Protective shield, shield wall and shield wall assembly

Abstract

A protective shield (100) comprises a body (105) for protecting a user from a projectile or impact, the body comprising a front strike face (110) and an opposing rear face (115); and a connector arrangement (125, 126) provided on the body adapted so as to allow the shield to connect to an adjacent protective shield, wherein the strike face has a perimeter defined by the edges of the strike face; and wherein the connector arrangement is arranged so that an adjacent protective shield can be connected to the connector arrangement with the body of the adjacent protective shield abutting and/or overlapping with the strike face of the protective shield at any point about the perimeter of the strike face.

Claims

1. A protective shield comprising: a body for protecting a user from a projectile or impact, the body comprising a front strike face and an opposing rear face; and a connector arrangement provided on the body adapted so as to allow the shield to connect to an adjacent protective shield, wherein the strike face has a perimeter defined by edges of the strike face; wherein the connector arrangement is arranged so that an adjacent protective shield can be connected to the connector arrangement with the body of the adjacent protective shield abutting and/or overlapping with the strike face of the protective shield at any point about the perimeter of the strike face; wherein the body comprises a composite structure comprising at least one layer comprising graphene and a second layer comprising an aerogel; and wherein the composite structure is arranged between (i) the strike face and rear face, and/or (ii) so as to at least partly define the strike face and/or the rear face.

2. The protective shield of claim 1, wherein the connector arrangement is adapted so that a plurality of adjacent protective shields can be connected to the connector arrangement.

3. The protective shield of claim 1, wherein the connector arrangement comprises first and second connector parts provided on the body, the first connector part being adapted to connect to a second connector part of another protective shield and the second connector part being adapted to connect to a first connector part of another protective shield.

4. The protective shield of claim 3, wherein the first connector part and the second connector part are each provided on the strike face or the rear face; and wherein each extend around the edge of the strike face or rear face on which they are provided.

5. The protective shield of claim 4, wherein at least one of the first and second connector parts is offset from the edge of the face on which they are provided.

6. The protective shield of claim 3, wherein the first connector part is provided on the rear face; and wherein the second connector part is provided on the strike face.

7. The protective shield of claim 3, wherein each of the first and second connector parts comprises a plurality of connector elements.

8. A protective shield comprising: a body for protecting a user from a projectile or impact, the body comprising a front strike face and an opposing rear face; and a connector arrangement provided on the body adapted so as to allow the shield to connect to an adjacent protective shield, wherein the body comprises a composite structure comprising at least one layer comprising graphene and a second layer comprising an aerogel, and wherein the composite structure is arranged: (i) between the strike face and rear face; and/or (ii) so as to at least partly define the strike face and/or the rear face.

9. The protective shield of claim 8, wherein the layer comprising graphene comprises graphene in the form of graphene platelets.

10. The protective shield of claim 8, wherein the composite structure comprises a plurality of first layers each comprising graphene; and a plurality of second layers each comprising an aerogel, wherein the first and second layers alternate in the composite structure.

11. The protective shield of claim 8, wherein a fastening element or means is provided to secure the first and second layers of the composite structure together, the fastening element or means being provided along an edge of the composite structure.

12. The protective shield of claim 8, wherein the composite structure further comprises a protective layer selected from the group consisting of aramid fibres, aromatic polyamide fibres, boron fibres, ultra-high molecular weight polyethylene, poly(p-phenylene-2,6-benzobisoxazole) (PBO) or combinations thereof.

13. The protective shield of claim 12, wherein the composite structure is arranged with the protective layer adjacent or defining the strike face.

14. The protective shield of claim 8, wherein the connector arrangement is arranged so that an adjacent protective shield can be connected to the connector arrangement with the body of the adjacent protective shield abutting and/or overlapping with the strike face of the protective shield at any point about the perimeter of the strike face.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Specific embodiments of the invention will now be discussed in detail with reference to the accompanying drawings, in which:

(2) FIGS. 1a to 1c shows a front view, rear view and perspective view, respectively, of a protective shield according to an embodiment of the invention;

(3) FIG. 1d shows a cross-sectional view through the protective shield of FIGS. 1a to 1c;

(4) FIG. 2 shows a front view of a plurality of protective shields of FIGS. 1a to 1c in a shield wall according to an embodiment of the invention;

(5) FIG. 3 shows a front view of a plurality of protective shields protective shields of FIGS. 1a to 1c in a shield wall according to an embodiment of the invention;

(6) FIG. 4 shows a front view of a plurality of protective shields in a shield wall according to an embodiment of the invention;

(7) FIG. 5 shows a perspective view of a protective shield according to an embodiment of the invention;

(8) FIG. 6 shows rear view of a plurality of protective shields of FIG. 5 in a shield wall according to an embodiment of the invention;

(9) FIG. 7 shows a cross-sectional view of a composite structure for use in an embodiment of the invention;

(10) FIG. 8 shows an SEM image of an aerogel layer with a graphene layer disposed thereon at 650× magnification;

(11) FIG. 9 shows an SEM image of an aerogel layer with a graphene layer disposed thereon at 2000× magnification;

(12) FIG. 10 shows a front view of a test rig;

(13) FIGS. 11a and 11b shows a front view of a composite material being tested in a test rig;

(14) FIGS. 12a and 12b show a front view of a composite material undergoing ballistic testing;

(15) FIGS. 13 and 14 show front views of an embodiment of a shield wall assembly;

(16) FIGS. 15 and 16 show side views of the embodiment of FIGS. 13 and 14; and

(17) FIGS. 17 and 18 show shield walls for use in an embodiment of a shield wall assembly.

(18) Like reference numerals are used for like parts; for example, “100”, “200” and “300” refer to a shield.

DETAILED DESCRIPTION OF THE INVENTION

(19) A protective shield 100 according to an embodiment of the invention is shown in FIGS. 1a to 1c. The protective shield 100 comprises a body 105, which in this embodiment has a cuboid shape. The body 105 has a front rectangular strike face 110 and an opposing rectangular rear face 115, which are interconnected by edges 111, 112, 113, 114. Thus, both the strike face 110 and rear face have a perimeter defined by edges 111, 112, 113, 114. Between the strike face 110 and the rear face 115 is provided a ballistic-resistant composite material 170, which is capable of stopping projectiles from passing through the body 105. The composite 170 is discussed in more detail, below.

