Pultrusion process mandrels

This is a variation of the pultrusion process for the manufacture of hollow tubes. The die used is similar to that used in conventional pultrusion but the mandrel which forms the... 

The composite can be made using the pultrusion process, but this is difficult to operate since the resins cure by a condensation reaction. Filament winding enables the fiber to be placed precisely onto a removeable mandrel and achieve a high fiber content. This technique more suited to handling untreated, unsized fiber and is used to make rocket motor nozzles. 

If the filaments are not wound onto a mandrel but simply gathered into relatively large bundles and led slowly into a heated consolidation zone, emerging from a die partly or completely cured, the primitive essentials of pultrusion are present (Fig. 2.3(b)). This process began as the thermosetting resin equivalent of extrusion, that is, it was a continuous operation for manufacturing profiles, such as rod and channels. The method has been extended to fibre reinforced thermoplastics. 

The process requires a mandrel, which sometimes can be complex or expensive. Usually, the mandrel is less costly than the dies or molds for forming methods other than pultrusion or RTM. Generally poor external surfaces are produced, which may hamper aerodynamics. A better outside surface can be obtained by... 

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