WO1999022195A9

WO1999022195A9 - Armor material and methods of making same

Info

Publication number: WO1999022195A9
Application number: PCT/US1998/022401
Authority: WO
Inventors: Katherine Tunison Leighton; Robert Allen Coffelt
Original assignee: Lanxide Technology Co Ltd
Priority date: 1997-10-24
Filing date: 1998-10-23
Publication date: 1999-07-01
Also published as: AU1273899A; WO1999022195A1

Abstract

The present invention is directed to lightweight armor systems which are simply and economically manufactured. Armor systems of the present invention comprise fiber encapsulated ballistic resistant core materials which are preferably coated or impregnated with a resin composition. Armor systems of the present invention have enhanced ballistic performance with multi-hit ballistic capacity and can withstand the rigors of everyday use. The armor systems may be used alone or in combination with other ballistic resistant materials, and are suitable for use as personnel armor, as well as for vehicles, buildings, and the like.

Description

ARMOR MATERIAL AND METHODS OF MAKING SAME

TECHNICAL FIELD

The present invention is directed to light weight armor systems which are simply and economically manufactured. Armor systems of the present invention comprise fiber encapsulated ballistic resistant core materials which are preferably coated or impregnated with a resin composition. Armor systems of the present invention have enhanced ballistic performance with multi-hit ballistic capacity and can withstand the rigors of everyday use. The armor systems may be used alone or in combination with other ballistic resistant materials, and are suitable for use as personnel armor, as well as for vehicles, buildings, and the like.

BACKGROUND ART

Armor materials including personnel armor, such as bulletproof vests, helmets, handheld shields, etc.. as well as vehicle and structural armor, such as tiles and panels for vehicles and buildings, and the like are known. Such armor has been produced from various materials including metal, ceramic, glass, plastic, fabric, and combinations thereof. Metallic armor materials, such as steel plates are effective against projectiles advantageously possessing multi- hit capacity, however, such armor products are often heavy and inflexible. Armor materials comprising multiple layers of fabric composed of high strength fibers, such as aramid fibers, glass fibers, nylon fibers, ceramic fibers, etc.. are also known. Such armor is advantageously flexible and light weight, however, armor materials exclusively comprising such fabric may be penetrated by a projectile at weakness inherent in the fiber or fiber weave. It is also known to encapsulate or embed such fibers with a resin composition to form desirable armor materials. Non-metallic armor materials, such as ceramics and ceramic composites are advantageously light weight, and are characteristically selected for the ability to dissipate the energy of a projectile. Combinations of two or more types of armor materials are also used, where specific combinations of materials are selected depending upon the anticipated threat.

It is well known to use metal armor materials, such as high hardness steel and aluminum alloys, for ballistic protection on armored vehicles, for example, as hulls, hatch covers, etc. For economical reasons, high strength, low weight titanium armor materials are often limited to aircraft where weight limitations are imposed. Increased hardness of metal armor materials result in armor which is often brittle, fragmenting and spalling upon impact.

To protect against spalling, fragmentation, and crack mitigation, metal armor materials are sometimes coated with rubber. Moreover, composite armor systems have been prepared To protect against spalling, fragmentation, and crack mitigation, metal armor materials are sometimes coated with rubber. Moreover, composite armor systems have been prepared wherein a layer of metal is attached to a layer of fiber and/or fiber resin matrix for protection against face-spalling or fragmentation. Where metal armor material is used as personnel armor, such as for helmets, and jacket and vest inserts, including breast plates and back plates, inherent limitations exist relating to weight, articulation, penetrability, and expense (for example, where titanium is used). Attempts to enhance ballistic or penetration resistance of metal armor materials have focused on increasing the hardness and/or the thickness of the metal often resulting in increased weight. Other attempts to overcome the inherent limitations of metal-containing armor materials include the use of alternate materials which provide enhanced penetration protection and flexibility at similar weights as metal armor, or which provide lighter weight armor having greater flexibility with similar levels of penetration resistance. Soft body armor comprising fabrics made from high strength fibers, such as KEVLAR® fiber, fiberglass, nylon, and the like, and light weight materials, such as ceramic, are used in personnel armor which is lighter weight and/or more penetration resistant than metal-containing armor. Personnel armor containing metal, metal alloys, and the like, is typically limited for use as protection against trauma and fragmentation, for example, as inserts into jacket and vest pockets, or alternately, in combination with ballistic resistant materials, such as ceramic. It is well known that the brittle nature of certain armor materials, for example, non- metallic materials, renders armor bodies constructed of such materials susceptible to damage by ballistic strikes, as well as from dropping onto hard surfaces. Multi-hit performance of non- metallic armor material is severely restricted in materials which are susceptible to shattering and spalling upon impact. Further, personnel handling of armor materials such as dropping onto hard surfaces, stacking multiple devices or tossing into vehicles, may generate microfractures reducing the protectiveness of the armor device against subsequent ballistic strikes. In armor applications of non-metallic materials, multiple hit capacity can be increased by constructing ballistic resistant materials comprising two or more ceramic tiles or blocks joined to form a mosaic. For example, tiles may be arranged as a mosaic whereby upon destruction of one section of the armor body, the remainder of the armor body remains effective against future threats. Ceramic tile mosaics often consist of several ceramic tiles joined by adhesives to form the mosaic, with the adhesive joints acting as crack stopping mechanisms confining damage to single sections of the mosaic.

However, known armor bodies comprising single or multiple non-metallic components, shatter or spall upon impact posing serious risk of injury to persons and objects at or near the impact sight. Spall shields inhibiting shattering or spalling are commonly utilized to contain fragments from propelling outward from the surface after impact. Spall shields are placed on Currently spall shield materials are typically insufficient to contain fragments, which often break out from the fabric when the armor component is struck at the edge by ballistic attack. Further, spall shield materials are currently insufficient to prevent damage such as the formation of cracks and microcracks developed through everyday personnel handling of armor materials. Additionally, the current methods of encapsulating armor material with spall shields often result in poor adhesion or bonding between the armor material and the spall shield material. This is particularly evident where the armor material to be encapsulated is a non- planar body; the spall shield material, applied, for example, by shrink-wrapping, pulls away from the non-planar surface of the armor material upon encapsulation, forming a void or air pocket between the armor surface and the spall shield material.

