Quantitative Electromagnetic Modeling and NDE of Carbon-Carbon Composites
There is much need for investigating the use of eddy-current inspection with advanced composite materials, including graphite-epoxy and carbon-carbon. One of the problems in evaluating the performance of eddy-current inspection is that it is often difficult to characterize the conductivity of the fiber composite material. For example, when the material is composed of conducting fibers and a nonconducting matrix, as is the case with graphite-epoxy, the overall conductivity is a complicated quantity that depends on fiber conductivity, fiber density, fiber layup order (sample geometry), and the frequency at which the eddy-currents are being excited. Dependency on frequency and layup order, in particular, give the investigator much difficulty in interpreting any eddy-current data from experiments. If these two factors cause a weak effect, there may be a suitable range of frequencies for inspecting the material via application of somewhat standard techniques.