複合材料風力葉片漸進破壞行為之分析

Abstract

本文主要探討複合材料風力葉片的漸進破壞行為及分析，分別對於不同尺寸之小型風力葉片進行討論，本實驗採用玻璃纖維製作葉片蒙皮，玻璃纖維與巴爾莎木之三明治層板製作腹板，以及玻璃纖維束來製作桁架，實驗將一米葉片於翼尖處施予位移直到結構失效破壞，分析則以有限元素軟體ANSYS進行分析，分別進行線性及幾何非線性漸進破壞分析，比較兩者差異以及何者較為適當，並探討不同龍骨模型之葉片其破壞行為，腹板型葉片因腹板不易局部變形，於葉片受彎蒙皮發生挫屈時，蒙皮凹折幅度大，應力較大，易發生纖維破壞，當蒙皮與腹板交界處出現大面積纖維破壞與腹板發生局部破壞後，結構失去支撐而崩塌，桁架相較於腹板易發生局部彎曲變形，因此葉片蒙皮發生挫屈時，蒙皮凹折幅度較小，應力相對腹板型葉片小，不易發生纖維破壞，但隨著葉片彎矩增加，桁架會發生明顯彎曲變形，導致蒙皮出現大量纖維破壞使結構失效，本文以幾何非線性漸進破壞分析可準確預測一米葉片之破壞行為及極限負載，驗證以幾何非線性漸進破壞分析較線性漸進破壞分析準確，再以同樣分析方法對二點五米葉片受靜態風載下的漸進破壞行為進行預估，為葉片可能發生的破壞行為提供一個參考。

This thesis is focus on the analysis of the progressive failure behavior of composite wind blades of different sizes. The blades have either plate- or truss-types shear webs. The skin of the wind blades is made of woven glass fabric, the shear web of woven glass fabric and balsa wood composite sandwich laminate, and the truss of glass fabric strands. In the structural failure test, the one meter long wind blade is under displacement control testing until the collapse of the blade has occurred. Failure analyses of the blades using different techniques of the finite element software ANSYS, linear and geometrically nonlinear progressive failure analyses, respectively, are performed. The comparison of the differences between the two techniques has shown that the nonlinear one is more appropriate. The theoretical and experimental results have shown that the blade with plate-type shear web buckles due to the slight local deformation of the web, the scale of blade skin bending is big, and the skin is prone to fiber damage due to large stress. When the skin is under large area fiber damage and the web local damage has occurred, the damage area will expand and eventually lead to the complete collapse of the blade structure. In contrast, the blade with truss-type shear web is prone to have local bending deformation of the truss. Comparing with the blade with plate-type web, after skin buckling has occurred, the scale of blade skin bending as well as the stress is smaller too, and the fibers are less prone to damage, However, with the increase of blade bending moment, the truss will obviously bend and deformed, resulting in a large area fiber damage of the skin which finally leads to the collapse of the structure. The failure behavior and the ultimate load of one meter long wind blade can be well predicted using the geometrically nonlinear failure analysis, which is more accurate than the linear progressive failure analysis. The proposed method is then used to study the progressive failure behavior of a 2.5m long wind blade under static wind load. The results so obtained are informative and can serve as a reference for assessing the actual failure behaviors of the blade.