A holistic assessment of the circularity potential of CFRP in aviation, under the scope of a hydrogen-fueled aircraft
Creators: name:  D. MARKATOS 
name:   S. PANTELAKIS 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: CLIMATE-NEUTRAL
AVIATION FUELS
ALTERNATIVE PROPULSION SYSTEMS

description: The aviation industry is responsible for 3% of the total CO2 emissions in the atmosphere [1]. To mitigate the environmental impact of aviation, during the last years, alternatives to petroleum-based fuels have emerged as potential aviation fuels. Among them, liquid hydrogen has been recognized as a promising fuel for sustainable transportation by providing clean, safe, reliable, and affordable energy [2]. Yet, towards fuel efficiency goals and thus, lowering the environmental burden of aviation, weight reduction remains a principal objective as weight is the main driver for fuel consumption and emissions. The current main approach to reduce weight is the utilization of polymer-based composites to replace metals. [3]. Additionally, significant issues represent the great environmental and economic impact related to the production of virgin carbon fibers, as well challenges concerning their recycling and recovery. The high value of said fibers has led to the intensification of the efforts towards identifying efficient ways to recycle and reuse carbon fibers, ideally in closed-loop applications. Currently, only demonstrators or prototypes, such as aircraft seat arm rests have been produced [4]. The current work aims to assess the circularity potential of CFRP for the production of high- performance aircraft components. To this end, a LCA data-driven material selection support tool, introduced in [5], will be further developed to assess and compare virgin and recycled CFRP aircraft components with regard to their sustainability. Towards sustainability and circular economy objectives, the tool will integrate environmental and economic impact metrics related to the materials/components under study, as well as a suitable quality-related circular economy indicator, evaluated at the material/component level. The type of fuel utilized during the use phase of the components will also be accounted for, namely kerosene and liquid hydrogen produced through a conventional method as well as through renewable sources. To compensate for material property variations between components made of different materials, thickness is treated as a variable which must be adjusted to achieve the same mechanical properties for all components. The tool is coupled with a multi-criteria decision analysis (MCDA) methodology for the determination of the considered criteria significance. Efficiency of the tool has been proved in [5], in which the impact of material selection on aviation sustainability from a circular economy perspective has been assessed. In the latter study, the specific stiffness of the materials after one or multiple recycling loops was selected as the relevant circular economy indicator. Output of the tool is a quantitative Index which represents a trade-off between potentially contradicting aspects associated with circularity, environment and costs, in conjunction with the type of fuel utilized. A ranking among the investigated aviation components occurs to support material selection. It could be demonstrated that in the aviation sector, the environmental impact and costs are mainly driven by component weight and are in direct relation with the type of fuel implemented during the energy-intensive use phase of aviation. In this context, the suitability of recycled CFRP for high-performance aviation applications and hence, the potential for the implementation of circular economy principles in the aviation sector are assessed and discussed. Considering that the implementation of circular economy (CE) principles is increasingly in demand in order to meet the goals of sustainable development, new tools are required to assist decision-makers, practitioners, and policymakers in achieving CE objectives [6].