HK1035572B - Penetration-resistant ballistic article - Google Patents

Description

Penetration-resistant ballistic articles

Background of the invention

Field of the invention-it is well known that soft garments made for ballistic threat protection are not necessarily effective against puncture by knives or sharp instruments. This is so: items that are puncture resistant need not be effective against ballistic threats. The present invention relates to articles that protect against the threat of ice pick and knife penetration and against ballistic threats.

Discussion of the prior art-U.S. patent No.5578358 (issued on 1996, 26/11 according to For et al) discloses a puncture resistant structure made from a woven aramid yarn having a very low linear density.

International publication No. wo93/00564, published on 7.1.1993, discloses ballistic protection using a fabric layer woven from high tenacity para-aramid yarns.

U.S. patent No.5472769 (issued on 5.12.1995) describes the combination of a layer of knitted aramid yarn and a deflecting layer of a material such as metal wire as one example of a structure that attempts to provide both stab resistance and ballistic resistance.

European patent application No.670466, published 6.9.1995, discloses a bullet and puncture resistant system in which chain armor (chain mail) is embedded in a polymer resin, thereby obtaining knife stab resistance.

Summary of the invention

The invention relates to a ballistic resistant article resistant to knife and ice pick puncture, comprising: a flexible metal-based structure, a plurality of densely woven puncture resistant fabric layers, and a plurality of ballistic layers, wherein the article has an inner surface and an outer surface, and the plurality of densely woven puncture resistant fabric layers are closer to the outer surface than the plurality of ballistic layers, i.e., closer to the strike face of the puncture threat. The flexible metal-based structure may be positioned anywhere in the article and the plurality of densely woven puncture resistant fabric layers are adjacent to the flexible metal-based structure when the flexible metal-based structure is on the exterior surface and the plurality of ballistic resistant layers are closer to the interior surface than the plurality of densely woven puncture resistant fabric layers.

Detailed Description

The protected articles of the present invention were developed specifically to provide protection against "triple threats": ice punch puncture, knife puncture, and ballistic threat protection. It is becoming increasingly important that police and security personnel wearing the same protective garment be able to protect against both types of threats, namely puncture threats and ballistic threats. The inventors herein have developed puncture resistant articles and ballistic resistant articles and have unexpected findings with respect to combinations of such articles.

Although protection against "triple threats" is an important part of the present invention, the present invention also develops new structures that improve the ice pick and knife penetration resistance even without the addition of the ballistic layers described above.

Generally, flexible articles having ice pick penetration resistance are constructed using fabric layers woven from yarn materials having high tenacity; the amount of ice pick penetration resistance is related to, among other factors, the linear density of the yarn and the tightness of the weave. The lower the linear density of the yarn and the tighter the weave, the greater the resistance to ice pick penetration. For example, it is well known that excellent ice pick resistant pierceable articles are made from aramid yarns having a linear density of less than 500dtex and a fabric tightness factor of at least 0.75.

The "fabric tightness factor" and "cover factor" are names that begin with the weave density of the fabric. The cover factor is a calculated value relating to the geometry of the weave, representing the total surface area of the fabric covered by the yarns of the fabric. The equations used to calculate the coverage factor are shown below (taken from "weaving": yarn converted to fabric, Lord and Mohamed, published by Merrow (1982), pp.141- & 143):

d_wwidth of warp in fabric

d_fWidth of weft in fabric

p_wPitch of warp (number of warp yarns per unit length)

p_fPitch of weft

c_w＝d_w/p_w c_f＝d_f/p_f

Fabric coverage factor c_febTotal shielding area/enclosed area

c_feb＝[(p_w-d_w)d_f+d_wp_f]/p_wp_f

＝(c_f+c_w-c_fc_w)

Depending on the kind of fabric weave, the maximum cover factor may be quite low, even if the yarns of the fabric are located very close to each other. For this reason, a more useful indicator of fabric tightness is referred to as the "fabric tightness factor". The fabric tightness factor is a measure of the tightness of the weave of the fabric as compared to the tightness of the maximum weave, and is a function of the coverage factor.

Fabric tightness factor-actual coverage factor/maximum coverage factor

For example, the maximum coverage factor possible for a plain weave fabric is 0.75; the fabric tightness factor of a plain weave fabric having an actual cover factor of 0.68 is 0.91. The preferred weave for the practice of the present invention is a plain weave.

