TECHNICAL FIELD
The present disclosure relates to bullet proof vests (BPV), which effectively resist or prevent the penetration of high energy fragments and bullets.
The BPV in accordance to the present invention having striking surface covered with a very high hardness hexagonal ceramic tiles and backing layer have the embedment of very tough ceramic spheres to increase its multi-hit capability.
BACKGROUND
[0001] Background description includes information that may be useful in
understanding the present subject matter. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed subject matter, or that any publication specifically or implicitly referenced is prior art.
Bullet proof vests (BPV) have been used for a long time, and initially made of high strength structural alloy steel (Patent RU 2102688). The front side of BPV consists of high strength titanium alloy, and then a multilayer package of ballistic fabric at the back side to absorb the shock and fragmentation. The disadvantage of steel alloy based BPV is that, it cannot withstand against the bullets having a highly hard core made of steel or any other hard alloy. The reason is that, the titanium alloys have a low level of hardness and tensile strength (1150-1200 MPa), and hence do not shatter the incoming projectile.
[003] As discussed above, the steel alloy based BPV are heavy and uncomfortable to use and often not reliable when many shots are fired into them and the risk of injury to the wearer increases. Hence there was a need for a vest that protects against multiple bullets without injury and comfortable to the wearer in terms of weight and protection area. Studies have shown that, an armored barrier

should have high hardness and crack resistance (or fracture toughness) comparable to that of a bullet’s core, so that small defragmentation of barrier elements does not occur upon impact.
[004] In the recent years, with increased threat level ceramics becomes an alternate material for the armor systems because of their light weight and high hardness. However, ceramics has low fracture toughness, hence a high tensile strength is required on the back of the ceramic based armor plate to take the loads. Thus, a typical armor using a ceramic comprises a ceramic front with a fiber composite as a backing material supported by soft armor plate. These dissimilar materials are usually bonded together by adhesion.
[005] Ceramic based armor typically includes a monolithic element, such as aluminum oxide (Al2O3), silicon carbide (SiC) or boron carbide (B4C), attached to a backing layer, such as KEVLAR para-aramid cloth, SPECTRA polyethylene fabric or fiberglass cloth etc. During impact, the projectile is blunted and cracked or shattered by the hard ceramic face (US7866248B2). Fragmentation and comminution are produced in the ceramic and the projectile, resulting in fine ceramic rubble traveling with the projectile. The incident momentum of the initial projectile is thus transferred to fragments of shattered projectile and the ceramic rubble. The ceramic rubble typically has a mass comparable to the initial projectile; hence, the final shattered projectile and ceramic rubble exhibit a much lower impact velocity on the backing plate.
[006] However, ceramics exhibit brittle fracture behavior, when monolithic element is subjected to a point load by a bullet, a continuous crack is formed over a large area and thus loses its protective action. In recent years, the idea of forming armor of a reaction bonded material, rather than a monolithic material, has been explored. A principal advantage of such material is that, it can provide improved fracture toughness relative to monolithic materials.
[007] In reaction bonding, a composite is formed of ceramic particles bonded in a matrix. In this process, ceramic particles are mixed with carbon and a sintering

aid, such as silicon. The mixture is then heated to a point at which a portion of the carbon and the sintering aid react to form a composite ceramic consisting of ceramic particles distributed throughout a matrix.
[008] The patent EP1166030A2, describe a method for making reaction bonded composite. In this process the plies of non- woven, mono filament SiC fibers are formed. To make the composite element a slip including SiC powder and silicon (Si) powder is cast around the plies to form a matrix around the plies. The matrix is then reaction-bonded to form a composite element of this invention.
[009] Brun et al. (U.S. Pat. No. 5,205,970) also disclose a method for fabrication of reaction-bonded SiC bodies, which are produced by reactively infiltrating Si into a porous carbonaceous preform. After infiltration, the excess infiltrant appears as excess droplets on the surface of the reaction-formed body. The formed body is then placed in contact with a wicking means, such as a piece of carbon cloth and re-heated above the infiltrant melting temperature. Excess infiltrant is wicked from the surface of the body into the wicking means by capillary force.
[010] Taylor et al. (U.S. Pat. No. 3,796,564) also disclose a B4C based ceramic composite for armor applications. Granular B4C is mixed with a binder, shaped as a preform, and rigidized. Then the preform is thermally processed in an inert atmosphere with a controlled amount of molten Si in a temperature range of about 1500° C to about 2200° C, whereupon the molten Si infiltrates the preform and reacts with some of the B4C. The fabricated body comprises B4C, SiC and Si.
[011] However, reaction bonded composite results in a semi-continuous phase of ceramic particles inside the matrix, which reduced the multi-hit capability of BPV. Hence, in order to defeat additional impacts of the threat that are near to previous impacts, the size of the damaged area produced in the BPV needs to be

