Liquid Armor

Liquid Armor is a material under research by United States Army Research Laboratory (ARL). It is liquid under low or normal pressure and solid under high pressure. This liquid is made with polyethylene glycol and the solid part is made of nano-particles of silica. This liquid is soaked into all the layers of a Kevlar vest.

BAE Systems has also been researching a similar Kevlar vest with a fluid between layers of the polymer, and this attracted a fair amount of press in August 2010. BAE took over the US research company Armor Holdings who were doing research based on suspensions of silica particles.

Fluids used for this purpose are non-Newtonian, and are usually referred to as shear thickening fluids (or STF), which are the same as dilatants.