Mechanical properties of carbon nanotubes

Abstract

A variety of outstanding experimental results on the elucidation of the elastic properties of carbon nanotubes are fast appearing. These are based mainly on the techniques of high-resolution transmission electron microscopy (HRTEM) and atomic force microscopy (AFM) to determine the Young's moduli of single-wall nanotube bundles and multi-walled nanotubes, prepared by a number of methods. These results are confirming the theoretical predictions that carbon nanotubes have high strength plus extraordinary flexibility and resilience. As well as summarising the most notable achievements of theory and experiment in the last few years, this paper explains the properties of nanotubes in the wider context of materials science and highlights the contribution of our research group in this rapidly expanding field. A deeper understanding of the relationship between the structural order of the nanotubes and their mechanical properties will be necessary for the development of carbon-nanotube-based composites. Our research to date illustrates a qualitative relationship between the Young's modulus of a nanotube and the amount of disorder in the atomic structure of the walls. Other exciting results indicate that composites will benefit from the exceptional mechanical properties of carbon nanotubes, but that the major outstanding problem of load transfer efficiency must be overcome before suitable engineering materials can be produced. PACS: 62.20.x; 62.20.Dc; 61.48.+c; 61.16.Ch; 61.16.ByRolling up a graphene sheet on a nanometre scale [1] has dramatic consequences on the electrical properties [2]. The small diameter of a carbon nanotube (CNT) also has an important effect on the mechanical properties, compared with traditional micron-size graphitic fibres [3]. Perhaps the most striking effect is the opportunity to associate high flexibility and high strength with high stiffness, a property that is absent in graphite fibres. These properties of CNTs open the way for a new generation of high performance composites. Theoretical studies on the mechanical properties of CNTs * Corresponding author are more numerous and more advanced than experimental measurements, mainly due to the technological challenges involved in the production of nanotubes and in the manipulation of nanometre-sized objects. However, recent developments in instrumentation (particularly high-resolution transmission electron microscopy (HRTEM) and atomic force microscopy (AFM)), production, processing and manipulation techniques for CNTs, have given remarkable experimental results. In this review, we cover different aspects of the mechanical properties of nanotubes and nanotube-based composites referring to theoretical and experimental work of different groups. We do not aim to be exhaustive, but prefer to focus on what we believe to be the most significant results.The mechanical properties are strongly dependent on the structure of the nanotubes. This is due to the high anisotropy of graphite. In our laboratory, three kinds of nanotubes have been studied: bundles of ...

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