WO2008153613A2

WO2008153613A2 - Armor system and method for defeating high energy projectiles that include metal jets

Info

Publication number: WO2008153613A2
Application number: PCT/US2008/002452
Authority: WO
Inventors: Vernon P. Joynt
Original assignee: Force Protection Technologies, Inc.
Priority date: 2007-03-02
Filing date: 2008-02-26
Publication date: 2008-12-18
Also published as: JP2010534817A; KR20090127285A; TW200905154A; EP2122293A2; CN101646917A; US20120017754A1; WO2008153613A3; EP2122293A4

Abstract

An armor system for defeating a solid projectile having an exterior rigid armor plate associated with a fiber-reinforced sheet armor affixed to the interior surface of the exterior armor plate, an interior armor plate, and an inner armor plate displaced from one another to form a first dispersion space between the sheet of self-bonded polymer and the interior armor plate. The first dispersion space is sufficiently thick to allow significant lateral dispersion of armor passing therethrough. The inner armor plate is disposed approximately parallel to the interior armor plate and displaced therefrom to form a second dispersion space between the interior armor plate and the inner armor plate. The second dispersion space is sufficiently thick to allow significant lateral dispersion of materials passing therethrough.

Description

ARMOR SYSTEM AND METHOD FOR DEFEATING HIGH ENERGY PROJECTILES THAT INCLUDE METAL JETS

Cross-reference to related applications

[001] This application claims priority to U.S. Patent Application No. 11/713,012, filed on March 2, 2007, which is a continuation-in-part of U.S. Patent Application No. 11/521 ,307, filed September 15, 2006 entitled, Apparatus For Defeating High Energy Projectiles, the contents of which are incorporated by reference herein. Field of the Invention

[002] The present invention relates to an armor construction that resists penetration by high energy solid projectiles designed to defeat vehicle armor. Background of the Invention

[003] 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 is projected at high velocity without physical penetration of the armor.

[004] 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."

[005] 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. [006] 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

[007] 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.

[008] 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.

[009] While the HC type weapons involve design features and materials that dictate they be manufactured by an entity having technical expertise, the later 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.

[010] 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 Hybrids 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.

[011] The present invention is effective against Hybrid charges because it must be placed close to the edge of the road to provide deep penetration and thus it must be angled upward to hit the desired portion of the target. As a result it does 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 intended to address.

[012] 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.

[013] 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.

[014] 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.

[015] 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. Summary of the Invention

[016] 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. 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.

[017] To achieve 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. The system includes an exterior rigid armor plate having an exterior surface and an interior surface. A fiber-reinforced sheet armor, comprised of a plurality of fibers having an ultimate tensile strength greater than 3GPa bonded to form the sheet by a polymer surrounding the fibers is affixed to the interior surface of the exterior armor plate. The system further includes an interior armor plate disposed approximately parallel to the fiber- reinforced sheet armor. An inner armor plate is disposed approximately parallel to the interior armor plate and is displaced therefrom to form a second dispersion space between the interior armor plate and the inner armor plate. The second dispersion space is sufficiently thick to allow significant lateral dispersion of materials passing therethrough.

[018] An embodiment of the invention is an armor system for defeating a solid projectile where the fiber in the fiber-reinforced sheet armor sheet consists essentially of a material selected from the group consisting of: poly-paraphenylene terephthalamide, stretch-oriented high density polyethylene, stretch-oriented high density polyester, a polymer based on pyridobisimidazole, and silicate glass. [019] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

[020] 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. Brief Description of the Drawings

[021] Fig. 1 is a perspective view of one embodiment of the present invention;

[022] Figs. 2A-B are schematic, cross-sectional views of one embodiment of the invention being challenged by a relatively heavy, non-elongated solid projectile preceded by an elongated metal jet;

[023] Fig. 3 is a perspective view of one embodiment of the present invention where the exterior armor plate has a plurality of projections on the outer surface;

[024] Fig. 4 is a perspective view of one embodiment of the present invention where the first dispersion space contains a plurality of dispersion inducing members, embodied here as glass spheres;

[025] Fig 5 is a cross-sectional view of an embodiment of the invention where the armor comprising the body of the vehicle is the inner armor plate of the invention;

[026] Fig. 6 is a schematic cross-sectional view of an embodiment of the invention where the armor comprising the body of the vehicle is the inner armor plate of the invention and the vehicle includes an interior projectile absorbing layer inside the body;

[027] Fig. 7 is a schematic cross-sectional view of an embodiment of the invention where the armor comprising the body of the vehicle is the inner armor plate of the invention and the vehicle includes an interior projectile absorbing layer inside the body of fabric and ceramic plates on the interior surface of the vehicle body;

[028] Fig. 8 is a schematic cross-sectional view of an embodiment of the invention where the armor comprising the body of the vehicle is the inner armor plate of the invention and the vehicle includes an interior projectile absorbing layer inside the body of fabric and ceramic plates spaced from the interior surface of the body to form a gap; and

[029] Fig 9 is a perspective view of one embodiment of the present invention where there is an electrically conductive sheet between the layered armor plates and a source of electrical power disposed to apply such power to adjacent conductive layers in the armor system.

