Mechanics of Nanoropes

Nanorope力学，Rod Ruoff和Wing Kam Liu，西北大学碳纳米管（CNT）是一种多功能材料，可以在各种复合材料中用作增强成分，其中基质可以是聚合物，陶瓷或金属，包括韧性金属，如铝。 此外，CNT可用作新型电缆材料，其将利用高刚度和潜在的高强度。 有两种类型的碳纳米管，“单壁碳纳米管”，SWCNT，和“多壁碳纳米管”，MWCNT。 这项来自美国国家科学基金会的资助通过实验和建模工作来解决单壁碳纳米管束的力学问题。 特别是，这个项目的目标是发展的平行和扭曲的单壁碳纳米管束的力学的详细了解。 这一努力的灵感来自于相当成熟的扭线、纺织、机械领域。 这些学科通常用连续介质力学来处理绞合线结构或纺织织物的力学。可以预期，将SWCNT的束绞合或实现“编织”束将增强SWCNT“绳”的承载能力。“管束中各个管之间的载荷传递程度是它们在复合材料结构应用中潜在应用的一个关键方面，例如电缆，甚至例如电磁铁中的绕组。我们的实验工作涉及使用纳米操纵器/测试阶段，其中我们将拾取SWCNT束，将它们安装用于拉伸负载，并使用该测试阶段的组件施加扭曲，该测试阶段的组件可以每360度旋转经历1800个单独的步骤，并且可以继续通过n个转弯“缠绕”SWCNT束。 刚度作为施加的扭曲的函数，以及作为施加的扭曲的函数的束强度，将与此工具，它以前已被用来研究单个MWCNT的和未扭曲的单壁碳纳米管束的拉伸载荷进行研究。 我们的建模工作涉及使用各种方法，包括分子动力学（MD），分子力学（MM）和连续介质力学，以研究两种理想化束的载荷传递作为扭曲和接触长度的函数等问题（例如在管束中的每个管都相同的情况下，例如所有管都是（10，10）具有完美的最紧密堆积的管）和可能更接近地模拟在实验中实际测试的那些的束，例如在束中具有不同直径的管，而没有完美的最紧密堆积。 理论和实验小组之间有着密切的合作，每一项努力都是为了指导另一项努力，并提供更深入的整体理解。

Nanorope Mechanics, Rod Ruoff and Wing Kam Liu, Northwestern UniversityCarbon nanotubes, CNTs, are a multifunctional material that may find applications as a reinforcing component in a variety of composites, where the matrix could be polymer, ceramic, or a metal, including ductile metals such as aluminum. Additionally, CNT's may be applied as a new type of cable material that would exploit the high stiffness and potentially the high strength. There are two types of carbon nanotubes, the "single walled carbon nanotubes," SWCNTs, and the "multiwalled carbon nanotubes," MWCNTs. This grant from the National Science Foundation addresses the mechanics of SWCNT bundles with a combined experimental and modeling effort. In particular, the goal of this project is to develop a detailed understanding of the mechanics of both parallel and twisted SWCNT bundles. Inspiration for this effort comes from the rather well established fields of twisted wire, and textile, mechanics. These disciplines have treated the mechanics of twisted wire structures, or textile fabrics, typically by continuum mechanics. One may expect that twisting a bundle, or achieving a "woven" bundle, of SWCNTs will enhance the load bearing capacity of the SWCNT "rope." The extent of load transfer between individual tubes in the bundle is a crucial aspect of their potential application in structural applications in either composites, as cabling, and even for example, as windings in electromagnets. Our experimental effort involves the use of a nanomanipulator/testing stage in which we will pick up SWCNT bundles, mount them for tensile loading, and apply twists with a component of this testing stage, which can undergo 1800 individual steps per 360 degree revolution, and can continue to "wind up" a SWCNT bundle through n turns. The stiffness as a function of applied twist, and also the bundle strength as a function of applied twist, will be studied with this tool, which has been previously used to study the tensile loading of individual MWCNT's and of untwisted SWCNT bundles. Our modeling effort involves using a variety of approaches, including molecular dynamics (MD), molecular mechanics (MM), and continuum mechanics, to study such issues as load transfer as a function of both twist and contact length, for both idealized bundles (for example, where every tube in the bundle is identical, such as all tubes being (10,10) tubes with perfect closest-packing) and bundles that might more closely mimic those actually tested in experiment, such as having different diameter tubes in the bundle, without perfect closest packing. There is a close collaboration between the groups doing theory and experiment, and each effort is meant in part to guide the other, and to provide deeper overall understanding.