| Popis: |
Space structures would benefit greatly from an ability to tune the dissipation and stiffness of the structural element. This would provide a compromise between large passive systems, and complex, real-time, active control implementations. Different elements of a structure could be altered based on the loads that they experience. This study will focus on thin piezoelectric film strips connected in parallel with an electronic circuit which provides a "negative capacitance," and an electrical load consisting of a resistor and a capacitor. Due to the inverse piezoelectric effect, each film forms an electromechanical system in conjunction with the parallel circuit. The overall impedance of this system can be controlled by correctly varying gain parameters within the circuit. This work models the PVDF strips of non-vanishing thickness and stretched under a constant, boundary applied tension. Both flexural stiffness and in-plane tension are accounted for in setting up the partial differential equation of motion. Harmonic excitation was provided with an acoustic speaker driven by a wave form generator. Measurements of out-of-plane deflection at a chosen point were taken using an LED/photodiode pair, which was calibrated experimentally. The voltage developed between the electrodes was also measured. Theoretical and experimental results are analyzed and compared. |
