EP3174680A2

EP3174680A2 - Manufacture of vehicle structures

Info

Publication number: EP3174680A2
Application number: EP15750802.9A
Authority: EP
Inventors: Anthony Richard Glover; Ronald DENNIS
Original assignee: McLaren Applied Technologies Ltd
Current assignee: McLaren Applied Ltd
Priority date: 2014-07-31
Filing date: 2015-07-31
Publication date: 2017-06-07
Also published as: GB201413637D0; WO2016016662A2; WO2016016662A3

Abstract

A method of forming a composite structure comprising: forming a substantially rigid former comprising a hollow region; arranging a spacer over the hollow region to increase the outer circumference of the former in the hollow region; wrapping the former and the spacer with reinforcing fibre; withdrawing the spacer; and coating the surface of the hollow region with the wrapped fibre.

Description

MANUFACTURE OF VEHICLE STRUCTURES

Field of the Invention

This invention relates to manufacturing vehicle structures. Background of the Invention

It is becoming increasingly common for vehicles to be manufactured from composite components. Some vehicles include a main structure or tub which extends between mountings for the front and rear wheels and encloses the occupants and which is made partly or wholly from composite materials. One way to manufacture such a tub is to prefabricate a set of composite parts and then join them together by coating the interfaces between them with adhesive and then bringing the parts together. This has the advantage of relatively low cost, but can require several tens of kilograms of adhesive to be used even for a small vehicle. Naturally, that impairs the performance of the resulting vehicle. Another approach is to form the tub from a single-piece moulding of matrix material over a framework of suitably laid up reinforcing fibres. This can provide a strong and relatively lightweight structure, but the mould tooling is relatively expensive and laying up fibres for an entire tub is a complex process that is difficult to automate.

There is a need for an alternative method for forming composite structures such as vehicle tubs.

Summary of the Invention

According to one invention there is provided a method of forming a composite structure comprising: forming a substantially rigid former comprising a hollow region; arranging a spacer over the hollow region to increase the outer circumference of the former in the hollow region; wrapping the former and the spacer with flexible elongate material; withdrawing the spacer; and coating the surface of the hollow region with the wrapped flexible material.

The flexible material may be in the form of a fibre, for example a reinforcing fibre material such as carbon, aramid or glass fibre. The flexible material may be in the form of a sheet, for example a fabric or a film. The fabric may be formed of a reinforcing fibre material, for example carbon, aramid or glass fibre.

The step of wrapping the former and the spacer with the flexible elongate material may comprise braiding or winding the flexible material over the former and the spacer. The flexible material may bind the former and the spacer together, for example by encircling them both.

The step of wrapping the former and the spacer with the flexible elongate material may comprise automatically draping each of a plurality of discrete elements of the flexible material over the former and the spacer. The discrete elements may be individual fabric sheets.

During the wrapping step the flexible material may comprise (e.g. as a coating) a curable resin. The method may comprise the step, after the wrapping step, of impregnating the flexible material with a curable resin. The resin may be curable to form a solid matrix. The fibre material may have greater tensile strength per unit mass and/or per unit volume than the matrix. The method may comprise curing the resin.

The spacer may be sized so that when the spacer is withdrawn the wrapped flexible material is capable of substantially fully coating the hollow region, optionally with substantially minimal excess material.

The step of coating the surface of the hollow region with the wrapped flexible material may comprise arranging the former such that the wrapped flexible material can sag under the action of gravity to coat the surface of the hollow region. The method may comprise permitting the wrapped flexible material to sag under the action of gravity to coat the surface of the hollow region. The method may comprise applying a tool to the exterior of the wrapped flexible material to press it against the surface of the hollow region. The tool may be an inflatable tool, for example an elastic or inelastic bag.

The step of withdrawing the spacer may comprise removing the spacer from the former. The step of withdrawing the spacer may comprise removing the spacer from between the surface of the hollow region and the wrapped flexible material. The step of withdrawing the spacer may comprise deflating the spacer. The step of withdrawing the spacer may comprise dissolving or melting the spacer.

According to a second invention there is provided method of forming composite articles comprising: forming a plurality of substantially rigid formers; coupling a plurality of the formers together to form a string of formers; and feeding the string of formers through a wrapping apparatus, the wrapping apparatus being configured to wrap articles being fed through it with flexible elongate material.

The method may comprise wrapping the formers with the flexible material by means of the wrapping apparatus. The wrapping apparatus may be a braiding apparatus configured to coat articles being fed through it with a braided tube of the flexible material. The method may comprise braiding the formers with the flexible material. The wrapping apparatus may be a winding apparatus configured to wind the flexible material over articles being fed through it. The method may comprise winding the flexible material over the formers. The wrapping apparatus may be configured to wrap articles being fed through it with flexible material that comprises a curable resin. When the flexible material is wrapped over the formers it may comprise a curable resin. The method may comprise the step, after one of the articles has been wrapped by the wrapping apparatus, of impregnating the flexible material wrapping that article with a curable resin. The method may comprise curing the resin. The resin may be curable to form a solid matrix. The fibre material may have greater tensile strength per unit mass and/or per unit volume than the matrix.

