Size effect in polymer nanofibers under tension

This article studies the size effect on the elastic behavior of solid and hollow polymer nanofibers (e.g., electrospun nanofibers) subjected to uniaxial tension. A one-dimensional nonlinear elastic tension model is proposed that takes into account the coupling effect of fiber elastic deformation and surface tension. The fiber axial force-displacement and stress-strain relations are obtained in explicit forms. It is shown that, at nanoscale, fiber radius has appreciable effect on the elastic response of polymer nanofibers. With consideration of the fiber radial effect, it is shown that the actual contribution of surface energy of the solid polymer fibers to the axial tensile force is pi r(0)gamma rather than 2 pi r(0)gamma (where r(0) is the fiber radius after deformation and gamma is the surface tension), as commonly used in literature. Compared to solid polymer fibers, the tensile behavior of hollow polymer nanofibers appears more complex with greater axial stiffening effect depending upon the combination effect of the fiber exterior and interior radii and the material properties. The results presented in this study can be utilized for data reduction of the nanoscale tension tests of polymer nanofibers and the analysis and design of nanofiber devices. (C) 2007 American Institute of Physics.