The forecast of growing air transport in the upcoming decades faces the challenge of an increasing environmental impact. Aviation industry is working on promising technologies to mitigate this environmental impact. Lightweight design is a strong lever to lower the fuel consumption and, consequently, with it the emissions of aviation. High performance composites are a key technology to help achieve these aims thanks to their favourable combination of mechanical properties and low weight in primary structures. However, mainly synthetic materials such as petrol based carbon fibres and epoxy resins are used nowadays to produce composite in aviation. Renewable materials like bio-based fibres and resin systems offer potential environmental advantages. However, they have not found their way into aviation, yet. The reasons are reduced mechanical properties and, especially for the use of natural fibres, their flammability. Improvements of these shortcomings are under investigation. Therefore the application of bio-based and recycled materials in certain areas of the aircraft could be possible in the future. Good examples for applications are furnishings and secondary structures. The motivation for this paper is to give an overview of potential environmental properties by using such eco-materials in aviation. Life cycle assessment (LCA) is a tool to calculate environmental impacts during all life stages of a product. The main focus is laid on the bio-fibres flax and ramie, recycled carbon fibres and bio-based thermoset resin systems. Furthermore an overview of environmental aspects of existing composite materials used in aviation is given. Generally, a lack of LCA results for the substitution of synthetic materials by bio-based/recycled composite materials in aviation applications has been identified. Therefore, available information from other transport areas, such as automotive, has been summarized. More detailed LCA data for eco-composite materials and technologies to improve their properties is important to understand potential environmental effects in aviation. aviation, composite, natural fibre, recycled carbon fibre, bio-resin, cabin interior, secondary structure, life cycle assessment (LCA) Citation:Bachmann J, Hidalgo C, Bricout S. Environmental analysis of innovative sustainable composites with potential use in aviation sector-A life cycle assessment review.

Can a hybrid composite made of recycled carbon fibres and natural fibres improve the flexural mechanical properties of epoxy composites compared to pure natural fibre reinforced polymers (NFRP)? Growing environmental concerns have led to an increased interest in the application of bio-based materials such as natural fibres in composites. Despite their good specific properties based on their low fibre density, the application of NFRP in load bearing applications such as aviation secondary structures is still limited. Low strength NFRP, compared to composites such as carbon fibre reinforced polymers (CFRP), have significant drawbacks. At the same time, the constantly growing demand for CFRP in aviation and other transport sectors inevitably leads to an increasing amount of waste from manufacturing processes and end-of-life products. Recovering valuable carbon fibres by means of recycling and their corresponding re-application is an important task. However, such recycled carbon fibres (rCF) are usually available in a deteriorated (downcycled) form compared to virgin carbon fibres (vCF), which is limiting their use for high performance applications. Therefore, in this study the combination of natural fibres and rCF in a hybrid composite was assessed for the effect on flexural mechanical properties. Monolithic laminates made of hybrid nonwoven containing flax fibres and recycled carbon fibres were manufactured with a fibre volume fraction of 30% and compared to references with pure flax and rCF reinforcement. Three-point bending tests show a potential increase in flexural mechanical properties by combining rCF and flax fibre in a hybrid nonwoven.

Today, mainly man-made materials such as carbon and glass fibres are used to produce composite parts in aviation. Renewable materials such as natural fibres or bio-sourced resin systems have not found their way into aviation, yet. The project ECO-COMPASS aims to evaluate the potential applications of ecologically improved composite materials in the aviation sector in an international collaboration of Chinese and European partners. Natural fibres such as flax and ramie will be used for different types of reinforcements and sandwich cores. Furthermore, the bio-based epoxy resins to substitute bisphenol-A based epoxy resins in secondary structures are under investigation. Adapted material protection technologies to reduce environmental influence and to improve fire resistance are needed to fulfil the demanding safety requirements in aviation. Modelling and simulation of chosen eco-composites aims for an optimized use of materials while a life cycle assessment aims to prove the ecological advantages compared to synthetic state-of-the-art materials. In this paper, the status of selected ecologically improved materials will be presented with an outlook for potential application in interior and secondary structures.

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Fiber reinforced polymers play a crucial role as enablers of lightweight and high performing structures to increase efficiency in aviation. However, the ever-increasing awareness for the environmental impacts has led to a growing interest in bio-based and recycled ‘eco-composites’ as substitutes for the conventional synthetic constituents. Recently, the international collaboration of Chinese and European partners in the ECO-COMPASS project provided an assessment of different eco-materials and technologies for their potential application in aircraft interior and secondary composite structures. This project summary reports the main findings of the ECO-COMPASS project and gives an outlook to the next steps necessary for introducing eco-composites as an alternative solution to fulfill the CLEAN SKY target.