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Multiple layers of novel coatings, composites and fabrics underpin a new-technology bag that an international team of scientists is developing to protect planes from bombs in passenger bags.
The so-called Fly-Bag is designed to be filled with passenger luggage and then secured in a plane’s hold. If a bomb in a passenger bag explodes inside the Fly-Bag, the bag would absorb the blast, reports the team, which is working with Blastech Ltd., a spinoff company owned by the UK’s University of Sheffield.
Elastomers and Thickening Fluids
Fundamental to the Fly-Bag’s design is the internal elastomeric coating and impregnation of fabric with Shear Thickening Fluids (STF).
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Images: University of Sheffield |
| Luggage fills the Fly-Bag’s interior before it is closed and secured in a baggage hold. |
Elastomers are very low-stiffness, high-failure-strain materials often used as adhesives, sealants or in structures where high strains are expected. An elastomer was developed to provide a gas seal in the bag at very high strain rates and very high deformations, while resisting flame and heat, according to a release from the University of Sheffield.
STFs work by increasing in viscosity in response to impact. A simple STF can be made from mixing corn starch with water. In the correct quantities, this simple STF could be rolled into a ball that would bounce on hard surfaces but return to a fluid once left alone, the university reports.
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| A trial version of the Fly-Bag filled with luggage awaits blast testing during trials. |
Under normal circumstances, the particles in STFs repel each other slightly. After sudden impact, however, the extra energy in the system proves stronger than the repulsive forces, causing the particles to clump together in structures called hydroclusters, which bump into each other, thickening the fluid.
This unusual behavior “has already generated significant commercial interest, and STFs are being considered to improve body armor designed to protect the wearer from weapons such as knives and bullets,” the university says.
Coated Fabric
With the Fly-Bag, the STF is used to coat the yarn of the fabric. As the fabric comes under strain, shearing forces between the yarns cause the STF to thicken, temporarily increasing the fabric’s stiffness and reducing the total deformation.
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| The Fly-Bag is secured inside the hold. |
Some airlines have developed hardened luggage containers to withstand luggage bomb blasts, but these are heavy, costly and can only be used on wide-body aircraft, the university reports.
The Fly-Bag may reach the market in less than two years, although the cost is not yet known. Researchers are optimistic about its potential.
"The use of explosives on aircrafts has had a renaissance in recent years, with recent attempted attacks coming not just from passengers, but also as loaded freight,” said Dr. Jim Warren, from the University of Sheffield´s Department of Civil and Structural Engineering.
“Since weight and operational flexibility is key for aircraft operators, this low-weight, removable solution would seem to be a paradigm shift in the hardening of aircraft structures."
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