FIELD

This invention relates to a method and apparatus for forming a composite article. In particular, the invention relates to an improved filament winding process, and to a nozzle suitable for use in that process.

BACKGROUND

The storage of fluids at high pressures is structurally demanding. Typical service pressures are in the order of 30 MPa. When considering hydrogen storage, typical storage pressures increase to 70 MPa when stored at ambient temperatures.

In many applications, the weight of an article such as a pressure vessel, is an important consideration. For example, pressure vessels of a heavy weight are undesirable when considered in the context of transport, due to the associated higher costs and environmental impact.

Reductions in the weight of a given pressure vessel may be achieved by reducing the susceptibility of the composite manufacturing process to processing defects.

Metallic pressure vessels are common. They provide a robust, damage-tolerant solution for storing fluids at high pressures. However, metals have a low specific strength (or strength to mass ratio). As a result, the vessels that are produced must be relatively heavy if they are to have a sufficient structural strength. This is undesirable in many industries, but is a particular concern in the aerospace sector, where the weight of the vehicle has a direct impact on its fuel efficiency.

Composite materials are one solution to this problem. Composites are high strength, low density materials and are commonly used in the design and manufacture of pressure vessels. Typically, fibres of carbon, glass and aramid are known to be used to produce composite structures such as pressure vessels. The orientation of the fibre reinforcement, in terms of its strength and stiffness, can be tailored to make efficient use of the material. This results in significant weight savings when compared to equivalent metallic structures. The fibre reinforcement is held within a matrix material. The matrix materials may include thermoset or thermoplastic polymers.

Such materials are, however, inherently prone to the presence of defects in the structure. Such defects often occur during the manufacturing processes used to produce the composite structure.

The presence of defects, such as voids, resin rich regions and fibre deviations, occurring during the processing of the composite structure may influence the weight and material usage of a composite component. The presence of such defects is accounted for in the design phase through the use of safety factors in design calculations. The safety factors account for the uncertainty of the presence of a defect in an article such as a pressure vessel. Safety margins are greater where a given manufacturing process is more susceptible to forming defects. This is of particular interest in the design and manufacture of composite pressure vessels (although the concern of such defects occurring is not limited to manufacture of pressure vessels). By design, the failure pressure of a composite pressure vessel is typically 2 to 3 times the required service pressure. When considering such factors of safety, the typical failure or “burst” pressure of a composite reinforced hydrogen storage vessel is in the region of 140 MPa to 210 MPa.

The strength and stiffness of a composite part is compromised by the presence of fibre deviations, voids, and resin rich regions. Fibre deviations occur when a fibre bundle moves from the optimum design direction during processing. The deviation may cause a reduction in strength or stiffness in a critical material direction. Voids are areas of the composite structure that are unfilled by either the fibres or matrix. Resin rich regions are areas of the material that are formed of only the matrix material. Such regions are particularly susceptible to damage and may act as the sites of crack initiation. Defects such as those listed above are often introduced during manufacturing.

Automation of composite manufacturing is desirable as it can lead to a process that is highly repeatable when compared to manual processes. When using an automated process, the level of defects such as voids or fibre path deviations, is likely to remain within a predictable threshold when the process is repeated. Any associated reduction in strength of the material owing to defects can then be accounted for in the design phase. This means that design of the article can be planned in advance in such a way that the resulting article is almost guaranteed to meet certain strength requirements, for example, minimising the material required to produce the vessel to that standard. This results in more efficient manufacturing, in terms of fewer resources being used both in terms of the materials and energy required, and results in a lighter vessel.

One such automated process is filament winding. The filament winding process involves winding either a single bundle or multiple bundles of fibres around a former, forming a fibrous wall multiple layers of bundles. Winding with a single bundle has the advantage of allowing greater control over the path of the fibre, this is of particular importance when considering complex geometries. The disadvantage of this approach is that manufacturing throughput times are increased due to the low material deposition rate. Furthermore, defects such as resin-rich regions and voids can occur where a subsequently deposited bundle does not lie directly adjacent to the previously laid bundle.