The present invention is directed to overcoming the limitations of current armor materials. Specifically, the present invention is directed to the formation of attractive armor systems which are light weight and can withstand everyday handling without compromising ballistic performance. Moreover, armor systems of the present invention may be prepared from surprisingly simple, low cost manufacturing processes, and exhibit higher levels of ballistic protection than would be expected from armor materials of similar weight and cost. The armor systems of the present invention are particularly significant because of the low cost and simplicity of manufacture. In addition, such armor systems desirably withstanding more than a single ballistic event, having multi-hit capability. To this end, the present invention provides light weight, ballistic resistant materials which can easily serve as personnel armor material, such as easily removable inserts which slide out of pockets of bulletproof jackets and vests, as well as a light weight shield, or briefcase armor and panels for vehicle or structural armor. The materials are tailorable to a wide variety of shapes and sizes.

DISCLOSURE OF THE INVENTION

The present invention is directed to armor material systems which are hard and light weight, and which may be used for personnel applications such as breast plates and back plates of armor vests, and helmets, as well as for structural and vehicle applications, such as tiles and panels for vehicles and structural materials, etc. The present invention comprises an armor system comprising at least one ballistic resistant core material which may comprise, for example, ceramic, ceramic matrix composite, metal, metal alloy, metal matrix composite, and combinations thereof, formed into a desirable shape. The present invention is particularly useful in attaining unexpected levels of protection from light weight core materials previously believed incapable of providing acceptable levels of ballistic protection. By increasing the level of ballistic protection, the present invention allows for the use of relatively inexpensive, light weight core materials to be used for protection levels for which these materials were level of ballistic protection, the present invention allows for the use of relatively inexpensive, light weight core materials to be used for protection levels for which these materials were previously deemed unacceptable, and which provide for increased durability against the rigors of day-to-day handling. For example, in one embodiment of the present invention multi-hit ballistic protection is provided by thin plates comprising inexpensive, light metal and metal alloys such as aluminum alloys and steel, where the same or comparable material would normally be used only for trauma and fragmentation protection, and further where normally a thicker, heavier steel or thicker, heavier, more expensive metal, such as titanium alloy would be necessary to achieve the desired ballistic resistance. In another embodiment of the present invention, the performance of light weight core material such as ceramic and ceramic composites have enhanced protection against cracking, breaking, shattering, or spalling upon impact, thus, having an improved ability to sustain multiple ballistic strikes, as well as withstanding the rigors of everyday personnel handling.

In addition to the at least one ballistic resistant core material formed from materials including, for example, metal, metal composite, metal alloy, ceramic, and ceramic composite, and combinations thereof, the armor systems of the present invention further comprise at least one fiber layer contacting one or more side and edge surfaces of the ballistic resistant core material. Preferably, at least one fiber layer applied to the core material comprises a high strength fiber as discussed above. In a preferred embodiment, a fiber layer is adhered to all side and edge surfaces of the at least one ballistic resistant core material thus, fully encapsulating the core. In a particularly preferred embodiment, more than one fiber layers having different fiber material compositions are applied to encapsulate the core material.

Preferably, an armor system comprising ballistic resistant core material with at least one fiber layer applied thereto, is coated or impregnated with at least one polymer-like composition. A most preferred embodiment comprises a resin system having more than one organic, polymer-like composition. Coating or impregnating compositions may be applied in any known manner. A preferred impregnation method is known as vacuum assisted resin transfer molding ("VARTM"). After coating or impregnating the fiber material, the coating or impregnating composition is allowed to dry and, depending on the composition selected. further may be cured.

In one embodiment of the present invention, an armor system is formed comprising at least one ballistic resistant core material comprising metal, metal alloy, metal composite, or combinations thereof, having at least one fiber layer contacting the ballistic resistant core, which has been coated or impregnated with at least one polymer-like composition and which comprises sufficient bonding between the at least one fiber layer and the metal core surface.

Without wishing to be bound by theory or explanation, it is believed that such bonding results in a change in certain ballistic phenomena, for example, where upon ballistic strike the core failure mode is changed from plugging to petalling, resulting in enhanced ballistic performance of the ballistic resistant core material. The term plugging is intended to comprise the rearward failure of a plate which occurs as penetration of a projectile causes shear stress or stress over a narrow area resulting in shear failure by which a portion of the plate, substantially the same size as the projectile is expelled through the rear of a plate. The term petalling is intended to comprise a rearward failure of a plate comprising a radial fracture, plastic flow, or significant plate bending upon penetration by a projectile whereby compression waves propagate less narrowly or radially as large circumferential stresses occur throughout the thickness of the plate. Thus, it is believed that where a sufficient bond is formed between a ballistic resistant metal core material and at least one fiber layer, shear stress is transferred thereby increasing radial stress, and thus changing failure from shear failure to radial failure. The change in the failure mechanism from plugging to petalling allows for the containment of the ballistic device within the armor system. In the absence of a change in mechanism from plugging to petalling, the armor system may fail to provide protection as the projectile is propelled through the armor plate. Thus, it has been surprisingly discovered that where a metal-containing armor material such as metal or metal alloy plate is contacted or encapsulated with fiber and a polymer-like composition to attained a sufficient bond between the metal-containing plate and the fiber, enhanced ballistic performance of the metal-containing plate can be attained.

Further, where sufficient bonding is formed between the core material and at least one fiber layer, crack mitigation and face spalling, which typically occurs in high hardness metal and metal alloys such as titanium, may be inhibited. In an alternate embodiment of the present invention, the armor system comprising at least one ballistic resistant core material selected from ceramic and ceramic composite, having at least one fiber layer contacting the core, which has been coated or impregnated with at least one polymer-like composition, results in. among other things, the containment of any shattered or spalled ballistic resistant core material upon ballistic strike, the prevention of cracking and microcracking from dropping and striking, and further, provides multi-hit capacity.

In a preferred embodiment, the resultant armor material system is an extremely attractive, light weight, ballistic resistant armor material with multi-hit capabilities which is formed from core materials previously deemed unacceptable for providing the level of ballistic performance demonstrated by the armor systems of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is an exploded view illustrating the arrangement of front and back layers of a ballistic resistant material, such as a breast or back plate made in accordance with one embodiment of the present invention. Fig. 2 is a cross-sectional view illustrating layers of a ballistic resistant material, such as a breast plate or back plate made in accordance with one embodiment of the present invention. Fig. 3 is a close-up view of that portion of Fig. 2 to the left of Section I -I. Fig. 4 is an illustration of a ballistic resistant core material to which an overlapping layer having overlapping portions has been applied.

