Title:
POLYMER AND BLOCK COPOLYMER, CERAMIC COMPOSITE ARMOR SYSTEM
Kind Code:
A1


Abstract:
Modern military operations, technology-driven war tactics and techniques, and availability of newly developed, current and surplus military ammunition necessitate the development of advanced ballistic protection for body armor, vehicle, vessel and aircraft systems that are damage-resistant, flexible, lightweight, capable of defeating multiple threats, while providing substantial energy absorbing capacity. A number of studies related to new technology concepts and designs of body armor materials (including those derived from or inspired by nature) have been conducted in the last decade to forge an attempt at meeting such demands. Ballistic textiles, ceramics, and laminated composites are among the leading materials used in modern body armor designs, and nano-particle and natural fiber filled composites are candidate materials for new-generation armor systems. Properties and ballistic resistance mechanisms of such materials have been extensively investigated, however, polymeric improvements have had limited scope and ceramic/polymer structured architectures have not been explored. The combination of these materials in an armor composite system with the high impact properties of ceramics and the extreme viscoelastic properties of polymers, would out-perform any of today's current lightweight rigidized polymeric systems, while maintaining superior lightweight ballistic and fragmentation performance capabilities as compared to the latest state-of-the-art lightweight ceramic glass and/or textile resin composite systems.



Inventors:
Neal, Murray L. (Missoula, MT, US)
Application Number:
14/212386
Publication Date:
09/10/2015
Filing Date:
03/14/2014
Assignee:
PHOENIX ARMOR, LLC
Primary Class:
International Classes:
F41H5/04
View Patent Images:
Related US Applications:



Primary Examiner:
WEBER, JONATHAN C
Attorney, Agent or Firm:
Whitley Legal Group, P.C. (Scottsdale, AZ, US)
Claims:
What is claimed is:

1. An apparatus for use in an armor system comprising: a plurality of discs or tiles, each of the plurality of discs or tiles having a strike face and a non-strike face connected by lateral sides; and a polymeric body wrap coupled to the non-strike face of each of the plurality of discs or tiles.

2. The apparatus of claim 1 wherein each of the plurality of discs or tiles comprise a ceramic material.

3. The apparatus of claim 1 wherein each of the plurality of discs or tiles comprise a polymeric material.

4. The apparatus of claim 1 wherein each of the plurality of discs or tiles comprise a ceramic and a polymer composite material.

5. The apparatus of claim 1 wherein each of the plurality of discs are discus shaped discs.

6. The apparatus of claim 1 wherein at least one of the strike face or the non-strike face is a non-planar surface.

7. The apparatus of claim 1 wherein at least one face of the plurality of discs or tiles is planar.

8. The apparatus of claim 1 further comprising: a glass fiber wrap coupled to the strike face of each of the discs or tiles.

9. The apparatus of claim 7 wherein the polymeric body wrap is coupled to only the non-strike face and the lateral sides of each of the discs or tiles and the glass fiber wrap is coupled to only the strike face.

10. The apparatus of claim 7 wherein the glass fiber wrap completely encases the discs or tiles and the polymeric body wrap is wrapped only around portions of the glass fiber wrap covering the non-strike face and the lateral sides.

11. The apparatus of claim 7 wherein the glass fiber wrap completely encases the discs or tiles and the polymeric body wrap completely encases the glass fiber wrap.

12. The apparatus of claim 1 further comprising: a titanium encasement wrap coupled to the polymeric containment wrap.

13. The apparatus of claim 2 wherein the ceramic material is selected from the group consisting of aluminum oxide, silicon carbide, silicon nitride, boron carbide and titanium diboride.

14. The apparatus of claim 1 wherein the polymeric body wrap is a matrix-reinforced polymeric composite material.

15. An apparatus for use in an armor system comprising: a plurality of discs or tiles comprising a polymer composite material; and a containment wrap coupled to each of the plurality of discs or tiles.

16. The apparatus of claim 15 wherein the polymer composite material is a ceramic and polymer bonded material.

17. The apparatus of claim 15 wherein the containment wrap comprises a titanium material completely encasing each of the plurality of discs or tiles.

18. A body armor comprising: a plurality of discs or tiles; a plurality of polymeric body wraps, each wrap at least partially encasing one of the discs or tiles; and a substrate coupled to the encased discs or tiles to retain the discs or tiles in a fixed pattern.

19. The apparatus of claim 18 wherein each of the plurality of discs or tiles comprise a ceramic material.

20. The apparatus of claim 18 wherein each of the plurality of discs or tiles comprise a polymeric material.

21. The apparatus of claim 18 wherein each of the plurality of discs or tiles comprise a ceramic and a polymer composite material.

22. The apparatus of claim 18 wherein each of the plurality of discs are discus shaped discs.

23. The apparatus of claim 18 wherein at least one face of the discs or tiles is a non-planar surface.

24. The apparatus of claim 18 wherein at least one face of the plurality of discs or tiles is planar.

25. The apparatus of claim 18 further comprising: a glass fiber wrap coupled to a face of each of the discs or tiles.

26. The apparatus of claim 25 wherein the polymeric body wrap is coupled to only a non-strike face and lateral sides of each of the discs or tiles and the glass fiber wrap is coupled to only a strike face.

27. The apparatus of claim 25 wherein the glass fiber wrap completely encases the discs or tiles and the polymeric body wrap is wrapped only around portions of the glass fiber wrap covering a non-strike face and lateral sides of the discs or tiles.

28. The apparatus of claim 25 wherein the glass fiber wrap completely encases the discs or tiles and the polymeric body wrap completely encases the glass fiber wrap.

29. The apparatus of claim 18 further comprising: a titanium encasement wrap coupled to the polymeric containment wrap.

30. The apparatus of claim 19 wherein the ceramic material is selected from the group consisting of aluminum oxide, silicon carbide, silicon nitride, boron carbide and titanium diboride.

31. The apparatus of claim 18 wherein the polymeric body wrap is a matrix-reinforced polymeric composite material.

32. The apparatus of claim 18 wherein the fixed pattern is an imbricated pattern.

33. The apparatus of claim 18 wherein the fixed pattern is a mosaic pattern in which the discs or tiles are laid out in a side-by-side pattern.

34. A method of making a body armor comprising: providing a plurality of discs or tiles, wherein each of the discs or tiles are either encased within a polymeric containment wrap or formed by a polymeric material; laying out the plurality of discs or tiles in a fixed pattern on a substrate; and adhering the substrate to a first side of the discs or tiles.

35. The method of claim 34 wherein the fixed pattern is an imbricated pattern comprising overlapping each disc or tile upon a successive disc or tile so that each disc or tile tilts from a horizontal plane defined by the substrate.

36. The method of claim 34 wherein the fixed pattern is a mosaic pattern comprising each disc or tile arranged in a side by side configuration.

37. An apparatus for use in an armor system comprising: a plurality of discs or tiles, each of the plurality of discs or tiles having a strike face and a non-strike face connected by lateral sides; and a body wrap coupled to the non-strike face of each of the plurality of discs or tiles.

38. The apparatus of claim 37 wherein the plurality of discs or tiles comprise one of a functionally graded material (FGM) and polymeric construction, cermet and polymeric construction, encapsulated ceramic-polymeric construction, encapsulated ceramic-polymeric-metal construction, encapsulated polymeric construction, solid polymeric composite, a solid polymeric ceramic induced constituent composite, a nano-ceramic or a nano-composite with matrices and filler materials.

39. The apparatus of claim 37 wherein the body wrap comprises a textile wrap material selected from the group consisting of aramids, para-aramids, carbon fiber, glass fiber, polyethylene fabrics carbon fibers, woven stainless steel textile, woven non-magnetic nitinol textile, E-Glass, S2 glass, and nano-infused aramid.

Description:

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a non-provisional patent application that claims the benefit of the filing date of, and priority to, U.S. Provisional Application No. 61/784,872, filed Mar. 14, 2013, the entirety of which is incorporated herein by reference.

FIELD

The invention relates to protective armor systems. More specifically, the invention relates to armoring systems suitable for body armor; and armoring vehicles, vessels, and aircraft, designed from polymer and block copolymer composite ceramic armor technologies.

BACKGROUND

There has been and the need will always be there for reduced weight for rifle, heavy machine gun (HMG), and 20 mm to 30 mm cannon threat defeating ballistic and fragmentation resistant armor products, utilized in body armor and light weight rigid armor applications for vehicles, vessels and aircraft applications, while increasing the ballistic and fragmentation performance threat defeating terminal impact capabilities of the specific components and ultimately complete composite armor systems.

Several additional material substrate compositions have been identified in this invention that have a substantial potential for weight reductions of such ballistic and fragmentation resistant defeating armor systems, while maintaining other physical and mechanical performance enhanced attributes and increased capabilities.

However, one of the most promising, and currently within technological reach is the utilization of polymeric compositions used in combination with ceramics and/or titanium for reduced weight without the sacrifice of rifle, HMG and 20 mm to 30 mm cannon defeating ballistic performance capabilities, and the secondary fragmentation and shrapnel resistance performance capabilities. The most severe threats being the multi-purpose high explosive (HE) HMG and 20 mm to 30 mm cannon projectiles which detonate upon impact.

The ability to have such a defeat capable armor technology system, with a reduced areal density below the current state-of-the-art systems, while gaining specific ballistic and/or fragmentation resistant performance capabilities, is paramount. The past has shown that in order to achieve reduced weight in an armor system there has always been a need to either reduce the performance capabilities of that armor system and/or the amount of protective armor fielded. That dilemma has now been surmounted.

A composite armor solution is a complex armor system comprised of several, uniquely different materials configured into a specific architecture, which forms a non-homogeneous single source armor material. This hybridized combining of multiple constituent materials can often have the physical and mechanical attributes of a homogeneous system or act uniquely different with attributes not fully sustainable in a homogeneous armor system. A truly refined and optimized composite system can be “tuned” to meet multiple threat resistance performance capabilities. More than a fundamental requisite understanding of material science such as the physical and mechanical properties, and the finite analysis of each constituent material, is necessary to link the specific material properties to the actual behavior of the materials independently or as an entire system is required.

Most armor systems are not well designed in that they are generally constructed then tested, then modified and tested again, often numerous times until some acceptable result is acquired. This does not provide any understanding to the constituent materials, let alone a composite system and the interactive attributes either positive or negative and their cumulative performance capabilities, let alone any “tunable attributes”, given that composite armors are rate dependent constructions with often varied architectures, adhesion, cohesion bonding influences, constituent glass transition phases, and mechanical impedance coupled with extensional wave transfers.

A current typical ceramic composite armor system for the use in body armor and transport armor applications providing protection from small arms threats to HMG threats, predominantly include a ceramic component backed by a fiber reinforced polymer matrix composite component, or an all aramid, polyethylene or combined textile composite (hybrid) polymer matrix textile backing component.

The system that surmounts these is the (Dragon Skin®) armor technology system. This technology has been seen as the forerunner in what is defined as a scaled lamellar design often referred to as the first biologically inspired modern armor technology.

This technology has provided the following eleven enhanced physical and mechanical attributes and increased capabilities not associated with any currently manufactured and deployed armor systems. These attributes are listed as currently employed in a flexible rifle defeating body armor system, but with the exception of flexibility in varied applications, these attributes also lend themselves to vehicle, vessel and aircraft rigidized applications. Additionally, these attributes have been substantiated by the U.S. Army Research Laboratories (ARL) and the Defense Science Testing Laboratory in the United Kingdom (DSTL).

1. Weighs Less

The Dragon Skin® technology's flexible rifle defeating body armor has the lightest weight for the ballistic and fragmentation protection capabilities provided. No other technology has the protection (coverage and impact capabilities) that the Dragon Skin® technology provides. Less Weight=Greater comfort+Increased Mobility=Increased Soldier Survivability.

2. Increased Multiple Repeat Hit Capability

The Dragon Skin® technology can sustain greater amounts of impacts than current monolithic ceramic plate technologies affording increased soldier survivability. Increased Hit Capability=Longer or Multiple Mission Soldier Survivability.

3. Less Trauma (Backface Signature)

The Dragon Skin® technology has demonstrated 52-64% reduction in average back face deformation/signature (reduced trauma to the body). This means the wearer can take multiple hits on the vest and keep fighting effectively. This aspect, by itself, is incredibly important, especially in urban warfare and CQB (Close Quarters Battle) scenarios. Less Trauma=Soldier Mission Sustainability.

4. Increased Flexibility

The Dragon Skin® technology has flexible mobility. This flexible mobility increases the comfort and mobility of the wearer. The flexible configuration of the imbricated discs architecture provides the flexibility to bend this technology in all directions, and to twist the armor in opposing directions, thereby, allowing the wearer to move with greater ease decreasing the level of energy required to move. Less Energy+Greater Comfort=Less BTU's=Cooler Soldier.