(20) The protective shield 100 also comprises a connector arrangement comprised of a set of corresponding male and female connector elements 125, 126 provided on the body 105 so that the shield 100 can be connected to adjacent protective shields 100. In particular, the connector arrangement comprises four releasable elongate male connector strips 125 provided around the perimeter of the strike face 110, with one of the male connector strips 125 provided adjacent each one of the four edges 111, 112, 113, 114 of the body 105. The connector arrangement also comprises four releasable elongate female connector strips 126 provided around the perimeter of the rear face 115, with one of the female connector strips 126 provided adjacent but offset from each one of the four edges 111, 112, 113, 114 of the body 105. In this way, the male connector strips 125 provided on the front strike face 110 of the protective shield 100 can be connected to female connector strips 126 on a rear face 115 of a second protective shield 100. Each male connector strip 125 extends along the majority of the length of the respective edge 111, 112, 113, 114 to which it is adjacent. Although this does not form a complete continuous connector strip array, due to the shape of these connector strips 125 and the arrangement of the female connector strips 126, this arrangement allows for the protective shield 100 to overlap with another protective shield 100 at any point about the perimeter of the strike face 110 (and similarly, the perimeter of the strike face 110 of the other protective shield 100).

(21) The protective shield 100 also comprises a handle 130 provided in the centre of the rear face 115 of the body 105 for allowing the shield to be held by a user with the strike face 110 facing outwardly. The handle 130 handle in this embodiment is an elongate strip of material with the top and bottom of the handle 130 stitched to the rear face 115 so as to allow a user to put their hand or arm between the middle of the handle 130 and the rear face 115. In this embodiment, although not necessary, the handle 130 is also provided with the same releasable female connector material as the female connector strips 126 so that it can also be connected to male connector strips 125.

(22) A cross-section through the shield 100 is shown in FIG. 1d, where a part of the composite structure 170 used in the structure is visible (for the sake of clarity, only a fraction of the height of the composite 170 is shown. The composite structure 170 comprises a plurality of graphene layers 172a, 172b, 172c, 172l and a plurality of aerogel layers 173a, 173b, 173c, 173l. The graphene layers 172a-c,l and the aerogel layers 173a-c,l alternative such that the composite structure 170 has a repeating structure of graphene layer/aerogel structure/graphene layer/aerogel layer. In this way, there is an outermost graphene layer 172a immediately adjacent the strike face 110, behind which is an aerogel layer 173a. This structure then repeats such that there is a second graphene layer 172b behind the first aerogel layer 173a, which is adjacent a second aerogel layer 173b, followed by a third set of layers 172c, 173c, which repeat until a final graphene layer 172l and a final aerogel layer 173l. Although not visible in FIG. 2, the layers 172a-c,l 173a-c,l of the structure 170 are bonded together by means of an adhesive which is provided between the layers. On either side of the composite structure is provided a cover layer 180, which forms the outermost layer defining the strike face 110 and the rear face 115 of the shield 100.

(23) In use, multiple protective shields 100 can be used to form a protective shield wall 150, as shown in FIGS. 2 and 3, when required. In particular, a male connector strip 125 of the protective shield 100 can be connected to a female connector strip 126 of an adjacent protective shield 100 to thereby secure the protective shields 100 together along an edge 112. In this case, since the connector strips 125, 126 are both provided on the rear and front strike faces 115, 110, this creates an overlap of the strike faces 110 of the two protective shields 100 so as to create a continuous strike face, which ensures that adequate protection is provided. In other words, the bodies 105 of the adjacent protective shields 100 overlap. By virtue of the arrangement of the elongate connector strips 125, 126, the protective shield 100 can receive another protective shield 100 with the second protective shield 100 overlapping with any part of the perimeter of the protective shield 100. In particular, by virtue of the positioning of the elongate male connector strips 125, which extend over the majority of the length of the edges 111, 112, 113 and 114 and the arrangement of the elongate female connector strips 126, this leads to the overlap of the strike faces 110 so as to create the continuous strike face 110.

(24) This interconnection can be continued by addition of further protective shields 100 to the protective shield wall 150, as shown in FIG. 2, where six protective shields 100 have been attached in this manner. In this case, a row of four protective shields 100 has been formed, with the elongate edges 112, 114 of the two protective shields 100 in the centre overlapping with the adjacent shields 100. A further two protective shields 100 have been added so as to overlap the top edges 111 of two of the other shields 100 in the wall 150 adding further protection. As can be seen from FIGS. 2 and 3, due to the arrangement of the connector strips 125, 126, the shields 100 can be arranged so that these do not need to be perfectly aligned and can be received at any part of the perimeter while still providing some degree of overlap of the strike faces 110. This makes the formation of the protective shield wall 150 easier in stressful situations.

(25) This is particularly advantageous as the protective shields 100 can be carried individually or stored individually and then assembled into a wall 150 when required. For example, the individual shields 100 can be carried in a rucksack or backpack (for example, as a component part of the rucksack) and then it can be taken out of the rucksack and assembled into a wall 150 with other proactive shields 100.

(26) The composite structure 170 in this embodiment is provided by forming a number of layers of aerogel substrate with graphene formed thereon and layering these into the composite structure 170. In this case, the graphene is disposed onto the aerogel substrate using the graphene in the form of an ink. This is achieved by dispersing graphene platelets in a solvent, applying the ink to the surface of the aerogel and removing the solvent to leave a layer of graphene platelets on the surface. This allows for the simple and relatively inexpensive application of a layer of graphene to the aerogel. Moreover, no further additives are required in the layer (e.g. a matrix). The presence of numerous layers of graphene and aerogel in repeating fashion in the composite structure 170 has been found to provide a particularly strong, yet still flexible, composite. Accordingly, the structure 170 is particularly useful for preventing penetration and absorbing impact as the presence of multiple discrete structures means that a failure of one aerogel layer (e.g. a fracture or breach) or protective layer will not necessarily result in failure of the structure, since there are other layers to absorb an impact. Further, a further effect has been observed whereby an increase in the number of layers leads to an increase in the effectiveness of the earlier layers in the structure.