controlled and minimized. With better damage control, the damage size produced will be smaller and more closely spaced hits can be defeated by the armor. The BPV containing segmented ceramics in the form of “tiles” can solve a part of this problem, because crack propagation from one tile to another can be minimized. The strong stress waves can still damage tiles adjacent to the impacted tile by propagating through the edges of the impacted tile to the adjacent tiles.
[012] U.S. Pat. No. 7866248B2 discloses a composite armor including a disrupting layer and a backing layer, which provides protection against blast and ballistic threats. The disrupting layer includes ceramic tiles that disrupt the incoming projectile, while the backing layer prevents penetration past the armor by the disrupted projectile. The disrupting layer includes a layer of polygonal ceramic tiles with a deflecting front surface, encased by a retaining polymer.
[013] U.S. Pat. No. 6,112,635 discloses a composite armor plate for absorbing and dissipating kinetic energy from a high velocity, armor-piercing projectile, the plate comprising a single layer of ceramic cylinders arranged in a plurality of adjacent rows. The cylinders are in direct contact with each other and are bound by a solidified material. US Patent 5,972,819, also describes a method for fabrication of ceramic cylinders based armor panel, having convexly curved end face, wherein the ratio D/R between the diameter D of said cylindrical body and the radius R of curvature of convexly curved end face is at least 0.64.
[014] U.S. Pat. No. 3,705,558 discloses another form of lightweight armor plate comprising a layer of ceramic balls in contact with each other. In one embodiment, the ceramic balls are encased in a stainless steel wire screen; and in another embodiment, the composite armor is manufactured by adhering nickel-coated alumina spheres to the base plate. U.S. Pat. No. 5,361,678 also discloses composite armor comprising ceramic spheres embedded in a matrix,

where spheres are fully coated with a binder to enhance the ballistic performance of the armor.
[015] U.S. Pat. No 2007/0017359 A1 also disclosed similar approach where ceramic spheres are positioned in contact with an armor base substrate. A polyuria layer is interposed between the plurality of ceramic spheres such that the polyuria layer partially encapsulates /partially exposed the ceramic spheres. The partially exposed ceramic spheres are oriented in a direction of anticipated impact.
[016] Even though aforesaid methods are available to fabricate the BPV using different shape ceramics (i.e. tiles, cylinders, sphere etc.) having high hardness but lower crack resistance. Still there is a need of a process, where combination of much higher hardness and toughness ceramic composite can be embedded over the surface of BPV to enhance the multi-hit capability. In addition, the surface object of BPV should be capable of great compression without fracture on impact and should also effectively distributes the impact force of a projectile over a much greater area of the armor by a chain reaction combination of very hard geometrically shaped objects being in contact with each other.
[017] However, as discussed above, a single ceramic material does not meet the requirement of high hardness and toughness together. Judicious combination of two different materials can meet the requirement of desired hardness and toughness, as hardness increases toughness decreases and vice-versa. On the basis of above issues following are the objectives of present invention.

