US20120192339A1

US20120192339A1 - Flexible Body Armor Vest with Breast Plate

Info

Publication number: US20120192339A1
Application number: US12/845,386
Authority: US
Inventors: Ashok Bhatnagar; David A. Hurst; David A. Steenkamer; Brian D. Arvidson; Lori L. Wagner
Original assignee: Honeywell International Inc
Current assignee: Honeywell International Inc
Priority date: 2010-07-28
Filing date: 2010-07-28
Publication date: 2012-08-02
Also published as: CN103118558A; CA2806199A1; BR112013001931A2; WO2012128782A2; JP2013538326A; WO2012128782A3; EP2597979A2; TW201211496A; MX2013000884A

Abstract

Body armor vests and other articles having combined ballistic performance and overall weight characteristics are described. A representative body armor vest comprises both a rigid breast plate and a flexible fabric adjoining the breast plate. Both components may comprise a plurality of unidirectionally oriented fibrous layers comprising fibers having high tenacity and a high tensile modulus.

Description

FIELD OF THE INVENTION

The present invention relates to a lightweight, high performance body armor vest having a rigid breast plate and a flexible fabric adjoining the breast plate. Both the breast plate and fabric comprise fibrous layers of unidirectionally oriented high tenacity, high tensile modulus fibers such as polyethylene fibers.

DESCRIPTION OF RELATED ART

Ballistic resistant articles containing high strength fibers that have excellent properties against deformable projectiles are known. These articles, including bulletproof vests, helmets, and structural components of military equipment, are typically made from fabrics having layers of high strength fibers. Fibers conventionally used include polyethylene fibers, para-aramid fibers (e.g., poly(phenylenediamine terephthalamide)), graphite fibers, nylon fibers, glass fibers, etc. For many applications, such as vests or parts of vests, the fibers may be used in a woven or knitted fabric. For other applications, the fibers are encapsulated or embedded in a matrix material to form either rigid or flexible fabrics.
Specific ballistic resistant articles, including vests, helmets, and panels, are described, for example, in U.S. Pat. No. 4,403,012; U.S. Pat. No. 4,457,985; U.S. Pat. No. 4,613,535; U.S. Pat. No. 4,623,574; U.S. Pat. No. 4,650,710; U.S. Pat. No. 4,737,402; U.S. Pat. No. 4,748,064; U.S. Pat. No. 5,552,208; U.S. Pat. No. 5,587,230; U.S. Pat. No. 6,642,159; U.S. Pat. No. 6,841,492; and U.S. Pat. No. 6,846,758. In particular, these patents describe ballistic resistant composites that include high strength fibers such as extended chain ultra-high molecular weight polyethylene fibers. These composites display varying degrees of resistance to penetration by high speed impact from projectiles such as bullets. U.S. Pat. No. 4,403,012 and U.S. Pat. No. 4,457,985 disclose ballistic-resistant composites having networks of high molecular weight polyethylene or polypropylene fibers, as well as matrices of olefin polymers and copolymers, unsaturated polyesters, epoxies, and other polymers moldable below the melting point of the fiber.
U.S. Pat. No. 4,623,574 and U.S. Pat. No. 4,748,064 disclose composites comprising high strength fibers embedded in an elastomeric matrix. U.S. Pat. No. 4,737,402 and U.S. Pat. No. 4,613,535 disclose rigid composites having good impact resistance and comprising a network of high strength fibers such as the ultra-high molecular weight polyethylene and polypropylene fibers, as disclosed in U.S. Pat. No. 4,413,110. The fibers are embedded in an elastomeric matrix material and at least one additional rigid layer on a major surface of the fibers in the matrix. U.S. Pat. No. 4,650,710 discloses a flexible article having a plurality of flexible layers comprising high strength, extended chain polyolefin (ECP) fibers. The fibers are coated with a low modulus elastomeric material.
U.S. Pat. No. 5,552,208 and U.S. Pat. No. 5,587,230 disclose articles comprising at least one network of high strength fibers and a matrix composition that includes a vinyl ester and diallyl phthalate. U.S. Pat. No. 6,642,159 discloses an impact resistant rigid composite having a plurality of fibrous layers. The layers have a network of filaments disposed in a matrix, and elastomeric layers are between the fibrous layers. The composite is bonded to a hard plate to increase protection against armor piercing projectiles. U.S. Pat. No. 6,841,492 discloses bi-directional and multi-axial fabrics, fabric composites, ballistically resistant assemblies thereof and the methods by which they are made. The fabrics include sets of strong, substantially parallel, unidirectional yarns lying in parallel planes, one above the other. U.S. Pat. No. 6,846,758 discloses woven fabric laminates having superior resistance to penetration by ballistic projectiles. The laminates include a fabric woven from a high strength, high modulus yarn, a surface coating of a low modulus elastomer and a plastic film bonded to its elastomer-coated surface.
Articles having a high resistance to penetration of fragments, such as shrapnel, are also known to include high strength fibers made from materials such as high molecular weight polyethylene, aramids, and polybenzazoles. These articles are described, for example, in U.S. Pat. Nos. 6,534,426 and 6,475,936, as well as “Lightweight Composite Hard Armor Non Apparel Systems with T-963 3300 dtex DuPont Kevlar 29 Fibre,” published in 1984 by E.I. duPont De Nemours International S.A. Fibers in these articles may be woven or non-woven. Non-woven fibers may be knitted, uniaxially aligned and cross-plied, or felted. The articles can be flexible or rigid depending upon the nature of their construction and the materials employed.
Each of the constructions cited above represents progress toward the goals to which they were directed. However, an ongoing problem associated with conventional ballistic resistant articles such as vests is the high material weight required to achieve a sufficient level of penetration resistance. In this regard, rigid body armor garments such as vests provide relative high ballistic resistance, but they are also very stiff and bulky. As a result, rigid body armor garments are generally less comfortable than flexible body armor garments. There is consequently a need in the art for ballistic resistant garments and other articles that provide effective protection to military and law enforcement personnel, are comfortable to wear, and do not significantly impede mobility due to excessive weight and/or bulk.

