自己センシングTDR法を用いたCFRP平板の損傷モニタリング

概要

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CFRP laminated structures are applied to many aerospace structures. Although the CFRP laminates have high specific strength and specific stiffness, an impact load easily creates damage of the CFRP laminates such as delamination cracking, matrix cracking and fiber breakages. The damages of the laminated CFRP are usually difficult to be detected by visual inspections. This requires a damage monitoring system for large laminated CFRP structures. Many researchers have already proposed self-sensing monitoring system using electrical resistance changes of the laminated CFRP. The method, however, requires a lot of electrodes. In the present study, Time Domain Reflectometry method is adopted using the reinforcement carbon fibers as sensors. The new self-sensing TDR method uses an electrical pulse signal and observes the reflected signal. The method is applied to a long CFRP strip plate specimen of 2 m length and an ideal damage of mechanical notch is detected from the reflected pulse signal. Effect of the orthotropic conductance of CFRP plate is experimentally investigated here using multiple electrodes. As a result, the effect of the orthotropic conductance is shown to be negligible.