TRUSSED STRUCTURE

Abstract

A trussed structure comprising a frame and at least one strut, wherein the frame is of composite material and includes sockets which are integral with the frame. The invention also provides a process of making the trussed structures. The struts are typically of composite material and the trussed structures of the invention are particularly suitable for use in aircraft, for example, as wing ribs or floor beams.

Claims

1. (canceled)

2. A trussed aircraft structure, comprising: a single member perimeter frame formed of layered and bonded composite material having at least two plies of fiber material bonded together, the perimeter frame having two long sides and two short sides, the two long sides comprising a first long side and opposing second long side separated by a space bounded by the perimeter frame; each of the first long side having formed therein at least two socket portions including a first socket portion and a second socket portion and the second long side having formed therein at least two further socket portions including a third socket portion and a fourth socket portion; the first socket portion being axially aligned with third socket portion and the second socket portion being axially aligned with the fourth socket portion; a first rectilinear strut having a first long axis, the first rectilinear strut extending through the first socket portion and the third socket portion, across the space separating the first long side and the second long side; a second rectilinear strut having a second long axis, the second rectilinear strut extending through the second socket portion and the fourth socket portion, across the space separating the first long side and the second long side; wherein the first long axis and the second long axis intersect at a location outside the perimeter frame when the first rectilinear strut is inserted in the first socket portion and the third socket portion and the second rectilinear strut are inserted into the in the second socket portion and the fourth socket portion and further wherein the first long axis and the second long axis are oriented parallel to a plane of the plies of fiber material.

3. The trussed aircraft structure as claimed in claim 2, wherein the struts are tubular and circular in cross section.

4. The trussed aircraft structure as claimed in claim 2, in which the composite material comprises a carbon fiber.

5. The trussed aircraft structure as claimed in claim 2, in which the matrix of the composite material is a thermosetting material.

6. The trussed aircraft structure as claimed in claim 2, in which the at least one strut is of composite material and has been co-cured with the frame.

7. The trussed aircraft structure as claimed in claim 2, in which the at least one strut is of composite material and has been co-bonded with the frame.

8. The trussed aircraft structure as claimed in claim 2, in which the at least one strut is fixed in the sockets with adhesive.

9. The trussed aircraft structure as claimed in claim 2, in which the frame is a 3D-woven structure.

10. The trussed aircraft structure as claimed in claim 2, in which the frame comprises stitching in a region of at least one of the sockets.

11. The trussed aircraft structure according to claim 2, in which the trussed aircraft structure comprises an airfoil rib or a floor beam for an aircraft.

12. An aircraft comprising: a trussed aircraft structure, the trussed aircraft structure comprising: a single member perimeter frame formed of layered and bonded composite material having at least two plies of fiber material bonded together, the perimeter frame having two long sides and two short sides, the two long sides comprising a first long side and opposing second long side separated by a space bounded by the perimeter frame; each of the first long side having formed therein at least two socket portions including a first socket portion and a second socket portion and the second long side having formed therein at least two further socket portions including a third socket portion and a fourth socket portion; the first socket portion being axially aligned with third socket portion and the second socket portion being axially aligned with the fourth socket portion; a first rectilinear strut having a first long axis, the first rectilinear strut extending through the first socket portion and the third socket portion, across the space separating the first long side and the second long side; a second rectilinear strut having a second long axis, the second rectilinear strut extending through the second socket portion and the fourth socket portion, across the space separating the first long side and the second long side; wherein the first long axis and the second long axis intersect at a location outside the perimeter frame when the first rectilinear strut is inserted in the first socket portion and the third socket portion and the second rectilinear strut are inserted into the in the second socket portion and the fourth socket portion and further wherein the first long axis and the second long axis are oriented parallel to a plane of the plies of fiber material.

