Patent Application
20160281271
The embodiments herein relate to fabrics, and in particular to woven fabrics for use in ballistic applications, and methods of making the same, as well as to rigid and semi-rigid composite armor panels made using such woven multi-layer fabrics and incorporating a resin therein.
Woven fabrics are fabrics in which two distinct sets of yarns are interwoven with each other to form the fabric. Typically, woven fabrics include warp yarns that run lengthwise along the fabric and weft yarns that run across the length of the fabric, and which are interwoven with and generally perpendicular to the warp yarns.
In some ballistic applications, it is desired that two or more layers of woven fabrics be secured together. This may be done by providing the woven fabrics separately and then combining them to produce a multi-layer structure. For example, separate layers of fabric may be laid up and then joined together using only a resin. In other cases, multiple layers of woven fabric may be stitched together after being manufactured as separate layers. However, there tends to be a number of drawbacks with stitching layers together. Since stitched fabrics use needles that penetrate through the layers of yarn, gaps may be formed where the stitches are provided. Furthermore, the penetration of the needles may cause damage to the yarns. These results are generally undesirable.
The drawings included herewith are for illustrating various examples of articles, methods, and apparatuses of the present specification and are not intended to limit the scope of what is taught in any way. In the drawings:
Generally illustrated in
The fabric 10 has a first (or upper) woven layer indicated generally as 11. The upper woven layer 11 includes first (or upper) warp yarns 12 and first (or upper) weft yarns 14 (e.g. 14a, 14b, 14c, 14d) that are interwoven together to form the first or upper woven layer 11. The first warp yarns 12 and first weft yarns 14 in the upper woven layer 11 are crimped, in the sense that each first yarn 12, 14 is bent around the other first yarns 12, 14 at crossover points or nodes to provide an interlocking or interwoven structure.
The fabric 10 also has a second (or lower) woven layer indicated generally as 13. The lower woven layer 13 includes second (or lower) warp yarns 15 and second (or lower) weft yarns 17 (e.g. 17a, 17b, 17c, 17d) that are interwoven together to form the second or lower woven layer 13. The second warp yarns 15 and second weft yarns 17 in the second layer 13 are crimped, in the sense that each second yarn 15, 17 is bent around the other yarns 15, 17 at crossover points or nodes to provide an interwoven structure.
It will be appreciated that the terms “upper” and “lower” as used herein are used for convenience only, and the actual relative positions of the first woven layer 11 and the second woven layer 13 may be varied (i.e., their relative positions may be inverted, for instance).
Generally in the multi-layer fabric 10 the yarns of one layer are not interwoven with the yarns of another layer because such interweaving tends to increase the degree of crimp for the yarn in relation to rest of the yarns in the fabric, which can create ballistic weak points. In particular, in this fabric 10 the first or upper yarns 12, 14 are not interwoven with the second or lower yarns 15, 17, and vice versa. Instead, as shown, the first or upper layer 11 and second or lower layer 13 are secured together by one or more securing yarns 22. The securing yarns 22 are interwoven with at least some of the upper yarns 12, 14 and some of the lower yarns 15, 17 so as to secure the upper and lower layers 11, 13 together.
The securing yarns 22 generally form part of the woven fabric 10. In particular, the woven fabric 10 is formed by interweaving the securing yarns 22 with the warp yarns 12, 15 and weft yarns 14, 17 as the fabric 10 is formed. Therefore, the upper and lower woven layers 11, 13 can be secured together without the need for stitching, resin or other mechanisms to join the woven layers 11, 13 together.
In this manner, a fabric 10 having two (or more) woven layers 11, 13 can be manufactured as a unified construction, without the need for joining two different fabric layers together after the fabric layers are formed individually.
Manufacturing the fabric as a unified construction also tends to provide a lower crimp level for each layer, which tends to maintain or improve potential ballistic performance of the individual layers while achieving additional advantages associated with securing the layers together, such as higher integrity, enhanced trauma and overall ballistic performance as well as manufacturing advantages.
As shown, in some embodiments the securing yarns 22 may be aligned with the warp or weft yarns. For example, the securing yarns 22 may be generally parallel to or aligned with the warp yarns 12, 15 and generally perpendicular to the weft yarns 14, 17. In other embodiments, the securing yarns 22 may be generally parallel to or aligned with the weft yarns 14, 17 and generally perpendicular to the warp yarns 12, 15. In yet other embodiments (e.g. as shown in
Turning now specifically to
While the illustrated embodiment shows a securing yarn extending over and under one weft yarn at a time, in other embodiments, the securing yarns may extend over or under more than one weft yarn at a time. For example, the securing yarns may be woven underneath two weft yarns, and then above five upper weft yarns adjacent the lower weft yarns. Accordingly, the securing yarns may be woven underneath at least one lower weft yarn, and then above at least one upper weft yarn adjacent the at least one lower weft yarn.
