Parameters identification of hyperelastic constitutive model by instrumented indentation of filled silicone rubber
Identification de paramètres de lois hyperélastiques d'un silicone chargé par indentation instrumentée
Résumé
Particle-filled elastomers are widely used in industries ranging from civil engineering to aeronautics and automotive. The specific phenomena of the mechanical behaviour of these materials are well known at the macro scale (hyperelasticity, viscoelasticity, Mullins effect). Indentation is therefore a well-suited method for studying them at lower scales. However, the indentation of polymers and therefore elastomers leads to experimental difficulties (surface state, adhesion). As a results, a combination of experimental and numerical studies is required. To that end, O. Ezzaamari et al. [1] show the possibility to use the entire indentation curve to identify parameters of hyperelastic constitutive models using model reduction. The main purpose of this work is to study the actual application of this identification methodology to filled Polydimethylsiloxane rubber. Experimental tests for identification purposes are carried out using spherical indentation. The induced stress state is studied numerically in order to compare the results with equivalent homogeneous macroscopic tests. Coupling spherical indentation and identification by model reduction allows to characterize the mechanical behaviour of RTV. However, a complete identification of the Mooney-Rivlin constitutive model parameters is not possible. This may be explain by the fact that spherical indentation reaches a low strain level (≈ 20%), so the Mooney-Rivlin model is applied in its low operating limit, where a simpler model such as Neo-Hooke would be adequate. Furthermore, another possible explanation is that spherical indentation does not show any real triaxiality in the stress state. The study of different tip shapes that would increase the triaxiality and the strain level would lead to better identification results. The main perspective of this work is to study visco-hyperelastic material through static and dynamic tests. The authors gratefully acknowledge the CEA le Ripault, Centre d'études du Ripault, 37260 Monts, France, for supplying the materials.
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