風機葉片為整隻風力機最重要的部分之一，為探討風力機運轉時葉片所產生的影響，本文利用ANSYS有限單元分析軟體模擬NREL 5MW風機葉片的自然振動，進行模態分析，並探討玻璃纖維/乙烯樹脂與碳纖維布/環氧樹脂兩種不同複合材料、及加強肋與箱型樑兩種不同支撐結構，對自然頻率及振型模態的影響。模擬結果顯示，具有雙向特性之碳纖維布材料葉片模型扭矩發生在較高頻的模態；碳纖維布材料葉片模型的自然頻率高於玻璃纖維葉片模型，可使共振現象較慢發生。
為呈現風機葉片受到風力負載之情形，本研究先於風機葉片外部進行流場分析，將風速轉換為風壓分佈，探討不同傾斜角(Pitch angle)之葉片受到的壓力分佈；並將壓力分佈做為風機葉片結構之負載設定，分析風機葉片受到風力負載之應力分佈，並探討葉片於停機時、運轉時、及在不同位置之應力與位移變化，以蔡希爾(Tsai-Hill)破壞準則判斷葉片是否受到破壞；另外探討改變葉片材料疊層角度與葉片結構厚度分佈對模擬結果之影響。
結果顯示0°傾斜角之葉片受到之壓力最大，升力也最大，隨著傾斜角增加，葉片受到之壓力漸小，因而升力越小，但受到之應力也越小；因為應力同向疊加及應力集中的影響使得葉片位於轉軸右側120度之位置時所承受之應力與位移最大；〖"[" 0_n "/±" 〖15〗_n "/" 〖90〗_n "]" 〗_s、〖"[" 0_n "/±" 〖30〗_n "/" 〖90〗_n "]" 〗_s、〖"[" 0_n "/±" 〖45〗_n "/" 〖90〗_n "]" 〗_s、〖"[" 0_n "/±" 〖60〗_n "/" 〖90〗_n "]" 〗_s四種玻璃纖維/乙烯樹脂複合材料之疊層角度比較結果中發現，60度之情況下葉片表面受到之應力及位移量為最小；葉片厚度以線性增厚、及最佳化厚度之設計皆能提升葉片結構之剛性，缺點則是使葉片重量增加。

Wind turbine blade is one of the most important parts of whole wind turbine. In order to investigate the operating condition of wind turbine, the modal analysis was carried out using finite element software ANSYS in this study, and the free vibration of NREL 5MW wind turbine blade was analyzed. Four different cases, including two materials of glass fiber/vinylester and carbon fiber fabric/epoxy, two supporting structures of reinforcing spar and box girder, were analyzed to explore their effects on the nature frequencies and mode shapes of NREL 5MW wind turbine blade. The results show that the blade made of carbon fiber fabric/epoxy composites has higher natural frequency for the torsional mode than that of blade made of glass fiber/vinylester composites. The natural frequencies of blade made of carbon fiber fabric/epoxy are higher than those of blade made of glass fiber/vinylester; these results can be used for wind blade to alter its resonance frequencies.
In order to apply the wind load on the wind blade, the flow field analysis was carried out to determine the pressure distribution on the wind blade with four different pitch angles. The resulting pressure distribution was then inputted to the static structure analysis of the blade model as distributed forces on the wind blade. Wind turbine blades were also analyzed during operation, shutdown status and at the different positions to examine their stress distribution and deflection, and the Tsai-Hill failure criterion was used for failure prediction. The composite fiber orientations and blade skin thickness were investigated in the analysis. The results show that the wind blade has a maximum pressure and lift force at the pitch angle of 0°. When the pitch angle increases, the pressure on the wind blade decreases, thus the lift force reduces and the stress in the wind blade becomes smaller. The blade at the 120 degrees of right side of shaft from the vertical axis has a maximum stress and displacement. Four different fiber orientations of glass fiber/vinylester composites, 〖"[" 0_n "/±" 〖15〗_n "/" 〖90〗_n "]" 〗_s, 〖"[" 0_n "/±" 〖30〗_n "/" 〖90〗_n "]" 〗_s, 〖"[" 0_n "/±" 〖45〗_n "/" 〖90〗_n "]" 〗_s, and 〖"[" 0_n "/±" 〖60〗_n "/" 〖90〗_n "]" 〗_s, were studied and the blade with 60° fiber orientation had a minimum stress and displacement. When varying the skin thickness of wind blade, both of linear and optimal skin thickness can enhance the rigidity of blade, though increasing the weight of blade.

