单壁枝节碳纳米管拉伸力学性能多尺度模拟-材料加工工程专业论文.docx

南昌航 南昌航空大学硕士学位论文 Abstract PAGE III PAGE III 万方数据 ABSTRACT Branched carbon nanotubes (BCNTs) can realize even more complex function in nanometer devices because of their multilevel structure. Before playing important potential applications, a comprehensive research of branched carbon nanotubes for their mechanical properties should be done to provide theoretical and experimental foundation for future applications. According to this, the atomic-scale finite element method (AFEM) and the molecular dynamics method (MD) are adopted to simulate the mechanical properties of the single-walled straight carbon nanotubes (CNTs) and Y shaped branched carbon nanotubes (Y-BCNTs) under axial tension. The effects of the diameter and the chirality of carbon nanotubes on the tensile mechanical behavior are discussed. The following conclusions can be drawn from the present study: First, atom models of branched carbon nanotube and straight carbon nanotube are built, and then by combining the atomic coordinates both programs of node transformation and element topology for AFEM simulations are developed to construct AFEM models of Y-BCNTs and CNTs. We investigate the tensile strengths of CNTs under axial tensile. Both AFEM and MD numerical results show that the tensile strengths of armchair and chiral CNTs are greater than that of the zigzag CNTs when their diameters are similar. The results also indicate that the tensile strengths of armchair and zigzag CNTs increase gradually with increasing the diameter while that of chiral CNTs fluctuates due to the influence of the diameter and chiral angle. Based on AFEM and MD method, the mechanical behavior of Y-BCNTs under axial tensile is investigated as a function of diameter and chirality. The results show that the tensile strengths of zigzag Y-BCNTs are greater than those of armchair and chiral Y-BCNTs, which is different from the CNTs. We find that the structure of the Y-BCNTs is not perfect. The C bonds at the junction of armchair and ch