DESCRIPTION OF THE DRAWINGS
The drawings which are appended hereto and made a part of this disclosure are provided by way of illustration and not by way of limitation. In the drawings:
FIG. 1 is a perspective schematic representation of one embodiment of a woven article according to the present invention;
FIG. 2 is a schematic representation of a woven article which is another embodiment of the present invention; and,
FIG. 3. is an embodiment of a woven article of the present invention showing the article in cross-section after the application of heat to an article similar to that shown in FIG. 2.
FIG. 4 is a schematic representation of a sectional side view of one embodiment of the invention which is a multi-layer article;
FIG. 5 is a perspective view of a wrapped yarn which is another embodiment of the invention;
FIG. 6 is a schematic representation of a woven article of the invention positioned in a heated press for the application of heat and pressure; and
FIG. 7 represents a stack of woven articles according to the invention ready to be pressed together.
DETAILED DESCRIPTION
Turning first to FIG. 1, a woven article, namely fabric 1 is shown in schematic perspective. In the longitudinal or warp direction warp threads 3 are shown which preferably comprise a polyetherimide (PEI) fiber which is the ULTEM® fiber supplied by General Electric Company and are selected from PEI formulations designated ULTEM® 1000, 1000 D, 1010, or 9011. Other warp fibers or yarns such as yarn 4 may be an inextensible or relatively inextensible yarn to give the fabric added dimensional stability. The yarn 4 may be mineral based comprising quartz, fiberglass or basalt, or it may be carbon, a metal or metal alloy, or a polymeric material having inextensible and heat resistance properties. In the weft or fill direction fibers 2 are also PEI fibers. These may be accompanied by weft inextensible fiber 5. In addition, other yarns may be optionally added to the fabric such as weft yarn 8, and warp yarn 9. These added or additional yarns may be polymeric, metal, or mineral and are used to impart desired properties to the woven article.
The woven article of FIG. 1 may have only warp yarn 3 which comprise PEI and the weft yarns may be of another material. Likewise, the warp yarns may be of a material other than PEI and the weft yarns may be PEI. Preferably, a minimum of 10% of PEI yarns should be included in the article and up to 65% or more may be included. It is desirable to have a relatively inextensible yarn woven into the article to provide dimensionally stability. In addition, the woven article may be of single-ply, multi-ply, or a Conform Fabric®; and any weave pattern may be used such as satin, twill, plain, crowfoot or similar pattern.
If a Conform Fabric® product is desired, the fabric may be first shaped into the desired geometric configuration and then heat applied which will cause the intersections of PEI strands 2 and 3 to bond at an intersection 7 as illustrated in FIG. 1. This tends to lock the fabric into its desired three-dimensional shape.
Looking now at FIG. 2, a schematic representation of a woven article 11 is shown in cross section, having warp threads 3 of PEI and a weft 5 of an inextensible fiber such as quartz or fiberglass. To a configuration such as this, heat is applied by pressing a heated plate against fabric 11 until the PEI becomes soft and flows. This will occur at or above the glass transition temperature as the melt temperature range is approached. As an alternate way of applying heat, the fabric 11 can be passed through the nip of heated rollers or a press or oven or autoclave or an alternative heating device. The result will appear as shown in FIG. 3 where the PEI yarns 3 have melted and have flowed together to form the sheet-like planar surface 6 which, upon cooling, becomes a semi-rigid to rigid surface. By varying the yarn density of PEI more or less sheet material 6 can be produced. FIG. 3 represents a preferred embodiment and a best mode of carrying out the invention.
The woven article 10 with the sheet-like PEI surface has remarkable toughness and impact resistance being able to withstand the impact of small to medium caliber projectiles and making it a desirable material for protective garments. Another application for the product due to its high frequency insulation properties is in aerospace components and in microwave communications. Other applications are for ballistic protection and for filtration applications.
Turning now to FIG. 4, an alternate embodiment 20 is shown where two layers 21, 22 or sheets of fabric have been positioned over each other before heat is applied. This is accomplished by taking sheets of fabric 11 as shown in FIG. 2 and applying heat to achieve a multi-layer structure of the article 10 of FIG. 3.
FIG. 6 shows a representative mold 60 having a movable pressure plate 61 which is heated and can compress a woven article 64 against stationary bottom heated plate 62 to produce a pressed article 10.
