WO2002085601A1

WO2002085601A1 - Composite injection moulding and process for manufacturing the same

Info

Publication number: WO2002085601A1
Application number: PCT/GB2002/001787
Authority: WO
Inventors: Carl-Eric Nielsen; Christopher Barry Price; Geoffrey Haswell; John Joyce
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-04-23
Filing date: 2002-04-23
Publication date: 2002-10-31
Anticipated expiration: 2003-10-23
Also published as: GB0109880D0

Abstract

A process for manufacturing a composite injection moulding consists of the steps of positioning a preform fibre core in a mould tool, and injection moulding a thermoplastic into and around the preform to form a thermoplastic matrix. The composite moulding includes at least 90% by weight of the fibres retained in the preform fibre core longer than 2mm, and the thermoplastic material which forms the thermoplastic matrix has a melt flow volume greater than 50 dg/min. Depending upon the intended application, at least 90% by weight of the fibres retained in the preform fibre core may be up to greater than 20mm in length, and the thermoplastic material which forms the thermoplastic matrix may have a melt flow volume of up to 800 dg/min.

Description

Title: Composite injection moulding and process for manufacturing the same.

The present invention relates to a composite inj ection moulding and process for manufacturing the same, more particularly, but not exclusi ely, to a lightweight, high performance fibre reinforced composite injection moulding and process for manufacturing the same.

Traditional manufacturing methods for the production of light weight, high performance fibre reinforced composite mouldings have remained largely unchanged for the last two decades, although a number of improvements have been made to both thermoplastic materials and thermoset materials. These include improvements to promote faster polymer injection, longer polymer flow lengths and improved wetting out (i.e. improved bonding between the inj ected polymer matrix material and the fibre reinforcement).

h fibre reinforced inj ection moulding-grade materials, it is well known that the viscosity of the thermoplastic matrix material can cause fibre attrition, poor impregnation and poor wetting out of the fibre reinforcement leading to a significant deterioration in the mechanical properties of the component. Hence, the manufacturing process for a composite moulding typically requires a low viscosity thermoplastic or thermoset resin to impregnate a high fibre-volume content fabric or tow preform core, and a secondary processing stage to chemically cure and cross-link the resin, after the resin has encapsulated and impregnated the preform core. These generic processes have confined the application of composite component to the high value, low volume product markets e.g. aerospace, low volume automotive andrail transport markets. This is due, mainly, to limitations of composite manufacture that require either high levels of labour input and inherently long fibre lay up times and injection cycle times, or the need to use expensive pre-processed materials, to produce composite components by various alternative processing routes, for example resin transfer moulding (RTM), reaction inj ection moulding (KM), structural reaction inj ection moulding (SRIM) and compression moulding. Additional problems are inherent with fibre reinforced injection moulding processes, since the basic principle involves moulding a hot viscous material into a cold, relatively rigid preform fibre core.

It is an object of the invention to provide a composite injection moulding in which the above disadvantages are reduced or substantially obviated.

It is a further object of the present invention to provide a process for the manufacture of a composite inj ection moulding in which the above disadvantages are reduced or substantially obviated.

According to a first aspect of the present invention, there is provided a composite injection moulding comprising a preform fibre core and a thermoplastic matrix, characterised in that at least 90% by weight of the fibres which comprise the preform fibre core are longer than 2 mm, and in that the thermoplastic material which forms the thermoplastic matrix has a melt flow volume greater than 50 dg/min.

In a composite inj ection moulding consisting of a preform fibre core and a thermoplastic matrix material, the melt flow volume of the thermoplastic material has a direct effect on the mechanical properties of the composite component. Inparticular, the melt flow volume of the thermoplastic material affects the ability of the tliermoplastic material to penetrate the voids in the preform fibre core, that is to say, to impregnate the preform fibre core, and the ability of the thermoplastic material to bond with the fibre tows in the preform fibre core. A thermoplastic material having a higher melt flow volume has better impregnation and wetting out characteristics than a thermoplastic material having a lower melt flow volume.

During the inj ection moulding process, the fibres of the preform fibre core will undergo shrinkage, as a result of the pressures, temperatures involved, as a result of the chemical interaction with the thermoplastic matrix material. The length of the fibres in a preform fibre core in a composite injectionmoulding, i.e. the retained length of the fibres of the preform fibre core, after the inj ection mouldingprocess, has an effect on the mechanical properties of the resultant composite component. To achieve a fibre reinforced composite moulding having practical mechanical performance properties, such as tensile or flexural strength and modulus combined with high impact performance, the maximum fibre content cun-ently achievable with conventional injectionmouldingmaterial grades is typically 40 to 50 % by weight.