In some embodiments, one or more of the warp yarns 12, 15 and/or weft yarns 14, 17 could be used in addition to, or in place of, one or more securing yarns 22 for holding the two or more layers together. For example, one or more the of the warp yarns 12, 15 and/or the weft yarns 14, 17 could be interwoven along a path similar to the path of the securing yarn 22 as shown in
Each of the warp yarns 12, 15 and weft yarns 14, 17 and securing yarns 22 may include a plurality of fibers or filaments of one or more materials as will be described in greater detail below. For example, in various cases each of the warp yarns 12, 15 and weft yarns 14, 17 and securing yarns 22 may include one or more ballistic yarns, one or more non-ballistic yarns, or both ballistic and non-ballistic yarns.
In some embodiments, the selection and arrangement of the securing yarns 22 may be varied to obtain desired performance of the fabric 10. For example, the size, ratio and/or spacing of securing yarns 22 may be different in different embodiments of the fabric 10.
In some embodiments, a plurality of securing yarns 22 could be spaced apart from each other by a distance of between one inch and three inches. In other embodiments, securing yarns 22 may be spaced apart by a distance of less than one inch. In yet other embodiments, securing yarns may be spaced apart by a distance of more than three inches.
The ratio between securing yarns 22 and ballistic yarns (e.g. warp yarns 12, 15 and weft yarns 14, 17) as well as the spacing therebetween tends to depend on the desired inter-layer stability (e.g. providing more securing yarns 22 and/or providing securing yarns 22 spaced closer together tend to result in a more stable fabric 10) versus the degree of interference between the woven layers 11, 13 (e.g. more securing yarns 22 tend to result in the woven portions deviating more from a conventional woven fabric, e.g. which may cause more distortion between the woven fabric layers).
In some embodiments, the securing yarns 22 are made from a high elongation yarn, a low strength, and/or a low modulus yarn, as generally described below.
In some embodiments, the warp yarns 12, 15 and weft yarns 14, 17 are ballistic yarns. For example, the warp yarns 12, 15 and weft yarns 14, 17 may be ballistic yarns having a tenacity of about 15 grams per denier and higher, and with a tensile modulus of at least about 400 grams per denier.
Some examples of suitable yarns could include carbon, basalt and glass fibers. Other examples include aramid and copolymer aramid fibers (produced commercially by DuPont and Teijin under the trade names Kevlar®, Twaron®, and Technora®), extended chain polyethylene fibers (produced commercially by Honeywell, and DSM, under the trade names Spectra®, and Dyneema®), polyethylene fibers and films produced by Synthetic Industries and sold under the trade name Tensylon®, poly(p-phenylene-2,6-benzobisoxa-zole) (PBO) (produced by Toyobo under the commercial name Zylon®), and Liquid crystal polymers produced by Kuraray under the trade name Vectran®. Other suitable yarns may also be used.
In some embodiments, the securing yarns 22 are generally of significantly smaller denier than the warp yarns 12, 15 and/or weft yarns 14, 17 and may have significantly lower tenacities and tensile moduli. As a result, the securing yarns 22 tend to greatly reduce or eliminate undesirable deflection or distortion of the first and second layers 11, 13. In particular, the securing yarn 22 may be substantially crimped while it may be desirable to have the layers 11, 13 be as flat as possible.
In some examples, the securing yarns 22 have a tenacity of less than about 10 grams per denier, and a tensile modulus of less than about 40 grams per denier. In one example, the securing yarns 22 are made of a 78 dtex Nylon, while the warp yarns 12, 15 and weft yarns 14, 17 may be made of a 3000 denier aramid (e.g. Kevlar®).
In some examples, the denier of the securing yarns 22 may range from between about 20 denier (or less), to about 1000 denier, depending on the size of the warp yarns 12, 15 and weft yarns 14, 17, and the desired ballistic applications.
In some embodiments, the securing yarns 22 may be generally of a much smaller size than the warp yarns 12, 15 and weft yarns 14, 17. The diameter of the securing yarns 22 may be selected based on the moduli and strength parameters of the securing yarns 22. In some embodiments, where the securing yarns 22 are made of non-ballistic yarns (e.g. Nylon, etc.), it may be desirable that the securing yarns 22 be high elongation yarns that are as stretchy as possible and as small as possible.
