In this chapter, we define some important terms and parameters that are commonly used with fibers and fibrous products, such as yarns, fabrics, etc., and then go on to describe some general features of fibers and some important products thereof. These definitions, parameters, and features serve to characterize a variety of fibers and products made therefrom. Thus, we exclude items such as fiber reinforced composites wherein fibers are added to a matrix. It is worth emphasizing that these definitions and features are generally independent of fiber type, i.e. polymeric, metallic, glass or ceramic fibers. They depend on the geometry rather than any material characteristics.

Fiber is the fundamental unit in making textile yarns and fabrics. Fibers can be naturally occurring or synthetic, i.e. manmade. There are many natural fibers, mostly organic but also some inorganic. Examples of natural organic fibers include cotton, jute, sisal, silk, wool, etc. while inorganic fibers occurring in nature include asbestos, wollastonite, and basalt. There is a much larger variety of synthetic fibers available commercially. Polymer fibers such as polypropylene (PP), polyethylene (PE), polyamide (PA), polyethylene terephthalate (PET), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), aramid, etc. are well established, commercially available, synthetic fibers. Metallic wires or filaments have been available for a long time. Examples include steel, aluminum, copper, tungsten, molybdenum, gold, silver, etc. Among ceramic and glass fibers, glass fiber for polymer reinforcement became available early in the twentieth century; optical glass fiber for telecommunication purposes made its debut in the 1950s, while ceramic fibers such as carbon, silicon carbide, alumina, etc. became available from the 1960s onward. We shall describe these fibers separately, in detail, later in this book.

One can transform practically any material, polymer, metal, or ceramic, into a fibrous form. As we pointed out in Chapter 1, historically and traditionally, fibers formed part of the textile industry domain for uses such as clothing, upholstery and draperies, sacks, ropes, cords, sails, and containers, etc. Gradually, their use entered the realm of more engineered items such as conveyor belts, drive belts, geotextiles, etc. With the advent of high modulus fibers, the use of fibers has extended to highly engineered materials such as composites.

Understandably, therefore, some of the terms commonly used with fibers have their origin in terminology derived from the textile industry. We examine some of this terminology next.