Bullet-proofing Your Car With An Affordable Composite Armor

Remember those actions movies like The Fast and the Furious where cars are constantly getting smashed by fast flying bullets? What would it have taken to protect the vehicles from AK-47s? In [PrepTech]’s three-part DIY composite vehicle armor tutorial, he shows how he was able to make his own bulletproof armor from scratch. Even if you think the whole complete-collapse-of-civilization thing is a little far-fetched, you’ve got to admit that’s pretty cool.

The first part deals with actually building the composite. He uses layers of stainless steel, ceramic mosaic tiles, and fiberglass, as well as epoxy resin in order to build the composite. The resin was chosen for its high three-dimensional cross-linked density, while the fiberglass happened to be the most affordable composite fabric. Given the nature of the tiny shards produced from cutting fiberglass, extreme care must be taken so that the shards don’t end up in your clothes or face afterwards. Wearing a respirator and gloves, as well as a protective outer layer, can help.

After laminating the fabric, it hardens to the point where individual strands become stiff. The next layer – the hard ceramic – works to deform and slow down projectiles, causing it to lose around 40% of its kinetic energy upon impact. He pipes silicone between the tiles to increase the flexibility. Rather than using one large tile, which can only stand one impact, [PrepTech] uses a mosaic of tiles, allowing multiple tiles to be hit without affecting the integrity of surrounding tiles. While industrial armor uses boron or silicon carbide, ceramic is significantly lower cost.

The stainless steel is sourced from a scrap junkyard and cut to fit the dimensions of the other tiles before being epoxied to the rest of the composite. The final result is allowed to sit for a week to allow the epoxy to fully harden before being subject to ballistics tests. The plate was penetrated by a survived shots from a Glock, Škorpion vz. 61, and AK-47, but was penetrated by the Dragunov sniper rifle. Increasing the depth of the stainless steel to at least a centimeter of ballistic grade steel may have helped protect the plate from higher calibers, but [PrepTech] explained that he wasn’t able to obtain the material in his country.

Nevertheless, the lower calibers were still unable to puncture even the steel, so unless you plan on testing out the plate on high caliber weapons, it’s certainly a success for low-cost defense tools.

35 thoughts on “Bullet-proofing Your Car With An Affordable Composite Armor

  1. remember to do the floor and firewall as well!!

    way back when, my mate bought an FN-FAL

    we went out to a place “folks” dump stolen cars

    I let go a burst of 7.62 at a Valiant (Chrysler) station wagon

    we had a giggle

    then I looked inside, over the tailgate

    there were these big, jagged holes in the floor, the roof, back seat

    I got in had a look down through the holes in the floor, must have hit the diff, it shattered into biggish chunks of metal, tore through the whole car

    the diff housing, crown wheel, spider gears had all turned into the biggest secondary projectiles I’ve ever seen

    after that we drove away a bit, I let go a whole 30 round mag of FMJ into the engine

    the damage was scary

    1. Ha! I shot an old jeep transmission and transfer case I found in the woods with a 30-30. It took out big pieces of the cast aluminum instead of just making holes. Couldn’t find some of them. 30-30 causes a pretty big impact and 45-70 even more, think I’d rather be shot with any NATO round versus either of those! 45-70 will bust rocks like nothing even from 100yds.

      1. I had an old GM truck block I used to use for target practice

        with my Lee Enfield @200 metres a .303 British 110gr FMJ round would go through without slowing down
        but a 160gr spire point or 180gr round nose just splattered

          1. This bring me to a rant. The current trends in archery are all about energy which drives me nuts because it’s all BS archery doesn’t work that way. It’s all about momentum with archery.

          2. Kinetic energy E_k = 1/2 * m * v²
            Momentum p = m * v
            -> E_k = 1/2 * p * v
            or E_k = p² / 2m

            What do you mean with that and your rant? Velocity is directly correlated with energy and momentum.
            I have no idea of ballistics in general or archery in particular but your statements bug/confuse me.

          3. Well what I mean is that with firearms when shooting tissue the wound/terminal ballistics have what’s called a temporary wound cavity and a permanent cavity. The temporary cavity is all the tissues wounded/destroyed by the “shock” of the impact. It is a direct result of the pressure wave that the bullet strike causes (energy being dumped). The permanent cavity is just where the bullet actually contacts and tears through (momentum). Watch some ballistic gel testing videos on YouTube that have slo-mo of it and you can see the effect. But firearm terminal ballistics has some quirks ie a lot of the time increasing projectile velocity (which increases both Mo & E) results in reduced penetration (in tissue) because of higher fragmentation. Also punching through steel like the persons above reference is totally different than tissue etc.

            With archery, arrows (bolts if fired from a crossbow) never travel fast enough to have this compression wave effect that can destroy tissue and even if there was a minuscule one you’d be better off to sacrifice it for larger permanent cavity. With archery what really only matters is the blade size of the broadhead and how much tissue you can push it through which only depends on momentum.

