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CERAMIC ARMOR REINFORCED WITH HIGH-STRENGTH FIBERS AND BALLISTIC RESISTANT ARTICLES FORMED FROM SAID ARMOR

BACKGROUND OF THE INVENTION

l. Field of the Invention

This invention relates to the field of complex composite articles having improved impact resistance. More particularly, this invention relates to such articles formed totally or in part from ceramic articles reinforced with high strength fibers.

2. Prior Art

Ballistic articles such as bullet proof vests, helmets, structural members of helicopters and other military equipment, vehicle panels, briefcases, raincoats and umbrellas containing high strength fibers are known. Fibers conventionally used include aramid fibers such as poly(phenylenediamine terephthalamide) , 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 o heat resistance; for example, a polyamide 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/polyvinyl butyral resin matrix). The aramid system was judged to have the most promising combination of superior performance and a minimum of problems for combat helmet development.

US Patent No. 4,403,012 and US Patent No. 4,457,985 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 Resin Concentration and Laminating Pressures of 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

-he resultant composite article.

US Patent Nos. 4,623,574 and 4,748,064 disclose a simple composite structure comprising high strength fibers embedded in 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 polyethylene and polypropylene such as disclosed in US Patent No. 4,413,110.

U.S. Patent Nos. 4,737,402 and 4,613,535 disclose complex rigid composite articles having improved impact resistance which comprise 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 least 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 .

Ballistic resistant armor made of rigid materials is known in the art. Included in useful rigid materials are composites which include tiles such as ceramic tiles connected to a suitable substrate or back-up material.

The rigid material is connected to the substrate by suitable means such as adhesives.

A review of the ballistic materials and penetration mechanics is presented in R.C. Laible, Ballistic Materials and Penetration Mechanics, Elsevier Scientific Publishing Company (New York, 1980). Of particular interest are chapters 5 through 7 which are directed to transparent, ceramic and metallic armor materials.

Armor made from hard brittle materials such as ceramics is known. A problem with ceramic armor is that broken ceramic pieces fly off upon impact. This feature results in a lack of multiple impact capability.

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:

Figure 1 is a schematic illustration of an embodiment of this invention comprising a ceramic tile having a reinforcing girdle composed of a fibrous layer encircling the tile about an axis. The fibrous layer comprises one layer of fibers oriented substantially parallel to the plane of the base of the tile.

Figure 2 is a cross-setional view of the embodiment of this invention depicted in Figure 1 along major axis 18-18.

Figure 3 is similar to Figure 2 and is a cross-sectional view of an embodiment of this invention which comprises two layers of fibers oriented substantially parallel to each other and to plane of the base of the tile.

Figure 4 is similar to Figure 1 and is a schematic illustration of an embodiment of this invention having a resin forcing girdle formed of two layers of fibers one layer in which fibers are aligned parallel to the plane of the base of the tile and one layer in which fibers are aligned at a 90 ^c angle to the plane of the base of the tile and at 90° to the fiber in the first layer.

Figure 5 is similar to Figure 1 and is a chematic illustration of an embodiment of this invention in which the encircling girdle includes three layers of fibers, one layer of fibers in which the fibers are parallel to the plane of the base of the tile, one layer in which the fibers are aligned at an angle of 90 to the plane of the base of the tile and 90° to the fibers in the first layer and one layer in which fibers are at a 90° angle with respect to the fibers in the first and second layers and at a 90 angle with respect to the plane of the base of the tile.

Figure 6 is a cross-sectional view of an embodiment of this invention is which the encircling girdle includes three layers offibers in which the direction of fiber length in adjacent layers is at an angle of 90

Figure 7 is a schematic drawing of a complex ballistic article of this invention comprising a substrate having a plurality of the articles of Figure 5 attached to surface thereof.

Figure 8 is a cross-sec ional view of the embodiment of Figure 6.

Figure 9 is a cross-sectional view of a modification of the embodiment of Figures 7 and 8 in which the article is wrapped with three layers of fibers in a matrix along three axis such that the direction of fiber length in adjacent layers is at an angle of 90 .

SUMMARY OF THE INVENTION

One aspect of this invention relates to an article of manufacture comprising a ceramic body and at least one

girdle encircling said body about an axis thereof, said girdle comprised of one or more 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. Still another aspect of this invention relates to such an article wherein the girdle is comprised of one or more layers of filaments in a matrix material. Yet another aspect of this invention relates to a multilayer ballistic resistant article comprising: a substrate having one or more layers selected from the group consisting of layers comprising one or more metals and layers 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 ballistic resistant ceramic article comprised of a ceramic body and at least one girdle encircling said body about an axis thereof, said girdle comprised of one or more of said filaments or of said network in said matrix material.

