Normalization and Processing of Rotational Eddy Current Scans for Layup Characterization of CFRP Laminates

Abstract

A method is presented using eigenvector-based principal component analysis (PCA) and signal decomposition to normalize rotational eddy current (EC) scans and determine the ply orientation layup up for carbon fiber reinformed plastic (CFRP) laminates. These unique rotational EC scans, herein termed “r-scans”, are formed by rotating a transmit-receive (TR) pair of high-frequency (15MHz) coils above the part and about an axis orthogonal to the part surface. The PCA normalization process standardizes the r-scan data for comparison and processing. Results are presented for a multi-laminate scan, and from its decomposition into a linear combination of shifted basis signals, the fiber orientations of the individual lamina are quantified throughout the part thickness.