Environmental and cost analysis of carbon fibre composites recycling

Meng, Fanran (2017) Environmental and cost analysis of carbon fibre composites recycling. PhD thesis, University of Nottingham.

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While carbon fibre reinforced plastic (CFRP) can reduce transportation energy use and greenhouse gas emissions by reducing vehicle weight, the production of virgin carbon fibre (CF) itself is energy intensive. CFRP recycling and the reutilisation of the recovered CF have the potential to compensate for the high impact of virgin CF production due to low cost and to open up new composites markets – e.g., in the automotive sector. The aim of the research is to examine the life cycle environmental and financial implications of a fluidised bed process to recycle CFRP wastes and to identify potential markets for CFRP reuse in automotive applications.

Firstly, process models of the fluidised bed carbon fibre recycling technologies are developed based on thermodynamic principles and established modelling techniques to quantify the heat and electricity requirements and predict the energy efficiency of a hypothetical commercial-scale plant. The energy model shows that the energy requirement of recycled CF production is generally less than 10% relative to virgin CF and results are robust across likely operating conditions. Further optimisation of the fluidised bed recycling process is needed to balance to the feed rate per unit bed area to minimise process energy use and potential implications for recycled CF properties. Opportunities exist for recovering stack heat loss which could further improve the energy efficiency of the fluidised bed process.

Secondly, process models for recycled CF processing (i.e., wet-papermaking/ fibre alignment) and subsequent CFRP manufacture (i.e., compression moulding/ injection moulding) technologies are developed to quantify the energy and material requirements of a hypothetical operating facility. Models are based on optimised parameters based on the best performance from previous experiments, where available, while target values are used for the fibre alignment technologies currently under development.

Thirdly, the life cycle environmental implications of recovering carbon fibre and producing composite materials as substitutes for conventional materials (e.g., steel, aluminium, virgin CFRP) are assessed and proposed as lightweight materials in automotive applications, based on process models of the fluidised bed recycling process and remanufacturing processes or available life cycle assessment databases. Life cycle impact assessments demonstrate the environmental benefits of recycled CFRP compared with end-of-life treatment options (landfilling, incineration). Recycled CF components can achieve the lowest life cycle environmental impacts of all materials considered, although the actual impact is highly dependent on the design criteria of the specific components. Low production impacts associated with recycled carbon fibre components are observed relative to lightweight competitor materials (e.g., aluminium, virgin CFRP). Recycled CF components also have low in-use fuel consumption due to mass reduction and associated reduction in mass-induced fuel consumption. The results demonstrate the potential environmental viability of recycled CF materials.

Finally, financial analysis of carbon fibre recycling, processing, and use in recycled CFRP materials is undertaken to assess potential market opportunities in the automotive sector. Cost impacts of using recycled CF as a substitute for conventional materials are also assessed in the full life cycle, making use of data from energy and cost models, manufacturers and existing cost databases. Recovery of CF from CFRP wastes can be achieved at $5/kg and less across a wide range of process parameters. CFRP materials manufactured from recycled CF can offer cost savings and weight reductions relative to steel and competitor lightweight materials in some cases, but are dependent on the specific application and associated design constraints– e.g., the material design index - as this drives the weight reduction/in-use fuel consumption and material requirements. Fibre alignment could potentially improve financial performance by inducing larger vehicle in-use fuel cost savings associated with weight reductions. Further investigations to monetise environmental impacts show larger cost benefits for recycled CFRP materials in replacement of conventional steel and lightweight competitor materials.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: McKechnie, Jon R.
Pickering, Steve J.
Keywords: Carbon fibre recycling, life cycle assessment, techno-economic analysis, carbon fibre reuse, automotive lightweight design
Subjects: T Technology > TA Engineering (General). Civil engineering (General)
Faculties/Schools: UK Campuses > Faculty of Engineering
Item ID: 46518
Depositing User: Meng, Fanran
Date Deposited: 13 Dec 2017 04:40
Last Modified: 14 Dec 2017 09:47
URI: https://eprints.nottingham.ac.uk/id/eprint/46518

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