AU2003283125B2

AU2003283125B2 - Improved linear shaped charge system

Info

Publication number: AU2003283125B2
Application number: AU2003283125A
Authority: AU
Inventors: Scott Allman; Chris Murray; James Sammons
Original assignee: Applied Explosives Technology Pty Ltd
Current assignee: Applied Explosives Technology Pty Ltd
Priority date: 2002-11-28
Filing date: 2003-11-28
Publication date: 2009-04-23
Anticipated expiration: 2023-11-28
Also published as: AU2003283125A1

Description

WO 2004/048880 PCT/AU2003/001585 IMPROVED LINER SHAPED CHARGE SYSTEM The present invention relates to systems and methods adapted to shaped charge systems for the controlled application of a destructive explosive charge and, more 5 particularly for the gaining of forced entry into buildings and structures in situations where such entry is required for military or law enforcement purposes and where such entry i-s denied. BACKGROUND 10 In both military and law enforcement operations it may become necessary to gain forced entry into buildings where such entry by normal .means is denied. Some examples of such situations may include the rescue of hostages or the interdiction of serious criminal activity. In such 15 situations the more conventional means of forced entry by the use of rams or sledge hammers and the like may be rendered ineffective by the particular structural or barricaded entry conditions of the building. In such situations the only recourse may be to use 20 explosive' entry techniques. These are high risk operations, with known methods making use of metal fragments to effect penetration at the desired point of entry, with risk of injury to the occupants of the building, or even of the operational personnel.

2 Numerous forms of linear shaped charges may be employed for these purposes as well as for a range of civil applications, particularly in controlled demolition work. Known systems suffer from a number of shortcomings depending 5 on the particular application and the type of charge system. Thus those systems which employ rigid metal liners cannot be applied to curved surfaces and the metal ejecta generated by the liner presents a danger to personnel. Malleable linear charges are known but only allow relatively limited bending. 10 It is an object of the present invention to address the above disadvantages, or at least provide a useful alternative. 15 BRIEF DESCRIPTION OF INVENTION Accordingly, in a first broad form of the invention, there is provided a flexible linear charge element adapted to the penetration of a structure; said linear charge element forming an elongate composite structure; said composite 20 structure including: (a) an extruded carcass of closed cell foam, (b) a first overlaid layer of a cutting sheet liner component, (c) a second overlaid layer of explosive sheet, and 3 (d) a third overlaid layer of an inertial mass tamping carapace; wherein said carcass is provided with side flange portions; said side flange portions providing termination elements for said first, second and third layers; each of 5 said first, second and third layers being affixed to said carcass by a suitable adhesive; said inertial mass tamping carapace comprising a dense non-toxic, flexible plasticized metal composite. Preferaly, said cutting sheet liner component is disposed 10 between said layer of explosive sheet and said extruded carcass. Preferaly, said cutting sheet liner component comprises a matrix of polymers incorporating a dense distribution of metal carbide particles. 1S Preferaly, said layer of explosive sheet is a shaped charge component; a shape of said shaped charge component adapted to produce a "Monroe Effect" when detonated. Preferaly, said inertial mass tamping carapace is formed of a dense inert compound. 20 Preferaly, said inert compound comprises powdered barium sulphate. Preferaly, said extruded carcass is adapted to provide a separation between said cutting sheet liner and said structure.

