The present invention relates to methods of making composite products from carbon fibre reinforced thermoplastics, preferably using recycled carbon fibre and filled or unfilled recycled or virgin thermoplastic.

Background of Invention:

Carbon-fiber-reinforced polymer composites are extremely strong and lightweight materials having a high strength-to- veight ratio. They have many applications such as for use in the manufacture of cars, boats, aeroplane and trains, etc to name but a few. The strength of these materials comes from the reinforcement layers which contain carbon fibres. Matrix _. , or binding layers (which may comprise a polymer resin, such as epoxy) bind the reinforcement, layers together. Carbon fibre composites are well known _. , although the materials produced using known technologies are very expensive since they use virgin polymer and reinforcement. Attempts have been made to reduce costs by making carbon fibre reinforced composites using carbon fibre reclaimed from vehicles, but this has been energy intensive and has used environmentally unfriendly solvents in the process. It has also been difficult to produce composites from recycled materials in a manner that is both efficient and provides a product of sufficient quality.

It is therefore desired to provide an improved method of producing a carbon fibre composite material. The present invention provides a meihod of producing a carbon fibre composite material comprising; shredding or chopping carbon fibre materiai; and extruding the shredded or chopped carbon fibre with thermoplastic.

The carbon fibre materia! may alternatively/also be cut or stamped. Any other means of cutting up the carbon fibre material may also be used. in some embodiments, the carbon fibre material may be waste materiai.

In one embodiment, the extruded materiai may be cut into peiiets and the peiiets may then be melted and used in an injection molding process to form a maided component formed from the carbon fibre and said thermoplastic, in this

embodiment, the melted material is forced into a mou!d cavity. The materia! is then cooled and hardens so as to retain the configuration of the cavity. In some embodiments, the final form of the harden material is a film form and so this method may therefore be used to produce a carbon fibre/thermoplastic film which may then he used in any of the methods described herein. in another embodiment, the method may comprise extruding the shredded or chopped carbon fibre with thermoplastic and cutting or forming the material into pellets before then forming a film from said peiiets. This film may be made from the peiiets using a method of compression moulding of said carbon fibre/thermoplastic pellets. The film or sheet formed may be 0.3mm to 1 mm thick and may then further be deposited between layers of dry fabric webs. Further compression molding of the layers may involve melting the peiiets to infuse the dry fibres of the adjacent dry fabric webs.

The step of forming said film via compression moulding may comprise a melting step which comprises raising [he temperature of said pellets to a temperature that is at or above the melting point of said peiiets. The method may further comprise the step of applying pressure to said peiiets during the melting step. In some embodiments, !he shredded or chopped carbon fibre with thermoplastic material may be extruded in the form of a strand or film. In some embodiments, the film may be a carbon fibre reinforced film. The method may further comprise the step of providing a plurality of any of said carbon fibre reinforced thermoplastic films described herein and providing a plurality of dry fabric webs and arranging said dry fabric webs between adjacent ones of said thermoplastic films. The method may further comprise the step of heating and pressing said thermoplastic films and said dry fabric webs together to form an integrated composite component.

The carbon fibre material used in any of the methods described herein may be carded after shredding or chopping and prior to said step of extruding.

Alternatively, or additionally, the carbon fibre material may be spun prior to said step of extruding. Preferably, the carbon fibre material is spun after it has been carded and prior to said step of extruding. The carbon fibres are preferably spun by open end spinning, during which the shredded or chopped fibres are twisted together by a rotating element. The fibres a e preferably spun in dry form and are not melted.

The extruding step may be performed by a screw extruder that draws carbon fibre into the extruder.

The present invention also provides a method of producing a carbon fibre composite material comprising: shredding, cutting or stamping carbon fibre material; arranging the shredded, cut or stamped material into a plurality of webs; arranging a thermoplastic material between adjacent ones of said webs, within said webs or on said webs; and heating and pressing said webs together to form an integrated composite component.

The waste carbon fibre material may alternatively/also be chopped. Any other means of cutting up the waste material may also be used.

In this method, the thermoplastic material may comprise any of the carbon fibre/thermoplastic fi!m(s) made by the methods as described herein, or

alternatively may comprise other films or layers. The carbon dry fibre material may be woven or non-woven.

At least one of said webs may be formed by randomly oriented carbon fibres, or orientated or random squares of woven or non-crimp fabric which have been cut or stamped into uniform sizes, In some embodiments, the sizes may range from dimensions of 15mm up to 2m. At least one of the webs may be formed by depositing carbon fibres on a thermoplastic film and the thermoplastic film may correspond to the thermoplastic materia! between adjacent webs. Alternatively, or additionally, the thermoplastic material may be a ressn deposited in or on said webs.

