Eddy current microscopy applied to graphite-epoxy composite

This work proposes the utilization of the phase information from the response signal of an eddy current transducer with orthogonal coils in order to get an enlarged image of carbon fibers from a graphite-epoxy composite type [-45(2)(0), +45(2)(0)](S) and [-45(2)(0),0(2)(0) + 45(2)(0)](S) consisting of 24 fiber layers. A 2D Fourier transform was then applied to the phase signal, which is propagated backward by means of an operator that represents the solution of a Helmholtz equation. The image can be focused on a fiber layer choosing an adequate phase multiplication constant. With the view to obtain a clear-cut fiber contour, a Canning optimal regularizing algorithm was used. By choosing another phase multiplication constant the image can be focused on another fiber layer (C) 2001 Elsevier Science B.V. ALI rights reserved.