(19)
(11)EP 2 635 427 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
29.11.2017 Bulletin 2017/48

(21)Application number: 11778944.6

(22)Date of filing:  27.10.2011
(51)International Patent Classification (IPC): 
B29C 70/30(2006.01)
B29C 70/08(2006.01)
(86)International application number:
PCT/GB2011/052091
(87)International publication number:
WO 2012/059740 (10.05.2012 Gazette  2012/19)

(54)

LAMINATE STRUCTURE

LAMINIERTE STRUKTUR

STRUCTURE STRATIFIÉE


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 05.11.2010 GB 201018753

(43)Date of publication of application:
11.09.2013 Bulletin 2013/37

(73)Proprietor: GKN Aerospace Services Limited
Isle of Wight, PO32 6RA (GB)

(72)Inventors:
  • GAWN, Marcus
    Hampshire PO32 6RA (GB)
  • ANDERSON, Paul
    Hampshire PO32 6RA (GB)
  • MARENGO, Giovanni
    Hampshire PO32 6RA (GB)

(74)Representative: D Young & Co LLP 
120 Holborn
London EC1N 2DY
London EC1N 2DY (GB)


(56)References cited: : 
EP-A1- 0 064 151
WO-A1-98/17852
US-A1- 2003 186 038
EP-A2- 0 396 281
DE-A1- 4 005 772
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    Field of the Invention



    [0001] The present invention relates to a method of forming a monolithic composite component with improved structural and impact properties.

    Background



    [0002] Composite materials have been employed in the aerospace industry for a number of years. The term composite material (also known more generally as 'composites') is used to describe materials comprising fibres such as carbon, glass or the like and an epoxy resin (or similar). Composite materials offer significant advantages for aerospace applications such as lower weight, improved fatigue/damage resistance, corrosion resistance and negligible thermal expansion.

    [0003] 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 established a limitation in the use of composite materials (such as carbon fibre) for components which are prone to possible impact or contact damage. Specifically, it has been established that conventional manufacturing methods do not provide components which are capable of withstanding the sort of impacts which can occur in aerospace applications.

    [0004] One such application in the aerospace industry is the fan containment case (sometimes referred to as a fan case) of a gas turbine engine. Fan cases are designed to absorb the impact of all or part of a blade in the event of fracture or damage, for example caused by a bird being ingested into the engine. Without the fan case all or part of the blade could impact the fuselage and/or fuel tank causing catastrophic damage.

    [0005] The present invention aims to provide a composite component with improved impact qualities and more specifically a component suitable for use as in fan containment case application.

    [0006] EP 0 064 151 A1 relates to a shaft coupling.

    [0007] DE 40 05 772 A1 relates to a braided rod or tube which uses resin immersed fibre strands spirally wound around a core to give a braided body with high torsional strength.

    [0008] WO 98/17852 A1 relates to rapid fabric forming.

    [0009] EP0396281 A2 relates to a method for producing a component from fibre-reinforced plastic materials.

    Invention Summary



    [0010] According to a first aspect of an invention described herein there is provided a method according to claim 1 of forming a composite component. Thus, according to the present invention there is provided a composite stack with a series of sub-layer or groups of plies wherein the sub-groups are displaced with respect to the other sub-layers in the stack. This advantageously results in each of the plies within the sub-layer being displaced with respect to the same plies extending in the same direction in adjacent sub-layers.

    [0011] In effect the boundaries defining the edges of the plies do not then align vertically (when viewed through the stack) with other ply boundaries. The inventors have established that alignment of plies in the same direction through a stack of composite material results in a cumulative protrusion or 'bulge' being created on the outer surfaces of the composite stack. This is caused by the repeated alignment of ply boundaries or joint butts. According to the present invention plies in common directions are displaced to prevent this alignment occurring.

    [0012] This feature of the present invention provides at least two advantages.

    [0013] First, the non or mis-alignment of ply boundaries permits a composite part to be formed with a significant improvement in surface finish i.e. the surface finish of the plies defining the inner and outer surfaces of the component are substantially more uniform that with conventional techniques. This provides significant advantages both aesthetically and technically for the component. For example, in an aerospace application a smooth and uniform surface provides a significant advantage to the aerodynamic properties of the part.

    [0014] Secondly, the non or mis-alignment of the ply boundaries significantly improves the structural performance of the component. In particular the mis-alignment prevents the propagation of cracks or break lines in the component which might occur and travel along the boundaries of adjacent plies and thereby through the component. The misalignment of the boundaries prevents propagation from occurring and improves the structural strength of the component. In particular it has been established that the impact performance of the component can be significantly improved.

    [0015] The component may be any suitable shape corresponding to the desired application provided that plies in each sub-layer are arranged such that plies extending in common directions are displaced laterally with respect to at least the adjacent plies. It will be recognised that not all plies need to be displaced in this way but it has been established that increasing the displacement can improve the structural strength of the part. Plies may advantageously be layed-up so that all plies are prevented from being in alignment with each other.

    [0016] The component may for example be substantially planar, in which case the sub-layers forming the stack would be aligned vertically with respect to one another and the lateral displacement measured in the x and y directions where the x and y axis correspond to the length and width of the component (not its depth).

