Up until the 1940’s, steel was one of the primary materials in both offensive and defensive arms. During WWII, a new ceramic material was developed for use in antitank projectiles, called Tungsten Carbide, or WC. These penetrators were heavier, harder, and denser than anything that had been used up until that time. At the close of the war, WC was commonly found in most high velocity anti-tank round cores.
WC was extremely hard (much harder than steel plate), but it was also extremely heavy. For armor, at least that worn by personnel, a lighter, yet still extremely hard material was needed. Silicon Carbide, and later Boron Carbide, were first used on armor during the Vietnam War, in derisively named “Chicken Plates.” These were very heavy, and typically were used as improvised seats by helicopter crews to protect against ground fire.
Another material also started to find use in armor, specifically Alumina (Al2O3, which is very similar to Sapphire).
Each of these ceramics underwent significant improvements over the years, both increasing their purity and density (higher purity and density result in better material properties).
Ceramics stop projectiles by a different mechanism than steel plates. While steel plates rely on their combination of hardness AND toughness to cause the impacting round to mushroom, fracture and subsequently splatter (with attendant danger to the wearer), ceramics use a combination of yawing and eroding to render the projectile ineffective. Since the ceramics used in rifle armor are all up in the high 8’s or low 9’s on the Moh’s hardness scale, there are few projectiles that are harder than they are (certain WC cored rounds come close). When a rifle round hits a ceramic plate, there is localized fracturing (causing the projectile to dump massive amounts of its energy) of the ceramic. The projectile will typically yaw off-axis, increasing its frontal area, as well as being eroded by the very hard ceramic particles. These residual projectile pieces are then caught by the backing material of the plate, typically rigid aramid or UHMWPE laminate.
It is important to note that UHMWPE laminates are wholly inappropriate for use in soft armor, due to their sensitivity to heat, poor resistance to contact shots, and poor breatheability. In a hard armor format, it appears that their heat sensitivity is diminished, and breathability is not an issue. It is still not recommended to leave your hard armor containing UHMWPE (either as part of a ceramic plate, or pure UHMWPE plates, more on those next time) in a high heat environment. Specifically, soft armor is at risk at or above 180 degrees, while hard armor is at risk above 200 degrees.
Due to their nature, and depending on their construction, ceramic plates still may experience front face spall, usually consisting of ejected ceramic particles.
Ceramic plates give wearers the option of upgrading their protection level to stop AP (Armor Piercing) rounds that typically blow right through level III plates. Level IV will stop M2AP (black tip) .30-06 rounds, which contain a VERY hard steel penetrator (often found undamaged after punching through up to 1/2″ mild steel). The level IV ceramics erode and yaw this round, increasing its frontal area, and making it easy for the backing material to catch it.
Ceramic plates are typically built using one of two types of construction: monolithic or mosaic. Monolithic utilizes a single piece of ceramic, while mosaic uses multiple smaller tiles arranged and bonded to the backing layer.
Monolithic plates are typically much more expensive, since sintering (hardening) larger plates requires larger autoclaves. Much more QC expense is also incurred, since if a larger plate has a flaw, the entire piece is discarded. This expense is compensated for, because monolithic plates can be built with complex curvature or shapes, compared to mosaic. Mosaic plates are conversely more affordable, using many smaller tiles arranged together and bonded with an adhesive, typically epoxy. It is typically more difficult to form complex plate shapes with mosaic construction.
There are currently three types of ceramic materials that find general use in rifle plates, in ascending order of cost/effectiveness/weight. They are:
Alumina (Al2O3): A whitish ceramic with a good combination of hardness (mid to high 8’s on the Moh’s hardness scale), toughness, and cost effectiveness. This ceramic is still the most-used for general low- to mid-priced ceramic plates. With good design, Alumina plates can be quite protective and comfortable. Chemical structure very similar to Sapphire.
Silicon Carbide (SiC): A dark grayish ceramic (with a bluish tinge), this ceramic is more expensive, and harder than Alumina (Moh’s 9). Also slightly lighter, it finds use in medium to medium-high price point level IV plates.
Boron Carbide (B4C): The most expensive ceramic used in armor, and the second hardest material on Earth (behind diamond), it is also much lighter than Alumina. This material is used in the highest-end rifle plates, and can be enhanced with new methods (such as sinterless pressing) to achieve nearly 100% theoretical density (meaning there are no gaps between particles). A dark gunmetal colored ceramic.
As with all materials, ceramic has its advantages and drawbacks. It is very effective, on a per-weight basis, compared to steel (can be up to 40% lighter than steel plates). It can be made to withstand much more potent threats, such as black tip AP rounds (which again, blast straight through level III). And finally, ceramic monolithic plates can be shaped into complex curvatures, far exceeding the capabilities of steel, to better conform to the shape of the body. With these advantages come weaknesses- ceramic plates are much thicker than steel, making them more difficult to wear concealed. They are MUCH more expensive, some 6th gen ceramic plates pushing $1.5K PER PLATE. And finally, their major Achilles heel is their fragility. Ceramics, especially monolithic plates, are susceptible to rough handling. Cracking, chipping, or even complete destruction of the strike face can occur if the end user mistreats their armor. It is recommended to floroscope (X-Ray) your armor once per year if at all possible, to detect cracks.
I will be making an effort to review several different options for ceramic rifle plates (as funds permit) over the next few months.
As always, it is imperative that the end-user assess their needs and mission requirements when making a determination of what sort of plates to purchase. Each subset of plate types has their definite advantages and disadvantages. In the next post, we will examine the final plate material. Until then, cheers!
d-rmor gear 