The Preparation, Characterization Andmechanics Problems Of Metal Core Piezoelectric Fibers

Metal-core piezoelectric fiber(MPF) has small size, and does not affect the performance of the structure when bonded on the surface or integrated with a host structure. The MPF with big thickness piezoelectric ceramic layer can generate larger strain as actuator. So that only one MPF can be act as sensor and actuator. Therefore, MPF have received special attention after successful fabrication. However, MPF as a new type piezoelectric device, there have been many problems unresolved as yet. In this thesis, the piezoelectric ceramic, fabrication and application of the MPF have been studied. The main content as follows:1. Research on piezoelectric materials and the technology for preparation of MPF. Firstly, this thesis has probed into the piezoelectric ceramics of MPF. Two piezoelectric ceramics, with high dielectric constant and high Curie point are prepared. Optimization of piezoelectric ceramics preparation technology is carried out. And the high performance piezoelectric ceramics are fabricated for MPF. The paste composition for MPF is researched, and the speed of metal core is optimized. The relationship between diameter of MPF and drawing speed of metal core is studied, and this information is important for the MPF extrusion and drawing process.2. Research on mechanical and electrical properties of MPF. After successful fabrication of the MPF, the vibration model of MPF is derived through the MPF piezoelectric equation. The electrical performance test procedures are standardized. The effect of existing test fixture on the measurement results are studied, and a measurement method without clamping as test standards for MPF piezoelectric parameters is proposed. The piezoelectric properties of MPF are lower than those of bulk ceramic counterpart, the origin of this discrepancy are investigated. The effect of geometrical shape and polarization are the cause of the low-properties of the MPF.3. Study on the interaction between MPF and Lamb wave. The theoretical model of excitation and sensing Lamb wave between MPF Actuator and MPF sensor are established. The strain response formula of excitation and sensing Lamb wave between MPF Actuator and MPF sensor is derived and verified by experiments. Effects of MPF length on Lamb wave excitation and sensing are researched. And the multiple MPFs with Lamb wave excitation is simulated and verified by experiments.4. The mechanics problems of HMPF(Half Coated Metal Core Piezoelectric Fiber) as air flow sensor. The HMPF as biological cilia sensor is analyzed in theory and the relationship between HMPF sensor voltage response and fluid velocity, direction is derived and verified by experiments. The result shows that HMPF has high directivity to sense airflow, the curve of response of voltage with the flow direction in polar coordinates is the typical "8" shape. Also the angular resolution of HMPF sensor is studied.