1. http://www.new-energy.org.tw/Papers_a01.htm, retrieved on October 16, 2015.
2. 熊治民，伏和中，黃聰文，陳芙靜，“台灣風力發電設備產業發展策略”，科技發展政策報導，2006年1月號，第14~15頁，2006。
3. https://zh.wikipedia.org/wiki/%E9%A2%A8%E5%8A%9B%E7%99%BC%E5%8B%95%E6%A9%9F, retrieved on August 15, 2015.
4. 劉瑞弘，“風力機結構負載與共振模態之分析”，機械工業，319期，第27~33頁，2009。
5. I. M. Daniel, J. Abot, “Fabrication, Testing and Analysis of Composite Sandwich Beam.” Composite Science and Technology, Vol. 60, pp. 2455-2463, 2000.
6. J. Kim, S. R. Swanson, “Design of Sandwich Structures for Concentrated Loading, Composite Structure.” Vol. 52, pp. 365-373, 2001.
7. C. A. Steevens, N. A. Flect, “Material Selection in Sandwich Beam Construction.” Script Materialia, Vol. 50, pp. 1335-1339, 2004.
8. T. Hobbiebrinken, M. Hojo, T. Adachi, C. D. Jong, B. Fiedler, “Evaluation of Interfacial Strength in CF/Epoxies Using FEM and In-Situ Experiments.” Composites:Part A, Vol. 37, pp. 2248-2256, 2006.
9. U. K. Vaidya, S. Pillay, S. Bartus, C. A. Ulven, D. T. Grow, B. Mathew, “Impact and Post-Impact Vibration Response of Protective Metal Form Composite Sandwich Plates.” Materials Science and Engineering A, Vol. 428, pp. 59-66, 2006.
10. J. H. Yim, S. Y. Cho, Y. J. Seo, B. Z. Jang, “A Study on Material of 0° Laminated Composites Sandwich Cantilever Beams with a Viscoelastic Layer.” Composites Structures, Vol. 60, pp. 367-374, 2003.
11. A. S. Hadi, N. Ashton, “Measuremant and Theoretical Modeling of the Damping Properties of a Uni-directional Glass/Epoxy Composites.” Composite Structures, Vol. 34, pp. 381-385, 1996.
12. M. Styles, P. Compston, S. Kalyanasundaram, “The Effect of Core Thickness on The Flexural Behaviour of Aluminium Foam Sandwich Structures.” Composites Stuctures, Vol. 80, pp. 532-538, 2007.
13. H. L. Fan, F. H. Meng, W. Yang, “Sandwich Panels with Kagome Lattice Cores Reinforced by Carbon Fibers.” Composites Structures, Vol. 81, pp. 533-539, 2007.
14. L. Zhao, H. Fan, S. Huang, “Out-of-plane Compression and Impact of Woven Textile Sandwich Composites.” The 3rd International Conference on Digital Manufacturing and Automation (ICDMA), China, Guilin, pp. 594-597, 2012.
15. U. A. Dar, Z. Weihong, X. Yingjie, “Modeling the Perforation Failure of Honeycomb Sandwich Structures through Numerical Homogenization,” The 10th International Conference on Applied Sciences and Technology (IBCAST), Pakistan, Islamabad, pp. 19-24, 2013.
16. M. Sadighi, S. A. Hosseini, “Finite Element Simulation and Experimental Study on Mechanical Behavior of 3D Woven Glass Fiber Composite Sandwich Panels.” Composites Part B: Engineering, Vol. 55, pp. 158-166, 2013.
17. X. Dang, X. Wang, M. Wei, J. Xiao, “Finite Element Analysis of X-cor Sandwich’s Compressive Modulus.” International Conference on Electronic and Mechanical Engineering and Information Technology (EMEIT), Heilongjiang, Harbin, Vol 55, pp. 2532-2535, 2011.