MODES FOR CARRYING OUT THE INVENTION

The present invention is directed, among other things, to armor systems with unexpected levels of ballistic protection. In its broadest aspects, armor systems of the present invention comprise at least one ballistic resistant core material formed into a desirable shape, fiber materials contacting or adhered to at least a portion of the at least one ballistic resistant core material, and at least one polymer-like composition. The armor systems may further comprise additional components such as fillers, bonding agents, water proofing and chemical resistant materials, materials for aesthetic enhancement, and the like. Surprising new protective properties as well as surprisingly enhanced traditional properties are imparted to the armor systems depending on the selection of components, the manner in which the components are arranged, and the technique used to incorporate the components in the system.

In one embodiment of the present invention, at least one ballistic resistant core material, is formed into a desirable shape, and fiber material is applied to one or more surfaces of the core material. In a preferred embodiment, fiber material is provided as a fiber layer, and is bonded to at least one surface of the ballistic resistant core material. In a further embodiment, the ballistic resistant core material having at least one fiber material applied thereto, further comprises at least one polymer-like composition capable of coating or impregnating the fiber material.

The ballistic resistant core material of the present invention may comprise, for example, ceramic, ceramic matrix composite, metal, metal alloy, metal matrix composite, plastic, glass, and combinations thereof. Preferred ballistic resistant core material comprises ceramic, ceramic composites, metal, metal alloys, and metal matrix composites. Although the ballistic performance of any type of metal, metal alloy or metal matrix composite may be enhanced by the present invention, certain materials may be preferentially selected for characteristics such as low weight, harder surfaces, high strength and economical production. Suitable materials for metal-containing ballistic resistant core materials include metal, metal alloy, and metal matrix composite comprising at least one of aluminum, titanium, iron, magnesium, tungsten, manganese, nickel, chromium, molybdenum, silicon, carbon, copper, cobalt, vanadium, and silver. Preferred metal-containing ballistic resistant core material comprises steel, aluminum alloys, and titanium alloys, and combinations thereof. Steel, aluminum alloys and combinations thereof may be particularly preferred. Low-carbon content, medium-carbon content, and high-carbon content steel materials are all suitable for use in the present invention. Steel ranging from about 300-600 BHN (Brinell Hardness Number) is preferred, with high hardness steel having from about 500-600 BHN being particularly preferred. Useful ceramic-containing ballistic resistant core material includes ceramic or ceramic matrix composite materials. Although the performance of any ceramic-containing ballistic resistant core material may be enhanced by the present invention, preferred ceramic-containing core material may be selected preferentially for characteristics such as low weight, projectile deformation, etc. Preferred ceramic-containing ballistic resistant core material comprises, for example, oxides, borides, carbides, and nitrides of compositions such as aluminum, boron, zirconium, beryllium, boron, silicon, titanium, tungsten, iron, and the like. Preferred ceramic matrix composite compositions include, but are in no way limited to compositions comprising, for example, alumina, boron carbide, silicon carbide, zirconium carbide, aluminum nitride, aluminum carbide, and combinations thereof. The ceramic core materials may be formed by any traditional, known techniques, including for example, sintering, hot pressing, reaction bonding, etc. Particularly preferred ceramic matrix composite compositions comprise silicon carbide reinforced alumina ceramic composites formed by the DIMOX ' directed metal oxidation process. Methods for making shaped ceramic matrix composite bodies by the DIMOX™ directed metal oxidation process and the composites made thereby, are disclosed, for example, in commonly owned U.S. Patent No. 5,236,786. the subject matter of which is incorporated herein by reference in its entirety.

Ballistic resistant core material may be formed into any desired size and shape depending on the application. For example, core material may be shaped to conform to the shape of exterior or interior surfaces of building structures and vehicles, vehicle hulls, helmets. vests, and the like. Thus, ballistic resistant core materials may be planar and non-planar. In a preferred embodiment, ballistic resistant core material is non-planar in at least one dimension, advantageously conforming to the shape of the object or individual for which protection is desired. Fig. 2 illustrates in a cross-section a single body non-planar ballistic resistant core material suitable for use as a breast plate, having generally curved, convex and concave surfaces, thus having increased comfort and protection. Ballistic resistant core materials may comprise monoliths (i.e., single bodies) or mosaics (i.e., two or more components or bodies bonded or joined together, as discussed above). In one embodiment comprising a mosaic of ceramic or ceramic matrix composite bodies, for example, in the manufacture of a breast plate or a back plate which optionally may be inserted into a ballistic resistant vest, two or more ceramic or ceramic matrix composite tiles may be adhesively bonded to form a core body. In an alternative embodiment, two or more ceramic or ceramic matrix composite bodies positioned adjacent to each other in a desired formation, may be bonded together by the formation of an oxidation reaction product bridge. The oxidation reaction product bridge between congruent surfaces of ceramic or ceramic matrix composite bodies, may be formed by the DIMOX directed metal oxidation process. Armor products comprising two or more bodies of ceramic or ceramic matrix composites which are bonded by the DIMOX™ directed metal oxidation process, may exhibit greater strength at the bonding zones of contiguous ceramic or ceramic matrix composite bodies, than ceramics having adhesively joined sections of ceramic or ceramic matrix compositions. Methods for bonding multiple ceramic or ceramic matrix composite bodies by the DIMOX directed metal oxidation process are disclosed, for example, in commonly owned U.S. Patent No. 4,884,737, the subject matter of which is incorporated herein by reference in its entirety.

Moreover, monolith ceramic or ceramic matrix composite core materials may be formed by a number of techniques. For example, monolith ceramic or ceramic matrix composite core materials may be formed into any desired shape by. for example, sintering, hot pressing, reaction bonding, or what have you to result in a core material having the desired shape, e.g., a breast plate, backing plate, vehicle part, etc.