    [0017] The term lateral displacement is intended to refer to the displacement of the start position of the first ply of a sub-group measured in a direction corresponding to the width of the ply or the length of the ply i.e. not in a depth or thickness direction of the ply. Put another way, and with reference to Figure 1B, if the width and length of the plies are measured along x and y coordinates and the depth along the z then the lateral displacement refers to a displacement only in the x and y directions.

    [0018] It is this lateral displacement with respect to an adjacent and other plies in the same direction that provides the advantageous features of the mis-alignment of ply boundaries or edges through the stack.

    [0019] It will be further recognised that the lateral displacement may be along one of the axes i.e. displaced in a direction along the elongate axis of the ply (the y axis shown in Figure 1B). Alternatively it may be displaced is a direction along the width axis of the ply (the x axis shown in Figure 1B). In the latter arrangement it will recognised that the distance of possible displacement is less than that available along the elongate axis of the ply. Advantageously the displacement may be in both the x and y directions.

    [0020] The component itself may for example be a cylindrical component, for example having the dimensions corresponding to the desired dimensions of a gas turbine fan case. In such an arrangement the plies may be arranged to spiral around the component (to maximise strength) and in such a case it will be recognised that the term laterally is intended to refer to a displacement along the width axis and/or the length axis of the relevant ply i.e. circumferentially or axially with respect to the mandrel.

    [0021] The plies themselves may be any suitable shape for the given application. However the use of plies which are substantially longer than they are wide advantageously allows more complex components to be manufactured such as cylindrical shapes. For example the plies may be in the form of an elongate tape facilitating storage and application.

    [0022] The laying-up process of composite plies to make composite components is itself well known to those skilled in the art. The purposeful mis-alignment of plies in the same direction is not.

    [0023] The laying-up process may advantageously be performed on a suitably programmed auto-lay-up machine (an automatic fibre placement machine or the like) capable of laying down a tape over a suitable mandrel corresponding to the desired component profile.

    [0024] As stated above, the displacement may be arranged in one or two directions i.e. the start position of the lay-up of a subsequent sub-layer may be displaced in both an x and a y direction (x and y corresponding to the elongate and width directions of the tape for example in Figure 1B). Thus, plies in common directions will be displaced or off-set in two directions thereby preventing not only the alignment of the elongate boundaries (y direction boundaries) but also the alignment of the width boundaries (x direction boundaries). This advantageously improves the strength still further.

    [0025] The displacement may be arranged for example so that the boundaries are only off-set for the current ply and the preceding ply in a given common direction. Advantageously the sub-layers, and thereby the plies forming the sub-layer, may be offset so that all plies in a common direction are off-set with respect to other plies in the same direction but in different sub-layers.

    [0026] The displacement concept is applied to sub-layers i.e. the sub-layers are displaced laterally. Additionally or alternatively plies forming the sub-layers may be displaced laterally in the same way (where there are multiple plies extending in the same direction which are layed-over one-another).

    [0027] The term direction will be understood to the person skilled in the art of composite component design. The component may advantageously be provided with sub-layers comprising plies in a plurality of directions. For example plies may be arranged in three directions: minus 60 degrees, 0 degrees and plus 60 degrees. The nomenclature for such a ply lay-up would be [-60 , 0 , +60]. The angle value being measured from a preselected datum of the component but common to all sub-layers and all plies.

    [0028] According to the invention the plies are lay-up in sub-layers or sub-groups commencing from the start position of the first sub-group. The first layer is layed-up onto the mandrel and the subsequent plies forming each sub-layer layed-up on top of the preceding sub-layer until the complete stack is formed. According to the invention the start position of the lay-up (for example the start position of the auto-lay-up machine) is moved according to the desired displacement in the x and y directions and the next sub-layer layed-up according to the predetermined ply direction pattern.

    [0029] It will be recognised that any suitable number of directions may be employed in each sub-layer according to the structural strength requirements of the component in each of said directions.

    [0030] The plurality of plies forming the sub-layers may be layed-up so as to be immediately adjacent to one another. That is, a plurality of plies may be layed-up in the same direction, for example substantially straight for a planar component or in a spiral for a cylindrical component. The plies are advantageously all substantially parallel so as to improve the uniformity of the component. Aligning the plies in this way provides an uninterrupted layer of plies in a first direction before the next layer of plies in the next direction are layed-up on top of this first layer. This process can be repeated until the complete sub-layer is layed-up.

    [0031] Advantageously however the inventors have established that an improved lay-up sequence can be employed to further enhance the geometric qualities of the sub-layer and additionally the structural performance of the sub-layer.

    [0032] Specifically, the sequence of laying-up plies is such that the plies in a common direction and forming a sub-layer are layed-up so as to be separated from adjacent plies by a distance substantially equal to the width of the ply. In effect a series of parallel plies are lay-up each separated by a width equal to the width of the ply (for example a tape). Then a plurality of plies are layed-up in a second and subsequent directions all separated by the same spacing. When parallel and spaced apart plies have been layed-up in each of the directions, plies are then layed-up in the spaces defined between adjacent plies in each of said directions. In effect all of the spaces are 'filled in' with a ply.

