三维编织复合材料整体加筋壁板结构稳定性研究

发布时间：2019-01-11 08:38

【摘要】：三维编织复合材料具有良好的结构整体性,能有效克服传统层合复合材料层间强度低、易分层等弱点,使其在飞行器机体结构上的应用前景日益广阔。三维编织复合材料整体加筋壁板作为一种新颖的轻质高效结构型式,研究该加筋壁板结构稳定性,探寻结构屈曲及后屈曲行为,评估结构极限承载能力,是确保结构安全需亟待解决的重要问题之一。然而,由于三维编织复合材料细观结构尤其复杂,显著增加了该材料整体加筋壁板设计与分析的难度。因此,如何根据三维编织复合材料整体加筋壁板宏细观结构特征,建立结构稳定性分析力学模型,并系统研究材料工艺参数及结构参数对结构稳定性的影响规律,具有重要的研究价值和工程意义。本文基于三维编织复合材料结构宏细观结构特征,采用跨尺度力学建模思想,深入研究了三维四向编织复合材料壁板和整体加筋板在典型载荷工况下的结构稳定性。首先,在细观尺度方面,根据四步法编织工艺,研究了不同区域纱线的空间运动规律和分布构型,重点建立了材料内胞和表胞的参数化实体单胞模型,提出了三维四向编织复合材料的双层表面胞元模型,建立了基于内胞和双层表面单胞的材料弹性性能有限元力学模型,结合实验数据验证了材料弹性性能预测模型的有效性,并详尽讨论了编织角和纤维体积含量对材料弹性性能的影响规律。其次,在宏观尺度方面,提出了三维四向编织复合材料“叠层胞元力学结构模型”,建立了壁板及加筋壁板稳定性有限元分析力学模型,研究了其在压缩及剪切载荷工况下的屈曲特性,系统讨论了编织角、纤维体积含量、壁板尺寸等对结构屈曲特性的影响。最后,设计了典型三维四向编织复合材料整体加筋壁板结构,采用非线性有限元方法研究了其在轴压载荷下的后屈曲行为,分析了压载作用下结构的平衡路径和屈曲模态,获得了结构内力分布特征,并详尽讨论了纤维体积含量、编织角、筋条数目等参数对结构后屈曲行为的影响规律。
[Abstract]:Three-dimensional braided composites have good structural integrity and can effectively overcome the weaknesses of traditional laminated composites such as low interlaminar strength and easy delamination. As a new type of lightweight and efficient structure, 3-D braided composite panels with integral reinforcement are studied for their stability, structural buckling and post-buckling behavior, and ultimate load-carrying capacity of the structures are evaluated. It is one of the important problems to be solved to ensure structural safety. However, the meso-structure of 3D braided composite is especially complex, which makes it more difficult to design and analyze the whole stiffened panel. Therefore, how to establish a mechanical model of structural stability analysis according to the macrostructure characteristics of 3-D braided composite panels, and systematically study the influence of material process parameters and structural parameters on structural stability. It has important research value and engineering significance. Based on the macro and meso-structure characteristics of 3D braided composite structures, the structural stability of 3D four-direction braided composite panels and monolithic stiffened plates under typical load conditions is studied by using the idea of cross-scale mechanical modeling. Firstly, in the aspect of meso-scale, according to the four-step braiding process, the spatial motion and distribution of yarns in different regions are studied, and the parameterized solid cell models of inner and surface cells are established. In this paper, the cell model of three dimensional four direction braided composites is presented, and the finite element mechanical model of material elastic properties based on inner cell and double layer surface unit cell is established. The validity of the prediction model is verified by the experimental data. The effects of braiding angle and fiber volume content on the elastic properties of the material are discussed in detail. Secondly, in macroscopical scale, a three-dimensional four-direction braided composite "stacking cell mechanical structure model" is proposed, and the finite element analysis mechanical model of the stability of the wall plate and stiffened panel is established. The effects of braiding angle, fiber volume content and panel size on the buckling behavior of the structure were studied. Finally, a typical three-dimensional four-direction braided composite reinforced wall structure is designed. The post-buckling behavior of the composite subjected to axial compression is studied by nonlinear finite element method, and the equilibrium path and buckling mode of the structure under ballast loading are analyzed. The characteristics of internal force distribution are obtained, and the influence of fiber volume content, braiding angle and the number of bars on the post-buckling behavior of the structure is discussed in detail.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：V214.8;TB33

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