[030] Fig 10 is a perspective view of another embodiment of the present invention where there is an electrically conductive sheet between the layered armor plates and an associated power source.

[031] Fig 11 is a perspective view of still another embodiment of the present invention where there is an electrically conductive sheet between the layered armor plates and an associated power source.

[032] Fig 12 is a perspective view of still another embodiment of the present invention where there is an electrically conductive sheet between the layered armor plates and an associated power source. Description of the Preferred Embodiments

[033] 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.

[034] 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 relatively, non-elongated, heavy, solid metal projectiles formed and propelled by either manufactured explosive devices or improvised explosive, its primary utility is to defeat devices of elongated metal "jets" produced by shape charges along with the heavy solid 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. [035] Some embodiments of the invention have a plurality of projections on the inner surface of at least one armor plate in the system. The purpose of the plurality of projections on the inner surface is to disperse solid projectiles erupting through the inner surface of the plate. The mechanism by which the inner surface induces dispersion of materials may not be the same as that of projections on a surface on which the projectile impinges but, irrespective of the mechanism, the projections on the inner surface disperse the material erupting therefrom and in doing so achieves one of the objectives of the system. 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

[036] 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 Ibs./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.

[037] Where the system contains a layer of fibrous material at or near the outermost layer of the armor system, the fibrous layer attenuates the energy of the penetrating material by resisting the enlargement of an opening therein by virtue of the extremely high tensile strengths of the fibers comprising the fibrous sheet. Even if penetrated by an elongated penetrator, the initial opening resists enlargement and exerts high shear forces on the lateral surfaces of the elongated penetrator. This slows the penetrator and reduces the energy in the penetrator. This increases the probability that the next layer in the armor system will either defeat the penetrator, or further slow the penetrator such that layers of the system that will encounter the penetrator may have a better chance of defeating it.

[038] As will be disclosed in more detail below, the system is comprised of a plurality of layered plates separated by what is termed a dispersion space. In some embodiments projections from the outer or inner surface used to induce dispersion of the material impinging on or erupting from a surface can be used on any one of the plates in the system on both opposing surfaces, the outermost surface, the innermost surface, or not at all.

[039] In another embodiment, where the trajectory of the projectile (and hence its expected line of penetration) is known, the armor plate may be angled so that the line of penetration is no longer perpendicular to the outer surface. In such an embodiment at least one of the armor plates are inclined with respect to the anticipated trajectory of the projectile. It is preferred that each of the plates be inclined at an angle of 20° or more with respect to the anticipated trajectory of the projectile.

[040] In accordance with the invention there is provided an exterior rigid armor plate having an exterior surface and an interior surface. The plate may have parallel, opposing flat surfaces, or in certain embodiments the surface of the plate on which a projectile would first impinge (the "outer" surface) may include a plurality of projections on the outer surface. The projections are disposed to at least partially fragment solid projectiles impinging on the outer surface of the plate. The size and configuration of the projections are determined by the properties of the projectile and the material forming the plate. It is not the purpose of the projections on the outer surface of the first plate to defeat the projectile but to deflect an elongated "jet" of metal moving at high velocity in front of a relatively heavy projectile moving at a lower velocity along the same trajectory. Such a penetrator is characteristic of what is termed herein as a Hybrid weapon. As will be disclosed further, the primary goal of the invention is to induce dispersion of the projectile as it passes through the armor system. What is meant by dispersion is the deflection of portions of the projectile and any portions of the material forming layers in the system from the initial trajectory of the projectile.

[041] The outer armor layer may consist essentially of a sintered material selected from the group consisting of: silicon carbide, boron carbide, alumina, and a blend of zirconia and alumina. One embodiment of the present invention includes a ceramic outer armor layer of CeraShield™ ceramics, products of the CoorsTek® Armor, Group CoorsTek, Inc., 16000 Table Mountain Parkway, Golden, Colorado, 80403. Other preferred embodiments include metals including steel, aluminum alloys, and titanium alloys.

