GB2554870A

GB2554870A - Fabricating a composite article

Info

Publication number: GB2554870A
Application number: GB1617004.5A
Authority: GB
Inventors: Collings Ed; Cole David; Clarke Jason; Du Jeffrey
Original assignee: Forward Composites
Current assignee: Forward Composites
Priority date: 2016-10-06
Filing date: 2016-10-06
Publication date: 2018-04-18
Also published as: GB201617004D0

Abstract

A method of fabricating a composite article (1, fig 11) includes providing a first fibre material layer (4) on a first mould tool (5). The method also includes providing one or more foam members (2) on the first fibre material layer (4), the foam member(s) (2) comprising closed cell polymeric foam. The method also includes providing a second fibre material layer (12) to at least partially cover each foam member (2). The method also includes providing a second mould tool (9) to form a seal with the first mould tool (5). A mould (13) formed by the first and second mould tools (5, 9) securely holds the first and second fibre material layers (4,12) and the foam member(s) (2) relative to one another. The method also includes injecting a polymeric resin (17) into the mould (13) to infiltrate the first and second fibre material layers (4, 12). Air or other gases may be pumped out of the mould through the outlet port(s). Air or other gases may be vacuum pumped out of the mould through the outlet port(s). Air or other gases displaced by the introduction of the resin may escape the mould through the outlet port(s). The method may include, following curing of the polymeric resin, trimming the resulting cured assembly to remove excess fibre composite and/or resin materials.

Description

(54) Title of the Invention: Fabricating a composite article

Abstract Title: Fabricating a composite article including a foam core (57) A method of fabricating a composite article (1, fig 11) includes providing a first fibre material layer (4) on a first mould tool (5). The method also includes providing one or more foam members (2) on the first fibre material layer (4), the foam member(s) (2) comprising closed cell polymeric foam. The method also includes providing a second fibre material layer (12) to at least partially cover each foam member (2). The method also includes providing a second mould tool (9) to form a seal with the first mould tool (5). A mould (13) formed by the first and second mould tools (5, 9) securely holds the first and second fibre material layers (4,12) and the foam member(s) (2) relative to one another. The method also includes injecting a polymeric resin (17) into the mould (13) to infiltrate the first and second fibre material layers (4, 12). Air or other gases may be pumped out of the mould through the outlet port(s). Air or other gases may be vacuum pumped out of the mould through the outlet port(s). Air or other gases displaced by the introduction of the resin may escape the mouldthrough the outlet port(s). The method may include, following curing of the polymeric resin, trimming the resulting cured assembly to remove excess fibre composite and/or resin materials.

1/11

Fig. 1

Fig. 2

2/11

Fig. 3

Fig. 4

3/11

I ! Evacuate mould j S5

co

I

Fig. 5

4/11

5/11

Fig. 10

Fig. 11 —

6/11

Fig. 12

4I I I I H- I I I I

IS I I I I I I I

Fig. 13

-4Fig. 14

7/11

Fig. 15 t

8/11

S13

S14

S15

S16

Trim article ! S17

Fig. 16

9/11

Fig. 19 ί

10/11

Fig. 22

11/11

I

Fig. 23

I

Fig. 24

- 1 Fabricating a composite article

Field of the invention

The present invention relates to a method of fabricating a composite article.

Background

Fibre-reinforced composites can offer many desirable properties, for example, low weight, high strength, high stiffness and good fracture toughness. Mechanical and mass properties of fibre-reinforced composites have led to their adoption in diverse areas such as sports equipment, boat hulls, aerospace parts, automotive components and building structures.

Fibre-reinforced composites are typically manufactured in the shape of the whole or a part of a finished product. Fibre-reinforced composites having complex shapes may be manufactured by “laying-up” fibres pre-impregnated with a matrix material, either manually or using a robot, followed by vacuum bagging and heating in an autoclave.

Fibre-reinforced composites have been fabricated using polymer foam materials as core or interior filling material. For example, FR 2 241670 Al describes building panels for a prefabricated dwelling which include two parallel skins of glass fibre reinforced polyester resin contacting a core of expanded polyurethane foam. A skin is prepared by laying successive layers of bonding agent, polyester resin, glass fibre which is rolled into the resin, polyester resin and finally glass fibre. The two skins are placed horizontally and parallel, and foam is introduced by a nozzle which disposes material initially at a rear corner and which fills the space between the skins during successive traverses.

EP 0 993 937 Ai describes a panel having a thermoplastic foam core which is bonded to a first outer layer including thermoplastic and natural fibers and a second outer layer including a second thermoplastic with second natural fibers. The outer layers are thermally-fused to the core.

Although basic materials for fabricating a fibre reinforced composite may typically be readily available such as, for example, pre-impregnated carbon fibre or glass fibre reinforcement and Nylon (RTM) or phenolic resin and so forth, methods of fabricating fibre-reinforced composites are frequently slow and/or labour intensive.

- 2 Summary

According to a first aspect of the invention there is provided a method of fabricating a composite article including providing a first fibre material layer on a first mould tool. The method also includes providing one or more foam members on the first fibre material layer. Each foam member(s) includes closed cell polymeric foam. The method also includes providing a second fibre material layer to at least partially cover each foam member. The method also includes providing a second mould tool to form a seal with the first mould tool. A mould formed by the first and second mould tools holds the first and second fibre material layers and the foam member(s) relative to one another. The method also includes injecting a polymeric resin into the mould to infiltrate the first and second fibre material layers.

The method may include curing the polymeric resin. The assembly including the first and second mould tools, first and second fibre material layers and the foam member(s) may remain sealed until the polymeric resin has cured or partially cured.

