Stretching process of single- and multi-walled carbon nanotubes for nanocomposite applications

Single- and multi-walled carbon nanotubes have being increasingly used as nanoreinforcements for polymer-based nanocomposites. Since the nanotubes are resilient and have an extremely high elastic modulus, only adding a few percentages of nanotubes into the composites during the manufacturing process could enhance the composites' mechanical strength and fracture toughness. However, many arguments have been arisen regarding which types of nanotube provide the better strengthening performance in composite structures. An experimental observation showed that the inner tubes of multi-walled nanotubes were pulled out after tensile testing. Similar observations were also made regarding multi-walled nanotube /polymer composites. The inner layers of nanotubes were pulled out after an outmost layer of some of the nanotubes was broken. There is no comprehensive study of the straining behaviour inside single- and multi-walled nanotubes to date. Without fully understanding this, it is hard to anticipate the strength and effectiveness of using nanotubes for nanotube/polymer composites. In this letter, the results extracted from molecular dynamic simulations of single- and multi-walled nanotubes subjected to uniaxial straining to study the mechanical properties of these nanotubes is reported.