5. Increased Durability

The Dragon Skin® technology has a substantial increase in durability as compared to the monolithic ceramic plate technology. Less Subject to Damage=Longer Service Life=Less Life Cycle Costs.

6. Edge Hit Capability

The Dragon Skin® technology has demonstrated reduced edge affected zone increasing effective area of coverage provided by the ceramic discs. Increased edge hit capability=increased protection.

7. Greater Coverage

The Dragon Skin® technology offers vastly greater amounts of coverage options. It is the first body armor system that can be tailored to be mission specific, up to covering the entire torso. This is especially needed in a heavily IED or VBIED laden battlefield. Greater Coverage=Increased Soldier Survivability.

8. Reduced Ricochet Threat

The Dragon Skin® technology has shown to eliminate ricochets from obliquity/angled shots up to 60°. The rigid plates have ricochet shots starting at approximately 32°-35°. This too increases soldier survivability by reducing the probability of one soldier being shot and the projectile ricocheting off him and into the next soldier injuring or fatally wounding him/her. Reduced Ricochet=Less Collateral Injuries.

9. Fit Flexibility

The Dragon Skin® technology is tailor-able for both male and females to the 97 percentile. It can be used not only in a tactical configuration but also in concealed variants for both genders. Greater Tailor-ability=More Soldiers Provided Adequate Armor Protection.

10. Increased Projectile Diversity

The Dragon Skin® technology defeats the compendium of projectile threats faced world-wide as threats to the military, not just regional threats per engagement. The military is deployed world-wide and so too should their armor have the ability to defeat all known projectiles within a specific threat category in both current and past conflict circulation, at and above muzzle velocity, not just a select few threats based on a single area of operation. Increased Projectile Diversity=Less Costs for Multiple Threat Resistant Systems=Fewer Dollars Spent.

11. Eliminate Ballistic Shatter-Gap Phenomenon

The Dragon Skin® technology due to its architecture and configurational design, eliminates the shatter-gap ballistic failure phenomenon exhibited in monolithic tile and plate ceramic armor composites. The elimination of ballistic failure mechanisms inherent in these types of armor composites, bridges a substantial life threatening capability hole in current ceramic body armor composite systems. Increased physical and mechanical material properties=increased Soldier Survivability.

SUMMARY

An armoring system for body armor; and armoring vehicles, vessels, and aircraft. A composite armoring architecture consisting of a plurality of discus-shaped discs or tiles with or without a flat planular surface or surfaces, which are individually wrapped in a textile and/or titanium containment wrap and encased within a polymeric substrate; or solely encased within a polymeric substrate; or comprised as a constituent component within a solid polymeric substrate, or encased within a titanium exterior wrap. These polymeric substrates are to have exceptionally high impact properties that absorb energy when subjected to high stress impact induced compressive shock loading before fracture, thereby increasing tensile elongation through its physical viscoelastic properties. Then such architectures are either laid out in a mosaic side-by-side single or multiple row pattern; or an imbricated pattern row by row such that each disc in a row is in substantially a straight line with other discs in the row and overlaps a segment of a disc in an adjacent row. The mosaic or imbricated pattern is then adhered to a flexible high tensile strength substrate and overlaid by a second high tensile strength layer such that the mosaic or imbricated pattern is enveloped between the substrate and the second layer. A second embodiment arranges the mosaic juxtaposed in a side-by-side pattern into a polymeric configuration that encapsulates the entire mosaic tiled arrangement.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments disclosed herein are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and they mean at least one.

FIG. 1 illustrates the encapsulation of a ceramic core with a titanium FGM shell.

FIG. 2 illustrates a cross-sectional side view of one embodiment of a composite disc.

FIG. 3 illustrates a cross-sectional side view of one embodiment of a composite disc.

FIG. 4 illustrates a cross-sectional side view of one embodiment of a composite disc.

FIG. 5 illustrates a cross-sectional side view of one embodiment of a composite disc.

FIG. 6 illustrates a cross-sectional side view of one embodiment of a composite disc.

FIG. 7 illustrates a cross-sectional side view of one embodiment of a composite disc.

FIG. 8 illustrates a cross-sectional side view of one embodiment of a composite disc.

FIG. 9 illustrates a cross-sectional side view of one embodiment of a composite disc.

FIG. 10 illustrates a cross-sectional side view of one embodiment of a composite disc.

FIG. 11 illustrates a cross-sectional side view of one embodiment of a composite disc.

FIG. 12 illustrates a cross-sectional side view of one embodiment of a composite disc.

FIG. 13 is a perspective view of one embodiment of a non-flat planar disc.

FIG. 14 shows a side view of another embodiment of a flat planar disc or tile.

FIG. 15 is a perspective view of a disc of an alternative embodiment of the invention.

FIG. 16 is a side view of the alternative embodiment shown in FIG. 15.

FIGS. 17A-17C illustrate one embodiment of a tile that may be used according to the instant invention.

FIGS. 18A-18C illustrate one embodiment of a tile that may be used according to the instant invention.

FIGS. 19A-19C illustrate one embodiment of a tile that may be used according to the instant invention.

FIGS. 20A-20C illustrate one embodiment of a tile that may be used according to the instant invention.

FIGS. 21A-21C illustrate one embodiment of a tile that may be used according to the instant invention.

FIGS. 22A-22C illustrate one embodiment of a tile that may be used according to the instant invention.

FIGS. 23A-23C illustrate one embodiment of a tile that may be used according to the instant invention.

FIGS. 24A-24C illustrate one embodiment of a tile that may be used according to the instant invention.

FIGS. 25A-25C illustrate one embodiment of a tile that may be used according to the instant invention.

FIGS. 26A-26C illustrate one embodiment of a tile that may be used according to the instant invention.

FIG. 27 shows an imbricated pattern of discs coupled to a substrate.

FIG. 28 is a frontal view of one embodiment of a body armor vest within which discs or tiles may be integrated.

FIG. 29 is a cutaway frontal view of one embodiment of a suit of body armor.

FIG. 30 illustrates one embodiment of a mosaic tile pattern.

FIG. 31 illustrates one embodiment of an imbricated tile pattern.

FIG. 32 illustrates one embodiment of an imbricated disc pattern.

FIG. 33 illustrates one embodiment of an imbricated tile pattern.

FIG. 34 illustrates one embodiment of an imbricated tile pattern.

FIG. 35 illustrates one embodiment of an imbricated tile pattern.

FIG. 36 illustrates a perspective view of one embodiment of a tile.

FIG. 37 illustrates a top plan view of one embodiment of a tile.

FIG. 38 illustrates one embodiment of an imbricated tile pattern.

FIG. 39 illustrates one embodiment of an imbricated tile pattern.

DETAILED DESCRIPTION

In this section we shall explain several preferred embodiments with reference to the appended drawings. Whenever the shapes, relative positions and other aspects of the parts described in the embodiments are not clearly defined, the scope of the embodiments is not limited only to the parts shown, which are meant merely for the purpose of illustration. Also, while numerous details are set forth, it is understood that some embodiments may be practiced without these details. In other instances, well-known structures and techniques have not been shown in detail so as not to obscure the understanding of this description.

Several specific processes occur during the terminal ballistic event/impact of such a rifle, heavy machine gun and 20 mm to 30 mm cannon defeating threat armor systems:

1. The projectile impacts the strike face of the armor system imparting its kinetic energy onto and through the surface of the armor system.

2. A shock wave (extensional shock wave transfer) is generated through each of the two primary component mediums; in the ceramic strike face and through the balance of the composite component behind the ceramics, the shock wave creates compressive, tensile and shear stresses.

3. These stresses in the ceramic component, usually create a circumferential (cone shape “conoidal shaped area”) crush zone with radial tensile fracturing cracks propagating outward from the epicenter of the impacting projectile. The size of the crush zone, combined with the quantity, depth, and widths of these tensile stress propagated cracks are dependent upon the shape and configurational design of the strike face component.

4. The ceramic will impart a specific amount of stress directly upon the projectile. The type and amount of stress is dependent upon the shape and configurational design of the strike face component. The greater the dwell time or the time that the projectile resides upon the surface of the armor before it breaches the surface, the greater the type and amount of imparted stresses there will be on the projectile.

5. The projectile is deformed, shattered and/or eroded, thereby dumping mass and reducing the amount of further energy transfer into the armor system.

6. The projectile and or its fragments may continue to penetrate through the ceramic component of the composite armor system.

7. The projectile or fragments of both the projectile and the ceramic component may enter into the composite backing directly behind the ceramic and are stopped within it.

8. Projectile impact and momentum energy is transferred through the armor resulting in a rearward deformation or bulge of the rear surface of the armor, created in the process of energy accumulated through the various armor system projectile defeat mechanisms. This bulge or deformation is often referred to as either “Behind Armor Blunt Trauma”, “Backface Signature” (BFS) or “Backface Deformation” (BFD), and will either stay deformed in a rearward parabolic shape in the case of a matrix composite or will stay pliable and slightly return back towards its original shape in the case of a flexible textile only backing. The latter is more preferable due to a wearer's perspective utilizing body armor, as it will not maintain that rearward bulge into the body subsequent to the impact. This rearward bulge if rigid can further cause irritation of the bruised area of the torso, if required to be worn for protection subsequent to impact. In vehicle, vessel and aircraft applications, appropriately selected matrix materials inducing rigidity will preclude obstructing or damaging mechanical, electrical, or hydraulic mechanisms, wires, or fluid transport lines.

Based upon the varied projectile design parameters, it is necessary to understand the specific criteria behind the design of projectiles whose sole purpose is the defeat of armor systems, these would be considered armor piercing projectiles. There are four (4) primary armor piercing projectile design constraints that attribute to the defeat of an armor. These are the projectiles velocity, the density or weight of the projectile material(s), the design geometry of the projectile, and the strength of the projectile material composition.

There is a descending order of importance of these projectile design attributes, though, and their importance on armor defeat. These are based solely on overmatch proficiencies of the projectile. The first most important aspect would be the material strength which is the parameter that permits the projectile to maintain the designed armor piercing shape during the penetration process. Then, the geometry takes the forefront, which represents the aspect ratio of the projectile and the meplat and ogive regions of the projectile. The first two are important until the armor material to be defeated matches or is stronger than the strength and geometry of the projectile. At that point the last two attributes step up, velocity and density. Velocity generally can overmatch an armor system provided that there is sufficient mass to aid in imparting kinetic energy displacement into the armor material to be penetrated. Exothermic heat transfer produced by the projectiles impact also aids substantially in the armor systems mechanical failure due to entropy.

Concepts—There are at least seven different synthesized manufacturing and processing concepts/embodiments that do work for the hybridized composite armor component as described in this invention. These resultant designs will provide for a lighter weight composite armor system that will maintain the superior proven performance capabilities of the Dragon Skin® technology armor system or other tile/plate technologies through the use of synthesized polymeric reinforcement to reduce the amount of ceramic and/or textile backing materials required to defeat the threats. The resultant armor design and composite configurations will be lighter in weight.

These are: Functionally graded material (FGM) and polymeric construction; Cermet and polymeric construction; Encapsulated ceramic-polymeric construction; Encapsulated ceramic-polymeric-metal construction; Encapsulated polymeric construction; Solid polymeric composite, solid polymeric ceramic induced constituent composite.

Functionally graded material (FGM) composite compositions consist of microstructurally engineered gradual transitions in microstructures and/or compositions of two or more materials. The material compositions and material properties transition gradually, rather than abruptly, from one end-phase material to another end-phase material. Therefore, there is a gradual, rather than abrupt interface between the two end surfaces of each material.

The foundation of the FGM is the graded porosity ceramic strike face, which is fully densified with little or no substantiated open porosity on the strike face and then gradually changing into an open porosity surface on the rear face of the ceramic. Polymers or metals are then infiltrated into the porous side of the ceramic disc to provide a lightweight energy absorbing backing material.

The finished tile or disc will consist of a very hard, dense and fracture tough ceramic strike face that will initiate the destruction of the projectile upon impact, and then provide a gradual transition to the tough ductile polymer and/or metal material that finalizes the energy absorption and fragment retention of the projectile jacket and core compositions through the encapsulating containment process. This too aids in attenuating and absorbing the resultant energy, extensional shock wave propagation transfer, and resultant backface deformation of the armor system.

This gradual method of providing a transitional interface also aids in the preclusion of extensional shock wave transfer collision between the outbound and inbound paths at the two dissimilar material boundaries. This is crucial in providing an armor system that has sustainable survivability from multiple repeat impacts, and precludes additional tensile stress fracturing of the ceramic component.