SUMMARY OF THE INVENTION

The present invention is associated with the discovery of lightweight body armor vests and other articles that provide high performance, in terms of resistance to penetration by bullets. Vests, as a representative article, beneficially utilize the lightest materials for both hard, or rigid armor for a breast plate and soft, or flexible, armor for a fabric adjoining the breast plate. The characteristics of the vests in terms of both weight and performance therefore offer significant benefits in military and law enforcement applications. According to embodiments of the invention directed to vests, both the breast plate and fabric comprise a plurality of unidirectionally oriented fibrous layers. The fibers of these layers (e.g., polyethylene fibers) have a tenacity of at least about 7 g/denier and an initial tensile modulus of at least about 150 g/denier. These high performance fibers may be held in their respective layer configuration with a resin matrix, preferably using a low modulus resin at a relatively low resin matrix content to provide exceptional ballistic performance and flexibility. In the case of the breast plate, the fibrous layers may be molded to obtain a rigid structure, whereas, in the case of the fabric, the fibrous layers may be consolidated to obtain a flexible structure. Ballistic components of varying properties are therefore combined to achieve overall performance and weight characteristics in the vest or other article that are desired commercially.
Advantageously, the weight of the vest, or combined weight of the breast plate and fabric may generally be less than about 3 kg (6.6 lbs), typically less than about 2.5 kg (5.5 lbs), and often less than about 2 kg (4.4 lbs). Such vests are preferably resistant, at least in the area of the breast plate, to a bullet having an energy generally of at least about 1000 J (740 ft-lb) and often at least about 1500 J (1110 ft-lb) (e.g., in the range from about 1600 J (1180 ft-lb) to about 4000 J (2950 ft-lb)).
These and other embodiments and aspects of the invention, and their associated advantages, are apparent from the following Detailed Description.

DETAILED DESCRIPTION

The invention is directed to body armor vests and other articles having the advantages discussed above, in terms of ballistic performance and overall weight. According to particular embodiments, a representative body armor vest comprises both a rigid breast plate and a flexible fabric adjoining the breast plate. In other embodiments, the vest may even consist of, or consist essentially of, the plate and fabric, in the absence of other structures (e.g., additional polymer films attached to the surface of the breast plate) that add weight or otherwise materially alter its basic and novel characteristics. In any of these embodiments, the flexible fabric, in the form of a vest or other article of clothing, adjoins the breast plate either with or without physical attachment. The terms “breast plate” and “plate” are used herein to refer to a breast plate specifically in the case of a vest, shirt, or jacket or other clothing article where the plate will normally occupy or cover the region of the user's chest. Otherwise, these terms are meant to include rigid structures incorporated into other clothing and non-clothing articles that do not necessarily cover the chest area.
The breast plate (or plate) is therefore typically characteristic of rigid armor, also referred to as “hard” armor, which has been defined in the art, for example in U.S. Pat. No. 5,690,526, to refer to components with sufficient mechanical strength for (i) maintaining structural rigidity when subjected to a significant amount of stress and (ii) being free-standing without collapsing. The fabric, in contrast to the breast plate, is characteristic of flexible or “soft” armor that does not have these attributes of hard armor. The rigid armor and flexible armor components have separate ballistic resistance/weight characteristics that are managed in the vests and other articles described herein, providing a high level of protection, especially in the most critical areas, with a low overall weight and the comfort/flexibility characteristics appreciated by military and law enforcement personnel. While the breast plate and fabric may both comprise, for example, fibrous layers of high tenacity, high tensile modulus fibers in a resin matrix, the formation of rigid and flexible components from these materials is possible using different methods, for example molding to form the rigid breast plate and consolidation to form the flexible fabric. Representative molding and consolidation techniques are described in greater detail below.

