GB2571088A

GB2571088A - A tool and method for forming an annular component

Info

Publication number: GB2571088A
Application number: GB1802432.3A
Authority: GB
Inventors: Barber Scott
Original assignee: Composite Technology and Applications Ltd
Current assignee: Composite Technology and Applications Ltd
Priority date: 2018-02-14
Filing date: 2018-02-14
Publication date: 2019-08-21
Also published as: GB201802432D0

Abstract

A tool 10 for forming an annular component comprises a diaphragm 14 extending around the mandrel (12, Figure 1) to define an expansion cavity 34. An outer mould 16 defines a profile for a component. When collapsed diaphragm 14 defines a lay-up surface for a pre-form 40 and in when expanded, such as by fluid introduced through port 32 to cavity 34, the diaphragm drives and deforms the pre-form 40 against the outer mould 16. Heaters may be provided on the mandrel for softening the preform and the outer mould for curing the formed component. The outer mould may comprise several parts which may be assembled around the mandrel and may clamp the diaphragm to the mandrel. Diaphragm portions may be bonded to the mandrel. The mould may have a flange forming portion and an arcuate diaphragm guide 22 which prevents the diaphragm expanding around the preform during flange formation. The tool may be used to form an annular component having a variable radius along its annular extent, such as a gas turbine casing.

Description

A TOOL AND METHOD FOR FORMING AN ANNULAR COMPONENT

The invention relates to a tool and method for forming an annular component.

It is known to form annular components with fibre reinforced composite materials. Examples of methods of forming such annular components include forming semiannular components by laying up and curing semi-annular portions of a material on a formed lay-up surface, and fixing the semi-annular components together to form an annular component.

According to a first aspect, there is provided a tool for forming an annular component comprising: a mandrel; a diaphragm extending around the mandrel to define an expansion cavity therebetween, the diaphragm having a lay-up configuration in which it defines a lay-up surface for a pre-form for the component, and in which the expansion cavity is collapsed; a port for introducing fluid into the expansion cavity to expand the diaphragm from the lay-up configuration to a forming configuration; an outer mould defining a profile for the component, the outer mould being configured to enclose a preform on the diaphragm so that in use, expansion of the diaphragm to the forming configuration causes the diaphragm to drive the pre-form against the outer mould to deform the pre-form.

The mandrel may be cylindrical within the diaphragm. The tool may comprise a heater configured to heat the mandrel such that heat is transferred from the mandrel to the pre-form.

Portions of the diaphragm may be bonded to the mandrel to form the expansion cavity between the diaphragm and the mandrel.

The port may be disposed in the mandrel. The port may be formed in a wall of the mandrel. In other words, the port may extend through a wall of the mandrel.

The outer mould may comprise two parts which are fixed together around the mandrel in use. The outer mould may be configured to cooperate with the mandrel to clamp the diaphragm between them.

The tool may comprise a heater configured to heat the outer mould such that heat is transferred from the outer mould to the pre-form.

The diaphragm may be elastically deformable.

The outer mould may comprise a mould portion and a diaphragm guide. The mould portion may define a flanged profile for the annular component configured so that in use an axial end of the pre-form folds around the mould portion to form a flange as the diaphragm expands to the forming configuration. The diaphragm guide may extend axially beyond the mould portion to oppose a portion of the diaphragm corresponding to the axial end of the pre-form when the diaphragm is in the lay-up configuration. The diaphragm guide may have a profile which corresponds to the path of the end of the pre-form as it folded, so as to prevent the diaphragm expanding around the end of the pre-form. The diaphragm guide may has an arcuate profile in a plane through a central axis of the tool, wherein the profile is configured such that it corresponds to the path of the end of the pre-form as it is folded around the mould portion in use.

The outer mould may comprise a mould portion which defines a profile for the annular component having a variable radius along an axial extent of the outer mould.

According to a second aspect, there is provided a method of forming an annular component using a tool according to the first aspect, the method comprising: laying-up fibre reinforcement material on the diaphragm in the lay-up configuration to form a composite pre-form; enclosing the pre-form on the diaphragm with the outer mould; introducing fluid through the port into the expansion cavity to expand the diaphragm to the forming configuration and drive the pre-form against the outer mould to deform the pre-form.

