Composite metal jacket

Lighter, cheaper and individually tailored body armour for police and special forces could be on its way after the discovery of a method for creating dense, tough ceramics in complex shapes.

The technique, Displacive Compensation of Porosity (DCP), uses a chemical reaction between molten metal and preformed porous ceramics. The process creates strong, lightweight moulded materials for applications such as thinner, lighter and stronger body armour and bullet-proof vests. These currently consist of ceramic plates wedged between layers of fabric.

The system allowed Prof Ken Sandhage and his team at Ohio State University to create lightweight items from composites of some of the world’s hardest materials, including boron carbide, zirconium carbide, titanium carbide and zirconium diboride.

‘Boron carbide is the third strongest material known to man,’ said Sandhage. ‘However, there is a need to make it lighter and easier to mould. Our method removes the necessity for machining and hot pressing, lowering costs, and makes it easy to create complex shapes. This means that it would be possible to create armour tailored to the individual.’

DCP involves dipping a preformed ceramic item into an alloy. The ceramic sucks the metal into its pores like a sponge, creating a dense, strong composite, though the external shape and size stay the same.

Removing the need to reshape the part after processing means manufacturers would no longer have to use expensive diamond tools. It would also save on electricity as the composite can be formed at lower temperatures, without the need for costly high-temperature furnaces or high-pressure environments.

The ability to create strong lightweight materials is particularly important for the aerospace industry. ‘We are also working on using the process to create solid fuel rocket nozzles,’ said Sandhage. ‘During use temperatures can exceed 2,500 degrees C, while the propellant moves through them at supersonic speeds, making it very corrosive.

‘Tungsten has a high melting point, but it is also very heavy, so we created a zirconium carbide tungsten composite by adding a zirconium copper liquid to porous tungsten carbide. The resulting composite weighs about a third less than tungsten and may be more resistant to corrosion.’

Sue Kelly, vice-chairwoman of the Essex Police Federation, said any advances aimed at improving the fit and reducing the weight of body armour would be welcomed by officers. ‘Things have moved on a lot since the days when female officers had to wear armour designed for men, which was uncomfortable as it basically didn’t fit,’ she said.

‘Nowadays vests are a good fit and relatively comfortable. Ideally one day wearing body protection will be as easy as pulling on a jumper, but any new design that meets relevant standards would be considered.’