A preferred method of making article 20 is to stack sheets of the types shown in FIGS. 1 and 2 in the manner shown in FIG. 7 to form stack 65 in a mold 60, and apply pressure and heat until the PEI strands 23 flow and join together as shown. The sheets may be stacked with warp yarns in the same direction, at right angles to each other, at 45° degree angles or other angular orientation. Each layer may have a different yarn make-up, that is, one layer may comprise PEI and quartz warp and weft yarns while the next or superposed layer of fabric may comprise PEI yarn and Innegra™ polyolefin yarn, that is, quartz, fiberglass, carbon, metal or Innegra™ strands may be strands 24. Each layer of fabric is chosen to impart desired characteristics to the composite, finished article. The significant feature is that a polymeric material having the desirable properties of PEI fiber or is a PET fiber, is used in each fabric layer. The faces 25 may be used as the outer surface of the article or the article may be adhered to another surface.
The embodiments of FIGS. 3 and 4 have many unique uses and applications and provide novel and useful articles. For example, circuit boards may be made according to the FIG. 4 embodiment and used directly eliminating the preparation step. An Ultemate Armor™ product for blast protection may be also produced. The products of this invention have the advantages of relatively low cost, low weight, corrosion resistance, flexibility and high impact resistance.
In a first example which is one best mode of the invention which employs 75 denier Ultem 100 D yarn as the fill and is identified as applicants' style 15382, an 8H Salem weave fabric with a 60×104 construction having a thickness 0.0208,″ and a weight of 15.97 oz/sq. yd. had a warp tensile strength of 545 lbs/sq. in. and a tensile fill strength of 605 lbs/sq. in. The warp is 75 denier fiberglass.
In a second example using 150 denier, cyclic polyolefin Innegra™ yarn as the fill, identified as applicants' style 15400 a fabric; a fabric having plain weave with a 60×46 construction with a thickness of 0.00392″ had a weight of 1.72 oz/sq. yd., a warp tensile strength of 147.9 lbs/sq. in., and a fill tensile strength of 30.6 lbs/sq. in. The warp yarn is fiberglass.
The fabrics of Examples 1 and 2 above may be stacked and pressed as described for FIGS. 6 and 7 to provide reinforced articles such as shown in FIGS. 3 and 4. The need to carefully position reinforcing sheets of carbon fiber or fiberglass in a mold and then pour in a molding resin such as epoxy is not required to produce a product such as a circuit board or other articles.
Another alternate and preferred embodiment of the invention is a wrapped yarn or composite fiber. Such a fiber is described in U.S. Pat. No. 6,127,035 which issued on Oct. 3, 2000 and which is incorporated herein by reference. Looking now at FIG. 5, composite fiber 30 is shown having a core 31 of a mineral fiber, preferably quartz or fiberglass, wrapped with PEI strands 32. This is a versatile, high strength composite fiber which can be used in the weaving of fabrics as described above. This composite fiber, being wrapped with PEI, readily bonds to adjacent PEI fibers under heat and pressure to form very strong woven articles.
As mentioned above, the thermoplastic fibers that may be used in this invention are useful for their chemical inertness, heat and flame resistance and dimensional stability. Among these are fibers of quartz, fiberglass including E, S, and S-2, and basalt. Carbon fibers are also of this type and may readily be used. Metal fibers that are of particular usefulness are those of copper, aluminum, nickel, gold, and platinum, and alloys including steel and bronze. The fibers of useful polymeric materials include Kevlar® aramid, polypropylene, and the ultra high molecular weight polyethylene fiber Innegra™.
The woven fabric of this invention is especially useful as reinforcing matrices in structures formed with epoxy resins such as those described in U.S. Pat. No. 6,720,080 to Murari, et al. which is incorporated herein by reference. In addition, finish can be applied such as those described in U.S. Pat. No. 6,036,735 to Carter, et al. which also is incorporated herein by reference.
While preferred embodiments of the invention have been described using specific terms, such description is for illustrative purposes only as it will be understood that upon reading the foregoing disclosure modifications and alterations may become apparent to those skilled in the art. but our invention is limited only by the scope of the claims which follow.
Patent Application
20080081528