Use of the girdle encircling the ceramic body provides one or more advantages. For example, use of the encircling girdle limits the amount of broken ceramic pieces flying away from the ballistic article upon impact, and also increases the effective hardness of the ceramic body which provides greater protection against ballistics. Also, use of the encircling girdle enhances the capability of the ceramic to resist multiple hits by a ballistic in part by preventing broken pieces of the ceramic resulting from impact from flying away. Moreover, broken pieces which do fly away from the ceramic article on impact preferen ially move through the hole generated by the ballistic; thus effectively opposing the movement of the ballistic and reducing the effectiveness of the ballistic.

DESCRIPTION OF THE PREFERRED

EMBODIMENTS OF THE INVENTION

The present invention will be understood by those skilled in the art by reference to the above figures. Referring to Figures 1 and 2, an article of manufacture for use in the fabrication of ballistic resistant composites is indicated at 10. Article 10 includes ceramic body 12 and encircling body 12 is girdle 14 comprised of one or more high strength fibers 16 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/grams preferably embedded or dispersed in a matrix. Figure 1 is a three dimensional schematic drawing of an article 10 of the present invention. Figure 2 is a cross-sectional view of the article of Figure 1, and Figure 3 is a cross-sectional view of another article of this invention having multiple layers of fibers is encircling body 12. Body 12 of Figure 1 has a base 20 and an axis 18 perpendicular to base 20.

Body 12 is formed of a ceramic material. Useful ceramic materials may vary widely and include those materials normally used in the fabrication of ceramic armor which function to partially deform the initial impact surface of a projectile or cause the projectile to shatter. Illustrative of such materials are those described in C.F. Laible, Ballistic Materials and Penetration Mechanics, Chapters 5-7 (1980) and include metal and non-metal oxides such as aluminum oxide, boron carbide, zirconium carbide, beryllium carbide, aluminum beride, aluminum carbide, boron carbide, silicon carbide, beryllium oxide, titanium oxide, aluminum carbide, zirconium oxide, titanium nitride, boron nitride, titanium boride, tungsten oxide, titanium diburide, iron carbide, aluminum nitride, iron nitride, barium titanate, aluminum nitride, titanium niobate, boron carbide, silicon boride, as well as other useful materials. Preferred materials

for fabrication of ceramic body 12 are aluminum oxide and metal and non metal nitrides, borides and carbides. The most preferred material for fabrication of ceramic body 12 is aluminum oxide and titanium diboride.

While in the figures, body 12 is depicted as a cubular solid, the shape of body 12 can vary widely depending on the use of the article. For example, body 12 can be an irregularly or a regularly shaped body.

Illustrative of a useful body 12 are cubular, rectangular, cylindrical, and polygonal (such as triangular, pentagonal and hexagonal) shaped bodies.

The size (width and height) of body 12 can also vary widely depending on the use of article 10. For example, in those instances where article 10 is intended for use in the fabrication of light ballistic resistant composites for use against light armaments, body 12 is generally smaller; conversely where article 10 is intended for use in the fabrication of heavy ballistic resistant composites for use against heavy armaments then body 12 is generally larger. In the preferred embodiments of this invention , body 12 is a regular geometrical solid having a major axis

18 with a base 20 and a top 22, each having an equal cross-sectional area of at least about 6.5 cm . In these preferred embodiments, the height of body 12 along its major axis 18 is from about 0.3 to about 50 cm and the width of said body 12 along the axis 24 orthogonal to the axis 18 and parallel to base 20 and top 22 is from about

0.3 to about 50 cm. The ra io of height of body 12 to the width of body 12 in these preferred embodiments is equal to or greater than about 0.1 to 2. In the particularly preferred embodiments of this invention, cross-sectional areas of base 20 and top 22 of body 12 are substantially equal, and are in the range of from about 7 to about

2 600 cm . The height of body 12 along axis 18 is in the range of from about 0.6 to about 26 cm, and the width of body 12 along axis 24 is from about 0.6 to about 26 cm.

The ratio of height of body 12 along axis 18 to the width

along axis 24 of body 12 in these particularly preferred embodiments is from about 0.2 to 1.5 to about 0.5 to 12. In the most preferred embodiments of this invention body 12 is of cubular, rectangular or cylindrical cross-section along major axis 18, has a cross-sectional area of from about 25 to about 400 cm2, a height along major axis 18 of from about 1 to about 25 cm and has a width along axis 24 orthogonal to major axis 18 of from about 5 to about 25 cm. The ratio of the height of body

12 along major axis 18 to the width of body 12 along axis

24 in these most preferred embodiments is from about 0.5 to 1.2 to about 0.7 to 1.1.

