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Old 04-24-2011, 03:11 PM
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Default DIY Armor Panels



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There's been a number of threads on these boards discussing home made
body armor and armor panels. Here's my contribution to the mix.

Inspired by an episode of Myth Busters, I made up some test panels
consisting of an assorted mix of polycarbonate and ceramic tile.

Polycarbonate is the plastic layer used to make bullet-resistant glass.
It's also used to make safety glasses, and the glass around hockey
arenas. It's probably most commonly known by the brand name "Lexan".
My variant happens to be called Tuffac. The thickness I used is nominally
sold as 1/4", but it actually measure just a nudge less, at about 0.20".
I have a place semi-close-by that sells plastic scrap, so I can often find
panels up to 48" long by 16" wide for $1 per pound in their scrap bins.
Significantly more expensive if ordered from a commercial retailer.

The tiles were obtained from Lowes, without a lot of science or research.
I just selected some lower-budget tiles that felt the heaviest, associating
"denser" with stronger. Maybe correct, maybe not. They were 0.38" thick.

Then I started gluing the test panels together. I made some that were
just polycarbonate layers, and some that were alternating layers of tile
with a polycarbonate layer backing. I used Liquid Nails adhesive to bond
the layers together. (Polycarbonate is actually commerically bonded with
some sort of nasty, watery chemical that chemically welds the layers
together. Far superior to Liquid Nails, but I didn't feel like tracking down
any of the special chemical for this little adventure. I can track down the
chemical name, if anyone is interested.)

The test panels were 4" x 4" square.

OK, on to the testing results. We were a little short on time, so we didn't
test as many calibers as I had originally planned, but I think we got a
pretty decent sampling for a first run.

Shooting range was about 30' (wanted to make sure we got good hits on
the test panels without a lot of off-centered strikes). The panels were
duct-taped to 1-gallon water-filled plastic milk jugs.

Single layer of Polycarbonate vs. .22 LR: This will stop a pellet from
a .22 RWS model 34 air rifle quite handily. However, a .22 long rifle from a
Marlin 795 punched a clean hole, and went on through the milk jug.

Single tile and single layer polycarbonate vs. .22 LR: This stopped
the .22 LR dead in it's tracks. The milk jug stayed intact. The ceramic tile
however shattered into a number of fragments. So it worked, but it's a
pretty much single-use panel.

Double layer polycarbonate, no tile vs. .22 LR: This also stopped
the .22 LR cold. There's a clean hole in the first poly layer, and the
back of the second layer has a minor bulge. But the milk jug escaped
unharmed. The two layers of polycarbonate did however completely
delaminate. The Liquid Nails just isn't up to the task of that impact.

Single tile and single layer of polycarbonate vs. .40 SW: Next we tried
a .40 caliber handgun. Surprisingly, the panel worked. Now, there was
absolutely nothing left to be found of the ceramic tile. Pretty much just
vaporized. However, the polycarbonate backing layer was entirely
undamaged. The milk jug did burst from the shock of the impact.
However, note that we were using 4"x4" tiles. A larger armor panel would
distibute the load better.

Double layer of polycarbonate, no tile, vs .40 SW: The .40 caliber
just barely managed to breach the two layers. There's a tiny hole in the
back of the second poly layer, maybe 1/8" in diameter. So just fragments
of the bullet got through. However, it was still enough to penetrate both
sides of the milk jug.

Triple layer of polycarbonate, no tile vs. 40 SW: A triple layer of
polycarbonate stopped the .40 caliber. The milk jug bulged and buckled
seriously, but didn't rupture.

We also tested a 9mm against the same configuration of armor panels, and
got absolutely identical results, right down to the minor penetration of
fragments through a double layer of poly.

OK, pretty decent results so far. The ceramic tile with a polycarbonate
backer layer seems to do the best at absorbing and blocking penetration,
but at the cost of a shattered tile every time. We decided that a triple
layer of polycarbonate was superior. Tough, light, and bullet-proof against
some serious high velocity pistol rounds. Testing a .44 magnum and a .357
magnum are in the future, but we didn't bring any on this first test run.

So we decided to step it up to the other end of the spectrum. Out came the
.308 rifle. No sense screwin' around, so we taped together four layers:
Tile / polycarbonate / Tile / polycarbonate. Those four layers add up to over
an inch of thickness. That seems like it's approaching a practical maximum
of becoming too bulky to be wearable. It's also heavy, with the two layers
of tile. However, we figured if anything could fragment and absorb the .308,
it would be two layers of tough ceramic tile. Yeah, total FAIL. I can't
really describe what happened to the first three panels. They're just gone.
Never did find them. I suspect the tiles were just powderized. We found one
small chunk of the first polycarbonate layer. So it will fragment under a hard
enough impact. All we could really lay our hands on was the last layer of
polycarbonate backing. It had a hole clean through. Now the hole was a
touch over 1/2" in diameter, so the bullet was starting to expand. But
not nearly fast enough.