When two or more foam members are provided, each foam member may be arranged on a different portion of the first fibre material layer. Two or more foam members may be placed on the first fibre material layer in contact with each other. Foam members may be secured to each other and/or the first fibre material layer using adhesive. The adhesive maybe chemically compatible with the polymeric resin.

The first and second fibre material layers may include woven fibre cloths. Woven fibre cloths may be woven according to a 2x2 fibre twill pattern or a plain weave pattern.

The first and second fibre material layers may include fibre felts. The first and second fibre material layers may include stitched fibre fabrics.

Thus, the first and second fibre material layers may be easily handled and will substantially conform to the shape(s) of the foam member(s) and the first mould tool under their own weight.

The first and second fibre material layers may be flexible. The first and second fibre material layers may be made from the same materials. The second fibre material layer may have different dimensions to the first fibre material layer. The fibres of the first and second fibre material layers may be treated to improve wettability and/or adhesion by the polymeric resin.

-3The method may also include evacuating the mould prior to and/or concurrently with injection of the polymeric resin.

This can help to reduce the number and/or size of voids.

The first and/or second fibre material layers may include woven fibre cloths, stitched fibre fabrics or fibre felts which include a layer or web of thermoplastic material. The method may also include thermoforming the first and/or second fibre material layers to conform to one or more foam members.

Thus, non-contact regions (that is, regions in which the second fibre material layer is intended to contact the foam member(s) but does not) may be reduced in volume or eliminated. This can help to reduce the chance of fibre bunching and or resin rich voids in a resulting composite article.

The layer or web of thermoplastic material may allow a woven fibre cloth or fibre felt to retain a shape. Thermoforming may include moulding the first and/or second fibre material layers to conform to one or more pre-form moulds having the same or similar shape as the foam member(s). Thermoforming may include moulding the first and/or second fibre material layers to conform to one or more surfaces of the first and/or second mould tools. Thermoforming may include vacuum moulding. Pre-form moulds may be made from materials exhibiting minimal shape changes under thermoforming conditions. Pre-form moulds maybe made from wood. Pre-form moulds maybe made from re-constituted wood such as medium density fibreboard. Pre-form moulds may be made from aluminium or steel.

The first fibre material layer may include two or more pieces of woven fibre cloth, stitched fibre fabric or fibre felt. The first fibre material layer may include two or more substantially identical pieces of woven fibre cloth, stitched fibre fabric or fibre felt arranged on top of each other. The first layer of fibre material may include two or more pieces of woven fibre cloth, stitched fibre fabric or fibre felt arranged to partially overlap each other. Each separate piece of woven cloth fibre, stitched fibre fabric or fibre felt may have the same or different dimensions.

-4The second fibre material layer may include two or more pieces of woven fibre cloth, stitched fibre fabric or fibre felt. The second fibre material layer may include two or more substantially identical pieces of woven fibre cloth, stitched fibre fabric or fibre felt arranged on top of each other. The second layer of fibre material may include two or more pieces of woven fibre cloth, stitched fibre fabric or fibre felt arranged to partially overlap each other. Each separate piece of woven cloth fibre, stitched fibre fabric or fibre felt may have the same or different dimensions.

The method may also include providing one or more further foam members and one or 10 more further fibre material layers and arranging them over the second fibre material layer. At least a portion of each fibre material layer may be separated from an adjacent fibre material layer by a foam member.

Thus, composite articles including internal supports made from fibre-reinforced resin may be fabricated in a single matrix injection and curing operation.

One or both of the first and second mould tools may be shaped to conform to one or more foam members.

The first and second mould tools may include respective first and second interior surfaces providing interior surfaces of the mould. The first and second interior surfaces may define the geometry of the composite article. The first and second fibre material layers and foam member(s) may be compressed between the first and second interior surfaces. The first and second mould tools may be clamped together. The first and second mould tools may be formed from steel.

The method may include treating the first and second interior surfaces with a release agent before providing the first fibre material layer.

The first and/or second mould tools may include one or more inlet ports for injecting polymeric resin. The first and/or second mould tools may include one or more outlet ports. Air or other gases may be pumped out of the mould through the outlet port(s).

Air or other gases may be vacuum pumped out of the mould through the outlet port(s). Air or other gases displaced by the introduction of the resin may escape the mould through the outlet port(s).

-5The method may include, following curing of the polymeric resin, trimming the resulting cured assembly to remove excess fibre composite and/or resin materials.

The foam member(s) may be expanded polypropylene. The foam members may be 5 polyurethane foam. The foam members may be expanded polystyrene. Each foam member may be formed directly into the required shape. Each foam member may be produced by casting into a mould. Each foam member may be produced by expansion to fill a mould. Each foam member may be machined from polymeric foam material

The polymeric resin may be a phenolic resin. The polymeric resin may be a polyester resin. The polymeric resin may be a vinylester resin. The polymeric resin may be an epoxy resin.

The polymeric resin may include short fibre segments. Short fibre segments may include chopped fibres and/or fibre whiskers. Short fibre segments may include carbon fibres, glass fibres, aramid fibres, silicon carbide fibres, cellulose fibres, nitrocellulose fibres and/or ultra-high molecular weight polyethylene fibres. Short fibre segments may have an aspect ratio of less than or equal to too, less than or equal to 500, or less than or equal to 1000.

The first and second fibre material layers may include carbon fibres. The first and second fibre material layers may include glass fibres. The first and second fibre material layers may include aramid fibres. The first and second fibre material layers may include silicon carbide fibres. The first and second fibre material layers may include cellulose fibres. The first and second fibre material layers may include nitrocellulose fibres. The first and second fibre material layers may include ultra-high molecular weight polyethylene fibres. The first and second fibre material layers may include natural fibres. The first and second fibre material layers may include silk fibres. The first and second fibre material layers may include flax fibres.

