A microstructural material model for adipose tissue under blunt impact considering different types of loading

Abstract

Modeling of subcutaneous adipose tissue (SAT) plays an important role in forensic biomechanics as blunt force trauma represents one of the most common types of injury. To better understand the involved injury mechanisms, a material model is needed that can (i) represent realistic behavior for combined loading scenarios and (ii) consider the microstructure of the SAT. Therefore, a SAT model was developed that consists of two parts for the strain–energy function – a neo-Hookean part representing the adipocytes and a part representing the surrounding reinforced basement membrane, which is modeled via three circular fiber families oriented in the three main planes, resulting in isotropic model behavior. To verify the performance of the model, the analytical and numerical model solution were compared with experimental data under biaxial tension at different stretch ratios ($1:1$, $1:0.5$, $0.5:1$) and under simple shear using an objective evaluation method. The material parameters were evaluated by fitting to the data under equibiaxial tension. For the numerical analysis, the model was implemented as a user-defined material in LS-DYNA to simulate the respective experimental setups. The analytical fitting of the model was robust. Using the resulting material parameters, both the analytical and numerical simulation results were able to represent the experimental data under biaxial tension as well as under simple shear quite well. Since the fitting was only performed with data under equibiaxial tension, these findings suggest that the model assumptions are reasonable. Therefore, the model could help to further investigate the injury mechanisms in blunt impacts.