WO1991000490A1

WO1991000490A1 - Ballistic-resistant composite article

Info

Publication number: WO1991000490A1
Application number: PCT/US1990/003358
Authority: WO
Inventors: Dusan Ciril Prevorsek; Young Doo Kwon
Original assignee: Allied-Signal Inc.
Priority date: 1989-06-30
Filing date: 1990-06-13
Publication date: 1991-01-10
Also published as: CA2059271A1; JPH04506325A; EP0479902A1

Abstract

A composite ballistic article comprising at least one hard rigid layer (1, 2), at least one fibrous layer (3) and a void layer (4) between said rigid layer and fibrous layer, wherein the relative weight percents of said hard rigid layer and said fibrous layer, and the relative positioning of said layers are such that said article exhibits a mass efficiency equal to or greater than about 2.5.

Description

BALLISTIC-RESISTANT COMPOSITE ARTICLE

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION This invention relates to ballistic resistant composite articles. More particularly, this invention relates to such articles having improved ballistic protection.

PRIOR ART

Ballistic articles such as bullet proof vests, helmets, structural members of helicopters and other military equipment, vehicle panels, briefcases, rain¬ coats and umbrellas containing high strength fibers are known. Fibers conventionally used include aramid fibers such as poly(phenylenediamine terephthala ide) , graphite fibers, nylon fibers, ceramic fibers, glass fibers and the like. For many applications, such as vests or parts of vests, the fibers are used in a woven or knitted fabric. For many of the other applications, the fibers are encapsulated or embedded in a composite material. In "The Application of High Modulus Fibers to Ballistic Protection" R.C. Laible et al., J. Macromol. Sci.-Chem. A7(l), pp. 295-322 (1973), it is indicated on p. 298 that a fourth requirement is that the textile material have a high degree of heat resistance; for example, a polya ide material with a melting point of 255 C appears to possess better impact properties ballistically than does a polyolefin fiber with equivalent tensile properties but a lower melting point. In an NTIS publication, AD-A018 958 "New Materials in Construction for Improved Helmets", A. L. Alesi et al., a multilayer highly oriented polypropylene film material (without matrix), referred to as "XP", was evaluated against an aramid fiber (with a phenolic/pol vinyl butyral resin matrix). The aramid system was judged to have the most pro ising combination of superior performance and a minimum of problems for combat helmet development. U.S. Patent Nos. 4,457,985, and 4,403,012 disclose ballistic-resistant composite articles comprised of networks of high molecular weight polyethylene or polypropylene fibers, and matrices composed of olefin polymers and copolymers, unsaturated polyester resins, epoxy resins, and other resins curable below the melting point of the fiber. A.L. Lastnik, et al.; "The Effect of Rising concentration and Laminating Pressures on KEVLAR Fabric Bonded with Modified Phenolic Resin", Technical Report NATICK/TR-84/030, June 8, 1984; disclose that an interstitial resin, which encapsulates and bonds the fibers of a fabric, reduces the ballistic resistance of the resultant composite article.

U.S. Patent Nos.4,623,574 and 4,748,064 disclose a simple composite structure comprising high strength fibers embedded in an elastomeric matrix. The simple composite structure exhibits outstanding ballistic protection as compared to simple composites utilizing rigid matrices, the results of which are disclosed in the patents. Particularly effective are simple composites employing ultra-high molecular weight poly ethylene and poly propylene such as disclosed in U.S. Patent No. 4,413,110. U.S. Patent No. 4,737,402 and 4,613,535 disclose complex rigid composite articles having improved impact resistance which comprises a network of high strength fibers such as the ultra-high molecular weight polyethylene and polypropylene disclosed in U.S. Patent No. 4_/413,110 embedded in an elastomeric matrix material and at one additional rigid layer on a major surface of the fibers in the matrix. It is disclosed that these composites have improved resistance to environmental hazards, improved impact resistance and are unexpectedly effective as ballistic resistant articles such as armor or helmets. SUMMARY OF THE INVENTION The present invention is directed to a complex ballistic resistant composite article of manufacture having improved impact resistance, said article comprised of two or more layers, at least one of said layers is a fibrous layer comprising a network of high strength filaments having a tenacity of at least about 7 grams/denier, a tensile modulus of at least about 160 grams/denier and an energy-to-break of at least about 8 joules/gram in a matrix material and at least one of said layers is a hard, rigid layer comprising at least one hard rigid material which is harder than said fibrous layer, wherein the relative weight percents of said layers and the relative positioning of said layers are such that said composite exhibits a mass efficiency (E ) equal to or greater than about 2.5. As used herein the "mass efficiency" of a composite is determined from the following equation:

"AD" of armor grade steel required to

Em= defeat a threat

"AD" of the material under consideration required to defeat a threat

wherein:

AD is the areal density of the armor or material in

Kg_. or lbs. m2 F2

The mass efficiency is determined by determining the AD required to defeat a threat of a designated projectile at a designated impact velocity with (1) armor grade steel and (2) the material under consideration, and computing Em by the above equation. Surprisingly, it has been discovered that the relative amounts of layers composed of high strength fibers in matrix and of hard rigid materials, and the spacing between the layers and the relative order in which these layers are assembled in the complex composite have an effect on the mass efficiency of the composite and the degree of ballistic protection provided.

Compared to conventional ballistic-resistant armor structures, the composite article of the present invention can advantageously provide a selected level of ballistic protection while employing a reduced weight of protective material. Alternatively, the article of the present invention can provide increased ballistic protection as compared to conventionally constructed composite armor of equal or substantially equal weight.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be more fully understood and further advantages will become apparent when reference is made to the following detailed description of the invention and the accompanying drawings in which:

Figures 1 to 8 are depictions of cross-sectional views of various embodiments of this invention showing various representative structural configurations.

DETAILED DESCRIPTION OF THE INVENTION

Composites of this invention include at least two essential components. One component is a fibrous layer comprised of a fiber network in a matrix material and the other component is a hard rigid layer composed of one or more hard rigid materials. The particular structure of the composite may vary widely. For example, the two layers may abut or may be separated by a void space. The composite may be in the form of a multiple composite which includes two or more fibrous layers and two or more hard layers,or may include more that one fibrous layer and only one hard, rigid layer or, alternatively may include more than one hard rigid layer and only one fibrous layer, either abutting or separated by void spaces. Various illustrative configurations of this invention are set forth in the figures.

