Thermographic non-destructive testing using inductive thermal excitation

This paper describes the utilization of induced radio frequency thermal excitation in conjunction with infrared (IR) imaging for the detection of discontinuities in embedded metal conductive mesh on composite structure. An electric current is inductively generated in the conductive media of the composite using a radio frequency coil held above the surface. As the generated current moves through the composite structure, any perturbation in the current flow caused by discontinuities in the grid or highly resistive areas becomes heated slightly above the surrounding. This small temperature variation is detected in real-time by means of an IR imaging system that includes an IR camera, a computer, and imaging software. The data is depicted as a thermogram on the computer monitor, and can be analyzed using specialized system software. From the detected thermal variations, one can determine electrical conductivity characteristics of the conductive composite layer.