Mapping of Impact Damage in Composite Materials Using Differential ECT Probe

Composite materials such as carbon fiber reinforced plastic (CFRP) have combined advantages of high strength and very low weight. There has been an increasing interest in the use of composite materials in the aerospace and automobile industries significantly. The industrial components made from CFRP, have to be tested for quality evaluation after manufacturing and inspection during the operation of structure to increase the lifetime of the component. In the present study a differential eddy current testing (ECT) probe has been developed and proposed for the detection of impact defects in the CFRP test specimen. Three different impact defects were made on the specimen in order to test the detectability of the differential probe. The probe consists of one rectangular shaped excitation coil and two detection coils that are connected in series opposite configuration to get the differential induced voltage. The probe was fixed to an automatic x-y scanning system which is controlled by Mat-Lab software program and obtained the image of the impact defect in the scanning area by acquiring the amplitude of the differential voltage from the probe. The experimental results show a clear indication of three defects with significantly distinguishable change in the detected probe response for different defects made with different impact energies in the CFRP test specimen.