Figure 1 shows one embodiment having three layers, a hard ceramic layer 1, a hard metal layer 2 and a fibrous composite layer 3. In this embodiment, ceramic layer 1 which is the layer first exposed to the threat functions to shatter or distorted the projectile. Ceramic layer 1 abuts metal layer 2 and the abutting layers 1 and 2 are separated from fibrous layer 3 by void space 4.

In Figure 2 is depicted an embodiment of this invention which consists of hard ceramic layer 1 having a metal or fibrous backing layer 5 which is separated from fibrous layer 3 by void space 4. In the embodiment of Figure 2, the hard ceramic layer 1 is the first layer exposed to the threat and functions to shatter or distort the projectile thereby increasing the effectiveness of fibrous layer 3.

Figure 3 depicts a representative embodiment of the invention in which metal layer 2 is the layer first exposed to the threat. Layer 2 is separated from ceramic layer 1 which abuts fibrous layer 3 by void space 4.

Figure 4 depicts a multilayer/multivoid space embodiment of this invention. The embodiment of Figure 4 has a metal layer 2 initially exposed to the threat, separated from ceramic layer 1 which abuts backing layer 5 by void space 4. The abutting ceramic layer 1 and backing layer 5 are separated from fibrous layer 3 by void space 4'. In Figure 5 is depicted an embodiment of the invention having multiple metal layer composed of layers 2 and 2' which are directly exposed the the thereat. Layers 2 and 2* are fabricated of metals having differing hardness and are separated from fibrous layer 3 by void space 4.

Figure 6 depicts an embodiment which is composed of only two layers. One layer is a ceramic layer 1 which is directly exposed to the threat and which abuts fibrous layer 3. Figure 7 depicts an embodiment of the invention having a ceramic layer 1 with abutting backing layer 5 which is directly exposed to the threat. Layer 1 is separated from metal layer 2 by void space 4 which, in turn, is separated from fibrous layer 3 by void space 4A

Figure 8 depicts an embodiment of the invention having three abutting layers. Ceramic layer 1, which is directly exposed to the threat abuts metal layer 2 which, in turn, abuts fibrous layer 3.

In the preferred embodiments of the invention, the composite comprises at least two hard rigid layers of varying hardness in addition to the essential fibrous layer. In these preferred embodiments, the various layers are preferably arranged in order of decreasing hardness with respect to the ballistic threat, such as ceramic layer exposed to the threat followed by a metal layer and a fibrous layer. In the particularly preferred embodiments of this invention, there is a void space between one or more of the layers of rigid materials, and the one or more layers which include the fibrous layer. The size and shape of the space may vary widely depending on various factors such as limitation to armor thickness, limitations in the construction of the armor, the perceived threat and the like. In general, the larger the space the better dispersion (divergance) and rotation of broken pieces of the ballistic threat, and hence the more effective the composite in defeating the threat. Conversely, the smaller the space the less the dispersion and relation of broken pieces of the ballistic threat, and, hence, the less effective the composite in defeating the threat. Space width usually will vary from about 0.5 cm to about 30 cm, preferably from about 1 cm to about 20 cm, more preferably from about 1.5 cm to about 10 cm and most preferably from about 2.5 cm to about 7.5 cm.

The relative weight percents of fibrous layer(s) and rigid hard layer(s) in the composite may vary widely. In general, the amount of either fibrous layer(s) or hard rigid layer(s) may vary from about 20% to about 80% by weight of the composite. In the preferred embodiments of the invention, the amount of fibrous layer(s) may vary from about 20 to about 80% by weight of the composite, and the amount of hard rigid layer(s) may vary from about 80 to about 20% by weight of the composite; and in the particularly preferred embodiments of the invention the amount of fibrous layer(s) may vary from about 20 to about 60% by weight of the composite and the amount of hard rigid layer(s) is from about 60 to about 40 based on the weight of the composite. Amongst these particularly preferred embodiments, most preferred are those embodiments in which the amount of fibrous layer is from about 25 to about 50% by weight of the composite, and the amount of the hard rigid layer(s) is from about 75 to about 50% be weight of the composite.

The structure of fibrous layer(s) may vary widely. In the composite articles of our invention, the filaments in fibrous layer(s) may be arranged in networks having various configurations. For example, a plurality of filaments can be grouped together to form a twisted or untwisted yarn bundles in various alignment. In preferred embodiments of the invention, the filaments in each layer are aligned substantially parallel and unidirectionally in which the matrix material substantially coats the individual filaments of the filaments. The filaments or yarn may be formed as a felt, knitted or woven (plain, basket, satin and cro feet weaves, ets.) into a network, fabricated into non-woven fabric, arranged in parallel array, layered, or formed into a fabric by any of a variety of conventional techniques. Among these techniques, for ballistic resistance applications we prefer to use those variations commonly employed in the preparation of aramid fabrics for ballistic-resistant articles. For example, the techniques described in U.S. Patent No. 4,181,768 and in M.R. Silyquist et al., J. Macromol Sci. Chem. , A7(l), pp. 203 et. seq. (1973) are particularly suitable.

The type of filaments used in the fabrication of the fibrous layer(sO of the article of this invention may vary widely and can be metallic filaments, semi-metallic filaments, inorganic filaments and/or organic filaments. Preferred filaments for use in the practice of this invention are those having a tenacity equal to or greater than about 10 g/d, a tensile modulus equal to or greater than about 150 g/d and an energy-in-break equal to or greater than about 8 joules/grams. Particularly preferred filaments are those having a tenacity equal to or greater than about 20 g/d, a tensile modulus equal to or greater than about 500 g/d and energy-to-break equal to or greater than about 30 joules/grams. Amongst these particularly preferred embodiments, most preferred are those embodiments in which the tenacity of the filaments are equal to or greater than about 25 g/d, the tensile modulus is equal to or greater than about 1000 g/d, and the energy-to-break is equal to or greater than about 35 joules/grams. In the practice of this invention, filaments of choice have a tenacity equal to or greater than about 30 g/d, the tensile modulus is equal to or greater than about 1300 g/d and the energy-to-break is equal to or greater than about 40 joules/grams.

