Environmental impacts of recycling carbon fibre reinforced high-performance thermoplastics for aerospace composite structures and uncertainty from modelling choices

Abstract

Advanced manufacturing processes such as Additive Manufacturing are considered for future aerospace structures because of their design freedom. They offer a high potential for lightweight construction and corresponding lower environmental impacts during the use-phase as well as reduced material consumption during production phase. Additionally, thermoplastics improve recycling possibilities compared to thermoset composites. Calculating the potential environmental impacts of cascading material use with Life Cycle Assessment (LCA) is subject to major challenges. Using the example of a carbon fibre reinforced high-performance thermoplastic, the effect of different refresh rates of virgin and recycled materials as well as the number of cycles and their downcycling effects influence the results. Data for the production of new materials like virgin carbon fibres (vCF) and low-volume thermoplastics, for which little or no primary information is available, are a first obstacle. Impact categories such as Global Warming Potential can vary by an order of magnitude depending on the choice background data (e.g. LCA database, Environmental Product Declaration, laboratory measurements or literature). Different modelling principles, including the choice of End-of-Life formula, further add to the difficulty to produce comparable results. In this presentation, the focus of the LCA lies on the new material production compared to the steps necessary for the recycling of materials as preparation for the cascading application in a generic aerospace structure, using different refresh rates. Primary data from laboratory trials on a twin-screw extrusion line for pellet production and material refresh are combined with secondary data sources. The influence of background databases and other modelling choices highlights the necessity for sensitivity analysis and transparency when presenting the results.