Patent Application
20120090451
The present invention relates to an armor construction that resists penetration by high energy solid projectiles designed to defeat vehicle armor.
Conventional armor is subjected to a variety of projectiles designed to defeat the armor by either penetrating the armor with a solid or jet-like object or by inducing shock waves in the armor that are reflected in a manner to cause spalling of the armor such that an opening is formed and the penetrator (usually stuck to a portion of the armor) passes through, or an inner layer of the armor spalls and the armor fragments are projected at high velocity without physical penetration of the armor.
Some anti-armor weapons are propelled to the outer surface of the armor where a shaped charge is exploded to form a generally linear “jet” of metal that will penetrate solid armor; these are often called Hollow Charge (HC) weapons. A second type of anti-armor weapon uses a linear, heavy metal penetrator projected at high velocity to penetrate the armor. This type of weapon is referred to as EFP (explosive formed projectile) or SFF (self forming fragment) or a “pie charge” or sometimes a “plate charge.”
In some of these weapons the warhead behaves as a hybrid of the HC and the EFP and produces a series of metal penetrators projected in line towards the target. Such a weapon will be referred to herein as a Hybrid warhead. Hybrid warheads behave according to how much “jetting” or HC effect it has and up to how much of a single big penetrator-like an EFP it produces.
Various protection systems are effective at defeating HC jets. Amongst different systems the best known are reactive armors that use explosives in the protection layers that detonate on being hit to break up most of the HC jet before it penetrates the target. The problem is that these explosive systems are poor at defeating EFP or Hybrid systems.
Another system has been proposed to defeat such weapons where the armor is comprised of two layers with an electrical conductor disposed therebetween. An significant electric potential is created between the electrical conductor and the adjacent surfaces of the armor. When a jet or elongated solid penetrator penetrates the armor it creates an electrically conductive path between the armor layers and the electrical conductor through which the electrical potential is discharged. When there is sufficient electrical energy discharged through the penetrator it is melted or vaporized and its ability to penetrate the next layer of armor is significantly reduced.
Another type of anti-armor weapon propels a relatively large, heavy, generally ball-shaped solid projectile (or a series of multiple projectiles) at high velocity. When the ball-shaped metal projectile(s) hits the armor the impact induces shock waves that reflect in a manner such that a plug-like portion of the armor is sheared from the surrounding material and is projected along the path of the metal projectile(s), with the metal projectile(s) attached thereto. Such an occurrence can, obviously, have very significant detrimental effects on the systems and personnel within a vehicle having its armor defeated in such a manner.
While the HC type weapons involve design features and materials that dictate they be manufactured by an entity having technical expertise, the latter type of weapons (EFP and Hybrid) can be constructed from materials readily available in a combat area. For that reason, and the fact such weapons are effective, has proved troublesome to vehicles using conventional armor.
The penetration performance for the three mentioned types of warheads is normally described as the ability to penetrate a solid amount of RHA (Rolled Homogeneous Armor) steel armor. Performances typical for the weapon types are: HC warheads may penetrate 1 to 3 ft thickness of RHA, EFP warheads may penetrate 1 to 6 inches of RHA, and Hybrid warheads may penetrate 2 to 12 Inches thick RHA. These estimates are based on the warheads weighing less than 15 lbs and fired at their best respective optimum stand off distances. The diameter of the holes made through the first inch of RHA would be; HC up to an inch diameter hole, EFP up to a 9 inch diameter hole, and Hybrids somewhere in between. The best respective optimum stand off distances for the different charges are: standoff distances for an HC charge is good under 3 feet but at 10 ft or more it is very poor; for an EFP charge a stand off distance up to 30 feet produces almost the same (good) penetration and will only fall off significantly at very large distances like 50 yards; and for Hybrid charges penetration is good at standoff distances up to 10 ft but after 20 feet penetration starts falling off significantly. The way these charges are used are determined by these stand off distances and the manner in which their effectiveness is optimized (e.g., the angles of the trajectory of the penetrator to the armor). These factors effect the design of the protection armor.