The mandrel may be heated such that heat is transferred from the mandrel to the preform until the pre-form reaches a forming temperature when the pre-form is enclosed with the outer mould. The outer mould may be heated such that heat is transferred to the pre-form to cure the pre-form.

Fluid may be removed from the expansion cavity through the port to collapse the diaphragm back to the lay-up configuration after expanding the diaphragm so that the mandrel can be removed from the annular component.

The invention may comprise any combination of the features and/or limitations referred to herein, except combinations of such features as are mutually exclusive.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 schematically shows a longitudinal cross section view of a tool for moulding an annular component;

Figure 2 schematically shows a mandrel of the tool of Figure 1;

Figure 3 schematically shows an axial cross section view of an outer mould of the tool of Figure 1;

Figures 4-6 schematically shows a longitudinal cross section view of the tool in Figure 1 at successive stages of forming the annular component; and

Figure 7 is a flow chart of the method of forming the annular component.

Figure 1 shows a longitudinal cross section of a tool 10 for moulding an annular component such as a casing for a gas turbine engine. An example component may be a flanged cylinder with a variable radius along a central axis A such as a condi barrel. The tool 10 comprises an assembly of a mandrel 12, a diaphragm 14 and an outer mould 16.

The mandrel 12 comprises a hollow cylinder defining a cylindrical outer surface and the diaphragm 14 extends around the outer surface of the mandrel 12. The outer mould 16 comprises a hollow, generally annular mould which is configured to surround the mandrel 12 and the diaphragm 14.

Figure 2 shows the tool 10 with the outer mould 16 removed, to show the mandrel 12 and the diaphragm 14 in more detail. In the following description, the term “axial direction” refers to a direction along a central axis of the mandrel 12 as described above.

The mandrel 12 is provided with heaters 30 inside the hollow interior of the mandrel 12. The heaters 30 in this example are in the form of mats which are distributed around and in contact with an internal surface of the mandrel 12 to selectively heat the mandrel 12.

The diaphragm 14 is elastically deformable and extends axially along the mandrel 12 and around the outer surface of the mandrel 12. The axial extent (i.e. length in the axial direction) of the diaphragm 14 is shorter than the axial extent of the mandrel 12 such that the diaphragm 14 terminates at a point offset from each axial end of the mandrel 12.

The diaphragm 14 comprises fixing portions 36 extending circumferentially around the diaphragm at axial ends of the diaphragm 14. The fixing portions 36 are bonded to the outer surface of the mandrel 12 so that an expansion cavity (best seen in Figures 5 and 6, with reference 34) is formed between the diaphragm 14 and the mandrel 12.

The diaphragm in this example is a rubber with a percentage elongation of at least 200%. In other examples, the diaphragm may comprise any elastically deformable material.

The mandrel 12 comprises ports 32 in the form of through holes in the wall of the mandrel 12. The ports 32 are positioned in the mandrel 12 to be in fluid communication with the expansion cavity 34. In this example, there are eight ports 32 equally distributed around the mandrel 12 at two axial locations. However, in other examples there may be more or fewer ports distributed around the mandrel 12. The ports 32 can be connected to a fluid source and pump so that fluid may be selectively introduced into the expansion cavity 34 and removed from the expansion cavity to expand and deflate the diaphragm 14 as required.

Figures 1 and 2 show the diaphragm 14 in a lay-up configuration, in which the expansion cavity 34 is in an unexpanded state such that the diaphragm 14 rests on the outer surface of the mandrel 12 and conforms to the profile of the mandrel 12. The diaphragm 14 in the lay-up configuration forms a lay-up surface on which a pre-form is laid-up in use.

Referring back to Figure 1, the outer mould 16 extends around the mandrel 12 and the diaphragm 14 such that the diaphragm 14 is enclosed between the outer mould 16 and the mandrel 12. A forming chamber 50 is defined between the outer mould 16 and the diaphragm 14. The diaphragm 14 is configured to expand within the forming chamber 50 to deform a laid-up pre-form and to drive the pre-form against the outer mould 16.

The outer mould 16 is a hollow component with a circular cross sectional profile having a varying diameter along its axial extent (i.e. axisymmetric). When fixed to the mandrel 12, the outer mould 16 is coaxial with the mandrel 12 about the central axis A of the mandrel 12.

