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28th January 2019, Modena

New wind tunnel model with Windform XT 2.0

The new wind tunnel model. © Leonardo Helicopter Division

The new wind tunnel model. © Leonardo Helicopter Division

The new wind tunnel model of the Leonardo tiltrotor AW609 has been designed, manufactured and assembled under the supervision of Leonardo Helicopter Division by Metaltech for a series of dedicated low speed wind tunnel tests, using materials by CRP Technology.

The project related to the manufacturing of some external parts (nose and cockpit, rear fuselage, nacelles, external fuel tanks, fairings) of the wind tunnel model for the prototype of the new Leonardo HD tiltrotor AW609, made by Selective Laser Sintering technology, and Windform XT 2.0 carbon-composite material, both supplied by CRP Technology.

“This project allowed CRP Technology, once again, to highlight the perfect union between advanced 3D printing technology (Selective Laser Sintering) and Windform high-performance composite materials. Thanks to the Windform materials, it was possible to complete and test the model in the wind tunnel within a very short time, with excellent results and with high-performing mechanical and aerodynamic properties.”

Aircraft propeller spinners. © Leonardo Helicopter Division

Aircraft propeller spinners. © Leonardo Helicopter Division

The low speed wind tunnel tests were intended to cover a standard range of flight attitudes to be performed at Leonardo HD wind tunnel facility and at Politecnico of Milan for the high angles of flight envelope. During the different test sessions various external geometries have been changed and checked in order to understand all the aerodynamic phenomena. The external main components redesigned and manufactured include: fuselage and nose components, fairings, nacelles and spinner shapes, empennage, wings and flaperons.

Goals

Leonardo Helicopter Division required a very short timetable, but with the highest level of reliability and commonality, the research of materials with high mechanical and aerodynamic characteristics for these components, and the design and manufacture an aluminium alloy internal main structure suitable to be easily implemented with new geometries for the future aircraft versions or improved solutions.

Aircraft nose and cockpit. © Leonardo Helicopter Division

Aircraft nose and cockpit. © Leonardo Helicopter Division

“This detail is crucial to the applied loads to be sustainable, and therefore they can’t be underestimated. In fact, the aerodynamic loads by the wind in the tunnel are very high,” CRP Technology explained. “The most critical aspect of the project is therefore the resistance to the loads, but also the necessity to maintain good dimensional tolerances of such a large dimensioned component under load.”

Design condition

To assure the model capacity to withstand the loads expected during the various wind tunnel testing phases, stress and strain calculation have been performed. Such structural strength assessments have been executed for all the critical model components and for the assigned loading conditions.

Windform XT 2.0

Windform XT 2.0 is a carbon fibre reinforced composite 3D printing material known for its mechanical properties, appreciable for many applications such as wind tunnel, because of its high heat deflection, stiffness, and first-rate detail reproduction. It replaces the previous formula of Windform XT in the Windform family of composite materials: Windform XT 2.0 features improvements in mechanical properties including +8% increase in tensile strength, +22% in tensile modulus, and a +46% increase in elongation at break, the manufacturer explains.

Process and result

From the beginning the work was focused on the design of the components, with a correct split of the parts. Identifying the parts to split was an operation undertaken with the CAD, evaluating the functional measures of the working volume. Not much more than one day was necessary to manufacture the jobs to set on the 3D printing machines and, after only four manufacturing days, all the various parts of the components were already physically created.

“Different confidential efficiencies, which are an integral part of CRP Technology’s specific know-how, allowed the reduction of the delivery lead time and allowed CRP to minimise the normal tolerances of this technology, and eradicate any potential problem of deformation or out of tolerance,” the company reports.

The final step was the complete model surface finishing, directly mounted on the rig assembly in order to optimise the small imperfections that could have come from the union of the single components.

www.crptechnology.com

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