Filaments for use in fibrous layer(s) may be metallic, semi-metallic, inorganic and/or organic. Illustrative of useful inorganic filaments are those formal from S-glass, silicon carbide, asbestos, basalt, E-glass, alumina, alumina-silicate, quartz, zirconia-silica, ceramic filaments, boron filaments, carbon filaments, and the like. Exemplary of useful metallic or semi-metallic filaments are those composed of boron, aluminum, steel and titanium. Illustrative of useful organic filaments are those composed of aramids (aromatic polya idesO, poly(m-xylylene adipamide) , poly(p-xylylene sebacamide), poly(2,2,2- trimethylbexamethylene terephthalamide) , poly(piperazine sebacamide), poly(metaphenylene isophthalamide) (Nomex) and ρoly(ρ-phenylene terephthalamide) (Kevlar) and aliphatic and cycloaliphatic polyamides, such as the copolyamide of 30% hexamethylene diammonium isophthalate and 70% hexamethylene diammonium adipate, the copolyamide of up to 30% bis-(-amidoclyclohexyl) methylene, terephthalic acid and caprolactam, polyhexamethylene adipamide (nylon 66), poly(butyrolactam) (nylon 4), poly(9-aminonoanoic acid) (nylon 9), poly(enantholactam) (nylon 7), poly(capryllactam) (nylon 8), polycaprolactam (nylon 6), poly(p-ρhenylene terephthalamide), polyhexamethylene sebacamide (nylon 6,10), polyaminoundecanamide (nylon 11), polydodecanolactam (nylon 12), polyhexamethylene isophthalamide, polyhexamethylene terephthalamide, polycaproamide, poly(nonamethylene azelamide) (nylon 9,9), poly(decamethylene azelamide) (nylon 10,9), poly(decamethylene sebacamide) (nylon 10,10), polyfbis- (4-aminocyclohexyl)methane 1,10-decanedicarboxamide] (Qiana)(trans), or combination thereof; and aliphatic, cycloaliphatic and aromatic polyesters such as poly(l,4- cyclohexylidene dimethyl eneterephathalate) cis and trans, poly(ethylene-1,5-naphthalate) , poly(ethylene-2,6- naphthalate), poly(l,4-cyclohexane dimethylene terephthalate) (trans), poly(decamethylene terephthalate), ρoly(ethylene terephthalate), poly(ethylene isophthalate) , ρoly(ethylene oxybenzoate) , poly(para-hydroxy benzoate) , ρoly(α ,β diamethylpropiolactone), poly(decamethylene adipate) , polytethylene succinate) and the like. Also illustrative of useful organic filaments are those composed of extended chain polymers formed by polymerization of α, 3-unsaturated monomers of the formula:

R_χ R₂-C CH.

wherein:

R., and R- are the same or different and are hydrogen, hydroxy, halogen, alkylcarbonyl, carboxy, alkoxycarbonyl, heterocycle or alkyl or arly either unsubstituted or substituted with one or more substituents selected from the group consisting of alkoxy, cyano, hydroxy, alkyl and aryl. Illustrative of such polymers of _α & -unsaturated monomers are polymers including polystyrene, polyethylene, polypropylene, polyd- octadecene) , polyisobutylene, poly(l-pentene) , poly(2- methylstyrene) , poly(4-methylstyrene), poly(l-hexene) , poly(l-pentene), ρoly(4- methoxystyrene) , poly(5- methyl-1-hexene), poly(4-methylpentene), poly(1-butene) , poly(3-methyl-l-butene) , poly(3-phenyl-l-propene) , polyvinyl chloride, polybutylene, polyacrylonitrile, pol (methyl pentene-1), poly(vinyl alcohol), poly(vinylacetate) , poly{vinyl butyral), poly(vinyl chloride), poly(vinylidene chloride), vinyl chloride-vinyl acetate chloride copolymer, poly(vinylidene fluoride), poly(methyl acrylate, poly(methyl methacrylate) , poly(methacrylonitrile), poly(acrylamide), poly(vinyl fluoride), poly(vinyl formal), poly(3-methyl-l-butene) , poly(l-pentene) , poly(4-methyl-l-butene) , poly(l-pentene) , poly(4-methyl-l-pentene) , poly(1-hexane) , poly(5- methyl-1-hexene), poly(l-octadecene), poly(vinyl cyclopentane) , poly(vinylcyclohexane) , poly(a- vinylnaphthalene) , poly(vinyl methyl ether), poly(vinylethylether), pol (vinyl propylether), pol (vinyl carbazole), poly(vinyl pyrrolidone), poly(2-chlorostyrene) , poly(4-chlorostyrene) , pol (vinyl formate), poly(vinyl butyl ether), poly(vinyl octyl ether), poly(vinyl methyl ketone), poly(methylisopropenyl ketone), poly(4- phenylstyrene) and the like.

In the most preferred embodiments of the invention, all or a portion of the fibrous layer(s) include a filament network, which may include a high molecular weight polyethylene filament, a high molecular weight polypropylene filament, an aramid filament, a high molecular weight polyvinyl alcohol filament, a high molecular weight polyacrylonitrile filament or mixtures thereof. USP 4,457,985 generally discusses such high molecular weight polyethylene and polypropylene filaments, and the disclosure of this patent is hereby incorporated by reference to the extent that it is not inconsistent herewith. In the case of polyethylene, suitable filaments are those of molecular weight of at least 150,00, preferably at least one million and more preferably between two million and five million. Such extended chain polyethylene (ECPE) filaments may be grown in solution as described in U.S. Patent No. 4,137,394 to Meihuzen et al., or U.S. Patent No. 4,356,138 of Kavesh et al., issued October 26, 1982, or a filament spun from a solution to form a gel structure, as described in German Off. 3,004,699 and GB 2051667, and especially as described in Application Serial No. 572,607 of Kavesh et al. filed January 20, 1984 (see EPA 64,167, published Nov. 10,

1982). As used herein, the term polythylene shall mean a predominantly linear polyethylene material that may contain minor amounts of chain branching or monomers not exceeding 5 modifying units per 100 main chain carbon atoms, and that may also contain admixed therewith not more than about 50 wt% 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 polyoxy ethylenes, or low molecular weight additives such as anti-oxidants, lubricants, ultra-violet screening agents, colorants and the like which are commonly incorporated by reference. Depending upon the formation technique, the draw ratio and temperatures, and other conditions, a variety of properties can be imparted to these filaments. The tenacity of the filaments should be at least 15 grams/denier, preferably at least 20 grams/denier, more preferably at least 25 grams/denier and most preferably at least 30 grams/denier. Similarly, the tensile modulus of the filaments, as measured by an Instron tensile testing machine, is at least 300 grams/denier, preferably at least 500 grams/denier and more preferably at least 1,000 grams/denier and more preferably at least 1,200 grams/denier. These highest values for tensile modulus and tenacity are generally obtainable only by employing solution grown or gel filament processes. Similarly, highly oriented polypropylene filaments of molecular weight at least 200,000, preferably at least one million and more preferably at least two million may be used. Such high molecular weight 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. Serial No. 572,607, filed January 20, 1984, of Kavesh et al. and commonly assigned. 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 is at least 8 grams/denier, with a preferred tenacity being at least 11 grams/denier. The tensile modulus for polypropylene is at least 160 grams/denier, preferably at least 200 grams/denier.

