Analysis of data processing methods for pulsed thermal imaging characterisation of delaminations

Pulsed thermal imaging is a commonly used infrared thermal imaging technology for non-destructive evaluation of engineering materials. It provides a complete interrogation and, therefore, a potentially complete quantification of the thermal properties and structures of a test material. The quantity and quality of material parameters that can be extracted depend mostly on the data processing methods. Although thermal property measurement is one important area for thermal imaging, this study is focused on the methods used mainly for subsurface flaw detections, including pulsed phase thermography, principal component thermography, derivative and a recently developed thermal tomography method. The characteristics of these methods were analysed and compared based on theoretical solutions and experimental data from a ceramic matrix composite plate with simulated delaminations. It was identified that although all methods have similar detection sensitivity and accuracy for delamination characterisation, there is a clear advantage in the interpretation of detailed flaw configurations when using spatially-resolved three-dimensional (3D) results from thermal tomography.