A constitutive material model with strain-rate dependency for brain tissue

In almost all scenarios of traumatic brain injuries (TBIs), the brain tissue goes under mechanical loading at high strain rates. In experimental works, it has also shown that brain tissue behavior is highly rate-dependent. We are presenting here the results of a study on mechanical properties of bovine brain tissue under unconfined compression tests at different rates. The tissue specimens are compressed with deformation rates of 10, 100, and 1000 mm/sec, respectively. We observed the tissue is showing a viscoelastic behavior and become stiffer under increasing strain rates. We developed a nonlinear viscoelastic rate-dependent constitutive model to be calibrated with the test results. The material parameters for this constitutive model have been validated for the above tested results. The model was examined against other rates and agrees well. The study will provide new insight into a better understanding of the rate-dependency behavior of the brain tissue under dynamic conditions. The work is a step forward in understanding the material characteristics of brain tissue for TBI analysis and prediction under loading or high kinematical motions.