Polar winding

The fiber tension is very important as this controls the resin pick-up, normally 35-40% volume fraction. Tensions are about lN/1000 filaments for wet winding and 3N/1000 filaments for other types of winding. If the tension is too high, the fiber does not spread and is damaged by abrasion in the guide and if too low, produces waviness in the applied fiber. The type of fiber size and size content must be carefully chosen to help achieve good resin wet out. The principal matrix materials are epoxy, polyester and vinylester resins, but thermoplastic prepregs such as PEEK can also be applied. 

When the thickness of the composite exceeds a certain value, it may be necessary to apply the cure in two stages. 

The final wound structure is removed from the winding machine, and the mandrel/ workpiece is placed in an oven for curing. Various mandrels are used and can be made of hard chrome plated and polished ground steel, which may be of a segmented collapsible construction, but must have no concave curvature. If the part has complex geometry, then fusible low melting point alloys, a soluble plaster that can be removed with hot water after curing, or an inflatable bag can be used. In some instances, such as compressed natural gas (CNG) tanks, the mandrel is left in position as a liner. 

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Mass loss in rotating star is asymmetric. Very hot star have a dominant polar wind. Stars with Teff below about 24 000 K, due to their larger opacities, may have an equatorial ejection forming a disc. Polar ejection removes little angular momentum, while equatorial ejection removes a lot. ft is thus also important to consider the wind asymmetries in massive rotating stars. Also, rotation produces a general enhancement of the mass loss rates [7]. 

Figure 7.93 A polar winding pattern. Reprinted, by permission, from P. K. Mallick, Composites Engineering Handbook, p. 184. Copyright 1997 by Marcel Dekker, Inc.

Polar Winding in which the filament path passes tangent to the polar opening at one end of the chamber and tangent to the opposite side of the polar opening at the other end. It is a one-circuit pattern that is inherent in the system. 

In the application of bidirectional patterns, the end domes can be formed by fibers that are laid down in polar winding patterns. The best geometrical shape of the dome is an oblated hemispheroid. Theoretically, the allowable stress level in the two perpendicular directions should be identical. However, the efficiency of the longitudinal fibers is less than that of the circumferential fibers. It is possible to estimate an optimum or length-to-diameter ratio of a cylindrical case for a given volume. 

Figure 21.60 Polar winding. Source Reprinted with permission from Shaw-Stewart D, Filament winding-materials and engineering. Materials and Design 6, No. 3, 1985. Copyright 1985, Elsevier.

Polar wind High-speed plasma outflow from the high-latitude ionospheres. 

Foremost among these are the electric fields generated by the solar wind-geomagnetic field interaction, the presence of intense particle precipitation within the auroral oval, the polar wind escape of thermal plasma, and other features resulting fi om the auroral disturbance of the neutral atmosphere. 

With a vertical axis, for polar windings and preferred for very large size members... 

Comparison of hoop, helical and polar winding (a winding angle). 

Another type is known as the orbital, or racetrack winder, where the winding heads move completely aroimd the mandrel, as shown in Figure 21. It is used primarily for rocket motor cases and where polar winding is desired high speed is attainable. 

In the tumble-type winder (Fig. 22), the mandrel is tumbled end over end during a polar wind, whereas the feed eye is traversed and the mandrel rotated in the normal lathe-type fashion for helical or circumferential winds. This type is widely used for high volume commercial products such as water-softener tanks and pool filter tanks. 

Whirling-arm filament winding is illustrated in Figures 23 and 24. Polar wind is accomplished hy means of the C-shaped arm, which supplies filaments from feed eyes at both extremities. While whirling on its horizontal axis, the arm winds on the polar axis of the mandrel, which is circumferentially indexed at appropriate intervals. During polar wind, the horizontal winding arm is retracted ... 

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