Bubble-wrap blast buffer on test bed

Aircraft manufacturers are watching with interest work at Manchester University which could thwart the efforts of terrorists to blow up planes. It also has less exotic applications. Researcher Bill Courtney has developed a flexible buffer material. One version could be used to make fuel tanks capable of withstanding an explosion by absorbing the energy from […]

Aircraft manufacturers are watching with interest work at Manchester University which could thwart the efforts of terrorists to blow up planes. It also has less exotic applications.

Researcher Bill Courtney has developed a flexible buffer material. One version could be used to make fuel tanks capable of withstanding an explosion by absorbing the energy from pressure waves.

The material, which is similar to bubble-wrap protected by an outer skin or bag filled with jelly, is said to be a better vibration damper than any solid material.

And, depending on the shape and size of the air cells (typically 1mm across), the material is up to three times better at absorbing shock than visco-elastic polymer or closed-cell foams. You get less kickback, says Courtney.

But there is more to the material than being a good shock absorber. In the fuel-tank application, the fuel itself becomes part of the damping system.

More ingenious still, air cells separate the fuel and stop it moving around, becoming part of an indirect and safer fuel pumping system.

As the fuel is used up the air cells expand to fill the space, reducing the area available to be filled with potentially explosive hydrocarbon gases. The air bags also insulate the fuel from adjacent hotspots like engines.

But the performance of the material is still the subject of mathematical modelling at Manchester’s department of mechanical engineering where Courtney, a former physics teacher, is testing his designs against traditional cushioning materials.

In one design the air cell takes the form of a tube, open at one end, inside which an air bubble is trapped. By narrowing the tube it is possible to increase the material’s visco-elasticity or damping effect.

Unlike foams, Courtney’s buffer material does not flatten under load because it works on the principle of hydraulic pressure redistribution. On impact, all the air bubbles are compressed so that in any such system the pressure is always equal.

The material could also be used as padding on dashboards and in steering wheels; as a highly resilient packaging material for sensitive goods in transit; and in protective clothing, particularly for sportswear.

A ‘smart’ version exploits the magnetic or electrical properties of certain materials so that viscous damping could be designed selectively into parts of a product to suit the application.