WO2014114955A1

WO2014114955A1 - Method and apparatus for production of carbon fibre components

Info

Publication number: WO2014114955A1
Application number: PCT/GB2014/050207
Authority: WO
Inventors: David Roche; Jevon Thurston Thorpe; Daniel HURCOMBE
Original assignee: Penso Holdings Ltd
Priority date: 2013-01-25
Filing date: 2014-01-27
Publication date: 2014-07-31
Also published as: GB201301364D0

Abstract

Apparatus for use in manufacturing a fibre composite article, such as a carbon fibre article, comprises a press (1) having a bed (3) for receiving a bolster, (5) and a means (6) for supporting a press part (7) or die above the bolster (5) and for providing relative movement between the bolster (5)and press part (7) during a pressing operation; a bolster (5) suitable for insertion into the press and defining a first press surface (5a); and a press part (7) suitable for insertion into the press (1) and defining a second press surface (7a) that faces towards the first press surface (5a), the press surfaces defining a space therebetween for receiving material to be pressed. At least one of the press part (7) and the bolster (5) includes a temperature control means that comprises a heating circuit adapted to raise the temperature of a part of at least one of the press part (7) and the bolster (5) and a cooling circuit adapted to lower the temperature of a part of at least one of the press part (7) and the bolster (5) in the event that an exothermic reaction in part of the component is identified during the cure process.

Description

METHOD AND APPARATUS FOR PRODUCTION OF CARBON FIBRE

COMPONENTS

This invention relates to a method of production of fibre reinforced components and to apparatus for use in processes for the production of especially carbon fibre reinforced parts. In particular it relates to the production of carbon fibre parts for use in automobiles.

Traditionally automobiles have been manufactured from steel, with body panels and non-structural components produced by pressing flat sheets of stock material into the required shape . Considerable amounts of energy are needed to produce steel panels, both in producing the stock sheets and in operating the heavy presses that are needed to form the panels. The resulting automobiles are also relatively heavy. Recently there has been a drive towards reducing the weight of vehicles. One way to do this is to reduce the amount of steel used in the construction of the vehicle. Aluminium can be used instead of steel, using the same types of press and stock sheets of aluminium. This process is still relatively energy intensive . An alternative solution is to use carbon fibre components instead of steel. A Carbon fibre article, in the context of this application, refers to an article of manufacture produced at least in part using fibre reinforced polymeric composite material. Typically this will comprise a composite of carbon fibre filaments and a resin as the polymer. However, the carbon fibres may be mixed with other filaments in the composite material.

Carbon fibre reinforced composite material is known to be capable of being formed into extremely strong and lightweight components. The carbon fibre provide the strength of the material, being difficult to stretch, while the resin holds the fibres in place . Varying the direction of the fibres enables the properties of the carbon fibre product to be varied. Carbon fibres are typically woven into sheets or mats that are laid one on top of the other in a mold and then soaked in resin which is heat cured and allowed to cure to form a rigid finished composite. The manufacture of parts in carbon fibre using traditional techniques is very time intensive and as such has mostly been limited to high value, low volume sportscar manufacture. It has found its way into more mainstream automobiles in the form of non-structural components such as bootlids or bonnets or seat parts, but again the manufacturing process has been slow making these parts expensive to produce.

The most widely used method of manufacturing components for automobiles, which are often large components, is to initially weave the carbon fibres into flexible sheets or mats of material that can be laid up in a mold in the shape of the final product. The mold is then filled with uncured resin before it is heated to cause the resin to melt and then cool where it is allowed to harden. To ensure there are no air bubbles in the finished component, the laid up sheets impregnated with resin are placed in a sealed bag that is evacuated using a pump, and the bag is then placed in an autoclave to cure the material.

Efforts have been made to use a press instead of the vacuum bag, the press comprising a mold and a die defining male and female parts. The carbon fibre is laid up directly into the press and the press closed and then heated in an autoclave as with the bag method. So far only very simple components have been made this way and there have been many problems with pressed parts such as inclusion of bubbles in the finished parts. This can lead to a poor surface finish making parts unsuitable for uses in which the surface will be visible .

In another approach, carbon fibre is laid up over a former along with resin, and then lifted carefully from the former to be placed in a press. The carbon fibre typically is pre-woven or braided into sheets known as performs, and several of these may be laid up one on top of the other before the impregnation with the resin. The orientation of the fibres in each sheet relative to the other sheets allows the behaviour of the finished article to be carefully controlled. The sheets may be pre-impregnated with resin, as so called Pre-preg material, or the resin may be added during or after the material has been cut to the rough shape of the finished article .

The present invention is aimed at ameliorating some of the problems of prior art carbon fibre component manufacture with the wider aim of opening up the process to mass production of parts for automobiles. According to a first aspect the invention provides apparatus for use in manufacturing a fibre composite article, such as a carbon fibre article, comprising:

a press having a bed for receiving a bolster, and a means for supporting a press part or die above the bolster and for providing relative movement between the bolster and press part during a pressing operation;

a bolster suitable for insertion into the press and defining a first press surface;

a press part suitable for insertion into the press and defining a second press surface that faces towards the first press surface, the press surfaces defining a space therebetween for receiving material to be pressed;

in which at least one of the press part and the bolster includes a temperature control means that comprises a heating circuit adapted to raise the temperature of a part of at least one of the press part and the bolster and a cooling circuit adapted to lower the temperature of a part of at least one of the press part and the bolster.