    [0033] Parallel plies may be layed-up with spaces substantially equal to the width of the ply or alternatively separated by a multiple of the width of a ply.

    [0034] This lay-up pattern creates interconnections between plies in each direction. In effect the plies overlap each other in a complex way. Once the part it cured the resin consolidates the component binding the plies and therefore the fibres into a complex and interconnected three dimensionally arrangement. Thus a sub-layer is created with a complex interaction of fibres all bound within the cured resin.

    [0035] This lay-up sequence is coupled with the displacement of the start positions of each sub-layer lay up so as to provide a component with a complex fibre structure limiting the possibility of crack propagation and optimising strength.

    [0036] The inventors have further established that a particular displacement profile or pattern of the sub-layers (with respect to other sub-layers) can still further enhance the component's properties. According to the invention the lay-up start position of the first sub-layer may define a datum line extending from the first to the final sub-layer of the composite stack. As stated above the first layer is layed-up onto the mandrel or tooling. The lay-up start position of each subsequent sub-layer is displaced so as to alternate between opposite sides of said datum line. Alternating the lay-up start position between either side of this arbitrary datum line extending through the stack means that not only are ply boundaries prevented from overlapping one another but they are advantageously separated by an increased distance. Increasing the distance of separation advantageously improves the structural strength by further preventing crack propagation through the stack and/or delamination of plies/sub-layers. This is illustrated with reference to Figure 9 described in detail below.

    [0037] Still further it has been established that the alternating displacement can itself be optimised.

    [0038] Specifically, the inventors have established that a predetermined unit distance can be used to optimise the component performance. Accordingly, a displacement distance a is predetermined which corresponds to the width of the tape ply divided by the number of plies per sub-layer:



    [0039] The start position of the first ply (defining the start position of the first sub-layer) is layed-up and this sets the origin or datum of subsequently sub-layer start positions. The lay-up start position of each subsequent sub-layer is then displaced relative to said datum according to the following sequence:



    [0040] The predetermined distance a may be measured along either or both of the first and or second axes of the plies i.e. either along the elongate y direction of the ply and/or the width direction x of the ply (as shown in Figure 1B).

    [0041] In the example sequence above an 8 sub-layer composite stack is created as shown in Figure 9 and described further below. The value zero indicates the first and final sub-layer position i.e. the final sub-layer is layed-up immediately over the start position of the very first sub-layer.

    [0042] This arrangement creates a 'diamond shape' of butt joints between plies when viewed through the thickness of the component. Such a pattern has been established to be optimal for structural performance since the majority of butt joints (that is the boundary or edge of a ply) on adjacent sub-layers are spaced far apart.

    [0043] Once the complete stack has been layed-up it may be cured using any suitable technique. In one arrangement the stack may be transferred to an autoclave and cured to consolidate the resin at elevated temperature and pressure. Alternatively the stack may be cured in an out of autoclave method, using a vacuum bag technique at ambient or near ambient conditions. The various curing methods are known to persons skilled in the art.

    [0044] In an arrangement where the component is layed-up around a cylindrical mandrel, for example to form a cylinder to a fan case, then the composite stack may be cured by heating the mandrel and surrounding the stack with a suitable vacuum bag to remove volatile gas during the cure. Again, the curing technique is known to the person skilled in the art.

    [0045] In either cure method the resin flow and consolidates the part resulting in a hardened composite component.

    [0046] The plies themselves may all be the same material. Alternatively to increase strength in certain parts of the component, for example where particular areas are identified as impact zones then alternatively materials may be used. For example Kevlar may be layed-up in a particular portion of the component (e.g. a fan case) at a location where impact is more likely to occur. This thereby improves the component strength further whilst minimising weight and material usage.

    [0047] The component itself may become a sub-part of a larger component. For example the method may be employed on a sub-part of a fan case with the distal portions of the case being lay-up using a conventional ply arrangement. In such a situation the boundaries of the component layed-up may be interconnected with adjacent layed-up portions using a ramp technique or the like.

    [0048] It will of course be recognised with the benefit of the teaching of the present application that the method can be applied to any number of applications where structural strength and/or surface finish are important. It will also be recognised that an elongate pre-impregnated tape according to the present invention is distinct from a thread of fibres or a bundle of individual fibres (know in the art as tows).

    [0049] As discussed above the present invention not only provides a method of manufacturing a composite component with an improved internal structure (interwoven plies) but also exhibits significantly improved surface finished owing to the offset of ply butts/boundaries. A misalignment of joints through the component thickness prevents a 'quilting effect' which causes uneven component surface finishes. Features described herein with reference to one embodiment or aspect may conveniently and advantageously be combined with each and every other aspect and embodiment defined herein without departing from the scope of the claims.

