The present invention relates to improvements in or relating to fibre reinforced composites. Composites comprising fibre reinforced materials and in particular prepregs comprising fibres and thermosetting resins may be stacked to form preforms. These preforms are subsequently cured in a mould or a vacuum bag to form a reinforced composite material. Such composite materials are known, they are lightweight and of high strength and are used in many structural applications such as in the automobile and aerospace industries and in industrial applications such as wind turbine components such as spars and the shells used to make the turbine blades.

Prepreg is the term used to describe fibres and/or fabric impregnated with a resin in the uncured state and ready for curing. The fibres may be in the form of tows or fabrics. The tows or fabrics generally comprise a plurality of thin fibres called filaments. The selection of fibrous materials and resins employed in the prepregs depends upon the properties required of the cured composite material and also the use to which the composite is to be put.

Various methods have been proposed for the production of prepregs, one of the preferred methods being the impregnation of a moving fibrous web with a liquid, molten or semi-solid uncured thermosetting resin. The prepreg produced by this method is then cut into sections of desired dimensions and a stack of the sections is moulded and cured by heating to produce the final fibre reinforced laminate. Curing may be performed in a vacuum bag which may be placed in a mould for curing as is preferred in the manufacture of wind energy structures such as shells for the blades and spars. Alternatively, the stack may be formed in a closed mould and cured directly in the mould by heating (compression moulding).

One preferred family of resins for use in such applications are curable epoxy resins, and curing agents and curing agent accelerators are usually included in the resin to shorten the cure cycle time. Epoxy resins are highly suitable resins although they can be brittle after cure causing the final laminate to crack or fracture upon impact and it is therefore common practice to include toughening materials such as thermoplastics or rubbers in the epoxy resin. The prepreg can be in the form of an integral layer of reinforcement material or it can be in the form of elements oriented in random directions to form a quasi-isotropic material layer. Multiple prepreg layers or elements are conventionally combined to form composite laminate structures. The prepreg layers may be arranged in parallel, randomly in an in-plane direction (quasi-isotropic) or as isotropic or quasi-isotropic prepreg elements.

Following formation of the laminate, it may be cut to the required shape. This produces off- cuts which can be wasteful and costly.

The composites can be used to provide strength and reinforcement to articles such as automobiles, aircraft, railroad vehicles, boats and ships. In particular they may be laminated to metal components to provide reinforcement, particularly whilst also reducing the weight of the component. The degree of reinforcement that is required may vary along the length or across the width of a component. For example, certain regions in a component may need extra strength as they may be more vulnerable to crash, or they may be at a location where any external force that may be applied to the article is greater than at other locations. To date the composite has been provided across the entire component in an amount that provides the maximum required reinforcement, albeit that the maximum reinforcement may be required only at certain locations of the component. This is wasteful and costly as more composite material than is required is used, and it also results in an unnecessary and undesirable increase in the weight of the component. This can lead to increased fuel consumption in vehicles and the like.

In the design of vehicles such as automobiles, boats and the like stresses to which the vehicle may be subjected are evaluated and the degree of reinforcement required in certain areas is adjusted accordingly.

The composite may be further adapted by cutting to suit particular applications. This has the disadvantage of creating scrap composite material which can be wasteful and inefficient.

The present inventions aim to obviate or at least mitigate the above described problems and/or to provide improvements generally.

According to the inventions there is provided a reinforcing composite, a reinforced substrate, an automobile component, a compound and a method as defined in any one of the accompanying claims.

According to another invention the number of layers of reinforcing composite material that are employed at locations that are potentially subject to stress is determined according to the potential stresses evaluated at those locations, wherein more layers of composite material are provided at locations where there is the potential for higher stress.

In a first aspect, the present invention provides a reinforcing composite comprising a plurality of layers of reinforcing composite material wherein the number of layers of reinforcing composite material that are employed at locations that are potentially subject to stress is determined according to the potential stresses evaluated at those locations, and wherein more layers of composite material are provided at locations where there is the potential for higher stress.

The reinforcing composite may be provided as strengthening material to any substrate particularly to metal substrates, wooden substrates and plastic substrates. The substrates may be components used in automobiles, boats, aerospace vehicles and the like. The invention therefore further provides a substrate that is reinforced by lamination with a composite material wherein the thickness of the composite material varies across the surface of the substrate, thicker sections of the composite material being provided at locations on the substrate that have the potential to being subject to higher stress.