According to a second aspect of the invention there is provided a composite article fabricated using the method.

According to a third aspect of the invention, there is provided a composite article including one or more foam members. Each foam member includes expanded

-6polypropylene. The composite article also includes a shell including resin impregnated fibres. The shell partially or fully encapsulates the foam member.

The resin may be phenolic resin. The resin may be polyester resin. The resin may be vinylester resin. The resin may be epoxy resin.

The fibres may include carbon fibres. The fibres may include glass fibres. The fibres may include aramid fibres. The fibres may include silicon carbide fibres. The fibres may include cellulose fibres. The fibres may include nitrocellulose fibres. The fibres may include ultra-high molecular weight polyethylene fibres. The fibres may include natural fibres. The fibres may include silk fibres. The fibres may include flax fibres.

The composite article may be a seat, or a part of a seat. The composite article may be a building structure or a part of a building structure. The composite article may be a part of an automobile. The composite article may be automobile bodywork. The composite article maybe an automobile bumper. The composite article maybe a structural part of an automobile. The composite article maybe a part for an aircraft. The composite article maybe a curved panel.

-ΊBrief Description of the Drawings

Certain embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings in which:

Figure l is a projection view of a composite article;

Figure 2 is a partial cut-away projected view of the composite article shown in Figure l; Figure 3 is a top view of a composite article;

Figure 4 is a cross-section along the line A-A’ shown in Figure 3;

Figure 5 is a process flow diagram of a first method of fabricating a composite article; Figures 6 to 10 illustrate fabricating a composite article using a first method of fabricating a composite article;

Figure 11 is a cross-sectional view of a composite article fabricated using the first method of fabricating a composite article;

Figure 12 illustrates a thermo-formable fibre cloth;

Figure 13 illustrates a thermo-forming process;

Figure 14 illustrates a preformed fibre cloth;

Figure 15 illustrates the first method of fabricating a composite article modified to include a preformed fibre material layer;

Figure 16 is a process flow diagram of a second method of fabricating a composite article;

Figure 17 is a projection view of a second composite article;

Figures 18 to 22 illustrate fabricating a second composite article according to the second method of fabricating a composite article; and

Figures 23 to 24 illustrate using fibre material strips in a first or second method of fabricating a composite article.

Detailed Description of Certain Embodiments

In the following description, like elements may be denoted by the same reference numerals.

Referring to Figures 1 to 4, a composite article 1 is shown which includes one or more foam members 2 and a shell 3 formed of resin impregnated fibres. The shell 3 partially or fully encapsulates the foam member(s) 2.

The foam members 2 (which may also be referred to as “foam cores” or “foam inserts”) are made from closed cell polymeric foam materials. Preferably, the foam members 2 are made from closed cell polymeric foam which may be formed directly into the

-8required shape, so that machining of the foam members 2 is not required. For example, the foam members 2 may be cast into, or expanded to fill, a mould. The foam members 2 may be made from expanded polypropylene. Expanded polypropylene can be easily and directly formed into a desired shape without any need for machining.

Expanded polypropylene may be low density, with reasonable stiffness, and is closed cell to prevent ingress of resin into the foam itself. Polypropylene tends to be a cheap and readily available material, and is chemically compatible with common resins, such as phenolic resins. Two materials may be chemically compatible if they do not adversely affect the structure and/or chemical composition of one other when placed in contact. For example, a polymeric foam is chemically compatible with a resin if the resin does not dissolve or react with the polymeric foam when the resin is liquid (uncured).

Alternatively, the foam members 2 may take the form of other materials such as, for example, polyurethane, polystyrene, or melamine foam.

The fibres included in the shell 3 maybe carbon fibres. Alternatively, any other suitable fibres may be used such as, for example, glass fibres, aramid fibres, silicon carbide fibres, cellulose fibres, nitrocellulose fibres or ultra-high molecular weight polyethylene fibres. Alternatively, fibres maybe natural fibres such as, for example, silk or flax fibres. The choice of fibres may depend on the application. For example, when fire resistance is required, aramid fibres may be selected. For example, glass fibres may be preferred for boat hulls.

The resin used to form the shell 3 may be a phenolic resin. However, any suitable thermosetting polymeric resin which is chemically compatible with the fibres and foam member 2 may be used instead of phenolic resin such as, for example, polyester, vinylester or epoxy resin systems.

The composite article 1 may take the form of a foam member 2 having a frustorectangular pyramid shape. The foam member 2 is completely encapsulated by the shell 3. The composite article 1 may have a substantially uniform cross-section and extend in a direction perpendicular to the cross section. In other examples, a portion of a foam member 2 may not be covered by the shell 3. For example, a foam member 2 may be exposed to the exterior or, alternatively, some regions of a foam member 2 may

-9be covered by the resin impregnated fibre shell 3 and other regions of that foam member may be covered by resin.

The composite article may be used for application including, but not limited to, seats or 5 portions of seats for aeroplanes or other vehicles; structural panels of buildings, cars or other vehicles; curved panels and/or car bumpers. In general, the composite article may be useful for any application in which it would be desirable to reduce the mass of a component whilst maintaining or improving the rigidity of the component.

First method of fabricating a composite article

Referring also to Figures 5 and 6, a first fibre material layer 4 is provided by arranging the first fibre material layer 4 on a first mould tool 5 (sometimes also referred to as a “mould plate”) (step Si). The first fibre material layer 4 is flexible. The first layer of fibre material 4 may be in the form of one or more sheets of pieces of woven fibre cloth.