18. J. W. Gillespie, L. A. Carlsson, A. A. Gawandi, T. A. Bogetti, “Fatigue Crack Growth at the Face Sheet-core Interface in a Discontinuous Ceramic-tile Cored Sandwich Structure.” Composite Structures, Vol. 94, pp. 3186-3193, 2012.
19. Y. B. Cho, R. C. Averill, “First-order Zig-zag Sublamination Plate Theory and Finite Element Model for Laminated Composite and Sandwich Panels.” Composites Structures, Vol. 50, pp. 1-15, 2000.
20. H. Y. Kim, W. Hwang, “Effect of Debonding on Frequencies and Frequency Response Functions of Honeycomb Sandwich.” Composites Structures, Vol. 55, pp. 51-62, 2002.
21. A. L. Mouritz, R. S. Thomson, “Compression, Flexure and Shear Properties of A Sandwich Composite Containing Defects.” Composites Structures, Vol. 44, pp. 263-278, 1999.
22. N. K. Alpaydin, H. S. Türkmen, “The Dynamic Response of the Sandwich Panel Subjected to the Impact Load.” The 4th International Conference on Recent Advanced in Space Technologies, Turkey, Istanbul, pp. 176-180, 2009.
23. W. J. Rankine, “On the Mechanical Principles of the Action of Ship Propellers.” Transactions of the Institute of Naval Architects 6, pp. 13-39, 1865.
24. H. Glauert, “Airplane Propellers.” Aerodynamics Theory, Dover Publication, Inc., New York, Vol. 4, 1943.
25. R. E. Wilson, P. B. S. Lissaman, “Applied Aerodynamics of Wind Power Machines.” Oregon State University, Report NSF/RA/N74113, 1974.
26. R. Lanzafame, M. Messina, “Fluid Dynamics Wind Turbine Design:Critical Analysis, Optimization and Application of BEM Theory.” Renewable Energy, Vol. 32, pp. 2291-2305, 2007.
27. S. Roger, “Blade Design Aspects.” Renewable Energy, Vol. 16, pp. 1272-1277, 1999.
28. M. M. Shokrieh, R. Rafiee, “Simulation of Fatigue Failure in a Full Composite wind Turbine Blade.” Composite Structures, Vol. 74, pp. 332–342, 2006.
29. M. Tarfaoui, O. Shah, H. Khadimallah, J. Y. Pradillon, “Effect of Spars Cross-section Design on Dynamic Behavior of Composite Wind Turbine Blade: Modal Analysis.” The 4th International Conference on Power Engineering, Energy and Electrical Drives (POWERENG), Turkey, Istanbul, pp. 1006-1011, 2013.
30. P. Sun, Z. Liu, Y. Gao, S. Wu, “Lay-up Design and Structural Analysis of 1.2MW Composite Wind Turbine Blade.” The 10th International Conference on Computer-Aided Industrial Design & Conceptual Design (CAID&CD), China, Wenzhou, pp. 581-585, 2009.
31. C. P. Chen, T. Y. Kam, “Failure Analysis of Small Composite Sandwich Turbine Blade Subjected to Extreme Wind Load.” Procedia Engineering, Vol. 14, pp. 1973-1981, 2011.
32. 童琮志，黃金城，江茂雄，蘇煒年，“離岸風機整合地震動態負載於時域系統之模式建立”，台灣風能學術研討會暨NEPII離岸風力及海洋能源主軸成果發表會，台灣，台北，第1~5頁，2014。
33. 黃慶民，蔡國忠，陳世雄，王晟桓，李啟勝，“50kW風力發電機複合材料葉片設計、分析與製作”，中華民國力學學會第三十一屆全國力學會議，台灣，高雄，第1~7頁，2007。
34. D. Ju, Q. Sun, “Wind Turbine Blade Flapwise Vibration Control through Input Shaping.” The International Federation of Automatic Control (IFAC), Africa, pp. 5617-5622, 2014.
35. W. Duan, F. Zhao, “Loading Analysis and Strength Cacluation of Wind Turbine Blade Based on Blade Element Momentum Theory and Finite Element Method.” Power and Energy Engineering Conference (APPEEC), Chengdu, pp. 1-4, 2010.
36. J. Arrigan, V. Pakrashi, B. Basu, S. Nagarajaiah, “Control of Flapwise Vibrations in Wind Turbine Blades using Semi-active Tuned Mass Dampers.” Structural Control and Health Monitoring, Vol. 18, pp. 840-851, 2011.
