COMPOSITE STRUCTURE AND METHOD OF MANUFACTURE

Abstract

A 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. A method for manufacturing a composite structure comprising first and second layers comprises providing a plurality of the second layers, each second layer comprising an aerogel, providing a plurality of first layers, each layer comprising graphene; and arranging the first and second layers so that the layers form a composite structure in which the plurality of first and second layers alternate.

Claims

1-22. (canceled)

23. A composite structure comprising: a plurality of graphene layers; and a plurality of aerogel layers; wherein the graphene layers and the aerogel layers alternate in the composite structure.

24. The composite structure of claim 23, wherein each graphene layer is bonded to an adjacent aerogel layer.

26. The composite structure of claim 24, wherein, except for the exterior layers of the composite structure, each layer is bonded to its immediately adjacent layer.

25. The composite structure of claim 23, wherein a fastening element is provided along an edge of the composite structure to secure the graphene layers and aerogel layers together.

27. The composite structure of claim 23, wherein the composite structure comprises between 2 and 250 graphene layers and/or 2 and 250 aerogel layers.

28. The composite structure of claim 23, wherein at least one of the graphene layers consists essentially of graphene.

29. The composite structure of claim 23, wherein each graphene layer independently has a thickness of from 0.34 nm to 20 m.

30. The composite structure of claim 23, wherein each graphene layer is applied directly on an adjacent aerogel layer.

31. The composite structure of claim 23, wherein at least one of the graphene layers is a planar layer of graphene extending in a plane parallel to a plane defined by an adjacent aerogel layer, and wherein the each of the graphene layers is a mono-layer, a bi-layer or a tri-layer of graphene.

32. The composite structure of claim 23, wherein at least one of the graphene layers comprises graphene in the form of graphene platelets.

33. The composite structure of claim 23, wherein each aerogel layer independently has a thickness of 20 m to 1000 m.

34. The composite structure of claim 23, wherein at least one of the aerogel layers is a polyimide aerogel.

35. The composite structure of claim 23, further comprising a protective layer, wherein the protective layer comprises one or more of aramid fibres, aromatic polyamide fibres, boron fibres, ultra-high molecular weight polyethylene, and poly(p-phenylene-2,6-benzobisoxazole) (PBO), including combinations thereof.

36. The composite structure of claim 23, further comprising a protective layer, wherein the protective layer is provided as an exterior layer to the alternating graphene and aerogel layers.

37. The composite structure of claim 23, wherein the graphene layer further comprises a polymer.

38. An article to be worn by a user, the article comprising the composite structure of claim 23.

39. A method for manufacturing a composite structure comprising graphene layers and aerogel layers, the method comprising: providing a plurality of aerogel layers, each aerogel layer comprising an aerogel, providing a plurality of graphene layers, each layer comprising graphene; and arranging the graphene and aerogel layers so that the layers form a composite structure in which the plurality of graphene and aerogel layers alternate.

40. The method of claim 37, wherein providing a plurality of graphene layers comprises: mixing a graphene powder with a solvent or carrier to form an ink; applying the ink to a substrate; and removing the solvent or carrier to leave a graphene layer comprising graphene on the substrate.

41. The method of claim 37, wherein providing a plurality of graphene layers comprises: providing a source of graphene and a substrate; and using the source of graphene and a thin-film deposition method to provide a graphene layer on the substrate.

42. The method of claim 38, wherein the substrate is an aerogel layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] An example of the invention will now be described with reference to the accompanying figures, in which:

[0042] FIG. 1 shows a first embodiment of a composite structure according to the invention from a side view;

[0043] FIG. 2 shows another embodiment of a composite structure according to the invention from a side view;

[0044] FIG. 3 shows an SEM image of an aerogel layer with a graphene layer disposed thereon at 650 magnification;

[0045] FIG. 4 shows an SEM image of an aerogel layer with a graphene layer disposed thereon at 2000 magnification;

[0046] FIG. 5 shows another embodiment of a composite structure according to the invention from a side view;

[0047] FIG. 6 shows another embodiment of a composite structure according to the invention from a side view;

[0048] FIG. 7 shows another embodiment of a composite structure according to the invention from a side view prior to an impact from an object;