In a preferred embodiment, a preform of a desirable ceramic filler material may be fabricated as set forth in, for example, commonly owned U.S. Patent No. 5,236,786, discussed above. Certain desirable filler materials disclosed in Patent '786 comprise, for example, silicon carbide and alumina. As disclosed in Patent '786 a mass of filler may be formed into a desired shape (in the present case, for example, into the shape of the desired core material) by, for example, mixing the filler with a suitable binder material to form a preform. The preform may be provided with a barrier material on at least one surface thereof and placed adjacent to a body of suitable parent metal to form an assembly. The assembly may be placed into a furnace and heated to a temperature above the melting point of the parent metal but below the melting point of its oxidation reaction product and exposed to a suitable oxidant. In this temperature range, the molten parent metal reacts with the oxidant to form a polycrystalline oxidation reaction product. At least a portion of the oxidation reaction product is maintained in contact with and between the molten metal and the oxidant, to draw molten metal through the polycrystalline material toward the barrier material and into contact with the oxidant such that the oxidation reaction product continues to form at the interface between the oxidant and previously formed oxidation reaction product. The reaction is continued to produce the ceramic body grown to the surface or boundary established by the barrier means. Preforms and, thus, the resulting ceramic matrix composite body are limited in shape and size only by the limitations of, for example, the methods available for forming preforms (e.g., slip casting, pressing, etc.) and the molds and presses available.

In further preferred embodiment, a monolith core could be formed by growing an oxidation reaction product into an assemblage of smaller, simple shaped (e.g., square, flat tiles) preforms. For example, a plurality of small, square preforms could be pressed or otherwise formed, as discussed above. The preforms could be arranged adjacent to each other in the general shape of a desired, more complex shaped core material. Any gaps between the small preforms could be filled in with a suitable filler material. Preferably the filler material utilized to fill the gaps could be essentially the same as, or may be based upon, the filler material which was utilized to form each preform. In one embodiment, the material used to fill in the gaps is a colloidal ceramic, e.g., colloidal silica. Further, the colloidal ceramic may be mixed with a filler material (usually the same filler as used to form each preform) to form a paste-like substance. In any case, the filler material, colloidal ceramic, paste-like substance, or the like can be placed into the gaps between each preform to form an assembly which corresponds in shape to the desired shape of the core material. The assembly can then be bisque fired to allow the assembly to be further handled or even green machined if desired. Ultimately, the result is an array of preforms which replicate the shape of the desired core material.

After bisque firing and/or green machining, the assembly can be provided with a suitable barrier material and formed into a ceramic matrix composite by growing an oxidation reaction product, as described above. The oxidation reaction product will grow through the preforms and the material used to fill the gaps between the preforms, resulting in a monolith ceramic matrix composite core material.

After the ballistic resistant core material is formed into a desired shape, at least one fiber material is applied to at least one surface of the core material. Fiber material suitable for the practice of the present invention comprises at least one high strength organic or inorganic fiber. High strength fibers suitable for use in armor materials are well known in the art, and include such fibers listed in U.S. Patent No. 5,376,426, issued in the name of Harpell, et al. which is hereby incorporated by reference in its entirety. Preferably, high strength fibers include, for example, carbon fibers, aramid fibers, amide-containing fibers, ethylene fibers, glass fiber, ceramic fibers, preceramic fibers, boron fibers, and the like. Particularly preferred fibers include, for example, S2-glass, E-glass, polyaramid fibers known under the tradename NOMEX® and KEVLAR®, polyethylene fibers, amide containing-fibers such as nylon, ceramic fibers, and the like, and combinations thereof. Fibers may be arranged in any manner known in the art suitable for forming fiber material, and are preferably arranged as fiber layers. Preferred fiber arrangements include parallel arrays, bundles, roving, mat, chopped strands, knitted, double bias, plain, satin and basket weave configurations. Double bias, plain, satin or basket weave fiber configurations are particularly preferred. The most desirable weight of the fiber material typically ranges from about 3 oz. to about 24 oz. per square yard; however, heavier or lighter fiber materials may be useful. Where the fiber layer comprises glass fiber material (for example, fiberglass), particularly preferred are fabrics having a weight of about 8 oz., 12 oz., and 24 oz. per square yard. Particularly preferred are polyaramid fiber layers having a weight of about 17 oz. per square yard. Factors to consider when selecting a specific fiber weight and composition and the specific arrangement of fiber layers include the level and type of threat, the composition of the ballistic resistant core material, the number and composition of other layers of fiber used, the position of the fiber material relative to the core material and other fiber materials, the composition of the polymer-like composition discussed below, and the desired final weight of the armor body.

A ballistic resistant core material may be fully or partially wrapped or encapsulated by at least one fiber layer. The number of fiber layers applied to the ballistic resistant core may be varied to achieve a desired final body weight. Minimally, at least one fiber layer is in contact with at least one ballistic resistant core material side or edge surface. Preferably, two or more ballistic resistant core material side or edge surfaces are contacted by at least one fiber layer. Where more than one fiber layer is used, the composition and the weights of the fiber layers may be the same or different. The term "contacting", as used herein, for example, in the phrase "contacting at least one ballistic resistant core material surface" is intended to include the application of at least one first fiber layer directly to at least a portion of at least one ballistic resistant core material surface. It should be understood that the fiber layer may be applied to a surface of a core material by utilizing a glue, adhesive, or the like, and for the purposes of the present invention, still be contacting that surface. Moreover, "contacting at least one ballistic resistant core material surface" further refers to the application of at least one fiber layer directly onto at least one first fiber layer which is applied directly to the ballistically resistant core material surface, and which, for example, forms an arrangement of fiber layers.

Although fiber layers may be any size or geometry, preferred fiber layers have a surface area substantially the same as or greater than the surface area of the side of the ballistic resistant core material to which they contact. In a preferred embodiment, at least one fiber layer is provided which has a surface area greater than the surface area of the ballistic resistant core material surface to which it contacts so that the at least one fiber layer may extend onto at least one edge surface providing a reinforced edge or edge support. In a particularly preferred embodiment at least one fiber layer having a surface area greater than the surface area of the side of the ballistic resistant core material to which it contacts, has sufficient surface area to overlap at least one edge and to further contact at least a portion of the opposing side surface of the ballistic resistant core material. In one embodiment of the present invention, such as that illustrated in Figures 1, 2, and 3, a ballistic resistant core material 10 comprises a first side surface 1 1 and second side surface 12, and at least one edge surface 13, wherein at least one fiber layer 20 is contacting the first side 11, and at least one fiber layer 30 is contacting the second side surface 12. At least one fiber layer 20 and 30 contacting the first and second side surfaces 1 1 and 12, may comprise any number or composition of fiber layers depending on the application. Preferably, at least one of the at least one fiber layers 20 and 30 contacting the first side 1 1 or second side surface 12, is contacting at least one edge surface 13.