The thickness of the reinforcing composite may be varied by adjusting the number of layers of reinforcing composite material provided at various locations across the surface of the substrate. The reinforcing composite material may be pre-made, cured and then laminated to the substrate that is to be reinforced, or layers of the uncured reinforcing composite material (prepreg) may be laid up on the substrate and cured to both form the cured composite and adhere the composite to the substrate.

The reinforcing composite used in this invention may be used for reinforcing a substrate. In a preferred embodiment the reinforcing composite further comprises an adhesive for adhering the composite to the substrate. The adhesive improves the bond between the reinforcing composite and the substrate material.

The substrate material and the reinforcing composite are conjoined to form an integral moulding material. The integral moulding material is located in a compression mould which is adapted to mould the integral moulding material to the desired shape followed by curing or whilst simultaneously curing the integral moulding material.

The integral moulding material may further comprise a release material for releasing the moulding material from a mould surface. Suitable release materials may comprise polyolefin filim materials. Preferably the polyolefin film material may comprise multiple layers of varying polyolefin polymers ranging from C2 (polyethylene) through to C6 and/or copolymers thereof. Other suitable release material may comprise fluorinated thermoplastic films (such as polytetrafluorethylene (PTFE), fluorinated ethylene propylene (FEP), ethylene tetrafluorethylene (ETFE), polyvinyl fluoride (PVF), chlorinated thermoplastic films such as polyvinylchloride (PVC), low surface energy thermoplastic films (such as polymethylpentene PMP), thermoplastic films chemically modified to have low surface energy (such as siloxane treated polyethylene terephthalate (PET), thin metal foils (such as aluminium), pre-cured thermoset fibre reinforced lamiantes, films of low melting temperature waxes (such as paraffin wax) or synthetic waxes (such as substituted amide waxes) or salts of fatty acids (such as calcium stearate), woven fibre or veil layers infused with low melting temperature waxes (such as paraffin wax) or synthetic waxes (such as substituted amide waxes) or salts of fatty acids (such as calcium stearate) or mixtures thereof. In a preferred embodiment the release film may have a release side and a non-release side.

Suitable adhesive materials may be applied in film form, as a paste, or sprayed and could be selected from the group consisting of thermoset resins such as epoxy, cyanate ester, and phenolic resins or from groups consisting of thermoplastic bonding adhesives such as polyurethane, polyvinylacetate (PVA) and PVC. Suitable epoxy resins include diglycidyl ethers of bisphenol A, diglycidyl ethers of bisphenol F, epoxy novolac resins and N-glycidyl ethers, glycidyl esters, aliphatic and cycloaliphatic glycidyl ethers, glycidyl ethers of aminophenols, glycidyl ethers of any substituted phenols and blends thereof. Also included are modified blends of the aforementioned thermosetting polymers. These polymers are typically modified by rubber or thermoplastic addition such as carboxy terminated butyl rubber (CTBN/RAM) combinations where the olefinic nature of the modifier enhances enables the ability of the adhesive to absorb oil from a substrate surface and form a better bond. These polymers are often further modified by a surfactant or adhesion promoting chemical. Any suitable catalyst may be used. The catalyst will be selected to correspond to the resin used. One suitable catalyst for use with an epoxy resin is a dicyandiamide curing agent. The catalyst may be accelerated. Where a dicyandiamide catalyst is used, a substituted urea may be used as an accelerator. Suitable accelerators include Diuron, Monuron, Fenuron, Chlortoluron, bis-urea of toluenediisocyanate and other substituted homologues. The epoxy curing agent may be selected from Dapsone (DDS), Diamino- diphenyl methane (DDM), BF3-amine complex, substituted imidazoles, accelerated anhydrides, metaphenylene diamine, diaminodiphenylether, aromatic polyetheramines, aliphatic amine adducts, aliphatic amine salts, aromatic amine adducts and aromatic amine salts. Preferably the adhesive comprises an epoxy resin, a dicyandiamide (DICY) curative, a substituted urea accelerator and an ethylene vinyl acetate. The adhesive layer preferably comprises a woven fabric or scrim. The scrim controls the bond line thickness between the moulding material and the substrate material. This ensures that the adhesive cannot leech away from the surface of the substrate when the sheet moulding compound or blank is subjected to pressure during moulding. The scrim may be provided on the moulding material before the application of the adhesive layer.

