Study of the Mechanical Properties of Single-Walled Carbon Nanotubes

Author(s):  
Paola Jaramillo ◽  
Haym Benaroya

Carbon nanotubes are composed of C-C covalent bonds, which are the strongest bonds found in nature. Hence, carbon nanotubes are identified as the “ultimate fiber” due to their great strength in the direction of the nanotube axis and their ability to enhance the elastic properties of materials. The first indications of synthesizing carbon nanotubes date back to 1952. Russian scientists Radushkevich and Lukyanovich [1] were able to produce nanosized hollow carbon filaments. Nevertheless, it was until 1991 that multi-walled carbon nanotubes (MWCNTs) were discovered by Sumio lijima [2, 3] at NEC Corporation Lab, which was followed by his study and synthesis of single-walled carbon nanotubes (SWCNTs) in 1993. Since their discovery, there has been a constant pursuit to understand the properties and identify the optimal applications of these structures. The paper focuses on the importance of carbon nanotubes and their ability to enhance the mechanical properties of other materials due to their unique elastic properties. Additionally, carbon nanotubes can improve the capabilities and properties of other materials, like polymer composite. Currently, there is an ongoing process to accurately understand the fundamental characteristics of these structures, in particular, to develop the governing laws necessary to control, predict, and manipulate these properties. This will eventually have an impact on the bulk properties of materials where carbon nanotubes may be incorporated. The current research focuses on the ability to create simplified models that can accurately predict the response of carbon nanotube structures undergoing different types of loading conditions. In this way, the mechanical characteristics regarding single-walled carbon nanotubes (SWCNTs) through finite element modeling are computed. A simplified finite element model is created in ANSYS for different types of SWCNTs with varying input parameters. An input array for the elastic modulus and load is generated to control the physical effects of these parameters in the nanotube structure. The geometries of the nanotubes are altered through various thicknesses employed for the construction of the C–C bonds. The current work contributes to the generation of different model responses to monitor the stress distribution employing a wide range of parameter values. The ability to introduce variability in the parameters and boundary conditions without altering the capabilities and computational time in the model represents the main contribution of this work.

2008 ◽  
Vol 33-37 ◽  
pp. 937-942 ◽  
Author(s):  
Cheng Wen Fan ◽  
Jhih Hua Huang ◽  
Chyan Bin Hwu ◽  
Yu Yang Liu

In this paper, the mechanical properties, such as the axial and radial Young’s moduli, shear moduli, buckling loads and natural frequencies, of single-walled carbon nanotubes, are estimated by a finite element approach. Each carbon nanotube is simulated as a frame-like structure and the primary bonds between two nearest-neighboring atoms are treated as isotropic beam members with a uniform circular cross-section. In the modeling work, the BEAM4 element in commercial code ANSYS is selected to simulate the carbon bonds and the atoms are nodes. As to the input parameters of the BEAM4 element, they are determined via the concept of energy equivalence between molecular dynamics and structural mechanics, and represented in terms of the force constants of the carbon bonds found in molecular mechanics. Based on this modeling concept, finite element models of both armchair and zigzag types of carbon nanotubes with different sizes are established and the mechanical properties of these tubes are then effectively predicted. Most of the computed results which can be compared with existing results show good agreement. Moreover, the effects of tube diameter, length etc., on the mechanical properties are also investigated.


Author(s):  
Mariana Ionita

Atomistic models of polyaniline (PANI)-single walled carbon nanotubes (CNTs) were built in order to assess the effect of quantity and quality of CNTs and temperature on the calculated mechanical properties of PANI. Three different types of CNTs were considered: single walled carbon nanotubes m-polyaminobenzene sulfonic acid functionalized (CNTs-PABS), single walled carbon nanotubes octadecylamine functionalized (CNTs-ODA) and single walled carbon nanotubes carboxylic acid functionalized (CNTs-CX). Atomistic models were built for PANI-functionalized CNTs with a range of CNTs content, contained within periodic boundary conditions and were subject of multistage equilibration procedure. In order to test the mechanical behaviour of the models virtual uniaxial traction tests along the three perpendicular edges of the models were performed. The Young’s moduli generally increased with increasing of CNTs content and values range from 0.48 GPa in the case of pure PANI to 1.35–1.83 GPa in the case of PANI-CNTs-PABS composite system.


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