Composite moulding techniques

Abstract

The present invention relates to a method of molding a component (1) having one or more features (5). At least one fibrous substrate (7) is located in a mold (31, 33). A matrix-forming material (29) is also provided in the mold (31, 33). Heat is applied to melt the matrix-forming material (29) to form a matrix (9) and to integrally mold said one or more features (5).

Claims

1. A method of molding a component having at least one feature, the method comprising: locating a first fibrous substrate in a mold, the mold including two recesses and the first fibrous substrate comprising a substrate matrix-forming material and a plurality of fibers; providing a feature-forming material in the mold, the feature forming material comprising a feature matrix-forming material; locating, in the mold, a second fibrous substrate at least partially overlapping the first fibrous substrate, wherein the feature-forming material is provided between the first and second fibrous substrates to form a core; and applying pressure to combine the first and second fibrous substrates and feature matrix-forming material to form a matrix and to integrally mold the at least one feature, wherein the mold comprises a first mold part comprising at least one of said recesses, whereby at least the feature matrix-forming material flows through one of the first and second fibrous substrates before flowing into the at least one recess during the application of pressure, and further wherein the feature matrix-forming material is provided as two or more discrete portions of material, each of said two or more discrete portions being positioned in the mold adjacent to a respective one of the recesses, and the feature-forming material forming the core between the first and second fibrous substrates further comprising a plurality of short fibers, wherein the short fibers are shorter than the plurality of fibers in the first fibrous substrate.

2. A method as claimed in claim 1, wherein the first and second fibrous substrates each comprises a plurality of fibers woven to form a sheet; and/or each fibrous substrate comprises a plurality of fibers arranged to form a uni-directional tape.

3. A method as claimed in claim 2, wherein said substrate matrix-forming material is the same material as the feature matrix-forming material.

4. A method as claimed in claim 1, wherein each of the first and second fibrous substrates is provided as a pre-consolidated sheet member.

5. A method as claimed in claim 1, wherein said feature-forming material is provided in the form of at least one ply.

6. A method as claimed in claim 1, wherein said feature-forming material is provided in the mold in a solid or a semisolid form.

7. A method as claimed in claim 1, wherein said feature-forming material comprises a polymer.

8. A method as claimed in claim 1, wherein the mold comprises a second mold part and wherein the pressure is applied by the second mold part.

9. A method as claimed in claim 1, wherein the pressure is applied by a vacuum bag.

10. A method as claimed in claim 8, wherein the second mold part comprises at least one recess, whereby at least the feature-forming material flows into the at least one recess.

11. A method as claimed in claim 8, further comprising cutting each fibrous substrate to size by closing the first and second mold parts.

12. A method as claimed in claim 1 further comprising the step of applying heat to melt the first and second substrates and/or feature matrix-forming fibers before or during the application of pressure.

13. A method as claimed in claim 1, wherein the plurality of fibers in the first fibrous substrate are natural or synthetic fibers.

14. A method as claimed in claim 1, wherein each of the plurality of short fibers in the feature-forming material are natural or synthetic fibers.

15. A method as claimed in claim 13, wherein the fibers are carbon fibers.

16. A method as claimed in claim 1, wherein the feature-forming material is provided in a quantity equivalent to the volume of the at least one recess.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying figures, in which:

(2) FIG. 1 shows a front perspective view of a moulded composite component formed using the method according to the present invention;

(3) FIG. 2 shows a rear perspective view of the composite component shown in FIG. 1;

(4) FIGS. 3 and 4 are images of the moulded composite component shown in FIGS. 1 and 2;

(5) FIGS. 5A and 5B show enlarged views of a yarn for forming the fibrous substrate used in the method according to the present invention;

(6) FIG. 6 shows a schematic representation of the lay-up arrangement for moulding the composite component;

(7) FIG. 7 shows sample woven materials that can be used in accordance with the present invention;

(8) FIG. 8 shows a schematic representation of the lay-up arrangement for moulding the composite component;

(9) FIG. 9 shows a schematic representation of the lay-up arrangement for moulding the composite component;

(10) FIG. 10 shows a schematic representation of the lay-up arrangement for moulding the composite component; and

(11) FIG. 11 shows a schematic representation of the lay-up arrangement for moulding the composite component.

