WO2006119165A1

WO2006119165A1 - Lightweight, projectile-resistant, composite armor

Info

Publication number: WO2006119165A1
Application number: PCT/US2006/016585
Authority: WO
Inventors: Harley J. Pattee
Original assignee: E Z Tanks, Inc.
Priority date: 2005-05-02
Filing date: 2006-05-02
Publication date: 2006-11-09

Abstract

A lightweight, composite armor is made of at least two distinct phases of material, preferably at least one layer of ballistic fabric plys sandwiched between at least two layers of copolymer polypropylene, and optionally comprising metal.

Description

DESCRIPTION

LIGHTWEIGHT, PROJECTILE-RESISTANT, COMPOSITE ARMOR

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of the United States Provisional Application No. 60/676,892, filed May 2, 2005, the disclosure of which is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

This invention relates to armor, providing protection against bullets and other projectiles.

BACKGROUND OF THE INVENTION Protective armor is used in wide variety of applications, including body armor for individuals (such as ballistic vests), armor plating for surfaces of vessels and vehicles, and as reinforcement for protective containers, to name a few. Ballistic vests have been available, in recent years as in protective panels having overlying layers of a fabric made from woven high-tensile strength fibers. Woven fibers from an aramid fiber known as KEVLAR, for example, have been used successfully in ballistic vests because of the high-energy absorption properties of the fabric material. In addition to woven KEVLAR fabric layers, ballistic vests have been made from other high-strength woven polymeric fibers. Such materials are reasonably light in weight and flexible, which provides improved comfort when compared with previous vests which were made of metal and were therefore heavier and more rigid.

The excessive weight of metal armor has also plagued users in a variety of other situations. When used as protection for armored vehicles or vessels, the quantity of metal armor required to protect the occupants from projectiles launched by weaponry commonly used against such vehicles or vessels adversely affects the speed and maneuverability of the vehicle or vessel. For example, various methods of armor plating have commonly been used by the marine industry in constructing warships. Thick steel plating is a most common solution to the protection problem. While this solution is valuable and acceptable on large "battlewagons" such as aircraft carriers, battleships, and the like, it is not always a viable alternative for swift, lightweight, pursuit-type patrol boats.

Although fabric vests have been developed that can protect individuals, most of these forms of protective clothing are directed to stopping small arms fire such as from pistols. Marine pursuit vessels such as those used by the U.S. Coast Guard and U.S. Customs Service require lightweight yet effective protection for vital spots including personnel, electronics, fuel supply, ammunition storage, and the like. Because these vessels must function in a hostile marine environment, usually saltwater, and often in rough seas, any armor must be resistant to water, to salt corrosion, and ideally is easily removable/transportable during storms so that the vessel's center of gravity can be lowered. Further, such vessels can be fired upon by automatic weapon fire wherein multiple rounds hit the armor in close proximity. Ideally, the armor should be able to withstand such repetitive hits. There is a continuing need for lightweight, rigid and semi-rigid panels of protective armor useful in a variety of applications.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 depicts a cross-section side view of one embodiment of armor panel according to the subject invention in the form of sheetstock comprising two layers of copolymer polypropylene plastic encapsulating a ballistic fabric layer comprising 12 sheets^' (or "plys") of KEVLAR 29 style 745 3000 denier ballistic fabric. The drawing is not to scale, and is merely illustrative.

Figure 2 depicts a not-to-scale top view cut-away of the embodiment represented in Figure 1 with partial exposure of the KEVLAR ballistic fabric.

Figure 3 depicts a side view of another embodiment of vented armor panel according to the subject invention. The drawing is not to scale.

Figure 4 depicts a not-to-scale cross-section side view of yet another embodiment of the subject invention wherein the armor panel comprises a plurality of ballistic fabric layers, each sandwiched between layers of copolymer polypropylene. Figure 5 depicts a not-to-scale cross-section sideview of still yet another embodiment of the subject invention which the armor panel comprises a metal layer in addition to layers of ballistic fabric and copolymer polypropylene.

DESCRIPTION OF THE INVENTION

As used herein, a composite armor is defined as an armor made up of at least two distinct phases of material that, when combined together, complement each other with their respective desirable physical properties, allowing the composite article to have better physical properties than either single phase has alone. In one embodiment, the composite armor is made of at least one layer of KEVLAR plys stacked on top of each other to form a ballistic fabric layer that is sandwiched between layers of copolymer polypropylene.