4 Preferaly, said extruded carcass is in the form of an elongate flexible closed cell foam structure. Preferaly, said extruded carcass includes an extruded flexible hollow tubular member. 5 Preferaly, said composite structure is provided with attachment means adapted to attach said linear charge element to a surface of said structure. Preferaly, said attachment means comprises at least one adhesive strip arranged along an underside of said composite 10 structure. Preferaly, said attachment means comprises at least one magnetic strip arranged along an underside of said composite structure. 15 20 5 5 BRIEF DESCRIPTION OF DRAWINGS Embodiments of the present invention will now be described with reference to the accompanying drawings wherein: Figures 1A to IL are cross sectional views of a variety 10 of elongate shaped explosive charge elements according to a first embodiment of the invention. Figure 2A to 2E are cross sectional views of a variety of elongate shaped explosive charge elements according to a second embodiment of the invention. is Figure 3 is a sectioned perspective view of a linear charge system. Figure 4 is a sectioned perspective view of a linear shaped charge element. Figure 5 is a section of a further preferred linear 20 charge element. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS In accordance with a first embodiment of a forced entry system, a principle component in this instance of which is a 6 flexible frangible cutting sheet intended for use with explosive charges to cut through obstructing material. The structure of this sheet is made up of a polymer matrix including plasticisers, stabilizers and flexible agents, 5 containing a substantially uniform distribution of powdered metal. The metal may be any one of a selection of metals including for example, copper, aluminium, brass, ferrous metals, ceramics or a combination of these. Preferably the particulate size of the metal or ceramic 10 powder is in the order of 1 to 10 microns but both smaller and larger particles may be used. Different combinations of sheet thickness, particle density and particle size may be formulated depending on the explosive charge to be used and the nature of the barrier structure to be penetrated. That 15 structure may comprise a wide range of materials including wood, metal, masonry, glass, polycarbonates and other plastics as well as composites. The flexible nature of the cutting sheet enables it to be combined into a variety of elongate shaped charges when 20 provided with an explosive agent. Desired shapes may also be achieved by extrusion, casting or fabricating. By suitable shaping and the use of a stand-off material the cutting sheet may be adapted to take advantage of the "Monroe Effect" wherein the detonation of the explosive 7 agent creates a high energy linear jet of gas. The stand-off material serves to provide that distance between the explosive agent and the target required for the accelerating gas and particles of the cutting sheet to reach an effective 5 penetration velocity. The stand-off material may be made of any light frangible material such as for example a polystyrene foam. Figures 1A to 1L show a number of examples of preferred configurations of a cutting sheet (2), stand-off material 10 (1) and explosive agent (3) . As shown for example in figures 1A, 1C, 1G, 114, 11 and 1J, an additional layer of flexible frangible cutting sheet (2) may be incorporated as a tamping layer. It is a feature of the flexible frangible cutting sheet 15 that the individual particles accelerated by the blast are of very low mass and thus lose energy rapidly from their initial high energy state after detonation of the explosive agent. As a result their penetration effect is limited to a very short range, thus minimizing fragmentation and the 20 likelihood of unintended injury to any persons within the structure to be penetrated. In an extruded form, the flexible frangible cutting sheet may be backed with a sheet explosive agent to obtain the desired cutting effect.

8 In a second preferred embodiment of the invention, the flexible frangible cutting sheet, may be combined in a variety of configurations with explosive agents and a metal liner, as shown in figure 2 in which (2) is a layer of 5 flexible frangible cutting sheet (3) is an explosive agent, (1) is a stand-off material and (4) is the metal liner. In this embodiment it is the metal liner which acts as the cutting or penetrating agent, with the cutting sheet providing a tamping effect and aiding. the shaping of the 10 "Monroe Effect". In yet a further embodiment of the invention as shown in figure 3, a linear charge system is provided in the form of a flexible elongate member 140 incorporating a malleable, in this example chevron shaped explosive 141, a liner 142 15 and a stand-off member 143, all held in the matrix of an inertial mass tamping carapace 144. The stand-off carcass may be in the form of an elongate flexible closed-cell foam structure or an extruded flexible hollow tubular member (as shown in figure 11). 20 In at least one preferred form of this embodiment the elongate member 140 may be provided with contact adhesive strips 145 along its underside or with flexible magnetic strips for retaining the elongate member against a surface to which the charge is to be applied.

