EP2208961A1

EP2208961A1 - Armour composite and production method thereof

Info

Publication number: EP2208961A1
Application number: EP09150758A
Authority: EP
Inventors: Gerrit Van Der Sar
Original assignee: Life Saving Solutions Ltd
Current assignee: Life Saving Solutions Ltd
Priority date: 2009-01-16
Filing date: 2009-01-16
Publication date: 2010-07-21

Abstract

The invention relates to an armour composite comprising (a) a continuous first layer (12) having a strike face and a backing face opposite to said strike face, the first layer (12) comprising a material having a hardness of at least 4 GPa; and (b) a second layer (30) comprising an elastomer at the backing face of the first layer (12), the layers (12,30) forming a unitary component, wherein the elastomer exhibits strain rate sensitivity-hardening under both ballistic and blast conditions, said elastomer having a microstructure comprising hard segments that are predominantly amorphous. The invention also relates to a production method of the armour composite.

Description

The invention relates to the subject of armour and specifically to an armour component including a hard layer, such as ceramic or ceramic composite, and a non- fibrous elastomeric layer.
Materials used in currently available armours can be divided into three types: metals, polymers and ceramics. Metal armours provide excellent protection from kinetic threats, are cheap and relatively easy to produce from alloys, usually including aluminum, magnesium, titanium and iron. Metal armours protect an object by deforming or deflecting an impacting kinetic threat and by dissipating the kinetic energy of the kinetic threat both by inelastic and elastic deformation. Metal armours are effective against multiple kinetic threats since damage to the armour caused during neutralization of the kinetic threat is generally local to the area of impact. However, the weight of metal armours is such that providing sufficient protection against increasingly common kinetic threats is impractical.
Polymer armours are considered lightweight, easy to produce in virtually any shape, simple to install and retrofit, and are relatively comfortable to wear as body armour. Most modern polymer armours are made of fibers made of semi-crystalline polymers. A common semi-crystalline polymer used for producing fibers for polymer armours is a poly(arylamide) made by the condensation of terephthalic acid and 1,4- benzenediamine (see, for example, U.S. Patent 3,671,542 ) and marketed under the name Kevlar (E.I. du Pont de Nemours and Company, Wilmington, Delaware, USA) or Twaron (Teijin Twaron B. V., Arnhem, The Netherlands).
Another common highly-oriented semi-crystalline polymer used for producing fibers for polymer armours are polyethylene fibers made according to method that yields exceptionally highly-oriented high molecular weight (HOHMW) polymer chains, see for example U.S. Patent 4,413,110 and references therein. Such polyethylene fibers are marketed under the name Spectra (AlliedSignal Inc., Morristown, New Jersey, USA) or Dyneema (Koninklijke DSM N.V., Heerlen, The Netherlands). Such fibers are characterized as having low stretch (e.g., 4% elongation at failure for Spectra) and high longitudinal tensile strength (e.g., 2300-3500 MPa).
For armour application, polymer fibers are generally woven to make a textile and a plurality of layers of such a textile stacked and mutually attached using a resin to make a single laminated textile armour. When a kinetic threat impacts such laminated woven textile armour, the kinetic threat is caught in the web of fibers.
The fibers absorb and disperse the energy of the impact to other fibers at the crossover points of the weave. Energy is dissipated by deformation (elastic and inelastic) of many interwoven fibers and by delamination of the armour. Generally, woven textile armours are suitable for protecting against low energy threats such as shrapnel and small caliber bullets having impact velocities up to about 450 m/sec.
