Abstract
When an electromagnetic wave transmission line is constructed inside a material or structure, or a material or structure itself can be treated as a transmission line, damage or change in material properties may be detected using time-domain response of the line to a step input voltage signal. In this paper, we will present the results of experiments on two applications of this method as a health monitoring tool of composites. One is the detection of fiber breakage of CFRP. A microstrip line was constructed with a copper foil tape and the CFRP plate, and fiber breakage near the surface was successfully detected as a rise of the time-domain response at the corresponding position. The other is to add a damage-sensing function to an FRP repair patch that is being developed for repairing a damaged metal structure, such as aged aircraft structure. In this case, the metal under the patch and a carbon fiber strand in a carbon/glass fiber hybrid layer embedded in the patch could be treated as a microstrip line, and the model damage (slit) under the patch was successfully detected as a rise of the response at the corresponding position.