In general, winding with multiple bundles involves first spreading the bundles using a series of rollers. The rollers enable bundles effectively to merge to form a band of fibrous material. Winding using a band increases the material deposition rate and therefore the manufacturing throughput rate is increased. The presence of voids and resin rich regions may also be reduced due to the fact that fewer passes are needed to form a given layer of material on the surface of the former.

The polymeric matrix material may be applied to the fibres either before or after, the fibrous wall is formed. In filament winding processes the polymeric material, in general, is applied before the band of fibres is formed, in a process known as ‘wet winding’. In a wet winding process a liquid resin is held in a resin bath. The fibre bundles are passed through the resin bath and the fibres are coated in the resin. In order to achieve low void content components, it is important that the fibres within the bundle are fully coated with resin or ‘wet-out’.

The fibre count in a given fibre bundle is an important variable when considering the level of wet out that is achievable, and a balance must be found between part quality and manufacturability. Smaller bundles with lower fibre counts, for example 3K (3,000 fibres) or 6K (6,000 fibres), are desirable from the point of view of part quality. The smaller bundle sizes are more likely to be fully wetted by the resin as the bundle travels through the bath. However, using a greater number of bundles with smaller fibre counts has resulted in more complex machinery being required due to the number of fibre bundle lines that need to be guided.

By comparison, when using larger bundles (for example 12K, 24K or 48K), fewer fibre bundle lines are required, and therefore fewer guiding arrangements are required resulting in simpler machinery. However, larger bundle sizes are more difficult to process in the wet winding arrangement. This is because in order to fully wet out, the resin must permeate to the fibres at the centre of the bundle. Therefore, in existing filament winding processes there exists a trade-off between the machine complexity and the quality of the article achieved by the process.

A further problem associated with filament winding arises when considering the need to wind complex geometries, such as the domed ends of a pressure vessel. The location and orientation of fibre bundles on the surface of a composite article is dependant on the relative movement of a former, onto which the fibre bundles are wound, and a winding head which supports and manipulates the fibre bundles prior to depositing them onto the former. The fibres bundle path extends from the winding head to the former. The angle and position of a fibre bundle deposited on the surface of the former can be by adjusting this path, for instance by changing the angle of the path relative to the former.

In order to prevent the fibre bundles from slipping on the surface of the former, the bundle must be laid onto a geodesic path on the surface of the former. When considering the case of winding using a wide band of fibrous material, the band of material is more difficult to manipulate than a single fibre bundle for instance. Winding with a single bundle allows precise control of a fibre bundle path and results in components with fewer defects. Structures formed using a wide band of material may experience a greater degree of fibre deviation in comparison to the structures formed using a singular fibre bundle, as it is more difficult to manipulate the band onto the geodesic path.

The strength and stiffness of a composite structure is dependent on the presence of processing defects. It is important to minimise the defects that may occur during the manufacturing process of the composite structures. It is also recognised that minimising weight is an important design goal. Known composite manufacturing processes are inherently prone to minor manufacturing defects, and this is often accounted for in the design of composite vessels by using high factors of safety. In other words, typically more material is used than is strictly thought to be required, to ensure that any diminished strength due to minor defects is compensated for by the additional material employed to create the article. This means that potential weight savings are often not realised, due to the uncertainty over the construction quality of the article.

The present invention seeks to reduce or overcome one or more of the deficiencies associated with the prior art.

BRIEF DESCRIPTION OF THE INVENTION

The present invention seeks to address the issues outlined above by providing a method and apparatus for forming a composite article. In particular the method and apparatus is suitable for use in the manufacture of composite components that have complex shapes. An example of such complexity is the domed ends of a pressure vessel.

It should be understood that the method and apparatus is not limited to formation of complex shapes, or the formation of pressure vessels, but is also suitable for forming other types of components including simple cylindrical or flat composite components, and for creating other articles that are not pressure vessels.

According to a first aspect of the invention we provide a winding device for forming a composite article, the winding device comprising: a winding head for deploying fibre bundles, having: an array of multiple nozzles offset from each other in a direction along a first axis, each nozzle of the array providing a guiding passage between a first end for receiving a fibre bundle and a second end from which the fibre bundle exits the nozzle, and a traversing mechanism attached to the winding head operable to move the winding head.

