AU2019206125B2 - Reactive protection element - Google Patents

Abstract

A flexible protection element for reactive protection against shaped charge warheads and kinetic energy projectiles comprises a formable doughy mixture of a powder dispersed within a matrix of plastic explosive and a binder.

Description

REACTIVE PROTECTION ELEMENT

Field of the Invention

The present invention relates to the field of reactive armour. More

particularly, the invention relates to a shapeable material for reactive

surfaces and to a process for its preparation.

Background of the Invention

Reactive armour has been employed in the art for quite some time to

defend against attacks by a variety of anti-tank charges (which are used

against all kinds of armoured vehicles) and to reduce the damage done to

the vehicle being protected. It is most effective in protecting

against shaped charge warheads and kinetic energy penetrators.

An element of explosive reactive armour consists of an explosive layer

sheet or slab of high explosive sandwiched between two plates, typically

metal ones. When hit by anti-armour threat, either Shaped Charge

warheads or Long Rod penetrators, the explosive detonates, forcibly

driving the metal plates apart to damage the penetrator. Against a shaped

charge, the projected plates disrupt the metallic jet penetrator, effectively

providing a greater path-length of material to be penetrated. Against a

kinetic energy penetrator, the projected plates serve to deflect and break

up the rod.

The disruption is attributed mainly to the following mechanism. Since the

plates are angled with respect to the impact direction of shaped charge

warheads, as the plates move outwards the impact point, the plates move

continuously over time, requiring the jet to cut through additional fresh

plate material. This effect actually increases the effective plate thickness

during the impact.

A complication to the use of reactive armour is the hazardous risks to the

surroundings - dismounted troops or vehicles, due to fragments or moving

plates emanating from the explosive detonation. Another complication is

that conventional reactive armour is made of flat plates and is not suited

to protect non-planar surfaces. It would therefore be highly desirable to

provide new reactive armour that reduces the collateral damage effects to

the surroundings and which can also be easily applied to non-planar

surfaces.

It is an object of the present invention to provide a novel reactive

component of reactive armour, which maintains its efficacy against

threats while reducing the damage to the surroundings, as compared to

prior art reactive armours.

It is another object of the invention to provide such an energetic

component of reactive armour, which can be applied to non-planar

surfaces.

It is yet another object of the invention to provide reactive armour

employing the novel energetic component.

Other objects and advantages of the invention will become apparent as the

description proceeds.

Summary of the Invention

The invention relates to a rigid or flexible protection element for reactive

protection against shaped charge warheads and kinetic energy projectiles,

comprising a powder dispersed within a matrix of plastic explosive and a

binder, which can be utilized as a stand-alone protection element or as a

part of protection system such as reactive cassette.

In one embodiment, the protection element is a flexible protection element

that comprises a formable doughy mixture of a powder dispersed within a

matrix of plastic explosive and a binder, wherein said doughy mixture

contains 23 to 33 wt% of said plastic explosive, 64 to 74 wt% of said

powder, and 2 to 4 wt% of said binder.

In one embodiment, the protection element is of a single layer when

utilized as a stand-alone protection element. The protection element may

be coated by explosive material or by fragments in one or more layers that

are caused to be propelled in different directions to damage or disrupt a

penetrator.

In one embodiment, the protection element comprises two or more layers

of the formable doughy mixture, each of which coated by explosive

material or by fragments that are caused to be propelled in different

directions to damage or disrupt a penetrator, wherein each pair of

adjacent layers are attached together by adhesive or bonding material.

The protection element may further comprise one or more explosive

sheets, each of which coated by explosive material or by fragments that

are caused to be propelled in different directions to damage or disrupt a

penetrator, wherein each of the explosive sheets is attached to an adjacent

layer of the formable doughy mixture or to an adjacent explosive sheet by

adhesive or bonding material.

In one embodiment, one or more faces of the protection element is

attached to a corresponding external metallic layer or to a corresponding

external non-metallic layer, such as a ceramic layer, a composite layer, or

a polymeric layer.

The protection element may be utilized as a part of a protection system

such as a reactive cassette.

In one embodiment, the protection element of the invention is configured

to be at least partially detonated, for example fully detonated, upon

impact by a shaped charge warhead or a kinetic energy projectile.

