Body armor is designed to protect the wearer from ballistic threats by stopping bullets, but is stopping the bullet really all that’s important?
One of the primary concerns associated with body armor is the phenomenon known as back face deformation (BFD).
This article will provide an explanation of back face deformation, its dangers, how it is worse with some types of armor, and ways to mitigate its effects.
What is Back Face Deformation?
Back face deformation occurs when a bullet strikes the outer surface of body armor, causing the armor to flex and deform on the side facing the wearer’s body.
This deformation results in blunt force to the wearer, even though the armor successfully stops the bullet from penetrating.
The extent of back face deformation is typically measured in millimeters and is an important judge in determining the overall effectiveness and safety of body armor.
The National Institute of Justice (NIJ) is the independent rating authority of body armor and accepts up to 44mm of back face deformation as a passing score. To put this into perspective that’s 1.73 inches of deformation that wasn’t there before the plate was shot. If you are wearing said plate, that’s going to hurt, a lot.
Dangers of Back Face Deformation
Although body armor may prevent a bullet from penetrating, the blunt force trauma caused by back face deformation can still result in serious injuries, even death.
The force of the impact can cause severe bruising and contusions leading to a lot of pain and discomfort.
In more dramatic examples, the force of the impact may be strong enough to break ribs or, cause further complications that require medical attention.
Have you ever had a broken or bruised rib? I don’t recommend it.
The energy transferred through the armor can cause damage to internal organs, potentially resulting in life-threatening injuries.
In the most severe cases, the blunt force trauma caused by back face deformation can be fatal, particularly if the impact causes damage to vital organs such as the heart, liver, or lungs even though the bullet was stopped by the armor.
Armor Material and Back Face Deformation
Soft body armor, typically made from layers of woven or laminated fibers is designed to absorb and disperse the energy of a bullet across a larger area.
While this reduces the risk of penetration, it may result in more significant back face deformation due to the flexible nature of the material.
Hard body armor made from materials such as steel, ceramic, or polyethylene, is designed to provide superior protection against high-velocity rounds and rifle threats.
The ridged nature of these plates will help minimize back face deformation.
BFD will be worse based on the size and velocity of the round.
I have seen fast-moving M193 5.56 rounds at 3,300fps create greater BFD than a 30-06 AP round at 2,800 FPS on a level 4 plate.
Steel armor typically has the least back face deformation, due to its rigidity however steel armor requires trauma pads because the plate itself offers no trauma protection.
Mitigating Back Face Deformation
There is really only one way to mitigate back face deformation and that is to put padding between the wearer and the bullet. Also known as Trauma Pads.
As mentioned in What You Need To Know About Traumam Pads article, trauma pads are designed to be worn behind body armor plates to help absorb and disperse the energy of an impact.
This can significantly reduce the severity of back face deformation and the associated risks.
You can also use soft body armor to accomplish this task, which has the added benefit of possibly catching a round if it squeaked through the armor plate but was slowed significantly enough.
Choosing body armor with advanced materials and construction techniques can help to minimize back face deformation.
For example, advanced ceramic plates and ultra-high molecular weight polyethylene (UHMWPE) can provide better energy absorption and dispersion than traditional materials.
Materials and construction play a large factor in back face deformation.
A general note is the rigidity of steel lends itself to the least deformation.
However, I advise wearing trauma pads with steel for blunt force trauma, which steel does nothing to mitigate.
Ceramic composite armor typically has a ultra-high molecular weight polyethylene (UHMWPE) as a backer, usually about .5 inch thick.
This helps absorb the blunt force of the bullet and distribute it leading to less deformation.
Pure polyethylene armor has the greatest back face deformation because it lacks a ‘strike face’ of ultra-hard material.
It can still stop certain rifle rounds but will be thicker than other materials in order to do so with acceptable BFD.
It is very important to select body armor that has been rigorously tested and certified to meet established performance standards set by the National Institute of Justice (NIJ).
This ensures that the armor has been proven to provide an adequate level of protection against back face deformation.
Back face deformation is a concern when considering body armor for personal protection.
Understanding the dangers associated with back face deformation allows the user to make the most informed decisions when purchasing plates, as well as choices to minimize this risk.
The opinions expressed in this post are those of the author and do not necessarily reflect the views and opinions of Tacticon Armament.