Woven preform for structural joints

• US 20030056847A1
• Filed: 09/10/2002
• Published: 03/27/2003
• Est. Priority Date: 09/12/2001
• Status: Active Grant

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Schmidt, Ronald P., Kalser, David A.
• Granted Patent: US 6,874,543 B2
• Time in Patent Office: Days
• US Class Current: 139/383R
• CPC Class Codes: B29B 11/16 comprising fillers or reinforcement non-woven fabrics per se D04H1/00, D04H3/00
• CPC Class Codes: B29C 70/24 oriented in at least three directions forming a three dimensional structure
• CPC Class Codes: D03D 25/005 Three-dimensional woven fabrics
• CPC Class Codes: Y10S 139/01 Bias fabric digest
• CPC Class Codes: Y10T 442/3195 Three-dimensional weave [e.g., x-y-z planes, multi-planar warps and/or wefts, etc.]

Abstract

A preform for structural joints has a three-dimensional weave architecture with fill fibers woven to provide layer-to-layer interlocking of layers of warp fiber as well as interlocking of fibers within each layer. At least two legs extend from a base, the base and legs each having at least two layers of warp fibers. The legs are connected at a symmetrical, distributed-column intersection, with an odd number of columns of warp fibers being located being the legs. The outer ends of the base and legs preferably have tapers formed from terminating layers of warp fibers in a stepped pattern. Tracer fibers that include a colored strand and an x-ray opaque strand are woven into the preform at selected locations as a warp fiber. The tracer fibers allow for identification of a selected location or a selected portion of the preform through visual inspection or by x-ray image.

Claims

1. A three-dimensional preform weave architecture, comprising:

a plurality of adjacent layers, each layer having a plurality of warp fibers, the warp fibers being generally parallel to each other and forming generally vertical columns;

a plurality of fill fibers woven among the layers of warp fibers to form a base and two legs extending from the base, the base and each leg being formed from at least two layers of warp fibers, the base having a first edge and a second edge, each leg having a inner end and an outer end;

wherein

each fill fiber has a beginning at the first edge of the base, then extends to the second edge of the base, then extends back toward a central section of the base, then exits the layers of the base and extends into the layers of one of the legs before extending into the layers of the other of the legs, then exits the layers of the legs and extends back into the layers of the base for returning to the first edge of the base, the fill fibers entering each leg at the inner end of each leg and extending to the outer end of each leg before returning to the inner end of each leg, the fill fibers interlocking the layers of the base and interlocking the layers of each leg, the fill fibers also interlocking the warp fibers within each layer; and

the columns of warp fibers include central columns of warp fibers located between the fill fibers connecting one of the legs to the base and the fill fibers connecting the other of the legs to the base, the central columns comprising an odd number of columns and allowing for a substantially mirror-image weave pattern about a central plane of symmetry of the weave architecture.

2. The weave architecture of claim 1, wherein:

the columns of warp fibers include separator columns of warp fibers adjacent opposite lateral sides of the central columns, each separator column dividing portions of the fill fibers into two groups, one group extending between the base and the leg from between the central set of columns and the adjacent separator column, the other group extending from between the separator column and the columns laterally outward of the separator column.

3. The weave architecture of claim 1, wherein:

the base has at least four of the layers.

4. The weave architecture of claim 1, wherein:

the base has more of the layers than each of the legs.

5. The weave architecture of claim 1, wherein:

the layers are interlocked by running a portion of a fill-tow pattern over a warp fiber in a first layer in a first column and below a warp fiber in an adjacent, second layer in an adjacent, second column, the second layer being below the first layer.

6. The weave architecture of claim 1, wherein:

each fill fiber additionally extends from the first edge of the base to the second edge of the base and back to the first edge of the base without entering each leg.

7. The weave architecture of claim 1, wherein:

at least a portion of the warp fibers comprises multi-strand tracer fibers for identifying selected locations in the weave architecture, the tracer fibers being formed from at least one strand that is x-ray opaque and at least one strand that has a color contrasting the color of surrounding warp and fill fibers.

8. The weave architecture of claim 7, wherein:

the tracer fiber is formed from stainless steel and aramid strands.

9. The weave architecture of claim 7, wherein:

the edges of the base are tapered; and

the tracer fibers are located in the base along the inner edge of each of the tapers.

10. The weave architecture of claim 1, wherein:

at least a portion of the warp fibers in the base has a smaller cross-sectional area than the warp fibers in the legs.

11. A woven preform, comprising:

a base having a central portion and two lateral edges;

at least two legs extending from one surface of the base;

wherein

the preform is woven with a three-dimensional weave pattern, the base and each leg being formed of at least two layers of warp fibers, the warp fibers being generally arranged in columns, at least one fill fiber being woven among the warp fibers for interlocking the warp fibers of the base to each other and interlocking the warp fibers of the legs to each other, the legs being connected to the base at intersections by portions of the fill fiber extending between each leg and the base, two groups of portions of fill fibers connecting each leg to the base;

an odd number of central columns of warp fibers in the base are located between the intersections of the legs and base, the odd number of columns allowing a substantially mirror-image weave pattern about a central plane of symmetry of the preform; and

separator columns are located adjacent the central columns, one of the groups of portions for each leg intersecting the base adjacent one side of the corresponding separator column, the other of the groups for each leg intersecting the base on the opposite side of the corresponding separator column.

12. The preform of claim 11, wherein:

the layers of warp fibers comprise at least four layers in the base and in the legs.

13. The preform of claim 11, wherein:

the base has more layers of warp fibers than each of the legs.

14. The preform of claim 11, wherein:

at least a portion of the warp fibers comprises multi-strand tracer fibers for identifying selected locations in the preform, the tracer fibers being formed from at least one strand that is detectable by x-ray imaging and at least one strand that has a color contrasting the color of surrounding fibers.

15. The preform of claim 14, wherein:

the tracer fiber is formed from stainless steel and aramid strands.

16. The preform of claim 11, wherein:

at least a portion of the warp fibers in the base has a smaller cross-sectional area than the warp fibers in the legs.

17. A method of forming a woven preform, the method comprising

(a) providing at least a pair of adjacent base layers of warp fibers for forming a base, the warp fibers being generally parallel to each other and generally arranged in columns;

(b) providing at least two layers of adjacent leg layers of warp fibers for forming a pair of legs, the warp fibers being generally parallel to each other and generally arranged in columns;

(c) weaving at least one fill fiber among the base layers and leg layers for interlocking the warp fibers of each base layer to each other and interlocking the warp fibers of the leg layers to each other, the legs being connected to the base at intersections by portions of the fill fiber extending between each leg and the base, two groups of fill fiber portions connecting each leg to the base;

(d) locating an odd number of central columns of warp fibers in the base between the intersections of the legs and base, the odd number of columns allowing a substantially mirror-image weave pattern about a central plane of symmetry of the preform; and

(e) locating separator columns adjacent the central columns, one of the groups of fill fiber portions for each leg intersecting the base adjacent one side of the corresponding separator column, the other of the groups of fill fiber portions for each leg intersecting the base on the opposite side of the corresponding separator column.

18. The method of claim 17, wherein:

step (a) comprises providing at least one multi-strand tracer fiber within the preform for identifying a selected location on the preform.

19. The method of claim 17, wherein:

step (a) comprises providing at least one multi-strand tracer fiber within the preform that is X-ray opaque for identifying a selected location on the preform.