WO2012085695A1

WO2012085695A1 - Reactive armour

Info

Publication number: WO2012085695A1
Application number: PCT/IB2011/054914
Authority: WO
Inventors: Frederik Johannes MOSTERT
Original assignee: Csir
Priority date: 2010-12-20
Filing date: 2011-11-04
Publication date: 2012-06-28

Abstract

A reactive armour lay-up element (10) includes a first body or layer (12), a body or layer (14) of reactive material enveloping or covering at least partially the first body or layer (12), the reactive material being capable of producing a pressure wave when impacted by a projectile, and a second body or layer (16) enveloping or covering at least a portion of the body or layer (14) of reactive material. The second body or layer (16) is configured to break up into sub-millimetre particles only, after being exposed to a pressure wave caused by the reaction of the body or layer (14) of reactive material to impact by a projectile, such as a shaped charge jet.

Description

REACTIVE ARMOUR

THIS INVENTION relates to reactive armour. In particular, the invention relates to a reactive armour lay-up element and to reactive armour lay-up.

Reactive armour, and in particular explosive reactive armour, is well- known and has been used with great success in the defeat of anti-armour shaped charge weapons. Conventional explosive reactive armour uses plates sandwiching an explosive, with the plates being accelerated by the detonation of the explosive upon impact by a projectile. The resultant high velocity and momentum of these plates transform these plates into lethal missiles up to vast distances. The use of explosive reactive armour on soft skinned vehicles is thus problematic, as the vehicles themselves may be destroyed by the plates. The use of explosive reactive armour in the vicinity of own or friendly forces on foot or near innocent civilians is also a problem. This is particularly relevant in asymmetric warfare, i.e. peace keeping scenarios and other non- conventional conflict, where there are often foot-patrols or innocent civilians near the vehicles when fire-fights ensue.

Reactive armour which does not suffer from the abovementioned disadvantages, or which addresses these disadvantages at least to some extent, would be desirable. According to one aspect of the invention, there is provided a reactive armour lay-up element which includes:

a first body or layer;

a body or layer of reactive material enveloping or covering at least partially the first body or layer, the reactive material being capable of producing a pressure wave when impacted by a projectile; and

a second body or layer enveloping or covering at least a portion of the body or layer of reactive material, the second body or layer being configured to break up into sub-millimetre particles only, after being exposed to a pressure wave caused by the reaction of the body or layer of reactive material to impact by a projectile. Preferably, the second body or layer is configured to break up into sub- millimetre particles within 500 s after being hit by said pressure wave caused by the reaction of the body or layer of reactive material to impact by a projectile. More preferably, the second body or layer is configured to break up into sub-millimetre particles within 100 s, most preferably within 25 s, after being hit by said pressure wave.

The lay-up element may have a geometry which has at least one plane of symmetry through the centre of gravity of the lay-up element. The lay-up element may have a geometry which has at least two planes of symmetry through the centre of gravity of the lay-up element. Examples of suitable geometries are spheres, circular cylinders, non-circular cylinders, cones and parallelepipeds. In a particularly preferred embodiment of the invention, the lay-up element is conical, e.g. circular conical. In one particularly preferred embodiment of the lay-up element of the invention, the lay-up element has a right circular conical geometry.

The first body or layer may be hollow and the lay-up element may define one or more openings into the hollow first body or layer, if desired. In other words, the first body or layer may define a cavity, which cavity may be open to the atmosphere, or at least not fully enclosed by the first body or layer.

The second body or layer may envelop or substantially envelop the entire body or layer of reactive material.

The second body or layer may comprise, or may consist predominantly of, compacted powdered metal in a green density or pressed density state. A particulate metallic material is in a green density state where the condition of the material is such that it still consists of individual metal particles loosely bound to each other by a compaction process. Green density is thus the density of a metal powder compact before sintering. As will be appreciated, by controlling the compaction of the metal particles, the rate and extent of disintegration of the second body or layer, i.e. a compact, after being hit by a pressure wave caused by the reaction of the body or layer of reactive material to impact by a projectile, can be manipulated.

