Nanoindentation behavior and mechanical properties measurement of polymeric materials

During sharp contacts, polymeric materials can exhibit elastic (reversible), plastic (instantaneous irreversible), and viscous (time-dependent irreversible) deformation. Due to viscous effects commonly observed in experiments conducted on polymeric materials, the analytical methods developed for instrumented indentation testing ("nanoindentation") of elastic-plastic materials cannot be used to determine polymer mechanical properties. Here, a viscouselastic- plastic sharp indentation model is reframed into normalized coordinates. The updated scheme allows the mechanical properties of polymeric materials to be determined simply from single- or multiple-cycle nanoindentation tests; output parameters are the relative resistance to plastic vs elastic deformation during indentation and the relative time scales for viscous flow during the contact event. The scheme allows the indentation behavior of all materials to be placed on a single map