[042] In accordance with the invention there is provided a fiber-reinforced sheet armor affixed to the interior surface of the exterior armor plate. The fiber- reinforced sheet armor is comprised of a plurality of fibers having an ultimate tensile strength greater than 2.5 GPa bonded to form the sheet by a polymer surrounding the fibers. Without being bound by theory it is believed that any jet of material penetrating the fibrous layer must separate the fibers laterally and hence apply a tensile load on the fibers. When the fibers are sufficiently strong (have a high tensile strength), the material surrounding the jet constricts the jet and slows it substantially. Because the jet defeats armor by the inertia of an elongated (explosive formed) penetrator, the reduction of the velocity of the jet significantly reduces its effectiveness. Because the fibrous layer is one of the first of several layers of armor in the system of the present invention, the latter layers can more readily defeat the jet.

[043] Recent developments in fiber technology have created fibers having tensile strengths in relatively light materials that are in excess of 3GPa. In a preferred embodiment the fiber in the fiber-reinforced sheet armor consists essentially of a material selected from the group consisting of: poly-paraphenylene terephthalamide, stretch-oriented high density polyethylene, stretch-oriented high density polyester, a polymer based on pyridobisimidazole, and silicate glass.

[044] Preferrably the fiber-reinforced sheet armor sheet consists essentially of a sheet of stretch-oriented, high molecular weight polyethylenes, especially linear polyethylenes, having an ultrahigh molecular weight of 600,000 to 6,000,000 g/mol and higher. Such fibers are bound together to form a sheet-like product with a polymeric matrix materials, for example thermosetting resins such as phenolic resins, epoxy resins, vinyl ester resins, polyester resins, acrylate resins and the like, or polar thermoplastic matrix materials such as polymethyl (meth)acrylate. A particularly preferred fiber-reinforced sheet armor of this type is known commercially as Dyneema®, a product of DSM Dyneema, Mauritslaan 49, Urmond, P.O. Box 1163, 6160 BD Geleen, the Netherlands.

[045] Another preferred fiber-reinforced sheet armor sheet consists essentially of a composite panel made of high molecular weight polypropylene. In such a product tape yarn of high molecular weight polypropylene is woven into a fabric. Multiple layers of fabric are stacked and consolidated with heat and pressure to form rigid sheets using low molecular weight polypropylene as a matrix. A particularly preferred fiber-reinforced sheet armor made of this type material is known commercially as MTF sheet, a product of Milliken & Company, 920, Milliken Road, P.O. Box 1926, Spartansburg, South Carolina, 29303 USA.

[046] As here embodied, and depicted schematically in Fig. 1 , there is a series of generally parallel plates 10, comprised of an outer armor plate 12, a fibrous outer armor plate 12', an interior armor plate 14, and an inner armor plate 15. In the embodiment depicted the fibrous armor plate 12' is bonded to the outer armor plate 12 on the interior surface 13 of the armor plate 12. In other embodiments a mechanical fastening can be used to join the fibrous armor plate 12' to the outer armor plate 12 or the fibrous armor plate 12' be confined between to adjacent armor plates with no dispersion space (not shown). In this embodiment the outer surface 11 of the armor plate 12 is planar.

[047] As used herein "armor plate" is a plate-like member disposed to fragment, deflect, or disperse a projectile or absorb energy from the projectile to facilitate its defeat by other portions of the system. It may be a know armor plate material (i.e. a metal plate of high strength), a conventional metal plate of lower strength than conventional armor plate, or a sheet-like member of fibrous material that is used in the present invention to affect a projectile such that other elements in the armor system defeat the projectile. In a preferred embodiment the inner armor plate 15 may comprise the body of an armored vehicle.

[048] As here embodied and depicted in Fig. 1 , the system includes a first dispersion space 18, separating plates 12' and 14 a distance 19, a second dispersion space 20, with the outer surface of the series of plates 10 being surface 11 of plate 12.