The method may comprise the step of separating the wrapped formers from each other. The method may comprise the step of moulding resin over each separated former individually. The method may comprise the step of subsequently curing the resin.

According to a third invention the method may comprise forming a plurality of substantially rigid formers. The method may comprise feeding the formers in series through a wrapping apparatus, the wrapping being configured to wrap articles being fed through it with flexible elongate material to form a string of wrapped formers. The method may comprise bending the string of formers at at least one zone between the formers to form a reconfigured string of formers. The method may comprise moulding resin over the reconfigured string of formers. The method may comprise subsequently curing the resin.

The step of feeding the formers in series may comprise, for each said former: holding the former in a first movable clamp located at an inlet of the wrapping apparatus; moving the first clamp so as to pass the former into the inlet; grasping the former by means of a second movable clamp located at an outlet of the wrapping apparatus; and withdrawing the former from the outlet by means of the second clamp.

The method may comprise, prior to the step of feeding the formers through the wrapping apparatus, locating a spacer in proximity to the said at least one zone so as to increase the effective outer circumference of the former in that zone. The method may comprise withdrawing the spacer prior to the said bending step.

According to a fourth invention there is provided a method of forming a composite body structure for a vehicle, the method comprising: forming a plurality of substantially rigid formers; wrapping at least one of the formers with flexible elongate material; bringing a set of the formers comprising the said one of the formers and another of the formers together; wrapping the said one of the formers and the other of the formers with reinforcing fibre so as to bind them together; moulding resin over the said one of the formers and the other of the formers; and curing the resin.

The said one of the formers may define a sill of the body structure. The said other of the formers may define a floor of the body structure. The body structure may be a vehicle tub. The said one of the formers may define a vehicle tub. The said other one of the formers may define a vehicle upper structure.

The said one of the formers and the other of the formers may be configured so as to mate positively together, for example by physically interlocking.

The step of moulding resin over the said one of the formers and the other may be performed by injection moulding or resin transfer moulding. The step of moulding resin may comprise moulding resin that contains reinforcing fibre segments dispersed therein over the said one of the formers and the other.

The mould in which the resin is moulded may have features capable of being filled by the resin so as to form extensions protruding from the formers.

One or more of the said extensions may constitute functional portion(s) of the body structure. The method may comprise introducing a rigid reinforcing element into one or more of the said features to serve as reinforcement for the extension(s). The rigid element may be a metal element.

The wrapping step may comprise forming a braided tube of the flexible material around the formers. The wrapping step may comprise winding the flexible material around the formers. According to a fifth invention there is provided a method of forming a composite body structure for a vehicle, the method comprising: forming a plurality of substantially rigid formers; wrapping each of the formers with flexible elongate material; curing resin over the flexible material wrapped on each former to form a respective body structure component; assembling the body structure components to form a body structure located in a mould; and moulding a material over the components to bind them together.

One of the body structure components may constitute a tub of the vehicle body structure. One of the body structure components may constitute an upper structure of the vehicle body structure

The formers may be configured so as enable the body structure components to mate positively together when assembled, for example by physically interlocking.

The step of moulding a material over the components and the other may be performed by injection moulding or by resin transfer moulding. The step of moulding a material may comprise moulding a resin that contains reinforcing fibre segments dispersed therein over the components.

The mould in which the resin is moulded may have features capable of being filled by the resin so as to form extensions protruding from the formers. One or more of the said extensions may constitute functional portion(s) of the body structure. The method may comprise the step of introducing a rigid reinforcing element into one or more of the said features to serve as reinforcement for the extension(s). The rigid element may be a metal element.

The flexible material may be in the form of a fibre, for example a reinforcing fibre material such as carbon, aramid or glass fibre. The flexible material may be in the form of a sheet, for example a fabric or a film. The fabric may be formed of a reinforcing fibre material, for example carbon, aramid or glass fibre. The wrapping step may comprise forming a braided tube of the flexible material around the formers. The wrapping step may comprise winding the flexible material around the formers.

According to a sixth invention there is provided method of forming a vehicle body structure comprising moulding the body structure in a volume defined at least partially a plurality of outer mould bodies and a plurality of interior mould bodies eatable within the plurality of outer mould bodies, the interior mould bodies defining at least the surfaces of the tub directed towards the interior volume of the body structure.

The body structure may define one or more door apertures. The method may comprise, subsequent to the step of moulding the body structure, removing the interior mould bodies from the interior of the body structure through one or more such door apertures.

The method may comprise the steps, prior to the step of moulding the body structure, of: assembling the interior mould bodies together to form a composite interior mould body; and locating the composite mould body in a predetermined relationship with the outer mould bodies so as to define the said volume.

