Polymer-metal matrix enables strains to be measured

Paul Boughton
A new polymer-metal material with sensory properties makes it possible to produce plastic component parts that monitor themselves. This material can be combined with others and used in a variety of different ways. Researchers from the Fraunhofer Institute will be unveiling this polymer-metal composite at the Electronica 2010 fair (9-12 November 2010 in Munich, Germany).
During a storm, wind turbine blades are subjected to very heavy loads as they cut through the air at more than 200km/h. Elsewhere, machine components made of plastic or airplane wings must withstand substantial loads as well.
Sensors today are normally used to measure whether these components are strained beyond capacity, and it requires a lot of effort to install them into the component parts or glue them onto their surface. Because these monitoring sensors usually only register tensile or pressure loads in a small range, several individual sensors are linked to create a network in order to record strains over larger areas of the component. Researchers at the Fraunhofer Institute for Manufacturing Technology and Applied Material Research (IFAM) in Bremen, Germany, are now making it easier to inspect these large-scale components because they have developed a new composite material that has sensory properties; this structural material that can be directly worked or installed into a synthetic component when it is manufactured.
Fraunhofer's researchers have created the new composite by blending plastic and metal in the form of a polymer-metal matrix. There is a wide range of plastics that are suited as a matrix material for manufacturing this composite, which means that it can easily be tailored for different purposes. But it also has other advantages. First of all, due to its synthetic character, this material can be easily processed. Beyond this, it is lightweight and conducts current and heat very well due to the high proportion of metal in it. What is especially fascinating about this material is the fact that it can be processed with conventional machines used in plastics manufacturing – among other things, in extruders or in injection-moulding machines. Finally, this material can be laminated as a type of mat on large surfaces. In the future, researchers want to use nozzles to apply this conducting plastic as a viscous liquid to geometrically complex surfaces.
Arne Haberkorn, the project manager for composite developments at the Fraunhofer Institute for Manufacturing Technology and Applied Material Research, comments: "We reach a metallic filling proportion of as much as 90 per cent in weight in this composite when needed." When loads are applied to the component, the composite's electrical resistance changes and the signal can be transmitted over a cable for analysis.
For more information, visit www.fraunhofer.de

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