WO2012046021A1

WO2012046021A1 - Advance fibre placement lay-up

Info

Publication number: WO2012046021A1
Application number: PCT/GB2011/051789
Authority: WO
Inventors: Gary Wiles
Original assignee: Gkn Aerospace Services Limited
Priority date: 2010-10-08
Filing date: 2011-09-22
Publication date: 2012-04-12
Also published as: GB2484350A; GB2484350B; GB201017058D0

Abstract

An apparatus and method for forming elongate composite components using an advance fibre placement (AFP) technique, such as a fan case for a gas turbine engine or the like, with an integral flange.

Description

Advance Fibre Placement Lav-Up

Field of the Invention

The present invention relates to a method of forming a composite component using an advance fibre placement (AFP) technique. Particularly, but not exclusively, the invention relates to an improved apparatus and method for forming composite components, such as a fan containment case for a gas turbine engine or the like, with an integral flange.

Background

Composite materials have been employed in the aerospace industry for a number of years. The term 'composite material' (known also as 'composites') is used to describe materials comprising fibres (such as carbon) and an epoxy resin (or similar). One example is known as carbon fibre reinforced composites. The carbon fibre reinforced composite material offers improved properties such as lower weight, improved fatigue/damage resistance, corrosion resistance and negligible thermal expansion.

The use of these materials has increased throughout the aerospace industry predominantly because of the fuel savings which can be achieved over the life of an aircraft by reducing the overall sum weight of the components making up the aircraft. Aerodynamic as well as structural components are formed of carbon fibre materials.

However, the inventors have identified limitations in the use of conventional manufacturing techniques and apparatuses for forming bodies, such as cylindrical bodies, which can be advantageously employed in aerospace applications. More specifically it have been established that conventional techniques do not allow flanges to be conveniently formed on such bodies which are required to secure/couple the composite part to the aircraft or engine component.

In particular the inventors have established that conventional automated techniques do not allow particular component shapes and profiles to be formed using existing automated equipment. This means that designers are prevented from selecting composite materials for particular component shapes. The only existing solution to this problem has been to manufacture the desired component using manual laying-up processes i.e. by hand.

The present invention aims to overcome the problems associated with existing manufacturing machinery and techniques and provides a method and apparatus capable of addressing these problems.

Invention Summary

According to an aspect of the invention there is provided a method of making a hollow object comprising a flange portion extending from one or both ends thereof, wherein the method comprises the steps of: a) applying composite material to the internal surface of a mandrel wherein the material is applied so as to extend along the length of mandrel and over a portion of the mandrel on one or each end thereof defining a respective flange; and b) curing the composite material to produce a hollow object comprising a flange portion on one or each end thereof.

Thus, according to one aspect of the invention there is provided a method of forming a body such as a tube or annular ring by placing or laying-up composite material onto the inner surface of a mandrel. Advantageously placing or laying-up the material in this way conveniently allows a flange portion of the component to be formed on one or each of the ends of the part with tight tolerances and close conformity to the desired geometry.

The term flange is intended to refer to a portion of the component extending inwards or outwards from the axis of the hollow body. This may for example be a perpendicular flange extending at 90 degrees to the surface of the component. This may extend at any suitable angle in a general radial direction.

According to prior art and conventional arrangements it is possible to form a component on the outer surface of a mandrel. Furthermore it is possible to form a flange portion by laying the composite material over a portion of the mandrel defining the desired flange shape. However, it has been established that the prior art, whilst allowing a flange to be fonned, does not provide a suitable flange profile because of the limitations of laying up fibres on an internal radius. Figure 1 illustrates the conventional method of forming a flange on a body such as a tube.

The flange 1 comprises first portion defining the body 2 of the tubular component and a second portion 3 defining the desired flange portion. An automated fibre placement machine 4 comprises a placement head 5 which is in the form of a rotatable wheel. The machine 4 contains a spool (not shown) of composite fibre 6 which is un-reeled as the head 5 moves over the mandrel 1. The machine and head are computer controlled and pre-programmed with the shape of the mandrel onto which fibre is to be placed.

