Delamination detection in glass-epoxy composites using step-phase thermography (SPT)

Inspection of Glass/epoxy composite using infrared has always been a challenge. This paper presents the use of step heating thermography to increase the maximum detectable defect depth. Fourier transform is applied to step heating data to obtain phase images. These images use to quantitatively characterize defect depth and dimensions in composites. Desired parameters of step heating test such as time step and heating rate are obtained from finite element modeling of composites. This model provides an estimation of defect depth thermal resistance from early time surface temperature. Therefore, it is possible to predict the best frame in an infrared video. Experimental results show the improvement of defect detectability by step heating thermography.