Ceramic composite

Abstract

The disclosure relates to a ceramic composite (2), in particular to a ceramic composite (2) with shock-absorbing, abrasion resistant or anti-ballistic properties. The composite (2) has a metallic layer (6) formed onto the surface of a ceramic layer (4) and a further layer (10) attached to the ceramic layer (4) via the metallic layer (6).

Description

[0001] Ceramic Composite

[0002] The present disclosure relates to a ceramic composite, particularly but not limited to, a ceramic composite with shock-absorbing or anti-ballistic properties.

[0003] Background of the invention

[0004] A prior art shock-absorbing composite is disclosed in DE19628105. The composite comprises a ceramic layer 4 formed of ceramic plates bonded to a metal layer 5 via an adhesive 7. The metal layer 5 comprises a high-strength metal configured to provide a rigid support layer (e.g. to hold the ceramic plates in position). A fibre composite layer 6 is bonded to the metal layer 5 via an adhesive 8.

[0005] The inventor has found problems with the prior art solutions. During impact of the ceramic via a bullet or other object, the ceramic layer 4 cracks, thus absorbing energy of the objection. However, as the metal layer 5 is substantially rigid, separation of the individual pieces of the cracked ceramic layer cannot be accommodated. Movement of the cracked pieces is therefore accommodated by delamination of the ceramic layer 4 from the metal layer 5. The impact causes the material to move and compromises the composites ability to absorb impact both during the event and any sequbsent impacts. The metal layer 5 also added significant weight to the composite, and so the overall thickness of the system must be reduced, or the user must bear a greater weight. Also, the ceramic damages the impacting projectile and its efficacy in doing so is dependent on its support from the metal layer which is lost after delamination and movement.

[0006] The present invention overcomes or ameliorates one or more of the above problems.

[0007] Statement of Invention

[0008] The metallic layer may be non-structural. According to an aspect there is provided: a shock-absorbing, abrasion resistant or anti-ballistic composite comprising: a ceramic layer; a metallic layer formed directly onto the surface of the ceramic layer; and a further layer attached indirectly to the ceramic layer via the metallic layer.

[0009] According to an aspect there is provided: a shock-absorbing, abrasion resistant or anti-ballistic composite comprising: a ceramic layer; a metallic layer formed directly onto the surface of the ceramic layer; and a polymer layer attached indirectly to the ceramic layer via the metallic layer.

[0010] According to an aspect there is provided: a composite comprising: a ceramic layer; a metallic layer formed directly onto the surface of the ceramic layer; and a further ceramic layer attached indirectly to the ceramic layer via the metallic layer.

[0011] Optional features of either aspect of the invention may be combined with any other aspect of the invention where practicable.

[0012] Detailed description

[0013] Workable embodiments of the invention are described in further detail below by way of example only, with reference to the accompanying drawings, of which:

[0014] Figure 1 shows a schematic cross-sectional view of a first embodiment of composite;

[0015] Figure 2 shows a schematic cross-sectional view of a second embodiment of a composite;

[0016] Figure 3 shows a schematic cross-sectional view of a third embodiment of a composite;

[0017] Figure 4 shows a schematic cross-sectional view of a fourth embodiment of a composite;

[0018] Figure 5 shows a schematic cross-sectional view of a composite bonding arrangement. Figure 1 shows a cross-sectional view of a composite 2. The composite comprises a ceramic 4. The ceramic 4 may comprise a plate, disc, or other substantially planar layer. The ceramic 4 may flat or may be non-flat (for example, curved or have a complex shape). It can be appreciated that the exact shape or form of the ceramic 4 is not pertinent to the invention at hand.

[0019] The ceramic 4 may comprise an oxide. The ceramic 4 may comprise alumina (AI2O3). The alumina may comprise any suitable form or allotrope. The ceramic 4 may comprise a carbide and / or nitride. The ceramic 4 may comprise one or more of: silicon carbide; boron nitride; tungsten carbide; or boron carbide. The ceramic 4 may comprise titanium diboride. The ceramic 4 may comprise any mixture / alloy / hybrid of the previously mentioned materials. The ceramic may be manufactured and / or shaped using sintering. The ceramic 4 generally comprises a rigid, hard and / or strong material.