In another embodiment, the protection element is configured to be only

locally detonated upon impact by a shaped charge warhead or kinetic

energy projectile.

The protection element can have a distribution of the powder within the

matrix which is homogeneous, or one which is non-homogeneous.

The invention also encompasses a combination of several reactive

elements as described above, which differ in the amount of the powder

dispersed within the matrix of plastic explosive and binder.

In another aspect the invention is directed to a protection element in

which the explosive is homogeneously dispersed throughout the entire

area of the cross section and in a further embodiment of the invention

there is provided a protection element in which the explosive is dispersed

in different concentrations throughout the entire area of the cross section.

Moreover, if another embodiment of the invention the protection element

is designed such that the explosive is dispersed only in partial region of a

cross section of the element.

In one aspect, the protection element is planar or non-planar in shape.

In one aspect, the protection element has a uniform or non-uniform

thickness.

The powder is preferably selected from the group consisting of metallic

powder, ceramic powder, polymer powder, glass powder, and a

combination thereof.

In one aspect, the metallic powder, ceramic powder and glass powder have

an average grain or particle size ranging from 10 to 200 micrometers (pm).

The metallic powder has a bulk density ranging from 2.6 to 19.5 g/cc, the

ceramic powder has a bulk density ranging from 1.5 to 17.5 g/cc, and the

glass powder has a bulk density ranging from 2.0 to 5.0 g/cc.

In one aspect, the metallic powder is a tungsten powder, and a median

diameter of tungsten particles is approximately 120 im.

In one aspect, the metallic powder is a tungsten carbide powder, and a

mean diameter of tungsten carbide particles is approximately 80 im.

In one aspect, the polymer powder has an average grain or particle size

ranging from 20 to 400 pm and a bulk density ranging from 1.0 to 3.0 g/cc.

While the invention is not limited to any specific explosive, according to

one embodiment of the invention the plastic explosive material is selected

from Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and 1,3,5

Trinitroperhydro-1,3,5-triazine (RDX).

Similarly, the solid particles can have a variety of shapes, and according to

one embodiment of the invention the particles have an essentially round

shape.

Binders suitable for use with the invention will be recognized by the

skilled person. According to one embodiment of the invention the binder is

selected from among Hydroxyl-terminated polybutadiene (HTPB),

polyurethane, polyester, polyether, acrylic, fluoroelastomers,

polyisobutene and Polydimethylsiloxane (PDMS).

In one aspect, the protection element is formed into a flexible sheet.

In one aspect, the protection element is a reactive layer.

The invention further encompasses a protective structure for protecting a

structure by the reactive layer, including but not limited to vehicles,

buildings and vessels. According to one embodiment of the invention at

least part of the protected surface is rounded or wavy.

Brief Description of the Drawings

In the drawings:

Fig. 1 schematically illustrates typical reactive armour;

Fig. 2 schematically illustrates a single-layer protection element;

Fig. 3 schematically illustrates a multi-layer protection element; and

Fig. 4 schematically illustrates another embodiment of a multi-layer

protection element.

Detailed Description of the Invention

Fig. 1 schematically illustrates a typical reactive armour 100, which

consists of upper metal plate 101, bottom metal plate 102, and explosive

layer 103, sandwiched between them. Alternatively, upper plate 101 and

bottom plate 102 may be made of non-metallic material, such as ceramic

material, composite material, or polymeric material. A typical angle at

which the reactive armour is positioned is 30 relative to the ground.

According to the invention this set-up can be maintained, if desired, but the intermediate layer of explosive material can also be used as a stand alone protection element without adding the metal or non-metallic plates, while maintaining the efficiency of protection. This is particularly important when it is desired to protect a non-planar (e.g. curved) surface such as a tank turret.

Fig. 2 illustrates a single-layer protection element 13, which may be made

of a formable doughy mixture of a powder dispersed within a matrix of

plastic explosive and a binder. Protection element 13 may be coated by one

or more coating layers 16 made of explosive material or fragments that are

caused to be propelled in different directions to damage or disrupt a

penetrator, although protection element 13 is also able to maintain its

efficiency of protection without a coating layer.

Fig. 3 illustrates a multi-layer protection element 23 configured with two

or more doughy layers 13. Each pair of adjacent doughy layers 13 are

attached together by adhesive or bonding material 26. Each doughy layer

13 may be coated by one or more coating layers 16 made of explosive

material or fragments that are caused to be propelled in different

directions to damage or disrupt a penetrator.

