以光纖光柵與導電性監測碳纖維複材膠合接口拉伸與疲勞破壞之應用

Abstract

本研究探討以光纖光柵與電壓監測碳纖維複合材料膠合接口受拉伸與疲勞負載之應用，利用環氧樹脂混入奈米碳管作為搭接劑，使其具有導電性，搭接物為熱壓成型的碳纖維強化複合材料試片。電壓監測方面，內埋銅箔電極至複合材料搭接物末端內來量測試片的整體電壓變化。光纖光柵感測方面，將光纖布拉格光柵(fiber Bragg grating, FBG)感測器內埋至搭接面，觀察其頻譜變化，並對每一個頻譜計算一Deviation值，作為頻譜波形變化的量化標準。最後運用螢光液滲檢測法證實電壓監測及光纖光柵感測的結果。實驗結果顯示，對於循環加載卸載拉伸試驗，電壓監測可進行定性分析，光纖光柵偵測則較不靈敏或不穩定，而對於疲勞試驗，電壓監測能夠評估膠合接口的損傷，但其只能監測搭接面的整體情況，需參考光纖光柵頻譜數據方能更有效監測搭接面上的疲勞破壞。

This study deals with monitoring single lap CNT-epoxy joints of carbon fiber reinforced plastics (CFRP) by conductivity and fiber Bragg grating (FBG). The adhesive is conductive because it’s made of epoxy resin mixed with carbon nanotubes. The material is of the sheet in this experiment is made of CFRP by thermoforming. For voltage change measurement, copper foil is embedded in CFRP and welded with wires to measure the voltage change of entire adhesive joint. For FBG sensors, it can measure the frequency spectrum by embedding FBG in the adhesive joint. Deviation value, which is created by this study, can be calculated from each frequency spectrum and evaluate the change of frequency spectrum’s change. Final step is using fluorescent penetrant testing method to show the damage position in adhesive joints. The result of the experiments showed that voltage change measurement could do qualitative analysis to the load and FBG sensors were not sensitive or not stable to the load for cyclic loading tensile test. And for fatigue test, voltage change measurement could effectively monitor the damage, but it could only monitor the damage of entire adhesive joint. By applying FBG sensors, it can monitor the damage of adhesive joint more effectively.