In some embodiments, one or more of the warp or weft yarns could be used as one or more securing yarns.
In some examples, the securing yarns 22 may be selected from a wide range of fibers. Some suitable example fibers include natural fibers, such as cotton, wool, sisal, linen, jute and silk. Other suitable fibers include manmade or synthetic fibers and filaments, such as regenerated cellulose, rayon, polynosic rayon and cellulose esters, synthetic fibers and filaments, such as acrylics, polyacrylonitrile, modacrylics such as acrylonitrile-vinyl chloride copolymers, polyamides, for example, polyhexamethylene adipamide (nylon 66), polycaproamide (nylon 6), polyundecanoamide (nylon 11), polyolefin, for example, polyethylene and polypropylene, polyester, for example, polyethylene terephthalate, rubber and synthetic rubber and saran. Glass, carbon or any other high performance fiber may also be used.
Staple yarns may also be used and may include any of the above fibers, low denier staple yarns or any combination of these yarns. Staple yarns, by the discontinuous nature of their filaments that form the yarn, tend to have much lower tensile and modulus properties as opposed to yarns composed of continuous filaments.
The performance of the fabric 10 is generally a function of the properties of the securing yarns 22 and the warp yarns 12, 15 and weft yarns 14, 17. In ballistic fabrics, maximizing the amount of the ballistic fibres (e.g. the warp yarns 12, 15 and the weft yarns 14, 17) in a given volume tends to be beneficial, as higher fibre to volume ratio fraction generally signifies improved ballistic properties. Therefore, in some examples it may be desirable that the securing yarns 22 have a denier that is as low as practical while still being able to weave the fabric 10.
In the fabric 10, it may be desirable to minimize the weight of the securing yarns 22 as a percentage of the total weight of the fabric 10, since the securing yarns 22 may not contribute as much to the strength of the fabric 10 as the ballistic yarns (e.g. the warp yarns 12, 15 and the weft yarns 14, 17). Conversely, an increased quantity of securing yarns 22 may result in a more durable, stable fabric 10; however, the fabric 10 may tend to be heavier.
In some examples, the securing yarns 22 may be selected to have the lowest denier, and the lowest strength as practical that can be woven between the layers, and that satisfy the requirements for a particular ballistic application.
In some embodiments, two or more fabrics 10 may be joined together to form a ballistic member having four or more woven layers (e.g. two fabrics 10 may be joined using a resin, film or other suitable techniques to form a fabric that has four woven layers).
The fabric 10 may also be fabricated into a prepreg using a film or a wet resin. Depending on the application, the film or resin may be applied to one side of the fabric 10, the fabric 10 may be totally impregnated with a resin, or the film may be worked into the fabric 10. In some examples, the film or resin may be a thermoplastic or a thermoset resin. Generally, any resin or film that can be used to create a prepreg may be used with this fabric 10. In some embodiments, two or more layers of fabric 10 may be laminated together to further increase the number of layers.
In some embodiments, three or more woven layers may be secured together to form a fabric using one or more securing yarns that are interwoven as the fabric is being made.
Turning now to
Referring now to the close up of
In one exemplary embodiment, a multi-layer woven fabric according to
As shown, the woven multi-layer fabric tends to provide similar performance as a conventional fabric while providing at least some of the advantages as generally described herein. For example, the new multi-layer fabric has gone through about half the number of processing steps in comparison to the conventional fabric, which is advantageous for both performance and cost.
In some embodiments, the multi-layer fabric might be used with a resin. If the fabric has high adhesion to the resin, the securing yarn can dissipate energy by breaking during the ballistic event while the resin keeps the other layers together and prevents trauma.
Turning now to
The offset design also tends to improve ballistic performance by reducing the number and/or size of openings between yarns in the fabric because the yarns of one layer cover openings in the adjacent layer, as described below.
In some ballistic applications, it is sometimes desirable to lower the cover factor of the fabric (e.g. by spacing apart yarns and providing openings therebetween) in order to increase the number of fabric layers in a pack for a given areal density. The increased number of fabric layers tends to enhance the ballistic V50 performance. However, there is a limit to the increase in performance because having a cover factor that is too low results in an open construction, which tends to increase the bullet penetration during a ballistic event and hence lowers the ballistic resistance. The offset design described above tends to enhance ballistic performance for a given yarn size and ballistic areal density by providing the layering effect while covering the openings in each layer with the yarns of the adjacent layer as the two layers are interwoven in an offset layering pattern.
