Quantifying effects of manufacturing methods on fiber orientation in unidirectional composites using structure tensor analysis

Important properties of fiber-reinforced composites, such stiffness, compression strength, and fatigue resistance, are sensitive to fiber alignment. In this paper, we use structure tensor analysis on CT images to characterize the fiber orientations in three samples of unidirectional fiber-reinforced composites: pultruded carbon, pre-preg carbon, and non-crimp glass fiber fabric. Our results show that the fibers in the pultruded sample are more aligned than fibers in the two other samples. Through local quantitative analysis, we show that misalignment of the individual pre-preg layers contributes to the overall fiber misalignment in the material. For the non-crimp composite, we show that both the stitching of the unidirectional bundles and the backing bundles affect the fiber alignment in unidirectional bundles. Quantifying the misalignment caused by these effects allows manufacturers to tune production parameters, such as stitching thread tension, to minimize the misalignment of the fibers. All our notebooks, code, and data are available online.