AU731698B2 - Blast attenuation apparatus and material - Google Patents

Description

WO 97/16697 PCT/GB96/2612 WO 9716697PCT/GB96/0261 2 Blast Attenuation Apparatus and Material The present invention relates to a material and apparatus for containing and minimising the effects of an explosive blast such that the blast shock wave does not cause damage to the surrounding environment including the fabric of buildings, vehicles and onlookers. The means can also be provided to minimise the effect of both the impulse of the explosion and any high velocity fragments created by the explosion and hence the means has a blast capability and a ballistic protection capability.

In a normal explosive event the rapid combustion produces gases which expand with a rapidity which causes the air surrounding the blast to compress. This compression causes a shock wave which travels ahead of the product gases and it is this shock wave which causes characteristic blast damage.

Typically the shock wave has a high peak pressure which lasts for a relatively short duration. After the shock wave an impulse phase exists which is formed by the expansion of the gases formed at the explosion. The phases of the explosion are illustrated in Figure 1 wherein the shock wave phase is illustrated by the numeral 1.

Conventionally there are many methods by which attempts are made to minimise the effects of the shock wave, such methods including providing thick steel armour plating or fibre reinforced composites. These systems defeat the effects of the blast mainly by reflecting the energy of the blast and hence, in order for the same to be capable of withstanding large blasts, the same have to be strong and therefore may be bulky, unadaptable and expensive. Despite these disadvantages WO 97/16697 PCT/GB96/I2612 WO 9716697PCT/GB96/0261 2 2 this type of protection has been the most common method used to date.

Work has also been undertaken in relation to the provision of blast containment on aircraft and in relation to containers for luggage in aircraft and this work is disclosed in patent applications GB2262798, GB2262885, GB2238283 and W09107337 but the feasibility of these arrangements is not proven in relation to aircraft use and there is no disclosure of these arrangements being adapted or adaptable for other uses.

The present invention is directed toward utilising blast management technology through attenuation whereby the shock wave of the blast is modified so that the damaging peak pressure 1 of Figure 1 is reduced and the energy of that peak is partially absorbed, the remainder being released in a controlled manner over an extended period of time as is shown by the line 3 in Figure 1.

The aim of the present invention is, in a first aspect, to provide an attenuating material which, when exposed to the blast allows the peak pressure to be attenuated upon impact on the material and, in a second aspect, to provide the said attenuating material in a form and as part of apparatus whereby the same can be used on, or to form, articles and to act as a protective layer for articles when applied thereto and also as an integral part of the same, such as in the form of a container, so that blasts within the container can be contained therein.

The present invention provides, in a first aspect, a material for use to minimise the effect of blast energy from a blast, by attenuating the shock wave of the blast and wherein the material is a resin bonded particulate material.

WO 97/16697 PCT/GB96/nO2!( i In one embodiment the particulate is an aggregate such as silica or can be a particulate of hollow form and formed of ceramic material. The particulate size in whichever form is preferably substantially uniform thereby leaving gaps between said particulates which serve to increase the effectiveness of the material. Typically the resin used can be a formulated urethane resin. Typically the resin and particulate are pressed into the required form, such as a sheet of a specified thickness for a specific function.

Typically the attenuation material of the invention has a structure with the gaps between the particulate allowing the passage therethrough of gases created during the blast but retards the speed and pressure of the same and also acts to modify the initial shockwave of the blast by attenuating its energy, and, in whichever form the attenuation material is used, the material is located such that it is directly exposed to the blast but decoupled from the support surface with which it is used.

Preferably the attenuating material is used in conjunction with a backing layer and at least one decoupling, intermediate layer filled with air or a suitable filler material such as foam. In one embodiment an intermediate layer is a filler material which further acts to contain the blast shock wave and the intermediate layer or layers can also be provided to act as any of a heat sink, to support the attenuating material under blast conditions, to improve performance of the attenuating material and/or as an environmental barrier.

In one embodiment the attenuating material is provided in a sheet form which is sufficiently flexible to allow the same to be shaped to the article to which the same is to be applied. In this embodiment the material is preferably used in WO 97/16697 PCT/C~RQC;~IJI;17 WO 9716697PCT/Cfl9iiin741i 4 conjunction with a layer of filler material which is adhesive thereby allowing the material to be adhered to the article.

It is envisaged that the attenuating material in this form is of particular use in relation to the lining or forming of the underside of vehicles and the lining of existing buildings and articles where the material can be retrofitted to provide the required attenuation and/or ballistic facility.

The material in the compliant form can be used in vehicles such as saloon vehicles where the perceived blast threat is from hand grenade or IED or small mines. In this form the backing layer for the same can be any of steel,, reinforced fibre composites or other metals and is located within or forms part of the vehicle such as the floor pan of the same.