The interior mould bodies may comprise a first body defining the upper part of the interior of the body structure and a second body defining the lower part of the interior of the body structure.

The method may comprise, prior to the completion of the moulding step, locating one or more additional components in the said volume; and performing the moulding step so as to incorporate those component(s) into the body structure.

The said moulding step may be performed by injection moulding or resin transfer moulding. Where a part of a formed component is defined as constituting a specific element of a vehicle, it may be such an element by virtue of a subsequent step of manufacturing a vehicle using the said component so that the said part of the component constitutes that specific element of the vehicle. A tub of the vehicle may comprises one or more of the floor, sills, bulkheads, engine attachment points and running gear attachment points of the vehicle. An upper structure of the vehicle may comprises one or more of a roof, an A pillar, a B pillar and a C pillar. A door aperture of the vehicle may have an exterior door of the vehicle positioned so as to close it. The exterior door may be a passenger door.

The hollow region could be defined between two sills of a vehicle tub. The hollow region could be defined between front and rear bulkheads of a vehicle tub.

Drawings

The present invention will be described by way of example with reference to the accompanying drawings.

In the drawings:

Figure 1 shows a vehicle tub in assembled form.

Figure 2 is an exploded view showing the components of the tub of figure 1 . Figure 3 illustrates steps in the formation of a lower tub part.

Figure 4 shows a first mechanism for braiding a concave part.

Figure 5 shows a second mechanism for braiding a concave part.

Figure 6 illustrates a first form of continuous braiding process.

Figure 7 illustrates a second form of continuous braiding process.

Figure 8 illustrates steps in the overmoulding of tub parts.

Detailed Description of the Invention

Figure 1 shows an assembled vehicle body structure. The body structure has a lower section comprising a floor 1 and a pair of side beams 2, 3 which strengthen the sides of the floor; and an upper section in the form of a framework defining a front beam or scuttle 4, A pillars, 5, 6 which extend upwards from the scuttle, longitudinal roof beams 7, 8 which extend rearwardly from the upper ends of the A pillars, C pillars 9, 10 which extend downwardly from the rear ends of the longitudinal roof beams and cross beams 1 1 , 12 which extend laterally between the longitudinal beams. Together the upper section and the lower section enclose an interior volume. That volume can form the passenger space of a vehicle. Running gear can be attached to the body structure, for example so that ground engaging wheels are located at the front and rear of the body structure, attached by suspension mountings to the body structure. An engine and/or motor can be attached to the body structure to drive the wheels. Other elements can be attached to the body structure, for example extending from the front and the rear, to mount to the driving gear, running gear and other components.

Figure 2 shows a set of discrete parts that can be assembled into the body structure of figure 1 . These comprises: a floor piece 20, two rocker sections 21 , 22, an upper cage 23 and two cross beams 24, 25. The upper cage is a single piece which makes up the scuttle, A pillars, longitudinal roof beams and C pillars of the superstructure of the body structure. The cross beams 24, 25 can be attached to bridge between the sides of the cage.

The six discrete parts shown in figure 2 can be manufactured individually and then joined together to form the body structure of figure 1 . This process will be described in more detail below.

Each of the six discrete parts is a substantially rigid part. In a generalised example, each part can be formed by wrapping a substantially rigid former with flexible reinforcing material (e.g. fibres) and then curing a matrix material (e.g. a resin) in contact with the fibres so fix the fibres in position. Some specific aspects of that process may be performed in the following ways.

- The substantially rigid former could be a block of material, conveniently a rigid or semi-rigid foam. Alternatively it could be a hollow vessel, for example a blow-moulded component in which air is sealed to allow it to retain its shape under compression. Alternatively it could be a vacuum bagged article comprising particles such as beads or sand which are held in a desired configuration by virtue of the vacuum in the bag. The particles could be removed after the part has been moulded, to save weight. The former could be a core of aggregated particles without an external wall, for example a sand core. Particles of a core of that sort could also be removed (e.g. by washing) after moulding.

- The flexible reinforcing fibres could, for example, be carbon fibre, glass fibre or polymer fibre, e.g. of an aramid such as Kevlar. The fibres are preferably of a material having a greater tensile strength per unit mass than the resin.

- The fibres could be wrapped around the former by draping a pre-formed sheet of fibres around the former, by winding fibre around the former or by braiding the former: that is by enveloping the former in a woven tube of fibres. The former can be braided by drawing a pre-formed woven tube over the former or by drawing the former through a braiding station.

- The fibres could be pre-impregnated with resin, or the resin could be applied to the fibres once they are in place on the former. A convenient approach is to place the wrapped former in a mould, then introduce the resin into the mould so as to diffuse around the fibres, and then apply conditions (e.g. sufficient heat) to cure the resin. This could be an injection moulding or resin transfer moulding (RTM) process.

