三维正交机织复合材料风机叶片纳米改性机理分析及弯曲疲劳性能研究

As the key part of wind turbine, the blade is the vital component for energy transformation. The reliability of wind turbine is affected by fatigue property of blade. As the main selection of skin and structural part for large wind turbine blade, the advanced composite has advantages of light weight, large specific strength and specific stiffness. The fatigue failure is mainly caused by the progressive failure of interface between fiber and matrix. So, it is important to investigate the surface organ modification with nanoclays and improve the interface strength between fiber and matrix. It is interesting to study the bending fatigue behavior of 3D orthogonal woven composite with experiment and numerical simulation..In this project, the 3D orthogonal woven composite structure is selected for investigating. The bonding strength of interface between fiber and matrix will be increased by adding the nanoclays and the influence of nanoclays addition on the mechanical properties of epoxy/3D orthogonal glass fiber woven composite will be studied. The modification mechanism will be characterized by using modern instrument for material characterization. The modification process will be optimized and applied in composite for blade. The critical stress at crack initiation will be obtained based on the quasi-bending test and acoustic emission. The mechanism of crack initiation and propagation, the mechanism of stiffness degradation of 3D orthogonal woven composite for blade will be researched and the relationship between the array of component material, mechanical behavior and the bending fatigue property, mechanism of stiffness degradation and anti-fatigue behavior will be clarified. In conclusion, the scientific basis will be provided in theoretical for improving the behavior of anti-fatigue, and analysis mechanism of stiffness degradation, which will establish theoretical foundations for manufacturing excellent fatigue behavior of epoxy/3D orthogonal woven composite and provide technical preparation for application of 3D orthogonal woven composite in wind turbine blade.

叶片是风力机中最基础和最关键的部件，是风机进行能量转换的重要组成部分，其疲劳特性影响风机可靠性。复合材料质量轻、比刚度和比强度大，是大型风机叶片蒙皮及结构件主要材料。叶片疲劳失效以纤维/树脂界面分层为主。因此，基于纳米改性复合材料，提高界面强度，实验和数值模拟复合材料弯曲疲劳性能具有重要的实用意义和科学价值。.本项目研究复合材料纳米改性机理及对其性能的影响，优化改性工艺并用于风机叶片。结合复合材料准静态弯曲和声发射检测确定临界损伤应力，研究三维正交机织复合材料风机叶片弯曲疲劳裂纹萌生、裂纹扩展，揭示裂纹萌生及扩展机理，刚度退化机理。阐明组份材料的排列、力学性能与复合材料弯曲疲劳特性、刚度退化机理、抗疲劳性能之间的相关性。本项目为提高复合材料耐疲劳性能、分析刚度退化机理等提供科学依据，为制备优异疲劳力学性能的复合材料奠定理论基础，为实现三维正交机织复合材料在风机叶片上的应用作好技术储备。

叶片是风力发电机中最基础和最关键的部件，也是获取较高风能利用系数和经济效益的基础。目前，大型叶片的结构中蒙皮和主梁采用多轴向织物增强的层板结构。复合材料中，玻纤与树脂分属于无机物与有机物，纤维/基体界面结合强度太低会导致材料无法有效分散外部载荷，力学性能下降。因此，有必要通过研究纤维/树脂界面改性，有效提高界面结合强度。.本项目以三维正交机织玻纤织物为增强体，经纳米粒子改性的环氧树脂和固化剂混合胶液为基体，基于真空辅助传递模塑成型工艺（VARTM）制备复合材料叶片试样。利用现代材料表征方法（XRD、FT-IR、TEM等）分析纳米粒子改性机理。基于复合材料试样拉伸、弯曲性能及纤维/基体接触角等指标分析纳米粒子改性对纤维/基体结合强度的影响，并以此为目标得到最优纳米粘土质量分数。.结合复合材料风机叶片试样准静态弯曲和声发射检测确定临界损伤载荷水平。实验测试复合材料试样在不同应力水平下的弯曲疲劳性能，基于改性前后试样的疲劳寿命曲线、应力-应变曲线、刚度变化曲线及剩余强度退化率，得到了改性处理对材料弯曲疲劳性能的影响。采用高清显微镜观察试样在不同循环次数下的损伤情况，得到了改性前后复合材料试样的弯曲疲劳裂纹扩展规律。.本课题研究成果首先阐释了复合纤维/基体界面改性机理，提高了界面结合强度，得到了纳米粒子最优质量分数。其次，采用声发射技术实时监测改性前后试样的准静态弯曲实验为复合材料力学性能的无损探测提供了依据，为设置弯曲疲劳实验的应力水平提供了科学手段。最后，改性前后复合材料弯曲疲劳特性及疲劳裂纹扩展规律的探索为深入研究复合材料疲劳性能提供了理论指导。为推广三维正交机织复合材料在风机叶片上的应用提供技术储备。