A simulation study on nonlinear mechanical responses of glassy polymer nanofibers

The confined polymer glasses, such as glassy polymer fibers, exhibit unique glassy behaviors that differ from bulk polymer glasses. We perform molecular dynamics simulations and study nonlinear mechanical responses of glassy polymer nanofibers under uniaxial deformation. We investigate not only nonlinear mechanical responses but also the dependence of mechanical properties on the strain rates of typical polymer glasses, which were also observed in previous experiments. We find from our simulations that the local stress in the surface regions of fibers is greater than that in the core region of fibers, for which the stress of glassy polymer fibers is greater than that of bulk polymer glasses in our simulations. The distance between monomers in glassy polymer fibers are more stretched than that in bulk polymer glasses. Also, the non-affine displacements in the surface regions of glassy polymer fibers are greater than those in bulk polymer glasses. These results indicate that the microscopic events during deformation relate closely to the mechanical responses of polymer glasses.