The second body or layer may comprise compacted powdered metal with a green density of the compacted powdered metal being between about 4 g/cm³ and about 12 g/cm³. Preferably the second body or layer comprise powdered metal with a green density of between about between about 5 g/cm³ and about 9 g/cm³, more preferably between about 7 g/cm³ and about 8 g/cm³. Advantageously, when the second body or layer consists predominantly of compacted powdered metal in a green density state, the second body or layer will, when accelerated outward away from the layer of reactive material when the layer of reactive material reacts to impact by a projectile, disintegrate rapidly over a short distance into individual metal particles. As will be appreciated, such metal particles, when of a sub-millimetre size, have a rapidly diminishing damage potential with increasing distance from the point of detonation. It is in fact expected that the metal particles will have no damage effect at a distance from the point of detonation which is about 100 times the maximum dimension of the lay-up element taken through the centre of gravity of the lay-up element. However, at a close distance from the point of reaction where the particles are still relatively close together the particles will act as a disrupting entity against a projectile, such as a shaped charge.

The second body or layer may have a thickness of between about 1 mm and about 10 mm, preferably between about 1 mm and about 5 mm, more preferably between about 1 mm and about 3 mm. As will be appreciated by those skilled in the art, the thickness of the second body or layer will at least to some extent be dependent on the density of the material making up the second body or layer, as well as the thickness or other characteristics of the layer of reactive material. The areal mass and the velocity of the second body or layer are balanced in this way. The mass and spatial requirements of the structure, e.g. a vehicle, to be protected by the lay-up element will also influence the thickness of the second body or layer. The second body or layer may be of a material having a density of at least about 5 g/cm³, more preferably at least about 6 g/cm³, most preferably at least about 7 g/cm³. The body or layer of reactive material may have a thickness within the same ranges as set out hereinbefore for the second body or layer, i.e. a thickness of between about 1 mm and about 10 mm, preferably between about 1 mm and about 5 mm, more preferably between about 1 mm and about 3 mm. As will be appreciated, the thickness of the body or layer of reactive material is dependent on the energy density of the reactive material. The thickness of the body or layer of reactive material is tailored to the characteristics of the second body or layer and the first body or layer.

Naturally, the material making up the second body or layer must not have undue incendiary properties at elevated temperatures of about 200°C and above, in order to prevent setting fire to adjacent lay-up elements when reacting to impact by a projectile. Examples of suitable materials for the second body or layer include copper, iron, zinc, molybdenum, tungsten, nickel, tantalum and mixtures or alloys of two or more of these. The reactive material of the lay-up element may be selected from the group consisting of an explosive material, a non-explosive material that creates an impedance mismatch between the first body or layer and the reactive material and between the reactive material and the second body or layer by releasing stored impact energy in the form of momentum onto adjacent bodies or layers on impact by a projectile, a propellant, a pyrophoric material, and mixtures of two or more thereof.

In one embodiment of the invention, the reactive material is an explosive material. Where the reactive body or layer of reactive material includes, or is an explosive material, it may be predominantly of an insensitive munitions explosive that does react on jet impact, or more conventional explosives such as Sheet explosive, Detasheet or typical RDX-based plastic explosives such as C4 and PE4. Preferably, the explosive has a detonation velocity of between about 6 km/s and about 10 km/s. Where the reactive body or layer of reactive material includes, or is an explosive material, the body or layer of explosive material may have a thickness selected to impart velocities of between 300 m/s and 2 km/s to the first body or layer and to the second body or layer after initiation of the explosive material of the body or layer of explosive material upon impact by a projectile.

Where the reactive body or layer of reactive material includes, or is a propellant, the propellant may be a single base powder or propellant, e.g. an ether- alcohol colloid of nitrocellulose, or a double base propellant, e.g. a nitroglycerin mixture with dissolved nitrocellulose, which may be cast.

Where the reactive body or layer of reactive material includes, or is a pyrophoric material, the pyrophoric material may for example be magnesium, aluminium or titanium, or mixtures of two or more of these.

The reactive body or layer may include additives, e.g. stabilizers or flash reducers.