So what did we learn:

- A tough ceramic tile is slightly superior to a layer of polycarbonate, but
it fragments completely on a single hit. The polycarbonate generally holds
together much better and it's ligher. The nod goes to the polycarbonate by itself.

- Liquid Nails ain't the glue for body armor panels. Get the professional
chemicals, or better yet, just buy the full thickness of polycarbonate you
want right from the supplier.

- You can stop some serious pistol rounds, and 3/4" of polycarbonate is
up to the task.

- And if someone points a high-powered rifle at you, either pray, or duck,
because this home made armor has about the same protective benefits
as a screen door.

- Oh, and if nothing else, its an interesting object lesson in what professional
grade body armor and panels will get you. Maybe -- if it's your rear in the
line of fire -- you should have spent some money on professional grade
gear instead of trying to cobble together some home made stuff on a
shoe-string budget. But still interesting to tinker around with.

As a side note, most of my shooting in the past has been done at controlled
shooting ranges, punching holes in paper. But I recently bought some rural
property, so we played without the adult supervision of a range master
barking over our shoulder. Holy Cow! Shooting reactive targets is a world
of fun! Watching a 1 gallon milk jug leap 10 feet in the air and explode into
a cloud of water has us laughing our tails off.

And it also drove home the point of gun safety once again. Watching the
incredible amount of energy being delivered into that water jug was truely
shocking. Don't want to even think about being on the receiving end of that.

Anyway, that's all for now. Maybe some useful info for anyone wanting to
tinker with their own armor panels. Just wanted to share a few successes
and failures.

Sorry, no pictures. There just wasn't enough left of many of the panels
to get any decent photos.
Old 04-24-2011, 05:13 PM
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thanks for the detailed experiment, maybe try the polycarbonate panels with one of the cheap European Kevlar vest
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Old 04-25-2011, 05:00 PM
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Great information and write up.

You need something solid like a metal plate to deform the bullet prior to it hitting the polycarbonate. But even with that a full metal jacket would still punch through it. If I recall (guess) correctly the ceramic plates in the tactical vests of SWAT and military are about 5/8" or 3/4" thick. They usually stop the round or deform and slow it down enough for the kevlar to catch it. The trick is trying to move fast enough to line up the ceramic plate with the incoming round. Thanks to the world of video games and gang executions it is hard to prevent injury from the way too common headshot.

Still interested in more results when you get them.
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Old 04-25-2011, 09:53 PM
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I'll help you out a little bit here. You're learning some good stuff, so I'll help with some understanding.

The layers are a key part of how ballistic armor works. If you were to, or wanted to, purchase a piece of bullet resistant polycarbonate, go here:
http://www.mcmaster.com/#bullet-resi...bonate/=c1c9yy
and when you get it, you'll see its actually layers of different grades of clear plastic. Not cheap, and I got a piece of it for the R&D lab I work in. Never wound up using it, but it's not that big anyway. I've supported a project that developed materials with ballistic properties, and got to gawk over several samples shot with a laboratory AK-47.

Airplane windshields are made from alternating layers of glass and plastic. Glass is actually one of the strongest materials, but it's so hard, it's brittle. However, the amount of energy it takes to break a piece of glass is actually a lot, but since it propagates cracks like crazy, it has to get backed up with something. Layer it with plastic sheets and the glass serves to dissipate the energy outward, perpindicular to the angle of impact. It breaks apart because that's what absorbs the energy. If you contain the glass as much as possible, the energy it takes to dissipate that energy continues to go up.

Your car windshield is two layers of glass, with a very high temper (like pyrex) separated by a thin film of plastic. The temper ensures that it breaks up into lots of very small pieces, and the plastic contains the pieces, which in the end provides a very safe and clear window you can see through, all the while breaking up into smaller, safer pieces while it's absorbing lots of energy. The plastic allows a heavily splintered windshield to stay in one, albeit floppy, piece, which protects the car occupants even more.

With the layers of ceramic and lexan, you've contained the ceramic tiles from flying apart, and the ceramic absorbs most of the energy. The ceramic is the sacrificial energy absorbtion mechanism while the plastic contains the bulk ceramic and helps it absorb more energy.