According to a second aspect of the invention we provide a winding device for forming a composite article, the winding device comprising: a winding head for deploying fibre bundles, having: an array of multiple nozzles, each nozzle of the array providing a guiding passage extending along a respective nozzle axis between a first end for receiving a fibre bundle and a second end from which the fibre bundle exits the nozzle, multiple actuation devices, each actuation device corresponding to a respective one of the nozzles, each actuation device operable to move its respective nozzle along its nozzle axis, independently of the other nozzles, and a traversing mechanism attached to the winding head operable to move the winding head.

The movement of each nozzle along its nozzle axis may be controlled using a programable controller.

The timing and extent of movement of each nozzle along its nozzle axis may be pre-programmed.

The winding device may further include one or more proximity sensors arranged relative to the or each respective nozzle, operable to determine a distance between the nozzle and a deposition surface at which the composite article may be being formed, wherein the timing and extent of movement of the nozzle may be controlled such that a constant distance between the nozzle and the deposition surface is maintained.

The nozzles may be offset from each other in a direction along a first axis.

The winding head may be moveable in a direction parallel to the first axis.

The winding head may be positioned relative to a former on which the composite article is formed, such that the first axis is substantially parallel to a central axis of the former.

The traversing mechanism may be a robotic arm having six degrees of freedom.

We provide a method according to a third aspect of the invention of forming a composite article using: a winding device of the type having: a winding head for deploying fibre bundles, the winding head having an array of multiple nozzles offset from each other in a direction along a first axis, each nozzle of the array providing a guiding passage between a first end for receiving a fibre bundle and a second end from which the fibre bundle exits the nozzle, and a traversing mechanism attached to the winding head operable to move the winding head, and a former on which the composite article is to be formed, arranged such that the first axis is substantially parallel to a lengthwise axis of the former; the method including steps of: passing multiple fibre bundles through the array of nozzles, such that a respective fibre bundle is passed through each nozzle in the array of nozzles, traversing the winding head relative to the former using the traversing mechanism, forming the composite article by depositing the fibre bundles onto a deposition surface of the article, such that the fibre bundles are deployed at positions offset from each other in a direction along the lengthwise axis of the former.

The fibre bundles may be deployed simultaneously at positions offset from each other in a direction along the lengthwise axis of the former.

We provide a method according to a fourth aspect of the invention of forming a composite article using: a winding device of the type having: a winding head for deploying fibre bundles, the winding head having: an array of multiple nozzles, each nozzle of the array providing a guiding passage extending along a nozzle axis between a first end for receiving a fibre bundle and a second end from which the fibre bundle exits the nozzle, and multiple actuation devices, each actuation device corresponding to a respective one of the nozzles, and each actuation device operable to move its respective nozzle along its nozzle axis independently of the other nozzles, and a traversing mechanism attached to the winding head operable to move the winding head, and a former on which the composite article is to be formed; the method including steps of: passing multiple fibre bundles through the array of nozzles, such that a respective fibre bundle is passed through each nozzle in the array of nozzles, each fibre bundle defining a respective fibre bundle path between the winding head and a deposition surface, traversing the winding head relative to the former using the traversing mechanism, and forming the composite article by depositing the fibre bundles onto a deposition surface of the article, including moving a first nozzle of the nozzle array independently of the other nozzles to adjust its respective fibre bundle path independently of the other fibre bundle paths.

The outer surface of the former may be curved, such that the deposition surface may be curved.

Depositing the fibre bundles onto the curved deposition surface, may include moving one or more nozzles of the nozzle array to adjust their respective fibre bundle paths such that the deployed fibre bundles lie on a geodesic path on the deposition surface. The former may be deflatable, and the method may further include, having formed the article, deflating the former before removing the article from the former.

The former may be made of a dissolvable material, and the method may further include, having formed the article, dissolving the former.

The method may further include passing the fibre bundles through a resin bath as the bundles are fed to the array of nozzles.

The fibre bundles may be co-mingled with a thermoplastic material.

The fibre bundles may be pre-impregnated with a thermosetting resin.

The formed article may subsequently be impregnated with resin using a liquid resin infusion process.

