A theoretical model for magnetic field mapping as a means of broken fiber detection in graphite epoxy composites

A technique for location of broken fibers by imaging magnetic fields generated from currents injected in the fibers is presented. It is concluded that the magnetic field pattern drops abruptly near the axis of a hole, or a break in fibers. The magnetic image of a hole gives contours with the shape of an ellipse. By measuring the semimajor and semiminor axis of image it is possible to determine the ratios of the conductivities. These ratios depend on feedthrough at sites where fibers of the different directions of the layup can make electrical contact with other fibers in adjacent layers. The effects of delaminations should alter these values.