A strain-rate dependent material model for adipose tissue under blunt impact considering microstructural aspects

Resumo

Subcutaneous adipose tissue (SAT) is one of the superficial soft tissue layers covering the human body.
Its mechanical behavior is important for various fields of impact biomechanics as it influences stresses and strains
that are transferred to the underlying tissues. Modeling of SAT is challenging as it exhibits non-linear, strain rate
and load case dependent characteristics. Here, we propose a new model of SAT under impact loading that considers
microstructural aspects. The approach is based on a hyperelastic model whose strain energy function is split into
a part for the incompressible lipid inside the cells and into a term for the collagen network encircling the spherical
cells. Strain rate dependency is realized via a normalized relaxation function represented by a Prony series. The
model is implemented as user defined material model into an FE code and used to simulate drop test experiments
on porcine SAT specimens (n = 12) with varying thickness at an impact velocity of 1 m/s. The model has a stable
and consistent behavior in the simulations. A reasonable match between experimental and simulation results is
achieved for different specimen thicknesses, i.e. varying strain rates.