The present invention is effective against Hybrid charges because they must be placed close to the edge of the road to provide deep penetration and thus they must be angled upward to hit the desired portion of the target. As a result they do not hit the armor at a right angle to its surface. The jet is therefore at least partially deflected from its trajectory and its penetration is reduced. An effective EFP can hit from a relatively long stand off distance and has a good chance of hitting square on with good penetration but the present invention is very effective against EFPs. The Hybrid and EFP are the threats the invention is primarily intended to address.
While any anti-armor projectile can be defeated by armor of sufficient strength and thickness, extra armor thickness is heavy and expensive, adds weight to any armored vehicle using it which, in turn places greater strain on the vehicle engine, and drive train.
Armor solutions that offer a weight advantage against these types of weapons can be measured in how much weight of RHA it saves when compared with the RHA needed to stop a particular weapon penetrating. This advantage can be calculated as a protection ratio, the ratio being equal to the weight of RHA required to stop the weapon penetrating, divided by the weight of the proposed armor system that will stop the same weapon. Such weights are calculated per unit frontal area presented in the direction of the anticipated trajectory of the weapon.
Thus, there exists a need for an armor that can defeat the projectiles from anti-armor devices without requiring excess thicknesses of armor. Preferably, such armor would be made of material that can be readily fabricated and incorporated into a vehicle design at a reasonable cost, and even more preferably, can be added to existing vehicles.
As the threats against armored vehicles increase and become more diverse, combinations of armor or armor systems are needed to defeat the various threats. The present invention is in addition to the common design features needed to protect the vehicle against military assault rifle bullets, bomb shrapnel and landmine explosions. An armor system that raises the protection level of an armored vehicle to include EFP and Hybrid charges is described.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. One or more of the objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
To achieve one or more of the objects and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention comprises an armor system for defeating a solid projectile. One embodiment of the system includes at least one armor plate positioned to first engage the projectile and having on an upstream surface, relative to the projectile trajectory, a metal coating of a composition disposed to friction weld or bond with the metal comprising the metal projectile.
A further embodiment of the invention is an armor system for defeating a solid projectile having a plurality of metal armor plates positioned along the projectile trajectory and spaced one from the other along the trajectory, the metal armor plate positioned to first engage the projectile having on its upstream surface, relative to the trajectory, a metal coating of a composition disposed to friction weld or bond with the metal comprising the metal projectile, and at least one of the other metal armor plates having on its upstream surface a metal coating of a composition disposed to friction weld or bond with the metal comprising the adjacent upstream metal armor plate.
Another embodiment of the system includes an outer metal armor plate positioned in the projectile trajectory; an interior metal armor plate positioned approximately parallel to the first metal armor plate and displaced downstream threrefrom a distance along the trajectory to form a first dispersion space; and a layer of a first metal positioned between the outer metal armor plate and the interior metal armor plate, the first metal layer being thin relative to the thicknesses of the outer metal armor plate and the interior metal armor plate, and the first metal being of a composition disposed to friction weld or bond to at least one of the outer armor plate metal and the interior armor plate metal. The system may further include an inner metal armor plate positioned approximately parallel to the interior metal armor plate and displaced downstream therefrom along the trajectory to form a second dispersion space; and a layer of a second metal positioned between the interior metal armor plate and the inner metal armor plate, the second metal layer being thin relative to the thicknesses of the interior metal armor plate and the inner metal armor plate, and the second metal being of a composition disposed to friction weld or bond to at least one the interior armor plate metal and the inner armor plate metal.