[049] In accordance with the invention, the series of plates are separated by a dispersion space. As noted above, a dispersion space is the space between adjacent plates and it is the function of the dispersion space to allow lateral dispersion of material passing therethrough. The term lateral means in a direction at an angle from the initial line of flight of the projectile, i.e. its trajectory. The more the moving material is dispersed the less concentrated is the energy impinged on the next successive layer. In addition, the greater the distance between layers (the greater the thickness of the dispersion space) the less kinetic energy per surface area will be possessed by the moving material. Clearly if the dispersion distance is very large, large amounts of kinetic energy will be spread out from the original penetration line and lost, but the resulting layered structure will be impractically thick. On the other hand, if the thickness of the dispersion space is too small the moving material is not dispersed, its kinetic energy and momentum is not dissipated, and it may have sufficient energy and concentration to defeat subsequent layers of the system. One skilled in the art to which the invention pertains, with the general guidance provided herein, in combination with the example below can devise a system to defeat a particular projectile or mix of projectiles traveling at a particular velocity along a particular trajectory.

[050] In a preferred embodiment of the invention the first armor layer is a relatively thin, hard material on its outer surface, e.g., a layer of ceramic material, to induce fracture and or deformation of the projectile. In this embodiment the function of the first armor layer is to absorb some of the energy of the projectile, to flatten it (laterally displace at least some of its mass) and to significantly reduce its velocity. The adjacent fibrous armor layer 12' absorbs energy from the projectile and reduces its velocity. [051] The weapon against which the present invention has particular utility is depicted in Figs. 2A and 2B. In those figures a projectile 16 has been formed by an explosive device to have a relatively heavy and slow moving portion 16'. Ahead of the portion 16' is an elongated "jet" of material moving at a higher velocity along the same trajectory. As disclosed previously, because the jet is moving at a high velocity and has a relatively small cross-sectional area, it poses a significant threat to armor systems. This is especially true because shortly after the jet encounters a target (and has whatever effect on that target such a jet may have) the same portion of the target receives a relatively large shock from the heavy portion 16' of the projectile at the same location that encountered the jet.

[052] Fig. 2B depicts an embodiment of the invention after the jet has penetrated the outer armor plate 12 and the inner plate 12" before the relatively heavy portion of the projectile 16' has imparted its energy to the armor system. At this time the constriction effect of the fibrous outer plate has slowed the jet portion 16" and even though the outer armor layer 12 and the fibrous outer plate 12' have been breached, the energy absorbed by the fibrous layer 12' and the energy that will be absorbed by the portion 16' of the projectile 16 fracturing the outer armor plate 12 and deforming and possibly fracturing the fibrous outer plate 12' will significantly attenuate the energy in the projectile 16. This significantly increases the probability that the projectile 16 will be defeated by the remaining portions of the armor system, as here embodied, layers 14 and 16.

[053] It is further preferred that 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, give a favorable tear line depicted in Fig. 2B as angle α. The larger the angle α, the more energy is absorbed in the deformation of the plate being penetrated, and the larger the combined weight of the penetrator and the portion of the armor adherent to it.

[054] The velocity of forced Shockwaves in steels and aluminum alloy plates 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 strikes 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.

[055] Once the penetrator 16" and the relatively heaving projectile portion 16' have been slowed and basically deformed into one projectile, the projectile penetrates or shears plates in a manner that can be predicted. The relationship of the mass and velocity of the projectile conforms to a conservation of momentum relationship of: M_P V_P = (M_p +M_S) (V_P&S), where M_p is the mass of the projectile, V_p is the velocity of the projectile at impact, M_s is the mass of the sheared portion of the plate and V_p&s is the velocity of the combined projectile and sheared portion of the plate.

[056] In a preferred embodiment, the first dispersion space is sufficiently thick to allow significant lateral dispersion of material passing though the first dispersion space. As here embodied in a system comprised of a series of armor plates shown in Fig. 1 , the first dispersion space 18 has a sufficient thickness (as indicated by arrow 19) to allow significant lateral dispersion of material (the projectile and portions of the plate 12.

[057] In a preferred embodiment the interior armor plate 14 and the inner armor plate 15 have an ultimate tensile strength of 50,000 IbsJin.² for steel plates and 30,000 Ibs./in.² for aluminum. Preferably such a layer will have an elongation at tensile rupture of greater than 10%. When these armor layers have a high fracture toughness the mass of the material penetrating the outer layer may increase, but its velocity decreases and the material is laterally dispersed.

[058] Where the armor plates 14 and 15 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-O, 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 armor plates 14 and 15 are steel it is preferred that such plates 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 Oxelόsund of Oxelδsund, Sweden), ROQ-TUF, ROQ-TUF AM700 (products of Mittal Steel, East Chicago, Indiana, 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.

[059] In another preferred embodiment the surface or surfaces of at least one of the armor plates is configured to induce fragmentation of the projectile and the material being penetrated by the projectile.

