Thermomechanisch gedrag van (over-) geëxtrudeerde polyvinylchloride producten

This dissertation investigates a hybrid extrusion-based process, termed over-extrusion, which combines the benefits of UD continuous reinforcing fibres with the high throughput of the extrusion process. The inclusion of reinforcing fibres in over-extruded products enhances mechanical performance but also introduces complexities in manufacturability and process modelling. A significant challenge arises from the mismatch in the coefficient of thermal expansion (CTE) between the fibres and the polymer, often resulting in excessive warpage or undesirable local shrinkage. Additionally, these products can experience substantial internal stresses, potentially reducing load-bearing capacity. This work presents a process model for extrusion as well as over-extrusion, focusing on temperature evolution and dimensional stability (warpage) of the final part. Residual stresses are assessed by use of a material removal strategy. Initially, the model was validated using a non-reinforced extrusion process, focusing on tubular asymmetric cross-sections. Following this validation, the model was applied to products with more complex cross-sections, namely window profiles. Ultimately, the methodology developed in this work can be used to assess deformations of the final product, for instance in the case of one-sided solar heating of window profiles. A thermomechanical prediction model was developed to anticipate temperature evolution and related warpage, and its results were compared to experimental data from a production environment. The simulated model predicted measured temperatures within 90% accuracy and warpage for five levels of unreinforced tube asymmetry (having wall thickness differences) within 86% accuracy, while also accurately predicting internal stress states. For reinforced products, the first iterations of the model overestimated warpage while showing heightened sensitivity to reinforcement location and its influence on warpage. The associated predictions of residual stress for these reinforced parts highlighted the significant role of bonding conditions and tool-part interaction forces, which also affect warpage predictions. Despite these challenges, the model proves valuable for relative assessments, and key parameters influencing warpage have been identified, providing a foundation for refining the model and guiding future research efforts.