Hyperelastic Description of Polymer Soft Foams at Finite Deformations

Abstract

Soft foams are gaining importancy as materials for mattress systems and seat cushions in such areas as aircraft and automotive industries and in the field of medical care. This study will demonstrate that a strain energy function of finite hyperelasticity for compressible media proposed by Hill (1978), Storakers (1986) and Ogden (1972) is applicable to describe the elastic properties of open cell soft foams. This strain energy function is implemented in the FE-tool ABAQUS and proposed for high compressible soft foams. To determine this constitutive equation, experimental data from a uniaxial compression test are used. As the parameters in the constitutive equation are linked in a non-linear way, non-linear optimisation routines are adopted. Moreover due to the inhomogeneities of the deformation field of the uniaxial compression test, the quality function of the optimisation routine has to be determined by an FE-tool. The appropriateness of the strain energy function is tested by a complex loading test. By using the optimised parameters the FE-simulation of this test is in good accordance with the experimental data.