Determining Mechanical Properties of Yarns and Two-Ply Cords from Single-Filament Data

Part I provided a detailed description of a model developed to predict the mechanical properties of yarns and cords from single-filament properties. The objective in Part II is to assess the accuracy of the model by comparing predicted results with experimental data. Multifilament PET yams were obtained from various manufacturing facilities. For all but one case, the bundles were formed into twisted yams and two-ply cords using laboratory- scale equipment. The model shows good agreement with experimental force-elongation data, although there is some deviation at higher twist levels. This discrepancy is likely due to slight non-uniformities present in the laboratory-produced yarns and cords. A cord with a high level of twist and uniformity produced at a manufacturing site demonstrates excellent agreement between model and experimental results. As an example of its predictive capabilities, the model calculates the elongation to break and tenacity at break within 5% of the experimental value for the vast majority of twisted yarns and cords studied.