High-rate bulk and shear responses of bovine brain tissue

This experimental study systematically investigates the dynamic response of bovine brain tissue under uniaxial strain and pure shear loading conditions. The combination of such stress states and strain rates are representative in the brain under blast loading in which both bulk and shear deformation may be involved. The dynamic uniaxial strain experiments (bulk response) were conducted on a modified Kolsky compression bar with an aluminum confinement collar. Bovine brain samples were sealed in the collar and loaded by the Kolsky bars so that the specimen only deformed in the axial direction. The resultant stress-strain curves reflected the pressure–volume relations from which the bulk modulus were obtained. The dynamic shear response was determined by using a recently developed Kolsky torsion bar technique for tissue materials characterization. Quasi-static torsion experiments were also conducted on an MTS system to construct a full set of shear stress-strain curves over a wide range of shear strain rates (0.01–700 s−1). The experimental results show that the dynamic bulk modulus of brain is in the range of 1.68–2.33 GPa which is close to the low rate values reported in the literature, while the shear responses show significant rate sensitivity over the tested strain rate range.