Reinforcing composites according to this invention may comprise a composite of a reinforcement material and a resin material that is cured to produce the reinforcing composite. The curing process transforms the resin from a plastic substance by a cross- linking process. Energy and/or catalysts are added that cause the molecular chains to react at chemically active sites linking into a rigid, 3-D structure. The cross-linking process forms a molecule with a larger molecular weight, resulting in a material with a higher melting point. During the reaction, the molecular weight increases to a point so that the melting point is higher than the surrounding ambient temperature, and the material forms into a solid material.

Suitable resin materials for use in the reinforcing composite materials used in this invention may be selected from the group consisting of thermoset resins such as epoxy, cyanate ester and phenolic resins. Suitable epoxy resins include diglycidyl ethers of bisphenol A, diglycidyl ethers of bisphenol F, epoxy novolac resins and N-glycidyl ethers, glycidyl esters, aliphatic and cycloaliphatic glycidyl ethers, glycidyl ethers of aminophenols, glycidyl ethers of any substituted phenols and blends thereof. Also included are modified blends of the aforementioned thermosetting polymers. These polymers are typically modified by rubber or thermoplastic addition. Any suitable catalyst may be used. The catalyst will be selected to correspond to the resin used. One suitable catalyst for use with an epoxy resin is a dicyandiamide curing agent. The catalyst may be accelerated. Where a dicyandiamide catalyst is used, a substituted urea may be used as an accelerator. Suitable accelerators include Diuron, Monuron, Fenuron, Chlortoluron, bis-urea of toluenediisocyanate and other substituted homologues. The epoxy curing agent may be selected from Dapsone (DDS), Diamino-diphenyl methane (DDM), BF3-amine complex, substituted imidazoles, accelerated anhydrides, metaphenylene diamine, diaminodiphenylether, aromatic polyetheramines, aliphatic amine adducts, aliphatic amine salts, aromatic amine adducts and aromatic amine salts. The resins may further contain a dicyandiamide (DICY) curative, a substituted urea accelerator. They may also contain an ethylene vinyl acetate copolymer.

The resin materials may comprise a toughening agent. Suitable toughening agents can be selected from liquid rubber (such as acrylate rubbers, or carboxyl-terminated acrylonitrile rubber), solid rubber (such as solid nitrite rubber, or core-shell rubbers) in the nano or macro size range, thermoplastics (such as poly (EtherSulphone), poly (Imide)), block copolymers (such as styrene-butadiene-methacrylate triblocks), High modulus particles (such as Silica) in the nano or macro size range or blends thereof.

The reinforcing composite material may comprise any fibrous material such as natural fibres (eg flax, hemp, straw, hay, seagrass, basalt), glass fibre, aramid, PAN or carbon fibre, including mixtures thereof, such as carbon fibres and glass fibres. As discussed, the fibrous reinforcement material may also comprise multiple layers of fibrous material. Preferably, the fibrous reinforcement layers comprises oriented fibres.

The fibrous material layer may comprise a weight ranging from 55 to 10000 gsm (g/m ² ), preferably from 100 to 8000 gsm and more preferably from 150 to 4000 gsm. The thickness of the fibrous layer may range from 0.05 mm to 10 mm, preferably from 0.1 mm to 8 mm.

The fibrous material may be unidirectional, woven, chopped, biaxial or triaxial. The fibre length may vary from 1 mm to several meters, preferably from 5 mm to 100 mm, more preferably from 10 mm to 100mm or less. In a preferred embodiment of this invention the fibres in the reinforcing composite are aligned in different directions in the various layers of material employed at any particular location in the reinforcing composite. For example, the base section of the composite material which is of uniform thickness may comprise several layers and the orientation of the fibres within the layers may be parallel or at 90° to each other. The additional layers of composite material that are provided at the locations where the potential for high stress is perceived may be aligned at 90° to the fibres in the base layer. Table 1 below illustrates how layers of moulding materials based on unidirectional fibres may be laid up with the fibres in differing orientations. Lay up

Lay up 1 (Orientation

weight ply)

Lay up 2 (Orientation

weight ply) Lay up 3 (Orientation

weight ply)

The invention is however equally applicable to composites in which the fibres within the layers have a random orientation or are parallel in all the layers. For example, the fibres may be provided as a woven fabric.

