Sensors and actuators based on multifunctional materials are a substantial component of smart structures and can, in the favorable case, also have load-bearing functions. Such multifunctional materials, also called smart or intelligent, are energy converters that respond in a technically usable manner to an external stimulus. The most widely employed types respond to an electric, thermal or magnetic field with a change in their mechanical properties. Well-known representatives are piezoceramics (load/deformation response to an electric field), shape memory alloys (temperature dependent load/deformation) as well as electro- and magnetorheological fluids (influence of shear transmission in an electrical or magnetic field respectively). Typically, the underlying actuation mechanism is caused by a microscopic reconfiguration in the material and functions in both directions. A change in the mechanical characteristics due to external loads can be detected and, thus, allows for sensor use also.
The reliable subsequent treatment and structural integration of the usually very sensitive materials is however connected with some expenditure and risk. A favourable and industry compatible concept is therefore to process the respective basic materials first to compact elements. During this step also necessary additional components, like electrodes, insulators etc., can be brought in. In a second step, the actuators and sensors are combined with a structural material or the structure itself. The development and design of such packaged device is therefore a central research topic in Adaptronics.
Special attention in Adaptronics is paid to patch actuators and sensors. With this kind of patch device the mechanical energy is not transmitted through discrete points (e.g. with piezo stack actuators), but by shear over a laminar layer of adhesive. This is of great importance for ultra lightweight structures in particular, since no discrete points of force transmission are necessary. The weight and size optimized actuators and sensors are brought into thin-walled, lightweight structures and suppress unsuitable vibrations and deformations directly at the place of their emergence.
For more information, see: Application Specific Design of Adaptive Structures with Piezoceramic Patch Actuators (pdf file, 0.5 MB)