Although expensive, armours made of plates of ceramic materials provide a high level of protection from kinetic threats and are light in weight in comparison to equivalent metal armours. The use of ceramic materials for protecting objects from kinetic threats is discussed in, for example, Medvedovski, American Ceramic Society Bulletin (2002), 81 (3), 27-32 and U.S. Patent 6,112,635 and U.S. Patent 6,408,733 . Ceramic materials used in armours neutralize kinetic threats by deforming the impacting kinetic threat and by dissipating absorbed kinetic energy through a combination of a pulverization energy mechanism and a fracture energy mechanism. In the pulverization energy mechanism, a comminution zone of pulverized ceramic in the shape of a conoid emerging from the impact point is produced. In the fracture energy mechanism, kinetic energy is absorbed by the ceramic plate, distributed throughout the plate and subsequently expended by the shattering of the ceramic plate through radial and circumferential cracks.
Ceramics most often used for protection of objects from kinetic threats are monolithic ceramics such as Al2O3, B4C, SiC and TiB2. Due to improved mechanical properties, ceramic-matrix composites are increasingly used instead of monolithic ceramics for protecting objects from kinetic threats. Suitable ceramic-matrix composites include fiber-reinforced materials such as Al2O3/SiC and ceramic/particulates such as TiB2/B4C and TiB2/SiC and cermets such as SiC/Al, TiC/Ni and B4C/Al. Energy dissipation through the fracture energy mechanism is most efficient in ceramic materials that are stiff and have a high sonic velocity. High stiffness leads to maximal post-impact stress in the ceramic with very little elastic deformation whereas a high sonic velocity spreads the stress throughout the ceramic plate before actual shattering occurs. Ultimately, the impact energy of the kinetic threat is used to break many chemical bonds of the ceramic plate, thereby shattering the entire ceramic plate, see for example U.S. patent 5,469,773 .
Very hard ceramics are preferred for use in armour application to ensure deformation of the kinetic threat in order to dissipate kinetic energy and to reduce the chance of follow-through penetration subsequent to ceramic plate shattering. The fact that ceramic materials shatter to dissipate the kinetic energy of a kinetic threat means that ceramic armour is generally useful for protecting an object only against impact from a single kinetic threat. Due to the extensive shattering of the ceramic, subsequent impacts have a statistically significant chance to impact on a crack and penetrate with little or no resistance. Further, the shards of the ceramic armour produced by the shattering are relatively small and have little mass: the small size means that there only a few bonds are available for dissipation of energy from subsequent kinetic threat impacting on such a shard and that such a shard may be pushed through by an impacting kinetic threat into the sensitive object being protected.
As stated above, monolithic ceramic armours neutralize an impacting kinetic threat by deforming the kinetic threat and by dissipating the kinetic energy of the kinetic threat by shattering. A significant danger when using ceramic armours is that of follow-through penetration: fragments of the kinetic threat or shards of ceramic have sufficient residual kinetic energy to penetrate into and damage the object being protected by the armour. To reduce the dangers of follow-through penetration armours generally include at least two layers.
In US patent 7,300,893 the use of a strain rate hardening elastomer is mentioned that is encapsulating or sandwiching a rigid inclusion for improved protection against blast and ballistic damage. The plurality of rigid inclusions are completely encapsulated in the elastomeric material.
In US patent 6532857 the use of elastomeric polysulfide for individual encapsulation of (multiple) ceramic tiles is mentioned. In W02006040754 the use of non-filamentous semi-crystalline polymers for armour application is mentioned. The polymers include polyamide, Nylons, and polyethylene.
Unitary armour components comprising a first hard layer, backed by highly-oriented semi-crystalline polymer fibers attached thereto with a resin or adhesive have a number of disadvantages. Importantly, such armour components are expensive, as both the first hard layer and the second laminated cloth layer require expensive raw materials and complex manufacturing steps to produce. A further problem results from the fact that delamination at the interface of first layer with second layer and delamination of second layer compromise the multiple threat neutralization capability of an armour component. A further problem results from the fact that second layer is a non-rigid cloth so that the rigidity of armour component is dependent on the structural integrity of first layer. When first layer is of a material that dissipates energy through the fracture energy mechanism, upon impact of a kinetic threat the shape of armour component is lost.