The reinforcing composite of the invention may comprise an insulating layer to prevent galvanic coupling between the fibrous reinforcement and a substrate to which the reinforcing composite is attached. This is particularly advantageous for metal substrates and carbon fibre reinforcement to prevent corrosion of the metal.

The adhesive layer when used may also comprise an insulating layer to prevent galvanic coupling between the substrate material and the fibrous reinforcement material. The insulating layer in the adhesive layer may be formed by the adhesive or by another material. The insulating layer material in the adhesive may differ from the insulating layer material of the moulding material. Insulating layers may comprise a suitable insulating layer material having a conductivity of 1 S.m ^"1 or less, preferably 0.1 S.m ^"1 or less, and more preferably of 0.01 S.m ^"1 or less, or combinations of the aforesaid ranges. Suitable insulating materials may comprise glass fibre, flax, hemp, rubber, thermoplastics such as polyamide, or ethylene/vinyl acetate copolymers. The insulating material may be in the form of a veil, scrim of fabric.

Curing of the reinforcing material may take place in a single stage or in multiple stages such as two, three or more stages. Curing may take place following compression moulding or during compression moulding. If curing occurs in multiple stages, one or more stages may coincide with compression moulding. For a multistage cure, typical initial cure cycles for the layer of the fibre reinforced composite include an increase in temperature from ambient to temperatures up to 30 to 200°C, preferably 30 to 160°C, and may be followed by a dwell stage at a fixed temperature ranging from 30 to 200°C, preferably 50 to 160°C, more preferably 80 to 150°C for a period of time ranging from 1 s to 10 hours, preferably 10s to 1 hour, 1 mins to 1 hour, 1 mins to 45 mins or 1 mins to 30 mins or 1 to 30 mins and/or combinations of the aforesaid periods. Following the dwell stage, the temperature is further increased to temperatures up to 60 to 200°C, preferably 60 to 160°C, followed by a cure stage at a fixed temperature ranging from 60 to 200°C, preferably 60 to 160°C, more preferably 80 to 160°C for a period of time ranging from 1 s to 10 hours, preferably 10s to 1 hour, 1 mins to 1 hour, 1 mins to 45 mins or 1 mins to 30 mins or 1 to 30 mins and/or combinations of the aforesaid periods.

At some time after the initial cure cycle and the moulded article has cooled to ambient temperatures it may undergo a second 'post cure' step to develop its full thermo and mechanical properties. Typical post cure cycles for the moulding material include an increase in temperature from ambient to temperatures up to 30 to 200°C, preferably 30 to 160°C, and may be followed by a dwell stage at a fixed temperature ranging from 30 to 200°C, preferably 50 to 160°C, more preferably 80 to 150°C for a period of time ranging from 1 s to 10 hours, preferably 10s to 1 hour, 1 mins to 1 hour, 1 mins to 45 mins or 1 mins to 30 mins or 1 to 30 mins and/or combinations of the aforesaid periods. Following the dwell stage, the temperature is further increased to temperatures up to 60 to 200°C, preferably 60 to 160°C, followed by a cure stage at a fixed temperature ranging from 60 to 200°C, preferably 60 to 160°C, more preferably 80 to 160°C for a period of time ranging from 1 s to 10 hours, preferably 10s to 1 hour, 1 mins to 1 hour, 1 mins to 45 mins or 1 mins to 30 mins or 1 to 30 mins and/or combinations of the aforesaid periods.

However, preferably and advantageously, the article is moulded in a single step at a temperature ranging from 60 to 200°C, preferably 80 to 160°C over a period of from 20s to 8 minutes, preferably from 40s to 3 minutes, more preferably from 60s to 120s and/or combinations of the aforesaid periods. The article may be cured or part cured. The part cured article may proceed through to cure during other subsequent production steps such as assembly or coating.

In a further embodiment of this invention at least one of the additional layers of composite material that are provided at the positions perceived to be vulnerable to high stress may be off cuts or scrap material, such as material obtained when prepregs are cut to the desired shape to provide the base reinforcement for the structure. In this way wastage can be reduced at the same time as providing the desired increased local reinforcement.