    Brief Description of the Drawings



    [0050] Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which:

    Figure 1A shows a cross-section through a gas turbine engine;

    Figure 1B illustrates the axes of a ply according to an embodiment of the invention;

    Figure 2 shows an automated lay-up arrangement;

    Figure 3 shows a planar composite component stack according to the present invention;

    Figure 4 shows a portion of a curved composite component stack according to the present invention;

    Figure 5 shows a magnified cross-section of the structure shown in Figure 3;

    Figures 6A, 6B and 6C show the laying up sequence for sub-layer;

    Figure 7 illustrates a completed sub-layer;

    Figure 8A to 8D show a particular lay-up sequence of plies; and

    Figure 9 shows a lay-up sequence for the sub-layers forming the composite stack.



    [0051] 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.

    [0052] Figure 1 shows a cross-section through a gas turbine engine.

    [0053] As see in figure 1 the gas turbine engine 1 comprises an inlet 2 for receiving air into the engine. The simplified figure illustrates the fan blades 3 located on the central rotatable shaft 4. It is a requirement of engine manufacture that some form of protective barrier is put in place around the turbine blades such that the complete or partial failure of one blade does not allow that part to travel radially out of the engine. It will be recognised that this could cause a catastrophic incident.

    [0054] In order to prevent this from happening and to retain the blades within the engine a fan case 5 is located around the blades. It has been established that manufacturing this component from composite materials could significantly reduce the weight of the engine and thereby substantially increase fuel efficiencies of the engine and thus the aircraft itself. The application therefore has real environmental benefits.

    [0055] The fan case 5 is formed of a generally cylindrical shape although the precise geometry will depend on the aircraft. The fan case may for example be a barrel shape with a 'bulged' waist and narrower distal ends.

    [0056] Figure 2 shows a basic illustration of an auto lay-up machine arranged to form a component according to the present invention in a cylindrical shape.

    [0057] It will be recognised that the invention is not limited to a cylindrical shape and can be applied equally to a curved, planar or other desired component.

    [0058] In figure 2 a rotatable mandrel 6 is shown rotatable about elongate axis 7. A movable tape laying head 8 is shown which can move along the axis of the mandrel as well as radially in and out with respect to the mandrel surface. The tape laying head 8 is supplied with a continuous roll of preimpregnated tape.

    [0059] The lay-up apparatus, that is the mandrel and lay up head, are computer numerically controlled and programmed to lay up plies according to a predetermined pattern.

    [0060] In one example a carbon epoxy preimpregnated resin having a 75mm width may be used. Other widths, such as a 150mm wide tape may be used. It will be appreciated that the width of the tape is dependent on the particular component and the geometries of the component. The material could be layed-up manually but is preferably layed-up using a commercially available machine such as that manufactured by MTorres. The present invention is not restricted to any particular resin/fibre combination. The present invention can in fact be advantageously applied to any tape based lay-up process or system.

    [0061] In use the mandrel 6 is rotated about the axis 7 whilst simultaneously the tape head 8 moves and lays-up lines of tape (termed plies) onto the mandrel. The mandrel may be provided with a first peel ply layer to improve surface finish and to aid removal of the component from the mandrel. In this regard the mandrel itself may collapse inwardly once the part is cured to allow the component to be safely removed.

    [0062] As shown in figure 2 a series of plies P1, P2, P3 have been layed-up in a generally spiral configuration around the mandrel. This may be a plurality of plies or a single helically would ply forming an equivalent series of parallel plies as illustrated in figure 2. These plies are layed-up at a first angle with respect to an arbitrary datum line. Figure 2 also shows a second series of plies P4, P5, P6 layed-up in a second direction. Although figure 2 shows two directions of layed-up plies it will be recognised that plies may be layed-up in any number of directions depending on the desired application. In figure 2 plies P1, P2, P3 are layed-up and then plies P4, P5, P6 are layed-up immediately on top of the first group. As shown spaces PS are left between adjacent plies. The width of the space PS is substantially equal to the width of the ply.

    [0063] Figure 3 shows an alternative view of the invention applied to a planar surface. It will be recognised that the method described herein applies equally to both planar and cylindrical components. The planar shape is now described.

    [0064] As shown in figure 3 the component is formed of a pre-cured stack 9 of composite material. The stack 9 is sub-divided into a plurality of sub-groups or layers. Each sub-layer comprises a plurality of plies. In figure 3 only three sub-layers are shown : sub-layers 10, 11, 12. Any number of sub-layers may be used.

    [0065] Figure 4 shows an alternative component profile, that is of a cross-section through a curved stack 9 with a plurality of sub-layers 13. Such a profile would correspond to a portion of a cross-section through a fan containment case manufactured according to the present invention.

    [0066] Figure 5 is a magnified view of one portion of the cross-section of the stack 9 shown in figure 3. As shown each sub-layer is formed of a plurality of individual plies 10.1, 10.2, 10.3 and so forth. Any suitable number of plies may be used to constitute each sub-layer 10, 11, 12.

    [0067] As shown in figures 3 to 5 each sub-layer is located on top of a preceding sub-layer to form the composite stack.

    [0068] One sub-layer will now be described in more detail.

    [0069] Each of the sub-layers comprises a series of plies extending in different directions. The actual angles of the plies with respect to one another are predetermined depending on the particular application of the component and are generally determined based on the forces which will be applied to the component.

