碳纳米管有限温度模型和热力学性能的理论分析
发布时间：2019-03-21 07:59
【摘要】：自从碳纳米管被发现以来,它就以极其优异的力学性能,吸引着国内外专家学者的广泛关注。目前,各国专家学者已经围绕碳纳米管的力学性质进行了大量的理论研究,但是碳纳米管力学性质随温度改变的研究成果还十分有限,而掌握碳纳米管的热力学性能,对碳纳米管高效而持久的工程应用具有有十分重要的现实意义。本文就着重分析了碳纳米管的热力学性能。本文以能使碳纳米管更好地实现工程应用为出发点,主要采用了分子力学和连续介质力学来研究碳纳米管力学性能随温度的变化关系。本文通过用分子力学的方法建立了一个与环境温度相关而与碳纳米管壁厚无关的力学模型来研究单壁碳纳米管在热环境中的弹性性能。在分子结构力学模型中首次采用了随温度连续变化的碳碳键的线性热膨胀系数,并详细讨论了单壁碳纳米管的杨氏模量和泊松比随外部环境温度的变化关系。结果表明,无论是扶手椅型碳纳米管杨氏模量还是锯齿型碳纳米管的杨氏模量都随温度的增加而下降,而它们的泊松比则不随温度变化。值得一提的是当管径相同时,扶手椅型碳纳米管的杨氏模量略大于锯齿型碳纳米管的杨氏模量,但是当温度相同时,两种碳纳米管的杨氏模量均随其管径的增加而增大。本文借助Cauchy-Born准则,通过连续介质力学的方法建立一个包含碳原子间相互作用势和有限温度的力学模型,来研究碳纳米管在热环境下的拉伸和压缩极限。为了更好地适应工程应用的要求,本文采用Euler-Bernoulli梁理论,建立了一个基于原子间相互作用势的非局部壳理论,来研究大长径比多壁碳纳米管在热环境中的轴压屈曲,并对双壁碳纳米管的屈曲应变做了详细讨论。
[Abstract]:Since the discovery of carbon nanotubes (CNTs), it has attracted extensive attention of experts and scholars at home and abroad for its excellent mechanical properties. At present, experts and scholars from all over the world have done a lot of theoretical research on the mechanical properties of carbon nanotubes, but the research results of the mechanical properties of carbon nanotubes with the change of temperature are still very limited, and the thermodynamic properties of carbon nanotubes are grasped. It is of great practical significance for the efficient and durable engineering application of carbon nanotubes (CNTs). In this paper, the thermodynamic properties of carbon nanotubes (CNTs) are emphatically analyzed. Based on the engineering application of carbon nanotubes (CNTs), molecular mechanics and continuum mechanics are used to study the relationship between the mechanical properties of CNTs and temperature. In this paper, the elastic properties of single-walled carbon nanotubes (SWNTs) in thermal environment are studied by means of molecular mechanics, which is independent of the wall thickness of carbon nanotubes (CNTs) and depends on the ambient temperature. The linear thermal expansion coefficient of carbon-carbon bonds continuously varying with temperature is used in the molecular structural mechanics model for the first time, and the relationship between Young's modulus and Poisson's ratio of single-walled carbon nanotubes with external ambient temperature is discussed in detail. The results show that the Young's modulus of both armchair carbon nanotubes and jagged carbon nanotubes decreases with the increase of temperature, but their Poisson's ratio does not change with the temperature. It is worth mentioning that the Young's modulus of armchair carbon nanotubes is slightly larger than that of saw-tooth carbon nanotubes when the diameter of the tubes is the same, but when the temperature is the same, the Young's modulus of the two carbon nanotubes increases with the increase of the diameter of the tubes. In this paper, with the help of Cauchy-Born criterion, a mechanical model including the interaction potential and finite temperature between carbon atoms is established by means of continuum mechanics to study the tensile and compressive limits of carbon nanotubes in the thermal environment. In order to meet the requirements of engineering application, a nonlocal shell theory based on the interaction potential between atoms is established in this paper to study the axial buckling of multi-walled carbon nanotubes with large aspect ratio in the thermal environment by using the Euler-Bernoulli beam theory. The buckling strain of double-walled carbon nanotubes is discussed in detail.
【学位授予单位】：燕山大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1
本文编号：2444740
[Abstract]:Since the discovery of carbon nanotubes (CNTs), it has attracted extensive attention of experts and scholars at home and abroad for its excellent mechanical properties. At present, experts and scholars from all over the world have done a lot of theoretical research on the mechanical properties of carbon nanotubes, but the research results of the mechanical properties of carbon nanotubes with the change of temperature are still very limited, and the thermodynamic properties of carbon nanotubes are grasped. It is of great practical significance for the efficient and durable engineering application of carbon nanotubes (CNTs). In this paper, the thermodynamic properties of carbon nanotubes (CNTs) are emphatically analyzed. Based on the engineering application of carbon nanotubes (CNTs), molecular mechanics and continuum mechanics are used to study the relationship between the mechanical properties of CNTs and temperature. In this paper, the elastic properties of single-walled carbon nanotubes (SWNTs) in thermal environment are studied by means of molecular mechanics, which is independent of the wall thickness of carbon nanotubes (CNTs) and depends on the ambient temperature. The linear thermal expansion coefficient of carbon-carbon bonds continuously varying with temperature is used in the molecular structural mechanics model for the first time, and the relationship between Young's modulus and Poisson's ratio of single-walled carbon nanotubes with external ambient temperature is discussed in detail. The results show that the Young's modulus of both armchair carbon nanotubes and jagged carbon nanotubes decreases with the increase of temperature, but their Poisson's ratio does not change with the temperature. It is worth mentioning that the Young's modulus of armchair carbon nanotubes is slightly larger than that of saw-tooth carbon nanotubes when the diameter of the tubes is the same, but when the temperature is the same, the Young's modulus of the two carbon nanotubes increases with the increase of the diameter of the tubes. In this paper, with the help of Cauchy-Born criterion, a mechanical model including the interaction potential and finite temperature between carbon atoms is established by means of continuum mechanics to study the tensile and compressive limits of carbon nanotubes in the thermal environment. In order to meet the requirements of engineering application, a nonlocal shell theory based on the interaction potential between atoms is established in this paper to study the axial buckling of multi-walled carbon nanotubes with large aspect ratio in the thermal environment by using the Euler-Bernoulli beam theory. The buckling strain of double-walled carbon nanotubes is discussed in detail.
【学位授予单位】：燕山大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1
【参考文献】
相关期刊论文 前1条
1 夏健明;魏德敏;;碳纳米管的连续介质方法研究进展[J];力学与实践;2008年02期
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