Abstract
For identifying a constitutive model of an incompressible hyperelastic material such as rubber, tensile tests under three deformations (simple tension, pure shear and equibiaxial tension) are sometimes performed by using an in-plane biaxial tensile tester. In the typical in-plane biaxial tensile tester, uniform deformation is not obtained in a rubber specimen due to stress concentration caused by clamps; however, its influence is often ignored to calculate stress and strain at uniformly-deformed region in the specimen. This study indicates a method for accurately estimating stress and strain at the uniformly-deformed region in the specimen by using the typical biaxial tensile tester. A unique rubber specimen with holes was prepared based on the analysis by FEM; then, their tensile tests were performed under three deformations (simple tension, pure shear and equibiaxial tension). The experimental stress and strain data were successfully fitted by a polynomial Mooney-Rivlin model. A biaxial tensile test of a cross-shaped specimen was also performed, and the relationship between force and displacement of the specimen simulated by using material constants identified from the specimen with holes had a good agreement with the experimental one, different from that simulated by using material constants identified from a conventional specimen without holes.
