MULTI-LAYERED IMPACT RESISTANT PLY AND COMPOSITE

Abstract: An embodiment of the present invention described and shown in the specification and drawings is a ballistic resistant fibrous ply including two or more layers of a fibrous network, each fibrous network having a plurality of unidirectional oriented fibers, when adjacent layers are aligned, the fibers in adjacent fibrous networks arranged at an acute angle top each other. An alternative embodiment disclosed is a ballistic resistant composite including two or more layers of a fibrous ply, each fibrous ply having a plurality of unidirectional oriented fibers. When the layers of plies are aligned, the fibers in adjacent fibrous plies are arranged at an acute angle to each other.

Description: MULTI-LAYERED IMPACT RESISTANT PLY AND COMPOSITE BACKGROUND OF THE INVENTION This invention relates to ballistic resistant fibrous plies and composites. More particularly, this invention relates to a ballistic resistant fibrous ply having improved ballistic protection. Additionally, this invention relates to a ballistic resistant fibrous composite having improved ballistic protection. SUMMARY The present invention relates to a multilayer ballistic resistant fibrous ply. Each layer of the ply includes a fibrous network and each fibrous network has a plurality of unidirectional oriented fibers. When adjacent layers are aligned, the fibers in adjacent fibrous networks are at an acute angle to each other. The present invention also relates to ballistic resistant composites formed from the plies of the present invention or commercially available plies. In one embodiment, the ballistic resistant composite has two or more fibrous plies, each ply having a plurality of unidirectional oriented fibers generally in a fibrous network. A surface of one fibrous ply is in contact with and at least partially bound to the surface of one adjacent fibrous ply so that, when adjacent layers are aligned, at least one network of unidirectional oriented fibers within each adjacent fibrous plies is at an acute angle to each other. The present invention provides a ballistic resistant ply or composite of plies which provide enhanced ballistic protection as compared to conventional plies or composites of plies. For example, the ply of the present invention can be used to construct ballistic resistant articles that are lighter while still providing comparable, and in some cases superior, ballistic protection than conventional plies formed from the same conventional fibers. Further, the composite of the present invention can be used to construct ballistic resistant articles formed of conventional fibrous plies which are substantially thinner, i.e., have fewer plies, than conventional articles formed from the same fibrous plies but which also exhibit comparable, and in some cases, superior ballistic protection. The composite of the invention can also be used to construct ballistic resistant articles that have improved ballistic performance formed of conventional fibrous plies as compared to articles of substantially the same weights, i.e., the same number of conventional fibrous plies. DETAILED DESCRIPTION OF THE DRAWINGS FIG. 1 is a top view of a plurality of unidirectionally oriented fibers within a fibrous network. FIG. 2 is a top view of a portion of an exemplified ply of the present invention, showing three cross-plied layers of fibrous networks, the fibers in adjacent fibrous networks arranged at an acute angle less than 45 ° to each other. FIG. 3 is a partial cross-sectional view of a ply of the present invention, showing layers of cross-plied fibrous networks. FIG. 4 is a partial side view of an exemplified multilayered penetration resistant composite including multiple layers of connected plies. FIG. 5 is an exploded view of two exemplified plies of the multilayered penetration resistant composite arranged so that the unidirectional fibers within one ply are at an angle γ less than 45° to the unidirectional fibers within the adjacent ply. FIG. 6 is a top view of the two plies in the embodiment of FIG. 5. FIG. 7 is an exploded view of two exemplified plies of the multilayered penetration resistant composite, each ply having a pair of fibrous networks oriented at about 90° to each other, the plies arranged so that the unidirectional fibers within one ply are at an angle γ less than 45° to the unidirectional fibers within the adjacent ply. FIG. 8 is a top view of the two plies in the embodiment of FIG. 7. DETAILED DESCRIPTION OF THE INVENTION The present invention is more particularly described in the following examples that are intended as illustrative only since numerous modifications and variations therein will be apparent to those skilled in the art. Thus, the embodiments of this invention described and illustrated herein are not intended to be exhaustive or to limit the invention to the precise form disclosed. They are chosen to describe or to best explain the principles of the invention and its application and practical use to thereby enable others skilled in the art to best utilize the invention. As used in the specification and in the claims, "a" can mean one or more, depending upon the context in which it is used. "Angle" refers