Yet another disadvantage of the use of a fibrous polymer backing layer is the relatively large back face deformation that occurs due to the fact that the fibers can only dissipate energy when axially stressed. This causes blunt trauma effects to the wearer when the armour plate is applied as body armour (insert).
The elastomeric materials in US 7,300,893 are encapsulating the individual ceramic components, which requires a complicated manufacturing process or several processing steps, which will increase the manufacturing costs and increase the number of potential fabrication flaws.
It is an object of this invention to provide a material and manufacturing process that do not exhibit the above drawbacks.
In particular it is an object of the present invention to provide an armour component which includes a first hard layer as a strike face to deform an incoming threat and dissipate kinetic energy and a second layer to prevent follow-through penetration of kinetic threat fragments and shards of the first layer from affecting a protected sensitive object, where the second layer is cheaper and easier to produce than known such layers made of highly-oriented semi-crystalline polymer fibers or complete encapsulation of the strike layer.
It is a further object of this invention to provide a material that provides protection from kinetic threats on par with or exceeding the protection provided by known armour components of comparable bulkiness and mass.
Another object of this invention is to provide a material that provides protection from multiple kinetic threats, including multiple high-velocity kinetic threats and blasts.
Yet another object of this invention is to provide a material that has reduced back face deformation in order to reduce blunt trauma effects when used as body armour.
According to the invention an armour composite comprises (a) a continuous first layer having a strike face and a backing face opposite to said strike face, the first layer comprising a material having a hardness of at least 4 GPa; and (b) a second, preferably continuous layer comprising an elastomer at the backing face of the first layer, the layers forming a unitary component, wherein the elastomer exhibits strain rate sensitivity-hardening under both ballistic and blast conditions, said elastomer having a microstructure comprising hard segments that are amorphous.
The present invention provides an armour component including a non-filamentous elastomeric polymer backing layer. It is disclosed herein that the protection afforded by embodiments of such armours is similar or better than the protection afforded by comparable prior art armour components having a laminated cloth layer.
An advantage of embodiments of an armour component of the present invention over comparable prior art armour components is the ease and low cost of production of a non-filamentous elastomeric polymer layer, as well as the assembly of the armour composite.
According to the present invention there is provided an armour composite for protecting an object from a kinetic threat comprising: a) a first continuous hard layer having a hardness of at least 4 GPa (Vickers), preferably including (or substantially comprising or even consisting essentially of) a material selected from the group consisting of ceramic matrix composites (e.g., Al2O3/SiC, Al2O3/C, TiB2/B4C, TiB2/SiC, SiC/Al, TiC/N, B4C/Al), monolithic ceramics (e.g., Al2O3, B4C, SiC, TiB2), cermets, glass-ceramics and glass; and b) a second layer, including at least one non-filamentous elastomeric polymer, the second layer attached to the first layer to form a unitary component. A hardness of 4 GPa is required for the first layer as the hardness of metal, from which bullets and other missiles are made, usually has a Vickers hardness of less than 4 GPa. To withstand armour piercing missiles advantageously the first layer has a hardness of at least 14 GPa. In view thereof monolithic ceramics like Al2O3 (16 GPa), SiC (24 GPa) and B4C (32 GPa) are preferred materials for the first layer. In the context of this specification the front face not covered by the elastomeric