The outer mould 16 comprises a mould portion 20 to define a profile of a pre-form, a diaphragm guide 22 on each side of the mould portion 20 along the axial direction and a clamp portion 24 at each axial end of the outer mould 16.

An inner surface 18 of the mould portion 20 defines the shape of the outer surface of the annular component which is to be formed with the tool 10. In this example, the inner surface 18 has a diameter which increases along the axial direction from the centre of the mould portion 20, up to a lip 28 on either side where the diameter decreases. The diameter then increases beyond the lip 28, such that the smallest diameter of the mould portion 20 is in the centre of the outer mould 16. At each axial end of the mould portion, the mould portion 20 extends radially outwardly to form a shoulder 26, configured to define a flange in the annular component.

The diaphragm guide 22 at each axial end extends axially beyond the mould portion 20 (i.e. away from the centre portion) so that there is a diaphragm guide 22 at each side of the mould portion 20. Each diaphragm guide 22 has a profile which corresponds to the path of the respective axial end of the pre-form as the diaphragm 14 expands and causes the pre-form to fold around the shoulder 26 and against the mould portion 20. In this example, each diaphragm guide 22 comprises an arcuate profile which follows the path of the respective end of the pre-form as it is deformed and folded around the shoulder 26 of the mould portion 20. Accordingly, the profile of the diaphragm guide 22 prevents the diaphragm 14 from expanding around the axial ends of the pre-form during forming.

Each clamp portion 24 is provided at a respective axial side of the outer mould 16 at axial ends. The clamp portions 24 extend over and axially beyond the fixing portions 36 of the diaphragm 14. The outer mould 16 is configured to clamp the diaphragm 14 at the fixing portions 36 between the clamp portions 24 and the mandrel 12. Each clamp portion 24 also fixes the outer mould 16 to the mandrel 12. In this example, the axial ends of the clamp portion 24 have an inner diameter which corresponds to the outer diameter of the mandrel 12 such that the outer mould 16 has a friction fit around and clamps to the mandrel 12. In other examples, the clamp portion may fix the outer mould to the mandrel by any suitable means which allows the outer mould and inner mould to be separated, such as with a mechanical fastener.

The outer mould 16 comprises heaters 52 in the form of mats disposed around the outer surface of the mould portion 20 of the outer mould 16. The heaters 52 are configured to selectively heat the outer mould 16.

Figure 3 shows a cross sectional view of the outer mould 16. In this example, the outer mould 16 comprises two semi-annular parts 16a, 16b which are detachably fixed together so that the outer mould 16 is removable from the assembly. The two parts 16a, 16b of the outer mould 16 form two halves of the outer mould 16. Each part 16a, 16b comprises radially extending fixings 38 at opposing sides of the semi-annular part. The two parts 16a, 16b are joined together by bolts through the fixings 38.

In other examples, two parts forming the outer mould may be fixed together by any suitable means that allows them to be fixed together around the mandrel and separated from one another (e.g. with a hinge).

Figures 4-6 show successive configurations of the tool 10 in use during a method of forming an annular component, in which the diaphragm is initially in a lay-up configuration, and is expanded to a forming configuration.

Figure 4 shows the tool 10 with the diaphragm 14 in the lay-up configuration (as in Figure 1), so that the expansion cavity 34 is in an unexpanded state. A pre-form 40 is laid-up on the lay-up surface of the diaphragm 14. The pre-form 40 in this example is laid-up in two layers, such that a first layer extends from one axial end of the forming chamber 50 to the other, and the second layer is laid on top of the first layer, to make a thicker section of the pre-form 40 which is aligned with the central part of the mould portion 20 between the lips 28. Each layer may comprise a plurality of plies. In this example, each layer comprises 60 plies. However, in other examples, each layer may comprise any suitable number of plies.

In this example, the plies are laid up at angles between 0 degrees to 70 degrees, where 0 degrees corresponds to laying up a ply in the axial direction, and 90 degrees corresponds to laying up a ply in the circumferential direction.

Figure 5 shows the tool 10 with the diaphragm 14 in a partially expanded state owing to partial expansion of the expansion cavity 34. The expansion cavity 34 has been expanded or inflated by introducing a fluid into the expansion cavity 34 through the ports 32 in the mandrel 12. This causes the diaphragm 14 to expand and to drive the pre-form 40 away from the mandrel 12 and against the mould portion 20 of the outer mould 16. Axial ends of the pre-form 40 are touching or adjacent the diaphragm guide 22 so that expansion of the diaphragm 14 is constrained by the pre-form 40 which remains between the diaphragm 14 and the inner surface 18 of the mould portion 20.

