Testing of delamination in multidirectional carbon fiber reinforced polymer laminates using the vertical eddy current method

This paper studies the testing of delamination in multidirectional carbon fiber reinforced polymer using the vertical eddy current (EC) method. Conditions for producing the EC component perpendicular to the sample surface are investigated. A bridge-type probe including coplanar dual rectangular coils placed perpendicular to the test sample is designed to generate vertical EC component. Where there is delamination that is parallel to the sample surface, the vertical EC is perturbed, which results in an output signal in form of variable differential voltage of the coils. The principle of testing is verified by finite element analysis. Experiments are performed to test the validity of the proposed probe. The results of simulation and experiments show that peaks appear in output signal when the coils cross delamination and the distance between the two peaks of scanning signal can be used to quantitatively estimate the range of delamination.