Figure 3 shows a variant of this process in which multiple components are wrapped together. In a first stage (A) the formers 31 , 32 for the rockers and the former 33 for the floor are formed. In a second stage (B) the rocker formers are wrapped with fibre. In a third stage (C) the rockers are located adjacent to the floor and the rockers and the floor are collectively wrapped, so that fibres run around the perimeter of the unit defined by the floor and the rockers collectively. Then resin is applied to that wrapped unit, and the resin is cured. This approach means that the fibres can help to hold the rockers to the floor. A similar approach may be used to hold other components together by wrapping them collectively. For extra strength one or more of those components can be wrapped individually, as with the rockers described above.

It will be noted that in figure 3 both ends of the floor finish roughly flush with the ends of the rockers as indicated at 34. This allows the three components to be wrapped together without the potential for the wrapping fibres to entangle each other. If desired, parts of the floor and/or the rockers could be cut away after wrapping or after moulding. It may be desired for one of the components to have a concave face. One example of this is the upper face of floor 33, as indicated at 35 in figure 3. Another example is the lower longitudinal end regions of the floor as indicated at 36. Whilst in general it is desirable for the fibre wrapping to be tight to the outer bounds of the former, in the case of a component having a concave portion that arrangement would prevent fibres from making contact with the inner parts of the concave portions 35, 36. To allow the former to be wrapped easily when it includes a concave portion a spacer 37 (see figure 4) can be located in the concave portion before the former 34 is wrapped with fibre. The spacer is designed so that when the component and the spacer are tightly wrapped, and the spacer is subsequently removed or reduced in size, sufficient fibre will go slack that that slack fibre can then make continuous contact with the walls of the concave portion. To permit the size of the spacer to be reduced, it could be an inflatable bladder (as shown in figure 4) or bag which is inflated to a suitable size before the former is wrapped, and then deflated after wrapping. Then resin can be introduced to the fibres and the resin cured. The spacer could be removed after wrapping, although this may not be necessary if the spacer is withdrawn by deflation. The spacer could be removed by being physically drawn out of engagement with the concave portion, or could be removed by a chemical process such as by dissolving it. The spacer can be sized so that the wrapped material freed once it has been removed is just sufficient to continuously coat the coat the concave/hollow portion. The exterior of the former on its side opposite the one that faces the concave surface may be convex. The former may be rigid or conformable. The former may be an inflatable bag. Once the former has been removed the freed material may be positioned against the concave surface by permitting it to sag under the effect of gravity or by pushing it against the concave surface by a tool. The tool may be an inflatable diaphragm.

Figure 5 illustrates another way of achieving sufficient loose fibre to coat the surface of a concave portion. In this example, one or more support fibres 38 are strung between parts of the former 34 so that the support fibres extend over the concave portion 35. The support fibres are under sufficient tension that when the former is wrapped they will hold the wrapping away from the concave portion of the former. Then the support fibres 38 are cut, allowing the wrapping to go loose and be laid against the surface of the concave region 35.

One way to enable the wrapped formers to be formed efficiently is to pass them through a substantially continuous braiding process. Figure 6 illustrates one way in which this may be done. A braiding frame 40 is set up with robotic handling stations 41 , 42 on either side of it. The braiding frame has a series of reels of fibre 43 arranged around its circumference. The free fibre ends of the reels are interwoven with each other as indicated at 44, to form a sock 45 of braided fibre. To provide a substantially continuous braiding process, the upstream handling station 41 picks up a trailing end of a former 46 that is to be braided. The upstream handling station inserts the former 46 into the sock 45 and may push the former 46 to some extent through the braiding station so as to at least partially wrap it in braided fibre. Then the downstream handling station 42 grips the lead end of the former 46 and the upstream handling station releases the former. The downstream handling station can now pull any remaining length of the former through the braiding station. Finally, the braid is cut on the upstream end of the former and the downstream handling station passes the former to the next stage of the process. Meanwhile the upstream handling station can be passing the next former to the sock. In this way the process can be operated substantially continuously.

Another substantially continuous braiding process is illustrated in figure 7. In this process successive formers 50 are physically attached together before being introduced to the braiding station 51 . The formers may be attached with intermediate components. Successive formers in the chain may be similar or dissimilar in shape. The chain of formers can then be drawn through the braiding station with each former being pulled or pushed through the station via its connection to the succeeding or preceding former. This creates a continuous chain 52 of inter-attached braided formers. The formers can subsequently be separated from each other. The formers can be separated so that individual formers are each freed from each other. Alternatively, two or more successive formers may be left attached to each other, the material joining them flexed so as to reposition those formers relative to each other, and then the formers fixed in that configuration, for example with adhesive or a mechanical fixing. This technique can allow the formers to adopt configurations that could not easily pass through the wrapping station.

The braiding reels may rotate around the article that is being passed through the braiding station, so as to wind the fibres around the article and/or to intertwine the fibres into a braid structure.