High molecular weight polyvinyl alcohol filaments having high tensile modulus are described in USP 4,440,711 to Y. Kwon, et al., which is hereby incorporated by reference to the extent it is not inconsistent herewith. In the case of polyvinyl alcohol (PV-OH), PV-OH filament of molecular weight of at least about 200,000. Particularly useful PV-OH filament should have a modulus of at least about 300 g/denier, a tenacity of at least about 7 g/denier (preferably at least about 10 g/denier, more preferably at about 14 g/denier, and most preferably at least about 17 g/denier), and an energy to break of at least about 8 joules/g. PV-OH filaments having a weight average molecular weight of at least about 200,000, a tenacity of at least about 10 g/denier, a modulus of at least about 300 g/denier, and an energy to break of about 8 joules/g are more useful in producing a ballistic resistant article. PV-OH filament having such properties can be produced, for example, by the process disclosed in U.S. Patent No. 4,599,267.

In the case of polyacrylonitrile (PAN), PAN filament of molecular weight of at least about 400,000. Particularly useful PAN filament should have a tenacity of at least about 10 g/denier and an energy to break of at least about 8 joule/g. PAN filament having a molecular weight of at least about 400,000, a tenacity of at least about 15 to about 20 g/denier and an energy to break of at least about 8 joule/g is most useful in producing ballistic resistant articles; and such filaments are disclosed, for example, in USP No. 4,535,027.

In the case of aramid filaments, suitable aramide filaments formed principally from aromatic polyamide are described in US. Patent No. 3,671,542, which is hereby incorporated by reference. Preferred aramid filament will have a tenacity of at least about g/d, a tensile modulus of at least about 400 g/d and an energy-to-break at least about 8 joules/gram, and particularly preferred aramid filaments will have a tenacity of at least about 20 g/d, a modulus of at least about 480 g/d and an energy-to-break of at least about 20 joules/gram. Most preferred aramid filaments will have a tenacity of at least about 20 g/denier, a modulus of at least about 900 g/denier and an energy-to-break of at least about 30 joules/gram. For example, poly(phenylenediamine terephalamide) filaments produced commercially by Dupont Corporation under the trade mane of Kevlar^R 29 and 49 and having moderately high moduli and tenacity values are particularly useful in forming ballistic resistant composites. (Kevlar 29 has 500 g/denier and 22 g/denier and Kevlar 49 has 1000 g/denier and 22 g/denier as values of modulus and tenacity, respectively) . Also useful in the practice of this invention is poly(metaphenylene isophthalamide) filaments produced commercially by Dupont under the tradename Nomex .

In the fibrous layer(s), the filaments are arranged in a network which can have various configurations. For example, a plurality of filaments can be grouped together to form a twisted or untwisted yarn. The filaments or yarn may be formed as a felt, knitted or woven (plain, basket, sating and crow feet weaves, etc.) into a network. or formed into a network by any of a variety of conventional techniques. In the preferred embodiments of the invention, the filaments are untwisted mono- ilament yarn wherein the filaments are parallel, unidirectionally aligned. For example, the filaments may also be formed into nonwoven cloth layers be conventional techniques.

In the fibrous layer(s), the filaments are most preferably dispersed in a continuous phase of a matrix material which preferably substantially coats each filament contained in the bundle of filament. The manner in which the filaments are dispersed may vary widely. The filaments may be aligned in a substantially parallel, unidirectional fashion, or filaments may be aligned in a multidirectional fashion with filaments may be aligned in a multidirectional fashion with filaments at varying angles with each other. In the preferred embodiments of this invention, filaments in each layer are aligned in a substantially parallel, unidirectional fashion such as in a prepare, pultruded sheet and the like. The matrix material employed may vary widely and may be a metallic, semi-metallic material, an organic material and/or an inorganic material. The matrix material may be flexible (low modulus) or rigid (high modulus). Illustrative of useful high modulus or rigid matrix materials are thermoplastic resins such as polycarbonates, polyether, ether ketones, polyarylenesulfides, polyarylene oxides, polyestercarbonates, polyesterimides, and polyimides, thermosetting resins such as epoxy resins, phenolic resins, modified phenolic resins, allylic resins, alkyd resins, unsaturated polyesters, aromatic vinylesters as for example the condensation produced of bisphenol A and methacrylic acid diluted in a vinyl aromatic monomer (e.g. styrene or vinyl toluene), urethane resins and amino (melamine and area) resins; or mixtures thereof, the major criterion is that such material holds the filaments together, and maintains the geometrical integrity of the fibrous layer(s) under the desired conditions. In the preferred embodiments of the invention, the matrix material is a low modulus elastomeric material. A wide variety of elastomeric materials and formulations may be utilized in the preferred embodiments of this invention. Representative examples of suitable elastomeric materials for use in the formation of the matrix are those which have their structures, properties, and formulations together with crosslinking procedures summarized in the Encyclopedia of Polymer Science, Volume 5 in the section Elastomers-Synthetic (John Wiley & Sons Inc., 1964). For example, any of the following elastomeric materials may be employed: polybutadiene, polyisoprene, natural rubber, ethylene-propylene copolymers, ethylene-propylene-diene, terpolymers, polysulfide polymers, polyurethane elastomers, chlorosulfonated polyethylene, polychloroprene, plasticized polyvinylchloride using dioctyl phthate or other plasticers well known in the art, butadiene acrylonitrile elastomers, poly(isobutylene-co-isoρrene) , polyacrylates, polyesters, polyethers, fluoroelastomers, silicone elastomers, thermoplastic elastomers, copolymers of ethylene.