second layer, of the first layer is also called strike face as it is the first surface being hit. The second layer functions as a backing layer at the back face of the first layer. The second layer comprises an elastomer that exhibits strain rate sensivity-hardening under both ballistic and blast conditions. Such elastomers comprise amorphous hard segments. Due to the presence of these amorphous hard segments a phase-separation between the soft (above Tg amorphous) and hard phases affects the effectiveness to a lesser extent. Preferably the strain rate sensitivity occurs at strain rates greater than 1/s, preferably in the range of about 10/s-1,000/s, more preferably between 10/s and 100/s .
In an embodiment of the present invention the first and second layers are substantially in contiguous contact. In an embodiment of the present invention the second layer is substantially parallel to the first layer.
In an embodiment of the present invention, the second layer is substantially a plate, either curved or flat.
In an embodiment of the present invention, the second layer is substantially box shaped, that is having a substantially plate-like bottom in contact with the first layer and walls extending from the bottom so as to at least partially surround the side edges of the first layer.
In an embodiment of the present invention, the polymer is elastomeric and has a large strain rate sensitivity hardening effect. In an embodiment of the present invention, the second layer is not laminated.
In an embodiment of the present invention, the second layer is monolithic. In an embodiment of the present invention, the second layer is homogeneous.
Any plate of a rigid material, such as ceramic, cermet or glass plate, is backed by an elastomer having high strain rate sensivity hardening. Typically, elastomers useful in the present invention have a strain rate sensitivity hardening effect occurring above 1/s , and include, for example, some polyurethanes, polyureas and mixtures thereof.
Generally, elastomers having this characteristic will meet the following criteria in low rate of loading conditions: Tensile strength of 20- 30 MPa; Young's modulus of about 13 MPa at 300% strain; elongation in the range of 200-800%, typically more than about 300%; hardness Shore A 70 to 95.
It is theorized that the present invention, while relying in-part upon conventional mechanisms, uses additional mechanisms to defeat blast and ballistic threats. In the case of ballistic impact, under the extremely high strain rate (up to 10<6> /sec), which is initially generated by the projectile impact on the outer surface of the ceramic layer, the elastomer will dynamically stiffen. The stiffening results from an extreme strain rate sensitivity and confinement which causes the elastomer to dynamically strengthen and stiffen and results in a significant increase of the wave speed in the elastomer. The high dynamic stiffness and strength of the polymer backing material allows to contain and stop the threat as well as the ceramic fragments.
The microstructure of polyureas, polyurethane and mixtures thereof generally consist of amorphous soft and semi-crystalline hard segments. The type of polymers that show the required special dynamic stiffening effect have a microstructure in which also the hard segments are predominantly amorphous. This special microstructure can be obtained using chain extenders during the polymerization reactions in which the polymer is synthesized. Typical examples comprise Clearflex 50/90, available from Smooth-on as 2 component (polyol and isocyanate prepolymer) system, Pearlthane D91T85 of Danquinsa and PE505 of Huntsman, both being thermoplastic poly urethanes, while other polymers having similar static mechanical properties like Pearlthane D15F85 of Danquinsa and PE399 of Huntsman do not show the required dynamic properties, due to the absence of the amorphous hard segments in the latter. Whether the microstructure comprises amorphous hard segments or crystalline segments can be determined by experiments, e.g. by high strain tests and differential scanning calorimetry.
In blast loading, the strain rates are of the order (10<2> -10<3> /sec), which also contribute to dynamic strengthening and stiffening and confinement of the elastomer.
The invention also relates to a method of producing an armour composite according to the invention, the method comprising the steps of