[0020] The ceramic may be flat or formed into a 3d shape with either an even or an irregular sectional thickness

[0021] The ceramic 4 comprises any suitable thickness for the intended purpose. Typically, the ceramic 4 at least 1 mm thick; preferably, at least 5mm thick. The ceramic layer 4 may comprises a plurality of discrete and / or bonded ceramic layers.

[0022] A metallic layer 6 is provided on the ceramic 4. The metallic layer 6 is provided directly on the ceramic 4. The metallic layer 6 is bonded directly onto the surface of the ceramic 4 (i.e. the metallic layer 6 is not connected via an intermediate layer, such as an adhesive). The metallic layer 6 is substantially continuous. In other embodiments, the metallic layer 6 may be provided in discrete portions or places.

[0023] The metallic layer 6 comprises any suitable metal. The metallic layer 6 comprises one or more of: iron; aluminium; titanium; copper; gold; nickel; or silver. The metallic material may comprise an alloy or mixture of the aforementioned metals and / or with other materials (e.g. steel).

[0024] The metallic layer 6 has a thickness less than or equal to 1000pm; preferably, less than or equal to 500pm; preferably, less than or equal to 250pm; preferably, less than or equal to 150pm. In a specific embodiment, the metallic layer 6 has a thickness of 40pm. The metallic layer 6 thus forms a thin layer or film. The metallic layer 6 is generally uniform in thickness. However, some variation in thickness may be tolerated. The metallic layer 6 is thinner than the ceramic layer. Typically, the metallic layer 6 is at least 10 times thinner than the ceramic; preferably, at least 100 times thinner.

[0025] The metallic layer 6 may be deposited on the ceramic 4 via a spray deposition process. The spray deposition may comprise a cold spraying process. In such a method, solid metal powders are accelerated in a supersonic gas jet. The particles may be accelerated up to velocities of 1200 m / s. The particles may between 1 and 50pm in diameter. However the particulars may be in excess of 50pm in diameter. During impact with the ceramic 4, the metal particles undergo plastic deformation and adhere to the surface. Without being bound by theory, cold spray techniques allow improved bonding between metals and ceramics, as the impact of the particles on the surface of the ceramic overcomes any surface tension in the metal, allowing the metal to more easily “wet” the ceramic. Cold spraying can also be performed in a compact environment and is generally low cost. Cold spraying can also provide consistent and thin metallic layers.

[0026] In other embodiments, thermal spraying may be used. Thermal spraying may comprise one or more of: plasma spraying; flame spraying; or high velocity fuel. In some embodiments, fusion may be used (e.g. welding, brazing or melting). However, fusion techniques may only be used where the metal is able to sufficiently wet the ceramic. In other embodiments, vapour deposition methods may be used, for example, chemical or physical vapour deposition. In other emboidments electroless plating or electrolytic plating methods may be used. A number of the above methods may be used in combination. An adhesive layer 8 is provided on the metallic layer 8. The adhesive 8 is used to adhere a further layer 10 onto the metallic layer 6. The adhesive 8 may comprise any suitable adhesive to bond the further layer 10 to the metallic layer 6. The adhesive may comprise one or more of: epoxy based; polyurethane based; cyanoacrylate based, polyisocyanates such as 4,4'-Diphenylmethane diisocyanate, Polymeric Diphenylmethane Diisocyanate or mixtures thereof based or Methyl Ether Ketone based. The adhesive is flexible and / or deformable to help reduce delamination.

[0027] In some embodiments, the further layer 10 comprises a polymer-based or polymer-based composite material ). The polymer-based composite may comprise one or more of: ultra high molecular weight polyethylene (UHMPE), in particular, Dyneema (RTM) or Spectra-shield (RTM); or aramid (e.g. Kevlar (RTM), Nomex (RTM), or Twaron (RTM)). The polymer may comprise any suitable polymer for the purpose. For example, for non-ballistic shock absorbers, the polymer may comprise a comparatively weaker and / or flexible material, such as one or more of: polyethylene; PVC; acrylic; ABS etc. The polymer layer 10 comprises a weaker and / or more flexible material than the ceramic. It can be appreciated that the composite 2 may be used for a wide variety of purposes, and the polymer may comprise any suitable form for such purposes.