For example, the first fibre material layer 4 may include one, two or more substantially identical pieces of woven fibre cloth laid on top of each other. Alternatively, the first layer of fibre material 4 may include two or more pieces of woven fibre cloth which partially overlap each other. Each separate piece of woven cloth fibre may have the same or different dimensions. Each separate piece of woven cloth fibre may be formed using a different weave style or pattern such as, for example, 2x2 fibre twill or a plain weave. The first layer of fibre material 4 may include fibres having different diameters. For example, a first piece of woven fibre cloth may include fibres of a first diameter and a second piece of woven fibre cloth may include fibres of a second diameter.

The first mould tool 5 has an interior surface 6 which may take the form of a substantially flat plate. The first mould tool 5 may have side walls 7 projecting perpendicularly from the interior surface 6. The side walls 7 can help with positioning and retaining the first layer of fibre material 4. The first mould tool includes sealing means 8 for cooperating with a second mould tool 9 (Figure 9). The sealing means 8 may take the form of, for example, an O-ring 8 received into a corresponding groove in the first mould tool 5. The first mould tool 5 may include one or more inlet ports 10 extending from the interior surface 6 through the first mould tool 5. The inlet port(s) need not be provided through the first mould tool, and may instead be provided through the second mould tool 9. The interior surface 6 of the first mould tool 5 maybe treated with a release agent (not shown) before arranging the first fibre material layer 4·

- 10 Referring also to Figure 7, one or more foam member(s) 2 are provided by arranging the foam member(s) 2 onto an upper surface 11 of the first fibre material layer 4 (step S2). The foam member(s) 2 are made from closed-cell polymeric foam materials. For example, the foam members(s) 2 may comprise expanded polypropylene. When more than one foam member 2 is used, each foam member 2 may have the same shape or some foam members 2 may have different shapes. When more than one foam member 2 is used, each foam member 2 is arranged at a different position on the first fibre material layer 4. Two or more foam members 2 may be arranged on the first fibre material layer 4 in contact with each other. Foam members 2 may be temporarily secured to the first fibre material layer 4 and/or each other using adhesive. Each foam member 2 is pre-formed to a desired shape, for example, by casting or forming the foam member 2 in a mould (not shown).

Referring also to Figure 8, a second fibre material layer 12 is provided by arranging the second fibre material layer 12 over the first fibre material layer 4 and the foam member(s) 2, so as to partially or fully cover the foam member(s) 2 (step S3). The second fibre material layer 12 is made from substantially the same materials as the first fibre material layer 4, but may have different dimensions. The second fibre material layer 12 is flexible. The second fibre material layer 12 may be in the form of one or more sheets of pieces of woven fibre cloth. For example, the second fibre material layer 12 may include one, two or more substantially identical pieces of woven fibre cloth laid on top of each other. Alternatively, the second layer of fibre material 12 may include two or more pieces of woven fibre cloth which partially overlap each other. Each separate piece of woven cloth fibre may have the same or different dimensions. The second fibre material layer 12 may have larger dimensions than the first fibre material layer 4 in one or two directions, in order to account for the extra material associated with the second fibre material layer 12 conforming to the foam member(s) 2.

Referring also to Figure 9, a mould 13 is completed by placing the second mould tool 9 over the first mould tool 5 and the arrangement of the first and second fibre material layers 4,12 and foam member(s) 2 (step S4). The second mould half 9 has an interior surface 14 which conforms to the foam member(s) 2. The sealing means 8 form a seal between the first and second mould tools 5, 9 which is at least liquid tight and preferably airtight. The second mould tool 9 includes one or more risers or outlet ports

15. The risers or outlet ports 15 extend from the interior surface 14 through the second

- 11 mould tool 9. The outlet port(s) 15 need not be provided through the second mould tool 9, and may instead be provided through the first mould tool 5. The interior surface 14 of the second mould tool 9 may be treated with a release agent (not shown) before completing the mould 13.

The interior surfaces 6,14 of the first and second mould tools 5, 9 define the exterior geometry of the composite article. The first and second fibre material layers 4,12 and foam member(s) 2 are held relative to one another between the interior surfaces 6,14. The first and second fibre material layers 4,12 and foam member(s) 2 may be compressed between the interior surfaces 6,14. The first and second mould tools 5, 9 may be clamped together or otherwise kept in contact by externally applied forces. The first and second mould tools 5, 9 are formed from strong, rigid materials such as steel.

Optionally, the mould 13 may be pre-evacuated by pumping air 16 out through the output port(s) 15 (step S5).

Polymeric resin 17 in introduced into the mould 13 under pressure through the inlet port(s) 10 to infiltrate the first and second fibre material layers 4,12 and fill the spaces between fibres making up the first and second fibre material layers 4,12 (step S6). The polymeric resin 17 may take the form of phenolic resin. The fibres of the first and second fibre material layers 4,12 maybe treated to improve wettability and/or adhesion by the resin 17. Air 16 or other gases displaced by the introduction of the resin 17 may escape the mould through the outlet port(s) 15, either naturally or under pumping. Any voids or other “dead space” are filled by the resin 17. Voids or “dead space” correspond to volumes between the interior surfaces 6,14 which are unfilled by the first and second fibre material layers 4,12 or the foam member(s) 2.

The resin 17 is left to cure, either under ambient conditions or at an elevated temperature (step S7). The particular curing profile of time and temperature depend the resin 17 used, and also on an amount of catalyst or hardener which is added. When the resin is phenolic resin, the curing procedure involves heating the mould 13 for between several minutes and several hours inclusive, at a temperature within a range between 30 °C and 200 °C. For example, using a between three and five weight percent of catalyst, a phenolic resin may be cured in about 6 minutes and 40 seconds be heating the mould to 80 degrees Celsius, corresponding to a rein 17 temperature of 35 degrees

- 12 Celsius. The mould 13 remains sealed until the resin 17 has cured. The mould 13 may be continuously evacuated during the curing process.