to an angle greater than 0°unless otherwise restricted. Reference will be made to the present embodiments of the invention, whenever possible, the same reference numbers are sued throughout to refer to the same or like parts. Referring to Figs. 1 - 3, in one embodiment, the invention is directed to a multilayered fibrous ply 10 having at least two layers of a fibrous network 12. Each network has a plurality of unidirectional oriented fibers 14 arranged substantially parallel to one another along a common fiber direction C. The fibrous networks 12 are layered so that the fibers 14 in adjacent fibrous networks 12 are arranged at an angle γ less than 45 ° to each other. The fibrous ply 10 of this invention exhibits improved penetration resistance when impacted by a projectile. In an alternative embodiment, referring now to Fig. 4-8, the invention is directed to a multilayered penetration resistant composite 40 having at least two layers of a fibrous ply 50. Here, each ply 50 of the composite 40 has at least one fibrous network 12 of unidirectionally oriented fibers and the fibers 14 in each fibrous network 12 are arranged substantially parallel to one another along a common fiber direction C. The layers of plies 50 of the composite 40 are arranged so that, with adjacent plies 50 aligned, the fibers 14 within one network 12 of oriented fibers 14 of one ply 50 are arranged at an angle γ less than 45° to the fibers 14 of one network 12 of oriented fibers of the adjacent ply 50. The composite 40 of this invention exhibits improved penetration resistance when impacted by a projectile. We have discovered that the value of the angle γ has a significant effect on the ballistic protection provided by the composite 40 and/or the ply 10. In general, the more acute the angle γ, the further the angle γ diverges from 45 °, the greater the ballistic protection provided, and conversely, the less acute the angle γ, the closer the angle γ approaches 45 °, the less ballistic protection provided. By forming the desired angle γ between the fibers 14 in respective layers of fibrous networks 12, or between the fibers 14 in respective layers of plies 50 containing a plurality of unidirectional fibers in a fibrous network 12, the present invention causes a projectile to be thrown or turned from its trajectory. A trajectory is a highly ordered kinetic path, and targets are generally destroyed by the release of the kinetic energy where the projectile strikes. The "web" created by the angular offset between the respective layers destabilizes the projectile on impact. This acts to increase the drag action on the projectile and therefore results in kinetic energy transfer from the projectile which degrades the lethality of the projectile. By angularly offsetting fibers 14 at the desired angle γ between adjoining layers, the layers of the ply 10 or composite 40 of the present invention alter the penetrating projectile's trajectory and reduces the projectile's energy. The angularly offset fibers 14 of successive adjoining layers continue to rotate the projectile and dissipate its energy. Additionally, because of the angular offset of the fibers of the adjoining layers, a projectile striking the ply 10 or composite 40 will transfer, or radiate, energy along the angularly offset fibers 14 of the successive layers which results in the dispersion of energy over a large surface area. For purposes of the present invention, fiber 14 is defined as an elongated body, the length dimension of which is much greater than the dimensions of width and thickness. Accordingly, the term fiber 14 as used herein includes a monofilament elongated body, a multifilament elongated body, ribbon, strip, and the like having regular or irregular cross sections. The term fibers 14 includes a plurality of any one or combination of the above. The cross-sections of fibers 14 for use in this invention may vary widely. They may be of circular, oblong, or irregular or regular multi-lobal cross-section having one or more regular or irregular lobes projecting from the linear or longitudinal axis of the fiber 14. In the particularly preferred embodiments of the invention, the fibers 14 are of substantially circular or oblong cross-section and in the most preferred embodiments have circular or substantially circular cross-section. In the plies 10 of our invention or the plies 50 used to form the composite 40 of our invention, the fibers 14 may be arranged in fibrous networks 12. In each network 12, the fibers 14 are arranged so that there are a plurality of fibers 14 that are aligned substantially parallel and unidirectionally along a common fiber direction C (the plurality of unidirectionally oriented fibers 14). The fibers 14 may be formed as a felt, knitted or woven (plain, basket, satin and crow feet weaves, etc.) into a network 12, fabricated into non-woven fabric, arranged in parallel array, layered, or formed into a ply or composite 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 or plies for ballistic-resistant articles. For example, the techniques described in U.S. Pat. 