[060] As here embodied, and depicted in Fig. 3, the outer surface 11 of the armor plate 12 includes a plurality of projections 28. The projections depicted in Fig. 3 are pyramidal, but the configuration of the projections is not known to be critical. The projections 28 are disposed to at least partially fragment solid projectiles impinging on the outer surface of the armor plate and induce as much lateral fragmenting of the material being penetrated as can be induced without the reduced thickness caused by the grooves 30 reducing the strength of the armor plate. It is also preferred that at least one of the armor plates in the armor system have an inner surface facing a dispersion space that includes a plurality of projections. In this embodiment the projections are disposed to disperse the solid material erupting through the inner surface of the armor plate by inducing lateral fracture of the penetrated layer. While the outermost armor layer of this embodiment has projections only from its outer surface, the interior armor plates may have projections on both. Due to the fragmentation of the layer and projectile the impact on the next adjacent plate will be a plurality of separate impacts that are dispersed over a wider area and the next plate receiving such materials will better resist penetration and if penetrated will more likely fracture in pieces.

[061] Another embodiment of the invention also induces lateral dispersion of material passing through the dispersion spaces in the layered device by placing dispersion elements 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.

[062] As here embodied and depicted in Fig. 4, the system 10 includes a plurality of spheres 34 located in the first dispersion space 18 between armor layers 12' and 14. The spheres may consist essentially of a material selected from the group consisting of brittle metal, ceramic, and glass. When the dispersion elements are surrounded by a liquid or gel that is able to conduct shock away, then the dispersion element in turn can accept more Shockwave energy without shattering or being moved out of the path of the penetrator. As here embodied the system 10 includes a gel 35 surrounding the spheres 34. One embodiment may use combinations of materials with complimentary forced Shockwave properties. Examples are spheres of glass or ceramics in which typically the speed of shock energy moves at more than 5,000 meters/sec, surrounded by a liquid like water (1 ,500 meters/sec.) or glycerin (1 ,800 meters/sec.) or glycol (1 ,800 meters/sec.) or mixtures of these liquids. The liquids can be gelled by a gelling agent like gelatin or fused silica, fused silica, potassiumpolyacrylate-polyacrylamide copolymers or similar organic polymer gel agents.

[063] In accordance with the invention there is provided an inner armor plate disposed approximately parallel to a separate armor plate and displaced therefrom to form a second dispersion space between the separate armor plate and the inner armor plate, the second dispersion space being sufficiently thick to allow significant lateral dispersion of materials passing therethrough.

[064] As here embodied and depicted in Fig. 1 the system includes an inner armor plate 15. As disclosed above, the primary purpose of the inner armor plate is to prevent any further penetration of material that has been dispersed and slowed by passage through the upper portions of the system, i.e., the outermost armor plate(s) and dispersion space(s). The embodiment depicted includes three plates but the inventions is not limited to that number of plates, hence reference in the disclosure to the "inner" armor plate adjacent the inner armor plate. Thus, the invention may include more than three armor plates, and it is still preferred that the inner armor plate be comprised of a material of high fracture toughness to resist any further penetration by material impinged thereon. [065] It 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 primary 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.

[066] Another embodiment 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 is further improved by the incorporation of the present invention on the exterior surface of the armored vehicle.

[067] An embodiment of an armored vehicle having its penetration resistance improved is depicted in Fig. 5, a schematic cross-sectional view of a blast-resistant armored land vehicle 36 having a monocoque body 38 comprised of sheet armor. In this embodiment the body 38 has a bottom portion 40 defining at least one V, with the apex of the V substantially parallel to the centerline of the vehicle. In this embodiment the armor system of the present invention is affixed to the exterior of the armored vehicle and the inner armor layer of the armor system of the invention comprises the sheet armor body of the vehicle.

[068] An alternative embodiment would be a separate assembly of layered armor plates added to an existing vehicle, or portions of the vehicle, to enhance its resistance to the weapons described above.

