ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

samples of brain tissue were extracted and subjected to uniaxial compression tests to
determine the subject-specific mechanical properties of the brain tissue. A model of the
brain indentation experiment was built in the FE solver ABAQUS TM . In the model, the
mechanical properties of the brain tissue were assigned as obtained from the uniaxial
compression tests and the properties of the brain-skull interface (represented using
linear springs connecting the brain model outer surface and skull) were calibrated so
that the calculated indentor reaction force and deformations within the brain match
those measured experimentally. This allowed identification of the overall mechanical
properties of the brain-skull interface.
3. MEASUREMENT OF THE BIOMECHANICAL RESPONSES OF SHEEP BRAIN
IN-SITU: INDENTATION EXPERIMENTS
3.1 Specimen preparation
Young sheep head was collected from the local abattoir and transported to the
o
laboratory and kept at constant temperature of 4 C. The dissection started one hour
prior to the experiment. The skin was removed from the head using a scalpel. A small
rectangular opening (craniotomy) in the skull (approximately 4 cm x 2 cm) was made
above the left hemisphere using a vibrating saw and a small chunk of brain close to its
surface was removed using a scalpel.
3.2 Experimental protocol
The Instron Model 5948 Microtester System was utilised in the experiment. The skull
was placed in a Perspex tray and was constrained using stainless steel screws attached to
the tray (Fig. 1a). An L shaped indentor (Fig. 1b) was used to compress the brain in-situ
in the craniotomy area. The indentor speed was kept constant at 12 mm/min. To ensure
a no slip boundary condition between the indentor and brain tissue, sandpaper was glued
on the indentor’s face.
Mobile C-arm
Instron 5948 Microtester
Sheep Head
Stainless Steel Screw
Perspex Tray
(a) (b)
Figure 1. (a) Experiment set up for brain indentation in-situ; (b) L shaped Indentor
The maximum indentation depth (the indentor displacement measured from start of the
contact between the indentor and the brain tissue until the indentor reaches maximum
point of indentation) was 4.8 mm.
3.3 Experimental results
The results (indentor reaction force-displacement) of only one (successful) indentation