Hence, acompositemjectionmouldmginaccordaiicewimtneinvention, in which the preform fibre core consists of ahigh proportion by weight of fibres, andin which the thermoplastic matrix material has a high melt flow volume, will exhibit high mechanical properties.

In dependence upon the intended application, the thermoplastic material which forms the thermoplastic matrix may have a melt flow volume greater than 100 dgmin, 200 dg/min, 500 dg/min or 800 dg/min.

Furthermore, depending upon the intended application, at least 90% by weight of the fibres which comprise the preform fibre core may be longer than 5 mm, 10 mm or 20 mm.

According to a second aspect of the invention, there is provided a process for manufacturing a composite injection moulding comprisingpositioning apreform fibre core in amould tool, and inj ection moulding a thermoplastic into and around the preform fibre core to form a thermoplastic matrix, characterised in that at least 90% by weight of the fibres which comprise the preform fibre core are longer than 2 mm, and in that the thermoplastic material which forms the thermoplastic matrix has a melt flow volume greater than 50 dg/min.

According to a third aspect of the invention, there is provided a process for manufacturing a composite inj ection moulding comprising positioning a fibre preform in a mould tool, and inj ection moulding a themioplastic into and around the preform to form a thermoplastic matrix, characterised in that at least 90% by weight of the fibres which comprise the preform fibre core are longer than 10 mm, and in that the thermoplastic material which forms the thermoplastic matrix has a melt flow volume greater than 100 dg/min. Preferably, the inj ection moulding of the thermoplastic involves inj ection compression moulding.

Preferably, the process includes induction heating of the mould tool, for example using an induction heating coil positioned within the mould tool. Depending upon the application, the mould tool may be induction heated to a temperature of between 200 and 245 degrees centigrade. Preferably, the surfaces of the mould tool are heated to a temperature of 220 degrees centigrade.

The invention is advantageous in that it provides a hybrid inj ection moulding process, in which a low viscosity, high flow thermoplastic matrix material is moulded around and through a preform fibre core positioned within the mould tool prior to inj ection, which achieves a high level of wetting out between the thermoplastic matrix and the fibre core, i.e. a high level of penetration of the thermoplastic matrix in the preform fibre core, and a high level of adhesion of the fibres with the thermoplastic matrix material, to produce a polymer matrix composite inj ection moulding of high strength and stiffness. Furthermore, the high percentage by weight ofthe fibres ofthe preform fibre core, provides a composite inj ection moulding having a low volume of porosity, typically less than 5%, which further increases the strength characteristics ofthe component.

The invention is also advantageous in that it can be carried out on conventional inj ection moulding equipment with no significant alteration to the moulding conditions or cycle times.

hi a preferred embodiment, the invention is advantageous in that it achieves a high level of wetting out between the polymer matrix material and the fibres ofthe preform fibre core by mechanically working the polymer through the fibre preform, using a process control technique, namely inj ection compression moulding.

The invention will now be described, by way of example only, with reference to the following description.

Inorderto achieve high fibre weight fraction mouldings of, for example, 45 to 85 %byweight, which having corresponding levels of increased mechanical performance properties, low viscosity thermoplastics, notconventionallyusedhiinjectionmoulding, are required to achieve satisfactory penetration and wetting out ofthe fibre tows.

The invention utilises polymers having low viscosity, and therefore high melt flow volumes (MFV), to aid the impregnation capacity. Examples of these are ISOPLAST thermoplastic Polyurethane (TPPU) and high flow polypropylene (PP) grades from Borealis and Montell, each having a melt flow volume of greater than 100 dg/min. With particular respect to the PP grades, the materials can have aMFV ofbetween 400 and 1200 dg/min, compared with conventional inj ection moulding grades which have a typical MFV between 5 to 50 dg/min. Two high MFV Polypropylene materials are also available: from Montell - Valtec HH 442H, which is a 800 dg/min homopolymer grade; and from Borealis - HM 520J and HL 520J, 400, which have a MFV of 800 dg/min, respectively.

