A smart curtain for safety

When an explosion’s shock waves reach this new type of ‘smart’ curtain and stretch it, its material gets thicker, not thinner, thus reducing the impact of bomb explosions.

The curtain is designed to capture razor-sharp wreckage such as flying glass and rubble when windows are blow in.  Flying building debris of this kind can cause severe, sometimes life-threatening, injuries to people working or living in cyclone or hurricane zones or in buildings that terrorists might attack.

The British-designed ‘smart’ curtain is meant to be placed over the inside of windows in buildings that are potential bomb targets, such as government and other high-profile commercial properties.  The curtain’s yarn is technically described as an auxetic material – one that gets thicker when stretched. 

Such materials could be used to make ‘self-healing’ auxetic bandages and in civil engineering to reinforce land and reduce flooding.

The project by the UK’s Engineering & Physical Sciences Research Council is being led by Exeter University in western England, in collaboration with its spin-out company Auxetix Ltd. and three other partners. It could be on sale in a few years, after testing.

Lets in light too

Today’s blast curtains consist of a thick type of net-curtain fabric and work together with an anti-shatter film applied to the window to stop smashed glass from tearing the material. The smart curtain lets in ample light and aims to remove the need for anti-shatter films by using stronger, more resilient fibres woven into a controlled textile structure. 

Made of a stretchy yarn

The secret lies in the yarn from which the curtain is made.  A stretchy fibre provides the core of the yarn and a stiffer fibre is then wound around it.  When the stiffer fibre is put under strain, it straightens.  This causes the stretchy fibre to bulge out sideways, effectively increasing the yarn’s diameter.

Another key feature of the new curtain is that, when stretched, small pores open up in it.  
Although too small for flying debris to penetrate, these pores are designed to let through some of an explosion’s shock waves, ensuring that the material does not rip.

Professor Ken Evans, who is leading the project, recalled that in 1995, when a government building in Oklahoma City (USA) was bombed, more than 150 people were killed and nearly 700 injured. The explosion shattered glass in 250 buildings nearby, and flying shards accounted for about 60 per cent of all eye and head injuries. 

“The blast curtain we are working on – which will be capable of dispersing the shock from an explosion extremely effectively – will be backed up by robust scientific understanding vital to ensuring that it really can block flying debris and achieve widespread use,” he added.

Testing of the ‘smart’ curtain at a government-approved facility has already started.  Following rigorous certification procedures, the curtain could be on the market within a few years.