    [0070] Figures 6A to 6C illustrate the lay-up process for one sub-layer. Here, three directions are to be employed -45 degrees, 0 degrees and +45 degrees [-45, 0, +45]. The auto-lay-up machine is configured to lay each of the parallel plies adjacent to each other and spaced from each other by a predetermined distance substantially equal to the width of the plies. Thus, a series of parallel plies is created with spaces therebetween sufficiently wide to accommodate a further ply in the same direction.

    [0071] Referring to figure 6A 4 parallel plies are layed-up each along the 0 degrees axis i.e. P1(0), P2(0), P3(0) and P4(0).

    [0072] The lay-up machine is then repositioned with respect to the mandrel and the second series of parallel plies are layed-up over the top of the first series of plies The second series of plies P1(45), P2(45), P3(45) and P4(45) are layed-up directly on top of the first series of plies of the sub-layer, again separated by a distance substantially equal to the width of a ply.

    [0073] As shown in figure 6C a third series of parallel plies, P1(-45), P2(-45), P3(-45) and P4(-45) are layed-up in the same way.

    [0074] In effect, and although not illustrated by the relative positions of figures 6A to 6C, the plies in 6B are layed over the plies in 6A and the plies in 6C are layed over the plies in 6B.

    [0075] The next stage of the formation of the sub-layer is to lay plies in between adjacent plies in each of the three directions (or however many directions there might be). Thus a further series of parallel plies are layed-up in alignment with the spaces between adjacent plies shown in figures 6A to 6C.

    [0076] This is illustrated in Figures 6A to 6C by the arrows A, B and C. These additional plies are layed-up over the plies formed by the lay-up steps described above. The plies may be layed-up in the same sequence i.e. 0 degrees, +45 and - 45 but the plies may be layed-up in an alternative order. Whichever order is selected all of the spaces defined between adjacent plies in the same direction are 'filled in'.

    [0077] The resulting sub-layer thus comprises a plurality of parallel plies in a plurality of directions where the plies are, in effect, woven within other plies in other directions. This interwoven arrangement of plies in the sub-layer substantially improves the structural strength of the sub-layer. For example, the propensity for a crack to propagate through a sub-layer layed-up to in this manner is substantially reduced because there is no clear path for the crack to travel along. In effect the normal path which might lead to the failure of the component is interrupted by the interaction of the plies on different individual layers of the sub-layer.

    [0078] The resulting sub-layer can be illustrated in figure 7 where some portions of plies in each direction are visible. It will be recognised that this lay-up method for each sub-layer can be applied in a curved or cylindrical arrangement.

    [0079] Figures 8A to 8D illustrate one advantageous lay-up sequence of plies. The sequence shown in figure 8A to 8D illustrates a single sub-layer comprising 4 plies in two directions.

    [0080] Referring to Figure 8A a first series of parallel plies is layed-up as shown by the series of arrows. Each ply is separated by a distance (illustrated by S1) which is equal to the width of a ply. Figure 8B shows the next step in the sequence where a second series of parallel plies are layed-up, again illustrated by the arrows. Here, the parallel plies are separated by space S2.

    [0081] Figure 8C illustrates the third step where a series of parallel plies are layed-up in the spaces defined between the plies layed-up in Figure 8A i.e. along the path defined by the space S1. Finally, referring to Figure 8D, a series of parallel plies are layed-up along the path defined by the space S2 in Figure 8B.

    [0082] Figures 8A to 8D show a two direction 4 ply lay-up sequence but it will be appreciated that any number of plies may form the sub-layer in any number of directions. The advantageous feature is the separation of plies and the laying-up of plies in the spaces defined between adjacent plies. This results in a complex interweaving of the tape fibres. Once cured the complex interactions provide for a significant improvement in strength and impact resistance.

    [0083] As stated above, this can be advantageously used in combination with a displacement of plies in consecutive sub-layers thereby creating a composite component comprising both (a) complex interwoven fibres and (b) off-set tape boundaries preventing crack propagation or delamination.

    [0084] The example shown in Figure 8A to 8D is a method of manufacturing a single sub-layer. The stack comprises a plurality of these sub-layers each layed-up over another adjacent sub-layer and optionally displaced from a preceding sub-layer in and x and/or a y direction as shown for example in Figure 1B and in Figure 9.

    [0085] The alignment of consecutive sub-layers with respect to each other will now be described.

    [0086] Figure 9 illustrates the off-set or 'mis-alignment' of each sub-layer with respect to another.

    [0087] As discussed above each sub-layer is offset by a predetermined distance with respect to the preceding sub-layer. This can be measured by off-setting the start position of the lay-up machine when it commencing laying-up of each of the sub-layers. By off-setting the start position each of the boundaries i.e. edges of the plies will be off-set with respect to plies extending in the same direction but being part of a preceding sub-layer.

    [0088] The off-set distance may be any suitable distance but is advantageously determined by dividing the ply width by the number of sub-layers forming the stack. This allows for the predetermination of a constant a.

