GB2550357A

GB2550357A - Moulding materials

Info

Publication number: GB2550357A
Application number: GB1608566.4A
Authority: GB
Inventors: James Thomas; Wessely Oliver
Original assignee: Hexcel Reinforcements UK Ltd
Current assignee: Hexcel Reinforcements UK Ltd
Priority date: 2016-05-16
Filing date: 2016-05-16
Publication date: 2017-11-22
Also published as: WO2017198571A1; GB201608566D0; DE112017002490T5

Abstract

A moulding material comprising a core comprising two opposing surfaces, wherein at least one of the opposing surfaces of the core is covered by a grid of continuous fibres. The moulding material may be used to form a vehicle component such as a body panel or fairing having improved strength and/or weight properties. The moulding material 19 comprises a core 21 which may be a polypropylene core. Additionally, channels 23 may be formed in each of the two opposing surfaces 25 and 27 of the core 21. The channels 23 may comprise longitudinal and perpendicular channels with a spacing between adjacent channels of 25mm, and therefore form a grid pattern in each of the two opposing surfaces 25 and 27 of the core 21. The channels may have a width of 10mm and a depth of 5mm, and entirely cover each of the two opposing surfaces 25 and 27 of the core 19. 5. A carbon fibre grid 29 is located within the channels 23 on each of the two opposing surfaces 25 and 27 of the core 21. Both faces 25 and 27 of the core 21 are may also be covered by a layer of randomly orientated short fibres 31, which also cover the carbon fibre grids 29. The covering layers 31 may be attached to the core 21 by stitching. Particularly, moulding materials and components for use in forming vehicle components such as body panels and fairings.

Description

MOULDING MATERIALS

INTRODUCTION

The present invention relates to curable moulding materials and cured components produced therefrom, particularly moulding materials and components for use in forming vehicle components such as body panels and fairings.

BACKGROUND

It is known to improve the fuel consumption and/or handling properties of vehicles, particularly heavy goods vehicles (HGVs), by incorporating aerodynamic structures, also known as fairings, as part of the bodywork of the vehicle. A particular example is a sloping roof on a HGV, which can save as much as 7% of the fuel costs. Such structures may be formed integrally with the bodywork during initial manufacture or may be added at later stages. In order to withstand the stresses encountered during operation of the vehicle, the aerodynamic structures must have high strength and stiffness, but if they are too heavy the increased weight of using such structures will have a negative effect on fuel consumption. Similarly, the safety and resilience of vehicles can be improved by incorporating reinforcing body panels having high strength and/or stiffness into the vehicles, but if such panels increase the weight of the vehicles they will have a negative impact on fuel consumption and/or handling properties of the vehicles.

Conventionally, reinforcing vehicle body panels and fairings are produced from materials comprising a core material sandwiched between two layers of chopped strand mat, a non-woven material consisting of glass fibres laid randomly across each other. This material may be shaped in a mould and then infused with a curable resin, which is cured to form the final cured composite product. This process is effectively a single step process, and is particularly convenient when the core and chopped strand mat are provided as a single component ready for moulding/resin infusion, i.e. with the chopped strand mat attached to the core, for example by stitching.

By varying the core material, the thickness of chopped strand mat and the type and amount of resin used, the final properties of the cured material may be adjusted. However, chopped strand mat comprising glass fibres is a relatively heavy material, and there is an inevitable trade-off between providing good strength and/or stiffness whilst not increasing the weight of the final material to unacceptable levels.

SUMMARY OF THE INVENTION

The present invention aims to obviate or at least mitigate the above described problems and/or to provide advantages generally.

According to the present invention, there is provided a moulding material, a cured component, a method and a vehicle component as defined in any of the accompanying claims.

In a first aspect, the present invention provides a moulding material comprising a core comprising two opposing surfaces, wherein at least one of the opposing surfaces of the core is covered by a grid of continuous fibres.

In a second aspect the present invention provides a method of forming a cured component comprising infusing a moulding material according to the present invention with a curable resin and curing the curable resin.