Following resin curing (step S7), the cured assembly 18 of the resin 17 impregnated first 5 and second fibre material layers 4,12 and foam member(s) 2 may be extracted from the mould 13 by releasing the first and second mould tools 5, 9. The cured assembly 18 includes the shell 3, and depending on the mould 13 and foam member 2 geometries, extraneous composite and/or resin 19. If the cured assembly 18 includes extraneous composite and/or resin 19, then this is trimmed (step S8) to finish the composite article 1. Alternatively, if the cured assembly 18 does not include extraneous composite and/or resin 19, then the cured assembly 18 maybe the composite article 1.

Composite articles produced according to the first method may be light because the interior volume is filled with low density, foamed polymeric material 2, for example expanded polypropylene, yet stiff because of the shell 3 of fibre-resin composite.

In this way, a composite article 1 may be formed in a simple process without the need for complex and time consuming fibre lay-up processes. The first method of fabricating is particularly well suited to large scale fabrication of composite articles 1, since the processes of placing the first fibre material layer 4, foam member(s) 2 and second fibre material later 12 are simple, and may be readily automated using a robotic arm. Additionally, the single stage resin injection followed by curing is well suited to either continuous line or batch production. Thus, among other advantages, the first method of fabricating allows the efficiency of fabricating composite articles to be improved.

As hereinbefore described, the interior surface 6 of the first mould tool 5 is substantially flat and the interior surface 14 of the second mould tool 9 conforms to the foam member(s) 2. Alternatively, the interior surface 6 of the first mould tool 5 may conform to the foam member(s) 2 and the interior surface 14 of the second mould tool

9 may be substantially flat. For some geometries of composite article 1, both interior surfaces 6,14 of both mould tools 4, 9 may conform to the foam member(s) 2.

The interior surface 6 of the first mould tool 5 may conform to the foam member(s) 2, since this will assist the accuracy and reproducibility of placing the foam member(s) 2 in the mould 13.

-13The first method of fabricating a composite article is not limited to simple shapes or shapes having one flat surface. Both interior surfaces 6,14 of both mould tools 4, 9 may conform to the foam member(s) 2, allowing manufacture of composite articles having any complex shape for which mould tools may be provided so as to allow extraction of the cured assembly 18 or composite article 1.

Woven fibre cloths providing the first and second fibre material layers 4,12 may use any known weave pattern such as, for example, 2x2 fibre twill or a plain weave.

The first and second fibre material layers 4,12 need not be made from woven fibre cloth. Alternatively, the first and second fibre material layers 4,12 maybe made from fibre felts. The first and second fibre material layers 4,12 may take any form with is sufficiently flexible to conform to the foam member(s) 2.

The first and second fibre material layers 4,12 may be made from stitched fibre fabrics. Stitched fibre fabrics take the form of bundles of fibres held together by stitches of a thread/fibre. Stitched fibre fabrics may include bundles of fibres arranged in one or more directions such as, for example, uni-axial, bi-axial or tri-axial stitched fibre fabrics.

The fibres forming the first and second fibre material layers 4,12 may be carbon fibres. Alternatively, any other suitable fibres may be used such as, for example, glass fibres, aramid fibres, silicon carbide fibres, cellulose fibres, nitrocellulose fibres or ultra-high molecular weight polyethylene fibres. The choice of fibres may depend on the application. For example, when fire resistance is required, aramid fibres may be selected.

The flexibility of the first and second fibre material layers 4,12 allows them to conform to the foam member(s) and/or the interior surfaces 6,14 of the first and second mould tools 5, 9.

The polymeric resin 17 need not take the form of phenolic resin and other resin systems maybe used such as, for example, polyester, vinylester or epoxy resin systems. The polymeric resin 17 injected into the mould 13 may additionally include additional reinforcements in the form of short fibre segments (not shown) such as, for example, chopped segments or carbon or glass fibre or whiskers or silicon carbide. When short

-14fibre segments are included in the polymeric resin 17 for injection, the volume fraction and lengths of short fibre segments should be low enough to prevent the inlet port 10 from becoming clogged.

Referring again to Figure 8, when the first and second fibre material layers 4,12 are simply draped, there will be non-contact regions 20 in which the first and second fibre material layers 4,12 lose contact from the foam member(s) 2 and/or the interior surfaces 6,14. Non-contact regions 20 may develop even when the first and second fibre material layers 4,12 have minimal stiffness. Non-contact regions 20 are generally not problematic, because intimate contact between first and second fibre material layer 4,12 and foam member(s) 2 is established once the mould 13 is closed, especially when the interior surfaces 6,14 compress the first and second fibre material layer 4,12 and foam member(s) 2. However, in certain geometries there may be a risk of bunching and/or voids developing in the non-contact regions 20 when the mould 13 is closed.

Referring also to Figure 12, non-contact regions 20 may be reduced or prevented by using a thermo-formable fibre cloth 21 to provide the first and/or second fibre material layers 4, 9. Each of the first and/or second fibre material layers 4, 9 may include one or more pieces of thermo-formable fibre cloth 21.

The thermo-formable fibre cloth 21 is made up of a woven fibre cloth 22 and a layer or web of thermoplastic material 23. The thermoplastic material 23 allows the thermoformable fibre cloth 21 to retain its shape compared to the woven fibre cloth 22 alone. The layer or web of thermoplastic material 23 may be disposed on a surface of the woven fibre cloth 22.

Referring also to Figure 13, the thermo-formable fibre cloth 21 maybe pre-shaped before being used to fabricate a composite article. One or more pre-form moulds 24 are placed on a gas permeable surface 25. The pre-form moulds 24 are made from rigid materials which will not substantially deform during the thermo-forming process, such as, for example, wood, steel or aluminium. The pre-form moulds 24 have the same shape as the foam member(s) and/or interior surfaces 6,14 to which it is desired the thermo-formable fibre cloth 21 should conform.

