Thermographic Evaluation of Aircraft Composite Materials

Lockin thermography is used by RSAF and other aircraft companies. It involves actively applying sinusoidal thermographic waves to the specimen and observing phase and amplitude changes at the specimen surface in order to evaluate structural information below the surface. Experiments were performed to evaluate defect characteristics such as depth, size and shape. The specimen contained very wide range of delamination defect sizes and depths. Finite Element and theoretical models, which included convection current considerations, were developed and will be presented. These showed good correlation with the experimental results. These models enable optimum frequencies and avoidance of blind frequencies to be predicted.