High Tenacity Fibers and Fibrous Layers

As discussed above, both the rigid breast plate and flexible fabric of the vest comprise a plurality of unidirectionally oriented fibrous layers. Each of the fibrous layers comprises fibers having high tenacity and a high tensile modulus. For the purposes of the present invention, a fiber is an elongate body the length dimension of which is much greater that the transverse dimensions of width and thickness. Accordingly, the term fiber includes monofilament, multifilament, ribbon, strip, staple and other forms of chopped, cut or discontinuous fiber and the like having regular or irregular cross-section. The term “fiber” includes a plurality of any of the foregoing or a combination thereof. A yarn is a continuous strand comprised of many fibers or filaments. A “layer” is a body that may be rigidly or flexibly curved in three dimensions, but if laid flat in a plane, would have length and width dimensions much greater than a thickness dimension.
As used herein, the term “high tenacity fibers” means fibers which have tenacities equal to or greater than about 7 g/d. Preferably, these fibers have initial tensile moduli of at least about 150 g/d and energies-to-break of at least about 8 J/g as measured by ASTM D2256. As used herein, the terms “initial tensile modulus”, “tensile modulus” and “modulus” mean the modulus of elasticity as measured by ASTM 2256 for a yarn or fiber and by ASTM D638 for an elastomer or matrix material. Preferably, the high tenacity fibers have tenacities equal to or greater than about 10 g/d, more preferably equal to or greater than about 15 g/d, even more preferably equal to or greater than about 20 g/d, and most preferably equal to or greater than about 30 g/d. For high tenacity polyethylene fibers, the preferred tenacities range from about 20 to about 55 g/d. Preferably, at least about 50% by weight, and more preferably at least about 75% by weight, of the fibers in the plurality of fibrous layers of both of the breast plate (or other rigid component) and fabric (or other flexible component) are high tenacity fibers. Most preferably all or substantially all of the fibers in the plurality of fibrous layers of both components are high tenacity fibers.
The cross-sections of fibers useful in this invention may vary widely. They may be circular, flat or oblong in cross-section. They also may be of irregular or regular multi-lobal cross-section having one or more regular or irregular lobes projecting from the linear or longitudinal axis of the filament. It is particularly preferred that the fibers be of substantially circular, flat or oblong cross-section, most preferably that the fibers be of substantially circular cross-section. The yarns of fibers such as high tenacity fibers used herein may be of any suitable denier, such as, for example, about 50 to about 5000 denier, more preferably from about 200 to about 5000 denier, still more preferably from about 650 to about 3000 denier, and most preferably from about 800 to about 1500 denier.
High tenacity fibers such as polyolefin fibers or aramid fibers are representative of those used in the fibrous layers of the rigid and flexible components, such as the breast plate and fabric components of a vest. Polyolefin fibers are preferably high tenacity polyethylene fibers and/or high tenacity polypropylene fibers. Most preferably, the polyolefin fibers are high tenacity polyethylene fibers, also known as extended chain polyethylene fibers or highly oriented high molecular weight polyethylene fibers. The polyolefin and aramid fibers useful herein are known and possess excellent ballistic resistant properties.
U.S. Pat. No. 4,457,985 generally discusses high molecular weight polyethylene fibers and polypropylene fibers. In the case of polyethylene fibers, suitable fibers are those of weight average molecular weight of at least about 150,000, preferably at least about one million and more preferably between about two million and about five million Such high molecular weight polyethylene fibers may be spun in solution, as described, for example, in U.S. Pat. No. 4,137,394 and U.S. Pat. No. 4,356,138. The fibers may otherwise comprise filaments spun from a solution to form a gel structure, as described, for example, in U.S. Pat. No. 4,413,110, German Off. No. 3,004,699 and GB Patent No. 2051667. In an alternate embodiment, the polyethylene fibers may be produced by a rolling and drawing process, as described, for example, in U.S. Pat. No. 5,702,657. As used herein, the term polyethylene means a predominantly linear polyethylene material that may contain minor amounts of chain branching or comonomers not exceeding about 5 modifying units per 100 main chain carbon atoms, and that may also contain not more than about 50 weight percent of one or more polymeric additives such as alkene-1-polymers, in particular low density polyethylene, polypropylene or polybutylene, copolymers containing mono-olefins as primary monomers, oxidized polyolefins, graft polyolefin copolymers and polyoxymethylenes, or low molecular weight additives such as antioxidants, lubricants, ultraviolet screening agents, colorants and the like which are commonly incorporated.
High tenacity polyethylene fibers are commercially available and are sold under the trademark SPECTRA® fiber by Honeywell International Inc. of Morristown, N.J., U.S.A. Polyethylene fibers from other sources may also be used.
Depending upon the formation technique, the draw ratio and temperatures, and other conditions, a variety of properties can be imparted to these fibers. The tenacity of the polyethylene fibers is in particular at least about 7 g/d, preferably at least about 15 g/d, more preferably at least about 30 g/d, still more preferably at least about 35 g/d and most preferably at least about 45 g/d. Similarly, the initial tensile modulus of the polyethylene fibers, as measured by an Instron tensile testing machine, is preferably at least about 300 g/d, more preferably at least about 500 g/d, still more preferably at least about 1,000 g/d and most preferably at least about 1,800 g/d. These highest values for tenacity and initial tensile modulus are generally obtainable only by employing solution grown or gel spinning processes. Many of the filaments have melting points higher than the melting point of the polymer from which they were formed. Thus, for example, high molecular weight polyethylene of about 150,000, about one million and about two million molecular weight generally have melting points in the bulk of 138° C. (280° F.). The highly oriented polyethylene filaments made of these materials have melting points from about 7° C. (13° F.) to about 13° C. (23° F.) higher. Thus, a slight increase in melting point reflects the crystalline perfection and higher crystalline orientation of the filaments as compared to the bulk polymer.
Similarly, highly oriented high molecular weight polypropylene fibers of weight average molecular weight at least about 200,000, preferably at least about one million and more preferably at least about two million may be used. Such extended chain polypropylene may be formed into reasonably well oriented filaments by the techniques prescribed in the various references referred to above, and especially by the technique of U.S. Pat. No. 4,413,110. Since polypropylene is a much less crystalline material than polyethylene and contains pendant methyl groups, tenacity values achievable with polypropylene are generally substantially lower than the corresponding values for polyethylene. Accordingly, a suitable tenacity for polyethylene fibers is preferably at least about 8 g/d and more preferably at least about 11 g/d. The initial tensile modulus for polypropylene is preferably at least about 160 g/d and more preferably at least about 200 g/d. The melting point of the polypropylene is generally raised several degrees by the orientation process, such that the polypropylene filament preferably has a main melting point of at least 168° C. (334° F.), and more preferably at least 170° C. (338° F.). Employing fibers having a weight average molecular weight of at least about 200,000 coupled with the preferred ranges for the above-described parameters (modulus and tenacity) can provide advantageously improved performance in the final article.
In the case of aramid fibers, suitable fibers formed from aromatic polyamides are described in U.S. Pat. No. 3,671,542, which is incorporated herein by reference with respect to its teachings of aramid fibers. Preferred aramid fibers have a tenacity of at least about 20 g/d, an initial tensile modulus of at least about 400 g/d and an energy-to-break at least about 8 J/g, and particularly preferred aramid fibers have a tenacity of at least about 20 g/d and an energy-to-break of at least about 20 J/g. Most preferred aramid fibers have a tenacity of at least about 28 g/d, a modulus of at least about 1000 g/d and an energy-to-break of at least about 30 J/g. For example, poly(p-phenylene terephthalamide) filaments which have moderately high moduli and tenacity values are particularly useful in forming ballistic resistant composites. Examples are DuPont's KEVLAR® 29, KEVLAR® 129, and KM2 (available in 400, 640 and 840 deniers) and Teijin's TWARON® fibers type 1000 and 2000 (having a denier of 1000), HERACRON® fibers from Kolon Industries, Inc., and a number of fibers produced commercially by Kamensk Volokno JSC and JSC Chim Volokno of Russia, such as RUSAR™, ARTEC™, ARMOS™, and SVM™ which have about 1250 g/d and 32 g/d as values of initial tensile modulus and tenacity, respectively. Other examples are KEVLAR® 129 and KM2 from du Pont, and TWARON® T2000 from Teijin Aramid fibers from other manufacturers can also be used in this invention. Copolymers of poly(p-phenylene terephthalamide) (e.g., co-poly(p-phenylene terephthalamide 3,4′ oxydiphenylene terephthalamide)) may also be suitable. Also useful are poly(m-phenylene isophthalamide) fibers sold by DuPont under the trade name NOMEX®. Aramid fibers from a variety of suppliers may also be employed.

