Detecting water ingress in aviation honeycomb panels: Qualitative and quantitative aspects

We have used infrared thermography to study water trapped in aviation honeycomb panels, namely: 1) possibility of quantitative evaluation of trapped water, 2) influence of honeycomb panel orientation on the efficiency of water detection, and 3) discrimination between honeycomb cells filled with water and adhesive. It is shown, both theoretically and experimentally, that it is difficult for TNDT to discriminate between the presence of water and epoxy trapped in honeycomb cells, by analyzing only the surface temperature patterns. It has been demonstrated that water trapped in honeycomb cells can be reliably detected by an increase in effusivity starting from the inflection time. This process is referred to as the "concept of apparent effusivity".