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An Eddy-Current Model for Three-Dimensional Nondestructive Evaluation of Advanced Composites
Final rept. 28 Nov 1984-28 Jul 1985
SABBAGH ASSOCIATES INC BLOOMINGTON IN
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The research problem is to develop a model and an inversion algorithm suitable for the three-dimensional quantitative nondestructive evaluation NDE of advanced composite materials by using eddy currents. The technical objectives are to determine the feasibility of using multifrequencies for this job, to determine in localized regions the fiber-resin ratio in graphite epoxy, and to determine more precisely the types of anomalies, whether flaws, delaminations, broken fibers, etc., that can be reconstructed by the inversion method. These objectives are met by 1 applying rigorous electromagnetic theory to determine a Greens function for a slab of anisotropic composite material, 2 determining the integral relations for the direct and inverse problems using the Greens function just derived, 3 determining suitable numerical algorithms for solving the inverse problem, and 4 writing a computer program to execute the model. These objectives have been met in addition we illustrate some interesting electromagnetic phenomena in composite materials.
APPROVED FOR PUBLIC RELEASE