Integrated modeling of injection pultrusion

Injection pultrusion (IP) process, which deceptively may look quite simple, is based on several different thermo- chemical and physical phenomena which interact and influence each other. The advancing fibers are pulled through a narrow tapered cavity, namely the injection chamber, that is the first section of the IP die. In this zone, a thermoset resin is injected and impregnates the reinforcement. The resin is in liquid state, and therefore it has an interaction of viscous nature with the other bodies of the system. Viscous resistance depends on the value of resin viscosity and the thickness of the liquid film between the fibers and the internal surfaces of the chamber. Resin viscosity initially decreases due to the temperature increase from room temperature until the activation of the curing process. Afterward, the solidification provokes a sharp rise of viscosity. In the early zone of the die, the resin behaves like an incompressible fluid, experiencing, due to the tapered shape of the cavity, hydrostatic pressures of tens of bars. On the other hand, when the resin changes to the solid state, substantial frictional resistance acts at the contact surface between the composite and the die. Finally, thermal expansion and chemical shrinkage influence the contact at the solid state. Theoretical modeling of the involved phenomena and the inherent loads is as challenging as fundamental, however, due to the mutual interaction, the reliability of the numerical predictions relies on the usage of integrated approaches. In this work four different submodels, mimicking respectively the resin constitutive model, fiber wetting, thermochemical evolution and mechanical interaction, were integrated to computationally reproduce the IP process. Numerical data were compared to quantitative measure of resistive loads acquired on a laboratory scale IP line. In particular, in each point of the die, the resistance has been isolated and measured. The post-process analysis of the acquired data allowed to define the behavior and the impact of each of the phenomena described above.