WO1992009861A2

WO1992009861A2 - Ballistic resistant composite armor

Info

Publication number: WO1992009861A2
Application number: PCT/US1991/003524
Authority: WO
Inventors: Kwok W. Lem; Hong B. Chin; Young D. Kown; Dusan C. Prevorsek
Original assignee: Allied-Signal Inc.
Priority date: 1990-11-21
Filing date: 1991-05-20
Publication date: 1992-06-11
Also published as: WO1992009861A3; AU1333992A; EP0558693A1; CA2095816A1; JPH06503159A

Abstract

A multilayer armor comprising a hard ceramic impact layer (12), a vibration isolating layer (14) positioned adjacent to said hard impact layer and in contact therewith, and a backing layer (16) attached to said vibration isolating layer on the side opposite the side thereof attached to the hard impact layer.

Description

BALLISTIC RESISTANT COMPOSITE ARMOR:

BftςygROUNp OF THE I VE TION 1. Field of the Invention

This invention relates to ballistic resistant composite articles. More particularly, this invention relates to such articles having improved ballistic protection. 2. Prior Art

Ballistic articles such as bulletproof vests, helmets, structural members of helicopters and other military equipment, vehicle panels, briefcases, raincoats, parachutes, 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 applications, the fibers are encapsulated or embedded in a matrix material.

In "The Application of High Modulus Fibers to Ballistic Protection", R.C. Liable et al., J. Macromol. Sci.-Chem. A7(l), pp. 295-322, 1973, it is indicated on p. 298 that a fourth requirement is that the textile material have a high degree of heat resistance. In an TIS 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. USP 4,403,012 and USP 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 on KEVLAR Fabric Bonded with Modified Phenolic Resin", Tech. Report NATICK/TR-84/030, June 8, 1984,* disclose that an interstitial resin, which encapsulates and bonds the fibers of a fabric, reduces the ballistic resistance of the resultant composite article.

US Patent Nos. 4,623,574 and 4,748,064 disclose a 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 weight polyethylene and polypropylene such as disclosed in US Patent No. 4,413,110.

US 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 US Patent No. 4,413,110 embedded in an elasto eric matrix material and at least one additional rigid layer on a major surface of the fibers in the matrix. It is disclosed that the composites have improved resistance to environmental hazards, improved impact resistance and are unexpectedly effective as ballistic resistant articles such as armor.

U.S. Patent 3,516,890 disclosed an armor plate composite with multiple-hit capability. US Patent No. 4,836,084 discloses an armor plate composite composed of four main components, a ceramic impact layer for blunting the tip of a projectile, a sub-layer laminate of metal sheets alternating with fabrics impregnated with a viscoelastic synthetic material for absorbing the kinetic energy of the projectile by plastic deformation and a backing layer consisting of a pack of impregnated fabrics. It is disclosed that the optimum combination of the four main components gives a high degree of protection at a limited weight per unit of surface area.

Ballistic resistant armor made of ceramic tiles connected to a metal substrate exhibit certain properties which substantially reduces the multiple hit capability of the armor. On impact of the projectile, substantial amounts of vibrational energy are produced in addition to the kinetic energy of the impact. This vibrational energy can be transmitted as noise and shock, or can be transmitted to vibration sensitive areas of the armor such as to the ceramic impact layer resulting in a shattering and/or loosing of tiles.

SUMMARY OF THE INVENTION This invention relates to a multilayer complex ballistic armor comprising: (a) a hard impact layer comprised of one or more ceramic bodies;

(b) a vibration isolating layer; and

(c) a backing layer comprised of a rigid material; wherein the portion of said vibration isolating layer at or about the surfaces thereof have flexural modulus equal to or greater than about 0.01 msi, an elongation-to-break equal to or less than about 40% and a fracture toughness equal to or greater than about 1 MPa. , and wherein the portion of said vibration isolating layer at or about the center thereof has an energy-to-break of at least about 8 joules/grams.

As used herein, "flexural modulus" is determined by ASTM D790, "elongation to break" is determined by ASTM 0638, fraction toughness is determined by the method of S.T. Rolfe and J.M. Barso , "Fracture and Fatigue Control in Structures Applications of Fracture Mechanics", Prentice-Hall, Inc., New Jersey, USA 1977, and the energy-to break is measured by ASTM D885. Through use of the vibration isolating layer, shock and vibration induced by impact of the projectile are minimized. Moreover, the transmission of existing shock and vibration which can damage portions of the ceramic layer not hit by the projectile is inhibited which substantially increases the multiple hit capability of the armor.

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:

FIG 1 is a prospective view of an armor plate according to this invention showing its essential elements of a ceramic impact layer, a vibration isolating layer and a backing layer;

FIG 2 is a view in cross-section and side elevation of a modified embodiment of this invention depicted in FIG 1.

FIG 3 is a view in cross-section and side elevation of an embodiment of this invention having a modified ceramic layer.

DETAILED DESCRIPTION OF THE INVENTION The present invention will be better understood by those of skill in the art by reference to the above figures. Referring to FIG 1, the numeral 10 indicates a ballistic resistant article 10. Article 10, as shown in FIG 1, comprises three maintain components; a ceramic impact layer 12, a vibration isolating layer 14, and a backing layer 16. In the preferred embodiments of this invention, ceramic impact layer 12 comprises a plurality of ceramic bodies 18, in the more preferred embodiments of the invention, ceramic impact layer 12 comprises at least about four ceramic bodies 12 and in the most preferred embodiments of the invention, ceramic impact layer 12 comprises at least about nine ceramic bodies 12, with those embodiments in which the number of bodies 12 in layer 12 is at least about sixteen being the embodiment of choice.

Ceramic impact layer 12 is excellently suitable for blunting the tip of the projectile, particularly because the ceramic material forming layer 12 will retain its hardness and strength despite the high increase in temperature that will occur in the region struck by a projectile. Ceramic impact layer 12 comprises of one or more of ceramic bodies 18.

Body 18 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 metal and non-metal ceramic materials are those described in C.F. Liable, Ballistic Materials and Penetration Mechanics. Chapters 5-7 (1980) and include single oxides such as aluminum oxide (A1₂0₃) , barium oxide (BaO) , beryllium oxide (BeO) , calcium oxide (CaO) , cerium oxide (Ce_{2 3} and Ce0₂) , chromium oxide (Cr₂0₃) , dysprosium oxide (Dy₂θ₃) , erbium oxide (Er₂0₃) , europium oxide: (EuO, Eu₂o*j, and EU₂O₄) , (Eu₁₆0₂₁)_; gadolinium oxide (Gd₂0₃) , hafnium oxide (Hf0₂) , holmium oxide (Ho₂0₃) , lanthanum oxide (La₂0-_$) , lutetium oxide (Lu₂0-_$) , magnesium oxide (MgO) , neodymium oxide (Nd₂θ₃) , niobium oxide: (NbO, Nb₂θ₃, and Nb0₂) , (Nb₂0₅) , plutonium oxide: (PuO, P ₂O₃, and Pu0₂) , praseodymium oxide: (Pr0_2/ Pr₆0_11f and Pr₂0-**) , promethium oxide (Pm₂0₃) , samarium oxide (SmO and

