Fig 1.
Coronal CT sections of tested helmets.
(a) Adrian helmet, (b) Brodie helmet, (c) Stahlhelm, (d) Advanced Combat Helmet (ACH). The Adrian helmet (a) is the thinnest steel followed by the Brodie (b) and the Stahlhelm (c). The ACH (d) is made with a fiber composite material.
Table 1.
Helmet abbreviations and properties.
Fig 2.
Helmets on Hybrid III head in test setup.
(a) Brodie helmet, (b) Adrian helmet, (c) Stahlhelm, (d) Advanced Combat Helmet, (e) No helmet.
Fig 3.
Exposure is in the direction of the crown, simulating overhead blast that is typical exposure for personnel in trenches or prone on the ground.
Table 2.
Number of blast tests performed for each case, 46 in total.
Fig 4.
Views of Hybrid III head with pressure sensor locations indicated.
(a) crown, (b) forehead, (c) eye, (d) back head, and (e) ear.
Fig 5.
Representative pressure traces.
Measured at the crown of the dummy head, for 12 membrane (3.048 mm PET) tests of the (a) Bare Head, (b) Advanced Combat Helmet, (c) Brodie Helmet, (d) Adrian Helmet, and (e) Stahlhelm.
Fig 6.
Equivalent distance to WWI shell explosions.
Distance from a WWI German shell explosion to experience blast conditions tested in this study. Pressure measurements from bare head testing conditions were used to calculate these distances.
Table 3.
German artillery rounds used in WWI [34].
Table 4.
Severity bins for bare head blasting conditions.
Fig 7.
High speed frames of blast impact on the head.
Frames from high speed video recording of high intensity blast tests immediately after blast wave impingement on the (a) Brodie helmet and (b) Adrian helmet.
Fig 8.
Higher crown pressures seen without helmet, lower with Adrian helmet.
Measured tube and crown pressure for each test performed, and the linear regression fit for each helmet type. Bare head crown pressure is higher than all helmets (p<0.0001), and the French Adrian helmet crown pressure is lower than all other helmets (p<0.01).
Fig 9.
Helmets reduce the risk of meningeal bleeding.
Tested blast conditions plotted on brain blast meningeal bleeding risk curves from Rafaels et al. [24]. Bare head testing conditions are roughly situated in the 50% mild, moderate, and severe meningeal bleed risk range, whereas the bleeding risk for helmeted tests is much lower (see Fig 10 for a more detailed example).
Fig 10.
Risk reduction for moderate bleeding in helmeted cases.
Mean peak pressure measured at the crown of the head for moderate severity blasts (Table 4), including standard error indicated on the bars. For approximately a 50% moderate bleeding risk in the bare head scenario, moderate bleeding risks for all helmets is more than 5x lower for the same testing condition.
Fig 11.
Helmets reduce blast overpressure at all sensor locations on the head.
Linear regression fit for each helmet for peak pressure measured in the blast tube and peak pressure measured at each location on the dummy head (Fig 4). (a) Forehead: Bare head higher than all helmets (p<0.0001), and Stahlhelm higher than ACH and Brodie (p<0.05). (b) Back of the head: Bare head higher than all helmets (p<0.0001), Stahlhelm higher than ACH and Brodie (p<0.01), and Adrian higher than ACH and Brodie (p<0.005). (c) Eye: Bare head higher than all helmets (p<0.0001), ACH higher than all other helmets (p<0.0001), and Adrian higher than Brodie (p<0.001). (d) Ear: Bare head higher than all helmets (p<0.0001), Adrian higher than Brodie, ACH (p<0.01), and Stahlhelm (p<0.05).
Fig 12.
Helmets reduce the risk of eardrum rupture.
Measured peak incident pressures at the ear and eardrum rupture risk curves from Richmond et al. [33]. Risk of eardrum rupture is lower in all helmeted cases compared to the bare head, and is higher in the French Adrian helmet compared to other tested helmets.