WO2008073803A2

WO2008073803A2 - Ballistic fabric

Info

Publication number: WO2008073803A2
Application number: PCT/US2007/086621
Authority: WO
Inventors: David S. Peacock; Mark Levine
Original assignee: Albany International Corp.
Priority date: 2006-12-11
Filing date: 2007-12-06
Publication date: 2008-06-19
Also published as: TW200914661A; US20080248708A1; WO2008073803A3

Abstract

The invention relates to a flexible fabric for use as for example in a roll-up shutter with improved ballistic properties. More specifically, the present invention is directed to a ballistic fabric (100) that is formed from a unique cabled yarn (70, 80) and allows less deformation on impact. The unique cabled yarn (80) may be a metal (60) reinforced aramid yarn (50) for giving the fabric additional strength.

Description

BALLISTIC FABRIC

BACKGROUND 1. Field of the Invention

This invention relates generally to flexible fabrics with improved ballistic properties. More specifically, the present invention is directed to a ballistic fabric that is formed from a unique cabled yarn and allows less deformation on impact.

2. Background Discussion

In south-east states like Florida and Louisiana, there is a need for protecting the openings of buildings such as windows and doors and other means of access, especially after looking at the aftermath of Hurricanes Charlie and Katrina. Often times such openings are covered with breakable glass, and during a storm when a loose object, such as a tree limb or the like, is blown into the glass covering the opening, there is a danger that people within the building will be injured or killed by the flying glass. For example, the states along the Gulf of Mexico, during certain times of the year, are prone to enormous and deadly storms known as hurricanes. Hurricanes often have winds which blow above 75 mph and between an average of 100 to 125 miles per hour, and in doing so, are able to blow foreign objects such as street signs, tree limbs and other types of debris into the windows of buildings, more particularly to individual homes within cities and towns affected by the storm. Shutters are mainly used to prevent flying debris from breaking the glass of the windows and letting the airflow into manufacturing plants or residential houses. Most of the damage in hurricanes is caused by the air blowing into the premises through the broken windows and shutters, which then lifts off the roof and can cause the plant or house to collapse. Preventing them from breaking prevents the majority of the damage. Rolling doors whose hanging portions are composed of individual lamella-type sections of metal or plastics material which are connected to each other by means of hinges transversely of the rolling direction have been known for decades. Rolling doors of this type can be moved only slowly because they have mechanical hinges and produce unwanted, sometimes shrieking noises when they are moved. These rolling doors are susceptible to damage during everyday operation, particularly due to impacts from vehicles, such as, stacker trucks. The repair of the damage is complicated because deformed pans, such as, steel lamellas, are difficult to replace.

Also known in the art are so-called high-speed doors which are composed of a relatively thin flexible hanging material made from webs of textile or plastics material. These doors can be moved several times faster, hi addition, they can be made air-tight against wind. However, the major disadvantage of these high-speed doors is the necessary complicated mechanism because the highly flexible materials used in the doors are not capable of transmitting thrust or pushing forces.

U.S. Patent 6,286,579 discloses a retractable storm/hurricane shade system mountable on an exterior wall above a window, which contains vertical pockets into which PVC rods arc inserted. The rods are of a length such that when they are engaged with upper and lower ends of the window frame, they are slightly bowed out and provide additional protection against the impact of wind and flying objects. This set up, however, is not mechanically stable to withstand the damage caused due to the impact of a hurricane storm.

U.S. Patent 6,296,039 discloses an apparatus for wind-locking a curtain over an opening in a building. It is mounted on an exterior wall above the window opening. A flexible corrugated curtain contains horizontal tension rods running in tracks on each side of the opening. The deployed curtain, similar to the previous one, is secured at the top, bottom, and sides of the window. The curtain in this case also does not have sufficient impact resistance to withstand the colossal impact due to a storm.

U.S. Patent 5,353,858 discloses a reinforced closing element for an industrial two-dimensional wall opening. The closing element is of a flexible material which can be rolled up and is reinforced transversely of its rolling direction by bending-resistant reinforcement layers which increase the transverse stiffness and which are embedded on both sides of a core zone within the closing element. This patent discloses that the elements can be formed of either textile or metal fibers, in which case, the closing element is either too flimsy or too stiff and does not provide the essential ballistic properties required in a door closing.