(27) Another embodiment is shown in FIG. 4, where there is a shield wall 250 comprising six flexible protective shields 200. Each shield 200 comprises a main body 210, in this case having a rounded cuboid shape, with a planar front strike face 210 and an opposing planar rear face (not visible). Between the strike face and the rear face 310 is a flexible composite structure (not visible), which serves to provide the impact protection. The shields 200 also comprise a connector arrangement in the form of a hook and loop (or hook and pile) releasable fastening arrangement (such as Velcro™), which comprises a first connector part in the form of a hook-containing connector element 225 provided on the strike face 210 and a second connector part in the form of a loop-containing connector element (not shown) provided on the rear face. The hook-containing connector element 225 in this case is an elongate strip which extends around the circumference of the strike face 210, adjacent the perimeter of the strike face 210. The loop-containing connector element is provided on the rear face and covers the entire surface of the rear face.

(28) In this way, in use, the entire rear face of a first shield 200, which comprises the loop-containing connector element, can be pressed against the hook-containing connector 225 on the front strike face 210 of a second shield 200 to secure the first shield 200 and to create an overlap of the strike faces 210 and to form the protective shield wall 250. The arrangement and type of connector elements 225 used allows for the quick and straightforward connection of the shields 200. Moreover, the shape and arrangement is readily customisable to form a particular wall 250 suited to the particular need at the time the wall is assembled. Moreover, the connector arrangement makes it very straightforward and intuitive such that the wall 250 can be assembled under pressure and stress. The wall in this embodiment 250 is both strong and flexible shield wall 250 and thus can be adapted to cover a person or persons more completely.

(29) Another embodiment is shown in FIG. 5, where there is a shield 300 comprising a cuboidal body 310 having a planar front strike face (not visible) and an opposing planar rear face 310. Between the strike face and the rear face 310 is a composite structure (not visible), which serves to provide the impact protection, and the strike face and rear face 310 are connected by four edges 311, 312, 313, 314. On the rear face 310 are two handles 330, which allow a user to grasp the shield 300 with the strike face facing away from the user. The shield 300 also comprises a connector arrangement, which consists of a series of pressure-sensitive adhesive spots 325 arranged in a space-apart array along each of the edges 311, 312, 313, 314, which are able to adhere to a second protective shield 300. In particular, these adhesive spots 325 can adhere to corresponding adhesive spots provided on the second protective shield 300 or to any other surface (e.g. the edges) of the second protective shield 300.

(30) Thus, in use, the shield 300 can be connected to other protective shields 300 to form a shield wall 350, as shown in FIG. 6. In particular, the shields 300 can be aligned and the edges 311, 312, 313, 314 pressed against one another to form a shield wall 350. In some cases, the adhesive spots 325 may be covered by a removable protective strip (not shown), which is removed prior to connection to adjacent shields 300. With the edges 311, 312, 313, 314 engaged with one another by virtue of the adhesive spots 325, the strike faces of the shields 300 abut one another to form a continuous strike face wall. This can then be used to protect a user, or multiple users.

(31) As shown in FIG. 7, the composite structure 470 comprises alternating aerogel 473 and graphene 472 layers, but also includes a further set of protective layers 474 which are intermediate each pair of an aerogel 473 and a graphene 472 layer. Thus, the composite 470 has a repeating pattern of protective layer 474/graphene layer 472/aerogel layer 473. The protective layer 474 is a ballistic or penetration resistant high-tensile layer which provided on the top of the composite 470 and is located forward (i.e. in the direction of incoming impact force) of each of the graphene 472 and aerogel layers 472. The protective layer absorbs a portion of the impact and assists in preventing penetration through the structure. In a specific embodiment of the composite 470, the protective layer 474 of the composite structure 470 is an ultra-high molecular weight polyethylene (UHMWPE) layer having a thickness of 180 micrometres. The graphene layer 472 in this embodiment is a 20 micrometre thick layer of graphene platelets disposed on the aerogel layer 473. In this case, the graphene platelets are disposed onto each aerogel layer 473 using the graphene in the form of an ink. This is achieved by dispersing graphene platelets in a solvent, applying the ink to the surface of the aerogel and removing the solvent to leave a layer of graphene platelets on the surface. This allows for the simple and relatively inexpensive application of a layer of graphene to each aerogel layer 473. Moreover, no further additives are required in the layer (e.g. a matrix). The aerogel used in the aerogel layer 473 is a 125 micrometre thick layer of polyimide aerogel. The composite structure 470 can be arranged in the body of a protective shield with the uppermost protective layer 474 facing the strike face or as the strike face. FIGS. 8 and 9 show SEM images of a single layer of graphene platelets on a single layer of aerogel at 650× and 2000× magnification. Here the structure of the graphene platelets can be clearly seen. Using the methods disclosed herein a dense layer of graphene can be formed on the aerogel providing a strong, resilient cover or protective layer.

(32) A deployable shield wall assembly 680 according to an embodiment of the invention is shown in FIGS. 13 to 16. As can be seen in FIG. 13, the deployable shield wall assembly 680 comprises a deployable shield wall 681 for providing protection from a projectile or impact and a frame 682 within which the deployable sidewall 681 is received. Frame 682 is defined by an upper member 691 of a holding element 690, which holding element 690 is connected to the deployable shield wall 681 at the top of the shield wall 681 thereby holding the shield wall 681 up, opposing vertically extending side members 697 and a lower member 689. In this embodiment, the frame 682 has a rectangular shape with a central opening or void 692, within which the shield wall 681 can be received. As will be set out in more detail below, the deployable shield wall 681 can be deployed between a retracted configuration (shown in FIG. 14) in which it is not received within the opening 692 and a deployed configuration (shown in FIG. 13) in which it is fully received within the opening 692 so as to provide protection from a projectile or impact.

(33) The deployable shield wall 681, which can be seen more clearly in FIGS. 13, 15 and 16, comprises a penetration-resistant support screen 683, several shield members 685, each of which comprises a composite structure and is attached to the support screen 683. The shield members each also comprise a pair of fastening elements 688 for providing further structure to the wall 681 when in a deployed configuration. Here, fastening elements 688 are placed on the side edges of the deployable shield wall 681. Each shield member 685 also comprises two fastening elements 688, one located at the uppermost edge of the shield member 685 and the other located at the lowermost edge such that the fastening devices 688 are within the overlap portion of the shield members 685.

(34) The support screen 683 is formed of a continuous sheet of ballistic fabric; in this case, the ballistic fabric is formed of woven ultra-high molecular weight polyethylene (UHMWPE) which is both cut and stab-proof. The penetration-resistant support screen 683 comprises multiple pockets 684 on its rear surface for receiving the shield members 685. In this embodiment, multiple pockets 684 are arranged vertically along the length of the penetration-resistant support screen 683, with each of the pockets 684 extending the entire width of the penetration-resistant support screen 683. The pockets 684 are secured to the penetration-resistant support screen 683 along their upper edge such that a given pocket 684 and shield member 685 combination is able to pivot away from the penetration-resistant support screen 683 about this upper edge. The pockets 684 entirely encapsulate their corresponding shield members 685 such that the shield members 685 cannot be removed without opening the pockets 684 first.