13. The aircraft as claimed in claim 12, wherein the struts are tubular and circular in cross section.

14. The aircraft as claimed in claim 12, in which the composite material comprises a carbon fiber.

15. The aircraft as claimed in claim 12, in which the matrix of the composite material is a thermosetting material.

16. The aircraft as claimed in claim 12, in which the at least one strut is of composite material and has been co-cured with the frame.

17. The aircraft as claimed in claim 12, in which the at least one strut is of composite material and has been co-bonded with the frame.

18. The aircraft as claimed in claim 12, in which the at least one strut is fixed in the sockets with adhesive.

19. The aircraft as claimed in claim 12, in which the frame is a 3D-woven structure.

20. The aircraft as claimed in claim 12, in which the frame comprises stitching in a region of at least one of the sockets.

21. The aircraft as claimed in claim 12, in which the trussed aircraft structure comprises an airfoil rib or a floor beam of the aircraft.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Embodiments of the invention will now be described for the purpose of illustration only with reference to the figures in which:

[0027] FIG. 1 shows an embodiment of a simple wing rib trussed structure according to the invention;

[0028] FIGS. 2a to 2e show steps in a method of making a frame for use in a trussed structure according to the invention;

[0029] FIG. 3 shows a 3D-woven fiber structure for use in a frame for a trussed structure according to the invention; and

[0030] FIG. 4 shows the fiber structure of FIG. 3 laid up in a molding tool with three struts in place and a fourth strut in alignment, ready for insertion into the socket portions of the fiber structure.

[0031] While various embodiments are amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the claimed inventions to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the subject matter as defined by the claims.

DETAILED DESCRIPTION OF THE DRAWINGS

[0032] Various embodiments of systems, devices, and methods have been described herein. These embodiments are given only by way of example and are not intended to limit the scope of the claimed inventions. It should be appreciated, moreover, that the various features of the embodiments that have been described may be combined in various ways to produce numerous additional embodiments. Moreover, while various materials, dimensions, shapes, configurations and locations, etc. have been described for use with disclosed embodiments, others besides those disclosed may be utilized without exceeding the scope of the claimed inventions.

[0033] Persons of ordinary skill in the relevant arts will recognize that the subject matter hereof may comprise fewer features than illustrated in any individual embodiment described above. The embodiments described herein are not meant to be an exhaustive presentation of the ways in which the various features of the subject matter hereof may be combined. Accordingly, the embodiments are not mutually exclusive combinations of features; rather, the various embodiments can comprise a combination of different individual features selected from different individual embodiments, as understood by persons of ordinary skill in the art. Moreover, elements described with respect to one embodiment can be implemented in other embodiments even when not described in such embodiments unless otherwise noted.

[0034] Although a dependent claim may refer in the claims to a specific combination with one or more other claims, other embodiments can also include a combination of the dependent claim with the subject matter of each other dependent claim or a combination of one or more features with other dependent or independent claims. Such combinations are proposed herein unless it is stated that a specific combination is not intended.

[0035] Any incorporation by reference of documents above is limited such that no subject matter is incorporated that is contrary to the explicit disclosure herein. Any incorporation by reference of documents above is further limited such that no claims included in the documents are incorporated by reference herein. Any incorporation by reference of documents above is yet further limited such that any definitions provided in the documents are not incorporated by reference herein unless expressly included herein.

[0036] For purposes of interpreting the claims, it is expressly intended that the provisions of 35 U.S.C. 112(f) are not to be invoked unless the specific terms means for or step for are recited in a claim.

[0037] FIG. 1 shows a trussed structure according to the invention for use as a wing rib in an aircraft. The trussed structure 1 comprises four tubular struts 2 and a frame 3 of generally rectangular shape with the two long sides being bowed outwards somewhat.

[0038] The frame 3 comprises eight sockets 4, 4, 5, 5, 6, 6 and 7, 7, arranged in four opposing pairs, each opposing pair of sockets holding the two end portions of one of the struts 2.

[0039] The sockets 4, 4, 5, 5, 6, 6 and 7, 7, are integral with the frame, that is, they are formed of the composite material of the frame where that material extends around the end portions of the struts.