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 fibrous network 12 may be formed from fibers 14 alone, or from fibers 14 coated with a suitable polymer, as for example, a polyolefm, polyamide, polyester, polydiene such as a polybutadiene, urethanes, diene/olefin copolymers such as poly(styrene-butadiene-styrene) block copolymers, and a wide variety of elastomers. The network 12 of a fibers 14 may also comprise oriented fibers 14 dispersed in a polymeric matrix material, as for example a matrix material of one or more of the above referenced polymers to form a ply as described in more detail in U.S. Pat. Nos. 4,623,574; 4,748,064; 4,916,000; 4,403,012; 4,457,985; 4,650,710; 4,681,792; 4,737,401; 4,543,286; 4,563,392; and 4,501,856, hereinafter incorporated by reference to the extent that they are not inconsistent. The type of fibers 14 which are useful in the plies 10, 30 of this invention may vary widely and can be metallic fibers, semi-metallic fibers, inorganic fibers and/or organic fibers. Exemplary fibers 14 include those having a tenacity equal to or greater than about 8 grams per denier (g/d), a tensile modulus equal to or greater than about 150 g/d and an energy-to-break equal to or greater than about 7 joules/gram (j/g). Tensile properties can be evaluated as known in the art, for example, by pulling a 10 inch (25.4 cm) filer length clamped in barrel clamps at a rate of 10 in./minute of an Instron Tensile Testing Machine. Preferred fibers 14 are those having a tenacity at least about 10 g/d, more preferably at least about 15 g/d, and most preferably at least about 25 g/d; a tensile modulus at least about 300 g/d, more preferably at least above 400 g/d, and most preferably at least about 500 g/d; and an energy-to-break at least about 15 j/g, more preferably at least above 20 j/g, and most preferably at least above 30 j/g. Useful inorganic fibers 14 include S-glass fibers, E-glass fibers, silicon carbide fibers, asbestos fibers, basalt fibers, carbon fibers, boron fibers, alumina fibers, zirconia-silica fibers, alumina-silica fibers, quartz fibers, ceramic fibers, and the like. Exemplary of useful metallic or semi-metallic fibers 14 are those composed of boron, aluminum, steel and titanium. Illustrative of useful organic fibers 14 are those composed of thermosetting resins, thermoplastics polymers and mixture thereof such as polyesters, polyolefins, polyetheramides, fluoropolymers, polyethers, celluloses, phenolics, polyesteramides, polyurethanes, epoxies, aminoplastics, polysulfones, polyetherketones, polyetheretherketones, polyesterimides, polyphenylene sulfides, polyether acryl ketones, poly(amideimides), and polyimides. Illustrative of other useful organic fibers are those composed of aramids (aromatic polyamides), such as poly(m-xylylene adipamide), poly(p-xylylene sebacamide), poly 2,2,2-trimethylhexamethylene terephthalamide), poly(piperazine sebacamide), poly(metaphenylene isophthalamide) (Nomex®) and poly(p-phenylene terephthalamide) (Kevlar®); 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-(-amidocyclohexyl)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-phenylene terephthalamide), polyhexamethylene sebacamide (nylon 6,10), polyaminoundecanamide (nylon 11), polydodeconolactam (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), poly[bis-(4-aminocyclothexyl)methane 1 , 10-decanedicarboxamide] (Qiana) (trans), or combination thereof; and aliphatic, cycloaliphatic and aromatic polyesters such as poly(l,4-cyclohexlidene dimethyl eneterephathalate) cis and trans, poly(ethylene- 1 ,5-naphthalate), poly(ethylene-2,6-naphthalate), poly( 1 ,4-cyclohexane dimethylene terephthalate) (trans), poly(decamethylene terephthalate), poly(ethylene terephthalate), poly(ethylene isophthalate), poly(ethylene oxybenozoate), poly(para-hydroxy benzoate), poly(dimethylpropiolactone), poly(decamethylene adipate), poly(ethylene succinate), poly(ethylene azelate), poly(decamethylene sebacate), poly(.beta.,.beta.-dimethyl-propiolactone), and the like. Also illustrative of useful organic fibers 14 are those of liquid crystalline polymers. Exemplified liquid crystalline polymers are disclosed for example, in U.S. Pat. Nos. 3,975,487; 4,118,372, 4,161,470, and 5,667,029, hereby incorporated by reference. Also illustrative of useful organic fibers 14 for use in the present invention are those composed of extended chain polymers formed by polymerization of α, β- unsaturated monomers of the formula _R 2 - C = CH 2 , wherein R_ and R 2 are the same or different and are hydrogen, hydroxy, halogen, alkylcarbonyl, carboxy, alkoxycarbonyl, heterocycle or alkyl or aryl either unsubstituted or substituted with one or more substituents selected from the group consisting of alkoxy, cyano, hydroxy, alkyl and aryl. For greater detail of such polymers of , β-unsaturated monomers, see U.S. Pat. Nos. 4,916,000 and 5,667,029, hereby incorporated by reference. In one example, the fiber network 12 may include a high molecular weight polyethylene fiber, a high molecular weight polypropylene fiber, an aramide fiber, a high molecular weight polyvinyl alcohol fiber, a high molecular weight polyacrylonitrile fiber or mixtures thereof. U.S. Pat. Nos. 4,457,985 and 5,677,029 generally discuss such high molecular weight polyethylene and polypropylene fibers, and the disclosure of these patents are hereby