Fig. 4 illustrates a multi-layer protection element 33 configured with one

or more doughy layers 13, and one or more explosive sheets 37. Each explosive sheet 37 is attached to an adjacent doughy layer 13 or to an adjacent explosive sheet by adhesive or bonding material 26. Each explosive sheet 37 may be coated by one or more layers 16 made of explosive material or fragments that are caused to be propelled in different directions to damage or disrupt a penetrator.

A typical reactive component according to the invention contains (23-33%

on a weight basis) of an explosive material, (64-74%wt) of a particulate

solid and (2-4%wt) of a binder, which may be, for instance, HTPB, or a

silicon-based or other binder. Binders are well known in the art and,

therefore, are not discussed herein in detail, for the sake of brevity. An

illustrative example is a reactive material made of 28%wt HMX explosive,

69%wt of tungsten carbide powder with a median diameter of 80pm and

3% of HTPB. A typical thickness of the resulting reactive layer is in the

range of 9-30 mm.

It should be noted that the amount of particulate material to be used

according to the invention, as well as the size of the particles, are

important. It has been found that a diameter of between 45-180pm

provides a suitable result, although the invention is not limited to such

sizes, which are provided for the purpose of illustration. The particles can

be rounded in shape or can be irregular, in which case the effective

diameter is referred to.

The reactive layer can be prepared by a simple process, which involves

mixing performed in Planetary-type mixers at 60 rpm and temperature of

-60°c. The explosive dough produced by mixing is injected in vacuum

conditions followed by pressing to explosive sheets in the required

thickness. After pressing, the material is cured in an oven, for example at

°C ±5C. For safety considerations, all the procedures are preferably

performed from a remote control room.

Examples

All the reactive layers prepared according to the following examples were

tested in a standard test using a 30 support and an RPG-7 as the charge.

All reactive layers gave results comparable to those of the prior art.

Example 1

HMX Class 3 (19%wt), HMX Class 5 (9%wt) was employed, together with

particles of tungsten carbide (69%wt) and HTPB up to 100%wt, to prepare

a reactive layer. The particle size distribution of the tungsten carbide was

d10=50 pm; d50=80 gm; d90=130 gm and the particles were rounded in

shape. Care was taken to obtain a substantially homogeneous distribution

of the particles in the mixture. The equipment used was a high shear

mixer and an injector and hydraulic press. The process involved the

following steps: Raw materials mixing followed by injection and dough pressing to get sheet with appropriate thickness. Final steps are curing and sheet cutting.

Example 2

Example 1 was repeated, with different particles. HMX Class 3 (16%wt),

HMX Class 5 (7%wt) were employed, together with tungsten particles

(73%wt) and HTPB up to 100%wt, to prepare a reactive layer. The particle

size distribution of the tungsten was d10=90 im; d50=120 im; d90=170

pm and the particles were rounded in shape. Care was taken to obtain a

substantially homogeneous distribution of the particles in the mixture.

The equipment used was a high shear mixer and an injector and hydraulic

press. The process involved the following steps: Raw materials mixing

followed by injection and dough pressing to get sheet with appropriate

thickness. Final steps are curing and sheet cutting.

Example 3

Example 2 was repeated with the following parameters: RDX Class 1

(23%wt), RDX Class 5 (10%wt) were employed, together with particles of

tungsten (64%wt) and HTPB (3%wt), to prepare a reactive layer. The

median particle size of the tungsten was d50=80 im.

All the above descriptions and examples have been provided for the

purpose of illustration and are not intended to limit the invention in any way, except as provided for by the appended claims. Many different metal and ceramic materials can be employed, a large range of diameters can be used, and many suitable binders can be utilized, which are known to the skilled person, without exceeding the scope of the invention.

Additionally, the explosive of the type described herein may be beneficially

used in other applications, where formability into curved structures and

minimum collateral damage are important. One such application is the

countermeasure of active protection system against shaped-charge

missiles warhead or rockets and kinetic penetrators. In the prior art, these

countermeasures have employed barrel-launched projectiles, spherical or

linear explosively-formed projectiles, fragmentation explosive charge, or

blast charge, all of which require very precise aiming and timing, and/or

exhibit highly intolerable collateral damage. Use of the explosive

according to the invention in such countermeasure will assure

neutralization of the threat under easier precision constraints of aiming

and timing, with minimal collateral damage. Another application of the

invention is in warheads of precision-guided munitions, which are meant

to assure minimal collateral damage.

