近年來，從黏著實驗文獻中發現，在薄膜材料界面破壞中，常有手指狀或波浪狀的不穩定圖騰出現，而目前尚未有一個合適的理論模型去解釋此種現象的發生。本文主要引用Rice與Gao推導的對稱無限域中平面裂縫尖端擾動的第一階擾動理論，延伸得到具有限厚度之雙層材料界面裂縫尖端擾動波形之穩定性準則。利用有限元素數值模型求得特定施力方式下裂縫尖端應力強度因子，並得到彈性層厚度 與施力位置 之比值和不穩定圖騰之臨界波長 的關係式，發現臨界擾動波長不只跟薄膜厚度有關，與施力位置也有關係，但因施力形式為力控制，所以結果與材料參數無關，藉由理論分析的結果得以解釋實驗觀察之現象。

In recent years, wavy patterns or fingers occurred in many adhesive experiments in the literature. These instability patterns were usually found at the interfacial fracture of thin film. So far, there is no adaptable analytical model to explain such a phenomenon occurring in the experiments. In this study, we refer to Rice and Gao’s first-order variation theory due to variation in location of planar crack front in the symmetric infinite body, and extended their theory to obtain a stability criteria for patterns at the interfacial crack between two dissimilar materials with finite thickness. We construct a finite element model to analyze the stress intensity factor near the crack tip at specified loading conditions. The relationship between the critical wavelength for the instability patterns and the ratio of the elastic layer thickness and the loading distance and was found. It is noted that the wavelength is related to not only the elastic layer thickness but also the loading distance. The results show no correlation with the materials’ properties because of load-controlled condition. Using this analytical model, we can explain the phenomenon observed in the experiments.

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