incorporated by reference to the extent that they are not inconsistent herewith. In regard to polyethylene, suitable fibers 14 are those of molecular weight of at least 150,000, preferably at least 300,000, more preferably at least one million and more preferably still, between two million and five million. Such extended chain polyethylene (ECPE) fibers may be grown in solution as described in U.S. Pat. No. 4,137,394 or U.S. Pat. No. 4,356,138, or may be a fiber spun from a solution to form a gel structure, as described in German Off. 3,004,699 and GB 2051667, and especially described in U.S. Pat. No. 4,413,110 and 4,551,296, also hereby incorporated by reference. Other high strength polyethlyene fibers and techniques known for forming such fibers, including variations of the above techniques, can also be used in accordance with the present invention. Depending upon the formation technique, a variety of properties can be imparted to the fibers 14. The previously described highest values for tenacity, modulus and energy-to- break are generally obtainable by employing these solution grown or gel fiber processes. An example of a useful high strength fiber 14 is an extended chain polyethylene known as Spectra® which is commercially available from Honeywell, Inc. As used herein, the term polyethylene refers to predominantly linear polyethylene materials that may contain minor amounts of chain branching or comonomers not exceeding 5 modifying units per 100 main chain carbon atoms, and that may also contain admixed therewith 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 polyolefms, graft polyolefm copolymers and polyoxymethylenes, or low molecular weight additives such as anti-oxidants, lubricants, ultra-violet screening agents, colorants and the like which are commonly incorporated by reference. Similarly, highly oriented polypropylene fibers 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 fibers by the techniques prescribed in the various references referred to above, and especially by the technique of U.S. Pat. Nos. 4,663,101 and 4,784,820 and published application WO 89 00213. 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 g/d, preferably at least 11 g/d, and more preferably is at least 15g/d. The tensile modulus (as measured by an Instron Tensile Testing Machine) for polypropylene is at least about 150 g/d, preferably at least about 200 g/d, more preferably at least about 200 g/d, and most preferably at least about 300 g/d. The energy-to-break of the polypropylene is at least about 8j/g, preferably at least about 40 j/g, and most preferably at least about 60j/g. Useful aramid fibers 14 are formed principally from aromatic polyamide and are described in U.S. Pat. No. 3,671,542, which is hereby incorporated by reference. Preferred aramid fibers 14 preferably have a tenacity of at least about 20 g/d; a tensile modulus preferably of at least about 400 g/d, more preferably of at least about 480 g/d, and most preferably of at least 900 g/d; and an energy-to-break of at least about 8 j/g, more preferably of at least about 20 joules/gram, and most preferably of at least about 30 j/g. For example, poly(phenylene terephthalamide) fibers produced commercially by Dupont Corporation under the trade name of Kevlar® are useful. Also useful in the practice of this invention is poly(metaphenylene isophthalamide) fibers produced commercially by Dupont under the tradename Nomex®. High molecular weight polyvinyl alcohol fibers 14 having high tensile modulus are described in U.S. Pat. No. 4,440,711, which is hereby incorporated by reference to the extent it is not inconsistent herewith. Preferred polyvinyl alcohol fibers 14 will have a tenacity of at least about 10 g/d , a modulus of at least about 200 g/d, and an energy-to-break of at least about 8 j/g. Particularly preferred polyvinyl alcohol fibers 14 will have a tenacity of at least about 15 g/d , a modulus of at least about 300 g/d, and an energy-to-break of at least about 25 j/g. Most preferred polyvinyl alcohol fibers 14 will have a tenacity of at least about 20 g/d , a modulus of at least about 500 g/d, and an energy-to-break of at least about 30 j/g. Suitable polyvinyl alcohol fiber 14 of molecular weight of at least about can be produced, for example, by the process disclosed in U.S. Pat. No. 4,599,267. In regard to polyacrylonitrile (PAN) fiber, PAN fibers for use in the present invention have a molecular weight of at least about 400,000. Particularly useful PAN fibers should have a tenacity of at least about 10 g/d and an energy-to-break of at least about 8 j/g. PAN fibers having a molecular weight of at least about 400,000, a tenacity of at least about 15 to about 20 g/d and an energy-to-break of at least 8 j/g is useful in producing ballistic resistant plies; and such fibers are disclosed, for example, in U.S. Pat. No. 4,535,027. Exemplary suitable commercially available high strength fibers 14 include: Nectran®; Trevar®; and Certran® from Hoechst Celanese Corporation of Charlotte, Ν. C; Kelvar® from DuPont of Wilmington, Del.; Spectra® from Honeywell Corporation; Dymemma® from DSM Corporation of Heerlen, The Netherlands; Twaron® from Akzo Nobel of Arnhem, The Netherlands; Technora® from