Abstract:

The explanation of strength enhancement effect of ply yarns has still remain in the qualitative description. As the two main elment forming yarn strength, fiber properties and yarn structure, their contribution to the total strength is unclear. To quan-tify these two parts, this paper firstly established a two-ply yarn model with its geometric configuration, then analyzed the effect of axial and radial tensile behavior on a short yarn segment under tensile loads, reflected in the relationship among tensile modulus, single yarn parameters and ply yarn twist angle. And we took cohesion force between single yarns into consideration as part of ply yarn strength, the formula is derived to predict ply yarn strength in the case of no single yarn slippage. Then, the effect of single yarn properties and twist level on ply yarn maximum strength is analyzed in quantitative, the results of which conform to the general understanding, and can be used to predict the strength of new yarn productions.

Key words: two-ply yarn, model, twist angle, cohesion force, tensile strength