As can be seen in figure 1, a right angle flange portion 3 is desired. However, because of the machine head 5, and more specifically the radius, it is not possible to lay or place material tightly into the corner of the flange i.e. where the flange meets the body portion 2 of the component. A clear or dead zone 7 is thereby created.

This zone 7 is not a problem for designers in many applications but in some, including aerospace, it is desired that the composite material conformed closely to the flange, for example so that the component can be secured to another component. According to the prior art the solution is to use a progressively smaller head or more commonly to lay-up material manually.

The present invention advantageously allows extremely tight angles to be conformed to including flanges extending greater than 90 degrees to the normal of the body portion of the component.

According to the present invention there is provided a method of laying composite material, such as a pre-impregnated carbon fibre along the length of a body and then around a portion of the mandrel forming the flange. Close conformity with the mandrel can be maintained. Additionally, the body portion and flange can be integrated into the same lengths of fibre thereby substantially increasing the structural strength of the resulting component. The fibres forming the body portion and flange portion are not therefore broken or separated by a joint or connection but are, according to the present invention, continuous.

Still further the invention allows for substantially increases in manufacturing speed and a concomitant reduction in manufacturing costs per unit part. The fibres forming the composite material and the associated resin may be any suitable material or resin system. For example, the composite may be an epoxy or bismaleimide (BMI) resin system with a woven glass, carbon or Kevlar composite cloth or fibre.

To allow for convenient and fast laying-up of the composite material may be layed-up from a length of pre-impregnated tape comprising a fibre and associated resin. Such a tape can be supplied from a roll or spool to allow for automated lay-up. Advantageously the material may be a unidirectional composite tape comprising a fibre and preimpregnated with resin.

According to the invention a plurality of layers of composite material may be applied to the mandrel to form a laminate stack of composite material ready to be cured. The fibres may be placed from just one end of the mandrel to define a body with a single flange. Alternatively, the composite material may advantageously be placed from either end of the mandrel to define a flange on either end of the body.

In an arrangement with a pair of flanges the composite material may be layed-up from the flange to the body in a single and uninterrupted lay-up step. In such an arrangement the laying-up or placement apparatus is arranged to extend into the mandrel and along its entire length to the opposing end.

Advantageously, so as to reduce the required complexity of the laying up apparatus the material may be layed-up from each end i.e. in two steps. In a first step a first length of composite (termed a ply) is layed-up from a first pre-determined drop-off position on the mandrel to the distal end of the flange portion of the mandrel. In a second step a second length of composite is layed-up from a second pre-determined drop-off position on the mandrel to the distal end of the flange portion on the opposing end of the mandrel.

Thus, two flanges can be created where the material forming the flange is continuous as it extends along a portion or the entire length of the mandrel. Advantageously, so as to securely couple the two plies extending from opposing directions along the mandrel the first and second drop-off positions may be selected so that consecutive plies overlap one another by a predetermined distance. Thus the ends or terminations of the plies extending along the body portion of the mandrel can interdigitate with adjacent plies. The interlocking or interdigitation of plies provides a secure coupling of plies together.

The component is conveniently formed by laying-up a plurality of lengths of composite material along and around the entire inner surface of the mandrel defining the body portion and the flange portion(s). Once a first layer of composite material has been layed-up a second and subsequent layer/layers can be layed-up over the preceding layers to create a composite stack. Any suitable number of layers may be employed. The composite material may be lay-up in a formation corresponding to the desired structural strength of the part. Alternatively, or additionally, the composite material may be applied in a spirally wound configuration around the mandrel as opposed to lengths parallel with the body axis of the mandrel. Such a spiral configuration can improve the torsional strength of the component. Still further alternating layers may be applied is opposing spiral directions to improve strength in different directions.