Further, the invention uses open structure fibre materials selected for processing with thermoplastic materials, due to their potential to aid moulding through good impregnation ofthe fibre materials by the polymer matrix material during the inj ection process. For example, fabrics comprising fibres with both high and low desitex forms, or comprising roving and/or filament fibres in various chopped and/or continuous forms, weft insertion or warp knitted fabrics and continuous filament mat (CFM) fabric or chopped strand mat (CSM) fabric.

Fabrics utilised in the invention maybe produced from fibres such as carbon, glass, Kevlar, Nomex, quartz or other rock wool based materials.

The following are examples of suitable fabrics for use in the invention: UP-CFM, 450g/m^Λ2 (a continuous filament mat with an unsaturated polyester binder), Polypropylene-CFM (having aPP binder system which holds the CFM tow together), Engineering fabric Cotech 96/08 from Brunswick (which consists of a stitched fabric as opposed to a woven fabric) and Knitted fabric from Brochier SA, 716802/03. Typically, to produce a preform fibre core for use in the invention, a selected fibre material is stacked in layers, to form a fibre pack of a predetermined fibre volume fraction. Once the required number of fibre material layers have been stacked together, the fibre pack is heated in an oven, and then compressed to a thickness corresponding substantially to the desired inj ection moulding cavity thickness, for example in a cold die or mould having a desired profile.

A binder resin can be applied to the fibre layers, prior to stacking, to help to bond the fibres within the preform fibre core into the desired shape. However, folding ofthe fibre pack may occur during shaping, in particular at a corner region ofthe desired shape. Any folds in the fibre pack will increase the localised fibre content in those regions, which will reduce the impregnation capacity of the thermoplastic matrix material into the preform fibre core.

A slip frame consisting of two rectangular frames bolted together can be used to trap the fibre layers ofthe fibre pack around their edges, thus restricting relative movement between individual fibre layers, to limit the degree of fibre folding in the compression stage and to thereby improve the moulding capability ofthe preform fibre core.

A preferred technique for the maiiufacturiiig of a perform fibre core utilises equipment of a type manufactured by the Swedishbased company, Aplicator System AB, of Metallvaegen, F-43533, Moelnlycke, Sweden. This equipment enables aperform fibre core to be manufactured withboth varying volume f action and varying isotrøpy, together with sufficient amounts of a binding polymer, to enable a hot forming process to produce a stable perform which can be handled by robotics to be positioned into the injection moulding tool.

A process control technique can be utilised to improve the performance characteristics of a composite moulding manufactured in accordance with the invention, for example induction heating and/or injection compression moulding, as will be described below.

During the process of manufacture of a composite moulding in accordance with the invention, heat loss during inj ection ofthe thermoplastic matrix material into the mould tool can occur, which can reduce the impregnation of the preform fibre core. Therefore, induction heating ofthe mould tool is carried out, to raise the mould tool temperature prior to inj ection ofthe thermoplastic matrix material. For example, the surface temperature ofthe mould tool can be raised from a typical working temperature of 80 °C to around 245 °C, using an induction heating coil positioned in the mould tool prior to the injection moulding process. Induction heating ofthe mould tool results in an improvement in the surface finish ofthe final composite moulding, since the degree of fibre wet out at the mould surface is improved.

Inj ection compression moulding involves placing the prefonn fibre core in one wall ofthe mould tool and closing the mould tool to apredetermined spacing. The thermoplastic matrix material is then inj ected into the mould tool, typically from a single inj ection gate in an opposing wall ofthe mould tool. The thermoplastic matrix material thereby occupies a region between the preform fibre core and the mould tool wall. The moulding tool is then compressed to its fully closed position, to force the thermoplastic matrix material through the preform fibre core. The advantage of this process stage is that the flow path ofthe polymer matrix material through the preform fibre core is reduced, since the polymer matrix material is only required to flow through the thickness ofthe prefonn fibre core, without flowing continuously through the preform fibre core from the injection gate, as is the case in conventional inj ection moulding. It is possible to achieve a moulding of higher mechanical performance properties, having a significantly higher fibre weight content, by inj ection compression moulding than can be achieved by conventional injection moulding techniques.

Using conventional inj ection moulding techniques, the maximum fibre weight content achievable in a composite moulding in accordance with the invention is approximately 65 weight %. With injection compressionmoulding, it is possible to achieve a composite moulding in accordance with the invention having up to 85 weight %.

