Mechanical model of the human head for simulation of head trauma and brain injury

In this thesis, a transparent model of the human head has been constructed which was filled with a substance that represented the brain. This model was later crash tested. This was done in order to examine how a transparent model of the human head can be constructed to generate accurate data from crash tests. It was also done in order to examine how impacts on the front of the head can deform the rear of the brain. When a head is decelerating, the brain moves forward inside the skull and may hit the front of the skull. It is believed that when the brain is bouncing back, it can hit the rear of the skull which can cause brain damage on the rear of the brain, so called contrecoup injuries. This work took place at SAFER Vehicle and Traffic Safety Centre at Chalmers University of Technology in Gothenburg. In order to choose the most suitable material for construction of the head model, several materials were evaluated with a quantitative method of materials selection with the help of a computer based material database. The chosen material was epoxy. In conjunction with the material selection, molding was chosen as the method for construction of the head model. The skull was filled with a gelatin mix which was used as the brain substitute. In order to observe brain movements within the skull, a number of colored pieces of the same gelatin mix were added as well. In the first crash test, the head model was mounted on a pendulum which hit a plastic plate. The impact process was recorded by a high-speed video camera. The video recording was analyzed by a motion analysis software. Accelerometers were mounted on the head model which recorded the head acceleration during the impact. The head was dropped from a greater height during the second crash test so the head model would hit the plastic plate at a higher speed. Unfortunately, this caused the head model to break and thus only the first crash test could be analyzed. Since the head model hit the plastic plate with a speed of only 19 km/h, no brain movements could be distinguished. The only part of the brain whose movements could be observed was located inside a tube at the foramen magnum which is a large opening near the head model’s rear. This could indicate a change in the skull volume. It could also indicate brain movements inside the skull which could cause contrecoup injuries