By cooling we mean actively removing heat energy from a part, and by heating we mean actively applying heat energy to a part.

The cooling circuit may comprise one or more passages which contain fluid and means for controlling the temperature of the fluid. The means may be arranged to heat and or cool the fluid, enabling the press part to be heated and/or cooled. The heating and cooling circuit may therefore be combined as a single circuit.

The cooling circuit, or heating circuit, or both, may include a flow controller which selectively connects the passages to pre-heated and pre-cooled fluid. The flow controller may be able to mix preheated and prechilled fluid to give precise control of the temperature.

The heating circuit may additionally or alternatively comprise one or more electrical heating elements. These may comprise resistive heating elements, and may be connected to an electrical supply.

The fluid passages and/or electrical heating elements may be located within the first and or second press parts. They may be located on the press surface of the press parts or just below the surface. They may be located on only one press part or both press parts.

A controller may be provided for controlling the operation of the heating and cooling circuits. The controller may be configured to control the circuits independently. The apparatus may include at least one temperature sensor that measures the temperature of a part of the apparatus and the controller may receive this temperature measurement as an input to a control strategy for the heating and cooling. The heating circuit, or the cooling circuit, or both, may be zoned to enable different parts, or zones, of the press part and/or bolster to be driven to a temperature that is different to the temperature of other parts and to enable those temperatures to be individually controlled independently of other zones. The temperature of each zone may be set independent of any other zone, or partially independently (there may for example be limits on the temperature gradient that can be achieved across the press part or bolster) . This enables the temperature of one part of the press surface to be maintained at a different temperature to other parts, or to enable them to be held to the same temperature independent of any heat energy produced by a part located in the mold when in use.

For example, where the cooling circuit comprises a plurality of fluid channels, each located at a different place in the press part or bolster (or both) the controller may provide independent control of the fluid flow and temperature of the fluid in one or more of the channels. Similarly, where the heating means provides a plurality of electrical heating elements the controller may be arranged to apply heat through at least one of the heating elements independently of applying heat through at least one other of the elements.

The controller may be configured to provide zoned control of the temperature, both by heating and cooling as required, of one or both of the press surfaces.

By enabling separate control of the temperature across the press surfaces, the applicant has found that it is possible to reduce the cure time of a molded part by driving heat into the part at a level which may cause an exothermic reaction in some areas of the molded part and to then provide local cooling of those parts whilst still driving heat energy into other parts which are not undergoing an exothermic reaction. This ability to overdrive the heating beyond a level that would be safe in a press that was not able to cool individual areas helps to reduce the overall cure time for a molded part.

The controller may therefore react to measurements of temperature from the temperature sensors in real time during the molding process and produce corresponding changes in temperature across the press surfaces to hold the part below an exothermic level whilst still allowing a maximum, or near maximum, level of heat energy to be driven into all regions of the part that is being molded.

The apparatus may be adapted to identify, from the measurement of temperature from the temperature and the heating applied to the press surface by the heating circuit, and optionally using a model of the thermal characteristics of the press assembly, the onset of an exothermic reaction in the material during the cure process, and in the event that this onset is identified may be adapted to apply localised cooling to the part of the press surface where the onset of the exothermic reaction is occurring, thereby to prevent an uncontrolled exothermic reaction occurring. It may be adapted to rapidly chill that area of the press surface using the cooling circuit.

The apparatus may be adapted to identify a need to apply cooling by applying sufficient heating across the press part of part to hold the temperature at a constant level and detecting an increase in the temperature in any part of the press part due to heat energy released from an exothermic reaction. For instance, it may hold the temperature across the press part at 130, 150, 160 or greater than 160 degrees centigrade for an extended period during the curing process. The press parts may be preheated or an initial heating period may be provided at which the temperature is rapidly elevated to the required steady temperature . The apparatus may include a removable support means suitable for supporting laid up carbon fibre material, the support being movable between an open position for use outside of the press when laying up the material and a closed position for use in the press in which the support means supports the laid up material to ensure that the material is located securely in the press, whereby in use the removable support means is located between the bolster and the press part during a pressing operation in which the bolster and press part are pressed together by the press in turn to apply a compressive force from the press surfaces onto the material gripped by the support means.

The support means may include a mold comprising at least two separable mold parts, one of the mold parts having an outer surface that is generally complimentary to the first press surface of the bolster and the other one of the mold parts having an outer surface that is generally complimentary to the second press surface of the press part, the mold parts being shaped so that when closed together they define a space therebetween that substantially matches the finished shape of at least one carbon fibre component that is to be produced by the apparatus.

The first press surface and second press surface may respectively correspond generally to the shape of opposed surfaces of a finished carbon fibre part that is to be manufactured, allowing the material to be contacted directly by the press surfaces.

Where a mold is used, there may be a considerable difference between the shape of the press surfaces and the finished shape of the part, although it is preferred that the mold has a thin wall so that the shapes will still generally correspond to the shape of the finished part.

The mold may, of course, comprise only one part, typically a base part onto which material is laid up.

The support means may be adapted to grip the material when in the closed position.

