【作者】 刘佳；

【导师】 杨庆生；

【作者基本信息】 北京工业大学 ， 工程力学， 2010， 硕士

【摘要】 纳米材料的研究是现在的热门研究方向,如对纳米管和纳米金属等的研究。由于纳米材料的尺寸达到纳米级,常常会表现出大尺寸材料不具有的性能。碳纳米管作为一维纳米材料由于具有层状中空、完美的六边形连接以及长径比很大等独特的结构,所以具有优良的力学、电学、热学和化学性能,因此引起了学术界和工艺界的广泛兴趣和关注。随着Ajayan等在1994年将碳纳米管加入到聚合物中制备聚合物复合材料以来,碳纳米管的化学改性以及碳纳米管与聚合物的复合等问题引起了人们广泛的关注,这也要求对其进行更深入的研究。本文分别以功能化碳纳米管、其复合材料以及含镀层石墨/铜材料为研究对象,采用分子动力学方法,对其力学性能进行模拟计算。主要研究内容如下:(1)研究不同功能化碳纳米管的拉伸和压缩性能。通过对不同密度、不同种类以及不同构型功能化碳纳米管拉伸过程的数值模拟,分析了这些参数对碳纳米管力学性能的影响;通过对不同构型功能化碳纳米管压缩过程的数值模拟,分析了构型对材料的屈曲模态和临界屈曲应变的影响规律。总结几种不同构型功能化碳纳米管,可以发现功能化原子越集中,材料性能越好。(2)采用分子动力学方法,对功能化碳纳米管增强聚乙烯复合材料的拉伸过程和碳纳米管的拔出过程进行了模拟,分析了复合材料的整体性能和界面性能。得到如下结论:功能化对复合材料的杨氏模量影响不大,但是材料的最大应力明显降低,功能化原子越集中,复合材料性能也越好;通过对碳纳米管拔出过程的模拟,发现与功能化原子相连的碳纳米管原子的轴向力较大,并且功能化明显增强了复合材料界面粘合作用,尤其是功能化原子集中的模型,界面剪切应力提高了20%左右。最后对比了对碳纳米管整体施加位移和端部施加位移两种模拟对结果的影响。(3)研究了镀层石墨/铜的界面性能。通过对石墨施加外载荷力分别模拟了镀铜石墨/铜和镀镍石墨/铜两种材料,得到模型中各个部分的能量以及各个界面的剪切应力,发现镀镍材料中石墨的界面剪切应力比镀铜大,并且在模拟中镀镍材料的能量变化明显,说明镍与石墨结合较好。本论文工作得到国家自然科学基金项目(10872011)和北京自然科学基金项目(3092006)资助。更多还原

【Abstract】 The research of nano-materials is a hot subject now, such as the studies of nano-tube, nano-film and nano-composites et al. Nano-materials have some properties different from normal materials because of the nano-dimension. As one-dimensional nano-materials, carbon nanotubes(CNTs) have excellent mechanical, electrical, thermal and chemical properties because of hollow structure, a perfect hexagonal connection and quite high slenderness ratio. As a result, it has become the focus of researchers. Since the CNTs were added into polymer by Ajayan in 1994, the chemically modification and the compounding with polymer have caused widespread concern, which ask for the profound study.In this paper, functionalized CNTs, their composites and coating graphite/metal materials are studied using molecular dynamics (MD) method to simulate the mechanical properties of materials. The main contents are as follows:(1) Tensile and compressed properties of different functionalized CNTs are studied. According to the MD simulations of the extension process of functionalized CNTs for different densities, types and configurations, their influences on the mechanical properties are analyzed. According to the MD simulations of the compression process for different configurations, its influences on the buckling mode and critical buckling strain are analyzed. As a result, the high convergence of functionalized atoms results in better mechanical properties.(2) The Young’s modulus and interfacial properties are studied by simulating the composites extension and the pulling-out process of CNTs. Some important conclusions are obtained as follows: Functionalization has little effect on the Young’s modulus, but the maximum stress of composites significantly decreases. The higher convergence functionalized atoms are, the better mechanical properties the composites are. The axial forces of carbon atoms connecting with functionalized atoms are larger. Functionalization significantly enhances the interfacial adhesive properties, and the interfacial shear stress increases 20% for high convergence of the functionalized carbon atoms. At last, the pull-out processes of applying displacement to the end of CNTs are simulated. The axial forces of carbon atoms and interfacial shear stresses are obtained and compared with previous results.(3) The interfacial properties of coating graphite/metal materials are studied. Copper coating graphite/metal and nickel coating graphite/metal are simulated separately by imposing forces on the graphite. The energies of every part of models and every interface shear stress are obtained. The interfacial shear stress and the change of energy of nickel coating graphite/metal are larger than those of the copper coating graphite/metal. The results of simulations illustrate that nickel and graphite are well connected. The authors gratefully acknowledge the financial support of the Natural Science Foundation of China (No. 10872011) and the Natural Science Foundation of Beijing (No. 3092006)更多还原