Ceramite

Ceramite is a form of bonded ceramic armour, incredibly tough, but light. Unlike metal, it doesn’t dent or rupture on impact and it takes a projectile of significant power and calibre to punch through it. Repairs are made by bonding new layers of ceramite over existing ones. Ceramite also conducts relatively little heat, making it ideal against heat-based and high-energy weaponry.



https://www.warhammer-community.com/2016/10/27/power-armour-through-the-ages/