Abstract

The mechanical properties of the human brain at high strain rate were investigated to analyse the mechanisms that cause backspatter when a cranial gunshot wound occurs. Different concentrations of gelatine and a new material (M1) developed in this work were tested and compared to bovine brain samples. Kinetic energy absorption and expansion rate of the samples caused by the impact of a bullet from .22 air rifle (AR) (average velocity (uav) of 290 m/s) and .22 long rifle (LR) (average velocity (uav) of 330 m/s) were analysed using a high speed camera (24,000 fps). The AR projectile had, in the region of interest, an average kinetic energy (Ek) of 42 ± 1.3 J. On average, the bovine brain absorbed 50 ± 5% of Ek, and the simulants 46–58 ± 5%. The Ek of the .22 LR was 141 ± 3.7 J. The bovine brain absorbed 27% of the .22LR Ek and the simulants 15–29%. The expansion of the sample, after penetration, was measured. The bovine brain experienced significant plastic deformation whereas the gelatine solution exhibited a principally elastic response. The permanent damage patterns in the M1 material were much closer to those in brain tissue, than were the damage patterns in the gelatine. The results provide a first step to developing a realistic experimental simulant for the human brain which can produce the same blood backspatter patterns as a human brain during a cranial gunshot. These results can also be used to improve the 3D models of human heads used in car crash and blast trauma injury research.

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