    [0089] The offset distance is therefore a = width of ply / number of plies per sub-layer The lay-up machine is then programmed to offset the start position with respect to a predetermined datum line which can be conveniently set as the lay up start position of the very first ply of the first sub-layer. Referring to figure 6A this might for example be point.

    [0090] Point A defining the datum is also shown in figure 9 as the start position for the first sub-layer. Figure 9 illustrates 8 sub-layers, each sub-layer formed as described above.

    [0091] The off-set distance a are also shown in figure 9. The first sub-layer is not offset and is therefore commenced at position 0 corresponding to Point 9. The plies forming the sub-layer are then layed-up as described above laying down plies in a plurality of directions and then filling in the defined spaces there between with further plies.

    [0092] The next and subsequent sub-layers are layed-up according to the following displacements. These displacements or offset are measured from the datum line extending through the stack from Point A as illustrated in figure 9.

    [0093] The displacements alternate either side of the datum as follows :



    [0094] Thus, the start position for laying up each sub-layer is offset with respect to a preceding sub-layer which misaligns all of the ply boundaries in the various sub-layers.

    [0095] Alternative displacement patterns may be used but it has been established that this pattern optimises the separation of the plies thereby optimising structural performance.

    [0096] The example shown in figure 9 is a displacement in a single direction. For example the displacement distance 'a' could be measured along the axis x shown in figure 6A. It will be recognised that this will offset the end boundaries or butt joints extending across the width of the plies. The offset could equally be applied in the y direction thereby offsetting the boundaries of plies extending in a longitudinal direction i.e. the length edge or butt joint of the tape forming the ply.

    [0097] Advantageously the offset may be applied simultaneously in both the x and y directions. Thus the butt joints defining both the width and lengths of the tapes forming the plies can be offset from plies in the same direction and in different sub-layers. This optimises the strength of the component since there is misalignment in both directions.

    [0098] It will be recognised that the lay-up process can be fully automated. The lay up process can be performed to lay up each consecutive ply forming the sub-layer and then proceed to lay-up the next ply forming the first layer of the second and subsequent sub-layers without interruption. This allows a component to be manufactured in a single automated process.

    [0099] Finally the layed-up stack is cured by means of an autoclave or by curing the stack in-situ on the mandrel or tool onto which the stack has been layed-up. Curing techniques are understood by the person skilled in the art and are not therefore described herein.

    [0100] Although the components described in the specific description are planar or generally cylindrical it will be recognised that any shape or combination may be used. For example a blade, such as for an aircraft or wind turbine could employ this method.

    [0101] Aspects of the invention extend to components formed according to the method and to components comprising multiple layers wherein plies in subsequent layers are offset as described above. The invention is particularly advantageous where the component is required to absorb an impact and/or to exhibit a smooth surface finish.


    Claims

    1. A method of forming a composite component, said component comprising a series of sub-layers together forming a composite stack, each sub-layer formed of a plurality of layers of plies;
    said method comprising the steps of:

    selecting a start position for laying up a first sub-layer of plies;

    laying-up from said position a plurality of plies to form a first sub-layer; and

    laying-up a plurality of subsequent sub-layers of composite plies each layed-up on top of a preceding sub-layer;

    wherein the start position for laying-up each subsequent sub-layer is selected so as to be displaced laterally in a lateral direction with respect to the start position of the preceding sub-layer; and

    wherein the lay-up start position of the first sub-layer defines a datum line extending through the composite stack and wherein the lay-up start position of each subsequent sub-layer is displaced so as to alternate in the lateral direction between each sides of said datum line.


     
    2. A method according to claim 1, wherein each ply is in the form of an elongate tape, each ply having a first axis extending along the length of the tape and a second axis across the width of the tape, wherein the lateral displacement is a lateral displacement with respect to the first and or second axis of a corresponding ply in a preceding sub-layer.
     
    3. A method as claimed in claim 1 or claim 2, wherein the displacement of each lay-up start position of each subsequent sub-layer is selected so that the start position of each sub-layer is displaced laterally with respect to all of the preceding layers.
     
    4. A method of claim 1, wherein the plies forming each sub-layer are arranged to extend in a plurality of directions and wherein a plurality of plies are layed-up in each direction.
     
    5. A method of claim 4, wherein plies layed-up in the same direction are separated from adjacent plies by a distance substantially equal to the width of the ply.
     
    6. A method according to claim 5, wherein a plurality of plies are layed-up in a first direction and then a plurality of plies are layed-up in a second and subsequent directions and wherein when plies have been layed-up in each of the directions, plies are then layed-up in the spaces defined between adjacent plies in each of said directions.
     
    7. A method according to claim 1 comprising laying-up a final sub-layer on top of the plurality of subsequent sub-layers wherein the start position for laying-up the final sub-layer is the same as the start position of the first sub-layer; wherein a predetermined displacement distance a is determined by dividing the width of the ply by the number of plies per sub-layer and wherein the lay-up start position of each sub-layer is displaced relative to said datum according to the following sequence position :

    wherein the predetermined distance a is measured along the first and or second axis of the plies.
     