As an alterative to randomly oriented fibres, the shredded, cut or stamped carbon fibres may be woven or stitched so as to form said webs. The carbon fibre material used in any of the embodiments described herein may be carded after shredding, cutting or stamping and prior to being woven. Alternatively, or additionally, the carbon fibre material may be spun prior to being woven. Preferably, the carbon fibre material is spun after it has been carded and prior to said step of weaving. The carbon fibre may be spun by open end spinning. The webs may be arranged in a thermoplastic charge bag or film and the charge bag or film may be melted onto the webs. The integrated composite component may be arranged in a thermoplastic charge bag or film and the charge bag or film may be melted onto the integrated composite component. The charge bag or film may be vacuum wrapped over the webs or integrated composite component prior to being melted. The charge bag may include an image, logo or pigments.

The heating and pressing of said webs may be performed in a press configured so as to impart a three dimensional structure to a surface of the integrated composite component. Alternatively, the integrated composite component may be

subsequently heated and pressed so as to impart it with a three dimensional structure on one of its surfaces.

The carbon fibre material described herein and which is shredded, cut or stamped is preferably waste carbon fibre material, and more preferably is dry waste material, For example, the waste carbon fibre material may be yam or fabric. The thermoplastic material that is described herein may be recycled waste material although less preferably it may be virgin material. The thermoplastic material may be from waste PET, such as from bottles or clothing, or other types of waste plastic such as Nylon. The waste thermoplastic material may be formed into chips or sheets and may then be washed and dried.

The present invention also provides a method of forming a carbon fibre composite comprising: forming said composite from shredded, cut or stamped carbon fibre material and thermoplastic material; arranging one or more thermoplastic film or sheet on one or more surface of the composite or arranging the composite in a thermoplastic charge bag; and melting the one or more film, sheet or charge bag onto the composite. The one or more film, sheet or charge bag may include an image, logo or pigments.

A method of forming a carbon fibre composite is also herein described which comprises providing a first thermoplastic film, and a second thermoplastic film, and bonding at least a first portion of a first surface of said first thermoplastic film to at least a first portion of a first surface of a second thermoplastic film.

The method may further comprise the step of bonding at !east a first portion of a second surface of the first thermoplastic film to a first carbon ply layer, and at least a first portion of a second surface of the second thermoplastic film to a second carbon ply film.

In some embodiments, the first and second surfaces of the first thermoplastic film may be opposing surfaces and the first and second surfaces of the second thermoplastic film may be opposing surfaces.

The method may further comprise the step of heating and pressing said

thermoplastic films and said carbon ply layers together to form an integrated composite component. In some embodiments, the first and second thermopiastic films may be made from the same material.

In some embodiments of this method, the first and second thermoplastic films layers that are bonded together may comprise the carbon fibre/thermoplastic films as produced via the methods described above.

The present invention also provides a carbon fibre reinforced composite formed according to any of the methods described above.

The present invention is able to use low cost waste plastic and waste carbon fibre in a low cost process. Textile based technology may be used to process and align short carbon fibres so as to achieve a composite material having good mechanical properties. The present Invention therefore provides an improved process which does not require the use of solvents.

Brief description of drawings:

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

Figures 1A-1 D show embodiments of the present invention which may be used to form a reinforced film or sheet;

Figures 2A-2D show embodiments of the present invention which may be used to form press-moulded composites;

Figure 3 shows part of a process for forming a three dimensionally shaped composite,

Figure 4 shows a film interleaving compression technique.

Figure 5 shows a compound compression method,

Figure 6 shows a patchwork layup technique.

Figure 7 shows a method whereby the film compression technique is employed to bond two separate components which may have been produced via the same film compression process

Detailed Description of Em odiments j^ _^^ ^ A set of preferred embodiments of the present invention will now be described with reference to the figures.

Figures 1 A~D depict the steps of different methods for producing, preferably from waste carbon fibre material, (such as off-cuts), a first carbon fibre reinforced film or layer. In particular, Figures 1 A to 1 D depict methods for producing carbon fibre films or Iayers that comprises relatively short carbon fibres (in comparison to reinforced fibre iayers produced by standard manufacturing methods). As described later with reference to Figures 3 to 7, the reinforced Iayers produced by the methods of Figures 1 A to D may then be used in combination with other Iayers to form a carbon fibre composite material having improved properties. They may also be used as the thermoplastic Iayers in the methods of Figures 2A to 2E.

