Damage Monitoring of CFRP Plate Using Self-Sensing TDR Method

Laminated CFRP structures are applied to many aerospace structures. Although CFRP laminates have high specific strength and specific stiffness, an impact load easily creates damage such as delamination cracking, matrix cracking, and fiber breakage. Damage to laminated CFRP is usually difficult to detect by visual inspection. As a result, damage monitoring systems are required for large laminated CFRP structures. Many researchers have already proposed self-sensing monitoring systems which measure electrical resistance changes in the laminated CFRP. This method, however, requires a lot of electrodes. In the present study, a new time domain reflectometry (TDR) method using an electrical pulse signal and reinforcement carbon fiber sensors is adopted as a monitoring method. The method is applied to a 2-m long CFRP strip plate specimen to detect an ideal damage mechanical notch using a reflected pulse signal. In addition, the effect of the orthotropic conductance of the CFRP plate is experimentally investigated using multiple electrodes, and is shown to be negligible.