GB2377006A

GB2377006A - Ballistic protection shield

Info

Publication number: GB2377006A
Application number: GB0116117A
Authority: GB
Inventors: David Adie
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-06-30
Filing date: 2001-06-30
Publication date: 2002-12-31
Also published as: GB0116117D0

Abstract

A ballistic protection shield 1 comprises a first ceramic (eg. silicon or boron carbide, silicon nitride or aluminium oxide) section 2 (consisting a plurality of slabs 4, which break upon contact with an oncoming projectile), a second polymer fibre section 3 (which arrests any ceramic or projectile fragments produced during impact), and possibly a 2-5 mm intermediate fibre-sheet layer (11, Fig 10) such as an aramid stiffened by epoxy resin for higher levels of protection. Adjacent slabs 4 (of area 40cm<SP>2</SP>) touch into the second section 3 and include flat-headed cylindrical or round-tipped conical projections 5 spaced between 0-3mm apart, symmetrically arranged and interconnected by a (possibly perforated/cavitied) latticed binding platform 6. Polyurethane (or aluminium) binding material is incorporated into gaps (7, Fig 6a) between projections 5. The second polymer section 3 may be (re)shaped/used by warming its polymer fibre layers to around 120{ and applying a pressure of between 5x10<SP>5</SP> to 10x10<SP>5</SP> Nm<SP>-2</SP> (5-10 bar) and bonding the ceramic slab portions 4 into it.

Description

BALLISTIC PROTECTION SHIELD The present invention relates to ballistic protection shields which may be used in various applications like vehicle bodywork and/or bulletproof vests.

Special steels are currently used in the ballistic protection industry but ceramics have been known for some time as a potentially excellent ballistic protection material due to their extreme hardness and their lightness. This is of particular advantage in the automotive industry where using conventional materials results in an armour-plated vehicle being extremely heavy and not so easy to handle as a vehicle without such armour. Lightness, which leads to improved handling and quick acceleration, especially in the case when the vehicle is under fire, is perceived as a strong market advantage for ballistic protection vehicle manufacturers.

However, ballistic protection products made from ceramics have two major disadvantages in comparison with existing steel applications, namely they are brittle and, for the higher performance ceramics such as silicon carbide, silicon nitride and boron carbide, are difficult to produce economically. Their brittle nature means that although the hardness of the ceramic material is such that the first fired projectile striking it becomes pulverized, a second fired projectile arriving in the same area, as is possible under continuous or multi-hit firing conditions, does not however meet such strong resistance due to the tendency of the ceramic to crack. In fact the ceramic can, itself, become a projectile under continuous fire. This is particularly a problem in applications which need to meet the Committee for European Norms (CEN) standard FB6, FB7 and higher levels of armour plating testing. In such tests the armour plating must be capable of withstanding the impact of a least three bullets of the type used in the recognized CEN standard FB6, FB7 and higher levels of armoured plating testing to the extent that none of the three bullets or parts of the bullets pass through the armour plating material or cause the material to become a projectile Itself and to the extent that the material can withstand the accepted criteria of the armour plating industry multi-hit test when the bullets strike within a limited triangular

zone in which the sides of the triangle are no longer than three times the diameter of the striking bullets.

It is an object of the present invention to provide a ballistic protection shield using ceramic which is adapted so as to mitigate effects of the ceramic cracking following ballistic impacts. It is a further object of the present invention to produce economically a ballistic protection shield made from ceramic.

According to a first aspect, the present invention consists in a ballistic protection shield comprising a first section of ceramic material and a second section of polymer fiber material in a compacted form of sheet layers, the first section having a plurality of projections which are held together by interconnecting means, the interconnecting means providing weak points in the first section so that upon Impact of an oncoming projectile on the projections the projectile IS broken into fragments and damage propagation within the first section is limited, and the first and second sections being so constructed that ceramic material fragments of either the ceramic material or projectile caused by a fragmentation thereof due to the impact are arrested by the polymer fiber material of the second section.

The first section may be formed from a plurality of ceramic slabs laid adjacent to one another on the second section so as to provide a shield with the required surface area.

The ceramic material may consist of silicon carbide but, for reasons of economy, lightness, supply, etc.. other ceramics could be used such as, silicon nitride, boron carbide or even aluminum oxide.