(35) The shield members 685 of the deployable shield wall 681 each have a front strike face 686 and a rear opposing face 687, with the composite structure arranged in layers defining and extending parallel to these faces 686, 687, as will be explained below in more detail. This configuration allows for maximum ballistic performance when the strike face is oriented towards an oncoming projectile. For the purposes of clarity, in this embodiment the strike or front face 686 is the face of a given panel 685 which is oriented towards the penetration-resistant support screen 683 when in its deployed configuration; similarly, the opposing face or rear face 687 is the opposite face of the panel 685. The composite structure of the shield member 685 in this embodiment can be the same as set out in respect of the earlier embodiments, such as that of FIG. 7.

(36) As set out above, the frame 682 is defined by holding element 690 opposing vertically extending side members 697 and a lower member 689. In this embodiment, lower member 689 and side members 697 are formed from hardened steel and are connected together, and with the holding element 690, to provide a rigid, self-supporting frame 682. As is visible in the front view of FIG. 13, the lower member 689 has a smaller profile than the remaining members such that it does not disrupt passage through the central opening 692, thereby allowing the assembly 690 to be placed in a doorway, for example. Although not shown, lower member 689 includes an engagement element (not shown) adapted to engage with the lower edge of the shield member

(37) In this embodiment, the deployable shield wall 681 is attached, at the uppermost point of the penetration-resistant support screen 683, the holding element 690 such that it hangs from this point when deployed. In particular, the upper edge of the support screen 683 is retained between the upper member 691 and a clamping member 693. The clamping member 693 is an elongate member which extends along the length of the upper member 691 so as to allow for equal pressure to be applied across the clamped area of the penetration-resistant support screen 683 thus minimising the risk of tearing or other failure. The clamping member 693 also allows for the deployable shield wall 681 to be easily replaced as a complete unit, for example after damage from a projectile or impact. Security fasteners (not shown) are used such that the clamping member 693 can only be released by an authorised person.

(38) The holding element 690 also comprises a deployment mechanism in the form of a release mechanism. The release mechanism comprises two releasable catches 694 (only one is visible in FIG. 16), each of which is located near a top of each side member 697 of the frame 682. Each catch 694 engages an engagement element 695 located at the bottom of corresponding side edges of the deployable shield wall 681 when the wall 681 is in its retracted configuration. The catches 694 are operatively connected to a controller (not shown) which is arranged to release the catches upon detection of an event (e.g. an alarm or manual trigger). The catches 694 are also configured such that they automatically engage when the shield wall 681 is retracted after use, i.e. moves the wall 681 from its deployed configuration into its retracted configuration. Suitable catches 694 and engagement elements 695 include manual latches or electromagnetic catches, for example.

(39) The deployable shield wall 681 is shown in its retracted configuration in FIG. 16. As can be seen, the penetration-resistant support screen 683 and shield members 685 are in a collapsed state in which they are folded together into a compact arrangement wherein the shield members 685 are stacked together and parallel to one another such that the strike face of one shield member 685 directly faces the opposing rear face of the shield member 685 below it; folds of the penetration-resistant support screen 683 itself lie partially in the gaps between these faces. In this figure, the pockets 684 are shown but their upper edge connections are not.

(40) The deployable shield wall 681 is shown in its deployed configuration in FIG. 15. Here, the composite shield members 685 are in an expanded state and effectively form a continuous strike barrier behind the penetration-resistant support screen 683; in other words, at any point of the penetration-resistant support screen 683 there is at least one shield member directly or indirectly (i.e. with the presence of an air gap) behind the penetration-resistant support screen 683, such that the deployable shield wall 681 has few or no points of weakness. The shield members 685 are configured to overlap with one another such that at certain points of the penetration-resistant support screen 683, there are two shield members 685 behind the penetration-resistant support screen 683. In particular, the lowermost portion of the strike face 686 of one shield member will lie against the uppermost portion of the opposing face 687 of the shield member 685 directly below it. In this embodiment, approximately 5 cm of the upper shield member overlaps the shield member directly below it. This is advantageous, as the joints between shield members 685 which may otherwise be a weak point, are reinforced.

(41) The deployable shield wall 681 is sized such that when it is deployed, the shield wall 681 covers the entirety of the central opening 692 of the holding element 690. In this embodiment, the deployable shield wall 681 overlaps each of the side members 697 and the upper member 690.

(42) In use, the deployable shield wall 681 is initially collapsed in its retracted configuration. In response to a perceived threat, the release mechanism can be operated (either manually, or automatically, depending on the control system used), thereby releasing the catches 694 and deploying the shield wall 681. As the shield wall 681 is released, it falls under the force over gravity. This moves the shield wall 681 from its retracted configuration wherein the shield members 685 are stacked parallel to one another in the collapsed state and into its deployed configuration wherein the shield members 685 overlap one another. On moving into its deployed configuration, the fastening devices located on the shield members 685 engage such that each shield member is secured to its adjacent shield members 685. This means that the shield members 685 are rigidly connected to one another. In addition, the engagement element provided on the lower member 689 also engages with the lower edge of the shield wall 681. This ensures that significant force is required to move the wall 681 away from the frame 682.

(43) In this position, the shield wall 681 provides a barrier through the opening 692 thereby protecting people or objections on either side of the barrier, but particularly behind the rear face, from threats, such as projectiles (e.g. bullets) or impacts (e.g. blunt force or bladed weapons). Moreover, the shield wall 681 acts as a barrier to prevent passage therethrough. The assembly can thus be placed in any opening such as a doorway or across a room to provide quick and safe protection in the case of a threat. In some embodiments, the lower member 689 of the frame 682 can be recessing into the floor or ground. This is advantageous in that access through the central opening 692 is improved.

(44) When the threat is over, the shield wall 681 can be retracted. In this embodiment, the shield wall 681 can be disengaged from the engagement element of the lower member 689 and fastening elements 688 can be disengaged. The shield wall 681 can be collapsed back into the state shown in FIG. 16 and reattached to catch 694. The deployable shield wall 681 can then be re-used assuming it is not damaged. Should the shield wall 681 have been damaged to the point where replacement is recommended, the shield wall 681 can then be released from the clamping member 693 and replaced. In view of the lightweight nature of the composite structure used in shield members 685 and the simplicity of the release mechanism and design of the assembly, this replacement can easily be carried out.