A specific embodiment of the invention is an armor system for defeating a solid copper projectile having an outer armor plate positioned to first engage the copper projectile and comprised of an alloy of aluminum with an ultimate tensile strength greater than 20,000 lbs/in.2 and a thickness in the range of from 8 to 40 millimeters. There is also an interior armor plate comprised of an alloy of aluminum having an ultimate tensile strength greater than 20,000 lbs./in.2 and a thickness in the range of from 8 to 40 millimeters. The interior armor plate is disposed approximately parallel to the outer armor plate and is displaced downstream therefrom, relative to the projectile trajectory, to form a first dispersion space between the outer armor plate and the interior armor plate a distance of from 25 to 150 millimeters. The system further includes an inner armor plate comprised of an alloy of aluminum having a tensile strength greater than 20,000 lbs./in.2, an elongation to break greater than 10% and a thickness in the range of from 8 to 40 millimeters. The inner aluminum armor plate is disposed approximately parallel to the interior armor plate and is displaced downstream therefrom to form a second dispersion space between the interior armor plate and the inner aluminum armor plate at a distance of from 25 to 150 millimeters. The outer metal armor plate has a metal coating on its upstream surface, relative to the trajectory, disposed to friction weld or bond with copper. The interior and inner metal armor plates have on their respective upstream surfaces metal layers or coatings disposed to friction weld or bond with aluminum.
The system may also include a steel armor plate having a Brinell hardness greater than 350 and a thickness in the range of from 4 to 20 millimeters. The steel armor plate is displaced downstream from the inner aluminum interior armor plate, relative to the trajectory, to form a third dispersion space of from 5 to 30 millimeters. This embodiment may preferably be used to improve the protection of a vehicle where the body of the vehicle includes a layer of a non-metal sheet armor affixed to its interior surface, as for example a rigid polymer/fiber composite and/or a layer of penetration resistant fabric.
It is to be understood that both the foregoing general descriptions and the following detailed descriptions are exemplary and explanatory only and are not restrictive of the invention, as claimed.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the invention and together with the description, serve to explain the principles of the invention.
Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
In accordance with the invention, there is provided an armor system for defeating a solid projectile. While the invention and its embodiments may impede penetration of elongated metal “jets” produced by shape charges, its primary utility is to defeat relatively non-elongated, heavy, solid metal projectiles formed and propelled by either manufactured explosive devices or improvised explosive devices. Embodiments of the invention may include systems for addressing metal jets and/or elongated heavy metal penetrators in addition to non-elongated solid metal projectiles. The parameters of the system can be selected to defeat a particular projectile if its weight, density, velocity, and size are known. The parameters of the system are the mechanical properties (ultimate tensile strength, hardness, elastic modulus, fracture toughness, and velocity of forced shock) of the layers of material comprising the layers of the invention, the spacing of the layers (the distance between layers, i.e. the thickness of the dispersion space) and the nature of any materials placed in the space between the layers.
In accordance with one aspect of the invention there is provided an outer plate positioned to first engage the projectile along the projectile trajectory. The plate may have parallel, opposing flat surfaces. On its upstream surface, relative to the projectile trajectory, the outer plate may include a metal coating of a composition disposed to friction weld or bond with the metal comprising the metal projectile. As embodied herein, and as shown in
By the term “metal,” applicant means to include elemental metals, alloys of the elemental metals, and unalloyed mixtures thereof.
By the term “friction weld or bond”, applicant means the adhering or attachment of one metal structure to another as a result of energy imparted by the projectile (or the projectile plus part of one or more metal armor plates) on a downstream structure, without reliance on a specific mechanism of adhering or attachment. Thus, the invention, as defined by the pending claims is not intended to be limited by the terms “weld” or “bond” if such have a narrower technical definition.
Projectiles impinging on solids induce shock waves in the solids. The shockwaves passing through the system provide the energy for the eruption at the inner surface of the plate but the direction of the eruption is dictated by the shape of the inner surface of the material with the shockwave energy in it and the material adjacent the inner surface into which the shock energy is to be transmitted. When the material receiving the shock energy from the solid has a significantly lower velocity of transmission of a forced shock wave the energy will be reflected at the surface and not transmitted. For example, where the material with the shock wave in it is a solid (e.g. aluminum or steel that conduct shockwaves at 5000 meters/sec.) and the material receiving the shock wave is air (having a velocity of transmission of a forced shock wave of only 330 meters/sec.) the mismatch will cause the energy to build up at the plate surface involved and then cause an eruption. One form of such an eruption is known as spalling.