An intermediate layer of fiber sheet material stiffened by epoxy or similar resin can be bonded between the first and second sections so as to enhance binding between the first and second sections.

The projections may be arranged in the first section so that the surfaces of the projections form a substantial part of the surface which the oncoming projectile contacts upon impact with the first section.

In one embodiment, the projections are arranged in the first section so that there are gaps between regions of the sidewalls of adjacent projections. Also, the projections may be arranged in the first section so that a region of the sidewalls of adjacent projections are in contact with one another. The gaps between the projections can be variable as can the profile and cross-sections of the projections themselves. The projections may be shaped so that at least a portion of the projection is substantially cylindrical or conical in shape. For example, the projections may be in the shape of flat headed cylinders or cylinders which have a frusto cone head section. In those examples, gaps are formed between the projections even when the projections are arranged in contact with each other by virtue of the curvature of the projection sidewalls.

The first section can include a platform for binding the projections together and the platform and/or projections can include perforations or cavities so as to reduce the weight of the shield. In order to further bind the projections together and increase resistance to fragmentation, a bonding material may be added between the gaps and/or ceramic joints may interpose adjacent projections.

Additionally, to reduce the weight of the shield, the platform may have a lattice framework or the projections may be bound together without a platform by means of the ceramic joints interposing adjacent projections.

The first section and second section may be arranged together so that the projections immediately face the oncoming projectile and so that the platform of the first section interposes the first section and the second section.

Alternatively, the first section can be arranged so that the projections interpose the second section and the platform and so that the platform immediately faces the oncoming projectile.

According to a second aspect, the present invention consists in a method of assembling a ballistic protection shield as described above Including the steps of shaping the second section by warming the polymer fiber sheet layers of the second section to around 1200C and applying a pressure of between 5 to 10 bar

and then bonding the first section of ceramic slab pieces onto the surface of the polymer fiber layer of the shaped second section.

According to a third aspect, the present invention consists in a method of reusing the polymer fiber material of the second section of the ballistic protection shield as described above including the steps of separating the polymer fiber material of the second section from the ceramic of the first section, and bonding a different plurality of ceramic slab pieces to the second section.

The ballistic protection shield can be reshaped to allow re-application of the same second section polymer fiber material in a different shape and application when the contours of the shield are to be modified. The polymer fiber material of the second section can be reshaped and a different plurality of ceramic pieces can be bonded to the re-shaped second section. For example, a ballistic protection shield fitted to a vehicle may be removed and re-shaped to a new model with modified profile and dimensions. Being able to re-use the materials in the shield provides opportunities for longer term cost reduction and increased ability to compete on price with other shield system suppliers.

The ballistic protection in this re-usable form will no longer present a disposal or recycling problem which is a distinct advantage in the automobile industry where vehicle manufacturers will shortly be required to accept used vehicles for disposal and recycling.

Specific embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which :- Figure 1 IS a perspective view of part of a ballistic protection shield according to the present invention in a flat sheet configuration having flat headed cylindrical projections; Figure 2 (a) is a fragmentary side view of the first section of the shield of Figure 1 showing flat headed cylindrical projections protruding from a platform ; Figure 2 (b) IS a top plan view of the first section of Figure 2 (a);

Figure 3 is a perspective view of part of a shield according to an embodiment In a profile sheet configuration showing the first section made up of slabs profiled to the second section polymer ; Figure 4 (a) shows a fragmentary side view of the shield of Figure 1 showing the second section polymer fiber together with a binding material between the projections; Figure 4 (b) is a sectional top view of Figure 4 (a); Figure 5 (a) is a fragmentary side view of a first section of the shield according to embodiment of the invention in which the protrusions have a frusto cone end section facing the oncoming projectile ; Figure 5 (b) is a top plan view of Figure 5 (a) ; Figure 6 (a) is a fragmentary side view of a shield having a first section as shown in Figure 5 (a) together with binding material between the projections; Figure 6 (b) is a sectional top view of Figure 6 (a); Figure 7 (a) shows a fragmentary side view of a first section of an embodiment of the shield in which the projections are bound together by ceramic joints; Figure 7 (b) is a top plan view of the first section shown in Figure 7 (a); Figure 8 (a) shows the first section of Figure 5 (a) including pinholes in the projections for the purpose for reducing weight; Figure 8 (b) shows a top plan view of Figure 8 (a) ; Figure 9 (a) shows the first section of Figure 5 including cavities extending from the platform into the projections so as to reduce weight; Figure 9 (b) is a top view of the first section of Figure 9 (a); Figure 10 shows a bottom plan view of a shield according to an embodiment having a platform in the form of a lattice framework so as to reduce weight,

