Theoretical modeling of the tensile behavior of low-twist staple yarns: Part I – theoretical model

Mechanics analysis of staple yarns provides an understanding of the yarn deformation and failure mechanisms. Work to date on the subject has mostly focused on the modulus and the strength rather than the progressive deformation mechanisms when a low-twist staple yarn is subjected to tensile loading. This paper presents a theoretical model to predict the entire load–extension response of low-twist staple yarns. The model is also used to study the response of such yarns when subjected to cyclic tensile loading. The work involves: (a) analyzing fiber end slippage effects due to fiber length discontinuities in a staple yarn and studying the stress distribution along the fiber under both tensile loading and unloading conditions; (b) conducting a fiber pull-out analysis to study the yarn post-peak response; and (c) predicting the entire load–extension curve of the yarn and the yarn response under cyclic tensile loading conditions.