Patent Description:
The use of reinforced composite materials to produce structural components is now widespread, particularly in applications where their desirable characteristics are sought of being light in weight, strong, tough, thermally resistant, self-supporting, and adaptable to being formed and shaped. Such components are used, for example, in aeronautical, aerospace, satellite, recreational (as in racing boats and autos), and other applications.

Typically such structural components may be used in reinforcement components. The structural components can include reinforced composites having reinforcement preforms in the shape of I-Beams, H-Beams, or C-Beams, for example, made from reinforcement materials embedded in matrix materials. The support beam may be made from materials such as glass, carbon, ceramic, aramid, polyethylene, and/or other materials, which exhibit desired physical, thermal, chemical, and/or other properties, chief among which is great strength against stress failure. Through the use of such materials, which ultimately become a constituent element of the completed reinforcement component, the desired characteristics of the materials, such as very high strength, are imparted to the completed reinforcement component. The constituent reinforcement preforms typically may be woven, knitted, nonwoven or otherwise oriented into desired configurations and shapes. Usually particular attention is paid to ensure the optimum utilization of the properties for which the constituent reinforcing materials have been selected. Usually such reinforcement preforms are combined with matrix material to form desired finished reinforcement structural components or to produce working stock for the ultimate production of finished reinforcement components.

After the desired reinforcement preform has been constructed, matrix material may be introduced to and into the preform, so that typically the reinforcement preform becomes encased in the matrix material and matrix material fills the interstitial areas between the constituent elements of the reinforcement preform. The matrix material may be any of a wide variety of materials, such as epoxy, polyester, vinyl-ester, ceramic, carbon and/or other materials, which also exhibit desired physical, thermal, chemical, and/or other properties. The materials chosen for use as the matrix may or may not be the same as that of the reinforcement preform and may or may not have comparable physical, chemical, thermal, or other properties. Typically, however, they will not be of the same materials or have comparable physical, chemical, thermal, or other properties, since a usual objective sought in using composites in the first place is to achieve a combination of characteristics in the finished product that is not attainable through the use of one constituent material alone. So combined, the reinforcement preform and the matrix material may then be cured and stabilized in the same operation by thermosetting or other known methods, and then subjected to other operations toward producing the desired component. After being cured, the then solidified mass of the matrix material normally is very strongly adhered to the reinforcing material (e.g., the reinforcement preform). As a result, stress on the finished component, particularly via its matrix material acting as an adhesive between fibers or other constituent material, may be effectively transferred to and borne by the constituent material of the reinforcing preform.

A typical combination of preform reinforcement support beams is made by the preforms at an angle (typically a right-angle) with respect to each other. Usual purposes for such angular arrangements of joined reinforcement preforms are to create a desired shape to form a reinforcement preform to strengthen the resulting composite structure that it produces against deflection or failure upon being exposed to exterior forces, such as pressure or tension. In any case, a related consideration is to make each juncture between the reinforcement support beams as strong as possible. Given the often desired very high strength of the reinforcement preform constituents, weakness of the juncture becomes, effectively, a "weak link" in a structural "chain".

The support beams are attached at the juncture where they intersect. Most attachment schemes center on those acceptable for metals, e.g., using fasteners such as rivets, bolts, clips and the like. In particular, support beams in the shape of C-Beams intersecting one another have little area for attachment where they intersect. The standard construction method for beams in general includes one continuous primary beam to which the ends of secondary beams are attached. An improvement on this design incorporates continuous fiber across the intersection in the web of both the primary and secondary beams. However, in the case of C-Beam preforms, there are cuts in the flanges in at least one direction at the intersecting portion. The cut flanges could form a small lap shear joint with the continuous flange (See <FIG>), but there is a limited overlapping area available in the intersecting portion requiring reinforcement with brackets, fasteners, and/or an additional separate piece that acts as a sill across the joint.

Examples of known woven preform and method of forming thereof are disclosed in <CIT>, <CIT>, <CIT>, <CIT>.

The aforementioned aims are solved by a woven preform and a method of forming a woven preform and a composite structure as claimed in the appended set of claims.

The accompanying drawings, which are included to provide a further understanding of the invention, are incorporated in and constitute a part of this specification. The drawings presented herein illustrate different embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings:.

The terms "threads", "fibers", "tows", and "yarns" are used interchangeably in the following description. "Threads", "fibers", "tows", and "yarns" as used herein includes monofilaments, multifilament yarns, twisted yarns, multifilament tows, textured yarns, braided tows, coated yarns, bicomponent yarns, as well as yarns made from stretch broken fibers of any materials known to those ordinarily skilled in the art. Yarns can be made of carbon, nylon, rayon, fiberglass, cotton, ceramic, aramid, polyester, metal, polyethylene glass, and/or other materials that exhibit desired physical, thermal, chemical, or other properties.