Figure 11 (a) is a fragmentary side view of a shield according to an embodiment in which the projections are bound together by ceramic joints between adjacent projections, Figure 11 (b) is a plan view of Figure 11 (a); Figure 12 shows a ceramic slab of a shield in an embodiment in which the projections are partially cylindrical and have frusto cone end sections ; Figure 13 shows the ceramic slab of Figure 12 including pinholes in the projections ; Figure 14 (a) shows the top view of sets of projections taken In isolation having circular, hexagonal, or square heads; and Figure 14 (b) shows the sets of projections of Figure 14 (a) with ceramic joints linking adjacent projections together.

Figure 15 shows a fragmentary sectional view of the shield according to an embodiment in which the ceramic slab of the first section has been shaped to the curvature of the second section.

Referring to Figure 1 of the accompanying drawings, there is shown a perspective view of a ballistic protection shield 1 according to an embodiment of the invention and which has a first section 2 of ceramic material and a second section 3 which comprises multiple layers of polymer fiber material.

As shown in Figure 1, the first section 2 is formed from a plurality of ceramic slabs 4 which are individually shaped so that they can be bonded adjacent to one another on a face of the second section 3.

As shown in Figures 2 (a) and 2 (b), the first section 2 compnses an interconnecting means in the form of a platform 6 and a plurality of projections 5 protruding from a face of the platform 6. In this particular embodiment, the platform 6 is formed in contact with the face of the second section 3 (not shown).

When a projectile, such as a bullet, impacts on the ballistic protection shield 1, ceramic material of the first section 2 Impacted by the bullet and the bullet Itself, fragment. However, the first section 2 hinders the spread of cracks therein and the polymer fibre material of the second section 3 catches fragments

of the bullet and ceramic which are still traveling with considerable residual energy in the original direction of the bullet. The concept can be summarised as "break and catch technique"as opposed to simply arresting the projectile.

Furthermore, the oncoming projectile is stopped by the shield 1 in various ways.

The projectile may impact on a substantial part of one or more of the projections 5, in which case the projectile will lose significant energy before continuing to penetrate into the shield 1 making the task of stopping the projectile easier.

Alternatively, the projectile may, on Impacting one or more of the projections 5, deflect sideways and continue to penetrate into the shield 1 at an angle so that the projectile must travel through a larger volume of the ceramic material for a given penetration depth thus making it easier to arrest the projectile.

The projections 5 are held together, preferably, in a substantially symmetrical arrangement, by the platform 6 which provides intentional weak points between the projections 5 so that, upon impact of an oncoming projectile on the first section 2, the projections 5 together act as a rigid integral structure for a brief fraction of a second before fracturing cleanly at the boundaries between the projections 5 and the platform 6. As a result, damage propagation within the ceramic material of the first section 2 and within the second section 3 of the shield 1 caused by the oncoming projectile is minimized.

The exact configuration of the projections 5 and platform 6 of the first section 2 depend upon the level of ballistic protection required and the type of oncoming projectile, as does the profile and cross-section of the projections 5.

The ballistic protection shield 1 is designed so that the shield 1 IS capable of withstanding an impact of at least three bullets of the type used In the recognised CEN standard FB6, FB7 and higher levels of armoured plating testing to the extent that none of the three bullets or parts of the bullets pass through the material or cause the material to become itself a projectile and to the extent that the material can withstand the accepted cnteria of the armour plating industry multi-hit test when the bullets strike within a limited triangular zone in which the size of the triangle IS no larger than three times the diameter of the striking

bullets. For applications up to and Including FB6 level of the CEN standard, the thickness of the ceramic slabs 4 of the first section 2 should not be less than 5mm and the thickness of the second section 3 is typically 10mm or more.

For applications which necessitate higher levels of protection, like for example for projectiles of 25 mm diameter or more, the thickness of the first and second sections should each be 20 mm or more.

