Metallic bubble wraps revolunise packaging to automobile body casting

A metallic bubble wrap developed by engineers at North Carolina State University has revolutionised everything from packaging of delicate things to manufacture of protective covers for a variety of uses from computer cases to automobile body parts.

The aluminium cushioning material, first developed by the researchers in 2013, is lighter, stronger and more flexible than sheet metal and more heat- and chemical-resistant than plastic or other polymer-based cushioning materials.

The bubble wrap metal sheets can now find wide applications in automobile body panels, the wing edges of airplanes, suitcases, helmets and cases for computers and other electronic devices.

The metallic bubble wrap was developed to offer protection in areas that are only a few millimeters thick as it is not quite as easy to pop it, while it could be a hell of a lot more useful.

For making the metallic bubble wrap, scientists take a thin sheet of aluminium, then use a studded roller to form small indents in the sheet. These voids are then filled with a foamed material like calcium carbonate, before being sealed with another flat sheet of metal. The series of bubbles absorb masses of energy, while the reconstructed material weighs 30 per cent less than regular sheet metal, and yet are nearly 50 times stronger.

This material does exactly what sheet metal and other cushioning materials do, but better,'' according to Dr Afsaneh Rabiei, professor of mechanical and aerospace engineering and the lead researcher on the project. ''And it won't cost businesses and consumers very much because producing it requires just a few steps.

To create the material, Rabiei used a thin sheet of aluminum and then made small indentations in the material with a studded roller. She then deposited a foaming agent - such as calcium carbonate or titanium hydrate - into the indentations. When heated, such agents decomposed and created bubbles.

Rabiei covered the aluminum with another sheet, sandwiching the foaming agent in its indentation troughs. She ran a heavy roller over the two sheets to bond them together. In the final step, she placed the combined sheet into a furnace, where the heat broke down the foaming agent and created air bubbles in the material.

The resultant material was tested using a variety of mechanical tests to evaluate its properties and compare it with the original bulk sheet metal. The cushioning material, which weighs about 20 to 30 per cent less than the bulk material, offered a 30 to 50 per cent increase in bending strength. The tensile strength - essentially the material's breaking point - was nearly identical to the non-bubbled metal.

''The way we created this material could be used for any sheet metal, not just aluminum,'' Rabiei said. ''We plan to further develop our metallic cushioning material and hope it eventually offers better protection for products and the public.''

It's easy to make, not too expensive - and is increasingly finding use in everything from shipping containers for fragile goods to bike helmets.

Rabiei announced the creation of the material on 24 June 2013, at the 8th International Conference on Porous Metals and Metallic Foams in Raleigh, NC.