The off-cuts or scrap may be consolidated in a sheet material. The off-cuts or scrap may be cut into multiple fiber elements prior to their consolidation. The sheet material may be applied to form protrusions, channels or surfaces of complex curvature.

The invention can employ a laminate comprising multiple plies of tape material with selected areas comprising additional plies. Each ply contains one or more sections of tape (also called courses) placed parallel to each other, and each ply is fused to one or more underlying plies. The shape of each ply and the orientation, or angle, of the fibers in the ply relative to fibers in other plies in the laminate are chosen such that the final produced article will have the desired structural characteristics across its surface. Layers may be tacked together and the method used to tack layers together and the degree to which they are tacked is another parameter that can vary in different embodiments. Methods for tacking the courses to underlying plies could include contact heating, ultrasonic welding, induction welding, laser heating, hot gasses, or other methods of adhering plies to each other. Also, the method could be used with an articulating head or a moving substrate surface, or a combination of the two positioning approaches. Although an embodiment described herein uses a fixed material placement head that is positioned over a flat substrate surface that can move in the x and y directions as well as rotate, the relative motion between the placement head and the substrate surface could also be achieved by moving the placement head or a combination of the two.

According to another invention there is provided a reinforcing composite comprising a plurality of layers of reinforcing composite material forming a stack wherein at least one layer of the composite material comprises a moulding compound comprising oriented resin impregnated fiber elements, wherein the fiber elements are obtained from off-cuts or scrap material derived from cutting the reinforcing composite material prior to its location in the stack.

In a preferred embodiment, the off-cuts or scrap material are derived from separating off- cuts or scrap material comprising multiple layers of reinforcing composite material. This enables scrap material to be re-used. The off-cuts or scrap material are preferably cut into the fiber elements. In a further embodiment, the moulding compound is in the form of a sheet or layer in which the fiber elements are randomly oriented. Preferably, the fiber elements comprise unidirectional fibers. In a further embodiment the fibre elements are consolidated following orientation.

The moulding compound layer is employed at one or more locations within the stack that are subject to elevated in-use stress in comparison with other locations within the stack according to an in-use stress evaluation of the stack.

In yet another embodiment of the invention there is provided a moulding compound comprising oriented resin impregnated fiber elements, wherein the fiber elements are obtained from off-cuts or scrap material derived from cutting a reinforcing composite comprising a plurality of layers of reinforcing composite material forming a stack. Preferably, the off-cuts or scrap material is derived from separating off-cuts or scrap material comprising multiple layers of reinforcing composite material.

The moulding compound may be adapted to form particular aspects of a moulded composite part including one or more of protrusions, rubs, channels and shapes of complex curvature.

The fiber elements may be consolidated by heating to form a sheet. The elements are heated to a temperature of between 60 to 80°C.

The fibre elements are consolidated following orientation.

Finally in a further embodiment, there is provided a method of manufacturing a moulding compound comprising

a) providing a plurality of layers of reinforcing composite material;

b) forming a stack;

c) cutting the stack to obtain off-cuts or scrap material;

d) separating the off-cuts or scrap material into fiber elements;

e) orienting the fiber elements; and

f) consolidating the fiber elements to form a layer. In a preferred embodiment, at least one layer of the composite material comprises a moulding compound obtained by means of the method of the present invention comprising the step of locating the moulding compound within the stack.

The present invention is illustrated by reference to the accompanying drawings in which Figure 1 shows four reinforcing parts of composite reinforcing material according to an embodiment of the invention. Figure 2 is a cross section on the line A-A of Figure 1. Figure 3 is a cross section on the line B-B of Figure 1. Figure 4 is a cross section on the line C-C of Figure 1 .

Figure 1 shows 4 parts each having a base section (1 ) from which a section of material has been removed from locations (2).

Figures 2, 3 and 4 show how the resulting multilayer composite provides additional reinforcement along the lines B-B and localized additional reinforcement at various locations along line A-A and C-C. Figures 2, 3 and 4 also illustrate how the orientation of the fibres in the various layers can be varied as required.

The materials shown are suitable for lamination to a substrate such as a metal automobile component, to provide structural reinforcement with localized additional reinforcement as shown for parts 1 and 3 in Figures 2 and 4.