The material properties of the solid material forming the plates effect the dissipation of energy and transmission of momentum away from the penetration line and thereby effect how spalling occurs at the rear of the metal plates. If the material is brittle (like with most ceramics) the hardness advantage at the front face is lost at the rear face where the spalling occurs because the material has a very low elongation to break and the material breaks into small pieces carrying less energy off the line of penetration. A large single spall can develop in materials like steels and other metals when they exhibit a value for elongation to break of 10% or more. A material with a high tensile strength (like more than 30,000 lbs./in.2 for aluminum) coupled to a high elongation value requires a larger amount of energy to tear loose a large spall. A heavy spall relative to the mass of the striking projectile will, through the laws of conservation of momentum, result in a larger drop in velocity of the components exiting rear of the plate and being carried across the dispersion space onto the next protection plate.
In accordance with another or second aspect the invention, the system includes a one or more successive armor plates positioned along the projectile trajectory, the successive armor plates being oriented approximately parallel to the outer armor plate and displaced relative to each other to form dispersion spaces between adjacent armor plates.
As here embodied, and depicted schematically in
As here embodied and depicted in
As will be disclosed in more detail below, the system is comprised of a plurality of layered plates with adjacent plates being separated by what is termed a dispersion space. At least one of the plates comprising the system has, between it and the downstream adjacent plate, relative to the projectile trajectory, a metal layer that is disposed to friction weld or bond to the metal of the fragments of the upstream plate that are dislodged when the projectile is impinged on that plate. While it is currently preferred to configure the friction weld/bond metal layer as a coating on the upstream surface of the downstream plate, one skilled would understand that the coating could be applied to the downstream surface of the upstream plate or as a separate sheet or film in the dispersion space. Also, two or more coatings or separate sheets may be provided in a given dispersion space.
One skilled in the art would be able to select appropriate metals and dimensions for the coatings 22, 24 and 26 of
While such references are primarily directed to the relationships necessary to produce reliable bonds between metal plates by using explosives, they do provide guidance as to what metals tend to bond to others when they impact at high velocities. Where the surface of the impinging object (whether it be a projectile or adjacent armor layer fragment) is expected to be copper the upstream surface of the armor system is preferably a metal selected from the group of copper, iron, aluminum, titanium. Where the surface of the impinging object (whether it be a projectile or adjacent armor layer fragment) is expected to be steel the upstream surface of the armor system is preferably a metal selected from the group consisting of iron, magnesium, molybdenum, copper, zirconium, titanium, nickel, and aluminum. Where the surface of the impinging object (whether it be a projectile or adjacent armor layer) is expected to be aluminum the upstream surface of the armor system is preferably a metal selected from the group of aluminum, iron, titanium, and copper. Where the impinging object (whether it be a projectile or adjacent armor layer fragment) is expected to be titanium the upstream surface of the armor system is preferably a metal selected from the group of titanium, iron, nickel, and aluminum.
It has been observed that, as a consequence of the friction welding/bonding phenomena, one or more fragments of the upstream plate become attached to the projectile metal and travel together with the projectile generally along the projectile trajectory, but with a diminished velocity relative to the projectile velocity, for the following reasons.
In accordance with the conservation of momentum, the velocity times the mass of the projectile will be less than or equal to the velocity times the sum of the mass of the projectile and any portion of the plates that is fractured from the plate and continues to move with the projectile. Stated in terms of a formula: Mp·Vp≧Mp+f·Vp+f, where Mp is the mass of the projectile, Vp is the velocity of the projectile, Mp+f is the mass of the projectile plus the portion of the plate that has friction welded or bonded to the projectile and fractured from the remainder of the plate, and Vp+f is the velocity of the combined mass of the projectile plus the portion of the plate that has welded to the projectile and fractured from the remainder of the plate, where the ≧ sign indicates energy dissipation in the fracture deformation of the plate manifested by a decreased exit velocity Vp+f.
