Identification of delamination defect in laminated composites by passive electric potential CT method

Abstract

This chapter describes the feasibility of passive electric potential Computed Tomography (CT) method which does not require electric current application for detection of damage in laminated composites. In this method, piezoelectric film is glued on the surface of composites as a sensor. Electric potential values on the piezoelectric film change because of the strain distribution on the composite, when the composite is subjected to external load. The strain distribution of the cracked body shows a characteristic electric potential distribution. Therefore, passively observed electric potential values on piezoelectric film can be used for defecting identification. This method may be applied to develop an intelligent structure with a function of self-monitoring of flaws and defects. An inverse method based on the least residual method is applied to the defect identification from the electric potential distribution. In this inverse method, square sum of the residuals are evaluated between the measured electric potential distributions and those computed by using the finite element method. Numerical simulations are carried out on the estimation of the location and size of delamination defect in composites. It is found that the location, size, and depth of the defect can be quantitatively identified by the passive electric potential CT method.