Where the reactive body or layer of reactive material includes, or is a non- explosive material, i.e. an inert material that creates an impedance mismatch between the first body or layer and the reactive material and between the reactive material and the second body or layer by releasing stored impact energy in the form of momentum onto adjacent bodies or layers on impact by a projectile, the non-explosive material may be a synthetic plastics or polymeric material, e.g. rubber. The extreme compression of these specific materials effectively absorbs the impact energy and then reacts in a manner analogous to a reactive material in expansion. The adjacent inert material layers, i.e. the first body or layer and the second body or layer, have free surfaces that convert this rapid expansion into kinetic energy by moving away from the inner layer. The first body or layer may be of a metallic of non-metallic material.

Preferably however the first body or layer is of a material with a density of at least about 5 g/cm³, more preferably at least about 7 g/cm³, most preferably at least about 9 g/cm³. Examples of suitable materials for the first body or layer include copper, steel, molybdenum, tungsten and mixtures or alloys of two or more of these. If desired, the material of the first body or layer may be a compacted powdered metal in a green density state, although this is not essential. The first body or layer may have a thickness of between about 0.5 mm and about 3 mm, preferably between about 0.5 mm and about 2 mm, more preferably between about 0.5 mm and about 1 mm. During reaction of the body or layer of reactive material, the first body or layer must implode fast enough to interfere hydrodynamically with the projectile, e.g. a shaped charge jet, and accordingly, the first body or layer will tend to be a thinner body or layer than the second body or layer thereby to achieve high imploding velocities. In contrast, the second body or layer should be thicker than the first body or layer since a momentum effect is used by the second body or layer against a projectile, such as a shaped charge jet, to disrupt the projectile.

The lay-up element may have a maximum dimension through the centre of gravity of the lay-up element of between about 25 mm and about 100 mm, preferably between about 30 mm and about 75 mm, more preferably between about 40 mm and about 60 mm, e.g. about 50 mm. In the case of a spherical lay-up element, this maximum diameter is thus the outside diameter of the spherical lay-up element.

According to another aspect of the invention, there is provided a reactive armour lay-up which includes a plurality of reactive armour lay-up elements arranged in at least one protective layer.

The lay-up may include at least two protective layers of lay-up elements arranged in parallel planes. The protective layers may be arranged staggered with respect to each other so that lay-up elements of one layer do not align, in a direction normal to a plane in which the lay-up elements are arranged, with lay-up elements of an adjacent layer.

Each lay-up element may be located in an associated dedicated compartment. The compartment may be rectangular in outline when viewed in a direction normal to a plane in which the lay-up elements are arranged. Typically, the compartment is parallellepipedic or cubic, typically with planar walls. The walls of the compartment may be metal walls.

Preferably, the compartment is closed on all sides except one. The open side may in use be a rear- or structure-facing side facing the structure which is to be protected by the lay-up.

Although the lay-up elements may touch the sides or walls of the compartments in which they are located at at least one point, if necessary there may be provided some space for the second body or layer to accelerate to high velocity and for inhibiting sympathetic reaction or initiation of adjacent lay-up elements. Thus, at least some sides or portions of sides of a lay-up element facing walls of its associated compartment may be buffered or spaced from said walls of the compartment to provide space for the second body or layer to accelerate to high velocity upon impact by a projectile.

The sides of the lay-up element that touch the compartment sides or walls may thus be buffered or spaced from the compartment sides or walls by spacer or buffer elements. The spacer or buffer elements may be of a synthetic material, e.g. glass reinforced plastics layers of typically 1 to 3 mm thickness.

The compartment may be of a metallic, polymeric or other inert material which is inert to the lay-up elements. In one embodiment of the lay-up of the invention, the compartment is of steel The steel compartment may have a wall thickness of between about 1 mm and about 5 mm, e.g. about 3 mm.