In a preferred embodiment of the invention the outer metal armor layer is a relatively tough, ductile material. It may have a relatively thin metal coating to facilitate welding/bonding with the projectile and/or a layer of hard non-metal material on its upstream surface, e.g. a layer of ceramic material, to induce fracture and or deformation of the projectile, but in each case the function of the outer armor layer is to absorb some of the energy of the projectile, to flatten it (laterally displace at least some of its mass), and/or to significantly reduce its velocity.
As depicted in
As depicted in the
The velocity of shockwaves in the armor plate should be significantly faster than the velocity of the penetrator. The toughness of the armor plate can then be brought to bear and the tear line can, by reflection and resonance phenomena, give a favorable tear line depicted in
The velocity of forced shockwaves in steels and aluminum alloys is about 5,000 meters/sec., so if the striking projectile has a velocity close to or higher than that, the penetration would behave more like an HC. The penetration of an HC depends on the density of the material it is penetrating and lower density materials perform better. When dealing with high velocity projectiles, aluminum armor is preferable to steel armor but when the velocity has been reduced by preceding penetrations then tough steel plates also become effective. EFP normally have a velocity of 2,500 meters/sec. or slower, and Hybrids have the smaller and lighter leading penetrators moving at 3,000 to 3,500 meters/sec. so they are more difficult to stop. For an EFP the energy absorbed by the plate 12 is directly proportional to the deformation of the plate and the angle a depicted in
In accordance with the invention, the first dispersion space is of sufficient length in the direction generally perpendicular to the plates to allow significant lateral dispersion of material passing though the first dispersion space. As here embodied in a system comprised of a series of metal armor plates shown in
In this second aspect of the invention, outer plate 12 may or may not have a metal coating 22 on its leading surface to facilitate welding/bonding between the first projectile 30′ and the outer plate 12. Specifically, one or more metal layers or coatings may be provided between one or more adjacent metal armor plates, such as metal coatings 24 and/or 26 on the upstream surfaces of interior armor plate 14 and inner armor plate 15, respectively, as depicted in
As shown schematically in
As shown schematically in
The combination of the projectiles 30′ and 30″ and portions of the armor plates (12″ and 14′) that have been sheared from the first two armor plates 12 and 14 encounter the final layer of armor in
In a preferred embodiment the outer metal armor layer has an ultimate tensile strength of 50,000 lbs./in.2 for steel plates and 30,000 lbs./in.2 for aluminum plates so that the high speed projectile can be substantially flattened when hitting the surface of the armor. The armor should however not be too brittle such as to allow the deformation shock to crack and break a hole through the initial armor layer without removing both energy and momentum from the projectile along the trajectory. Such a non-preferred occurrence is depicted in
Where the armor plates are an aluminum alloy it is preferred that they consist essentially of an aluminum alloy having an elongation at fracture of at least 7% and more preferably 10%. Examples of preferred aluminum alloys include: 7017, 7178-T6, 7039 T-64, 7079-T6, 7075-T6 and T651, 5083-0, 5083-H113, 5050 H116, and 6061-T6. When the armor layer consists essentially of an aluminum alloy it is preferred that it have a thickness in the range of from 8 to 40 millimeters. Where the outer armor plate is steel it is preferred that such a plate consist essentially of material having an elongation at fracture of at least 7% and more preferably 10%. Examples of preferred steels include: SSAB Weldox 700, SSAB Armox 500T (products of SSAB Oxelosund of Oxelosund, Sweden), ROQ-TUF, ROQ-TUF AM700 (products of Mittal Steel, East Chicago, Ind., USA), ASTM A517, and steels that meet U.S. Military specification MIL-46100. When the armor layer consists essentially of steel it is preferred that it have a thickness in the range of from 5 to 20 millimeters.