Particularly useful elastomer are block copolymers of conjugated dienes and vinyl aromatic monomers. Butadiene and isoprene are preferred conjugated dien 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 A-B-A, multiblock copolymers of the type (AB) (n=2-10) or radical configuration copolymers n of the type R-(BA)_χ(x=3-150); wherein A is a block from a polyvinyl aromatic monomer and B is a block from a conjugated dien elastomer. Many of these polymers are produced commercially by the Shell Chemical Co. and described in the bulletin "Kraton Thermoplastic Rubber", SC-68-81. Most preferably, the elastomeric matrix material consists essentially of at least one of the aobve-mentioned elastomers. The low modulus elastomeric matrices may also include fillers such as carbon black, silica, glass microballons, and the like up to an amount preferably not to exceed about 50% by volume of the elastomeric material, preferably not to exceed about 40% by weight, and may be extended with oils, may include fire retardants such as halogenated parafins, and vulcanized by sulfur, peroxide, metal oxide, or radiation cure systems using methods well known to rubber technologists. Blends of different elastomeric materials may be used together or one or more elastomer materials may be blended with one or more thermoplastics. High density, low density, and linear low density polethylene may be cross-linked to obtain a matrix material of appropriate properties, either alone or as blends. In every instance, the modulus of the elastomeric matrix material should not exceed about 6,000 psi (41,300 kPa) , preferably is less than about 5,000 psi (34,500 kPa) , more preferably is less than 1000 psi (6900 kPa) and most preferably is less than 500 psi (3450 kPa) .

In the preferred embodiments of the invention, the matrix material is a low modulus, elastomeric material. The low modulus elastomeric material has a tensile modulus, measured at about 23°C, of less than about 6,000 psi (41,300 kPa) . Preferably, the tensile modulus of the elastomeric material is less than about 5,000 psi (34,500 kPa), more preferably, is less than 1,000 psi (6900 kPa) and most preferably is less than about 500 psi (3,450 kPa) to provide even more improved performance. The glass transition temperature (Tg) of the elastomeric material (as evidenced by a sudden drop in the ductility and elasticity of the material is less than about 0°C. Preferably, the Tg of the elastomeric material is less than about -40°C, and more preferably is less than about -50°C. The elastomeric material also has an elongation to break of at least about 50%. Preferably, the elongation to break of the elastomeric material is at least about 100%, and more preferably is at least about 300%.

The proportions of matrix to filament in the fibrous layer(s) is not critical and may vary widely depending on a number of factors including, whether the matrix material has any ballistic-resistant properties of its own (which is generally not the case) and upon the rigidity, shape, heat resistance, wear resistance, flammability resistance and other properties desired for the composite article. In general, the proportion of matrix to filament in the composite may vary from relatively small amounts where the amount of matrix is about 10% by volume of the filaments to relatively large amounts where the amount of matrix is up to about 90% by volume of the filaments. In the preferred embodiments of this invention, matrix amounts of from about 15 to about 80% by volume are employed. All volume percents are based on the total volume of the composite. In the particularly preferred embodiments of the invention, ballistic-resistant articles of the present invention contain a relatively minor proportion of the matrix (e.g., about 10 to about 30% by volume of composite), since the ballistic-resistant properties are almost entirely attributable to the filament, and in the particularly preferred embodiments of the invention, the proportion of the matrix in the composite is from about 10 to about 30% by weight of filaments.

The fibrous layer(s) can be fabricated using a number of procedures. In general, the layers are formed by molding the combination of the matrix material and filaments in the desired configurations and amounts by subjecting them to heat and pressure.

The filaments may be premolded by subjecting them to heat and pressure. For ECPE filaments, molding temperatures range from about 20 to about 150°C, preferably from about 80 to about 145°C, more preferably from about 100 to about 135°C, and more preferably from about 110 to about 130 °C. The pressure may range from about 10 psi (69 kpa) to about 10,000 psi (69,000 kpa) . A pressure between about 10 psi (69 kpa) and about 100 psi (690 kpa), when combined with temperatures below about

100°C for a period of time less than about 1.0 min. , may be used simply to cause adjacent filaments to stick together. Pressures from about 100 psi (6900 kpa) to about 10,000 psi (69,000 kpa), when coupled with temperatures in the range of about 100 to about 155°c for a time of between about 1 to about 5 min. , may cause the filaments to deform and to compress together (generally in a film-like shape). Pressures from about 100 psi (690 kpa) to aboutl0,000 psi (69,000 kPa) , when coupled with temperatures in the range of about 150 to about 155°C for a time of between 1 to about 5 min., may cause the film to become translucent or transparent. For polypropylene filaments, the upper limitation of the temperature range would be about 10 to about 20°C higher than for ECPE filament.

In the preferred embodiments of the invention, the filaments (premolded if desired) are precoated with the desired matrix material prior to being arranged in a network and mold as described above. The coating may be applied to the filaments in a variety of ways and any method known to those of skill in the art for coating filaments may be used For example, one method is to apply the matrix material to the stretched high modulus filaments either as a liquid, a sticky solid or particles in suspension, or as a fluidized bed. Alternatively, the matrix material may be applied as a solution or emulsion in a suitable solvent which does not adversely affect the properties of the filament at the temperature of application. In these illustrative embodiments, any liquid capable of dissolving or dispersing the matrix material may be used. However, in the preferred embodiments of the invention in which the matrix material is an elastomeric material, preferred groups of solvents include water, paraffin oils, ketones, alcoholic, aromatic solvents or hydrocarbon solvents or mixtures thereof, with illustrative specific solvents including paraffin oil. xylene, toluene and octane. The techniques used to dissolve or disperse the matrix in the solvents will be those conventionally used for the coating of similar elastomeric materials on a variety of substrates. Other techniques for applying the coating to the filaments may be used, including coating of the high modulus precursor (gel filament) before the high temperature stretching operation, either before or after removal of the solvent from the filament. The filament may then be stretched at elevated temperatures to produce the coated filaments. The gel filament may be passed through a solution of the appropriate matrix material, as for example an elastomeric material dissolved in paraffin oil, or an aromatic or aliphatic solvent, under conditions to attain the desired coating. Crystallization of the polymer in the gel filament may or may not have taken place before the filament passes into the cooling solution. Alternatively, the filament may be extruded into a fluidized bed of the appropriate matrix material in powder form.

The proportion of coating on the coated filaments or fabrics may vary from relatively small amount (e.g. 1% by weight of filaments) to relative large amounts (e.g. 150% by weight of filaments), depending upon whether the coating material has any impact or ballistic-resistant properties of its own (which is generally not the case) and upon the rigidity, shape, heat resistance, wear resistance, flam ability resistance and other properties desired for the complex composite article. In general, ballistic-resistant articles of the present invention containing coated filaments should have a relatively minor proportion of coating (e.g., about 10 to a bout 30 percent by volume of filaments) , since the ballistic-resistant properties are almost entirely attributable to the filament. Nevertheless, coated filaments with higher coating contents may be employed. Generally, however, when the coating constitutes greater than about 60% (by volume of filament), the coated filament is consolidated with similar coated filaments to form a simple composite without the use of additional matrix material.