As used herein, "fabric" means warp fibers interwoven with weft fibers and a fabric can be either a single layer fabric or a multilayer fabric. The term "multilayer fabric" is used herein for convenience and includes single layer fabrics as well.

The term "folded" is broadly used herein to mean "forming", which includes unfolding, bending, and other such terms for manipulating the shape of a woven fabric. The terms "C-flange" and "C-Beam" are used interchangeably to refer to a structure having a C-shaped cross-section. Similarly, the terms "H-Beam", "I-Beam", "T-Beam", "L-Beam", and "π-Beam" (Pi-Beam) are used to refer to structures having an H-, I-, T-, L-, or π-shaped (Pi-shaped) cross-section, respectively. However, this listing of cross-sectional shapes is not to be considered exhaustive. That is, all cross-sectional shapes are contemplated. The term "support beam" is used to include a beam having any cross-sectional shape.

In the following description, it is understood that such terms as "front", "back", "left", "right", "transverse", "longitudinal", "above", "below", "over", "under" and the like are words of relational convenience and are not to be construed as limiting terms.

For a better understanding of the invention, its advantages, and objects attained by its uses, reference is made to the accompanying descriptive matter in which non-limiting embodiments of the invention are illustrated in the accompanying drawings and in which corresponding components are identified by the same reference numerals.

The disclosure is directed to structural components with reinforcing preforms in the shape of a support beam. In one embodiment, disclosed is a three-dimensional (3D) woven cruciform preform having arms with a C-shaped cross-section (C-Beams) and fiber continuity across the length of the arms or fiber continuity over at least the crossover portion where the C-Beam arms of the cruciform intersect. Accordingly, the disclosure provides for a woven C-Beam support preform that avoids the need to cut the fibers in the C-beam arms or to use fasteners in order to attach the arms where they intersect.

<FIG> illustrates a model of a desired final shape of a 3D preform cruciform <NUM> having C-Beams <NUM>,<NUM>. As discussed below, the C-Beams are woven to have continuous warps along the intersecting flanges <NUM> of the C-Beams. This arrangement provides a cruciform with C-Beams or arms having continuous fiber in both directions X, Y of the cruciform. Where the X-direction is the direction of the warp fibers in a first arm and the Y-direction is the direction of the warp fibers in a second arm. That is, the flanges <NUM> of the C-beams have continuous warp tows across the length of the cruciform and, in particular, across crossover portion <NUM>, which is the location where the C-Beams of the cruciform intersect.

The flanges of the C-Beam can provide an increase to the bending stiffness of the resultant cruciform reinforcing preform over C-Beam cruciform without fiber continuity across the crossover portion. The present disclosure provides for simultaneously achieving fabric continuity of fibers in both the X and Y direction of the cruciform. The simultaneous continuity is prevented in prior-art C-Beam cruciforms because the desired as-formed crossover location is different than the as-woven crossover location. That is, the weft fibers of the flanges prohibit the necessary sliding of the warp fibers in the crossover location to enable forming of the C-Beam flanges. 2C illustrates the change in position of this crossover location.

<FIG> illustrates forming a C-Beam cruciform structure (from a top view) by rotating the arms (not visible) using a paper model for illustration. The added flanges (<NUM>, <NUM>, and as in <FIG>) that form a C-Beam cruciform structure increases the stiffness over an un-flanged cruciform (that is, without flanges <NUM>) when a force or load is applied along the line formed by the intersecting arms <NUM>, <NUM>. However, cutting the warp fibers in the flanges to facilitate intersection of the cruciform arms results in a discontinuity of fibers in one of the flange directions. The discontinuity of the warp fibers creates a weak spot that can degrade the performance of a structure to the limit of what a subsequently applied resin bond can transfer across the crossover portion.

Maintaining continuous fiber throughout the flanges in both directions of a C-Beam cruciform can increase the tensile and compressive stiffness along the length of each arm of the resultant preform. The present invention enables warp fiber continuity simultaneously along each of the flanges of the arms of a C-Beam cruciform.

In an embodiment, at least some of the warp fibers float - that is, are not interwoven with weft fibers - in the crossover portion of the flanges throughout the range of motion of the arms. That is, the warp fibers in a flange of a first arm of the cruciform are free to slide against the warp fibers of a second arm of the cruciform in the crossover portion. This feature can enable the flat woven arms of a C-Beam to be rotated about the crossover portion into the as-formed geometry of the arms.

