The failure modes of ZnO nanowires (NWs) with hexagonal cross section subjected to a uniaxial load are systematically investigated by using molecular dynamics (MD) simulations and two theoretical models considering the surface effect. Our results show that two different failure modes of the phase transition and buckling are triggered when the NWs are under uniaxial compression along the [0001] direction, in which the transformation between the two modes is related to the slenderness ratios of the NWs. Such slenderness-ratio-dependent mode transformation is mainly attributed to the competition between the critical stresses of phase transition and buckling. The Euler and Timoshenko models considering surface effect are further proposed to derive the critical slenderness for such mode transformation. The obtained analytical threshold values agree well with those of present MD simulations. Our results should be of great help for shedding some light on the design and application of functional devices based on ZnO NWs.

is an extremely significant reinforcing phase in nickel-based single crystal superalloys. As an alternative strengthening method to improve its mechanical properties, carbon nanotube (CNT)-reinforced composites have recently been synthesized in experiments. Here, in order to explore the corresponding influence factors and the underlying mechanism, tensile and compressive mechanical properties of CNT- composites are systematically investigated by using molecular dynamics simulations. It is shown that the dispersion of a minor fraction of a CNT into matrix leads to a sufficient enhancement in the stiffness of CNT- composites compared with the pure . It is demonstrated that CNT reinforcement takes effect in the elastic stage under compression while it works continuously during tension. Compared with armchair CNTs, zigzag CNTs are predicted to provide more strength for raising the elastic modulus while armchair CNTs can provide superior elongation. Particularly, CNTs are found to hinder the generation of slip bands under tensile loading owing to the robust interfacial interactions. Furthermore, quantitative analysis reveals that the impact of volume fraction of CNT is much more significant than the size effect. The role of chirality, temperature and volume fraction of CNT obtained in the present work could provide beneficial references for subsequent theoretical and experimental investigations, and shed some light on the design of CNT-reinforced composites in nanoscale engineering.

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