Double active thermographic inspection of additive manufacturing composites: numerical modelling and validation

•Polymer-matrix composites (PMC) produced by Additive Manufacturing were inspected.•Active and Double Active Transient Thermography (ATT / DATT) were performed on PMC.•Composite finite element models were developed to simulate ATT and DATT.•Simulations results were validated taking the experiments results as reference. This study investigates the Non-Destructive Testing (NDT) inspection of 3D-printed fibre-reinforced polymers, comparing the conventional Active Transient Thermography (ATT) technique with a novel variant known as Double Active Transient Thermography (DATT). Finite element models for the simulation of both inspection techniques are validated by evaluating two statistical measures to correlate the numerical results with the experimental responses. The thermal contrast obtained with DATT was approximately twice the one obtained with ATT, for all tested samples. Numerical models allowed an insight evaluation of the heat dissipation along the thickness of the specimens, specifically around the fibres and the defects. These validated numerical models evidenced a relevant tool to predict the results of thermal contrast and to optimize the inspection parameters.