模擬含脫層複合材料三明治結構之破壞強度

Abstract

本研究主要目的為探討含脫層缺陷之複合材料三明治結構在承受軸向壓縮負載時的破壞行為。藉由實驗觀察與數值模擬了解表層厚度與脫層長度對三明治結構破壞強度的影響。透過實驗結果發現，當表層較厚或是脫層長度較短時，三明治結構具有較高的挫屈負載與破壞強度。此外，脫層較短的試片趨向總體挫屈導致的破壞，而脫層較長的試片則趨向局部挫屈導致的破壞且造成裂紋由脫層邊緣向外延伸。為了更進一步了解其破壞機制，本研究以有限元素法模擬三明治結構模型，其中，考慮結構存在之缺陷，並藉由最大主應變準則或破壞區域方法預估含脫層三明治結構的破壞強度。結果發現由總體挫屈導致破壞的試片，其破壞位置主要位於上下兩段芯材的中間部位，且可利用最大主應變準則預估結構之破壞強度；另一方面，當破壞是由局部挫屈導致時，初始破壞位置位於脫層兩側的尖端，且其破壞強度可利用破壞區域法進行預估。

The research aims to investigate the failure behaviors of the composite sandwich structures with debond defect subjected to compression loading. Both experimental observations and numerical simulation were conducted to understand the effect of face-sheet thickness as well as the debond length on the strength of the composites sandwich structures. Experimental results revealed that the sandwich structures with either thick face-sheet or short debond length exhibit higher buckling load and failure strength. Moreover, as the debond length is short, the failure is dominated by global buckling, however, when the debond length is long, the failure mechanism becomes the local buckling in conjunction with the crack extension from the debond edge. In order to characterize the failure mechanism, the nonlinear finite element (FEM) simulation was implemented on the sandwich samples with imperfection. In addition, the failure load was predicted based on either the maximum principal strain criterion or the damage zone method. It was found that when the failure is dominated by the global buckling, it occurs at intermediate portion of the foam core and the strength can be obtained from the maximum principal strain criterion. On the other hand, when the failure mode is local buckling, the failure initiates from the debond tip and the strength can be predicted using the damage zone method.