Comparative study on pulsed thermography and modulated thermography of composite honeycomb panels

To investigate the optimal infrared thermography testing technique and thermographic data processing methods for the flaw inspection of composite honeycomb panels, the defect detection capabilities of pulsed thermography(PT), modulated thermography(MT) and several thermographic data processing algorithms were compared. In PT, pulsed phase thermography(PPT) was applied to the thermographic signal processing, and compared with the best raw image. In MT, discrete Fourier series(DFS) and correlation coefficient(CC) algorithm were newly proposed to process the experimental data, and compared with the classical Four-point method. The obtained results indicate that, MT is better than PT for debonding inspection of honeycomb panels. The effects of both DFS and CC are better than Four-point method for signal processing of MT. At the best modulation frequency, the MT-DFS method shows the maximum detection capability for debondings in honeycomb panels.