OBJECTS OF THE DISCLOSURE
[0002] Some of the objects of the present disclosure, which at least one
embodiment herein satisfy, are listed hereinbelow.
It is therefor, a general object of the Present disclosure is to provide bullet proof vests (BPV), which effectively resist or prevent the penetration of high energy fragments and bullets.
Another object of the present disclosure is to provide bullet proof vests (BPV), having muti hit capability and also having very high hardness object over the surface to crush the incoming projectile.
Another object of the present disclosure is to provide bullet proof vests (BPV), where crack propagation from one geometrically shaped object to another can be minimized.
A further object of the invention is to design a BPV, where ceramic object deflects the bullet and do not fracture on impact and effectively distributes the impact force of a projectile over a much larger area.
Further object of the present invention to propose a process to fabricate the BPV, where much higher hardness and toughness ceramic composite can be embedded over the surface to enhance the multi-hit capability.
[0003] These and other objects and advantages of the present invention will
be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred form of the present invention is illustrated.

SUMMARY
[0004] The concepts are further described below in the detailed description.
This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
The present invention describes a process to fabricate the bullet proof vests (BPV), which effectively resist or prevent the penetration of high energy fragments and bullets. The striking surface of BPV is covered by a very high hardness hexagonal ceramic tiles and backing layer have the embedment of very tough ceramic spheres to increase the multi-hit capability. The ceramic tiles are made of B4C ceramic composite, which exhibit hardness of 2800-3000 Hv and toughness of around 5-8 MPam1/2. Ceramic spheres inside the backing layer are made of ZrO2 doped with Y2O3 and exhibits the toughness of around 20-25MPam1/2, which is around 5 times higher than the toughness of ceramic tiles of striking surface. Due to very high fracture toughness of ceramic spheres, damage caused by a projectile impact drastically reduces and BPV can withstand against very high threat levels.
A bullet proof vest (BPV) for prevention of penetration of high energy fragments and bullets, said vest comprises three different layers
i. striking layer (surface) (102) made up of hexagonal ceramic tiles to
absorb stress waves produced by impact ;
ii. backing layer (101) comprises of plurality of fibrous layers, bonded
to a layer of ceramic spheres
iii. soft armor panel (100) made up of fibrous layer to minimize the
impact to the wearer.
[0005] Various objects, features, aspects, and advantages of the inventive
subject matter will become more apparent from the following detailed description

of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.
[0006] It is to be understood that the aspects and embodiments of the
disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined to form a further embodiment of the disclosure.
[0007] The foregoing summary is illustrative only and is not intended to be in
any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The accompanying drawings, which are incorporated in and constitute
a part of this disclosure, illustrate exemplary embodiments and, together with the description, serve to explain the disclosed principles. In the figures, the left¬most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the figures to reference like features and components. Some embodiments of system and/or methods in accordance with embodiments of the present subject matter are now described, by way of example only, and with reference to the accompanying figures, in which:
Figure 1 illustrates Schematic of BPV showing the different layers therein.
Figure 2 illustrates Schematic of the striking surface showing the arrangement of hexagonal tiles over the backing layer.
Figure 3. Illustrates the arrangement of very tough ceramic spheres inside the backing layer.

Figure 4. Illustrates the role of different layer and mechanism of bullet crushing on impact.
DETAILED DESCRIPTION
[0009] In the present document, the word "exemplary" is used herein to mean
"serving as an example, instance, or illustration." Any embodiment or implementation of the present subject matter described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.
[0010] While the disclosure is susceptible to various modifications and
alternative forms, specific embodiment thereof has been shown by way of example in the drawings and will be described in detail below. It should be understood, however that it is not intended to limit the disclosure to the forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure.
[0011] The terms “comprises”, “comprising”, “includes” or any other variations
thereof, are intended to cover a non-exclusive inclusion, such that a setup, device or method that includes a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or device or method. In other words, one or more elements in a system or apparatus proceeded by “comprises… a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or method.
[0012] In the following detailed description of the embodiments of the
disclosure, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized and that changes

