Composite connectors and methods of manufacturing the same

Abstract

A method of manufacturing a composite (e.g. fiber-reinforced polymer) connector for a fluid transfer conduit comprises: manufacturing a tubular pre-form which extends substantially parallel to a central axis C, the tubular pre-form comprising continuous circumferentially-oriented fiber reinforcement; manufacturing a continuous fiber pre-form net, the pre-form net comprising a support layer and continuous fiber reinforcement, the continuous fiber reinforcement being secured by being stitched to the support layer; placing the tubular pre-form and the pre-form net together into a mould to form a tubular hub portion from the tubular pre-form and a flange portion from the pre-form net, the flange portion extending from the hub portion at an angle to the central axis C; and introducing polymer into the mould so as to form a composite connector comprising the flange portion and the hub portion.

Claims

1. A connection system comprising a composite connector and fiber-reinforced polymer fluid transfer conduit, the composite connector comprising: a hub portion comprising a tube which extends substantially parallel to a central axis; and a flange portion which extends from the hub portion at an angle to the central axis; wherein the hub portion comprises a polymer reinforced with continuous circumferentially-oriented fiber reinforcement; wherein the flange portion comprises the same polymer reinforced with continuous fiber reinforcement and a support layer to which the continuous fiber reinforcement is secured by being stitched thereto; wherein the flange portion comprises at least one fixing point for securing the composite connector to another structure, and the continuous fiber reinforcement at least partially encircles the at least one fixing point; wherein the fluid transfer conduit is connected to the hub portion; and wherein the composition and orientation of the continuous fiber reinforcement at least within the hub portion is selected such that the coefficient of thermal expansion and/or the stiffness of the hub portion substantially matches that of the fluid transfer conduit; the connection system further comprising an elastomeric O-ring positioned between an outer surface of the fluid transfer conduit and an inner surface of the hub portion.

2. The connection system as claimed in claim 1, wherein the continuous fiber reinforcement comprises multiple layers stitched to the common support layer.

3. The connection system as claimed in claim 1, wherein the flange portion is substantially perpendicular to the central axis of the hub portion.

4. The connection system as claimed in claim 1, wherein the flange portion comprises one or more tabs which extend along a surface of the hub portion.

5. The connection system as claimed in claim 1, wherein the polymer comprises a thermosetting polymer.

6. The connection system as claimed in claim 1, wherein the elastomeric O-ring is seated between a pair of retaining ridges that allow for axial movement between the fluid transfer conduit and the hub portion.

7. The connection system as claimed in claim 1, wherein the at least one fixing point is a through-hole.

8. The connection system as claimed in claim 1, wherein the at least one fixing point is surrounded by unbroken fiber reinforcement.

9. The connection system as claimed in claim 1, wherein the flange portion comprises a plurality of fixing points and the continuous fiber reinforcement is arranged to encircle an adjacent pair of fixing points.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Features of any example described herein may, wherever appropriate, be applied to any other example described herein. Where reference is made to different examples or sets of examples, it should be understood that these are not necessarily distinct but may overlap.

(2) Certain examples of the present disclosure will now be described with reference to the accompanying drawings in which:

(3) FIG. 1 is a cross sectional view of the connection between a connector and a fluid transfer conduit;

(4) FIG. 2 shows a schematic perspective view of a composite connector for a fluid transfer conduit according to an example of the present disclosure;

(5) FIGS. 3, 4 and 5 show various examples of pre-form nets;

(6) FIG. 6 shows a partially manufactured composite connector comprising the pre-form net of FIG. 5 with a tubular pre-form; and

(7) FIG. 7 shows in cross-section a moulding step in a method of manufacturing a composite connector according to an example of the present disclosure.

DETAILED DESCRIPTION

(8) FIG. 1 shows the interface between a connector 2 and a cylindrical fluid transfer conduit 4 that extends parallel to a central axis C. The connector 2 comprises a cylindrical hub portion 6, which also extends parallel to the central axis C, and a flange portion 8, which extends from an end of the hub portion 6 in a direction perpendicular to the central axis C. The flange portion 8 further comprises a through-hole 10, by which the connector 2 may be secured to another structure, e.g. an aircraft wing rib.