Unidirectionally Oriented Fiber Plies

Regardless of the type of high tenacity fibers used, including any of the polyolefin and/or aramid fibers described above, the fibrous layers of both the rigid breast plate and the flexible fabric of vests described herein are incorporated into non-woven fabrics, such as in plies of unidirectionally oriented fibers. In this case, the layers or plies of unidirectionally oriented fibers are preferably used in a cross-ply arrangement in which one layer of fibers extends in one direction and a second layer of fibers extends in a direction 90° from the first fibers. Where the individual plies are unidirectionally oriented fibers, the successive plies are preferably rotated relative to one another, for example at angles of 0°/90°, 0°/90/0°/90 or 0°/45°/90°/45°/0° or at other angles. In a preferred embodiment, the plurality of fibrous layers of both the breast plate and the fabric are in a cross-ply arrangement of unidirectionally oriented fibers, with adjacent layers of fibers extending in a direction of 90° relative to one another.
The number of fibrous layers used in the rigid component (e.g., breast plate) or flexible component (e.g., fabric) of the vest or other article may vary widely, depending on the desired performance and the desired weight. For example, the number of layers may range generally from about 2 to about 100 layers, and often from about 2 to about 10 layers. In a more specific embodiment, the plate and fabric each comprise from about 2 to about 8 fibrous layers, and often may comprise from about 2 to about 4 fibrous layers. The fibrous layers may be of any suitable thickness, and the thickness of each layer of the plurality of fibrous layers may be the same or may vary. Likewise, the areal density of each layer of the plurality of fibrous layers of the plate and/or the fabric may vary widely, but these are usually chosen so that the overall weight of the vest or other article is within an acceptable range for both the protection and comfort of the wearer or user. According to other embodiments, body armor vests as described herein may have a number of plies/layers required to meet a particular National Institute of Justice (NIJ) Threat Level, for example an NIJ Threat Level IIIA.