Sm₂0*₃) , scandium oxide (Sc₂O ) , silicon dioxide (Si0) , strontium oxide (SrO) , tantalum oxide (Ta₂Os) , terbium oxide Tb₂θ₃ and Tb₄0₇) , thorium oxide (Th0₂) , thulium oxide (Tm₂θ₃) , titanium oxide: (TiO, Ti₂θ₃, Ti₃0₅ and Ti0₂) , uranium oxide (U0₂, U₃0₈ and Uθ₃) , vanadium oxide (VO, V₂θ₃, V0₂ and V₂0₅) , ytterbium oxide (Yb ) , yttrium oxide (Y₂0₃) , and zirconium oxide (Zr0₂) . Useful ceramic materials also include boron carbide, zirconium carbide, beryllium carbide, aluminum beride, aluminum carbide, boron carbide, silicon carbide, aluminum carbide, titanium nitride, boron nitride, titanium carbide, titanium diboride, iron carbide, iron nitride, barium titanate, aluminum nitride, titanium niobate, boron carbide, silicon boride, barium titanate, silicon nitride, calcium titanate, tantalum carbide, graphites, tungsten; the ceramic alloys which include cordierite/MAS, lead zirconate titanate/PLZT, alumina-titanium carbide, aluminum-zirconia, zirconia-cordierite/ZrMAS; the fiber reinforced ceramics and ceramic alloys; glassy ceramics; 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 18 is aluminum oxide and titanium diboride.

The structure of ceramic body 18 can vary widely depending on the use of the article. For example, body 18 can be a unitary structure composed of one ceramic material or multilayer construction composed of layers of the same material or different ceramic materials. While in the figures ceramic body 18 is depicted as a cubular solid, the shape of ceramic body 18 can vary widely depending on the use of the article. For example, ceramic body 18 can be an irregularly or a regularly shaped body. Illustrative of a useful ceramic body 18 are cubular, rectangular, cylindrical, and polygonal (such as triangular, pentagonal and hexagonal) shaped bodies. In the preferred embodiments of the invention, ceramic body 18 is of cubular, rectangular or cylindrical cross-section.

The size (width and height) of body 18 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 18 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 18 is generally larger. The ceramic bodies 18 are attached to vibration isolating layer 14 which isolates or substantially isolates vibrational and shock waves resulting from the impact of a projectile at a body 18 from other bodies 18 included in layer 12, and reduces the likelihood that bodies 18 not at the point of projectile contact will crack, shatter or loosen. The armor of this invention has relatively higher efficiency of shock absorbence. The efficiency of shock absorbence can be measured by the number of completely undamaged (i.e. free of cracks and flaws) ceramic bodies 18 immediately adjacent to the body or bodies 18 at the point of impact retained after impact. The % efficiency of shock absorbence can be calculated from the following equation: % efficiency of shock absorbence = 100% x [1-d/t] where "t" is the theoretical maximum number of ceramic bodies 18 immediately adjacent to the ceramic body or bodies 18 at the point of contact and "d" is the difference between the theoretical maximum number of ceramic bodies 18 minus the actual number of completely undamaged ceramic bodies 18. Ceramic bodies 18 at the point of contact may vary from one for as for example for impacts at the center of a ceramic body 18 or at the corner of a body 18 at the edge of ceramic impact layer 12, to two for impacts at the seam of two adjacent ceramic bodies 18 or at the corner of two adjacent ceramic bodies 18 at the edge of impact layer 12 to four where the impact is at the intersecting corner of four adjacent ceramic bodies 18. In the preferred embodiments of the invention, % efficiency of shock absorbence is at least about 70%, in the more preferred embodiments of the invention, the % efficiency of shock absorbence is at least about 95%, and in the most preferred embodiments of the invention, the % efficiency of shock absorbence is about 99 to about 100%.

The amount of a surface of vibration isolating layer 14 covered by ceramic bodies 18 may vary widely. In general, the greater the area percent of the surface vibration isolating layer 14 covered or loaded, the more effective the protection, and conversely, the lower the area percent of the surface vibration isolating layer 14 covered the less effective the protection. In the preferred, embodiment of the invention, the area percent of the surface of vibration isolating layer 14 covered by ceramic bodies 18 is equal to or greater than about 95 area percent based on the total surface area of vibration isolating layer 14, and in the more preferred embodiments of the invention the area percent of surface covered is equal to or greater than about 97 area percent on the aforementioned basis. Amongst the more preferred embodiments of the invention, most preferred are those in which the areas percent of the surface of vibration isolating layer 14 covered by ceramic bodies 18 is equal to or greater than about 98 or 99 area percent based on the total surface area of vibration isolating layer 14.

Means for attaching ceramic bodies 18 to vibration isolating layer 14 may vary widely and may include any means normally used on the art to provide this function. Illustrative of useful attaching means are adhesive such as those described in Liable, Chapter 6, supra, bolts, screws, mechanical interlocks adhesives such as metal and non-metal adhesives, organic adhesives and the like. In the preferred embodiments of this invention attaching means is selected from the group consisting of flexible adhesive bonding agents. Such flexible bonding agents provide several useful functions. For example, such agents enhance structural performance such that the composite is capable of withstanding severe impact loads, and they enhance the retention of segmented tiles which are not at the point of impact and the retention of spall/particles created by the shattering of tiles on impact. Such adhesives also enhance the conversion of absorbed energy into heat. As used herein, a "flexible adhesive" is a polymeric adhesive which exhibits a Shore A Hardness of from about 20 to 100.

In the preferred embodiments of the invention, the adhesive material is a low modulus, elastomeric material which has a tensile modulus, measured at about 23°C, of less than about 7,000 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 (3450 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^βC. Preferably, the Tg of the elastomeric material is less than about -40^βC, and more preferably is less than about -50^βC. The elastomeric material also has an elongation to break of at least about 5%. Preferably, the elongation to break of the elastomeric material is at least about 30%. Representative examples of suitable elastomeric materials for use as a flexible adhesive are those which have their structures, properties, and formulation together with cross-linking procedures summarized in the Encyclopedia of Polymer Science, Vol. 5 in the section Elastomers-Synthetic (John Wiley & sons Inc., 1964) and "Handbook of