a) providing a first continuous layer having a strike face and a backing face opposite to said strike face, the first layer comprising a material having a hardness of at least 4 GPa;
b) applying a second, preferably continuous layer comprising an elastomer at the backing face of the first layer, the layers thereby forming a unitary component;

In a preferred embodiment step a) comprises placing the first layer in a mould with the backing face upwards, and step b) comprises providing a thermoplastic polymer at least on top of the backing face of the first layer, heating the thermoplastic polymer to a temperature above its softening point and allowing to cool the thermoplastic polymer thereby forming a unitary component.
In another preferred embodiment, step b) comprises spray-coating mixed reactive starting materials on the backing face of the first layer and allowing the mixed reactive starting materials to polymerize to the elastomer on the first layer thereby forming a unitary component.
In yet another aspect the invention relates to a method of armouring a surface of an object comprising a step of applying the armour composite according to the invention to the surface of the object. Advantageously the object is a vehicle, a building, or an article of clothing.
The actual backing can be accomplished by casting, spraying, or adhering the elastomer layer behind and at least partly along the edges of the rigid plate. An advantage of the armour composite of the present invention is that it combines protection from both ballistic and blast threats in a relatively low-weight, low-cost configuration. Making use of the high-rate properties of certain rate-sensitive polyurethanes and polyureas as a backing layer for enhancing damage resistance permits design of the dual-purpose armour.
Further cost savings could be realized using low-cost ceramics, e.g. glass, or alumina whose response could be made equivalent to that of more costly siliconcarbide or boroncarbides through augmentation by the elastomer backing. For protection of structures where the threat was well defined, the dual armour could result in weight savings where benefits derived from thinner/lighter ceramic, for example, with the low density elastomer dual armour combination could offset a heavier configuration containing only thicker/heavier ceramic tiles. The flexibility of the concept enhances the capability to develop armours in complex contours and irregular surfaces such as body armour and aircraft armour and to use complex shapes of encapsulated volumes.
In an embodiment of the present invention, at least one of the non- filamentous polymers is selected from the group consisting of polyurethane or polyurea and mixtures thereof. Such type of materials can be made by mixing of two or more liquid chemical components (prepolymers containing diisocyanate and polyols), and casting of the mixture onto the first layer before polymerization takes place. Another method would make use of thermoplastic polyurethane (TPU) granules that are heated and pressed into (essentially a plate) shape and attached to the first layer at the same time or afterwards in a second process step.
In an embodiment of the present invention, typically the first (rigid) layer is between about 5 mm and about 25 mm thick, preferably between about 5 mm and about 12 mm thick. In an embodiment of the present invention, the second layer is thicker than about 2 mm, preferably thicker than about 4 mm and more preferably thicker than about 6 mm.
In an embodiment of the present invention, the second layer is thinner than about 40 mm, preferably thinner than about 35 mm and more preferablythinner than about 30 mm.
In an embodiment of the present invention, there is a third adhesive layer disposed between the first layer and the second layer. Preferably the third adhesive substantially attaches the first layer to the second layer. In an embodiment of the present invention, the third adhesive layer comprises at least one material selected from the group consisting of thermosetting resins and thermoplastic resins. In an embodiment of the present invention, the third layer is thinner than about 2 mm, preferably thinner than about 1 mm, more preferably thinner than about 0.5 mm, even more preferably thinner than about 0.2 mm, and most preferably thinner than about 0.1 mm.
In an embodiment of the present invention, the article has a shape, for example of an armour plate, armour sheet, bullet-proof vest, body armour, panel, door panel, floor panel, wall panel, helmet, seat, aircraft, rotary wing aircraft, fixed wing aircraft, armoured fighting vehicle, limousine and motor vehicle.
In an embodiment of the present invention, the first layer is a strike face of the article. According to the teachings of the present invention there is also provided the use of an article as described above for protecting an object from a kinetic threat. In an embodiment of the present invention, at least one non- filamentous elastomeric polymers is selected from the group consisting of polyurethane (aliphatic, aromatic, thermoplastic or thermosetting), polyurea and mixtures thereof.
In an embodiment of the present invention, providing the second component comprises: i) providing a thermoplastic polymer resin or granulate, ii) heating the polymer resin to yield a molten or softened polymer; iii) shaping the polymer into the shape of the second component, iv) cooling the polymer.
In an embodiment of the present invention, shaping the polymer into the shape of the second component includes a process selected from the group consisting of molding, injection molding, compression molding and extrusion of the molten polymer, preferably compression molding.
In an embodiment of the present invention, providing the second component comprises: i) providing a prepolymer mixture, ii) evacuation of the liquid mixture; iii) casting the polymer using a mould into the shape of the second component, iv) curing the polymer.
In an embodiment of the present invention, subsequent to melting of the polymer resin, the molten resin is not formed into a filament.
In an embodiment of the present invention, attaching the first and second components includes contacting the first component with the second component so as to cause the second component to adhere to the first component.
In an embodiment of the present invention, attaching the first and second components includes, during the transforming of the molten polymer into the elastomer, maintaining contact of the incipient elastomeric polymer making up the incipient second component with the first component. In an embodiment of the present invention, attaching the first and second components includes using at least one adhesive {e.g., a thermosetting resin or a thermoplastic resin) to adhere the first component to the second component. In an embodiment of the present invention, using an adhesive includes applying the adhesive to one or both of the two components, for example by spraying the adhesive, painting the adhesive, brushing the adhesive, depositing the adhesive, pouring the adhesive or laying a sheet of adhesive. In an embodiment of the present invention, an adhesion promoter is applied to the first component so as to increase adhesion of the adhesive to the first component.
The invention is illustrated hereinbelow by examples and by reference to the attached drawings, wherein