[0028] The polymer layer 10 comprises any suitable thickness for the intended purpose. Typically, the polymer layer 10 is at least 1 mm thick; preferably, at least 5mm thick.

[0029] The polymer may be provided as a fibre or filament. The fibre / filament may be woven or non-woven. The polymer may be provided in a composite. The polymer may provide the matrix and / or the fibre.

[0030] The polymer layer 10 is at least partially bonded to metallic layer 6. The adhesieve properties are improved between the polymer layer 10 and metallic layer 6 by the adhesive layer during the bonding process.. In the embodiment shown in figure 2, the adhesive layer is not provided, and the polymer layer 10 is bonded directly to the metallic layer 6. This may be provided where the polymer is sticky / tacky, where the polymer layer 10 be clamped / fixed to the ceramic 4 without affecting the manufacturing process or where the melt properties of the polymer allow for direct adhesion through application of external energy.

[0031] The polymer layer 10 is bonded to the metallic layer 6 using a radiative energy and / or sound method. This allows the radiation / sound to penetrate the polymer layer 10 to the interface between the polymer layer 10 and the metallic layer 6. This allows focussing of the heating of the polymer layer 10 at the interface, without the need for significant heating of the bulk of the polymer layer 10. This allows greater control of the temperature at the interface and / or reduces the risk of the thermal damage to the polymer 10 or ceramic 4.

[0032] The radiative energy bonding method may comprise an electromagnetic energy method, for example, one or more of: microwave heating; or inductive heating. The metallic layer 6 thus acts an inductor for the electromagnetic energy, providing heating thereof. The sound energy bonding method may comprise ultrasonic welding. The metallic layer 6 may act as a transducer for the ultrasonic waves. Apparatus to perform the above techniques are known. Such techniques are suitable for use with a broad range of polymers, metals and / or ceramics.

[0033] In other embodiments, the polymer layer 10 is bonded by at least partial melting or softening thereof. For example, the polymer layer 10 may be heated in situ on the ceramic layer 4. This may be performed in an oven or the like. The polymer layer 10 may be melted, or brazed into the ceramic layer 4.

[0034] Pressure may be applied to the composite 2 before, during (i.e. when the weld head is active) and / or after bonding of the polymer layer 10 to the ceramic layer 4. The pressure may be applied by a weld head and / or separate tool, for example a clamp or weight. The pressure is greater than or equal to 0.5 bar; preferably, greater than or equal to 1 bar; preferably, greater than or equal to 1 .5 bar; preferably, greater than or equal to 2 bar; preferably, greater than or equal to 3 bar . The pressure may be between 1 and 5 bar, preferably, between 1 .5 and 3.5 bar, preferably, between 2 and 3 bar. The pressure may be applied for greater than or equal to 1 second; preferably, greater than or equal to 5 seconds; preferably, greater than or equal to 10 seconds; preferably, greater than or equal to 20 seconds. The pressure may be applied for less than or equal to 600 seconds; preferably, less than or equal to 300 seconds; preferably, less than or equal to 120 seconds; preferably, less than or equal to 60 second; preferably, less than or equal to 30 seconds; preferably, less than or equal to 10 seconds.. The pressure may be applied for between 1 and 300 seconds; preferably, for between 1 and 150 seconds; preferably, between 1 and 10 seconds

[0035] It can be seen that the metallic layer 6 provides numerous benefits. The metallic layer 6 provides intermediate layer between the polymer layer 10 and the ceramic 4, which are conventionally unable to be bonded to a sufficient degree. Without being bound by theory, it is believed the metallic layer 6 provides an intermediate wettability, that can be bonded to both ceramic and polymer. The polymer layer 10 and the ceramic 4 can be bonded to one another without the use of generally weak adhesive layers, which can cause delamination. The metallic layer 6 further provides an interface to intercept radiation / sound to provide heating and / or bonding between the metallic layer 6 and the polymer layer 10. It can be appreciated that the metallic layer 6 provides little or no structural strength or penetration reduction, and is primarily to aid with the bonding of the ceramic 4 to the polymer layer 10.

