Inspection on CFRP sheet with subsurface defects using pulsed thermographic technique

•The pulsed thermographic technique was used to detect flat-bottomed hole defects in CFRP sheet.•PPT was used to extract the characteristic information of the thermal wave signal generated by thermal pulse.•The defects’ edges were extracted by Fuzzy C-Means clustering algorithm.

The pulsed thermographic technique was used to detect flat-bottomed hole defects in CFRP sheet. Pulsed phase thermography (PPT) was used to extract the characteristic information of the thermal wave signal generated by thermal pulse. The difference of the phases between the sound and defective areas were analyzed. The defects’ edges were extracted by Fuzzy C-Means clustering algorithm.