Automated Characterization of the Ply Stacking Sequence of a Woven Carbon Fiber Composite Using Pulse-Echo Ultrasound

Abstract

Carbon fiber composites are a popular design material due to their high specific strength. The directional strength of woven composites can be customized by changing the orientation and sequencing of individual lamina within the ply stack. This allows for the potential of specialized parts designed for specific applications, leading to both performance gains and weight savings. One challenge is the ability to characterize non-destructively the orientations of the individual lamina after the manufacturing process. Current industrial methods used to verify the ply stack are destructive to the part, increasing costs and material waste. This creates the need for a non-destructive technique capable of determining the ply stack, both for quality control and for in-service parts, including when there may be access to just a single side of the composite. This research introduces a procedure to scan a fabricated laminated composite using pulse-echo ultrasound coupled with an automated algorithm to determine the layer-by-layer orientation of the ply stack with a specific focus on woven composites. In this work, 12 unique plain-weave laminates ranging from 3 lamina to 18 lamina thick are studied. The orientations of each stacking sequence are different, with some following standard composite design methodologies and others randomly stacked. The mathematical technique presented in this work correctly characterizes non-destructively the orientation of each individual lamina to within 1° with 73% confidence and to within 3° with 98.3% confidence of the as-manufactured orientation.