Providing an apparatus in which a bolster and a press part, or die, can receive a removable support means allows a carbon fibre material to be laid up into the mold outside of the press along with uncured resin. The filled mold can then be moved into the press where the mold is compressed which will compress the material laid up into the mold. After pressing, the bolster and press part, or die, are moved apart and the mold removed. Finally the finished part or parts are removed from the shells. The application of pressure to material that is held in a support which is removable from the press allows for safe operation as carbon fibre does not have to be laid up directly into the press. The combination of a press and a support means allows accurate laying up of the carbon fibre outside of the press where it is more convenient to work whist securely holding the material as it is moved into and out of the press. It may also allow the total time needed to make a carbon fibre part to be reduced as material can be laid up in the support means while the press is in use .

When inserted into the bolster/press part the full outer surface, or a major part of the outer surface of the mold, should be in contact with the bolster and press part. This allows the mold to be evenly compressed. The first press surface of the bolster may be concave and generally complimentary to an outer surface of one of the mold parts. In fact, the first press surface may correspond to a enlarged shape of the finished product, being enlarged by the thickness of the mold. This helps with location of the mold in the correct position when inserting it into the press and as will be described later helps with transfer of heat from the press to the content of the mold by conduction. Of course, the first press surface may be convex with one of the mold parts having a complimentary concave surface and sitting on the protrusion defined by the convex surface . The press surface may include one or more locating lugs or depressions which co-operate with corresponding locating lugs or depressions in the mold outer surface. The first and second press surfaces may correspond generally to the finished shape of the carbon fibre component to be produced enlarged by an amount equal to the thickness of the mold parts.

At least one of the mold parts may be generally rigid to provide support from the material laid up in the shell insert when it is moved across to the press. Both mold parts may be generally rigid. They may be solid aluminium or another metal. Of course the mold may have more than two parts, and may be formed in three or more parts if particularly complex. The mold parts when in a closed position may define a single space therebetween corresponding to the finished shape of a carbon fibre part that is to be manufactured. When closed the mold parts may be spaced slightly apart from one another allowing them to be compressed towards each other during pressing to consolidate the material when pressed, which is initially unconsolidated laminate material.

The mold parts may define two or more spaces therebetween, each one corresponding to a finished shape of a carbon fibre part that is to be manufactured. There may be four, eight or more spaces, or any number of spaces from one to ten, or more. Providing more than one space allows multiple parts to be made at the same time, reducing the manufacturing time for a set of parts using one apparatus.

Where the mold parts define two or more spaces, each space may be the same shape or at least one space may be a different shape to at least one other space. This allows either a set of identical shaped carbon fibre parts to be manufactured, or a plurality of different shaped parts to be manufactured at the same time using a single mold.

The apparatus may comprise more than one pair of mold parts, each pair of mold parts defining a mold that is suitable for manufacturing one or more carbon fibre parts. It is envisaged that the press part and bolster may be used with a large number of different or the same molds.

The press part and the bolster may be metal blocks, perhaps aluminium blocks. The blocks may comprise unitary bodies or may be made up from a number of components fixed together to form the block. This material is preferred as it has a relatively low thermal mass compared with iron or steel materials and yet is relatively heavy compared with composite or plastic materials to enable sufficient press force to be applied solely due to the weight of the press part acting on the bolster if desired. The low thermal mass allows it to be rapidly heated or cooled.

Where the support means does not include a mold the material is directly in contact with the press surfaces of the bolster and press, in which case those surfaces should have a shape that corresponds closely with the finished surfaces of the part that is being manufactured. Where the support means includes a mold, the surfaces of the bolster and press parts should be a match to the outer surfaces of the mold. Where a thin walled mold is used, the surfaces of the press part will still generally correspond to the finished surfaces of the finished part plus any additional detail required to match the outer surfaces of the mold.

The press part and bolster should be large enough in width and length to accommodate any carbon fibre component that is to be manufactured by the press part. For instance, it may have a length of at least 2 metres and width of at least 1 metre. On the other hand if small parts are being made the press could also be small, perhaps only a few cms across.

The bolster may be fixed in position on a bed of the press and the press part may be movable relative to the first press part. The apparatus may include one or more hydraulic rams and controls system that controls the position of the ram during pressing.

The first press part may be supported on a bed with the first press surface facing upwards and the press part may be supported above the first press part with the second press surface facing downwards towards the first press surface, the second press part being lowered onto the first part when in use and raised above it when not in use. This allows the weight of the first press part to provide a compressive force on the second press part when in use .

The apparatus may include a seal comprising one or more seal parts that are located on, or at least partially embedded into, one ore more of the press part, the bolster and the mold parts, such that when the mold parts are located in press a closed space is defined at least partially by the seal which contains the shell inserts.

The apparatus may include one or more vacuum passages connected to the closed space through which air or other gases in the closed space can be wholly or partially evacuated. These passages may be formed in the bolster or the press part, and passages may also be provided in the shell inserts connecting the space or spaces defined inside the shell inserts to the closed space defined by the seal.

The apparatus may include means for connecting the vacuum passages to a source of below atmospheric pressure. The source may comprise a part of the apparatus, it may comprise a vacuum pump.

The seal may define a wall enclosing the closed space . It may define a double wall, a first wall enclosing the closed space and a second wall enclosing the first wall. The apparatus may include a support means that includes a clinch frame that secures the material in position relative to at least one of the press surfaces. The clinch frame may be removable from the press. Where the support means includes a mold, the clinch frame will support the mold, allowing the mold to be moved by gripping the clinch frame.

