Drop the weight: alternatives to all-metal armour

The challenge of keeping vehicles well protected, while light and agile, is taking a number of directions. Alternatives to all-metal armour have been around for some time, but have mostly been limited to a handful of heavy vehicles such as Challenger 2 tanks and the US Army’s Stryker armoured combat vehicle.

Now, backed by government investment, lightweight composite technology for protective armour and vehicle components is being rolled out for vehicles of all sizes and roles. In June 2016, it was announced that these materials will form a key element of the ballistic armour protection system for the British Army’s Ajax vehicle, which is currently in development. The materials are being delivered to vehicle manufacturer General Dynamics by Permali Gloucester in a £15-million contract.

The latter has worked on previous Ministry of Defence (MoD) projects, including appliqué armour for the Warthog platform and the Oshkosh heavy equipment transporter and wheeled tanker; a roof for the Panther command and liaison vehicle; blast protection for the Land Rover revised weapons mounted installation kit (RWMIK); and blast protection panels and side skirts on the Wedgewood counter-improvised explosive device disposal (CIEDD) vehicle.

The company’s ballistic panels are manufactured using glass, aramid or ultra-high-molecular-weight polyethylene (UHMWPE) materials and thermoset resin systems or advanced thermoplastic matrices. These can include ceramic tiles for protection against armour piercing rounds, and aluminium or steel skins for greater rigidity and increased protection levels.

Ceramic possibilities

Ceramics are a type of composite armour that entered mainstream use around 50 years ago when the material was developed for the British Army’s heavy vehicles. Known as Chobham armour, the success of this design led to it being used on M1 Abrams and Challenger 1 and 2 vehicles.

The advantage of ceramic is its extreme hardness and very low weight. It also offers high strength, chemical resistance, corrosion resistance, wear and heat resistance and thermal expansion, insulation and conductivity.

The make-up and property combinations of ceramic armour vary between the many manufacturers that produce it. Each material has a unique mechanical, thermal, biochemical and electrical properties, which can be altered and developed to suit specific applications.

CeramTec, the supplier of advanced technical ceramics, works with four groups of ceramic materials: silicate ceramics (natural materials in conjunction with alumina); oxide ceramics (primarily metal oxides); non-oxide ceramics (based on carbon, nitrogen and silicon compounds); and piezo-ceramics (materials used to convert mechanical parameters into electrical parameters or electrical signals into mechanical movement or vibration).

The company’s ceramics have been supplied as critical components in systems that offer ballistic protection for land vehicles, and it is one of the first to work in the area of transparent ceramics, with a system called Perlucor. The material weighs 30% less than conventional bullet-proof glass systems.

This ceramic can withstand extreme conditions and can be applied as transparent ballistic vehicle protection. As with typical ceramic armour, Perlucor comes in a standard 90×90mm tile that can be shaped with individual contours based on customer requirements. It can also be tailored to a specific thickness, generally between 2–10mm. The gluing technology used means that joints and edges are ‘invisible’, making it possible for an optical surface to be manufactured to produce large windows.

Composite approach

Ceramic hybrids – including metal-ceramic and metal-ceramic-composite hybrids – are also an option for providing increased protection by combining ceramics with materials that offer improved performance, such as increased strength. These hybrids delay ceramic failure in the event of a strike and help reduce spalling. The Stryker has been fitted with the composite modular expandable armour system (MEXAS, as have armoured vehicles in the German, Canadian, Swedish and Austrian military.

CPS Technologies also works in this type of armour. Its HybridTech Armor tiles are ceramic tiles, reinforced with metal and metal matrix composites, which are packaged in a hermetic layer of high-pressure cast aluminium. CPS believes this approach results in more consistent ballistic performance near tile edges, and makes assembly easier as the modules are tough enough to drill and bolt like metal, eliminating the need for steel inserts at attachment points.

The use of composite materials to reduce weight is beginning to move beyond armour to infiltrate every aspect of defence equipment, as manufacturers look to address customers’ transportability and manoeuvrability requirements. In June, FN Herstal introduced a newly developed carbon connection plate prototype for pintle weapon systems. By using composite materials, the company has reduced by 30% the weight of the plates that connect carriers’ hard points to their weapon systems, while maintaining the structural properties of earlier versions.

Tencate provides lightweight 3D components for military vehicles for areas – such as hatches, doors and bonnets – where weight hampers mobility. The company supplies ceramic composite armour to counter specific battlefield threats, as well as fibre-based protection against small-calibre ammunition.

The development and manufacture of ceramic composite armour is increasingly backed at government level in order to cultivate and protect sovereign capabilities.

The MoD’s Defence and Science Technology Laboratory (dstl) is working in this sector with Kennametal Manufacturing UK. In 2013, a spark plasma sintering (SPS) facility opened at the firm’s Newport facility, where specialised manufacturing capabilities for full-size ceramic armour components for vehicles and body armour are being developed.

With the ability to manufacture these components domestically, the hope is that the UK will no longer be reliant on buying materials from foreign countries.

The future

The US military is focusing on avoiding being hit with projectiles, rather than simply being able to survive them.

This idea is being developed as part of the Defense Advanced Research Projects Agency’s (DARPA’s) Ground X-Vehicle Technology (GXV-T) programme. This recognises that today’s ground-based armoured fighting vehicles are better protected than ever, but face increasingly effective armour- piercing weapons. While adding more armour provides incremental increases in protection, it also impedes speed and mobility, and causes development and deployment costs to balloon.

Future vehicles may be designed around survivability through agility, rather than ruggedness, combining manoeuvrability with actively repositionable armour.