Detection of delamination in laminated CFRP composites using eddy current testing: Simulation and experimental study

The applicability of conventional eddy current (EC) testing to detect delamination in laminates of carbon fiber reinforced polymers (CFRP) was assessed. As delamination impedes the induced currents flowing across the layers, the EC technique offers the potential for delamination in CFRPs to be detected by sensing the change in probe output signals caused by distortions in the magnetic field. In a numerical study, ECs distribution in CFRPs alters considerably in multidirectional and cross-ply laminates and currents drop steeply when delamination is present. In experiments, the detectability of delamination at different depths was investigated using 24-layer laminates, each with different stacking sequences. The change in amplitude of the probe output signal obtained from data agrees qualitatively with the numerical analysis. The size and location of the delamination defect were compared with those obtained in ultrasonic scanning images. Experiments show that delamination at a maximum depth of 0.75 mm in cross-ply samples could be detected, whereas subsurface defects in the unidirectional plate went undetected.