- 學位論文
含裂縫奈米複材三明治結構之能量釋放率研究
Energy Release Rate of Sandwich Structure with MWNTs/Polymer Nanocomposite as Core Material Containing Facesheet/Core Debonding
摘要
三明治結構為最常見之複合材料結構，係由高比強度(Strength-to-Weight)及高比勁度(Stiffness-to-Weight)之面材(Facesheet)與質輕之芯材(Core Material)膠結構成，因此易於面材與芯材之接合面產生裂縫形成脫膠(Debonding)，進而影響整體結構強度造成損壞。 本文採用由兩複合材料構成之奈米複材三明治結構；面材為碳纖維疊層板，芯材為多壁奈米碳管/環氧樹脂高分子材料，以環氧樹脂為黏著劑接合。文中利用田口法(Taguchi’s Method)，以面材疊層角度、芯材多壁奈米碳管含量與預裂縫長度三者為參數，規劃兩組實驗跨距與試片尺寸，探討此含預裂縫之奈米複材三明治結構在三點彎曲末端刻痕(End Notched Flexure, ENF)試驗下的最大負載與臨界能量釋放率。文中，利用信號雜訊比 (S/N ratio)與因子反應分析找出三明治樑最大負載之最佳參數組合，並以變異數分析(ANVOA)產生最佳值預測；最後以虛擬裂縫擴展法(Virtual Crack Extension Method)進行臨界能量釋放率(Critical Energy Release Rate, Gc)之有限單元分析，並與實驗結果相互比較。結果顯示，在跨距80 mm實驗中，最佳參數組合為面材疊層角度[0°/±45°/90°]s、芯材碳管含量1 wt%、裂縫長度57 mm；在跨距50 mm實驗中，最佳參數組合為面材疊層角度[0°/±45°/90°]s、芯材碳管含量1 wt%、裂縫長度45mm。
並列摘要
Sandwich structure is one of the most common composite structures. It combines a high specific strength, high specific stiffness facesheet glued with light-weighted core material, so it is easy to have interfacial crack which induces debonding and influence structural strength to produce structural collapse. Sandwich structure in this study fabricated by two composites to form a nano-composite sandwich structure; graphite fiber reinforced polymer(GFRP) laminate is used as facesheet and MWNTs/epoxy corematerial is glued to it by epoxy. With three parameters, facesheet stacking sequence, weight percent of MWNTs in core and length of pre-crack, Taguchi’s method is used in this article to discuss the maximum load and critical energy release rate of two different test spans and specimen size in three point bending end notched flexure (ENF) test. The optimal parameters were determined by Signal to Noise ratio (S/N ratio) and influences of paramenters, then Analysis of Variance ANOVA is used to find the optimal maximum load. Virtual crack extension method is used to calculate the critical energy release rate in finite element analysis and results were compared to experimental results. The test results showed that when test span is 80 mm, the optimal parameters are facesheet stacking sequence [0°/±45°/90°]s, 1 wt% MWNTs/epoxy corematerial and 57 mm pre-crack length; for test span is 50 mm, the optimal parameters are facesheet stacking sequence [0°/±45°/90°]s, 1 wt% MWNTs/epoxy corematerial and 45 mm pre-crack length.