The lay-up elements may be arranged in a two-dimensional array or matrix to form a reactive armour lay-up panel, e.g. a 4x3 matrix of 12 lay-up elements may form a reactive armour lay-up panel. Each matrix, or two or more of such matrices arranged in spaced parallel planes, i.e. arranged major face to major face, may thus form a reactor armour lay-up panel or box. Typically, such a lay-up panel or box includes at least one two-dimensional array or matrix of compartments, each with a lay- up element, housed in a common housing for all of the compartments. As it is however preferred that the lay-up includes at least two protective layers of lay-up elements which are staggered with respect to each other, each panel or box thus typically includes only a single two-dimensional array or matrix of compartments.

Where the lay-up elements are conical, each with a base spaced from an apex, they may be arranged in pairs to form a protective layer with the base of one conical lay-up element in a pair facing the base of the other conical lay-up element in the pair. Such an arrangement acts to ensure that any jetting of material caused by a collapsed conical structure (i.e. imploding) during reaction of the reactive material to the impact of a projectile is opposed by the jetting of material formed by the implosion of the opposite structure. In this way the debris from the colliding material jets have an additional disruptive effect on the projectile which set off the lay-up elements through which it is passing.

The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings and x-ray photographs.

In the drawings,

Figure 1 shows a horizontal section through a spherical reactive armour lay-up element in accordance with the invention;

Figure 2 shows a three-dimensional rear view of reactive armour lay-up in accordance with the invention, in the form of a lay-up panel;

Figure 3 shows a top view of four of the lay-up panels of Figure 2, in use, with an upper wall removed for clarity and without a spacer or buffer element;

Figure 4 shows another embodiment of reactive armour lay-up elements in accordance with the invention, in the form of cones, arranged in two protective layers to provide explosive reactive armour lay-up in accordance with the invention;

Figure 5 shows a section through a preferred arrangement of conical reactive armour lay-up elements; and

Figure 6 shows x-ray photographs of a spherical explosive reactive armour lay- up element in accordance with the invention being penetrated by a shaped charge jet.

Referring to Figure 1 of the drawings, reference numeral 10 generally indicates a reactive armour lay-up element, more particularly an explosive reactive armour lay-up element in accordance with the invention. The lay-up element 10 is spherical and has an outside diameter of 50 mm.

The lay-up element 10 includes a hollow spherical first body or layer 12 with an inside diameter of about 40 mm and a radial thickness of about 1 mm. The hollow first body or layer 12 is of copper with a density of about 8.93 g/cm³. The interior or cavity 13 of the hollow first body or layer 12 is entirely enclosed and empty, containing only atmospheric gasses at atmospheric pressure. A spherical body or layer 14 of reactive material comprising an RDX- based plastic explosive with a detonation velocity in the range of 6 km/s to 7 km/s completely envelops the first body or layer 12. The body or layer of explosive material 14 has a thickness of about 3 mm. The RDX-based plastic explosive used in the lay-up element 10 is entirely conventional and of the kind conventionally used for explosive reactive armour lay-ups.

A second body or layer 16 completely envelops the body or layer 14 of explosive material. The second body or layer 16, in the embodiment shown in the drawings, has a thickness of about 3 mm and comprises compacted powdered copper metal in a green density state, with a green or pressed density of about 5 g/cm³.

As will be appreciated, the lay-up element 10 has at least one plane of symmetry through the centre of gravity of the lay-up element, where the plane of symmetry is in one of the planes of a conventional three-axis Cartesian co-ordinate system centred on the centre of the spherical lay-up element 10. In fact, for the spherical lay-up element 10, the lay-up element 10 has three planes of symmetry where the planes are each in one of the three planes of a conventional Cartesian co-ordinate system. Referring to Figure 2 of the drawings, reference numeral 20 generally indicates reactive armour lay-up, more particularly explosive reactive armour lay-up, in the form of a lay-up panel. The lay-up panel 20 includes 12 of the explosive reactive armour lay-up elements 10, arranged in a 4x3 matrix to define a protective layer of lay- up elements 10. Each lay-up element 10 is housed snugly in a cubic compartment 22. Each compartment 22 has planar walls 23 of 3 mm thick steel. The compartments 22 are located within a common housing 24 which thus also has a wall thickness of 3 mm.

