Towards digital process simulation of closed injection pultrusion

This work describes the modelling of the injection and impregnation chamber (ii-chamber) in a resin injection pultrusion (RIP) process. RIP enables the use of fast-curing resins such as polyurethane or reactive thermoplastics and reduces potentially harmful emissions. The presented method for simulation of the resin flow and the reaction inside the ii-chamber can support optimisation of its design and allow for conclusions concerning viable processing conditions.
In order to produce pultruded profiles with maximum mechanical properties, it is desirable to achieve high fibre volume fractions within the profile. A higher number of fibres being pulled through the ii-chamber increases the flow resistance to the resin due to smaller gaps between the rovings. The geometry of the ii-chamber must allow the resin to infiltrate all fibres completely since voids in the profile deteriorate its mechanical properties causing rejection of the product. For the same reason, the infiltration has to take place before the resin gels during the reaction.
The presented work is based on RIP of a reactive thermoplastic resin reinforced by unidirectional fibre rovings. ... mehrIt is based on a multiphase model for resin and air, where the fibres are considered as porous medium with direction-dependent (anisotropic) permeability. Flow of resin and air is driven by drag of moving fibres and pressure differences. This is described by the fundamental laws of continuous fluid dynamics. The reaction kinetics and viscosity developments due to rising polymerisation degree and varying temperature are included in the modelling. Thus, the method gives insight into the ii-chamber. It can predict poor impregnation quality, since air is modelled as a separate phase. Furthermore, simulation results on deposit formation next to the ii-chamber walls show good agreement in comparison to experimental results. The iterative optimisation process of ii-chamber design will become more time- and cost-efficient by application of this method, and it can also be used to optimise process parameters such as pulling speed and target values of heating devices.