U.S. Patent 6,374,551 discloses a moveable structural reinforcement system with a moveable panel adapted to substantially close a building opening. The panel has shear load resistance means for regulating the shear stiffness of the building when the panel is in the closed position to assist in resisting earthquake forces. This property, however, is not useful in instances where the debris impacts the building surface at high speeds.

U.S. Patent 6,715,529 is a rolling shutter assembly including a plurality of interconnected metal slats. The slats travel in parallel tracks mounted on each side of the covered opening. The shutter will withstand high wind velocities and forced entries without disengagement of the slats from the track.

Although there are many references directed to protective coverage for openings, no patents disclose or teach a roll-up shutter that is both flexible and strong and allows entry of light, making it ideal for example a hurricane shutter system. Therefore, there was an immediate need for a shutter that is flexible and strong, ideal for a hurricane shutter system, something that incorporates reinforcing yarns and something that could be both flexible and ballistic at the same time.

As an existent solution to this problem, aramid based ballistic cloth/fabric have a well established application as a protective barrier (bullet proof vests, military vehicle body armor, aircraft engine containment, etc.) and therefore may be used. Most of these materials are woven to less than Im widths in very dense, multiply structures with no open area. However, as a result of the stranded nature of aramid materials, producing wide width (1 — 12m) panels of open mesh designs for protection of large objects like windows for housing, office, or business store fronts is often not feasible. Yarns produced of aramid strands tend to dimensionally flatten during weaving producing a fabric with little open area/porosity and poor dimensional stability as a result of the lack of crimp in the aramid yarns. Additionally, aramid yarns are difficult to weave as the individual strands that make up an aramid yarn, while having good tensile strength tend to abrade resulting in continuous breaks across the width during weaving. The wider the weaving width, the larger the variation in tension and degree of breakage across the face of the fabric produced.

Therefore, there is a void space in this area and the present invention provides for filling this void space with a ballistic hurricane shutter that overcomes the drawbacks of the prior art discussed above and therefore would be an advancement in the state of the art.

SUMMARY OF THE INVENTION

Briefly the invention relates to a flexible fabric, for example a roll-up shutter with improved ballistic properties. More specifically, the present invention is directed to a ballistic fabric that is formed containing unique cabled yarns. The unique cabled yarn may be a metal reinforced aramid yarn giving the fabric additional strength, and allowing less impact deformation.

Accordingly, one embodiment of the present invention is directed to a cabled metal reinforced aramid yarn for use in high-strength, high-modulus applications such as industrial, commercial or consumer shutters.

Another embodiment is directed to a ballistic fabric made from cabled metal reinforced aramid yarns that have enhanced ballistic properties and may be used in industrial applications such as industrial plant doors, shutters or coverings.

Yet another embodiment of the present invention is directed to a hurricane shutter made from cabled metal reinforced aramid yarns and has improved flexibility as well as enhanced ballistic properties. Yet another embodiment of the present invention provides for the shutter having a variety of weave patterns based on the required characteristics of the fabric. Yet another embodiment of the present invention provides for the shutter whose yarns are UV coated for outdoor exposure of such a fabric. Yet another embodiment of the present invention is directed to a ballistic fabric made from yarns with aramid strands that are used as a core material within a thermoplastic sheath. As with the use of the cabled steel, the thermoplastic sheath allows for the maximum strength of the aramid core to be realized, protects the aramid from abrasion/cutting, maintains diameter uniformity, and allows for crimp generation via plastic deformation of the sheath. Yet another embodiment of the present invention is directed to a hurricane shutter made from yarns comprising aramid strands that are used as a core material within a thermoplastic sheath, which shutter has improved flexibility as well as enhanced ballistic properties.

Other embodiments of the present invention include fabrics described above but implemented using different weave patterns and yarn combinations with one or more layers in conjunction with one or more coatings to the cabled yarn.

