An assessment on effect of process parameters on pull force during pultrusion

This research investigates the process behaviour by prediction of the pull force required to drag the raw materials through heated die at different reinforcing material configuration during pultrusion. Pultrusion is a continuous manufacturing process that is widely used in manufacture for composite profiles. A specially designed device, friction force by virtue of pulling on ‘resin impregnated’ fibres with both liquid resin and partially cured resin, was employed to measure pulling force against temperature and resin conversion. This allowed to experimentally simulate materials tracing in short and long die length used in process. Differential scanning calorimetry (DSC) was used to determining polymer conversion. The results shows that the downstream part of a die has no significant effect on the pulling force before a specific conversion level is achieved and that higher resin conversion leads to a higher friction at viscous/liquid zone. The difference noted is much more significant when the temperature is low (e.g. room temperature) and considerably drops due to on rising temperature. Further, a new mathematical model is proposed that predicts the rise in compaction pressure on increasing fibre volume fraction and drag velocity which is an opposite characteristic to tapping angle and part thickness considerations. Similarly, many parameters including shrinkage, viscous force and dry friction were modelled and simulated for ortho polyester resins as a function of temperature and resin conversion during dynamic pulling. The study has direct application in configuring pultrusion manufacturing customisation for a specific configured material, components manufacturing and respective designing of the die for the profile to be manufactured.