The final added benefit would be the built-in frontal, rearward and lateral constraint which would enhance in retarding and containment of the ceramic dilatancy as illustrated in FIG. 1.

FIG. 1 shows the encapsulation of a ceramic core with a titanium shell. This design can be conducted through a modified FGM process, cermet process or an adhesive applied and welded application.

A cermet is a composite material composed of ceramic (cer) and metallic (met) materials. A cermet is ideally designed to have the optimal properties of both a ceramic, such as high temperature resistance and hardness, and those of a metal, such as the ability to undergo plastic deformation. The metal is used as a binder for an oxide, boride, or carbide. Generally, the metallic elements used are nickel, molybdenum, and cobalt. Depending on the physical structure of the material, cermets can also be metal matrix composites, but cermets are usually less than 20% metal by volume.

Ceramic/Polymer bonded composition, & solid polymer composition. This does offer the best of a polymer technology combined with the attributes of ceramics. This is currently in the compositional optimization process with the ceramic disc configurations of one embodiment. Various reinforced disc configurations are illustrated in FIGS. 2-12.

NOTE: The drawings provided herein are not to scale, and are for visual representations of constituent component configurations for the disc shaped ceramics of one embodiment of this invention.

FIG. 2 illustrates a cross-sectional side view of one embodiment of a composite disc. This is a ceramic disc with an E-glass wrap on the strike face of the ceramic disc and a polymer body wrap from the lateral sides through to the rear containment in a single unitized configuration.

FIG. 3 illustrates a cross-sectional side view of one embodiment of a composite disc. This is a ceramic disc with an E-glass wrap on the front, rear and sides of the ceramic and a polymer body wrap from the lateral sides through to the rear containment in a single unitized configuration.

FIG. 4 illustrates a cross-sectional side view of one embodiment of a composite disc. This is a ceramic disc without an E-glass wrap on the ceramic disc and a complete polymer body encasement.

FIG. 5 illustrates a cross-sectional side view of one embodiment of a composite disc. This is a ceramic disc with an E-glass wrap on the front, rear and sides of the ceramic disc and a complete polymer body encasement.

FIG. 6 illustrates a cross-sectional side view of one embodiment of a composite disc. This is a ceramic disc with an E-glass wrap on the front, rear and sides of the ceramic disc and a polymer body wrap with a titanium encasement.

FIG. 7 illustrates a cross-sectional side view of one embodiment of a composite disc. This is a ceramic disc without an E-glass wrap on the ceramic disc and a complete polymer body surround with a titanium encasement.

FIG. 8 illustrates a cross-sectional side view of one embodiment of a composite disc. This is a ceramic disc with an E-glass wrap on the front, rear and sides of the ceramic disc and a complete polymer body surround with a titanium encasement.

FIG. 9 illustrates a cross-sectional side view of one embodiment of a composite disc. This is a solid polymer disc with a titanium encasement on the front, rear and sides of the polymer disc.

FIG. 10 illustrates a cross-sectional side view of one embodiment of a composite disc. This is a solid polymer disc without any encasement on the front, rear and sides of the polymer disc.

FIG. 11 illustrates a cross-sectional side view of one embodiment of a composite disc. The disc of FIG. 11 is a composite disc made of a ceramic and a polymeric material without any encasement.

FIG. 12 illustrates a cross-sectional side view of one embodiment of a composite disc. The disc of FIG. 12 is a composite disc made of a ceramic and a polymeric material with a titanium encasement on the front, rear and sides of the disc.

Ceramic Substrate Attributes

Fracture at high strain rates is another seriously important consideration in armor penetrator and armor performance capabilities. Although fracture is generally detrimental to armor penetrators, certain types of armor may, in fact, turn a fracture event into an advantage.

For example, ceramic armors can be designed into a system that will provide for an allowance of fracturing through controlled dilatancy, i.e., the ceramic's tendency to readily expand into any free volume when fractured. A critical factor in this process is the method with which the material expansion is controlled and/or confined. The effect of containment on dilatancy can easily be demonstrated by using rice to represent the ceramic armor and a pencil to represent the projectile. The rice depicts unevenly shaped fractured ceramic pieces. If a pencil is pressed down into a beaker filled with rice, resistance against the pencil is low. As the pencil is pushed down farther into the beaker, the rice continues to move around and away from the pencil by moving into the unoccupied space provided by the beaker. This space is upward toward the top of the beaker, and through voids between unevenly filled and distributed rice orientation within the beaker.

However, if the rice is confined to a flask with a narrow neck, the resistance to the pencil will be much greater as the rice is unable to quickly move out of the way of the pencil. This is due to the bottle-necked restriction of the flask. The free volume for expansion has now been mitigated allowing for a greater resistance to the pencil. Controlling the fractured ceramic pieces in armor further confines the ceramic and only allows for the coarse highly abrasive ceramic to grab against the penetrator, thereby reducing its ability to effectively penetrate through a combination of the resistance, hardness, strength, and friction associated with the abrasiveness of the ceramic material. This further works against the penetrator to aid in erosion of the core, and allowing for the angle of incidence relative to impact, to change upon the projectile core through the penetration phase. Typically, unconstrained ceramic armors simply blow away on impact with little or no abrasive and destructive effect on the projectile. However, a properly designed armor system that totally constrains any fractured ceramic material will provide for continued resistance to that projectile as highly erosive ceramic particles are precluded from separating a great distance and grind at the sides of the projectile eroding it and its energy.

The extremely hard, strong, and tough AP penetrators combined with their mass and velocity, always impart higher dilatancy rates than other types of bullet configurations. Containing and controlling the ceramic dilatancy is the primary part of the essential mechanics of dwell and interface defeat—the phenomenon where an impacting projectile flows radially outward (erodes) along the surface of the target without significant penetration. During dwell, the projectile loses kinetic energy due to mass loss and deceleration.

This pre-penetration phase delineates a series of events from the initial interactions of the projectile and the ceramic facing component of the armor system prior to the projectile actually entering into the ceramic. During this phase the high hardness of the ceramic overmatches the impact load of the projectile and its material composition, which in turn causes the projectile to dwell upon the surface of the ceramic creating disintegration of the projectile's meplat, jacket and ogive section of the core.

This initial disintegration and/or comminuted damage of the projectile is directly related to the impact stress loads applied to the projectile from the impact which in turn leads to the erosion, fracture, and subsequent brittle fracture shattering and/or core component separation, and the pulverization of the meplat.

The time history of this pre-penetration phase ranges roughly from 0 to 10 milliseconds before the projectile starts to enter through the surface of the ceramic as the hardness and fracture toughness stress capabilities of the ceramic is exceeded and the material failure phase starts with the remaining penetration transition velocity of the projectile core.

The Armor and projectile material failure phase starts roughly from 10 milliseconds and goes through approximately 18 milliseconds. This phase defines the exact condition of the penetrator as a result of dwell time resistance that leads to the eroding, fracturing and core component shattering and/or separation. Additionally, this defines the ceramic armor and its ability to attenuate and absorb the projectile momentum and energy while maintaining its integrity to resist tensile damage while grossly limiting compressive damage through a delayed mechanism and to increase the dwell and lateral shear stress applied to the penetrator core. The ceramic/polymeric composite armor listed in various embodiment's of this invention deals with each of these as a multi-phased component.

However, another problem facing armor designers is weight. Ultimately, high threat-defeating body armor may become too thick and heavy in which to move. As a result, there is a need for body armor systems that are thin and light, but difficult to penetrate. Current fielded systems employ ballistic/fragmentation soft textile-grade fabrics that have rifle-defeating upgrade monolithic plate(s) attached to or mounted in front of the textile armor panels. There is very limited flexibility surrounding the plates, and it is important to note that this limited flexibility around the plate is often in areas that the body generally does need to bend or twist. The areas of plate insertion or addition can be as thick as 1.250″/31.75 mm to 2.0″/50.8 mm depending upon the composition of the plate, in addition to the textile portion of the vest. This precludes the wearer from various types of activities often encountered during deployment, such as rappelling, fast roping, climbing, underwater diving, running, entering or exiting vehicles, etc.

One approach to weight reduction is the modified use of ceramics, which can provide exceptional protection for very lightweight (compared to various metallic) configurations and densities.

Ceramics have been developed with exceptional hardness, upwards of RC65, a prerequisite to initiating bullet/projectile deformation and/or destruction. Some of the relevant ballistic-grade opaque ceramic materials are aluminum oxide (Al2O3), silicon carbide (SiC), silicon nitride (Si3N4), boron carbide (B4C), and titanium diboride (TiB2), and sialon a high temperature refractory ceramic with high strength, fracture toughness, and increased hardness, in all three phases—α (MexSi12-(m+n)OnN16-n), β (Si6-zAlzOzN8-z), and the gradient α/β where there is a higher concentration of harder a phase on the strike face region and the softer β phase in the central region, exhibiting higher fracture toughness; all of which have high hardness with an associated abrasiveness, high compressive and tensile strengths, and good elastic properties to high stress values. Additionally, hybridized ceramic compositions of boron carbide with silicon carbide, or sialon with silicon carbide are just two more examples of applicable ceramic compositions capable for utilization within the scope of this invention.

Compared to metals, opaque or transparent ceramics have the following relative characteristics:

    • brittleness,
    • high strength and hardness, especially at elevated temperatures,
    • high elastic modulus,
    • low toughness, and
    • density and thermal expansion.

However, due to the wide variety of ceramic material compositions (inclusive of constituent enrichment minerals/materials for increased physical and mechanical properties), and grain sizes, the mechanical and physical properties of ceramics vary significantly. Ceramics are inherently sensitive to flaws, defects, surface or internal cracks, different types and levels of impurities, porosity, and manufacturing processes, and can have a wide range of properties. Such inherently adverse characteristics can, however, be manipulated through various manufacturing processes to bring the physical and mechanical properties in line with the requisite requirements necessary for ballistic resistance at a substantially low areal density. Ceramic composites will, for the most part, be somewhat thicker as compared to most metallurgical armor systems in the final configuration when coupled with the appropriate fracture control material backings, etc.

Two of the prime advantages of the use of ceramics over other materials are the extreme hardness and light weight.

Associated ballistic-grade ceramic types and their approximate weight differences are:

Material Characteristics

Aluminum Oxide—Al2O3 Primary ballistic-grade opaque ceramic; least manufacturing cost; approximate density 3.4-3.6 g/m3.
Silicon Carbide—SiC approximate density 3.1 g/m3.
Silicon Nitride—Si3N4 approximate density 3.2 g/m3.
SiC/B4C composite hybrid ˜12% lighter than SiC or Si3N4
Boron Carbide—B4C approximate density 2.34 g/m3.
Titanium Diboride—TiB2 approximate density 4.52 g/m3.
Alon—AL23O27N5 approximately 3.69 g/m3
α Sialon—MexSi12-(m+n)OnN16-n, Y0.4Si9.6Al2.4O1.2N14.8, CaxSi12-3xAl3xOxN16-x, others not presented for brevity, approximately 2.53-3.26 g/m3
βSialon—Si6-zAlzOzN8-z, Si5.55Al0.45O0.45N7.55, others not presented for brevity. approximately 2.53-3.26 g/m3
Saphire—AL2O3 approximately 3.97 g/m3
Spinel—MgAl2O4 approximately 3.59 g/m3

Limited gains have been achieved utilizing silicone carbide, however, the technology has reached a point where the offset gains are better than the standard increased areal density ballistic grade ceramics, but all six opaque types, and all four transparent types should be considered for a type of embodiment regarding ceramics.

Numerous advances have been achieved in reducing the areal density of ceramic composite systems. The majority of these efforts have been directed in two distinct directions: 1) synthesizing new ceramic materials with improved mechanical properties, and 2) synthesizing backing materials with increased rigidity to enhance support of the ceramic component. However, an alternative approach of reducing the areal density of a ceramic composite armor system is to utilize a ceramic/polymer structure system where the ceramic component are supported by the polymer component as opposed to a layered laminated ceramic/polymer structure such as those utilized in transparent armor applications. One of the primary advantages of such a ceramic armor system as compared to the layered laminated ceramic/polymer structure such as those utilized in transparent armor applications is its ballistic resistance performance capability to defeat such threats as the depleted uranium and tungsten heavy alloy penetrators.

Containment Substrate Attributes

Another approach to weight reduction has been the use of composite materials such as reinforcing fibers and the matrix materials utilized to form lightweight composites. These fibers are strong and stiff, and they have high specific strengths (strength-to-weight ratio) and specific stiffnesses (stiffness-to-weight ratio). The fibers by themselves have little structural value. The polymer matrix is less strong and less stiff, but it is tougher than the fibers. Reinforced polymeric resin composites possess the advantages of each of the two constituents.

