On microindentation of viscoelastic polymers

Indentation testing as a tool for determination of the mechanical properties of viscoelastic polymers is examined in some detail. Both ball (Brinell) and flat punch (Boussinesq) indentation are analysed theoretically and simple but rigorous formulae for a complete characterization of linear materials are presented. In particular for the Brinell test the relation between actual contact area and the size of the residual imprint left on the surface after unloading is analysed using the finite element method. Indentation experiments are performed for two polymers of commercial interest. The mechanical properties determined experimentally by indentation are compared with corresponding results from standard uniaxial relaxation rests, and good agreement was found. (C) 1998 Elsevier Science Ltd. All rights reserved.