Fiber cross-section

Cross-sectional area or fiber fineness also affects textile processing efficiency and the quatity of the end product. The number of fibers in a cross section of yam of a given size is related to fiber fineness, that is, the smaller the fiber cross section the more fibers will be needed in the yam. Other factors being equal, yam strength increases as the number of fibers in the yam cross section increases. However, fibers with too small a cross section caimot be processed efficiently. 

Microscopical Examination. All fibers have distinguishing features which either allow outright identification or classification iato narrower grouping for specialized analysis. Fiber cross sections are particularly usehil for identification. 

Fiber cross sections are also deterrnined by the coagulation conditions or, in the case of dry spinning, by the solvent evaporation process. The skin that forms early in the solvent removal process may remain intact as the interior of the filament deflates from solvent removal. Wet spun fibers from organic solvents are often bean shaped, while those from inorganic solvent systems are often round. Dry spun fibers, such as Du Font s Odon, are... 

Specific Gravity. Fiber cross sections are often irregular and specific gravity is measured by an immersion technique. The values of 1.32 for acetate and 1.30 for triacetate are accepted for fibers of combined acetic acid contents of 55 and 61.5%, respectively (13—15). 

Permanent chemical crimp can be obtained by creating an asymmetric arrangement of the skin and the core parts of the fiber cross section. Skin cellulose is more highly ordered than core cellulose and shrinks more on drying. If, during filament formation in the spin bath, the skin can be forced to burst open to expose fresh viscose to the acid, a fiber with differing shrinkage potential from side-to-side is made, and crimp should be obtained (Fig. 5a). 

Fiber dimensions have been studied for hemodialysis. When blood is circulated through the fiber lumen (m vivo), a significant reduction in apparent blood viscosity may occur if the flow-path diameter is below 100 p.m (11). Therefore, current dialy2ers use fibers with internal diameters of 180—250 p.m to obtain the maximum surface area within a safe range (see Dialysis). The relationship between the fiber cross section and the blood cells is shown in Figure 5. In many industrial appUcations, where the bore fluid is dialy2ed under elevated pressure (>200 kPa or 2 atm), fibers may burst at points of imperfection. Failure of this nature is especially likely for asymmetric fibers that display a large number of macro voids within the walls. 

Fig. 13. Typical nylon fiber cross-section shapes.

Develop a schematic model with fiber springs and matrix springs in which the actual surrounding of the fiber with matrix material is taken into account, i.e., for a cross section such as that with the dimension lamina thickness in Figure 3-2, except make the fiber cross section square instead of round. 

Processing. The process requires a monofilament carbon-fiber core which is heated resistively in a tubular glass reactor shown schematically in Fig. 19.1. PI A carbon monofilament is pre-coated with a 1 pm layer of pyrolytic graphite to insure a smooth deposition surface and a constant resistivity. 1 1 SiC is then deposited by the reaction of silane and a hydrocarbon. Other precursors such as SiCl4, and CH3SiCl3 are also being investigated. A fiber cross-section is shown in Fig. 19.2.P1... 

Histopathological examination shows the typical corelike lesions in a high proportion of muscle fibers in older patients this may amount to 100%. Most typically the cores are large and centrally-placed, but multiple cores may occur in the same fiber cross section. Most older patients show a striking predominance of type 1 (slow twitch oxidative) fibers and virtually all fibers with cores are type 1. Sometimes younger family members have more normal proportions of type 1 and type 2 fibers but, again, the cores are confined to the type 1 fibers. It is well established that muscle fiber types can interconvert due to altered physiological demands, and it is likely that fibers with cores convert to a basically slow twitch-oxidative metabolism to compensate for the fact that up to 50% of their cross sectional area may be devoid of mitochondria. 

Figure 8.37a shows the projected intensity100 as a function of the elongation of the material. The resulting 2D CLDs are presented in Fig. 8.37b. Equatorial streaks are observed from an elongation of e = 1.73. Only at this elongation there are some faint correlations among the microfibrils the CLD becomes slightly negative at r 8 nm. For higher elongation the structure in the fiber cross-section conforms to a hard-disc fluid.

Fig. 7.6 (a) Microscopic image of the micromachined hole introduced on the fiber cross section, (b) Microscopic image of the fabricated sensor head. Reprinted from Ref. 12 with permission. 2008 Optical Society of America... 

In addition to the aforementioned methods, fiber cross-sectional shape is used to produce differences in appearance. Surface lobes can break up smoothness and reduce glitter, and triangular or T shapes can generate subtle sheen effects to fabrics and yams. The patent literature is filled with various cross-sectional shapes which have been used to provide visual and tactile effects that are not possible with natural fibers. 

This process (using one of the modes previously described) was applied to a set of 3 to 12 different selected areas on the transverse section of one fiber. The photographic series is a completed record of the whole fiber cross-section at an adequate magnification. On the latter micrograph the irradiated areas can be seen because of their lesser electron density in bright field conditions. In some cases, these irradiated areas could also be seen under dark field conditions. 

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