涂层蜂窝结构和纤维增强复合材料的均匀化方法有限元模拟

发布时间：2018-06-13 06:04

本文选题：蜂窝结构 + 表面涂层　；参考：《南昌航空大学》2015年硕士论文

【摘要】：蜂窝材料作为一类重要的多孔材料,由于其具有优异的机械力学性能被广泛应用在各行各业。但是由于传统蜂窝材料自身结构的局限性,使得蜂窝材料在应用方面有着很大的局限性。为了打破这一局限性,本文将通过在蜂窝结构表面添加涂层来改善传统蜂窝多孔结构材料的整体性能。然而由两种或两种以上的异质材料所制成复合材料的性能不仅取决于各组分的结构和性能,而且在相当程度上受到界面性能的影响。由于在研究涂层蜂窝结构时没有考虑这种界面效应,所以本文先探索性的研究了界面性能对纤维增强复合材料整体宏观性能的影响。具体研究的内容和结果包括以下几个方面:(1)本文采用均匀化有限元方法,建立了三维(3D)代表体积单元(RVE)单胞模型,并进行了用户子程序代码的编写。(2)分别建立了正方形、三角形、圆形和正六边形孔型的RVE模型。假定这几种孔型的孔隙率保持一致,预测了它们的等效弹性性能参数。通过对这四种不同孔型结构的蜂窝材料进行分析,我们发现正六边形孔型的蜂窝结构材料的面内剪切性能最优。(3)在正六边形蜂窝多孔结构材料的表面添加涂层,通过均匀化方法成功预测了其等效弹性性能参数,并与解析值进行对比分析。数值与解析结果均表明:基于均匀化有限元模拟所得到的结果与解析公式所得到的数值相吻合。随着涂层厚度的增加,面内弹性模量以及轴向弹性模量均随之增加;当涂层厚度达到某一个数值时,其面内和轴向等效模量会超过实体材料的模量。(4)建立了纤维增强复合材料的均匀化三维RVE模型,在模型中分别采用了周期性或者均匀化边界条件。先模拟计算了单向纤维增强陶瓷基复合材料(FRCs)的宏观等效弹性模量并与理论结果进行了对比验证。同时引入内聚力模型来分析在纤维与基体的不完美粘结的情况下界面性能对等效弹性常数和抗拉强度的影响。结果表明:完美粘结界面情况下,采用不同的边界条件所计算的纤维增强陶瓷宏观等效弹性模量与其理论结果相一致;与界面强度相比,界面刚度和断裂能对复合材料的抗拉强度有显著影响;复合材料的纵向抗拉强度几乎独立于界面性能,并且随纤维体积分数的增加而急剧增加。
[Abstract]:Honeycomb material, as an important kind of porous material, is widely used in all walks of life because of its excellent mechanical and mechanical properties. But because of the limitations of the structure of the traditional honeycomb material, honeycomb material has a great limitation in the application. In order to break this limitation, this paper will add the surface of honeycomb structure. Coatings are added to improve the overall performance of the traditional honeycomb porous material. However, the properties of the composites made from two or more than two kinds of heterogeneous materials depend not only on the structure and properties of the components, but also on the interfacial properties to a considerable extent. Therefore, the effect of interface performance on the overall macro performance of fiber reinforced composites is studied in this paper. The contents and results of this study include the following aspects: (1) in this paper, a three-dimensional (3D) representative volume unit (RVE) single cell model is established by using the homogenization finite element method, and the code of the user subroutine is written. (2) the RVE model of square, triangular, circular and hexagonal pass is established respectively. It is assumed that the porosity of these kinds of pores is consistent and their equivalent elastic properties are predicted. By analyzing the honeycomb materials of these four different pore structures, we present the in-plane shear of the honeycomb structure material of the hexagonal pass. The performance is optimal. (3) the coating on the surface of a hexagonal honeycomb porous material is added. The equivalent elastic properties are predicted by homogenization and compared with the analytical values. Both numerical and analytical results show that the results based on the homogenization finite element simulation coincide with the numerical values obtained by the analytical formula. With the increase of coating thickness, the elastic modulus and the axial elastic modulus of the surface all increase. When the thickness of the coating reaches a certain value, the internal and axial equivalent modulus will exceed the modulus of the solid material. (4) the three-dimensional RVE model of the fiber reinforced composites is established, and the periodicity or the uniformity of the model is used respectively in the model. The macroscopic equivalent elastic modulus of the unidirectional fiber reinforced ceramic matrix composite (FRCs) was simulated and the results were compared with the theoretical results. The cohesion model was introduced to analyze the effect of the interfacial properties on the equivalent elastic constant and tensile strength under the imperfect bond between the fiber and the matrix. In the case of perfect bonding interface, the macro equivalent elastic modulus of fiber reinforced ceramics calculated by different boundary conditions is in accordance with the theoretical results. Compared with the interfacial strength, the interfacial stiffness and fracture energy have significant influence on the tensile strength of the composite; the longitudinal tensile strength of the composite is almost independent of the interfacial properties, and the tensile strength of the composite is almost independent of the interfacial properties. It increases sharply with the increase of fiber volume fraction.
【学位授予单位】：南昌航空大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB33

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