GB2596050A

GB2596050A - Improvements to stab armour

Info

Publication number: GB2596050A
Application number: GB2006695.7A
Authority: GB
Inventors: Skertchly David
Original assignee: Helmschmied Ltd
Current assignee: Helmschmied Ltd
Priority date: 2020-05-06
Filing date: 2020-05-06
Publication date: 2021-12-22
Also published as: GB202006695D0

Abstract

Armour plate comprises at least one layer that exhibits auxetic behaviour. The armour plate does not include a ceramic layer. The armour plate may include a central layer 1 and at least one external layer 2 having different properties. One of the central or external layers 1, 2 may exhibit auxetic behaviour. At least one of the layers 1, 2 may be formed of fibres in a matrix. The central layer 1 may comprise glass fibres. The external layer 2 may comprise carbon fibres. Auxetic behaviour may be provided by properties of the fibres or the matrix. At least one layer 1, 2 may be a knitted layer and the knitting patter provides auxetic behaviour. The armour plate may be used in armoured clothing.

Description

IMPROVEMENTS TO STAB ARMOUR

Background

This invention relates to improvements in armour and in particular to the improvement of stab armour using auxetic composite materials.

The use of composite materials such as glass fibre, carbon fibre and Kevlar is well known. The material is formed into shaped plates to defend a person or object from impacts from weapons such as knives, spikes, baseball bats and low velocity bullets. For example, plates may be formed into body armour for use in garments to protect people, or may be located on or in vehicles to protect that vehicle.

When a knife or other item strikes the composite material the impact causes the composite reinforcement to fracture. The penetration is eventually stopped as the energy of the strike is absorbed by cutting of the reinforcement and by friction as the cut matrix acts on the blade. The penetration may be stopped entirely within the composite or within a backing layer of lightweight foam or other soft light layer before they harm the person or object being protected.

When a composite plate is struck by a knife or spike the reinforcement is cut and penetration of the knife or spike is stopped by the friction between blade and the composite.

A stab armour with improved ability to stop penetration of a sharp item is desirable.

Summary

The following presents a simplified summary of the disclosure in order to provide a basic understanding to the reader. This summary is not an extensive overview of the disclosure and it does not identify key/critical elements of the invention or delineate the scope of the invention. Its sole purpose is to present some concepts disclosed herein in a simplified form as a prelude to the more detailed description that is presented later.

There is provided an armour plate for resisting a low energy threat such as stabbing or small arms, comprising at least one layer which exhibits auxetic behaviour, wherein the armour plate does not include a ceramic layer.

The armour plate may comprise a central layer and at least one external layer, the central layer and at least one external layer having different properties; at least one of the central and external layer(s) exhibiting the auxetic behaviour.

At least one of the central layer and external layer(s) may be formed of fibres in a matrix.

The central layer may comprise glass fibres.

The at least one external layer may comprise carbon fibres.

The auxetic behaviour may be provided by the lay up of the fibres.

The auxetic behaviour may be provided by properties of the fibres. The auxetic behaviour may be provided by properties of the matrix.

At least one of the central and external layer(s) may be a knitted layer, wherein the knitting pattern provides the auxetic behaviour.

There is also provided an item of armoured clothing comprising an armour plate as claimed in any preceding claim.

In further examples of the disclosure there is provided an armour plate, comprising a composite of one or more layers, and a component which exhibits auxetic behaviour.

The composite reinforcement, the composite matrix or the configuration of the composite layers may comprise the component which exhibits auxetic behaviour.

The component which exhibits auxetic behaviour may be comprised in a composite layer on the surface or layers within the composite.

The auxetic composite layer may be bonded to the surface by an adhesive.

There may be two or more composite layers, each formed with a different auxetic or non auxetic construction.

The component exhibiting auxetic behaviour may be at least one auxetic fibre.

The component forming the auxetic behaviour may be formed from a particular configuration of the layers. The laminate may be formed of non-auxetic fibres The component exhibiting auxetic behaviour may be a knitted or woven fabric. The fabric may be formed of non-auxetic fibres.

There is also provided an item of armoured clothing comprising an armour plate or panel as described herein.