An advantage of the described technology is that the formation of manufacturing defects is minimised. The defects, such as fibre misalignment, voids and resin rich regions occur during the manufacturing process. Such defects cause a reduction in the strength and stiffness of a composite structure and can lead to articles being scrapped if the defects are deemed to compromise the strength sufficiently.

As a result, the design of composite articles is compromised as safety factors are introduced to account for the reduction in material properties. This adds to the cost and weight and resources required to produce a composite article. By reducing the occurrence and severity of manufacturing defects, this reduces the resources needed to produce a given composite article.

BRIEF DESCRIPTION OF THE FIGURES

In order that the present disclosure may be more readily understood, preferable embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIGURE 1 is a schematic showing a winding device and controller arrangement, embodying aspects of the described technology;

FIGURE 2 is a schematic showing a winding device depositing material on a complex surface, embodying aspects of the described technology;

FIGURE 3 is a detailed view of a winding head, embodying aspects of the described technology; FIGURE 4A is a cross-sectional view of a nozzle, embodying aspects of the described technology; FIGURE 4B is a cross-sectional view of a tapered nozzle, embodying aspects of the present disclosure;

FIGURE 5A is a top view showing a preforming frame, for use with aspects of the described technology;

FIGURES 5B and 5C are top-down views of multiple fibre bundles formed onto the preforming frame of Figure 5A, in accordance with embodiments of the described technology, and FIGURE 6 is a diagrammatic view of a method of producing a composite article.

DETAILED DESCRIPTION OF THE DISCLOSURE

With reference to the drawings, we describe a winding device 10 for forming a composite article. Figure 1 shows the winding device 10. The winding device 10 comprises a winding head 12 for deploying fibre bundles, having an array of multiple nozzles 14. Fibre bundles 16 are threaded into the nozzles 14 on the winding head 12, with each nozzle 14 providing a guiding passage 18 between a first end 20 (an inlet) for receiving the fibre bundle 16 and a second end 22 (an outlet) from which the fibre bundle 16 exits the nozzle 14.

The winding device 10 further comprises a traversing mechanism 24 attached to the winding head 12. The traversing mechanism 24 is operable to move the winding head 12.

In embodiments of the described technology, and as can be seen in Figures 1 to 3, the nozzles 14 are offset from each other in a direction along a first axis X. The nozzles 14 may be arranged in a straight line along the first axis X, either directly adjoining one another or spaced apart from each other. Providing multiple nozzles 14 allows multiple fibre bundles 16 to be deposited simultaneously (and in a single pass of the winding device 10).

In embodiments, one or more of the nozzles 14 may be offset from the first axis X so that the nozzles are not positioned along a straight line. Such an arrangement allows the nozzles 14 to be positioned closer together along the direction of the first axis X, for example, so that there is overlap between adjacent nozzles in that axial direction. An advantage of this layout is that the fibre bundles 16 can be deposited closer together. This is particularly beneficial when depositing small (i.e. , low fibre count) bundles 16 in order to reduce the occurrence of gaps between the deposited bundles 16.

Larger fibre bundles 16 are desirable in traditional filament winding techniques, as a higher deposition rate may be achieved within a given time period when using the fibre bundles 16 of high fibre count, for example, the fibre bundles 16 may have a 48K or 96K fibre count. This may lead to a higher manufacturing throughput. By using the winding device 10 described below, multiple fibre bundles 16 of a smaller size may be used. Therefore, the deposition rate of traditional filament winding using the larger fibre bundles 16 may be matched. The smaller fibre bundles 16 may be produced by splitting the larger fibre bundles 16. For instance, a 48K fibre bundle may be split to form two 24K fibre bundles.

Prior to manufacturing composite articles, the fibre bundles 16 are loaded onto a frame commonly known as a creel. The fibre bundles 16 are fed from the creel to the winding device 10. Fibre bundles 16 of carbon, glass or aramid can be used in order to produce composite articles, but suitable alternative materials may be used as appropriate. In some embodiments of the described technology, the fibres first pass through a resin bath 44 as described below.

