结构和变形对单壁碳纳米管力学性能的影响

使用分子动力学方法模拟了单壁碳纳米管的拉伸变形行为和泊松比,并从单壁碳纳米管晶胞单元的结构特征角度,系统分析了管径、螺旋性和应变对力学性能的影响．模拟结果显示,单臂性碳纳米管(8,8)-(22,22)和锯齿性碳纳米管(9,0)-(29,0)的拉伸弹性变形可以分别达到35％-38％和20％-27％,拉伸条件下这些碳纳米管的弹性模量随管径的增大从960 GPa下降到750 GPa,并且锯齿性碳纳米管的弹性模量比单臂性碳纳米管的弹性模量要高．通过对三根具有相同直径和不同螺旋性的碳纳米管(9,9),(12,6)和(16,0)分别在拉伸和压缩条件下的模拟发现,随着变形的增大,碳纳米管的泊松比将减小;在相同的拉伸应变下,碳纳米管的泊松比随其螺旋角的减小而减小,而在相同的压缩应变下,碳纳米管的泊松比随其螺旋角的减小而增大．

Atomic Simulation of Structure and Deformation's Influence on the Mechanical Properties of Single-walled Carbon Nanotubes

Tensile deformation behaviors and the Poisson's ratio of single-walled carbon nanotubes (SWCNTs) are numerically studied, using the molecular dynamics (MD) method. Effects of several structural features of crystal cells of SWCNTs, i.e., the size, chirality and strain, on their mechanical properties are analyzed systematically. The simulations indicate that Armchair SWCNTs (8, 8)-(22, 22) and Zigzag SWCNTs (9,0)-(29,0) can be stretched by 35%-38% and 20%-27% without sign of plasticity, respectively. The Young's modulus of SWCNTs under tension ranges from 960 GPa to 750 GPa as their radii increase. The Young's modulus of zigzag SWCNTs is higher than that of armchair SWCNTs. Additionally, three SWCNTs (9,9), (12,6) and (16,0) are investigated to obtain their Poisson's ratio under tensile and compressive loading. The results show that the Poisson's ratio of nanotubes decreases generally as the strain increases. Under the same tensile strain, the Poisson's ratio decreases as the chiral angles of SWCNTs decrease, while their Poisson's ratios increase under the same compressive strain.