碳纖維奈米複合材料機械性質及潛變行為之研究

Study on the Mechanical Properties and Creep Behaviour of Carbon Fiber Nano-composites

李懿倫(YI-LUEN LI)

指導教授 ： 葉銘泉

國立清華大學/工學院/動力機械工程學系/博士(2013年)

https://doi.org/10.6843/NTHU.2013.00326

摘要

摘要

由於奈米碳管具有質量輕、導電性、高熱傳導度及熱穩定性等特殊物理特性故廣範的應用在航空、航太、電磁波遮蔽(EMI)材料及靜電釋放材料(ESD)等上。本研究首先利用超音波震盪方式將表面改質後之奈米碳管均勻分散於環氧樹脂基材，並將此高分子基材與碳纖維製備成奈米高分子預浸材積層板(Nano-prepreg Laminates)，以供後續研究所需之實驗與測試使用。
本研究探討不同積層板製程包括疊層板預材製作方式、熱壓時間、熱壓程序及後硬化溫度與時間等對其積層板[(±45) 8]機械強度(抗拉、抗彎、奈衝擊強度)之影響，以歸結出較佳之製程方法與條件。隨後探討添加不同比例的奈米碳管對積層板[016], [(±45)8]機械性質之影響，並觀察在不同溫、濕度環境下材料之強度，再者利用SEM觀察奈米積層板之破壞面，討論材料的破壞機制。結果顯示積層板之機械強度隨著奈米碳管含量增加而提升。另外對碳纖維熱固性複材在不同應力、不同溫度、不同濕度、不同奈米碳管含量、不同纖維角度、不後硬化溫度及時間與潛變循環測試等不同條件下執行一系列之潛變測試，並對測試結果所得之潛變行為做一詳盡比較與分析，可發現應力、溫度及濕度對其潛變行為亦有非線性之加速作用。再者，嘗試以Findley Equation 及Larson-Miller參數式建立最佳化之潛變數學模式，對長時間潛變行為分析能提供具參考價值之依據，俾利據以探討複合材料長期安全性質。

關鍵字

奈米碳管 ； 碳纖維 ； 環氧樹脂 ； 機械性質 ； 潛變行為

並列摘要

Abstract

The surface modification of carbon nanotubes (CNTs) has been recently observed to influence the distribution of CNTs in epoxy resin and the mechanical properties and electrical conductivities of these CNTs. Accordingly, the treatment of CNTs to with organic acids to oxidize them generates functional groups on the surface of CNTs. This investigation studies the consequent enhancement of the mechanical properties and electrical conductivities of CNTs. The influence of adding various proportions of CNTs to the epoxy resin on the mechanical properties and electrical conductivities of the composites thus formed is investigated, and the strength of the material is tested at different temperatures.
The test results also indicate that mechanical strength and electrical conductivity increase with the amount of CNTs added to the composites. Different coefficients of expansion of the matrix, fiber and CNTs, are such that overexpansion of the matrix at high temperature results in cracking in it. An SEM image of the fracture surface reveals debonding and the pulling out of longitudinal fibers because of poor interfacial bonding between fiber and matrix, which reduce overall strength.
Moreover, the creep behaviors of carbon fiber (CF) /epoxy resin thermosetting composites and CNTs/CF/ epoxy resin composites were tested and analyzed at different stresses, orientations of fiber, temperatures and humidities. The creep exhibits only two stages- primary creep and steady-state creep. The effects of creep stress, creep time, and humidity on the creep of composites that contain various proportion of CNTs were investigated at various temperatures.
Additionally, increasing the number of cycles in cyclic creep tests at room temperature resulted in a decrease in creep strain even at a high temperature of 55℃. Possible room temperature creep mechanisms have been proposed and discussed. With increasing number of creep tests, the creep strain decreased due to strain hardening which occurred during creep. Creep strain is believed to increase with applied stress, creep time, humidity, temperature and degree of the angle θ between the orientation of fiber and the direction of the applied stress.
Furthermore, the decrease of creep strain of CF/epoxy resin composites performed aging pretreatment in a constant temperature and humidity chamber for different long-term days prior to creep testing was also investigated.
Finally, the test results of creep strain of CF/epoxy resin composites and CNTs/CF/epoxy resin composites tested under various conditions can be smoothly fitted by the fitting curves of Findley power law. And Larson-Miller equation can be adopted to precisely predict the low-temperature-long-term creep behavior by the high-temperature-short-
term creep behavior.

並列關鍵字

Carbon Nanotubs ； Carbon Fiber ； Epoxy Resin ； Mechanical Property ； Creep Behavior

參考文獻

28. C. Y. Yen, Shu-Hang Liao, Yu-Feng Lin, Chih-Hung Hung, Yao-Yu

1. S. Iijima and T. Ichlhashi, “Single-shell carbon nanotubes of 1-nm

diameter,” Nature, 363, 603–5. (1993)

Wang, “ Growth of a single freestanding multiwall carbon nanotube

Colbert and K. A. Smith, “Gas-phase catalytic growth of