Each compartment 22 is closed on all sides, except a rear side, as shown in Figure 2 of the drawings.

In the embodiment shown, each lay-up element 10 abuts against the five planar sides of the associated dedicated compartment 22 in which it is located. In other words, the compartments 22 each has a length, a width and a height of about 50 mm. In a potentially more preferred embodiment however, glass reinforced plastic buffer panels (not shown) reside between each lay-up element 10 and the side walls 23 which will imply a larger compartment size. These buffer panels may be required to prevent or inhibit sympathetic reaction or initiation of adjacent lay-up elements 10. Referring to Figure 3 of the drawings, four of the lay-up panels 20 are shown protecting a structure 30. The lay-up panels 20 are arranged to form two protective layers of explosive reactive armour lay-up elements 10. As can be clearly seen in Figure 3 of the drawings, the protective layers of explosive reactive armour lay- up elements 10 are arranged in parallel planes, but staggered with respect to each other so that lay-up elements 10 of a front layer do not align, in a direction 32 normal to a plane in which the lay-up elements 10 are arranged, with lay-up elements 10 of a rear layer. As will be appreciated, the direction 32 also represents the shot line of a projectile, e.g. a shaped charge jet, hitting the lay-up panels 20 at an angle normal to the plane in which the lay-up elements 10 are arranged.

As shown in Figure 3 of the drawings, the lay-up panels 20 may be spaced, e.g. 200 mm to 500 mm, from the structure 30 to be protected by the lay-up panels 20. When the structure 30 is a wall of an armoured tank or vehicle, the lay-up panels 20 may however be right up against the wall 30.

Referring to Figure 4 of the drawings, another embodiment of reactive armour lay-up elements, in the form of truncated cones 40, is shown. As can be clearly seen in Figure 4, the cones 40 can also be arranged in two protective layers to form explosive reactive armour lay-up. Each cone 40 has a vertical and a horizontal plane of symmetry through the centre of gravity of the cone and comprises a hollow first body or layer 12, a body or layer 14 of explosive material surrounding the first body or layer 12, and a second body or layer 16 surrounding the body or layer of explosive material, as is the case with the explosive reactive armour lay-up elements 10. Each body or layer is conical, with the cone 40 being open-ended, or closed at one or both ends if desired. In the embodiment shown in Figure 4, the cones 40 are open at their larger ends, with the first body or layer 12 defining an opening at the larger end of each cone 40.

Referring to Figure 5 of the drawings, a pair of reactive armour lay-up elements in accordance with the invention is shown, with each lay-up element being generally indicated by reference numeral 100. Each lay-up element 100 is in the form of a right circular cone with an open bottom or base.

Each lay-up element 100 includes a first body or layer 1 12 similar to the first body or layer 12 of the lay-up element 10, 40. The first body or layer 1 12 defines a conical cavity 1 13 containing only atmospheric gasses at atmospheric pressure as it is open to the atmosphere via the open bottom of the lay-up element 100. A conical body or layer 1 14 of a reactive material substantially covers the entire first body or layer 1 12. The reactive material of the body or layer 1 14 shown in Figure 5 is an explosive material. The reactive material may however be a non-explosive material that creates an impedance mismatch between the first body or layer 1 12 and the reactive material of the layer 1 14, and between the reactive material of the layer 1 14 and a second body or layer 1 16, by releasing stored impact energy in the form of momentum onto the adjacent bodies or layers 1 12, 1 14 on impact by a projectile such as a shaped charge jet. Instead, or in addition, the reactive material of the body or layer 1 14 may be or may include a propellant or a pyrophoric material that will react by igniting rapidly and violently upon impact by a projectile such as a shaped charge jet. The layer 1 14 may also comprise a mixture of two or more of these reactive materials. The second body or layer 1 16 is similar to the second body or layer 16 of the lay-up element 10, 40.

