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| CSIRO | SOLVE | Issue 10 | FEB 07 | |
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ARTICLE
ADVANCED MATERIALS:
Baked Body Armour By Rebecca Thyer
While the material of choice for knights and Ned Kelly was metal, soon soldiers, police and security personnel will be safe under fire in lightweight ceramic.Body armour has come a long way since the days of Australian outlaw Ned Kelly. When facing colonial police in his final stand at Glenrowan in the late 1800s, Kelly's protective armour weighed more than 40 kilograms. And while it was effective in deflecting bullets, its weight prevented him from running away. Today, body armour aims to protect the wearer from small-arms ammunition and high-velocity fragments, or shrapnel, that travel at speeds of up to 1000 metres per second. And weight is still an important consideration. To this end, Australian Defence Apparel (ADA) is working with CSIRO to produce effective, lightweight, ceramic-based armour products, which break up or shatter bullets and, in combination with the rest of the breastplate system, prevent penetration. Further, the armour will weigh less than two kilograms.
The new lightweight armour is part of a project funded under the Defence Capability and Technology Demonstrator program, administered by Australia’s Defence Science and Technology Organisation. Nigel Stone, of CSIRO Manufacturing and Materials Technology (CMMT), says offering a high level of performance at minimal associated weight is crucial: “No combat soldier or policeman wants to carry a heavy plate system that, though offering good protection, quickly tires the wearer so that their physical performance becomes rapidly impaired. Weight reduction without performance reduction is very important.” One lightweight material that gives a high level of protection is boron carbide, a hard ceramic with one-third the density of steel. However, boron carbide components – usually imported into Australia – are generally expensive. CMMT researchers are addressing this by applying an innovative approach to the manufacturing process. The team has an extensive background in advanced ceramics, Mr Stone says, including in-depth knowledge of the properties, processing and performance relationship and manufacturability, without losing sight of the economic drivers. “So we’ve been able to use this expertise to address body armour challenges.” There are a number of ways to produce boron carbide ceramics, but the most common method for this application is hot isostatic pressing, also referred to as HIP. It is a relatively slow batch process, but results in high-density products that normally exhibit very good mechanical properties. The downside, of course, is that it is expensive. Armour Solutions managing director Dr Ian Crouch, who is managing the project on behalf of ADA, says hot-pressed boron carbide has been used in protective applications for more than 30 years. “It was first used on helicopter seats in the Vietnam War,” he says. “However, its production process makes it 10 times more expensive than other ballistic materials, such as aluminium oxide products, restricting its use.” Dr Crouch says boron carbide is only used in extreme cases where an ultra-lightweight material is required, because it is 40 per cent lighter than aluminium oxide. However, with a lower cost of production its uses could include personal body armour and other weight-sensitive military and civilian items. The team has developed a forming and pressureless sintering process that will cut costs – making boron carbide only three times as expensive as aluminium oxide – and produce a superior product. Dr Crouch says the approach is innovative: “Rather than creating a new product altogether, we are using a smarter processing approach.” The traditional HIP process is also limited in its production capabilities. “The process normally creates 50-square-millimetre tiles that are used to build up a larger mosaic,” Dr Crouch says. “So we have developed and implemented a complex shape-forming process.” Tests on a new lightweight product have been encouraging. “We have successfully undertaken ballistics tests against small-arms ammunition, the sort of objects we are trying to protect the end-user from, and plan to deliver a new demonstrator prototype by June.” Mr Stone expects that the technology will be transferred to either an existing Australian manufacturer or a new facility established on a brownfield site. “The system’s economic efficiency, coupled with its complex shape-forming process, will make it very attractive to manufacturers.” Dr Crouch says that with innovative science behind it, the Australian manufacturing industry could be a world leader in this technology. “The market for body armour and associated products is huge. About half a million to a million people would be using body armour of some type every day, so there is definitely a market need for this type of product.” For further information contact: |
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