Application of air – coupled ultrasonic technique for sizing of delamination type defect in multilayered materials

Abstract

In this article the measurement of the defect dimension by the air coupled ultrasonics is analysed. The method of the measurement through the air gap, the test sample geometry (aluminum plates and carbon fiber reinforced plastic (CFRP)), the experimental setup and obtained results are presented. Main attention is paid to the analysis of the accuracy of the determination of the defect shape and dimensions. The fluctuations of the signal amplitude in through transmission mode have been observed around the defect. The simulation by the finite difference method has been carried out to determine the origin of this phenomenon. The dimensions of the defect obtained by the ultrasonic measurements are compared with the results obtained by the optical microscope.