The percentage of fibers (by volume) in reinforced polymers usually ranges between 10% and 60%. Practically, the percentage of fiber in a matrix is limited by the average distance between the adjacent fibers or particles. The highest practical fiber content is ˜65%; higher percentages generally result in lower structural properties.

In addition to high specific strength and specific stiffness, reinforced-polymeric composite structures have improved fatigue resistance, greater toughness, and higher creep resistance. Matrix materials are usually thermoplastics or thermosets; they commonly consist of epoxy, polyester, fluorocarbon, polyethersulfone, or silicone.

The matrix in a reinforced polymer composite has three functions:

    • to support the fibers in place and transfer the stresses to them, while they carry most of the load,
    • to protect the fibers against physical damage and the environment, and
    • to reduce the propagation of cracks in the composite, by virtue of the greater ductility and toughness of the polymer composite matrix.

The primary focus with reinforced polymers is to allow for the ductility and elongation of the fibers, while maintaining the toughness of the matrix material. This is completed with the proper selection of matrix polymeric materials that provide for the best overall performance characteristics of the total matrix constituent materials and the fibers/fabrics through controlled delamination.

Providing for a controlled delamination of woven textiles is slightly altered from that of the matrix polymeric material and is designed to aid in the composition being manufactured with very little resin matrix, which reduces weight and relies heavily upon the ultimate strengths and elongation mechanisms of the fibers/fabrics to provide for the defeat mechanism during the ballistic impact. Too much resin composite matrix inhibits the elongation requirements of the fabrics/fibers and results in poorer ballistic performance, and increased weights.

Fiber-reinforced textile armors are not limited solely to the matrix-reinforced polymeric composite designs and formulations. Aramids, para-aramids, carbon fiber, glass fiber, and polyethylene fabrics are often used in standalone configurations such as soft or hard rigid armor with ballistic resistance capabilities. Often hybridized/composite configurations are designed to have a greater penetration resistance-to-weight ratio, albeit at a higher nominal thickness than matrix reinforced composites.

The percentage of resin matrix by volume for woven materials would be from 12 to 18% for aramids, with the highest performance tested embodiment having 14.5% and from 34% to 40% with the highest performance tested embodiment having 38% for E-Glass/S2 glass configurations. These percentages are based on the materials physical and mechanical property attributes for elongation of yield through a controlled delamination.

Additional fiber/fabric materials utilized in various embodiments in addition to the aramids and para-aramids are the use of carbon fibers, woven stainless steel textile, woven non-magnetic nitinol textile, E-Glass, S2 glass; as well as nano-infused aramid, carbon fibers and para-aramid textiles, E-Glass and S2 glass.

Ceramic/Polymer Attributes

Ceramic/Polymer
Composition Type
by FigureProsCons
2Lightest Weight, Good DilatancyBiased Configuration, Disc
ControlOrientation Prerequisites,
Increased QC requirements
3Improved Dilatancy ControlBiased Configuration, Increased
Fabrication Costs, Disc
Orientation Prerequisites,
Increased QC requirements,
Increased Weight
4Lighter Weight, ReducedLimited dilatancy control,
Fabrication Costs, Reduced QCIncreased Thickness
requirements
5Improved Dilatancy Control,Increased Weight, Increased
Reduced QC requirementsManufacturing Costs
6Lighter Weight, TitaniumBiased Configuration, Disc
EncasementOrientation Prerequisites,
Increased QC requirements,
Increased Manufacturing Costs
7Better Dilatancy Control, ReducedIncreased Weight, Increased
Fabrication Costs, TitaniumThickness, Increased
EncasementManufacturing Costs
8Greatest Dilatancy Control, ReducedIncreased Weight, Increased
QC requirements, TitaniumManufacturing Costs
Encasement
9Lighter weight, TitaniumIncreased weight and
encasement, Great dilatancy controlmanufacturing costs over type 10,
increased thickness
10Lightest weight, Reduced QCLimited dilatancy control,
requirementsincreased thickness
11Lighter weight, increased coreIncreased weight over type
erosion.10, increased costs.
12Light weight, titanium encasement,Increased weight and
great dilatancy controlmanufacturing costs over type 11,
increased thickness.

Nano-Composite Attributes

Newer pretested nano-ceramics have demonstrated limited promise, as the ceramic is infused with carbon nano-materials. The long tube shaped nano-materials (CNT's) do not perform nearly as well as the “bucky-ball” shaped nano-materials. The CNT materials tend to fail in lateral shear stress instances and often pull-out under brittle facture failure like the whisker shaped E-glass, S-2 glass and aramid materials used in the reinforcing of ceramics as an aid to increasing fracture toughness. Nano infused ceramics tend to induce failure in the ceramics due to the carbonaceous defects of the nano-materials themselves which for most part are purely carbon, which in-turn directly affects the fracture path and mode of fracture morphology.

Experimental evidence shows that some nano-composites with special matrices and filler materials, and nanostructured polymeric composites have achieved significant and simultaneous improvements in stiffness, fracture toughness, impact energy absorption and vibration damping, for textile, resin, polymer and copolymer materials; and these characteristics could be of particular importance for impact energy absorption based on important influence factors, such as shape, dimension and stiffness of particles, type of matrix, particle volume fraction, distribution of particles and the particle-matrix interfacial properties. These would be useful upon full production capability for various embodiments of this invention. However, as of this application none of these has yet reached the full maturity for production, let alone finite validation of the ballistic and/or fragmentation threat resistant performance capabilities.

Polymeric Material Attributes

Amorphous polymers have been used extensively as the structural material of engineering components that are designed to resist impact, ranging from bus windows and eyeglasses to helmets and body armor. The choice of polymeric materials for these applications has been made appealing by their relative low density, as well as the transparency that is characteristic of amorphous homopolymers. Thermoplastic polymers are distinctly divided into two classes of crosslinked (non-linear), and uncrosslinked (linear). Crosslinked polymers are typically utilized as high strength or in other specialty polymers, where the uncrosslinked polymers gain their advantage through the ease of forming “moulding” configurational shapes of varying dimensions without unrealistic production costs. Crosslinking is a process by which the degree of molecular re-arrangement of molecules can be manipulated. However, transparency in a polymer for this invention is not a prerequisite. Polymers, unlike glass and ceramics, are viscoelastic materials, and exhibit strong rate-sensitivity not only in mechanical deformation, but also in failure behavior. One prerequisite for an armor system would be the nonlinear viscoelastic deformation mechanisms and the associated dynamics in polymers during and immediately following a ballistic impact. Polymers due to their viscoelastic behaviors, generate heat under cyclic deformation which raises the temperature if the rate of heat generation exceeds the heat flow to the surroundings resulting in fatigue loading failure. This characteristically high temperature sensitivity of the mechanical properties of polymers provides validation of hysteristic heating which can have a dominant effect on the failure behavior under cyclic loading. This hysteristic failure behavior can create excessive softening of the bulk material thereby ensuring failure by deformation without fracture to the result of localized heating at the tip/point of a tensile fracture or crack accompanied by a redistribution of the stresses and the complicated resultant failure mechanisms. Utilizing the ceramic constituent components to abate this hysteristic failure behavior will increase the multi-repeat hit capability of a ceramic/polymer composite architecture.

Polymers exhibit strong rate-dependent mechanical behavior and in different frequency regimes, the rate sensitivities of polymers change as various primary (α) and secondary (β) molecular mobility mechanisms are accessed. An extensional shock wave is a disturbance or oscillation that travels through a medium or multiple mediums which is accompanied by a transfer of energy, which imparts deformation in the medium. The deformation reverses itself owing to restoring forces resulting from its deformation, however, brittle media tends to degrade through brittle fracturing where ductile media tend to remain plastically deformed or regain some of the initial pre-shock induced form.

High stress induced tensile fracture/crack velocity is usually measured as a function of the stress intensity factor such as that in an elastomeric fracture, assuming a continuous fracture/crack propagation in the polymer constituent component as compared to the brittle failure response of the tensile fracture in a ceramic material. High stress induced tensile fracture/crack behavior under cyclic loads can comprise the differentiation between continuous and discontinuous propagation/growth, the effects of temperature changes, both due to the environment and the ballistic impact mechanisms themselves, the frequency of the stress applied loading and the loading range. Polymer tensile fracture/crack propagation in rigid polymers exhibit nonlinear material responses which on a macroscopic level exhibit those similar to metallic plasticity/ductility. However, metallic plasticity/ductility in contrast to elastomeric polymers, does not have a strong influence on the rate of propagation/growth per cycle unless it is so high that dissipative heating performs a distinct role. Fracture/crack velocity on a time basis is almost proportional to the frequency. Tensile fracture or crack propagation/growth behavior in polymers can be uniquely different to that of metallic systems where the fracture/crack propagates a specific distance with each cycle depending upon the stress intensity range. In polymers, the fracture/crack may not even propagate of many cycles from one to several hundred, but in the latter case would then jump or propagate in a substantial “jump ahead” by a specific amount depending on the size of the stress intensity range.

Controlling the extensional shock wave propagation transfer from one dissimilar material to another is required to preclude composite armor deterioration during the ballistic impact in the regions surrounding the epicenter of the projectile core trajectory from force tensile stress fracturing. Inertia and the inner kinetics of the materials used in a composite is a vitally important factor, and the dynamic induced deformation of the materials is often created by the extensional wave propagations and transference, which can either be mitigated by the dissimilar materials or amplified though the rapid delivery of the high mechanical stress/strain energy transfer during the ballistic or fragmentation impacting event.

Precluding the molecular deterioration from the stress induced extensional shock wave transfer is germane to the development of any high-performance armor material substrate. The secondary effects of this are additionally prevalent due to the fact that the rheological effects of the armors loading required to resist failure is translated into the personnel wearing the armor or the mechanical, electrical, pneumatic pressurized gas or hydraulic pressurized fluid transfer systems of an aircraft, vehicle or vessel. This is more so in personnel as shock wave propagation is easily continued or amplified by tissues, organs, biopolymers and gels due to either the fluid content or the amorphous state of a solid, which are comprised of particles atoms, grains, bubbles, molecules, which are arranged so that the locations of their centers of mass are disordered; thereby arranging their structure in a manner that is essentially indistinguishable from a liquid.

A ballistic impact will create an extensional shock wave which is a violent disturbance in the equilibrium of an armor system. They are in fact high-speed, large amplitude mechanical transients generated by a time dependent violent impact. The dynamics of structural changes induced by ballistic impact and that dissipation of mechanical energy on the dynamic time scale of the extensional shock wave event are of obvious concern for the appropriate design and effectiveness of any protective armor system and its constituent materials.

The extensional shock wave travels through a material at a velocity (Ua) equal to the sum of the particle velocity (Up) and the substrate medium's acoustic velocity ©:Ua≈Up+c. The particle velocity is the speed with which the armor material at the point of impact is repositioned, and the velocity of the armor material flow behind the primary extensional shock wave. Any region impacted directly by the extensional shock wave transfer will demonstrate a higher density than the regions less effected by the extensional shock wave transfer specifically due to the hierarchical structural arrangement of ballistic component zones. The cause of an extensional shock wave transfer in a material's property is that it transmits sound quicker with increased pressure (density). The fundamental prerequisite for the creation of an extensional shock wave transfer is that the velocity of the pulse (Us), increases with increasing pressure (P) (density) of any constituent material.

The extensional shock wave impulse in both the longitudinal, transverse (shear), and diagonal directions coupled with the wavelength dimensions and amplitudes themselves, create numerous rebound complexities due to the multitude of colliding points from outbound and inbound reflected impulses.

The amplitude of a shock wave may be constant (in which case the wave is a continuous wave), or may be modulated so as to vary with time and/or position. The outline of the variation in amplitude is called the envelope of the extensional shock wave.

A shock wave can be transverse or longitudinal depending on the direction of its oscillation.

Transverse shock waves occur when a disturbance creates oscillations perpendicular (at right angles) to the propagation (the direction of energy transfer). Longitudinal waves occur when the oscillations are parallel to the direction of propagation. While mechanical waves can be both transverse and longitudinal, mechanical shock waves propagate through a medium, and the substance of this medium is deformed. The deformation reverses itself owing to restoring forces resulting from its deformation. For example, sound waves propagate via air molecules colliding with their neighbors. When air molecules collide, they also bounce away from each other (a restoring force). This keeps the molecules from continuing to travel in the direction of the wave.

The extensional shock wave transfer velocity rates are used to determine elastic constants through both longitudinal and shear velocities. For various embodiments of this invention, the primary material substrate backings are:

Polyethylene—

    • VL=2,430 F.P.S.
    • Vs=946 F.P.S.

Polystyrene—

    • VL=2,350 F.P.S.
    • Vs=1,120 F.P.S.

