Macroindentation of a soft polymer: Identification of hyperelasticity and validation by uni/biaxial tensile tests

• Three hyperelastic models for polymer have been identified from macroindentation.
• Elastic modulii are evaluated by semi-analytical methods from macroindentation.
• The identified models are verified with uni/biaxial tensile tests.
• Results are explained by invariant plane, stress/strain states in the three tests.

In the present study, macroindentation tests are performed by means of a spherical indenter on silicone rubber. The load-depth curves during the indentation process reveal only slightly viscous effects but main hyperelastic properties. The hyperelasticity is identified from the load-depth data using an inverse method. The elastic modulus is calculated according to the most often used Oliver and Pharr method in indentation from the unload stage of the monitored load-depth data. The identified material parameters of the hyperelastic constitutive laws are firstly compared with the elastic modulus obtained from this semi-analytical solution. In a second step, specimens of the considered silicone rubber are also prepared for uniaxial and biaxial tensile tests, which are performed in order to compare with the indentation. In the uniaxial tensile tests, the parameters of the three hyperelastic models: neo-Hooke, Mooney–Rivlin and Yeoh model are determined by fitting the experimental tensile stress–strain data with an analytical solution. The correlation between the identified results obtained from indentation tests and uniaxial tensile tests, is investigated. Finally, the simulation of biaxial tensile tests is performed based on the three chosen hyperelastic models and the identified parameters. Comparing the simulation results with the experimental data validates the characterization of the hyperelasticity by using macroindentation and tensile tests.