In Figures 1A-D, these methods are shown as using waste carbon fibre material, which may be in the form of off-cuts of woven or non-woven material, 10A-10D. This waste material is then shredded, chopped, cut, stamped etc, 11A-1 1 D. For ease of reference a method using shredded is described hereinafter, however, any other method of culling or shredding the material could be used, The shredded material may then be carded, 12A, 12B and/or spun, 13A, 13C as shown in Figures 1A-1 C. The carding, 12A, 12B and/or spinning, 13A, 3C, may be performed using modified textile producing equipment. This is something that is new and has never been done before with carbon fibres. When the fibres are subjected to spinning, 13A, 13C, this may be performed with dry fibres. The spinning is preferably performed by open end spinning, during which the shredded fibres are twisted together by a rotating element, in a preferred process, the fibres are both carded and spun, as shown in Figure 1 A, This produces a higher quality continuous fibre, as compared to one which has not been carded before spinning. After the material has been shredded, and optionally carded and/or spun, the materia! is subjected to extrusion with a thermoplastic, 14A-14D. The method preferably utilises a screw exiruder and the screw mechanism of a single or twin screw extruder may be used to draw the material into the barrel of the extruder at a predetermined rate. This Is advantageous as it negates the requirement for hoppers or feeders (e.g. volumetric or gravimetric) for the fibrous material and enables an accurate quantity of carbon fibre to be incorporated into the extruded material without the expense and complexity of a hopper or feeder system, t has been discovered that by using spinning, the individual fibres entering the heater barrel of the extruder are better aligned with respect to the direction of extrusion, This enhances the fibre orientation within the extruded material.

As shown in Figures 1A-1 D, the extruded material may exit the extruder as a continuous strand or film, 14A-140 and may then either be formed into pellets, 15A~ 15D, or left in the film form, 16A, 168, 16C, When left in the film form, 16A, 16B, 18C, the films can be used in the methods described below with reference to Figs 2A to 2E. in one embodiment, (see Figure 10, 18), the pellets formed in steps 15A-15C may alternatively be melted and used in an injection moulding process, 180. to form a moulded component formed from the carbon fiber and thermoplastic composite. . In this embodiment (not shown in the figures), the melted material is forced into a mould cavity similar to that shown in Figure 5. The material is then cooled and hardens so as to retain the configuration of the cavity. In some embodiments, the final form of the harden material may therefore be in a film form and so this method may therefore be used to produce a carbon fibre/thermoplastic film which may then be used in any of the methods described herein.

The extruder effectively acts to pulverise the fibres in the screw zone which means that both the extruded film/sheet as well as the pellets, 51 (shown in Figure 5), will have relatively short fibres in comparison to carbon fibre films manufactured according to conventional methods.

The pellets may be produced by chopping the extruded strand using any convention means that, is capable of chopping through the carbon fibre reinforced material, such as a rotating blade cutter. in some embodiments, as shown in Figures 1A to 1C, 17A-17C, and Figure 5, the carbon fibre/thermoplastic pellets, 51 , may then be used in a compression moulding process, wherein the carbon fibre/thermopiastic pellets, 51 , are melted to form a carbon-fibre/thermopiastic film or sheet, 53, The materia! is then cooled and hardened so as to retain the configuration of the cavity, 50.

This is described in detail with reference to figure 5A, wherein, in this embodiment, the pellets, 51 , are provided within a cavity, 50, between two platens or moulds, 52, which are then pressed together and compressed to optimise the fibre volume fraction and heated to a sufficient degree above the meit temperature to cause the pellets, 51 , to melt and form a single film or sheet, 53, see figures 5A to 5C, The material is then cooled and hardened so as to retain the configuration of the cavity and the resulting sheet, 53, removed therefrom, as shown in figure 5C. This method is able to produce layers or sheets, 53, of compressed short fibre carbon thermoplastic films having a range of different thicknesses, depending on the depth of the cavity between the molds, 52; however in a preferred embodiment, the sheet may have a thickness of between 0.3mm and 1 mm,

These thermoplastic and short fibre carbon reinforcement sheets/films, 53, described here with reference to Figs 1A to 1 D, (i.e. the extruded films which are left in the film form, 18A-16D of Figures 1A -1 D, and/or the films, 53, produced via the compound compression method, 17A, 17Β _» 17C of figure 5, and/or the films produced via the injection moulding technique, 18D), may then be used as an inter- ply insert between dry carbon plies, 54, in order to produce a final composite material, as described below with reference to figures 3 and 4. Any of these films may also be used in the methods described in Figures 8 and 7.