Polycarbonate—

    • VL=2,200 F.P.S.
    • Vs=910 F.P.S.

Polyurethane—

    • VL=2,559 F.P.S.
    • Vs=1,049 F.P.S.
      Polymethyl methacrylate (PMMA)—
    • VL=2,690 F.P.S.
    • Vs=1,344 F.P.S.

Where: B=Bulk modulus, G=shear modulus, and P=Density

VL—is the velocity of plane longitudinal shock wave in bulk material, with the velocities in feet per second. (1)


VL=√{square root over ((B+4p)}

Vs—is the velocity of plane transverse (shear) shock wave, with the velocities in feet per second. (2)


Vs=√{square root over (G÷p)}

For an isotropic solid, such as the various polymers listed in the embodiments of this invention, there are only two independent elastic constraints. These two can be taken to be G and B, but it is sometimes convenient to use other elastic constants, such as Young's modulus, Y, and Poisson's ratio, σ.

These constants can be calculated using the standard relations:

Y=3G1+G/3B(3)σ=12-Y6B(4)

The four constants G, B, Y and σ are referred to as engineering constants. Other constants are also used, and they can be calculated from the engineering constants. For example, the Lame' constants μ and λ are given by:


μ=G (5)

λ=B-23G(6)

The elastic constants can also be expressed using the elastic stiffness matrix. In generalized form, Hook's law is given by:

σi=i=16cijɛj(7)

Where the σI are the stress components, the ci are the strain components, and the cij are the isothermal elastic stiffness coefficients.

For an isotropic solid:


c44=c55=c66=G (8)


c11=c22=c33=B+4G/3 (9)


c12=c13=c23=c21=c31=c32=B−2G/3. (10)

All other coefficients are zero. If any other constants are desired, they can be calculated using the equations (5) to (10).

Impacting shock waves exhibit eight common behaviors within typical standard conditions. They are: the media through which the shock waves are transmitted and the type of transmission; absorption capabilities of the media; reflection by which a shock wave may be re-directed relevant to the angle of incidence of the shock wave direction; interference that may be encountered when two shock waves superimpose upon each other to form a new shock wave; refraction when the shock wave transfers from one media to another, thereby changing the directional velocity of the shock wave; diffraction of the shock wave when it encounters an obstacle that bends the shock wave or spreads it after emerging from an opening in the media; dispersion of the shock wave; and polarization if the shock oscillates in a single direction or plane. Polymers exhibit two distinct types of fracture/crack propagation responses: one where the crack propagation moves in a “near-rigid” polymer (crack propagation velocity >39″/1 m-min), or in a strongly viscoelastic polymer material (crack propagation velocity <39″/1 m-min).

The behavior of the thermoplastic polycarbonate has been investigated in both longitudinal and lateral orientations. These have been used to determine the impacting shock stress, shock wave velocity, particle velocity, release velocity and shear strength. The relationship between shock velocity and particle velocity has been shown to be linear. Shear strength has been observed to increase behind the shock front, a feature observed in other polymers such as Polymethl methacrylate (PMMA) or polyether ether ketone (PEEK). It also increases with stress amplitude, although the projected intercept with the calculated elastic response indicates that the Hugoniot elastic limit (HEL) is lower than in other polymers, for example PMMA (ca. 0.75 GPa) or PEEK (ca. 1.0 GPa). This further suggests that the yield strength of polycarbonate does not obey a Mohr-Coloumb criterion, and hence is not as strongly pressure dependent as other polymers.

Polycarbonate (PC)

embedded image

The paramount ballistic resistant armor polymer, mass produced on the market today is polycarbonate (PC) based (Lexan®). Armor laminates using Lexan® are currently in service throughout the military and law enforcement sectors, however, their effectiveness is ultimately limited by their impact strength.

Polycarbonate is a polymer which is used for lightweight transparent armor in a wide range of applications. This material has an unusually high yield strain and ductility; this combined with a significant amount of strain hardening enables it to display impressive impact and perforation resistance. Polycarbonates have also shown benefits to the physical and mechanical structure changes required for high impact resistance, once going through a hot drawn process if kept within the 10 to 15% hot drawn percentage draw ratio.

Polycarbonate polymer is produced by reacting bisphenol A with phosgene. Polycarbonate typically exhibits five mechanisms of deformation and subsequent fracture during the terminal ballistic impact with handgun projectile threats and velocities. They are: elastic dishing, petalling, deep penetration, cone cracking and plugging. Thin plates impacted by spherical missiles exhibit elastic dishing, whereas thick plates suffer a deep penetration process. In both cases, final failure is by petalling. Cylindrical missiles impacting thick plates also cause deep penetration with final failure occurring by plugging. For thin plates impacted by cylindrical missiles, cone cracking develops from the leading edge of the missile.

Recent unpatented industry research on polycarbonate improvements at the Shell Chemical Company has led to the development of a co-polyester derived from 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO), 1,3-propanediol (PDO), and dimethyl terephthalate (DMT). By varying the percent incorporation of the monomers, the thermal/mechanical properties of this copolyterephthalate are tunable. Shell found that interesting impact properties arose from the material when 40 mol % CBDO was incorporated into the polymer. This material displayed a notched Izod value of 1070 J/m while maintaining Tg near 100° C. This new material shows improvement over bisphenol A polycarbonate in both notched Izod as well as ballistic impact values.

Polycarbonate: an amorphous polymer made by SABIC Innovative plastics (GE Plastics) under the tradename Lexan®, and Bayer material Science under the trade name Makrolon®. Other secondary manufactures are listed in Appendix A.

Polymethyl Methacrylate (PMMA)

embedded image

Polymethyl methacrylate (PMMA) has seen widespread use in applications such as lightweight transparent enclosures for aircraft and as added spalling components for personnel. PMMA, however, while much tougher and more impact resistant than glass, is relatively brittle and it too, will spall upon ballistic impact, leading to possible injury to personnel behind the PMMA armor. Thermal, morphological, and mechanical properties of PMMA copolymers have been proven as well as the changes in highly hot drawn techniques, have demonstrated improved ballistic impact performance. PMMA is not as hard as glass, yet its extraordinary response in mechanical strengthening at high rates results in a drastic increase in the effective hardness.

Polymethylmethacrylate: an amorphous polymer made by the Rohm and Haas Company, Philadelphia, Pa., under the trade name Plexiglas® II UVA. Other secondary manufactures are listed in Appendix A.

Polyurethane (PU)

embedded image

Polyurethane is a polymer composed of a chain of organic units joined by carbamate (urethane) links. While most polyurethanes are thermosetting polymers that do not melt when heated, thermoplastic polyurethanes are also available.

Polyurethane polymers are formed by reacting an isocyanate with a polyol. Both the isocyanates and polyols used to make polyurethanes contain on average two or more functional groups per molecule.

Polyurethanes are in the class of compounds called reaction polymers, which include epoxies, unsaturated polyesters, and phenolics. Polyurethanes are produced by reacting an isocyanate containing two or more isocyanates groups per molecule (R—(N═C═O)n≧2) with a polyol containing on average two or more hydroxy groups per molecule (R′—(OH)n≧2), in the presence of a catalyst. The most commonly used isocyanates are the aromatic diisocyantes, toluene diisocyanate (TDI) and methylene diphenyl diisocyanate, MDI.

The properties of a polyurethane are greatly influenced by the types of isoyanates and polyols used to make it. Long, flexible segments, contributed by the polyol, produce a soft, elastic polymer. High amounts of crosslinking produce tough or rigid polymers. Long chains and low crosslinking produce a polymer that is very stretchy, short chains with lots of crosslinks produce a hard polymer while long chains and intermediate crosslinking produce a polymer useful for making foam. The crosslinking present in polyurethanes means that the polymer consists of a three-dimensional network and molecular weight is very high. In some respects a piece of polyurethane can be regarded as one giant molecule. One consequence of this is that typical polyurethanes do not soften or melt when they are heated as they are thermosetting polymers. The choices available for the isocyanates and polyols, in addition to other additives and processing conditions allow polyurethanes to have the very wide range of properties that make them such widely used polymers.

Isocyanates are very reactive materials. This makes them useful in making polymers but also requires special care in handling and use. The aromatic isocyanates, diphenylmethane diisocyanate (MDI) or toluene diisocyanate (TDI) are more reactive than aliphatic isocyanates, such as hexamethylene diisocyanate (HDI) or isophorone diisocyanate (IPDI). Most of the isocyanates are difunctional, that is they have exactly two isocyanate groups per molecule. An important exception to this is polymeric diphenylmethane diisocyanate, which is a mixture of molecules with two-, three-, and four- or more isocyanate groups. In cases like this, the material has an average functionality greater than two, commonly 2.7. Isocyanates with functionality greater than two act as crosslinking sites as mentioned in the previous paragraph.

Polyols are polymers in their own right and have on average two or more hydroxyl groups per molecule. Polyether polyols are mostly made by polymerizing ethylene oxide and propylene oxide. Polyester polyols are made similarly to polyester polymers. The polyols used to make polyurethanes are not “pure” compounds since they are often mixtures of similar molecules with different molecular weights and mixtures of molecules that contain different numbers of hydroxyl groups, which is why the “average functionality” is often mentioned. Despite the fact they are complex mixtures, industrial grade polyols have their composition sufficiently well controlled to produce polyurethanes having consistent properties. As mentioned earlier, it is the length of the polyol chain and the functionality that contribute much to the properties of the final polymer. Polyols used to make rigid polyurethanes have molecular weights in the hundreds, while those used to make flexible polyurethanes have molecular weights up to ten thousand or more.

Copolymer

A copolymer or rheteropolymer is a polymer derived from two (or more) monomeric species, as opposed to a homopolymer where only one monomer is used. Copolymerization refers to methods used to chemically synthesize a copolymer. Copolymerization is used to modify the properties of manufactured polymeric materials to meet specific needs, for example to reduce crystallinity, modify glass transition temperature or to improve solubility. It is a way of improving mechanical properties, in a technique known as rubber toughening. Elastomeric phases within a rigid matrix act as crack arrestors, and so increase the energy absorption when the material is impacted.

Block copolymers are generally defined as macromolecules with a linear and/or radial arrangement of two or more different blocks of varying monomer compositions. Block copolymers are interesting as they can “microphase separate” to form periodic nanostructures. Block copolymers consist of two or more chemically distinct polymer chains (blocks) linked by covalent bonds. These blocks can micro-phase separated into nanometer-sized domains whose structure depends upon the size and interactions of the blocks. Block copolymers can also control the ordering of inorganic precursors that selectively associate with one block. The importance of block copolymers can be seen in their wide array of properties. These properties are made possible due to the combination of different polymers in alternating sequence. Due to the rapid progress in these areas block copolymers now stand on the verge of a new generation of sophisticated materials applications, in which particular nanostructures will play a crucial role in armor applications.

Polyurethane based energy absorbing copolymers and block copolymers are a recent development and have improved the fragmentation and blast resistance of lightweight polymeric based single constituent armors, including but limited to acrylics, polycarbonates, polynethyl methacrylates, and hybridized composite systems of either.

In an extension of previous work on polyurethane block copolymers for transparent armor applications, several additional variations of the basic 2,4-toluene diisocyanate/polytetramethylene oxide/1,4-butanediol formulation have been investigated. It has been found that excess diisocyanate in a given formulation improves ballistic resistance and that decreasing the amount of polyether (soft segment) has the same effect. More generally, it has been found that increased sample hardness (Shore D) parallels improved ballistic performance. High-speed photographic data has shown that these materials continue to absorb large amounts of ballistic energy, with relatively little of this energy manifested as fragment kinetic energy. A technique for the preparation of void-free ballistic resistant specimen involving the use of a polytetrafluoroethylene mold is also described; and a technique for a zero VOC ballistic resistant void-free cast specimen.

In one embodiment, one specific type of synthesized polymer that was tested, was a solid polyurethane zero VOC polymer cured material in which demonstrated definite “standalone” performance capabilities had the following mechanical and physical properties test results:

Cured Flexibility

−40F ½ Mondreal Bend 74%

−60F ½ Mondreal Bend 76%

−40F Elongation 2.4%

−60F Elongation 1.8%

Ambient 72F 7.7%

Strength/Impact Resistance

Tensile Strength 1,892 PSI

Compression 1 hour 27,740 PSI

Recovery at Ambient 87.4%

This type of polymer was mixed and cast (it is a two part voc polyurethane resin in which the poliol has been tweaked) on-site and poured into 2″×3″×4″ blocks. The strength and compression tests were conducted on the thin 2″ face. Ceramics or other organic particles can be added into the mixture.