As shown in Figures 1 and 2 , the article of this invention includes a girdle 14 comprised of one or more high strength fibers 16 encircling all or a portion of body 12 about its major axis 18. Girdle 14 can be wound around body 12 and maintained in place by tension, or by other suitable attaching means such as adhesives such as polysulfides, epoxies, phenolics, elastomers, and the like, or mechanical means such as staples, rivets, bolts, screws or the like. The reinforcing girdle 14 encircles the body 12 around the axis 18. In the specific embodiment illustrated in Figures 1 and 2 reinforcing girdle 14 comprises one layer of fibers 16. In the embodiment illustrated in Figure 3, girdle 14 consists of two layers of fibers 16 wrapped about body 12. In this embodiment of the invention, the two layers of fibers 16 are wrapped about axis 18 in a sheet-like array and aligned parallel to one another along a common filament direction.

Reinforcing girdle 14 can further comprise one or more layers of fibers 26 oriented at an angle i.e. 90° ,45° etc. to one or more layers of fiber 16 oriented substantially parallel to base 20. This embodiment of the invention is illustrated in Figure 4 where in addition to a layer of fibers 16 which are substantially parallel to base 20 there is an additional layer of fibers 26 which are at a 90° angle to layer of fibers 16. While the

figures show only one additional layer of fibers 26, it should be appreciated that any number of additional layers of fibers at varying angles with respect to fiber direction in adjacent layers may be employed.

In the preferred embodiments of the invention, there is a fibrous girdle 14 encircling body 12 and substantially parallel to the direction of all the axes of body 12.

This is illustrated in Figure 5. In Figure 5, body 12 is a cubular solid shape tile. As is apparent from Figure 5, body 12 is wrapped in all three dimensions with layers of fibers 16, 26 and 28 one of which layers is parallel to each of the three axes of cubular body 12. Here again, additional layers of fibers parallel to fibers 16, 26 and

28 may be used to wrap body 12 to provide additional ballistic protection.

The fibers forming girdle 14 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

²⁰ are aligned substantially parallel and unidirectionally to form a uniaxial layer in which a matrix material substantially coats the individual filaments. Two or more of these layers can be used to wrap body 12 to form a composite girdle 14 with multiple layers of coated

25 undirectional filaments in which each layer is rotated with respect to its adjacent layers as depicted in Figure

5. An example is a multilayer girdle 14 with the second, third, fourth and fifth layers rotated +45 , -45 , 90 and o

0 with respect to the first layer, but not necessarily in that order. Other examples include a multilayer girdle 14 with a 0°/90° layout of yarn or filaments.

The type of filaments used in the fabrication of girdle 14 may vary widely and can be metallic filaments, semi-metallic filaments, inorganic filaments and/or r> c 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 then about 1000 g/d, and energy-to-break is equal to or greater than about 35 joules/gram. In the practice of this invention, filaments of choice have a tenacity equal to or greater than about 30 g/d and the energy-to-break is equal to or greater than about 40 joules/gram.

Filaments for use in the fabrication of girdle 14 may be metallic, semi-metallic, inorganic and/or organic. Illustrative of useful inorganic filaments are those formed 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 ara ids (aromatic polyamides), 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) 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-(-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), 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), polytbis- ( 4-aminocyclohexyl) methane 1,10- decanedicarboxamide] (Qiana) (trans) , or combination thereof; and aliphatic, cycloaliphatic and aromatic polyesters such as poly(1,4-cyclohexlidene dimethyl eneterephathalate) cis and trans, poly(ethylene-l, 5-naphthalate) , poly(ethylene-2,6-naphthalate) , polyd, 4-cycolohexane diamethylene terephthalate) (trans), poly(decamethylene terephthalate), poly(ethylene terephthalate), poly(ethylene isophthalate) , poly(ethylene oxybenozoate) , poly(para-hydroxy benzoate), poly (, dimethylpropiolactone) , pol (decamethylene adipate), poly(ethylene succinate) and the like.

Also illustrative of useful organic filaments for use in the fabrication of girdle 14 are those composed of extended chain polymers formed by polymerization ofγ,β -unsaturated monomers of the formula:

^R l V ^{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. Illustrative of such polymers of γ ,β-unsaturated monomers are polymers including polystyrene, polyethylene, plypropylene, polyd- octadecene), polyisobutylene, poly(1-pentene), poly(2- ethylstyrene, poly(4-methylstyrene) , poly( 1-hexene) , poly(1-pentene) , poly(4-methoxystrene) , poly(5-methyl-l-

hexene), poly(4-methylpentene) , poly( 1-butene) , poly(3- methyl-1-butene) , poly(3-phenyl-l-propane) , polyvinyl chloride, polybutylene, polyacrylonitrile, poly(methyl pentene-1), poly(vinyl alcohol), poly(vinylacetate) , ρoly(vinyl butyral), poly( inyl chloride), poly(vinylidene chloride), vinyl chloride-vinyl acetate chloride copolymer, ρoly(vinylidene fluoride), poly(methyl acrylate, poly(methyl ethacrylate) , poly(methacrylo- nitrile), poly(acrylamide), poly(vinyl fluoride), poly(vinyl formal), poly(3-methyl-l-butene) , poly(1-pentene) , poly(4-methyl-l-butene) , poly( 1-pentene) , poly(4-methyl-l-pentene) , poly(1-hexane) , poly(5-methyl-l- hexene), poly(1-octadecene) , poly(vinylcyclopentane) , poly(vinylcyclohexane) , poly(a-vinylnaphthalene) , poly(vinyl methyl ether), poly(vinylethylether) , poly(vinyl propylether), poly(vinyl carbazole), poly(vinyl pyrrolidone) , poly(2-chlorostyrene) , poly(4- chlorostyrene) , poly(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 preferred embodiments of the invention, girdle

