Analysis of nanoindentation creep for polymeric materials

This article presents studies on nanoindentation creep for polymeric materials at room temperature. A semi-empirical method has been established from a generalized Kelvin model. This model includes the elastic-viscoelastic-viscous effects on indentation creep. It is shown that this method can fit the experimental creep data well, to give the exact changes of creep behavior during nanoindentations for numbers of amorphous polymeric materials. A method has also been proposed to determine the elastic modulus based on this model; the elastic modulus determined from this method is independent of the holding and unloading processes of nanoindentations. Creep deformation is further used to derive creep compliance and retardation spectrums for the polymeric materials studied, which are very useful to predict other mechanical properties of polymeric materials.