A lightweight bulletproof cockpit window capable of withstanding multiple rounds is the goal of a 24-month US Army project to develop "transparent armour".
The army's Aviation Applied Technology Directorate plans to award Phoenix, Arizona-based Simula Aerospace & Defense Group a contract to develop and test transparencies that can protect cockpit occupants from small-arms fire and high-velocity fragments from larger explosive weapons.
At present, bulletproof windows are made by bonding together multiple layers of toughened glass. "Transparencies constructed in this way are extremely heavy, particularly for aviation applications are only single-shot capable due to fracture and disbanding obscuring visibility and tend to environmentally degrade and disbond over time, rendering them opaque," says the US Army.
Materials that have been considered as alternatives include aluminium oxynitride, synthetic spinel, synthetic sapphire and ceramic glasses, which tend to be lighter and tougher than glass. The drawback with these materials is that they are prohibitively expensive, due to the high cost of polishing the raw materials to a transparent state.
Source: Flight International