Ballistic protection for windshields and the like, unfortunately, isn't very well understood, and its mostly trial and error with a little true science behind it. However, what I just gave you is a small tidbit of useful information. Since you now understand just enough to be dangerous, you may proceed with more adventurous experiments.

Some things to think about: When you secure the ceramic tiles between the lexan, try completely encapsulating the tiles with something soft and squishy like RTV or some sort of silicone compound (two part.) A key component is layering materials with significantly different properties such as hardness, toughness, softness, and so on. The Lexan, as tough as it is, tends to stretch a lot under impact, which passes the energy through the material while still retaining its strength. The glass does the absorbing. What it can't absorb it merely passes on to the next layer. Try lexan and plexiglass type materials, and put a little air space between the layers. Put a thin sheet of something soft like polyethylene in there. Fiberglass sheet would be a great choice as well. Carbon fiber or Kevlar. Heavy cloth, even. Remember that silk was the material that up the first bullet resistant vests. It essentially acted as a "catcher's mitt" for the bullet, but left you with massive bruises and broken ribs. Interesting history there as well.

I'm interested in what you learn. My interest is strictly what can be made out of easily available materials and will last long enough to do the job (once a ballistic windshield has been shot, it's toast and has to be replaced, and there is no ballistic window that can take multiple shots and survive; the energy it has absorbed is too high.)

Most of all, have fun and be safe.
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Old 04-25-2011, 10:09 PM
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Forgot to add one thing. The size and mass of the sample means a lot. A small sample can't absorb as much energy for a couple reasons. One, it's a relatively low mass with no inertia up against a smaller mass with a lot of inertia. The energy being diverted outward towards the sides, if it runs into an open A larger test sample will behave a lot differently than a smaller one. Try mounting your samples in a plywood "window." Let the plywood be part of the energy absorbing structure, or even a layer in the "stack."

There's another key component I should add. If you have a panel of something rigid, when it gets hit, the impact will spread out and the surrounding surface can even ripple like water (I've seen it on the samples I mentioned and on high speed video.) This is actually ideal, because it's true redirection of the energy. Redirection of the energy from the impact is better than trying to absorb it locally. The physics get complicated from here on out, but you can get a good feel for how things behave with some experimentation. If you could video record the impacts, you'll only be able to play it back with more cameras at a slow frame rate, but even that will tell you a lot.

Last edited by CarlMc; 04-25-2011 at 10:23 PM.. Reason: forkin' new eyes; can't see sheep!
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Old 04-25-2011, 11:01 PM
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Though I wouldn't use solids like in your tests for body armor, it is interesting for hardening other things. I have wondered about layers of sheet metal/plywood/polycarb in various configurations. The theory being, first layer breaks up and or mushrooms the round, the plywood absorbs and slows the fragments and particles and the last layer catches them.
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Old 04-26-2011, 08:17 AM
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Thanks for all the feedback. Based on what I saw, and all the info everyone
provided, I think a "generation 2" test panel might be a tile with polycarbonate
backing, and the whole thing wrapped in a kevlar outer layer. Maybe use
a fiberglass resin to bond the whole thing together. The ceramic will still
shatter, but it would keep it all intact.

I'll post new results when I get some new panels made and tested.

(In the end, would have been cheaper to just buy a commercially made
armor panel, but hey, where's the fun in that?)
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Old 04-26-2011, 08:28 AM
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The fiberglass resin by itself won't gain you much; it's too brittle. Glass fiber added will. The longer the strands you can use the better.
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Old 04-26-2011, 06:32 PM
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I like to dissect armor. The average sapi or esapi ceramic plate nowadays is 4.5 mm thick. This is less than 3/16 of an inch. The idea is to get a tile that has the highest hardness you can. this breaks the bullet up and starts the process. everything behing that is meant to catch the fragmentation. It sounds like you have a great start. If you duct taped the entire sample thoroughly as well as assured that the entire back was glued or siliconed down, the tile would stay together and take multiple hits. This is why a ceramic esapi is wrapped in kevlar and usually has a thick coating (similar to bedliner) around it. other items that are lightweight and make great backer for the homemade route are- HDPE- polyethylene (commonly used in the soft type white cutting boards. Sections or tire (not sidewall) with the radial in it, hardened fiberglass layered (like sections of scrap boat hull. Also aluminum would be great to put behind the tile to aid in fragmentation. try to encapsulate the tile so it can break repeatedly without falling out of the test sample- maybe sandwich it between 1/8" aluminum- then duct tape tightly around everything. i love the homemade armor stuff- great topic that is lots of fun- thanks
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Old 04-26-2011, 06:34 PM
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the 4.5 mm i refer to is the thickness of the ceramic alone- not the whole plate- most have 1/2 to 3/4 inch of unidirectional spectra or dyneema behind them- just to clarify above
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Old 04-26-2011, 08:32 PM
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Quote:
Originally Posted by tactical1 View Post
This is why a ceramic esapi is wrapped in kevlar and usually has a thick coating (similar to bedliner) around it.
That reminds me. I saw something years ago about some military testing where they sprayed bedliner material on a cinder block wall to improve it's blast resistance properties. Googled it and they said that while the blocks took a beating, the wall stayed together and didn't allow any shrapnel into the area protected by the liner material.