Description of the drawings

Embodiments of the present invention will now be further described, by way of example, with reference to the figures, wherein:-Figure 1 shows a cross-section of a structure according to an embodiment of the invention; and Figures 2 and 3 are flow-charts of methods of manufacturing an embodiment of the invention.

Detailed description

The detailed description provided below in connection with the appended drawings is intended as a description of the present examples and is not intended to represent the only forms in which the present example may be constructed or utilized. The description sets forth the functions of the example and the sequence of steps for constructing and operating the example.

However, the same or equivalent functions and sequences may be accomplished by different examples.

Figure 1 shows a cross-section of a composite structure for providing protection against penetration of sharps items.

The composite structure comprises a central layer 1 with external layers 2 on the faces of the central layer 1. In certain examples only one external layer may be provided. The layers function together to protection. An optional comfort layer 3 may be provided on one or more sides of the external layers for comfort during use. One or more of the central 1 and external layers 2 may comprise a material with auxetic properties to improve the protection provided. It is believed that the auxetic properties increase friction between a stabbing weapon to reduce penetration compared to conventional materials.

The layers are joined together in an appropriate way, for example by laminating the layers together and then curing them as one construction or by bonding the layers together.

Auxetic materials have a negative Poisson's ratio and thus when a tensile stress is applied to an auxetic structure, its size in a direction perpendicular to the applied stress increases On contrast to conventional materials whose size reduces when a tensile stress is applied).

When a weapon strikes the armour, the consequent deformation of the armour is transferred to the layers. The deformation causes tensile stresses in the auxetic component which expands in a direction perpendicular to the stress. That expansion resists the penetration of the weapon into the armour plate thus increasing the friction imparted on the blade penetration of the weapon and improving the protection offered to the wearer of the armour.

The central layer 1 may be formed of one or more plies (for example 3 to 5) of material, for example non-woven multi axial glass fibres in a matrix material.

The fibres may be arranged in an auxetic lay-up, or the layer may be provided with auxetic properties using any other appropriate technique, for example the matrix may be auxetic. The matrix may contain auxetic fillers. The fibres may be a fabric weave which has auxetic properties.

The external layer(s) 2 may be formed from layer(s) of fibres in a matrix material having a greater hardness and Young's modulus than those used in layer 1, for example these are carbon fibres. The fibres may be arranged in an auxetic lay-up. One or more formed layers which are known to be auxetic may be included. The matrix may be auxetic. The matrix may contain auxetic fillers. The reinforcement may be a fabric weave which has auxetic properties.

The comfort layer 3 may be a polymer foam and may be auxetic.

PCT publication number W02000/053830 discloses a manufacturing technique for auxetic fibres.

1 5 It has been shown that auxetic behaviour can be obtained with certain fibre orientations, even if the fibres themselves are non-auxetic (see phys. Stat. sol. (b) 244, No. 3, 883-892 (2007, E.H.Harkati, A.Bezazi, F.Scarpa, K.Alderson and A.Alderson).

The auxetic component of the external layers 2 may also be a knitted structure having auxetic behaviour (see for example PCT publication number W02008/016690), or an auxetic woven fabric (see for example European publication number EP1786962).

The auxetic properties of the external layer(s) 2 may be provided as an auxetic polymer matrix, or a liquid crystal polymer. A suitable auxetic foam for layer 3 is disclosed in European Patent No. 1957253.

A specific example structure is described below:- * Central layer 1 -6 plies of non-woven multiaxial e-glass arranged at ±22° to the part datum in a suitable matrix material.

* External layer 2 -6 plies unidirection carbon fibre arranges at ±22°to the part datum in a suitable matrix material.

* Comfort layer 3 -1 ply of 6mm polyurethane foam.

Figure 2 shows a flow-chart of a method of manufacture of the structure shown in Figure 1.

At step 201 reinforcement fibres for layers 1 and 2 are pre-impregnated with a suitable matrix material. The reinforcement includes the auxetic component in one of the forms described above. At step 202 the layer is placed in a mould. At step 203 the structure is cured in an appropriate fashion determined by the materials and structure utilised. For example, a vacuum bag may be applied around the structure, and cure maybe performed at a pressure and temperature of 90psi and 135°C for 1 hour.