One or more layers or pieces of thermo-formable fibre cloth 21 are draped over the preform mould(s) 24. The thermo-formable fibre cloth 21 is less flexible than the woven

-15fibre cloth 22 alone, but flexible enough to at least partially conform to the shape of the pre-form mould(s) 24. Non-contact regions 20 can form at edges or in regions where the curvature of a surface of a pre-form mould 24 exceeds the curvature of the thermoformable fibre cloth 21 due to loading by its own weight. Non-contact regions 20 can also form where a surface of the pre-form mould 24 meets the gas permeable surface 25 at an angle.

A rigid rim 26 has a resilient elastic membrane 27 stretched across it. The membrane 27 is substantially gas impermeable. The membrane 27 is made from natural or synthetic rubber, silicone rubber or materials with similar properties of elasticity and resilience. The rim 26 is brought into contact with the gas permeable surface 25 and extends entirely around the perimeter of the assembly of the thermo-formable fibre cloth 21 and pre-form mould(s) 24. The elastic membrane 27 is placed in tension by the assembly of the thermo-formable fibre cloth 21 and pre-form mould(s) 24.

Air 16 is evacuated from the volume enclosed by the membrane 27 and through the gas permeable surface 25. This sucks the elastic membrane 27 against the thermoformable fibre cloth 21 which is in turn pressed against the pre-form mould(s) 24 and the gas permeable surface 25 to reduce the size of non-contact regions 20. A heat source 28, for example a heat lamp, is applied to soften or melt the thermoplastic layer or web 23. Once the thermoplastic layer or web 23 has softened or melted, the noncontact regions 20 maybe further reduced to small, residual volumes or eliminated.

The evacuation is maintained whilst the heat source 28 is switched off and the thermoplastic material cools. Several layers of thermo-formable fibre cloth 21 may be thermoformed in the same operation for use in preparing a thicker first or second fibre material layer 4,12.

Referring also to Figure 14, a preformed fibre cloth 29 can substantially maintain the desired shape when removed from the pre-form mould(s) 24.

If the thermoplastic layer or web 23 was merely softened during the thermoforming, then a layer or web 23 of thermoplastic material may lie on the surface. However, if the thermoplastic layer or web 23 melted, then it may have been absorbed by the fibres of the woven fibre cloth 22. When the fibres of the woven fibre cloth absorb otherwise become embedded in the thermoplastic, the preformed fibre cloth 29 may be stiffer

- ιόthan the thermo-formable fibre cloth 21, because the ability of fibres to move relative to one another has been reduced.

The thermoforming method may equally be applied to a thermo-formable fibre felt (not 5 shown) including a fibre felt (not shown) and a layer or web (not shown) of thermoplastic material.

Referring also to Figure 15, a second fibre material layer 12 in the form of a preformed fibre material layer 30 made from one or more preformed fibre cloths 29 or preformed fibre felts (not shown), may be used in fabricating a composite article 1 using the hereinbefore described method. The main difference is that with the reduction or elimination of non-contact regions 20, the probability of forming voids or fibre bunching may be substantially reduced when the first and second mould tools 5, 9 are brought together. Either or both of the first and second fibre material layers 4,12 may take the form of a preformed fibre material layer 30.

Second method of fabricating a composite article

In some applications, for example large area panels such as automobile bodywork panels, the mechanical properties of a composite article 1 maybe improved by including internal ribs, struts or other supports.

Referring to Figure 16, a second method of fabricating a composite article may be used to produce a second composite article 31 (Figure 17) which includes internal composite supports 32a, 32b. The second method is an adaptation of the first method.

Referring also to Figure 17, a second composite article 31 may include foam members 2a, 2b, 2c which are partially encapsulated by a composite shell 3. A first composite support 32a separates first and second foam members 2a, 2b, and a second composite support 32b separates first and third foam members 2a, 2c. The first and second composite supports 32a, 32b increase the rigidity of the second composite article 31 and may help to prevent bowing of the shell 3 due to compression of an underlying foam member 2 when a force is applied to a surface of the second composite article 31.

A first fibre material layer 4 may be provided by arranging the first fibre material payer

4 on a first mould tool 5 (step S9), in substantially the same way as for the first method (step Si). One or more foam members 2 may be provided by arranging the foam

-17members 2 on the first fibre material layer 4 (step S10), in substantially the same way as for the first method (step S2). For example, referring also to Figure 18, a first foam member 2a may be placed on the first fibre material layer 4. The first foam member 2a is a trapezoidal prism having a cross section which is a trapezium having long and short parallel sides 33, 34 connected by first and second inclined sides 35a, 35b having equal lengths. The sides 33, 34, 35a, 35b of the trapezium extend to form corresponding surfaces of the first foam member 2a. The long side surface 33 of the first foam member 2a rests on the first layer of fibre material 4.

A second fibre material layer 12 is provided by arranging the second fibre material layer 12 onto the first fibre material layer 4 and the foam member(s) 2, so as to partially or fully cover the foam member(s) 2 (step S11), in substantially the same way as for the first method (step S3). For example, referring also to Figure 19, a second fibre material layer 12 in the form of a preformed fibre material layer 30 is arranged over the first fibre material layer 4 and the first foam member 2a. The second fibre material layer 12 is preformed to conform to the short side surface 34 and the inclined side surfaces 35a, 35b of the first foam member 2a.

If no further fibre material layers and foam members 2 are to be included in a composite article (step S12), then the mould 13 is completed and polymeric resin injected and cured in the same way as for the first method (steps S13 to S17, corresponding to steps S4 to S8).