Figure 6 shows the tool 10 with the diaphragm 14 in a forming configuration (i.e. a fully expanded state). The expansion cavity 34 has been inflated further by introducing more fluid into the expansion cavity 34. This causes the diaphragm 14 to fully expand, so that the axial ends of the pre-form 40 are folded around the respective shoulders 26 of the mould portion 20 and the pre-form 40 is deformed to the desired shape against the inner surface 18 of the mould portion 20. As the axial ends of the pre-form 40 fold around the respective shoulders 26, they follow the profile of the diaphragm guides 22, so that the diaphragm 14 is prevented from expanding around the pre-form 40.

Figure 7 is a flow chart showing the steps of the method for forming an annular component using the tool described with reference to Figures 1-6. At the beginning of the method, the tool 10 is separated into two parts: the mandrel 12 with the diaphragm 14 fixed to it in a lay-up configuration, and the outer mould 16.

In block 102, carbon fibre reinforced plastic plies are laid up around the mandrel 12 on the lay-up surface of the diaphragm 14 to provide a pre-form 40 for an annular component.

In block 104, the outer mould 16 is fixed to the mandrel 12 by fixing the two parts 16a, 16b of the outer mould 16 together around the mandrel 12 and over the diaphragm 14 to enclose the pre-form 40 and the diaphragm 14 between the mandrel 12 and the outer mould 16. The outer mould 16 also clamps the fixing portion 36 of the diaphragm to the mandrel 12 and clamps itself around the mandrel 12.

In block 106, the heaters 30 positioned around the inner surface of the mandrel 12 heat the mandrel 12. As the mandrel 12 is heated, heat is transferred through the diaphragm 14 to the pre-form 40 on the diaphragm 14. The heaters 30 heat the mandrel 12 until the pre-form reaches a forming temperature. In this example, the forming temperature is approximately 100 degrees Celsius. At the forming temperature, the pre-form is malleable and can be formed easily.

In block 108, the expansion cavity 34 is inflated to expand the diaphragm 14 to the forming configuration. In this example, the expansion cavity 34 is inflated by introducing compressed air through the ports 32 in the mandrel 12. In other examples, any suitable fluid may be introduced into the expansion cavity through the port, or any other means of expanding the diaphragm may be employed. In this example, compressed air is introduced into the expansion cavity until there is a pressure of approximately seven bar in the expansion cavity 34. The pre-form 40 on the diaphragm 14 is driven against the inner surface 18 of the outer mould 16. The preform 40 is malleable and therefore deforms to the shape of the inner surface 18 of the mould portion 20, as described above.

In block 110, the heaters 52 around the outer surface of the outer mould 16 heat the outer mould 16. As the outer mould 16 is heated, heat is transferred to the pre-form 40 which is driven against the mould portion 20 of the outer mould 16. The heaters 52 heat the outer mould 16 until the pre-form reaches a curing temperature. In this example, the curing temperature is 180 degrees Celsius. The heaters 52 continue heating the outer mould 16 to maintain the temperature of the pre-form 40 at the curing temperature for a predetermined amount of time. In this example, the pre-form is maintained at the curing temperature for approximately 2 hours.

In block 112 the pre-form 40 is allowed to cool to room temperature. In this example, this is simply done by removing the heat source (i.e. by deactivating the heaters). In other examples, the pre-form may be cooled by actively cooling the outer mould 16.

For example, cooling of the outer mould 16 may be accelerated by replacing heated compressed air or fluid in the cavity with cooler compressed air or fluid. The cooled pre-form 40 is a cured annular component.

In block 114, the expansion cavity 34 is deflated by removing the compressed air from the expansion cavity 34 through the ports 32 in the mandrel 12. The diaphragm 14 therefore collapses back onto the outer surface of the mandrel 12 in the lay-up configuration.

In block 116, the outer mould 16 is removed from the mandrel 12, and the mandrel 12 is removed from the annular component. In other examples, the outer mould may be removed before the expansion cavity is deflated.

