Second-order effects at microindentation of elastic polymers using sharp indenters

Sharp indentation of elastic polymers is investigated numerically using the finite element method. Large deformation theory is relied upon for accuracy. Both cone and Vickers indentation is considered and in particular, the study focuses on second-order effects on relevant indentation quantities in the microindentation regime. The second-order effects include indenter tip roundness, friction and also, for generality, effects due to different values on the included angle of the cone indenter, α. It is shown that frictional effects as well as effects due to indenter tip roundness are small at cone indentation but friction can substantially influence the results in case of Vickers indentation. The latter feature is most likely due to frictional effects at the ridges of the indenter and as such behavior is not accurately described using conventional theory of friction, a numerical approach for this purpose is discussed.