Strength distribution and interactions of spinnable carbon nanotubes

Carbon nanotubes are innovative materials with high potential for applications in various industries. However, it is very hard to perform direct experimentation to characterise their mechanical behaviour due to their dimensional constraints. There is wide scatter in the re- ported mechanical strength of individual carbon nanotubes in the literature. Nevertheless, theoretically it is very well established that individually they are amongst the strongest materials so far. However, this strength has yet to transfer to macro scale structures such as carbon nanotube yarns. Individual nanotube has 100 GPa of strength with 1 TPa of modulus of elasticity. But nanotube yarns have reached so far 1.5 GPa of strength. To address the issue of this huge differences in strengths in different structural scales of same material, this thesis embarks on logical step wise investigation of strength distribution and interaction properties of spinnable carbon nanotubes. First, to address the scattering strength issue, this thesis undertake extensive experi- mental investigations utilizing the newly developed nano tensile stage to test the individ- ual carbon nanotubes under uni axial tensile load inside a Scanning Electron Microscope (SEM). It was shown that the strength distribution of spinnable nanotubes depends on the geometric features of the specimen such as the number of broken walls. It increase with the higher numbers of broken walls. However, the probability of getting all the walls of a nanotube broken without any external aid or modification is extremely low. To improve this probability and to enhance their strength, the effect of post synthesis treatments such as gamma irradiation technique is investigated. It is shown that the irradiation doses and environment have influence on strength of spinnable carbon nanotubes. The interaction among the carbon nanotubes has been investigated through macro scale peel tests. It was found that the orientation angle of the nanotubes with respect to each other has profound influence on their interaction characteristics. Simulation of this peeling mechanics revealed that nanotube interface undergo mode transformation which assisted the production of their macro scale constructs. As a result of the findings of this research, it would enhance the understanding of spinnable carbon nanotube characteristics.