Test methodAn efficient method for obtaining the hyperelastic properties of filled elastomers in finite strain applications

An efficient methodology for obtaining hyperelastic material parameters for filled elastomers utilizing unloading curves in uniaxial tension, pure shear and the inflation of a rubber membrane is presented. Experimental results from biaxial extension are crucial when fitting hyperelastic material parameters, and the bubble inflation technique is an excellent method of obtaining this data when specialized test equipment is unavailable. Moreover, filled elastomers have considerable hysteresis, and the hysteresis grows with increasing strain amplitudes. Therefore, the loading curve is in general comprised of both elastic and inelastic contributions, even at very low strain rates. Consequently, it is deemed more accurate to use experimental data from the unloading curve to describe the elastic behavior of the material. The presented methodology enables obtainment of parameters related to both the first and second strain invariant, which is required for a good fit between measurement and simulation results. Finally, it is essential that a chosen material model is accurate in all deformation modes when designing components subjected to a complex, multi-axial load history. An accurate material model enables more concepts and geometries of a component to be studied before a physical prototype is available.