A spacer of the type discussed above may be placed adjacent to a concave zone of one of the formers before it is wrapped. Then the former can be withdrawn (e.g. by deflation and/or removal) and the wrapping that had covered the former can be used to fully and intimately cover the concave zone, again as in the methods discussed above. The concave zone may be configured so that when the wrapping material connecting that former to an adjoining former is flexed the adjoining former can fit snugly into the concave zone. This can help to strengthen the joint between the formers.

Another way to achieve a substantially continuous process is for a series of formers to be threaded or otherwise attached to a transfer line that passes through the braiding station. Then that line can be drawn through the braiding station, bringing the formers with it.

These processes can be used with other forms of wrapping than braiding, by replacing the braiding station with a unit that can wind individual fibres or drape cloth around the formers. The winding unit could reciprocate along the feed axis of the formers, to allow it to wind overlapping runs of fibre.

There could be multiple braiding or winding stations in series, to apply multiple layers of reinforcing fibres over the formers.

In order to form a body structure of the type illustrated in figure 1 the components must be joined together. One option is to bond the components together using adhesive applied between the components. Another option is to join the components together by placing them together in a mould and then moulding a joining material over them. In a preferred example all the components of the body structure are brought together in a single mould and overmoulded with a composition that joins them all together.

Figure 8 illustrates one way in which this can be done. The rocker sections have been over-wrapped together with the floor and form a combined lower component 60. The lower component is placed in a mould base 61 . (Stage A). Then a series of mould bodies 62 are assembled over the surfaces of the lower component that will be directed towards the interior volume of the eventual body structure. These mould bodies could be pre-assembled and placed on the lower tub of the body structure as one item. (Stage B). By using multiple mould bodies to define the shape of the interior surfaces of the body structure the mould can be assembled relatively easily even against surfaces of the final tub that cannot readily be contacted by mould tools laid on in directions extending directly from the top or bottom of the body structure. Then the upper structure formed of an upper cage 63 and cross-beams 64 is assembled in place on the lower component. (Stage C). Then an upper mould body 65 is applied over the upper parts of the body structure. (Stage D). The structure to form the body structure is now fully enclosed by the mould bodies. Now a curable compound is injected into the void between the components and the mould bodies. The curable compound could, for example, be a polymerisable resin. Then the curable compound is solidified, for example by imposing conditions of temperature under which it will polymerise. Once the compound is set the process of assembling the mould can be reversed to permit the body structure to be removed. The individual components of the body structure are now held together by virtue of intimate contact between them and the moulded compound. The moulded compound extends between the components where they abut each other and/or bridges across the interfaces between the components. The components may incorporate relief features such as recesses or projections near the ends where they meet other components. Those features could be enveloped by the overmoulded compound to hold the components positively together. The overmoulded features could represent attachment points for other parts such as seats, doors and so on. By overmoulding the entire body structure in a single step it is possible to achieve good dimensional control across the entire body structure. The mould bodies defining the interior of the vehicle structure could be configured so that they can be removed through a door opening of the vehicle structure. The overmoulding may be performed by compression moulding or transfer moulding.

The components of the body structure could butt together. Alternatively, one or more of them may mate positively together using inter-engaging mechanical joints such as dovetail joints or mortice and tenon joints. These could be snug fitting, or could leave room for the overmoulding compound to flow into the joint to lock it in place once set.

The overmoulded compound could define additional functional features on the body structure, for example fixing points for additional parts. These could protrude from the formers. The overmoulded compound could define detailed features that are difficult to form when the components themselves are being made. The overmoulded compound could contain short reinforcing fibres. Rigid reinforcing elements such as metal rods or plates could be placed in the mould volumes or on the exterior of the mould volumes that define the additional functional features prior to the introduction of resin into the mould, so as to strengthen the features after moulding. The additional features could, for example, be glazing flanges, seal paths or attachment points for other components such as doors.

Using this technique, a fibre reinforced composite body structure can be manufactured simply and with relatively high strength.

The components could be trimmed after being wrapped or after resin is cured on to them, for example using laser or water jet cutting. After the overmould is applied the body structure can be machined to a desired shape.

One or more of the components could incorporate hard points that allow for subsequent components to be mated firmly to the body structure. The hard points could be metal studs or metal blocks incorporating smooth or threaded holes.

Component 23 of figure 2 is of an arcuate shape. To facilitate drawing such a component through a wrapping process, particularly a continuous wrapping process of the types illustrated in figures 6 and 7, it may be desirable for the component to be capable of flexing, for example at one or more of its corners. In this example the component could flex at the corners between the scuttle and the A pillars. To permit it to flex, the component could be formed using multiple rigid formers. Those formers could be wrapped in series so that they are held together by the fibre wrapping but are still capable of relative rotation. Then they could be placed in a mould whilst still unified by the wrapping, and impregnated with resin which is then set. It may be desirable to minimise the length of free fibre between the individual formers once they are wrapped. To enable that to be done whilst still permitting relative rotation of the formers a spacer could be incorporated at the zone between the formers during the wrapping process. The spacer is then overwrapped with the formers. The spacer causes additional fibre to be drawn out around the zone between the formers. Then once the spacer is removed or reduced in volume (e.g. by deflation) the additional lengths of fibre that had been wrapped around the additional bulk of the spacer serve to run around the outermost part of the bend.

