TerraN_EmpirE
Tyrant King
Each type has advantages and disadvantages. Steel plate has a disadvantages of weight, spalling and causing fragments of defeated projectiles to deflect up into the neck and face.
Ceramic can be lighter but as you said tends to have a shelf life and be more sensitive to smaller abrasions.
Kevlar is a material that have proven protection against low velocity fragmentation like explosive debris, yet it adds a lot of bulk getting in the wearers way it also has a disadvantage in hot weather or high activities as the Kevlar or other soft synthetic doesn't breathe meaning excess heat is trapped and in hot sunny weather the Kevlar vest is a personal oven.
This is why you have Plate carriers getting more popular. A ceramic stand alone plate will protect to a degree against fragmentation and will stop bullets, as it doesn't wrap the wearer in layers of synthetic materials it also reduces bulk and allows for the wearers body to manage heat.
The main function of a combat helmet in the post world war era is to protect debris not bullets. Bullets is a secondary function that evolved with advanced materials. That is why in The world wars they adopted steel helmets on all sides and those remained until the 1980s with the replacement by Kevlar and other synthetic materials.
The combat helmet came about as troops in fighting positions started taking artillery shells, now no matter what if the shell was inside the fighting position it was game over but it was rare for that to happen more often a shell would fall long or short and explode launching fragmentation and kicking up debris like wood and stones the helmet was designed to try and prevent that from impacting the least protected part of a soldier in a fighting hole. His head.