(9) The hub portion 6 encloses a connection portion 12 of the fluid transfer conduit 4. An elastomeric O-ring 14 is located between the hub portion 6 and the connection portion 12, retained between an inner wall of the hub portion 6 and an outer wall of the fluid transfer conduit 4. The O-ring 14 is confined by two retaining ridges 16 which extend radially outwards from the connection portion 10 of the fluid transfer conduit 4.

(10) The O-ring 14 provides a seal between the connector 2 and the conduit 4, such that fluid may flow along the conduit 4 and into the connector 2 without escaping. In addition, the configuration of O-ring 14 between the connection portion 12 and the hub portion 6 allows the fluid transfer conduit 4 to move a small distance in the direction of the central axis C relative to the connector 2 without compromising the seal. This enables a structure to which the connector 2 is secured to move or flex a small amount without imparting large stresses on the conduit 4 (as would be the case if the connector 2 was rigidly attached to the conduit 4). Instead, the conduit 4 floats on the O-ring 14 such that it can slide longitudinally a small distance without breaking the seal. For example, the structure to which the connector 2 is attached may be an aircraft wing rib, which is designed to move a small amount during flight as the wing flexes due to aerodynamic load and/or temperature fluctuations. The fluid transfer conduit 4 may comprise a fuel pipe located within the wing which must therefore be able to cope with the wing flex during flight.

(11) FIG. 2 is a schematic perspective view of a composite connector 102 according to an example of the present disclosure. The connector 102 comprises a cylindrical hub portion 106 which extends parallel to a central axis C and a flange portion 108 which extends perpendicularly from an end of the hub portion 106. The flange portion 108 comprises four through-holes 114 which allow the connector 102 to be fixed to a further structure (e.g. an internal rib of an aircraft wing).

(12) The hub portion 106 comprises polymer resin matrix reinforced with continuous hoop-wound (circumferentially-orientated) fiber 110. The hoop-wound fiber 110 provides the hub portion 106 with high hoop strength such that the hub portion can resist large internal pressures. It also makes the hub portion 106 very stiff, such that large internal pressures cause negligible hoop expansion.

(13) The flange portion 108 comprises the same polymer resin matrix with its own continuous fiber reinforcement 112 (only shown partially for clarity).

(14) The composite connector 102 is manufactured using a pre-form net and a tubular pre-form. FIG. 3 shows an example of one such pre-form net 300. The pre-form net 300 comprises an annular disc 302 defining a central hole 303. The annular disc 302 is formed from fiber reinforcement 304 (although only a small portion of the total fiber reinforcement present is depicted in FIG. 3 to aid clarity), which has been stitched onto a non-structural support layer 306 made of a fiber veil (e.g. using a polyester or nylon thread, not shown). The support layer 306 holds the fiber reinforcement 304 in a desired position and orientation.

(15) The pre-form net 300 further comprises four through-holes 308 spaced around the annular disc 302 which will become fixing points in the flange portion of the finished connector, allowing the connector to be fixed securely to a further structure.

(16) The fiber reinforcement 304 extends both radially and circumferentially in the annular disc 302, providing the finished connector with resistance to torques and bending loads. The fiber reinforcement 304 partially encircles the through-holes 308 (and may completely encircle the through-holes one or more times) to increase their strength and thus the strength of a connection between the finished connector and a further structure.

(17) An alternative pre-form net 400 is shown in FIG. 4 which comprises four flange lobes 402 arranged around and defining a central hole 403. Continuous fiber reinforcement 404 runs between each of the flange lobes 402 (only partially shown for clarity). The fiber reinforcement 404 is stitched onto a non-structural support layer 406 comprising a fiber veil to hold the fiber reinforcement 404 in a desired position and orientation. The pre-form net 400 further comprises four through-holes 408 spaced around the annular disc 402, in this example one through-hole 408 in each lobe 402. The through holes 408 will become fixing points in the flange portion of the finished connector. The lobed pre-form net 400 may produce a finished connector with lower weight than the annular pre-form net 300.

(18) As with the pre-form net 300 shown in FIG. 3, the fiber reinforcement 404 extends both radially and circumferentially in the flange lobes 402, providing the finished connector with resistance to torques and bending loads. The fiber reinforcement 404 encircles the through-holes 408 (possibly several times) to increase their strength.

