石墨/環氧樹脂複合材料之機械性質與動態特性研究

Mechanical and Dynamic Properties of Graphite/Epoxy Composites

康玳瑋(Dai-Wei Kang)

指導教授 ： 葉孟考 ； 戴念華

國立清華大學/工學院/動力機械工程學系/碩士(2013年)

摘要

工業上的環氧樹脂普遍作為複合材料中之基材，但本身機械與電熱性質不佳，溫度與時間也會影響到環氧樹脂的機械性質，天然石墨具有耐高溫、優秀之機械性質、導電性與導熱性等優越之物理性質，最重要的是在價錢方面比起奈米碳管而言更為低廉。本研究首先探討純環氧樹脂在1、2、3 小時熱壓時間下，對於機械性質的影響；也探討分別添加150 μm天然石墨、官能化石墨與膨脹石墨對整體複合材料之機械性質與動態特性的影響。
實驗結果顯示純環氧樹脂在溫度控制在120℃，熱壓時間2小時，其撓曲模數與撓曲強度上最佳；在純環氧樹脂中混入150 μm天然石墨、官能化石墨與膨脹石墨皆可有效提升複合材料撓曲模數與楊氏模數，其中補強效果為添加官能化石墨最優良，混入8 wt%的天然石墨，相較於純環氧樹脂撓曲模數可提升29.9%，撓曲強度則下降16.4%，楊氏模數提升26.9%；動態測試的部分透過實驗得到的共振頻率與有限元素分析的結果比較，其誤差值皆在5%以下，經由阻尼係數的測量，得到石墨/環氧樹脂複合材料之最大的阻尼係數為添加2 wt%的150 μm天然石墨/環氧樹脂複合材料阻尼係數為0.0345，相較於純環氧樹脂的阻尼係數提升了87.5%。本文也探討在官能化石墨表面成功接上COOH鍵，並且找出製造膨脹石墨時依照硫酸與硝酸比例1:1，所得到的膨脹體積最佳；最後以SEM觀察其複合材料斷裂面，了解複合材料受拉伸負載的破壞機制。

關鍵字

複合材料 ； 石墨 ； 動態特性 ； 機械性質

並列摘要

Epoxy is commonly used in the composite materials, though its mechanical and electric properties is poor. Graphite with high temperature resistance, good mechanical properties, low electrical resistivity, and cheaper than carbon nanotubes, is an excellent reinforcing material when mixed with epoxy. In this study, 150 μm natural graphite, functionalized graphite, and expanded graphite were used to fabricate composites, using epoxy as the matrix material. Different percentages (0, 2, 4, 6, 8 wt%) of natural graphite, functionalized graphite and expanded graphite were added in epoxy-based composites, and their mechanical and dynamic properties were assessed.
From the results of tensile and bending tests, the addition of 150 μm natural graphite, functionalized graphite, expanded graphite into epoxy can effectively improve the flexural and Young's moduli. The composites with functionalized graphite had best mechanical properties, for the cases studied. For the 8 wt% functionalized graphite/epoxy composites, the Young’s modulus increased 26.9%, the flexural modulus increased 29.9%, and the flexural strength decreased 16.4%. From the dynamic test, the difference in experimental and analytical natural frequencies of the composites tested is less than 5%. For damping measurement, 2 wt% 150 μm natural graphite/epoxy composites showed a higher damping ratio 0.0345, which is 87.5% higher than that of neat epoxy. Finally, the fracture surfaces of tested composites were observed using scanning electronic microscopy (SEM), and the failure mechanism of the composites was discussed.

參考文獻

[2] M. F. Yu, O. Lourie, M. J. Dyer, K. Moloni, T. F. Kelly and R. S. Ruoff, “Strength and breaking mechanism of multiwalled carbon nanotubes under tensile load,” Science, Vol. 287, pp. 637-640, 2000.

[3] B. G. Demczyk, Y. M. Wang, J. Cumings, M. Hetman, W. Han, A. Zettl, and R.O. Ritchie, “Direct mechanical measurement of the tensile strength and elastic modulus of multiwalled carbon nanotubes,” Materials Science and Engineering A, Vol. 334, pp. 173-178, 2002.

[4] C. F. Cornwell and L. T. Wille, “Elastic properties of single-walled carbon nanotubes in compression,” Solid State Communications, Vol. 96, pp. 555-558, 1997.

[5] E. T. Thostenson, Z. Ren, T. W. Chou, “Advances in the science and technology of carbon nanotubes and their composites: a review,” Composites Science and Technology, Vol 61, pp. 1899-1912, 2001.

[6] K. T. Lau and D. Hui, “The revolutionary creation of new advanced materials carbon nanotube composites,” Composites Part B: Engineering, Vol. 33, pp. 263-277, 2002.