Osaka and Tokyo, Japan. The fibers, for example, may be precoated with a suitable polymer, such as a low modulus or high modulus elastomer material prior to being arranged in the network. A wide variety of suitable coating materials and teclmiques for coating fibers using the same are well known in the art, for example, as described in U.S. Pat. Nos., 4,650,710, 4,737,401, and 5,124,195. Any of the known matrix materials can be used in manufacturing the ply 10 of the invention, for example by coating the ply of the invention with a matrix material. The matrix material may be flexible (low modulus) or rigid (high modulus). A wide variety of matrix materials and techniques are known to those skilled in the art, for example, those described in U.S. Pat. Nos. 4,916,000 and 5,677,029. The proportions of matrix material to fiber 14 in the ply 10 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 fiber 14 in the composite may vary from relatively small amounts where the amount of matrix is about 10% by volume of the fibers to relatively large amounts where the amount of matrix is up to about 90% by volume of the fibers. 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 ply 10. In the particular embodiments of the invention, ballistic-resistant plies and/or composites of the present invention contain a relatively minor proportion of the matrix (e.g., about 10 to about 30% by volume), since the ballistic-resistant properties are almost entirely attributable to the fiber 14, and in the particular embodiments of the invention, the proportion of the matrix in the composite is from about 10 to about 30% by weight of fibers 14. As shown in Figs. 1-3, in a multilayered fibrous ply 10 containing such fibers 14, the fibers 14 are arranged in a fibrous network 12. As noted above, the fiber 14 may be formed as a felt, knitted or woven (plain, basket, and satin etc., and preferably plain weave) into a network 12, or formed into a network 12 by any of a variety of conventional techniques. In the present invention, and as shown in Fig. 1, the fibrous network 12 formed by the conventional techniques has a plurality of unidirectional fibers 14 arranged substantially parallel to one another along a common fiber direction C. In an exemplary arrangement of the fibrous network 12, the coated fibers 14 are arranged in a sheet-like fiber array so that the fibers 14 are aligned parallel to one another along the common fiber direction C. Successive layers of such coated, unidirectional fibers 14 forming the fibrous networks 12 can be rotated at an angular offset, the desired angle γ, with respect to the previous layer to form the multilayered impact resistant fibrous ply 10 of the first embodiment of the invention. Successive layers of fibrous networks 12 are rotated at an angle γ less than about 45 ° which allows the fibers 14, when the adjacent layers of fibrous networks 12 are aligned, within one layer of fibrous network 12 to be oriented at the desired angle γ relative to the fibers 14 within the adjoining layer of fibrous network 12. Preferably, the angle γ between the fibers 14 in adjacent fibrous networks 12 is less than about 45 °. In the particularly preferred embodiments, the angle γ is less than about 25 °. In the more particularly preferred embodiments, the angle γ is less than about 10°. Amongst those particularly preferred embodiments, most preferred are those embodiments in which the angle γ is less than about 4°. In the practice of this invention, the angle γ of choice is between about 1 ° to about 3 °. As depicted in Fig. 2, an example of a ply 10 includes three stacked layers of fibrous networks 12a to 12c. The second layer, 12b, is rotated at an angle γ, relative to the first layer, 12a. Similarly, the third layer, 12c, is rotated at an angle γ 2 relative to the second layer, 12b. As one skilled in the art will appreciate, multiple layers of the fibrous networks 12 can be applied in like fashion until the desired degree of impact resistance is achieved. An example of a ply 10 has the second, third, fourth, fifth and sixth layers rotated +10°; -5°; +5°; 0° and -10° with respect to the first layer, but not necessarily in that order. Another example would have the second, third, fourth, fifth and sixth layers rotated +2°; 0°; -2°; 0° and +2° with respect to the first layer, but not necessarily in that order. In yet another example, the second, third, fourth , fifth and sixth layers would be rotated +3 °; +6°; +9°; +12 and +15 ° with respect to the first layer, but not necessarily in that order. It should be clear that there is no requirement that the angle γ used between successive layers of the fibrous networks 14 be consistent throughout the buildup of the layers of the ply 10. Further, there is no requirement that the successive layers of the fibrous networks 14 be rotated in the same direction, i.e., there is no requirement that successive layers of the fibrous networks 14 be rotated clockwise or counter clockwise relative to the previously applied layer. For example, it is contemplated that a second layer of fibrous network 14 may be rotated clockwise relative to the first layer by an angular offset, a third layer rotated counter-clockwise to the second