[0049] FIG. 8 shows the embodiment of FIG. 7 from a side view after impact from an object;

[0050] FIG. 9a shows another embodiment of a composite structure according to the invention from a side view;

[0051] FIG. 9b shows another embodiment of a composite structure according to the invention from a side perspective view;

[0052] FIG. 10 shows another embodiment of a composite structure according to the invention from a side view;

[0053] FIG. 11 shows a front view of a test rig;

[0054] FIG. 12a shows a single sheet of a graphene and aerogel composite;

[0055] FIG. 12b shows an embodiment of a composite structure according to the invention from a side view;

[0056] FIGS. 13a and 13b show another embodiment of a composite structure according to the invention from side and side perspective views, respectively; and

[0057] FIGS. 14a and 14b show another embodiment of a composite structure according to the invention from a top perspective view and a bottom perspective view, respectively.

[0058] Like components are given like reference numerals. For example, a graphene layer may be referred to as 102a, 102b or 202a.

DETAILED DESCRIPTION

[0059] A first embodiment of the invention is shown in FIG. 1 in the form of a composite structure 1. The composite structure 1 comprises two graphene layers 2 and two aerogel layers 3. In this embodiment, the layers are arranged so that each aerogel layer 5 is provided behind the graphene layers 2, which are applied directly to the upper surface of the adjacent (in this case, lower) aerogel layers 3. In use, the composite structure 1 can be used as a very lightweight structure in an article, such as body armour, to prevent impact or penetration or as a component in an aircraft or vehicle. The composite structure 1 can be arranged in an article with the graphene layer 2 forming the outermost layer (i.e. towards the direction from which the force is expected). In the case of body armour, the composite structure 1 would be arranged with the graphene layer 2 directed away from the body and with the aerogel layer 3 being the layer closest to the body of the wearer. In the case of an impact, such as a projectile impact (e.g. a bullet hitting the body armour), the graphene layer 2 is the first layer the projectile comes into contact with. A similar arrangement would be used in a vehicle or aircraft.

[0060] By way of example, in one embodiment, the graphene layer 2 of the composite structure 1 is a multi-layer graphene structure having a thickness of approximately 10 nm. The aerogel layer 3 in this embodiment is a 100 micrometre thick layer of a flexible silicon aerogel. The aerogel layer 3 has voids or bubbles within the structure with an average diameter of 50 nm. The composite structure 1 is constructed by using atomic layer deposition to provide a layer of graphene on a flexible silicon aerogel substrate, followed by layering of multiple silicon aerogel substrates with graphene disposed thereon to form a composite structure 1. Although aerogels have a highly porous structure, due to methods of manufacture, some have a matte face comprising a substantially sealed and flat surface (compared to the other faces which tend to be dominated by the open pore structure) and, therefore, it can be advantageous to use this sealed flat surface as the substrate for applying the graphene layer by atomic layer deposition (this is also true of other methods of application of graphene layer, e.g. ink based application).

[0061] A further embodiment of the invention is shown in FIG. 2, where a composite structure 101 comprises a plurality of graphene layers 102a, 102b, 102c, 1021 and a plurality of aerogel layers 103a, 103b, 103c, 103l. The graphene layers 102a-c,l and the aerogel layers 103a-c,l alternative such that the composite structure 101 has a repeating structure of graphene layer/aerogel structure/graphene layer/aerogel layer. In this way, there is an outermost graphene layer 102a, behind which is an aerogel layer 103a. This structure then repeats such that there is a second graphene layer 102b behind the first aerogel layer 103a, which is adjacent a second aerogel layer 103b, followed by a third set of layers 102c, 103c, which repeat until a final graphene layer 1021 and a final aerogel layer 103l. Although not visible in FIG. 2, the layers 102a-c,l 103a-c,l of the structure 101 are bonded together by means of an adhesive which is provided between the layers.

[0062] In this embodiment, the composite structure 101 is provided by forming a number of layers of aerogel substrate with graphene formed thereon and layering these into the composite structure 101. 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).

