Cooperation Projekt C2

The development of so-called adaptive material composites directly enabling the integration of the sensor-actuator systems in terms of an intelligent semifinished product within the process when the component is being produced is a big challenge. The sensor and actuator materials considered in this research project are based on the piezoelectrical effect that makes a transformation from mechanical into electrical energy and vice versa possible. The physical description of the piezoelectricity results from the elasticity sensor, the piezoelectrical coupling tensor and the dielectrical tensor. So, the ratio between the electrical values (electrical field intensity, dielectric shift) and the mechanical values (mechanical distortion, mechanical tension) are modelled. Therefore, an overall characterization of such materials requires a determination of the tensor entries (e.g. the piezoelectrical material PZT includes ten material parameters) in order to determine the variables, such as the coupling coefficient, electrical impedance etc. that are essential for the design process. For determining these material data, the standard methods cannot be used as the necessary sample geometries cannot particularly be produced for the piezo fiber materials considered in this research project. Moreover, it needs to be bore in mind that in contrast to the bulk-material, significant material changes resulting from mechanical and thermal stressing in the forming process may occur.
A central application field for the adaptive material composites can be found in the active and passive vibration compensation. This mainly concerns the production of components that are preferably light and which additionally have high noise absorption and a low noise emission (during mechanical activation). This is to be realized by sensor-actuator systems integrated into the material by means of which active vibration compensation can be reached. For developing and optimizing such complex systems it requires a computer-assisted workplace enabling the highly precise stimulation from the mechanical vibration to the acoustical emission that also include the sensor-actuator systems. Since the concise description of the mechanical, piezoelectrical and electrical variables requires the solution of the underlying partial differential equation which cannot be solved analytically, efficient numerical arithmetic techniques for this coupled multi-body problem are necessary. Relying on a chair-developed finite elements method, specific finite elements are to be derived and implemented, by which the piezoelectrical composite materials can efficiently and accurately be modelled. This especially includes shell and fiber elements that correctly describe the critical non-linear features of the piezoceramics and its ambient passive materials. Finally, the FE method is to cover the entire chain “component – sensor – regulator – actuator” simultaneously. Particularly for describing the actuator, partially also the component, both the non-linear material laws and the geometrical non-linearities need to be considered.