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Light weight airframe structures through combination with high performance materials

Periodic Reporting for period 1 - LightAir (Light weight airframe structures through combination with high performance materials)

Reporting period: 2018-11-01 to 2019-10-31

The new rotorcraft architecture developed by the Topic Manager and which will be demonstrated under FRC IADP aims at demonstrating that the compound rotorcraft configuration implementing and combining cutting-edge technologies as from the current Clean Sky Programme opens up new mobility roles that neither conventional helicopters nor fixed wing aircraft can currently cover in a way sustainable for both the operators and the industry.

The project will ultimately substantiate the possibility to combine in an advanced rotorcraft the high cruise speed, low fuel consumption and gas emission, low community noise impact, and productivity for operators. A large scale flightworthy demonstrator embodying the new European compound rotorcraft architecture will be designed, integrated and flight tested.

Innovation target is to achieve a weight reduction of about 15% for general airframe parts (monolithic and sandwich) and particularly shell structures like side shells, tailboom, horizontal and vertical stabilizer and the wings. Some of these shell structures, like the tailboom and wings have
mainly stiffness driven designs, were materials with higher stiffness increase directly the performance. By a combination of the standard structural materials with new high performance materials in the relevant areas, a weight saving potential is obvious.

The general objective of the LightAir project is to perform a complete characterization of three new materials proposed in the call (adhesive, composite and honeycomb) as well as to account for the scatter of material properties using statistical analysis to obtain design allowables.
To achieve the main objective several partial sub-objectives were defined. These sub-objectives are listed below along with a brief description of the work done during the reporting period towards its achievement.
• Manufacturing of coupons, elements and details according to aeronautical standards.
• Determination of design allowables from mechanical and physical characterization tests of coupons and elements.
• Implementation of new experimental techniques, at industrial scale, to obtain translaminar fracture properties of the composite, and complete constitutive traction separation laws (cohesive laws) under different environmental conditions
• Analysis of sub-structural details and implementation of new instrumentation techniques to reduce the number of specimens
• Statistical analysis of design allowables, and implementation of Bootstrapping to reduce the number of samples.
A Qualification Test Plan to characterize the new materials has been defined and discussed. It covers 3 levels of testing of the building block approach, from coupons to structural details.

The design and manufacturing of specimens for the three levels of testing is completed at 65% and the design of structural details and elements and their test rigs is already finished

The qualification test campaign has started and is progressing as expected. Its preparation includes the generation of the internal test procedures based on test standards and the discussions and iterations with the topic manager, the preparation of data reduction methods and calculations, the validation and approval of these data reduction sheets and the design and manufacturing of specific test fixtures and rigs. The preparation stage of this WP is completed at 90%. As for the tests themselves, AMADE-UdG has recently started the level-1 tests and completed about 10%.
A comprehensive understanding of the mechanical behaviour of the new materials evaluated will be reached at the end of the project.

LightAir project will design and perform a material qualification campaign and performance assessment that will contribute to (i) have a better understanding of three mainly used materials in an airframe structure and to (ii) improve design allowables with respect to existing materials. A direct impact from these two contributions is a significant drop in the weight of the aircraft structure. The weight reduction is directly related to the efficiency of the aircraft, therefore reducing fuel consumption, operational costs, power requirements and the level of emissions.
From a certification point of view, the qualification of new materials and seting up their manufacturing process will launch the technology to TRL9 in short time, which will reduce the time to market of the new materials evaluated in this project.
Specimen manufacturing
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Specimen testing