Adhesives", Van Nostrand Reinhold Company (1977), 2nd Ed., Edited by Irving Skeist. Illustrative of such materials are block copolymers of conjugated dienes such as butadiene and isoprene, and vinyl aromatic monomers such as styrene, vinyl toluene and t-butyl styrene; polydienes such as polybutadiene and polychloroprene, polyisoprene; natural rubber; copolymers and polymers of olefins and dienes such as ethylene-propylene copolymers, ethylene-propylene-diene terpolymers and poly(isobutylene-co-isoprene) , polysulfide polymers, polyurethane elastomers, chlorosulfonated polyethylene; plasticized polyvinylchloride using dioctyl phthate or other plasticizers well known in the art, butadiene acrylonitrile elastomers, polyacrylates such as poly(acrylic acid), poly(methylcyanoacrylate) , poly(methylacrylate) , poly(ethyl acrylate) , poly(propylacrylate) and the like; polyacrylics such as poly(acrylonitrile) , poly(methylacrylonitrile) , poly(aerylamide) , poly(N-isopropylacrylamide) and the like, polyesters; polyethers; fluoroelastomers; poly(bismaleimide) ; flexible epoxies; flexible phenolics; polyurethanes; silicone elastomers; epoxy-polyamides; poly(alkylene oxides); polysulfides; flexible polyamides; unsaturated polyesters; vinyl esters, polyolefins, such as polybutylene and polyethylene; polyvinyls such as poly(vinyl formate) , poly(vinylbenzoate) , poly(vinyl- carbazole) , poly(vinylmethylketone) , poly(vinyl-methyl ether), polyvinyl acetate, polyvinyl butyral, and poly(vinyl formal) ; and polyolefinic elastomers. Preferred adhesives are polydienes such as polybutadiene, polychloroprene and polyisoprene; olefinic and copolymers such as ethylene-propylene copolymers, ethylene-propylene-diene copolymers, isobutylene-isoprene copolymers, and chlorosulfonated polyethylene; natural rubber; polysulfides; polyurethane elastomers; polyacrylates; polyethers; fluoroelastomer; unsaturated polyesters; vinyl esters; alkyds; flexible epoxy; flexible polyamides; epichlorohydrin; polyvinyls; flexible phenolics; silcone elastomers; thermoplastic elastomers; copolymers of ethylene, polyvinyl formal, polyvinyl butryal; and poly(bis-malei ide) . Blends of any combination of one or more of the above-mentioned adhesive materials. Most preferred adhesives are polybutadiene, polyisoprene, natural rubber, ethylene-propylene copolymers, ethylene-propylene-diene terpolymers, polysulfides, polyurethane elastomers, chlorosulfonated polyethylene, polychloroprene. poly(isobutylene-co-isoprene) , polyacrylates, polyesters, polyethers, fluoroelastomers, unsaturated polyesters, vinyl esters, flexible epoxy, flexible nylon, silicone elastomers, copolymers of ethylene, polyvinyl formal, polyvinyl butryal. Blends of any combination of one or more of the above-mentioned adhesive materials.

The structure of vibrating isolating layer 14 is critical to the multiple hit capability of ballistic resistant article 10. As depicted in FIG. 1, vibration isolating layer 14 includes three distinct regions or layers; center region or layer 20 and surface regions or layers 22 and 24 which sandwich region or layer 20. Regions or layer 20, 22 and 24 have properties which allow them to interact to provide a multi-hit capability. Region or layer 20 functions to absorb the shock of the projectile's impact and can be formed of any material which performs this function. The shock absorbing capability of a material can be expressed in terms of its energy-to-break. In general, region or layer 20 is formed of a material which has an energy-to-break equal to or greater than about 8 joules/grams. Preferred materials for fabrication of layer or region 20 are those which have an energy-to-break equal to or greater than about 20 joules/grams, more preferred materials are those which have an energy-to-break equal to or greater than about 30 joules/gram and most preferred materials are those having an energy-to-break equal to or greater than about 35 joules/grams. In the practice of this invention materials of choice for use in the fabrication of region or layer 20 are those having an energy-to-break of 40 joules/grams.

In the preferred embodiments of the invention, layer 20 comprises a net work of polymeric fibers having a tenacity of at least about 7 grams/denier as measured by ASTM D885, and a tensile modulus of 160 grams/denier as measured by ASTM D885 (pulling a 10 inc. (25.4cm) fiber length clamped in barrel clamps at a rate of lOin/min (25.4cm/min) on an Instron Tensile Tester) and an energy-to-break of at least about 8 joules/gram also as measured by ASTM D885. Preferred fibers 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-to-break equal to or greater than about 8 joules/grams. Particularly preferred fibers 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 fibers are equal to or greater than about 25 g/d, and energy-to-break is equal to or greater than about 35 joules/gram. In the practice of this invention, fibers 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. The type of fibers used in the fabrication of layer or region 20 of the preferred embodiments of the invention may vary widely and can be metallic fibers, semi-metallic fibers, inorganic fibers and/or organic fibers. Illustrative of useful organic fibers are those composed of polyesters, polyolefins, polyetheramides, fluoropolymers, polyethers, celluloses, phenolics, polyesteramides, polyurethanes, epoxies, amimoplastics, silicones, polysulfones, polyetherketones, polyetherether-ketones, polyesterimides, polyphenylene sulfides, polyether acryl ketones, poly(amidei ides) , and polyimides. Illustrative of other useful organic filaments are those composed of aramids (aromatic polyamides) , such as poly(m-xylylene adipamide) , poly(p-xylylene sebacamide) , poly 2,2,2-trimethyl- hexamethylene 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-l, 5-naphthalate), poly(ethylene-2,6-naphthalate) , poly(l, 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(a,a-dimethyl-propiolactone) , and the like.

Also illustrative of useful organic fibers are those of liquid crystalline polymers such as lyotropic liquid crystalline polymers which include polypeptides such as poly (g-benzyl L-glutamate) and the like; aromatic polyamides such as poly(l,4-benzamide) , poly(chloro-1,4-phenylene terephthalamide) , poly(1,4-phenylene fumaramide) , poly(chloro-1,4-phenylene fumaramide), poly(4,4'-benzanilide trans, trans- uconamide) , poly(1,4-phenylene mesaconamide) , poly(1,4-phenylene) (trans-l,4-cyclohexylene amide), poly(chloro-1,4- phenylene) (trans-l,4-cyclohexylene amide), poly(l,4- phenylene l,4-dimethyl-trans-l,4-cyclohexylene amide), poly(1,4-phenylene 2.5-pyridine amide), poly(chloro-1,4-phenylene 2.5-pyridine amide), poly(3,3*-dimethyl-4,4'-biphenylene 2.5 pyridine amide), poly(1,4-phenylene 4,4'-stilbene amide), poly(chloro-1,4-phenylene 4,4•-stilbene amide), poly(1,4-phenylene 4,4'-azobenzene amide), poly(4,4'-azobenzene 4,4'-azobenzene amide), poly(l,4-phenylene 4,4'-azoxybenzene amide), poly(4,4'- azobenzene 4,4'-azoxybenzene amide), poly(l,4- cyclohexylene 4,4'-azobenzene amide), poly(4,4'-azobenzene terephthal amide), poly(3,8-phenanthridinone terephthal amide), poly(4,4'-biphenylene terephthal amide), poly(4,4'-biphenylene 4,4'-bibenzo amide), poly(1,4- phenylene 4,4'-bibenzo amide), poly(1,4-phenylene 4,4'-terephenylene amide), poly(1,4-phenylene 2,6-naphthal amide), poly(l,5-naphthylene terephthal amide) , poly(3,3'-dimethyl-4,4-biphenylene terephthal amide), poly(3,3'-dimethoxy-4,4'-biphenylene terephthal amide) , poly(3,3•-dimethoxy-4,4-biphenylene 4,4'-bibenzo amide) and the like; polyoxamides such as those derived from 2,2'dimethyl-4,4'diamino biphenyl and chloro-1,4-phenylene diamine; polyhydrazides such as poly chloroterephthalic hydrazide, 2,5-pyridine dicarboxylic acid hydrazide) poly(terephthalic hydrazide) , poly(terephthalic- chloroterephthalic hydrazide) and the like; poly(amide-hydrazides) such as poly(terephthaloyl 1,4 amino-benzhydrazide) and those prepared from 4-amino-benzhydrazide, oxalic dihydrazide, terephthalicdihydrazide and para-aromatic diacid chlorides; polyesters such as those of the compositions include poly(oxy-trans-