In a third aspect the present invention provides a cured component obtainable by the method of the present invention.

In a fourth aspect the present invention provides a vehicle component comprising a cured component according to the present invention or obtained by the method of the present invention, preferably wherein the vehicle component is a body panel or a fairing.

SPECIFIC DESCRIPTION

The incorporation of a grid formed from continuous fibres covering at least one of the surfaces of the core in the moulding materials of the present invention improves the strength and/or stiffness of the core, and therefore such materials may be used directly as moulding materials by being infused with a suitable curable resin. Alternatively, one of both of the surfaces of the core may be covered by a covering layer before being infused with resin, and the covering layer may be any material contributing to the final properties of the moulding materials after resin infusion/curing. Where the covering materials are conventional materials, such as chopped strand mat, lower amounts of such materials are required to produce comparable strength/stiffness compared to conventional materials because of the presence of the grid, and therefore strength/stiffness may be maintained at conventional levels whilst reducing the weight of the moulding materials, or moulding materials of conventional weight may be produced but having increased strength/stiffness. In a particularly advantageous embodiment, moulding materials having improved strength/stiffness and reduced weight compared to conventional materials may be produced.

In moulding materials according to the present invention at least one of the opposing surfaces of the core is covered by a grid of continuous fibres, i.e. a network of interconnecting continuous fibres with spaces between, and preferably the fibres are in a regular arrangement of two sets of parallel fibres arranged to form a grid, preferably generally perpendicularly to each other, so that the spaces between the fibres are generally rectangular or, more preferably, square in shape. By "continuous fibres" it is meant that each individual fibre is unbroken along the length or breadth of the grid, but it is not necessary that all of the strands of the grid running in a particular direction are formed from a single fibre (although this is possible in certain embodiments). Thus, the grid may be formed from a first set of parallel, separate, unbroken/continuous fibres running in a first direction, and a second set of parallel, separate, unbroken/continuous fibres running in a different, preferably perpendicular, direction. Preferably the parallel fibres are spaced apart by a distance of from 5 to 100mm, more preferably from 20 to 50mm. For example, the fibres may be in the form of a grid having 25mm square spaces between the fibres.

The fibres forming the grid may be unconnected, i.e. fibres running in one direction are simply placed on top of fibres running in a generally perpendicular direction, or they may be connected at the crossing points. Where the fibres are connected, this may be by any suitable means, such as by weaving fibres together, or, more preferably, by use of an adhesive or by stitching, or they may be comingled and heat-set.

The grids covering at least one surface of the core of moulding materials according to the present invention may be formed from any fibrous materials providing improved strength and/or stiffness to the final cured component. Examples of suitable materials include carbon, glass, aramid and natural fibres, such as cellulose fibres, or combinations thereof. Where mixtures of materials are used to form the grids the materials may be mixed in each fibre of the grid, or different grid fibres may be formed from different materials, for example all of the fibres running in a first orientation of the grid may be made from a first material and all of the fibres running in a second orientation of the grid may be made from a second material.

In a preferred embodiment of the present invention, the grid covering at least one of the opposing faces of the core material comprises carbon fibres. In this embodiment the grid may comprise any suitable carbon fibres, but generally the carbon fibres will be in the form of commercially available carbon fibre tows, i.e. bundles of multiple carbon fibre filaments. The carbon fibre filaments may be of conventional size, such as approximately 7pm in diameter and each tow may comprise any number of individual filaments, but preferably each tow comprises approximately the same number of filaments, preferably ranging from 1,000 to 50,000 filaments per tow, although even higher numbers of filaments per tow are possible. The tows are of suitable length so that the grid matches the dimensions of the core in the finished cured component.

In embodiments of the invention in which not all of the fibres of the grid of continuous fibres are carbon fibres, the non-carbon fibres may be any suitable material, such as glass, aramid or natural fibres; for example at least a portion of the fibres may be glass fibres. In embodiments of the present invention in which at least a portion of the fibres of the grid of continuous fibres are glass fibres, any suitable glass fibres may be present, such as commercially available glass fibres.