The present invention provides a composite armor for use in protecting people, vessels, vehicles, and the like wherein the armor panels must not only withstand small arms fire (typically pistol), but also high power rifle fire, and in some uses additionally the corrosive atmosphere of saltwater. Further, the armor of the present invention can be conformed to the contours of a vessel; yet at the same time be of lightweight material having a weight of, for example, from one to ten pounds per square foot (in some embodiments, but less or more in others as desired) so as not to materially affect the weight of the overall vessel. Typically, various embodiments of the present invention can handle a Class 1 threat (e.g., .22 caliber) through and including a Class 6 threat (e.g. a .50 caliber U.S. machine gun with armor piecing bullets). Different thicknesses of the armor have the ability to offer different strengths, depending on the ultimate intended use. The armor can effectively "catch" bullets or other projectiles causing them not to fragment or ricochet, problems that are frequently encountered with standard metal-plate armor.

One embodiment of the subject invention comprises a layer of woven polymeric fiber plys sandwiched between two layers of copolymer polypropylene, as illustrated in Figure 1. In a preferred embodiment, the woven polymeric fiber plys are plys of KEVLAR, the armor comprising a first layer 101 of copolymer polypropylene on a strike side of the armor, a second flexible layer 102 comprising a plurality of plys of KEVLAR arranged in a stack in face-to-face surface contact, and a third back layer 103 comprising copolymer polypropylene plastic on an interior side of the armor that in use would face the person or object to be protected. The first and third layers 101, 103 are connected to each other such that the second layer 102 is sandwiched therebetween in a manner so as not to fall out from between the first and third layers. The means for connecting the first and third layers can be rivets or other mechanical fasteners (such as, for example, stainless steel screws); alternatively, the means for connecting the first and third layers can be spot-welding or heat-crimping of the copolymer plastic layers one to another at points along their periphery that extend beyond the edges of the plys stacked in the second layer; or in yet another alternative means for connecting the first and third layers, they may be molded or melted together along their periphery. At a minimum, the means for connecting the first and third layers must extend along at least a portion of one edge of the armor plate, such that the second layer of ballistic fabric plys cannot fall out of the armor plate. In a number of embodiments, a plurality of the ballistic fabric plys are not fastened to the panels between which they are sandwiched, such that they are more freely able to move when impacted by a projectile. However, in other embodiments they may be attached by virtue of rivets or other mechanical fasteners passing through the fabric, or by contact with melted copolymer polypropylene, for^' example, during the manufacturing of the composite armor. The result of the subject invention is an armor plate that is relatively light in weight, and rigid or semi-rigid, such that it can be used as a structural component where desired, such as in buildings, vehicles, or vessels, as well as being used in a variety of other applications, such as for individual body armor.

Although in a preferred embodiment the layers or panels of the subject invention are made from a woven fabric comprising high-strength ballistic-resistant polymeric fibers such as aramid fiber, which include fibers available under the designation KEVLAR, other similar high-strength ballistic-resistant polymeric fabrics such as those comprised of woven extended chain polyethylene fibers, nylon fibers, polyolefm fibers such as polypropylene, and polyvinyl alcohol fibers (and others that are well known in the art), could be used according to the teachings herein. Depending on the intended use and placement of the composite armor, the thickness of each layer and the number of layers can vary, as will be readily evident to the skilled artisan.

In the event of a ballistic attack the composite armor plate provides a gap between the front layer (or "strike side" layer) of the armor and the back layers of armor. This gap allows the ballistic projectile some room to continue to tumble or yaw so as to present a larger surface with more area to the final layers of the composite armor. The at least one layer of sandwiched ballistic fabric plys provides flex and an elastic deformation medium for dispersing the energy of a projectile that has passed through the initial, strike side layer of copolymer polypropylene.

Some high tensile strength fragment-resistant materials, such as copolymer polypropylene tend to deform and slow down a projectile, while other types of high tensile strength ballistic materials such as KEVLAR tend to grab and turn a fragment projectile. Typically higher tensile strength materials having lower relative elongation of yield grab' at the projectile and tug it toward a side, rather than deforming it as the projectile impacts the material.