[0063] The presence of numerous layers of graphene and aerogel in repeating fashion in the composite structure 101 has been found to provide a particularly strong, yet still flexible, composite. Accordingly, the structure 101 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. Thus, the composite 101 can be used as a material for situations where damage from impacts needs to be avoided (e.g. the outer skin of aircraft or vehicles, or as a protective armour). Given the repeating structure of aerogel/graphene layers, the particular orientation of the composite is not critical to its performance; however, it can be advantageous to have the composite structure 101 of FIG. 2 orientated in an article with the outermost protective graphene layer 102a facing outwardly, towards the direction of expected impact (i.e. the direction from which an impact is most likely to occur). In this way, each of the aerogel layers 103a-c,l in the structure have an adjacent corresponding graphene layer 102a-c,l provided in front of them (i.e. in the direction of impact).

[0064] With existing prior art graphene/carbon fibre composites and/or aluminium, the strength of the article primarily comes from the cumulative tensile strength of the materials involved. Thus, the thicker the aluminium/titanium/carbon fibre composite skin, the stronger it is. Embodiments of the invention, including for example that of FIG. 2, provide advantages over these prior art composites because the thin graphene layer (and, where present, graphene-containing polymer layer) provides tensile strength, whilst the thicker, but extremely light aerogel layer provides force dispersion and vibration dampeningthus reducing the strain on the layer below it. When bonded together in a multi-layered sandwich, the resulting composite has both high strength and extreme lightness.

[0065] As set out above, the graphene layer can comprise a layer of graphene platelets, which in some embodiments is provided directly on the aerogel layer. FIGS. 3 and 4 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.

[0066] A further embodiment is shown in FIG. 5, in which there is a composite structure 301 comprising alternating graphene 302 and aerogel 303 layers. In this embodiment, the graphene layer 302 is a layer of graphene platelets dispersed in a polymer matrix, with the graphene-doped polymer being directly laminated onto the aerogel layer 303.

[0067] A specific embodiment of the composite 301 of FIG. 5 comprises a 20 micrometre thick layer of polyurethane doped with 5 wt % of graphene platelets and the aerogel used in the aerogel layer 5 is a 125 micrometre thick layer of polyimide aerogel.

[0068] In combination with a polymer-containing graphene layer, the aerogel layer becomes more effective in preventing damage caused by an impact or penetration. The polymer contained in the graphene layer can help to maintain the structure of aerogel during an impact event (e.g. preventing or reducing the risk of cracking and holding any fragments of aerogel together). For example, the polymer layer can hold the aerogel layer together as it is deformed and collapsed under the force of the impact. This allows the aerogel layer to continue to resist a force against it or resist subsequent forces (e.g. a multi-hit impact event) and retain its high tensile properties to a greater degree. As a result of its location, the polymer layer advantageously holds together the forward face of the aerogel layer (i.e. the face directed towards the impact), which is subject to the greatest force and is at risk of disintegration or separation. The polymer layer itself may also provide some impact resistance and disperse impact efficiently along the graphene layer. Furthermore, a polymer can be used to help optimise the properties of the graphene layer for a specific use. For example, certain polymers will make the composite more flexible.

[0069] A further embodiment is shown in FIG. 6. In this embodiment, the composite 401 includes alternating aerogel 403 and graphene 402 layers, but also includes a further set of protective layers 404 which are intermediate each pair of an aerogel 403 and a graphene 402 layer. Thus, the composite 401 has a repeating pattern of protective layer 404/graphene layer 402/aerogel layer 402. The protective layer 404 is a ballistic or penetration resistant high-tensile layer which provided on the top of the composite 401 and is located forward (i.e. in the direction of incoming impact force) of each of the graphene 402 and aerogel layers 402. The protective layer absorbs a portion of the impact and assists in preventing penetration through the structure.

[0070] In a specific embodiment of the composite 401, the protective layer 404 of the composite structure 401 is an ultra-high molecular weight polyethylene (UHMWPE) layer having a thickness of 180 micrometres. The graphene layer 402 in this embodiment is a 20 micrometre thick layer of graphene platelets and the aerogel used in the aerogel layer 5 is a 125 micrometre thick layer of polyimide aerogel.

[0071] In an embodiment shown in FIG. 7, a composite structure 501 comprises a plurality of protective layers 504, a plurality of graphene layers 502, and a plurality of aerogel layers 503. The protective layers 504, the graphene layers 502 and the aerogel layers 503 repeat through the structure 501 such that the graphene layers 502 and aerogel layers 503 alternate, with a protective layer 504 between each alternating pair of graphene/aerogel layers 502, 503.

