Modern helmets are mainly composed of helmet shells, linings and suspension systems. Due to the different requirements for use in various activities, there are many structures and styles of helmets.
Usually, the shell of the helmet is made of high-strength materials, such as metal, engineering plastics, Kevlar fibers, etc., which absorb most of the impact through its deformation; the lining material has sweat-absorbing, warm, shock-absorbing properties Military helmets often have the function of further reducing the impact force and preventing shell fragments from hurting the head; the suspension system is the part between the shell and the lining, which can usually be adjusted to suit different wearers difference in head shape.
Some special-purpose helmets are also equipped with headphones, microphones, and sockets for additional equipment such as cameras and lighting torches.
