Foot and ankle blast injury and its mitigation

The improvised explosive device (IED) has been the characteristic weapon of conflicts in Iraq and Afghanistan. Under-vehicle explosions result in rapid floor deformation, transmitting short duration, high amplitude loading to the occupant's foot and ankle. Current operational vehicles are subjected to full-scale explosions to assess the level of protection they offer their occupants. The decision to pass or fail a vehicle design is made through assessing the axial force transmitted through the lower extremity of a 'dummy' which has been designed to behave like a human. This thesis investigates the ability of combat boots to reduce the severity of injuries during under-vehicle explosions. Both experimental and numerical techniques were used to gain a better understanding of the behaviour of the combat boot under high rate loading. Initially, drop rig experiments were conducted to assess the shock absorbing capacity of the two combat boot designs most commonly used by UK troops. Following on, more complex experiments were conducted using an anti-vehicle under-belly injury simulator (AnUBIS) which was designed, developed and characterised to simulate floor displacement during an under-vehicle explosion. AnUBIS was used to compare the response of cadaveric specimens against two dummy designs; the Hybrid-III and the MiL-Lx. The MiL-Lx was found to be more biofidelic than the Hybrid-III. Finite element models of both the MiL-Lx and a combat boot were developed and used to investigate the sensitivity of the materials and geometry of the combat boots in reducing the force transmitted to the MiL-Lx during an under-vehicle explosion. Finally, two commercially available blast mat designs were assessed using AnUBIS and both the MiL-Lx and Hybrid-III. The two ATDs ranked the mats in the same order; however, the percentage reduction in peak force was different. The experimental and numerical approach used in this thesis has developed a greater understanding of both the biofidelity of current ATDs and the capacity of current mitigating technologies. This approach can be used to develop and assess mitigation technologies for use in future conflicts where under-vehicle explosions are a significant threat.