In a preferred embodiment of the present invention, the grid of continuous fibres is in contact with the surface of the core, and in a particularly preferred embodiment the grid is located in channels on the surface of the core. In this embodiment, the channels on the surface of the core may be of any size suitable for the fibres to fit into, but are preferably only slightly wider than the fibres, so that the fibres fit into the channels relatively tightly. The channels may be pre-formed during the construction of the core or may be added subsequently by any suitable means, such as by machining.

In embodiments of the present invention in which the grid of continuous fibres is in contact with the surface of the core, the grid may simply be placed in contact with the surface of the core before the infusion of resin into the moulding material during construction of the final cured component, or alternatively, the grid may be attached to the core. In this embodiment, the grid may be attached to the core in any suitable way, such as by being covered by a layer which is attached to the core and therefore holds the grid in place, or by direct attachment, such as by stitching or bonding.

In a preferred embodiment of the moulding materials of the present invention both opposing surfaces of the core are covered by grids of continuous fibres. In this embodiment the two grids of continuous fibres may be the same or different, but preferably at least one of the grids of continuous fibres, and more preferably both grids of continuous fibres, comprise carbon fibres.

In preferred embodiments of the moulding materials of the present invention at least one of the two opposing surfaces of the core is covered by a covering layer, and most preferably the at least one surface covered by a grid of continuous fibres is also covered by a covering layer which also covers the grid of continuous fibres.

In preferred embodiments of the moulding materials of the present invention at least one of the opposing surfaces of the core is covered by a layer of randomly orientated short fibres, preferably so that the layer of randomly orientated short fibres covers the at least one grid of continuous fibres.

The fibres forming the layer of randomly orientated short fibres used in the preferred embodiments of the present invention may be of similar lengths to the fibres used in conventional chopped strand mats, but preferably the fibres are from 5 to 150mm in length, more preferably from 25 to 75mm.

In embodiments of the present invention in which at least one of the opposing surfaces of the core is covered by a layer of randomly orientated short fibres the short fibres may comprise any suitable material providing strength and/or stiffness to the finished product. Suitable materials include carbon fibres, glass fibres, aramid fibres and natural materials such as cellulose fibres. However, in particularly preferred embodiments of the present invention at least a portion of the fibres of the layers of randomly orientated short fibres are carbon fibres and, optionally, substantially all of the fibres of the layer of randomly orientated short fibres may be carbon fibres. In such embodiments, from 5 to 100% of the fibres of the layer of randomly orientated short fibres may be carbon fibres, preferably from 10 to 100%, and more preferably from 50 to 100%.

The carbon fibres forming at least a portion of the fibres in the layers of randomly orientated short fibres in the moulding materials according to this embodiment of the present invention may be any suitable carbon fibres, but generally will be in the form of commercially available carbon fibre tows, i.e. bundles of multiple carbon fibre filaments. The carbon fibre filaments may be of conventional size, such as approximately 7pm in diameter and each tow may comprise any number of individual filaments, but preferably each tow comprises approximately the same number of filaments, preferably ranging from 1,000 to 50,000 filaments per tow. The tows may be any suitable length, but are preferably within the range of from 5 to 150mm in length, more preferably from 25 to 75 mm in length.

Preferably in embodiments of the invention in which at least a portion of the carbon fibres in the layer of randomly orientated short fibres are carbon fibres at least a portion of the carbon fibres are recycled carbon fibres and, optionally, substantially all of the carbon fibres may be recycled carbon fibres. Recycled carbon fibres may be produced by any suitable methods, and are preferably produced from processing waste or end-of-life sources. The use of recycled carbon fibres provides potential cost reductions and/or a convenient use for recycled materials rather than disposal thereof.