may be made without departing from the scope of the present disclosure. The following description is, therefore, not to be taken in a limiting sense.
Hereinafter, a description of an embodiment related to an improved bullet proof vests (BPV), which effectively resist or prevent the penetration of high energy fragments and bullets.
The schematic of the developed BPV is shown in Figure 1, which consists of three different layer namely, striking surface 102, backing layer 101 and soft armor panel (SAP) 100. All three layers in combination, absorb a large portion of kinetic energy from the ballistic projectile and simultaneously spread the force of the impact by deforming, deflecting, or fragmenting the incoming projectile without much damage due to combination of high hardness and toughness of ceramic objects.
The striking surface 102, in the proposed structure is made of very high hardness ceramic. During impact, the projectile is blunted and cracked or shattered by the hard ceramic face, resulting in fine ceramic rubble traveling with the fragmented projectile at much lower impact velocity towards the backing layer. Striking surface of BPV is subjected to high energy fragments and bullets and shatter easily after few shots due to low crack resistance of ceramics.
The striking surface 102, comprises the arrangement of ceramic hexagonal “tiles” over the backing layer 101, is shown in Figure 2. The hexagonal tiles 103, 104, 105, 106, 107 (and many more) of striking surface 102, is bonded to the backing layer 101, by way of a polymer adhesive 108, which may be a polyurethane adhesive or any other suitable epoxy compounds such as DER331 (Dow Chemicals) and Curing agent named as Cycloaliphatic polyamine. Another polymeric elastomeric material 109, is placed around the ceramic tiles of striking surface 102, which absorbs the stress waves produced by impact, preferably limiting the damage caused by a projectile impact to the neighboring tiles.

[033] The ceramic tiles of striking layer 102, is made of B4C and have
thickness limited to not more than 3.5 mm. Other material like Al2O3, SiC, ZrO2, and TiB2 etc., also can be attached to the backing layer 101, depending on the weight requirement and threat level. The average hardness of ceramic tiles of striking layer 102, ranges from 2800-3000 Hv with toughness of around 5.0-8.0
MPam1/2.
The striking surface of BPV is subjected to high energy fragments and bullets and shatter easily after few shots due to low crack resistance of ceramics. Embodiments of the present invention describe a fabrication process for BPV, which effectively resist or prevent the penetration of high energy fragments and bullets. In the present invention, striking surface of BPV is covered by a very high hardness ceramic and backing layer have the embedment of very tough ceramic to increase the multi-hit capability.
The inner backing material 101, (comprising a plurality of fibrous layers) then acts as a support for the damaged ceramic and also continues to stop the projectile. The fibrous layers collect debris from both the projectile and broken ceramic, thereby preventing their further penetration, due to this impact on SAP 100, or wearer minimized.
According to present invention, the number of fibrous layers in backing material ranges preferably from 25 to 40. To improve the multi-shot capability, a layer of ceramic spheres are positioned in contact with backing layer 101. Ceramic spheres are further covered by the backing material 101, having 10 to 15 layers. The ceramic spheres are sandwich between the backing layer at temperature of around 100-140oC and pressure of 80-100 bar. The ceramic tiles layer that faces towards a potential incoming projectile forms a striking surface 102, which is bonded to the backing layer 101.