layer by an angular offset, a fourth layer rotated counter-clockwise to the third layer by a chosen angular offset, and so forth, until the desired number of layers of the fibrous networks 14 are applied. The number of layers of the fibrous networks 12 included in the multilayered impact resistant ply 10 of this invention may vary widely depending on the uses of the ply 10, for example, in those uses where the ply 10 would be used as ballistic protection, the number of layers of the fibrous networks 12 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 of the fibrous networks 12 included in the ply 10. Conversely, the lessor the degree of ballistic protection required, the lessor the number of layers of fibrous networks 12 included in the ply 10. In the ply 10 embodiment of the invention, the number of layers of fibrous networks 12 preferably is between 2 and about 120, more preferably, the number of layers of fibrous networks 12 is between 2 and about 60; and most preferably between 2 and about 40. In an alternative embodiment of the invention, as shown in Figs. 4-8, a multilayer penetration resistant composite 40 is formed from two or more layers of fibrous plies 50. Each fibrous ply 50 has at least one fibrous network 14 which has a plurality of unidirectional oriented fibers 14. The fibers 14 are arranged so that the plurality of unidirectional oriented fibers are substantially parallel to one another along a common fiber direction C. It is preferred that the plurality of unidirectional oriented fibers be arranged in a sheet-like array and aligned parallel to one another along the common fiber direction C. Referring to Fig. 4, an exemplified composite 40 is shown comprised of 7 stacked layers of fibrous plies 50a, 50b, 50c, 50d, 50e, 50f, and 50 g. The layers of plies 50a - 50g of the composite 40 are arranged so that, with adjacent plies 50 aligned, the fibers 14 within one fibrous network 12 of oriented fibers 14 of one ply 50 are arranged at an angle γ less than 45° to the fibers 14 of one fibrous network 12 of oriented fibers of the adjacent ply 50. Preferably, the angle γ is less than about 45°. In the particularly preferred embodiments, the angle γ is less than about 25 °. In the more particularly preferred embodiments, the angle γ is less than about 10°. Amongst those particularly preferred embodiments, most preferred are those embodiments in which the angle γ is less than about 4°. In the practice of this invention, the angle γ of choice is between about 1 ° to about 3 ° . Still referring to Fig. 4, the example of a composite 50 of the present invention includes seven stacked layers of fibrous plies 50a - 50g. The second layer, 50b, is rotated at an angle γ, relative to the first layer, 50a. Similarly, the third layer, 50c, is rotated at an angle γ 2 relative to the second layer, 50b. The fourth layer, 50d, is rotated at an angle γ 3 relative to the third layer, 50c. The fifth layer, 50e, is rotated at an angle γ 4 relative to the fourth layer, 50d. The sixth layer, 50f, is rotated at an angle γ 5 relative to the fifth layer, 50e. Finally, the seventh layer, 50g, is rotated at an angle γ 6 relative to the sixth layer, 50f. As one skilled in the art will appreciate, multiple layers of the fibrous plies 50 can be applied in like fashion until the desired degree of impact resistance is achieved. An example of a composite 40 has the second, third, fourth, fifth and sixth layers rotated +10°; -5 °; +5 °; 0° and -10° with respect to the first layer, but not necessarily in that order. Another example would have the second, third, fourth, fifth and sixth layers rotated +2°; 0°; -2°; 0° and +2° with respect to the first layer, but not necessarily in that order. In yet another example, the second, third, fourth , fifth and sixth layers would be rotated +3°; +6°; +9°; +12 and +15 ° with respect to the first layer, but not necessarily in that order. As in the discussion of ply 10 above, it should be clear that there is no requirement that the angle γ used between successive layers of the fibrous plies 50 be consistent throughout the buildup of the layers of the composite 40. Further, there is no requirement that the successive layers of the fibrous plies 40 be rotated in the same direction, i.e., there is no requirement that successive layers of the fibrous plies 40 be rotated clockwise or counter clockwise relative to the previously applied layer. For example, it is contemplated that a second layer of fibrous ply 50 may be rotated clockwise relative to the first layer of fibrous ply 50 an angular offset, a third layer of fibrous ply 50 rotated counter-clockwise to the second layer of fibrous ply 50 by an angular offset, and so forth, until the desired number of layers of the fibrous plies 50 are applied. The number of layers of the fibrous plies 50 included in the multilayered composite 40 of this invention may vary widely depending on the uses of the ply 50, for example, in those uses where the ply 50 would be used as ballistic protection, the number of layers of the fibrous plies 50 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 of the fibrous plies 50 included in the composite 40. Conversely, the lessor the degree of ballistic protection