Figure 2 shows the winding device 10 forming a composite article having a complex geometry. The figure illustrates the independent relative movement of one or more of the nozzles 14a, 14b with respect to the other nozzles 14c in the array. The movement of a nozzle 14a, 14b results in an adjusted fibre bundle path 36, which is beneficial when manufacturing composite articles with complex geometries. This is discussed in more detail below.

Figure 3 is a close-up view of the winding head 12 of the winding device 10 of Figures 1 and 2. The independent relative movement of one or more nozzles 14a, 14b, 14c is illustrated.

By independent relative movement of the nozzles, we mean that an individual nozzle 14a, 14b, 14c is able to move independently of other nozzles 14 in the nozzle array. In general terms the nozzle 14 moves in a direction that is along the lengthwise axis of the nozzle Y. The independent movement of each nozzle 14 allows the paths 36 of individual fibre bundles 16 to be adjusted. When forming composite structures having complex geometries, such as curved surfaces, the adjustment of individual fibre bundle paths 36 allows the fibre bundle 16 to be deposited onto a surface with a high degree of precision. This limits the occurrence of manufacturing defects during forming of a composite article.

Figures 4A and 4B show a cross-sectional view of a nozzle 14. As noted above, the fibre bundles 16 are threaded into the nozzles 14 on the winding head 12, and each nozzle 14 provides a guiding passage. Each nozzle 14 defines a nozzle axis Y extending between the its inlet at the first end 20 and the outlet at the second end of the nozzle 22 (i. e. , a central lengthwise axis). The cross- sectional shape of the nozzle 14, perpendicular to nozzle axis Y is typically circular or oval, and preferably circular. Figure 4A shows the nozzle 14 having a constant cross-section along its length. Alternatively, as shown in figure 4B the nozzle 14 may be tapered along the length of the nozzle axis Y such that the cross-sectional area of the second end 22 is smaller than that of the first end 20. In embodiments of the technology, each nozzle 14 may provide one or more guides 50 positioned at either or both ends 20, 22 of the nozzle 14. The purpose of the guide 50 is to prevent damage to the fibre bundle 16 when entering or leaving the nozzle 14. Such guides 50 are made of a material such as an oxide ceramic material such as aluminium oxide, zirconium oxide, titanium oxide, silicon nitride, silicon carbide, for example.

As mentioned above, the winding device 10 includes a traversing mechanism 24 attached to the winding head 12. The traversing mechanism 24 is operable to move the winding head 12. In use, the winding device 10 is positioned relative to a former 26 on which the composite article is formed. The movement of the winding head 12 is made relative to the former 26, in order to manipulate the fibre bundles 16 into a desired arrangement on the former 26, and in this way the former 26 provides a shape to the composite article being manufactured. Such formers are known in the field of composite manufacturing as mandrels, patterns or moulds, for example.

In the simplest form, the traversing mechanism 24 may have a single degree of freedom, so that it moves widthways or lengthways of the former. Where the nozzles 14 are positioned along the first axis X, typically that axis X is aligned with the movement of the winding head 12. In other words, if the winding head 12 moves lengthways of the former 26, then the nozzles 14 are preferably disposed at positions along a central axis of the former Z.

The arrangement described above has benefits when winding a ‘hoop’ reinforcement layer. The hoop reinforcement is formed by wrapping one or more fibre bundles 16 around the periphery of a cylindrical former 26, so that the fibre bundles 16 are deposited in bands around the circumference of the former. In other words, the fibre bundles 16 are deposited in hoops around the former, each hoop lying approximately on or slightly offset from a plane perpendicular to the central axis Z. The hoop may be offset at an angle relative to the plane by up to 10° for example, and each band is approximately centred on the central axis Z. The hoop reinforcing layer is produced by winding multiple bands along the length of former.

The configuration described is preferable to a system in which the nozzles are disposed in a plane perpendicular to the central axis Z, i.e. in a ring spaced around the central axis and thus around the periphery of the former. In that case fibre bundles would be deposited substantially on top of one another when winding at higher angles as the multiple fibre bundles would be placed on the same portion of the former at the same time. If using such a system a large number of fibre bundles are wound at the same time, it is likely that the fibre bundles deposited on the former would slip, causing defects and inconsistencies in the final component. By contrast, with the configuration described, the spacing of the nozzles 14 along the central axis Z allows the fibre bundles 16 to be deposited adjacent to one another on the former 26 as the hoops are formed. Therefore, multiple fibre bundles 16 can be deposited on the surface of the former 26 without slipping. Typically, the winding head 12 is moveable in a direction parallel to the first axis X (i.e. , the direction in which the nozzles are aligned or spaced). Where the traversing mechanism provides more than a single degree of freedom, the winding head 12 may also be moveable in a direction perpendicular to the first axis X.

