Auxetic Textiles for Blast Mitigation

在21世纪的世纪，恐怖主义已成为对全世界人民生活方式的持续威胁。恐怖主义威胁最常见的表现形式之一是爆炸装置，往往在人口稠密的平民区引爆。埃克塞特大学正在领导一个由政府和工业专家组成的团队，开发一种新型的“智能”防爆幕，旨在减少炸弹爆炸造成的伤亡。这种智能纺织品使用了大学首创的拉胀材料。不像传统材料在拉伸时会变薄，拉胀材料会变胖。这种有趣的和反直觉的性质也存在于一些天然材料中，如猫皮和人的胫骨。当恐怖分子的炸弹在城市地区爆炸时，它会产生毁灭性的影响，包括对建筑物的结构和非结构性破坏，受伤和死亡。爆炸中的许多伤害直接或间接地由窗户玻璃破裂造成。在俄克拉荷马州的爆炸案中，玻璃占所有眼睛和头部受伤人数的近三分之二。当爆炸发生时，能量会迅速释放。这是以热、声、光的形式出现的，也是以冲击波的形式出现的。正是最初的冲击波造成了建筑物的大部分损坏，包括窗户的破碎。如果破坏性还不够，那么爆炸前沿产生的真空就会产生高强度的风，可以将碎片输送到很远的地方。目前的防爆窗帘设计倾向于使用比窗户更长更宽的半透明芳纶网：多余的窗帘长度被放置在窗户底部的盒子里。当窗户破碎时，窗帘会翻滚而出，并捕获相当大一部分玻璃碎片。该系统通常使用薄膜窗口涂层进行增强，以帮助确保玻璃碎片保持在一起。然而，在实践中，网织物经常被爆炸的力量撕裂。这是因为网丝必须做得很薄，以防止窗帘挡住光线。我们需要的是一种智能纺织品，它允许光线通过，但也能够包含爆炸所涉及的巨大力量，并为飞行碎片提供屏障。

In the 21st century terrorism has become a constant threat to the way-of-life of people all around the world. One of the most common manifestations of the terrorist's threat is an explosive device, often detonated in the midst of a densely-populated civilian area. The University of Exeter is leading a team of government and industrial experts in the development of a new type of 'smart' blast curtain aiming to reduce death and injury caused by bomb blasts. This smart textile uses auxetic materials pioneered at the University. Unlike conventional materials that get thinner when stretched, an auxetic material will get fatter. This interesting and counter-intuitive property is also found in some natural materials such as cat skin and bone from human shins.When a terrorist bomb explodes in an urban area it produces devastating effects, including structural and nonstructural damage to buildings, injuries, and deaths. Numerous injuries in explosions result directly and indirectly from window glass failure. In the Oklahoma City bombing, glass accounted for nearly two thirds of all eye and head injuries. When an explosion occurs, there is an extremely rapid release of energy. This is takes the form of heat, sound and light, but also as a shock wave. It is the initial shock wave that is responsible for the majority of damage to buildings, including shattering of windows. If this was not destructive enough, the vacuum that follows the blast front then creates a high intensity wind which can transport debris across large distances. Current blast curtain design favours the use of translucent aramid nets that are longer and wider than the window: the excess curtain length is placed into a box at the base of the window. When the window shatters, the curtains billow out and capture a significant portion of the glass fragments. The system is often augmented with a film window coating to help ensure that the glass fragments stay together. However in practice, the net fabric is often torn by the force of the blast. This is because the net filaments have to be made thin to keep the curtain from blocking light out. What is needed is a smart textile that allows light through but is also capable of containing the huge forces involved in an explosion and providing a barrier to flying debris.