A novel force-temperature model for evaluating internal forces in CFRP by means of infrared thermography

Carbon fibre reinforced polymer (CFRP) composites are commonly used in the aerospace industry due to their excellent mechanical properties. The extreme mechanical environments make CFRP to exceed its yield limit, which is associated with composite defects, such as delaminations and cracks. Therefore, it is important to develop a stable, non-contact and highly accurate stress measurement technique. In this work, a novel internal stress measurement technique is proposed being based on the elastic plate theory and thermal stress analysis. By analyzing the temperature distribution on the material external surface, one can evaluate composite mechanical behaviour and internal stresses. To validate the proposed novel method, the theoretical investigations, including numerical simulations and experiments, have been performed, and the experimental results were optoimized by applying the Levenberg-Marquardt. Theoretical and experimental results have been used to predict the force loaded on the sample surface. Furthermore, the effects of coating on the stress inversion problem have also been discussed.