Fabric (woven – knitted – or nonwoven textile or cloth – etc.) – Woven fabric – Woven fabric is characterized by a particular or...
Reexamination Certificate
1998-10-30
2001-06-26
Morris, Terrel (Department: 1771)
Fabric (woven, knitted, or nonwoven textile or cloth, etc.)
Woven fabric
Woven fabric is characterized by a particular or...
C442S187000, C442S208000, C442S210000, C442S212000, C442S213000, C442S219000, C442S220000, C442S229000, C428S196000, C428S198000
Reexamination Certificate
active
06251809
ABSTRACT:
BACKGROUND AND FIELD OF THE INVENTION
This invention relates to composite materials with highly aligned discontinuous fibers, and a method for preparing such composites.
In the weaving of composite fibers, it is common to employ a loom. Typically, the loom includes a supply of filament or fiber materials which are arranged on a beam or a creel. The creel is loaded with a plurality of spools or bobbins upon which the filament or fiber is wound, and from which the filament or fiber can be extended onto the weaving area. The creel thus supplies continuous fiber to the loom. In conventional systems, a substantially large number of bobbins or spools containing the filament can be loaded on to the creel.
Each filament is thread through a comb and an appropriate harness heddle, extended across a loom bed which forms part of the loom, and is held in a pin block. The pin block is drilled with a plurality of holes each of which is designed to accept a filament extending from the creel. A steel pin or other suitable means is used to wedge a filament in the hole and therefore to ensure that it remains securely fixed across the loom bed. The filaments may be fastened to a cloth beam, which winds up material. Alternately, they may be securely fixed across the loom bed in an otherwise acceptable manner.
The plurality of filaments which extend across the loom bed are referred to as the warp. The heddle, which is one of a set of parallel cords or wires that when mounted compose the harness, is used to guide the warp filaments to facilitate weaving. Thus, a particular warp filament, or set of warp filaments, is raised or lowered over the loom bed with respect to other filaments or sets of filaments. According to conventional weaving technology, a complement of filaments or fibers is raised or lifted by two or more harnesses on the loom, creating a space with respect to another complement of fibers and in which a shuttle trailing a fiber is able to pass. Those fibers interspaced between the complements of warp filaments are known as the weft fibers, or weft, and run at angles which are typically transverse to those of the warp filaments. The weft passes between fiber groups, keeping them separate. The positions of the harnesses alternate in a continuing cycle, and between each change of position of each fiber set, a weft is introduced between the warp filaments. The repetition of this cycle and the introduction of the weft between each change repeats as necessary to create the woven ply or panel.
SUMMARY OF THE INVENTION
In one aspect, the present invention is directed towards the production of a composite material having highly aligned discontinuous fiber arrays. Such discontinuous fiber arrays are of importance in that their study leads to an increased understanding of basic principles behind the forming process of such fiber arrays. Additionally, highly aligned discontinuous fiber arrays have been shown to possess not only improved strength and an ease of processing, but also the ability to create fiber arrays with properties tailored for specific applications.
The invention comprises a composite material of continuous warp filaments which have been woven, the warp filaments comprising a reinforcing fiber and an associated matrix polymer which may be either thermoplastic or thermoset. The matrix polymer may be interspersed with the reinforcing fiber or the reinforcing fiber may be coated with the thermoplastic or thermoset matrix polymer. The continuous filaments form a warp in a loom and are woven into a desired pattern using a weft which holds the warp filaments apart in a specific manner and pattern. The weft may be a polymer filament which can remain in the composite and the completed product, or it may be a removable filament which is extracted from the fabric once the fabric has been stabilized as will be discussed below. With the filament warp and weft woven into a specific pattern, a preconsolidation follows whereby the polymer may be treated with heat and/or pressure to stabilize the fabric. Once stabilized, at least some of the continuous filaments are cut in selected locations. Stabilization of the material ensures that it will not disintegrate or fall apart once these selected fibers have been cut. The weft, if removable, is withdrawn at this stage. If the weft is to remain in the finished product, the warp cut preferably passes through selected warp fibers, and a part of the way through the weft, leaving the warp fibers below the weft intact.
In another aspect of the invention, the warp may be comprised of a reinforcing fiber filament, either monofilament or tow, and a matrix polymer filament which may be either thermoplastic or an incompletely cured thermoset. Once more, the matrix polymer filament may also be a monofilament or tow. Additionally, various combinations and commingling of the different types of reinforcing fiber filament and matrix polymer filaments may be used. The polymer-coated reinforcing fibers may be continuous or discontinuous, but, if discontinuous, are bonded together by the polymer to form a continuous strand.
In another aspect, the invention also discloses the use of a weft material which may be comprised of a polymer sheet, rod, plate, filament or wire. As appropriate, the weft may be thermoplastic or thermoset. When the weft is a sheet, rod, plate, filament, wire or the like, it may be made of metal, ceramic or glass. Furthermore, the weft in any one application need not be confined to one type of material or shape, but may be any one of a number of combinations of the materials mentioned above.
With the various types of warp, weft and matrix polymer filament materials described above, or any combination thereof, the preconsolidation takes place in substantially the same way as with the use of a regular reinforcing fiber and polymer filament. The heat and pressure in the preconsolidation step makes the fabric stable, allowing cutting of selected fibers without the fabric falling apart. The weft may be removable and withdrawn once the warp fibers are cut, or the weft may remain so that the cut passes through the warp fibers and also part of the way through the weft, leaving intact the warp fibers below the cut. With respect to the thermoplastic matrix polymers which may be used, these soften or melt during the preconsolidation stage. Where thermoset materials are used, alone or in combination with other materials, they receive a staging treatment that allows them to flow and then cure during further processing.
Looms allow for control of specific fiber placement in woven fabrics with continuous warp filaments. As mentioned above, the warp fibers are strands of thread that run from many spools on the creel, through the loom bed for weaving, and finally wind around a take-up roll as part of the finished fabric. The harness/pedal set-up permits predetermined patterns in the finished fabric by lifting specific warp fibers from the array before the shuttle adds the weft fiber. For the most part, the weft fibers run perpendicular to the warp, keeping the warp strands or fibers separate as the harnesses change position. The patterns produced in the woven fabric are the result of warp fibers which have varied lengths appearing on one side of the fabric.
The warp fiber composite, which is preferably comprised of a filament and associated matrix polymer material, can each be chosen from a wide selection of materials depending on the pattern required, and the ultimate use of the material. Fibers may be carbon, glass, Kevlar, nylon, polyethylene or other reinforcing filaments. They may be used as a single fiber type within the weave in both warp and weft positions, or, two or more of these fibers can be combined to produce the reinforcement. For example, carbon and Kevlar may be combined in the warp direction with carbon or Kevlar alone or in combination used as the weft. The matrix can be thermoplastic material such as polyethylene, polypropylene, PEEK, PEKK nylon or other melting polymer. The matrix could also be a thermoset polymer such as phenolic, epoxy, poly
Morris Terrel
Ruddock Ula C.
Schaap Robert J.
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