGS-diagrams (Distance-Gain-Size) for defect sizing using ultrasonics is considered for anisotropic materials. Based on far-field formulations for transducers with circular apertures, it is shown that the general DGS-diagram for isotropic materials can be applied to anisotropic media as well, if some modifications in the evaluation are performed. The modified procedure is illustrated and validated using ultrasonic inspection data acquired at a unidirectionally carbon-fiber reinforced composite test block with flat-bottomed holes as model defects.