14 is fabricated from 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. Highly oriented polypropylene and polyethylene filaments of molecular weight at least 200,000, preferably at least one million and more preferably at least two million may be used in the fabrication of girdle 14. Such high molecular weight polyethylene and 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. Patent Nos.

4,413,110, 4,457,985 and 4,663,101 and preferable U.S.

Patent Application Serial Nos. 895,396, filed

August 11, 1986, and 069,684, filed July 6, 1987. 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 5 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 preferred for use in the fabrication of girdle 14 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 on 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

25 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. 0 In the case of polyacrylonitrile (PAN), PAN filament for use in the fabrication of girdle 14 are 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 ⁵ 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 ballistics resistant articles; and such filaments are disclosed, for example, in U.S. 4,535,027.

In the case of aramid filaments, suitable aramide filaments for use in the fabrication of girdle 14 are those formed principally from aromatic polyamide are described in U.S. Patent No. 3,671,542, which is hereby incorporated by reference. Preferred aramid filament will have a tenacity of at least about 20 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 tradenames of Kevlar ^® 29, 49, 129 and 149 are particularly useful in forming ballistic resistance composites. Also useful in the practice of this invention is poly(metaphenylene isophthalamide) filaments produced commercially by Dupont under the tradename Nomex.

In the more preferred embodiments of this invention, girdle 14 is formed of filaments 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 flet knitted or woven (plain, basked, 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-filament yarn wherein the filaments are parallel, unidirectionally aligned. For example, the filaments may also be formed into nonwoven cloth layers be convention techniques.

In the most preferred embodiments of this invention, girdle 14 is composed by one or more layers of continuous fibers dispersed or embedded in a continuous phase of a matrix material which preferably substantially coats each filament contained in the bundle of filament. This is illustrated in Figure 6 in body 12 which is encircled along all axis by girdle 14 which comprises layers of fibers 16, 26 and 28 in a polymeric matrix 29. The manner in which the filaments are embedded and spersed in the matrix may vary widely. The filaments may be aligned in a substantially parallel, unidirectional fashion, or filaments may be aligned in a multidirectional fashion, or 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 forming girdle 14 are aligned in a substantially parallel, unidirectional fashion such as in a prepreg, pultruded sheet and the like.

Wetting and adhesion of organic filaments such as polyethylene, to compatible and incompatible matrixes, such as epoxy resins, is enhanced by prior treatment of the surface of the yarn. The method of surface treatment may be chemical, physical or a combination of chemical and physical actions. Examples of purely chemical treatments are used of S0 ₃ or chlorosulfonic acid. Examples of combined chemical and physical treatments are corona discharge treatment or plasma treatment using one of several commonly available machines.

The matrix material employed may vary widely and may be metallic, semi-metallic material, an organic material and/or an inorganic material. The matrix material may be flexible (low modulus) or rigid (high modulus) and mixtures of flexible and/or rigid materials. Illustrative so useful high modulus or rigid matrix materials are thermoplas ic resins such as polycarbonates; polyarylenesulfides; polyaryleneoxides; polyester- carbonates; polyetheretherketones; polyesteramides; poly arylenesulfones; polyetherketones; polyimides; and

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 urea) resins. The major criterion is that such material holds the filaments together in the network, transfers ballistic or structural load, and/or maintains the integrity of girdle 14 under the desired use conditions to prevent or limit the amount of broken ceramic pieces flying away from body 12 upon impact by the ballistic.

In the preferred embodiments of the invention, the matrix material is a low modulus elastomeric material. A wide variety of elastomeric materials and formulation 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 formulation 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: Polybutadiane, polyisoprene, natural rubber, ethylene-propylene copolymers, ethylene-propylene-dien 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-isoprene) , polyacrylates, polyesters, polethers, fluoroelastomers, silicone elastomers, thermoplastic elastomers, copolymers of ethylene.