required, the lessor the number of layers of fibrous plies 50 included in the composite 50. In the composite 40 of the invention, the number of layers of fibrous plies 50 preferably is between 2 and about 120, more preferably between 2 and about 60; and most preferably between 2 and about 40. As one skilled in the art will appreciate, a surface of each fibrous ply 50 is in contact with and at least partially bound to the surface of one adjacent fibrous ply 50. The fibrous plies 50 may be secured together in any conventional manner including, but not limited to bolts, rivets, adhesive, staples, stitches, thermal bonding, welding, and the like, or combinations thereof. Once the fibrous plies 50 are secured together the fibrous networks 12 within the respective fibrous plies 50 are maintained in desired orientation to each other. For example, a fibrous ply 50 may be bonded to an adjacent fibrous ply 50 through the use of an appropriate adhesive. In another example, the layers of the fibrous plies 50 may be arranged as desired and the composite stitched together to maintain the respective fibrous plies 50 in proper orientation. Alternatively, in an example which exemplifies the use of a combination of securing means, in addition to using an adhesive between the adjoining layers of the plies 50, the plies 50 of the composite 40 may be further secured by stitching. If stitching is used, the type of stitching employed may vary widely. Stitching and sewing methods such as lock stitching, chain stitching, zig-zag stitching and the like are illustrative of the type of stitching for use in this invention. Useful threads for stitching may vary widely. However, exemplified threads would include those fiber 14 that are described in more detail herein above in the discussion of fiber 14 for use in the fabrication of fibrous plies 10, 50. However, the thread used in stitching is preferably an aramid fiber or thread (as for example Kevlar® 29, 49, 129 and 149 aramid fibers), an extended chain polyethylene thread or fiber (as for example Spectra® 900 and Spectra® 1000 polyethylene fibers) or a mixture thereof. While the embodiment of the ply 10 described above may be used in this embodiment of the invention, all that is required within the ply 50 for this particular embodiment is one plurality of unidirectional oriented fibers 14. If the ply 50 has multiple layers of fibrous networks 12, it can still be used effectively in the practice of the invention since it is still possible to angularly offset, by the angle γ less than 45°, the fibers 14 of at least one plurality of unidirectional oriented fibers within one ply 50 relative to the fibers 14 of a plurality of unidirectional oriented fibers within the adjoining ply 50. In one example, depicted in Figs. 5 and 6, each fibrous ply 50a, 50b has a plurality of unidirectional oriented fibers 14a, 14b that form a single fibrous network 12a, 12b . In this example, the fibers 14a, 14b of the pluralities of unidirectional oriented fibers of the joined plies 50 are angularly offset to each other by an angle γ which is less than 45°. In another example, depicted in Figs. 7 and 8, each fibrous ply 50a, 50b has a pair of fibrous networks 12a, 12b, 12a', 12b', the adjacent fibrous networks 12a, 12b, 12a', 12b' arranged at about a 90° angle with respect to the common axis Cl, Cl ', C2, C2' of the fibers 14a, 14b, 14a', 14b' contained in the pair of networks 12a, 12b, 12a', 12b'. In this example, each plurality of unidirectional oriented fibers of one ply 50 is angularly offset by an angle γ,, γ 2 less than 45° to a plurality of unidirectional oriented fibers in the adjoining ply 50. Commercial examples of exemplary plies suitable for use with the composite of this invention include Kevlar® 129, an aramid fiber ply manufactured by E.I. DuPont de Nemours and Company, Twaron®, Spectra Shield®, Spectra Shield Plus®, and Gold Flex®. Spectra Shield®, Spectra Shield Plus®, and Gold Flex® are a polymetric ply, having high molecular weight polyethylene fibers in a flexible resin matrix, manufactured by Honeywell. If multiple fibrous networks are used, as for example in the Kevlar® 129 aramid fiber woven ply or the Spectra Shield® ply mentioned above, the fibers within each ply are typically oriented 0°, 45° or 90° to each other (the fibers being either woven or cross-plied to form the desired layout of fibers by methods known to those skilled in the art). Most commonly, the fibers are oriented at 90° to each other. The composites of this invention can be used for conventional purposes. For example, such composites can be used in the fabrication of penetration resistance articles and the like using conventional methods. For example, such penetration resistant articles include meat cutter aprons, protective gloves, boots, tents, fishing gear, and the like. The ply 10 and the composite 40 are particularly useful as a "bulletproof vest material or ballistic resistant articles such as "bulletproof lining for example because of its enhanced ballistic resistance. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirt of the invention. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirt of the invention being indicated by the following claims.

