近年來有許多複合材料產品，以三明治結構之方式進行設計，使其達到有效減輕結構重量、增加結構機械特性、防火與隔音效果等目的，因此三明治結構之複合材料具有極高之研究價值。三明治複合材料之表面材料通常選用強度較佳之材料，如金屬或纖維強化複合材料，以保有結構本身之剛性；核心材料則選用添加填充物如多壁奈米碳管或中空玻璃珠之高分子複合材料，以增加結構之動態特性或減輕結構本身之重量。本計畫所探討之三明治結構，表面材料為纖維強化複合材料，核心材料則為添加奈米碳管之高分子複材。
本研究將以三點彎曲測試方法研究三明治結構複合材料之機械特性，探討不同碳纖維疊層角度之表面材料和改變核心材料之碳管含量對彎曲強度與破壞機制之影響。由於有限元素分析需材料常數，因此也進行材料拉伸實驗，由實驗結果探討三明治結構複合材料之機械特性，以有限元素分析模擬結果與三明治結構三點彎曲測試結果比較。文中也研究含有裂縫之多壁奈米碳管高分子複材，討論改變碳管含量對其破裂韌度之影響；以含缺口拉伸試驗(Compact Tension Test)，探討多壁奈米碳管/環氧樹脂之Mode I破裂特性，並利用非對稱四點彎曲試驗(Asymmetric Four-Point Bending Test)，最後實驗結果與有限元素分析結果比較。

Composite materials have advantages of high specific strength, high specific stiffness, and can be used in many industries, such as musical instrument, acoustical tile, fire wall, sports equipment, aerospace and vehicle applications. Moreover composite products are used in sandwich structures to reduce the weight of structure, and to increase the mechanical properties, sound insulation and fire prevention properties 0f structure in recent years. In this paper, the mechanical properties of sandwich structure made by graphite face laminates and core material made by multi-walled carbon nanotubes (MWNTs) reinforced polymer were investigated.
In the experiment, the three-point bending test was used to measure the mechanical properties of sandwich structure. The influences of carbon fiber orientation, in the face laminates, and content of MWNTs, in polymer reinforced nanocomposite core material, on the bending strength of sandwich structure were discussed in this paper. In analysis, the finite element method was used to obtain the numerical values of mechanical properties of sandwich structures. The Mode I and II fracture toughness of MWNTs/Polymer nanocomposites were investigated, and the effects of MWNTs content in the nanocomposites were evaluated. The Mode I fracture toughness was tested using compact tension specimens. For determination of the Mode II fracture toughness, the asymmetric four-point bending test were used. The experimented results were compared with ours obtained from the finite element analysis.

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