Design aspects of ballistic helmets

Aeeording to Salvaterra (2006), the energy management system of the liner and shell mnst have lYi thiekness variation, allowing atty possible deformation to 

These elements can be seen in the design basis of a typical baUistic helmet. The typical helmet components are  

A typical helmet is expected to be between 5 and 10 mm thick, dependent on both material type and applicatioa The shell thickness is normally determined experimentally by the penetration test. The shell canbe made of either an injection-moulded thermoplastic or a pressure-moulded resin system, reinforced with ballistic resistance fabrics/fibres (Mills, 1996). Energy is absorbed when the helmet is impacted, with the shell bending and deformation of the underlying foam. The amount of the impact energy absorbed by the foam depends on  

The quality of the helmet shell in terms of its hardness is a significant factor in the shock absorption capability. Helmets are generally fabricated spherically to block and divert blows. Salvaterra (2006) reported that softer helmet shells sustain more focal impact with a higher peak force. The more rigid a shell, the more diffuse the impact would be with lower peak force. Newer helmet prototypes or models employ thin plastic for decreased weight, with better ventilation (for cooling effect) and material (for improvement in helmet strength). 

The human head varies widely in circirmference and shape. Most helmet manufacturers sell four sizes of helmet, covering head circumferences of 53, 55-6, 58-9 and 60-1 cm, with the length to breadth ratio of the finer usually constant, meeting tfie standard. Helmets must fit well to allow the retention system to work effectively. There are three types of retention system on the market  

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