In a preferred embodiment, at least one of the at least one fiber layers 20 or 30 is an overlapping layer 21. The overlapping layer contacting the first or second sides 11 or 12 of the ballistic resistant core material may be applied directly to the ballistic resistant core material, or may be applied to at least one other fiber layer contacting the first side 11 or second side surfaces 12. As illustrated in Figs 3 and 4, overlapping layer 21. contacting the first side 1 1 of the ballistic resistant core material 10, has overlapping portions 22. Overlapping portions 22 may overlap at least one edge surface 13 to contact the opposing second side surface 12. In a particularly preferred embodiment, as illustrated in Fig. 4, at least one overlapping fiber layer contacting first side surface 11 has a surface area greater than the surface area of the ballistic resistant core material side 1 1 or 12, so that overlapping portions 22 overlap and contact all edge surfaces 13, and further contact the second side surface 12 adjacent to each of the edge surfaces.

Preferably, where the armor system comprises an overlapping layer, at least one fiber layer further provided is a locking ply. For example, in Figs. 2 and 3, locking ply 31, contacting the second side surface 12. further contacts the overlapping portions 22 of the overlapping layer 21. Preferably a locking ply has a surface area substantially the same or greater than the surface area of the core side surface to which it contacts.

In a preferred embodiment, as illustrated in Fig. 3, at least one fiber layer 30, may further comprise at least one stacking ply 33. Preferably, one to ten stacking plies 33 contact a second side surface 12 and have a surface area substantially the same or greater than the surface area of the second side surface 12. Most preferably two to six stacking plies are used. In another preferred embodiment comprising stacking layers, at least one overlapping layer is also provided. For example, in one preferred embodiment, at least one fiber layer comprising at least one stacking ply is in contact with a side surface of the core material, and an overlapping layer is applied to an opposing core side surface. Overlapping portions of the overlapping layer overlap at least one, but preferably all core edge surfaces and further overlap to contact at least a portion of the stacking plies on the opposing side surface. The overlapping layer may assist in confining and/or preventing delamination of the stacking plies to the second side surface upon ballistic impact. Optionally, at least one locking ply is further provided to the second side surface to contact the overlapping portions of the overlapping layer.

At least one fiber layer may further comprise at least one front ply and at least one back ply. In one preferred embodiment, as illustrated in Fig. 3, the at least one front ply 24 contacting the first side surface 1 1 of the ballistic resistant core material 10, and the at least one back ply 34 contacting the second side surface 12 of the ballistic resistant core material 10, comprise the outer most fiber layers of the fiber encapsulated ballistic resistant core material. In a particularly preferred embodiment, the at least one front and back ply have a surface area substantially the same or greater than the surface area of the core. Where the surface area of the front and back plies 24 and 34 are greater than the surface area of the core, and portions of the front and back plies 24 and 34 extend beyond the ends of the core material, front and back ply portions may be folded over the core edge surface 13. or the opposing front and back ply portions may be pressed or pinched together.

Moreover, in addition to overlapping layers, locking plies, stacking plies, and front and back plies, ballistic resistant core side surfaces may be optionally contacted with additional fiber layers. For example, in Fig. 3 at least one fiber layer 32 is contacting the second side surface 12 of the ballistic resistant core material. Optionally addition materials such as fillers, bonding agents, pigments, and the like may be provided to the fiber encapsulated ballistic resistant core material. In a preferred embodiment, at least one shock absorbing layer may be provided as at least one of the at least one fiber layers 20 and 30. Materials suitable for shock absorption include, for example any material capable of absorbing energy from, for example, a non- ballistic strike, such as from dropping or other trauma, and/or inhibit cracking or microcracking of the ballistic resistant core material. A particularly preferred shock absorbing layer comprises organic foam materials. Shock absorbing layers are useful particularly where the at least one ballistic resistant core material comprises a ceramic or a ceramic composite material or a brittle high hardness metal or metal alloy.

Additionally, at least one edge support material optionally may be provided to at least one edge surface of the ballistic resistant core. Edge support material may be in direct contact with the ballistic resistant core material, or it may be provided to at least one edge surface subsequent to the application of at least one fiber layer, thus directly contacting at least one fiber layer. Edge support material may comprise any material which is suitable for aesthetic enhancement, improving the resistance of the ballistic resistant core material from cracking (for example, from edge drops), inhibiting fragments from propelling outward from the armor system upon ballistic strike, etc. Edge support materials may comprise, for example, organic or inorganic material, including but not limited to glass, ceramic, metal, organic and inorganic polymers. Preferred edge support material includes, but is not limited to felt, cotton, polyester, polyaramid, polyimide, rubber, and the like. In one preferred embodiment, an organic or inorganic fiber material in the form of chopped fiber, rope, woven fiber, strands, bundles, or the like, may be provided to one or more edge surfaces. Particularly preferred materials include fiber rope, chopped fiber, or fiber layers comprising the same material as at least one of the at least one fiber layer contacting the first or second side surfaces. In an alternate embodiment, the edge support material may comprise, for example, a resin-enhanced area contacting at least a portion of the fiber encapsulated ballistic resistant core material. In a preferred embodiment, a resin composition is used for edge support material which is the same as the polymer-like composition used for coating or infiltrating the fiber encapsulated ballistic resistant core material.

Fiber layers having ends which extend beyond the end of the core side surface to which they contact, ma}' be folded or adhered, to remain in contact with the edge surface of the ballistic resistant core. Alternately, for example, as with overlapping layers, the fiber layers which extend beyond the end of the core side surface may be overlapped and optionally adhered to the opposing side surface. In another alternate embodiment, first and second core side surfaces 1 1 and 12 (Fig. 3) each having at least one fiber layer 24 and 34 contacted thereto, which extends beyond the end of at least one core side surface 13, wherein the ends of the opposing fiber layers extending beyond the core edge surface, may, for example, be pressed or pinched together, forming a tapered perimeter around at least a portion of at least one edge surface of the ballistic resistant core material.