One example of producing the composite material In this way Is shown in figure 5D, which shows a method whereby a sheet/film comprised of thermoplastic and short fibre carbon reinforcement, 53, may be used as an inter-ply Insert between dry carbon plies, 54. The compressed short fibre carbon thermoplastic film, 53, is used as an inter-ply insert between dry carbon plies, 54. A method of interleaving of layers Is further depicted In Figures 4A and 4B, Following interleaving of these layers, (also depicted In Figure 3A), the assembled interleaved plies, 53, 54, are consolidated by applying heat and pressure, as shown in figure 3B. The thickness of the structure Is therefore compressed, as shown In figures 4C to 4E and the polymer melts and the thickness of the overall structure Is reduced as the polymer melts and infuses the dry fibres. Composites produced using such methods and with these Iayers containing such compounded short fibres have enhanced interlaminar properties in that the short fibres act as anchors within [he composite, anchoring the Iayers together.

In another embodiment, these compressed short fibre carbon thermoplastic sheets, 53, can also/alternatively be used in the methods described below with reference to Figs 2A to 2E.

Another set of embodiments of the present invention will now be described with reference to Figures 2A-E. These methods may also use waste carbon fibre material, which may be in the form of off-cuts of woven or non-woven material. This waste matenai is then shredded, cut or stamped. Alternative cutting methods may also be used.

According to the embodiment of Figure 2B, the shredded material may be deposited as a web of randomly oriented fibres or segments of fabric which could be random or aligned. A web comprising these fibres of segments of fabric can be preformed using resin or stitching methods (not shown in Figure 2b). In a preferred embodiment, the segments are cut to a uniform size ranging from 15mm to 2m dimension, however, other dimensions and also non-uniform segments could be used. This method is described herein as the Patchwork layup technique, and is depicted in figure 6. This may be achieved by depositing the shredded fibres or fabric segments onto or into contact with, a thermoplastic or thermoset film. The fibres may be deposited using, for example, an air feed, gravimetric dispensing, volumetric dispensing, sieving or any other known technique for depositing fibres or fabrics. Alternatively, and as shown in Figures 2A, ,and 2E, the shredded fibres may be subjected to weaving to form a web of woven material. The shredded fibres may be subjected to carding and/or spinning prior to the step of weaving.

With reference to the particular embodiment shown in figure 6, i.e. the Patchwork layup technique, shredded fibers or segments of waste carbon off-cuts, 61. are laid onto a surface such as a platen, 62. These multiple small sheet sections, 61 , of waste/recycled carbon ply may be attained via uniformed downsizing of larger Industrial off-cuts and end rolls of carbon. They may be layered up either 0 ^* 790° or in random sequence to each other on the platen, 62, to develop an accumulative carbon fibre layer, or web, 63, as shown in Figure 88. In some embodiments, (e.g. Figures 2A, 2C, 2D, 2E, and as described above), the shredded fibres or segments may be subjected to weaving to form this web of woven material.

Multiple webs are formed for consolidation into an integral composite component. An in-situ poiymerisable or pre~polymerised resin may be deposited onto at least some of the webs or may be co-extruded with the fibres of the webs (as shown in Figure 2E). The webs may then be stacked together to be consolidated at a subsequent stage. Additionally, or alternatively, multiple webs may be formed and interleaved with thermoplastic material between adjacent webs, as shown in figures 3A, 4A-4E. This thermoplastic material may comprise any of the carbon fibre/thermoplastic films described herein. Alternatively/additionally other thermoplastic materials may be used.

In the embodiment depicted in Figure 6A-6C, the web, 63, is interleaved with a layer, 53, of thermoplastic material. Figures 8C and 6D depict this thermoplastic layer being deposited onto the web, 63 of waste carbon off cuts. Figure 6E then depicts a further layer of waste dry carbon off cuts then being deposited onto this thermoplastic layer, thereby creating the interleaving. In some preferred embodiments, the thermoplastic layer used, 53, may comprise the carbon- fibre/thermoplastic iayer or film, 53, which was produced via the methods of Figures 1A-1 C and/or the compound compression method of Figure 5, In the methods wherein the fibres are woven, the woven webs can he arranged in a predetermined sequence and/or orientation, thus improving the fibre orientation and characteristics of the final product.