          4. I think I explained the wrong thing there…

            What I meant about the archery BS was the trends are shooting really light-weight 90 grain (weight) broadheads at the tip of ultra-light-weight carbon fiber shaft arrows at 350 feet per second or some such nonsense. I guess under the guise that somehow having a slightly flatter trajectory is better but it won’t matter when their shot is stopped by a rib of a deer etc.

            The old 145 grain (or more) broadhead on an old aluminum (or cedar) shaft will far outperform the new whiz-bang archery stuff on actually going through game. So maybe it goes 150 fps instead and you have actually be able to estimate range but they will punch right through scapula bones or whatever and do the job humanely. But to each their own.

          5. ah okay, I think now I do understand what you meant.
            I have seen some clips on YT with balisitic gel tests but never thought about the differences between penetration and impact damage.
            Probably never thought about the later one at all….

            From what you said I’d assume the newer arrows are more for sports archery maybe? And less for real world applications.

      2. Careful what you wish for. The 50 cal BMG /12.5 is a NATO round and has around 14,000 ft-lbs of energy. One of the rounds is a 300 grain (23 gram) tungsten penetrator at 4,000 feet per second.

      1. Michael,

        Keep things in perspective. You say we’re scary but we’re talking about doing (admittedly foolish) things having fun. People don’t get hurt. It’s not like if you go to America you’re going to get shot. Keep in mind, England banned guns and now they have to ban pointy knives (what a joke!) because the murder rate in London is higher than NYC.

  2. Coquina is bulletproof. The tiny shells its made of spread the impact and sprays it and bullet back out. Don’t know how thick it would have to be to prevent it cracking and being light enough though. That’s why the Castillo in St. Augustine is made with it. Cannonball would basically bounce off with just a divot left in the wall where the material got blasted out.

    1. When I was at the fort at St. Augustine (18+ years ago), I recall that the walls of the fort (very thick) “swallowed” cannon balls. The rock they used acted like ballistics cotton, slowly absorbing the impact.

      1. This makes sense. Coquina is shells that are poorly sorted and cemented together. Essentially it’s a brittle foam since the shells aren’t compacted well, so as something hits it the shells progressively fail and collapse the surrounding air voids.

    1. I can only assume that this sentence was supposed to be something like:

      The plate survived shots from a Glock, Škorpion vz. 61, and AK-47, but was penetrated by the Dragunov sniper rifle.

  3. This is all well and good, but only works for a single shot due to the nature of the ceramic layer. We’ve done tests on materials that have a similar although more advanced makeup. Upon impact the first round will shatter the cermaic layer in a dramatic manner which extends outward from the POI for a relatively dramatic distance, sometimes exceeding 60cm and greater depending on the round and energy involved. Whenever ceramics break, the energy is pushed outward and due to the high rigidity the energy absorbing cermaic breaks into fine pieces which then are not longer able to absorb/transfer energy afterwards. This means that all subsequent rounds that impact even near the previous one will pass almost unihibited. Gel is preferable because once it *heals* it will be able to retain this ability. Still cool though.

    1. Hence why, per what is specifically mentioned in the video, the person used the grid of tiny tiles with silicone filler between them instead of one large tile like others have done. A couple of tiny tiles are destroyed, but the rest are untouched. They even used two different materials to test the difference in performance between the two.

      1. If you look at approx. 1:33 in his second video he shows a spot where her fired repeatedly into the same area. He states he is very proud of the results, as the bullets did not pennetrate, however if you look, the tiles are *gone*. They provide nothing to stoping that projectile. I am curious as to what exactly is really taking up the energy. I suspect the steel plating and composites are what is actually doing the work.

        1. The powdered remains of the tile that got trapped between the steel and the rest probably distributed a lot of the energy, helping to transfer it to the rest of the thing. It may not be as effective as a proper tile, but better than just air. In addition many of the bullets don’t hit the exact same tiles, and subsequent videos show that the damage doesn’t spread even to the immediate neighboring tiles.

  4. I think you are mixing up the meaning of “caliber”. There are two primary meanings in ammunition and guns. Big guns, like naval guns and artillery have 0ften been rated in “calibers” that are the length of the barrel divided by the diameter of the bore. Giving the caliber and the of round ball shot describer the power, range, and accuracy. An 8 caliber 6 pounder for example. (I wonder if it came from the device for measuring the bore diameter?)

    In modern firearms it means simple bore diameter with metric measure including ‘mm’ and ANSI calibr having and implied decimal point for inches. So, your 9mm (357 caliber) Glock is a bigger caliber than the 7.62 (30 caliber) AK or FN-FAL rounds or the 5.56mm (22 caliber) of the M16.

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