1,4-cyclohexyleneoxycarbonyl-trans-l,4-cyclohexylenecar bonyl-S-oxy-l,4-phenyl-eneoxyterephthaloyl) and poly(oxy-cis-l,4-cyclohexyleneoxycarbonyl-trans-l,4-cyc lohexylenecarbonyl-/S-oxy-l,4-phenyleneoxyterephthaloyl) in methylene chloride-o-cresol poly[(oxy-trans-1,4-cyclohexylene- oxycarbonyl-trans-1,4-cyclohexylenecarbonyl-?-oxy-(2-me thyl- 1,4-phenylene)oxy-terephthaloyl) ] in 1,1,2,2-tetrachloro-ethane-o-chlorophenol-phenol (60:25:15 vol/vol/vol) , poly[oxy-trans-1,4-cyclohexyleneoxycarbonyl-trans-l,4- cyclohexylenecarbonyl-β-oxy(2-methyl-l,3-phenylene)oxy- terephthaloyl] in o-chlorophenol and the like; polyazomethines such as those prepared from 4,4'-diaminobenzanilide and terephthalaldephide, methyl-l,4-phenylenediamine and terephthalaldelyde and the like; polyisocyanides such as poly(-phenyl ethyl isocyanide) , poly(n-octyl isocyanide) and the like; polyisocyanates such as poly(n-alkyl isocyanates) as for example poly(n-butyl isocyanate) , poly(n-hexyl isocyanate) and the like; lyotropic crystalline polymers with heterocylic units such as poly(l,4-phenylene-2,6-benzobisthiazole) (PBT) , poly(l,4-phenylene-2,6-benzobisoxazole) (PBO) , poly(1,4-phenylene-l,3,4-oxadiazole) , poly(l,4-phenylene-2,6-benzobisimidazole) , poly[2,5(6)-benzimidazole] (AB-PBI) , poly[2,6-(l,4- phneylene)-4-phenylquinoline] , poly[1,1'-(4,4'- biphenylene)-6,6'-bis(4-phenylquinoline)] and the like; polyorganophosphazines such as polyphosphazine, polybisphenoxyphosphazine, poly[bis(2,2,2' trifluoroethyelene) phosphazine] and the like; metal polymers such as those derived by condensation of trans-bis(tri-n-butylphosphine)platinum dichlόride with a bisacetylene or trans-bis(tri-n-butylphosphine)bis(1,4- butadinynyl)platinum and similar combinations in the presence of cuprous iodine and an amide; cellulose and cellose derivatives such as esters of cellulose as for example triacetate cellulose, acetate cellulose, acetate-butyrate cellulose, nitrate cellulose, and sulfate cellulose, ethers of cellulose as for example, ethyl ether cellulose, hydroxymethyl ether cellulose, hydroxypropyl ether cellulose, carboxymethyl ether celulose, ethyl hydroxyethyl ether cellulose, cyanoethylethyl ether cellulose, ether-esters of cellulose as for example acetoxyethyl ether cellulose and benzoyloxypropyl ether cellulose, and urethane cellulose as for example phenyl urethane cellulose; thermotropic liquid crystalline polymers such as celluloses and their derivatives as for example hydroxypropyl cellulose, ethyl cellulose propionoxypropyl cellulose; thermotropic copolyesters as for example copolymers of 6-hydroxy-2-naphthoic acid and p-hydroxy benzoic acid, copolymers of 6-hydroxy-2- naphthoic acid, terephthalic acid and hydroquinone and copolymers of poly(ethylene terephthalate) and p-hydroxybenzoic acid; and thermotropic polyamides and thermotropic copoly(amide-esters) .

Also illustrative of useful organic fibers for use in the fabrication of region or layer 20 of vibration isolating layer 14 are those composed of extended chain polymers formed by polymerization of α,S-unsaturated monomers of the formula:

R, R₂-C = CH₂ wherein: R-i and R₂ 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 α,S-unsaturated monomers are polymers including polystyrene, polyethylene, polypropylene, poly(l-octadecene) , polyisobutylene, poly(l-pentene) , poly(2-methylstyrene) , poly(4-methylstyrene) , poly(l-hexene) , poly(l-pentene) , poly(4-methoxystrene) , poly(5-methyl-l-hexene) , poly(4-methylpentene) , poly (l-butene) , polyvinyl chloride, polybutylene, polyacrylonitrile, poly(methyl pentene-1) , poly(vinyl alcohol) , poly(vinylacetate) , poly(vinyl butyral) , poly(vinyl chloride), poly(vinylidene chloride) , vinyl chloride-vinyl acetate chloride copolymer, poly(vinylidene fluoride) , poly(methyl acrylate, poly(methyl methacrylate) , poly(methacrylo-nitrile) , poly(aerylamide) , poly(vinyl fluoride), poly(vinyl formal), poly(3-methyl-

1-butene) , poly(l-pentene) , poly(4-methyl-l-butene) , poly(l-pentene) , poly(4-methyl-l-pentence, poly(l-hexane) , poly(5-methyl-l-hexene) , poly(vinyl- cyclopentane) , poly(vinylcyclothexane) , poly(a-vinyl- naphthalene), poly(vinyl methyl ether), poly(vinyl- ethylether) , 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.

Illustrative of useful inorganic fibers for use in the fabrication of layer 20 of vibration isolating layer 14 are glass fibers such as fibers formed from quartz, magnesia aluminosilicate, non-alkaline aluminoborosilicate, soda borosilicate, soda^' silicate, soda lime-aluminosilicate, lead silicate, non-alkaline lead boroalumina, non-alkaline barium boroalumina, non-alkaline zinc boroalumina, non-alkaline iron aluminosilicate, cadmium borate, alumina fibers which include "saffil" fiber in eta, delta, and theta phase form, asbestos, boron, silicone carbide, graphite and carbon such as those derived from the carbonization of polyethylene, polyvinylalcohol, saras, polyamide (Nomex®) type, nylon, polybenzimidazole, polyoxadiazole, polyphenylene, PPR, petroleum and coal pitches (isotropic) , mesophase pitch, cellulose and polyacrylonitrile, ceramic fibers such as those of the ceramic materials discussed earlier for the use in the fabrication of ceramic body 18, metal fibers as for example steel, aluminum metal alloys, and the like. In the preferred embodiments of the invention, layer 20 is fabricated from a fiber network, which may include a high molecular weight polyethylene fiber, a high molecular weight polypropylene fiber, an aramid fiber, a high molecular weight polyvinyl alcohol fiber, a high molecular weight polyacrylonitrile fiber or mixtures thereof. Highly oriented polypropylene and polyethylene fibers 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 layer or region 20. Such high molecular weight polyethylene and 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 US Patent Nos. 4,413,110, 4,457,985 and 4,663,101 and preferable US Patent No. 4,784,820. 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 about 8 grams/denier,with a preferred tenacity being at least about 11 grams/denier. The tensile modulus for polypropylene is at least about 160 grams/denier, preferably at least about 200 grams/denier. High molecular weight polyvinyl alcohol fibers having high tensile modulus preferred for use in the fabrication of layer 20 are described in USP 4,440,711 which is hereby incorporated by reference to the extent it is not inconsistent herewith. In the case of polyvinyl alcohol (PV-OH) , PV-OH fiber of molecular weight of at least about 200,000. Particularly useful PV-OH fiber should have a modulus of at least about 300 g/denier, a tenacity of at least about 7 g/denier (preferably at least about 10 g/denier, more preferably at about 14 g/denier, and most preferably at least about 17 g/denier) , and an energy to break of at least about 8 joules/g. P(V-OH) fibers having a weight average molecular weight of at least about 200,000, a tenacity of at least about 10 g/denier, a modulus of at least about 300 g/denier, and an energy to break of about 8 joules/g are more useful in producing a ballistic resistant article. P(V-OH) fiber having such properties can be produced, for example, by the process disclosed in US Patent No. 4,599,267. In the case of polyacrylonitrile (PAN) , PAN fiber for use in the fabrication of layer or region 20 are of molecular weight of at least about 4000,000. Particularly useful PAN fiber should have a tenacity of at least about 10 g/denier and an energy-to-break of at least about 8 joule/g. PAN fiber having a molecular weight of at least about 4000,000, 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 fibers are disclosed, for example, in US 4,535,027.

