複合材料具有質量輕與強度高之優點，非常適合用於軍事、汽車、船舶、航太等工業。在複合材料需求量大增與與廣泛應用之同時，複合材料缺陷問題也顯得更加重要，而脫層是複材疊層板最常見的缺陷之一；由於製作過程中疊層不良、低速碰撞或承受負載時自由端產生過大層間剪應力都有可能使複材板產生脫層，而脫層存在會影響原本結構之動態穩定性。
本文主要以理論分析並配合實驗研究含脫層複材疊層板受到電磁激振器激發下所引發之參數不穩定行為。文中探討脫層大小、脫層位置與複材板疊層角度、疊層數目及寬度對自然頻率與動態不穩定區之影響。實驗中之激振力是非接觸式之橫向電磁力，且此電磁激振器之激發頻率與激發振幅可由交流電源控制器控制，所以此種激振器可以避免實驗中因軸向施力可能產生的干擾問題。結果顯示隨複材板脫層寬度增加，各單頻與混頻不穩定區之激發頻率往低頻處偏移。各單頻與混頻不穩定區之激發頻率因脫層位置接近厚度中間時，不穩定區激發頻率整體而言以上升為主要之趨勢。隨複材板疊層數目增加，各單頻與混頻不穩定區之激發頻率往高頻處偏移，且各不穩定區激發頻率之間距亦增加。各單頻與混頻不穩定區之激發頻率隨複材板寬度增加或上升或下降，但整體看來以降低為主要之趨勢。隨複材板疊層角度增加，各單頻與混頻共振區之激發頻率會因模態不同而往高頻或低頻偏移；其中單頻不穩定區 之激發頻率隨疊層角度增加而下降，單頻不穩定區 之激發頻率在疊層角度為 時有最大值，單頻不穩定區 之激發頻率在疊層角度 度時有最大值。

Composite materials have advantages of light weight, high strength and are very suitable to be used in military, automobile, ship, aerospace and other industries. As the demand for composite materials increases, the defect problems in composite materials become more important. Among them, the delamination is one type of the common defects, which induced by improper handling in the process of manufacturing, low-velocity impact, or excessive interlaminar stresses at the free edge under loading. The existence of delamination may affect the dynamic stability of the laminated composite structures.
In this paper, the analytical and experimental methods were used to investigate the parametric instability behavior of delaminated composite plates under the transverse excitation of electromagnetic device. The influence of various parameters, such as delamination size, delamination position, ply-angle, the layer numbers and the delaminated width in composite plates, on the dynamic behavior and the dynamic instability regions were investigated. The results show that the excitation frequencies of all simple and combinational instability regions shifted to lower frequencies with increasing delaminated width in composite plates. The excitation frequencies of instability regions shifted to higher frequencies as the delamination closer to the middle of the thickness and with increasing layer numbers of the composite plates. As the width of composite plates increases, the excitation frequencies of all simple and combinational instability regions shifted mainly to lower frequencies. The excitation frequencies of all simple and combinational instability regions shifted because of the mode variations with increasing ply-angle of the composite plates. The excitation frequency of instability region of simple resonance decreases as the ply-angle of the composite plate increases. The excitation frequency of instability region of simple resonance is largest for the composite plates with 45o ply-angle. The excitation frequency of instability region of simple resonance is largest for the composite plates with 30o ply-angle.

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