On the other hand, in some embodiments (particularly hard armor embodiments), it may be desirable to have higher cover factors, as they tend to perform better in hard armor applications This tends to be dependent on the resin type (i.e., thermoset vs. thermoplastic) and fiber type (i.e., PE vs. aramid).
In some embodiments, some of the warp yarns and/or weft yarns may at least partially overlap, which the inventor believes may tend to increase the ballistic performance.
As shown, the first layer 211 and second layer are secured together by a plurality of first securing yarns 222a and a plurality of second 222b (generally similar to the securing yarns 22 as described above) that are generally perpendicular to each other and which are arranged in an array or pattern. For example, the first securing yarns 222a may be oriented in a first direction (e.g. the warp direction), while the second securing yarns 222b may be oriented in a second direction (e.g. the weft direction).
As shown, the first securing yarns 222a may be separated from each other by a first spacing T, while the second securing yarns 222b may be separated from each other by a second spacing S. The first and second spacings T, S may be similar or different. Generally, the spacings T, S may be selected so as to obtain desired properties for the fabric 210.
In some embodiments, the first spacing T may be between one inch and three inches. In other embodiments, the first spacing T may be less than one inch, or more than three inches.
In some embodiments, the second spacing S may be between one inch and three inches. In other embodiments, the second spacing S may be less than one inch, or more than three inches.
In some embodiments, the layers of fabric may be secured using securing yarns that extend in only one direction (e.g. the weft direction only).
Turning now to
At step 102, warp yarns are provided. For example, first warp yarns 12 and second warp yarns 15 may be provided on a loom or weaving machine (e.g. standard 2D weaving looms, including rapier, shuttle, air jet and water jet looms).
At step 104, weft yarns are interwoven with the warp yarns to form at least two woven layers (e.g. a first woven layer and a second woven layer). For example, the first weft yarns 14 could be interwoven with the first warp yarns 12 by alternatively moving the first warp yarns 12 up and down and passing a shuttle with the first weft yarns 14 therebetween, as will generally be understood. Similarly, the second warp yarns 15 could be interwoven with the second weft yarns 17 to form the second woven layer 13.
At step 106, the securing yarns are interwoven with the warp yarns and/or the weft yarns as the fabric is being made (e.g. as the weft yarns and warp yarns are being woven together) to secure the first and second woven layers together. For example, the securing yarns 22 may be alternatively interwoven with the first and second warp yarns 12, 15 by selectively moving the warp yarns 12, 15 up and down and passing a shuttle with the securing yarns 22 therethrough as the warp yarns 12, 15 and weft yarns 15, 17 are being woven together.
It will be appreciated that the steps 102, 104 and 106 of the method 110 generally do not have to be done in a specific order and that the order as listed is in no way meant to be limiting.
Turning now to
The upper woven layer 311 includes warp yarns 312 and upper weft yarns 314 (e.g. 314a, 314b, 314c, 314d) that are interwoven together to form the first or upper woven layer 311. The lower woven layer 313 includes lower warp yarns 315 and lower weft yarns 317 (e.g. 317a, 317b, 317c, 317d) that are interwoven together to form the second or lower woven layer 313. The upper and lower woven layers 311, 313 are secured together using one or more securing yarns 322 generally as described previously.
As shown, the upper weft yarns 314 and lower weft yarns 317 are offset so that, for example, the first upper weft yarn 314a overlaps the first lower weft yarn 317a by an overlap amount P. Accordingly, the securing yarn 322 tends to be less crimped and more spread out (as compared to the more compact path of the securing yarn 22 described above).
In some embodiments, the overlap amount P is between 10% and 95%. In other embodiments, the overlap amount P is between 30% and 70%. In other embodiments, the overlap amount is around 50%. In some embodiments, the overlap amount P may be above 95%. In some embodiments, the overlap amount P may be above 98%, or even 99%, or even approaching or at 100%.
Turning now to
The upper woven layer 411 includes warp yarns 412 and upper weft yarns 414 (e.g. 414a, 414b, 414c, 414d) that are interwoven together to form the first or upper woven layer 411. The lower woven layer 413 includes lower warp yarns 415 and lower weft yarns 417 (e.g. 417a, 417b, 417c, 417d) that are interwoven together to form the second or lower woven layer 413. The upper and lower woven layers 411, 413 are secured together using one or more securing yarns 422 generally as described above.
