Researchers at the Fraunhofer Institute of Silicate Research ISC in Germany have developed new sensor concepts using plastics reinforced with piezoelectric ceramic fibres to record the mechanical load in all three dimensions.
‘The basic principle is old – what is new is the scale,’ says Dieter Sporn, a chemist at Fraunhofer ISC. ‘Our ceramic fibres have a dimeter of a fraction of a millimetre. This makes the filiform sensors so supple that they can be incorporated in formable plastic materials.’ Sporn believes the new sensor technology will be suitable for all monitoring tasks on fibre composite material subject to heavy loads.
The researchers plan to use two bundles of fibres, embedded as sheets and offset by an angle of 90°. A third piezoelectric sensor on the surface of the component enables the position of the weakened or damaged area to be localised.
Apart from its obvious use in aircraft manufacturing to detect material fatigue of failure in critical components, the new technology also offers a means of making wind turbines safer and more durable.
Siemens is also working on another application that will soon be ready for mass production. Piezoelectric fibres incorporated in car seats send signals to the airbag system informing it of the weight carried by the seat. Such information enables the airbag to inflate at a variable rate that provides the same soft landing for a small child as well as an adult.
A number of other sensor concepts are currently being worked on by an interdisciplinary team, including other research groups from the Fraunhofer Institute and a private company, Neue Materialien Wurzburg GmbH.