(45) The above embodiment is purely for the purposes of demonstrating how an implementation of the invention could be provided. Other embodiments are possible. Modifications include, for example:

(46) In other embodiments, the fastening devices 688, catches 694, engagement elements 695 and engagement element on the lower member 689 could be electromagnet fastening devices. In some embodiments, the side edges and lower edges of the shield wall 681 may be provided with are electromagnets configured to engage the corresponding side members 697 or the other way around. In some embodiments, the fastening devices 688 placed on each shield member are located and configured to engage the side members 697 of the frame 682, through the penetration-resistant support screen 683. This configuration is advantageous as the fastening devices can hold both the penetration-resistant support screen 683 and individual shield members 685 securely to the holding element 690. However, both the penetration-resistant support screen 683 and shield members 685 can comprise fastening devices in some embodiments.

(47) A further embodiment of a shield wall 781 is shown in FIG. 17. This shield wall 781 is shown in isolation to a shield wall assembly, but could be employed in the shield wall assembly 681 of FIGS. 13 to 16 or as part of any other shield wall assembly according to the invention. In the embodiment of FIG. 17, the shield wall 781 comprises a plurality of shield members 785 which do not overlap each other, but are instead sized so that when in a deployed configuration the top shield member 785 meets the bottom of an adjacent shield member 785 (i.e. abuts the adjacent shield member 785). Without overlap, there is less interaction between the shield members 785 such that the wall 781 can more easily be stored in a rolled configuration rather than the stacked configuration of the embodiment of FIGS. 13 to 16. Moreover, the shield members 785 are attached to a penetration-resistant support screen 783 about their entire periphery, rather than only the upper edge as in the aforementioned embodiment; because of this, the shield members 785 maintain their positions relative to the penetration-resistant support screen 783 without any fastening devices 688 therebetween. It will be appreciated that the shield members 785 of this shield wall 781 could also be stacked as in the earlier embodiment, as shown in FIG. 17.

(48) A further development of the embodiment of FIG. 17 is shown in FIG. 18, in which there are two shield members 885 making up a shield wall 881. In this embodiment, the edges of the shield members 885 are complimentary. In particular, the bottom of the upper shield member 885 is shaped so as to correspond to the top of the shield member 885 directly below it. In the embodiment shown in FIG. 18, a ball and cup design is shown. This design may provide improved ballistic performance at the joints between shield members 885.

(49) Although shown with a frame, such a frame is not necessary. For example, the holding element may be suspended by attaching to a ceiling or another surface. Alternatively, the holding element may be located on the floor and the shield wall deployed sideways or vertically upwards.

EXAMPLES

(50) Specific examples of composite structures that are used in the shields and shield walls of the invention are provided below:

Example 1

(51) A 125 μm flexible polyimide aerogel layer (AeroZero 125 micrometer polyimide aerogel film; BlueShift Inc (US)) was cut to size and coated with a 20 μm layer of a polyurethane (PX30; Xencast UK Flexible Series PU Resin system. Manufacturer reported properties: Hardness of 30-35 (Shore A); Tensile strength 0.7-1.2 MPa; Elongation 100-155% at break; Tear Strength 3.5-3.8 kN/m) using a slot die process. After coating, the polyurethane layer was left to cure at room temperature for 12 hours. The aerogel/polyurethane composite layer (backing structure) was then cut to size.

(52) An ultra-high molecular weight polyethylene (UHMWPE) fabric (Spectra 1000; 200D; Honeywell; 80 gsm; Warp Yarn 24 Tex; Weft Yarn 25 Tex; Encs×Picks/10 cm 177×177; Plain Weave) was cut to the same size as the backing structure and was applied to the upper surface of the backing structure (i.e. the exposed surface of the polyurethane layer).

(53) The laminate structure was then further built up by adding additional, alternating layers of the backing structure (i.e. the combined aerogel/polyurethane layers) and UHMWPE fabric to form a multi-layered composite. In particular, an additional backing structure layer (i.e. the aerogel layer and the polyurethane layer in combination) was then applied to the top of the first UHMWPE fabric layer with the aerogel layer of the additional backing structure layer being applied to the UHMWPE fabric layer. An additional UHMWPE fabric layer was then applied to the top of the second backing structure. This process was repeated to provide a multi-layered composite comprising 60 alternating layers of aerogel/polyurethane and UHMWPE (i.e. 30 backing structures and 30 UHMWPE layers).

(54) This laminate structure was both flexible and lightweight and therefore can be incorporated into body armour. The laminate structure also provided effective protection against damage from a knife impact by absorbing the force of the impact and preventing penetration of the knife through the laminate structure.

Example 2

(55) A 125 μm flexible polyimide aerogel layer (AeroZero 125 micrometer polyimide aerogel film; BlueShift Inc (US)) was cut to size and coated with a 20 μm layer of graphene (Elicarb graphene powder; Thomas Swan & Co Ltd UK Product No. PR0953) in a polyurethane matrix (PX30; Xencast UK Flexible Series PU Resin system. Manufacturer reported properties: Hardness of 30-35 (Shore A); Tensile strength 0.7-1.2 MPa; Elongation 100-155% at break; Tear Strength 3.5-3.8 kN/m) using a slot die process. After coating, the graphene/polyurethane layer was left to cure and subsequently cut to size.

(56) The graphene/polyurethane layer comprised 5 wt % functionalised graphene (Elicarb graphene powder; Thomas Swan & Co Ltd UK Product No. PR0953), which was dispersed in the polyurethane prior to slot die processing. More specifically, prior to dispersion, the graphene was treated with a plasma treatment of “oxygen” functionalisation using the Hydale HDLPAS process, which is set out in WO 2010/142953 A1 (alternatively, plasma functionalised graphene nanoplatelets are commercially available from Hydale “HDPLAS GNP” e.g. HDPlas GNP-O.sub.2 or HDPLAS GNP—COOH). Following treatment, the graphene and polyurethane are premixed in a planetary centrifugal mixer and the resin was degassed under vacuum to remove air bubbles. The mixture was then passed through a dispersion stage using a Three Roll mill (at 40° C. with a <5 μm gap) and with eight passes. The graphene/polyurethane mixture was then mixed with a hardener, followed by subsequent degassing using a planetary centrifugal mixer.

