Extracting the mechanical properties of a viscoelastic polymeric film on a hard elastic substrate

A semi-analytical approach was developed to study the creep response of a viscoelastic polymeric thin film on a hard elastic substrate under flat-ended punch indentation. This approach allows one to separate mechanical properties of the film from its substrate. To verify the approach, flat-ended punch creep indentation tests were performed to obtain the long-time viscoelastic behaviors of a polymethyl-methacrylide film overlying on an aluminum substrate. Three viscoelastic models describing the constitutive equations of the polymer film are compared in this paper. “Film-only” viscoelastic parameters were extracted by fitting with the experimental creep curves of flat-ended punch indentation. It is shown that the present approach provides an effective way to characterize the mechanical properties of a polymeric film on an elastic substrate.