[0036] In some embodiments, a second composite 12 may be provided. The second composite is affixed to the ceramic layer 4. The second composite 12 is provided on an opposing side of the ceramic layer 4 to the polymer layer 10 (i.e. the ceramic layer 4 is intermediate the second composite 12 and the polymer layer 10).

[0037] As shown in figure 3, the composite 2 may comprise multiple layers of the ceramic

[0038] 4. A first ceramic layer 4A may be provided as described above. A second ceramic layer 4B may be provided on an opposing side of the polymer layer 10. The second ceramic may be bonded to the polymer layer 10 as previous described (i.e. in a mirrored arrangement to the first ceramic 4A). It can be appreciated that any number of layers of ceramic 4 may be provided.

[0039] As shown in figure 4, the ceramic 4 may be bonded to a further ceramic layer. A ceramic layer 4A is bonded to a second ceramic layer 4B via the metallic layer 6. The first and second ceramic layers 4A,B are both bonded directly to the metallic layer 6. A third ceramic layer 4C is bonded to the second ceramic layer 4B via a metallic layer 6. Any number of layers 4 may be provided as required. The ceramic 4 and metallic layers 6 are interleaved / alternating.

[0040] As shown in figure 5, where the ceramic layer 4 is provided as a plurality of tiles or plates, the tiles / plates overlap one another between layers (i.e. they are staggered). Therefore, a divide / gap 14 between adjacent tiles overlies an undivided portion of an adjacent tile. In the example shown in figure 5, the divide / gap 14 in the ceramic layer 4C overlaps the centre points of the tile in the ceramic layer 4B. This provides a stretcher bond. It can be appreciated that the bonding layers may be provided in any suitable arrangement, and the divide 14 may overlap any portion of the adjacent tile. For example, the divide 14 may overlie a point at a third, quarter or fifth (or multiples thereof) of the length of the tile. Typically, the divide 14 overlies a point at greater than or equal to 10% of the length of the tile. The tiles may comprise different sizes or shapes (e.g. to provide a Flemish bond or the like).

[0041] The composite 2 may be used in a number of applications where shockabsorption, abrasion resistance or ballistic resistance is required. The composite 2 may be used as ballistic armour. The composite 2 may be used for personnel. The composite 2 may be incorporated into clothing or the like (e.g. body armour). The composite may be incorporated into a helmet or hat. The composite 2 may be incorporated into or on a vehicle. This may provide vehicle armour. The composite 2 may be incorporated into a vehicle panel or the like. The composite 2 may be incorporated into an aircraft or spacecraft (e.g. to protect from fast moving debris). The composite may be incorporated into marine platforms. As previously discussed, the composite 2 may be provided as a plurality of tiles (of regular or variable thickness) as either single flat or curved tiles or a plurality of tiles to form either a flat or curved surface; or plates; or pellets taking the form of cylinders, round ended cylinders, hollow cylinders, spheres, spheroids, cones (including truncated). The tile may comprise a width of between 5mm and 200mm; preferably 10mm and 100mm; preferably 50mm. The plates / tiles may be mounted to a substrate or backing etc (e.g. textile). The plates / tiles may be pivotable relative to one another to allow a flexible piece. The tiles / plates may be shaped or contoured (e.g. a fit a human body shape). The tiles / plates may have a regular or irregular shape. For example the tiles or plates may be circular, triangular, square, rectangular, pentangle, hexagonal or octagonal. The tiles / plates may overlap in a non-bound fashion (e.g. a scale-like arrangement).

[0042] The composite 2 may be enclosed in a protective sheath. This may help to prevent scratching or other surface damage or the like. The sheath may comprise a textile. The textile may be woven or non-woven. The textile may provide a vest or the like. The sheath may comprise a polymer. The polymer may be flexible.

[0043] The composite 2 may be used in mining or other earth-moving industries. For example, the composite may line conveyors or bin to prevent damage thereto from rocks.