<FIG> illustrates one arm <NUM> of a C-Beam as woven. The C-Beam is flat woven. Edges <NUM>, <NUM> of the flat-woven C-Beam will later be formed into flanges of the C-Beam. Warp fibers in edge portions <NUM>, <NUM> of edges <NUM>, <NUM> are not interwoven with weft fibers. As such, warp fibers in portions <NUM>, <NUM> float. The floating of the warp fibers in edges <NUM>, <NUM> can enable the warp fibers in the arm <NUM> to slide over warp fibers in another intersecting arm to fold the edges of the arm into the C-Beam cross-sectional shape. The dimension of edge portions <NUM>, <NUM> in which the warp fibers are floating across the width of the arm <NUM> can determine the length of the C-Beam flange when folded, which is typically in the range of <NUM>,<NUM> to <NUM>,<NUM> (<NUM> inch to <NUM> inches), but greater and lesser lengths of flanges are contemplated. The dimension of edge portions <NUM>, <NUM> along the length of arm <NUM> may be any width and length, but typically the width will match the width of edge portions <NUM>, <NUM> and the length will accommodate the width of a crossing arm (not illustrated in <FIG>). However, the dimensional ranges of edge portions <NUM>, <NUM> range is not a limiting factor in the disclosed structure.

<FIG> illustrates a top view of the intersection of flanges after a flanged C-Beam cruciform has been formed. In <FIG>, the cross hatching on the horizontal arm represents a flange of a first arm <NUM> of the C-Beam cruciform that is visible from the top and the cross hatching on the vertical arm represents a flange of a second arm <NUM> of the C-Beam cruciform. Flanges <NUM>, <NUM> may be formed perpendicular to one another or at any desired angle for the final cruciform structure.

The horizontal lines along the length of first arm <NUM> represent warp tows <NUM> of first arm <NUM>. The lines perpendicular to the warp tows <NUM> represent the weft tows <NUM> of first arm <NUM>. Similarly, the vertical lines <NUM> along the length of the second arm <NUM> represent warp tows <NUM> of second arm <NUM>. And the lines perpendicular to the warp tows <NUM> represent the weft tows <NUM> of second arm <NUM>.

The location where the first arm <NUM> and second arm <NUM> cross is the intersection - crossover portion <NUM> - of the cruciform. In <FIG> the weft tows <NUM>, <NUM> are not present in the flanges of the first and second arms in crossover portion <NUM> of the formed preform.

<FIG> illustrates a cross-sectional view in the warp direction of as-woven fabric preform <NUM> as the fabric comes off a loom. The preform illustrated includes two multilayer fabrics <NUM>, <NUM> that will form a cruciform structure having one crossover portion <NUM>. Multilayer fabric <NUM> is woven under multilayer fabric <NUM> before the crossover portion. Multilayer fabric <NUM> is woven over multilayer fabric <NUM> after the crossover portion.

For identification in later figures, multilayer fabric <NUM> has surface 514A on one side of the fabric and 514B on the opposite side of the fabric before the crossover portion. Multilayer fabric <NUM> has surface 512A on one side of the fabric and 512B on the opposite side of the fabric after the crossover portion. Similarly, multilayer fabric <NUM> has surface 510A on one side of the fabric and 510B on the opposite side of the fabric before the crossover portion. Multilayer fabric <NUM> has surface 516A on one side of the fabric and 516B on the opposite side of the fabric after the crossover portion.

The warp fibers of the first and second multilayer fabrics float in the crossover portion where they will be folded into flanges and the warp fibers in the first and second multilayer fabrics are continuous across the crossover portion. The first multilayer fabric can later be used to form a first arm of the C-Beam cruciform. Likewise, the second multilayer fabric can later be used to form a second arm of a C-Beam cruciform. The first and second multilayer fabrics are rotated about the crossover portion so that the fabrics are at a desired angle to one another. In a particular embodiment, the angle between the first and second multilayer fabrics is <NUM> degrees. However, other angles such as <NUM> degrees, etc. are contemplated. The edges of the first multilayer fabric are folded to form flanges so the first multilayer fabric has a C-shaped cross-section. Similarly, the edges of the second multilayer fabric are folded to form flanges so the second multilayer fabric has a C-shaped cross-section.