Claims: What is claimed is: 1. A multilayer impact resistant fibrous ply comprising two or more layers of a fibrous network, each fibrous network having a plurality of unidirectional oriented fibers, wherein the fibers in adjacent fibrous networks are arranged at an angle less than 45° to each other. 2. The fibrous ply of Claim 1, wherein there are from 2 to 120 layers of fibrous networks. 3. The fibrous ply of Claim 1, wherein there are from 2 to 60 layers of fibrous networks. 4. The fibrous ply of Claim 1, wherein there are from 2 to 40 layers of fibrous networks. 5. The fibrous ply of Claim 1 , wherein the angle is less than 25 ° . 6. The fibrous ply of Claim 1, wherein the angle is less than 10°. 7. The fibrous ply of Claim 1 , wherein the angle is less than 4° 8. The fibrous ply of Claim 1, wherein the fibers are polyethylene fibers, nylon fibers, aramid fibers or mixtures thereof. 9. The fibrous ply of Claim 1, wherein the fibers are selected from a group consisting of: metallic fibers, semi-metallic fibers, inorganic fibers, organic fibers or mixtures thereof. 10. The fibrous ply of Claim 1 , wherein each fibrous network comprises a sheetlike fiber array in which the fibers are arranged substantially parallel to one another along a common longitudinal fiber direction. 11. The fibrous ply of Claim 1 , wherein the fibers are embedded in a matrix material. 12. The fibrous ply of Claim 11 , wherein the matrix material. 13. A multilayer penetration resistant composite comprising two or more fibrous plies, each ply having at least one fibrous network, each fibrous network having a plurality of unidirectional oriented fibers, wherein the fibers of each fibrous network are arranged substantially parallel to one another along a common fiber direction within the network, and wherein the fibers of one fibrous network of one fibrous ply are at an angle of less than 45° to the fibers of one fibrous network of the adjacent fibrous ply. 14. The composite of Claim 13, wherein a surface of one fibrous ply is in contact with and at least partially bound to the surface of one adjacent fibrous ply. 15. The composite of Claim 13, wherein there are from 2 to 80 fibrous plies. 16. The composite of Claim 13, wherein there are from 2 to 60 fibrous plies. 17. The composite of Claim 13, wherein there are from 2 to 40 fibrous plies. 18. The composite of Claim 13, wherein the angle is less than 25°. 19. The composite of Claim 13, wherein the angle is less than 10°. 20. The composite of Claim 13, wherein the angle is less than 4°. 21. The composite of Claim 13, wherein the fibers are polyethylene fibers, nylon fibers, aramid fibers or mixtures thereof. 22. The fibrous ply of Claim 13, wherein the fibers are selected from a group consisting of: metallic fibers, semi-metallic fibers, inorganic fibers, organic fibers or mixtures thereof. 23. The composite of Claim 13, wherein the fibers are embedded in a matrix material. 24. The composite of Claim 23, wherein the matrix material is flexible. 25. The composite of Claim 13, wherein the fibrous ply comprises a non-woven ply. 26. The composite of Claim 13, wherein the fibrous ply comprises a woven ply. 27. The composite of Claim 13, wherein the network of oriented fibers comprises a sheet-like fiber array. 28. The composite of Claim 27, wherein each fibrous ply has two fibrous networks, wherein adjacent fibrous networks are at a 90° angle with respect to the longitudinal axis of the fibers contained within the networks. 29. The composite of Claim 13, wherein each fibrous ply has two fibrous networks, wherein adjacent fibrous networks are at about a 90° angle with respect to the longitudinal axis of the fibers contained within the networks. 30. A multilayer penetration resistant composite comprising two or more fibrous plies, each fibrous ply having a plurality of unidirectional oriented fibers, wherein the fibers in adjacent fibrous plies are at an angle of less than 45 ° to each other. 31. The composite of Claim 30, wherein a surface of one fibrous ply is in contact with and at least partially bound to the surface of one adjacent fibrous ply. 32. The composite of Claim 30, wherein each fibrous ply has a sheet-like fiber array in which the fibers are arranged substantially parallel to one another along a common longitudinal fiber direction. 33. The composite of Claim 32, wherein each fibrous ply has a pair of sheet-like fiber arrays in which adjacent arrays are aligned at an angle about 90° with respect to the common fiber direction of the parallel fibers contained in the adjacent array. 34. The composite of Claim 30, wherein there are from 2 to 80 plies. 35. The composite of Claim 30, wherein there are from 2 to 60 plies. 36. The composite of Claim 30, wherein there are from 2 to 40 plies. 37. The composite of Claim 30, wherein the angle is less than 25 ° . 38. The composite of Claim 30, wherein the angle is less than 10°. 39. The composite of Claim 30, wherein the angle is less than 4°. 40. The composite of Claim 30, wherein the fibers are polyethylene fibers, nylon fibers, aramid fibers or mixtures thereof. 41. The fibrous ply of Claim 30, wherein the fibers are selected from a group consisting of: metallic fibers, semi-metallic fibers, inorganic fibers, organic fibers or mixtures thereof. 42. The composite of Claim 30, wherein the fibers are embedded in a matrix material. 43. The composite of Claim 42, wherein the matrix material is flexible. 44. The composite of Claim 30, wherein the fibrous ply comprises a non- woven ply. 45. The composite of Claim 30, wherein the fibrous ply comprises a woven ply.

Inventors: HENDERSON WILLIAM J IV, HENDERSON, WILLIAM, J., IV
Applicants: MILLENNIUM BODY ARMOUR INC, MILLENNIUM BODY ARMOUR, INC.
Application year: 2000
Main classification: F41H
IPC codes: F41H5