In the case of aramid fibers, suitable aramid fibers for use in the fabrication of layer or region 20 are those formed principally from aromatic polyamide are described in US Patent No. 3,671,542, which is hereby incorporated by reference. Preferred aramid fiber 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 fibers 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 fibers 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) fibers produced commercially by Dupont Corporation under the trade name of Kevlar® 29, 49, 129 and 149 and having moderately high moduli and tenacity values are particularly useful in forming ballistic resistant composites. Also useful in the practice of this invention is poly(metaphenylene isophthalamide) fibers produced commercially by Dupont under the trade name No ex®.

In the more preferred embodiments of this invention, region or layer 20 of vibration isolating layer 14 is formed of fibers 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 bundles in various alignment. The fibers or any may be formed as a felt, knitted or woven (plain, basket, satin and crow feet weaves, etc.) into a network, fabricated into non-woven fabric, arranged in parallel array, layered, or formed into a woven fabric by any of a variety of conventional techniques. Among these techniques, for ballistic resistance applications we prefer to use those variations commonly employed in the preparation or aramid fabrics for ballistic-resistant articles. For example, the techniques described in U.S. Patent No. 4,181,768 and in M.R. Silyquist et al., J. Macromol Sci. Chem.. A7(l), pp. 203 et. seq. (1973) are particularly suitable. In preferred embodiments of the invention, the filaments are aligned substantially parallel and undirectionally to form a uniaxial layer. Two or more of these layers can be used to form a layer 20 with multiple layers of coated undirectional filaments in which each layer is rotated with respect to its adjacent layers. An example is a 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 a layer 20 with a 0°/90° layout of yarn or filaments. In the most preferred embodiments of this invention, layer 20 is composed by one or more layers of continuous fibers embedded in a continuous phase of an elastomeric matrix material which preferably substantially coats each fiber contained in the bundle of fibers. The manner in which the fibers are dispersed may vary widely. The fibers may be aligned in a substantially parallel, unidirectional fashion, or fibers may be aligned in a multidirectional fashion, or with fibers at varying angles with each other. In preferred embodiments of this invention, fibers in each layer forming layer 20 are aligned in a substantially parallel, unidirectional fashion such as in a prepreg, pultruded sheet and the like.

Wetting and adhesion of fibers in the polymer or matrices, is enhanced by prior treatment of the surface of the fibers. 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 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 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 cross-linking 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, unsaturated polyesters, vinyl esters, polyethers, fluoroelastomers, silicone elastomers, thermoplastic elastomers, and copolymers of ethylene. Particularly useful elastomers are polysulfide polymers, polyurethane elastomers, unsaturated polyesters vinyl esters; and block copolymers of conjugated dienes such as butadiene and isoprene are vinyl aromatic monomers such as 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 (n=2-10) or radial configuration copolymers of the type R-(BA)x (x=3-150) ; wherein A is a block from a polyvinyl aromatic monomer and B is a block from a conjugated 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-mentioned elastomers. The low modulus elastomeric matrixes may also include fillers such as carbon black, glass microballons, and the like up to an amount preferably not to exceed about 250% by volume of the elastomeric material, more 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 thermoplastics. 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 23°C, of less than about 7,000 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^βC. 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 fiber in layer 20 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, flam ability resistance and other properties desired for layer 20. In general, the proportion of matrix to fiber in layer 20 may vary from relatively small amounts where the amount of matrix is about 10% by volume of the fibers to relatively large amount 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 layer 20. lii "the particularly preferred embodiments of the invention, ballistic-resistant articles of the present invention, layer 20 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 fibers, and in the particularly preferred embodiments of the invention, the proportion of the matrix in layer 14 is from about 10 to about 30% by weight of fibers.

Layer 20 can be fabricated using conventional procedures. For example, in those embodiments of the invention in which layer 20 is a woven fabric, layer 20 can be fabricated using conventional fabric weaving techniques of the type commonly employed for ballistic purposes such as a plain weave or a Panama weave. In those embodiments of the invention in which layer 20 is a network of fibers in a matrix, layer 20 is formed by continuing the combination of fibers and matrix material in the desired configurations and amounts, and then subjecting the combination to heat and pressure. For extended chain polyethylene fibers, molding temperatures range from about 20 to about 150^βC, 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^βC. 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 fibers 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 in., may cause the fibers 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^βC for a time of between 1 to about 5 min., may cause the film to become translucent or transparent. For polypropylene fibers, the upper limitation of the temperature range would be about 10 to about 20°C higher than for extended chain polyethylene fiber.

In the preferred embodiments of the invention, the fibers (pre-molded if desired) are pre-coated with the desired matrix material prior to being arranged in a network and molded into layer 20 as described above. The coating may be applied to the fibers in a variety of ways and any method known to those of skill in the art for coating fibers may be used. For example, one method is to apply the matrix material to the stretched high modulus fibers 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 fiber 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 fibers may be used, including coating of the high modulus precursor (gel fiber) before the high temperature stretching operation, either before or after removal of the solvent from the fiber. The fiber may then be stretched at elevated temperatures to produce the coated fibers. The gel fiber may be passed through a solution of the appropriate matrix material, as for example an elastomeric material dissolved in paraffin oil, or an aromatic oraliphatic solvent, under conditions to attain the desired coating. Crystallization of the polymer in the gel fiber may or may not have taken place before the fiber passes into the cooling solution. Alternatively, the fiber may be extruded into a fluidized bed of the appropriate matrix material in powder form.