Figure 3 illustrates the backing layer 101 also comprises arrangement of very tough ceramic spheres. The ceramic spheres 111, 112, 113, 114 (and many more) are bonded to the backing layer 101, by way of a polymer adhesive 110. Another polymeric elastomeric (polyurea) 115 material is placed around the spheres to absorb the stress waves produced by projectile impact.
Ceramic spheres inside the backing layer 101, are very tough having adequate hardness and made of yttria (Y2O3) doped with ZrO2. Doping by 3 mol % Y2O3 leads to phase transformation and put the crack into compression, retarding its growth, and enhance the fracture toughness of composite. The toughness of ceramic spheres 111, 112, 113, 114 is around 20-25MPam1/2, which is around 5 times higher than the toughness of ceramic tiles of striking surface 102. Due to very high fracture toughness of ceramic spheres, damage caused by a projectile impact drastically reduced and BPV can withstand against very high threat levels. The diameter of ceramic spheres inside the backing layer 101, is limited to not more than 2.5 mm.
The SAP 100, minimize the impact /injury to the wearer and is made of fibrous layers such as KEVLAR para-aramid, or SPECTRA polyethylene fabric etc. According to particular embodiments, the number of fibrous layers in SAP ranges from 10 to 25, preferably from 15 to 20, and more preferably from 12 to 15. Combinations of different types of fibers and fabrics may be used in SAP network in the form of a woven, knitted, or non-woven fabric.
Figure 4 illustrates the role of different layer of fabricated BPV and mechanism of bullet crushing on impact. On impact of high energy projectile 116, (having sharp tip 117) the ceramic tiles of striking face 102, defeat the incoming projectile by blunting, shattering, and deforming due to very high hardness of tiles. In addition to this, kinetic energy dissipation is achieved by the spaced relation of

the tiles where each tiles absorbs some of the energy and transferred to neighboring tiles by chain reaction.
[037] The polymeric elastomeric 109, around the ceramic tiles of striking surface 102, also absorbs the stress waves limits the damage to the neighboring tiles. The incident momentum of the initial projectile is thus transferred to fragments, 118, 119, 120 (and many more) of shattered projectile 116, and the ceramic rubbles 121, 122, 123 (of tiles), which travels at much lower impact velocity toward the backing plate 101. The fragments of shattered projectile and the ceramic rubbles encounter the very tough ceramic spheres 111, 112, 113, 114 (and many more) of backing layer 101. The ceramic rubbles and fragmented projectile is further blunted, crushed and deflected by very tough ceramics spheres. Due to very high toughness and adequate hardness, spheres of backing layer 101, do not get crushed completely and provide the protection against higher threat levels. Now ceramic rubbles (of tiles, spheres) and blunted /shatter projectile have very low impact energy and hence their debris completely entrapped by the back portion of backing layer 101, depicted by 124, 125, 126, 127 (and many more). The remaining energy is absorbed by the SAP 100, of backing layer 101, which reduced shock/trauma to the wearer completely.
In accordance to the embodiment of the present invention, there is provided a method of fabrication process for BPV, which effectively resist or prevent the penetration of high energy fragments and bullets. In the present invention, striking surface of BPV is covered by a very high hardness ceramic and backing layer have the embedment of very tough ceramic to increase the multi-hit capability.
To improve the multi-shot capability, a layer of ceramic spheres are positioned in contact with backing layer 101. Ceramic spheres are further covered by the backing material 101, having 10 to 15 layers. The ceramic spheres are sandwich between the backing layer at temperature of around 100-140oC and pressure of

80-100 bar. The ceramic tiles layer that faces towards a potential incoming projectile forms a striking surface 102, which is bonded to the backing layer 101.
TECHNICAL ADVANTAGES
The present disclosure provides an improved BPV having three layers , where striking surface 102, is covered by a very high hardness ceramic tiles and backing layer 101, have the embedment of very tough ceramic spheres to increase the multi-hit capability.
The hardness of ceramic tiles of striking surface 102, ranges from 2800-3000 Hv (with toughness of around 5.0-8.0 MPam1/2) and defeat the incoming projectile by blunting, shattering, and deforming due to very high hardness of tiles.
The backing layer (fibrous layers) 101, collect debris from both the projectile and broken ceramic, thereby preventing their further penetration.
To improve the multi-hit capability of BPV, the ceramic spheres of diameter around 3.5 are bonded to the backing layer 101, by way of a polymer adhesive.
Ceramic spheres inside the backing layer 101, are made of yttria (Y2O3) doped with ZrO2. Doping by Y2O3 leads to enhance the fracture toughness of composite.
Ceramic spheres inside the backing layer 101, have toughness of around 20-25MPam1/2, which is around 5 times higher than the toughness of ceramic tiles of striking surface 102.
Due to very high toughness (and adequate hardness), the spheres of backing layer 101, further blunt, crush and deflected the fragmented projectile (which pass through the striking surface) and provide the protection against higher threat levels.