Any suitable setting material could be used as the matrix for moulding over the fibres of each component. Similarly, any suitable setting material could be used as the overmoulding compound. However, it is convenient if both setting materials are the same since that promotes good adhesion between them. One convenient arrangement is for both setting materials to be precursors of nylon, for example by comprising a caprolactam. The setting materials may comprise a polymerisable component together with any one or more of an accelerator, a plasticiser and a pigment. Caprolactam-comprising precursors can provide a relatively fast cycle time, particularly when presented as a snap cure composition. The matrix or resin could have reinforcing fibres dispersed therein, for example at the point when it is introduced to the wrapped fibres. The dispersed reinforcing fibres could be of relatively short length, for example less than 10cm or less than 5cm or less than 2cm. The dispersed fibres could be of, for instance, carbon, aramid or glass fibre material.

The wrapping material could be any suitable elongate flexible material, for example a fibre material (e.g. of reinforcing fibres such as carbon fibre, aramid fibre or glass fibre) or a sheet material (e.g. a fabric or film). The wrapping material could be braided or wound around the other elements, or discrete pieces of the wrapping material could be draped onto the other elements, for instance using an automatic placement machine. The wrapping material could carry a curable matrix material/resin at the time it is wound on to the other elements (as in the case of a pre-preg fibre or fabric). Alternatively, the wrapping material could be impregnated or coated with curable matrix material/resin after the winding step.

The wrapping may preferably take place outside a mould. When the wrapping is performed by winding or braiding it may be performed with the wrapping material under tension. The wrapping is preferably performed so that the wrapping material adopts the exterior profile of the element(s) that is/are being wrapped.

The methods described above could be used to form structures other than vehicle body structures, for example, boats, truck cabs, crane jibs and architectural components. The methods could be used to form whole or partial vehicle body structures: for example to form body structure lower parts or upper parts only.

The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features, to the extent that such features or combinations are capable of being carried out based on the present specification as a whole in the light of the common general knowledge of a person skilled in the art, irrespective of whether such features or combinations of features solve any problems disclosed herein, and without limitation to the scope of the claims. The applicant indicates that aspects of the present invention may consist of any such individual feature or combination of features. In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention.

Claims

1 . A method of forming a composite structure comprising:

forming a substantially rigid former comprising a hollow region;

arranging a spacer over the hollow region to increase the outer circumference of the former in the hollow region;

wrapping the former and the spacer with flexible elongate material;

withdrawing the spacer; and

coating the surface of the hollow region with the wrapped flexible material.

2. A method as claimed in claim 1 , wherein the flexible material is in the form of a fibre.

3. A method as claimed in claim 2, wherein the flexible material is a reinforcing fibre material.

4. A method as claimed in claim 1 , wherein the flexible material is in the form of a sheet.

5. A method as claimed in claim 4, wherein the flexible material is a fabric.

6. A method as claimed in claim 4, wherein the flexible material is a film.

7. A method as claimed in any preceding claim, wherein the step of wrapping the former and the spacer with the flexible elongate material comprises braiding the flexible material over the former and the spacer.

8. A method as claimed in any of claims 1 to 6, wherein the step of wrapping the former and the spacer with the flexible elongate material comprises winding the flexible material over the former and the spacer.

9. A method as claimed in any of claims 1 to 6, wherein the step of wrapping the former and the spacer with the flexible elongate material comprises automatically draping each of a plurality of discrete elements of the flexible material over the former and the spacer.

10. A method as claimed in any preceding claim, wherein during the wrapping step the flexible material comprises a curable resin.

1 1 . A method as claimed in any preceding claim, comprising the step, after the wrapping step, of impregnating the flexible material with a curable resin.

12. A method as claimed in claim 10 or 1 1 , comprising curing the resin.

13. A method as claimed in any preceding claim, wherein the spacer is sized so that when the spacer is withdrawn the wrapped flexible material is capable of substantially fully coating the hollow region.

14. A method as claimed in any preceding claim, wherein the step of coating the surface of the hollow region with the wrapped flexible material comprises arranging the former such that the wrapped flexible material can sag under the action of gravity to coat the surface of the hollow region.

15. A method as claimed in claim 14, comprising permitting the wrapped flexible material to sag under the action of gravity to coat the surface of the hollow region.

16. A method as claimed in any of claims 1 to 14, comprising applying a tool to the exterior of the wrapped flexible material to press it against the surface of the hollow region.

17. A method as claimed in claim 16, wherein the tool is an inflatable tool.

18. A method as claimed in any preceding claim, wherein the step of withdrawing the spacer comprises removing the spacer from the former.

