Extracting the elastic and viscoelastic properties of a polymeric film using a sharp indentation relaxation test

A new approach is proposed to extract the elastic and viscoelastic properties of a polymeric film on a hard substrate using a sharp indentation relaxation test. In the theoretic formulation, a sharp indentation relaxation test on a film/substrate system was interpreted by its equivalent flat-ended punch indentation relaxation test. The radius of the equivalent flat-ended punch was determined by the residual depth of the sharp indentation. A semi-analytical solution for a flat-ended punch relaxation test was derived. Sharp indentation relaxation tests on a polymethyl methacrylate film and a polycarbonate film on a glass substrate were performed. The semi-analytical solution and the experimental results were used to extract the elastic-viscoelastic parameters of the films. The extracted elastic-viscoelastic parameters of both films were found to be in a good agreement with data sheets of the films. The proposed approach provides a simple and yet feasible way to extract “film-only” elastic and viscoelastic properties.