Resin Matrix

The high tenacity, high tensile modulus fibers of the fibrous layers (or fiber plies) of the rigid breast plate and the flexible adjoining fabric (e.g., high tenacity, high tensile modulus polyethylene fibers or high tenacity, high tensile modulus aramid fibers) may be in a resin matrix. The resin matrix for the fibers, whether in plies in the plate or the fabric, may be formed from a wide variety of elastomeric and other resins having desired characteristics. A low modulus resin such as an elastomer is used in such resin matrix, for example, possessing an initial tensile modulus (modulus of elasticity) of at most about 41.4 MPa (6,000 psi) as measured by ASTM D638. In other embodiments, the resin has initial tensile modulus of at most about 16.5 MPa (2,400 psi), at most about 8.23 MPa (1,200 psi), or at most about 3.45 MPa (500 psi). The glass transition temperature (Tg) of the resin is preferably at most about 0° C. (32° F.) and more preferably at most about −40° C. (−40° F.) and most preferably at most about −50° C. (−58° F.). The resin also has a preferred elongation to break of at least about 50%, more preferably at least about 100%, and most preferably at least about 300%. The resin may be selected to have a high tensile modulus when cured, such as at least about 10⁶psi (6895 MPa) as measured by ASTM D638. Examples of such resins are described, for example, in U.S. Pat. No. 6,642,159. The resin is typically thermoplastic in nature but thermosetting materials are also useful.
The proportion of the resin matrix material to fiber in either the fibrous layers of the plate or the fabric may vary widely, depending on the specific choice of fiber(s) and resin matrix. The resin matrix preferably comprises from about 0% (i.e., no resin) to about 98% by weight, and more preferably from about 5% to about 95% by weight. According to preferred embodiments, the resin matrix, especially when comprising or consisting of one or more resins having a low modulus, may be used at relatively lower proportions, for example such that the fibrous layers of both the plate and the fabric are in a resin matrix that is present in an amount from about 10% to about 40% by weight, and often from about 15% to about 25% by weight, of the plate (i.e., the total weight of fibers and resin matrix of the plate) and fabric (i.e., the total weight of fibers and resin matrix of the fabric), respectively. The use of lower amounts of low modulus resins beneficially improves both flexibility and performance of the vests or other articles.
A wide variety of resins may be utilized in the resin matrix, including thermoplastic resins, thermosetting resins, blended resins, and hybrid resins. Representative examples of low modulus resins include polybutadiene, polyisoprene, natural rubber, ethylene-propylene copolymers, ethylene-propylene-diene terpolymers, polysulfide polymers, thermoplastic polyurethanes, polyurethane elastomers, chlorosulfonated polyethylene, polychloroprene, plasticized polyvinylchloride using dioctyl phthalate or other known plasticizers, butadiene acrylonitrile elastomers, poly (isobutylene-co-isoprene), polyacrylates, polyesters, polyethers, fluoroelastomers, silicone elastomers, thermoplastic elastomers, and copolymers of ethylene. Examples of thermosetting resins include those which are soluble in carbon-carbon saturated solvents such as methyl ethyl ketone, acetone, ethanol, methanol, isopropyl alcohol, cyclohexane, ethyl acetone, and combinations thereof. Among the thermosetting resins are vinyl esters, styrene-butadiene block copolymers, diallyl phthalate, phenolic resins such as phenol formaldehyde, polyvinyl butyral, epoxy resins, polyester resins, polyurethane resins, and mixtures thereof, and the like. Included are those resins that are disclosed in the aforementioned U.S. Pat. No. 6,642,159. Preferred thermosetting resins include epoxy resins, phenolic resins, vinyl ester resins, urethane resins and polyester resins, and mixtures thereof. Preferred thermosetting resins for polyethylene fiber fabrics include at least one vinyl ester, diallyl phthalate, and optionally a catalyst for curing the vinyl ester resin.
One preferred group of resins are thermoplastic polyurethane resins. A preferred group of elastomeric materials for the resin matrix includes block copolymers of conjugated dienes and vinyl aromatic copolymers. Butadiene and isoprene are preferred conjugated diene elastomers. Styrene, vinyl toluene and t-butyl styrene are preferred conjugated aromatic monomers. Block copolymers incorporating polyisoprene may be hydrogenated to produce thermoplastic elastomers having saturated hydrocarbon elastomer segments. The polymers may be simple tri-block copolymers of the type R-(BA)_x(x=3-150); wherein A is a block from a polyvinyl aromatic monomer and B is a block from a conjugated diene elastomer. A preferred resin matrix is an isoprene-styrene-isoprene block copolymer, such as Kraton® D1107 isoprene-styrene-isoprene block copolymer available from Kraton Polymer LLC. Another resin matrix useful herein is a thermoplastic polyurethane, such as a copolymer mix of polyurethane resins in water.
Types of resin matrix that may be disposed on the fibrous layers of the plate and/or fabric, include nitrile rubber polymers that are resistant to dissolution, penetration and/or transpiration by water and organic solvents. Such nitrile rubber polymers are described, for example, in US 2009/0163105, hereby incorporated by reference with respect to its teachings of these polymers. According to particular embodiments, therefore, composites described herein comprise a nitrile rubber polymer disposed on the high tenacity fibers of the fibrous layers of the breast plate and/or the fabric. In a preferred embodiment, the nitrile rubber polymer is present in either of these components in an amount from about 2% to about 50% of the combined weight of the resin matrix and the fibers.

Coating/Impregnation of the Resin Matrix

According to representative embodiments, each of the plurality of fibrous layers of the unidirectionally oriented fibers of the breast plate is coated or impregnated with the resin matrix prior to molding. Likewise, the fibers of the fabric may similarly be coated or impregnated with a resin matrix, as described above, prior to consolidation. The fibrous layers of the breast plate or fabric may therefore be formed by constructing a fiber network initially and then coating the network with the matrix composition. As used herein, the term “coating” is used in a broad sense to refer to a fiber network wherein the individual fibers either have a continuous layer of the matrix composition surrounding the fibers or a discontinuous layer of the matrix composition on the surface of the fibers. In the former case, it can be said that the fibers are fully embedded in the matrix composition. The terms coating and impregnating are used interchangeably.
The resin matrix composition may be applied in any suitable manner, such as a solution, dispersion or emulsion, onto fibers or fibrous layers of either the breast plate or the fabric. In all cases, the resulting matrix-coated fiber network is then usually dried. The solution, dispersion or emulsion of the resin matrix may be sprayed onto the filaments. Alternatively, the fibers may be coated with the aqueous solution, dispersion or emulsion by dipping or by means of a roll coater or the like. After coating, the resulting coated fiber network may then be passed through an oven for drying in which the coated fibers are subjected to sufficient heat to evaporate the water or other liquid in the resin matrix composition. The dried, coated fiber network may then be placed on a carrier web, which can be a paper or a film substrate. Otherwise, the fibers may initially be placed on a carrier web before coating with the resin matrix. In either case, the substrate and the coated fiber network comprising one or more fiber layers can then be wound up into a continuous roll in a known manner.
Otherwise, yarn bundles of the high tenacity, high tensile modulus fiber filaments may be supplied from a creel and led through guides and one or more spreader bars into a collimating comb prior to coating of the unidirectionally oriented fiber networks with the matrix material. The collimating comb aligns the filaments substantially unidirectionally and substantially in the same plane.

