Tuesday, September 04, 2012

Homemade Bulletproof Armor - Fiberglass

I wanted to see how difficult it would be to build a relatively lightweight armor plate that could stop pistol bullets. The summary video how I built this armor is here:

This armor is constructed by layering multiple plies of fiberglass cloth called woven roving. Woven roving is a heavy weave of bundled glass fibers that is very strong, cheap, and available from boat building suppliers. However, when not cured with a resin, it is very flexible and unravels/frays when cutting using ordinary household scissors. Instead I am using a utility knife to cut it on a wooden board, this works well. Scotch tape applied first along the cut line holds the strands together on the freshly cut edge.

After cutting to size, the sheets are layered, soaked with polyester resin, and pressed together using pieces of 3/4" plywood with clamps until cured. The pieces are 1 inch larger in both directions than the final size of the plates, to allow for final trimming.  In this case the final armor plate are to be 12"X10", so the plywood peices are 13"x11".

The plywood needs some sort of mold release applied (I used saran wrap), otherwise when the resin is cured the plywood peices would be glued permanently to the armor. The resin is mixed with the MEKP catalyst in the proper proportions according to the directions, but I added slightly less catalyst to increase the working time. Each sheet was layed in place, brushed with resin to saturate it, and then a new sheet was added. I am fairly sure that every other sheet could have been saturated to save time, with a dry sheet in between. The pressing action of the plywood distributes the resin throughout the layers well, which I tested by leaving the last sheet dry before pressing.

Once the sheets were put in place, I clamped around the perimeter of the plywood "sandwich". The excess resin leaked out on the edges, so I put some newspaper underneath to catch that. It was left overnight to cure. The polyester resin makes heavy fumes so needs to be used with good ventilation.

The result is this once curing was finished:

The saran wrap peeled off easily from both sides of the armor.  I was very happy with how well it worked as a mold release. The resulting plate is very strong.

It is .343" thick. It contains 23 layers of the woven roving cloth and used a pint of polyester resin. I think that probably 1/2 to 2/3 of the resin could have been used instead since so much squeezed out. The armor may have too much resin in it - commercially available fiberglass armor used for buildings is more opaque than what I produced, indicating (I would think) less resin saturation, which will help with de-lamination. It could also be that commerical operations add something to the resin making it opaque, but not necessarily for appearance.

Final trimming would need to used a diamond grit jigsaw or circular saw blade because the plate is extremely tough.

One note here is that fiberglass armor stops bullets by de-laminating to absorb the energy. The layers "catch the bullet" in the same way that a soft kevlar vest does. As a result, epoxy resin should not be used. It is much too strong to allow the sheets to separate and the bullet will more likely punch through the armor. In this thickness, the plate hopefully will be able to stop most shotguns and pistols.

Updated Test Results:

The armor test video is here:

The armor successfully stopped 9mm Ball FMJ bullets with multiple shots fired from a pistol barrel.


smacksak said...

Curious about the test results. How did it fare?

Anonymous said...

I recently purchased two yards of 50 inch wide Class III Kevlar from a firm in Ohio. The cost was about $200. If I put 2 or 3 layers of Kevlar in between the layers of fiberglass what do you think might be the results?
The Old Fart

Josh Davis said...

Hmmm, very interesting YouTube video and a blog for it too! Good to know that there still are some intelligent people out there that still wish to innovate and do stuff in a different way rather than buying it in a store. Keep up the good work!

Anonymous said...

test it allready

Jacob said...

Would one layer of this Woven Roving stop a knife? Would it without the resin, or only with the resin applied?

Anonymous said...

uhm how heavy is it?

-im yolo

Anonymous said...

Where can we find these materials at the cheapest?

Gunner Jacky said...

Most of he gun incidents are caused because of ignorance and negligence of various kinds. You people can also take help from the MA Gun License to get guns and license but more then that you need to do is get proper training and duties that you are supposed to perform while having them.

Anonymous said...


Anonymous said...

Wow that is some great knowledge.thank you sir.