The other material properties and compositions are:

Basic Physical Properties within matrix

Iso 100 parts

Polyol 50 parts

Iso visc 3000 mpa Brookfield

Polyol visc 150 mpa Brookfield

Pot life 15 min. set 150 gms pour in place

Cured Mechanical/Physical Properties

Shore D 60

Tensile Modulus Mpa 630

Tensile Mpa 27

Elongation at break 120%

Flexural Modulus Mpa 450

Flexural Strength Mpa 28

Tear Strength 84

Impact Strength Charpey KMm2—unbreakable

Resilliance Bay Shore test 62%

Abrasion 1000 rev HZZ wheel 54

Polymer Testing

The limited testing that was completed consisted of two projectile types.

The first was a sharp pointed rod shaped projectile and the second was a rounded sphere projectile.

Stainless steel dart fired from 26′ at 109,000 PSI— 3/16″ penetration; 20 mm Ball Bearing fired from 26′ at 4,750 FPS—⅜″ penetration.

In one embodiment, one specific type of synthesized polymer was a polytetramethylene oxide based solid, void-free ballistic resistant specimen involving the use of a pour in cast mold. Each formation contained 2,4-toluene diisocanate (TDI), polytetramethylene oxide (PTMO) and 1,4-butanediol (BD).

The optimal results were attained from the following formulas:

CompositionCure TemperatureBallistic V50 velocity &
Test SpecimenMole RatiosConditionsRange of Results
1TDI 5.25212° F./100° C. overnightV50 - 950 F.P.S/290 M.P.S.
#03222005PTMO 1070-1.0~12 Hrs.ROR - 73 with 6 impacts
BD 4.0
2TDI 5.25140° F./60° C. overnightV50 - 900 F.P.S/274 M.P.S.
#10092005PTMO 1090-1.0~12 Hrs.ROR - 75 with 10
BD 4.0impacts.
3TDI 5.2572° F./22.2° C. overnightV50 - 930 F.P.S/283 M.P.S.
#06142006PTMO 1090-1.0~12 Hrs.ROR - 70 with 10
BD 4.0impacts.

The effect of cure duration and temperature have a definite impact in the substrates overall ballistic performance. All V50 data appears to increase steadily with the allotted cure times. The threat for these specimens was in accordance with the military standard MIL-P-utilizing the .22 caliber, 17 grain, steel fragment simulating projectile, with the nominal thickness of each specimen tested diagnostic sample dimensioned at 4″×4″×0.25″, with an approximate areal density of 22.0 ounces per square foot. The fragmentation tests revealed that the performance capability was almost linear with an approximate 18-20 foot per second increase in fragmentation impact defeat velocity for approximately every 1 ounce per square foot of areal density increase.

Additionally, the higher molecular weight of PTMO created a significant drop in the ballistic performance. It also appears that the larger or more fully developed domains of the PTMO (soft segments in the block copolymers) confer upon the entire specimen by the increased weight percent of soft material in the higher molecular weight formulation. This observed mechanical performance capability is reinforced by the increased weight percent of soft ductile material in the higher molecular weight formulation of the specimens that exhibited poor ballistic performance resistance capabilities. The ductile response of the tested specimens lead to the following characteristics:

1. The lower the PTMO molecular weight by volume, the greater the V50 velocities were of the impacting threats. 2. The ductile response during the projectile impact demonstrates the typical evidence of lack of any radial tensile fracturing and absence of brittle failure leading to spall or rearward exit of polymer ejecta/armor substrate towards the protected side. 3. The water soluble hydrophilic group demonstrated that water absorption induces a direct impact on the polymeric material hardness. The higher the content percentage of water absorption, the lower the modulus will be of the material, and generally not uniformly throughout the specimen. The water performed in much the same manner as a plasticizer would. Decreasing the modulus results in decrease hardness. It was also determined that “drying” the polymers through a process of ambient desiccation would remove the moisture content and limited hardness, but could not eliminate of the moisture induced elastic response or ductility, decreasing the mechanical performance attributes required in an composite armor material.

In the last decade, the synthesis techniques have been widely extended, and primarily ionic and controlled free radical methods can now be employed to prepare block copolymers with well-defined compositions, molecular weights and structures with varying elaborate architectures.

The increasing interest in block copolymers arises mainly from their unique solution and associative properties as a consequence of their molecular structure.

There is almost no limit to the design and optimization for novel types of block copolymers and of new structures. For example, several embodiments of this invention include: metal containing co-polymers, ceramic containing copolymers, metal/ceramic hybrid containing polymers, metal containing nano-reinforced co-polymers, ceramic containing nano-reinforced copolymers, metal/ceramic hybrid containing nano-reinforced polymers, metal containing mixed media-reinforced co-polymers, ceramic containing mixed media-reinforced copolymers, metal/ceramic hybrid containing mixed media-reinforced polymers, molecularly aligned crosslinked polymers and/or copolymers, molecularly aligned uncrosslinked polymers and/or copolymers, etc.

The increasing interest in block copolymers arises mainly from their unique solution and associative properties which is a byproduct of their molecular structure. In particular, their surfactive and self-associative characteristics leading to micellar systems are directly related to their segmental incompatibility. Block copolymer micellization, is a unique process by which to achieve self-assembled nanoparticles with well-defined morphologies.

Block copolymer micellar systems are generally produced by one of the following two procedures. In the first technique, the copolymer is dissolved molecularly in a common solvent e.g. that is ‘good’ for both blocks, and then the conditions such as temperature or composition of the solvent, are changed in the way that requires formation of micelles. This is commonly achieved by adding gradually a selective precipitant of one of the blocks, eventually followed by stripping the common solvent. An alternative, which improved upon the first process is the dialysis technique by which the common solvent is gradually replaced by the selective solvent. In this second technique, a solid sample of the copolymer is directly dissolved in a selective solvent; the micellar solution is left to anneal by standing and/or the annealing process is accelerated by thermal treatment, eventually under ultrasonic agitation. These process are necessary to avoid void formation during the cure process.

However, through both of these techniques, and depending on the block copolymer system, an equilibrium situation is not necessarily reached, especially if the core-forming polymer has a high glass transition temperature (Tg).

A micelle is an aggregate of surfactant molecules dispersed in a liquid colloid. The micelles consist of a more or less swollen core of the insoluble blocks surrounded by a flexible fringe of soluble blocks. A colloid is a substance microscopically dispersed throughout another substance. The dispersed-phase particles have a diameter of between approximately 1 and 1000 nanometers. Homogeneous mixtures with a dispersed phase in this size range may be called colloidal aerosols, colloidal emulsions, colloidal foams, colloidal dispersions, or hydrosols. The dispersed-phase particles or droplets are affected largely by the surface chemistry present in the colloid. Micelles form only when the concentration of surfactant is greater than the critical micelle concentration (CMC), and the temperature of the system is greater than the critical micelle temperature. The formation of micelles can be understood using thermodynamics, (heat and its relation to energy and work). It defines macroscopic variables (such as temperature, internal energy, entropy, and pressure), that characterize the materials, and defines how they are related and by what laws they change with time). Micelles can form spontaneously due to a balance between entropy and enthalpy. For example, in water, the hydrophobic effect (the observed tendency of nonpolar substances to aggregate in aqueous solution and exclude water molecules), is the driving force for micelle formation, despite the fact that assembling surfactant molecules together reduces their entropy.

Surfactants are compounds that lower the surface tension (or interfacial tension) between two liquids or between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming agents, and dispersants. Surfactants are usually organic compounds that are amphiphilic, meaning they contain both hydrophobic groups (their tails) and hydrophilic groups (their heads). Therefore, a surfactant contains both a water insoluble, (or oil soluble) component, and a water soluble component. Surfactants will diffuse in water and adsorb (the adhesion of atoms, ions, or molecules from a gas, liquid, or dissolved solid to a surface), at the interfaces between air and water, or at the interface between oil and water, in the case where water is mixed with oil. The water-insoluble hydrophobic group may extend out of the bulk water phase, into the air or into the oil phase, while the water-soluble head group remains in the water phase. This alignment of surfactants at the surface modifies the surface properties of water at the water/air or water/oil interface.

Entropy is a measure of the number of specific ways in which a thermodynamic system may be arranged, often considered as a measure of progress towards achieving a thermodynamic equilibrium.

Enthalpy is a measure of the total energy of a thermodynamic system. It includes the system's internal energy and thermodynamic potential, as well as its volume and pressure (the energy required to “make room for it” by displacing its environment, which is an extensive quantity). Enthalpy change accounts for energy transferred to the environment at constant pressure through expansion or heating.

One of the most useful properties of micellar aggregates is their ability to enhance the aqueous solubility of hydrophobic substances which otherwise are only sparingly soluble in water. The enhancement in the solubility arises from the fact that the micellar cores, for classical low molar mass surfactants as well as for block copolymer micelles, can serve as a compatible microenvironment for water-insoluble solute molecules. This phenomenon of enhanced solubility is commonly referred to as ‘solubilization’, the ability of micelles to solubilize or encapsulate various compounds, is important in the binding phase for mixed media such as ceramics, metals, textiles, etc. This is an incredibly important prerequisite for composite in that adhesion from one adhered to another is important for attenuation, absorption and transference of the extensional shock wave transfer and the further containment of the brittle ceramic components the amount of encapsulation and retardation of the ceramics reduced ability to flex.

A stiff polymer increases shock wave transmission propagation and reduces the impacting stresses which in turn reduces the flexure of the ceramic component through absorption of energy. Conversely, the reduced stiffness of the polymer encapsulating component decreases the extensional shock wave transfer but in turn typically reduces the adhesion between the ceramic component allowing for increased flexure, which increases the failure of the brittle ceramic component. A centralized compromise must be maintained through the proper “mixing” of the constituent chemicals, while reducing or eliminating insolubility through the control of solubilization. The quality of the interlamina bond (adhesion of the ceramic and the polymeric structure), has a significant influence on the dispersive characteristics of the extensional shock wave transfer, and the preclusion of dilatancy of the ceramic constituent components.

Micelles can in block copolymer compositions change shape under the influence of external parameters, such as temperature or solvent composition, leading to other copolymer and block copolymer structural architectures.

Therefore, the micellization of block copolymers processed in a selective solvent of one of the blocks is a typical aspect of their colloidal properties. In fact when a block copolymer is dissolved in a liquid that is a thermodynamically good solvent for one block and a precipitant for the other, the copolymer chains may associate reversibly to form micellar aggregates which resemble in most of their aspects to those obtained with classical low molecular weight surfactants. It is therefore a prerequisite to ensure an appropriate dissolving technique is utilized as applicable, for the constituent materials such as stirring under vacuum or inert gas pressure, etc.

Great attention has to be paid to the preparation step of the micellar system. In fact, one has to be aware that the simple dissolution of the block copolymer in a selective solvent, or even the preparation of the micellar system by step-wise dialysis could lead to non-equilibrium situations to so-called ‘frozen micelles’.

Water is absorbed by most polymers resulting in polymer property changes by the water in various opposing ways at low and high temperatures, affecting such properties as moduli, changes in the dampening spectra, and thermal expansion due to the moisture absorption.

Polyether Ether Ketone (PEEK)

embedded image

Polyether ether ketone (PEEK), is a colorless organic polymer thermoplastic, that is manufactured by step-growth polymerization by the dialkylation of bisphenolate salts. PEEK is a semi-crystalline thermoplastic with excellent mechanical and chemical resistance properties that are retained to high temperatures, and is not traditionally a shape memory polymer; however, recent advances in processing have allowed shape memory behavior in PEEK with mechanical activation.

The behavior of the polymer polyether ether ketone (PEEK) has been investigated under conditions of one-dimensional shock loading. This has involved measurement of the Hugoniot in terms of stress, extensional shock wave velocity and particle velocity, and measurements of the lateral stress, which have been used to determine the shear strength, and its variation with extensional shock wave stresses. Analysis of the relationship between shock wave velocity and particle velocity shows a simple linear response, in common with many other materials. Shear strength has also been shown to increase with shock wave stress. Below this stress, the material appears to behave in a simple elastic manner. Shear strength has also been observed to increase significantly behind the shock front. This behavior has been observed in other polymeric materials, where it is suggested that these materials were responding by a viscoplastic mechanism.

None of these polymeric compositions or hybridized composites are fully capable of defeating high velocity rifle defeating threats nor armor piercing or armor piercing incendiary threats. The limited impact strength coupled with the lack of hardness preclude that performance resistance capability. Adding a ceramic composite strike face or ceramic media to the polymeric composition in a hybridized component system would provide that performance resistance capability.