In embodiments of the invention in which none, or not all, of the fibres of the layer of randomly orientated short fibres are carbon, the non-carbon fibres may be any suitable material, such as glass, aramid or natural fibres; for example at least a portion of the fibres of the layer of randomly orientated short fibres may be glass fibres or, optionally, substantially all of the randomly orientated short fibres may be glass fibres. In particular embodiments of the present invention from 5 to 100% of the fibres of the layer of layer of randomly orientated short fibres may be glass fibres, preferably from 5 to 90%, and more preferably from 5 to 50%.

In embodiments of the present invention in which at least a portion of the fibres of the layer of randomly orientated short fibres are glass fibres, any suitable glass fibres may be present, such as commercially available glass fibres, but the fibres should substantially all have lengths in the range of from 5 to 150mm, preferably from 25 to 75mm.

The layers of randomly orientated short fibres used in this embodiment of the moulding materials of the present invention may comprise additional materials, such as any conventional materials used in commercially available chopped strand mats, including binders, such as starch emulsion binders, and stitching, such as polyester stitching.

Carbon fibres are generally lighter, stronger and/or stiffer than glass fibres, and therefore, when at least a portion of the randomly orientated short fibres in the covering layers of the moulding materials of the present invention are carbon fibres, it is possible to use reduced amounts of the covering materials compared to conventional moulding materials not comprising carbon fibres, whilst maintaining comparable strength/stiffness, and this is particularly advantageous in combination with the additional strength and/or stiffness provided by the grid of continuous fibres also present in moulding materials of the present invention. Thus, moulding materials having weights after resin infusion and curing of from 25% to 95% of conventional non-grid/non-carbon fibre containing materials, but having comparable strength/stiffness to the conventional materials may be obtained by the present invention. Alternatively, increased amounts of the lighter covering materials may be used to produce moulding materials for forming finished products having increased strength/stiffness, but comparable weights, to conventional non-grid/non-carbon fibre containing materials. In particularly preferred embodiments of the invention moulding materials for forming finished products having increased strength/stiffness and reduced weight compared to conventional non-grid/non-carbon fibre containing materials may be obtained.

In certain embodiments of the present invention the layer of randomly orientated short fibres may be unattached to the core until the resin infusion/bonding step; however, in preferred embodiments the layer of randomly orientated short fibres is attached to the surface of the core before the resin infusion stage. In such embodiments the layer of randomly orientated short fibres may be attached to the surface of the core in any conventional manner, such as by use of a binder/adhesive, for example a thermoplastic binder, or by stitching. The layer of randomly orientated short fibres may be attached to the core by stitching using any suitable stitching process, such as conventional stitching processes by which chopped strand mat is attached to cores in conventional products.

In preferred embodiments of the moulding materials according to the present invention at least one of the two opposing surfaces of the core is covered by a layer of randomly orientated short fibres, and more preferably any surface of the core covered by a grid of continuous fibres is also covered by a layer of randomly orientated short fibres, particularly so that the grid of continuous fibres is covered by the layer of randomly orientated short fibres. In particularly preferred embodiments of the present invention, both opposing surfaces of the core are covered, and, more preferably, both opposing surfaces of the core are covered by layers comprising randomly orientated short fibres, and, most preferably at least a portion of the randomly orientated short fibres of each of the two layers of randomly orientated short fibres are carbon fibres. Different properties may be provided to different surfaces of the moulding materials according to the present invention by applying different layers to the two opposing faces, and any combination of the surface layers discussed above may be used.

Any suitable material may be used as a core in moulding materials according to the present invention. However, in preferred embodiments the core is at least partially permeable in order to allow at least partial penetration into the core of resin during infusion/curing.

Additionally or alternatively, the core of the moulding materials of the present invention is preferably flexible. In particular, it is preferred that the core is sufficiently flexible that the moulding materials of the present invention are mould conformable, i.e. that the moulding materials may be pressed into a shaped mould and will conform to the shape of the mould.