Molding/Consolidation

The fibrous layers used for the rigid plate or the flexible fabric components of the vest or other article, which are optionally coated/impregnated with a resin matrix to form coated fibrous networks as discussed above, are molded or consolidated. In particular, the fibrous layers, optionally with prepared “prepregs” of coated and/or laminated fiber networks, are combined to form the molded or consolidated breast plate and fabric components. Consolidation can occur via drying, cooling, heating, pressure or a combination thereof. Representative consolidation methods include the use of a heated nip roll to provide both the temperature and pressure for carrying out the consolidation.
While molding and consolidation techniques are similar, each process is also different in several respects. Particularly, molding is a batch process and consolidation is a continuous process. Further, molding typically involves the use of a mold, such as a match-die mold when forming a relatively flat component, or otherwise a shaped mold. Molding, however, does not necessarily result in a planar product, as is typically made with consolidation. Normally, consolidation is done in a flat-bed laminator, a calendar nip set or as a wet lamination to produce flexible or soft armor, such as the fabric used in vests described herein. Molding is typically reserved for the manufacture of rigid or hard armor, such as the breast plate used these vests. Molding techniques to form rigid articles are described, for example, in U.S. Pat. No. 4,623,574; U.S. Pat. No. 4,650,710; U.S. Pat. No. 4,748,064; U.S. Pat. No. 5,552,208; U.S. Pat. No. 5,587,230; U.S. Pat. No. 6,642,159; U.S. Pat. No. 6,841,492; and U.S. Pat. No. 6,846,758.
Molding or consolidation may therefore be achieved by stacking the individual fibrous layers of the plate or fabric, or otherwise coated or impregnated prepregs of these layers, one on top of another, followed by bonding them together under heat and pressure to heat set the overall structure, causing the matrix material to flow and occupy any remaining void spaces. As discussed above, individual fibrous layers of both the plate and the fabric are preferably cross-plied to achieve excellent ballistic resistance such that the fiber alignment direction of one layer is rotated at an angle with respect to the fiber alignment direction of another layer (i.e., the layers are non-parallel). For example, a preferred structure has two fiber layers positioned together such that the longitudinal fiber direction of one layer is perpendicular to (extends in a direction of 90° relative to) the longitudinal fiber direction of the other layer.
Suitable bonding for molding or consolidating the fiber layers may be achieved at a temperature from about 93° C. (200° F.) to about 177° C. (350° F.), more preferably from about 93° C. (200° F.) to about 149° C. (300° F.), and most preferably at a temperature from about 93° C. (200° F.) to about 121° C. (250° F.) and at a pressure from about 172 kPa (25 psi) to about 3.45 MPa (500 psi), although higher pressures may be used. The molding or consolidation may be conducted in an autoclave. In a typical vacuum bagging molding operation, the lay up of fibrous layers and resin matrix is transferred to a sealable bag and a vacuum is applied to the bag contents, thereby inducing up to one additional atmosphere of pressure differential between the autoclave environment and the bag environment. The bag under vacuum is typically heated in the autoclave, for example at representative temperature from about 93° C. (200° F.) to about 177° C. (350° F.) at an autoclave pressure from about (345 kPa) 50 psi to about 2.1 MPa (300 psi), followed by cooling to room temperature.
When heating, it is possible that the resin matrix can be caused to stick or flow without completely melting. However, generally, if the resin matrix is caused to melt, relatively little pressure is required to form the composite, while if the resin matrix is only heated to a sticking point, more pressure is typically required. The time period for which the molding and consolidation temperatures and pressures are held generally varies from about 10 seconds to about 24 hours, typically from about 5 minutes to about 3 hours, and often from about 10 minutes to about 2 hours. However, the molding and consolidation temperatures, pressures and times are generally dependent on the content(s) and type(s) of resin matrix, as well as the content(s) and type(s) of fiber(s).
Accordingly, the molded or consolidated, layered composites of the plate and fabric have a preferred thickness of from about 25 μm (0.98 mils) to about 500 μm (20 mils) per fibrous layer of the high tenacity fibrous layers used, and more preferably from about 75 μm (3.0 mils) to about 385 μm (15 mils) per fibrous layer and most preferably from about 125 μm (4.9 mils) to about 255 μm (10 mils) per fibrous layer. While such thicknesses are preferred, it is to be understood that other layer thicknesses may be produced to satisfy a particular need and yet fall within the scope of the present invention.
The areal density of each layer preferably may range from about 0.034 kg/m²(0.0070 lb/ft²) to about 3.1 kg/m²(0.63 lb/ft²), more preferably from about 0.17 kg/m²(0.035 lb/ft²) to about 2.2 kg/m²(0.45 lb/ft²), and most preferably from about 0.17 kg/m²(0.035 lb/ft²) to about 0.85 kg/m²(0.17 lb/ft²). The thicknesses and areal densities of each of the fibrous layers of the breast plate and fabric may be the same or different.