[0044] The composite 2 may be manufactured in a substantially continuous process. For example, ceramic tiles or sheets may move along a conveyor. A spraying station applies the metallic layer 6. An adhesive station applies the adhesive 8. A further station overlays the polymer layer 10. The partially assembled composite passes through a bonding station to bond the polymer layer 10 to the ceramic 4. Rollers or the like may be used to apply the pressure to promote bonding.

[0045] The present invention provides an improved bond between a ceramic and a polymer or a ceramic. This provides particularly benefit in ballistic armour or the like, as it prevents delamination / separation of the ceramic and the polymer. The invention further enhances the use of radiant energy / ultrasonic bonding techniques.

[0046] It can be appreciated that the present drawings are schematic and provided merely to aid with the understanding of the invention. Specific shapes, sizes or dimensions (absolute or relative) should not be inferred therefrom.

Claims

Claims1 . A shock-absorbing, abrasion resistant or anti-ballistic composite comprising: a ceramic layer; a metallic layer formed directly onto the surface of the ceramic layer; and a further layer attached indirectly to the ceramic layer via the metallic layer.

2. A composite according to claim 1 , where the further layer comprises a polymeric material.

3. A composite according to claim 2, where the polymeric material comprises an ultra-high molecular weight polyethylene and / or aramid.

4. A composite according to any preceding claim, where the metallic layer comprises a thickness than less than or equal to 1000pm.

5. A composite according to claim 4, where the metallic layer comprises a thickness less than or equal to 250pm.

6. A composite according to claim 4 or 5, where the metallic layer comprises one or more of: iron; aluminium; copper; gold; nickel; and / or silver.

7. A composite according to any preceding claim, where the ceramic layer comprises an oxide, carbide and / or nitride.

8. A composite according to claim 7, where the ceramic layer comprises alumina.

9. A composite according to any preceding claim, where an adhesive layer is provided between the metallic layer and the further layer.

10. A composite according to claim 9, where the adhesive layer comprises an epoxy based adhesive and / or a polyurethane based adhesive and / or a cyanoacrylate based adhesive and / or a polyisocyanate such as 4,4'-Diphenylmethane di isocyan ate, Polymeric Diphenylmethane Diisocyanate or mixtures thereof based adhesive and / or a Methyl Ether Ketone based. adhesive.

11. A composite according to any preceding claim, comprising a plurality of ceramic layers.

12. A composite according to claim 11 , where at least two of the ceramic layers are provided on opposing side of the polymer layer.

13. A composite according to claims 11 or 12, where at least two ceramic layers are attached to one another by directing bonding to the intermediate metallic layer.

14. A composite according to any of claims 11 -13, where at least one of the ceramic layers comprises a plurality of ceramic tiles or plates, and the divide between adjacent tiles / plates overlies an undivided portion of an adjacent ceramic layer.

15. A vehicle, aircraft, spacecraft, or navel craft comprising the composite of any preceding claim.

16. Body armour comprising the composite any preceding claim.

17. A method of manufacturing a shock-absorbing or ballistic composite comprising: providing a ceramic layer; forming a metallic layer directly onto the surface of the ceramic layer; and bonding a further layer to the ceramic layer via the metallic layer.

18. A method according to claim 17, where the metallic layer is formed on the ceramic layer via spray or vapour deposition technique.

19. A method according to claim 17, where the metallic layer is formed on the ceramic layer via cold spraying, hot spraying, plasma spraying, electrolytic plating or electroless plating.

20. A method according to any of claims 17-19, where the further layer is bonded to the metallic layer via radiant energy or ultrasound energy technique.21 . A method according to claim 20, where the further layer is bonded to the metallic layer via one or more of: ultrasonic; electromagnetic induction; or microwave bonding.

22. A method according to any of claims 17-21 , where the radiant energy or sound is directed at the interface between the metallic layer and the further layer, such that heating / bonding primarily occurs at the interface.

23. A method according to any of claims 17-22, where pressure is applied to the composite during / after attachment of the further layer to the ceramic layer.

24. A method according to claim 23, where the pressure is between 0.5 and 5 bar.

25. A method according to claim 23 or 24, where pressure is applied for between 5 and 150 seconds.

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