    8. A method according to any preceding claim wherein the plies are elongate tapes pre-impregnated with an epoxy resin.
     
    9. A method according to any preceding claim wherein the component is substantially planar.
     
    10. A method according to any of claims 1 to 8 wherein the component is cylindrical and wherein at least some plies are arranged in a spiral configuration around said component.
     
    11. A method according to claim 10, wherein the plies are layed-up onto a cylindrical mandrel.
     
    12. A method according to any preceding claim wherein the lay-up start position defined a butt joint between adjacent plies and/or sub-layers.
     
    13. A method according to any preceding claim wherein the layed-up composite stack is cured to consolidate the resin in each ply and sub-layer.
     
    14. A method according to claim 5, further comprising the step of laying-up plies over pre-layed plies along paths defined between adjacent plies in the same direction.
     


    Ansprüche

    1. Verfahren zum Herstellen einer Verbundkomponente, wobei die Komponente eine Reihe von Teilschichten umfasst, die gemeinsam einen Verbundstapel bilden, wobei jede Teilschicht aus einer Vielzahl von Schichten von Lagen gebildet ist;
    wobei das Verfahren die Schritte umfasst:

    Auswählen einer Anfangsposition zum Stapeln einer ersten Teilschicht aus Lagen;

    von der Position aus Stapeln einer Vielzahl von Lagen, um eine erste Teilschicht zu bilden; und

    Stapeln einer Vielzahl von nachfolgenden Teilschichten von Verbundlagen, jeweils auf eine vorhergehende Teilschicht gestapelt;

    wobei die Anfangsposition zum Stapeln jeder nachfolgenden Teilschicht so ausgewählt wird, dass sie in einer seitlichen Richtung bezogen auf die Anfangsposition der vorhergehenden Teilschicht seitlich versetzt ist; und

    wobei die Stapel-Anfangsposition der ersten Teilschicht eine Bezugslinie definiert, die durch den Verbundstapel verläuft, und wobei die Stapel-Anfangsposition jeder nachfolgenden Teilschicht so versetzt wird, dass sie in der seitlichen Richtung zwischen den beiden Seiten der Bezugslinie alternieren.


     
    2. Verfahren gemäß Anspruch 1, wobei jede Lage in der Form eines langgestreckten Bands vorliegt, wobei jede Lage eine erste Achse, die entlang der Länge des Bands verläuft, und eine zweite Achse quer zu der Breite des Bands aufweist, wobei die seitliche Verschiebung eine seitliche Verschiebung bezogen auf die erste und/oder die zweite Achse einer entsprechenden Lage in einer vorhergehenden Teilschicht ist.
     
    3. Verfahren gemäß Anspruch 1 oder Anspruch 2, wobei die Verschiebung jeder Stapel-Anfangsposition jeder nachfolgenden Teilschicht so ausgewählt wird, dass die Anfangsposition jeder Teilschicht bezogen auf alle vorhergehenden Schichten seitlich versetzt ist.
     
    4. Verfahren gemäß Anspruch 1, wobei die Lagen, die jede Teilschicht bilden, so angeordnet werden, dass sie in einer Vielzahl von Richtungen verlaufen, und wobei in jeder Richtung eine Vielzahl von Lagen gestapelt wird.
     
    5. Verfahren gemäß Anspruch 4, wobei in der gleichen Richtung gestapelten Lagen von benachbarten Lagen um einen Abstand getrennt sind, der im Wesentlichen gleich der Breite der Lage ist.
     
    6. Verfahren gemäß Anspruch 5, wobei eine Vielzahl von Lagen in einer ersten Richtung gestapelt wird und dann eine Vielzahl von Lagen in einer zweiten und nachfolgenden Richtung gestapelt wird, und wobei, wenn Lagen in jeder der Richtungen gestapelt worden sind, Lagen in den Räumen gestapelt werden, die zwischen benachbarten Lagen in jeder der Richtungen definiert sind.
     
    7. Verfahren gemäß Anspruch 1, umfassend Stapeln einer letzten Teilschicht auf die Vielzahl von aufeinanderfolgenden Teilschichten, wobei die Anfangsposition zum Stapeln der letzten Teilschicht die gleiche ist wie die Anfangsposition der ersten Teilschicht; wobei ein vorgegebener Verschiebungsabstand a durch Teilen der Breite der Lage durch die Anzahl von Lagen pro Teilschicht bestimmt wird und wobei die Stapel-Anfangsposition jeder Teilschicht bezogen auf die Bezugslinie gemäß folgender Reihenposition relativ verschoben ist:

    wobei der vorbestimmte Abstand a entlang der ersten oder zweiten Achse der Lagen gemessen wird.
     
    8. Verfahren gemäß einem der vorstehenden Ansprüche, wobei die Lagen langgestreckte Bänder sind, die mit einem Epoxyharz vorimprägniert sind.
     
    9. Verfahren gemäß einem der vorstehenden Ansprüche, wobei die Komponente im Wesentlichen planar ist.
     
    10. Verfahren gemäß einem der Ansprüche 1 bis 8, wobei die Komponente zylindrisch ist und wobei wenigstens einige Lagen in einer spiralförmigen Konfiguration um die Komponente angeordnet werden.
     
