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: https://www.youtube.com/watch?feature=player_embedded&v=LxoYwUPOmBE 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: https://www.youtube.com/watch? feature=player_embedded&v=oPvaDs-mibc The armor successfully stopped 9mm Ball FMJ bullets with multiple shots fired from a pistol barrel.
Homemade Bulletproof Armor - Ceramic / Fiberglass Shard This armor is a ceramic-fiberglass composite constructed from an ordinary bathroom tile and fiberglass woven roving which are glued together with polyester resin. Either porcelain or ordinary ceramic tile can be used. Check out the video here: https://www.youtube.com/watch?feature=player_embedded&v=L3IfUiq1ocE The basic design is to encapsulate the tile in a sheet of fiberglass and resin, where there is at least one layer on the threat side to keep it held together and control fragmentation, and many more layers on the back side to capture and prevent spall. The idea is that the hard tile will fracture or blunt the incoming bullet so it can be stopped with fewer layers of fiberglass than an armor that is made from only fiberglass. The fiberglass fabric is cut to the right size with a sharp box-cutter blade, the tile centered on the ply, and the excess material is folded around the back. This gives 1 layer of fiberglass on the front, and 8 layers on the back due to the folds. This will thicken the tile by about 1/8th of an inch. The shard is saturated with resin and clamped between two wood sheets using saran wrap as a mold release. An additional armor shard was constructed with two sheets of woven roving which gives 2 fragmentation layers on the front and 16 spall layers on the back. This was done to provide another
test piece in case the first armor piece failed to stop the bullet. The armor pieces can be any size, which is dictated by the size of the tile used. The two armor pieces were created with a tile that 4.25" square. The armor "shards" can either be incorporated into a larger solid panel, or perhaps used individually in an overlapping configuration to create a flexible vest. Either way they are easy to construct and test in bulk without using much material. Test Results and Analysis: The first armor tile with 1x8 layers successfully stopped a single 9mm FMJ bullet fired from a pistol-length barrel. The second piece also stopped 9mm without any issues. Therefore it was determined that a single ply of WR is all that is needed to make this armor stop one round of 9mm FMJ. Multiple shots to the same piece were not tested. The video of the test is here: https://www.youtube.com/watch?feature=player_embedded&v=SVpYUNi9zMo The 1x8 tile below with the bullet fragments extracted from the front using a pair of needle nose pliers. The full metal jacket bullet was completely mushroomed and broke into multiple fragments within the tile itself - I didn't find any evidence that the fragments even reached the spall liner.
There were numerous granules of the ceramic tile in the impact crater as well. The combination of the bullet and armor fragments (spall), and have been easily caught by the layers of woven roving on the back of the tile.
It would be interesting to see what additional pistol bullets that this armor could stop. Scribed by mindtomachine at 11:53 AM No comments: Links to this post