(57) Once the graphene/polyurethane mixture was created it was layered down onto a polypropylene sheet with a 20 μm drawdown wire rod (which regulates the thickness to 20 μm). After the layering down has been completed, the layer was left to dry out. However, before the graphene/polyurethane layer fully cures, the aerogel is stuck onto the layer so as to bond the layers together. The combined layers making up the structure were then left to cure for 24 hours, and after which the combined layer of aerogel and the polyurethane/graphene resin mixture was cut into shape.

(58) An ultra-high molecular weight polyethylene (UHMWPE) fabric (Spectra 1000; 200D; Honeywell; 80 gsm; Warp Yarn 24 Tex; Weft Yarn 25 Tex; Encs×Picks/10 cm 177×177; Plain Weave) was cut to the same size as the backing structure and was applied to the upper surface of the backing structure (i.e. the exposed surface of the polyurethane layer).

(59) The composite structure was then further built up by adding additional, alternating layers of the graphene layers and aerogel layers, together with UHMWPE fabric between each pair of graphene and aerogel layers to form a multi-layered composite. This process was repeated to provide a multi-layered composite comprising 90 layers comprising 30 aerogel layers, 30 graphene/polyurethane layers and 30 UHMWPE layers with the repeating structure: UHMWPE/graphene layer/aerogel layer. The layers of the composite were bonded together.

(60) This composite structure was both flexible and lightweight and therefore can be incorporated into body armour. The composite structure also provided effective protection against damage from a knife impact by absorbing the force of the impact and preventing penetration of the knife through the composite structure.

Example 3

(61) Using the techniques described in respect of Examples 1 and 2, above, a composite structure comprising 26 layers of UHMWPE fibre (DOYENTRONTEX Bulletproof unidirectional sheet; WB-674; 160 g/m.sup.2; 0.21 mm thickness) alternating with 25 layers of backing structure was prepared. The backing structure comprised 125 μm flexible polyimide aerogel (AeroZero 125 micrometer film from BlueShift Inc (US)) layered with a 20 μm layer of a polyurethane (PX60; Xencast UK) (i.e. 25 layers of aerogel alternating with 25 layers of polyurethane). In this Example, the polyurethane was infused with 0.2% graphene (Elicarb graphene powder; Thomas Swan & Co Ltd UK Product No. PR0953) using the technique set out in respect of Example 2. Thus, the composite had the following repeating pattern arrangement of layers “ . . . UHMWPE layer/polyurethane+graphene layer/aerogel layer/UHMWPE layer/polyurethane+graphene layer/aerogel layer . . . ”.

Example 4

(62) Using the techniques described in respect of Examples 1 and 2, above, a composite structure comprising 26 layers of UHMWPE fabric (Spectra 1000; 200D; Honeywell; 80 gsm; Warp Yarn 24 Tex; Weft Yarn 25 Tex; Encs×Picks/10 cm 177×177; Plain Weave), 25 layers of 125 μm flexible polyimide aerogel (AeroZero 125 micrometer film from BlueShift Inc (US)) and 25 layers of a 20 μm layer of a polyurethane (PX60; Xencast UK) doped with 1% graphene (Elicarb graphene powder; Thomas Swan & Co Ltd UK Product No. PR0953). Thus, the laminate had the following repeating pattern arrangement of layers “ . . . UHMWPE layer/polyurethane+graphene layer/aerogel layer/UHMWPE layer/polyurethane+graphene layer/aerogel layer . . . ”.

Example 5

(63) Another composite structure comprises a repeating structure comprising an aerogel film (125 μm flexible polyimide aerogel; AeroZero 125 micrometer film from BlueShift Inc (US)), a graphene particle infused epoxy (Elicarb graphene powder; Thomas Swan & Co Ltd UK Product No. PR0953) and a high-tensile polyoxymethylene (POM) layer (Delrin). Thus, the composite structure has a sub-unit of aerogel/graphene-infused epoxy/POM which repeats throughout the structure to form a composite having alternating graphene and aerogel containing layers.

(64) The composite structure 1101 is manufactured by firstly functionalising the graphene nanoplatelets in a Haydale plasma reactor (using a carboxyl process) and subsequently dispersing the graphene nanoplatelets in a flexible epoxy. The graphene/epoxy mixture was subsequently slot die coated onto the Aerogel film and then layered with the POM layer (in the form of a fabric). This sub-unit is then vacuum-cured at room temperature. The structure was then built up by bonding multiple sub-units together on top of one another to form the composite structure. In this way, an aerogel layer of one sub-unit was bonded to a POM layer of an adjacent sub-unit. Furthermore, the lowermost sub-unit of the composite structure was provided with a POM layer on its underside so that POM layers form the uppermost and lowermost layers.

(65) The composite structure was flexible, strong and light.

Example 6

(66) A composite structure comprising of 12 individual sets of sub-structures layered on top of one another was prepared, each sub-structure comprising 9 layers of UHMWPE fibre (DOYENTRONTEX Bulletproof unidirectional sheet; WB-674; 160 g/m.sup.2; 0.21 mm thickness) on top of 9 layers of 125 μm flexible polyimide aerogel (AeroZero 125 micrometer film from BlueShift Inc (US)) layered with a graphene layer. The graphene layer was formed by an inking technique.

(67) In particular, a graphene-containing ink (LTR4905; Heraeus Noblelight Ltd) was used to form the graphene layer. The graphene-containing ink was a combination of 4-hydroxy-4-methylpentan-2-one and dipropylene glycol monomethyl ether as solvent and carrier, with 20 weight % graphene loading. The graphene in the ink is Perpetuus graphene with 15 μm lateral flake size and had been functionalised using amine species.

(68) The ink was applied to the surface of the aerogel using a 6 μm k-bar (K hand coater; Testing Machines, Inc.). It is thought that the shear rates associated with the application of the ink on the aerogel aligns the graphene flakes parallel to the aerogel surface. As the layer dries, the solvent evaporates leaving a final layer thickness of 2 to 3 μm. It is thought that the solvent evaporation leads to further alignment of the graphene platelets parallel to the aerogel surface. The ink is subsequently heat treated at 125° C. for 10 minutes to drive off remaining solvent and to harden the polymer. This left a layer of graphene platelets on the surface. Thus, the composite had the following arrangement of layers “ . . . UHMWPE layer/UHMWPE layer/UHMWPE layer/graphene layer/aerogel layer/graphene layer/aerogel layer/graphene layer/aerogel layer . . . ” with 12 repeat units or sub-sets.