As shown, the upper weft yarns 414 and lower weft yarns 417 are offset similar to the fabric 310, so that, for example, the first upper weft yarn 414a overlaps the first lower weft yarn 417a by an overlap amount P. In this embodiment, the upper weft yarns 414 and lower weft yarns 417 are generally more evenly spaced apart by the overlap distance P.
Turning now to
In this embodiment, the plain woven portions 525 and satin woven portions of the upper and lower layers 511, 513 are aligned. For example, as shown a first plain woven portion 525a on the upper layer 511 is aligned with and positioned above a second plain woven portion 525b on the lower layer.
Turning now to
While the embodiments of
Multi-layer woven fabrics made with Platin™, and as described above, were created and tested in a ballistic 9 mm V50 test, with the following results:
As show, the performance of the 2 layer Platin fabric with matching patterns performed better than the other two fabrics.
In another exemplary embodiment, a multi-layer woven fabric with offset woven layers was created and tested in a ballistic 9 mm test as well as a .22 CAL 17 grain FSP test and compared to a plain fabric. The offset woven layers were secured together using securing yarns aligned with the weft yarns only. The securing yarns were spaced separated by a spacing of about a ¼ of an inch. The ballistic tests for these fabrics were conducted in a standard setting for a 16″×16″ pack using a 9 mm Remington and a .22 CAL FSP at an areal density of 1.1 lb/ft2 for both samples, with the following results:
The performance in the 9 mm and .22 CAL FSP tests were both improved. Furthermore, the performance in the .22 CAL FSP test was improved with the offset fabric by 33 feet, an increase of approximately 5.3%.
The new fabric with offset woven layers had a higher performance in both tests with fewer layers of fabric. This is despite the conventional understanding that a fabric having a lower cover factor and more layers of fabric for a given areal density should perform better. The inventor believes that the increased performance is due to the offset design, in which the coverage for each yarn within the fabric structure is maximized by having each direction yarn (warp or weft) sitting at two levels with overlaps.
While the exemplary embodiment tested utilized securing yarns aligned with the weft yarns and spaced apart by about a ¼ of an inch, in other embodiments, the securing yarns may be aligned with the warp yarns and/or the weft yarns, and may be separated by a spacing of less than three inches.
Some of the fabrics described herein may generally be used in any combination with the materials listed above and may replace any one material or combination of materials in an existing ballistic fabric. In addition, the fabrics described herein may be laminated together or laminated with films to produce ballistic elements for various applications, including soft armor applications, hard armor applications, and rigid and/or semi-rigid applications. The proportions of each material selected and the design of the ballistic elements may vary depending on the intended application (i.e. particular specifications for military or police applications).
Generally, the multi-layer fabrics described herein utilize a unique technique to secure fabric layers together and limit the use of extra stitching and resin application unless desired for providing particular properties.
Turning now to
Similarly,
Lastly,
It has been discovered that in some cases the multi-layer fabrics as described herein may be particularly suitable for forming rigid and semi-rigid composite armor panels. Such rigid and semi-rigid composite armor panels may be useful for the formation of helmets and other protective members, for example as protective panels inserted in vehicles or to be worn or carried by an individual (i.e., as a chest plate, or a shield).
As shown, the multi-layer fabric 700 has a first woven layer 711 and a second woven layer 713. Similar to as generally described above, the first yarns (warp and weft) of the first woven layer 711 are not interwoven with the second yarns (warp and weft) of the second woven layer 713. Rather, the first layer 711 and second layer 713 are secured together by one or more securing yarns. More particularly, the securing yarns are interwoven with at least some of the first yarns of the first woven layer 711 and at least some of the second yarns of the second woven layer 713 so as to secure the first and second woven layers 711, 713 together.
Note that in these photographs, the securing yarns are generally not visible as they are of relatively small size as compared to the warp and weft yarns of the first and second woven layers 711, 713. However, the securing yarns may be interwoven with the warp and weft yarns according to various patterns and arrangements, such as the specific examples described above.
In one example, the securing yarns may be made of non-ballistic yarns (i.e., Nylon), while the warp yarns and weft yarns may be made of aramid (e.g. Kevlar®). In other examples, the securing yarns and the warp yarns and weft yarns may be made of any suitable combination of ballistic or non-ballistic yarns.
Each woven layer 711, 713 generally has an outer surface (i.e., outer surface 711a) and an inner surface (i.e., inner surfaces 711b, 713b). The inner surfaces 711b, 713b of the woven layers 711, 713 generally face each other and are in contact with each other when the multi-layer fabric 700 is assembled, while the outer surfaces (i.e., outer surface 711a) face outwardly from each other when the multi-layer fabric 700 is assembled.
