Characterization and Modeling of a Thermoplastic Elastomer Tissue Simulant under Uniaxial Compression Loading for a Wide Range of Strain Rates.

Characterization and modeling of the mechanical behavior of biological tissues are critical to many biomedical related applications. For research and development, various soft materials have often been used as a tissue substitute. Among them, the mineral oil-based synthetic polymer styrene-ethylene-butylene-styrene (SEBS) gel has gained some popularity due to its superior mechanical and physical properties. Tissue materials or their simulants are often characterized with quasi-static loading and are treated and modeled as a nonlinear hyperelastic material. As tissues are often subjected to loadings with a wide range of strain rates, understanding of the mechanical behavior and development a predictive capability for such loadings are essential. In this work, a comprehensive study of the mechanical behavior of SEBS gels with different chemical compositions and polymer concentrations was conducted under uniaxial compression loadings over a wide range of strain rates, from 1×10-3/s to 6×103/s. In addition to experiments, a comprehensive but simple visco-pseudo-hyperelasticity model was developed. The model was demonstrated to be able to capture all the material features observed in the experiments, such as rate sensitivity, strain-induced softening, and permanent deformation after unloading. Because of its simple functional form, the model can be conveniently used for practical applications such as prediction of the rate dependence of the shear modulus.