Experimental and numerical investigation of cure kinetics in pultrusion of Elium®-based thermoplastic fibre reinforced composites

Pultrusion is a continuous manufacturing technique for producing fibre-reinforced composites with high efficiency and consistent quality. Recent efforts have focused on replacing traditional thermosetting resins with recyclable thermoplastic alternatives due to growing sustainability concerns. However, selecting appropriate process parameters such as die temperature, pultrusion velocity, and fibre volume fraction to achieve uniformly cured, high-quality products remains challenging for newly adopted reactive thermoplastic systems. This paper presents an integrated experimental and numerical investigation of the thermochemical curing process during the pultrusion of fibre-reinforced composites using reactive thermoplastic Elium® acrylic resin. Differential scanning calorimetry (DSC) experiments were conducted to characterise the polymerisation kinetics and establish a kinetic model tailored for Elium®. A multiphysics simulation model coupling heat transfer and cure kinetics was subsequently developed and implemented in COMSOL Multiphysics®. The model was validated through embedded thermocouple measurements during pultrusion trials, showing good agreement with the predicted temperature profiles. It also captured the spatial evolution of temperature and degree of cure across the composite cross-section, highlighting thermal gradients driven by the exothermic reaction. Parametric studies revealed a strong influence of pulling speed and die temperature, with a milder effect from fibre volume fraction, on the curing process. Finally, practical design charts and contour maps were derived, linking process parameters to the required die length for achieving complete and uniform curing, offering valuable guidelines for process optimisation.