Particularly useful elastomers are block copolymers of conjugated dienes and vinyl aromatic monomers. Butadine and isoprene are preferred conjugated diene elastomers. Styrene, vinyl toluene and t-butyl styrene

are preferred conjugated aromatic monomers. Block copolymers incorporating polyisoprene may be hydrogenated to produce thermoplastic elastomers having saturated hydrocarbon elastomer segments. The polymers may be simple tri-block copolymers of the type A-B-A, multiblock copolymers of the type (AB) (n=2-10) or radial configuration copolymers of the type R-(BA) A (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 above-men ioned elastomers. The low modulus elastomeric matrixes may also include fillers such as carbon black, silica, glass microballons, and the like up to an amount preferably not to exceed about 250% by volume of the elastomeric material, preferably not to exceed about 100% by weight, and most preferably not to exceed about 50% by volume. The matrix material 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 blended with one or more thermoplas ics. High density, low density, and linear low density polyethylene 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 500 psi (3450 kPa) .

In the preferred embodiments of the invention, the matrix material is a low modulus, elastomeric material has a tensile modulus, measured at about 23oC, 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. Preferable, 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 300%.

The proportions of matrix to filament in girdle 14 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 girdle 14. In general, the proportion of matrix to filament in girdle 14 may vary from relatively small amounts where the amount of matrix is about 10% by volume of the filaments to relatively large amount 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 girdle 14. In the particularly preferred embodiments of the invention, ballistic-resistant articles of the present invention, girdle 14 contains 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 filaments, and in the particularly preferred embodiments of the invention, the proportion of the matrix in girdle 14 is from about 10 to about 30% by weight of filaments.

The articles of this invention can be fabricated using conventional procedures. For example, the fibers

-In¬ forming girdle 14 can be wrapped around body 12 as individual or multiple filaments to form the girdle 14 having the desired number of fiber layers and the desired fiber orientation. In the preferred embodiments of this invention where girdle 14 comprises fibers in a matrix material, girdle 14 is formed by molding the combination of the matrix material and filaments about body 12 in the desired configurations and amounts and then subjecting the combination to heat and pressure.

In the preferred embodiments of this invention, the filaments forming girdle 14 may be premolded into the desired network prior to placing about body 12 in the desired configuration 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 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 about 10,000 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 mn., 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 molded into girdle 14 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 in a single stage or in multiple stages. 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 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 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, alcohols, 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 in girdle 14 may vary from relatively small amounts of (e.g. 1% by weight of filaments) to relatively 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, flammability resistance and other properties desired for the complex composite article. In general, girdle 14 containing coated filaments should have a relatively minor proportion of coating (e.g. about 10 to about 30 percent by volume of filaments), since the ballistic-resistant properties of girdle 14 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 fiber layer without the use of additional matrix material. one or more of these layers can be wrapped around body 12 in the desired amount and configura ion and the contination may then be molded under heat and pressure to form the desired article of this invention.

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 exerogel 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

23

-22- 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 girdle 14. A filament is substantially coated by using any of the coa ing 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 proportion of matrix material to filament is variable for girdle 14, with matrix material amounts of from 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 girdle 14 having only about 10 to about 50 Vol. % matrix material, by volume of girdle 14, 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 girdle 14. Preferably, however, the filament network comprises at least about 30 volume percent of girdle 14. 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.

The number of layers of fibers included in girdle 14 may vary widely. In general, the greater the number of layers the greater the degree of ballistic protection provided and conversely, the lesser the number of layers the lessor the degree of ballistic protection provided.

One preferred configura ion of girdle 14 is to wrap body 12 about an axis with one or more layers as laminates in which the filaments cooled with matrix material

(premolded if desired) are arranged in a sheet-like array

and aligned parallel to one another along a common filament direction. Successive layers of such coated unidirec ional filaments can be rotated with respect to the previous layer and then wrapped around body 12. After which, the combination of body 12 and girdle 14 can be molded under heat and pressure to form the article of this invention. An example of such layered girdle 14 are layered structure in which the second, third, fourth and fifth layers are rotated and wrapped about body 12 45°, -45 , 90 and 0° with respect to the first layer, but not necessarily in that order. Similarly, another example of such a layered girdle 12 is a layered structure in which the various unidirectional layers forming girdle are aligned such that the common filament axis in adjacent layers is 0°, 90°.

A particularly effective technique for forming the layers of substantially parallel, unidirectionally aligned filaments for use in the fabrication of girdle 14 includes the steps of pulling a filament or bundles of filaments through a bath containing a solution of a matrix material preferably, an elastomeric matrix material, and circumferentially winding this filament into a single sheet-like layer around and along a bundle 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 the cylindrical form. Alterna ively, a plurality of filaments or bundles of filaments can be simultaneously pulled through the bath containing a solution or dispersion of 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 lamination about body 12 to form girdle 14 as described above.

Similarly, girdle 14 may be formed of 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 wrapped around body 12 in the desired amount and configuration to form girdle 14, or the coated yarn can be directly wound body 12 in the desired amount and configuration to form girdle 14. Moreover, the coated yarn can also be processed into a simple composite containing parallel, undirec ionally aligned yarn by employing conventional filament winding techniques which can be laminated about body 12 in the desired amount and configuration to form girdle 14.

