Of all the twisted fibrous structures for industrial applications, ropes are probably the most complex in terms of structural compositions and application scenarios. Because ropes contain all forms of
PROPERTIES OF TWISTED STRUCTURES. II 611
Figure 1 A rope structure.
industrial twisted structures, in this article, they will be dealt with principally.
Materials Marine ropes are composed of millions of individ-
ual fibers twisted and combined into many levels of substructures such as yarn, plied yarn, rope yarn, and strand (Fig. 1). The levels of structure are dependent on the complexity of the rope geometry. However, in principle, at least three levels can be identified, i.e., fiber, yarn, and strand.
In natural fibers, manila and cotton are common materials for rope, and in synthetic materials, nylon, polyester, polypropylene, and recently, Aramid (Kevlart) fibers are all good candidates as rope-making fibers.
the concentric cylinders, so that its distance from the yarn axis remains constant. A fiber at the center will follow the straight line of the yarn axis; but, going out from the center, the helix angle gradually increases, since the number of turns of twist per unit length remains constant in all the layers. The density of packing of fibers in the yarn remains constant throughout the model; and the structure is assumed to be made of purposes lies in the requirement in durability, load-carrying capacity, and other physical, chemical, or service-related properties. Another distinction is that the majority of modern industrial yarns are often made of filament instead of staple fibers.
The mechanics of twisted fibrous structures is such a classic topic in textile science that there have been several books or monographs devoted to it.
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It is therefore not our purpose to provide all the detailed treatment on related topics. Rather, we list the major important issues and contributors in the area, the current status of the fields, and more importantly, stress, whenever possible, the issues or problems that have yet to be solved.