Formation of Body Armor Vests and Other Articles

After formation of layered composites of the plate and fabric using molding or consolidation, they may be formed into a vest or other article by adjoining these components. The term “adjoining” includes physically attaching as well as coupling or juxtaposition without physically attaching. Physical attachment between the plate and fabric may be achieved for example, with adhesives (e.g., polysulfides, epoxies, phenolics, elastomers, etc.), with mechanical fasteners (e.g., stitches, staples, rivets, bolts, screws, etc.), or with combinations of these. In the absence of physical attachment, the fabric may be adjoined using un-attached coupling or juxtaposition with the plate, for example by inserting a breast plate into a strategically placed pocket of the fabric in a removable manner. This allows the vest to be used without the breast plate in applications where only moderate protection is needed, while also permitting use of the breast plate with other garments or non-clothing articles having similarly configured pockets. The use of rigid armor, for example provided by the breast plate, in only a portion of the vest area affords control over the both the vest locations receiving the highest ballistic protection and the overall weight of the vest. In another representative embodiment using non-physical attachment to adjoin the breast plate and fabric, a portion of the fabric may be wrapped around the breast plate (e.g., with tension to maintain the breast plate in place). Otherwise, both physical and non-physical attachment may be used, for example by stitching the wrapped portion of the fabric to the breast plate.
Regardless of whether the plate and fabric are adjoined in a physical or non-physical manner, the fabric preferably overlies or covers at least one face of the plate, such that it is hidden from view when the vest or other article is worn. The faces of the plate refer to the surfaces (e.g., anterior and posterior surfaces), of the more or less planar structure, having high surface areas relative to, for example four surfaces having much lower surface areas. The opposite faces are therefore directed toward and away from a user when wearing a vest or other clothing article. In many cases, the fabric can cover both faces of the breast plate, for example when the breast plate is inserted completely within a pocket of the fabric, as described above. In this case, the fabric, which itself provides significant ballistic protection, is disposed between the incoming projectile (e.g., a bullet or shrapnel) and the breast plate, in addition to being disposed between the breast plate and the user, thereby providing protection both before and after the breast plate.

Properties of the Body Armor Vest and Other Articles

Although a body armor vest serves as an exemplary article of clothing throughout the present disclosure, it will be readily appreciated that the breast plate and fabric components described herein are broadly applicable to other articles (e.g., protective shields, blankets, and panels, etc.) and particularly clothing articles such as such as shirts, jackets, pants, and hats, which can similarly utilize the rigid and flexible structures of the plate and fabric, respectively.
Vests and other articles (e.g., clothing articles) comprising the plate and fabric components described herein have good flexibility and comfort, coupled with excellent ballistic protection and fragment resistance. A small pointed projectile can penetrate armor by laterally displacing fibers without breaking them. In this case, the penetration resistance depends on how readily fibers may be pushed aside, and therefore, on the nature of the fiber network. Important factors in the ballistic or fragment resistance of an article comprising fibrous layers is the periodicity of cross-overs in cross-plied fibrous layers, fiber denier, fiber-to-fiber friction, resin matrix characteristics, inter-laminar bond strengths, and others. In terms of performance, the vests and other articles have a number of desirable properties for use in military, law enforcement, and other applications in which a high degree of protection of the user is required. These properties include the penetration resistance values, at least in the area of the breast plate, and overall weight, as discussed above.
The total thickness of the vest or other article, even in the area of the plate is advantageously less than about 12 mm (0.47 in) (e.g., in the range from about 4 mm (0.16 in) to about 12 mm (0.47 in)), and normally less than about 10 mm (0.39 in) (e.g., in the range from about 4 mm (0.16 in) to about 10 mm (0.39 in)). The total areal density of both the fabric and plate combined (e.g., the areal density of the vest in the area of the breast plate) is advantageously less than about 39.2 kg/m²(8 lb/ft²) (e.g., in the range from about 2.44 kg/m²(0.5 lb/ft²) to about 29.3 kg/m²(6 lb/ft²)), typically less than about 29.3 kg/m²(6 lb/ft²) (e.g., in the range from about 4.89 kg/m²(1 lb/ft²) to about 29.3 kg/m²(6 lb/ft²)), and often less than about 24.4 kg/m²(5 lb/ft²) (e.g., in the range from about 9.77 kg/m²(2 lb/ft²) to about 24.4 kg/m²(5 lb/ft²)).
A representative vest having the high penetration resistance and overall weight characteristics discussed above, according to a preferred embodiment, comprises (a) a rigid armor breast plate comprising a plurality of unidirectionally oriented fibrous layers comprising polyethylene fibers having a tenacity of at least about 7 g/denier and a tensile modulus of at least about 150 g/denier, wherein the fibrous layers of the breast plate are in a resin matrix having a tensile modulus of at most about 27.6 MPa (4,000 psi), adjacent fibrous layers of the breast plate extend in a direction of 90° relative to one another, and the plurality of fibrous layers of the breast plate are molded; and also comprises (b) a flexible fabric containing the breast plate (e.g., within a pocket of the fabric) and comprising a plurality of unidirectionally oriented fibrous layers comprising polyethylene fibers having a tenacity of at least about 7 g/denier and a tensile modulus of at least about 150 g/denier, wherein the fibrous layers of the fabric are in a resin matrix having a tensile modulus of at most about 27.6 MPa (4,000 psi), adjacent fibrous layers of the fabric extend in a direction of 90° relative to one another, and the plurality of fibrous layers of the fabric are consolidated.
In this representative embodiment, therefore, the breast plate and fabric components both comprise a plurality of high tenacity fibrous layers in a cross-ply arrangement of unidirectionally oriented fibers, with adjacent layers of fibers extending in a direction of 90° relative to one another. These components, according to preferred embodiments, can therefore include SPECTRA SHIELD®, having 2 to 4 layers of unidirectionally oriented SPECTRA® fiber, as discussed above, with adjacent layers being cross-plied at 90° relative to one another.
Overall aspects of the present invention are associated with lightweight, high performance vests and other articles comprising both rigid and flexible components (e.g., a rigid breast plate and a flexible fabric). Those having skill in the art, with the knowledge gained from the present disclosure, will recognize that various changes can be made in these vests and other articles, and methods for making them, without departing from the scope of the present disclosure. The subject matter described herein is therefore representative of the present invention and its associated advantages and is not to be construed as limiting the scope of the invention as set forth in the appended claims.

