Mechanical stability of Carbon Nanotubes

Publication Type:
Thesis
Issue Date:
2011
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NO FULL TEXT AVAILABLE. Access is restricted indefinitely. ----- Consideration of stability of carbon nanotubes (CNTs) as one dimensional carbon based materials and building blocks of numerous advanced devices and potential components of many more instruments is the subject of this project. CNTs are cylindrical structure with honey comb lattice that gives them exceptional mechanical, electrical, chemical and thermal properties which distinguish them from other known material as the most promising material for numerous advanced applications such as composite materials, hydrogen storage, electron microscopy, optoelectronic, etc. However, before practical application of CNTs as components of future materials and devices, their mechanical properties and especially their mechanical stabilities should be investigated in detail. Molecular dynamics simulation and continuum mechanics are two common theoretical approaches which have been employed herein to study the mechanical properties of CNTs. Buckling behaviour and critical axial properties of single-, double-, and multi-walled carbon nanotubes have been studied. Axial and bending stability of double-walled carbon nanotube and its inner and outer tubes with different dimensions and mechanical properties in different buckling modes have been considered. Effects of surrounding elastic medium on the outer tube and the van der Waals interaction between adjacent tubes of multi-walled CNTs and growth in the radius, length, and aspect ratio (length/radius) on the stability of CNTs have been considered thoroughly. Stress-strain curves, elastic modulus, tensile, compressive and bending stiffness of zigzag and armchair CNTs are investigated to figure out the effect of variation in radius and different chirality on mechanical properties of CNTs. Effects of van der Waals interaction and variation in dimensions of CNTs on Young’s modulus, compressive elastic modulus, tensile, compressive, and lateral stiffness, critical buckling strain, critical axial force and pressure of armchair and zigzag CNTs have been investigated. Destructive effects of Stone-Wales, atom vacancy, cell vacancy and cell deformed structural defects on axial and bending stability and buckling behaviour of armchair and zigzag CNTs have been studied Obtained results revealed remarkable agreement between predictions of continuum mechanics analysis and molecular dynamics simulation results. CNTs with different dimensions revealed different mechanical properties and different level of stability against mechanical loading conditions; however, obtained results of this study categorized their properties and found relationships between variations in lengths and radius with alterations in mechanical stabilities and mechanical properties of CNTs. Consideration of destructive effects of defects on the stability of CNTs led to more reliable predictions about the resilience of CNTs under axial forces and bending moments. Comparative style of this study facilitates selection of suitable size and chirality of CNTs for in nanostructures, nanoelectromecanical devices, and numerous other practical applications of CNTs.
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