In the embodiment of the shield 1 shown in figures 1,2 (a) and 2 (b), the projections 5 are in the form of flat headed cylinders and arranged in parallel rows which are staggered with respect to each other to form a matrix so that the surfaces of the projections form a substantial part of the surface which the oncoming projectile contacts upon impact with the first section 2. The projections are therefore spaced apart in close proximity so as to form gaps between the projections. Typically, the spacing between adjacent projections is of the order of 0 to 3 mm and about 20 to 40 projections, typically of a diameter of between 10 and 16 mm, are arranged on the platform 6. In this embodiment, the thickness of the platform 6 is of the order of 2 mm.

The use of ceramic slabs 4 to form the first section 2 allows the shield 1 to be produced to a different form and profile as required by the shape of the article to which the shield is to be applied. If it is impractical to use flat ceramic slabs 4 because the radius of curvature of the second section 3 is too small to allow flat ceramic slabs 4 to be bonded to the second section 3 as required, ceramic slabs 4 which are shaped to the curvature of the second section 3 can be used (see Figure 15). Figure 3 shows part of the shield 1 in a profile sheet configuration in which the first section 2 is made up of ceramic slabs 4 profiled to the second section 3. The second section polymer fiber material is formed in one or more slabs which can be profiled and joined together to form the second section 3 to the required form and the ceramic slabs 4 of, say 40cm2, are profiled so that when they are laid adjacent to each other on the profiled second section 2, the required profile of the shield 1 is formed. The second section 3 is profiled by warming the multi-layers of polymer fiber material to around 1200C and applying

pressure of between 5 to 10 bar, whereafter the profiled shield 1 is completed by bonding the ceramic slabs 4 onto the face of the second section 3.

In the embodiment shown in Figure 2, because the rows of projections 5 extend between a first and second side of the ceramic slab 4 and are staggered with respect to each other, the rows of projections 5 are arranged relative to the ceramic slab 4 so that the projections 5 at the ends of alternate rows overlap the first side of the slab 4 and so that the projections 5 at the other ends of the alternate rows are offset inwardly from the second side 4. When the ceramic slabs 4 are joined together, the portions of the projections overlapping the first sides of the slabs 4 sit on the second sides of the adjacent slabs 4 and occupy spaces next to the projections offset from the second sides 4. The overlapping projections may contact the faces of the ceramic slabs 4 and may be bonded thereto. Arranging the rows of projections 5 on each ceramic slab 4 in this manner enables a uniform matrix of projections 5 to be formed on the first section when the ceramic slabs 4 are joined together.

If the profile of the shield 1 needs to be changed to enable its use in a different application, the second section polymer fiber material is separated from the first section 2 by means of dissolving the bond material between the first and second section in a solution as is known in the art. The second section polymer fiber matenal is then reshaped and a new plurality of appropnately profiled ceramic slabs 4 are bonded to the reshaped second section polymer fiber material so as to modify the contours of the protection shield 1. Thus, the second section polymer fiber material of the shield 1 can be reshaped and reapplied in a shield of different shape. For example, a shield fitted to a vehicle may be removed and reshaped to a new vehicle with modified profile and dimensions. Being able to re-use the materials in the two section shield provides opportunities for longer term cost reduction and increased ability to compete on price with steel shields and other shield systems. Another advantage of the ballistic protection shield over conventional steel systems is its significant weight

reduction without loss of protection performance and without increasing cost at the point of application.

Furthermore, a ballistic protection shield having a reusable section will reduce disposing and recycling problems which is a distinct advantage in the automobile industry where vehicle manufactures will shortly be required to accept used vehicles for disposal and recycling.

In order to further enhance binding between the first and second sections 2,3 an additional layer of material consisting of a polymer fibre material, such as an aramid fibre sheet, may be bonded between the first and second section (not shown). The additional layer has a typical thickness of between 2mm to 5mm and is stiffened with an epoxy or similar resin. The application of this intermediate layer is designed to minimise ceramic material breakaway from the back face of the first section material which tends to be caused by the hard-core armour-piercing ammunition. The thickness of the intermediate layer should be increased when protection above the FB7 level is required.

