New approach for monitoring piezoceramic fibers during joining by forming

A new joining by forming technology for integrating piezoceramic fibers as functional elements into microstructured aluminum sheets proved its feasibility in experimental investigations. Thereby five piezoceramic fibers with geometrical dimensions of 12 mm x 0.56 mm x 0.46 mm are placed into cavities with dimensions of 10 mm x 0.6 mm x 0.6 mm. The joining is performed through narrowing of the cavities by applying a vertical force of up to 20 kN to the 400 µm wide webs between the cavities of the microstructure. For later smart sensor or actuator applications the mechanical interconnection and preload between the fibers and the surrounding metal structure is an important key issue. Preliminary investigations characterize the mechanical interconnection of the joining partners after the joining operation with microscopic methods. Scope of the paper is the development of a novel method for monitoring the condition of piezoceramic fibers during the joining by forming process. The paper presents the latest scientific results on the electro-mechanical behavior of piezoelectric ceramics during joining by forming. Numerical results of the stress distribution and resonance characteristics of the piezoceramic-metal-composites are presented. Furthermore fabricated test samples are characterized by impedance spectroscopy. Based on the experimental and numerical results, a novel monitoring method for the piezoceramic fibers during the joining by forming process is proposed. For this purpose, the piezoceramic fibers are electrically contacted inside the forming.