[0072] FIG. 7 shows the composite structure 501 prior to impact by a force, where the layers are in an initial stacked structure. FIG. 8 shows the composite structure 501 in use, where the top of the structure 501 has been impacted by a projectile in a direction perpendicular to the surface of the layers. As can be seen in this Figure, the force of the impact (designated as arrows A in FIG. 8), causes the deformation of the layers of the composite structure 501, starting with the uppermost protective layer 504, and followed by the remaining layers depending on the magnitude of the force A. As the force impacts the upper layers, these layers deform and the force begins to be dissipated by these layers (see arrows A). One of the major mechanisms for this absorption of force is the deformation of the aerogel (which is essentially compressed by the force of the impact) and penetration is resisted by the high-tensile properties of the graphene 502 and protective layers 504. As the force continues, other adjacent layers in the structure 501 will begin to deform thereby further disappoint the force. Eventually, the projectile or source of the force will be stopped thereby preventing penetration and reducing or completely avoiding the transfer of force to the object or person protected by the composite structure 501.

[0073] A further embodiment is shown in FIG. 9a, in which there is a composite structure 601 comprising alternating graphene 602 and aerogel 603 layers. In this embodiment, the graphene layer 602 is formed of multiple layers of graphene to form a single layer 603, which is then directly bonded onto the aerogel layer 603. Each of the aerogel layers 603 is directly bonded to the immediately adjacent graphene layer 603 such that the composite 601 provides a unitary structure. This embodiment is particularly advantageous when used as an outer skin for vehicles, such as aircraft. FIG. 9a shows how the composite 601 deals with the vibrations caused by airflow 620 across its surface. Vibrations (depicted by arrows 625) are dampened and absorbed by the aerogel layers 603 in the structure so as to minimise vibration through the structure, with the graphene layers 602 and aerogel layers 603 acting together to prevent damage.

[0074] An example of an aircraft skin 650 is shown in FIG. 9b. This contains a composite having a similar structure to that of FIG. 9a.

[0075] A further embodiment is shown in FIG. 10. In this embodiment, there is a composite structure 701 shown which is for use in a cable or tape (only a portion of the structure is shown). The structure 701 comprises a number of aerogel layers 703 which alternate with graphene layers 702. This structure 701 provides a useful backbone for a cable or tape as the aerogel and graphene present in the first 702 and second 703 layers provides the strength and resilience required to function where significant sheer forces 720 (dissipated in the structure 701 by the mechanisms depicted by arrows 725) will be acting on the elongate designs.

[0076] For exemplary purposes, FIG. 12a shows a single structure 910 (not in accordance with the invention) comprised of a graphene layer formed on an aerogel layer. This single structure 910 is bonded together 10 other single structures 910 to form a composite structure 901 in accordance with the embodiment, as shown in FIG. 12b.

[0077] A further composite structure 1001 is also shown in FIG. 13a, where a plurality of graphene layers are provided on a corresponding polyimide aerogel layers to form a graphene/aerogel/graphene/aerogel repeating pattern with the layers bonded together. As can be seen in FIG. 13b, the composite structure 1001 is flexible due to the flexibility of the graphene and aerogel layers.

[0078] As set out above, manufacturing the above laminates can be carried out by a number of methods. For example, where the graphene is a planar layer, the graphene may be deposited using a thin-film deposition method or, alternatively, by using an exfoliation technique.

[0079] In one embodiment, a roll-to-roll manufacturing process is used. In particular, a flexible aerogel layer (for example, a cross-linked aerogel) is provided on a flexible substrate (e.g. a polymeric substrate film) and a graphene layer is formed on the aerogel using a thin film deposition method.

[0080] In another embodiment, graphene can be formed using an epitaxial formation of graphene on a flexible metal substrate, which can then be layered with a flexible aerogel. Thus, graphene can be grown on a metal (e.g. ruthenium) and placed on aerogel, before these are removed from the substrate and used to construct a composite structure comprising multiple layers of graphene and aerogel.