At step 204 the structure is removed from the curing process and at step 205 the component is finished cosmetically and at step 206 a soft backing layer 3 is applied if required.

The resulting structure is a shaped armour with a reinforcement layer incorporating an auxetic component. As will be appreciated, this method, with suitable modification, is also applicable to the manufacture of a plate with reinforcement on only one surface.

Figure 3 shows a flow chart of an alternative method of manufacturing the structure shown in Figure 1.

At step 301 dry reinforcement fibres suitable for layers 1 and 2 are placed in the mould as described above, the auxetic effect may be provided by the use of auxetic fibres, an auxetic knit/weave or an auxetic lay-up. At step 302 the reinforcement is infused with a liquid polymer which may be a thermoplastic or thermosetting plastic or an auxetic polymer. At step 303 the structure is cured or hardened in an appropriate fashion determined by the materials and structures utilised.

At step 304 the laminate is removed from the curing process and at step. At step 305 the component is finished and at 306 a soft backing layer 3 may be applied if required.

Not all of the reinforcement layers necessarily include an auxetic component, and embodiments may be provided which only have an auxetic component in some of the layers. As will be appreciated the multi-layered principles of this embodiment may be applied to various structures having a combination of layers.

The armour plates described hereinbefore may be formed in any suitable dimensions as required by the application. The plates maybe utilised in personal body armour, in vehicle armour or armour for any other structure or device. The plates may be formed in any shape or contour suitable for the required use and the parameters of the structures are defined according to the protection required for that use.

Any suitable matrix may be utilised for the reinforcement layers, for example thermoplastics, thermosetting plastics, ceramics or metals.

Any suitable fibres may be utilised which will resist processing in the reinforcement layer, for example glass fibre, carbon fibre, aramid fibres and polyethylene fibres.

The reinforcement techniques described herein may also be applied to the soft backing liner.

In more conventional armour for providing protection against larger firearms a ceramic plate is commonly utilised in combination with a composite material In the current examples, which are intended to protect against cutting and stabbing, or small firearms, no ceramic plate is utilised.

Any range or device value given herein may be extended or altered without losing the effect sought, as will be apparent to the skilled person.

It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. It will further be understood that reference to 'an' item refers to one or more of those items.

The steps of the methods described herein may be carried out in any suitable order, or simultaneously where appropriate. Additionally, individual blocks may be deleted from any of the methods without departing from the spirit and scope of the subject matter described herein. Aspects of any of the examples described above may be combined with aspects of any of the other examples described to form further examples without losing the effect sought.

It will be understood that the above description of preferred embodiments is given by way of example only and that various modifications may be made by those skilled in the art. The above specification, examples and data provide a complete description of the structure and use of exemplary embodiments of the invention. Although various embodiments of the invention have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this invention.

Claims

Claims 1. An armour plate for resisting a low energy threat such as stabbing or small arms, comprising at least one layer which exhibits auxetic behaviour, wherein the armour plate does not include a ceramic layer.
2. An armour plate according to claim 1, wherein the armour plate comprises a central layer and at least one external layer, the central layer and at least one external layer having different properties; at least one of the central and external layer(s) exhibiting the auxetic behaviour.
3. An armour plate according to claim 2, wherein at least one of the central layer and external layer(s) are formed of fibres in a matrix.
4. An armour plate according to claim 3, wherein the central layer comprises glass fibres.
5. An armour plate according to claim 3 or claim 4, wherein the at least one external layer comprises carbon fibres.
6. An armour plate according to any of claims 3 to 5, wherein the auxetic behaviour is provided by the lay up of the fibres.
7. An armour plate according to any of claims 3 to 5, wherein the auxetic behaviour is provided by properties of the fibres.
8. An armour plate according to any of claims 3 to 5, wherein the auxetic behaviour is provided by properties of the matrix.
9. An armour plate according to claim 1, wherein at least one of the central and external layer(s) is a knitted layer, wherein the knitting pattern provides the auxetic behaviour.
10. An item of armoured clothing comprising an armour plate as claimed in any preceding claim.