壓電纖維複材換能器於纖維補強複材基板的性能評估

Abstract

本文比較實驗室開發之兩種壓電纖維複材，評估激發複合材料層板蘭姆波及水平偏振橫波換能器的性能。實驗試片主要以單層玻璃纖維及巴沙木三明治複材板為主，四層玻纖複材板、四層碳纖維複材板為輔，進行比較。本研究以脈衝雷射點波源激發熱彈性板波，量測複材層板及三明治複材板之板波頻散曲線，實驗結果顯示板波擾動主要於纖維/樹脂層上傳遞，並量測兩換能器黏貼於複材板之輻射聲場、機械響應與衰減係數。另以數值模擬比較兩換能器於複材板之機械響應，做為實驗結果的參考與輔助說明。 本研究以兩種換能器檢測離型布與硬幣製作之人工缺陷，實驗結果發現時域訊號振幅與無缺陷基板有明顯差異，差距達14%以上，換能器具有檢測複材層板缺陷之能力。

This thesis evaluates the performance of two kinds of piezoelectric fiber composite (PFC) transducers, which are used to actuate and sense the Lamb waves and transverse horizontal waves in fiber-reinforced composite laminates. Composite specimens include single layer glass/epoxy plates, a balsa wood sandwiched between two skins of woven glass/epoxy; 4-ply glass/epoxy and graphite/epoxy specimens were also considered. A pulse Nd:YAG laser was used to generate thermo-elastic plate waves for experimental determination of the dispersion curves of plate wave propagation in composite specimens. The experimental results indicate that most energy carried by the plate wave localizes in the skin layer. The radiation patterns and mechanical response spectrum induced by both PFC transducers adhered on composite specimens were measured. The measured mechanical responses have been compared with the simulated results to assist explaining phenomena. Examination of defect detection using both PFC transducers has been carried out. Two artificial defects are considered. The first is an inclusion of release cloth in a composite laminate. The second is a coin attached on to the surface of a specimen. The signal amplitudes appear with significant differences, up to 14%. It has been shown that the PFC transducers have a capability to detect the embedded and surface defects in composite laminates.