複合材料結構的彈性常數識別

Abstract

近幾年來，工業界已大量且廣泛的使用複合材料構件，特別是高強度複合材料結構的製造。為了確保結構件使用的高可靠性，複合材料的力學行為表現必須被正確的預知和仔細的監控，眾所皆知；不同的製造或固化成型方法會導至複合材料構件有不同的材料性質；另一方面複合材料構件承受動態載荷或在各種外在、內在缺陷影響下導致結構剛性衰減以致結構突然破壞。因此正確的結構力學分析有賴於識別實際結構的彈性常數；特別是複合材料結構，所以識別真實的材料機械性質已成為一個重要的研究課題。 本文介紹一種非破壞性方法識別複合材料結構之彈性常數，藉由實驗測量與有限單元法之理論分析，預測構件之變形量或自然頻率形成最小二乘方誤差之目標函數，配合多起始點能量總域極小化法識別複合材料積層板之彈性常數，一系列的範例說明本方法之可行性與精確性。

Composite laminates have been used extensively in the mechanical and aerospace industries for fabricating high performance structures. To ensure high reliability of the structures, the actual behaviors of the laminated composite parts in service must be accurately predicted and carefully monitored. It has also been pointed out that accurate determination of current stiffness or material properties of a laminated composite structure can help prevent sudden failure of the structure. The attainment of the actual behavioral predictions of the structures depends on the correctness of the elastic constants of the structures. Therefore, the determination of realistic material or mechanical properties of laminated composite components has become an important topic of research. In this paper, a method for nondestructive evaluation of elastic constants of composite structures is presented. An error function is established to measure the differences between the theoretically and experimentally predicted system deformations and/or natural frequencies. The identification of the elastic constants is formulated as a constrained minimization problem in which the elastic constants are determined to make the error function a global minimum. A global minimization method together with an appropriate bounding technique for constraining the variations of the elastic constants are used to solve the above minimization problem. The applications of the proposed method are demonstrated by means of several examples on the elastic constants identification of laminated composite plates.