The preform is a two-dimensional (flat-woven) structure having a first multilayer fabric woven over a second multilayer fabric for a desired length of the preform. The first multilayer fabric intersects with the second multilayer fabric at a crossover portion of the preform so that after the crossover portion the first multilayer fabric is woven underneath the second multilayer fabric. That is, the first and second multilayer fabrics are interwoven with one another at the crossover portion and are elsewhere not interwoven with one another in the preform in a cruciform structure having one crossover portion according to the present disclosure.

<FIG> show views in the forming of woven preform <NUM> having one crossover portion using the identification of surfaces in <FIG>. <FIG> is a top view of the flat-woven fabric preform prior to forming into a C-Beam structure with one crossover portion <NUM>. Warp fibers in portions <NUM>, <NUM> on edges <NUM>, <NUM> of the fabric are not interwoven with weft fibers. As such, warp fibers in portions <NUM>, <NUM> float. Surfaces 510A, 512A identified in <FIG> are seen in the top view of the woven fabric preform on respective sides of a midpoint <NUM>.

<FIG> is a bottom view of the fabric preform <NUM> of <FIG> where areas <NUM>, <NUM> interwoven in the top view are not interwoven in the bottom view. Surfaces 514A, 516A identified in <FIG> are seen in the bottom view of the woven fabric preform on respective sides of midpoint <NUM>.

<FIG> shows forming the flat-woven fabric illustrated in <FIG> into a C-Beam cruciform by rotating fabrics <NUM>, <NUM> with respect to one another. For purposes of explanation, fabric surfaces 512A, 512B and 514A, 514B of multilayer fabric <NUM> are rotated in the direction of the arrows J and K shown in <FIG>.

<FIG> is a top view showing the forming of the C-Beam cruciform of <FIG> into a C-Beam cruciform. Edges <NUM>, <NUM> are folded to form flanges <NUM>, <NUM>, respectively, resulting in the C-Beam cross-sectional shape. Warp fibers in crossover portion <NUM> are floating, which enables edges <NUM>, <NUM> to be folded. The warp fibers in portion <NUM>, for example, in the crossover portion <NUM> are not interwoven with weft fibers. As such, the warp fibers in multilayer fabric <NUM> in the crossover portion can slide over the floating warp fibers of multilayer fabric <NUM> in the crossover portion without being obstructed by weft fibers. Remaining edges are similarly folded to form C-Beam cross-sectional shapes on the other arms of the cruciform structure.

<FIG> shows a bottom view of the C-Beam cruciform formed in <FIG>. Similar to <FIG> described above, warp fibers in crossover portion <NUM> are floating, which enables edges <NUM>, <NUM> to be folded. The warp fibers in portion <NUM>, for example, in the crossover portion <NUM> are not interwoven with weft fibers. As such, the warp fibers in multilayer fabric <NUM> in the crossover portion can slide over the floating warp fibers of multilayer fabric <NUM> in the crossover portion without being obstructed by weft fibers.

After forming the C-Beam cruciform structure, the preform can be impregnated with a matrix material to form a composite. An example of the composite C-Beam cruciform is shown in <FIG>.

<FIG> illustrates three warp columns A, B, and C in the flange crossover portion of a C-Beam cruciform (after forming). Warp tows <NUM> of the flange of the first arm and warp tows <NUM> of the flange of the second arm are not interwoven with weft fibers. As shown, warp tows of the first arm <NUM> are interwoven with warp tows <NUM> of the second arm across the crossover portion <NUM>. This feature enables the arms of the C-Beams to rotate about the crossover portion when being formed from the as-woven preform into the desired cruciform shape.

The subject invention can also be applied to make an I-Beam cruciform preform <NUM>, shown in <FIG>. The preform comprises a first arm <NUM> and a second arm <NUM>. Each of first arm <NUM> and second arm <NUM> has two opposing flanges <NUM>. The first and second arms intersect at crossover portion <NUM>.

The present invention is not limited to woven preforms having only one crossover portion that may be formed into C-Beam cruciform structures. Cruciform structures having C-Beam cross-sectional forms that are flat-woven with multiple crossover portions may be formed. <FIG> illustrate cross-sectional views of multilayer fabrics that may be used to form cruciform structures. Preforms with other cross-sectional forms including, but not limited to, "H-Beam", "I-Beam", "T-Beam", "L-Beam", and "π-Beam" are contemplated as well.

<FIG> illustrates a cross-sectional view of a flat-woven preform having two multilayer fabrics <NUM>, <NUM> and a single crossover portion <NUM><NUM>. Multilayer fabric <NUM> is woven over multilayer fabric <NUM> on one side of crossover portion <NUM><NUM> and under multilayer fabric <NUM> on another side of the crossover portion. As discussed in detail above, the preform can be formed in a C-Beam structure having a "cross" or "X-shape".