The spiral lay-up may be achieved by moving the mandrel and laying-up apparatus with respect to eachother. In one arrangement the mandrel may be arranged to rotate about its longitudinal axis and the laying-up apparatus arranged to move along the axis of the mandrel (or parallel thereto). Using a stepwise motion the composite material can then be applied to the entire surface of the mandrel and flange.

Advantageously the mandrel may be arranged to rotate about an axis perpendicular to its longitudinal axis. Thus, the mandrel can be rotated by 180 degrees to allow the composite material to be layed-up from the opposing end. This advantageously allows a single lay-up apparatus to be used to lay-up composite material from both ends of the mandrel. Alternatively a first and a second lay-up apparatus may be used, one positioned at either end of the mandrel. In such an arrangement the first and second apparatus may be controlled (pre-programmed) to operate in sequence, one after the other. For high production rates the laying-up apparatus may be adapted to operate simultaneously, for example on diametrically opposing portions of the mandrel (the mandrel internal diameter permitting a pair of laying-up machines to extend into the mandrel).

Thus, composite material can be layed-up quickly and accurately to form the plurality of layers. In a still further arrangement each of said apparatuses may be provided with a plurality of equally circumferentially spaced composite tape/material lay-up heads allowing material (tape) to be layed simultaneously at a plurality of positions within the mandrel.

Once the composite stack has been layed-up on the mandrel and comprises the desired number of layers the stack may then be cured to consolidate the resin and harden the component. The part may advantageously be cured in-situ in which case the mandrel may be conveniently provided with heating means to heat the composite material to a predetermined temperature. Alternatively the component may be cured in an autoclave or the like. In either arrangement the mandrel is arranged so as to be disassembled to allow the component to be released from the mandrel itself.

The composite material may be conveniently layed-up using a computer controlled automated fibre placement machine. Thus, a pre-programmed path can be entered such that the placement head of the machine follows the desired contour of the mandrel. The placement head itself may be advantageously adapted so that it can extend into and along the hollow portion of the mandrel to allow for fibre placement.

The automated placement machine may be provided with the requisite movement to allow the placement head to extend into the mandrel and then radially out of the opposing end so as to be able to lay a flange on a distal end of the mandrel.

Viewed from yet another aspect there is provided a composite component forming apparatus comprising a hollow mandrel and at least one automated fibre placement apparatus, wherein a portion of the automated fibre placement apparatus is adapted to extend into the mandrel and to place fibre onto the inner surface of the mandrel or onto a preceding fibre placed by said apparatus.

Viewed from a still further aspect there is provided a method of operating an automated fibre placement machine, said machine programmed to make a hollow object comprising a flange portion extending from one or both ends thereof,

wherein operation of the machine comprises the steps of programming the machine to apply composite material to the internal surface of a mandrel wherein the material is applied so as to extend along the length of mandrel and over a portion of the mandrel on one or each end thereof defining a respective flange.

Brief Description of the Drawings

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

Figure 1 shows a prior art arrangement of placing fibre;

Figure 2 shows an embodiment of an advanced fibre placement machine according to the present invention;

Figure 3 is a cross-section of the mandrel and fibre placement;

Figure 4 shows an arrangement with a continuous layer of composite material defining two flanges;

Figure 5 shows an arrangement with a series of overlapping and interwoven layers of composite material defining two flanges;

Figure 6 shows an exploded view of two adjacent layers; and

Figure 7 shows a multi AFP machine arrangement.

While the invention is susceptible to various modifications and alternative forms, specific embodiments are shown by way of example in the drawings and are herein described in detail. It should be understood however that drawings and detailed description attached hereto are not intended to limit the invention to the particular form disclosed but rather the invention is to cover all modifications, equivalents and alternatives falling within the scope of the claimed invention. Detailed Description

As described above Figure 1 shows a conventional manner in which flanges are formed. The alternative is to manually lay-up the composite plies into the corner shown by reference 7.

Figure 2 shows one embodiment of an apparatus according to the present invention.

In this embodiment the advanced fibre placement (AFP) machine 8 is based on a multi-axis robotic arm comprising a movable arm 9 which can extend into and through the inner diameter of the mandrel 10.