The frame may be connected to the mold to securely fix the mold parts in position relative to one another, for example during movement of the mold into an out of the press. The clinch frame may clamp the mold parts together. The clinch frame may comprise a rigid frame having an upper subframe and a lower subframe . The subframes may lock together to securely fix the mold parts together. This holds the laid up carbon fibre and resin in the mold as it is placed into and subsequently removed from the press. It may provide a convenient way of lifting the shell inserts and of locating them in position in the press parts.

The clinch frame may include one or more alignment marks which may be used in conjunction with an optical alignment apparatus to assist in automated loading of the frame and shell inserts onto the press part. Most preferably the clinch frame when fixed to the mold may directly contact material laid up in the mold so that during pressing the material is gripped by the clinch frame to stop it moving in the mold. This may help in controlling the movement of the material during pressing, ensuring that any alignment of the laid up material is not lost during pressing. The bolster and press part may include recesses into which the clinch frame is received when the press is closed.

The apparatus may include one or more press setting parts which may be located between the bolster and the press part and which set the minimum spacing between the first and second press surfaces when the apparatus is in use during pressing. The press setting parts therefore act as spacers between the bolster and press part.

Four press setting parts may be provided, each being received in a complimentary recess in a corner, or close to a corner, or along a respective edge, of the first press part.

The apparatus may include many press setting parts of differing sizes to enable different spacings to be set. Alternatively the press setting parts may be adjustable, either hydraulically, electrically, manually or by a combination, to enable the spacing to be adjusted.

The apparatus may be arranged so that with no press setting part used the second press part rests on top of the first press part.

In a refinement, the press setting parts may each include a pressure sensor that measures the pressure applied to the parts during pressing. The output of each sensor may be passed to a processor which compares the pressures with one or more expected pressures. If the pressures differ from the expected pressures the processor may raise an alarm. For example, it may be expected that all the pressures will be the same at any given time during a pressing operation, and a difference in pressures may indicate that the press is not applying even pressure to the shell inserts.

The press may include a control means that includes a processor that operates the press in response to a set of computer instructions stored in a memory of the control means. The instructions may cause the press during a press operation initially to move the bolster and press part closer together to close the seal (where provided), to reduce pressure inside the seal to remove air and other gases from the space inside the shell insert, to then allow the pressure in the shell to increase, to move the bolster and press part closer together to partially compress the space inside the shell inserts and finally to move the bolster and press part away from each other to permit removal of the shell inserts.

During the press operation, the controller may instruct the temperature controller to increase, then hold, then decrease the temperature of the bolster and/or press part. The temperature controller may be an integral part of the control means.

According to a second aspect the invention provides a removable support part comprising a clinch frame and at least one pair of mold parts for use in providing an apparatus according to the first aspect of the invention.

The mold parts may define two or more spaces therebetween, each one corresponding to a finished shape of a carbon fibre component that is to be manufactured. There may be four, eight or more spaces, or any number of spaces from one to ten, or more in the mold. Providing more than one space allows multiple parts to be made at the same time, reducing the manufacturing time for a set of parts using one mold.

Where the mold parts define two or more spaces, each space may be the same shape or at least one space may be a different shape to at least one other space. This allows either a set of identical shaped carbon fibre parts to be manufactured, or a plurality of different shaped parts to be manufactured at the same time .

The mold parts may be metal, preferably aluminium. They may be stamped from a flat sheet or machined from a solid billet to form the required shapes. They may be relatively thin parts, by which we mean the thickness of the parts is considerably less than the width and length of the mold. Because they do not directly apply pressure to the content of the mold they only need enough strength to retain their shape during lay up. Each mold part may have a uniform wall thickness, or the thickness may be varied across different parts of the mold.

The mold parts may be compatible with a clinch frame that supports the mold parts around their edges. The clinch frame provides additional rigidity as the mold is moved into and out of a press, allowing think mold parts to be used for even relatively large carbon fibre parts.

One of the mold parts may be connected to the other by one or more hinges. They may be integral parts or discrete parts, and may be completely separable.

According to a further aspect the invention provides a method of manufacturing a carbon fibre component comprising the steps of:

Providing a press tool having a first press part and a second press part each defining a press surface,

Placing uncured material that will form the carbon fibre component into the press tool, Applying pressure to the material by pressing the press surfaces onto the material to compress the material;

applying heat to at least one of the press part to cure the material;

monitoring the temperature of the press part as the heat is applied to provide an estimate of the temperature of the component that is being cured; and

in the event that the estimate indicates a localised area of the part is undergoing or about to undergo an exothermic reaction, applying localised cooling to that area of the component whilst continuing to heat one or more other areas of the component to continue the curing process.

The method may comprise driving heat into the press in a first stage to hold the component at a temperature that is known to create an exothermic reaction in a localised region of the component if that is maintained for the duration of the cure time and maintaining that temperature until the component is about to be exothermic or an exothermic reaction has started and then applying cooling to that part of the component prevent the exothermic reaction occurring or continuing whilst maintaining the temperature of the other parts of the component. The method may comprise estimating the temperature of at least three, or at least five or more, localised areas of the component.

The applicant has appreciated that a faster cure can be achieved by driving more heat into the component but this may cause some areas to become exothermic before others, for instance in places where the component is thicker. By driving in more heat and then reducing the temperature in any areas that are at risk of becoming exothermic

The method may comprise applying cooling unit the exothermic reaction has stopped and thereafter reapplying heat to that local portion.

The method may comprise using a press that has a heating circuit and a cooling circuit built into one or both of the press parts. The method may also comprise using a press that has a plurality of temperature sensors built into one ore more of the press parts from which an estimate of the temperature of different parts of the molded part may be derived.

