Novel approaches for the determination of the process specific polarization of piezoceramic modules embedded in thermoplastic composites

Fiber-reinforced thermoplastic composites with embedded sensors promise the implementation of advanced functionalities. Currently, the technological gap for industrial applications arises from the lack of high-volume manufacturing technologies. The DFG research project CRC/TR 39 is aimed at the development of the required production technologies. One process route focuses on the matrixhomogeneous integration of thermoplasticcompatible piezoceramic modules (TPM) in fiberreinforced thermoplastic structures. Hence, a crucial question concerns the determination of the piezoceramic polarization during the hot pressing process. The paper introduces a new approach to determine and monitor the polarization state of piezoceramic elements during thermal load of the production process. The new method is based on the measurement of the free charge that is released from the poled, ferroelectric material due to the temperature increase. This signal is measured with respect to temperature and time. Alternatively, the polarization state is determined using an advanced thermal wave method. This newly developed method was shown to be well suited to measure packaged piezoceramic modules with a heterogeneous, multilayer design.