    11. Verfahren gemäß Anspruch 10, wobei die Lagen auf einen zylindrischen Dorn gestapelt werden.
     
    12. Verfahren gemäß einem der vorstehenden Ansprüche, wobei die Stapel-Anfangsposition eine Stoßfuge zwischen benachbarten Lagen und/oder Teilschichten definiert.
     
    13. Verfahren gemäß einem der vorstehenden Ansprüche, wobei der gestapelte Verbundstapel gehärtet wird, um das Harz in jeder Lage und Teilschicht zu verfestigen.
     
    14. Verfahren gemäß Anspruch 5, ferner umfassend den Schritt des Stapelns von Lagen über vorgestapelte Lagen entlang von Wegen, die zwischen benachbarten Lagen in der gleichen Richtung definiert sind.
     


    Revendications

    1. Procédé de formation d'un composant composite, ledit composant comprenant une série de sous-couches formant ensemble un empilement composite, chaque sous-couche constituée d'une pluralité de couches de plis ;
    ledit procédé comprenant les étapes consistant à :

    sélectionner une position de départ pour empiler une première sous-couche de plis ;

    empiler à partir de ladite position une pluralité de plis pour former une première sous-couche ; et

    empiler une pluralité de sous-couches consécutives de plis composites, chacune empilée au-dessus d'une sous-couche précédente ;

    dans lequel la position de départ pour l'empilage de chaque sous-couche consécutive est sélectionnée de manière à être déplacée latéralement dans une direction latérale par rapport à la position de départ de la sous-couche précédente ; et

    dans lequel la position de départ d'empilage de la première sous-couche définit une ligne de référence s'étendant à travers l'empilement composite et dans lequel la position de départ d'empilage de chaque sous-couche consécutive est déplacée de manière à alterner dans la direction latérale entre chaque côtés de ladite ligne de référence.


     
    2. Procédé selon la revendication 1, dans lequel chaque pli se présente sous la forme d'un ruban allongé, chaque pli ayant un premier axe s'étendant le long de la longueur du ruban et un deuxième axe à travers la largeur du ruban, dans lequel le déplacement latéral est un déplacement latéral par rapport au premier et/ou au deuxième axe d'un pli correspondant dans une sous-couche précédente.
     
    3. Procédé selon la revendication 1 ou la revendication 2, dans lequel le déplacement de chaque position de départ d'empilage de chaque sous-couche consécutive est sélectionné de telle sorte que la position de départ de chaque sous-couche est déplacée latéralement par rapport à toutes les couches précédentes.
     
    4. Procédé de la revendication 1, dans lequel les plis formant chaque sous-couche sont agencés pour s'étendre dans une pluralité de directions et dans lequel une pluralité de plis sont empilés dans chaque direction.
     
    5. Procédé de la revendication 4, dans lequel des plis empilés dans la même direction sont séparés de plis adjacents par une distance sensiblement égale à la largeur du pli.
     
    6. Procédé selon la revendication 5, dans lequel une pluralité de plis sont empilés dans une première direction et ensuite une pluralité de plis sont empilés dans une deuxième et des directions consécutives et dans lequel, quand des plis ont été empilés dans chacune des directions, des plis sont ensuite empilés dans les espaces définis entre plis adjacents dans chacune desdites directions.
     
    7. Procédé selon la revendication 1 comprenant l'empilage d'une sous-couche finale au-dessus de la pluralité de sous-couches consécutives, la position de départ pour empiler la sous-couche finale étant la même que la position de départ de la première sous-couche ; dans lequel une distance de déplacement prédéterminée a est déterminée en divisant la largeur du pli par le nombre de plis par sous-couche et dans lequel la position de départ d'empilage de chaque sous-couche est déplacée par rapport à ladite référence selon la position séquentielle suivante :

    la distance prédéterminée a étant mesurée le long du premier et/ou du deuxième axe des plis.
     
    8. Procédé selon une quelconque revendication précédente dans lequel les plis sont des rubans allongés préimprégnés avec une résine époxy.
     
    9. Procédé selon une quelconque revendication précédente dans lequel le composant est sensiblement plan.
     
    10. Procédé selon l'une quelconque des revendications 1 à 8 dans lequel le composant est cylindrique et dans lequel au moins certains plis sont agencés dans une configuration en spirale autour dudit composant.
     
    11. Procédé selon la revendication 10, dans lequel les plis sont empilés sur un mandrin cylindrique.
     
    12. Procédé selon une quelconque revendication précédente dans lequel la position de départ d'empilage a défini un joint bout à bout entre plis adjacents et/ou sous-couches adjacentes.
     
    13. Procédé selon une quelconque revendication précédente dans lequel l'empilement composite empilé est durci pour consolider la résine dans chaque pli et sous-couche.
     
    14. Procédé selon la revendication 5, comprenant en outre l'étape consistant à empiler des plis par-dessus des plis prédéposés le long de chemins définis entre plis adjacents dans la même direction.
     




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    Cited references

    REFERENCES CITED IN THE DESCRIPTION



    This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

    Patent documents cited in the description