Importantly, as illustrated in Figure 5 of the drawings, the lay-up elements 100 are arranged with their open bases facing each other. Preferably, the lay-up elements 100 touch each other. The arrangement of the lay-up elements 100 illustrated in Figure 5 advantageously acts to ensure that any jetting of material caused by the imploding of the first body or layer 1 14 during reaction of the reactive material of the body or layer 1 14 to the impact of a projectile such as a shaped charge jet, is opposed by the jetting of material formed by the implosion of the adjacent lay-up element 100. This results in debris from the colliding material jets produced by the two adjacent lay- up elements 100 having an additional disruptive effect on the projectile passing through the lay-up elements 100. Lay-up elements 100 all orientated in the same direction may be arranged to form a lay-up panel similar to the lay-up panel 20. By placing two such lay-up panels against each other so that the bases of the lay-up elements 100 in one panel face the bases of the lay-up elements 100 in the other panel, i.e. with the panels arranged back to back, an arrangement can be created by means of identical lay-up panels where the lay-up elements 100 are substantially as arranged in Figure 5. As will however be appreciated, a lay-up panel can also be constructed in which two of the lay-up elements 100 are combined as shown in Figure 5. In other words, in such a panel two lay-up elements 100 can be housed together in a common compartment with the open bases of the two lay-up elements 100 facing each other. A single lay-up panel will then provide the arrangement shown in Figure 5 and it is then unnecessary to arrange two lay-up panels in parallel planes to obtain the arrangement illustrated in Figure 5. Naturally however, a plurality of panels may be used to form a plurality of protective layers of reactive armour lay-up elements similar to the arrangement illustrated in Figure 3 of the drawings.

It is also to be noted that a lay-up element can be constructed as a unitary or monolithic body which has the appearance of the combined lay-up elements shown in Figure 5. Such a lay-up element will thus have the appearance of two cones fused or joined at their bases.

The explosive reactive armour lay-up elements 10 (and the lay-up elements 40, 100) are configured to disrupt a projectile such as a shaped charge jet when the body or layer of explosive material of the reactive armour lay-up element is detonated by the shaped charge jet. The x-ray photographs of Figure 6 clearly show the disruptive effect of a spherical explosive reactive armour lay-up element in accordance with the invention, on a shaped charge jet. In the photograph marked "static", a prototype spherical explosive reactive armour lay-up element similar to the lay-up element 10 is shown, spaced from a copper cone surrounded by an explosive charge. In the x-ray photograph marked "20 s", the explosive charge surrounding the copper cone has been detonated and it can be clearly seen how the resultant shaped charge copper jet forms a projectile that approaches the lay-up element. In the x-ray photograph marked "30 s", it can be seen that the shaped charge jet has penetrated the lay-up element after 30 s. In the x-ray photograph marked "50 s", it can be seen that the shaped charge jet has started to pass through the lay-up element after 50 s, with the detonation of the body or layer of explosive material of the lay-up element having commenced so that the first body or layer is being imploded radially inwardly and the second body or layer is being exploded radially outwardly. In the x-ray photograph marked "80 s", the disruptive effect of the lay-up element on the shaped charge jet can be clearly seen. The second body or layer explodes outwardly and disintegrates against the shaped charge jet, transferring momentum to portions of the shaped charge jet and thereby disrupting the shaped charge jet. Simultaneously, the first body or layer implodes radially inwardly and focuses on the shaped charge jet, disrupting the shaped charge jet by means of hydrodynamic impact. A further disruptive effect against the shaped charge jet is obtained by gas, resulting from the detonation of the body or layer of explosive material, streaming out through the entrance and exit holes caused by the shaped charge jet in the lay-up element, thereby further to disrupt the shaped charge jet. Jet segments start escaping the lay-up element within about 75% to 80% of the penetration time (100 s) of the shaped charge jet through the lay-up element. Although the first few segments of the jet may not be all that disturbed by the lay-up element, later jet segments are disturbed by the momentum transfer and hydrodynamic effect, and the last elements of the jet are also heavily disturbed by the expanding gasses so that these jet segments cannot penetrate a target at longer stand-offs. Simultaneously and advantageously, the second body or layer disintegrates rapidly into sub-millimetre particles so that after about 4 or 5 m they have substantially zero collateral damage potential.