Figure 4 shows a shield according to another embodiment which is similar to the shield of Figures 1 and 2 but it has a bonding material 7 added to the first section 2. The additional bonding material 7 is added in the gaps between the projections and, if necessary, above the projections to encapsulate them in the bonding material, so as to provide the first section 2 with increased resistance against fragmenting as a result of projectile impact. The bonding material may be any with tough, elastic properties which will bond with the ceramic slab such as polyurethane or a lightweight alloy, such as an aluminum alloy.

A ceramic slab 4 of an alternative embodiment of the shield with and without the bonding matenal 7 is shown in Figures 5 and 6, respectively, in which each projection 5 consists of a cylindrical base section and a round tipped conical like head section.

Also, to provide the first section 2 with further resistance against fragmenting, according to another embodiment shown in Figure 7, the projections are formed with ceramic joints 8 so as to link the sidewalls of adjacent projections

5 to one another. The joints 8 extend vertically between part of the sidewalls of the projections so as to link together opposing regions of the sidewalls of adjacent projections.

In alternative embodiments of the shield 1, like for example shown In Figures 8 & 9, cavities 10 or holes 9 can be introduced into the first section 2 in order to reduce the weight of the shield 1. Figure 8 shows the first section 2 of Figure 5 in which each projection 5 includes a pinhole which extends along the vertical axis of the projection 5 into and through the platform 6. In Figure 9, cavities extend through the platform 6 into part of the cylindrical base section of each projection 5.

According to other embodiments, like for example shown in Figure 10, more extreme weight reduction may be achieved by adopting a platform 6 consisting of a lattice framework. The platform 6 consists of ceramic formed into two sets of substantially parallel bars 1 which intersect with one another to form a lattice framework structure. The projections 5 are arranged so that at least part of each projection 5 protrudes from a respective intersection of the bars 11 of the framework. Alternatively, in another embodiment as shown in Figure 11, a reduction in the weight of the shield can be achieved by dispensing with the platform 6 and using the ceramic joints 8 as the sole means of binding the projections together.

In yet another embodiment of the shield 1 as shown in Figures 12 and 13, the projections 5 are shaped so as to have a cylindrical base section which are in contact with one another and a frusto cone section. In this embodiment gaps are formed between the projections even though the projections are in contact with one another because of the cylindrical shape of the base sections. Figure 14 shows fragmentary plan views of sets of projections 5 taken in isolation for shields of various embodiments in which the projections 5 of each set are all circular, hexagonal or square headed and with or without ceramic joints 8 interposing the adjacent projections 5.

According to yet another embodiment, the ceramic slabs 4 are orientated with respect to the second section 3 such that the platform 6 of the first section 2 IS immediately facing the oncoming projectile and so that the projections are situated between the second section 3 and the platform (not shown).

In all the embodiments, the ceramic material of the first section 2 may be, for example, silicon carbide, silicon nitride, boron carbide or aluminum oxide. The ceramic slabs 4 are formed using ceramic production processes for manufacturing thin wall complex ceramic shapes, as developed and applied by the company SiCeram in Weimar, Germany. Raw or green material treated with plasticising components and prepared by SiCeram, is moulded to form the platform 6 and projections 5 as one integral piece. A variable surface forming technique can be used to shape the integral piece prior to sintering so that the ceramic slab 4 is produced with a desired curvature. These process can be carried out by SiCeram or the company Keramprotect in Weimar, Germany.

After moulding, the plasticising components are removed from the ceramic slab 4 and the ceramic is sintered ready for combining with the second section 3. Both the removal of plasticising components and sintering of the ceramic can be carried out by SiCeram The polymer fiber material of the multi-layers of the second section 3 may be for example a polyethylene-fiber, such as Dyneema, (RTM) from the company DSM Holland, or any other which has tough and elastic properties. Layers of the polymer fiber are machined to size, laid on top of each other and bonded together through heating and pressing into a compact form so as to form one or more slabs of the second section 3. The ceramic slabs 4 are bonded onto the second section 3 using a typical bonding material, like for example an epoxy resin or polyurethane. Machining of the polymer fiber, forming of the second section 3, and bonding of the ceramic slab 4 onto the second section 3 can be carried out by Keramprotect. Also, the resulting first and second section 2,3 can be shaped and profiled by Keramprotect using a variable surface forming machine technique.

