5. Conclusion

The formalism of linear viscoelasticity enables us to successfully interpret instrumented indentation tests involving creep, relaxation and frequency rheology (very low amplitude oscillations). Rheological models including a skid allow indentation tests with a sphere under constant force to be interpreted quite simply, with tracking of the sphere's displacement. The interpretation of force-displacement curves for penetration and shrinkage tests at various loading speeds is more delicate, and generally requires recourse to numerical simulation, as the elastic deformation of the polymer is not negligible. Two behavioral models were explored: an elasto-viscoplastic model with strain-hardening of the same type as the metal behavior model, and a more complex non-linear viscoelastic model. The first model has proved very useful for characterizing the mechanical properties of polymer films used...