That's useful information to ponder in your quest.
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Old 04-26-2011, 08:55 PM
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I am going back a few years when I did private security, but the standard for bullet proofing that was expectable by the NYS banking department for insurance purposes was 1.5 inch "Lexan" that would stop up to a 12 gauge slug. as per the information given to me anything else would provide some protection but would not withstand multiple hits
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Old 04-26-2011, 10:17 PM
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If you were to have a larger piece, I think it might be beneficial for use against multiple impacts if the tile layer was comprised of smaller sections of tile. That way when one piece of tile shatters, it's neighbors are still good to go. Really, the polycarbonate should be the one dissipating the energy, right? Perhaps have a layer of thick canvas or kevlar on the back of the polycarbonate to catch any fragments from the polycarbonate if it undergoes a partial failure.

Oh and for anyone suggesting any metal in this project, a 1/4" of steel plate you find in a scrapyard is not the same as 1/4" of steel RHA.
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Old 04-27-2011, 12:59 AM
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I would look into finding some kevlar weave or the generic kevlar/nylon that is available (which is almost identical). Being that both the polycarbonate and kevlar are petroleum products they can probably be fused together with a solvent of some kind. I'd try bonding it to either one side of the plastic of both. If it can somehow be bonded to the ceramic tile that would be very effective I would think.

Also, I have seen sheets of 1"x1"tile strung together in larger 12"x12" or 16"x16" sheets. These might be interesting to take a look at as a bullet would shatter one small tile and then the remaining tiles would still be able to absorb following shots..
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Old 04-27-2011, 12:07 PM
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Quote:
Originally Posted by tankman1989 View Post
Also, I have seen sheets of 1"x1"tile strung together in larger 12"x12" or 16"x16" sheets. These might be interesting to take a look at as a bullet would shatter one small tile and then the remaining tiles would still be able to absorb following shots..
Several things to think about when approaching this plan. The amount of energy that a small tile can absorb is obviously very small, and what it doesn't absorb will get passed on through to the next layer. The larger and thicker the tile that you use, the more energy it will absorb. This is part of the compromises that scientists and engineers have to make, balancing the energy distribution (the non-brittle layers) and the energy absorbtion (such as the tiles) until it all works.

However, it's is foolish to think any ballistic material will be able to do its job for more than one impact. All it buys you is the opportunity to save yourself befor the next impact. The first impact creates fracture lines spreading out from the point of impact. When the next impact comes along, the shock wave will stop at those fracture lines, and the material won't be able to absorb much energy at all, and none beyond that first fracture line. Any change of feature, such as a fracture line, crack, groove, side of the tile, and so on, will have an energy absorbing _arresting_ component, which is what you want to avoid. So in essence, you want the largest, thickest tile you can fit in there, as rarely will someone hit the exact center of your tile, which is where it will do the most good.
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Old 04-27-2011, 10:42 PM
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Quote:
Originally Posted by CarlMc View Post
So in essence, you want the largest, thickest tile you can fit in there, as rarely will someone hit the exact center of your tile, which is where it will do the most good.
Well, it seems the first test had an adequate tile size. What you say is true, but if you have more tile pieces then wouldn't that increase the chance of the center of the tile catching the bullet (thus being more efficient) rather than one large one? If weight restrictions allow, a second layer of tile that is situated on the gaps of the first tile layer should be more than sufficient to counteract the inefficiency of a smaller tile vs larger.

