FEM-aided Identification of Gage Factors of Unidirectional CFRP by Multipoint Potential Measurement

概要

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Carbon fiber reinforced plastic (CFRP) has electrical conductivity both in parallel and transverse direction of fiber. Since the electrical network may be changed with applied strain, the electrical conductivity of the CFRP would also be changed for the piezoresistivity. Strain monitoring of CFRP, therefore, can be performed without any additional sensor but by measuring the electrical resistance change. There has been many studies on the gage factors of unidirectional CFRPs, although significant mutual differences were found out in the results reported. It is considered that the differences may be caused by the strong electrical anisotropy and inhomogenity of the unidirectional CFRP. In this study, a new concept was introduced to measure the gage factors of a unidirectional CFRP precisely. Finite element analysis was utilized to take into considered non-uniform electrical potential field in the unidirectional CFRP. The gage factors were obtained as a result of minimizing the error sum of squares of electrical potentials between experimental and analytical results. Gage factor in fiber direction was affected by that in thickness direction depending on the specimen configuration. FEM analysis showed the possibility that the unidirectional CFRP may show both positive and negative gage factor in fiber direction.