(69) The composite structure, which had a width of 25 cm and a height of 18 cm, was placed inside a bag made from UHMWPE fabric, the bag comprising a handle on one face and hook and loop fastenings on both the major front and rear surfaces to form a connector arrangement. The composite structure and the shield were flexible, strong and light.

Example 7

(70) Using the techniques described in respect of the Examples above, a composite structure comprising five UHMWPE layers (UHMWPE fabric (Spectra 1000; 200D; Honeywell; 80 gsm; Warp Yarn 24 Tex; Weft Yarn 25 Tex; Encs×Picks/10 cm 177×177; Plain Weave)) alternating with five backing layers (five layers of 1% graphene platelet doped polyurethane layers, prepared as set out in the previous examples, and five layers of 125 μm flexible polyimide aerogel (AeroZero 125 micrometer film from BlueShift Inc (US)). The laminate structure also comprised a crocheted swatch of 1.0 mm UHMWPE braided thread (see FIG. 9 and accompanying description) with UHMWPE thread whipping around the tile edges to improve performance. The test results showed no penetration in a stab test and only a minimal dent in a plasticine clay-bed, which is significantly better than commercially available standards.

Example 8

(71) A composite structure comprising of 6 individual sets of sub-structures layered on top of one another was prepared, each sub-structure comprising 9 layers of UHMWPE fibre (DOYENTRONTEX Bulletproof unidirectional sheet; WB-674; 160 g/m.sup.2; 0.21 mm thickness) on top of 9 layers of 125 μm flexible polyimide aerogel (AeroZero 125 micrometer film from BlueShift Inc (US)) layered with a graphene layer. The graphene layer was formed by the inking method described above in respect of Example 6. In particular, a graphene-containing ink (LTR4905; Heraeus Noblelight Ltd) was used to form the graphene layer by applying the ink to the surface of the aerogel, as set out in respect of Example 6. Thus, the composite had the following arrangement of layers “ . . . UHMWPE layer/UHMWPE layer/UHMWPE layer/graphene layer/aerogel layer/graphene layer/aerogel layer/graphene layer/aerogel layer . . . ” which repeats 6 times. An additional set of 9 layers of UHMWPE fibre (DOYENTRONTEX Bulletproof unidirectional sheet; WB-674; 160 g/m.sup.2; 0.21 mm thickness) was provided on the base of the composite structure (below the final set of graphene/aerogel layers).

(72) The composite structure was flexible, strong and lightweight. For testing purposes, the composite was placed into a pocket made from UHMWPE fibres, which can be seen in FIGS. 11a and 11b.

Example 9

(73) Using the techniques described in respect of the Examples above, a laminate structure comprising 52 layers of UHMWPE fabric (Spectra 1000; 200D; Honeywell; 80 gsm; Warp Yarn 24 Tex; Weft Yarn 25 Tex; Encs×Picks/10 cm 177×177; Plain Weave) alternating with 51 layers of a backing structure was prepared. The backing structure comprised 125 μm flexible polyimide aerogel (AeroZero 125 micrometer film from BlueShift Inc (US)) layered with a 20 μm layer of a polyurethane (PX60; Xencast UK Flexible Series PU Resin system. Manufacturer reported: Hardness of 60-65 (Shore A); Tensile strength 3.4-3.8 MPa; Elongation 200-260% at break; Tear Strength 19.0-23.0 kN/m) (i.e. 51 layers of aerogel alternating with 51 layers of polyurethane). Thus, the laminate had the following repeating pattern arrangement of layers “ . . . UHMWPE layer/polyurethane layer/aerogel layer/UHMWPE layer/polyurethane layer/aerogel layer . . . ”.

Example 10

(74) Using the techniques described in respect of the Examples above, a laminate structure comprising a stack of 52 layers of UHMWPE fabric (Spectra 1000; 200D; Honeywell; 80 gsm; Warp Yarn 24 Tex; Weft Yarn 25 Tex; Encs×Picks/10 cm 177×177; Plain Weave) and a stack of 51 backing structures was prepared. The laminate structure thus comprised 52 layers of UHMWPE fabric followed by 51 backing structures. Each backing structure comprised 125 μm flexible polyimide aerogel (AeroZero 125 micrometer film from BlueShift Inc (US)) layered with a 20 μm layer of a polyurethane (PX60; Xencast UK). Thus, the laminate had the following pattern arrangement of layers “UHMWPE layer/UHMWPE layer . . . UHMWPE layer/UHMWPE layer/polyurethane layer/aerogel layer/polyurethane layer/aerogel layer . . . polyurethane layer/aerogel layer”. Example 10 therefore differs from Example 9 by virtue of the order of the protective layer and the backing structures.

Example 11

(75) Using the techniques described in respect of the Examples above, a laminate structure comprising 26 layers of UHMWPE fabric (Spectra 1000; 200D; Honeywell; 80 gsm; Warp Yarn 24 Tex; Weft Yarn 25 Tex; Encs×Picks/10 cm 177×177; Plain Weave) alternating with 25 layers of a backing structure was prepared. The backing structure comprised 125 μm flexible polyimide aerogel (AeroZero 125 micrometer film from BlueShift Inc (US)) layered with a 20 μm layer of a polyurethane (PX60; Xencast UK) (i.e. 25 layers of aerogel alternating with 25 layers of polyurethane). Thus, the laminate had the following repeating pattern arrangement of layers “ . . . UHMWPE layer/polyurethane layer/aerogel layer/UHMWPE layer/polyurethane layer/aerogel layer . . . ”.

Example 12

(76) Using the techniques described in respect of the Examples above, a laminate structure comprising 51 layers of a front structure on top of 52 layers of a protective backing layer (UHMWPE fabric (Spectra 1000; 200D; Honeywell; 80 gsm; Warp Yarn 24 Tex; Weft Yarn 25 Tex; Encs×Picks/10 cm 177×177; Plain Weave)) was prepared. The front structure comprised 125 μm flexible polyimide aerogel (AeroZero 125 micrometer film from BlueShift Inc (US)) layered with a 20 μm layer of a polyurethane (PX60; Xencast UK) (i.e. 25 layers of aerogel alternating with 25 layers of polyurethane). Thus, the laminate had the following arrangement of layers “polyurethane layer/aerogel layer/polyurethane layer/aerogel layer . . . polyurethane layer/aerogel layer/UHMWPE layer/UHMWPE layer . . . UHMWPE layer/UHMWPE layer”.