Fiber layers and edge support layers may be held in contact with the ballistic resistant core material or secured to other fiber material layers by any suitable method, such as folding, tucking, gluing or adhering. Where adhesive materials are used, spray adhesives are preferred for ease of application. A ballistic resistant core material with at least one fiber layer applied thereto, may be optionally coated or impregnated with at least one composition. Preferred compositions include those having a high modulus of elasticity or high tensile elongation. Compositions suitable for use in the present invention include, for example, organic and inorganic monomeric, oligomeric. and polymeric compositions, as well as hybrid compositions comprising both organic and inorganic components. Examples of suitable inorganic compositions include, for example, oligomers and polymers comprising silicon, aluminum, and boron-containing structural units. Examples of silicon-containing compositions include monomeric, oligomeric. or polymeric silanes, carbosilanes, siloxanes, silazanes, ureasilazanes, and thioureasilazanes. Preferred coating or impregnating compositions comprise organic monomers, oligomers or polymers. Particularly preferred compositions are polymer-like compositions. The term "polymer-like compositions" is intended to include oligomeric and polymeric resins or compositions, as well as monomeric compositions which react to form oligomers or polymers, or are otherwise known in the art as resin materials. Organic polymer-like compositions suitable for the practice of the present invention include, for example, conventional thermoplastic or elastomeric compositions. Compositions comprising one or more organic groups selected from substituted and unsubstituted vinyl, aromatic vinyl, allyl, ether, ester, urethane, acrylate, methacrylate, amine, amide, imide, epoxide, isocyanate, carbonate, styrene. acrylonitrile, phenolic, isoprene, styrene. ethylene, propylene, butadiene, and butylene, are particularly preferred. Specifically, compositions comprising polyvinyl resins such as vinyl chloride, vinyl ester, vinyl acetyl, and vinyl butyral polymers, and mixtures thereof, are particularly preferred compositions. One preferred embodiment of the present invention comprises a polymer-like composition comprising a mixture of a vinyl ester and a urethane acrylate resin blend. In a most preferred embodiment of the present invention, a composition is prepared comprising a mixture of a 1 : 1 ratio by weight of vinyl ester, such as a vinyl ester manufactured under the tradename Derakane, and urethane acrylate. such as an unsaturated urethane acrylate in styrene, manufactured under the tradename Crestomer.

Compositions may further comprise, for example, initiators and catalysts. Initiators and catalysts are known in the art as compositions which aid in the reaction of resin compositions to cure or gel, and are selected depending on the resin system used. In a preferred embodiment, wherein the composition comprises a polymer-like resin system comprising vinyl ester and urethane acrylate resin blend, preferred initiators include cobalt napthanate and peroxides.

Polymer-like compositions may be applied to fiber materials by any method known in the art including, for example, spraying, brushing, dipping, and molding. An example of a suitable dipping technique is hot melt dipping. Preferred methods for molding include resin transfer molding techniques, such as vacuum assisted resin transfer molding. One preferred vacuum assisted resin transfer molding technique suitable for impregnating the fiber encapsulated ballistic resistant material includes the SCRIMP process, which is disclosed, for example, in U.S. Patent No. 5,316,462, the subject matter of which is incorporated herein by reference in its entirety.

An alternate, preferred resin transfer molding system for coating or impregnating the fiber encapsulated ballistic resistant core material has been developed, and is described herein in Example 1. After coating or impregnating the fiber material with a polymer-like composition, the polymer-like composition is partially or fully dried or cured, for example, at ambient temperature, or by thermal or chemical processing, or any suitable method depending on the polymer-like composition selected. Additional composition may be further applied, if desired, to fill any voids or imperfections.

Preferably, the polymer-like composition contacts at least one ballistic resistant core side or edge surface, and at least a portion of at least one fiber layer. In a most preferred embodiment at least one bond is formed, comprising an arrangement of polymer-like material, a portion of a core side surface, and at least a portion of at least one fiber layer. In a particularly preferred embodiment, the bond extends substantially over the surface area of at least one side surface of the ballistic resistant core material. In an even further preferred embodiment, the bond has sufficient strength to withstand ballistic impact, wherein the bond remains intact and the at least one fiber layer remains in contact with the side surface of the ballistic resistant core surface. Additionally, where the at least one ballistic resistant core material comprises a non-planar or curved surface, such as a concave side surface, a bond comprising polymer-like composition, at least a portion of at least one fiber layer, and optionally at least a portion of at least one side or edge core surface, inhibits delamination of fiber layer from non-planar or curved core surfaces upon impact.

The above-described armor systems of the present invention may be used alone o. in combination with any ballistic resistant materials known in the art. In one embodiment of the present invention, where the armor system is intended for use in a protective vest or jacket, the armor system may be used alone as a breast plate or a back plate of a bullet proof vest or jacket. The light weight armor system may be easily slipped into and out of pockets of armor vests and jackets.

Where the above-described armor systems are used in combination with other ballistic resistant materials, preferred materials include, but are not limited to fiber materials, and fiber- polymer matrices such as materials known under the name of KEVLAR®, NOMEX®,

SPECTRA®, or SPECTRA® SHIELD. For example, an armor system may be prepared in which the resin impregnated fiber encapsulated ballistic resistant core material is further combined with an additional ballistic resistant material, to form a combination plate and thus, increase the level of ballistic protection. For purposes of the present invention, a combination plate includes any armor system in which a resin coated or impregnated fiber encapsulated ballistic resistant core material is combined with another layer, substrate, material, etc., to form a single body. For example, in one preferred embodiment of the present invention, a combination plate is formed comprising a resin coated, fiber encapsulated ballistic resistant core, and a backing layer comprising, for example, an organic fiber and resin matrix, such as the material known under the tradename SPECTRA® SHIELD. The backing layer may be attached to the resin coated, fiber encapsulated core material in any manner known in the art for combining ballistic resistant materials. In a particularly preferred embodiment, an armor system comprising a backing layer may be further coated or impregnated by resin transfer molding, most preferably using the same technique and resin system which was used to coat or impregnate the fiber encapsulated ballistic resistant core material. Depending on the composition of both the backing layer and the fiber encapsulated core, the combination plate armor system of the present invention may exhibit even higher levels of ballistic protection than resin coated or impregnated fiber encapsulated ballistic resistant core materials alone. The resultant armor system has been found to be extremely attractive, light weight, ballistic resistant armor with multi-hit capabilities and which can withstand the rigors of everyday handling. Surprisingly enhanced levels of ballistic performance are attained using low cost materials, and simple, economical manufacturing or processing steps.