It is also preferred that the cores used in moulding materials according to the present invention are elastically compressible, so that when a moulding material according to this embodiment is compressed to fit into a tight fitting mould the core will expand causing the moulding material to fill the mould, thereby expelling air from the mould and ensuing that the component produced in the mould matches the shape of the mould.

In embodiments of the present invention in which the grid of continuous fibres are located in channels on the surface of the core it must be possible for such channels to be formed in the core, i.e. the core must be capable of being formed by a process in which suitable channels are created in the core, or the core must be sufficiently robust for the channels to be formed after formation of the core, for example by machining.

Suitable materials for forming the core of moulding materials according to the present invention include balsa, open-cell and closed-cell foam materials and composite materials, and particularly preferred core materials include polypropylene, such asHacoloft ® PP available from Ziegler, and polyester, such as Soric ® SF available from Lantor.

The cores used to form moulding materials according to the present invention may be any suitable thickness, shape and size. Preferred core thicknesses are from 1 to 100mm, more preferably from 3 to 30mm, but preferably, in embodiments in which the grid of continuous fibres is located in channels on the surface of the core, the core is sufficiently thick that the channels do not significantly reduce the strength/stiffness of the core. Possible core shapes include square, oblong, circular and oval, but in embodiments in which at least one of the two opposing surfaces of the core is covered by a layer of randomly orientated short fibres, the core is in the form of a sheet having a much greater length than width, so that the moulding materials may be produced in an effectively continuous process, i.e. a roll of core material may be gradually unwound while a grid of continuous fibres and a layer of randomly orientated short fibres are applied to at least one face of the core and, optionally, are attached thereto, before the covered core is cut to the final shape. In this embodiment, preferably the core is at least 50mm wide and up to any length that may be produced or stored as a roll, such as 1.25 metres wide and 22 metres long.

According to a second aspect of the present invention cured components according to a third aspect of the present invention may be obtained by infusing a moulding material according to the present invention with a curable resin and curing the curable resin.

Any suitable resin may be used to form cured components according to the present invention, but preferred resins include low viscosity resins, particularly low viscosity epoxy resins or low viscosity polyester resins, such as Crystic® from Scott Bader or Aropol® from Ashland.

The infusion of moulding materials according to the present invention with a curable resin may be carried out in any suitable way, such as in a mould and by using increased pressure and/or vacuum to improve penetration of the curable resin at least partially into the core and the grid of continuous fibres, and also into any layers of randomly orientated short fibres present in the moulding material. Curing of the curable resin may also be carried out in any suitable manner, such as by use of curing agents and/or increased temperature. In a particular embodiment of the present invention, a resin and a curing agent are mixed immediately before infusion into a moulding material according to the present invention, the infusion preferably being carried out in a mould, and curing of the infused resin optionally being enhanced by a steady increase in temperature within the mould.

Cured components according to the present invention and/or obtained by the methods of the present invention may be used as vehicle components, particularly as body panels or fairings to provide light weight reinforcement and/or aerodynamic surfaces, particularly for HGVs. Cured components obtained by the processes of the present invention may be ready to use as vehicle components, or they may be further processed before use, for example by reshaping, changing the surface properties and/or by the addition of additional surface materials.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be clarified by way of example only and with reference to the following Figures and Example in which:

Figure 1 shows a diagrammatic cross-sectional view of a moulding material according to a first embodiment of the present invention;

Figure 2 shows a diagrammatic cross-sectional view of a moulding material according to a second embodiment of the present invention, and

Figure 3 shows a diagrammatic cross-sectional view of a moulding material according to a third embodiment of the present invention.

Figure 1 shows a moulding material 1 according to a first embodiment of the present invention. The moulding material 1 comprises a core 3 which is a Hacoloft® polypropylene core available from Ziegler. A first face 5 of the core 3 is covered by a carbon fibre grid 7, which is a flat grid formed from two sets of parallel carbon fibres with a 25mm spacing between fibres, arranged perpendicularly to each other to form a grid with square spaces measuring 25mm by 25mm. The individual fibres forming the carbon fibre grid 7 are all continuous fibres, i.e. they are unbroken along their length. The carbon fibre grid 7 is attached to the core 3 by stitching (not shown).