BRIEF DESCRIPTION OF THE DRAWINGS

To the accomplishment of the foregoing and related ends, certain illustrative aspects of the invention are described herein in connection with the following description and the annexed drawings. These aspects are indicative, however, of but a few of the various ways in which the principles of the invention may be employed and the present invention is intended to include all such aspects and their equivalents. Other advantages and novel features of the invention may become apparent from the following description of the invention when considered in conjunction with the drawings. The following description, given by way of example, but not intended to limit the invention solely to the specific embodiments described, may best be understood in conjunction with the accompanying drawings, in which: Figures 1-3 illustrate the problems associated with weaving an aramid based ballistic fabric;

Figure 4(a) illustrates the cabled metal reinforced aramid yarn according to one embodiment of the present invention;

Figure 4(b) illustrates the breaking of a cabled metal reinforced aramid yarn at the aramid's maximum tensile strength;

Figure 5 illustrates the ballistic fabric according to one embodiment of the present invention; and

Figure 6 shows a cross-section of the yarn according to one embodiment of the present invention.

DETAILED DESCRIPTION

It is noted that in this disclosure and particularly in the claims and/or paragraphs, terms such as "comprises," "comprised," "comprising," and the like can have the meaning attributed to it in U.S. patent law; that is, they can mean "includes," "included," "including," "including, but not limited to" and the like, and allow for elements not explicitly recited. Terms such as "consisting essentially of and "consists essentially of have the meaning ascribed to them in U.S. patent law; that is, they allow for elements not explicitly recited, but exclude elements that are found in the prior art or that affect a basic or novel characteristic of the invention. These and other embodiments are disclosed or are apparent from and encompassed by, the following description. Aramid based ballistic cloth/fabric have a well established application as a protective barrier (bullet proof vests, military vehicle body armor, aircraft engine containment, etc.) and therefore may be used in this area. Most of these materials are woven to less than Im widths in very dense, multiply structures with no open area. However, as a result of the yarns comprising strands of aramid materials, producing wide width (1 — 12m) panels of open mesh designs for protection of large objects like windows for housing, office, or business store fronts is often not feasible. Yarns of aramid strands or filaments tend to dimensionally flatten during weaving producing a fabric with little open area/porosity and poor dimensional stability as a result of the lack of crimp in the aramid yarns. Additionally, aramid yarns are difficult to weave as the individual strands that make up an aramid yarn, while having high tenacity tend to have continuous breaks 10 across the width during weaving, as shown in Figures 1 and 2. The wider the weaving width, the larger the variation in tension and degree of breakage across the face of the fabric produced. As an example, the fabric showed in Figure 3, formed from aramid yarns in the machine direction ("MD") and metal or stainless steel yarns in the cross-machine direction ("CD"), has fuzzy yarns 20 all over the surface of the fabric due to frequent yarn breaks during weaving. This creates undesired effects in the fabric and could also cause the fabric to fail on impact. Therefore, the present invention is directed to producing a fabric that is ballistically functional while retaining the aesthetics, open area and porosity of an open fabric.

The invention according to one embodiment of the invention is a ballistic fabric 100 made from cabled metal reinforced aramid yarns 80 that has enhanced ballistic properties and this fabric may be used in industrial applications such as industrial plant doors, or window shutters or coverings. In the cabled yarn 80, the metal part or strand 60 imparts additional strength and yarn "crimping" to stabilize the weave, while the aramid part 50 of the yarn imparts flexibility as well as impact resistance to the fabric. In any ballistic fabric, two features are most important in reducing the fabric's deformation: reinforcement beams and the mass of the fabric. The cabling of metal strands 60 with aramid strands 50 produce yarns which satisfy both these conditions in the present invention.

The invention according to another embodiment of the invention is a roll-up shutter fitted to cover the outside of residential windows to protect the window glass from breakage by tropical storm-type winds. The shutter can be made from cabled metal reinforced aramid yarns 80 of the present invention, which shutter has enhanced ballistic properties.

Specifically, the invention involves the use of modified aramid yarns to address the shortcomings of the straight aramid yarns outlined above. According to one embodiment, this invention uses yarn 50 that uses aramid as a core material in a cabled stainless steel structure 80.