The reactive armour lay-up element of the invention, as illustrated, uses a very small mass of explosive material or other reactive material compared to conventional explosive reactive armour lay-ups known to the inventor. With such a small mass of explosive or reactive material, the lay-up element of the invention has a low collateral damage signature, which is virtually zero for vehicles, but still has a high efficiency in terms of penetration reduction per m².

Claims

CLAIMS:

1 . A reactive armour lay-up element which includes:

a first body or layer;

a second body or layer enveloping or covering at least a portion of the body or layer of reactive material, the second body or layer being configured to break up into sub-millimetre particles only, after being exposed to a pressure wave caused by the reaction of the body or layer of reactive material to impact by a projectile.

2. The lay-up element of claim 1 , in which the second body or layer is configured to break up into sub-millimetre particles within 500 s after being hit by said pressure wave caused by the reaction of the body or layer of reactive material to impact by a projectile.

3. The lay-up element of claim 1 or claim 2, in which the second body or layer comprises compacted powdered metal in a green density or pressed density state.

4. The lay-up element of claim 3, in which the second body or layer comprises compacted powdered metal with a green density of the compacted powdered metal being between 4 g/cm³ and 12 g/cm³.

5. The lay-up element of any of claims 1 to 4, in which the second body or layer has a thickness of between 1 mm and 10 mm, and is of a material having a density of at least 5 g/cm³.

6. The lay-up element of any of claims 1 to 5, in which the first body or layer has a thickness of between 0.5 mm and 3 mm, and is of a material having a density of at least 5 g/cm³.

7. The lay-up element of any of claims 1 to 6, in which the first body or layer defines a cavity.

8. The lay-up element of claim 7, in which the cavity is open to the atmosphere, or at least not fully enclosed by the first body or layer.

9. The lay-up element of any of claims 1 to 8, in which the second body or layer envelops or substantially envelops the entire body or layer of reactive material, and in which the lay-up element has a geometry which has at least one plane of symmetry through the centre of gravity of the lay-up element.

10. The lay-up element of any of claims 1 to 9, which is conical.

1 1 . The lay-up element of any of claims 1 to 10, in which the reactive material is selected from the group consisting of an explosive material, a non-explosive material that creates an impedance mismatch between the first body or layer and the reactive material and between the reactive material and the second body or layer by releasing stored impact energy in the form of momentum onto adjacent bodies or layers on impact by a projectile, a propellant, a pyrophoric material, and mixtures of two or more thereof.

12. The lay-up element of any of claims 1 to 1 1 , in which the reactive material is an explosive material.

13. The lay-up element as claimed in claim 12, in which the body or layer of explosive material has a thickness selected to impart velocities of between 300 m/s and

2 km/s to the first body or layer and to the second body or layer after initiation of the explosive material of the body or layer of explosive material upon impact by a projectile.

14. A reactive armour lay-up which includes a plurality of reactive armour lay- up elements according to any of claims 1 to 13 arranged in at least one protective layer.

15. The reactive armour lay-up of claim 14 which includes at least two protective layers of lay-up elements arranged in parallel planes, and in which the protective layers are arranged staggered with respect to each other so that lay-up elements of one layer do not align, in a direction normal to a plane in which the lay-up elements are arranged, with lay-up elements of an adjacent layer.

16. The reactive armour lay-up of claim 14 or claim 15, in which each lay-up element is located in an associated dedicated compartment, and in which the compartment is closed on all sides except one.

17. The reactive armour lay-up of claim 16, in which at least some sides or portions of sides of a lay-up element facing walls of its associated compartment are buffered or spaced from said walls of the compartment to provide space for the second body or layer to accelerate to high velocity upon impact by a projectile.

18. The reactive armour lay-up of any of claims 14 to 17, in which the lay-up elements are arranged in a two-dimensional array or matrix to form a reactive armour lay-up panel.

19. The reactive armour lay-up of any of claims 14 to 18, in which the lay-up elements are conical each with a base spaced from an apex and in which the conical lay-up elements are arranged in pairs to form a protective layer with the base of one conical lay-up element in a pair facing the base of the other conical lay-up element in the pair.