In embodiments of the technology, and as shown in figures 1 and 2, the traversing mechanism 24 of the winding device 10 is a robotic arm having six degrees of freedom.

The winding head 12 comprises multiple actuation devices or actuators 46. The actuators 46 may be electro-mechanical devices (i.e., using servomotors), pneumatic devices, or hydraulic devices, for example. Each of the actuators 46 corresponds to a respective nozzle 14. This enables each nozzle 14 to move independently of the other nozzles 14 in the array. In this manner, the actuator 46 is operable to move its respective nozzle 14 along its nozzle axis Y, in the lengthwise direction of the nozzle. Where the nozzles 14 are arranged so that they extend generally towards the former 26, the actuator 46 moves the nozzle 14 towards / away from the central axis Z of the former 26.

When forming a complex shape of article, the former 26 may provide a sloped or curved surface that is not parallel to its central axis Z or the first axis X - when forming a domed surface of a pressure vessel, for example. In that case, the distance from the surface of the article being formed and the first axis X along which the nozzles are arranged is not constant. With reference to Figure 3, it can be seen that where the first axis X is aligned parallel to the central axis Z of the former 26, then as the domed surface curves inwardly towards that central axis Z of the former 26, the nozzles 14 in their default unextended position (illustrated at 14c) may naturally each sit at a different distance from the surface being formed. In order to control or maintain the distance between the nozzle outlet at its second end 22 and the surface being formed, the nozzles 14 can be moved towards the central axis Z of the former 26 using the actuators 46 - this can be seen at 14a and 14b in Figure 3.

The movement of each nozzle 14 along its nozzle axis Y is controllable using a programable controller 28. A schematic of the controller 28 and winding device 10 is shown in figure 1 . The programmable controller 28 is a device capable of controlling an automated manufacturing process, such as a numerical controller, a programmable logic controller or a programmable automation controller. The controller 28 can be pre-programmed in order to coordinate the timing and extent of movement of each nozzle 14. Additionally, the controller 28 can coordinate the movement of the traversing mechanism 24.

In embodiments of the technology, the movement of the nozzle 14 may also be, at least in part, controlled by the input of one or more proximity sensors 48 arranged relative to each respective nozzle 14. The proximity sensors 48 are mounted on each individual nozzle 14 and be capable of sensing the distance between the second end 22 of the nozzle 14 and the former 26.

Figures 1 , 2 and 3 shows the winding head 12 positioned relative to the former 26, on which the composite article is formed. Where the former 26 is used to form a cylindrical component such as a cylindrical portion of a body of a pressure vessel, the first axis X is substantially parallel to a central axis Z of the former 26. In such cases a motor 42 may be used to rotate the former 26 about its central axis Z.

In embodiments of the technology, and as shown if Figures 5A, 5B and 5C, the winding device 10 may instead be used to form a component having a planar surface. The surface may be rectangular, and have boundaries defined by orthogonal lines. In such examples, the article may be formed on a frame 30 which may be a rectangular frame as illustrated. In this case the winding head 12 may align along one of the frame boundaries.

In more detail, Figure 5A shows a frame 30 used to form a composite article. The frame 30 can retain the fibre bundles 16 at its boundaries, and this may be achieved by mechanical means such as the use of pins, or by adhesively bonding the fibre bundles 16. The frame 30 may be held securely, by clamping to a worktable for instance.

Providing nozzles spaced along axis X allows multiple fibre bundles 16 to be deployed across the width of the frame 30 simultaneously. By deploying multiple bundles at once, a larger portion of the frame can be covered in a single pass of the winding head.

