Infrared Thermography to Study Damage During Static and Cyclic Loading of Composites

The anisotropy and heterogeneity of composites influence unavoidably the mechanical response of the material to external excitation and the failure mechanisms. As an effect, the mechanical behaviour assessment of composites by means of experimental techniques requires to pay attention to the influence of the specific layup of laminae, viscous properties of the matrix, pattern described by the yarns or fibers. It follows that specific quantitative and qualitative analysis are required for the data processing. The study of thermal signal can be a successful strategy to assess and to understand the damage processes. In effect, if compared to other experimental techniques, it allows a localised analysis of the material degradation in terms of stiffness reduction or damage progression (transverse cracks or delamination). The present research is aimed at providing innovative methods and algorithms for processing the thermal signal of a composite obtained by Automated Fiber Placement process, in order to determine when and where damage occurred during static and cyclic loading in terms of transverse crack number.