The proportion of coating on the coated fibers or fabrics in layer 20 may vary from relatively small amounts of (e.g. 1% by volume of fibers) to relatively large amounts (e.g. 150% by volume of fibers) , 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, layer 20 containing coated fibers should have a relatively minor proportion of coating (e.g. about 10 to about 30 percent by volume of fibers) , since the ballistic-resistant properties of layer 20 are almost entirely attributable to the fiber. Nevertheless, coated fibers with higher coating contents may be employed. Generally, however, when the coating constitutes greater than about 60% (by volume of fiber) , the coated fiber are consolidated with similar coated fibers to form a fiber layer without the use of additional matrix material.

Furthermore, if the fiber 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 fiber. IN such cases, the desired and preferred tenacity, modulus and other properties of the fiber should be judged by continuing the manipulative process on the fiber precursor in a manner corresponding to that employed on the coated fiber precursor. Thus, for example, if the coating is applied to the xerogel fiber described in US No. 4,537,296 and the coated xerogel fiber is then stretched under defined temperature and stretch ratio conditions, then the fiber tenacity and fiber modulus values would be measured on uncoated xerogel fiber which is similarly stretched. It is a preferred aspect of the invention that each fiber be substantially coated with the matrix material for the production of layer 20. A fiber is substantially coated by using any of the coating processes described above or can be substantially coated by employing any other process capable of producing a fiber coated essentially to the same degree as a fiber coated by the processes described heretofore (e.g., by employing known high pressure molding techniques) . The fibers and networks produced therefrom are formed into "simple composites" as the precursor to preparing the complex composite articles of the present invention. The term, "simple composite", as used herein is intended to mean composites made up of one or more layers, each of the layers containing fibers as described above with a single major matrix material, which material may include minor proportions^*-U other materials such as fillers, lubricants or the like as noted heretofore. The proportion of elastomeric matrix material to fiber is variable for the simple composites, with matrix material amounts of from about 5% to about 150 vol %, by volume of the fiber, representing the broad general range, within this range, it is preferred to use composites having a relatively high fiber content, such as composites having only about 10 to about 50 vol % matrix material, by volume of the composite, and more preferably from about 10 to about 30 vol % matrix material by volume of the composite. Stated another way, the fiber network occupies different proportions of the total volume of the simple composite. Preferably, however, the fiber network comprises at least about 20 volume percent of the simple composite. For ballistic protection, the fiber network comprises at least about 50 volume percent, more preferably about 70 volume percent, and most preferably at least about 95 volume percent, with the matrix occupying the remaining volume.

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

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

The number of layers of fibers included in layer 20 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 lesser the degree of ballistic protection provided. One preferred configuration of layer 20 is a laminate in which one or more layers of fibers coated with matrix material (pre- olded if desired) are arranged in a sheet-like array and aligned parallel to one another along a common fiber direction. Successive layers of such coated unidirectional fibers can be rotated with respect to the previous layer after which the laminate can be molded under heat and pressure to form the laminate. An example of such a layered vibration isolating layer is the layered structure in which the second, third, fourth and fifth layer are rotated 45°, 45°, 90" and 0° with respect to the first layer, but not necessarily in that order. Similarly, another example of such a layered layer 20 is a layered structure in which the various unidirectional layers forming layer 20 are aligned such that the common fiber axis is adjacent layers is 0°, 90°.

As depicted in FIG. 1, vibrating isolating layer 14 includes two surfaces regions or layers 22 and 24 which, in the embodiments of FIG. 1, are adjacent impact layer 12 and backing layer 16, respectively, and which sandwich layer 20. Layers or regions 22 and 24 function to improve the overall performance of vibration isolating layer 14 by improving the surface characteristics of vibrating isolating layer 14; providing a surface on which ceramic bodies 18 can be attached; and retaining dimensional stability (i.e. flatness and straightness) of the surface of vibration isolating layer 14 when subjected to severe impact deformation. The construction of regions 22 and 24 and the materials used in such construction are such that the regions have a flexural modulus equal to or greater than about 0.01 msi, an elongation at break equal to or less than about 40% and a fracture toughness equal to or greater than about IMPa.m¹⁷². As a result of these properties, undue deformation of the surface geometry of vibration isolating layer 14 does not occur during impact. In the preferred embodiments of the invention, the flexural modulus of regions or layers 22 and 24 are from about 0.05 to about 100 msi, elongation at break is equal to or less than about 30% and the fracture toughness is equal to or greater than about 5 MPa.m¹². In the more preferred embodiments of the invention, the flexural modulus of regions or layers 22 and 24 are from about 0.1 to about 80 msi, the elongation at break is less than about 20% and the fracture toughness is equal to or greater than about 10MPa.m^1/2; and in the most preferred embodiments of the invention the flexural modulus is from about 0.5 to about 50 msi, the elongation at break is equal to or less than about 10% and the fracture toughness is equal to or greater than about 15MPa.m ².

Any material which can provide the desired flexural modulus, elongation-to-break and fracture toughness can be used in the fabrication of layers or regions 22 and 24. The materials used in the construction of layers 22 and 24 may vary widely and may be metallic, semi-metallic material an organic material and/or an inorganic material. Illustrative of such materials are those described in G.S. Brady and H.R. Clauser, Materials Handbook. 12th edition (1986) . Materials useful for fabrication of layers 22 and 24 include high modulus thermoplastic polymeric materials such as polyamides as for example aramids, nylon-66, nylon-6 and the like; polyesters such as polyethylene terephthalate polytutylene terephthalate, and the like. polyacrylates, acetalo; polysulfones; polyethersulfones; polyacrylates; polydienes, acrylonitrile/butadiene/styrene copolymers; poly(amide-amide) ; polycarbonates; polyarylates, polyphenylenesulfides; polydienes, polyurethanes, polyphenyleneoxides; polyestercarbonates; polyesterimides; polyamides; and polyetheretherketone; thermosetting material such as epoxy resins; phenolic resins; vinyl ester resins; modified phenolic resins; polyimides; unsaturated polyester; allylic resins, alkyd resins; melamine and urea resins; allylic resins; alkyd resins; melamine and urea resins; polymer alloys and blends of thermoplastics and/or thermosets; and interpertrating polymer networks such as those of a thermosetting resin as for example polycyanate ester of a polyol such as the dicyanoester of bisphenol-A and a thermoplastic such as a polysulfone. These materials may be reinforced by high strength filaments described above for use in the fabrication of region or layer 20, such as aramid fibers, boron fibers, S-glass fibers, ceramic fibers, E-glass fibers, carbon and graphite fibers, silicone carbide fibers, zirconia-silica fibers, alumina-silica fibers and the like. Other useful materials for the fabrication of layers 22 and 24 include non-shattering glass such as bullet proof glass, and hardwood panels.

In the preferred embodiments of the invention, layers 22 and 24 are formed from thermosetting resins or blends of thermosetting resins and thermoplastic resins preferably filled with inorganic, non-metallic fibers such as carbon, boron, graphite, S₂-glass, E-glass, S-glass and the like.

At their contact points, constituent layers 20, 22 and 24 are bonded together with a suitable agent such as an adhesive described above for attachment of ceramic bodies 12 to vibrating isolating layer 14 as for example a polysulfide or an epoxy.

In the composite 10, backing layer 16 is of double layers construction, layers 26 and 28. However, it should be appreciated that the number of individual layers forming layer 16 is not critical and any number of layers can be employed to provide the desired results.