Claims

1. A body armor vest comprising

(a) a rigid breast plate, and

(b) a flexible fabric adjoining the breast plate

wherein the breast plate and the fabric each comprise a plurality of unidirectionally oriented fibrous layers comprising fibers having a tenacity of at least about 7 g/denier and a tensile modulus of at least about 150 g/denier,

wherein the vest has a total weight of less than about 3 kg (6.6 lbs).

2. The vest of claim 1, wherein the fabric overlies at least one face of the breast plate.

3. The vest of claim 1, wherein the plurality of fibrous layers of the breast plate are molded and the plurality of fibrous layers of the fabric are consolidated.

4. The vest of claim 1, wherein the fibrous layers of the breast plate and the fabric independently comprise polyolefin fibers or aramid fibers.

5. The vest of claim 4, wherein the fibrous layers of the breast plate and the fabric comprise polyethylene fibers.

6. The vest of claim 1, wherein the vest is resistant, in the area of the breast plate, to a rifle bullet having an energy from about 1600 J (1180 ft-lb) to about 4000 J (2950 ft-lb).

7. The vest of claim 1, wherein the fibrous layers of the both the breast plate and the fabric are in a resin matrix.

8. The vest of claim 7, wherein the fibrous layers of both the breast plate and the fabric are in a resin matrix having a tensile modulus of at most about 27.6 MPa (4,000 psi).

9. The vest of claim 8, wherein the fibrous layers of the breast plate and the fabric are in a resin matrix comprising a resin independently selected from the group consisting of polybutadiene, polyisoprene, natural rubber, ethylene-propylene copolymers, ethylene-propylene-diene terpolymers, polysulfide polymers, thermoplastic polyurethanes, polyurethane elastomers, chlorosulfonated polyethylene, polychloroprene, plasticized polyvinylchloride, butadiene acrylonitrile elastomers, poly (isobutylene-co-isoprene), polyacrylates, polyesters, polyethers, fluoroelastomers, silicone elastomers, thermoplastic elastomers, and copolymers of ethylene.

10. The vest of claim 7, wherein the fibrous layers of the breast plate and the fabric are in a resin matrix that is present in an amount from about 10% to about 40% by weight of the breast plate and the fabric, respectively.

11. The vest of claim 1, wherein the plurality fibrous layers of both the breast plate and the fabric are in a cross-ply arrangement of unidirectionally oriented fibers with adjacent layers of fibers extending in a direction of 90° relative to one another.

12. The vest of claim 11, wherein the breast plate and the fabric comprise from 2 to 8 fibrous layers.

13. The vest of claim 12, wherein the breast plate and the fabric comprise from 2 to 4 fibrous layers.

14. The vest of claim 1, wherein the breast plate and the fabric have a combined areal density of less than about 39.2 kg/m²(8 lb/ft²).

15. The vest of claim 1, wherein the breast plate and the fabric have a combined areal density from about 4.89 kg/m²(1 lb/ft²) to about 29.3 kg/m²(6 lb/ft²).

16. The vest of claim 1, wherein the fabric adjoins the breast plate by physical attachment.

17. The vest of claim 1, wherein the fabric adjoins the breast plate without physical attachment.

18. The vest of claim 17, wherein the breast plate is inserted into a pocket of the fabric and is removable from the fabric.

19. A vest having high penetration resistance and comprising:

(a) a rigid armor breast plate comprising a plurality of unidirectionally oriented high tenacity fibrous layers comprising polyethylene fibers having a tenacity of at least about 7 g/denier and a tensile modulus of at least about 150 g/denier, wherein the fibrous layers of the breast plate are in a resin matrix having a tensile modulus of at most about 27.6 MPa (4,000 psi), adjacent fibrous layers of the breast plate extend in a direction of 90° relative to one another, and the plurality of fibrous layers of the breast plate are molded; and

(b) a flexible fabric containing the breast plate and comprising a plurality of unidirectionally oriented high tenacity fibrous layers comprising polyethylene fibers having a tenacity of at least about 7 g/denier and a tensile modulus of at least about 150 g/denier, wherein the fibrous layers of the fabric are in a resin matrix having a tensile modulus of at most about 27.6 MPa (4,000 psi), adjacent fibrous layers of the fabric extend in a direction of 90° relative to one another, and the plurality of fibrous layers of the fabric are consolidated,

wherein the vest has a total weight of less than about 3 kg (6.6 lbs).

20. The vest of claim 19, wherein the vest is resistant, in the area of the breast plate, to a rifle bullet having an energy from about 1600 J (1180 ft-lb) to about 4000 J (2950 ft-lb).