Equivalents:
The illustrated steps are set out to explain the exemplary embodiments shown,
and it should be anticipated that ongoing technological development will change
the manner in which particular functions are performed. These examples are
presented herein for purposes of illustration, and not limitation. Further, the
boundaries of the functional building blocks have been arbitrarily defined herein
for the convenience of the description. Alternative boundaries can be defined so
long as the specified functions and relationships thereof are appropriately
performed. Alternatives (including equivalents, extensions, variations,
deviations, etc., of those described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternatives fall within the scope and spirit of the disclosed embodiments. Also, the words "comprising," "having," "containing," and "including," and other similar forms are intended to be equivalent in meaning and be open-ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items. It must also be noted that as used herein and in the appended claims, the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise.
Finally, the language used in the specification has been principally selected for readability and instructional purposes, and it may not have been selected to delineate or circumscribe the inventive subject matter. It is therefore intended that the scope of the invention be limited not by this detailed description, but rather by any claims that issue on an application based here on. Accordingly, the embodiments of the present invention are intended to be illustrative, but not limiting, of the scope of the invention, which is set forth in the following claims.

We claim:
1. A bullet proof vest (BPV) for prevention of penetration of high energy
fragments and bullets, said vest comprises three different layers
i. striking layer (surface) (102) made up of hexagonal ceramic tiles to
absorb stress waves produced by impact ;
ii. backing layer (101) comprises of plurality of fibrous layers, bonded to a
layer of ceramic spheres
iii. soft armor panel (100) made up of fibrous layer to minimize the impact
to the wearer.
wherein the ceramic tiles layer that faces towards a potential incoming projectile forms a striking surface 102, which is bonded to the backing layer 101.
2. The vest (BPV) as claimed in claim 1, wherein the ceramic hexagonal tiles (103,104,105, 106,107 etc.) are bonded to the backing layer (101) through polyurethane adhesive and/or other epoxy compounds such as DER331 (Dow Chemicals) and Curing agent named as Cycloaliphatic polyamine.
3. The vest (BPV) as claimed in claim 1, wherein a polymeric elastomeric 109 is placed around the ceramic tiles of said striking surface 102 to absorb the stress waves limits the damage to the neighboring tiles.
4. The vest (BPV) as claimed in claim 1, wherein the fibrous layer used in all layers selected from KEVLAR para-aramid, or SPECTRA polyethylene fabric.
5. The vest (BPV) as claimed in claim 1, wherein the striking layer (102) is made up of B4C and have s thickness limited to not more than 3.5 mm.
6. The vest (BPV) as claimed in claim 1, wherein number of fibrous layers of the backing layer is preferably from 25 to 40.

7. The vest (BPV) as claimed in claim 1, wherein the backing layer (101) having 10 to 15 of layers of ceramic spheres.
8. The vest (BPV) as claimed in claim 1, wherein the ceramic spheres are bonded to the backing layer (101) through a polymer adhesive or more particularly polyurea.
9. The vest (BPV) as claimed in claim 1, wherein the ceramic sphetes is made up of yttria (Y2O3) doped with ZrO2 in order to phase transformation and put the crack into compression.
10. The vest (BPV) as claimed in claim 1, wherein the diameter of said
ceramic spheres is limited to not more than 1.7 -2.5 mm.
11. The vest (BPV) as claimed in claim 1, wherein the number of fibrous layers in SAP ranges from 10 to 25, preferably from 15 to 20, and more preferably from 12 to 15.
12. A method for fabrication of BPV as claimed in claim 1, comprises the steps of :
i. Providing a layer of ceramic spheres in the contact with backing layer;
ii. Covering of ceramic sphere by the backing material 101;
iii. Subjected to compaction of ceramic spheres between the backing layer.
13. The method as claimed in claim 12, wherein the compaction takes place
at a temperature of 100-140oC and pressure of 80-100 bar.