The AFP machine comprises a placement head 11 which is supplied with a spool of pre-impregnated composite tape (not shown). The tape feeds onto a placement wheel described further below.

The mandrel 10 in this embodiment is a mandrel corresponding to the desired shape of a fan containment case for a gas turbine engine. Advantageously forming the fan case from a composite material such as a carbon fibre material reduces the overall weight of the component when compared to conventional materials. Thus, amongst other things, fuel consumption of the engine can be reduced.

The mandrel 10 is separable into 4 segments via the coupling lines 12 (only two of which are visible). Thus, once the composite component has been formed the mandrel can be removed.

It will be recognised that the AFP machine can move in a plurality of axes allowing the placement head to lay material at any angle around or along the mandrel. Thus, the multiple layers forming the composite component can be layed at the required angles to each other to provide the desired component strength. The selected angles used are dependent on the application and are well known to the person skilled in the art. The mandrel 10 is itself mounted on controllable rollers 13 thus allowing the mandrel to be rotated. The mandrel is rotated by electric motors of the like (not shown) which are controlled by a computer controller (not shown). This also controls the AFP machine.

In operation the controller is pre-programmed with the mandrel dimensions and the lay-up programme. The lay-up programme defines the location, orientation, number of layers and so forth for the component. The controller then controls the AFP machine and mandrel rotation means to lay the material according to the lay-up programme. Depending on the desired lay-up pattern the mandrel and machine may be moved simultaneously as the composite material is applied.

Figure 3 shows a cross section through the mandrel 10. The AFP machine head portion 9 is also illustrated and comprises an arm 14 and roller 15.

The AFP machine contains a spool of tape for of unidirectional carbon fibres preimpregnated with a resin. The spool feeds directly onto the roller 15.

The AFP machine is adapted to move the head 9 along a path corresponding to the profile of the mandrel 10. The path is illustrated in figure 3 by dashed line 16. Figure 3 shows a tape 17 which has been layed-up over the mandrel. As shown the roller rolls the tape over the mandrel surface following the path 16.

In contrast to figure 1, because the lay-up is performed on the external angle or corner 17 it is possible the lay the composite material in close conformity with the mandrel profile. Thus, the dead zone 7 shown in figure 1 can be avoided.

The ends of the composite tape can be automatically cut by the AFP machine header by means of an integral tape cutter (not shown). Thus the tape can be layed and terminated at the edges of the mandrel 10.

As shown in Figure 3 the component (a fan containment case) comprises a pair of flanges 18,19 connected by the body portion 20 of the component. According to this embodiment the tape and therefore the fibres can be applied in a continuous way from flange to flange thereby optimising strength.

It will be recognised that Figure 3 is largely magnified and illustrates a single layer of composite in a magnified way. The component itself comprises a plurality of plies forming each layer, with a plurality of layers forming the stack.

Figure 4 illustrates the lay-up profiles of the stack according to the embodiment shown described above where the plies are placed continuously from one flange to the other. In Figure 4 4 continuous plies a, b, c and d can be seen forming the two flanges and the body portion therebetween.

Figure 5 shows an alternative embodiment in which the plies are placed in two steps, a first from one end of the mandrel and a second from the other. In this arrangement six plies are layed a, b, c, d, e and f in opposing directions. As shown the drop-off points (i.e. the position at which the ply placement begins) are arranged to overlap one another such that the plies are interlinked or interdigitated with adjacent plies. This arrangement creates a strong link between the two parts and ensures that the joint is in the middle of the component and not at the distal ends near to the flanges. A scarf joint or other joint may alternatively be used, a scarf joint being known in the art.

