GB2090725A

GB2090725A - Body armour

Info

Publication number: GB2090725A
Application number: GB8138925A
Authority: GB
Original assignee: LIGHTWEIGHT BODY ARMOUR Ltd
Current assignee: LIGHTWEIGHT BODY ARMOUR Ltd
Priority date: 1981-01-06
Filing date: 1981-12-24
Publication date: 1982-07-21
Also published as: GB2090725B

Abstract

Disclosed is a lightweight body armour formed from a plurality of layers of anti-ballistic fabric, such as a fabric woven from an aromatic polyamide yarn; cross-stitched together, a layer of abrasive material such as aluminium oxide particle, bonded onto a mesh fabric being adhesively attached to the front layer of anti- ballistic fabric. The armour may be covered by a waterproof envelope and contained in a conventional vest for wear by security forces. The weight of fabric used in the armour disclosed is 15.8% less than that used in equivalent armour formed from layers of the same fabric held together by light stitching only.

Description

SPECIFICATION Body armour The present invention relates to body armour and in particular to light weight flexible body armour such as bullet resistant vests.

The present invention provides a lightweight flexible body armour consisting of at least one protective element, which element comprises a plurality of layers of anti-ballistic fabric constructed to provide additional resistance to the penetration of a projectile therethrough and to reduce the blunt trauma attenuation, the said additional resistance to penetration being provided by either cross-stitching together the said plurality of layers of anti-ballistic fabric or including a layer of flexible abrasive material at or adjacent an outer layer of said fabric.

The invention also includes a light weight flexible body armour consisting of at least one protective element, which element comprises a plurality of layers of anti-ballistic fabric constructed to provide additional resistance to the penetration of a projectile therethrough and to reduce the blunt trauma attenuation, the said additional resistance to penetration being provided by cross-stitching together the said plurality of layers of antiballistic fabric and further including therein a layer of flexible abrasive material at or adjacent an outer layer of said fabric.

The expression "blunt trauma", in connection with e.g. bullet resistance vests, means "shock to the body".

In one construction the multiple layers of antiballistic fabric are cross-stitched together, the distance between the rows of stitching being in the range 1/2 to 5 calibres, preferaly 1/2 to 2 calibres. The stitch direction relative to the fabric weave in the anti-ballistic fabric can be varied, but is preferably at an angle to the said fabric weave to enable each line of stitching to interact with the maximum number of yarns in the fabric.

In this context a calibre is the diameter of the projectile for which the armour is designed to offer protection.

Cross-stitching significantly increases the protection, i.e. resistance to penetration, offered by the armour against ammunition that normally has a pointed nose and is hard cased.

In another construction the construction includes a layer of flexible abrasive material on or in the outer layer of anti-ballistic fabric forming the armour.

The abrasive material will preferably be in particulate form, e.g. grit, and may include ceramic materials such as aluminium oxide, boron carbide, silicon carbide or silicon nitride. The grit size may be between 40 and 360 grade, the size range 150 to 180 grade being especially useful.

The particulate material may be embedded in the outer layer of fabric or deposited directly thereon. It may also be retained on a separate carrier such as a paper or fabric backing sheet, which is then bonded or otherwise attached to the said outer layer of anti-ballistic fabric.

The effect of the abrasive material is to roughen the surface of the projectile, against which the armour offers protection, as it contacts the armour thereby enhancing the effectiveness of the anti ballistic fabric, especially against pointed nosed, hard cased ammunition, which can more readily retain a projectile having a roughed surface than an equivalent projectile having a smooth surface.

In a third construction the layers of anti-ballistic fabric are cross-stitched together and additionally include a layer of flexible abrasive material to provide enhanced effectiveness against projectile penetration.

The number of layers of anti-ballistic fabric employed in either construction will vary depending upon the level of protection required.

The body armour of this invention is especially suitable for use as bullet-proof vests that may be worn by police, security guards or soldiers. The number of elements of protective material contained in a vest can be varied as required.

The invention will now be more fully described with reference to the following examples.

In the examples the anti-ballistic fabric material employed was constructed from 1110 D. Tex Kevlar 29 polyamide yarn woven into a plain weave fabric at a yarn count of 12.2 ends and 12.2 picks per cm., the fabric having a nominal weight of 280 g/metre2 and finished with a water repellent coating.

Kevlar 29 is a trade mark of the Dupont Company Limited and is applied to yarns manufactured from aramatic polyamides.

The efficacy of armour specimens of the present invention was tested by the method described in NILECJ standard 0101.01 (September1977) of the Law Enforcement Standard Program issued by the United States Department of Justice. This test required that the armour test specimen be backed by a backing material comprising a 45 x 45 x 10 cm thick block of non-hardening oil-based modeling clay.

The test weapon was a 0.375 Magnum colt trooper 4 inch barrel revolver having a muzzle velocity of 350 to 390 m/sec, and the ammunition full steel jacket lead alloy core, 158 grain metal piercing projectile, manufactured by Dynamit Nobel sold under the trade name "GECO". The range of the test was three meters.

Penetration of the armour is defined as being complete perforation of the armour test sample by a test bullet or a fragment of the bullet or armour, as evidenced by the presence of that bullet or fragment in the backing material or by a hole which passes through the backing material.

Each of the test specimens of armour was covered by a water resistant envelope comprising a polyeurathene treated lightweight polyester fabric contained in an outer vest of light weight polyester/ cotton fabric.