The method may comprise a step of placing the part in the mold by laying it in direct contact with the press surfaces. The method may comprise placing the part in the mold using a support means.

According to a still further aspect the invention provides a method of manufacturing a carbon fibre component comprising the steps of:

Providing at a location spaced apart from the tool an open support means,

Laying up the carbon fibre material into the open support means,

Closing the support means so that it grips the laid up carbon fibre material to restrict movement of the laid up material;

moving the support means and material into the press tool,

applying heat and pressure to the material using the press tool, and

removing the support means from the tool and releasing the molded part.

The steps may be performed in the order listed in the preceding paragraph.

The support means may comprise a mold comprising a pair of mold parts compatible with the press tool, the outer surfaces of the mold parts being generally complimentary to the press surfaces of the press parts, and the method may comprise laying up material into the mold before closing the mold and moving it into the press. The method may comprises adding resin to the one or more layers of material before it is moved into the press or after it is moved into the press but before pressing.

Use of a support means into which carbon fibre material is laid up before transferring to the press has many advantages compared with laying up directly into a press or laying up on a former and them moving only the laid material carefully over into the press. The support means provides support for the laid up material when moving it into the press, which enables more accurate manufacture of parts. The mold also helps reduce the overall process time, as the press can be used while laying up of subsequent parts into molds is being performed.

The step of laying up the carbon fibre material into or onto the support means may be performed with the support means on a suitable workbench or table or workstand. This may support the material at a convenient working height, typically between 80cm and 120cm above the ground.

Laying up will typically be performed by hand, with sheets of preformed carbon fibre material being pressed into a lower mold part of a mold of the support means along with resin to help secure the sheet material in the mold. Once the correct number of layers have been laid up, the other mold part is offered up to close the mold around the material.

The support means may comprise a clinch frame and a mold and the method may comprise fixing the clinch frame to the mold once the material has been laid up and the mold closed such that the clinch frame traps a part of the laid up material, perhaps between two parts of the frame or the frame and part of the shell inserts . The method may comprise laying up material so that it extends beyond the edges of the shell and applying the frame around the edge onto the material. . The method may also comprise heating the support means before laying up, or during laying up, of the carbon fibre material to an elevated temperature. This may be a temperature of between 40 and 60 degrees.

The method may therefore comprise laying the carbon fibre sheet material into one half of the mold before placing the other half onto the top and then fixing the clinch frame . During this laying up process one or more inserts may be placed in the shell insert that are at least partially surrounded by carbon fibre material. These are typically aluminium blocks which provide a solid surface into which fixing elements can be securely attached once the finished carbon fibre product is formed.

Once the material has been laid up and the support means closed, the method may next comprise moving the closed support means that restrains the laid up material into the press part of the press with the press open. Laying up material outside of the press in this way is a safer working practice than laying up into the press itself, keeping workers hands clear of the press parts.

Once inserted the method may comprise closing the press onto the material.

The method may comprise heating the press prior to inserting the support means and the material, during or after, or a combination of those things. It may comprise heating the press to a temperature sufficient to cause the resin that forms the matrix with the carbon fibre material to flow.

Once inserted into the press, the method may comprise evacuating (fully or partially) the air and other gases from within the shell inserts . The space may then be held at a below ambient pressure for a defined period of time before releasing allowing pressure to return to ambient or higher. This step preferably is carried out before the press applies pressure to the shell inserts. Reducing pressure helps remove any air which could form bubbles in the finished part.

The method may comprise, after heating, actively cooling the press parts. Once cooled or during cooling the support means may be removed and allowed to cool further or to carry the carbon fibre part onto a further processing stage. For instance the part may be placed in an oven and put through one or more additional heat cycles.

The method may comprise removing the cured carbon fibre part from the shell parts after it has been removed from the press parts.

The method may comprise moving the support frame into and out of the press parts by holding the clinch frame when provided. The method may comprise providing a support means that includes a mold that defines a set of spaces, each space corresponding to one carbon fibre part, material being laid up into each space before moving the mold to the press. This allows multiple carbon fibre parts to be made in a batch.

The method may be used industrially to manufacture carbon fibre reinforced parts in bulk, material being laid up into shell inserts whilst another shell insert already filled with material is being heated and pressed in the press. Once pressed, the insert is removed from the press and the newly filled shell insert is placed in the press. The finished part is released and the shell inserts reused.

Depending on the length of time needed to fill a shell insert and the length of time it must spend in the press, there may be as many as three or four or more support means being laid up at any one time to ensure that whenever a press operation finishes a newly laid up support means is ready to go in the press.

For additional safety, the support means may be inserted and removed from the press using one or more robots. These may pick up the shell inserts by the clinch frame where provided.

Any of the steps of the third aspect may be combined with the steps of the fourth aspect of the invention. According to a yet further aspect the invention provides apparatus for use in manufacturing a carbon fibre component comprising:

a press part suitable for insertion into the press and defining a second press surface that faces towards the first press surface,

a removable support means suitable for supporting laid up carbon fibre material, the support being movable between an open position for use outside of the press when laying up the material and a closed position for use in the press in which the support means supports the laid up material to ensure that the material is located securely in the press,

whereby in use the removable support means is located between the bolster and the press part during a pressing operation in which the bolster and press part are pressed together by the press in turn to apply a compressive force from the press surfaces onto the material gripped by the support means.

