Cost and strength determinationsPlates designed for infantry use and plates designed for mass production are invariably going to cost different prices, with mass production being chaper. A standard
AR500 steel plate for the chest, which is actually less than 1 square foot in area (10 x 12 inches, or 120 inches, 1.2 times less than a full square foot at 144 inches) is approximately 65 dollars, giving a price fairly close to 90 dollars per square foot for a quarter inch of steel. However, an
AR500 half inch thick steel plate designed for target practice that's 22 x 30 inches is only 300 dollars, which equates 4.6 square foot or 65 dollars per square foot, for half an inch, double the thickness, which is over half the price of standard AR500 steel plates. Buying in bulk often saves prices, and so on a large vehicle the price of the armor is likely to go down. How much so depends on the product, with as much as half the reduction in price being possible. This is in part based on manufacturer's intent, and in part based on the price of cutting, with cutting or shaping of the armor being a large chunk of the price, especially when that requires CNC lasers. For titanium this is particularly true, being 9% of the earth's crust and almost as common as iron while being more common than even nickel or zinc, but being very hard to process. Titanium alloys are used instead, when reduces the price, and new manufacturing methods have dropped the price considerably in recent years, hence it's use in the M240L, Mk. 48 and M777 howitzer. Titanium is an attractive option, because it is just as strong but only twice the price of steel,
whilebeing 40% lighter weight, and is inherently temperature and corrosion resistant, being submersible in salt water without accruing much damage. While a protective coating can be used instead to prevent corrosion, titanium is nice to have, and typically a bit stronger, although more brittle than steel. Titanium
plates are approximately 6.2 pounds, or 7.5 pounds per square foot, a bit lighter than AR500 at 10 pounds or more, or between 25-35% lighter, but 150 dollars per plate (2-4 times more expensive than AR500, although in mass production it's likely cheaper).
Dyneema, is perhaps the strongest material for it's weight, but is best paired with a ceramic to give it the ability to stop armor piercing rounds. At least 5-6 pounds are needed per square foot in order to stop and armor piercing 7.62mm x54mm, with 5 pounds being used on Navy seal boats, and 3.3 pounds per square foot or 2.75 pounds being used for hard plates to stop level III-A.308 rounds. Certain types of dyneema configurations are stronger, such as those with a dome shape or reinforcing matrix, which is not as commonly used. By
itself 3.3 pounds are needed per square foot to stop a .308, and 6 pounds are needed for an armor piercing rounds, with slightly less if a ceramic outer coating is used. Nonetheless this results in the lightest armor possible, although it is expensive, around 200-400 dollars per square foot. Going by .308 plate prices it's 200 dollars, but mass production is often cheaper.
Ceramics are not stronger than steel per say, but their high hardness is able to stop bullets steel often cannot, such as tungsten tipped armor piercing rounds, which is why they are better for use against high end threats, but often requires a backing of kevlar or dyneema, or another material. Ceramics are also cheaper in mass production, and can be made stronger via a superior configuration, such as using a chobham style armor matrix to increase the strength and reduce the chance of the entire sheet of material cracking at once. Chobham armor is often more expensive due to the difficulty of making the armor, but can be mass produced if some strength is lost, as the tightness of the tiles in the matrix determines it's strength. The looser the tiles the lower the price, and the weaker the armor. Exacting pricing various considerably based on performance type.
Ceramics are the most difficult to determine, with a wide arrangement of prices and configurations available. The best are dyneema backed ceramics, with ceramics of different types being used. At approximately 7 pounds and 300 dollars per plate [
1], ceramic armor varies widely but is consistently around this weight and size when backed with dyneema, although it can be
more or less depending on the armor type. Mass production armor is bound to be cheaper, especially if it is not curved, but how much so depends heavily on production style.
AR500 ceramic armor for example is only 150 dollars per plate, but 7.5 pounds instead. This comes down to approximately 8.5 to 10 pounds per square foot for the armor, with the lightest
plate being 4.4 pounds, or 5.3 pounds per square foot at 400 dollars per plate, or 480 per square foot . Like AR500 steel, doubling the thickness usually allows for .50 caliber protection (up from .30 caliber), and tripling it allows for slightly better protection than that. Ceramic armor is decidedly more expensive at 150-360, or even up to 480 dollars per square foot (multiplied by the thickness needed to stop certain rounds, single double or tripple), but some variants are comparable to dyneema or titanium armor.
Kevlar and Twaron are the most difficult to determine. While widely used in many vehicles, such as the Humvee and Stryker, their strength varies considerably and often is not very good in comparison to other sources. Twaron by far is better than kevlar due to it's higher chemical, UV, and heat resistance, as well being better at both high and low velocity projectiles, but has only recently come in to use. Kevlar and Twaron suffer from high brittleness and low hardness which marks them susceptible to high velocity or armor piercing rounds, and thus while it's energy absorption is high, it's ability to stop bullets is lower than it's strength would suggest, especially against rifle rounds. Twaron and Kevlar are best used as a backing to harder armor, such as steel or ceramics, to increase the overall strength and energy absorption, and to absorb fragmentation, but not stop projectiles themselves. Humvees for example ran Kevlar and Twaron are approximately 1 pound for level III-A armor, and 5 pounds for the ability to stop a 7.62mm x 51mm NATO round, but the truth is that armor piercing rounds will get though, as well as other high velocity rounds. The effectiveness depends on the surface material which will fragment or break-up rounds before it enters the softer armor below, and to reinforce the armor without needing the same weight. So, instead of using .75 inches of AR500 armor, you might use .5 inches with 5 pounds of backing from kevlar or twaron to boost the strength and impact resistant. It also increases volume, which has an effect similar to spaced armor, as typically a pound or so of material is 1 inch thick, much more than steel. Typically, this armor is made in to laminated sheets and hardened through the use of epoxy resin and pressure, which can weaken it a bit given that less material is kevlar or twaron, but strengths it by making it harder. It typically ends up being the same strength as kevlar, but can be slightly more or less depending on the configuration.
AR-500 Steel- Plate comparison, 10 pounds per square foot, 35-80 dollars per square foot
8,000 pounds (4 tons) for .25 inch, 16,000 pounds (8 tons) for .5 inch, 24,000 pounds (12 tons) for .75 inch.
Titanium- Plate Comparison 7.5 pounds per square foot, 80-150 dollars per square foot
6,000 pounds (3 tons) for .25 inch, 12,000 pounds (6 tons) for .5 inch, 18,000 pounds (9 tons) for .75 inch.
Dyneema- Plate comparison, 3-6 pounds per square foot (.7 to 1.4 inches) 100-200 (200-400) dollars per square foot
4,800 pounds (2.4 tons) for 7.62mm, 9,600 pounds (4.8 tons) for .50 caliber, 14,400 pounds (7.2 tons) for .75 inch.
Ceramic - Plate comparison, 8.5-12 pounds per foot, 300-400 dollars per square foot,
150 dollars
6,800 pounds (3.4 tons), 13,600 pounds (6.8 tons), 20,400 pounds (10.2 tons)
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