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TWIST AND FIBER PACKING IN YARNS: Yarn structure can be described in a simple idealized form is the packing of fibers in yarns. Schwarz has theorized that the packing of circular fibers can be described by two basic forms; I) Open packing and   2) Hexagonal close packing. OPEN PACKING: In this form the fibers lie in layers between successive concentric circles, as shown in figure below. In this assembly, the first layer is a single core fiber around which six fibers. arranged so that the fibers first touch the circle that circumscribes the second layer. Additional layers are added between the successive circumscribing circles. The number of fibers in each layer and the total number of fibers in an ideally packed open structure are given in table below: CONCENTRATING FACTORS: 1)       One of the concentrating features is the general tendency of the fibers to follow the path of minimum energy. In addition, they tend to settle down and co...

yarn geometry has been discussed by Schwarz and later by Woods and Treloar. Schwarz argued that in the measurement of yarn diameter, the value obtained corresponds to the diameter of the circle (d), which circumscribes the outer layer of fibers as shown in image. But in the measurement of twist angle (by a microscopy technique), it is the edges of the fibers in the outer layer that are observed. Therefore, the effective twist angle measurement is made at a diameter represented by the cylinder containing the centers of fibers in the outer layers. The modified equation (B) then becomes:                      tan α     = π (d -   d’ / h)/ h   ……………………………………….( 8)                                 ...

The translation of the physical properties of textile fibers into textile structures, such as yarns and fabrics is a function of both the fiber properties and the geometric configuration they assume in the ultimate end product. Earlier studies of the relationship between yarn structure and properties have been along empirical or semi-empirical lines. However, many technologists who are concerned with the evaluation of the physical properties of textile structures have realized that these relationships are governed by same physical and engineering concepts as those e\used so successfully in the characterization of more classic structural materials such as steel and concrete. Hearle and Backer have given an excellent account of the progressive development of the ideas in this field of study. Nevertheless, it is considered appropriate to consider some basic concepts that are relevant to the study of yarn structure and properties. One such aspect is the understanding of the geometry of t...