Flexible articles having knife penetration resistance are made using a flexible metal-based structure that is combined with an impact energy absorbing material or a second layer of penetration resistant material. The impact energy absorbing material or second layer puncture resistant material must enhance the performance of the flexible metal based structure. The impact energy absorbing material may be a soft material whose thickness decreases sharply upon impact of the energy, such as a needle-punched felt material or a non-woven material, such as rubber or an elastic sheet or foam. The second puncture resistant material may be a fabric of high strength fibers impregnated with additional chain armor or flexible resin. The materials used in conjunction with the metal-based structures are either substantially compressible when in the nature of a fabric, or impregnated with a resin.

Flexible ballistic resistant articles are made using sufficiently multiple layers of high tenacity materials to effectively resist a particular threat. These layers may include aramid, polyamide, polyolefin, or other materials commonly used for ballistic protection. Fabrics for ballistic protection typically use yarns having a fairly high linear density, and when woven, the tightness of the weave is of little concern, but not so tight as to damage the fibers of the yarns due to excessive forces of weaving.

In order to produce protective structures effective against both piercing and ballistic threats, there have been some combinations of materials, as described above and in U.S. patent No. 5472769. The inventors herein have discovered a different combination of materials that provides significant improvements in knife and ice punch penetration resistance and ballistic threaten.

This particular combination of the invention utilizes special stab and ballistic resistant materials, exhibiting good ballistic and knife and ice pick stab resistance properties, which are much greater than expected for the sum of stab resistance properties for the individual elements in the combination. Each element in the combination of the invention has a specific element to element relationship.

It has been found that the flexible metal-based structure used in the combination of the present invention does not require a material capable of absorbing impact energy, or a second layer of puncture resistant material (foam or compressible or resin impregnated fabric). Such flexible metal-based structures may be positioned anywhere in the articles of the present invention. Generally, this structure has interlocking rings, or a combination of rings and plates. The metal-based structure is made of steel, titanium, or the like. The chain armor should be light and soft and should also be puncture resistant. There is no particular requirement for the chain armour, except that the chain armour is made of metal rings, preferably from about 1.0mm to about 20mm in diameter. The diameter of the wire used to make the ring is from 0.2 to 2.0 mm.

The multi-layer densely woven fabric layer is made of yarns of high-strength fibers, the linear density of the yarns being usually less than 500dtex, and the linear density of the individual filaments in these yarns is preferably 0.2 to 2.5dtex, more preferably 0,7 to 1.7 dtex. These layers may be made of aramid yarn, polyamide, polyolefin, or other fibers commonly used to resist puncture. The preferred material for these layers is para-aramid yarn. The preferred linear density of the yarns is 100-500dtex, and the yarns are preferably woven to have a fabric tightness factor of 0.75 to 1.00, perhaps higher, and more preferably greater than 0.95. Most preferably, the tightly woven fabric layer has a correlation between the linear density (dtex) of the yarns and the fabric tightness factor as shown in the following formula:

Y＞X6.25×10^-4+0.69, wherein: y-fabric tightness factor and X-linear yarn density as shown in us patent No. 5578358.

The multiple ballistic layers can be woven or non-woven, if non-woven, the multiple ballistic layers are single woven in a single direction, and so forth. These layers may be made of aramid, polyamide, polyolefin, or other polymers commonly used for ballistic protection. The preferred structure of these ballistic layers is a woven para-aramid yarn having a linear density of 50 to 3000 dtex. If woven, a plain weave is preferred, although other weave types may be used, such as a basket weave, a satin weave, or a twill weave. The preferred para-aramid is poly (p-phenylene-terephthalylidene amide).

The tenacity of the yarns used in any fabric layer in the present invention is greater than 20 grams per dtex and up to 50 grams per dtex or greater; elongation at break of at least 2.2% and can be as high as 6% or greater; the modulus is at least 270 grams per dtex and can be as high as 2000 grams per dtex or greater.

The combination of three elements of the present invention is made by placing the three elements together face-to-face, with or without additional layers of material between each layer of material as desired. Other layers of material that may be placed between the three elements include, for example, waterproof materials, atraumatic materials, and the like. As described above, according to the present invention, it is sufficient to obtain resistance to penetration of knives and ice penetrators using only two of the elements. Also, it will be understood that the outer surface or strike face of the article of the invention need not be the entire outer surface or exposed face of the article. It is sufficient if this outer surface is the outer surface of the article of the invention. The same is true for the inner surface. By "interior surface" is intended to represent the interior surface of the article of the present invention.

It has been found that the combination of elements according to the invention results in a resistance to penetration by knives and ice penetrators which is much greater than the sum of the individual resistances to penetration by knives and ice penetrators exhibited by the elements individually.

