Ballistic helmet materials and the process of manufacturing ballistic helmets has changed drastically since their first inception. This ranges from metal fabrication, fibers, and ceramics. This article will cover what most modern-day ballistic helmets are made out of, and what the future may hold.
Some of the earliest ballistic helmets on the "modern day" battlefield can be seen during WWI. Long before advanced fiber manufacturing techniques, the ballistic helmets, and other armor were made out of metal, much like you would find on ancient battlefields. While the metalworking processes were much-improved at this point, their weight made them mostly impractical for anything other than stationary fighting.
These metal helmets would prove to be the norm, with increases in ballistic capability and decreases in their weight until the late 20th century. In the 1980's ballistic materials such as Kevlar and aramid would be implemented to improve the ballistic protection and of course weight.
DuPont developed what we know to be kevlar in 1965. It's been used in more clothing, accessories, and ballistic equipment than any other modern day material. In terms of ballistic helmets, it has been used in Personnel Armor System For Ground Troops (PASGT) helmets. DuPont Kevlar® KM2 fibers were then used for the ACH (Advanced Combat Helmet) fielded in 2003. The new KM2 was able to absorb 20% more kinetic energy than the PASGT helmets it was replacing. This same ballistic material was also used in the Advanced Combat Vehicle Crew Helmet or CVC Helmet. (DuPont Helmet Materials)
Even more exciting though is Kevlar® XP™ for Hard Armor that DuPont has released. It's still 100% Kevlar but provides for a much more lightweight helmet. It can provide a 20% decrease in helmet weight while maintaining the same performance or a 20% increase in performance using the same level of material. DuPont Kevlar® XP™ for Hard Armor can be processed on existing helmet manufacturing machinery as well. Which as will see is a huge advantage when looking at the production and manufacturing process of other materials.
Speaking of this process, the manufacturing of kevlar fiber type ballistic helmets starts with the desired number of preform fiber sheets. These sheets are typically impregnated (prepreg) with a resin to bind the layers together further along in the process. The sheets themselves are cut into various shapes. These shapes and the position that they are placed into a press for helmet molding can make significant improvements in the performance of ballistic helmets. Below are a few such shapes pulled from patent filings.
These layers of shapes would then be pressed, or compression molded at a constant temperature and pressure for a set amount of time. Using a Kevlar/PVB-phenolic PASGT helmet as an example, it would require constant temperatures around 340 degrees F. and pressures over 500 psi for 12-15 minutes.
The mold or press itself for this process is most commonly a male and female matched metal die set using hydraulics to achieve the desired pressures.
These molds may be self-trimming or once pressed the helmet may require additional trimming later in the production stream. While this is a very simplified version of a process that contains numerous nuances. It should serve to give the reader a broad overview of how a ballistic helmet is actually made.
Ultra-high-molecular-weight polyethylene (UHMWPE, UHMW) is another commonly used fiber in ballistic helmets. Typically referred to as Dyneema or Spectra it's a lightweight high-strength strand type fiber. First invented by Albert Pennings in 1963, but it became commercially available by DSM in 1990.
Companies such as OPS-CORE, 3M, Team Wendy, and others all use some type of UHMWPE fibers in their helmets. The major advantage of UHMWPE is the weight savings over aramid for the same protection levels. This weight savings can be as much as 20-30%. There are always trade-offs though, and the process to construct a UHMWPE fiber helmet is much more intensive.
Following US Patent US13844109, we can show the detailed process of manufacturing a ballistic helmet with UHMWPE. Once again we start with a stack of sheets or fabric layers that will be heated in an oven for a set period of time. They are then placed in a hydroforming press opposed to a male/female compression/stamp molding press. The hydroforming press uses pressurized hydraulic oil in a flexible rubber diaphragm to shape the fabric layers around a punch. High pressure ensures no wrinkles, cuts or seams.
When the hydroforming cycle is complete, the helmet is removed from the press and any downstream production processes are completed. This will include trimming, painting, QC checks, drilling, and accessory attachment.
Again there is much more to this entire process, and various nuances in the actual process. This broad overview will give you a solid grasp on how ballistic helmets are actually made.
So what's next in ballistic helmet manufacturing? Many believe that the fibers themselves will still be improving. Fibers can be spun together to create unique blends. Take for example the U.S Army investing close to a million dollars in genetically engineered spider silk. Believing that the energy absorption of the spider silk could be much higher than kevlar. While others believe the next advances may come from "next generation metals" that perform better ballistically and are lightweight. Either way, we have come a long way from wearing boar's tusks for our head protection!
Citations
Aramid, T. (n.d.). Safety first with new helmet press | Aramid Vision. Retrieved March 01, 2018, from http://www.aramidvision.com/issue-03/ballistic-helmets-testing-endumax-twaron-aramid-teijin/
Military and Law Enforcement | Industries. (n.d.). Retrieved March 01, 2018, from https://www.dsm.com/products/dyneema/en_GB/industries/military-law-enforcement.html
Tucker, P. (2017, August 02). US Army Boosts Spending on Genetically Engineered Spider Silk for Body Armor, Underwear. Retrieved March 01, 2018, from http://www.defenseone.com/technology/2017/08/us-army-boosts-spending-genetically-engineered-spider-silk-possible-use-body-armor-soldier-underwear/139923/
W. (n.d.). Kevlar® Fibers | DuPont USA. Retrieved March 01, 2018, from http://www.dupont.com/products-and-services/fabrics-fibers-nonwovens/fibers/brands/kevlar/products/dupont-kevlar-fiber.html
US9307803B1 - Ballistic helmets and method of manufacture thereof. (n.d.). Retrieved March 01, 2018, from https://patents.google.com/patent/US9307803B1/en