It has been discovered that when the multi-layer fabric 700 is exposed to a suitable resin under appropriate conditions (i.e., temperature, pressure, time, etc.) then the fabric 700 can become at least partially impregnated with resin in a manner that seems to encourage ballistic performance. More specifically, under certain conditions the fabric 700 with suitable resins may provide good ballistic performance in rigid and semi-rigid composite armor panels.
As shown in
The generally uniform darker color of the outer surfaces (i.e., outer surface 711a) indicates that the resin has at least substantially covered and penetrated into the outer surfaces of the fabric 700 in a relatively homogenous manner.
However, inspection of the inner surfaces of the fabric 700 shows a different result. For instance,
In particular, generally speaking, the use of flexible resins with fabrics woven from high performance fibers to form composite armor panels has been the subject of much research. Some research suggests that the more flexible the resin system used in a rigid or semi-rigid composite armor panel, the better the ballistic properties of the resulting panel.
In addition, there is evidence that suggests that adhesion of the resin to the ballistic yarn should be sufficiently poor so that delamination of the composite (i.e., separation and/or relative movement of layers of fabric) can occur during a ballistic event. This delamination consumes energy and helps avoid injury.
Delamination may still occur in cases of good adhesion if the resin in the composite ruptures at a sufficiently low strength to allow energy to dissipate during the ballistic event.
The multi-layer fabric 700 is believed to permit yarns to move and allow a composite to delaminate during a ballistic event, thus permitting energy to dissipate. In particular, the freedom for the yarns to move and for the composite to delaminate during a ballistic event is believed to be facilitated by the securing yarns (which may be made for example of a high elongation, low strength yarn) and the non-homogenous distribution of resin between the two layers of fabric.
More particularly, the securing yarns of the multi-layer fabric 700 hold the first layer 711 and second layer 713 together, but still generally permit relative movement between the layers, such as during a ballistic event.
Moreover, when the multi-layer fabric 700 is impregnated with a resin, the outer surfaces (i.e., outer surface 711a) become substantially covered and penetrated with resin. Moreover, at least some resin penetrates through the fabric 700 (covering a portion of the inner surfaces) and thus joining the two layers 711 and 713 together. This arrangement with good resin coverage on the surfaces of the fabric 700 and some resin coupling the two layers 711, 713 together encourages a strong fabric with good rigidity, which is suitable for rigid and semi-rigid armor panels.
However, as shown in
In some cases, this arrangement (with securing yarns and non-homogeneous resin distribution) may allow the use of resins and adhesives with more aggressive adhesion to the yarns than that previously used in other ballistic composites. Furthermore, this arrangement may allow the use of resins and adhesives with much higher tensile modulus than otherwise employed.
In some embodiments, at least a portion of the strength of the delamination layer can be controlled by the securing yarns, while the stiffness or hardness (or both) of the composite may be at least partially determined by the type and amount of the thermoplastic and/or thermoset resin and its adhesion to the fibers.
In some embodiments, the resin may be a high modulus resin having a modulus of at least about 7,000 psi. In some embodiments, the modulus of the resin may be in the range of about 25,000 to about 30,000 psi, with an aggressive bond to the yarns and where the resin does not completely penetrate through the fabric 700 (i.e., there are non-homogeneous areas of resin distribution between the layers 711, 713 of the fabric 700) nor substantially encapsulating all of the ballistic yarns. This may encourage the yarns to dissipate energy through movement during ballistic events.
In some embodiments, the placement of the resin on the outer surfaces and between the layers of the fabric 700 can be controlled by several techniques.
One technique may be to restrict the amount of resin used such that there is insufficient resin to wet the entire inner surface of the fabric 700, thus resulting in non-homogeneous resin distribution. For example, in some cases the amount of resin used is less than about 20 wt % of the weight of the composite. To produce a rigid composite with such a low amount of resin, it may be helpful if the resin adheres very, very well to the ballistic yarns. The stiffness in the composite may then be facilitated by two layers of high modulus yarns strongly adhered together using the resin.