19. A method as claimed in claim 18, wherein the step of withdrawing the spacer comprises removing the spacer from between the surface of the hollow region and the wrapped flexible material.

20. A method as claimed in any of claims 1 to 19, wherein the step of withdrawing the spacer comprises deflating the spacer.

21 . A method as claimed in any of claims 1 to 17, wherein the step of withdrawing the spacer comprises dissolving or melting the spacer.

22. A method of forming composite articles comprising:

forming a plurality of substantially rigid formers;

coupling a plurality of the formers together to form a string of formers; and feeding the string of formers through a wrapping apparatus, the wrapping apparatus being configured to wrap articles being fed through it with flexible elongate material.

23. A method as claimed in claim 22, wherein the flexible material is in the form of a fibre.

24. A method as claimed in claim 23, wherein the flexible material is a reinforcing fibre material.

25. A method as claimed in claim 22, wherein the flexible material is in the form of a sheet.

26. A method as claimed in claim 25, wherein the flexible material is a fabric.

27. A method as claimed in claim 25, wherein the flexible material is a film.

28. A method as claimed in any of claims 22 to 27, comprising wrapping the formers with the flexible material by means of the wrapping apparatus.

29. A method as claimed in claim 28, wherein the wrapping apparatus is a braiding apparatus configured to coat articles being fed through it with a braided tube of the flexible material.

30. A method as claimed in claim 28, wherein the wrapping apparatus is a winding apparatus configured to wind the flexible material over articles being fed through it.

31 . A method as claimed in any of claims 22 to 30, wherein the wrapping apparatus is configured to wrap articles being fed through it with flexible material that comprises a curable resin.

32. A method as claimed in any of claims 22 to 30, comprising the step, after one of the articles has been wrapped by the wrapping apparatus, of impregnating the flexible material wrapping that article with a curable resin.

33. A method as claimed in claim 31 or 32, comprising curing the resin.

34. A method as claimed in any of claims 22 to 33, comprising the steps of:

separating the wrapped formers from each other; and

moulding resin over each separated former individually; and

curing the resin.

35. A method of forming a composite article, comprising:

forming a plurality of substantially rigid formers;

feeding the formers in series through a wrapping apparatus, the wrapping being configured to wrap articles being fed through it with flexible elongate material to form a string of wrapped formers;

bending the string of formers at at least one zone between the formers to form a reconfigured string of formers;

moulding resin over the reconfigured string of formers; and

curing the resin.

36. A method as claimed in claim 35, wherein the step of feeding the formers in series comprises, for each former:

holding the former in a first movable clamp located at an inlet of the wrapping apparatus;

moving the first clamp so as to pass the former into the inlet;

grasping the former by means of a second movable clamp located at an outlet of the wrapping apparatus; and

withdrawing the former from the outlet by means of the second clamp.

37. A method as claimed in claim 36, wherein the flexible material is in the form of a fibre.

38. A method as claimed in claim 37, wherein the flexible material is a reinforcing fibre material.

39. A method as claimed in claim 36, wherein the flexible material is in the form of a sheet.

40. A method as claimed in claim 39, wherein the flexible material is a fabric.

41 . A method as claimed in claim 39, wherein the flexible material is a film.

42. A method as claimed in any of claims 36 to 41 , comprising wrapping the formers with the flexible material by means of the wrapping apparatus.

43. A method as claimed in claim 36, wherein the wrapping apparatus is a braiding apparatus configured to coat articles being fed through it with a braided tube of the flexible material.

44. A method as claimed in claim 36, wherein the wrapping apparatus is a winding apparatus configured to wind the flexible material over articles being fed through it.

45. A method as claimed in any of claims 36 to 44, comprising: prior to the step of feeding the formers through the wrapping apparatus, locating a spacer in proximity to the said at least one zone so as to increase the outer circumference of the former in that zone; and

withdrawing the spacer prior to the said bending step.

46. A method of forming a composite body structure for a vehicle, the method comprising:

forming a plurality of substantially rigid formers;

wrapping at least one of the formers with flexible elongate material;

bringing a set of the formers comprising the said one of the formers and another of the formers together;

wrapping the said one of the formers and the other of the formers with reinforcing fibre so as to bind them together;

moulding resin over the said one of the formers and the other of the formers; and

curing the resin.

47. A method as claimed in claim 46, wherein the said one of the formers defines a sill of the body structure.

48. A method as claimed in claim 46 or 47, wherein the said other of the formers defines a floor of the body structure.

49. A method as claimed in any of claims 46 to 48, wherein the body structure is a vehicle tub.

50. A method as claimed in any of claims 46 to 48, wherein the said one of the formers defines a vehicle tub.

51 . A method as claimed in claim 50, wherein the said other one of the formers defines a vehicle upper structure.

52. A method as claimed in any of claims 46 to 51 , wherein the said one of the formers and the other of the formers are configured so as to mate positively together.

53. A method as claimed in any of claims 46 to 52, wherein the step of moulding resin over the said one of the formers and the other is performed by injection moulding.

