Throughout Operation Enduring Freedom (OEF) and Operation Iraqi Freedom (OIF), explosive devices have become more powerful, their detonation systems more creative, and their additives more devastating. According to the Department of Defense (DoD) Personnel and Procurement Statistics, 75% of all US military casualties in OEF and OIF are caused by explosive weaponry (DMDC, 2008). As of January 2008, DoD reported that over 5,500 soldiers had suffered TBIs (CRS, 2008). As a continuing threat to troops, blast injury, especially BINT, has been called the signature wound of the war in Iraq. Explosive devices are also used against civilians. Indeed, the use of explosive weaponry is the most common cause of casualties in terrorist incidents. Terrorists increasingly use suicidal-homicidal bombers that deliberately accompany the explosive device, often wearing it, to ensure the maximal harm. The bombers walk or drive into buses, subways, residential areas, shopping malls, and government buildings.
In both civilian and military environments, exposure to a blast (see Figure 2.3) might cause instant death, injuries with immediate manifestation of symptoms, or injuries with delayed manifestation.
Protection from blast injuries presents several challenges. Body armor protects from shrapnel and projectiles, but it also constitutes an improved contact surface for shock-front–body interaction and energy transfer and may also serve as a reflecting surface that can concentrate the power of an explosion as the blast wave is reflected by the armor front and back (Phillips et al., 1988). The improved interceptive properties of body armor have increased the survival rate of soldiers by protecting them from penetrating injuries. In parallel with the increased survival rate, however, the rate of severe debilitating long-term consequences has also increased (Warden, 2006). Moreover, besides being acutely injured, soldiers serving in theater and some military professionals during their daily activity or training are also subjected to repeated low-level blast