Some important attributes of fibers

Rope represents a very useful form of fibrous product. A rope or cord consists of a bundle of fibers. The fibers may be continuous or they may be made of staple fibers, i.e. short, fine fibers. The tensile strength of a rope comes from the strength of individual fibers and the friction between them. The interliber friction prevents their slip past one another. Quite obviously, a rope or a cord has very anisotropic properties. It is strong in tension along the axis direction but not in the transverse or radial direction. Strength in compression is also very poor. 

A material in fibrous form has a series of attributes characteristic of its fibrous state. Some of these are obvious, e.g. the properties of a fiber are highly biased in the fiber direction, while others are not so obvious. Some of these characteristics stem mainly from their small cross-section and large aspect ratio, for example  

These characteristics of fibers lead to some unique features which must be considered in any product that uses fibrous materials. In this section, we describe some of these features that stem from its fibrous nature. 

We can readily obtain some simple geometric relationships. For example, fiber length per unit weight or volume. We can write fiber volume v as 

Similarly, if we consider the mass of the fiber, m, rather than its volume, we can write 

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We first define some terms commonly used in the field of fibrous materials. We should add that some of these definitions are expanded upon later in this chapter. However, before one can define the term fiber, one needs to define the most important attribute of the fiber that serves to define a fiber, namely the fiber aspect ratio. The aspect ratio of a fiber is the ratio of its length to diameter (or thickness). A fiber can be defined as an elongated material having a more or less uniform diameter or thickness less than 250 p,m and an aspect ratio greater than 100. This is an operational definition of fiber. It is also a purely geometrical one in that it applies to any material. Having defined the basic unit, the fiber, we are now in a position to define some other commonly used terms related to fibers. These are given below in alphabetical order ... 

Flexibility of a fiber, i.e. its ability to be bent to an arbitrary radius is one of the important attributes of a fibrous material and worth discussing in some detail. It is easy to visualize that many operations such as weaving, braiding, winding, etc., depend on the ability of a fiber to be bent without breaking. This flexibility is also of great importance in composites because it permits a variety of techniques to be employed for making composites with these fibers. If we treat the fiber as an elastic beam of circular cross-section, then we can easily see that the fiber flexibility corresponds to the ability of the elastic beam to be bent to an... 

Many simple physical attributes of fibers can be quite important. We describe some of these attributes and the methods used to measure them. 

The density of fibers is a very important attribute. We mentioned above the use of linear density or mass per unit length. That term is really suitable for giving m idea of the fiber size. Bulk density or mass per unit volume tells us how heavy a material is. Bulk density values of some important fibers are given in Table 2.2. The reader can easily verify that if we divide the linear density of a fiber by its... 

The HWM staple fibers have essentially all of the best attributes of regular rayon except for a few important differences. They swell less in water, are somewhat stiffer due to higher cellulose DP (IV) and orientation, and are almost twice as strong and resist dimensional change. Fabrics made from HWM fibers can be dyed and later finished (cross-linked) by much the same techniques as those used for cotton fabrics. In 50-50 blends of polyester and HWM rayon, fabrics can be made that are virtually indistinguishable from some cotton counterparts [282]. 

The composition of avocado, in tenns of macronutrients, has been widely studied and is compiled in different tables of food composition. According to the United States Department of Agriculture (USDA) National Nutrient Database for Standard Reference [83], 100 g of avocado are an important source of energy (160 kcal) and contain 73.23 g of water, 2 g of proteins, 14.66 g of total fat (67% monounsaturated, 12% polyunsaturated, and 14% saturated fatty acids), and 8.53 g of carbohydrates, of which 6.70 g are total dietary fiber and 0.66 g are sugars. As it can be seen, one of the main components of avocado is the fat, and thus it is not surprising that it is also known as butter fruit. Besides, some of the principal health benefits of avocado have been attributed to its high monounsaturated fatty acid content. These facts make lipids one of the most studied families of compounds in avocado. 

There are several aspects of diabetic dietary management which have not been covered in this chapter salt intake and the effect of carbohydrate and fiber on blood coagulation, minerals, and trace elements are examples. It is important to remember that a benefit from change in diet can be offset by other unforeseen effects. There are, however, no known detrimental effects attributable to the consumption of mixed Western diets rich in complex carbohydrate and fiber. The optimum proportion of calories to be taken as carbohydrate remains open to question. The British Diabetic Association has suggested 50-55%, and some studies have shown benefit when even greater quantities of carbohydrate have been used. For practical purposes, a 50% proportion seems a sensible aim, but it must be remembered that while this figure represents a considerable increase for most diabetics, all the studies cited in this chapter have involved a higher proportion of calories from carbohydrate. 

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