[0081] In another embodiment, the graphene layer may be formed as an ink which is used to coat an aerogel layer or film. In this way, the graphene, in the form of platelets or a powder, for example, can be readily applied to a number of substrates in a relatively straightforward manufacturing process. The other components making up the ink may remain in the graphene layer or may be removed after the layer has been applied.

EXAMPLES

[0082] Specific examples of composite structures that are provided below:

Example 1

[0083] A 125 m flexible polyimide aerogel layer (AeroZero 125 micrometer polyimide aerogel film; BlueShift Inc (US)) was cut to size and coated with a 20 m 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.

[0084] 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 GNPCOOH). 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 m gap) and with eight passes. The graphene/polyurethane mixture was then mixed with a hardener, followed by subsequent degassing using a planetary centrifugal mixer.

[0085] Once the graphene/polyurethane mixture was created it was layered down onto a polypropylene sheet with a 20 m drawdown wire rod (which regulates the thickness to 20 m). 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.

[0086] An ultra-high molecular weight polyethylene (UHMWPE) fabric (Spectra 1000; 200D; Honeywell; 80 gsm; Warp Yarn 24 Tex; Weft Yarn 25 Tex; EncsPicks/10 cm 177177; 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).

[0087] 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.

[0088] 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 2

[0089] Using the techniques described in respect of Example 1, 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 m flexible polyimide aerogel (AeroZero 125 micrometer film from BlueShift Inc (US)) layered with a 20 m 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 3

[0090] Using the techniques described in respect of Example 1, above, a composite structure comprising 26 layers of UHMWPE fabric (Spectra 1000; 200D; Honeywell; 80 gsm; Warp Yarn 24 Tex; Weft Yarn 25 Tex; EncsPicks/10 cm 177177; Plain Weave), 25 layers of 125 m flexible polyimide aerogel (AeroZero 125 micrometer film from BlueShift Inc (US)) and 25 layers of a 20 m 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 4

[0091] A composite structure 1101 is shown in FIGS. 14a (top view) and 14b (underside view). The composite structure 1101 comprises a repeating structure comprising an aerogel film (125 m 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 1101 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.

[0092] 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 1101. 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 1101 was provided with a POM layer on its underside so that POM layers form the uppermost and lowermost layers.

[0093] The composite structure 1101 was flexible, strong and light and thus provides an excellent composite for use in aerospace and/or vehicle skin applications. The composite structure 1101 shown (dimensions 143 mm193 mm) had a weight of 61 g, whereas a comparative example of similarly-sized (with the exception of thickness) carbon-fibre aerospace composite having similar properties weighed 514 g. The comparative carbon-fibre aerospace composite panel was 4 thicker than the prototype panel; however, even scaling the composite structure 1101, the comparable weight of the composite structure would have been 244 g, or less than half the weight of the carbon fibre aerospace composite, with improved properties.

Comparative Example 1

[0094] 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

[0095] 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.

[0096] Testing

Penetration Resistance Testing

[0097] Testing was carried out using a test rig 620, which is depicted in FIG. 11. The test rig 830 comprises a base 831 on which is provided a jig 832 with clamps 833 for mounting a sample (shown as laminate structure 201 in FIG. 11) thereon. The test rig 830 also comprises a weighted sled 835, to which a knife 840 is attached. The test rig 830 is arranged with the weighted sled 835 and knife 840 suspended above the sample, with the blade of the knife 840 facing the sample (i.e. downwards). The sled 835 and knife 840 can then be dropped and travel along vertical guide rails 834 (using a series of linear bearings (not shown) to minimise friction) until the knife 840 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 832 and clamps 833 were not used to restrain the sample used (referred to as free standing).

[0098] The depth of penetration of the blade into each structure is shown below in Table 1:

TABLE-US-00001 TABLE 1 Depth Penetration Sample Jig (mm) Example 2 Jig Constrained 2-6 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)

[0099] 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.

Ballistic Testing

[0100] Ballistic testing of Example 7 was carried out. The tests involved firing a .22 Long Rifle bullet at point-blank range. The composite structure of Example 7 was 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.

[0101] Although the invention has been described with reference to specific embodiments and examples above, it will be appreciated that modifications can be made to the embodiments and examples without departing from the invention.