For utility vehicles and light trucks the main threat is the land mine and the backing layer used in these vehicles is typically armour steel and is used to mount the system as a whole to the underside of the vehicle. The backing layer in this application has the dual function of providing support to the material of the invention and also as a ballistic protection against the high energy fragments created by the land mine. In one form the system fitted to utility vehicles and light trucks such as 4 x 4 vehicles comprises a trough with the attenuating material attached thereto and the trough is attached to the underside of the vehicle which is possible due to the relatively high ground clearance of the same. This system is bulkier than that used for a saloon vehicle but does have the required higher blast capability. Typically the material is attached via an adhesive foam which acts to adhere the material and also acts as a decoupling layer.

WO 97/16697 PCT/GB96/02612 In a further embodiment of the invention, the attenuating material can be used as an integral part of a container provided to contain a blast therein. Such container can be for any of ammunition, suspect devices such as letter bombs and such like or, on a larger scale, for containers for volume sorting and distribution operations such as for containing luggage or parcels for courier delivery services, containers to provide isolation for any devices detected during the handling of these articles and also, but on a smaller scale, for containing devices brought in to the passenger cabin to be carried in aircraft. This is a valuable alternative to the current procedure of padding devices with cushions and luggage from throughout the cabin. In a preferred form the attenuating material is provided as an integral part of each of the walls of the container.

Typically each wall of the container comprises at least three layers, a backing layer, a decoupling, intermediate layer and the internal layer which is formed of the attenuating material of the invention. In whichever form the attenuating material of the invention is provided to form the first layer of the wall against which the blast impacts.

Typically the intermediate layer can be either of an air gap or, alternatively, a filler material such as,, for example, glass wool. Preferably the backing layer is formed from a material which provides the degree of mechanical support and ballistic protection appropriate to the application.

In a preferred embodiment the backing layer is perforated such that a percentage of the same is open. In one embodiment the open area is approximately 40% of the area of the layer. Preferably there is provided a plurality of smaller WO 97/16697 PIT/GB96/n26i? 6 perforations rather than a smaller number of larger perforations as this improves the controlled release of the gases and the blast and optimises bowing of the walls.

The perforated backing layer allows venting of the blast from the container, the same being controlled by a combination of factors including the perforated area, the intermediate layer and the attenuating material.

In one embodiment there is provided a perforated damage limitation screen in front of the layer of the attenuating material of the invention.

In one preferred embodiment the backing layer has a number of protruding members formed on or attached thereto which, in combination, form a frame to support panels of the attenuating material of the invention. The frame is provided to ensure that the material panels are retained in the required spacing from the backing layer thereby forming the decoupling, intermediate layer between the same and to ensure that the panels are held in the required formation to form the inner layer of the wall. Typically, a number of the panels, in combination, form the inner layer of the wall. The panels can be provided with matching location means to allow the same to be interconnected when held in position.

The face of the attenuating material which is positioned to face the blast may be moulded to have a specific surf ace shape to suit specific requirements in order to further improve the performance of the material in blast conditions.

WO 97/16697 Prr/raarm rrr r The decoupling, intermediate layer, if of a filler material, may be bonded to either of the attenuating material panels or the backing layer prior to the construction of the wall and in whichever form the effect of the decoupling layer is to allow the effect of the blast to be attenuated and thereby minimising the damaging effect on the support structure and allowing the attenuating material to break up in the "correct" way upon a blast occurring and thereby again minimising the damaging affect of the blast.

In a further aspect of the invention there is provided a container for the containment of a blast in the interior thereof, said container formed from a plurality of walls, each wall having an inner layer of a resin bonded particulate material.

Typically each of the walls are joined together by angled section and welded or otherwise attached thereto or alternatively bonded metal, fibre reinforced composite or non reinforced plastics material could be used for the outer walls of the container.

Typically the container is dimensioned and constructed such that the walls of the same can expand to a limited degree upon the blast but the integrity of the container is maintained. The container is provided with a door in at least one of the walls said door formed in the same manner as the walls of the container.

Typically the door is formed and hung from hinges of a strength to give the wall in which the door is provided substantially the same blast containment properties and strength as the other walls of the container. In particular, the catch or catches which are used to retain the door in a closed position are provided to be sufficiently strong to prevent the door from being blown open upon a blast and WO 97/16697 PCT/GB96/2n61 8 thereby forming a weakened area. Thus the container of the invention is preferably provided with no faces which are weaker than the others.

The layer of the attenuation material on each wall can be provided in a single panel form or alternatively, and particularly to form larger walls, a series of panels can be held in an abutting relationship.

In whichever form it is envisaged that it can be advantageous to provide the attenuating material in a corrugated form.

