Most military helmets are designed to prevent penetration by small firearms using composite materials in their construction. However, the transient deformation of the composite helmet during a non penetrating impact may result in severe head injury.
Two experimental designs were undertaken to characterize the extend of injuries imparted by composite panels using in protective helmets. In the first series, 21 dry skulls were protected by polyethylene plates, with gaps between the protective plate and skull ranging from 12 to 15 mm. In another design, using 9 cadavers, heads were protected by aluminum, aramid, or polyethylene plates. Specimens were instrumented with pressure gauges to record the impact response. The ammunition used in these experiments was 9 mm caliber and had a velocity of 400 m/s. A macroscopic analysis of the specimens quantified fractures and injuries, which were then related to the measured pressures.
Protective plates influenced both the levels of injury and the intracranial pressure. Injuries were accentuated as the plates was changed from aluminum to composite materials and ranged from skin laceration to extensive skull fractures and brain contusion. Fractures were associated with brain parenchymal pressures in excess of 560 kPa and cerebrospinal fluid pressure of 150 kPa. An air gap of a few millimeters between the plate and the head was sufficient to decrease these internal pressures by half, significantly reducing the level of injury.
Ballistic helmets made of composite materials could be optimized to avoid extensive transient deformation and thus reduce the impact and blunt trauma to the head. However, this deformation cannot be completely removed, which is why the gap between the helmet and the head must be maintained at more than 12 mm.
From the Direction Centrale du Service de Santé des Armées (J.-C.S.), Action Scientifique et Technique - Bureau recherche (DCSSA/AST/REC), France; the Ecole Centrale de Nantes (M.D.), Eurocrash, Nantes, France; the Centre Hospitalier Universitaire de Nantes (A.F., R.R.), Hôtel Dieu, Service de Neurotraumatologie, Nantes, France; the Centre d’Etudes du Bouchet (J.-P.C.), Vert le Petit; and the Etablissement technique de Bourges (J.D.C.), Rocade Est, Echangeur de Guerry, Bourges, France.
Submitted for publication February 28, 2003.
Accepted for publication April 19, 2004.
This work was supported by the Etablissement Technique de Bourges, and Ecole Centrale de Nantes with funding from Délégation Générale pour l’Armement (DGA/DSP/STTC/DT-SH) under contracts 01ci031 and 00ci040, respectively.
Address for reprints: Médecin en Chef JC Sarron, Direction Centrale du Service de Santé des Armées, Action Scientifique et Technique - Bureau recherche, BP 125, 00459 Armees, France; email: firstname.lastname@example.org.