Nondestructive Detection of In-Plane Wrinkles in Carbon Fiber Laminates Using Eddy Current and Ultrasonic Testing

Nondestructive detection of the in-plane wrinkles (sometimes termed marcelling in various industrial settings) of unidirectional carbon fiber reinforced plastic (CFRP) laminates is of interest in a wide variety of industries as the in-plane wrinkles significantly reduce the mechanical performance of the manufactured composite structure. In this work, a comparative study is presented to detect in-plane wrinkles on a 5 ply unidirectional CFRP laminate with a customized eddy current testing (ECT) and ultrasonic testing (UT) system. A manufacturing method to inducing controlled marcelling within a specified lamina is introduced, and fabricated components are then inspected using both ECT and UT. Data suggests that the results from the directionally biased ECT system effectively captures both the presence of an in-plane wrinkle and quantify the shape of the wrinkle, whereas the results from the ultrasonic inspection were not able to properly quantify the wrinkle extent. Using the anisotropic conductive property of CFRP, the eddy current system was able to clearly detect spatial variations in the local fiber orientation, waviness steepness angle, and waviness amplitude, three different parameters used to quantify the wrinkle impact on the structural performance.