Furthermore, if the filament achieves its final properties only after a stretching operation or other manipulative process, e.g. solvent exchanging, drying or the like, it is contemplated that the coating may be applied to a precursor material of the final filament. In such cases, the desired and preferred tenacity, modulus and other properties of the filament should be judged by continuing the manipulative process on the filament precursor in a manner corresponding to that employed on the coated filament precursor. Thus, for example, if the coating is applied to the xerogel filament described in U.S. Application Serial No. 572,607 of Kavesh et al., and the coated xerogel filament is then stretched under defined temperature and stretch ratio conditions, then the filament tenacity and filament modulus values would be measured on uncoated xerogel filament which is similarly stretched.

It is a preferred aspect of the invention that each filament be substantially coated with the matrix material for the production of the fibrous layer(s) having improved impact protection and/or having maximum ballistic resistance. A filament is substantially coated by using any of the coating processes described above or can be substantially coated by employing any other process capable of producing a filament coated essentially to the same degree as a filament coated by the processes described heretofore (e.g., by employing known high pressure molding techniques) .

The filaments and networks produced therefrom are formed into the fibrous layer(s) which is a "simple composites". The term, "simple composite", as used herein is intended to mean composites made up of one or more layers, each of the layers containing filaments as described above with a single major matrix material, which material may include minor proportions of other materials such as fillers, lubricants or the like as noted heretofore.

The proportion of elastomeric matrix material to filament is variable for the simple composites, with matrix material amounts of form about 5% to about 150

Vol %, by volume of the filament, representing the broad general range. Within this range, it is preferred to use composites having a relatively high filament content, such as composites having only about 10 to about 50 Vol % matrix material, by volume of the composite, and more preferably from about 10 to about 30 Vol % matrix material by volume of the composite.

Stated another way, the filament network occupies different proportions of the total volume of the simple composite. Preferably, however, the filament network comprises at least about 30 volume percent of the simple composite. For ballistic protection, the filament network comprises at least about 50 volume percent, more preferably about 70 volume percent, and most preferably at least about 75 volume percent, with the matrix occupying the remaining volume.

A particularly effective technique for preparing the fibrous layer(s) for use in a preferred composite of this invention comprised of substantially parallel, unidirectionally aligned filaments includes the steps of pulling a filament or bundles of filaments through a bath containing a solution of a matrix material preferable an elastomeric matrix material, and circumferentially winding this filament into a single sheet-like layer around and along a bundly of filaments the length of a suitable form, such as a cylinder. The solvent is then evaporated leaving a sheet-like layer of filaments embedded in a matrix that can be removed from he cylindrical form. Alternatively, a plurality of filaments or bundles of filaments can be simultaneously pulled through the bath containing a solution or dispersion of a matrix material and laid down in closely positioned, substantially parallel relation to one another on a suitable surface. Evaporation of the solvent leaves a sheet-like layer comprised of filaments which are coated with the matrix material and which are substantially parallel and aligned along a common filament direction. The sheet is suitable for subsequent processing such as laminating to another sheet to form composites containing more than one layer.

Similarly, a yarn-type simple composite can be produced by pulling a group of filament bundles through a dispersion or solution of the matrix material to substantially coat each of the individual filaments, and then evaporating the solvent to form the coated yarn. The yarn can then, for example, be employed to form fabrics, which in turn, can be used to form more complex composite structures. Moreover, the coated yarn can also be processed into a simple composite by employing conventional filament winding techniques; for example, the simple composite can have coated yarn formed into overlapping filament layers.

The number of layers included in the fibrous layer(s) of may vary widely depending on the uses of this composite. The number of layers would depend on a number of factors including the degree of ballistic protection desired and other factors known to those of skill in the ballistic protection art. In general for this application, the greater the degree of protection desired, the greater the number of layers included in the fibrous layer(s) for a given weight of the article. Conversely, the lessor the degree of ballistic protection required, the lessor the number of layers required for a given weight of the article. It is convenient to characterize the geometries of the fibrous layer(s) by the geometries of the filaments and then to indicate that the matrix material may occupy part or all of- the void space left by the network of filaments. One such suitable arrangement is a plurality of layers or laminates in which the coated filaments are arranged in a sheet-like array and aligned parallel to one another along a common filament direction. Successive layers of such coated. undirectional filaments can be rotated with respect to the previous layer. An example of such laminate structures are composites with the second, third, fourth and fifth layers rotated +45°, -45°, 90° and 0°, with respect to the first layer, but not necessarily in that order. Other examples include fibrous layer(s) composed of layers of coated, undirectional filaments in which adjacent layers are oriented 0 /90 with respect to their common filament direction. One technique for forming fibrous layer(s) having more than one layer includes the steps of arranging coated filaments into a desired network structure, and then consolidating and heat setting the overall structure to cause the coating material to flow and occupy the remaining void spaces, thus producing a continuous matrice. Another technique is to arrange layers or other structures of coated or uncoated filament adjacent to and between various forms, e.g. films, of the matrix material and then to consolidate and heat set the overall structure. In the above cases, it is possible that the matrix can be caused to stick or flow without completely melting. In general, if the matrix material is caused to melt, relatively little pressure is required to form the composite; while if the matrix material is only hated to a sticking point, generally more pressure is required.

Also, the pressure and time to set the composite and to achieve optimal properties will generally depend on the nature of the matrix material (chemical composition as well as molecular weight) and processing temperature. The complex composite of the invention includes at least one rigid layer which is preferably comprised of an impact resistant material. Illustrative of useful impact resistant materials are steel plates, composite armor plates, ceramic reinforced metallic composites, ceramic plates, concrete, and high strength filament composites

(for example, a S-glass, a E-glass or an aramifilament and a high modulus, resin matrix such as epoxy or phenolic resin vinyl ester, unsaturated polyester, thermoplastics. Nylon 6, nylon 6,6 or polyvinylidine halides rean. Preferably, the rigid impact resistant layer is one which is ballistically effective, such as ceramic plates or ceramic reinforced metal composites. A desirable embodiment of our invention is the use of a rigid impact resistant layer which will at least partially deform the initial impact surface of the projectile or cause the projectile to shatter such as a layer formed of a ceramic as for example aluminum oxide, boron carbide, silicon carbide, titanium borides, beryllium oxide and the like and/or a layer formed from a metal as for example stainless steel, copper, aluminum, titanium, and the like (see Laible, supra. Chapters 5-7 for additional useful rigid layers) . In the preferred embodiments of this invention, the complex composites include at least one rigid layer comprised of a ceramic material such as aluminum oxide, silicon carbide, boron carbide and titanium diboride. The various ceramic materials can be made into different grades having varying physical properties as desired such as purity, density, hardness, strength, modulus and the like by manipulation of raw materials and manufacturing processes.