DETAILED DESCRIPTION

(12) Detailed descriptions of specific embodiments of a method of moulding a component according to the present invention are disclosed herein. It will be understood that the disclosed embodiments are merely examples of the way in which certain aspects of the invention can be implemented and do not represent an exhaustive list of all of the ways the invention may be embodied. Indeed, it will be understood that the method of moulding a component described herein may be embodied in various and alternative forms. The Figures are not necessarily to scale and some features may be exaggerated or minimised to show details of particular components. Well-known components, materials or methods are not necessarily described in great detail in order to avoid obscuring the present disclosure. Any specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the invention.

(13) A method of moulding, in particular compression moulding, a composite component 1 in accordance with the present invention will now be described. FIGS. 1 and 2 show perspective views of the component 1; and images showing portions of the moulded component 1 are shown in FIGS. 3 and 4.

(14) As shown in FIGS. 1 and 2, the component 1 is semi-structural member for mounting on an interior of a motor vehicle door. The component 1 comprises a panel section 3 having a plurality of integrally moulded features (denoted generally herein by the reference numeral 5). The component 1 is formed from a fibrous substrate 7 held in a solid matrix 9. As shown in FIGS. 3 and 4, the features 5 are integrally moulded from the material which forms the matrix 9 in a single, contemporaneous process step. Detents and recesses can be formed in the panel section 3. In the present embodiment, the features 5 include (four) mounting brackets 11, (two) flanges 13, and (two) locating spigots 15. The features 5 could also include reinforcing ribs, ridges, bushes and the like.

(15) The substrate 3 in the moulded component 1 comprises two layers of fabric 17 each woven from a yarn 19. The yarn 19 is formed from a plurality of natural fibres 21 (such as flax) interspersed with thermoplastic, e.g. polypropylene polyester or polyamide, matrix-forming fibres 23, as shown in the cross-sectional view in FIG. 5A. To preserve the longitudinal strength of the natural fibres 21, the yarn 19 is wrap spun by supporting a central aggregate of natural fibres 21 and thermoplastic (e.g. polypropylene) fibres 23 inside a helically-wound outer fibre 25, as shown in FIG. 5B. The yarn 19 is woven to form each layer of fabric 17 in conventional manner and different weaving patterns can be employed to provide different mechanical properties in the substrate 3.

(16) The thermoplastic fibres 23 are provided in the yarn 19 to enable the layer of fabric 17 to be consolidated into a fibrous sheet 27 (i.e. a sheet containing fibres). In particular, heating the layer of woven fabric 17 causes the polypropylene fibres 23 to melt and bond the natural fibres 21 together thus forming a matrix. The application of pressure allows the layer of fabric 17 to be formed into the fibrous sheet 27. The distribution and alignment of natural fibres 21 in the fibrous sheet 27 is substantially uniform. Moreover, the fibrous sheet 27 is resilient and can be readily handled.

(17) The features 5, and all or part of the matrix 9, are formed from a feature-forming material comprising polypropylene and optionally a filler material, such as wood fibre or pulp. This material can, for example, be that which is supplied under the trade name Arbofill by TECNARO GmbH of Burgweg 5, D 74360 Ilsfeld-Auenstein, Germany. To facilitate handling, the feature-forming material in the present embodiment is supplied as a continuous feature-forming sheet 29. However, the sheet may be discontinuous as described below.

(18) The moulding process according to the present invention will now be described with reference to FIG. 6. The component 1 is formed in a compression mould comprising first and second cooperating mould parts 33, 31 each having profiled surfaces to define the component 1. Recesses (denoted generally by the reference numeral 35) are formed in the surfaces of the first and/or second mould parts 33, 31 to define the features 5.

(19) First and second fibrous sheets 27a, 27b and a feature-forming sheet 29 are positioned between the first and second mould parts 33, 31. The feature-forming sheet 29 is provided between the first and second fibrous sheets 27a, 27b to form a core. The first and second fibrous sheets 27a, 27b and the feature-forming sheet 29 can optionally be pre-heated before they are introduced into the mould.

(20) The first and second mould parts 33, 31 are brought together to compress the first and second fibrous sheets 27a, 27b and the feature-forming sheet 29, as illustrated by the arrows A in FIG. 6. The first and second mould parts 33, 31 have shearing edges which trim the fibrous sheets 27a, 27b and the sheet 29 to the required size when the mould is closed. The edge(s) of the fibrous sheets 27a, 27b could be held between the first and second mould parts 33, 31 to maintain the fibrous sheets 27a, 27b in position within the mould. The first and second fibrous sheets 27a, 27b conform to the profile of the first and second mould parts 33, 31, for example to form detents and ridges in the component 1. The mould is heated to reduce the viscosity of the matrix-forming material in the feature-forming material sufficiently to enable it to penetrate between the natural fibres 21 in the woven fabric 17 and flow into the recesses 35 in the first and/or second mould parts 33, 31. In the present embodiment the mould is heated to 180-200° C. to melt the polypropylene, but different temperature ranges may be suitable for different materials. By applying pressure to the first and second mould parts 33, 31, the flow of the molten polypropylene within the mould is promoted.

