Integration of piezoceramic composites in aluminium die casting structures and their functional characterization

Smart structures are using integrated sensors and actuators in combination with modified drive and control electronics for the active influence of dynamic structural characteristics, like noise control, vibration damping or structural health monitoring. The direct integration of sensors and actuators into structural body parts possess some benefits concerning process efficiency and margin but demand in return resilient sensor-actuator modules, which can withstand the forming process. For integration into metal structures, electrical isolation against the matrix has to be solved. We developed a fully inorganic module consisting of piezoceramic plates (PZT) embedded in an LTCC (low temperature co-fired ceramic) multilayer which could be successfully integrated into aluminium die casting parts for the first time. The LTCC/PZT modules are connected internally by screen-printed silver electrodes and pathways, and externally by a laser-based droplet joining method (LDJ). A hybrid support structure is used for the die casting process, in order to protect the braze joints and prevent drifting of the LTCC/PZT modules during melt immersion. The functionality of the embedded LTCC/PZT modules was determined by electro-mechanical methods like impedance analysis, ferroelectric hysteresis and deflection measurements. Permittivity and remnant polarization decreased slightly during the integrations steps: 1) laminating and 2) die casting. Measurement of deflection of a cantilever with integrated LTCC/PZT modules proved the actuator performance after die casting.