[0040] FIGS. 2a to 2e show steps in one method of making a frame for a trussed structure according to the invention. FIG. 2a shows a partial view of a carbon fiber ply 8 which is a cut shape for use in a wing rib, laid up in a molding tool (not shown). The molding tool has a groove of semi-circular cross-section running transverse to the length of the carbon fiber ply 8. That carbon fiber ply 8 has been forced into the groove so that it conforms to the shape of the groove. As shown in FIG. 2b, a cylindrical mandrel 9 is then placed in the groove on top of the first ply 8. The mandrel 9 has a radius substantially equal to the radius of the groove minus the thickness of the first ply 8 so that it fits snugly into the depression in the carbon fiber ply 8 where it conforms to the groove. The mandrel 9 extends (not shown in FIG. 2b) across the molding tool so that its other end lies in a similar groove on the other side of the fame, such that two aligned sockets are formed on opposite sides of the frame.

[0041] A second ply 10 of carbon fiber (shown in part in FIG. 2c) is then laid on top of the first ply 8 and over the mandrel 9. The second ply 10 is forced down so that it lies snugly over the mandrel 9, which is thereby sandwiched between the first ply 8 and the second ply 10.

[0042] The first and second plies 8 and 10 are then stitched together on either side of the mandrel 9 for extra reinforcement with the stitches 11 being arranged in rows running parallel to the mandrel 9. The molding tool is then closed, aerospace epoxy resin is infused into the carbon plies 8 and 10 and the resin is then cured. The cured frame is then released from the molding tool and the mandrel 9 is withdrawn to leave the formed socket 12 as an open ended recess of constant circular cross-section extending transversely across the frame 13 of cured composite material. The full frame 13 is shown in FIG. 2e, without struts. As can be seen from FIG. 2e, the opposite side of the frame 13 from socket 12 includes an opposing socket 14 which was formed around the same mandrel 9 and is, in consequence, aligned with socket 12 for receiving a strut. The frame 13 can then be drilled and machined as required. Struts are then inserted into the sockets and fixed in place with adhesive to form the trussed structure.

[0043] In a variation of the method shown in FIGS. 2a to 2e, cured struts are used in place of the mandrels 9. In that variation, the resin of the frame cures (co-bonds) around the end portions of each strut, thereby forming a strong bond with the strut. In a further variation, carbon fiber filament coated with uncured (wet) resin is wound onto strut mandrels and the uncured carbon fiber/resin/mandrel assemblies are used in place of mandrels 9. In that variation, the resin of the strut is co-cured with the resin of the frame, thereby providing an especially strong bond. The strut mandrels are removed subsequently and the frame drilled and finished as before.

[0044] FIG. 3 shows a 3D-woven carbon fiber structure 15 which includes eight socket portions 16 arranged in four opposed pairs, which are woven as one with the rest of the structure 15. The warp and weft directions are indicated by arrows A and B respectively. If desired, additional plies 17 having a particular desired orientation may be added to the fiber structure 15 in the regions between sockets 16 (only one section of addition ply 17 is shown in FIG. 3 for clarity) to add strength in a particular direction.

[0045] FIG. 4 shows the fiber structure 15 with three cured composite struts 18 in place in respective opposed pairs of socket portions 16 and a fourth strut 19 in alignment with the fourth pair of socket portions 16, ready to be inserted into those socket portions 16. The frame/strut assembly lies in an open molding tool 20. When the last strut 19 is in place in socket portions 16, the molding tool 20 is closed, resin is infused into the fiber structure 15 and cured, thereby co-bonding with the struts 18, 19.

[0046] While the present invention has been described and illustrated by reference to particular embodiments it will be appreciated by those of ordinary skill in the art that the invention lends itself to many variations not illustrated herein. For those reasons, reference should be made to the claims for purposes of determining the true scope of the present invention.