APPENDIX A
Polycarbonate Manufacturers
KolonSPELLOY ®
LANXESSPocan ®
Polymer Technology and Services (PTS)
Polymer Technology and Services (PTS)Tristar ®
Quadrant Engineering Plastics Products
Quadrant Engineering Plastics ProductsQuadrant LSG
Quadrant Engineering Plastics ProductsQuadrant PC
RTP CompanyEMI
RTP CompanyESD
RTP CompanyEXT
RTP CompanyPermaStat ®
RTP CompanyRTP
A. Schulman ComAlloy
A. Schulman ComAlloyComtuf ®
A. Schulman ComAlloyHiloy ®
A. Schulman ComAlloyLubrilon ®
A. Schulman, Inc.ComAlloy ®
A. Schulman, Inc.COMTUF ®
Aaron Industries CorporationAAROPRENE ® AE
PC/ABS
Aaron Industries CorporationAAROPRENE ®
AEPC
Aaron Industries CorporationAAROPRENE ®
GFPC
ABW Plastics
Aclo CompoundersAccucomp
Aclo CompoundersAccuguard
Aclo CompoundersAcculoy
Aclo CompoundersAccutech
Adell Plastics, Inc.
AdvanSource BiomaterialsChronoFlex ®
(formerly CardioTech International)
Albis Plastics
Ashley PolymersAshlene ®
BASFLuran ®
BASFUltradur ®
Bayer MaterialScienceApec ®
Bayer MaterialScienceBayblend ®
Bayer MaterialScienceBayfol ®
Bayer MaterialScienceMakroblend ®
Bayer MaterialScienceMakrofol ®
Bayer MaterialScienceMakrolon ®
Bayer MaterialSciencePetlon ®
Bayer MaterialScienceTexin ®
Bayer MaterialScience AGApec ®
Bayer MaterialScience AGBayblend ®
Bayer MaterialScience AGMakrolon ®
CENTROPLAST Engineering Plastics GMBHCENTROCARB
Chase PlasticsCP Pryme ®
Cheng Yu Plastic Company Limited
(formerly Luen Cheong Hong)
Chengdu Polyster Co.
Chi Mei Corporation (ChiMei)Wonderlite ®
Chi Mei Corporation (ChiMei)Wonderloy ®
Clariant
ClariantRenol
Cool Polymers, Inc.Coolpoly ®
Diamond and Network Polymers
Dow ChemicalCALIBRE ™
MEGARAD ™
Dow ChemicalRetain ®
DSM BiomedicalBionate ®
DSM BiomedicalCarboSil ®
DSM Engineering PlasticsArnite ®
DSM Engineering PlasticsElectrafil ®
DSM Engineering PlasticsPlaslube ®
DSM Engineering PlasticsStapron ®
DSM Engineering PlasticsStapron ® C
E-Polymers Co. Ltd.TEKALOY ®
E-Polymers Co. Ltd.TEKANATE ®
E-Polymers Co. Ltd.TEKANATE ™
Eastman ChemicalEastalloy
Ecomass Technologies
Engineered Plastics Corporation
EnsingerHydel ®
EnsingerTecanat ™
Entec Engineered ResinsHybrid ®
Entec Engineered ResinsHylex ®
Entec Engineered ResinsHysun ™
EPICHEM srlEpiblend
EPICHEM srlEpicarb
EPICHEM srlEpilon
EPMG, Inc.
Erhard Hippe KG
EurotecTecodur ®
Evonik CorporationEuroplex ®
Evonik CYROCYREX
Evonik CYROCyrex ®
Evonik CYROCyrolon ®
GEHR Plastics Inc
Gichem srlGIBLEND
Gichem srlGILON
Global Polymers Corporation
Isoflon
Kazanorgsintez
Kingfa Sci. & Tech. Co.
Kingfa Sci. & Tech. Co.LONOY
Kleerdex CompanyElson ®
Kostat
KostatICP-STAT
Kotec CorpCarbotex
LATILASTILAC
LATILATILON
LATILATILUB
LATILATISHIELD
LATILATISTAT
Lehmann & Voss & Co.ELECTRAFIL
Lehmann & Voss & Co.LUVOCOM ®
Lehmann & Voss & Co.PLASLUBE
LG ChemicalLUPOY
LNPCYCOLOY ®
LNPFaradex
LNPLexan ®
LNPLubricomp ®
LNPLubriloy ®
LNPStat-Kon ®
LNPStat-Loy ®
LNPThermocomp ®
LNPVALOX ®
LNPVerton ™
Loxim Industries
LTL Color CompoundsColorFast ®
LTL Color CompoundsColorRx ™
Lucent Polymers
M. Holland Company
Mitsubishilupilon ®
MitsubishiXantar ®
MRC PolymersNAXALOY ™
MRC PolymersNAXELL ™
NanocylPLASTICYL ™
Network Polymers
Nylene ®Naxel ™
Omni PlasticsOmniTech ™
Omni PlasticsOmniTuff ™
Omnia Plastica s.p.a.
Ovation PolymersGIENALL
Ovation PolymersNemcon ™
Ovation PolymersNima ™
Ovation PolymersOpteSTAT ™
Ovation PolymersRIGITRON
Ovation PolymersTRIZIN
Ovation PolymersUTTAP
Owens Corning
Oxford Polymers
Parker ChomericsDuralan II ™
Parker ChomericsPREMIER ™
Parker ChomericsWIN-SHIELD ™
Plaskolite
Plastomer TechnologiesAmicon ™
PlastxWorld, Inc.CEVIAN ®
Polimeri Europa (Former EniChem)KOBLEND
Polykemi ABPOLYblend
Polykemi ABPOLYlux
Polykemi ABSCANBLEND
Polykemi ABSCANTEC
Polymer Resources Corporation
PolyOne CorporationEdgetek ®
PolyOne CorporationLubriOne ™
PolyOne CorporationLubri-Tech ™
PolyOne CorporationStat-Tech ™
Polyram
PolyramRamLloy
PolyramRamTough
Premix Thermoplastics Inc.PRE-ELEC ®
Prima PlasticsPRIMABLEND
Prima PlasticsPRIMANATE
Proto3000
Quinn Group
Quinn GroupSPC
RedEye On Demand
Reliance Industries
SABIC Innovative Plastics (GE Plastics)Cycolac ®
SABIC Innovative Plastics (GE Plastics)Cycoloy ®
SABIC Innovative Plastics (GE Plastics)Geloy
SABIC Innovative Plastics (GE Plastics)Lexan ®
SABIC Innovative Plastics (GE Plastics)LNP Colorcomp
SABIC Innovative Plastics (GE Plastics)LNP Faradex
SABIC Innovative Plastics (GE Plastics)LNP Lubricomp
SABIC Innovative Plastics (GE Plastics)LNP Lubriloy
SABIC Innovative Plastics (GE Plastics)LNP Staramide
SABIC Innovative Plastics (GE Plastics)LNP Stat-kon
SABIC Innovative Plastics (GE Plastics)LNP Stat-loy
SABIC Innovative Plastics (GE Plastics)LNP Thermocomp
SABIC Innovative Plastics (GE Plastics)LNP Thermotuf
SABIC Innovative Plastics (GE Plastics)LNP Verton
SABIC Innovative Plastics (GE Plastics)Remex
SABIC Innovative Plastics (GE Plastics)SABIC PC
SABIC Innovative Plastics (GE Plastics)Valox ®
SABIC Innovative Plastics (GE Plastics)Xenoy
SABIC Innovative Plastics (GE Plastics)Xenoy ®
SABIC Innovative Plastics (GE Plastics)Xylex
Samsung, Cheil IndustriesStaroy ®
SamyangTriloy ®
SamyangTrirex ®
Shinil ChemicalSHINCON
Shinil ChemicalSHINFLAME
Shinil ChemicalSHINSTAT
Shinil ChemicalSHINSTRA
Shinkong Synthetic Fibers CorpShinblend ®
Shuman
Sibur
SO.F.TERBlendfor A ®
SO.F.TERCabofor ®
Spartech
SpartechMillennium
SpartechRoyalite
SpartechSungard
SpartechUltraTuf
SPS Guang ZhouPOLLITE ™
SPS Guang ZhouPOLLOY ™
Star Plastics, Inc
Stratasys
StyronCALIBRE ™
StyronEMERGE ™
StyronPulse ®
Techmer Lehvoss Compounds (TL Compounds)Electrafil ®
Techmer Lehvoss Compounds (TL Compounds)Luvotech ™
Techmer Lehvoss Compounds (TL Compounds)Plaslube ®
TeijinMultilon
TeijinPanlite ®
Ter Hell Plastic GMBHTerez ®
The Matrixx Group
The Plastics Group of AmericaPolifil ®
Tipco Industries Ltd., IndiaTipcofil ®
Tisan Engineering PlasticsTISARBON ®
Tisan Engineering PlasticsTISBLEND ®
ToyoboVYLOPET ®
TP Composites, IncElastoblend ®
TP Composites, IncElectrablend ®
TP Composites, IncHiFill FR ®
TP Composites, IncHiFill ®
TP Composites, IncLuriblend ®
TP Composites, IncPlastiblend ®
TP Composites, IncStatiblend ®
Wanshijie Plastic Sheet Co
Westlake PlasticsZelux ®
Wico PlastWicolon
Zhejiang Juner New Materials Co.

FIGS. 13-16 illustrate several embodiments of discs which may be used according to the instant invention.

FIG. 13 is a perspective view of one embodiment of a disc. In this embodiment, the disc 52 has a discus shape of varying thickness, ¼″ in the center tapering with a uniform slope to ⅛″ at the circumferential edge. In an imbricated pattern, edges of adjacent discs will overlap, creating areas of increased thickness having multiple disc layers. Ordinarily, this pattern will not overlap the center, or thickest region, of the disc. Thus, a projectile striking the disc pattern at any point will impact either a singular disc near its thickest region, or multiple layered discs at least as thick, and likely thicker, than the thickest region of the singular disc. Moreover, the slope of the discus shape between areas of varying thickness discourage any perpendicular ballistic impact.

FIG. 14 shows a side view of another embodiment of a disc or tile. In this embodiment, the disc or tile includes planar faces. Similar to the disc of FIG. 13, the disc may be a substantially circular disc, or may have other shapes such as oval, triangular, square or the like.

FIG. 15 is a perspective view of a disc of an alternative embodiment of the invention. In this embodiment, formation of the disc is substantially as described above in reference to FIG. 13, varying only in the slope of the end result. While varying in thickness from the center to the edge, the slope of tapering is not uniform, leaving a more pronounced bulging center having a domed shape. This leaves the surface area extending from the circumference edge to the domed center substantially planar. This embodiment allows for the discs to have a greater overlapped surface area, increasing the surface area in which a projectile would encounter multiple layers of disc. However, the substantially planar region increases the probability of a perpendicular strike. The domed discs can be laid out in an analogous manner to that described above and assembled into body armor capable of defeating rifle threat levels three to five.

FIG. 16 is a cross-sectional side view of the alternative embodiment shown in FIG. 15.

FIGS. 17A-26C illustrate several embodiments of tiles that may be used according to the instant invention. Each of the tiles may be partially or completely encased within any of the previously discussed containment wraps, e.g. an E-glass/resin wrap, a polymer wrap and/or a titanium wrap. In on embodiment, each of the tiles may be laid out in a side-by-side mosaic configuration and not overlapped to form an armor system. The tiles may have outside dimensions (e.g. a length and/or width) of anywhere from ½ inch to 6 inches, for example, from about 1 inch to about 3 inches, for example, 2 inches.

In other embodiments, the discs or tiles are overlapped in an imbricated pattern. The overlap of the imbricated placement pattern has been found to effectively spread the force of a high-velocity projectile hit to adjacent discs, thereby preventing penetration and backside deformation. Additionally, because of the slight tilt of each overlapping disc in the imbricated pattern, a perpendicular hit is very unlikely and some of the energy will be absorbed in deflection. In the discus embodiment, the tapering of thickness, forming a non-planar inclined surface renders a perpendicular strike extraordinarily unlikely.

FIG. 27 shows an imbricated pattern of discs 52 (such as disc 52 illustrated in FIG. 13) coupled to a substrate. The substrate could be an adhesive impregnated polyethylene or aramid fiber fabric. Suitable fabrics include the fabric sold under the trademark SPECTRA® by AlliedSignal of Morristown, N.J., TWARON® microfiliment by Akzo-Nobel of Blacklawn, Ga., SB31 and SB2, sold under the trademark DYNEEMA, by DSM of Holland, PBO sold under the trademark ZYLON® by Toyobo of Tokyo, Japan (pursuant to a license from Dow Chemical, Inc. of Midland Mich.), KEVLAR® or PROTERA® by E.I. Dupont de Nemours & Company of Chattanooga, Tenn. Other suitable fabrics will occur to one of ordinary skill in the art.

