炭素繊維強化積層複合材中のき裂検出法に関する研究 (第2報)

電流による発熱を用いたCFRP材中の欠陥の検出

抄録

A method for detecting flaws and local fiber concentrations in CFRP composites by using Joule effect is presented. The method involves passing an electric current through CFRP specimen and to probe the surface distribution of temperature for irregularities. The current path is disturbed due to the presence of any discontinuities and the steep gradient of electrical potential is produced in their neighborhood. Then the Joule heat is generated and the temperature becomes different from that of the far-field. Therefore, defects can be detected by evaluating irregularities in surface temperature distribution in the current carrying specimen. The closed form solution of the Joule heat generation around an elliptic hole in an infinite plate with orthotropy has been obtained utilizing complex variable method. It is shown that the anisotropy of the material brings about the considerable change in the generation of Joule heat around the hole. Finite element analysis procedures have also been for mulated to obtain the transient temperature responses of rectangular orthotropic plates containing various kinds of defects. A simple experimental verification has been done using cholesteric liquid crystals. The results compare very fabourably with both the analytical solutions and numerical ones. The present technique provides a useful method for detecting flaw-type defects, local fiber concentrations and the fiber directions.