Researchers test bomb-proof luggage hold for aircraft

It could replace the heavier, more expensive hardened luggage containers that are currently used as a precaution against the threat of in-flight explosions.

The Fly-Bag has multiple layers of novel fabrics, composites and coatings, and is designed to be filled with passenger luggage and then placed in the hold of an aircraft.

Fundamental to the design of the bag is the internal elastomeric coating and impregnation of fabric with shear thickening fluids (STFs), as project collaborator Dr Jim Warren of Sheffield University’s Department of Civil and Structural Engineering explained to The Engineer.

‘If you imagine the yarns of the fabric sliding across each other and changing orientations as you stretch it in both directions at once. What happens is the fluid that’s sprayed into each fibre of the yarn starts to stiffen up and resist that mechanical strain.’

STFs work by increasing their viscosity in response to impact. 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, consequently thickening the fluid.

‘The real damage is caused by impulse rather than the energy and that’s a very important concept,’ Warren said.

‘What we’re actually interested in is taking that impulse and, rather than have it all applied to a structure over a very tiny time period, we want to take the same amount of momentum and stretch it out over as long a time period as we can so that the peak stress falls.’

The group has built a full-scale prototype that Warren says has been tested with an explosive device of a similar potential as the bomb that brought down Pan Am Flight 103 over Lockerbie in Scotland in 1988.

‘The bag is showing no sign of failing yet, so we have to just keep putting bombs in bags and blowing them up until something fails, and then we can say this design is good up to this sort of level — which we’d only be able to discuss with secured parties,’ Warren said.