Extreme softness of brain matter in simple shear

Abstract

We show that porcine brain matter can be modelled accurately as a very soft rubber-like material using the Mooney-Rivlin strain energy function, up to strains as high as 60%. This result followed from simple shear experiments performed on small rectangular fresh samples (2.5 cm(3) and 1.1 cm(3)) at quasi-static strain rates. They revealed a linear shear stress-shear strain relationship (R-2 > 0.97), characteristic of Mooney-Rivlin materials at large strains. We found that porcine brain matter is about 30 times less resistant to shear forces than a silicone gel. We also verified experimentally that brain matter exhibits the positive Poynting effect of non-linear elasticity, and numerically that the stress and strain fields remain mostly homogeneous throughout the thickness of the samples in simple shear. (C) 2015 Elsevier Ltd. All rights reserved.