(21) The molten polypropylene impregnates the woven fabric 17 and flows into the recesses 35 formed in the surfaces of the first and second mould parts 33, 31. The polypropylene of the feature-forming material thereby forms the features 5 in a single process step. The filler material contained in the feature-forming sheet 29 can pass between the fibres in the woven fabric 17 and thereby travel through the first and second fibrous sheets 27a, 27b into the recesses 35. The flow of molten polypropylene within the mould thereby forms the features 5 integrally with the rest of the component 1 in a single process step. It is noted that the feature-forming material may be provided to aid formation of the matrix encapsulating the fibres of the fibrous substrate. Equally, some of the thermoplastic fibres in the fibrous substrate may move, during moulding, into the recesses and thus, in-part, form the features.

(22) The first and second mould parts 33, 31 are cooled and the moulded component 1 is removed. As shown in FIGS. 3 and 4, the mounting brackets 11 and the locating spigots 15 are formed integrally with the rest of the component 1. In the present embodiment, the features 5 are moulded at least substantially completely from polypropylene with a relatively small degree of penetration of the natural fibres 21. To provide further reinforcement for the features 5, additional natural fibres 21 could be provided proximal some or all of the recesses 35 in the first and second mould parts 33, 31.

(23) If necessary, the component 1 can be trimmed to remove excess material after it has been removed from the mould. For example, the component 1 can be trimmed to remove one or more sprues (not shown) provided in the first and/or second mould parts 33, 31 to enable excess polypropylene to be removed during the moulding process. In another example, the component may be trimmed to remove flashes (not shown).

(24) The present embodiment has been described with reference to pre-consolidated fibrous sheets 27a, 27b, but it will be appreciated that it is not essential that the woven fabric 17 is pre-consolidated. Rather, the woven fabric 17 could be introduced directly into the mould as a flexible material. This approach may, for example, be appropriate for mould parts having a larger draw. Similarly, it is not essential that the matrix-forming material is introduced into the mould in the form of a pre-consolidated fibrous sheet 27. For example, the matrix-forming material could be provided in a granular or powder form.

(25) To provide a smoother finish on the component 1, a surface film could be provided in the first and/or second mould parts 33, 31. The surface film could, for example, be provided on a surface of the component 1 which will be exposed in use (referred to as an A-surface).

(26) As mentioned above, the yarn 19 can be woven in different patterns to form the fabric 17. By way of example, three different samples of fabric 17a, 17b, 17c having different weaving patterns are shown in FIG. 7 alongside a pre-consolidated fibrous sheet 27. The different weave patterns arrange the natural fibres 21 in different orientations which can provide different mechanical properties in the moulded component 1.

(27) Furthermore, the angular orientation of the first and second fibrous sheets 27a, 27b within the mould can be offset to alter the mechanical properties of the moulded component 1. The pre-consolidated fibrous sheet 27 could be formed from more than one layer of fabric 17. The layers of fabric 17 could be aligned or angularly offset from each other. Different types of fibres could be used in different layers of fabric 17 or different fibrous sheets 27.

(28) Rather than use a woven fabric 17, an elongate tape consisting of aligned natural fibres 21 and/or synthetic fibres 23 could be used. The tape can be woven and optionally pre-consolidated in the same as the fabric 17.

(29) It will be appreciated that various changes and modifications can be made to the embodiment described herein without departing from the scope of the present invention.

(30) The invention has been described with reference to a woven fabric 17 having a uniform distribution of natural fibres 21. However, a non-uniform distribution of natural fibres 21 could be employed. The fabric 17 could be woven with a non-uniform distribution to provide localised reinforcement. Indeed, three dimensional weaving could be employed to provide enhanced material properties.

(31) The matrix-forming material can be provided in a variety of forms, for example powder, granules and sheet(s). Furthermore, a non-uniform distribution of matrix-forming material can be provided in the mould. For example, additional matrix-forming material can be provided proximal recesses 35 in the mould to form the features 5.

