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Smart Intelligent Aircraft Structures

Periodic Report Summary - SARISTU (Smart intelligent aircraft structures)

Project context and objectives:

The 'Smart intelligent aircraft structures' (SARISTU), is a level 2 project conducted within the European Union (EU)'s Seventh Framework Programme (FP7) addressing the air travel cost reduction aspect of the 4th call.

As such, SARISTU's principal aims target a reduction of the manufacturing and in particular the operational cost of civil airliners. For this purpose, it matures and integrates different concepts which enable further fuel burn reductions through aircraft drag and weight reductions, reduces aircraft downtime in case of unscheduled inspections and improves the manufacturing times and subsequent performance of advanced fuselage structures.

Organised along the major principal components of an aircraft, development and integration activities centre on wing specific applications on one hand and fuselage applications on the other hand.

Project results:

At present, SARISTU has completed its first year out of the four year project duration. With a very large consortium maturing an equally large set of smart technologies, the prime concern during this period has been the successful launch of the programme and related activities, the completion of the initial requirements and specification phase, the launch of initial test activities and the start of specific design activities for the different test articles used for demonstration and performance validation testing in SARISTU's fourth year. While at such an early stage in the project it would of course be premature to draw firm conclusions as to the final performance of the developed concepts, some key aspects can already be highlighted.

Although a very ambitious fuel saving target has been set for SARISTU, early calculations and Computational fluid dynamics (CFD) analysis indicates that the target is likely to be exceeded but will still need to be offset against a possible weight penalty. Similarly, structural health monitoring-related trials indicate that specific aircraft inspections may gain higher benefits than originally anticipated. While work on the most suitable functionality integration is progressing, testing will continue throughout the coming years so that an assessment of the achievability of these goals is, at present, premature.

With respect to the incorporate of carbon nanotubes into the structure, initial testing indicated the principal feasibility of industrial laminate manufacture. However, it is again too early to come to definite conclusions as to the final performance with respect to cost reductions.

Potential impact:

With respect to the wing specific applications, the further maturation and development of conformal morphing technologies, which enable a smooth shape change of aerodynamic surfaces, as well as the integration of structural health monitoring are at the focus of activities. To date, conformal morphing surfaces cannot be implemented in practice due to the conflicting requirements of a high required structural stiffness and the ability to be actively deformed. Furthermore, additional functionalities have to address specific aircraft requirements such as lightning strike protection, bird strike protection, erosion protection and a reliable integration of different sensor systems into the control architecture. By enabling the consideration of conformal moving surfaces at the aircraft design stage, SARISTU expects to reduce the fuel consumption of future airliners by up to 6 % while at the same time offering improvements in flight path noise.

Fuselage specific applications centre on the integration of structural health monitoring technologies in the aircraft architecture as well as the further maturation of multifunctional structures and the improvement of a typical fuselage's robustness. By enabling a significantly more rapid damage assessment and categorisation than is currently possible, aircraft structural inspections due to accidental damages are expected to be performed with a significantly reduced flight delay. This in turn is expected to result in a cost reduction of such in-service inspection activities of up to 1 % for carbon fibre based fuselage structures. Furthermore, advantages from such on- and off-line monitoring systems can be combined with achievable improvements in the structures damage tolerance. Such improvements are investigated and developed within SARISTU's multifunctional structures approach which, among other solutions, integrates carbon nanotubes in the basic skin-stringer-frame system. Resulting improvements can be exploited either directly for an improved structural robustness or translated into structural weight savings of up to 5 % for the skin-stringer-frame system.

Multifunctional structures also incorporate the exploitation of carbon nanotube electrical conductivity in order to enable a carbon fibre based structure to perform low level electrical functionalities. Together with further technological integration targeting the higher electrical functions such as electrical grounding and bonding, it is expected that the currently heavy and costly electrical structure network required with a black fuselage can be designed significantly lighter and installed approximately 15 % more cheaply. Culminating in wing and fuselage specific demonstration and performance verification activities in its fourth and final year, SARISTU is expected to bring benefits beyond its current scope of more affordable air travel. While conformal morphing can in principle be applied to further aerodynamic surfaces, it could also bring benefits to other industries where active aerodynamic or fluidic control is beneficial. Similarly, structural health monitoring can be expected to bring in particular operational benefits wherever light weight construction is of primary importance. Last but not least, overcoming technical obstacles related to the electrical properties of composite structures, as well as the integration of data generation and transmission into composite structures will be applicable well beyond the aircraft industry.

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