As shown in Figure 4(a), steel strand 60 is wrapped, twisted or cabled around an aramid core 50 so as to obtain the benefits such as: (a) maintaining the strength of the aramid material 50 by allowing for more elongation of the steel strands 60 under tensile stress, which allows for the steel 60 to break at the aramid 50 break elongation (shown in Figure 4(b));

(b) protecting the aramid strands 50 from abrasion/cutting during weaving;

(c) maintaining diameter uniformity of the strands during weaving to maintain mesh/count, open area, and air permeability; (d) developing crimp in the final woven fabric via deformation of the cabled steel; and (e) allowing for production of uniform fabric in any width, especially widths wider than Im.

In a preferred embodiment of the present invention, the ballistic fabric 100 is produced using for example a 0.76 mm yarn, which is produced by cabling for example a 1420 denier Kevlar® 49 yarn 50 with for example a 6 x 0.20 mm 316L stainless steel wire 60 with for example 5 twists/cm, as shown in Figure 4(a). The mesh count for a fabric thus produced may be for example 5 x 4 strands per cm.

Aramids used can be made of various grades/manufacturers such as Nomex® although the Kevlar® 49 type is preferred for maximum ballistic strength. Other materials for yarns such as certain polyethylenes like

Dyneema® and Spectra® may also be used for this purpose. Steel type is not critical although stainless is preferred. A UV coating may be applied to the fabric or the component yarns individually for outdoor exposure of such a fabric.

According to another embodiment, the invention uses yarns comprising aramid strands that are used as a core material 30 within a thermoplastic sheath 40 as shown in Figure 6. As with the use of the cabled steel, the thermoplastic sheath 40 allows for maximum strength of the aramid core 30 to be realized (via elongation of the sheath, which is greater than the aramid), protects the aramid 30 from abrasion/ cutting, maintains diameter uniformity, and allows for crimp generation via plastic deformation of the sheath 40.

In a preferred embodiment of the invention, the ballistic fabric 100 is produced as using for example a 0.76 mm strand 70 produced using for example a 1420 denier Kevlar® 49 yarn 30 of 0.33 mm diameter and for example a black UV stabilized polyethylene terepthalate sheath 40 applied over the core Kevlar® strands 30. This yarn may be produced by for example a cross head extrusion method or a coating process. The mesh count for a fabric thus produced may be for example 5 x 4 strands per cm.

Aramids can be used of various grades/manufacturers such as Nomex® although the Kevlar® 49 type is preferred for maximum ballistic strength. Other materials for yarns such as certain polyethylenes like Dyneema® and Spectra® may also be used for this purpose. The UV coating may be applied to the fabric or the component yarns individually for outdoor exposure of such a fabric.

The fabric described in different embodiments of the invention can be constructed with various weave patterns known in the art including leno weaves. Combination of materials listed in different embodiments, for example cabled aramid-steel yarns and sheath core yarns, can also be employed to meet the desired ballistic properties of the fabric structure. The fabric may also be formed by combining cabled aramid-steel yarns 80 and sheath-core yarns 70 in either CD or MD directions, as shown in Figure 5 and yarns in either direction may not be limited to the same type and may comprise a combination of yarn types.

The fabric can also be made via techniques such as knitting or braiding instead of weaving. Depending upon the width or length of the shutter required techniques to form the braided or knitted sections together may be employed.

Although illustrative embodiments of the invention have been described in detail herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope and spirit of the invention as defined by the appended claims.

Claims

CLAIMSWhat is claimed is:

1. A ballistic fabric for use in a roll-up shutter or the like, the fabric comprising: a plurality of cabled yarns in MD and CD directions; wherein said cabled yarns are formed by cabling high tenacity aramid yarns with metal.

2. A method for producing a ballistic fabric, the method comprising the steps of: cabling high tenacity aramid yarns with metal; and weaving said cabled yarns in a preferred pattern to a predetermined width.

3. A ballistic fabric for use in a roll-up shutter or the like, the fabric comprising: a plurality of composite yarns in MD and CD directions; wherein said composite yarns are formed from aramid strands used as a core material within a thermoplastic sheath.

4. A method for producing a ballistic fabric, the method comprising the steps of: producing composite yarns with aramid strands used as a core material within a thermoplastic sheath; and weaving said composite yarns in a preferred pattern to a predetermined width.

5. The fabric according to claim 1, wherein said yarns are UV coated for outdoor exposure of said fabric.

6. The fabric according to claim 1, wherein the metal is stainless steel.