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Title:
MOULDING MATERIALS
Document Type and Number:
WIPO Patent Application WO/2017/198568
Kind Code:
A1
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 layer of randomly orientated short fibres, and wherein at least a portion of the randomly orientated short fibres are carbon 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.

Inventors:
JAMES THOMAS (GB)
WESSELY OLIVER (GB)
Application Number:
PCT/EP2017/061492
Publication Date:
November 23, 2017
Filing Date:
May 12, 2017
Export Citation:
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Assignee:
HEXCEL REINFORCEMENTS UK LTD (GB)
International Classes:
B32B5/06; B29C70/08; B29C70/22; B32B3/06; B32B3/08; B32B3/10; B32B3/14; B32B3/16; B32B3/30; B32B5/10; B32B5/12; B32B5/22; B32B5/24; B32B5/26; B32B5/28; B32B27/32; B32B27/36
Domestic Patent References:
WO2011029275A12011-03-17
WO2007059566A12007-05-31
WO2002009934A12002-02-07
Foreign References:
EP2295235A12011-03-16
US20130309001A12013-11-21
EP0507322A21992-10-07
US20130136931A12013-05-30
Attorney, Agent or Firm:
EDDOWES, Simon (GB)
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Claims:
CLAIMS

I. 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 layer of randomly orientated short fibres, and wherein at least a portion of the randomly orientated short fibres are carbon fibres. 2. A moulding material according to claim 1, wherein substantially all of the randomly orientated short fibres are carbon fibres.

3. A moulding material according to claim 1, wherein at least a portion of the randomly orientated short fibres are glass fibres.

4. A moulding material according to any preceding claim, wherein at least a portion of the carbon fibres are recycled carbon fibres.

5. A moulding material according to any preceding claim, wherein the layer of randomly orientated short fibres is attached to the covered surface of the core.

6. A moulding material according to claim 5, wherein the layer of randomly orientated short fibres is attached to the core by stitching. 7. 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 1 to 6.

8. A moulding material according to any preceding claim, wherein the core is at least partially permeable. 9. A moulding material according to any preceding claim, wherein the core is flexible.

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

II. A moulding material according to any preceding claim, wherein the core comprises a polypropylene or polyester material. 12. 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.

13. A cured component obtainable by the method of claim 12.

14. A vehicle component comprising a cured component according to claim 13 or obtained by the method of claim 12, preferably wherein the vehicle component is a body panel or a fairing.

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 layer of randomly orientated short fibres, and wherein at least a portion of the randomly orientated short fibres are carbon 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 carbon fibres in the covering layers of the moulding materials of the present invention improves the strength and/or stiffness of the moulding materials compared to the use of the same weight of glass fibres alone, 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. The fibres forming the layer of randomly orientated short fibres used in 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.

At least a portion of the fibres of the layers of randomly orientated short fibres used in the present invention are carbon fibres and, optionally, substantially all of the fibres of the layer of randomly orientated short fibres may be carbon fibres. Preferably from 5 to 100% of the fibres of the layers of randomly orientated short fibres are carbon fibres, more preferably from 10 to 100%, and most 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 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 7μιτι 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 at least a portion of the carbon fibres in the layer of randomly orientated short 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. Suitable recycled carbon fibres, chopped recycled carbon fibres and layers of randomly orientated short fibres comprising recycled carbon fibres can be obtained from Carbon Conversions, Lake City, South Carolina, USA.

In embodiments of the invention in which 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. In particular embodiments of the present invention from 5 to 95% 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 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, because at least a portion of the randomly orientated short fibres in the coating layers of the moulding materials of the present invention are carbon fibres, it is possible to use reduced amounts of the coating material compared to conventional moulding materials not comprising carbon fibres whilst maintaining comparable strength/stiffness. For example, moulding materials having weights after resin infusion and curing of from 50% to 95% of conventional 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 coating materials may be used to produce moulding materials for forming finished products having increased strength/stiffness but comparable weights to conventional materials. In particularly preferred embodiments of the invention moulding materials for forming finished products having increased strength/stiffness and reduced weight compared to conventional 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 covered surface of the core before the resin infusion stage. In such embodiments the layer of randomly orientated short fibres may be attached to the covered 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 the conventional stitching processes by which chopped strand mat is attached to cores in conventional products.

In 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. However, in preferred embodiments of the present invention, both opposing surfaces of the core are covered by a covering layer 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. 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 as Hacoloft ® 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. Possible core shapes include square, oblong, circular, oval, but preferably 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 layer of randomly orientated short fibres is applied to at least one face of the core and, optionally, is attached thereto, before the covered core is cut to the final shape. 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 and 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 into the layer of randomly orientated short fibres and, preferably, also at least partially into the core. 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 lightweight 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 Figure and Examples in which: Figure 1 shows a diagrammatic cross-sectional view of a moulding material according to an embodiment of the present invention.

Figure 1 shows a moulding material 1 according to an 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 1 is covered by a layer of randomly orientated short fibres 7. Substantially all of the fibres of the layer of randomly orientated short fibres 7 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 7 may be replaced by alternative fibres, such as glass fibres. In an alternative embodiment, the recycled carbon fibres in the layer of randomly orientated short fibres can be obtained from carbon

Conversions, lake City, south Carolina, USA.

The layer of randomly orientated short fibres 7 is attached to the first face 5 of the core 3 by stitching with polyester yarn from J. H. Ashworth (not shown). A further layer 9 covers the opposing face 11 of the core 3. In this embodiment, the layer 9 covering the opposing face 11 of the core 3 is the same as the layer 7 covering the first face 5 of the core 3, but in alternative embodiments the layer 9 may 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 moulding material 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 in a mould and by subsequent curing.

EXAMPLES

A moulding material generally corresponding to the material shown in figure 1 was produced comprising a polypropylene core with both opposing faces of the core covered by a layer of randomly orientated short carbon fibres (Carbicore 200). 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). The results are shown in Table 1 below.

Table 1

As can be seen from Table 1, the use of carbon fibres to replace the glass fibres in the layers of randomly orientated short fibres resulted in a 17% increase in flexural strength and a weight saving of 15% with no loss of flexural stiffness.




 
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