Optimal material properties for mitigating brain injury during head impact

We present a methodology for identifying constitutive responses of crushable, linear-softening materials that would reduce the severity of brain injury caused by head impact in a typical automobile or sports collision. It is based on analysis of accelerations imparted to a spherical mass (representative of the human head) upon impact at prescribed velocity onto a flat padded structure. The resulting acceleration–time histories are used to calculate the corresponding Head Injury Criterion (HIC): a weighted product of acceleration and impact duration that has been found to correlate with the severity of brain injury. In the best-case scenario, the HIC is reduced by a factor of 1.84 relative to that obtained for a system optimized with a perfectly plastic foam. The optimal combinations of yield stress and crushing strain are not unique; that is, the optimum can be achieved with a range of strengths and crushing strains. The present solutions are expected to find utility in guiding the design of new polymer lattice materials for use in impact protection systems.

M. R. Begley and F. W. Zok
J. Appl. Mech.
Volume: 81
Number: 3
Pages: 031014
Date: October, 2013
ICB Affiliated Authors: Matthew R Begley, Frank Zok