具反對稱指插電極之壓電纖維複材超音波換能器及應用

Abstract

本計畫為兩年期研究計畫，發展一種嶄新的聲波換能器(簡稱AE-PFC)，並評估其 在質子交換膜燃料電池的應用潛力，偵測質子交換膜的濕度。AE-PFC 是由單一方向排 列的壓電纖維黏著於兩片軟性指叉電極之間，形成三明治結構。反對稱排列的指叉電極 之電力線與纖維方向成一夾角，提供斜向極化及撓曲致動所需的電場。AE-PFC 的質量 輕、柔軟度適中，激發固定波長的撓性板波，不僅可以平順黏貼於具有曲率的結構表面， 還可以作為超音波檢測及聲波感測研究的關鍵元件。本研究以有限元素分析探討 AE-PFC 的動態特性，其頻率響應為電極節距的函數，主結構的材料性質及厚度對於聲 波的工作頻率僅有稍微的影響，AE-PFC 的撓曲共振不因黏貼於主結構基材而消失。

A novel acoustic wave transducer AE-PFC and its potential application in moisture detection of the proton exchange membrane fuel cell are proposed in this two-year research program. The acoustic transducer is formed with unidirectional piezoelectric fibers sandwiched between two thin flexible sheets printed with interdigitated electrodes (IDE). The electric field lines induced by the anti-symmetrically aligned electrodes are inclined to the piezoelectric fibers. The IDE provides necessary electric field for polling and excitation of flexural plate waves. Because of light mass and moderate flexibility, AE-PFC is ideally conformable to the curved surface of the host structures. It can be used as a key component to generate fixed-wavelength flexural waves for ultrasonic inspection and acoustic wave sensing applications. A further numerical simulation for understanding the dynamic characteristics of AE-PFC was carried out using finite element analysis. The frequency responses of AE-PFC are explored as a function of the electrode pitch. The operating frequency of AE-PFC is almost independent of the material properties and thickness of the host structures. The flexural resonances of AE-PFC still remain when it is adhered to a host structure.