Detection of osmotic damages in GRP boat hulls

•Osmotic process in boat hulls has been briefly described.•Infrared thermography as a tool of non-destructive testing is used for evaluation and detection of osmotic process.•Three methods are addressed; Pulsed thermography, Fast Fourier Transform and Continuous Morlet Wavelet.•Additional image processing based on gradient approach is applied on all addressed methods.•It is shown that the Continuous Morlet Wavelet is the most appropriate method for detection of osmotic damage. Infrared thermography as a tool of non-destructive testing is method enabling visualization and estimation of structural anomalies and differences in structure’s topography. In presented paper problem of osmotic damage in submerged glass reinforced polymer structures is addressed. The osmotic damage can be detected by a simple humidity gauging, but for proper evaluation and estimation testing methods are restricted and hardly applicable. In this paper it is demonstrated that infrared thermography, based on estimation of heat wave propagation, can be used. Three methods are addressed; Pulsed thermography, Fast Fourier Transform and Continuous Morlet Wavelet. An additional image processing based on gradient approach is applied on all addressed methods. It is shown that the Continuous Morlet Wavelet is the most appropriate method for detection of osmotic damage.