Processing of self-reinforced poly(ethylene terephthalate) composites for automotive applications

Abstract: The vehicles of the future must have less negative environmental impact during their use phase than the vehicles of today in order to avoid major climate change on earth. Consequently electric vehicles are currently under development with the purpose of reducing CO2 emissions when the vehicle isdriven. There are also efforts put in to reducing the weight of vehicles in order to reduce the demand for energy to drive them. One important aspect of weight reduction is that new materials and technologies are developed. Plastic materials have low a density and can therefore be used to reduce the weight of vehicle components and with composite materials there is further potential for weight reduction. Self-reinforced thermoplastic composite materials are materials in which both reinforcement and matrix are thermoplastic materials and thanks to their low density and relatively good mechanical properties, these materials may be used for weight reduction of vehicle components. The aim of this thesis is to study selected process parameters for component manufacturing with self-reinforced poly(ethylene terephthalate) (SrPET) in order to increase knowledge and thereby advance the field of self-reinforced PET composites. This thesis shows that stretching the material in the manufacturing process increases the mechanical performance of the material due to increased orientation of the amorphous phase in the PET reinforcement. However, stretching introduces stresses in the material that give rise to negative shape distortions in the formed component. The degree of stretching during forming must therefore be controlled in order to achieve a robust serial production. The concept of a SrPET component over-moulded for integration of stiffeners and attachments has been evaluated in a life-cycle-assessment. This evaluation shows that the component weight can be reduced compared to technology currently in use and thereby contribute to increased sustainability of transport.