Specific embodiments of the invention will now be described with reference to the accompanying drawings; wherein Figure 1 illustrates a graph illustrating the attenuation of blast pressure; Figure 2 illustrates the attenuating material according to the invention in use on the underside of a utility vehicle; Figure 3 illustrates a container formed according to the invention; Figure 4 illustrates a detailed view of catch for the door of the container; Figure 5 illustrates a wall of the container; and Figure 6 illustrates a cross section of the wall of Figure WO 97/16697 PCT/GB96/2612 WO 9716697PCT/GB96/02612 9 Referring firsdtly to Figure 2 there is illustrated a first use of the attenuating material 2 according to the invention to form the underside of a vehicle 4.

Typically the material 2 is provided on the underside of the vehicle and may also be provided internally of the vehicle if required. The attenuating material can be formed to the required shape of the underside for any particular design of vehicle thereby ensuring that the mechanical requirements for that vehicle can still be achieved. In one form the attenuating material is provided in conjunction with an adhesive filler which allows the attenuating material 2 to be adhered to the backing layer 6 which can be of steel to form a multilayered floor to the vehicle.

In this case the attenuating material 2 is provided to face outwardly of the vehicle as it is from this direction that the blast will come such as from a hand grenade, land mine or other device and will thereby act to prevent the blast from substantially impinging on the interior of the vehicle thus reducing the risk to the occupants of the same. Typically the adhesive material used to attach the material to the vehicle also acts as an intermediate or decoupling layer.

Figure 3 illustrates a container 10 for containing a blast which is constructed incorporating a layer of the attenuating material according to the invention. The container comprises a plurality of walls joined together along the edges and corners by angled members 12. The members 12 can also be interconnected by steel straps 14 as shown to further strengthen the walls. To aid the movement of the container, wheels or rollers 15 can be provided. At least one of the walls is provided with a door 16 to allow access to the container and the door is hinged 18 and held in a closed position by the catch 20 which is shown in more detail in Figure 4 which is provided with a lever handle 17 for locking and releasing member 19 from the socket 21. Both the hinges and catches are provided to be of sufficient strength so that the same do not represent a weakened part of the WO 97/16697 PCT/GB96/n2612 WO 97/ 6697PCT/GR96/0261 7 10 container and the catch is of a type which is operable by conventional remote controlled suspect device EOD vehicles for use with luggage containers and are operable without the requirement for specialist equipment for smaller containers.

The outer or backing layer 30 of each wall is provided of a perforated sheet steel.

The perforations allow the blast product gases from within the container to be released in a controlled manner such that the release is at a sustainable over pressure for personnel and structures in the vicinity of the blast. Typically the perforated open area represents 4 0% of the area not covered by the joining angle, catches or binding straps and may also include the door of the container opening slightly to aid the release of product gases.

Figure 5 illustrates a wall 22 from the interior of the container 10. The inner face of the wall is shown to comprise a number of formed portions 24 of the attenuating material according to the invention. The material 22 is provided to provide a shaped face as required, and other shaped faces can be formed if required. The panel 24 is held in position by discrete supports 26 which protrude from the outer layer 30, of the wall. Thus, to construct the wall, the backing layer is provided with the supports 26 connected thereto in the required position whereupon the attenuating material 22 according to the invention can be fitted into position to form the inner face of the wall against which the blast impacts.

In a preferred form a decoupling intermediate layer 32 is provided between the panels 24 and the backing layer 30 of the wall and this is illustrated in Figure 6.

Figure 6 illustrates the manner in which the attenuating material 24 is held in position by the supports 26 offset from the backing layer 30 of the wall. The offset allows a gap for the intermediate layer 32 to be provided. In the embodiment shown the intermediate layer 32 is an air gap but in other WO 97/16697 PrTICIRO~IClr;l? embodiments a filler material such as glass or steel wool or foam or any other combination can be inserted to form the intermediate layer.

In use therefore the container can be used to contain suspected explosive or incendiary devices. For example, if a suspect device is found in a post office or is delivered to a premises and a container according to the invention is available, the suspect device can be inserted into the container by opening the door 16 and then closing and locking the same to await inspection but, if the same detonates unexpectedly the container acts to limit the damage created. In this situation each of the walls of the container is of substantially equal strength.

If the container is to be used for larger devices such as parcel bombs, or bombs in briefcases and luggage the thickness of the attenuating material of the invention and the walls in general will be scaled up and the container will be much larger and be movable by forklift truck or other suitable lifting means.

It should therefore be easily appreciated that the container formed can be adapted to suit specific uses and to suit the perceived threat and type of suspect devices to be dealt with. In whichever form, the attenuating material of the invention allows the impact of the blast to be attenuated and partially absorbed by allowing the shock wave phase of the blast to be substantially reduced and thus one or more of the damaging phases of the blast are reduced to an extent wherein the same have little or no impact on the surrounding environment.

