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ABSTRACT
A theoretical approach is adopted in this paper based on the existing literature in order to present an explicit relationship between the strengths of fibers and yarns. This provides a relatively simple method for quick estimation of staple yarn strength, while avoiding some limitations of an empirical method. The CV values of the strengths are given as well. The effects of important factors such as fiber variation, fiber length and thickness, yarn twist, and yarn packing density are considered, and some are discussed in detail. The results are verified by previously published data.
A fundamental and classical problem in textile materials science is the connection between strengths of fibers and yarns, and so it is significant both in theory and in practice to establish this relationship.
A given large number of single fibers forms a fiber bundle, and with twist, the bundle becomes a yarn. How the fiber properties translate into yarn properties thus depends on, among other factors, the twist level.
Because of variations in fiber strength, the breaking stress of a parallel fiber bundle is smaller than that of its constituent fibers. On the other hand, predicting yarn strength is also different from predicting that of a parallel fiber bundle, because in the latter case, the effect of fiber interaction is negligible. Also, because fibers are all parallel to the axis of the fiber bundle (the loading direction), the fiber obliquity effect is nonexistent. Moreover, the strength prediction of a fibrous structure is unlike its modulus prediction, for the strength of a material is not a volume average quantity but rather an extremum quantity, dictated by the weakest cross section of the structure. This so-called weakest link theorem was first elucidated by Peirce [13] in 1926 and has since been investigated by several authors [8, 18]. The relationship between fiber strength and yarn strength has also been studied by numerous authors [5, 9, 12, 14-17, 20, 21].
In 1978, Harlow and Phoenix [6] proposed...