Dissertation

Recycling of Continuous Fibre Reinforced Thermoplastic Composites

de Bruijn, Thomas A

2020

Overview

Due to the material’s intrinsic benefits, the volume of continuous fibre reinforced thermoplastic composites (TPCs) is growing and leading to a rise of industrial waste, though a high-quality recycling route is not yet available. TPC recycling enables reclaiming the high economic value, reducing the environmental impact and to be in-line with environmental directives. In this study a new TPC recycling route was developed and successfully validated allowing to achieve, maximum cost effectiveness and minimum environmental impact.The trade-off between mechanical performance and processability or degree of mixing for long and short fibres respectively, is optimised by developing a micromechanical model. The model was used to predict stiffness and strength and includes distributions for fibre length and the degree of mixing, by local fibre volume variation and fibres per bundle. An appropriate recycling route consisting of shredding, low-shear mixing and compression moulding, was established to experimentally validate the mechanical performance of recycled TPCs. G/PP and C/PPS at various fibre orientations, contents and length distributions and waste material consolidation stages were processed both without mixing and by different levels of low-shear mixing. Characterisation was performed by flexural, impact and cross-sectional microscopy testing. The experimental properties of the recycled material were found to be in-line with theoretical predictions and increase with degree of mixing.Three demonstrator products were designed, produced and tested to prove their technical and application feasibility; a bracket, a safety shoe nose cap and an aerospace access panel. While made of recycled material with inferior material properties, the panel was even lighter than the current solution and gave enough confidence to be flight tested. Life cycle analysis and cost assessment were used to compare the recycled material and demonstrators to currently used alternatives. A significant reduction in cost and environmental impact was found for both the panel and nose cap. The panel made from recycled material offered reductions of over 80% in greenhouse gases (GHG) and 60% in cost, when compared to the virgin C/epoxy benchmark.The work carried out demonstrates that recycling is feasible and enables applications currently made by using virgin materials at a significant reduction in costs and environmental impact and already led to the world’s first flying fully recycled thermoplastic composite application in aerospace*.

• Publisher: ProQuest Dissertations & Theses
• Subject: Carbon / Design / Economic impact / Energy consumption / Environmental impact / Environmental management / Geometry / Impact tests / Industrial engineering / Manufacturing / Microscopy / Recycling / Stress concentration / Sustainability / Thermoplastic composites / Waste materials
• ISBN: 9798383885918