Search

Hybrid boron nitride?carbon nanotubes (BN-CNTs) have attracted considerable attention in recent research. In this effort, molecular dynamics simulations were performed to study the fundamentals of BN-CNTs in tensile tests, i.e. Young's modulus and fracture strength (strain). Particular attention was paid to the influence of the atomic structure, hybrid style, and BN concentration on the tensile properties. The morphological changes were also investigated for the BN-CNTs at the onset of fracture. It is noted that the Young's modulus of BN-CNTs decreases almost linearly with increasing the BN concentration with a rate of change independent of the hybrid style. In contrast, the sensitivity of the fracture strength and fracture strain to the variation of BN concentration depends strongly on the hybrid style of BN-CNTs. These results are expected to significantly expand the knowledge of the elastic and fracture properties of novel nanostructures and facilitate their applications in bandgap-engineering.

The effect of temperature and strain rate on mechanical properties remains an open topic in research of hexagonal boron nitride (h-BN) nanosheets. To examine these fundamental issues we have performed molecular dynamics simulations to record the stress–strain curves in tensile tests and measure Young's modulus, fracture strength and fracture strain in armchair and zigzag directions. Comparing the results obtained at different temperatures and strain rates we have quantified the effects of the two factors on the tensile properties of the h-BN nanosheets. The influence of crystal orientation is also examined in the present study. It is found that the h-BN nanosheets are basically an anisotropic material whose tensile properties vary substantially with temperature and strain rate. In particular, a yielding platform is observed for the h-BN nanomaterial at relatively low temperature.

A sandwich-plate model is developed to account for the effect of surface layers on the buckling of piezoelectric nanofilms (PNFs) due to an electrical voltage. The physical mechanisms of the surface effects are investigated and the contributions to the resultant effect are evaluated for surface piezoelectricity, surface stress and surface elasticity. It is found that the surface effect originates primarily from the residual surface stresses and enhanced piezoelectric coefficient due to the surface piezoelectricity. Its influence on the critical buckling voltage of a PNF depends sensitively on the thickness, the length-to-thickness ratio and the nature of residual surface stress. In addition, the intrinsic buckling may occur for a thin PNF where the relatively strong residual surface compression is achieved.