Mechanical strength of carbon nanotube ropes and characterization of intertube binding and friction

Abstract

The works presented in this thesis discuss the effects arising from intertube friction while single-walled carbon nanotubes (SWCNTs) aggregate into rope structure, including enhancement of tensile strength, Young’s modulus, damping effect and energy transmission and dissipation. The mechanical properties are found to be significantly depending on tube-tube interactions and current work has developed a effective technique in promoting the tensile strength through enhancing the intertube interaction by winding SWCNT ropes. The variation in Young’s modulus during tensile test and fracture of SWCNT ropes are also discussed. The damping factor of SWCNT ropes have been evaluated and compared with various materials, including tungsten wire, silk, spider silk and carbon fibers. Chapter 1 the basic information of carbon nanotubes (CNTs) is introduced, including structures, deformation mechanisms, mechanical properties of SWCNTs and SWCNT ropes. Chapter 2 briefly describes experimental setup, and characterization techniques employed in this study. Chapter 3 shows a conventional method for enhancing the strength of SWCNT ropes. The Young’s modulus of the winding SWCNT ropes is calculated based on strain-stress profiles. A model is also demonstrated for step-wise fracture of SWCNT ropes under tensile test. Chapter 4 discusses a vibration experiment on a doubly clamped SWCNT rope, tungsten wire, carbon fibers, silks and spider silks. Elastic wave propagation through the SWCNT rope is strongly scattered by intertube junctions and excitation energy is found to dissipate via tube-tube friction. Intertube scattering also accounts for the low energy transmission rate and high damping factor. Chapter 5 concludes the experimental results.