Determination of the percentage of wrapper fibers in air-jet yarn by computed tomography cross-sections

Air-jet spun yarn is specific to its core and wrapper surface layer. The core comprises a roughly parallel bundle of fibers, while the cover is a ribbon of fibers twisted around the core (wrapper fibers). Regarding yarn structure, the percentage of wrapper fibers to core fibers significantly influences the yarn tenacity of air-jet spun yarns. This work aims to determine the percentage of wrapper fibers from a total number of fibers in an air-jet spun yarn computed tomography (CT) cross-section. It first obtains, through image arithmetic, information about the degree of fibers’ inclination and their position within the cross-section. The dependence of these two parameters defines a radius (a limiting radius) that imaginatively divides the yarn cross-section into a core section and a ribbon section. Finally, from a certain number of pairs of yarn cross-section images, it evaluates the percentage of wrapper fibers in the air-jet spun yarn surface ribbon. The correctness of the described approach is validated by assessing the ring-spun yarn using the same procedure as the air-jet spun yarn. This paper presents the whole procedure of processing the pairs of cross-section images, finding the optimal pairs of images for the implementation of image arithmetic, the segmentation of the monochromatic image, the measurement of the geometric parameters of the objects on the binary image, and the processing of the data by a specially prepared code in the MatLab environment. The methodology determines the average percentage of wrapper fibers of 100% Tencel 23 tex air-jet yarn to be 36.3%.