Flat indentation of a viscoelastic polymer film on a rigid substrate

Abstract

A systematic method of flat indentation was developed to measure the elastic and viscoelastic properties of polymer films. A flat indentation problem oil an elastic film perfectly bonded to it rigid substrate was revisited, from which the relationship between the applied Force and the penetration depth was obtained in a simple form. Application of the elastic-viscoelastic correspondence principle converts the force-depth relationship for elastic films to the Laplace transform of that for viscoelastic films. Indentation experiments with a flat diamond tip were performed oil polymer films (SU-8 and NR4-8000P). Analysis of the measured data with the viscoelastic force-depth relationship provides the shear moduli, Poisson's ratios, and relaxation moduli of these films. Viscoplastic deformations produced in the films that Underwent the flat indentation process were quantified by measuring the residual deformation after Unloading with all atomic force microscope. (c) 2008 Acta Materialia Inc. published by Elsevier Ltd. All rights reserved.