The key point of the invention lies in the following findings: different materials arranged in one way produced very poor results, but arranged in another way gave unexpectedly good results. The high knife penetration resistance of the present invention is provided by the flexible metal-based structure, which does not require a secondary layer that is compressible or impregnated with resin, because it is incorporated with other components within the article of the present invention. The flexible metal-based structure may be positioned anywhere in the article. The high ice punch penetration resistance of the present invention is provided by the densely woven fabric layer, and in order to achieve high ice punch penetration resistance, the densely woven fabric layer must be located closer to the ice punch threat impact point, the strike face, than the ballistic layer. The high ballistic penetration resistance of the present invention is provided by ballistic layers that can be positioned anywhere within the article, but not on the strike face.

If the above-described limitations are specified for the location of the elements, it will be appreciated that there are only 3 different arrangements for the 3-element embodiment of the invention. That is, from the outer surface (face): (1) a flexible metal-based structure, a densely woven fabric layer, a bulletproof layer; (2) a densely woven fabric layer, a bulletproof layer and a flexible metal base structure; (3) a tightly woven fabric layer, a flexible metal-based structure, a ballistic layer.

Test method

Linear density ofThe linear density of the yarn is determined by weighing a known length of yarn. "dtex" is defined as the weight in grams of 10000 meters long yarn.

In practice, the measured dtex, test conditions, and sample identifier of the yarn sample are all added to the computer, and the test is then restarted; the computer records the load-elongation curve of the yarn at break and then calculates the properties of the yarn.

StretchabilityThe yarns tested for stretchability were conditioned first and then twisted to a twist multiplier of 1.1. The Twist Multiplier (TM) of the yarn is defined as:

TM ═ number of turns/cm (dtex)^1/2/30.3

The yarns to be tested were conditioned at 25 ℃ and 55% relative humidity for a minimum of 14 hours and tensile tests were carried out under these conditions. Tenacity (break tenacity), elongation at break, and modulus were determined by testing the yarns at break on an Instron tester (Instron Engineering corp., Canton, Mass).

Tenacity, elongation, and initial modulus were determined in ASTM D2101-1985 using 25.4cm yarn to measure length and elongation at 50% strain/min. The modulus is calculated from the slope of the stress-strain curve at 1% strain and is equal to 100 times the stress (in grams) at 1% strain (absolute) divided by the linear density of the test yarn.

ToughnessTenacity, which is the area (a) under the stress-strain curve up to the yarn breaking point, was determined using the stress-strain curve obtained from the tensile test. This area is typically determined using an area meter to provide an area in square centimeters. Dtex (D) is "linear density" as described above. Tenacity (To) is calculated as follows:

To＝A×(FSL/CFS)(CHS/CS)(1/D)(1/GL)

wherein;

FSL-full scale load, g

CFS-chart full scale, cm

CHS-crosshead speed, cm/min

CS ═ chart speed, cm/min

GL-measured length of the test specimen

The digitized stress/strain data can of course be added to a computer to directly calculate the toughness. This result is To, in dN/tex. And multiplied by 1.111 to convert to grams per denier. When the units of length are the same before and after, the unit in which To is calculated from the above equation is determined only by the unit selected for Forces (FSL) and D.

Puncture resistanceThe puncture resistance of an ice punch was determined on a multilayer fabric using an ice punch 18 cm (7 inches) long, 0.64 cm (0.25 inches) axial diameter, and a rockwell C-42 hardness. The tests were performed according to HPW test TP-0400.03 from h.p.white lab, inc. The test specimens were placed on 10% gelatin pads, impacted with an ice punch weighing 7.35 kilograms (16.2 pounds), and allowed to fall from various heights until penetration of the test specimens was achieved. The ability to resist knife penetration was determined using the same procedure as described above. Except that the ice punch was replaced by a boning knife (manufacturer; Russell Harrington Cutlery, inc., Southbridge, Massachusetts, USA.) having a single-sided edge length of 15cm (6 inches), a width of about 2cm (0,8 inches), and a rockwell hardness of C-55 as the blade becomes thinner toward the tip. The result is the penetration energy (joule) obtained by multiplying the energy at the penetration height by 9.81 in kilograms.

Bulletproof performanceThe ballistic testing of the multilayer panels was carried out as follows in order to determine the ballistic limit (V50) according to MIL-STD-662E, except for the choice of bullets: the plate to be tested is placed on the sample holder to keep the plate taut and perpendicular to the path of the test bullets. The bullet was a 9mm full metal case pistol cartridge weighing 124 grains (1 grain 64.8 mg) and was fired from a test chamber capable of firing the bullet at different speeds. The first shot for each panel was to make the estimated bullet velocity the ballistic limit (V50) possible. When the first shot produced a complete penetration, the next shot was to reduce the bullet velocity by about 15.2 meters (50 feet) per second to obtain a partial penetration of the panel. On the other hand, when the first shot did not penetrate or partially penetrated, the next shot was made to be about 15.2 meters (50 feet) per secondIs increased in speed in order to obtain complete penetration of the plate. After partial and full bullet penetration is achieved, the bullet velocity is then increased or decreased at about 15.2 meters (50 feet) until sufficient shots are taken to determine the ballistic limit (V50) of the panel.

