The Defence and Security Challenge Area is concerned with the development of novel materials in which structural control can be achieved at the nanoscale to yield dramatic improvements in strength, stiffness and toughness, and yet are still able to be produced in large quantities at a reasonable cost. Our vision is to provide greater resilience for defensive structures, combined with enhanced flexibility of deployment through lightweighting, improved thermal stability and excellent performance at high strain rates. We are working actively with defence research establishments and commercial manufacturers in both UK and worldwide to translate these developments into materials for practical use.
Applications include steels for gun barrels and armour plating, fibrous materials for personnel and light armoured vehicle protection, and composite panel structures for vehicular and aeronautical use.
Imagine a material that is cheap, can be made large in all its three dimensions, in huge quantities, has a nanocrystalline structure, and does not require severe processing or dramatic heat treatments during manufacture. This has been achieved by developing the theory for solid-state phase changes to create a steel which can be transformed at incredibly low temperatures into slender plates of bainitic ferrite, only 20-40 nm thick embedded in austenite, as shown in Fig 1. Bhadeshia and his research team have worked with the Ministry of Defence (MOD) on designing a steel for gun-barrels, and discovered a bainitic steel that had very desirable ballistic and mechanical properties (strength 2.5 GPa; toughness 40 MPa m1/2). Furthermore, the Defence Science and Technology Laboratory (DSTL) found that when perforated the steel has a ballistic resistance exceeding that of well-established armour materials. Drilling and hole-punching prior to heat-treatment results in an ultra-hard perforated plate (as shown in Fig 2.). The steel as a perforated strike face is one of the best metallic armours ever produced.
One of the main challenges to realising the ultra-high strength (over 2 GPa) and stiffness (over 400 GPa) of carbon nanotube (CNT) fibres is the production of macroscopic assemblies that retain the properties of the original materials. Elliott and his research team are exploiting the hierarchical properties of CNTs fibres (shown in Fig 3.) to obtain materials with specific properties exceeding the best available commercial polymer fibres (such as Dyneema or Kevlar) but with improved thermal stability and performance at high strain-rates. The fibres can be assembled into 2D sheets in both woven (see Fig 4.) and non-woven forms, and impregnated with polymer resin, making them suitable for lightweight armour application. The group is currently working with several defence companies and US Army and US Navy to develop commercial prototypes.