Mechanical Properties of SBR Vulcanizates under Finite Deformation

Abstract

In order to obtain the solutions for some problems involving inhomogeneous strain of an incompressible isotropic elastic material undergoing finite deformation, it is necessary to assume an explicit form for the strain energy function W. For the purpose of investigating the form of W for vulcanized rubbers which are known as typical incompressible isotropic elastic material, three kinds of SBR vulcanizates of different degrees of crosslinking were prepared, and their stress-deformation behaviors under biaxial finite deformation were observed. The experimental results confirm the applicability of the Valanis-Landel hypothesis that W can be expressed as the sum of three indentical fuctions w of the extension ratios. Therefore when the function w (λ) was proposed as a form of w(λ)=Σ^^∞__(n=-∞)μ2n(λ2n-1) good agreement with experimental data was obtained. Then application of this equation to the formulation in terms of strain invariants I1, I2 enables ∂W/∂I1 ∂W/∂I2 and W to be accurately calculated for any values of I1 and I2