The ballistic limit (V50) is calculated by taking the arithmetic average of an equal number of at least 3 highest partial penetration impact velocities and at least 3 lowest full penetration impact velocities, provided that the difference between the highest and lowest individual impact velocities is no greater than 38.1 meters (125 feet) per second.

Comparative examples 1 to 4The tests of the comparative examples were carried out using various densely woven ballistic layers made from aramid yarns. The yarns are poly (p-phenylene-terephthalamide) sold by E.I.du Pont de Nemours and Company under the trademark Kevlar^。

A densely woven puncture resistant fabric layer was made using a 10 layer fabric woven from 220dtex aramid yarn having a tenacity of 24.3 g/dtex, a modulus of 630 g/dtex, an elongation at break of 3.5%, a plain weave of 27.5 x 27.5 ends per square centimeter and a fabric tightness of 0.995. The areal density of this element was 1.27 kg/m²(hereinafter, represented by "A").

The ballistic element was made using 18 layers of fabric woven from 930dtex aramid yarn with a tenacity of 24.0 g/dtex, a modulus of 675 g/dtex, an elongation at break of 3.4%, a plain weave of 12.2 x 12.2 ends per square centimeter, and a fabric tightness of 0.925. The areal density of this element was 4.00 kg/m²(hereinafter, represented by "B").

The purpose of the comparative example is to provide a data base for the ice pick and knife penetration resistance without using a flexible metal based structure.

The layers are tested individually and in combinationTrials were conducted at the ballistic limit in both cases. The assembly is achieved by bringing the elements together face to face. The results of the tests are shown in the lower table, where "outer" represents the tested face.

			Penetration energy (Joule)
						Comparative example	Outer face	Inside is provided with	Ice wear	Knife with cutting edge	Bulletproof Limit V50 (m/s)
1	B	Is free of	0.8	4.5	442
						2	A	Is free of	20.1	1.8	-
3	B	A	3.7	8.5	-
						4	A	B	137	8.5	478

For the "puncture resistance test" described in "test methods", the result of the test is the penetration energy in joules. It should be noted that the ballistic element ("B") alone has little penetration resistance against ice penetrators and has a rather small penetration resistance against knives. The individual "a" elements exhibit a corresponding resistance to penetration by ice pick, but have minimal resistance to penetration by a knife. When a and B were tested in combination and B was used as the strike face, both the ice pick resistance and the penetration ability of the blade were low.

When a and B were tested in combination and a was used as the striking face, both ice pick resistances were high.

Examples 5 to 9

The following example tests were carried out using the same elements a and B as in comparative examples 1 to 4; and using a flexible metal based structure as follows:

c1-1 layer of chain armor sheet having 4 welded rings of 0.8mm diameter stainless steel passing through each ring, basis weight 3.19kg/m²。

C2-1 layer of chain armor sheet having 4 welded rings of 0.9mm diameter stainless steel passing through each ring, basis weight 4.11kg/m²。

Various combinations of ice pick and knife penetration resistance test elements were performed at the ballistic limit in both cases. The results of the tests are shown in the lower table, where "outer" represents the tested face.

				Penetration energy (Joule)
							Examples	Outer face	Middle surface	Inside is provided with	Ice wear	Knife with cutting edge	Bulletproof Limit V50 (m/s)
5	C1	A	B	114	＞180	473
							6	B	C1	A	7.3	54.2	469
7	A	C1	B	114	164.7
							8	C2	A	B	128.3	＞180
9	B	C2	A	12.8	137.3

It should be noted that the addition of the flexible metal-based structure greatly improves the penetration resistance against the knife compared to the comparative example. However, the most significant feature and the most representative one of the embodiments of the invention consists in the improved penetration resistance against knives, which is obtained when the densely woven element (a) is located closer to the striking face than the ballistic element (B). And (3) comparison: examples 5 and 6, examples 7 and 6, and examples 8 and 9.

Examples 10 and 11

The following example tests were performed using the same elements a and B as used before; and using a flexible metal based structure as follows:

a layer of C3-1 consisting of a plurality of aluminum plates of about 2cm by 2.5cm by 0.1cm held together by rings passing through each corner of each plate, having a basis weight of 4.13kg/m²。

Various combinations of elements were tested for ice pick resistance and knife penetration ability. The results of the tests are shown in the lower table, where "outer" represents the tested face.

