Current regulations on helmet certification drop tests insufficiently account for sustainable injuries to the human head. Main limitations are the use of a rigid head form and the single measurement of its resultant translational acceleration, whereas rotational accelerations are believed to be the cause of a major part of brain injuries. The objectives of this research project are to improve the head form in terms of anatomical detail and biofidelity on the one hand, and to develop a finite element model of the improved head form giving access to field parameters possibly correlated to injuries on the other hand. A standard head form was studied and its geometry was determined using a three dimensional co-ordinate measuring device. Relevant anatomical structures of the human head were appointed and their mechanical properties have been investigated. The structures turned out to be the brain, the skull - including the neurocranium -, the chin and the falx and tentorium cerebri. Using this information an improved physical head form was designed. Also a finite element model of the improved physical head form has been developed, containing the relevant structures. Representation of the relevant anatomical structures will yield more insight in possible injury mechanisms in the head under impact conditions, both for the physical and the numerical model. The finite element model proved to be suitable for numerical simulations and therefore contributes to a better understanding of the phenomena taking place in the head during impact. The numerical model has to be validated against experimental data from the improved physical head form. In its turn this physical head form has to be evaluated using data from literature. Once validated, quantitative conclusions can be drawn from numerical simulations. (A)
Samenvatting