Usually, better ballistic performance is obtained from ceramic materials of relatively higher purity, high density, high hardness, high modulus and higher toughness, and such materials are employed in the most preferred embodiments of the invention.

The shape of the ceramic material can vary widely. In the most preferred embodiments of the invention, the ceramic layer is formed from flat ceramic tiles of various sizes.

Ceramic materials for use in this invention can be made by various processes know to those of skill in the ceramic art. Typically, a ceramic powder is prepared from the raw material by milling and screening. The resulting powder is processed further to achieve better processibility in the subsequent processes by specific treatments and addition of blending additives know in the art. The resulting, processed powder is then cold-formed into the desired shape by pressing or molding, afterwhich the shaped powder is densified by sintering or hot pressing at elevated temperature. In some cases, the densified product is finished by machining with diamond or other means.

In the more preferred embodiments of the invention, the composite will comprise at least three layers, one of which is composed of a fibrous layer such as high molecular weight polyethylene in a polymer matrix, and a ceramic layer or a glass or glass reinforced layer. ^' It is even more preferred that these composites also include a metal layer, such as a layer composed of steel. In the most preferred embodiments, the metal layer is perforated. The perforations cause the projectile to tilt, rotate and preferably break up into smaller pieces which can be stopped by the fibrous layer more effectively. Tilting or rotating the projectile helps improve ballistic performance because the projectile will hit the fibrous layer on its side rather than by its nose enabling the composite to receive the impact over a greater area. The degree of perforation may vary widely, and is preferably is at least about 20 Vol% based on the total volume of the metal layer is more preferably from about 20 Vol% to about 70 vol% on the aforementioned basis and is most preferably from about 30 to about 60 Vol%. In general the spacing and size of the perforation in the metal layer may vary widely. The larger the size of threat projectile, the larger the spacing and size of perforation in the metal layer is suitable for greater impact on the mass efficiency of the composite. An example of a perforated steel plate is shown in Fig. 9. The size of the perforation may vary widely. In general, the size depends on the particular ballistic threat being countered, and is usually of such a size as to allow tilting and/or rotation of the projectile. The shape of the perforations may also vary widely. Such perforation may be circular, oblong, square, rectangular and the like. In the preferred embodiments of this invention, the perforations are oblong.

The composites of this invention are useful for the fabrication of ballistic resistant article such as landing craft hull and other type of armor, and helmets. The protective power of a structure may be expressed in term of its mass efficiency (E ). The mass efficiency of the composite of this invention exhibits superior mass efficiency of at least about 2.5. In the preferred embodiments of the invention, the mass efficiency is at least about 3 and in the particularly preferred embodiments is at least about 3.5. Amongst these particularly preferred embodiments, most preferred are those embodiments in which the mass efficiency is at least about 4.0.

Usually, a composite armor has the geometrical shape of a shell or plate. The specific weight of the shells and plates can be expressed in terms of the areal density (AD). The areal density corresponds to the weight per unit area of the structure. In the cast of filament reinforced composites, the ballistic resistance of which depends mostly on the filament, another useful weight characteristic is the filament areal density of composites. This term corresponds to the weight of the filament reinforcement per unit area of the composite (AD).

The following examples are presented to provide a more completes understanding of the invention. The specific techniques, conditions, materials, proportions and reported data set forth to illustrate the principles of the invention are exemplary and should not be construed as limiting the scope of the invention.

EXAMPLE 1

A ballistic panel was prepared by molding a plurality of sheets comprised of Spectra^R-900 uni-directional high strength extended chain polyethylene (ECPE) yarn impregnated with a Kraton D1107 thermoplastic elastomer matrix ( a polystyrene-polyisoprene-polystrene-block co- polymer having 14 wt% styrene and a product of Shell Chemical). The yarn had a tenacity of 30 g/denier, a modulus of 1,200 g/denier and energy-to-break of 55 joules/g. The elongation to break of the yarn was 4%, denier was 1,200 and individual filament denier was 10, or 118 filaments per yarn end. Each filament has a diameter of 0.0014" (0.0036 cm). A total of 360 layers were used, and were stacked or laminated together with a 0°/90° yarn orientation with each layer having filament length perpendicular to the filament length of the adjacent layers.

The laminated composite panel was then molded between two parallel plates of 24" (61 cm) X 24" (61 cm) square at a temperature of 124°C and a pressure of 420 psi (2900 k Pa) for a period of 40 minutes. After molding, the panel was allowed to cool to room temperature over a 30 minute period. The molded panel measured 24" (61 cm) X 24" (61 cm) X 0.93" (2.36 cm), and had an areal density of 24 kg/m .

A complex ballistic panel was fabricated using titanium diboride tile [4" (10.1 cm) X 4" (10.1 cm)] x 0.858" (2.18 cm) having areal density of 97 kg/m² (Ceralloy 225, Ceradyne, Inc.), and the fibrous panel containing the Spectra^R polyethylene fiber. The titanium diboride tile abutted the fibrous panel. Total areal density for the complex ballistic article was 121 Kg/m². Using conventional testing procedures, the complex ballistic article was tested with a designated projectile which required approximately 400 kq/m of roll-hardened armor plate (RHA) to defeat. The impact velocity of the projectile was 3,069 ft/sec (935 m/sec) . In the test, the projectile penetrated the titanium diboride tile but only partially penetrated the fibrous composite formed from the Sρectra^R fiber, and 12 kg/m² of the Spectra ^R composite remained unpenetrated. The Em of the article was approximately 3.3.

EXAMPLE II

Using the procedure of Example I, a complex ballistic article having the structural features set forth in Table I was fabricated. The features are listed in the order in which they are exposed to the projectile during testing.

