VOLUMETRIC FULL-MATRIX ULTRASONIC IMAGING OF ANISOTROPIC CFRP LAMINATES WITH ADAPTIVE TOTAL FOCUSING METHOD

The anisotropy of Carbon fiber reinforced plastics (CFRP) arising from the laminated structure presents a formidable challenge in ultrasonic imaging of internal defects. The adaptive total focusing method (TFM) based on anisotropic correction has shown its capability on the improvement of imaging resolution contrast for CFRP laminates. However, the previous studies were mainly demonstrated for two-dimensional (2D) ultrasonic imaging using a linear phased array, which greatly hamper the efficiency and information content for nondestructive evaluation of CFRPs, particularly for the components large in size. In this work, a volumetric TFM imaging method is proposed for anisotropic CFRP laminates using a 2D phased array. Based on the acquired full-matrix data, four elastic constants can be derived, through which the formula of group velocity of quasi-pressure (QP) wave is used to obtain the profiles in arbitrary planes. Thereafter, the time delays between the transmitter and receiver pairs for TFM can be corrected in three dimensions for volumetric imaging. For proof-of-concept demonstration, a [-45/0/45/90](10s) CFRP specimen with a round delamination defect is inspected and the volumetric results show better image improved image quality than paintbrush method's results. This research may provide a three-dimensional (3D) quantitative approach for CFRP laminates.