Backing layer 16 is comprised of a rigid ballistic material which may vary widely depending on the uses of article 10, and may offer additional ballistic protection. The term "rigid" as used in the^" present specification and claims is intended to include semi-flexible and semi-rigid structures that are not capable of being free standing, without collapsing. The backing material employed may vary widely and may be metallic, semi-metallic material, an organic material and/or an inorganic material. Illustrative of such materials are those described in G.S. Brady and H.R. Clauser, Materials Handbook. 12th edition (1986) . Materials useful for fabrication of backing layer 16 include high modulus polymeric materials such as polyamides as for example aramids, nylon-66, nylon-6 and the like; polyesters such as polyethylene terephthalate polybutylene terephthalate, and the like, acetalo; poylsulfones; polyethersulfones; polyacrylates; acrylonitrile/butadiene/styrene copolymers; poly(amide-imide) ; polycarbonates; polyphenylenesulfides; polyurethanes, polyphenyleneoxides; polyester carbonates; polyesterimides; polyimides; polyetheretherketone; epoxy resins; phenolic resins; polysulfides; silicones; polyacrylates; polyacrylics; polydienes; vinyl ester resins; modified phenolic resins; unsaturated polyester; allylic resins; alkyd resins; melamine and urea resins; polymer alloys and blends of thermoplastics and/or thermosets of the materials described above; and interpenetrating polymer networks such as those of polycyanate ester of a polyol such as the dicyanoester of bisphenol-A and a thermoplastic such as a polysulfone. These materials may be reinforced by high strength fibers described above for use in the fabrication of vibration isolating layer 14, such as aramid fibers, Spectra® polyethylene fibers, boron fibers, glass fibers, ceramic fibers, carbon and graphite fibers, and the like.

Useful backing materials also include metals such as nickel, manganese, tungsten, magnesium, titanium, aluminum and steel plate. Illustrative of useful steels are carbon steels which include mild steels of grades AISI 1005 to AISI 1030, medium-carbon steels of grades AISI 1030 to AISI 1055, high-carbon steels of the grades AISI 1060 to AISI 1095, free-machining steels, low-temperature carbon steels, rail steel, and superplastic steels; high-speed steels such as tungsten steels, molybdenum steels, chromium steels, vanadium steels, and cobalt steels; hot-die steels; low-alloy steels; low-expansion alloys; mold-steel; nitriding steels for example those composed of low-and medium-carbon steels in combination with chromium and aluminum, or nickel, chromium, and aluminum; silicon steel such as transformer steel and silicon-manganese steel; ultrahigh-strength steels such as medium-carbon low alloy steels, chrominum-molybdenum steel, chromium-nickel-molybdenum steel, iron-chromium- molybdenum-cobalt steel, quenched-and-tempered steels, cold-worked high-carbon steel; and stainless steels such as iron-chromium alloys austenitic steels, and choro ium-nickel austenitic stainless steels, and chromium-manganese steel. Useful materials also include alloys such as manganese alloys, such as manganese aluminum alloy, manganese bronze alloy; nickel alloys such as, nickel bronze, nickel cast iron alloy, nickel-chromium alloys, nickel-chromium steel alloys, nickel copper alloys, nickel-molydenum iron alloys, nickel-molybdenum steel alloys, nickel-silver alloys, nickel-steel alloys; iron-chromium-molybdenum-cobalt steel alloys; magnesium alloys; aluminum alloys such as those of aluminum alloy 1000 series of commercially pure aluminum, aluminum-manganese alloys of aluminum alloy 300 series, aluminum-magnesium-manganese alloys, aluminum- magnesium alloys, aluminum-copper alloys, aluminum-silicon-magnesium alloys of 6000 series, aluminum-copper-chromium of 7000 series, aluminum casting alloys; aluminum brass alloys and aluminum bronze alloys. Still other materials useful in the fabrication of backing layer 16 are the fiber composites used in the fabrication of vibration isolating layer 14 which comprises fibrous network in a rigid matrix. Yet, other materials useful in the fabrication of backing layer 16 are non-shattering glass such as bulletproof glass.

FIG 2 shows a variant of the embodiment of FIG 1, which is indicated at 30, corresponding parts being referred to by like numerals. In composite 30, ceramic impact layer 10 is covered with cover layer 32 which functions as an anti-spall layer to retain spall or particles resulting from the shattering of ceramic bodies 18 by the striking projectile, and which functions to maintain ceramic bodies 18 which are not hit by the projectile in position. In FIG 2, cover layer 32 consists of top cover 36 and release layer 38. Top cover 36 is formed from a rigid material as for example the metals and non-metals described above for use in the fabrication of backing layer 16 and is preferably composed of a metal such as steel, titanium and aluminum alloys, or of a rigid high strength polymeric composite such as a thermoplastic resin such as a polyurethane, polyester or polyamide, a thermosetting resin such as epoxy, phenolic or vinylester resin or a mixture thereof reinforced with polymeric filaments such as aramid or extended chain polyethylene or inorganic filaments such as S-glass fibers, silicon carbide fibers, E-glass fibers, carbon fibers, boron fibers and the like. Release layer 38 is formed from materials similar to those used to form vibration isolating layer 14 and functions to eliminate or to substantially reduce the strain on unhit ceramic bodies 18 in the deformation of the composites from impact by the projectile. The construction of vibration isolating layer 14 and backing layer 16 in composite 30 and their materials of construction are the same as in composite 10 of FIG 1. FIG 3 depicts composite 40, which is a variation of the embodiment of FIG 1, corresponding parts being referred to by like numerals. Composite 40 includes ceramic body retaining means 42 between individual ceramic bodies 18 and peripheral impact layer retaining means 44. Ceramic body retaining means 42 reduces the differences in performance of segmented ceramic impact layer 12 at the seams formed by adjacent ceramic bodies 18 which is usually a weak area, and at the center of ceramic body 18 which is usually a strong area. Ceramic body retaining means 42 also allows maximum loading of ceramic bodies 18 in segmented ceramic impact layer 12, provides optimized spacing between adjacent ceramic bodies 18 retains unhit ceramic bodies 18 in place upon severe impact deformation, and transmitts and distributes the impact shock to the entire composite 40 upon impact. Peripheral impact layer retaining means 44 minimizes the differences in the performance at the edges of the composite armor (which because of the segmented nature of the ceramic impact layer 14 tends to be a relatively weak area) and at the center of the ceramic which tends to be a relatively strong area.