There will now be described, by way of example only several embodiments of apparatus and methods for manufacture of carbon fibre components in accordance with the present invention of which:

Figure 1 shows in plan a press that can be used to manufacture carbon fibre parts according to an embodiment of the invention; Figure 2 is a view of a bolster that is to be fitted to the press of Figure 1 ;

Figure 3 shows a press part that is to be fitted to the press of Figure 1 ;

Figure 4 shows two parts of a clinch frame and a pair of shell insert parts that are shaped to co-operate with the bolster and press parts of Figures 2 and 3 ;

Figure 5 is an illustration of the carbon fibre part that can be produced using the shell inserts of Figure 4; Figure 6 is an exploded view of the various parts that are to be inserted into the press in the order in which they are placed with the press part at the top and the bolster at the bottom;

Figure 7 shows an alternative shell insert for use in simultaneously pressing multiple carbon fibre parts; and

Figure 8 shows the connection of the press to a temperature control circuit.

As shown in Figure 1 , a hydraulic press 1 which can be used to form an embodiment of an apparatus of the present invention comprises a press frame 2, a bed 3 having a recess 4 into which a removable bolster 5 can be inserted, and a ram 6 to which a removable press part 7, or die, can be fixed. The frame 2 supports the ram 6, and the ram 6 supports the press part 7 above the bolster 5. A lockable protective cage may be provided around the press frame to ensure that an operator cannot become trapped in the press when it is in use .

The removable bolster 5 and the removable press part 7 each comprise relatively massive metal blocks, typically of aluminium. Each one has a respective press surface 5a,7a, the press surface of the bolster facing upwards when it is secured to the bed, and the press surface of the removable press part faces downwards towards the bolster.

In operation of the hydraulic press 1 , the bed and bolster 5 remain stationary and the press part 7 is moved by the ram. Initially, in a pre-use position, the ram holds the press part a distance above the bolster, typically about a metre to allow access by a robot if required, to allow access to the press surfaces. This is shown in Figure 1.

During pressing the ram forces the press part 7 down towards the bolster to reduce the spacing of a few mms (perhaps 20 percent thicker than the finished size of a carbon product that is being manufactured). The actual spacing during use will depend on the part that is being pressed as will be explained later. Of course, other types of press could be used within the scope of the invention. For example, the bed may move and the upper part may be fixed, or both the bed and upper part may move. The press surfaces 5a, 7aof the bolster and press part are shaped so that with the press in the pressing position a space is defined between the surfaces into which carbon fibre material can be placed. The material may be laid directly onto the lower press surface, having been preshaped into a perform. In this case, the shape of the press surfaces will correspond to the shape of the outer surfaces of the finished molded part.

Optionally, as will be described here, the material may be supported by a support means that optionally includes a mold 8 with the support and mold then being loaded into the press. An exemplary mold 8 of a support means is shown in Figure 4 of the drawings. It comprises two mold halves, 8a and 8b, although each mold half could be formed from multiple pieces. The mold 8 and bolster and press part are specifically tailored to each other. The bolster has a recess in the press surface 5a into which a half of the mold can be placed and the press part has a protrusion on its surface 7a which at least partially protrudes into the recess when the press is in the use position during pressing. Generally the space defined between the bolster and press part may correspond to an enlarged version of the finished shape of one or more carbon fibre components that are to be manufactured. Typically the space may be between 10mm and 30mm oversized in all dimensions compared with the shape of the final product or products. The press part and bolster are shown in more detail in Figures 3 and 2 of the drawings.

The mold in the example comprises a pair of matching seperable mold parts 8a and 8b that can be inserted and removed from the press. One mold part defines a lower half of the mold and the other an upper half. The shape of the two mold parts depends on the shape of the carbon fibre part, or parts, that are to be produced using the mold parts. Each mold part 8a, 8b comprises a thin walled rigid shell that has an inner surface that corresponds to a negative of a respective side (either an A side of B side) of the carbon fibre part that is to be produced. Figure 5 shows the part 20 that can be produced using the mold of Figure 4. When the mold is closed the space between the two halves of the mold roughly corresponds to the shape of the part that is to be produced, the spacing between the two mold halves being set by the thickness of the part to be produced. Each mold half typically is relatively rigid and has a relatively thin cross section and may itself be made by stamping or pressing from a sheet of metal, by casting or machining from a solid billet. The thickness of the mold parts will typically be between 1mm and upwards, perhaps up to 3mm or even up to 10mm or so, so that when inserted into the press the outer surface of the mold parts fully contacts the press surfaces to enable thermal conduction between the bolster and press part and the mold.