The behavior of high tensile strength ballistic material is a function of the material's tensile strength, elongation of yield, and pick count. The tensile strength of the fibers in a ballistic fabric is a leading indicator of that fabric's ability to induce yaw into the path of projectile. A higher tensile strength gives the fabric a better ability to grab the projectile before yielding to penetration by the projectile than a ballistic fabric with a lower tensile strength. The fabric's grabbing at the projectile before yielding is what induces yaw into the path of the projectile. Yaw is a pivoting motion that tends to be perpendicular to the direction in which the projectile is traveling.

A projectile undergoing yaw will either roll onto its side or tumble. If the projectile rolls or tumbles, more surface area is exposed to be caught by the armor. The armor typically will have better stopping ability against a projectile with a large area of surface in contact with it, than with a small area of surface in contact with it. The tensile strength of a ballistic fabric can be increased by increasing the denier of the thread of material used to weave the fabric. . Thus, for example, a ballistic fabric with a thread having a denier of about 2000 will have a higher tensile strength than a ballistic fabric made from an identical chemical with a thread having a denier of about 1000.

The elongation of yield of a ballistic fabric is a leading indicator of that fabric's ability to induce deformation into a projectile. When struck by a fragment projectile, a high tensile strength ballistic material with a high pick count and a low elongation of yield will tend to grab at the projectile and turn it to induce yaw, but will not cause much deformation of the projectile. A ballistic material with a higher elongation of yield will tend to hang on the projectile as the fibers of the material stretch. The stretching of the material allows additional time for the fabric to hang on to the projectile, deforming the projectile and slowing it down as fibers elongate, before yielding to penetration.

It has been found that by confronting a high- velocity projectile with an alternating series of tougher and softer layers, greater stopping power is achieved over a similar number of layers of either individual material type. The composite armor of the subject invention confronts a high velocity projectile with a number of different layers that have different reactions to impact.

It should be noted that similar fabric materials with different deniers and pick counts effectively constitute "different material." This is because they will have different mechanical properties. Higher denier generally means that the fiber filament has a larger cross-sectional area, and there is more of the fiber per length of thread.

This additional material . gives the thread greater tensile strength. Greater tensile strength gives the fabric greater resistance to penetration. Higher pick counts mean there are more threads per area to be struck by the projectile. These additional threads in higher pick count materials add their tensile strength to the resistance to penetration of fabric.

While materials with similar deniers and pick counts might be thought to have similar stopping power and ballistic abilities, a varying elongation of yield can make these materials respond to ballistic events differently. Thus it is not always possible to base exact ratios of projectile stopping ability based on only denier and pick counts. ■ One embodiment of the composite armor uses various lay ups of KEVLAR 29

3000 denier fabrics sandwiched between layers of copolymer polypropylene. One of ordinary skill in the art would recognize, however, that with adequate notice given to denier, pick count, and elongation of yield, various materials might be substituted for the fabrics mentioned above. Such substitutions can be, but are not limited to, para aramids such as PBO; ZYLON; various denier KEVLAR KM2 materials such as 800, 600, 500, or 400 denier material; and KEVLAR 129 400 denier material. In some embodiments it is preferred that the composite armor panel comprise metal. Weight considerations may dictate the type and amount of metal used, as will be readily apparent to the skilled artisan. However, it has been found that inclusion of metal can assist in causing further deformation of an incoming projectile, decreasing its velocity and making it easier to stop. Metal can be incorporated into any or all layers of the copolymer polypropylene, preferably as flattened pieces laying parallel to the plane of the copolymer. Alternatively, or in addition, metal can be used at any surface of a copolymer polypropylene layer. Alternatively, or in addition, metal can constitute its own layer at any point in the composite panel. However, if a metal layer is incorporated, it is generally preferred to be disposed proximal to the strike side layer of copolymer polypropylene, either on the interior surface, on the exterior surface (making the metal layer the true strike side surface), or sandwiched between two layers of copolymer propylene. While it can be envisioned that most types of metal could be used in construction of the composite armor of the present invention, steel, tungsten, or titanium are generally preferred. Various shapes of panels might be substituted in the manufacture of the composite armor. The basic shape of copolymer polypropylene panels is rectangular. However, other shapes may be substituted, depending on intended use and placement. Such substitutions can be, but are not limited to, circular, elliptical, triangular, square, pentagonal, hexagonal arid, octagonal. As will be apparent to the skilled artisan, due to the nature of the constituents of the composite panels, virtually any shape desired can be achieved.

