A new material that gets thicker, not thinner, when stretched is being developed to provide better protection from bomb blasts.
The curtain is designed to capture debris such as flying glass when windows are blown in. It's designed for use in buildings that are potential terrorist targets, such as government and high-profile commercial properties.
other uses could include protection against severe weather events such as typhoons and hurricanes.
"In the 1995 Oklahoma City bombing, glass accounted for nearly two thirds of all eye and head injuries," says Professor Ken Evans of the University of Exeter, who is leading the project.
"The blast curtain we’re 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 it really can block flying debris and achieve widespread use."
Blast curtains currently in use essentially consist of thick net-curtain fabric and are used with an anti-shatter film applied to the window to prevent fragments of glass from tearing the material.
The new curtain aims to remove the need for anti-shatter films by using stronger, more resilient fibres woven into a carefully controlled textile structure.
The yarn from which the curatin is made consists of a stretchy fibre core with a stiffer fibre wound around it. When the stiffer fibre is put under strain, it straightens, causing the stretchy fibre to bulge out sideways and effectively increasing the yarn’s diameter.
The research team has identified a range of widely available, tough fibres that can be used in the yarn. Producing and weaving the yarn are also conventional processes.
Altering the angle at which the second fibre is wound around the first and adjusting their relative stiffness and diameters allows the yarn to be fine-tuned for specific types of blast.
Another key feature of the new curtain is that, when stretched, small pores open up in it. Although too tiny for flying debris to penetrate, these pores are designed to let through some of an explosion’s shock wave. This reduces the force the curtain is subjected to and so helps ensure it doesn’t rip.
Testing at a government-approved facility has already started, and the developers say the new curtain could be on the market within three to five years.