TABLE I

Composition of Layer Areal Density

(a) Aluminum oxide Tile [4" (10.1 cm) X 4"(10.1 cm)] obtained from Coors Ceramics Co. 49 Kg/m2

(b) RHA steel plate

20" (50.8 cm) x 20" (50.8 cm), perforated with 0.9 cm by 2.1 cm oblong holes obtained from Detroit Puncher and Retainer Corporation 19 Kg/m2

(c) Void space 3 in (7.6 cm)

(d) Fibrous composite fromed from Spectra^R Fiber 24" (61 cm) x 24" (61 cm) fabricated as in EXAMPLE I 45 Kg/m2

2

Total areal density of the article was 113 Kq/m ,

Using the procedure of Example I, the complex article was struck by the projectile at an impact velocity of 3,125 ft/s_e_c_ (953 m/sec) . The projectile penetrated the aluminum oxide and steel layers but

20 Kg/m 2 of the fibrous SpectraT? composite unpenetrated. The E of the complex composite was approximately 3.5. EXAMPLE III

Using the procedure of Example I, a complex ballistic article having the structural features set forth in Table II was fabricated. The features are listed in the order in which they are exposed to the projectile during testing.

TABLE II

Composition of Layer Areal Density

(a) Aluminum oxide tile

[4" (10.1 cm) X 4" (10.1 cm)] obtained from Coors Ceramics

Co. 49 Kg/m2

(b) Glass Fabric Reinforced Panel obtained from Martin Marietta Corp.

[20" (50.8 cm)] X 20" (50.8 cm)] 28 Kg/m2

(c) Space 3" (7.5 cm)

(d) Fibrous Composite of Spectra^R Fiber

24" (61 cm) X 24" (61 cm) fabricated as in EXAMPLE I. 45 Kg/M²

2 Total areal density of the composite was 122 Kq/m .

Using the procedure of Example I, the complex ballistic article was struck by the projectile at an impact velocity of 3,058 ft/sec„ (932 m/s_βec). The projectile penetrated the aluminum oxide tile and glass

2 reinforced layers, but 21 Kq/m of the fibrous

Spectra composite was unpenetrated. The E of the complex composite was approximately 3.3.

EXAMPLE IV

Using the procedure of Example I, a complex ballistic article having the structural features set forth in Table III was fabricated. The features are listed the in order in which they are exposed to the projectile during testing. TABLE III

Composition of Layer Areal Density

(a) Perforated RHA steel plate

20" (50.8cm) X 20" (50.8 cm) obtained from Detroit Punch & Retainer Corp. 19 Kg/m2

(b) Aluminum Oxide tile

4" (10.1 cm) X 4" (10.1 cm) obtained from Coors Ceramics Co. 49 Kg/m²

(c) Glass fabric reinforced panel 20" (50.8 cm) X 20" (50.8 cm) obtained from Martin Magietta Corp. 28 Kg/m²

(d) Fibrous Composite formed from Spectra^R Fiber

24" (61 cm) X 24" (61 cm) prepared as in EXAMPLE I. 24 Kg/m²

Total areal density for the complex composite was

120 k/m².

Using the procedure of Example I, the complex article was struck by the projectile at an impact velocity of

3,047 ft/s _Λe_rc (929 m/sec). The projectile penetrated the steel, aluMinum oxide and glass reinforced layers, but

2KG/m 2 of fibrous SpectraR composite was unpenetrated. The E of the complex composite was approximately 3.3.

EXAMPLE V

Using the procedure of Example I, a complex ballistic artidle having the structural features set forth in the following Table IV was fabricated. The features are listed in the order in which they are exposed to the projectile during testing. TABLE IV

Composition of Layer Areal Density

(a) RHA steel plate

20" (50.8 cm) X 20" (50.8 cm) perforated with 0.9 cm by 2.1 cm oblong holes obtained from Detroit Punch & Retainer Corp. 19 Kg/π»2

(b) Space - 2 in (5.1 cm)

(c) Aluminum Oxide tile 4^» (10.1 cm) by 4" (10.1 cm) obtained from Coors Ceramics Co. 49 Kg/m²

(d) Glass Fabric Reinforced Panel

20" (50.8 cm) by 20" (50.8 cm) 45 Kg/m²

(e) Space 1" (2.54 cm)

(f) Fibrous Layer Formed from Spectra^R Fiber

12" (30.5 cm) by 12" (30.5 cm) fabricated as in EXAMPLE I 10 Kg/m²

The total areal density of the complex composite was 123 Kq/m².

3,104 ft/„_Λ .(946 m/„_). The projectile penetrated sec sec the steel, aluminum oxide and glass fabric reinforced

2 R layers, but 2 Kg/m of fibrous Spectra composite was unpenetrated. The E of the complex composite was approximately 3.2.

Claims

WHAT IS CLAIMED IS:

1. A composite article of manufacture comprising:

(a) at least one hard rigid layer comprising one or more hard rigid materials; and (b) at least one fibrous layer comprising a network of filaments having a tensile modulus of at least about 160 grams/denier and a tenacity of at least about 7 g/denier in a matrix; wherein the relative weight percents of said fibrous layer and said hard rigid layer, and the relative positioning of said layers are such that said article exhibits a mass efficiency equal to or greater than about 2.5.

2. An article according to claim 1 wherein said hard rigid materials are selected from the group consisting of ceramics, metals and fiber reinforced polymers.

3. An article according to claim 1 wherein said article comprises at least two hard rigid layers.

4. An article according to claim 1 wherein at least one of said hard rigid layers is a perforated metal layer.

5. An article according to claim 1 wherein said article further comprises a void layer between the portion of said article comprising at least one of said fibrous layer and the portion of said article comprising at least one of said hard rigid layers.

6. An article according to claim 1 wherein said tenacity is equal to or greater than about 20 g/d, said modulus is equal to or greater than about 500 g/d and said energy-to-break is equal to or greater than about 15 J/g.

7. An article according to claim 1 wherein said network of filaments comprises at least two sheet-like filament arrays, in each array filaments are arranged substantially parallel to one another along a common filament direction, wherein adjacent arrays are aligned at an angle with respect to the longitudinal axis of the parallel filaments contained in said arrays.

8. An article according to claim 1 wherein said network of filaments comprises a non-woven or woven fabric,

9. An article according to claim 1 wherein said filaments are aramid filaments, polyethylene filaments or a combination of aramid and polyethylene filaments.

10. An article according to claim 2 wherein said filaments are polyethylene filaments.