The surface finish of a composite moulding in accordance with the invention can contain a substantialnumberof exposed fibres, because ofthe high fibre content. However, apolymerrich surface finish can be achieved, by the use of surface enhancement fabrics positioned on the outer layers ofthe fibre pack during production ofthe prefonn fibre core, to promote the flow ofthe thermoplastic matrix material at the moulding surface. Examples of surface enhancement fabrics include polyester mesh, unwoven polyester fabric, or polypropylene felt fabric.

Alternatively, a second polymer can be moulded over the composite moulding, using inj ection compression moulding. The application of a second outer layer typically uses a two shot inj ection compression moulding machine. A first tool cavity is used to apply the high flow thermoplastic matrix material into the preform fibre, and a second tool cavity is then used to apply a resin rich outer protective surface, for example.

fn addition, polymeric-based paint films maybe introduced into the mould tool, during moulding, to achieve improvements in the surface finish.

Alternatively, by using multi-gating positions on each side of a tool cavity, the surface finish onboth sides of a composite moulding can be improved, along with a higher degree of impregnation.

The inj ection moulding process in accordance with the invention reduces the labour requirement, speeds up production and lowers the material costs, in comparison to conventional composite moulding processes.

It is possible to use the inj ection moulding process ofthe invention to manufacture fibre/polymer composite components at high volume. Composite mouldings according to the invention can be achieved within a comparable cycle time for similar size inj ection moulded components. Mouldings according to the invention can be produced using standard injection moulding or injection compression moulding equipment. For the same fibre/polymer combination, the application of inj ection compression moulding allows a higher fibre volume fraction to be incorporated into the composite, than if conventional injectionmoulding is used. If ahigh quality surface finish is required, for example to improve the environmental resistance ofthe composite moulding, the full cycle time will be increased by the application of two station and/or multiple gating injection compression moulding, to allow over moulding ofthe composite moulding. Applications of composite mouldings in accordance with the invention will now be described:

Application 1 : Instrument panel with integrated cross car beam.

The use of short fibre reinforced thermoplastic mouldings in the field of automotive instrument panel armatures is well established. The use of composite mouldings and cast magnesium, in various forms, is growing, due to the trend in legislation towards higher impact performance, particularly the side impact of vehicles. In this application, a single piece composite moulding is provided, whereby a high volume fraction fibre reinforced composite moulding, in accordance with the invention, form a load bearing structural element of a type known as a cross car beam, in combination with a lower volume fraction material, sufficient to enable the interior impact requirements for vehicles to be met, which combines dimensional stabiUty, impact resistance and heat resistance.

Application 2: Automotive seating

Automotive seating, particularly two-th ds/one-third split rear seats have in the past been attempted in composite materials. Whilst, in general, a material such as glass mat thermoplastic (GMT), which is a long fibre reinforced mat thermoplastic, has sufficient impact performance, it lacks other physical properties. In particular, it has a low volume fraction, as well as correspondingly low tensile and flexural moduli and strength, hi this application, a seat back and squab is provided, having a seat belt mechanism mountable directly into the seat, without substantial metal reinforcement. A preform fibre core is manufactured from a mixture of isorropically laid fibre layers of high volume fraction, combined with preferentially oriented areas of fibre reinforcement of high volume fraction such that, when moulded, it produces a composite moulding in accordance with the invention, having high volume fractions of material in the most desirable locations and with the most appropriate orientation, to withstand the stresses and strains dictated by the various impact conditions stipulated by law. Application 3: Automotive bumper

Automotive bumpers have been made from various composite materials as well as sheet moulding compound (SMC) or its orientated version known as ZMC. These are thermoset materials and therefore have recycling limitations. Highly orientated thermoplastic composites such as Twintex (50vf) and GMTex (30vf) have also been manufactured to form bumpers using injection compression moulding. However, for this application, a composite moulding in accordance with the invention utilises a preform fibre core which consists of a central, highly orientated preform section having, at its intended fixation points, areas of isotropically laid fibre, over-moulded with polymer matrix material. The resultant composite moulding has high stiffness in the central axis, as required to meet the relevant legislation, for example 5mph no damage, combined with an excellent resistance to impact at the fixation points, to obviate the need to incorporate steel crush cone structures. This combination of design and high volume fraction material yields both cost saving and weight saving over conventional approaches.