54. A method as claimed in any of claims 46 to 53, wherein the step of moulding resin comprises moulding resin that contains reinforcing fibre segments dispersed therein over the said one of the formers and the other.

55. A method as claimed in claim 53 or 54, wherein the mould in which the resin is moulded has features capable of being filled by the resin so as to form extensions protruding from the formers.

56. A method as claimed in claim 55, wherein one or more of the said extensions constitute functional portion(s) of the body structure.

57. A method as claimed in claim 56, comprising the step of introducing a rigid reinforcing element into one or more of the said features to serve as reinforcement for the extension(s).

58. A method as claimed in any of claims 46 to 57, wherein the flexible material is in the form of a fibre.

59. A method as claimed in claim 58, wherein the flexible material is a reinforcing fibre material.

60. A method as claimed in any of claims 46 to 59, wherein the flexible material is in the form of a sheet.

61 . A method as claimed in claim 60, wherein the flexible material is a fabric.

62. A method as claimed in claim 60, wherein the flexible material is a film.

63. A method as claimed in any of claims 46 to 62, wherein the wrapping step comprises forming a braided tube of the flexible material around the formers.

64. A method as claimed in any of claims 46 to 62, wherein the wrapping step comprises winding the flexible material around the formers.

65. A method of forming a composite body structure for a vehicle, the method comprising:

forming a plurality of substantially rigid formers;

wrapping each of the formers with flexible elongate material;

curing resin over the flexible material wrapped on each former to form a respective body structure component;

assembling the body structure components to form a body structure located in a mould; and

moulding a material over the components to bind them together.

66. A method as claimed in claim 65, wherein one of the body structure components constitutes a tub of the vehicle body structure.

67. A method as claimed in claim 65 or 66, wherein one of the body structure components constitutes an upper structure of the vehicle body structure

68. A method as claimed in any of claims 65 to 67, wherein the formers are configured so as enable the body structure components to mate positively together when assembled.

69. A method as claimed in any of claims 65 to 68, wherein the step of moulding a material over the components and the other is performed by injection moulding.

70. A method as claimed in any of claims 65 to 69, wherein the step of moulding a material comprises moulding a resin that contains reinforcing fibre segments dispersed therein over the components.

71 . A method as claimed in any of claims 65 to 70, wherein the mould in which the resin is moulded has features capable of being filled by the resin so as to form extensions protruding from the formers.

72. A method as claimed in claim 71 , wherein one or more of the said extensions constitute functional portion(s) of the body structure.

73. A method as claimed in claim 71 or 72, comprising the step of introducing a rigid reinforcing element into one or more of the said features to serve as reinforcement for the extension(s).

74. A method as claimed in any of claims 65 to 73, wherein the flexible material is in the form of a fibre.

75. A method as claimed in claim 74, wherein the flexible material is a reinforcing fibre material.

76. A method as claimed in any of claims 65 to 73, wherein the flexible material is in the form of a sheet.

77. A method as claimed in claim 76, wherein the flexible material is a fabric.

78. A method as claimed in claim 76, wherein the flexible material is a film.

79. A method as claimed in any of claims 65 to 78, wherein the wrapping step comprises forming a braided tube of the flexible material around the formers.

80. A method as claimed in any of claims 65 to 78, wherein the wrapping step comprises winding the flexible material around the formers.

81 . A method of forming a vehicle body structure comprising moulding the body structure in a volume defined at least partially a plurality of outer mould bodies and a plurality of interior mould bodies locatable within the plurality of outer mould bodies, the interior mould bodies defining at least the surfaces of the tub directed towards the interior volume of the body structure.

82. A method of forming a vehicle body structure as claimed in claim 80, wherein the body structure defines one or more door apertures and the method comprises, subsequent to the step of moulding the body structure, removing the interior mould bodies from the interior of the body structure through one or more such door apertures.

83. A method as claimed in claim 81 or 82, comprising the steps, prior to the step of moulding the body structure, of:

assembling the interior mould bodies together to form a composite interior mould body; and

locating the composite mould body in a predetermined relationship with the outer mould bodies so as to define the said volume.

84. A method as claimed in any of claims 81 to 83, wherein the interior mould bodies comprise a first body defining the upper part of the interior of the body structure and a second body defining the lower part of the interior of the body structure.

85. A method as claimed in any of claims 81 to 84, comprising:

prior to the completion of the moulding step, locating one or more additional components in the said volume; and

performing the moulding step so as to incorporate those component(s) into the body structure.

86. A method as claimed in any of claims 81 to 85, wherein the said moulding step is performed by injection moulding.

87. A method as claimed in any of claims 81 to 85, wherein the said moulding step is performed by resin transfer moulding.

88. A composite article or a tub formed by the method of any preceding claim.

89. A method for forming a composite article substantially as herein described with reference to the accompanying drawings.

90. A composite article formed by a method substantially as herein described with reference to the accompanying drawings.