When the attenuating material is applied to surfaces such as the undersides of vehicles, walls, floors and ceilings of buildings the material serves to absorb the shock wave of the blast and thus prevent the shock wave from causing the normal WO 97116697 PT/d 1 0 /11?1" WO 97/16697 1 -t~l7t&1 damage. The shock wave is thus attenuated in a form which allows the risk of penetration of the wall or vehicle body to be reduced.

When the attenuating material is used as an integral part of a container within which the blast is contained, the material serves to absorb the shock wave of the blast and then allow the gradual release of the gases and pressure through the perforated backing layer of the walls. Hence the actual shock wave is once again prevented from having the damaging effect on the container and so the blast is contained within the container. Typically the walls may bow outwardly due to the force of the blast but the effects of the blast are dissipated by the container.

In each form it is preferred that the material is used in conjunction with an intermediate decoupling layer to further reduce the impact of the blast in conjunction with the material.

In one series of tests the blast shock wave was found to be reduced by 94.7% by the container in comparison to an equivalent sized charge which was detonated in free air.

It is known that the material and apparatus of this application can be used for numerous advantageous benefits, some of which have already been mentioned in a non-limiting manner. It should also be appreciated that the material can be used in airport luggage scanners so as to prevent devices, which can be programmed to go off when passing though the same, to have minimum impact on the equipment, the material can be used to line litter bins and or lids to minimise the effect of a blast and to line scrap metal shredders which can be subjected to damage and causes environmental concern if, for example, a gas canister or the WO 97/16697 PCT/GB96/02612 like explodes when it passes through the shredder. These are yet further examples and it is clear that there are many further uses for this material and apparatus incorporating the same.

Claims (26)

1. A structure for minimising the effect of blast energy created by a blast, said structure including an attenuating material formed of resin bonded particulate to attenuate the shock wave of the blast, and a support structure wherein said attenuating material is directly exposed to the blast and said attenuating material and support structure are decoupled during said blast.

2. A structure according to claim 1 wherein the particulate used is all of substantially the same dimension.

3. A structure according to claim 1 wherein the particulate is an aggregate.

4. A structure according to Claim 1 wherein the resin and particulate are cold pressed into a required form of a specified thickness for a specific function.

A structure according to claim 1 wherein there is provided a decoupling layer between the support structure and the attenuating material.

6. A structure according to Claim 1 wherein said structure allows the passage therethrough of gases created during the blast and retards the speed and pressure of the same S* and acts to modify the initial shock wave of the blast by attenuating the energy.

7. A structure according to Claim 1 wherein the structure further includes a backing layer and at least one decoupling, intermediate layer.

8. A structure according to Claim 7 wherein the intermediate layer is a filler material which further acts to contain the blast shock wave.

9. A structure according to Claim 7 wherein the intermediate layer or layers are .0 provided to act as any of, or any combination of, a heat sink; to support the attenuating material under blast conditions; to improve performance of the attenuating material; and/or as an envirnamnental barrier.

Z-N 2 7. A structure according to any of the preceding claims wherein the attenuating material is provided in a sheet form which is sufficiently flexible to allow the attenuating material to be shaped to the article to which the attenuating material is to be applied.

11. A structure according to Claim 10 wherein the attenuating material is used in conjunction with a decoupling layer of filler material which is adhesive, thereby allowing the attenuating material to be adhered to the article.

12. A structure according to any one of claims 7 to 11 wherein the backing layer is made of steel.

13. A structure according to any one of claims 7 of 11 wherein the backing layer is made of reinforced fibre composite.

14. A structure according to any one of the preceding claims wherein the attenuating material is formed in a corrugated fashion.

A structure according to any of the preceding claims wherein the attenuating material is perforated.

16. A container provided to contain a blast therein, wherein each wall of the container S: includes at least three layers, being a backing layer, a decoupling intermediate layer and an S'o O: internally facing layer which is formed at least partially of resin bonded particulate material.

17. A container according to Claim 16 wherein the decoupling intermediate layer is an air gap.

18. A container according to claim 16 wherein the decoupling intermediate layer is a filler /o v" material. oo V o O, ZI

19. A container according to Claim 15 wherein the backing layer is perforated such that a percentage of the backing layer is open.

A structure according to claim 3 wherein the aggregate is silica.

21. A structure according to claim 3 wherein the particulate is formed of hollow particles.

22. A structure according to claim 21 wherein the hollow particles are made from ceramic combined with resin.

23. A structure according to claim 5 wherein said decoupling layer comprises an air gap.

24. A structure according to claim 5 wherein said decoupling layer is a foam material.

A structure substantially as herein described and with reference to the accompanying drawings.

26. A container substantially as herein described with reference to the accompanying drawings. Dated this 7t day of February, 2001 DAVID CHRISTIAN and STEVEN JOHN HOLLAND By their Patent Attorneys MADDERNS