Fig. 1a-c show a prior art armour component and its behaviour upon impact;
Fig. 2a-c show an embodiment of an armour composite according to the invention and its behaviour upon impact; and
Fig. 3a-b show another embodiment of an armour composite according to the invention.

Example 1

A flat alumina plate with 8 mm thickness was positioned in a polyethylene box. A polyurethane prepolymer mixture was mechanically mixed, vacumized and poored on top and around the alumina plate to a thickness of 20 mm behind the plate. After full polymerisation at room temperature of the prepolymer, the armour composite is ready for use.

Example 2

A flat glass plate of 6 mm thickness was positioned in a heated die. A predetermined mass of TPU granulate was preheated (to 90 centigrade) to lower its moisture content and poured into the die on top and around the glass plate. After closing the die and heating the content to the working temperature of the TPU (typically 140 centigrade), the die was pressed uniaxially. After cooling the die, the composite armour was ejected.

Example 3

A curved siliconcarbide front plate (10 mm thickness) was positioned in a heated and formed die. A predetermined mass of TPU granulate (enough for a thickness of the backing layer of 15 mm) was preheated to lower its moisture content and poured into the die on top and around the curved siliconcarbide plate. After closing the die and heating the content to the working temperature of the TPU (typically 140 centigrade), the die was pressed uniaxially. After cooling of the die including the ceramic plate and TPU, the composite armour was taken out.

Example 4

A curved alumina body armour plate (8 mm thickness) was positioned in a heated and formed die. A flat TPU plate with the right thickness (of about 16 mm) was heated and pressed on top and around the curved alumina plate. After cooling of the TPU, the composite armour was taken out of the die.

Example 5

A ceramic plate was placed with its strike face down allowing the back side to be coated with a layer of polyurethane or polyurea (or mixture thereof). A 15 mm thick backing layer of polyurea was applied on the 9 mm thick curved alumina plate by spray coating. In this technique the reactive components of the polymer are pre-heated in order to reduce the viscosity and to increase the reactivity. The two liquid reactants flow through two heated hoses and are mixed inside a nozzle. Due to the intense mixing inside the nozzle as well as the high temperature of the pre-heated reactants (about 70 centigrade) the polymer reaction occurs within seconds. This allows the droplets of the mixed reactants to be sprayed onto any surface at which the polymer will adhere.

Example 6

A mould releasing agent was applied on the walls of a rectangular metallic box. A ceramic plate (8 mm armour garde SiC) was positioned inside the box. A predetermined mass was applied on top of the ceramic plate. The box was placed inside an oven which was vacumized thereafter. The oven heated the box and its contents to a temperature above the melting range of the TPU. After cooling of the box (at normal or increased gas pressure condition) the finished sample can be taken out.
In Figure 1a, a unitary armour component 10 includes a first layer 12 of ceramic or cermet as a strike face and second layer 14 of laminated woven or non-woven cloth as a spall liner. Second layer 14 is generally attached to first layer 12 with a resin or adhesive so as to make a unitary armour component. Since such cloths are invariably impregnated with a resin or adhesive, in some instances attachment does not include a separate adhesive layer, although in some instances a separate adhesive layer is used. Incoming kinetic threat 16 impacts with first layer 12 and is deformed thereby while first layer 12 absorbs the kinetic energy of impact, Figure 1 b. If the kinetic energy absorbed is sufficient to shatter 18 and/or pulverize 20 first layer 12, any fragments and shards are trapped and residual kinetic energy absorbed by second layer 14. Subsequently, Figure 1c, energy transferred to second layer 12 is dissipated by delamination at the first layer 12 / second layer 14 interface 22 and tearing and delamination 24 of the cloth layers making up second layer 14. Damage to a sensitive object being protected by unitary armour component 10 from penetrating fragments and shards is prevented. Backface deformation 26 of unitary armour component 10 may cause damage to the sensitive object being protected, although the severity of the damage is mitigated by distribution over a relatively large area.
Fig. 2a-c show an embodiment of an armour composite 28 according to the invention, comprising an uncovered first layer 12 of a hard material having a hardness of at least 4 GPa, backed by a second layer of an elastomer exhibiting strain hardening. See fig. 2a. Upon impact of a kinetic threat 16 shattering 18 and pulverization 20 of the first layer 12 occurs (Fig. 2b). Due to strain hardening of the backing layer 30 the resulting back face deformation of the second layer 30 is far less than in the prior art armour component of fig. 1, as is shown in Fig. 2c.
Fig. 3a and 3b show a perspective view and cross-section respectively of an embodiment of a curved armour composite 32, wherein the backing layer 30 of a strain hardening elastomer is shaped as a box or tray having a convex upper bottom surface 34 and upright walls 36 along the periphery. The first layer 12 is also curved and fits in the box of the first layer. The first layer has a thickness exceeding the height of the inner face of the upright walls 36, such that the side edges 38 of the first layer are partially surrounded by the upright walls 36.