Example 13

(77) A composite structure comprising of 4 individual sets of sub-structures layered on top of one another was prepared, each sub-structure comprising 9 layers of UHMWPE fibre (DOYENTRONTEX Bulletproof unidirectional sheet; WB-674; 160 g/m.sup.2; 0.21 mm thickness) on top of 9 layers of 125 μm flexible polyimide aerogel (AeroZero 125 micrometer film from BlueShift Inc (US)) layered with a graphene layer. The graphene layer was formed by the inking method described above in respect of Example 6. Thus, the composite had the following arrangement of layers “ . . . UHMWPE layer/UHMWPE layer/UHMWPE layer/graphene layer/aerogel layer/graphene layer/aerogel layer/graphene layer/aerogel layer . . . ”. Each sub-structure was then provided with a bottom UHMWPE fibre layer and bonded around its edges with UHMWPE thread to form discrete sub-structures.

(78) The composite structure also comprised a crocheted swatch of 1.0 mm UHMWPE braided thread (see FIG. 9 and accompanying description) with UHMWPE thread whipping around the tile edges to improve performance. The crocheted swatch was placed on top of the composite structure. The structure can be seen in FIGS. 12a and 12b.

Comparative Example 1

(79) An existing commercially available laminate structure widely used in stab-resistance worn articles was selected as a comparison for the embodiments described above. The comparative example comprises a laminate structure comprising: 12 layers of Kevlar fabric/finely stitched felt/a layer of chainmail/finely stitched felt/12 layers of Kevlar fabric. The laminate structures of Examples 1 and 2 were tested together with the comparative Example.

Comparative Example 2

(80) It was apparent through observations and testing that a significant portion of the force of any impact in the structure of Comparative Example 1 was being dispersed in the plane of the layers by the chainmail layer and so the laminate structure of Comparative Example 1 was also tested with the chainmail removed. Thus, Comparative Example 2 consists of a laminate structure comprising 12 layers of Kevlar fabric/finely stitched felt/12 layers of Kevlar fabric.

(81) Testing

(82) In addition to testing referred to in respect of specific examples mentioned above, further testing was carried out:

(83) Penetration Resistance Testing

(84) Testing was carried out using a test rig 590, which is depicted in FIG. 10. The test rig 590 comprises a base 591 on which is provided a jig 592 with clamps 592a for mounting a sample (shown as laminate structure 170 in FIG. 10) thereon. The test rig 590 also comprises a weighted sled 593, to which a knife 594 is attached. The test rig 590 is arranged with the weighted sled 593 and knife 594 suspended above the sample, with the blade of the knife 594 facing the sample (i.e. downwards). The sled 593 and knife 594 can then be dropped and travel along vertical guide rails 595 (using a series of linear bearings (not shown) to minimise friction) until the knife 594 impacts the sample. In the test referred to hereinbelow, the test rig used a Home Office Science Development Branch (HOSDB) P1/B Test blade supplied from High Speed and Carbide Limited. In some of the tests, the jig 592 and clamps 593 were not used to restrain the sample used (referred to as “free standing”).

(85) The rig was adjusted such that the knife was dropped from a height of 1 m and the total weight of the knife and the weighted sled was 1.75 kg. This created a force on impact of 17.17 Joules and a velocity on impact of 4.43 m/s. In some of the tests set out below, a modelling clay plate was located behind each of the samples to measure the “cut length”. The cut length is the length of an indentation from a blade in the clay, which can be present even where the blade does not fully penetrate the fabric and provides an indication of the impact absorbing and penetration resistant properties of the structure. The depth of penetration of the blade into each structure and cut lengths (where measured) are shown below in Table 1:

(86) TABLE-US-00001 TABLE 1 Depth Penetration Cut Length Sample Jig (mm) (mm) Example 3 Jig Constrained 2-6 — Example 8 Free standing <2 — Example 9 Jig Constrained 2-3 1.1 Example 10 Jig Constrained 2-3 0.9 Example 12 Jig Constrained 6-7 2.7 Comparative Free standing (no jig 2-3 — Example 1 constraint) Comparative Jig Constrained 2-3 — Example 1 Comparative Free standing (no jig 39-41 — Example 2 constraint)

(87) Table 1 demonstrates that the laminate structures in accordance with an embodiment of the invention provide very high penetration resistance and perform at least as well as the laminate structures used in existing stab-proof vests which include a metal chainmail layer and significantly better than the laminate structures where the metal chainmail layer is removed. Thus, these laminate structures can be used in articles without requiring chainmail or heavy metal plate layers, thereby providing significant advantages. Furthermore, the specific results for Example 2 also show significant protection afforded by a laminate structure with less layers and a thinner structure.

(88) The testing of Example 8 is shown in FIGS. 11a and 11b. As mentioned above, penetration into the composite structure contained in the UHMWPE outer was less than 2 mm. This is well below the required penetration limits (KR-1 testing) of 7 mm.

(89) Ballistic Testing

(90) Ballistic testing of Examples 4 and 11 was carried out. The tests involved firing a .22 Long Rifle bullet at point-blank range. The composite structures of Examples 4 and 11 were able to stop the .22LR rifle bullet. Examination of the sample after the test showed that the bullets were stopped and held in the composite around the 17.sup.th layer of UHMWPE and backing structure. Thus, the laminate structures provide effective ballistic protection.

(91) Ballistic testing of Example 13 was also carried out. This was carried out using a high powered .22 Long Rifle bullet at 250 Joules and the bullet was fired towards the face on which the crocheted layer was provided. The composite structure was able to stop the bullet without penetration, as can be seen in FIGS. 12a and 12b. FIG. 12b, in particular, shows that the bullet did not even penetrate the first sub-structure (see arrow which shows the indentation).

(92) Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. For example:

(93) although in the above embodiments, the shields have generally cuboidal shapes with planar surfaces, it will be appreciated that the shape of the shields can be varied and can include circular prisms (e.g. cylinders, with the upper and lower faces defining strike faces), any other polygonal prism and the other shapes mentioned herein; and

(94) although the connector arrangements in the above embodiments have hook and loop or adhesive attachment means, any other attachment means can be used, including connectable clips or buttons, zips, magnets, and ties, for example.