Pull-winding process

A combination of the pultrusion with the winding process is commonly known as the pull-winding process (Rg. 8.13). The fibers are laid to the... 

Manufacturing methods for composites vary from manual to fully automated processes, whereby the latter have better quality control than the former. Wet layup, pultrusion, and filament winding are all discussed in some detail, while other techniques such as pull-winding, resin transfer moulding, vacuum bag moulding, and injection moulding are left to specialized composite materials texts. 

In a filament winding process the filament is applied on a mandrel. Mandrel types can be distinguished in heated mandrels, non-heated mandrels, dissolvable cores and liners. Using a heated or non-heated mandrel the quality of the mandrel surface is an important factor due to the fact that the finally wound component must be stripped (pulled or pushed) over the surface. By using a liner or a dissolvable core the surface quality is not so relevant, due to the fact that the liner remains in the product and the dissolvable core is removed after the winding process. 

For mobile liquids, the use of this kind of controllable instruments is practically impossible. For these liquids, the non-controllable measurement techniques are available only and in general an apparent transient viscosity will be obtained. Nevertheless these measurements are still of great value, because in many cases they approximate industrial process conditions. Mostly used is the spinning line rheometer, where an elastic liquid is pressed through a spinneret and the liquid is pulled from the die by winding the filament around a rotating drum or by sucking the tread into a capillary tube. This is schematically shown in Fig. 15.25. A serious problem is the translation of the obtained data to the extensional viscosity. Many other non-controllable devices are discussed by,... 

Unidirectional rovings can be used directly in composite manufacture, or they can be converted to otho- intmnediate products. Direct applications include the unidirectional rovings used in processes such as spray lay up, filament winding, and pultrusion. Pul-tmsion is the process in which glass rovings or tows, in a preselected orientation, are saturated with resin and pulled through a heated die, where the part is formed and cured. 

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