Long discontinuous fiber

T.S. Creasy, S.G. Advani, and R.K. Okine, Transient rheological behavior of a long discontinuous fiber-melt system. J. Rheology, 1996, 40, 497-519. 

T.S. Creasy and S.G. Advani, A model long-discontinuous-fiber filled thermoplastic melt in extensional flow. J. Non-Newtonian Fluid Mech. 1997, 73, 261-278. 

Du Pont s long discontinuous fiber sheet products with PEEK and J-2 resins provide easier fabrication of complex shapes. This product form is particularly attractive to helicopter manufacturers for the press forming of highly contoured secondary structure parts. 

The reinforcements amenable to RTM are similar to those used for pultrusion, except that they need not be continuous in nature. Thus, E-glass, S-glass, aramid, and carbon fibers are commonly used, as are discontinuous filaments such as wood fiber and polyesters. Even metal and ceramic fibers can be used in this technique. In one method, the preform is fabricated by spraying 12- to 75-mm-long chopped fiber rovings onto a preshaped screen. A binder sprayed with the fibers keeps them in place and holds the preform shape, which is then placed in the mold. 

Fiber-reinforced polymer composites can contain short, discontinuous fibers (usually in thermoplastics see Fig. 1.14) or long, continuous fibers in thermoset resins. Fibers can vary from the usual glass fibers with thicknesses of some tens of micrometers up to nanofibers or carbon nanotubes (single-waiied or multiwalled, SWCNT or MWCNT) about 10 nm thick. The properties of fiber-reinforced composites depend on thickness, length, and volume content of the fibers, as well as on adhesion (interfacial strength) and matrix properties. 

Fine Structure of Nerves. The conducting elements of the nervous system are the long nerve fibers, most of whieh are clad in relatively thick myelin sheaths (myelin-containing nerves). The sheath is discontinuous at the rings of Ranvier and only a thin membrane separates the neuroplasm from its surroundings at these points. Neural excitation leaps from one such ring to the next (saltatory conduction). 

FIGURE 8.8 General forms for discontinuous phase materials, from left, are continuous or long fibers, short fibers, whiskers, and particulates. 

The second factor that affects performance in discontinuously reinforced FMCs is fiber length. This has an effect primarily on the ease with which the composite can be manufactured. Very long fibers can create difficulties with methods used to create discontinuously reinforced FMCs and can result in nonuniform mechanical properties. The third factor is also related to fiber geometry, namely, the fiber shape. Recall that the... 

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