Effect of microstructure of metal-core piezoelectric fiber/aluminum composites on output voltage characteristics

Effect of the microstructure of a metal-core piezoelectric fiber/aluminum composite on the characteristics of its output voltage was investigated. The metal-core piezoelectric fiber/aluminum composite was developed to overcome the problems associated with piezoelectric ceramics, such as has poor mechanical properties, reliability; brittleness and low fracture strain. This composite contains piezoelectric fiber embedded in aluminum matrix by using interphase forming/bonding method, which significantly improved the fracture strain of the metal-core piezoelectric fiber. The composite is expected to be used in long-term, high reliability sensors and energy harvesting devices. However, it was observed that the output voltage variation is caused by the residual Al-Cu eutectic alloy from the embedding process and contributes to the eccentricity of the core. These drawbacks, interfere with the practical use of this composite. In this study, the influence of the composite microstructure, such as the presence of the residual eutectic alloy and the eccentricity of the metal-core on the output voltage characteristics, is evaluated using finite element analysis. First, it was succeeded establishing a method considering that the radial direction of polarization, and confirmed the validity of the proposed method by reproducing the output voltage anisotropy of the composite and comparing the experimental values obtained in conventional studies with analysis value. Using this method, it was shown that the decrease of the output voltage is caused by the following; 1) The eutectic alloy having a high Young's modulus inhibits the stress transmission between the matrix and the piezoelectric ceramics, the stress of the piezoelectric ceramics decreases, 2) Eccentricity of the core lowers the stress in the portion where the piezoelectric constant is high near the core. From these results, possibility of design and suppress variations of the output voltage characteristics by adjust the structure of the composite was suggested.