EXAMPLES Example 1 The present example is directed to the formation of a fiber encapsulated plate which is impregnated with a polymer-like resin composition.

A steel ballistic resistant core material comprising Mars 300 (Creusot-Loire Industries, distributed by Creusot-Marrel, Inc., Wayne, PA) is formed into a curved steel plate weighing approximately 2.04 pounds (926 grams) measuring approximately 7.75" x 7.75" x 0.125" (1 140 mm xl 750 mm x 3.2 mm), having a cord length of approximately 7.2 inches and having approximately one inch corner cut outs. The curved steel core, having a convex face surface and a concave back surface is encapsulated in fiber as follows.

A spray adhesive, 3M Super 77® (3M Corp., Minneapolis, MN), is sprayed on the convex face surface of the steel core. One overlapping layer of S-2 fiberglass (Hexcel S-2 12 oz/sq.yd., double bias, silane finish, distributed by RP Associates. Inc. Bristol, RI) measuring approximately 9" x 10" is centered on the convex face surface of the steel core, with overlapping portions extending beyond each end of the steel core. About a one inch perimeter of the concave back surface of the core is lightly sprayed with 3M Super 77® adhesive spray, and the overlapping portions of the overlapping layer are folded over the edge surfaces of the steel core and adhered to the sprayed convex back surface of the core. A locking ply of S-2 fiberglass substantially the same size as the back surface of the core, measuring approximately 7.75" x 7.75" (Hexcel 12 oz/sq.yd., S-2 double bias, silane finish, distributed by RP Associates. Inc. Bristol, RI) is adhered to the concave back surface of the core which has been lightly sprayed with 3M Super 77® adhesive spray, covering the overlapping portions of the overlapping layer.

The overlapping layer is lightly sprayed with 3M Super 77® adhesive spray, and a front fiber layer of S-2 fiberglass (Hexcel 8 oz/sq.yd., S-2 Satin weave, silane finish, distributed by RP Associates, Inc. Bristol. RI) measuring approximately 8.25" x 8.25" is placed on the front convex surface of the core onto the overlapping layer covering the convex face surface of the steel core, with the ends of the front fiber layer extending beyond each edge of the front core surface core. The locking ply is sprayed lightly with 3M Super 77® adhesive spray, and one fiber layer of S-2 fiberglass (Knytex 24 oz./sq.yd., S-2 5x5 plain weave, silane finish, distributed by RP Associates, Inc. Bristol, RI) measuring approximately 8.25" x 8.25" is placed onto the concave back surface of the core covering the locking ply, with the ends of the one fiber layer extended beyond each end of the back surface of the core.

Four stacking plies of KEVLAR® 29 (Kevlar 29, 3000 denier, 16.5 oz./sq.yd., 2x2 basket weave, Sioux Manufacturing, Corp., Fort Totten, ND) measuring approximately 7.75" x. 7.75" are placed on the concave back surface of the core, covering the one fiber layer which covered the locking ply. Each of the one fiber layer and the four stacking plies are lightly sprayed with 3M Super 77® adhesive spray. The stacking plies are centered on the core and do not substantially extend beyond the edges of the back surface of the core.

One backing ply fiber layer of S-2 fiberglass (Hexcel 8 oz/sq.yd., S-2 Satin weave, silane finish, distributed by RP Associates, Inc. Bristol. RI) measuring approximately 8.25 x " 8.25", is then centered onto the concave back surface on the core covering the stacking plies and extending beyond each edge of the core. The ends of all fiber layers which extend beyond the edges of the front surface and the back surface of the core are sprayed lightly with Super 77 adhesive spray, and are pinched together along the edges of the core forming a fiber encapsulated ballistic resistant steel core.

A resin transfer molding system, for impregnating resin into fiber material encapsulating a ballistic resistant core material, is constructed as follows. A steel mold having walls and a base which define an arcuate chamber is provided. The steel mold is sandblasted and the interior of the chamber is coated with CERASET SN inorganic polymer (Lanxide Corporation, Newark, DE), and the coated mold is heated to about 150°C for about one hour to allow the inorganic polymer to cure. One port for the introduction of resin material is provided to a wall of the mold structure defining the width of the mold chamber, and one port for evacuation of the resin material is provided to an opposing wall. The ports are positioned approximately at the center of the chamber walls. The ports, comprising an internal diameter of 3/8", accommodate 3/8" o.d. tubing, which is attached to the ports via compression fittings. The tubing used for both the introduction and evacuation of resin is polyethylene (489 polyethylene FDA. NALGENE brand products. Nalge Company, Rochester, NY), and has a

1/4" i.d. and a 1/16" wall.

The interior of the chamber is sprayed sparingly with a release agent (Release Agent Dry Lubricant MS-122DF, Miller-Stephenson Chemical Company, Inc., Danbury, CT). One layer of roving woven material (#HWR240, 24 oz./sq. yd. E-glass, R. P. Associates, Bristol, PA), is placed within the mold chamber. A layer of 3 mil. plastic release ply is positioned within the mold on top of the roving woven material. A distribution media (Shade Cloth Black #5512 50%, Roxford Fordell, Greenville, SC) is placed within the mold on top of the plastic release ply. A layer of peel ply (60001 SRB Peel Ply, purchased from Northern Fiber Glass Sales, Hampton, NH), is placed within the chamber on top of the distribution media.

A pliable insert is provided which is conformable to the curvature of the mold, having an external dimension substantially the same as the mold chamber, having an internal dimension which substantially replicates the external dimensions of the ballistic core material, and having approximately 1.5" width between the internal dimension and the external dimension. A gap measuring approximately 0.12" is provided between the internal surfaces of the pliable insert and the fiber encapsulated core. The internal dimension of the insert comprises an upper lip of approximately 0.25". The insert is prepared from P45 Selastic rubber (Silicones, Inc. High Point, NC) from a mixture of about 1 : 10 weight ratio of part A (activator) to part B (rubber base) is mixed, degassed, and poured into a mold, curing in air for about 24 hours.

