應用能量指標法於編織複合材料疊層板之非破壞檢測

Nondestructive Detection of Damage in Woven Fabric Composite Laminates Using Energy Index Method

10.6346/NPUST.2008.00137

王桀民

平面編織複合材料 ； 應變能法 ； 等效模型 ； 模態分析 ； 掃描破壞指標法 ； woven fabric composite ； modal strain energy ； equivalent models ； experimental modal analysis ； scanning damage index

屏東科技大學車輛工程系所學位論文

2008年

碩士

胡惠文

繁體中文

本文應用模態應變能法(SEM)針對平面編織複合材料疊層板之表面裂縫進行非破壞檢測。材料採用Hexcel 所生產平織型編織複合碳纖維/環氧樹酯(F3T-282/ epoxy (DICY))製造疊層板。並以美工刀切割一個不影響整體剛性的表面裂縫作為代表性的破壞。以三種模型cross-ply、orthotropic與representative cell來模擬編織複合材料疊層板。首先應用有限元素分析軟體(ANSYS)與實驗模態分析，採用逆向法獲得三種模型疊層板未知的等效機械性質，經比對分析與實驗之模態參數，確認有限元模型之等效性。進行模態分析以獲得破壞前後疊層板之自然頻率與模態振型位移，經由將破壞前後之模態振型位以區塊應變能法定義一破壞指標用來檢測破壞的位置，其中應變能之計算採用微分值積法(DQM)。裂縫檢測方式以整體模態、局部敲擊之模態與以整體模態模態掃描應變能指標三種方式進行檢測。結果顯示分析與實驗之整體與局部檢測破壞指標均可成功地預測出複合材料疊層板之表面裂縫位置，掃描應變能指標法則顯示可能找出裂縫方向。

The work presents the detection of surface cracks in a woven fabric composite laminate using a modal strain energy method. A carbon fabric F3T-282/epoxy (DICY) is used to fabricate a plain woven laminate. In the first place, the unknown material properties are computed by utilizing an inverse method through the finite element analysis and experimental modal analysis. Three equivalent models, i.e. cross-ply [0/90]ns, orthotropic and representative cell, are established to simulate the woven laminate. A surface crack is created to represent a nominal damage which is comparatively small and not to significantly affect the global stiffness of the woven laminate. Experimental modal analysis is conducted on the woven laminate to obtain the modal displacements before and after damage. The modal displacements are used to compute the modal strain energies through the three equivalent models. A damage index is defined by employing the fractional modal strain energy of the woven laminate before and after damage, and then used to identify the location of surface crack. Limited by grid points in measurement, a differential quadrature method is utilized to compute the partial differential terms in strain energy formula. Global, locate and scanning damage index three detection way are developed. Results show, the damage indices obtained from global and local measurements successfully locate the surface crack in woven laminate. The scanning damage index well identify the surface crack location and crack direction. Only few measured mode shapes are required in this method, which holds a relatively low cost and flexibility in measurement, nondestructive evaluation, and feasibility of real-time monitoring in woven laminates.

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