37. C. Yanbin, S. Lei, Z. Feng, “Modal Analysis of Wind Turbine Blade Made of Composite laminated plates.” Power and Energy Engineering Conference (APPEEC), Chengdu, pp. 1-4, 2010.
38. 吳鴻筠、葉友順，“風力發電機之結構動態分析”，臺灣風能學術研討會，台灣，澎湖，第248~251頁，2010。
39. 蔡易陞，李志中，林輝政，黃心豪，“大型風力發電機Vestas V47葉片流場及結構應力分析”，海洋工程研討會，台灣，高雄，第1~5頁，2013。
40. A. Brahim, “Recent Advances in Composite Materials for Wind Turbine Blades.” Advances in Materials Science and Applications, pp. 172–173, 2013.
41. http://www.small-wind.org.tw/content/wind/wind_info.aspx, retrieved on October 11, 2015.
42. J. Jonkman, S. Butterfield, W. Musial, and G. Scott, “Definition of a 5-MW Reference Wind Turbine for Offshore System Development.” Technical Report, NREL/TP-500-38060, 2009.
43. B. R. Resor, “Definition of a 5MW/61.5m Wind Turbine Blade Reference Model.” SANDIA REPORT, SAND2013-2569, 2013.
44. I. H. Abbott, V. D. Albert and L. Stivers, “Summary of Airfoil Data.” National Advisory Committee for Aeronautics, NACA Technical Report 824, pp. 5-17, 1945.
45. R. F. Gibson, Principles of composite material mechanics, 3rd ed., CRC Press, U.S, 2011.
46. ANSYS, Inc., PA, 2013.
47. ANSYS Mechanical APDL Structural Analysis Guide, ANSYS, Inc.
48. R. D. Cook, D. S. Malkus, M. E. Plesha, R. J. Witt, Concepts and Applications of Finite Element Analysis, 4th ed., Wiley, Danvers, 2002.
49. S. S. Rao, Mechanical Vibrations, 5th ed., Pearson Education, Inc., Singapore, 2011.
50. 王栢村，“振動知多少?”，科學發展，413期，第46~52頁，2007。
51. Solidworks, Inc., 2012.
52. 鄭有成，“複合材料風機葉片結構之有限單元應力分析”，國立清華大學碩士論文，台灣，新竹，2015。
53. 陳建亨，“複合材料木琴鍵之結構最佳化設計與動態分析”，國立清華大學碩士論文，台灣，新竹，41頁，2007。
54. A. K. Saraf, M. Singh, A. Kumar, “Analysis of the Spalart-Allmaras and k-ω standard models for the simulation of the flow over a National Advisory Committee for Aeronautics (NACA) 4412 airfoil.” International Journal of Scientific and Engineering Research (IJSER), Vol. 3, Issue 8, pp. 881-887, 2012.
55. http://www.wind-power-program.com/turbine_characteristics.htm, retrieved on April 11, 2016.
56. https://zh.wikipedia.org/wiki/%E8%92%B2%E7%A6%8F%E9%A2%A8%E7%B4%9A, retrieved on April 11, 2016.
57. S. M. Domnica, C. Ioan, T. Ionut, “Structural Optimization of Composite from Wind Turbine Blades with Horizontal Axis Using Finite Element Analysis.” Procedia Technology, Romania, Vol. 22, pp. 726-733, 2016.
58. W. B. Young, W. H. Wu, “Optimization of the Skin Thickness Distribution in the Composite Wind Turbine Blade.” International Conference on Fluid Power and Mechatronics (FPM), Beijing, pp. 62-66, 2011.
59. J. Paquette, D. Laird, D. Griffith, L. Rip, “Modeling and Testing of 9m Research Blades.” American Institute of Aeronautics and Astronautics (AIAA), USA, pp. 2006-1199, 2006.
60. 林法正，鄧禮濤，余孟勳，林正文，“風力發電技術之發展概況”，電工通訊，2008年6月號，第44~51頁，2008。
61. https://www.acpsales.com/upload/Mechanical-Properties-of-Carbon-Fiber-Composite-Materials.pdf, retrieved on April 11, 2016.