[069] In a preferred embodiment the interior layer of armor comprises the body of a vehicle. In the embodiment depicted in Fig. 5 the sheet material used to form the interior layer 16 of the body 38 may be at least two different sheet materials. In the embodiment depicted the portion of the body 16 that comprises the V-shaped portion 42, here a "double-chined" V, may be formed of a tough sheet material. As used herein the word "tough" is a material that resists the propagation of a crack therethough, generally referred to as a material that has a high fracture toughness. As here embodied the portion of the interior layer of the body 16 that comprises the bottom portion 40 (comprising the V shaped portion 42) is preferably sheet steel known as "ROQ-tuf AM700 (a product of Mittal Steel, East Chicago, Indiana). Another material known as SSAB Weldox 700 (a product of SSAB Oxelδsund of Oxelosund, Sweden) is also preferred as the material for the bottom portion 40. Steels normally used for the construction of boilers like A517, A514 and other steels having similar yield strengths and elongation to break comparable to ROQ-tuf and Weldox 700 may also be used. The upper portion 44 of the interior layer 16 of the body 38 is preferably formed of armor plate. A particularly preferred material is known as SSAB Armox 400 (a product of SSAB Oxelosund of Oxelosund, Sweden), although an armor meeting U.S. MIL-A-46100 will be operable. Generally, the sheet material for layer 16 preferably consists essentially of a metal selected from the group consisting of: steel, steel armor, titanium alloys, and aluminum alloys. In this preferred embodiment there is an interior armor layer 14 and two outer layers 12 and 12'. Preferably, the outer armor layer 12 consists essentially of a sintered material selected from the group consisting of: silicon carbide, boron carbide, alumina, and a blend of zirconia and alumina and a fiber- reinforced sheet armor 12' affixed to the interior surface of the exterior armor plate. The fiber-reinforced sheet armor 12' is comprised of a plurality of fibers having an ultimate tensile strength greater than 2.5 GPa bonded to form the sheet by a polymer surrounding the fibers. The preferred composition of the layer 14 has been disclosed above. T

[070] In a further preferred embodiment the vehicle body includes a layer of sheet armor 46 adjacent the interior surface of the body. As here embodied, and depicted in Fig. 6, the system includes outer armor layers 12 and 12", inner armor layer 14 and interior armor layer 15. The body of the vehicle, here 16 also has a layer of sheet armor 46 adjacent the interior surface of the body. In a further preferred embodiment, this sheet armor 46 comprises a rigid polymer/ fiber composite.

[071] The sheet armor 46 may also comprise a woven fabric comprised of fiber. A still further preferred embodiment includes an interior layer of armor of woven fabric 46' comprised of fiber and a plurality of ceramic plates 48, as schematically depicted in Fig. 7. [072] In another embodiment, depicted in Fig. 8 the fibrous sheet armor 46' (or the rigid polymer/ fiber composite 46, or another layer of metal armor plate (not shown)) adjacent the interior surface of the body 38 is spaced from the interior surface to form a gap 50.

[073] While the present invention provides resistance to solid projectiles, it also provides an opportunity to add protection from elongated solid and jet-like projectiles. As disclosed above in the background section there are systems having two layers of armor 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. Because such a system can be readily incorporated into 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.

[074] As here embodied and depicted in Fig. 9, a source of electrical power 52 is disposed to apply electrical power to the electrically conductive member 54 while the two adjacent electrically conductive armor plates are grounded. In such an embodiment the electrical power applied to the electrically conductive member 54 poses no threat of electric shock to personnel contacting the outer conductive armor plate, here embodied as outer armor plate 12. In this embodiment interior armor plate 14 is also grounded so that an elongated penetrator in electrical contact with the electrically conductive member 54 and the interior armor plate 14 is also subjected to electrical power to degrade the penetrator therebetween. The presence of the fibrous sheet armor 12', an electrical and thermal insulator further improves the performance of the system by reducing the dissipation of both heat and electrical energy from the surface of the penetrator. By confining the heat and electrical energy applied to the penetrator within it, the energy more effectively degrades the penetrator. As here embodied the electrically conductive member 54 is between plates 12 and 14 with electrical power being applied to the screen 54 and the armor layer 12. Alternatively, the screen could be placed between armor layers 14 and 15 with conductive armor layer 14 and 15 being grounded and the electrically conductive member 54 receiving electrical power. The source of electrical power supplies sufficient electrical power to disperse, melt, vaporize, or otherwise degrade at least a portion of an elongated projectile making electrical connection between at least one of the two adjacent armor plates and the electrically conductive member 54. In this embodiment the first dispersion space is the space 18' because the fiber-reinforced armor layer 12' does not allow dispersion of material passing through the fiberous material.

[075] Fig. 10 shows another embodiment of the invention using electrical power to enhance the performance of the armor system of the present invention. In this embodiment the electrically conductive member 54 is adjacent to the interior surface of the fiber-reinforced sheet armor 12'. In a preferred embodiment it is adhered thereto facilitating the fabrication of this preferred armor system. In the embodiment of Fig. 10 the armor plates 12 and 14 are electrically grounded and the electrical power is applied to the electrically conductive member 54. As with the embodiment of Fig. 9, the first dispersion space in this embodiment is the space 18' because the fiber-reinforced armor layer 12' does not allow dispersion of material passing through the fiberous material.

