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Bernard Stervinou, a lecturer at the Institut Universitaire de Technologie (IUT) of Brest (France) and keen aviation enthusiast, has created a group comprising his own students along with manufacturers in order to produce the first fuselage for a light aircraft by means of one-shot infusion: the Nijal, whose name means "to fly" in Breton.
(Published on January-February 2009 – JEC Magazine #46)
The objective was to construct France's first light aircraft with an integrally stiffened one-piece fuselage made from carbon/epoxy in a single step. The result: an award at the JEC Show 2008 in Paris.
Bernard Stervinou has been teaching the use of composite materials since 1984, and has been a Vocational Degree lecturer at Brest IUT since 1999. Already a pilot and the manufacturer and owner of an aircraft made out of composites, the idea came to him to design and manufacture a brand-new aircraft. He opted for a classic design in order to focus exclusively on the composite processes.
This aircraft has served as a basis for the training of around 70 students, who have thus been able to discover the world of aviation and who today, for the most part, are working in this particular field (following their training, around 75% of the Vocational Degree students of Brest IUT find work in aerospace and 25% in boat building).
With each passing crop of alumni, a number of these students have become increasingly involved in the development of new processes, testing and validation, and in manufacturing the tools.
A few years ago, Mr Stervinou created an association called "Savoir-Faire, Savoirs Aéronautiques et Composites" ("Knowhow, Aerospace Skills and Composites") which finances the aircraft and which will take charge of it.
Mr Stervinou has managed to gather many partners around him:
The innovation that characterises this project lies in the infusion moulding on a complex carbon preform of an integrallystiffened one-piece carbon aircraft fuselage in a single step. The composite materials comply precisely with the mechanical characteristics / mass ratio. This technology makes the industrial process competitive. It offers the integration of functions, time savings in manufacturing and improved working conditions, not to mention the absence of expiry limits, the disadvantage with prepregs.
This development began in 2000 with a study of the wing and its tools, all of which were produced by infusion (technology transfer to Rex Composites of the know-how acquired at Brest). The complete instrumented wing, with flaps and ailerons, was tested for combined flexion and torsion up to the point of rupture (in the presence of the DGAC). The model for the lower part of the fuselage was produced in PS foam via numerically-controlled machining. The corresponding mould was produced in high-temperature carbon/epoxy in order to be able to carry out in parallel aeronautical developments using the LRI process. The lower part of the integrally-stiffened fuselage is produced with this tool, via cold infusion of high-performance epoxy resin (frames, stringers, top hat sections, reinforced fire bulkhead).
Another fuselage was manufactured in a single step using experimental processes that prefigure more complex fuselages for airliners (integrally stiffened one-piece fuselage, spars, top hat sections, stringers, tailfin, fire bulkhead).
The small team has rattled off one exploit after another including, in particular, the development of an innovative process for high-temperature (130°C) epoxy resin infusion, for reducing viscosity and improving the impregnation of carbon fibres.
The Nijal airframe was produced in just three weeks before being presented at the JEC Show 2008 in Paris. Today, all that remains is to finish the mechanical sections in order to complete the aircraft that is due to take to the air by 2010. This project has attracted the interest of several aircraft manufacturers. As far as Bernard Stervinou is concerned, he has already moved on to his next project, still in association with his students. This involves inventing and producing in the workshop of his IUT a solar hydrofoil that will ride the waves powered exclusively by solar energy.
JEC Composites Magazine: What has been the impact of the JEC Award that you received in 2008 on the students who took part in the project? Has it had an effect on the number of applicants for the vocational degree that you are running?
BERNARD STERVINOU: Clearly, this has had a major impact on the student group first and foremost in terms of bringing the project to fruition. No one had ever previously produced a complete fuselage via infusion in a single step, and this represented quite a challenge. Yet, as one by one the hurdles were overcome, they started to believe in it and the prospect of putting the aircraft on show in Paris gave them a real boost. It got to the point where everyone's free time and weekends were taken up by the project and we were all working to ensure that it was completed on time. This experience will stay with them for many years. In business, it will serve as a calling card for them, since manufacturers are always on the lookout for young people who have worked on innovative projects. These manufacturers are also sure to appreciate the energy that these young people are capable of investing in a professional project.
Receiving the award on the stage at the Louvre was the reward for their efforts, and also a gesture of acknowledgement from the industry. All the JEC show visitors saw the aircraft. It also enjoyed good media exposure. When these young people are able to demonstrate that they took part in this project the confidence of their interlocutors is assured, and this is what they need most in their incipient careers.
These young people have friends in the schools they came from, and when they recount their adventures during this year and at the JEC show we get great publicity for our course and subsequently have no difficulty in recruiting applicants. We receive approximately 80 application files from which we select 12 students.
JCM: Rex Composites, with its “Lionceau”, was the first company to present an aircraft entirely made from carbon. Is it planned in the short to medium term to use the technologies that you used for the Nijal?
B. S.: Rex Composites has indeed come up with an all-carbon aircraft. I undertook a technology transfer with them, under the Technical Institute of the University of Brest structure named SYRTEF, for the infusion process in 2002. Right now I don't know if they're using this technology, and the Lionceau was certified with a different type of technology (prepreg and wet lay-up). There can be no doubt that this technology will make inroads in the aerospace industry. It has already started to happen at Airbus, and the light aircraft manufacturers are sure to take it up. Socata has begun development (FUSCOMP project) and has short-term objectives (LRI technology, which involves hot infusion moulding).
JCM: Could you tell us more about your new project, the solar hydrofoil?
B. S.: This involves propelling a boat that resembles a trimaran on foils (without a sail) using nothing but the energy from solar panels. It also serves as a demonstrator to show that, using solar power and optimising the yield, it is possible to obtain excellent performance. The vessel is piloted like an aircraft with a mini-joystick in the right hand which controls pitch and roll, a steering lever in the left hand and an accelerator foot pedal. The objective of this project is to acquire know-how in the management and encapsulation of photovoltaic cells in diverse and varied composite material structures.