Final part quality

Part heat-up rate during autoclave processing can dramatically influence final part quality. At least three variables can affect the autoclave heat-up rate for composite parts (1) tool material and design, (2) the actual placement of the tool within the autoclave, and (3) the autoclave cure cycle used. Recommendations for the design of an individual tool are fairly obvious and well understood in industry (e.g., thin tools heat faster than thick tools materials with a high thermal conductivity heat faster than those with lower thermal conductivity and tools with well-designed gas flow paths heat-up faster than those with restricted flow paths [e.g., tools... 

There are a number of general references available that contain detailed descriptions of the winding process and equipment itself [5,6], The purpose of this work, however, is to focus on the relationship between processing conditions and final part quality for both thermosetting and thermoplastic matrix filament wound cylinders. In the subsequent sections, an overview of the process will be presented, followed by detailed descriptions of current process modeling techniques and methods for determining cylinder quality. 

Another specificity of flexible tooling is that the flow doesn t stop as the inlet is shut at the end of filling there is a pressure and thickness gradient remaining that needs to equilibrate to ensure a consistent and uniform quality to the finished part [76, 127, 128, 130-133], As the reinforcement compaction is provided by the pressure difference between the cavity and the environment, it is possible to have a limited control over the final part quality by controlling the vacuum pressure during post-filling [125, 134, 135],... 

The parameters of mould filling, packing and cooling have been shown to be more important to final part quality than the plastication stage. All of these processes will be described in greater detail in Chapter 8. 

The control system is there to ensure repeatability during moulding operation. It monitors both the hydraulic system and the process parameters such as temperature, injection speed, screw retraction speed and injection and back pressure. The ability to control the process has a direct impact on final part quality, part to part consistency and economy. The nature of the control system may vary from a simple relay switch to a complex microprocessor system with closed-loop control. Some of the components of the machine control system will now be introduced. 

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