Composite armor panels can be made by combining various layers of aramid fabrics, polyethylene fabrics, and copolymer polypropylene, and optionally, metal. Because of its ease of molding and manufacture, sheets of copolymer polypropylene can be made that comprise pieces or plates of metal, or that incorporate other substances, such as fiberglass, into the^" copolymer sheet itself such that a single layer of the copolymer polypropylene has these other materials embedded in it. Layers of copolymer polypropylene, with or without other materials embedded, should in most cases be at least disposed on the strike-surface layer and on the opposite outermost back layer, and then optionally between the different layers of fabric and/or metal.

Figure 2 is a top down cut away schematic view of one embodiment of a composite armor panel showing strike side layer 101 and ballistic fabric layer 102.

The composite armor is a combination of layers designed to alternately cause deformation to a ballistic projectile and to induce yaw to the path of the projectile. The panel also provides a small amount of flex and elastic deformation that absorbs and dissipates the energy from a forced-entry or ballistic attack over an area that is larger than the area that is directly attacked.

A number of methods of making composite armor according to the subject invention will become readily apparent to those of ordinary skill in the art in view of the teachings herein. For example, the armor panels can be made by stacking a plurality of plys of ballistic fabric face-to-face on top of each other and extruding them between layers of copolymer polypropylene formed in a desired thickness. If the width of the ballistic fabric layer is less than the width of copolymer polypropylene sheets, as they are extruded the edges of the plastic can be melted together, thereby fastening the layers of copolymer polypropylene to each other and encasing the sandwiched layer of ballistic fabric. Alternatively, layers of copolymer polypropylene can be provided in prefabricated form of desired size, shape, and thickness. A layer of ballistic fabric is provided having a plurality of individual plys of ballistic fabric stacked face-to-face on top of each other. This layer is then sandwiched between the layers of copolymer polypropylene, which are then fastened to one another by rivets or other mechanical fasteners. The rivets or other type of mechanical fastener (such as, for example, stainless steel screws) can optionally be used to fasten the copolymer polypropylene layers to each other by penetrating the ballistic fabric layer, thereby more securely holding the fabric layer in place, or alternatively can be positioned closer to the periphery of the panel such that if the dimensions of the copolymer polypropylene layers allow, penetration of the sandwiched fabric layer is avoided, thereby allowing freer movement of the fabric layer when impacted by a projectile. Alternatively, if the. edges of the copolymer polypropylene extend beyond the edges of the ballistic fabric layer, the copolymer polypropylene sheets can be heat- crimped together or spot welded together at points along their periphery, yielding a composite panel which, viewed edge-on, could appear as depicted in Figure 3. Figure 3 is not to scale, but depicts strike side. layer 301, ballistic fabric layer 302, back layer

303, vents 304, and attachment points 305. .One advantageous characteristic of this configuration is that vents 304 are formed between attachment points 305, and through which air is allowed to flow in and out of the interior of the composite panel providing desirable reactivity when the armor is impacted by a high-speed projectile, while more easily assuring that the ballistic fabric is flexible and moveable within the armor panel after its construction, and also thereby providing desirable energy absorption and deflection characteristics.

In yet another method of manufacturing the subject invention, a layer of copolymer polypropylene can be provided in a mold, a plurality of plys of ballistic fabric can be placed thereon, and another layer of copolymer polypropylene provided in the mold. The layers copolymer polypropylene are pressed together at temperatures under which their edges melt together, thereby fastening the ballistic fabric panel between copolymer polypropylene layers. This method of manufacture is particularly suited to making relatively small panels of desired shapes and sizes. As will be readily apparent to the skilled artisan, the number of layers of copolymer polypropylene and ballistic fabric plys can be increased depending on the thickness of armor panel desired, and the various anti-ballistic characteristics desired. An example of such an armor panel, having a plurality of ballistic fabric layers, each comprising a plurality of ballistic fabric plys, is depicted in Figure 4. Although not drawn to scale, Figure 4 shows strike side copolymer polypropylene layer 401, ballistic fabric layers