The wrap-confined ceramic article 10 of this invention may be incorporated into complex ballistic articles as in integral part of various armor configurations. Referring to Figures 7 and 8 a complex ballistic article is indicated at 30. Complex ballistic article 30 is a trilayer composite consisting of ceramic layer 32, an optional rigid layer 34 and polymeric composite layer 31. Ceramic layer 32 is composed of a plurality of ceramic articles 10 attached to the surface of rigid layer 34 by a suitable attaching means. In those embodiments of the invention, in where the rigid layer is omitted, the ceramic layer 32 is attached to the surface of polymeric composite layer 36 by some suitable attaching means. Ceramic layer 32 ordinarily forms the impact portion of complex ballistic article 30; that is the portion that is initially exposed to the environment e.g. the impact of an oncoming projectile. In the embodiments of Figures 7 and 8, ceramic layer 32 is formed of a plurality of the article of this invention depicted in Figure 5. Ceramic layer 32 will at least partially deform the initial impact surface of the projectile or cause the projectile to shatter and as described above is formed of

materials such as aluminum oxide, boron carbide, silicon carbide and beryllium oxide (see Laible, supra. Chapters

5-7 for additional useful rigid layers). Means for attaching ceramic layer 32 to rigid layer 34 or polymeric layer 36 may vary widely and may include any means normally used in the art to provide th s function.

Illustrative of useful attaching means are adhesives such as those described in Laible, Chapter 6, supra, bolts, screws, mechanical interlocks and the like. In the preferred embodiments of this invention attaching means is an adhesive and/or a mechanical attachment through use of a rigid metal or composite cover, e.g. aluminum or a composite of a fiber such as extended chain poly ethylene, aramid or glass fiber in a rigid matrix such as epoxy, vinylester resin or phenolic, fastened to the main body by nuts and bolts. In the particularly preferred embodiments of the invention, attaching means is a metallic cover, e.g. aluminum plate covering the ceramic layer which is fastened to the main body by bolts and nuts and adhesive.

Hard rigid layer 34 is formed from a rigid material which may vary widely depending on the uses of complex ballistic article 30. The term "rigid" is used in the present specification and claims is intended to include semi-flexible and semi-rigid structures that no capable of being free standing, without collapsing.

In the preferred embodiments of the invention, hard rigid layer is preferably comprised of an impact resistant material, such as steel plate, copper, titanium, composite armor plate, ceramic reinforced metallic composite, ceramic plate, concrete, and high strength filament composites (for example, a ceramic fiber, boron fiber, aramid filament or carbon fiber and a high modulus, thermoset ing resin matrix such as epoxy, allylic, alkyd, urethane, phenolic resin, vinyl ester resin, and unsaturated polyester; thermoplas ic resin such as polyetherether ketones, polyarylene sulfides, polyarylene oxides, polysulfones, nylon 6, nylon 6,6 and polyvinylidine halides) and combinations thereof. More

preferably, rigid layer 34 is one which is ballistically effective, such as metal plates or ceramic reinforced metal composites. In the most preferred embodiments of the invention rigid layer 34 is a metal layer preferably perforated.

While rigid layer 34 is depicted in Figures 7 and 8 as a single layer sandwiched between ceramic layer 32 and polymeric layer 36 it should be appreciated that multiple rigid layers can be used and that the layers can be ordered as desired. It should also be appreciated that rigid layer 34 is optional and may not be included.

Complex ballistic article 30 also includes a polymeric layer 36. As depicted in figures 7 and 8 polymeric layer 36 forms a remote portion of complex composite article 24; that is a portion that is not initially exposed to the environment, e.g., the impact of an oncoming projectile. While in Figures 6 and 7 there is only one polymeric layer 36, in other embodiments then can be more than one layer, for example, polymeric layer 36 may form a core portion that is sandwiched between two rigid layers 34. Other forms of the complex composite are also suitable, for example a composite comprising multiple alternating layers 34 and 36.

Materials used in the construction of polymeric layer 36 may vary widely. Illustrative of such materials on the fibers and fiber/matrix combination described herein above for formation of encircling girdle 14. For example, in the fabrication of polymeric layer 36 comprised of high strength polymeric fibers useful fibers such as high strength aramid and polyethylene can be grouped together to form a twisted or untwisted yarn. The fibers or yarn may be formed as felt, knitted or woven (plain, backed, stain, crow feet weaves or the like) into a network fabricated into non-woven fabric, arranged in unidirectional parallel array or formed in a fabric by any of a variety of conventional techniques such as those described in U.S. Pat. No. 4,181,768 and in M.R. Silyquest et al., J. Macromal. Sci. Chem., A7(l), pp 203 et. seq.