Another technique is to use a resin with a high viscosity such that the resin may not flow very quickly at temperatures required for adhesion. Many resins in film form may meet this requirement. For example, in some embodiments low density polyethylene may be suitable as a resin. In particular, a low density polyethylene may soften and adhere to the outer surfaces of the layers 711, 713 of the woven multi-layer fabric, without easily penetrating the fabric at the temperatures required for adhesion (and hence creating a non-homogeneous resin distribution between the layers 711, 713, with less than 100% resin coverage across the inner surfaces). Other polymer films, such as thermoplastic nylon films and ionomer and polyurethane films, may perform in a similar fashion.
The ability to control the stiffness and the hardness of the laminate while maintaining the ballistic performance may provide several advantages.
For instance, when the threat to be stopped is a relatively deformable threat, such a 9 mm bullet, a hard laminate will tend to deform the bullet more than a soft laminate, and this larger deformed bullet is usually easier to stop. Note that this does tend to be dependent on the package mass in relation to the bullet velocity, since in some cases the opposite trend may be observed.
On the other hand, a relatively non-deforming bullet, such as a steel jacketed Tokarev bullet, may be more easily stopped with a more flexible laminate where the bullet is more gradually stopped. Note that this tends to be dependent of resin properties and may not always apply.
In some embodiments, a composite armor panel may be fabricated with layers of different hardness or stiffness. For example, one composite structure could include a two component laminate used to back a ceramic armor plate. A stiff, hard laminate layer may be placed on one side (i.e., directly behind the ceramic plate) where it provides support to the ceramic during the ballistic event. However, softer layers of the laminate may form the back of the composite (i.e., on the other side of the composite) and absorb energy by delamination, thus helping minimize or at least reduce the energy transferred to the wearer of the armor plate.
In some embodiments, the ballistic resistant yarns used herein may have a tenacity of about 15 grams per denier and a tensile modulus of at least about 400 grams per denier. Examples of some ballistic resistant yarns which may be used could include are aramid fibers, extended chain polyethylene fibers, poly(p-phenylene-2,6-benzobisoxazole) (PBO) fibers and glass fibers. Aramid and copolymer aramid fibers are produced commercially by Du Pont, Twaron Products and Teijin under the trade names Kevlar, Twaron and Technora, respectively. Extended chain polyethylene fibers are produced commercially by Honeywell, DSM, Mitsui and Toyobo under the trade names Spectra, Dyneena. and Telemilon. Polyethylene fiber and film are produced by Synthetic Industries and sold under the trade name Tensylon. PBO is produced by Toyobo under the trade name Zylon. Liquid crystal polymers are produced by license under the trade name Vectran. In some cases, other ballistic yarns may be used.
In some embodiments, the securing yarns may be selected from a wide range of fibers, which may include ballistic and/or non-ballistic fibers. Some fibers for the securing yarns might include natural fibers, such as cotton, wool, sisal, linen, jute and silk. The fibers might also, include manmade fibers and filaments, such as regenerated cellulose, rayon, polynosic rayon and cellulose esters. The fibers might further include synthetic fibers and filaments, such as acrylics, for example, polyacrylonitrile, modacrylics, such as acrylonitrile-vinyl chloride copolymers, polyamide, for example, polyhexamethylene adipamide (nylon 66), polycaproamide (nylon 6), polyundecanoamide (nylon 11), polyolefin, for example, polyethylene and polypropylene, polyester, for example, polyethylene terephthalate, rubber, synthetic rubber and saran. Glass fiber may also be used.
In some embodiments, the denier of some securing yarns may range from about 20 to about 1000 denier, depending on the sizes of the ballistic fibers. In general, some securing yarns may have a diameter of up to about 14% of the diameter of the ballistic yarn, or in some cases around about 2.5%. In some cases, the securing yarns may have a maximum tensile modulus of 1777 grams per tex and a maximum strength at 3% elongation that is about 0.31% of the ballistic yarn.
In some alternative embodiments, one or more warp or weft yarns may be used as securing yarns and hence may have the same denier yarn size.
In some embodiments, the non-homogenous distribution of resin between the layers 711, 713 can have various different patterns and shapes, and various quantities of areas of high and low resin concentration. For instance, in some embodiments, the inner surfaces of the fabric 700 may have between 10 and 90% resin coverage (i.e., with between 10 and 90% of the surface covered with resin, and the other 90 to 10% having substantially no resin).