402, internal copolymer polypropylene sandwich layers 404, and back layer 403. In this particular embodiment, strike side layer 401 is intended to be depicted as thinner than internal sandwich layers 404, which are in turn thinner than back layer 403. As will be readily apparent to the ordinary artisan, the thickness of the various layers can be modified to optimize' the projectile stopping properties of the composite armor panel. Specific embodiments that comprise metal have proven particularly adept at stopping projectiles while still retaining light weight. An exemplary embodiment is depicted in Figure 5, and comprises a Vs" thick layer of cold roll steel 507 at the strike surface, backed by a ¹A" layer of high density copolymer polypropylene 501, followed by a ballistic fabric layer 502 comprising 12 plys of sheet KEVLAR 29 style 745

3000, and a back layer of ¹A" high density copolymer polypropylene 503. In this specific embodiment, retaining bracket 506 holds the layers of the composite armor in their proper respective positions. One or more brackets may be used, depending on their size and as desired for the context of use. The retaining bracket(s) can be substituted with one or more clamps or one or more channels to hold the layers together in position. Such means for holding the layers together can be chosen based on what is most convenient or desirable for a particular situation, as will be evident in view of the teachings herein. Other means for holding the layers such as adhesives, rivets, brads, screws, nails, heat crimping, spot welding, or melting of copolymer or other materials to cause the layers to be held in desired position can be used for these and all other embodiments of the claimed invention.

In some embodiments the layers can be stacked within a fabric pouch. The pouches can be integral parts of garments, or sown into place, or affixed in a removable fashion by, for example, use of VELCRO or other means of removably affixing the "armor pouch" in a desired location.

As will be readily apparent to the skilled artisan, the number, type, and thickness of layers can be varied as desired. If projectile ricochet is undesirable, a layer of copolymer polypropylene can be placed on the strike side of the metal layer. In addition, embodiments having a metal layer to the strike side of the KEVLAR, in between the plys of KEVLAR, or even to the back side of the KEVLAR, have also proven quite effective at stopping projectiles.

A wide variety of uses are contemplated for the composite armor panels of the subject invention. Because of the ease of shaping and working with the various components of the composite armor according the subject invention, it can readily be used in a variety of applications such as aircraft uses, including cock-pit doors and walls; motorized vehicle doors, roofs, floorboards, and any other body panels or undercarriage protection uses; encasement of sensitive equipment to protect it from damage by externally-originating projectiles; encasement of materials, such as luggage, that might have explosive characteristics thereby protecting the external environment from projectiles that would originate within the encased object; and due to the variety of rigid and semi-rigid characteristics that can be obtained it can be used in a variety of other structural applications such as marine vessels, cargo containers, bank and convenience store construction, toll booth construction, hunting blinds or shooting ranges, personal body armor, and many other applications that will be readily apparent to those of skill in the art.

Claims

CLAIMS I claim:

1. (original) A composite armor comprising at least three layers, and having a strike side and a back side; a first of said layers comprising copolymer polypropylene, a second of said layers comprising a plurality of plys of ballistic fiber, and the third of said layers comprising copolymer polypropylene; the first layer being disposed to the strike side of the ballistic fiber layer, and the third layer being disposed to the back side of the ballistic fiber layer.

2. (original) The composite armor according to claim 1, wherein the first layer comprises at least one metal piece embedded in the copolymer polypropylene.

3. (original) The composite armor according to claim 1, further comprising a metal layer.

4. (original) The composite armor of claim 3, wherein the metal layer is disposed to the strike side of the first copolymer polypropylene layer.

5. (original) The composite armor according to claim 3, wherein the metal layer is disposed to the back side of the first copolymer polypropylene layer.

6. (original) The composite armor according to claim 5, wherein the metal layer is disposed to the strike side of the ballistic fiber layer.

7. (original) The composite armor according to claim 5, wherein the metal layer is disposed between ballistic fiber plys.

^• 8. (original) The composite armor according to claim 5, wherein the metal layer is disposed to the back side of the ballistic fiber layer.

9. (original) The composite armor according to claim 5, comprising the following layers in order from strike side to back side: a layer comprising copolymer polypropylene, a metal layer, a layer comprising copolymer polypropylene, a layer comprising a plurality of ballistic fiber plys, and a layer comprising copolymer polypropylene.