[076] Fig. 11 shows another embodiment of the invention using electrical power to enhance the performance of the armor system of the present invention. In this embodiment the electrically conductive member 54 is adjacent to or adhered to the interior surface of the fiber-reinforced sheet armor 12'. In this embodiment there is included an layer 60 comprised of an electrical insulator. In a preferred embodiment the outer layer 60 consists essentially of a ceramic material providing both electrical insulation and advantages in defeating certain types of anti-armor projectiles by virtue of the high compression strength of such materials. The outer layer 12" need not be armor but could include any electrical insulator. In the embodiment of Fig. 11 the electrical power is applied to armor plates 12 and 14 and the electrically conductive member 54 is electrically grounded. The presence of the outer electrically insulating layer 12" reduces the electrical hazard to personnel coming in contact with the surface of the armor system. As with the embodiment of Figs. 9 and 10, the first dispersion space in this embodiment is the space 18' because the fiber-reinforced armor layer 12' does not allow dispersion of material passing through the fiberous material.

[077] Fig. 12 shows another embodiment of the invention using electrical power to enhance the performance of the armor system of the present invention. In this embodiment the electrically conductive member 54 is adjacent to or adhered to the interior surface of the fiber-reinforced sheet armor 12'. Another fiber-reinforced sheet armor 12" is adjacent the electrically conductive member 54 and the inner armor layer 14. This embodiment may include an outer layer 60 comprised of an electrical insulator. In a preferred embodiment the outer layer 60 consists essentially of a ceramic material providing both electrical insulation and advantages in defeating certain types of anti-armor projectiles by virtue of the high compression strength of such materials. The outer layer 60 need not be armor but could include any electrical insulator. In the embodiment of Fig. 12 the electrical power is applied to armor plates 12 and 14 and the electrically conductive member 54 is electrically grounded. The presence of the outer electrically insulating layer 60 reduces the electrical hazard to personnel coming in contact with the surface of the armor system. There is no first dispersion space in this embodiment because the fiber- reinforced armor layers 12' and 12" does not allow dispersion of material passing through the fiberous material.

[078] In the embodiments where electrical power is used to enhance the performance of the armor system the electrical power can be applied to any conductive layer in the system with other adjacent layers being grounded. While configurations that apply power to the outermost layer are not preferred due to personnel hazard, such a configuration is operable and within the scope of the invention. One skilled in the art of high energy systems can readily devise an appropriate system to supply the requisite power to the armor systems of the present invention. The presence of the electrically insulating layers of fiber- reinforced armor facilitate the use of such systems by providing an electrically insulative layer with a higher dielectric constant than a simple air gap. This allows the application of higher levels of electrical power while reducing the likelihood of electrical discharge between adjacent conductive layers.

[079] In addition, the source of electrical power may be a capacitor system connected to adjacent conductive layers of the present invention. Moreover, the adjacent conductive layers of the armor system of the present invention may comprise the plates of the capacitor system storing the electrical energy used to defeat a projectile or penetrator passing therethrough.

[080] 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.

Claims

WHAT IS CLAIMED IS:

1. An armor system for defeating a solid projectile, said system comprising: an exterior rigid armor plate having an exterior surface and an interior surface; a fiber-reinforced sheet armor comprised of a plurality of fibers having an ultimate tensile strength greater than 2.5 GPa bonded to form the sheet by a polymer surrounding the fibers, the sheet armor being affixed to the interior surface of the exterior armor plate; an interior armor plate disposed approximately parallel to the fiber- reinforced sheet armor and displaced therefrom to form a first dispersion space between the fiber-reinforced sheet armor and the interior armor plate; and an inner armor plate disposed approximately parallel to the interior armor plate and displaced therefrom to form a second dispersion space between the interior armor plate and the inner armor plate, the second dispersion space being sufficiently thick to allow significant lateral dispersion of materials passing therethrough.

2. The system of claim 1 wherein the fiber in the fiber-reinforced sheet armor sheet is bonded into sheet form with a matrix of polymer material that consists essentially of a material selected from the group consisting of: phenolic resins, epoxy resins, vinyl ester resins, polyester resins, acrylate resins, and polymethyl (meth)acrylate.