Perhaps thinner tiles layered in scales, with a backing of polycarbonate to maximize coverage against multiple impacts without compromising the overall integrity of the armor. Then, behind that, a final layer of polycarbonate in a solid sheet with a backing of kevlar for spall.
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Old 04-28-2011, 04:13 AM
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Testing of ballistic armor is also done over a clay backing to measure its deflection. You might be able to stop the round but if the deflection is deep enough you can still very well die either then or hours/days later from internal bleeding and so on. Grant it, thats probably better than a having a small hole in the front and big hole in the back of ya... but depending on the weight and bulk of the material I might be more inclined to take my chances without it.
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Old 04-28-2011, 02:33 PM
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Quote:
Originally Posted by Risky View Post
Testing of ballistic armor is also done over a clay backing to measure its deflection. You might be able to stop the round but if the deflection is deep enough you can still very well die either then or hours/days later from internal bleeding and so on. Grant it, thats probably better than a having a small hole in the front and big hole in the back of ya... but depending on the weight and bulk of the material I might be more inclined to take my chances without it.
My low-budget approach to that was to use 1-gallon water filled plastic milk
jugs behind the armor panels, on the notion that the jug might provide a
passing similarity to human skin, tissue, icky innards. I figured that would
be a more realistic simulation that backing the armor panel up with a
sand bag, wooden board, etc. which would probably affect its performance.

But as you noted, the clay provides a way to actually measure the blunt
force trauma, while the milk jug provides little in the way of feedback.
(I did notice the jug bulged alarmingly under the impact of the .40 caliber,
but no real way to quantify that -- aside from -- "wow, really bulged.")

Agreed -- just because the armor panel doesn't get breached doesn't
mean the target hasn't taken a serious hit. A 40 mph hit from a Buick
probably wouldn't breach the panel either, but I'd probably look a bit
worse for wear after the impact.

Thanks again to everyone for the feedback. I'm learning a lot.

Sounds like for my release version 2A, I need to find a better method
of constraining the tile material from fragmenting (maybe three layers -
poly - tile - poly), and maybe a kevlar or carbon fiber wrap around the
whole panel assembly with a resin binder to keep everything together.

And I'll snoop around to see what sort of clay backer I can come up with
to gauge the blunt trauma of the impact.

I'll take a look at the segmented tile approach. I know the ones in question.
Typical for showers, bathroom floors, etc. 1" tiles +/-. My concern with
those is the gaps between the tiles. But maybe a two layers of the tiles,
offsetting the gaps would work.
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Old 04-29-2011, 09:07 AM
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Quote:
Originally Posted by Voracity View Post
Well, it seems the first test had an adequate tile size. What you say is true, but if you have more tile pieces then wouldn't that increase the chance of the center of the tile catching the bullet (thus being more efficient) rather than one large one? If weight restrictions allow, a second layer of tile that is situated on the gaps of the first tile layer should be more than sufficient to counteract the inefficiency of a smaller tile vs larger.

Perhaps thinner tiles layered in scales, with a backing of polycarbonate to maximize coverage against multiple impacts without compromising the overall integrity of the armor. Then, behind that, a final layer of polycarbonate in a solid sheet with a backing of kevlar for spall.
I think you're missing the point of what Carl was trying to say. the bullet impacting in the center is indeed best, but meaningless if your tile is small. Compare it to snapping a towel. The SNAP of the towel is the excess kinetic you've put into coming out the other end. Now, is it easier to snap a handtowel or a jumbo shower towel? the handtowel of course, because it can't deflect/absorb as much of the energy. There is more excess energy released because there's less area for it to be deflected/absorbed.

Same concept with the small tile. the bullet can hit it dead center, but the energy will only deflect/absorb according to the amount the tile is capable of handling, which is determined by it's size/mass. a small tile will accept energy up to the edge of itself, and at that point can no longer take anymore, so whatever is left over (which is a lot when you compare a small tile vs high energy projectile), is retained in the projectile and continues forward.
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Old 06-14-2011, 10:13 PM
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Nice project

What your building is a nice prototype, but I think a tile is hard to utilize as body armor. Maybe try working with laminations that can be shaped to fit over a vest or atleast contour to your body or even plates on a backpack so you can lie down behind it for emergency cover, also not get shot in the back.

You should layer stiff and flexible materials, like metal screens, truckbed liner, fiberglass mat fabric or carbon fiber, its both strong and flexible, epoxy resin, even thin plexiglass heated to mold to desired shape, panels cut from milk jugs and shaped with a heatgun or hairdryer, bamboo, porcelain is stronger than ceramic, maybe even a layer of pennies or nickles, or resin mixed with polyester rope fibers, metal

Im trying to build a plate for my backpack, I'm thinking a few dozen layers of metal screen, fiberglass, rhino liner, and epoxy resin
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