The moulding material 1 shown in Figure 1 may be converted to a construction component suitable to form a vehicle body panel or a fairing by infusion with a curable resin such as Crystic® from Scott Bader or Aropol® from Ashland in a mould and by subsequent curing.

Figure 2 shows a moulding material 9 according to second embodiment of the present invention.

The moulding material 9 comprises a core 3 which is a polypropylene core similar to the core 3 shown in Figure 1. Alternatively, the core 3 may be a different core material such as a Soric® SF polyester core available from lantor. A first face 5 of the core 3 is covered by a carbon fibre grid 7 similar to the grid 7 shown in Figure 1. Alternatively, the carbon fibre grid 7 may be replaced by a grid of continuous fibres formed from any other suitable material, such as a glass fibre grid.

The first face 5 of the core 3 is also covered by a layer of randomly orientated short fibres 11, which also covers the carbon fibre grid 7. Substantially all of the fibres of the layer of randomly orientated short fibres 11 are carbon fibres having lengths of approximately 50mm. The carbon fibres are recycled carbon fibres obtained from ELG Carbon Fibre, Carbiso M, producing a coating thickness of approximately 0.5mm. In an alternative embodiment of the invention, up to 95% of the fibres of the layer of randomly orientated short fibres 11 may be replaced by alternative fibres, such as glass fibres.

The layer of randomly orientated short fibres 11 is attached to the first face 5 of the core 3 by stitching with polyester yarn from J. H. Ashworth (not shown). The stitching also holds the carbon fibre grid 7 in contact with the first face 5 of the core 3.

The opposing face 13 of the core 3 is also covered by a carbon fibre grid 15 which is similar to the carbon fibre grid 7 covering the first face 5 of the core 3, but alternatively, the carbon fibre grid 15 may be replaced by a grid of continuous fibres formed from any other suitable material, such as a glass fibre grid. A covering layer 17 covers the opposing face 13 of the core 3 and the carbon fibre grid 15. In this embodiment, the covering layer 17 covering the opposing face 13 of the core 3 is the same as the layer 11 covering the first face 5 of the core 3, but in alternative embodiments the layer 17 may be formed from any materials, such as conventional chopped strand mat, or may be a layer of randomly orientated short fibres in which some of the fibres are carbon fibres and some of the fibres are glass fibres. The layer covering 17 may be attached to the opposing face 13 of the core 3 by stitching in the same manner as the first layer 11 is attached to the first face 5 of the core 3, but alternatively the covering layer 17 may be attached to the core 3 during the resin infusion/curing step, the resin passing through the grid 15 and adhering the covering layer 17 to the second face 13 of the core 3.

The moulding material 9 shown in Figure 2 may be converted to a construction component suitable to form a vehicle body panel or a fairing by infusion with a curable resin such as Crystic® from scott Bader in a mould and by subsequent curing.

Figure 3 shows a moulding material 19 according to a third embodiment of the present invention. The moulding material 19 comprises a core 21 which is a polypropylene core similar to the core 3 shown in Figure 1, or a polyester core 3 similar to the alternative core discussed with respect to Figure 2. Flowever, the core 21 additionally comprises channels 23 in each of the two opposing surfaces 25 and 27 of the core 21. The channels 23 comprise longitudinal and perpendicular channels 23 with a spacing between adjacent channels 23 of 25mm, and therefore form a grid pattern in each of the two opposing surfaces 25 and 27 of the core 21. The channels 23 have a width of 10mm and a depth of 5mm, and entirely cover each of the two opposing surfaces 25 and 27 of the core 19. A carbon fibre grid 29 is located within the channels 23 on each of the two opposing surfaces 25 and 27 of the core 21. The carbon fibre grid 29 is similar to the carbon fibre grid 7 shown in Figure 2.

