전압강하 특성 분석을 통한 탄소섬유의 손상 감지

Abstract

The electrical properties of conductive fibers can be utilized in various fields such as composite materials that require structural health monitoring, and also the special clothes for damage detection. In this study, the characteristics of voltage drop in carbon fibers to detect the level of damage were analyzed, and then the location of fiber damage with area could be perceived based on the results. The two unidirectional carbon fibers, namely NR73 and CF730 from Korea Carbon Co., Ltd, were used as specimens in fiber cutting test for the analysis of voltage drop resulting from the damage, and a Multi ADC output instrument was used for the measurement of the dropped voltage with electrodes arranged perpendicular to the fiber orientation. As a result of experiment, the voltage drop was identified by the short current in fiber direction followed by the flowing in the transverse direction with large contact resistance, and thus the damage position together with range could be detected. Meanwhile, the impact drop test using sharp and blunt instruments was performed for the comparative analysis of failure characteristics caused by the difference of damage cause. Three plies with different fiber orientations were laminated in a specimen and the voltage drop after damage was measured by arranging electrodes on each ply. The damage center was set as a point where the voltage drop was the highest in each ply and the damage boundary consists of the coordinates of the electrode where the voltage drop exceeding the threshold value. As a result, the agreement between the damage center point and the damage radius was confirmed within 10% error comparing with the actual damage location and radius. As a compaction with lightweight becomes available, the damage detection method by using the voltage drop of the carbon fiber proposed in this study therefore may be applied to detecting the damage of the portable equipment in real time.