In other embodiments, the inner surfaces of the fabric 700 may have between 20 and 80% resin coverage. In yet other embodiments, the inner surfaces of the fabric 700 may have between 30 and 70% resin coverage. In yet other embodiments, the inner surfaces of the fabric 700 may have between 40 and 60% resin coverage. In yet another embodiment, the inner surfaces of the fabric 700 may have about 50% resin coverage
Several experiments were conducted to investigate the performance of multi-layer fabrics impregnated with resin as generally described above. For these experiments, the resin coating on an aramid fabric was a Polyvinyl butyral (PVB) Phenolic thermoset system and the panel included multiple layers to a total areal density of 2 lb/ft2. The panel was pressed into a hard panel at a high pressure press at elevated temperatures for 20-30 min until crosslinking of the resin was completed.
The experimental results are summarized in Table 1 below, with the experimental composite referred to as KM2® PLUS 940 dtex SOS39 PL12, and is compared to a traditional plain weave fabric (referred to as KM2® 940 dtex 1X1P 31X31 PL12).
As shown in the table, the experimental composite seems to provide a reduced back face deformation as compared to the plain weave composite. The experimental composite also has an improved flexural modulus and maximum flexing force. However, the 4 gn V50 and 17 gn V50 test results show generally similar performance.
These experimental results suggest that in this case the experimental composite may provide for at least comparable ballistic results as compared to plain weave composites, while providing a more rigid product.
As used herein, the term “rigid or semi-rigid” include ballistic composites comprising a fabric and a resin wherein the addition of a resin decreases axial flexural deformability of the fabric in contact with the resin.
Greige fabrics or fabrics that are not treated with a resin system are generally deformable and suitable for “soft-armor” applications. In contrast, “rigid or semi-rigid” composites are generally not deformable such that the shape of the composite may be readily altered by relative flexural movement of the fibers or filaments along their axis, as the fibers or filaments are held in place by resin.
Generally, “rigid” may be used to refer to composites made using thermosetting resin, while “semi-rigid” may refer to composites made using thermoplastic resins and/or a low resin content of thermosetting resin. In various embodiments, both or either of thermoset and thermoplastic resin systems may be suitable for use with the multi-layer fabrics as described above to form composite panels.
In one embodiment, the dry-resin resin content of a ballistic composite panel is less than 50%. In a further embodiment, the dry-resin content of the ballistic composite panel is less than 30%. In some embodiments, the dry-resin content of the ballistic composite panel is between 5 and 20%. In some embodiments, the dry-resin content of the ballistic composite panel is 8% or greater.
Some resins believed to be effective include appropriate formulations of polymeric materials, including thermosets or thermosetting resins and thermoplastics, such as polyesters, polypropylenes, polyurethanes, polyethers, polybutadiene, polyacrylate, copolymers of ethylene, polycarbonates, ionomers, ethylene acrylic acid (EAA) copolymers, phenolics, vinyl esters, PVB phenolics, natural rubbers, synthetic rubbers (e.g. chloroprene rubbers), styrene-butadiene rubbers, etc.
In some embodiments, the resin material may additionally include additives to control or alter the physical or chemical properties of the resin, such as nano-particles to increase toughness of the composites and/or fillers to reduce density and/or increase stiffness of the composites. In some embodiments, the resin material may also contain substances selected so as to alter the surface properties of the composite, such as, for example, dyes for coloring or the like.
In some embodiments, the fibers or fabrics as described herein may be processed to form a rigid or semi-rigid composite material or panel. For example, a multi-layer fabric may be fabricated into a prepreg using a film or a wet resin. Depending on the application, the film or resin may be applied to one side of the fabric, the fabric may be impregnated with a resin, and/or the film may be worked into the fabric. In some examples, two or more layers of multi-layer fabric may be laminated together to create a fabric comprising desired properties.
Articles Made from Ballistic-Resistant Composites
In some embodiments, the ballistic-resistant composites and panels described herein may be used in armor systems.
In some embodiments, the ballistic-resistant composites as described herein may be used in the manufacture of multi-threat articles that may include a stab, spike or puncture resistant component in addition to a ballistic component. In some embodiments, the ballistic-resistant composites described herein may be used with ceramics or other materials suitable for stab-resistant product designs for spikes and edged weapons
Finished articles that may make use of the ballistic-resistant composites include, but are not limited to, body armor, personal armor plates and shields, commercial vehicle armor, military vehicle armor, such as spall liners, fragmentation kits, IED protection, EFP protection, ship armor, helmets, structural armor, or generally any application that uses rigid or semi-rigid ballistic and/or blast resistant composites.
While the above description provides examples of one or more fabrics, processes or apparatuses, it will be appreciated that other fabrics, processes or apparatuses may be within the scope of the present description as interpreted by one of skill in the art.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CA2014/000821 | 11/14/2014 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 61904420 | Nov 2013 | US |