The pliable insert is placed within the mold, on top of the distribution media and the peel ply material, and the fiber encapsulated ballistic resistant steel core is centered within the pliable insert. An additional layer of peel ply, is placed on top of the fiber encapsulated ballistic resistant steel core. A layer of distribution media is placed on top of the peel ply, to facilitate the uniform distribution of the resin across the surface of the fiber encapsulated ballistic resistant steel core.

A sealant tape (RS Sealant Tape, purchased through Northern Fiber Glass Sales, Hampton, NH) is applied to the perimeter of the mold to serve as a gasket between the mold and a cover. A cover comprising high density polyethylene having a geometry substantially the same as the mold chamber, and a size sufficient to cover the mold chamber, is placed onto the mold set-up, enclosing the fiber encapsulated ballistic resistant core.

A resin composition comprising about 750 grams of DERAKANE 8084 vinyl ester resin (Dow Chemical Company, Midland, MI) and about 750 grams of Crestomer 1080 urethane acrylate in styrene (Scott Bader Company, Ltd, Northamptonshire, England), is prepared by stirring by hand in a plastic liner placed in a metal secondary container. Further, initiators comprising about 0.6% by weight of cobalt napthanate 6% (Huls America, Inc., repackaged by Mahogany Co., Mays Landing, NJ) and about 3% by weight of Trigonox 239A (AZKO Chemicals. Inc., Chicago, IL) are further stirred into the mixture. Tubing, which connects to the entry port of the mold, is placed into the mixture. The resin composition is provided to the inlet port of the mold by drawing a vacuum at approximately -28" Hg at the evacuation port of the mold. The resin is pulled into and through the mold chamber wetting and infiltrating the fiber plies, as air and uninfiltrated resin are evacuated through the evacuation port, and the vacuum is maintained at -28"Hg for approximately 15 minutes. The vacuum is lowered to approximately -18 to -20" Hg for about 15 minutes or until the resin gels, and the vacuum is continued for approximately 1 hour after the resin has gelled to speed drying of the resin. The resin is tacky and the article can be removed from the mold. The article is heated in an air oven at a temperature of about 150-160°F. for about 24 hours.

The finished armor system weighing approximately 2.64 pounds (1200 grams), measuring approximately 8.25" x 8.25" x .325 inches, is attractive, light weight, with enhanced ballistic resistance.

Claims

What is claimed is:

1. A ballistic resistant article comprising: a core material having first and second sides and at least one edge; at least one fiber layer contacting said first side; at least one fiber layer contacting said second side; and at least one polymer-like composition impregnating at least one fiber layer.

2. The ballistic resistant article of claim 1, wherein the core material is curved.

3. The ballistic resistant article of claim 1 , wherein the core material is selected from metal, metal alloy, and metal composite.

4. The ballistic resistant article of claim 3, wherein the core is selected from steel, aluminum alloy, titanium alloy, and composites thereof.

5. The ballistic resistant article of claim 1, wherein the core material is selected from ceramic and ceramic composite.

6. The ballistic resistant article of claim 1, wherein at least one of the at least one fiber layers contacting the first and second sides has a surface area greater than or substantially the same as the surface area of the core material.

7. The ballistic resistant article of claim 1 , wherein at least one fiber layer contacting the first side and at least one fiber layer contacting the second side is selected from organic and inorganic fiber material.

8. The ballistic resistant article of claim 7, wherein at least one of the at least one fiber layers is selected from polyaramid, polyethylene, and polyamide fiber material.

9. The ballistic resistant article of claim 7, wherein at least one of the at least one fiber layers is glass fiber material.

10. The ballistic resistant article of claim 1, wherein at least one of the at least one fiber layers contacting the first side and the at least one fiber layers contacting the second side is substantially bonded to at least one of the first and second sides with at least one polymerlike material.

11. The ballistic resistant article of claim 10, wherein the core material has a rearward mode of failure, and at least one fiber layer contacting least one of the first and second sides is bonded sufficiently to change the rearward mode of failure from plugging to petalling.

12. The ballistic resistant article of claim 10, wherein the at least one polymer-like composition comprises at least one composition selected from elastomeric and rigid materials.

13. The ballistic resistant article of claim 11, wherein the at least one polymer-like composition comprises at least one composition selected from monomer, oligomeric and polymeric epoxides. phenolics, allylics, esters, vinyl ester, urethanes, amines, carbonates, imides, amides, butadiene, isoprene, chloroprene, styrene, ethylene, vinyl chloride, butadiene acrylonitrile, ethers, aromatic vinyls, acrylics, and methacrylics.

14. The ballistic resistant article of claim 13, wherein the at least one polymer-like composition comprises at least one composition selected from vinyl ester and urethane acrylate.

15. The ballistic resistant article of claim 1 , wherein the at least one fiber layer contacting the second side comprises at least one stacking layer.

16. The ballistic resistant article of claim 15, wherein the at least one stacking layer is selected from glass and polyaramid fiber material.

17. The ballistic resistant article of claim 1, wherein at least one of the at least one fiber layers contacting the first side comprises at least one overlapping layer having overlapping portions, wherein overlapping portions of the overlapping layer at least partially overlap at least one edge surface of the core material and contact at least a portion of the second side.

18. The ballistic resistant article of claim 17, wherein the at least one overlapping layer is selected from glass and polyaramid fiber material.

19. The ballistic resistant article of claim 17, wherein the at least one fiber layer contacting the second side comprises at least one locking ply contacting the edges of the overlapping layer.

20. A ballistic resistant article comprising: a curved core material having a convex side and a concave side, and at least one edge; at least one fiber layer contacting the convex side, wherein at least one of the at least one fiber layers contacting the convex side is an overlapping layer having a surface area greater than the surface area of the convex side, and having overlapping portions which extend beyond the convex side and contact at least a portion of the concave side; at least one fiber layer contacting the concave side, wherein at least one of the at least one fiber layers contacting the concave side is bonded to the concave side, and further, wherein at least one of the at least one fiber layers contacting the concave side is a locking ply at least partially contacting the overlapping portions of the overlapping layer; and at least one polymer-like material impregnating at least one fiber layer, and bonding at least one fiber layer to the concave side.