Figure 5B shows the deposition of a first layer 32 of fibre bundles 16. Each layer 32, 34 may be formed in a single pass of the winding head 12. The winding head 12 is aligned along a first edge 30a of the frame 30 boundary. The fibre bundles attached mechanically or adhered to the first edge 30a of the frame 30 boundary. The traversing mechanism 24 moves the winding head 12, depositing fibre bundles 16 across the width of the frame 30. Once the winding head 12 has passed across the frame 30, the fibre bundles 16 are fixed to a second edge 30b of the frame boundary. The winding head 12 is then re-positioned prior to depositing a subsequent layer of fibre bundles 16. Figure 5C shows the deposition of a subsequent layer 34 of fibre bundles 16 at right angles to the first layer between frame edges 30c and 30d. Each layer 32, 34 may be formed in a single pass of the winding head 12, depending on the desired number of bundles to be deployed and the number of nozzles being used. In embodiments of the described technology, the fibre bundles 16 may be deposited at an angle that is offset from the edges 30a, 30b, 30c, 30d of the frame 30. Now looking at the embodiments illustrated in Figures 1 and 2, in these examples the traversing mechanism 24 is a robotic arm (which may have six degrees of freedom). The robotic arm is able to articulate robotic joints in order to provide translational and rotational movement to the winding head 12. The robotic arm may be specifically designed to allow humans to interact safely and to collaborate with the robot. Such robots are commonly known in the field as ‘cobots’.

Programming of the robotic arm can be performed using a teach pendant 40. The teach pendant 40 allows the programming of a robotic arm to be simplified. The operator is able to manipulate the robot the required positions using simplified controls. The positions can then be recorded by the controller 28 in order to direct the motion of the equipment during manufacture of the composite article.

In embodiments the traversing mechanism 24 having a single degree of freedom may also be capable of traversing the winding head 12 along the first axis. Electro-mechanical linear actuators 46 are commonly used to provide linear motion. Alternatively, the linear motion may be provided by pneumatic or hydraulic actuators 46.

Figure 3 shows the fibre bundle path 36 during manufacture of a composite article. As previously explained, multiple fibre bundles 16 are passed through the array of nozzles 14, such that a respective fibre bundle 16 is passed through each nozzle 14 in the array. The nozzles 14 are offset from each other along the first axis X, and so the fibre bundles 16 are therefore also offset from each other in a direction along that axis X as they exit the respective nozzles 14.

The traversing mechanism 24 is then used to traverse the winding head 12 relative to the former 26. A composite article is formed by depositing the fibre bundles 16 onto a deposition surface 38 of the article, such that the fibre bundles 16 are deployed at positions offset from each other in a direction along the lengthwise axis Z of the former 26. Initially the deposition surface 38 may be the surface of the former 26, more specifically the outer surface of the former 26. The deposition surface 38 may also be formed of previously deposited fibre bundles 16. Such fibre bundles 16 may have been applied earlier in the winding process by the winding device 10, or have been applied to a former 26 by other means.

In embodiments of the technology, the fibre bundles 16 are deployed simultaneously at positions offset from each other along the first axis X, which when aligned with the central axis Z of the former 26, is in a direction along the lengthwise axis of the former 26. For instance, in the case of a cylindrical component a first fibre bundle 16 may be deployed at a first position on the former 26 at a first end of the former 26. At the same time, a second or further fibre bundle 16 may be deployed at a second position (or further position where more than two nozzles 14 are provided) that is offset from the first position along the lengthwise axis Z of the former 26. In embodiments of the technology, the process of forming the composite article by depositing the fibre bundles 16 onto a deposition surface 38 of the article may include moving a first nozzle 14 of the nozzle array independently of the other nozzles 14 to adjust the respective fibre bundle path 36 independently of the other fibre bundle paths 36. The fibre bundle path 36 is formed between the second end of the nozzle 22 and the deposition surface 38. The fibre bundle path 36 can be adjusted through the movement of the nozzle 14. As the movement of the nozzles 14 is independent of the other nozzles 14 in the array, the path 36 of an individual fibre bundle 16 can be moved independently of other bundles 16 that are deposited.

