Matched Filter-Based Post Processing Approach for Active Infrared Thermography for Nondestructive Testing and Evaluation of Carbon Fibre Reinforced Polymer Materials

Abstract

This article reports on the effectiveness of infrared thermography (IRT) in detecting blind holes of varying depth and diameter in carbon fiber reinforced polymer (CFRP) sample. It utilises halogen lamps as the heat source and implements three excitation techniques: pulse thermography (PT), lock-in thermography (LT) and frequency modulation thermal wave imaging (FMTWI); along with that, it compares two post-processing approaches, cross-correlation (CC) and frequency domain phase (FDP) on the obtained thermal images. The signal-to-noise ratio (SNR) is considered a figure of merit for evaluating the effectiveness of each technique and its associated post-processing approaches. The results demonstrate that the CC post-processing technique consistently outperforms the FDP method in enhancing defect visibility and improving SNR values across all excitation techniques and configurations. This research highlights the potential of IRT as a reliable, non-destructive testing method for detecting and characterising defects in a chosen CFRP test sample.