???aural:Bildanfang???Aircraft sensors can detect stresses in the fuselage before cracks can form. © Micropelt GmbH???aural:Bildende???

When birds collide with a plane the consequences can be fatal - for both birds and humans. Fuselage damage can cause stresses which may later become cracks. Future aircraft sensors will detect such damage at an early stage. They are light, do not require cables or batteries, and can be located wherever needed. 

Researchers at the Fraunhofer Institute for Physical Measurement Techniques (IPM) in Freiburg are developing an energy supply for the sensors. "Together with Micropelt GmbH, we have created specially adapted thermoelectric generators," says Dr. Dirk Ebling from IPM. Thermoelectric materials are semiconductors which generate electric power through temperature differences. In case of the aircrafts, this is the temperature difference between the outside air (from -20°C to -50°C) and the passenger cabin (about 20°C). Connected in series, they produce enough power to run small sensors and a radio device to send the measured results to a central unit. "We are optimising the heat flow," says Ebling. A key question is how to couple the thermoelectric generator to warm and cold environments so that enough heat is transported. Scientists have addressed this problem by developing a climate chamber to simulate the temperature profile of the aircraft fuselage. The first optimised prototypes have been built. A finished prototype is scheduled for completion in about three years.

Many applications exist for such sensors. In automobiles they can reduce weight. In old buildings they can monitor damp. Medical applications are feasible, too. Sensors integrated into a running shirt could monitor an athlete’s pulse during training, and hearing aids could draw their energy from body heat.

More information: www.ipm.fhg.de