<FIG> illustrates a cross-sectional view of a flat-woven preform having four multilayer fabrics <NUM>, <NUM>, <NUM>, <NUM> and four crossover portions <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>. Each multilayer fabric includes two crossover portions with each of two other multilayer fabrics. In each case, a first multilayer fabric is woven over a second multilayer woven fabric on one side of the crossover portion and under the second fabric on the other side of the crossover portion. For, example, multilayer fabric <NUM> includes two crossover portions <NUM><NUM>, <NUM><NUM> with multilayer fabrics <NUM> and <NUM>, respectively. Fabric <NUM> is woven over fabric <NUM> on one side of crossover portion <NUM><NUM> and under fabric <NUM> on the other side of crossover portion <NUM><NUM>. Fabric <NUM> is woven over fabric <NUM> on one side of crossover portion <NUM><NUM> and under fabric <NUM> on the other side of crossover portion <NUM><NUM>. A similar weaving may be accomplished for each of remaining fabrics <NUM>, <NUM>, <NUM>. In this embodiment, the result is a cruciform structure having the form of a "hash" or "number" symbol shape that bounds an open area <NUM>.

<FIG> is an illustration of the cruciform structure formed from the fabric illustrated in <FIG>. The cruciform structure shown in <FIG> includes four arms <NUM>, <NUM>, <NUM>, <NUM>. Each arm intersects with two other arms at crossover portions. As such, each arm has two crossover portions. Arm <NUM> includes crossover portions <NUM><NUM>, <NUM><NUM> with multilayer fabrics <NUM> and <NUM>, respectively; arm <NUM> includes crossover portions <NUM><NUM>, <NUM><NUM> with multilayer fabrics <NUM> and <NUM>, respectively; arm <NUM> includes crossover portions <NUM><NUM>, <NUM><NUM> with multilayer fabrics <NUM> and <NUM>, respectively; arm <NUM> includes crossover portions <NUM><NUM>, <NUM><NUM> with multilayer fabrics <NUM> and <NUM>, respectively. As discussed above, the result is a structure having the form of a "hash" or "number" symbol that bounds an open area <NUM>.

<FIG> illustrates a cross-sectional view of a flat-woven preform having six multilayer fabrics <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> with nine crossover portions <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>. Each of the fabrics includes three crossover portions with three other fabrics. For example, fabric <NUM> includes crossover portions <NUM><NUM>, <NUM><NUM>, <NUM><NUM> with fabrics <NUM>, <NUM>, <NUM>, respectively. The preform woven in this manner results in the complex cruciform pattern illustrated.

Other implementations are contemplated that expand this structure or create other structures from the basic two-arm cruciform described herein. The pattern described in <FIG> may be continued for the desired structure. Such structures include, but are not limited, to triangular, rhomboid, pentagonal, hexagonal, etc. shaped structures.

In any of the embodiments, the woven preform can be impregnated with a matrix material. The matrix material includes epoxy, bismaleimide, polyester, vinyl-ester, ceramic, carbon, and other such materials.

Claim 1:
A method of forming a woven preform, comprising:
weaving a first fabric (<NUM>, <NUM>, <NUM>, <NUM>) over a second fabric (<NUM>, <NUM>, <NUM>, <NUM>) in a first portion of the woven preform, the first and second fabrics (<NUM>, <NUM>, <NUM>, <NUM>) each including warp fibers interwoven with weft fibers;
interweaving warp fibers of the first fabric (<NUM>, <NUM>, <NUM>, <NUM>) with warp fibers of the second fabric (<NUM>, <NUM>, <NUM>, <NUM>) at a crossover portion (<NUM>, <NUM><NUM>) of the woven preform such that after the crossover portion (<NUM>, <NUM><NUM>) the first fabric (<NUM>, <NUM>, <NUM>, <NUM>) is woven under the second fabric (<NUM>, <NUM>, <NUM>, <NUM>) in a second portion of the woven preform;
wherein the warp fibers in the first and second fabrics (<NUM>, <NUM>, <NUM>, <NUM>) are continuous across the crossover portion (<NUM>, <NUM><NUM>), characterized in that
the warp fibers on edges of the first fabric (<NUM>, <NUM>, <NUM>, <NUM>) and the warp fibers on edges of the second fabric (<NUM>, <NUM>, <NUM>, <NUM>) are floating in the crossover portion (<NUM>, <NUM><NUM>).