However, if further fibre material layers and foam members 2 are to be included (step

S12), then one or more further foam members 2 are provided by arranging the further foam members 2 onto the second fibre material layer 12 (step S18). For example, referring also to Figure 20, second and third foam members 2b, 2c in the form of trapezoidal prisms are placed onto the preformed second fibre material layer 12. Each of the second and third foam members has a cross section which is a trapezium having long and short parallel sides 36,37, one perpendicular side 38 making a right angle with both long and short sides 36, 37 and one inclined side 39. The sides 36,37,38,39 the trapezium providing the cross section of the second foam member 2b extend to form corresponding surfaces of the second foam member 2b. The surfaces of the third foam member 2c are defined in a similar way.

-18The inclined side surfaces 39 of second and third foam members 2b, 2c make an angle with the corresponding long side surfaces 36 which is equal to an angle made between either inclined side surface 35a, 35b of the first foam member 2a and the corresponding long side surface 33.

The second foam member 2b is arranged with the short side surface 37 and the inclined side surface 39 in contact with the preformed second fibre material layer 12. The inclined side surface 39 of the second foam member 2b is arranged parallel to the first inclined side surface 35a of the first foam member 2a, such that the inclined side surfaces 39, 35a oppose each other across the preformed second fibre material layer 12. The third foam member 2c is arranged in a similar way to second foam member 2b, with inclined side surface 39 of the third foam member 2c arranged parallel to the second inclined side surface 35a of the first foam member 2a and on opposite sides of the preformed second fibre material layer 12.

The portion of the preformed second fibre material layer 12 which is sandwiched between the inclined side surfaces 35a, 39 of the first and second foam members 2a, 2b will become the first support 32a of the second composite article 31. Similarly, the portion of the preformed second fibre material layer 12 which is sandwiched between the inclined side surfaces 35b, 39 of the first and third foam members 2a, 2c will become the second support 32b of the second composite article 31.

A third fibre material layer 40 is provided by arranging the third fibre material layer 40 over the second fibre material layer 12 so as to so as to partially or fully cover the foam member(s) 2 arranged on the second fibre material layer 12 (step S19). For example, referring also to Figure 21, a third fibre material layer 40 in the form of a preformed fibre material layer 30 may be arranged to cover second and third foam members 2b,

2c. The preformed third fibre material layer 40 is preformed to conform to the second and third foam members 2b, 2c and a portion of the second fibre material layer 12 which lies between the long side surfaces 36 of the second and third foam members 2b, 2C.

-19However, if further fibre material layers and foam members 2 are to be included (step S12), then one or more further foam members 2 are provided be arranging the further foam members 2 onto the third fibre material layer 40 (step S18), and a fourth fibre material layer (not shown) is provided and arranged to fully or partially cover the foam members 2 supported on the third fibre material layer 40 (step S19). Further foam members 2 and further fibre material layers (not shown) may be repeatedly added in this way (steps S18, S9 and S20), with at least a portion of each subsequent fibre material layer separated from a previous fibre material layer by a foam member 2. In this way, composite articles having multiple internal composite supports 32 may be fabricated in a single resin injection and curing process.

The inlet and outlet ports 10,15 to the mould 13 may be arranged on the first and second mould tools 5, 9 so as to enhance polymeric resin 17 infiltration through portions of fibre material layers 4,12,30, 40 which are sandwiched between foam members 2.

Referring also to Figure 22, an inlet port 10 for injecting polymeric resin 17 may connect to a resin runner 10b running around the perimeter of the mould 13. An outlet port or ports 15, through which air 16 is evacuated may be arranged though either the first mould plate 5 or the second mould plate 9.

Although the second method of fabricating a composite article has been described with reference to an example of the second composite article 31 which includes particularly shaped foam members 2a, 2b, 2c, the second method of fabricating a composite article may be used to produce composite articles 1 having any shape and including any number of foam members 2, provided that fibre material layers 4,12, 30, 40 sandwiched between foam members 2 may be infiltrated with polymeric resin 17. In particular, the second method is not restricted to forming prismatic composite articles using prismatic foam members 2.

Modifications

It will be appreciated that many modifications may be made to the embodiments hereinbefore described. Such modifications may involve equivalent and other features which are already known in the design, manufacture and use of composite articles and which may be used instead of or in addition to features already described herein.

- 20 Features of one embodiment maybe replaced or supplemented by features of another embodiment.

The first layer of fibre material 4 need not be made from a woven fibre cloth. Instead, the first layer of fibre material 4 may be made from one or more pieces of fibre felt.

Edges, vertices and corners of foam members 2, mould tools 5, 9 or pre-form moulds 24 may be rounded, chamfered or bevelled to assist the conformance of fibre material layers 4,12,30.

When two surfaces of a foam member 2, mould tool 5, 9 or pre-form mould 24 meet at an edge, the conformance of a fibre material layer4,12,30 is typically not problematic. When three surfaces of a foam member 2, mould tool 5, 9 or pre-form mould 24 meet at a vertex or corner, further consideration may be required. When the angles between the three surfaces are obtuse and/or when the vertex or corner is rounded, chamfered or bevelled, the first or second methods may not encounter problems. However, for sharper vertices or corners, simply draping a fibre material layer 4,12, 30 may result in unwanted bunching of fibre material. Such bunching may be avoided by using strips of fibre material or pre-formed strips 41a, 41b of fibre material.

