The Helmet used by US military has changed dramatically over the years.
World war I- Dishpan
World war II- M-1 steel pot
After 1980- helmet made of Kevlar 29 ballistic fiber.
In future may contain something more extra protection from flying shrapnel (fragment from an exploded bomb).
New research trying to develop a military helmet equipped with technology to regulate soldier’s brain
The technology is TRANSCRANIAL PULSED ULTRASOUND which delivers high frequency sound waves to specific regions of brain under the influence of these sound waves, neurons send impulse over them. Using a controller a soldier could release ultrasound pulses to stimulate different area of brain.