Size Effects on Tensile Strength and Fracture Behavior of Carbon Nanotubes

In this paper, the differences in mechanical properties and fracture behavior between singlewalled (SW), bundled, and yarned carbon nanotubes (CNTs) are described.The three types of CNTs are subjected to a quasi-static uniaxial tensile test to investigate their Young's modulus, strength, and fracture behavior.All the samples were fractured in a brittle manner.The mean Young's modulus and strength of SWCNTs were 1 TPa and 60 GPa, respectively, which markedly decreased with increasing diameter for bundled and yarned CNTs.Fracture surface observation suggested that each type of CNT fractured in a different manner: SWCNTs were split instantly, bundled CNTs broke as the outer and inner CNTs slipped against each other, and yarned CNTs were torn apart and fractured.The differences in fracture mechanisms are discussed on basis of Raman mapping results.