As discussed previously, high strength materials can be used on the outer surface of outer armor plate 12 in place of, or in addition to, metal coating 22 used to facilitate friction welding or bonding with projectile metal. An example of such a material would be ceramic armor. Such an outer layer can induce fragmentation of the projectile and address other types of projectiles than the relatively heavy, soft projectiles addressed by the present invention.
Another embodiment of the invention also induces lateral dispersion of material passing through the dispersion spaces in the layered device by placing dispersion elements (not shown) in the dispersion space. At very high velocity impact conditions the induced forced shockwaves transmitted into the dispersion elements carry a large percentage of the energy exerted on the dispersion elements by the penetrator. The dispersion elements are then launched by this energy as a spall or the object containing the shock energy must pass the energy on to another receiver.
In accordance with an aspect of the invention, there may be provided an inner metal armor plate disposed approximately parallel to the interior metal armor plate and displaced downstream therefrom to form a second dispersion space, the second dispersion space being sufficiently thick to allow significant lateral dispersion of materials passing therethrough.
As here embodied and depicted in
t is preferred that the inner plate be comprised of a material that has a Brinell hardness in excess of 350. It is further preferred that the inner plate consist essentially of a material selected from the group consisting of: an aluminum alloy, a steel alloy, and a titanium alloy, a metal matrix composite, and a polymer matrix composite. As has been repeatedly disclosed, one of the goals of the system is to induce dispersion of the material passing through the armor system to improve the probability that such material will not penetrate the system.
Another aspect of the invention is the incorporation of an armor system on an existing vehicle, armored or unarmored. For an unarmored vehicle the inner armor plate should resist penetration of any material passing through the armor system so the material does not enter the vehicle. In that way the ability of an unarmored vehicle to survive attack by armor-piercing munitions or devices is significantly improved. Armored vehicles can have their resistance to attack by armor-piercing munitions or devices further improved by the incorporation of the systems present invention on the exterior surface of the armored vehicle.
An embodiment of an armored vehicle having its penetration resistance improved is depicted in
An alternative embodiment would be one or more separate assemblies of layered armor plates in accordance with the disclosed systems added to an existing vehicle, or portions of the vehicle, to enhance its resistance to the weapons described above.
In a preferred embodiment the sheet material 16 used to form the body 38 may be at least two different sheet materials. In the embodiment depicted in
In a further preferred embodiment the vehicle body includes a system of interior sheet armor 46 configured and designed to be adjacent the interior surface of sheet armor 16 of the body 38 of vehicle 36. As here embodied, and depicted in
The interior sheet armor 46 of vehicle 36 may also comprise a woven fabric comprised of fiber. A still further preferred embodiment includes an interior armor layer of woven fabric 46′ comprised of fiber and a plurality of ceramic plates 48, as schematically depicted in
In yet another embodiment of vehicle 36, depicted in
While the present invention provides resistance to solid projectiles, it also provides an opportunity to add protection from elongated solid and liquid projectiles. As disclosed above in the background section there are systems having two layers of armor with an electrical conductor disposed therebetween. A significant electric potential is created between the electrical conductor and the adjacent surfaces of the armor. When a liquid or solid penetrator penetrates the armor it creates an electrically conductive path between the armor layers and the electrical conductor through which the electrical potential is discharged. When there is sufficient electrical energy discharged through the penetrator, it is melted or vaporized and its ability to penetrate the next layer of armor is significantly reduced. Because such a system can be readily incorporated into the armor system of the present invention without significant disadvantage, a preferred embodiment of the present invention includes an electrically conductive member disposed in the dispersion space between two adjacent armor plates.
As here embodied and depicted in
It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention. The present invention includes modifications and variations of this invention which fall within the scope of the following claims and their equivalents.
This application is a Continuation-In-Part of application Ser. 11/713,012 filed Mar. 2, 2007, which was a Continuation-In-Part of application Ser. 11/521,307 filed Sep. 15, 2006.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11713012 | Mar 2007 | US |
| Child | 12010268 | US | |
| Parent | 11521307 | Sep 2006 | US |
| Child | 11713012 | US |