Although the mandrel has been described as having a cylindrical profile, in other examples, the mandrel may have a different profile which allows a diaphragm to extend around the outer surface of the mandrel. The mandrel may have a profile which is uniform along an axial extent of the mandrel.

Although it has been described that the heaters are in the form of mats, the heaters may be in any form such that they heat the mandrel or the outer mould respectively.

Although it has been described that the diaphragm is bonded to the mandrel at fixing portions of the diaphragm and clamped to the mandrel by the outer mould at fixing portions of the diaphragm, in other examples the diaphragm may only be clamped to the mandrel in use, or only bonded to the mandrel in use. In yet other examples, the diaphragm may be fixed to the mandrel at portions which are not at axial ends of the diaphragm.

Although it has been described that the outer mould comprises two parts, the outer mould may comprise any number of semi-annular parts which, when fixed together, provide an annular outer mould.

Claims

CLAIMS:

1. A tool for forming an annular component comprising:

a mandrel;

a diaphragm extending around the mandrel to define an expansion cavity therebetween, the diaphragm having a lay-up configuration in which it defines a lay-up surface for a pre-form for the component, and in which the expansion cavity is collapsed;

a port for introducing fluid into the expansion cavity to expand the diaphragm from the lay-up configuration to a forming configuration;

an outer mould defining a profile for the component, the outer mould being configured to enclose a pre-form on the diaphragm so that in use, expansion of the diaphragm to the forming configuration causes the diaphragm to drive the pre-form against the outer mould to deform the pre-form.

2. A tool according to claim 1, wherein the mandrel is cylindrical within the diaphragm.

3. A tool according to claim 1 or 2, further comprising a heater configured to heat the mandrel such that heat is transferred from the mandrel to the pre-form.

4. A tool according to any preceding claim, wherein portions of the diaphragm are bonded to the mandrel to form the expansion cavity between the diaphragm and the mandrel.

5. A tool according to any preceding claim, wherein the port is disposed in the mandrel.

6. A tool according to any preceding claim, wherein the outer mould comprises two parts which are fixed together around the mandrel in use.

7. A tool according to any preceding claim, wherein the outer mould is configured to cooperate with the mandrel to clamp the diaphragm between them.

8. A tool according to any preceding claim, further comprising a heater configured to heat the outer mould such that heat is transferred from the outer mould to the pre-form.

9. A tool according to any preceding claim, wherein the diaphragm is elastically deformable.

10. A tool according to any preceding claim, wherein the outer mould comprises a mould portion and a diaphragm guide;

wherein the mould portion defines a flanged profile for the annular component configured so that in use an axial end of the pre-form folds around the mould portion to form a flange as the diaphragm expands to the forming configuration; and wherein the diaphragm guide extends axially beyond the mould portion to oppose a portion of the diaphragm corresponding to the axial end of the pre-form when the diaphragm is in the lay-up configuration, and has a profile which corresponds to the path of the end of the pre-form as it is folded, so as to prevent the diaphragm expanding around the end of the pre-form.

11. A tool according to claim 10, wherein the diaphragm guide has an arcuate profile in a plane through a central axis of the tool, wherein the profile is configured such that it corresponds to the path of the end of the pre-form as it is folded around the mould portion in use.

12. A tool according to any preceding claim, wherein the outer mould comprises a mould portion which defines a profile for the annular component having a variable radius along an axial extent of the outer mould.

13. A method of forming an annular component using a tool according to any of claims 1-12, the method comprising:

laying-up fibre reinforcement material on the diaphragm in the lay-up configuration to form a composite pre-form;

enclosing the pre-form on the diaphragm with the outer mould;

introducing fluid through the port into the expansion cavity to expand the diaphragm to the forming configuration and drive the pre-form against the outer mould to deform the pre-form.

14. A method according to claim 13, wherein the mandrel is heated such that heat is transferred from the mandrel to the pre-form until the pre-form reaches a forming temperature when the pre-form is enclosed with the outer mould.

15. A method according to claim 13 or 14, wherein the outer mould is heated such that heat is transferred to the pre-form to cure the pre-form.

5

16. A method according to any of claims 13-15, wherein fluid is removed from the expansion cavity through the port to collapse the diaphragm back to the lay-up configuration after expanding the diaphragm so that the mandrel can be removed from the annular component.

Intellectual Property Office