(32) The present invention has been described with reference to compression moulding techniques. Compression moulding techniques may be in the form of using the first mould part 33 and a second mould part 31. In view of the above description, the second mould part 31 may apply pressure (via arrows A) to the components to be moulded against the first mould part 33. The second mould part 31 may therefore be replaced by a bag whereby a vacuum compression method is used to compress the bag onto the components 27a, 27b, 29 and into the first mould part 31. It is noted that the present invention could be employed in other moulding processes, for example blow moulding or vacuum forming.

(33) Although the present invention has been described with particular reference to natural fibres, it will be appreciated that it could be implemented using synthetic fibres, such as glass fibres, carbon fibres or aramid fibres. Indeed in another embodiment of the present invention, the fibrous substrates 27a, 27b are formed using carbon fibre, and in particular recycled carbon fibres. Recycled carbon fibres may be retrieved from offcuts of other known carbon fibre moulding processes and the resulting components. The recycled fibres are combed to achieve substantially aligned long fibres, which are combined with thermoplastic (matrix-forming) fibres (for example, polypropylene, polyester or polyamide) into a fabric or tape as mentioned above. The long carbon fibres are substantially aligned and optionally woven into a substantially perpendicular weave, thus giving the resulting component excellent strength properties in its planar configuration, i.e. across the component.

(34) In this example, the feature-forming material 29 also optionally comprises synthetic fibres. In one embodiment the feature-forming material comprises short carbon fibres that are preferably recycled carbon fibres. The short nature of the fibres in the feature-forming material permits egress of the short fibres through the long fibres of the fibrous substrate and into the recesses of the mould part so as to form the features. This has the advantage of providing strength to the feature.

(35) Components formed using synthetic materials may be suited to external applications, i.e. those applications which are subject to moisture and gas and should be impermeable to one or both. For example, the method may be used to form exhaust ducts, aerofoils, car panels, etc.

(36) As shown in FIG. 8, in a further embodiment of the present invention, the feature forming material 29a may be provided only over the region of the mould part where there is a recess 35 and indeed, a feature is to be formed. This is possible because the matrix-forming fibres in the fibrous substrates fuse during moulding to form a matrix. Therefore, this embodiment further reduces the weight of the component produced by the method because only the feature is formed from the feature-forming material. With reference to FIG. 9, it is noted that the second mould part 31, as described above, may be provided with at least one recess 35. In this example, a section of feature forming material 29a is positioned over the recess 35. As the mould closes, e.g. as the second mould part 31 is moved toward the first mould part 33, the feature forming material 29a flows into the recess 35. Preferably, the volume of feature forming material 29a provided is substantially equivalent to the volume of the recess and indeed, the feature to be formed.

(37) With reference to FIGS. 10 and 11, in another embodiment of the method according to the present invention, the method of moulding takes the form of the first mould part 33′ being a cylindrical mould whereby the moulding components 27a′, 27b′ and 29a′, are placed inside or outside the cylinder (see 33′ FIG. 10 and 33′ FIG. 11, respectively). In the embodiment where the components are placed inside the cylinder (FIG. 10), a second mould part 31′ in the form of a mandrel is drawn through the cylinder to provide a force in the A direction to promote formation of the matrix and flow of the feature-forming material 29a′ into recesses 35′ positioned on the inside surface of the first mould part 33′ so as to form features. It should be noted that the mandrel is schematically shown to have a smaller diameter than the first mould part. The diameter may be smaller for a leading edge of the mandrel (with respect to its drawn direction) but to exert force, the mandrel diameter is substantially equal to the internal diameter of the first mould part less the thickness of the moulding components 27a′, 27b′. In the embodiment where the moulding components are placed outside of the cylinder (FIG. 11), a second mould part 31′ in the form of a cylindrical bag or the like is placed around/over the moulding components 27a′, 29a′ and 27b′, and the first mould part 33′. Inflation of the bag or withdrawal of air between the bag and the moulding components applies pressure in the A direction to the moulding components to promote formation of the matrix and flow of the feature-forming material 29a′ into recesses 35 positioned on the outside surface of the first mould part 33′ so as to form features. As with the foregoing embodiments, it should be noted that the feature forming material 29a′ in FIGS. 10 and 11 may be provided in the form of a continuous sheet around the mould. Components produced by these methods may be used, for example, in exhaust ducts or the like, where tubular structures are required and integrally moulded features provide for those tubular structures to be strong and lightweight.