To make modern aircraft ever lighter, faster and more fuel efficient, manufacturers are continually introducing new advanced materials, composites and super lightweight structures. Before using them on a plane, the integrity and performance of these materials have to be tested in a non-destructive way, to see how they would perform in the real-life pressure and temperature conditions of flight. Among the techniques aero-space testing facilities currently rely on are two important tests: one using laser beams and one using thermal imaging to see inside the material under stress and detect problems in structures caused by hidden defects. European researchers have found a way to replace these two with a single test.
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Dr Marc Georges, head of the Non-Destructive Testing and Laser lab at the Space Centre in Liège, Belgium, saw an opportunity for a technology breakthrough that would save both time and cost in the aerospace testing process. "Leading aerospace companies traditionally use two separate measurement devices to gather the testing data. We found there was a stability problem with laser-based testing systems and I believed that this could be resolved by using infrared-based technology. That would even offer many additional benefits. Our suggestion that we would be better off using a single device generated considerable interest."
The basis of his idea was to create a more stable system that permits the simultaneous capture of both temperature and structural change in-formation. That would offer the aerospace industry a quicker and less expensive testing process. "The real beauty of using holography in the infrared spectrum," Georges explains, "is that it allows you to capture a thermal image of the object as well as a spatial image."
At the hub of the project is the Centre Spatial de Liège (a leading space research centre at the University of Liège), which houses a specialist laboratory for non-destructive optical measuring methods. The Institut für Technische Optik at the University of Stuttgart specialises in holog-raphy, while the Dresden-based InfraTec GmbH is a producer of thermal imaging systems. Building on specialist infrared technology developed in former East Germany, this young SME designed a new cooled camera, which could meet the exacting requirements of holography in term of resolution, frame rate and noise characteristics.
For the testing phase of the project a transportable version of the instrument was built by Optrion s.a., a spin-off company from the Liège Space Centre. This FANTOM device lived up to expectations, proving its ability to characterise material behaviour under high levels of thermal stress and out-of-lab conditions. Meanwhile, its unique thermography-holography combination offers improved detection capabilities compared to current techniques.
The finished prototype was put through its paces in real-life working conditions in the structural testing facilities of a group of potential end-users.
The technology is now being fine-tuned for aerospace applications and spin-offs of the innovation are already hitting the market: the German SME InfraTec has already taken derivatives of its new infrared cameras to the market and sold them to customers in a variety of industrial sectors.