9 As can be seen in figure 3 the inertial mass tamping carapace in cross section completely envelops the explosive 141 and liner 142 elements as well as the stand-off member 143 except for the gap 146 at its underside. This gap 146 is 5 to allow the focussed passage of the high energy linear jet of gas and particles of the explosive. The liner 142 is in the form of a separately extruded plastic matrix .incorporating an extremely dense distribution of metal carbide as the main liner ingredient. This allows 10 the generation of a high velocity, high density, extremely abrasive jet with superior penetrative performance. The malleable explosive may be any readily available commercial sheet explosive with sufficient flexibility and an adequate detonation velocity. Exemplary products are 15 Ensign Bickford Primasheet 2000, Dyno HLX sheet explosive, Royal Ordnance SX2 sheet explosive or Royal Ordnance Demex 200. All have adequate physical properties and velocity of detonation above 7600 metres/second, which is sufficient to enable efficient liner jetting. 20 The addition of a dense, non toxic, flexible, plasticized metal composite mass tamping carapace over the explosive chevron enables the detonation of the explosive to be effectively tamped at the detonation instant, thus focusing more detonation energy to effectively collapse and 10 accelerate the liner into an effective penetrating jet. The mass tamping carapace may be composed of a dense inert compound, for example powdered barium sulphate or other dense non-toxic metal or metal compound and plasticizer. On 5 detonation the carapace disintegrates as a cloud of fine particles, with a very small lethal or injurious radius compared to totally metal enclosed linear shaped charges. A tubular stand off member may optionally be pressurized for underwater use by the addition of elastomer 10 bungs at the ends of the tube, one of which at least may be provided with one way valve means to introduce and retain a gas under the required pressure. This system has advantages over a comparable closed cell foam stand off which will gradually compress as the gas filled bubbles in the foam 15 contract with increased water pressure, thus reducing the optimum stand off that a linear shaped charge needs for adequate cutting performance. Since a gas filled pressurized tubular support is better able to withstand water pressure it enables the liner 20 to jet with more effect into the target and without the jet degrading by passage through foam. Although the present embodiment'has made reference to a chevron shaped explosive charge, it will be clear to a person skilled in the art that any shape inducive of 11 producing a "Monroe Effect", such as for example an arcuate sectional shape or an arrangement in a number of segments may also be effectively employed. The present embodiment may be pre-assembled for "off 5 the-shelf" availability in a number of configurations to suit a variety of commonly encountered requirements. Alternatively, it may be provided in kit form. The kit may include one or a number of standard lengths of closed cell foam or open tubular stand-off carcass, and a quantity of 10 pre-cut sheet explosive so as to enable a user to assemble a desired thickness on-site. The kit would also contain an appropriate length or lengths of liner of nominated properties and composition as well as one or more lengths of tamping carapace produced in a form allowing insertion of 15 the explosive, liner and carcass components. Accessories, such as adhesive or magnetic strips, closing bungs and adhesives to fix them in place, and a hand pressurization pump for example, may also be provided. In yet a further preferred embodiment of the invention 20 as shown in figure 4 a linear shaped charge element 200 is formed of an extruded carcass 210 of closed cell foam having a hollow tubular center 211. The carcass has side flange portions 212 and 213 which form termination elements for a first overlaid layer 214 of a composite liner material, a 12 second overlaid layer 215 of explosive sheet and a third overlaid layer 216 of an inertial mass tamping carapace. Both layers are affixed to the carcass 210 by a suitable adhesive. Preferably, the liner material is formed of 5 tungsten carbide particulates in a flexible plastic matrix. The underside 217 of the linear shaped charge element may be provided with an adhesive layer 218 so as to allow the charge to be applied to any suitable surface. The flexible nature of this embodiment allows of its application 10 to complex curved surfaces, such as for example to circular section pylons, steel tanks and even the surfaces of vessels for example. In a further preferred embodiment of a linear charge element 300 as shown in figure 5, a section of explosive sheet 311 15 is affixed to a plastic carrier 310 in the form of a portion of a plastic tube such as for example PVC pipe. In this embodiment the explosive charge covered by a layer of cardboard backing 312. The above describes only some embodiments of the present 20 invention and modifications, obvious to those skilled in the art, can be made thereto without departing from the scope of the present invention.

Claims

1. A flexible linear charge element adapted to the penetration of a structure; said linear charge element 5 forming an elongate composite structure; said composite structure including: (a) an extruded carcass of closed cell foam, (b) a first overlaid layer of a cutting sheet liner component, 10 (c) a second overlaid layer of explosive sheet, and (d) a third overlaid layer of an inertial mass tamping carapace; wherein said carcass is provided with side flange portions; said side flange portions providing termination elements for said first, second and third layers; each of 15 said first, second and third layers being affixed to said carcass by a suitable adhesive; said inertial mass tamping carapace comprising a dense non-toxic, flexible plasticized metal composite.

2. The linear charge element of claim I wherein said 20 cutting sheet liner component is disposed between said layer of explosive sheet and said extruded carcass.

3. The linear charge element of claim 1 or 2 wherein said cutting sheet liner component comprises a matrix of polymers incorporating a dense distribution of metal 25 carbide particles.

4. The linear charge element of any one of claims 1 to 3 wherein said layer of explosive sheet is a shaped charge - 14 component; a shape of said shaped charge component adapted to produce a "Monroe Effect" when detonated.

5. The linear charge element of any one of claims 1 to 4 wherein said inertial mass tamping carapace is formed of a 5 dense inert compound.

6. The linear charge element of claim 5 wherein said inert compound comprises powdered barium sulphate.

7. The linear charge element of any one of claims 1 to 6 wherein said extruded carcass is adapted to provide a 10 separation between said cutting sheet liner and said structure.

8. The linear charge element of any one of claims 1 to 7 wherein said extruded carcass is in the form of an elongate flexible closed cell foam structure. 15

9. The charge element of any one of claims 1 to 8 wherein said extruded carcass includes an extruded flexible hollow tubular member.

10. The linear charge element of claim 1 wherein said composite structure is provided with attachment means 20 adapted to attach said linear charge element to a surface of said structure.

11. The charge element of claim 10 wherein said attachment means comprises at least one adhesive strip arranged along an underside of said composite structure. - 15

12. The linear charge element of claim 10 wherein said attachment means comprises at least one magnetic strip arranged along an underside of said composite structure. 5