Ceramic body retaining means 42 and peripheral impact layer retaining means 44 are composed of an "elastic" material which may vary widely and be metallic, semi-metallic material, an organic material and/or an inorganic material. The term "elastic" as used in the present specification and claims is intended to include materials inherently capable of free standing without collapsing. Illustrative of such materials are those described in G.S. Brady and H.R. Clauser, Materials Handbook. 12th Edition (1986) . Also illustrative useful materials suitable for use in the fabrication of ceramic body retaining means 42 and peripheral impact layer retaining means 44 are those materials described herein abovefor use in the fabricaton of the backing layer 16 and cover layer 34. These materials include in the embodiments of FIGs. 1, 2 and 3 high modulus polymeric materials with or without fibrous fillers such as a thermosetting or thermoplastic resin such as a polycarbonate or epoxy which is optionally reinforced by high strength filaments such as aramid filament, Spectra extended chain polyethylene filaments, boron filament, glass filaments, ceramic filaments, carbon and graphite filament, and the like; metals and metal alloys such as nickel, manganese, tungsten, magnesium, titanium, aluminum, steel, manganese alloys, nickel alloys, magnesium alloys, and aluminum alloys with or without creramic fillers such as silicone carbide; and non-shattering glass such as bulletproof glassdescribed above. The construction of vibration isolating layer 14 and backing layer 16 in composite 40 and their ateials of construction are the same as in composite 20 of FIG 2.

Complex ballistic articles of this invention have many uses. For example, such composites may be incorporated into more complex composites to provide a Vigid 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, conditions, materials,proportions and reported data set forth to illustrate the principles of the invention are exemplary and should not be construed as limiting the scope of the invention. EXAMPLE I

Eight layers of 16" (40.6 cm) x 16" (40.6 cm) Spectra Fabric (of the style 952 plain 65 d) stitched together with a Spectra® 1000 polyethylene fiber were placed between two pieces of 1/32" (0.08 cm) thin glass reinforced epoxy plastic sheet (sold by Ryerson

Plastics under the trade name GP0-2Grade PEF 2002) . The sandwich is placed in a mold. A mixture (100 grams) of a vinyl ester resin (VE 8520 sold by Interplastics) , a peroxide (Benzoate Peroxide) sold by Lucidol under the tradename Luperco AFR-400) and a promoter (N,N-dimethyl aniline) was poured in the mold until the sandwich surface was completely covered. The composition of the mixture of vinyl ester resin/peroxide/promoter is 10/0.1/0.006. The material was cured for two hours at room temperature under pressure. The thickness of the cured material was about 1/8" (0.32 cm) .

Example 2 A panel consisting of a 4 by 24 checker board with square cells of dimensions of 4" (10.2cm) by 4"

(10.2cm) by 1/2" (1.3 cm) depth was constructed. The cells of panel were filled with marble tiles. The panel was constructed on a Spectra® composite of Example 1. The checker board was placed into a 16" (40.6 cm) by 16" (40.6 cm) by 1/2" (1.3 cm) aluminum frame, and was covered with a piece of 1/8" (0.32 cm) thick polycarbonate. The whole unit was mounted on a 1/4" (0.64 cm) thick steel plate (AR 400 sold by Ryerson Aluminum and Steel Company) , and the entire arrangement was consolidated into a single unit with the thermosetting vinyl ester resin mixture used in Example 1. After the first shot at the center of tile, 9 neighboring tiles at the point of impact remained undamaged. Thus, the efficiency was 100%. After 5 bullets were shot at a speed of 3100 ft/sec (944.9 m/sec) at the center of the tiles, 11 tiles were retained. Among these, 9 were undamaged and 2 were slightly cracked. However, 9 out of 9 of these undamaged tiles were neighboring tiles. Therefore, the efficiency remained 100% after 5 hits. Furthermore, the composite remained flat and straight even though the steal backing plate had buckled after 5 hits.

Comparative Example 1 A panel was constructed using the same procedure described in Example 2 with the exception that the Spectra® composite was not included. The panel was tested under the same conditions. After the first shot at the center of tile, no neighboring tiles at the point of impact remained undamaged. Thus, the efficiency is 0%. After 5 hits, all tiles had shattered. The efficiency remained 0% after 5 hits.

Comparative Example 2 A panel was constructed using the same procedure described in Example 2 except that a known vibration and shock isolation material - felt replaced the

Spectra composite sandwich. The felt used was a 1/8" (0.32 cm) think 100% dense wool pad (sold by McMaster-Carr under the trade name of 8757K1 with a weight of 1.53 lbs/sq.yd) . The sample was tested under the same conditions described in Example 2. After the first shot at the center of tile, 2 out of 9 meighboring tiles at the point of impact remained undamaged. Thus, the efficiency was 22%. After 5 hits, 5 tiles were retained but they were slightly cracked. Therefore, the efficiency was 0% after 5 hits. The other tiles were all shattered. The piece of felt used was torn into pieces after 5 shots.

Comparative Example 3 A panel was constructed using the same procedure as Example 2 except that a 1/8" (0.32 cm) thick glass reinforced epoxy composite (GRP) replaced the Spectra composite. This GRP is sold by Ryerson Plastics under the trade name Ryertex G-10 PHPP4008. The sample was tested under the same conditions as described in Example 2. After the first shot at the center of tile, 1 out of 9 neighboring tiles at the point of impact remained undamaged. Thus the efficiency was 10%. After 5 hits, 2 tiles were retained but were damaged. The remaining tiles were shattered. Therefore, the efficiency was 0% after 5 hits. The GRP was badly damaged after 5 shots.

Claims

WHAT IS CLAIMED IS:

1. A multilayer complex armor comprising:

(a) hard impact layer comprised of one or more ceramic bodies; (b) vibration isolating layer; and

(c) a backing layer comprised of a rigid material; wherein the portion of said vibrating isolating layer at or about the surfaces thereof have flexural modulus equal to or greater than about 0.01 msi, an elongation to break equal to or less than about 40% and a fracture roughness equal to or greater than about 1 MPa.m^{1 2}, and wherein the portion of said vibration isolating layer at or about the center thereof has an energy-to-break of at least about 8 joules/grams.

2. The armor of claim 1 which further comprises a cover layer and a release layer, said release layer being in contact and attached to said hard impact layer opposite to the side thereof attached to said vibration isolating layer, and said cover layer in contact with and attached to said release layer on the side opposite to the side thereof attached to and in contact with said hard impact layer.

3. The armor of claim 1 which further comprises: (a) peripheral retaining means position about and in contact with the periphery of said hard impact layer; and

(b) ceramic body retaining means comprising a net work of interconnecting walls positioned about the periphery of each of the ceramic bodies comprising said hard impact layer.

4. The armor of claim 1 wherein said hard impact layer is segmented and comprises a plurality of ceramic bodies.

5. The armor of claim 1 wherein the area of the surface of said vibration isolating layer covered by said ceramic bodies is equal to or greater than about 95 area percent of said vibration isolating layer based on the total surface area of said vibration isolating layer.

6. The armor of claim 1 wherein said vibration isolating layer comprises a network of fibers having a tenacity equal to or greater than about 20 grams/denier (g/d) , a tensile modulus equal to or greater than about 500 g/d and and energy-to-break equal to or greater than about 15 joules/gram (j/g) .

7. The armor of claim 6 wherein said vibration isolating layer comprises two or more sheet-like fiber arrays in which said fibers in each array are arranged substantially parallel to one another along a common fiber direction in a polymeric matrix, and in which adjacent arrays are aligned at an angle with respect to said common fiber direction.

8. The armor of claim 7 wherein said adjacent arrays are aligned 0°/90° with respect to said common fiber direction.

9. The armor of claim 6 wherein said network of fibers comprises a non-woven fabric.

10. The armor of claim 1 wherein the % efficiency of shock absorbance of said armor is at least about

95%.