Although Figs 2.A-2E show embodiments wherein a melt fiim charge bag is used, this is not a requirement and in some embodiments, the multiple webs are then processed (without such a charge bag) with heat and pressure so as to consolidate the webs into an integral composite component. An example of this is shown in Figure 3, wherein the webs are interleaved with thermoplastic material, such as thermoplastic films, as shown in Figure 3A. The webs are then consolidated into an integral laminate using heat and pressure, as shown in Figure 38. The laminate may be heated and pressed i a iherrnoform press such that the laminate achieves its desired shape at this stage or at a subsequent stage in the process (e.g. as shown in Figures 3d-3f)- The laminate is then released from the iherrnoform. The method of consolidating webs and/or layers into an integral composite component as shown in figure 3 and as described herein may be used with any of the different methods of forming a composite as described herein,

These heat and pressure techniques may also be used to consolidate webs that have been impregnated with thermoplastic resin, rather than interleaved with thermoplastic films.

Other methods (e.g. as shown in Figs 2A~E) may be used to apply heat and pressure such as vacuum bag moulding. For example, prior to the webs being press-formed (Figure 3B), the webs may be encapsulated in a thermoplastic shrink- wrap or vacuum-wrap film or charge-bag (26A-26E). This film or charge-bag is then melted during the subsequent heated stages of production, such as during the press forming, The melted film or bag can provide a high quality surface finish on the component, especially at the edges. The bag also provides for ease of transit of the component, charging of the press, and has the advantage that the fibres and resin are encapsulated in a film so as to provide a cleaner and safe working environment for operators. Furthermore, the film or bag may be pigmented with one or more colours or an image such as a logo, or may be embossed, When the film or bag is melted onto the composite, this effect will then be arranged on the composite. As an alternative to using a charge-bag, the webs may be arranged between two thermoplastic film layers.

In a further embodiment described herein, a composite material may also be made by bonding at least a first portion, 75, of a first surface, 80, of a first thermoplastic film, ?3A to at least a first portion, 76, of a first surface, 81 , of a second

thermoplastic film, 73B.

The method may further comprise the step of bonding at least a first portion, 77, of a second surface, 82, of the first thermoplastic film, 73A, to a first carbon ply layer, 74A and at least a first portion, 78, of a second surface, 83, of the second thermoplastic film, 73B, to a second carbon ply layer, 74B. In some embodiments, the first and second surfaces of the thermoplastic film(s) are opposing surfaces, such as in the embodiments of Figure 7, In theory, the composite may simply therefore comprise four layers of material bonded together, i.e. two thermoplastic films bonded to each other, with their opposing surfaces bonded to a carbon ply layer each.

In the embodiment shown in Figure 7, however, at least a second portion, 84, of the first surface, 80, of the first thermoplastic film, 74A, as well as at least a second portion, 85, of the first surface, 81 , of the second thermoplastic film, 74B. are further bonded to a third carbon ply layer, 74C.

Although Figure 7A depicts two thermoplastic films, 73A and 73B, which are arranged between three layers of carbon ply, 74A, 748, 74C, Differing numbers of layers could alternatively be used, however. For example, the composite could comprise four thermoplastic films and four carbon ply layers (not shown, positioned for example in the shape of a cross) to achieve the same bonding effect between the thermoplastic films.

The layers may be bonded to each other using a film compression technique such as that described with reference to Figure 3, wherein pressure is applied to the carbon ply layers, 74A-74C as shown by the arrows in the presence of heat. In order for the bond to form sufficiently well between the thermoplastic layers, 73A, 738, they should be layers of the sarne type, or at least having the same or similar melting properties. In a preferred embodiment, two thermoplastic layers or films are bonded to each other wherein the layers or films have Identical properties due to the fact that they have been made by the same technique. One example of this Is the bonding together of thermoplastic films such as those described herein with reference to those produced via the methods of Figs 1 and/or 5. Thermoplastic such as nylon, PBT, PPS etc may also be used. Film bonding may therefore be performed using the same polymer film (with or without short fibres). The heat and compression provided by this technique results in the melting of the bonding film layers, which wiii subsequently impregnate the adjacent component polymer/carbon surface, 74A--C. Two or more structures may therefore be bonded via a single film bonding process, as shown in figures 7A-7E.

Such film bonding techniques have advantages in that they may be proposed as an 'add-on' product/technology to be offered to customers of film compression techniques and/or products.

Such types of film bonding may also/alternatively be proposed as a repair method/technology for either of the customers, or as a separate technical ability.

This method is also advantageous as there is no need for adhesives or fasteners when combining sub-assembly parts; this provides fast cycle time and reduced cost. The bond strength is further increased by the use of short fibre reinforced polymer films to join the components.