Claims

Armour composite comprising (a) a continuous first layer having a strike face and a backing face opposite to said strike face, the first layer comprising a material having a hardness of at least 4 GPa; and (b) a second layer comprising an elastomer at the backing face of the first layer, the layers forming a unitary component,
wherein the elastomer exhibits strain rate sensitivity-hardening under both ballistic and blast conditions, said elastomer having a microstructure comprising hard segments that are predominantly amorphous.
Armour composite according to claim 1, wherein the strain rate sensitivity-hardening occurs at strain rates greater than 1/s, preferably in the range of about 10 /s - 1,000/s.
Armour composite according to one of the preceding claims, wherein the elastomer comprises polyurea, polyurethane, or a blend thereof.
Armour composite according to one of the preceding claims, wherein the first layer is essentially a plate.
Armour composite according to one of the preceding claims, wherein the second layer also at least partially surrounds the side edges of the first layer.
Armour composite according to one of the preceding claims, wherein the first layer comprises a material selected from the group consisting of ceramic matrix composites, monolithic ceramics, cermets, glass-ceramics and glass.
Armour composite according to one of the preceding claims, wherein the first layer comprises a material having a hardness of at least 14 GPa.
Armour composite according to one of the preceding claims, wherein the first layer layer comprises a monolithic ceramic selected from the group consisting of Al2O3, B4C, SiC and TiB2.
Armour composite according to one of the preceding claims, wherein the first layer has a thickness in the range of 5- 25 mm.
Armour composite according to one of the preceding claims, wherein the second layer has a thickness equal to or less than about 40 mm.
Armour composite according to one of the preceding claims, wherein the elastomer has an elongation of at least 300% and a Shore A hardness in the range of 70-95.
Method of producing an armour composite as defined in one of the preceding claims, the method comprising the steps of
a) providing a first continuous layer having a strike face and a backing face opposite to said strike face, the first layer comprising a material having a hardness of at least 4 GPa;

b) applying a second layer comprising an elastomer at the backing face of the first layer, the layers thereby forming a unitary component;
wherein the elastomer exhibits strain rate sensitivity-hardening under both ballistic and blast conditions, said elastomer having a microstructure comprising hard segments that are predominantly amorphous.
Method according to claim 12, wherein step a) comprises placing the first layer in a mould with the backing face upwards, and step b) comprises providing a thermoplastic polymer at least on top of the backing face of the first layer, heating the thermoplastic polymer to a temperature above its softening point and allowing to cool the thermoplastic polymer thereby forming a unitary component.
Method according to claim 12, wherein step b) comprises spray-coating mixed reactive starting materials on the backing face of the first layer and allowing the mixed reactive starting materials to polymerize to the elastomer of the first layer thereby forming a unitary component.
Method for armouring a surface of an object comprising a step of
applying the armour composite as defined in one of the preceding claims 1-11 to the surface of the object, wherein preferably the object is a vehicle, a building, or an article of clothing.