3. The system of claim 1 wherein the fiber in the fiber-reinforced sheet armor sheet consists essentially of a material selected from the group consisting of: poly-paraphenylene terephthalamide, stretch-oriented high molecular weight polyethylene, stretch-oriented high molecular weight polyester, a polymer based on pyridobisimidazole, and silicate glass.

4. The system of claim 1 wherein the fiber-reinforced sheet armor comprises a sheet of self-bonded polymer comprised of a plurality of polymer fibers, each having an interior core of high melting point, high strength polymer and an exterior sheath of low melting point, low strength polymer.

5. The system of claim 4 wherein the fiber-reinforced sheet armor consists essentially of a material selected from the group consisting of: polypropylene and polyethylene.

6. The system of claim 1 wherein the outer armor layer consists essentially of a sintered material selected from the group consisting of: silicon carbide, boron carbide, alumina, and a blend of zirconia and alumina.

7. The system of claim 1 the interior armor plate being displaced from the fiber-reinforced sheet armor to form a first dispersion space between the fiber- reinforced sheet armor and the interior armor plate, the first dispersion space being sufficiently thick to allow significant lateral dispersion of material passing though the first dispersion space.

8. The system of claim 1 the fiber-reinforced sheet armor being bonded to the interior armor plate.

9. The system of claim 1 including a plurality of spheres located in the second dispersion space, the spheres consisting essentially of a material selected from the group of brittle metal, ceramic, and glass.

10. The system of claim 9 wherein the spheres are surrounded by a material selected from the group of: a liquid and a gel, said material having a velocity of forced shock greater than 1 ,000 meters/sec.

11. The system of claim 1 further including an electrically conductive member disposed in the dispersion space between two adjacent electrically conductive armor plates, a source of electrical power disposed to apply electrical power to the electrically conductive member the source of electrical power being disposed to supply sufficient electrical power to disperse at least a portion of an elongated projectile making electrical connection between at least one of the two adjacent armor plates and the electrically conductive member.

12. The system of claim 1 wherein at least one armor plate, having an outer surface opposite a dispersion space, includes a plurality of projections on the outer surface, the projections being disposed to at least partially fragment solid projectiles impinging on the outer surface of the armor plate.

13. The system of claim 1 wherein at least one armor plate, having an inner surface facing a dispersion space, includes a plurality of projections on the inner surface, the projections being disposed to disperse solid material erupting through the inner surface of the armor plate.

14. The system of claim 1 wherein the surface of the inner armor plate facing the dispersion space, includes a plurality of projections on the inner surface, the projections being disposed to disperse solid material impinging on the outer surface of the inner armor plate.

15. The system of claim 1 where each of the armor plates are comprised of materials having different values for the velocity of a forced shock wave passing therethrough.

16. The system of claim 1 wherein the system is an assembly affixed to the exterior of an armored vehicle.

17. The system of claim 1 , wherein the vehicle includes a body and the body includes a layer of sheet armor affixed to the interior surface of the body.

18. The system of claim 17, wherein the sheet armor affixed to the interior surface of the body comprises a rigid polymer/fiber composite.

19. The system of claim 18, wherein the sheet armor affixed to the interior surface of the body comprises a woven fabric comprised of fiber.

20. The system of claim 18, wherein the sheet armor affixed to the interior surface of the body comprises a woven fabric comprised of fiber and a plurality of ceramic plates.

21. The system of claim 17, wherein the sheet armor is spaced from the interior surface to form a gap.

22. The system of claim 16, wherein the vehicle is a blast-resistant armored land vehicle having a monocoque body comprised of sheet steel, the body having a bottom portion defining at least one V, with the apex of the V substantially parallel to the centerline of the vehicle.

23. A method of defeating a hybrid, anti-armor projectile, comprising the steps of: interposing a rigid exterior armor plate as the outer layer of a multilayer armor system; the exterior armor plate having an exterior surface and an interior surface; and interposing a fiber-reinforced sheet armor comprised of a plurality of fibers having an ultimate tensile strength greater than 3GPa bonded to form the sheet by a polymer surrounding the fibers adjacent the exterior armor sheet such that any projectile defeating the exterior armor sheet next encounters the fiber- reinforced sheet armor.

24. The method of claim 23, including the further steps of: interposing an interior armor plate approximately parallel to the fiber- reinforced sheet armor; and interposing an inner armor plate approximately parallel to the interior armor plate and displaced therefrom to form a second dispersion space between the interior armor plate and the inner armor plate, the second dispersion space being sufficiently thick to allow significant lateral dispersion of materials passing therethrough.