The first bulletproof barriers were made of dirt.
Classic medieval castles were imposing fortifications: Tall, flat wood or stone walls were hard to scale and offered archers a terrific vantage for picking off charging foot soldiers and cavalry. With the advent of gunpowder, it quickly became apparent that these same baileys proved poor protection against cannons and mortars. The solution was to bury the walls. Dirt slopes–called glacis–absorbed and redirected the energy of a cannon round. Although rudimentary, the design is sound, and is even seen today in modern sloped armor for vehicles (often called “glacis plates”).
GRANITE, STEEL, CINDERBLOCK, CONCRETE
While dirt can be an excellent ballistic barrier–earthworks still have a respected place in modern military design–they obviously leave much to be desired, especially in the commercial market: Not a lot of banks are interested in doing business from a hobbit hole.
During World War II military engineers shifted away from relying on earthworks, and instead embraced steel, cinderblock, and poured concrete. These became the first “bullet proof systems” to enter the commercial market. Concrete, stone, and cinderblock are excellent for building bullet proof exterior walls–think of all those small-town granite-block banks–but awkward for interiors, and impossible to add to an existing structure. Although steel plates can be retrofitted and used to line interior walls, the weight of the steel bullet resistant panels calls for substantial reinforcement, often tantamount to building entirely new walls.
Worst of all, these aren’t terribly reliable materials. Poured concrete is notoriously fickle: relatively small fluctuations in temperature or humidity can cause the material to cure improperly, resulting in crumbling and cracking. Granite, as a natural material, can hide all manner of unseen flaws. Steel, brick, and concrete are likewise prone to voids and microscopic fractures that, while invisible to the naked eye, can cause the material to fail under strain or as they age.
Modern fiberglass–a rigid material made from cloth reinforced with liquid resin that is then cured–came into its own during World War II. But it wasn’t until the discovery of DuPont™ Kevlar® fiber and other bullet-resistant para-aramid fibers that bullet resistant fiberglass panels were born. In many ways, these were the ideal bullet resistant panel: Lightweight, easy to produce, and easy to work on site with hand-tools. Fiberglass also has the advantage of being highly malleable prior to curing: making a form-fitting bullet proof helmet is just as easy as making a flat bullet resistant panel. And while bullets tend to ping off of steel, ricocheting unpredictable, a fiberglass bullet resistant panel “delaminates” when struck by a bullet, absorbing the projectile’s momentum and thus minimizing ricochet.
The only hitch is in production. In contrast to steel and concrete, there was a very limited demand for bullet resistant fiberglass. Subsequently, it was produced exclusively by hand in small lots. According to Total Security Solutions vice president Jim Richards “each of these little shops had its own way of laying these panels up and cutting them to size.” Not only does this make it hard to acquire large numbers of these bullet resistant panels for extensive projects, but manual lay-up and finishing are also susceptible to human error and variance in quality and size.
PRECISION PULTRUDED FIBERGLASS
This all changed a decade ago, at the beginning of Operation Iraqi Freedom. At that time just three small fiberglass makers in Texas supplied bullet resistant panels for the entire US Army. But their manual processes couldn’t keep pace with the sudden military demand, which quickly spiked as Homeland Security grants filtered out to local communities. This surge in demand for fiberglass bullet resistant panels attracted large players–and large scale mechanization. Martin Marietta Materials of Georgia was the first large company to make the jump to entirely automated bullet proof panel manufacturing using. Pultrusion doesn’t just speed up and standardize production, but also makes it possible to create arbitrarily large panels–and drives down cost. Suddenly high-quality bullet resistant panels were within the budget of even relatively small businesses.
NEXT-GENERATION CERAMIC BULLET RESISTANT PANELS
While various configurations of ceramic tiles have shown promise in both personal body armor and bullet resistant panels, these seem to be stalled in the “computer-simulated concept art” stage. As a commercial domestic bullet proof system manufacturer, Jim Richards isn’t all that impressed with ceramics. Ceramic plates fail to offer the weight advantages and ease-of-handling fabricators and installers enjoy with fiberglass-based bullet proof panels.