Example 1 (control) A. An armour specimen composed of 50 layers of the anti-ballistic fabric referred to above lightly stitched to hold the layers together and in position and having a weight of 14.0 kgim2, was subjected to a series of tests according to the method specified above. The armour repeatedly failed to prevent penetration by bullets fired from the test weapon.

B. A second armour similarly constructed as A, but composed of 52 layers of fabric of total weight 14.6kg/m2, resisted penetration by single impact of bullets fired from the test weapon, producing a trauma depression in the clay backing typically 77mm diameter x 44mm deep. This armour did not have a reliable multi-hit capability.

Example 2 An armour specimen was formed from 2 x 24 packs of fabric as described above, each fabric layer being diagonally cross-stitched ata 1cm pitch (approximately 1 calibre), and in direct contact with each other. The total fabric weight being 13.5kg/m2.

This armour specimen repeatedly resisted penetration by single impact from bullets fired from the test weapon and had a multi-hit capability. Trauma depressions formed in the clay were typically 71 mm diameter x 38mm deep.

Compared with the armour of example 1 B, the armour specimen of the present example used 7.5% by weight less fabric and was significantly more effective as indicated by the test results.

Example 3 An armour specimen was formed from 2 x 21 layer packs of diagonally stitched (1 cm) fabrics with a single layer of grit mesh fabric adhesively bonded to the front face of the outside of the fabric. (Bonding was achieved by a point of adhesive at top and bottom of the outer layer of fabric). The total weight of the armour specimen was 12.3kg/m2.

The grit mesh fabric was composed of 180 grade aluminium oxide grit bonded to a flexible fabric mesh and had a total nominal weight of 540 gm/m2.

Such grit is manufactured by Koyo Sha Co. Ltd., of Tokyo, Japan and marketed in the United Kingdom by Siaco Limited, Saffron Waldon and sold underthe trade name SIANET.

The armour specimen of this construction also repeatedly resisted penetration by bullets from the test weapon and had a multi-hit capability. The trauma depression in the clay backing was typically 70mm diameter x 32 mm deep.

Compared with another specimen of example 1 B, the armour of this example was 15.8% lower in weight, which is equivalent to about 8 layers of fabric. Again the armour specimen was significantly more effective than that of example 1 B.

In addition to being equally effective against penetration of bullets fired by the test weapon using a lower fabric weight, the armour of the present invention also reduces blunt trauma as evidenced by the small depressions made in the clay backing.

In the above examples multi-hit capability means that the armour pack is capable of resisting penetration by a series of impacts provided no impact is closerthan 50mm to a previous hit or pack edge, subsequent impacts closerthan 50mm may be resisted.

Although, in the above examples, the armour was formed from two packs of fabric, it is equally effective when formed from a single pack comprising the total number of layers of fabric which are cross-stitched in the manner described.

An armour specimen manufactured according to example 2 but without cross-stitching and including a layer of grit mesh fabric adhesively bonded to the outer pack of fabric, as in example 3, was resistant to penetration by bullets fired from the test weapon at a fabric weight of 6-7% lower than that employed in example 1B.

The fabric employed in the above identified invention is not restricted to that manufactured by Kelvar yarn; any equivalent fabric manufactured from yarn would be equally satisfactory.

Claims

1. A lightweight flexible body armour consisting of at least one protective element, which element comprises a plurality of layers of anti-ballistic fabric constructed to provide additional resistance to the penetration of a projectile therethrough and to reduce the blunt trauma attenuation, the said additional resistance to penetration being provided by either cross-stitching together the said plurality of layers of anti-ballistic fabric or including a layer of flexible abrasive material at or adjacent an outer layer of said fabric.

2. A lightweight flexible body armour consisting of at least one protective element, which element comprises a plurality of layers of anti-ballistic fabric constructed to provide additional resistance to the penetration of a projectile therethrough and to reduce the blunt trauma attenuation, the said additional resistance to penetration being provided by cross-stitching together the said plurality of layers of anti-ballistic fabric and further including therein a layer of flexible abrasive material at or adjacent an outer layer of said fabric.

3. An armour according to claim 1 or claim 2 wherein, in a cross stitched layer of fabric, the distance between rows of stitching is in the range of 1/2 to 5 calibers.

4. A body armour according to claim 3 wherein the distance between the rows of stitching is in the range 1/2 to 2 calibers.

5. A body armour according to any one of the preceding claims wherein cross stitching is at an angle to the fabric weave.

6. A body armour according to claim 1 or any one of claims 3,4 or 5 as dependent upon claim 2, wherein the abrasive material is in particulate form and is adhesively bonded to a layer of flexible material.

7. A body armour according to claim 1 or any one of claims, 3,4 or 5 as dependent upon claim 2 wherein the abrasive material is in particulate form and is embedded in an outer layer of anti-ballistic fabric.

8. A body armour according to claim 6 wherein the material to which the particulate abrasive material is bonded is a fabric.

9. A body armour according to any one of claims 6,7 or 8 wherein the abrasive material is silicon carbide aluminium oxide, boron carbide, or silicon nitride grit having a particle size in the range 40 to 360 grade.

10. A body armour according to claim 9 wherein the grit size is in the range 150 to 180 grade.

11. A body armour according to any one of the preceding claims wherein the fabric is formed from an aromatic polyamide filament yarn 1110 D tex.

12. A body armour according to any one of the preceding claims wherein the fabric is a plain weave fabric.

13. A body armour according to claim 12 wherein the plain weave fabric has a yarn count of 12.2 ends and 12.2 picks per cm and has a nominal weight of 280 g/m2.

14. A body armour substantially as herein described with reference to example 2.

15. A body armour substantially as herein described with reference to example 3.