Molecular dynamics simulations of brittle to ductile transition in failure mechanism of silicon nitride nanoporous membranes

We use Molecular Dynamics simulations to study mechanical behaviors of crystalline silicon nitride nanoporous membranes with different pore distribution upon tensile loading along the armchair direction. Our results suggest that the proper introduction of the pores in nanoporous membranes leads to the transition from brittle failure into ductile failure mechanism. This transition is accompanied with the change of plastic deformation mechanism from either localization of Von-Mises strain within isolated regions or a network of zigzag shear bands into the formation of a network of straight shear bands. We also found that the formation of zigzag shear bands upon plastic deformation leads to strain hardening and thus increases the strength. Our results suggest new strategies for improving strength and ductility of nanoporous membranes.