Multi-mode ultrasonic visualization of porosity in composites using a focused transducer with high sensitivity and near-surface resolution

Porosity ranging from 0.15% to 2.33% in carbon fiber-reinforced polymer composites (CFRPs) is detected and characterized by multi-mode visualizations including ultrasonic A-Scan, B-Scan, C-Scan and Tomography-Scan using a focused ultrasonic transducer. Three-dimensional visualizations are also reconstituted from the ultrasonic tomography scan images. The result shows: UT using the focused transducer possesses high sensitivity, near-surface resolution and depth estimation for porosity in composites. Using this transducer, multi-mode visualizations can characterize porosity feature and fiber orientations through the entire volume. The amplitude and transit time of A-Scan waveforms have correlations with porosity size and depth. B-Scan imaging characterizes porosity distribution with depth estimation up to one-ply thickness, which is approximate 0.18 mm. C-Scan imaging characterizes porosity size and distribution in the integral composite bulk. Tomography scan can give detailed information about porosity feature and fiber orientations ply by ply, with detection sensitivity of no more than 1.0 mm and excellent near-surface resolution of one ply.