SHEFFIELD, UK - A bag, which can protect planes from bombs in passenger luggage, has been developed by an international team of scientists, including academics from the University of Sheffield, Sheffield, South Yorkshire, UK, working within university spinout company Blastech Ltd.

The bag, named the Fly-Bag, features multiple layers of novel fabrics, composites and coatings and is designed to be filled with passenger luggage and then placed in the hold of a plane. If a bomb in a piece of luggage in the bag exploded during the flight, the resulting blast would be absorbed by the bag due to its complex fabric structure, preventing damage to the plane.

Fundamental to the design of the bag is the internal elastomeric coating and impregnation of fabric with shear thickening fluids (STF).

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.

STFs work by increasing viscosity in response to impact. A simple STF can be made from mixing cornstarch with water. Providing quantities are correct, it would be possible to roll this simple STF into a ball that will bounce on hard surfaces but return to a fluid once it is left alone.

Under normal circumstances, the particles in STFs repel each other slightly. However, following sudden impact, 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.

In the case of the Fly-Bag, the STF is coated onto the yarn of the fabric, and as the fabric comes under strain, shearing forces between the yarns cause the STF to thicken, temporarily increasing the stiffness of the fabric, reducing the total deformation.

Hardened luggage containers have been developed to deal with bombs hidden in passenger luggage, but these containers are heavier and more costly than conventional equivalents and are only suitable for wide-body aircraft.

It is expected that the Fly-Bag will be on the market in one to two years, although cost would depend on a range of variables, such as the structure of the plane.