(19) FIG. 5 shows a further alternative pre-form net 500, comprising an annular disc 502 which surrounds a central tabbed section 505. Continuous fiber reinforcement 504 extends around the annular disc 502 and into the central tabbed section 505. The fiber reinforcement 504 is stitched onto a support layer 506 comprising a fiber veil to hold the fiber reinforcement 504 in a desired position and orientation. The pre-form net 500 further comprises four through-holes 508 spaced around the annular disc 502. The through holes 508 will become fixing points in the flange portion of the finished connector (as seen in FIG. 6).

(20) The tabbed section 505 comprises a plurality of radially extending tabs 507, which may be formed by stitching the fiber reinforcement 504 to the support layer 506 in which tabs have already been cut, or by cutting tabs into the pre-form net 500 after the fiber reinforcement 504 has been stitched to the support layer 506. The pre-form net 500 is flat while the fiber reinforcement 504 is stitched onto the support layer 506, but the tabs 507 may then be folded out to extend perpendicularly from the annular disc 502. As shown in FIG. 6, when the pre-form net 500 is used to form a composite connector (described in more detail below), the folded-out tabs 507 are arranged to extend around an outer surface of a fiber-reinforced tubular pre-form 600. It is shown schematically how the tubular pre-form 600 comprises continuous circumferentially-oriented fiber reinforcement 604, e.g. hoop fiber reinforcement. The tabs serve to increase the area over which the fiber reinforcement 504 of the pre-form net 500 contacts the tubular pre-form 600 and its fiber reinforcement 604, when compared with the contact area possible with alternative pre-form nets, such as those shown in FIGS. 3 and 4. With these pre-form nets 300, 400, the tubular pre-form 600 may contact the pre-form net 300, 400 only around the inner edge of the central hole 303, 403.

(21) Increasing the contact area between the fiber reinforcement 504 of the pre-form net 500 and the tubular pre-form 600 strengthens the connection between the flange portion and the hub portion in the resultant connector, increasing its strength and, in particular, its resistance to bending loads.

(22) As shown in FIG. 7, manufacturing a composite connector according to the present disclosure comprises placing the pre-form net 300 (for example) into a mould 700 with a tubular pre-form 310.

(23) The tubular pre-form 310 comprises continuous circumferential fiber reinforcement 312 and has an outer diameter which matches the diameter of the central hole 303. The tubular pre-form 310 may be formed in a preceding manufacturing step by filament winding dry fiber onto a mandrel, with the mandrel being removed or left in situ when the tubular pre-form 310 is assembled with the pre-form net 300 in the mould 700.

(24) The mould 700 into which the pre-form net 300 and the tubular pre-form 310 are placed comprises a first portion 702 and a second portion 704. The first and second portions 702, 204 are shaped such that when they are brought together they define an annular cavity, into which the pre-form net 300 is placed, and a tubular cavity, into which the tubular pre-form 310 is placed. Both the annular and tubular cavities are symmetrical about a central axis C. Although not shown in FIG. 7, a mandrel on which the tubular pre-form 310 has been formed may also be placed into the mould 700 and may even form part of first or second portions 702, 704 of the mould 700.

(25) When placed in the mould 700, the tubular pre-form 310 extends into the central hole 303 of the pre-form net 300 (as seen in FIG. 3) such that any gap between the fiber reinforcement 304, 312 of the pre-form net 300 and the tubular pre-form 310 is minimised.

(26) In this example, thermosetting polymer resin is pumped into the annular and tubular cavities through one or more input channels (not shown) and penetrates into and around the fiber reinforcement 304, 312 of both the pre-form net 300 and the tubular pre-form 310. Of course the support layer 306 is stitched to the fiber reinforcement 304 in the pre-form net 300 and becomes encapsulated as well. The mould 700 holds both the pre-form net 300 and the tubular pre-form 310 in position during this process.

(27) Heat is applied to the mould 700 to cure the resin and form a composite connector comprising a flange portion (formed from the pre-form net 300) and a hub portion (formed from the tubular pre-form 310). The finished composite connector may then be removed from the mould 700. FIG. 2 provides an example of the resultant connector 102.