Ultrasonic Testing (UT) method is frequently used for non-destructive testing of aerospace structures and components. When inspecting structures made of composite materials, ultrasonic testing provides high-resolution C-Scan images which are used to locate and size defects. The -6 dB drop technique is often applied to the ultrasonic pulse-echo or through transmission C-Scan results in order to perform 2D defect sizing. For the case of ultrasonic testing of composite structures in through-transmission, defect sizing require selecting a reference area from the C-Scan image with relatively constant signal amplitudes and free of defects. However, selecting such a baseline reference is difficult to achieve due to the natural amplitude variation caused by the fiber matrix of composites as well as the presence of small indications or else.
Ultrasonic Testing (UT) method is frequently used for non-destructive testing of aerospace composite structures. Defect-Sizing in these structures using simple -6 dB amplitude drop technique is difficult to achieve.
When scanning a composite structure at a high frequency, the internal fiber matrix can be observed in the form of amplitude variation of the ultrasonic waves. The following example shows a 0-90° carbon fiber reinforced plate (CFRP) scanned using an ultrasonic gantry system in through-transmission setup where we can clearly see the fiber alignments.