				Penetration energy (Joule)
						Example (b)	Outer face	Middle surface	Inside is provided with	Ice wear	Knife with cutting edge
10	C3	A	B	＞180	＞180
						11	B	C3	A	45.8	173.9

It should be noted that although C3 improves the penetration resistance against ice-strike and knife in both configurations tested, the greatest improvement in penetration resistance against knife can be obtained if a configuration is used in which the closely woven element (a) is located closer to the strike face than the ballistic element (B), compared to the same configuration previously used with C1 and C2.

Comparative examples 12 and 13 and example 14

These tests were performed in order to improve the ice pick and knife penetration resistance of the article, provided that the article omits the ballistic element.

The flexible metal-based structure is the chain from example 5Armor element C1, a densely woven puncture resistant fabric layer designated "A1", element A1 being identical to element A described above, but made using 30 fabric layers instead of the 10 fabric layers described above, and element A1 having an areal density of 3.81kg/m²。

Also, as one component in the comparative example, an aramid fabric structure was used which was made using an aramid fabric woven from 930dtex aramid yarn and which had a tenacity of 24.0/dtex, a modulus of 675 g/dtex, an elongation at break of 3.4%, a plain weave of 12.2X 12.2 warps/square centimeter, and a fabric tightness factor of 0.925. A total of 30 layers of this part were used and the areal density of this part was 6.81kg/m²(hereinafter, this component is denoted by A2).

The ice pick and knife penetration resistance was tested for various combinations of a1, a2, C1. The results of the tests are shown in the table below.

Example (b)	Outer face	Inside is provided with	Penetration energy (Joule)
								Ice wear	Knife with cutting edge
Comparative example 12	A1	Is free of	＞180	9.0
					Comparative example 13	C1	A2	3.7	＞180
14	C1	A1	＞180	＞180

It should be noted that while a1 provides penetration resistance against ice penetrators, the combination of C1 and an aramid fabric layer that is not so densely woven provides minimal penetration resistance against ice penetrators. However, the combination of C1 and a1 exhibited significant penetration resistance against both ice pick and knife as the article of the present invention.

Claims (13)

1. A ballistic resistant article resistant to puncture by knives and ice penetrators comprising: a flexible metal structure, a plurality of densely woven puncture resistant fabric layers, and a plurality of ballistic layers, the flexible metal structure being comprised of interlocking metal rings or a combination of metal rings and plates, wherein the article has an inner surface and an outer surface, the flexible metal structure being positionable at any location in the article, the plurality of densely woven puncture resistant fabric layers being positioned at or near the outer surface when the flexible metal structure is at the outer surface, and the plurality of ballistic layers being closer to the inner surface than the plurality of densely woven puncture resistant fabric layers.

2. The article of claim 1, wherein: the outer surface is the strike face of the puncture threat.

3. The article of claim 1, wherein: the densely woven puncture-resistant layer comprises a fabric woven from aramid yarns having a linear density of less than 500dtex, and is further characterized by: the fabric is woven to have a fabric tightness factor of at least 0.75.

4. The article of claim 1, wherein: the densely woven puncture-resistant layer comprises a fabric woven from aramid yarns having a linear density of less than 500dtex, and is further characterized by: the fabric is woven to have a fabric tightness factor of at least 0.95.

5. The article of claim 3, wherein: the aramid yarn is a para-aramid yarn.

6. The article of claim 3, wherein: the yarn of the puncture resistant layer has a linear density of 100-500dtex and the monofilament has a linear density of 0.7-1.7 dtex.

7. The article of claim 1, wherein: the elongation at break of the fibers used to make the ballistic layer is greater than 2.2%, the modulus is greater than 270 g/dtex, and the tenacity is greater than 20 g/dtex.

8. The article of claim 7, wherein: the fibres of the ballistic layer are yarns with a linear density of 50-3000 dtex.

9. The article of claim 7, wherein: the yarns of the ballistic layer are woven.

10. The article of claim 8, wherein: the yarns of the ballistic layer are non-woven.

11. The article of claim 8, wherein: the yarns of the ballistic layer are para-aramid.

12. The article of claim 8, wherein: the yarns of the ballistic layer are polyethylene.

13. An article resistant to puncture by knives and ice piercers comprising: a flexible metal structure comprising interlocking metal loops or a combination of metal loops and metal plates, a plurality of densely woven puncture resistant fabric layers, said fabric layers being woven from aramid yarns having a linear density of less than 500dtex, characterized in that: the fabric is woven to a fabric tightness of at least 0.95.