發(fā)布時間：2019-03-21 07:59

【摘要】：自從碳納米管被發(fā)現(xiàn)以來,它就以極其優(yōu)異的力學性能,吸引著國內外專家學者的廣泛關注。目前,各國專家學者已經圍繞碳納米管的力學性質進行了大量的理論研究,但是碳納米管力學性質隨溫度改變的研究成果還十分有限,而掌握碳納米管的熱力學性能,對碳納米管高效而持久的工程應用具有有十分重要的現(xiàn)實意義。本文就著重分析了碳納米管的熱力學性能。本文以能使碳納米管更好地實現(xiàn)工程應用為出發(fā)點,主要采用了分子力學和連續(xù)介質力學來研究碳納米管力學性能隨溫度的變化關系。本文通過用分子力學的方法建立了一個與環(huán)境溫度相關而與碳納米管壁厚無關的力學模型來研究單壁碳納米管在熱環(huán)境中的彈性性能。在分子結構力學模型中首次采用了隨溫度連續(xù)變化的碳碳鍵的線性熱膨脹系數(shù),并詳細討論了單壁碳納米管的楊氏模量和泊松比隨外部環(huán)境溫度的變化關系。結果表明,無論是扶手椅型碳納米管楊氏模量還是鋸齒型碳納米管的楊氏模量都隨溫度的增加而下降,而它們的泊松比則不隨溫度變化。值得一提的是當管徑相同時,扶手椅型碳納米管的楊氏模量略大于鋸齒型碳納米管的楊氏模量,但是當溫度相同時,兩種碳納米管的楊氏模量均隨其管徑的增加而增大。本文借助Cauchy-Born準則,通過連續(xù)介質力學的方法建立一個包含碳原子間相互作用勢和有限溫度的力學模型,來研究碳納米管在熱環(huán)境下的拉伸和壓縮極限。為了更好地適應工程應用的要求,本文采用Euler-Bernoulli梁理論,建立了一個基于原子間相互作用勢的非局部殼理論,來研究大長徑比多壁碳納米管在熱環(huán)境中的軸壓屈曲,并對雙壁碳納米管的屈曲應變做了詳細討論。
[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.
【學位授予單位】：燕山大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TB383.1

【參考文獻】

相關期刊論文 前1條

1 夏健明;魏德敏;;碳納米管的連續(xù)介質方法研究進展[J];力學與實踐;2008年02期

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本文編號：2444740