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Lockin thermography is a well-suited method for the characterization of structures made of both metal and fiber reinforced plastic. In most cases, only phase images are analyzed, although the amplitude images might contain useful information as well. Thus, systematic studies of lockin thermography are presented, assessing amplitude and phase images for the detection and quantification of defects in isotropic (steel) and anisotropic (carbon fiber reinforced plastic) materials. Characterized defects are flat bottom holes with different diameters and various remaining wall thicknesses as well as crossed notches at different depths. The excitation frequency was varied while keeping the number of analyzed excitation periods nearly constant for each material. The data analysis was focused on the detectability of the defects both in the amplitude and phase images, including the determination of the signal-to-noise ratio and of the spatial resolution. As a result, the limits of defect detectability and spatial resolution are given for each material.

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Standards for the application of flash thermography as well as of lock-in thermography are urgently required. Both methods are applied more and more often in research and industry, but still extensive validation procedures are required for each individual application. In this paper, the results of two research projects concerning the validation and standardisation of both methods are presented. This includes results of a detailed study of the influence of measurements parameters on flash thermography, of the comparison of the lateral resolution obtained with flash and lock-in thermography and the description of a draft standard for flash thermography.