(1973). The fibers or fabrics may be premolded by subjecting likeness to heat and pressure. The fibers or fabrics may be coated with elastomeric matrix materials described above before or after being arranged in a network as described above to form a fibrous network in an elastomeric matrix using the techniques described hereinabove for fabrication of encircling girdle 14. For example, a particular preferred layer 36 comprises a simple composite comprised of aramide filaments or highly- oriented high molecular weight polyethylene filaments in an elastomeric matrix such as block copolymers of conjugated dienes such as butadiene and isoprene and vinyl aromatic monomers such as styrene, vinyl totuene and -butyl styrene.

The number of simple composite layers included in layer 36 may vary widely depending on the uses of the composite 30. For example, in those uses where the composite 30 is used for ballistic protection, the number of simple layers forming polymeric layer 36 depends 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 simple composite layers included in layer 36 for a given weight of the article. Conversely, the lessor the degree of ballistic protection required, the lessor the number of simple composite layers included in layer 36 for a given weight of the article. It is convenient to characterize the geometries of such composites 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 preferred suitable arrangement for layer 36 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. Layer 36 consists of a plurality of such layers of coated, unidirectional filaments in which

adjacent layers are rotated with respect to each other. 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 composites with 00/900 layout of yarn or filaments.

As depicted in figure 9, the layers 32, 34 and 36 can be wrapped in a fibrous layer 38, about one or more axis of article 40. Layer 38 retains ceramic particles or spall resulting from projectile contact and retains ceramic bodies 32 in place after and during such contact which enhances the multiple hit copability of the armor. In the preferred embodiments of the invention, layer 38 is wrapped about three or more axis of article 40 with a plurality of unidirectional high strength fibers such as Spectra extended chain polyethylene fibers and aramid fibers in a matrix in which the linear axis of fibers in adjacent layers are at an angle 45°, 90° or the like.

Complex ballistic articles 30 have many uses. For example, such composites may be incorporated into more complex composites to provide a rigid complex composite article suitable, for example, as structural ballistic-resistant components, such as helmets, structural members of aircraft, and vehicle panels.

The following examples are presented to provide a more complete understanding of the invention. The specific techniques, condition, 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.

In the examples described below, the following technical terms are used.

AD is the areal density and is the weight of the armor material per unit area. Unit: kg/sq. meter or lbs/sq.ft.

V50 is the projectile velocity which is statistically at the borderline of complete penetration and partial penetration (i.e. the projectile velocity

which has a 50% probability of penetrating the target. )

SEA is the specific energy absorption of the target.

This is defined as the projectiles' kinetic energy at V50 divided by the areal density of target. Unit: J/(kg/sq. meter).

EXAMPLE 1

A ballistic panel was prepared by molding a plurality of sheets comprised of Spectra ^® -900 uni-directional high strength extended chain polyethylene (ECPS) yarn impregnated with a Kraton D1107 thermoplas ic elastomer matrix (a polystyrene-polyisoprene-polyestrene-block copoly er 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 33 joules/g. The elongation to break of the yarn was 4%, denier was 1,2000 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 260 layers were used, and were stacked or

0 o laminated together with a 0 /90 yarn orientation with each layer having filament length perpendicular to the filament length of the adjacent alyers.

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 0.276" (0.71 cm), and had an areal density of 7 kg/m ² .

A 4" (10.2 cm) x 4" (10.2 cm) size armor target was assembled with the fibrous panel containing the Spectra extended chain polyethylene fiber and an aluminum oxide tile which was wrapped about three axis with a composite of Spectra extended chain polyethylene in a matrix.

The structural features of the armor target are set forth in the following Table I.

TABLE I

Compnents AD Thickness

Kg/sg.m. inch (cm)

Spectra^ Composite 4.0 0.157 (0.4) 85% A1203 31.6 0.375 (0.953) Spectra® 7.0 0.276 (0.7) Spectra ^® Composite 4.0 0.157 (0.4)

Total 46.6 0.965 (2.45)

Composite of Spectra ^® extended chain polyethylene in the Kraton matrix which was wrapped about the target armor in three, mutually perpendicular directions.

Using conventional testing procedure, the complex ballistic article was evaluated. The results are set forth in the following Table II.

TABLE II

Property Value

V50 (ft/sec) (m/sec) 1,104 (331.2) SEA (J/kg/m ² ) ) 55.9

EXAMPLE II

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 in the order in which they are exposed to the projectile during testing,

TABLE I I I

Components AD Thickness

Kg/sq.m. inch (cm)

Spectra ^® Composite- 6.5 0.256 (0.65) GRP panel 39.0 0.768 (1.95) Spectra ^® Composite 6.5 0.256 (0.65)

Total 110.6 2.03 (5.16)

1. Spectra ^® Composite used in confining the target by wrapping in three, mutually perpendicular directions.

2. DJS ceramics was prepared by mixing A1203 powder with epoxy resin and heat-curing for hardening.

3. GRP panel is made by impregnating the S glass roving fabric with epoxy resin and heat-curing in molding press.

Using the procedure of Example I, the ballistic article was tested. The results are set forth in the following Table IV.

