Endless fibers

One is shown in Fig. 4-5B. The hydrogen bonds and van der Waals forces bind the chains into sheets which are stacked to form fibers. A typical fiber of plant cellulose has a diameter of 3.5-4 nm and contains 30-40 parallel chains, each made up of 2000-10,000 glucose units. The chain ends probably overlap to form essentially endless fibers that can extend for great distances through the cell wall. They interact with other polysaccharides as is illustrated in Fig. 4-14. A single cotton... 

The fibers are produced continuously (endless fibers, filaments) or discontinuously (short or staple fibers) depending upon the application. Most of the fibers are obtained by extruding a flowable form (melt or solution) of appropriate chemieal composition (Section 5.2.3 - 5.2.4). Other processes are based on deposition from the gas phase (Section 5.2.6.2) or thermal transformation (pyrolysis) of organic (Section 5.2.5) or organometallic polymers (Section 5.2.7). 

Carbon fibers are commercially available us endless fiber-hanks with 1000 to 160 000 individual filaments. Carbon fibers are flexible and can be treated as textile fibers, due to the small fiber diameter of the individual fibers (ca. 8 pm). Therefore two-dimensional woven articles, knitted articles and felts are available in addition to yarn and thread. Staple fibers are formed by cutting or grinding endless fibers and are available in different lengths (0.5 to 50 mm). 

Carbon in the form of endless fibers is a relatively young industrial field, which has developed explosively since its introduction in the 1970 s. Whereas in the beginning it was predominantly utilized in the field of military aviation, its utilization in the fields of sports articles and civil aviation has since grown apace. The utilization of C-fibers in civil aviation increased on the 1980 s (I t C-fibers per Boeing 767). At the beginning of the 1990 s there was a decline in their use in military aviation, which was more than compensated by increases in the sports article field. In 1995 1200 t of C-fibers was utilized just for the shafts of golf-clubs. Table 5.2-13 shows the evolution in consumption of C-fibers in the different sectors for the period 1979 to 1995. 

Ceramic reinforcing fibers are utilized both in a continuous form (endless fibers) and in a discontinuous form (e.g. whiskers, short fibers). Most of the continuous fibers are utilized in the manufacture of composites with polymer matrices (PMC), where they are in competition with other high performance fibers (boron, carbon fibers), mainly for military or aerospace applications. Discontinuous fibers are generally used for the manufacture of metal matrix (MMC) and ceramic matrix (CMC) composites. 

Abstract. In the 60ties engineers started to combine short glass fibers with a concrete matrix. Today engineers combine endless fibers with the concrete matrix. Hence, the so called textile-reinforced concrete offers more and more opportunities to manufacture consumer goods like desks or chairs and to build face elements for houses and even load-bearing structures. This revolution is only feasible because a lot of research work has been done - into textile, into concrete, into the combination and the bonding. 

LFT-G are produced by means of pultrusion. In a variant of the pultrusion process, endless fibers are drawn through a thermoplastic melt then partially or completely impregnated, depending on the production process, by means of a mold. Fig. 35. In another variant, mixtures of glass filaments and polymer filaments are used for pultrusion, so-called hybrid fibers. 

Fibers can be worked into the plastic in various forms. An endless fiber of extreme length is called a filament, whereas one of short length is called a staple (see also Section 38.1). A compact bundle of filaments without twist is called a strand, a loose bundle of low twist is called a roving, and yarn is a bundle of fibers or filaments suitable for weaving. Fiber-like single crystals of... 

Regenerated cellulosic fibers are made out of cellulose from wood or cotton lint. The most used fibers are viscose, acetate, cupro (very small quantity), and lyocell. These fibers are produced in various titers as filament (endless fiber) or staple fiber. 

Short (or discontinuous) fibers are best prepared in a batch process, e.g., in a small cylindrical reaction chamber. The value of the technology, however, lies in its capability to facilitate the growth of continuous (potentially endless) fibers with a recently discovered automatic self-regulating growth mechanism [2], Finally, the diameter of the laser focus determines the diameter of fibers grown by laser assisted chemical vapor deposition, just as the diameter of the metal particles determines the diameter of the whiskers grown by metal catalyzed chemical vapor deposition. 

In order to close the gap between possible technical application of endless fiber reinforced composite material and the actual practice, limited by consolidation and forming processes, various joining techniques were adapted and developed for glass fiber reinforced PP (GF/PP). 

Blaurock, J. and Michaeli, W. (1996) Pultrusion of endless fiber-reinforced profiles with a thermoplastic matrix system, Engng Plast., 9(4), 282-292. 

Endless fiber-textile yarns, smooth or textured, represent a relatively large capacity of production which is increasing all over the world. They are used in ... 

As a general rule, self-reinforced composites consist either of layers of highly-oriented thermoplastic textiles [4-7] or of a combination of self-reinforced textiles and a similar thermoplastic matrix material, which is added in the form of a film, powder or melt [1]. These are then hot-compacted to structurally consolidated mono-composites under pressure and temperature in a pressing process. For the most part, the fiber composite concept relies upon the embedding of stretched endless fibers or tapes made of PP into a chemically identical matrix. 

The films and fibers are then both processed into the previously discussed semifinished products by means of conventional textile processing methods. Filament yams, woven fabrics and unidirectional fabrics, but also endless fiber fleeces and staple fiber fleeces, can be made from the fibers [40]. The films can be employed as semifinished products directly after being mono-, bi- or (rarely) multiaxially stretched. For the most part, the fibers are tailored into tapes, monoaxially stretched and woven into oriented textile products in order to produce the essentially woven fabrics. 

This energy absorption is based upon several fundamental structural elements, whose interaction benefits the high energy intake. These elements include the presence of endless fibers (fiber pull-out or break), the layered structure (delamination) [6,25,30,77], the high macromolecular orientation (defibrillation of the fibers) and the ductility inherent to the basic fiber (plastic deformation) [36]. Additionally, these characteristics contribute to splinter-free composite failure [78] even at temperatures below freezing. This is especially advantageous for protective applications. Moreover, the technical design aspect CFC-optics results from the endless, often dark fiber structure and promotes use in visible applications. 

Additionally, the stress-strain-curves must be regarded for the application in semistruc-tural components. Only fabric-based materials display a distinct decrease in stiffness (knee), which is typical for endless fiber composites and is triggered by inter-fiber cracks in the matrix component that occur transversely to the loading direction [13,81], see Figure 22.9. 

State of the art are composite base-layers with endless fiber reinforcements, which allow a gradual adjustment of the mechanical and thermal properties of the cover in a radial direction. This results in a gradual adjustment of the shear forces created by the nip load within the cover layers. Two layer designs with a harder polyurethane underlayer are also used to provide bonding to the shell. 

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