Nondestructive testing electromagnetic methods

EDDY CURRENT TESTING - An electromagnetic nondestructive testing method in which eddy-current flow is induced in the test object. Changes in flow caused by variations in the object are deflected into a nearby coil or coils where they are measured. 

Libby, H.L. Introduction to Electromagnetic Nondestructive Test Methods, John Wiley Sons, New York ( 1971). 

Many polymers and most PMC show no or only comparatively low electrical conductivity, which limits application of electromagnetic test methods. One of the main exceptions is CFRP. The continuous network of carbon fibers in CFRP allows for electrical resistance measurements, eg, based on the four-probe method. Electrical potential (101) or resistance methods are used in fracture mechanics to detect delaminations (102) and to monitor damage in CFRP (103). Whether the application of electrodes is nondestructive depends on the intended use. 

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