Some suitable substrates are available with an aggressive adhesive coating covered by a release paper. In addition to being aggressive, it is important that the adhesive once cured remains flexible to reduce separation of the discs and substrate during a ballistic event and to aid in flexibility. The substrate of a desired size may be cut and the release paper peeled back to expose the adhesive surface. The disc can then be laid out directly onto the adhesive which retains them in position relative to one another. Because the substrate is flexible and the discs flex about their intersection, pivoting somewhat within the imbricated layout, the combined unit is significantly flexible; on the order of 60% more flexible than the prior art metal plate and coin configuration armor. Alternatively, the pattern may be laid out and the substrate adhered over the top.

The next step is to place another layer of this adhesive coated flexible substrate on the other side of the discs to secure them in a flexible position that does not change when the panel is flexed. The actual position of each disc remains substantially in the same place it was laid. This second layer of adhesive fabric used to envelop the imbricated pattern provides further staying power, thereby reducing the risk that a disc will shift and the body armor will fail.

It has been found that the above-disclosed invention will defeat in a body armor system, rifle level three to five threats, and all lesser threats. Additional layers of the adhesive coated flexible substrate material may be added to either side in any proportion (i.e., it is within the scope and contemplation of the invention to have more substrate layers on one side of the panel than the other side of the panel) in multiple layers to achieve different performance criteria. Some situations benefit from allowing the discs to move slightly during the ballistic event, while others make it desirable that the disc remain as secure in place as possible.

In an alternative embodiment of the invention, a “dry” high tensile strength flexible substrate is provided. It is then coated with a flexible bonding agent, for example, a silicon elastomer resin. The discs may then be laid out as described above. The bonding agent is then cured to flexibly retain the relative locations of the discs. A similarly coated layer can be used to sandwich the plate from the opposite side. It is also within the scope and contemplation of the invention to use one layer with a flexible bonding agent while a facing layer is of the peel and stick variety described above. As used herein, “adhesive impregnated substrate” refers to suitable flexible high tensile strength material having an adhesive disposed on one side, whether commercially available with adhesive in place or coated later as described above.

In yet another embodiment, an adhesive impregnated substrate is created by either above described method and the (sandwiching) layer is non-adhesive and merely coupled to the underlying substrate about the periphery of the panel. This will somewhat degrade the retention of the disc as compared to sandwiching between adhesive layers. Accordingly, this configuration will not survive as many hits and the front layer attached about the periphery serves primarily as a spall shield.

FIG. 28 is a frontal view of one embodiment of a body armor vest within which the previously discussed discs or tiles may be integrated. Representatively, in one embodiment, the armor is a suit of body armor. The body armor 10 covers a user's torso and is designed to protect the vital areas from high-velocity projectiles. Flaps 20 on the body armor extend around the wearer's body to extend protection to the wearer's sides. In one embodiment the body armor wraps around a segment of the wearer, for instance the torso, providing substantially uniform armor protection in an enveloping circumference.

FIG. 29 is a cutaway frontal view of one embodiment of a suit of body armor. Discs 52 are arrayed in an imbricated pattern to cover vital areas where the body armor is worn. Unlike the 10″×12″ rigid plates of prior art, the imbricated pattern can flex around body contours and is therefore considerably more comfortable and also more readily concealable. Each disc 52 is formed of a high hardness material. In one embodiment, each disc is discus shaped having a maximum thickness in the center of the disc and declining in thickness towards the outer edge by providing one or more downwardly inclined surface segments. In one embodiment, the thickness of the discus shaped disc declines in a uniform downward inclined slope from the center towards the outer edge. In another embodiment the discus shape has an internal circumference within which the disc is uniformly thick and slopes uniformly downward between the internal circumference and the circumferential edge of the disc.

Typically, the edge thickness will be approximately one-half the thickness in the center. As such, when laid out in the imbricated pattern the discs exhibit a pivot capability which allows on the order of 60% greater flexibility than metal plates or existing coin arrangements. Many such suitable ceramic materials exist which are also of relatively lighter weight when compared to steel or other high hardness metals.

The tapering design intrinsic to the discus shape of one embodiment of the invention renders the disc surface non-planar, providing a slope to deflect ballistic impacts as compared with a uniform flat planar surface. In this regard, the ceramic composite material can be sintered and/or molded into a homogenous ballistic grade discus shape more easily and less expensively than can a metal disc, which must either be lathed or tooled to produce a similar tapering discus form. However, discus shaped metal discs are within the scope and contemplation of the invention. Through appropriately laying out discs in an imbricated pattern, the overall body armor 10 remains flexible and also provides good protection against high velocity projectiles.

Additionally, the lighter weight and greater flexibility of the ceramic composite as compared to prior art protection from high velocity projectiles, allows for greater mobility and range of motion by the wearer. For instance, body armor vests composed of imbricated ceramic discs of ballistic grade hardness and fracture toughness may wrap entirely around a segment of the wearer, for instance the torso, extending disc protection up to 360 degrees about the wearer. The lighter ceramic material also avoids pronounced negative buoyancy of high hardness metal coins, tiles, or plates typical of prior art body armor. This provides for climbing or swimming uses in the field for which prior art body armor is not suitable.

The imbricated pattern is typically sandwiched between two layers of fabric 14 made of high tensile strength fibers, such as aramid fibers or polyethylene fibers. The fabric 14 should be tear and cut resistant and is preferably ballistic grade material designed to reduce fragmentation. This fabric 14 can be adhesive impregnated, thus, the adhesive on the fabric adheres to the discs that compose the imbricated pattern and retains their relative position. One or more additional layers of the fabric 14 may be added to the sandwich. This will be discussed further below.

Underlying the imbricated pattern of discs 52 that is sandwiched between two or more layers of tear and cut resistant fabric layers 14 is conventional soft body armor 16. A high-velocity projectile is deemed defeated even if it penetrates the discs of the imbricated pattern and all fabric layers if it does not penetrate the underlying soft body armor or cause backside deformation of greater than 1.73″, as backside deformation is defined by the National Institute of Justice (NIJ). In one embodiment, multiple layers of fabric are added to the side between the ceramic discs and the wearer as additional protection against backside deformation and to catch projectiles and fragments thereof. Attachment straps, such as strap 18, connect the armor to a body segment, for instance the shoulders, to provide additional support. Attachment strap 18 could be any conventional strapping common in the industry.

To arrange the imbricated pattern, the discs are laid out from left to right. Each subsequent row is also laid out left to right. It has been found that switching from left to right, then to right to left, creates weakness in the resulting pattern that often causes failure. Discs within each row form a substantially straight horizontal line. Because the discs overlap, each disc lies on a slight tilting slope relative to a line normal to the horizontal layout surface. In one embodiment, this slight slope of the discs complements their inclined discus shape to increase the probability of impact deflection.

After the discs are laid out from left to right and top to bottom and sandwiched between a pair of adhesive layers, the entire pattern is inverted for assembly into body armor. It has been found that the majority of threats arrive at a downward trajectory. Thus it is desirable that each row of discs overlap the row below it as the armor is worn. It is, however, within the scope and contemplation of the invention to lay out the discs in an alternative order, e.g., right to left, bottom to top. It is also contemplated that inverting the imbricated pattern in the course of assembling the body armor may be connected such that each row overlaps the row above it.

In one embodiment, suitable ceramic composites for the discs or tiles would have relatively high hardness and fracture toughness. Typically, such materials would have at least approximately 12 GPa in hardness and at least 3.5 MPa m1/2 in fracture toughness in order for the armor to withstand a level three ballistic event as defined by the National Institute of Justice (NIJ). A level three threat is a full metal jacket 7.62×51 mm 150 grain round traveling at 2700-2800 ft./sec. Ultimately, hardness and fracture toughness levels will depend on the type of ceramic composite employed. For exemplary embodiments of the present invention using alumina bases, the fracture toughness minimum for alumina would be 3.8 MPa m1/2 and 4.5 MPa m1/2 for zirconia toughened alumina. The hardness for alumina would be in the approximate range of 12 to 15 GPa, and for zirconia toughened alumina, the hardness would be at least approximately 15 GPa.

The ceramics are mixed in ways commonly known in the art. Sintering and molding, including injection molding, methods to form the disc are well known in the art. In one embodiment, the discs may be formed by injection molding and then pressing to the desired shape. Once formed, certain embodiments of the discs are then encompassed with a containment wrap material. This material provides greater integrity to the disc and increases its fracture toughness, consequently enhancing its ability to absorb the impact of ballistic projectiles without disassociation. In one embodiment, this wrap is a glass fiber wrap adhered by an adhesive substrate. Suitable glass fiber materials include E-glass and S-2 Glass available from Owens Corning Fiberglas Technology, Inc. of Summit, Ill. Suitable adhesives include modified epoxy resins. The containment wrap and epoxy resin substrate can be applied to the disc by autoclaving, or in other ways known to the art. Strength, cohesion and structural integrity may also be imparted by overlaying the disc surface with aramid fibers, layered or cross-laid on an adhesive substrate.

Typically, disc 52 has a radius between ½″ and 3″. Longer radii reduce flexibility but also manufacturing cost. In a current embodiments, a 1″ or 2″ radius is employed. Each disc tapers in thickness varying between its center region (where the thickness is at its maximum) and its edge (where the thickness is at a minimum). Maximum and minimum thicknesses will vary according to the level of ballistic threat to be defeated. For instance, to defeat a high velocity armor piercing or armor piercing incendiary ballistic rifle threat, a maximum thickness of ⅜″ in the center tapering to 3/20″ minimum thickness at the edge may be used. A low velocity rifle threat (or a high velocity pistol threat) may only require a thickness of between ⅛″ (maximum) and 1/10″ (minimum). In one embodiment, the discus shaped discs have a center thickness of approximately ¼″ and an edge thickness of ⅛″.

FIG. 30-FIG. 35 illustrates further embodiments of possible patterns within which the discs or tiles may be arranged.

In particular, FIG. 30 illustrates one embodiment of a mosaic side-by-side tile configuration. In this embodiment, the tiles are hexagonal tiles. The mosaic pattern may be formed by arranging tiles in a single row in a side-by-side configuration in which each tile is laid next to the other but without overlapping the other. Each row is then arranged next to another row such that tiles in each row abut tiles of an adjacent row. The tiles illustrated in FIG. 30 may be flat or have a non-planar surface on either side.

FIG. 31 illustrates one embodiment of an imbricated tile configuration. In this embodiment, the tiles are arranged in rows which overlap tiles of adjacent rows. The tiles may be hexagonal tiles with flat or non-planar surfaces.

FIG. 32 illustrates one embodiment of an imbricated overlapping disc pattern. The discs may be substantially similar to those described in reference to FIG. 13.

FIG. 33 illustrates one embodiment of an imbricated tile pattern using multi-thickness tiles such as that described in reference to FIG. 15 and FIG. 16.

FIG. 34 illustrates one embodiment of an imbricated tile pattern. More specifically, a single row imbricated overlapped tile configuration is shown. In this embodiment, the tiles may be octagonal shaped armor tiles having a flat or non-planar surface.

FIG. 35 illustrates one embodiment of a multi-thickness diamond shaped tile similar to the multi-thickness round tile illustrated in FIG. 15 and FIG. 16. The multi-thickness perimeter shapes of the tiles are shown as diamond shaped but can also be rectangular, square, octagonal, hexagonal, etc.

FIG. 36 illustrates a perspective view of one embodiment of a tile. In one embodiment, the tile is a multi-thickness diamond shaped tile such as those shown laid out in FIG. 35. The tile is considered a multi-thickness tile because it is thicker at a center portion than the perimeter portion.

FIG. 37 illustrates a top plan view of one embodiment of a tile. The tile may be a multi-thickness diamond shaped tile such as that illustrated in FIG. 36. From this view, the shape of the tile can be more clearly seen.

FIG. 38 illustrates one embodiment of an imbricated tile pattern. The imbricated tile pattern may be formed by a plurality of diamond shaped multi-thickness tiles such as those illustrated in FIGS. 36 and 37. As can be seen from this view, the thinner perimeter regions of each of the tiles overlap.

FIG. 39 illustrates one embodiment of an imbricated tile pattern. The imbricated tile pattern may be formed by a plurality of diamond shaped multi-thickness tiles such as those illustrated in FIGS. 36 and 37. As can be seen from this view, the thinner perimeter regions of each of the tiles overlap.

It should also be appreciated that reference throughout this specification to “one embodiment”, “an embodiment”, or “one or more embodiments”, for example, means that a particular feature may be included in the practice of the invention. Similarly, it should be appreciated that in the description various features are sometimes grouped together in a single embodiment, Figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects may lie in less than all features of a single disclosed embodiment. Thus, the claims following the Detailed Description are hereby expressly incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment of the invention.

In the foregoing specification, the invention has been described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes can be made thereto without departing from the broader spirit and scope of the invention as set forth in the appended claims. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.