In this paper, a technique based on a new model from finite differences discretization of Fourier heat propagation in 3D, is presented in order to be applied on a sequence of infrared images to enhance contrast and automatically detect and characterize flaws in composite slabs.The performance of this technique is evaluated using artificial thermal sequences from a simulated CFRP slab generated by ThermoCalc6L software.Results show that this technique offers a better contrast between defect and background than other common techniques like modified differentiated absolute contrast, and it runs faster than the classic 3D thermal filtering method.