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Structural pOweR CompositEs foR futurE civil aiRcraft

Periodic Reporting for period 3 - SORCERER (Structural pOweR CompositEs foR futurE civil aiRcraft)

Reporting period: 2020-02-01 to 2021-01-31

Airbus aspires to make all-electric regional aircraft by 2050, to maintain its leading technological and environmental credentials, which are central to its competitive advantage. This goal is extremely challenging, especially for energy storage: replacing the current requirement for 30 kg of kerosene per passenger with existing battery technology would introduce an additional 1000 kg/passenger. Structural power composites provide one possible solution: in this concept, the existing fabric of the aircraft structure is made multifunctional, fulfilling both mechanical demands and providing electrical energy storage, simultaneously. By using the same mass for two traditionally disparate functions, considerable weight savings can be obtained; specifically, the potential to make secondary structures or interior parts from structural power materials is very appealing. Furthermore, Airbus has more than 30,000 kg of cables on an A380 aircraft. Distributed energy storage in the airframe and interiors, as well as materials with an intrinsic cable functionality, offer potentially significant weight and volume reductions to the system. With the development of structural power composites in SORCERER, we offer the aircraft industry a stepping-stone for realisation of ‘massless’ energy storage for future aircraft.

The overall objective of the proposed project SORCERER is to advance structural power materials such that they can start to be adopted in Large Passenger Aircraft (LPA), as set out in the call JTI-CS2-2016-CFP03-LPA-02-11 Structural Energy Storage and Power Generation Functionalities in Multifunctional Composite Structures.

There were three overarching objectives of SORCERER:

Regarding Objective 1 (Structural Battery), a demonstrator was delivered, which consisted of three multifunctional cells within a composite laminate (370 x 120 x 1.1mm) which had a flexural modulus of 4.3 GPa and a voltage of 9.2V.

Regarding Objective 2 (Structural Energy Generation), the concept of morphing and the potential for energy harvesting was demonstrated, but the final device was not completed by the end of the project.

Regarding Objective 3 (Structural Supercapacitor), a prototype, consisting of structural supercapacitors of CNT fibre veils, with a polymer electrolyte, were encapsulated in a CFRP laminate with a GFRP skin by IMDEA. An array of 16 supercapacitors was assembled, and demonstrated to provide an energy buffer (200 ms distruption of power). At the end of the project Imperial College had manufactured cells (A5 size), for a cabin door demonstrator, with the final component consisting of a C-beam with eight cells in the web.
Airbus aspires to make all-electric regional aircraft by 2050, to maintain its leading technological and environmental credentials, which are central to its competitive advantage. This goal is extremely challenging, especially for energy storage: replacing the current requirement for 30 kg of kerosene per passenger with existing battery technology would introduce an additional 1000 kg/passenger. Structural power composites provide one possible solution: in this concept, the existing fabric of the aircraft structure is made multifunctional, fulfilling both mechanical demands and providing electrical energy storage, simultaneously. By using the same mass for two traditionally disparate functions, considerable weight savings can be obtained; specifically, the potential to make secondary structures or interior parts from structural power materials is very appealing. Furthermore, Airbus has more than 30,000 kg of cables on an A380 aircraft. Distributed energy storage in the airframe and interiors, as well as materials with an intrinsic cable functionality, offer potentially significant weight and volume reductions to the system. With the development of structural power composites in SORCERER, we offer the aircraft industry a stepping-stone for realisation of ‘massless’ energy storage for future aircraft.

There were three overarching objectives of SORCERER, with the achievements over the project shown below:

• Objective 1: We have addressed the technical issues associated with structural batteries, which were currently at TRL3, and have now reached TRL4, such that a laboratory scale element, approximately 1/2 A4 sized structural battery composite laminate, with three cells connected in series operating at a voltage of 9 V has been delivered. The structural battery cells demonstrated the following properties: an energy density of the structural battery cell was 109 Wh/kg and a tensile modulus of 25 GPa was reached and a tensile strength exceeding 300 MPa was recorded.

• Objective 2: The function of energy generation utilising ion-intercalated carbon fibres has been demonstrated in a much simplified manner at a small lab-scale. We now need to look in depth as to how this function works in more detail, how to improve the efficiency and power output, and move this potential technology up towards TRL3.

• Objective 3: We have addressed the critical issues associated with structural supercapacitors that hinder adoption of this technology into aerospace platforms. We addressed the TRL3 technological hurdles such that TRL4 was achieved by integrating supercapacitors into a structural component: this was done by IMDEA (energy buffer for aircraft systems) and Imperial (emergency cabin door supply). During SORCERER we improved the power and energy densities, encapsulation and laminate hybridisation, and multifunctional design methodologies. The aspiration was to achieve energy and power densities of 2Wh/kg (not achieved) and 1kW/kg (achieved), respectively, coupled with achieving 80% of the fibre dominated performance of conventional composites (not demonstrated).
As described in the previous Section, there have been considerable steps forward beyond the state of the art in the field of structural power devices.

It is anticipated that structural battery and structural supercapacitor constituents will be further improved, with particular focus on improving mechanical performance. Similarly, device assembly and performance will be investigated further, with an aim to demonstrating a high enough performance to provide weight savings compared to conventional systems. The long-term aspiration of the modelling is to couple the mechanical and electrochemical analysis procedures to establish a holistic multifunctional optimisation methodology. The main focus of the final half of the project was in delivery of the structural power demonstrators, which was partly achieved, but hindered by the impact of Covid. It is anticipated these will herald considerable adoption of structural power materials by transport and portable electronic industries, leading to a paradigm change in energy storage for these industries.
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