Enhancing thermoplastic resin transfer moulding using in-situ homogenisation

The automotive industry is engaged on the development of new vehicles with more sustainable and lightweight materials. Recent manufacturing technologies are being developed to respond to these challenges. Thermoplastic-Resin Transfer Moulding (T-RTM), a liquid moulding technology, emerged in this field has a promising approach for the manufacture of lightweight thermoplastic composites for structural applications. This process is based on the in-situ polymerisation of a thermoplastic monomer. This material is suitable for impregnation of continuous fibres and is prone to recycling, in opposition to conventional thermosetting composites. However, T-RTM remains a complex manufacturing technology mainly due to the instability of the resin in the presence of moisture or oxygen as well as thermal and pressure gradients within the mould. These gradients lead to non-uniform initial conditions for polymerisation along the mould cavity and, consequently, to a considerable variability in the T-RTM process. This study aims to contribute to the upscaling of this technology towards its industrial application, through the implementation of an innovative dynamic resin mixing and vibrational apparatuses designed to increase the homogeneity of the resin mixture after its injection into the mould. The parts’ homogeneity and process reproducibility were evaluated based on the statistical analysis of the mechanical and physical properties assessed in different areas of glass fibre-reinforced parts. This study has shown that both apparatuses can improve homogeneity regarding the mechanical behaviour and density of the parts. Furthermore, the dynamic mixing enhanced the polymerisation reactivity, assessed through dielectric analysis, compared to the standard T-RTM manufacturing method.