The arrangement shown in figure 5 can be created using the AFP machine shown in figure 5 programmed in a suitable way, that is to alternate between either side of the mandrel. Alternatively a pair of less complex AFP machines may be used, each extending from an opposing end to alternately lay-up each ply. In such an arrangement the AFP machine need only be able to place material in a plane corresponding to the plane of the flange and to the plane of the body portion of the mandrel. It will thus be recognised that a less expensive machine can be employed. Still further a single machine of the same type may be used and the mandrel arranged to rotate by 180 degrees to align the opposing end of the mandrel with the AFP machine. This may still further reduce the capital cost of the apparatus. Figure 6 shows the plies forming the layers shown in figure 4 and 5. It will be recognised that the plies a, b, c, d and so forth are layed-up so as to be adjacent each other to create a uniform layer is a first direction. This layer 21 is layed-up over a previous layer 22 having plies layed at a different direction to adjacent layers. Arranging layers at different angles optimises the strength.

Returning to figure 5, the overlap between adjacent layers is optimised depending on the application. Advantageously the adjacent plies may extend so as to be close to the opposing flange so as to optimise the strength and coupling of adjacent layers together. Disadvantageous^ this increases the thickness and weight of the component because it utilises more material. Thus, alternatively the overlap may be small to reduce weight. This however reduces the area of coupling between the adjacent layers.

The overlap distances between adjacent layers may be any suitable amount but increasing the overlap advantageously increases the strength of the connection. The unidirectional preimpregnated tape is advantageously narrow to prevent any creasing or folding of the tape over the edges of the mandrel which would occur if the tape is unnecessarily wide. The width is selected depending on the curvature i.e. the radius of the mandrel. A tape width of less than 500mm is preferably employed.

Figure 7 illustrates an alternative arrangement as discussed above that may advantageously reduce manufacturing time. In the arrangement the mandrel (shown by a broken line) is disposed between two opposing AFP machines each located diametrically opposite to one another. Locating the two machines in this way prevent interference as the respective plies are layed. It also allows the two machines to operate simultaneously.

In operation the two machine would extend into the mandrel to a pre-determined drop-off position. The composite material is then layed onto the mandrel (or the preceding layer) at that point and the machines retracts towards the outer edge of the mandrel. At the periphery the respective machine moves around the profile of the mandrel to define the flange (as shown for example in figure 3). The mandrel is then rotated about its axis by a predetermined angular distance defined according to the width of the tape being applied. The process is then repeated. It will be recognised that such a method and apparatus increases the speed with which the composite material can be applied.

In one arrangement one of the layers may be layed circumferentially around the inner surface of the mandrel. In such an arrangement the AFP head would remain stationary and the mandrel rotated around by 360 degrees. In the arrangement where a pair of machines are used both can operate independent and simultaneously (as described above) to lay a layer circumferentially around the mandrel. The invention thus allows plies to be created at any angle by causing relative movement between the mandrel (rotation) and AFP machine head or heads (linear).

There has been described a method of making a hollow object comprising a flange portion extending from one or both ends thereof, wherein the method comprises the steps of: a) applying composite material to the internal surface of a mandrel wherein the material is applied so as to extend along the length of mandrel and over a portion of the mandrel on one or each end thereof defining a respective flange; and b) curing the composite material to produce a hollow object comprising a flange portion on one or each end thereof.

There has also been described a composite component forming apparatus comprising a hollow mandrel and at least one automated fibre placement apparatus, wherein a portion of the automated fibre placement apparatus is adapted to extend into the mandrel and to place fibre onto the inner surface of the mandrel or onto a preceding fibre placed by said apparatus.

Still further there has been described a method of operating an automated fibre placement machine, said machine programmed to make a hollow object comprising a flange portion extending from one or both ends thereof, wherein operation of the machine comprises the steps of programming the machine to apply composite material to the internal surface of a mandrel wherein the material is applied so as to extend along the length of mandrel and over a portion of the mandrel on one or each end thereof defining a respective flange.

Claims

1. A method of making a hollow object comprising a flange portion extending from one or both ends thereof, wherein the method comprises the steps of:

a) applying composite material to the internal surface of a mandrel wherein the material is applied so as to extend along the length of mandrel and over a portion of the mandrel on one or each end thereof defining a respective flange; and

b) curing the composite material to produce a hollow object comprising a flange portion on one or each end thereof.

