Contact Stiffness of Polymer with Nominally Flat Surfaces

Abstract

The normal contact stiffness between two polymer blocks with nominally flat surfaces in contact is investigated. Contact stiffness is experimentally determined on a tension-compression machine at small loading steps from zero to about 15 kN. The contact stiffness of steel specimens with the same dimensions as those of the polymer blocks is also investigated to examine the differences between polymers and metals. The three-dimensional surface parameters of the samples are obtained by using an optical profiler. The experimentally measured contact stiffness of Nylon shows a trend similar to that of steel, whereas Teflon and Polyimide show different trends. This discrepancy is shown to be related to the non-homogeneous distribution of surface summits on the contact area. Such a distribution may reduce the real elastic contact area, which in turn changes the surface condition from a rough to smooth contact.