TABLE IV

Property Value

Impact velocity, ft/sec (m/sec) 3,000 (914.4) Residual velocity, ft/sec (m/sec) 2,551 (777.5) Energy absorbed per unit AD J/(kg/sq.m. ) 64.9

EXAMPLE III

Using the procedure of Example I, a complex ballistic article having the structural features set forth in Table

V was fabricated. The features are listed in the order in which they are exposed to the projectile during testing.

TABLE V

Compnents AD Thickness

Kg/sq.m. inch (cm)

Spectra® Composite 6.5 0.256 (0.65)

99.5% A1203 49.0 0.5 (1.27)

GRP panel 45.0 0.88 (2.24)

Spectra ^® Composite 19.4 0.256 (1.93)

Spectra ^® Compsoite ¹ 6.5 0.256 (0.65)

Total 126.4 2.65 (6.74)

Spectra® composite used in confining the target armor by wrapping in three, mutually perpendicuar directions.

Using the procedure of Example I, the ballistic characteristics of the article were evaluated. The results are set forth in the following Table VI.

TABLE VI

Property Value

Impact velocity, ft/sec (m/sec) 3,078 (938.2)

Residual velocity, ft/sec (m/sec) 939 (286.2)

COMPARATIVE EXAMPLES

A series of experiments were carried out to show the superior ballistic resistance properties of the confined armor of the invention and corresponding unconfined armor.

COMPARATIVE EXAMPLE I

A ballistic target in which the ceramic was not confined was fabricated using the aluminum oxide tile and Spectra ^® composite of Example I. The structural features of this panel are set forth in the following Table VII.

TABLE VII

Compnents AD Thickness

Kg/sq.m. inch (cm)

85% A1203 31.6 0.375 (0.952) Spectra ^® Composite 7.0 0.276 (0.701)

Total 38.6 0.651 (1.653)

Using the procedure of Example I, the ballistic resistant characteristics of this armor was evaluated. The results are set forth in the following Table VIII in side by side comparison with the results of the evaluation of the same ballistic properties of the armor of Example I.

TABLE VIII

Property Comparative Example I Example I

V50, ft/sec (m/sec) 945 (283.5) 1,104 (331.2) SEA 49.8 55.9

COMPARATIVE EXAMPLE 2

A ballistic target in which the ceramic was not confined was fabricated using the Spectra ^® composite, DJS ceramic and GRP panel of Example II. The structural features of this panel are set forth in the following Table IX.

TABLE IX

Compnents AD Thickness

Kg/πr inch (cm)

Spectra ^® Composite' 6.5 0.256 (0.65) DJS ceramics 58.6 0.75 (1.91) GRP panel 39.0 0.768 (1.95) Spectra ^® Composite ^' 6.5 0.256 (0.65)

Total 110.6 2.03 (5.16)

Spectra ^® composite used in confining the ceramic layer and glass layer.

Using the procedure of Example I, the ballistic resistant characteristics of this armor was evaluated. The results are set forth in the following Table X in side by side comparison with the results of the evaluation of the same properties for the armor of Example II.

TABLE X

Comparative

Property Example 2 Example 2

Impact velocity, ft/sec (m/sec) 3,000 (914.4) 3,000 (914.4) Residual velocity, ft/sec (m/sec) 2,653 (808.6) 2,551 (777.5) Energy absorbed per unit AD J/(kg/sq.m. ) 51.1 64.9

Thus, the embodiment of Example II in which the ceramic body was confined showed an energy absorption capability which is approximately 27% higher than the unconfined target of Comparative Example 2.

COMPARATIVE EXAMPLE 3

A ballistic target in which neither the target nor the ceramic body was not confined was fabricated using the Spectra composite, aluminum oxide tile and GRP Panel of Example III. The structural features of this panel are set forth in the following Table XI.

Total 129.2 2.78 (7.07)

Using the proceudre of Example I, the ballistic resistance properties of the target were evaluated. The results are set forth in the following Table XII in side by side comparison with results for the evaluation of the same properties of the armor of Example III.

TABLE XI

Comparative

Property Example 3 Example 3

Impact velocity, ft/sec (m/sec) 3,152 (960.7) 3,078 (938.2) Residual velocity, ft/sec (m/sec) 2,081 (634.3) 939 (286.2) Energy absorbed per unit AD J/(kg/sq.m. ) 124.9 191.5

Thus, the target of this invention of Example 3 showed an energy absorption capability which is approximately 53% higher than of the target of Comparative

Example 3.