Associated with the mold 8 is a clinch frame 18. The clinch frame forms part of the support means. This is shown in Figure 4. The function of the clinch frame is to grip the material that is being used to form the part, and where molds are provided it also performs a function of fixing the two parts 8a, 8b of the mold together. The clinch frame has an upper part and a lower part that connect together around the edges of the mold parts and in so doing pinch some of the material laid up in the mold between the two parts of the frame to help control the shape of the finished carbon fibre component, and to provide a convenient component by which the mold parts can be lifted and moved in and out of the press. It is envisaged that many support means- molds and clinch frames- may be provided for use with one press, perhaps being shaped differently internally to allow different carbon fibre parts to be manufactured, but a single common shape of clinch frame may be used. Of course, there may be differences between clinch frames depending on where the material is to be gripped, so there may be reasons for having clinch frames that are only suitable for use with specific molds. Or course, if the outer shape of the mold varies then different shaped bolster and press parts may then be needed to receive the mold. The press includes recesses in the surface of the bolster and press part into which the frame, typically thicker than the optional mold, will fit as the press is closed. The recesses held with location of the frame in the correct position, and also ensure the frame does not impede the engagement of the press with the material. Figure 6 is an exploded view of the parts of the apparatus and their relative positions, the view being exploded in the vertical direction. The bolster 5 and press part 7 each contain a set of through bores 10, 1 1 which define passageways that form a part of a temperature control circuit. The open ends of the passageways 1 1 in the bolster are connected together using multiple connecting lines 12 to form a flow path for heated or cooled fluid. The connected passageways are terminated with an input port and an output port which can be connected to a fluid source and outlet when inserted into the press. Similarly the open ends of the passageways 10 in the press part and connected by multiple connecting lines 13 and terminated in an input port and output port which can be connected to the same, or a different, source of heated or cooled fluid when connected to the press.

In addition to the fluid heating and cooling, the bolster 5 is provided with a set of resistive heating elements 14 and connectors that enable them to be connected to a suitable electrical supply when connected to the press during pressing. Resistive heating elements may also be provided in the press part but are not shown in Figure 6. In use the heating elements 14 are used to rapidly raise the temperature of the bolster and optionally the press parts. This heating can be applied alongside the use of heating fluid in the fluid passages. Unlike fluid heating electrical heating can achieve much more rapid heating of the bolster 5 and optionally the press part 7, but resistive elements cannot be used to cool them down. When finished cooling will continue to post cooling.

The temperature control circuit selectively applies heated or cooled fluid and applies resistive heating to the bolster and/or press part to cause the bolster and press part to achieve a desired temperature during a pressing operation. Typically this will vary from around 60 to 80 degrees at the start of pressing to around 120 or more degrees during pressing. The exact temperatures will depend on the curing properties of the resin used in the carbon fibre material.

To best utilise the press, the press surface should be heated to a temperature at which it is possible that the material starts to undergo an exothermic reaction. This will occur at different times for different regions of the material depending on the thickness of the material in each region. The controller monitors the temperature and when an exothermic reaction is identified, the part of the cooling circuit that cools the associated part of the press surface is cooled to control the reaction. The heat continues to be applied to those parts which are not exothermic, as they can take more heat at that time. This helps drive the material towards a fully cured state as fast as possible.

Once cured, the cooling is used to rapidly cool the carbon fibre part prior to releasing the pressure on the mold.

The press 1 in this example optionally includes a set of four press setting parts 15. The press setting parts 15 in this embodiment comprise metal blocks of specified dimensions that are each received in respective recesses provided towards the four corners of the bolster. When the press part is pressed down towards the bolster, the press setting parts initially start to move into corresponding recesses in the press part, until eventually the press part is prevented from moving further by the press setting parts that are then wedged between the bolster and press part. The height of the parts determines the spacing between the bolster and press part when fully pressed. These press setting parts can be used to provide accurate control of the press position when pressing. A proposed method of use of the apparatus to produce a carbon fibre component will now be described.

In a first step, the press is loaded with the bolster and the press part that match a support means. In this example the support means comprises a clinch frame and a two part mold. The inlet and outlet of the temperature control circuit are then connected to the fluid supplies and the temperature control circuit preheats the bolster and press part by circulating heated fluid through the passages. Press setting parts are placed in the recesses in the bolster which are of a size chosen according to which carbon fibre parts are being manufactured.

The mold is opened and placed on a workbench with the parts of the mold split apart, and carbon fibre material is laid up into a first one of the mold parts, pressing it into the contours of the inner surface of the mold. The orientation of the fibres in the material and the number of layers of material that are laid up will depend on the specific requirements of the finished part, as may be determined by both structural and aesthetic considerations. At this stage, the mold parts may have been pre-heated.

Having finished laying up the required carbon fibre sheets into the mold, the mold is filled with resin and the mold is closed to encase the laid up material. The parts of the mold may need to be pressed firmly together as the mold is overfilled.

Once the two parts of the mold are offered up, they are held together by fixing the clinch frame to the mold parts. This step of the process causes part of the clinch frame to grip regions of the material, or to clamp parts of the mold onto parts of the material. Where a mold is not used, the material can be laid up on a former before gripping it with the clinch frame, or perhaps laid up into or onto the clinch frame .

Once the clinch frame is fixed to the mold, it is grabbed manually or by a robot and moved to place the shell inserts into the press. The inserts are held in an orientation where one is directly above the other, and the lower one is placed in the corresponding recess, or on the corresponding protrusion, of the bolster. Alignment marks on the bolster and clinch frame may be used to assist in the positioning of the frame in the press. Once in place, the control unit causes the ram of the press to operate, moving the press part down towards the bolster until pressure is applied to the top and bottom shell inserts, squeezing together slightly and compressing the material laid up in the space between the shells. The end position of the press is set by the press inserts engaging the press part.

When pressure is applied, the temperature control circuit applies an electrical current to the resistive heating elements of the bolster and press part, rapidly elevating the temperature of the press and in turn of the uncured component that is in the press. Because the outer faces of the shell inserts are generally complimentary to the press surfaces of the bolster and press part heat energy is conducted from the bolster and press part into the shell inserts and then into the material in the inserts.