Whilst particular embodiments have been described, it will be understood that modifications can be made without departing from the scope of the present invention as defined by the appended claims. In particular, the skilled man would know that the shield of the present invention may Include a first section having projections other than of substantially cylindrical or conical shape. Also, the skilled man would know that the projections can be shaped so as to be in direct contact with each other with or without gaps between part of the projections.

Claims

CLAIMS 1. A ballistic protection shield comprising a first section of ceramic matenal and a second section of polymer fiber matenal in a compacted form of sheet layers, the first section having a plurality of projections which are held together by interconnecting means, the interconnecting means providing weak points in the first section so that upon Impact of an oncoming projectile on the projections the projectile is broken into fragments and damage propagation within the first section is limited, and the first and second sections being so constructed that ceramic matenal fragments of either the ceramic material or projectile caused by a fragmentation thereof due to the impact are arrested by the polymer fiber material of the second section.
2. A ballistic protection as claimed in claim 1, wherein the first section IS formed from a plurality of ceramic slabs laid adjacent to one another on the second section
3. A ballistic protection shield as claimed In claim 1 or 2, wherein an intermediate layer of fiber sheet material stiffened by epoxy or similar resin is bonded between the first and second sections.
4. A ballistic protection shield as claimed in claim 1,2 or 3, wherein the projections are so arranged that the surfaces of the projections form a substantial part of the surface which the oncoming projectile contacts upon impact with the first section.
5. A ballistic shield as claimed in any preceding claim, wherein the projections are so arranged that a region of the sidewalls of the adjacent projections are in contact with one another.
6. A ballistic protection shield as claimed in any preceding claim, wherein the projections are so arranged that there are gaps between a region of the sidewalls of adjacent projections.
7. A ballistic protection shield as claimed in claim 6, wherein the first section Includes a bonding material between the gaps formed by the projections.

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8. A ballistic protection shield as claimed in any preceding claim, wherein the interconnecting means comprises a platform for binding the projections together.
9. A ballistic protection as claimed in 8, wherein the platform includes perforations or cavities so as to reduce the weight of the shield.
10. A ballistic protection shield as claimed in 8 or 9, wherein the platform has a lattice framework.
11. A ballistic protection shield as claimed in any preceding claim, wherein the interconnecting means comprises ceramic joints interposing adjacent projections.
12. A ballistic protection shield as claimed in any of claims 8 to 11, wherein the first section is so arranged that the projections immediately face the oncoming projectile and so that the platform of the first section interposes the first section and the second section.
13. A ballistic protection shield as claimed in claim any of claims 8 to 11, wherein the first section is so arranged that the projections interpose the second section and the platform and so that the platform immediately faces the oncoming projectile.
14. A ballistic protection shield as claimed in any preceding claim, wherein the ceramic material is silicon carbide.
15. A ballistic protection shield as claimed in any preceding claim, wherein the ceramic material is silicon nitride, boron carbide or aluminum oxide.
16. A ballistic protection shield as claimed in any preceding claim, wherein at least a portion of each projection is substantially cylindrical in shape.
17. A ballistic protection shield as claimed in any preceding claim, wherein at least a portion of each projection is substantially conical in shape.
18. A ballistic protection shield as claimed In any preceding claim, wherein the head of each projection is flat or rounded.
19. A ballistic protection shield as claimed in any preceding claim, wherein the projections are arranged together in a substantially symmetncal pattern.
20. A method of assembling a ballistic protection shield according to any preceding claim including the steps of shaping the second section by warming

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the polymer fiber sheet layers of the second section to around 1200C and applying a pressure of between 5 to 10 bar and then bonding the first section of ceramic slab pieces onto the surface of the polymer fiber layer of the shaped second section.
21. A method of reusing the polymer fiber material of the second section of the ballistic protection shield according to any of claims 1 to 19 including the steps of separating the polymer fiber material of the second section from the ceramic of the first section, and bonding a different plurality of ceramic slab pieces to the second section
22. A method as claimed in claim 21, including the step of re-shaping the polymer fiber material of the second section, the different plurality of ceramic pieces being bonded to the re-shaped second section.
23. A ballistic protection shield constructed and arranged substantially as herein before described with reference to the accompanying drawings.