2. A method according to claim 1 , wherein the applied composite material is formed of a plurality of layers or plies forming a laminate structure.

3. A method according to claim 2, wherein the plies are applied from a length of pre-impregnated unidirectional tape.

4. A method according to claim 3, wherein the ply is unrolled from a roll of pre- impregnated tape as the respective ply is applied to the mandrel/preceding layer.

5. A method according to any of claims 2 to 4, wherein each respective ply is applied from a ply drop-off position at a predetermined length along the mandrel and extends along the mandrel and over a flange portion of the mandrel.

6. A method according to claim 5, wherein individual plies are applied so as to extend in alternating directions from a first drop-off position to a flange on a first end of said object and alternately from a second drop-off position to a flange on an opposing end of said object.

7. A method according to claim 6, wherein the first and second drop-off positions are selected so that consecutive plies overlap one another by a predetermined distance and the terminations of respective plies interdigitate with adjacent plies.

8. A method according to claims 6 and 7 wherein the alternating steps are repeated to create a stack of laminate plies on the mandrel.

9. A method according to any preceding claim wherein the composite material is applied in a spirally wound configuration around the mandrel.

10. A method as claimed in any preceding claim wherein the composite material is applied by means of one or more automated arms adapted to reciprocate within the mandrel.

11. A method of claim 10, wherein a pair of arms are used to apply the composite materials from opposing ends of the mandrel.

12. A method as claimed in any preceding claim wherein the mandrel is rotatable about its elongate axis.

13. A method as claimed in any of claims 10 to 12, wherein the mandrel and arm(s) is/are configured to move relative to eachother as the respective composite material is applied.

14. A method as claims in any of claims 1 to 13 further comprising the step of heating the mandrel to cure the composite material.

15. A composite component forming apparatus comprising a hollow mandrel and at least one automated fibre placement apparatus, wherein a portion of the automated fibre placement apparatus is adapted to extend into the mandrel and to place fibre onto the inner surface of the mandrel or onto a preceding fibre placed by said apparatus.

16. A composite component forming apparatus as claimed in claim 15, wherein the mandrel is rotatable with respect to its elongate axis.

17. A composite component forming apparatus as claimed in claim 15 or 16, wherein a first automated placement apparatus is arranged at a first end of said mandrel and a second automated placement apparatus at a second end of said mandrel, and wherein each apparatus is arranged to place fibre onto the inner surface of a mandrel or a preceding fibre.

18. A composite component forming apparatus as claimed in claim 17 wherein the first and second automated placement apparatuses are configured to alternately place fibres to form a laminate stack of fibres on the inner surface of said mandrel.

19. A composite component forming apparatus as claimed in any of claims 15 to

18 wherein the or each automated placement apparatus is configured to be movable radially with respect to the mandrel and to place fibre over a portion of the mandrel defining a flange.

20. A composite component forming apparatus as claimed in any of claims 15 to

19 wherein the mandrel is separable into a plurality of parts so as to release the composite material.

21. A composite component as claimed in any of claims 15 to 20 wherein the mandrel further comprised heating means to cure the composite component.

22. A hollow cylindrical body comprising at least one radially inwardly or outwardly extending flange on an end portion thereof wherein the hollow cylindrical body is manufactured according to the method of any of claims 1 to 15.

23 A method of operating an automated fibre placement machine, said machine programmed to make a hollow object comprising a flange portion extending from one or both ends thereof, wherein operation of the machine comprises the steps of programming the machine to apply composite material to the internal surface of a mandrel wherein the material is applied so as to extend along the length of the mandrel and over a portion of the mandrel on one or each end thereof defining a respective flange.

24. A fan containment case for a gas turbine engine manufactured according to the method of any of claims 1 to 14 or 23.

25. A gas turbine engine comprising a fan containment case according to claim 24.

26. An apparatus as substantially described herein with reference to the accompanying figures 1 to 6.

27. A method substantially as described herein.