As shown in Figures 1 , 2 and 3 the outer surface of the former 26 is curved, such that the deposition surface 38 is curved. As mentioned, a curved surface of an article may be a surface such as the dome of a pressure vessel. When considering the cross-sectional profile of the surface of the former 26, in a plane parallel to the central axis of the pressure vessel, the cylindrical section of the pressure vessel is effectively a straight line. When considering the domed end in the same cross-sectional plane the profile of the vessel wall at the dome forms a curve. This presents problems when depositing fibre bundles 16 in that an incorrectly positioned fibre bundle 16 will tend to slip along the curved surface (i.e. , inwardly, towards the central axis Z). Such fibre bundle 16 slippages result in defects and reduced material strength.

In other embodiments a curved surface may be the surface of a wind turbine blade, propeller blade, aircraft wing or other aerofoil shape.

In order to prevent the slippage of fibre bundles 16 one or more nozzles 14 of the nozzle array may be moved to adjust their respective fibre bundle paths 36 such that the deployed fibre bundles 16 lie on a geodesic path on the deposition surface 38. The geodesic path represents the shortest arc between two points on a surface. Therefore, the arc of the fibre bundle 16 between two points along the curved surface must be the shortest arc possible, if slippage of the fibre bundle 16 is to be avoided. The arc of the fibre bundle 16 on a curved surface can be controlled by adjusting the fibre bundle path 36 between the deposition surface 38 and the nozzle 14. This can be achieved by adjusting the position of the nozzle 14 as described in previously.

It may be desirable to remove the former 26 once the composite article has been consolidated. In such cases a deflatable former 26 is used. Having formed the article as described above the former 26 may be deflated, before removing the article from the former 26. The deflatable former 26 may be made of a flexible polymeric material. A flexible former 26 is inflated before fibre bundles 16 are wrapped onto the former 26. Once the composite article has been consolidated the inflatable former 26 can be removed by deflating and removing from the composite article. In alternative embodiments, the former 26 is made of a dissolvable material. Having formed a composite article using the method described above, the former 26 may be dissolved in order to remove it from the composite article. Fibre bundles 16 can be wrapped onto the dissolvable former 26 to produce a composite article as described above, and the former 26 can then be dissolved in order remove the former 26 from the composite once it has been completed.

In embodiments of the technology, the fibre bundles 16 are passed through a resin bath 44 as the bundles are fed to the array of nozzles 14. Passing the fibre bundles 16 through the resin bath 44 impregnates the fibres with a liquid resin prior to winding onto the deposition surface 38. The fibre bundles 16 are passed through the resin bath 44 prior to entering the nozzle 14. Therefore, the fibres are coated with resin or ‘wetted’ before reaching the winding head 12. During processing, the wetted fibre bundles 16 are deposited onto the deposition surface 38. Once the process is complete the component can then be consolidated. The consolidation process typically involves heating the composite article in order to cure the resin. The consolidation process may also include applying pressure to the composite article.

Figure 6 shows a schematic of the steps of the passing 52 multiple fibre bundles 16 through the array of nozzles, traversing 54 the winding head relative to the former and forming 56 the composite article by depositing the fibre bundles onto a deposition surface of the article.

In some embodiments the polymeric matrix may be formed through a liquid resin infusion process. In other embodiments the polymeric material may be contained within the fibres prior to the winding steps. Such methods employ the use of a fibre bundles 16 that are pre-impregnated with a thermosetting resin or fibre bundles 16 that are co-mingled with a thermoplastic material.

In embodiments of the described technology, the composite article may be impregnated with resin by a liquid resin infusion process after the winding process is complete. In other embodiments the resin may be contained within the fibre bundles 16 such as a pre-impregnated fibre bundle. In further embodiments a thermoplastic material may be commingled with the fibre bundle 16.

When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

The invention may also broadly consist in the parts, elements, steps, examples and/or features referred to or indicated in the specification individually or collectively in any and all combinations of two or more said parts, elements, steps, examples and/or features. In particular, one or more features in any of the embodiments described herein may be combined with one or more features from any other embodiment(s) described herein. Although certain example embodiments of the invention have been described, the scope of the appended claims is not intended to be limited solely to these embodiments. The claims are to be construed literally, purposively, and/or to encompass equivalents.