title: Experimental investigation of the mechanical properties of brain simulants used for cranial gunshot simulation.
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 290m/s) and .22 long rifle (LR) (average velocity (uav) of 330m/s) were analysed using a high speed camera (24,000fps). The AR projectile had, in the region of interest, an average kinetic energy (Ek) of 42±1.3J. On average, the bovine brain absorbed 50±5% of Ek, and the simulants 46-58±5%. The Ek of the .22 LR was 141±3.7J. 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.
authors.affiliation: Department of Mechanical Engineering, University of Canterbury, Private Bag 4800, Christchurch 8041, New Zealand.
authors.forename: Milad Soltanipour
authors.initials: MS
authors.lastname: Lazarjan
authors.affiliation: Department of Mechanical Engineering, University of Canterbury, Private Bag 4800, Christchurch 8041, New Zealand.
authors.forename: Patrick Henry
authors.initials: PH
authors.lastname: Geoghegan
authors.affiliation: Department of Mechanical Engineering, University of Canterbury, Private Bag 4800, Christchurch 8041, New Zealand. Electronic address: mark.jermy@canterbury.ac.nz.
authors.forename: Mark Christopher
authors.initials: MC
authors.lastname: Jermy
authors.affiliation: Christchurch Science Centre, Institute of Environmental Science and Research, 27 Creyke Road, Ilam, Christchurch 8041, New Zealand.
authors.forename: Michael
authors.initials: M
authors.lastname: Taylor
mesh_terms: D000818:Animals; D002417:Cattle; D005389:Firearms; D044709:Forensic Ballistics / Q000295:instrumentation*; D005780:Gelatin; D005990:Glycerol; D020197:Head Injuries, Penetrating / Q000473:pathology*; D006801:Humans; D007700:Kinetics; D008954:Models, Biological; D058105:Polymerization; D014948:Wounds, Gunshot / Q000473:pathology*
chemical_list: D005780:Gelatin; D005990:Glycerol
keywords: Backspatter; Bloodstain pattern analysis; Brain simulant; Cranial gunshot; Kinetic energy loss