Claims (20)

1. A flexible protection element for reactive protection against shaped

charge warheads and kinetic energy projectiles, comprising a

formable doughy mixture of a powder dispersed within a matrix of

plastic explosive and a binder, wherein said doughy mixture

contains 23 to 33 wt% of said plastic explosive, 64 to 74 wt% of said

powder, and 2 to 4 wt% of said binder.

2. The element as claimed in claim 1, which is of a single layer when

utilized as a stand-alone protection element.

3. The element as claimed in claim 2, wherein the single layer is

coated by explosive material or by fragments that are caused to be

propelled in different directions to damage or disrupt a penetrator.

4. The element as claimed in claim 1, which comprises two or more

layers of the formable doughy mixture, each of which coated by

explosive material or by fragments that are caused to be propelled

in different directions to damage or disrupt a penetrator, wherein

each pair of adjacent layers are attached together by adhesive or

bonding material.

5. The element as claimed in claim 4, further comprising one or more

explosive sheets, each of which coated by explosive material or by

fragments that are caused to be propelled in different directions to

damage or disrupt a penetrator, wherein each of the explosive sheets is attached to an adjacent layer of the formable doughy mixture or to an adjacent explosive sheet by adhesive or bonding material.

6. The element as claimed in claim 1, wherein one or more faces

thereof is attached to a corresponding external metallic layer or to a

corresponding external non-metallic layer.

7. The element as claimed in claim 1, when utilized as a part of a

protection system such as a reactive cassette.

8. The element as claimed in claim 1, which is at least partially

detonated, only locally detonated or fully detonated upon impact by

a shaped charge warhead or kinetic energy projectile.

9. The element as claimed in claim 1, in which distribution of the

powder within the matrix is homogeneous or non-homogeneous.

10.A combination of several elements, each one as claimed in claim 1,

which differ in an amount of the powder dispersed within the

matrix of plastic explosive and binder.

11. The element as claimed in claim 1, in which the explosive is

a) homogeneously dispersed throughout an entire cross section of

the element; or

b) dispersed in different concentrations throughout an entire cross

section of the element; or

c) dispersed only in a partial region of a cross section of the

element.

12. The element as claimed in claim 1, which is

a) planar; or

b) non-planar in shape; or

c) is formed into a flexible sheet; or

d) has a uniform thickness; or

e) has a non-uniform thickness.

13.The element as claimed in claim 1, wherein the powder is selected

from the group consisting of metallic powder, ceramic powder,

polymer powder, glass powder, and a combination thereof.

14. The element as claimed in claim 13, wherein

a) the metallic powder, ceramic powder and glass powder have an

average grain or particle size ranging from 10 to 200 pm; or

b) the metallic powder has a bulk density ranging from 2.6 to 19.5

g/cc; or

c) the metallic powder is a tungsten powder; or

d) a median diameter of tungsten particles is approximately 120

m; or

e) the metallic powder is a tungsten carbide powder; or

f) a mean diameter of tungsten carbide particles is approximately

80 im; or

g) the ceramic powder has a bulk density ranging from 1.5 to 17.5

g/cc; or h) the glass powder has a bulk density ranging from 2.0 to 5.0 g/ce; or i) the polymer powder has an average grain or particle size ranging from 20 to 400 pm and a bulk density ranging from 1.0 to 3.0 g/cc.

15.The element as claimed in claim 1, wherein the plastic explosive is

selected from HMX and RDX.

16.The element as claimed in claim 1, wherein particles of the powder

have an essentially round shape.

17.The element as claimed in claim 1, wherein the binder is selected

from among HTPB, polyurethane, polyester, polyether, acrylic,

fluoroelastomers, polyisobutene and PDMS.

18. The element as claimed in claim 1, which is a reactive layer.

19.A protective structure for protecting a structure by the reactive

layer according to claim 18.

20. The structure according to claim 19

a) which is a vehicle; or

b) which is a building; or

c) which is a vessel; or

d) wherein at least part of its surface is rounded or wavy.

Fig. 2 1/2

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