For example, referring also to Figures 23 and 24, a first pre-formed strip 41a is preformed to cover a top surface 42 and first and second, opposed side surfaces 43, 44 of a cuboidal foam member 45. A second pre-formed strip 41b is pre-formed to cover the top surface 42 and third and fourth opposed side surfaces 46,47 of the cuboidal foam member 45. Discontinuities, along the edges between, for example, first and third side surfaces 43, 46 may be reinforced with fibre material using additional pre-formed strips which fold over the edge between the first and third side surfaces 43, 46. Fibre strips 41a, 41b may be employed in the first or second methods.

Although claims have been formulated in this application to particular combinations of features, it should be understood that the scope of the disclosure of the present invention also includes any novel features or any novel combination of features disclosed herein either explicitly or implicitly or any generalization thereof, whether or not it relates to the same invention as presently claimed in any claim and whether or not it mitigates any or all of the same technical problems as does the present invention. The applicant hereby gives notice that new claims may be formulated to such features

- 21 and/or combinations of such features during the prosecution of the present application or of any further application derived therefrom.

Claims

Claims

l. A method of fabricating a composite article, comprising: providing a first fibre material layer on a first mould tool;

5 providing one or more foam members on the first fibre material layer, the foam member(s) comprising closed-cell polymeric foam;

providing a second fibre material layer to at least partially cover each foam member;

providing a second mould tool to form a seal with the first mould tool, wherein a io mould formed by the first and second mould tools holds the first and second fibre material layers and the foam member(s) relative to one another; and injecting a polymeric resin into the mould to infiltrate the first and second fibre material layers.

15
2. A method according to claim 1, wherein the first and second fibre material layers comprise woven fibre cloth.
3. A method according to claim 1, wherein the first and second fibre material layers comprise fibre felts.
4. A method according to claim 1, wherein the first and second fibre material layers comprise stitched fibre fabric.
5. A method according to any preceding claim, further comprising evacuating the 25 mould prior to and/or concurrently with injection of polymeric resin.
6. A method according to any preceding claim, wherein the first and/or second fibre material layers comprise woven fibre cloth, stitched fibre fabric or fibre felts, the first and/or second fibre material layers further comprising a layer or web of

30 thermoplastic material, the method further comprising:

thermoforming the first and/or second fibre material layers to conform to one or more foam members.
7. A method according to any preceding claim, wherein the first fibre material 35 layer comprises two or more pieces of woven fibre cloth, stitched fibre fabric or fibre felt.

-238. A method according to any preceding claim, wherein the second fibre material layer comprises two or more pieces of woven fibre cloth, stitched fibre fabric or fibre felt.
9. A method according to any preceding claim, further comprising: providing one or more further foam members and one or more further fibre material layers and arranging the further foam member(s) and further fibre material layers over the second fibre material layer;

io wherein at least a portion of each fibre material layer is separated from an adjacent fibre material layer by a foam member.
10. A method according to any preceding claim, wherein one or both of the first and second mould tools is shaped to conform to one or more foam members.

it. A method according to any preceding claim, wherein the foam member(s) comprise expanded polypropylene.
12. A method according to any preceding claim, wherein the polymeric resin is a 20 phenolic resin.
13. A method according to any preceding claim, wherein the polymeric resin is a polyester resin.

25
14. A method according to any preceding claim, wherein the polymeric resin is a vi nylester resin.
15. A method according to any preceding claim, wherein the polymeric resin is an epoxy resin.
16. A method according to any preceding claim, wherein the polymeric resin comprises short fibre segments.
17. A method according to any one of claims 1 to 16, wherein the first and second 35 fibre material layers comprise carbon fibres.

-2418. A method according to any one of claims l to 16, wherein the first and second fibre material layers comprise glass fibres.
19. A method according to any one of claims 1 to 16, wherein the first and second 5 fibre material layers comprise aramid fibres.
20. A method according to any one of claims 1 to 16, wherein the first and second fibre material layers comprise silicon carbide fibres.

10
21. A method according to any one of claims 1 to 16, wherein the first and second fibre material layers comprise cellulose fibres.
22. A method according to any one of claims 1 to 16, wherein the first and second fibre material layers comprise nitrocellulose fibres.

15
23. A method according to any one of claims 1 to 16, wherein the first and second fibre material layers comprise ultra high molecular weight polyethylene fibres.
24. A method according to any one of claims 1 to 16, wherein the first and second fibre material layers comprise natural fibres.
25. A composite article fabricated using a method according to any preceding claim.
26. A composite article comprising:

at least one foam members, each foam member comprising expanded 25 polypropylene; and a shell comprising resin impregnated fibres, the shell partially or fully encapsulating the foam member.
27. A composite article according to claim 26, wherein the resin comprises phenolic 30 resin.
28. A composite article according to claim 26, wherein the resin comprises polyester resin.

35 29. A composite article according to claim 26, wherein the resin comprises vi nylester resin.

-2530. A composite article according to claim 26, wherein the resin comprises epoxy resin.

5 31. A composite article according to claim 26, wherein the resin comprises short fibre segments.
32. A composite article according to any one of claims 26 to 31, wherein the fibres comprise carbon fibres.
33. A composite article according to any one of claims 26 to 31, wherein the fibres comprise glass fibres.
34. A composite article according to any one of claims 26 to 31, wherein the fibres 15 comprise aramid fibres.
35. A composite article according to any one of claims 26 to 31, wherein the fibres comprise silicon carbide fibres.

20
36. A composite article according to any one of claims 26 to 31, wherein the fibres comprise cellulose fibres.
37. A composite article according to any one of claims 26 to 31, wherein the fibres comprise nitrocellulose fibres.
38. A composite article according to any one of claims 26 to 31, wherein the fibres comprise ultra high molecular weight polyethylene fibres.
39. A composite article according to any one of claims 26 to 31, wherein the fibres 30 comprise natural fibres.

Intellectual

Property

Office

Mr Darren Williams

13 March 2017

GB 1617004.5

1-25