IMPORTANT: Testing of any new design is recommended for those companies or individuals trying to manufacturer bullet resistant items using Kevlar or Spectra / Dyneema Fabrics. It can take many plies of ballistic fabric such as Kevlar to stop a bullet or sharp objects, so testing of any new design is highly encouraged.
Note: We do not have the answer to how many plies your design will need.
KEVLAR® is the registered trademark for a para-aramid synthetic fibers. Developed by Stephanie Kwolek at DuPont in 1965, this high-strength material was first commercially used in the early 1970s. Typically it is woven into fabric or spun into ropes that can be used as such or as an ingredient in composite material components.
KEVLAR® is five times stronger than steel on an equal weight basis, yet, at the same time, is lightweight, flexible and has many uses. Kevlar® Fabric is mainly used in making Bullet and Stab Resistant Vests not only used by the Military and Law Enforcement agencies around the world, but by private citizens as well.