The pressure and temperature are maintained for a predefined time that is long enough time to cure the resin. This will vary from resin to resin, and depending on how large the component is, with a temperature of around 130 to 160 degrees being typical and a cure time which is typically between 5 and 10 minutes depending on the properties of the material and the number of layers. Throughout this time the temperature of the component is held at an elevated level. As described above the amount of heat applied is chosen deliberately so that if it was applied evenly over the whole press surface for the full duration of the cure process then some parts of the carbon fibre material would experience an exothermic reaction. To prevent this happening, the temperatures are actively monitored by the controller and selective and rapid cooling is applied to parts of the press surface as required to prevent this exothermic reaction running away and potentially causing a fire in the press.

After the predefined time has elapsed cooling fluid is circulated through the whole of the bolster and press part in place of the heating to cause rapid cooling of the material in the shell inserts. This is maintained for a predefined time. Once that has elapsed the press is released and the inserts removed by grabbing the clinch frame . The optional clinch frame is finally used to help break apart the two halves of the shell inserts and the finished part is removed. If it has not already fully cooled to ambient temperature it is then left in a rack to finish cooling. In a modification, the press may be provided with a twin wall seal 16 that fits between the bolster and press part surrounding the mold. The press 1 , prior to applying the full pressure to the mold halves, is held in a pre-pressing position in which the bolster and press part each contact the seal 16 to form a closed and sealed space surrounding the mold. The bolster or the press part (or both) may be provided with at least one passageway 17 that has an open end inside of the region surrounded by the seal 16 from which gas or air in the space can be extracted using a source of below ambient pressure . This draws gas and air from the mold and hence from the material. This reduced pressure is maintained for a predefined time and then the pressure is increase in the sealed space.

Only after the pressure has been reduced and then increased again will the press be moved fully to the press position in which the full required pressure is applied to the shell inserts. Use of a mold 8 into which carbon fibre material is laid up before transferring to press has many advantages. The material does not have to be laid up directly into the press . The mold halves can be much lighter than the bolster and press part and are easier to move than removing a bolster and press part. They also provide support for the laid up material when moving it into the press, which enables more accurate manufacture of parts. The shell inserts also help reduce the overall process time, as the press can be used while laying up of subsequent parts is being performed.

The skilled person will understand that various modifications can be made within the scope of the present invention. For instance, as shown in Figure 7 a mold can be provided which allows three carbon fibre components to be made in one pressing operation. This includes three interior spaces, each one corresponding to a finished shape of one carbon fibre part. Note that Figure 7 only shows on half of the alternative mold. Where the outer surface of the mold has been changed then it will require a different bolster and press part, to ensure even pressure is applied onto the outer surfaces of the mold halves to squeeze them together during pressing.

Claims

1. Apparatus for use in manufacturing a fibre composite article, such as a carbon fibre article, comprising:

2. Apparatus according to claim 1 in which the cooling circuit comprises one or more passages which contain fluid and control means for controlling the temperature of a fluid flowing through the passages.

3. Apparatus according to claim 2 in which the cooling circuit is combined with the heating circuit and the control means is further adapted to heat as well as cool a fluid flowing in the passages.

4. Apparatus according to claim 2 or claim 3 in which the heating circuit comprises one or more electrical heating elements .

5. Apparatus according to any preceding claim which includes at least one temperature sensor that measures the temperature of a part of the apparatus and the control means is adapted to receive the temperature measurement as an input to a control strategy for the heating and cooling of the or each press part.

6. Apparatus according to any preceding claim in which the heating circuit, or the cooling circuit, or both, is zoned to enable different parts, or zones, of the press part and/or bolster to be temperature controlled independently of other zones.

7. Apparatus according to any preceding claim including a removable support means suitable for supporting laid up carbon fibre material, the support being movable between an open position for use outside of the press when laying up the material and a closed position for use in the press in which the support means supports the laid up material to ensure that the material is located securely in the press,

8. Apparatus according to claim 7 in which the support means includes a mold comprising at least two separable mold parts, one of the mold parts having an outer surface that is generally complimentary to the first press surface of the bolster and the other one of the mold parts having an outer surface that is generally complimentary to the second press surface of the press part, the mold parts being shaped so that when closed together they define a space therebetween that substantially matches the finished shape of at least one carbon fibre component that is to be produced by the apparatus.

9. A method of manufacturing a carbon fibre component comprising the steps of: Providing a press tool having a first press part and a second press part each defining a press surface,

Placing the material that will form the carbon fibre part into the press tool,

Applying pressure to the material by pressing the press surfaces onto the material to compress the material;

applying heat to at least one of the press part;

monitoring the temperature of the press part to provide an estimate of the temperature of the part that is being pressed; and

in the event that the estimate indicates a localised portion of the part is undergoing an exothermic reaction or about to do so, applying localised cooling to that region of the part whilst continuing to heat one or more other localised portions of the part.

10. A method according to claim 9 which further comprises driving heat into the press in a first stage at a level that is known to create an exothermic reaction in a localised region of the part and maintaining that heating until it is about to be exothermic or an exothermic reaction has started, and prior to completion of the molding process the method further comprises applying cooling to the localised region until the exothermic reaction has stopped whilst continuing to heat the parts of the material that are not exothermic.

1 1. A method according to claim 9 or claim 10 which comprises using a press that has a heating circuit and a cooling circuit built into one or both of the press parts and a plurality of temperature sensors built into one ore more of the press parts from which an estimate of the temperature of different parts of the molded part may be derived.