Both faces 25 and 27 of the core 21 are also covered by a layer of randomly orientated short fibres 31, which also cover the carbon fibre grids 29. The layers of randomly orientated short fibres 31 are similar to the layer of randomly orientated short fibres 11 shown in Figure 2 or the alternative covering layers 17 discussed therein.

The covering layers 31 are attached to the core 21 by stitching, as discussed with respect to Figure 2.

The moulding material 19 shown in Figure 3 may be converted to a construction component suitable to form a vehicle body panel or a fairing by infusion with a curable resin such as Crystic® from Scott Bader in a mould and by subsequent curing.

EXAMPLES A moulding material generally corresponding to the material shown in Figure 2 was produced comprising a polypropylene core with both opposing faces of the core covered by a grid of continuous carbon fibres having a spacing between adjacent fibres of 25mm. Each face was also covered by a layer of randomly orientated short carbon fibres (Carbicore 200) which completely covered the grid on each face. The flexural strength (ultimate bending moment) and flexural stiffness (section modulus) were measured as well as the areal mass. These properties were compared to a moulding material comprising the same core covered by layers of commercially available chopped strand glass mat (CPPC300) and with no grid present. The results are shown in Table 1 below.

Table 1

As can be seen from Table 1, the use of a grid of continuous carbon fibres and the replacement of glass fibres by carbon fibres in the layers of randomly orientated short fibres resulted in a 33% increase in flexural stiffness and a weight saving of 28% with no loss of flexural strength.

Claims

1. A moulding material comprising a core comprising two opposing surfaces, wherein at least one of the opposing surfaces of the core is covered by a grid of continuous fibres.

2. A moulding material according to claim 1, wherein the grid comprises carbon fibres.

3. A moulding material according to claim 1 or claim 2, wherein the grid is in contact with the covered surface of the core.

4. A moulding material according to claim 3, wherein the grid is located in channels on the surface of the core.

5. A moulding material according to claim 3 or claim 4, wherein the grid is attached to the surface of the core, preferably wherein the grid is attached by stitching.

6. A moulding material according to any preceding claim, wherein both opposing surfaces of the core are covered by grids of continuous fibres, preferably wherein both grids comprise carbon fibres.

7. A moulding material according to any preceding claim, wherein at least one of the opposing surfaces of the core is covered by a layer of randomly orientated short fibres.

8. A moulding material according to claim 7, wherein at least a portion of the randomly orientated short fibres are carbon fibres.

9. A moulding material according to claim 8, wherein substantially all of the randomly orientated short fibres are carbon fibres.

10. A moulding material according to claim 8 or claim 9, wherein at least a portion of the carbon fibres are recycled carbon fibres.

11. A moulding material according to claim 7 or claim 8, wherein at least a portion of the randomly orientated short fibres are glass fibres.

12. A moulding material according to claim 7, wherein substantially all of the randomly orientated short fibres are glass fibres.

13. A moulding material according to any of claims 7 to 12, wherein the layer of randomly orientated short fibres is attached to the covered surface of the core, preferably wherein the layer of randomly orientated short fibres is attached by stitching.

14. A moulding material according to any preceding claim, wherein both opposing surfaces of the core are covered by coating layers, preferably wherein each coating layer is a layer of randomly orientated short fibres as defined in any of claims 7 to 13.

15. A moulding material according to any preceding claim, wherein the core is at least partially permeable.

16. A moulding material according to any preceding claim, wherein the core is flexible.

17. A moulding material according to any preceding claim, wherein the core is elastically compressible.

18. A moulding material according to any preceding claim, wherein the core comprises a polypropylene or polyester material.

19. A method of forming a cured component comprising infusing a moulding material according to any preceding claim with a curable resin and curing the curable resin.

20. A cured component obtainable by the method of claim 19.

21. A vehicle component comprising a cured component according to claim 20 or obtained by the method of claim 19, preferably wherein the vehicle component is a body panel or a fairing.