Mechanics of Nanoropes

碳纳米管(CNTs)是一种多功能材料，可用作各种复合材料中的增强部件，其中基质可以是聚合物、陶瓷或金属，包括延性金属，如铝。此外，碳纳米管可以作为一种新型的电缆材料，利用其高的刚性和潜在的高强度。有两种类型的碳纳米管，“单壁碳纳米管”和“多壁碳纳米管”，多壁碳纳米管。这项来自国家科学基金会的拨款通过实验和建模相结合的努力解决了单壁碳纳米管束的力学问题。特别是，这个项目的目标是详细了解平行和扭曲的SWCNT束的机理。这一努力的灵感来自于绞合线、纺织和机械等相当成熟的领域。这些学科通常是通过连续介质力学来研究绞合线结构或纺织织物的力学。人们可能会认为，缠绕一束或实现一束“编织”的单壁碳纳米管将增强单壁碳纳米管“绳”的承载能力。管束中各个管子之间的载荷转移程度是它们在两种复合材料的结构应用中潜在应用的一个关键方面，例如作为电缆，甚至作为电磁铁的绕组。我们的实验工作涉及使用纳米操纵器/测试阶段，在该阶段中，我们将拿起SWCNT束，将其安装在拉伸载荷下，并使用此测试阶段的一个组件施加扭曲，该组件每360度旋转可经历1800个单独的步骤，并可继续通过n个转弯来“缠绕”SWCNT束。使用该工具将研究作为施加扭度的函数的刚度以及作为施加扭度的束强度的函数，该工具以前曾用于研究单个MWCNT和未扭曲的SWCNT束的拉伸载荷。我们的建模工作涉及到使用各种方法，包括分子动力学(MD)、分子力学(MM)和连续介质力学，来研究作为扭度和接触长度的函数的载荷传递等问题，对于理想束(例如，束中的每根管都是相同的，例如所有管都是具有完美最紧密填充的(10，10)管)和可能更接近于实验测试的那些管，例如在束中有不同直径的管，而没有完美的最紧密填充。进行理论和实验的小组之间有密切的合作，每一次努力都在一定程度上指导对方，并提供更深层次的整体理解。

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.