Electromechanical analysis of CFRP for real-time structural self-sensing and non-destructive evaluation

Carbon fiber (CF) holds structural self-sensing capability using its electrical resistance so that electromechanical behavior of carbon fiber reinforced plastic (CFRP) was investigated for using CF and carbon-glass hybrid fiber (CGHF). CGHF contains CF in either warp or weft, whereas glass fiber is perpendicularly woven in the other. Electrical resistance of CF monofilament whose diameter is 8 μm was increased when tensile strain was applied in fiber direction, which is called piezoresistive effect. When CF is gathered into a bundle, similar piezoresistive effect was observed. Moreover, distance change between the adjacent CF also led to the resistance change, because the number of electrical contacts can be differed with respect to the tow gap. We call this phenomenon “inter-tow interaction.” Another discriminative electromechanical contact is “inter-ply interaction” which has electromechanical contact between adjacent plies. Likewise, several electromechanical factors hold structural self-sensing capability. Therefore, real-time non-destructive evaluation (NDE) and structural health monitoring (SHM) can be realized with carbon fiber. The CF for the self-sensing can be constituted in various forms in a polymer matrix such as a plain-woven fabric, a uni-directional fabric and a grid. The self-sensing CF grid can be a compromised arrangement between the sensing performance and the material cost. In addition, the self-sensing algorithms of CFs can be comprehended by electrically equivalent circuit models. Reversely, the sensor design can be aided by the equivalent model which contains the aforementioned interactions.