Application 4: Inlet Manifold

Modern vehicles contain increasing amounts of sophisticated electronics including fuel inj ection systems and emission control devices. The use of glass filled nylon up to 20%volume fraction is well established in this field. High volume fraction composite mouldings in accordance with the invention, for use in this application, illustrate the potential to save both weight and money. The higher the volume fraction ofthe reinforcement material, i . e in the preform fibre core, the higher the strength ofthe resulting composite moulding. Hence, for any given set of performance criteria such as stiffness or strength, the wall sections ofthe composite mouldings canbe reduced, saving weight. In addition, because, generally, glass fibre is found to be cheaper than plastic resins which are known to be used for this type of application, such as heat and or hydrolyticaliy stabilised nylon PA 6 and 66, 11 , 12, the substitution ofthe volume of nylon with the volume of fibre reinforcement leads to cost savings. Application 5: Safety shoe cap

40% volume fraction safety shoe toe caps manufactured from polypropylene and glass are known to exist. These known toe caps are able to reach the highest level of impact performance required by the marketplace (EN 1268), 200 joules. However, a wider range ofpolymers and fibres, in use in a composite in accordance with the invention, can be utilised in the production of safety shoes, for example PA12 plus Kevlar, a combination of fibre and polymer matrix material not currently available in the market place. The higher properties obtained by this combination of material, in accordance with the invention, enables the weight of a toe cap to be further reduced from the considerable weight saving already achievable by polypropylene/ glass composite, in comparison with the more conventional steel components. The use of a preform/polymer inj ection moulding in accordance with the invention enables a higher volume fraction polypropylene based composite moulding to be achieved, which would also be lighter and cheaper to manufacture than standard toe caps.

The invention will now be further described with reference to the following example.

Example 1

A moulded toe cap for safety footwear is to be manufactured using a combination of apolymer matrix material, Montell PP, having amelt flow volume of 800dg/min, continuous fibre mat (CFM) fabric, a woven fabric manufactured from continuos filament glass fibres and a conventional injection compression moulding machine.

Firstly, the preform fibre core is prep ared, as follows . S everal rolls of CFM are placed, one on top of another, with intermediate layers ofthe woven continuous filament glass fibre fabric, to form a stack having a predetermined fibre volume fraction of 65%. The stack is then cut to a predetermined shape, using a shaped die cutter. Using an oven heated to 160 °C, the shaped stack is heated, before being transferred to a cold compression tool, in which the heated stack is then formed into a preform fibre core ofthe desired toe cap shape. The preform fibre core is then picked up using a needle gripper robotic arm and positioned ready for placement into the tool cavity of a first moulding tool ofthe injection compression moulding machine.

The first mould tool consists of apair of opposing walls. A first wall includes a recess into which the preform fibre core is placed prior to the start ofthe inj ection moulding processes, as described below. The second wall has a formation of an external profile which substantially matches the internal profile ofthe recess, hi use, the walls are movable towards one another, with the formation on the second wall aligned for movement within the recess, to a fully closed position in which the two walls are in contact with one another.

The recess in the first wall is deeper than the extent ofthe formation on the second wall. Hence, when the two walls are in contact with one another, the mould tool defines a tool cavity which is shaped to correspond to the desired profile ofthe toe cap.

The formation includes a central passageway which forms an inj ection gate through which the thermoplastic matrix material is injected under pressure, in use.

Prior to placement ofthe preform fibre core in the mould tool, the mould tool is opened and an induction heating coil is positioned between the two walls. To promote enhanced flow and impregnation ofthe thermoplastic matrix material into and around the preform fibre core, during the inj ection moulding process, the induction heating coil is maintained inbetween the tool walls until the surface temperature ofthe two walls reached 220 degrees centigrade.

The preform fibre core is then positioned in the recess in the first wall ofthe mould tool by the robotic arm. The preform fibre core is held in place in the recess by specially adapted needle grippers retractably provided in the recess surface, which protrude into the preform fibre core, to hold the core in place prior to initiation ofthe thermoplastic inj ection. After the preform fibre core is located in the recess in the first wall, the mould tool is partially closed to leave a spacing of 2mm between the walls ofthe mould tool. h the meantime, the thermoplastic matrix material is plasticised to its optimum melt flow temperature, in the barrel ofthe injection moulding machine. During the inj ection moulding process the themioplastic matrix material is maintained at this optimum temperature, to promote flow ofthe thermoplastic matrix material, to enable the molten material to penetrate the dense fibre core before the onset of solidification of the polymer.

During a first injectionmoulding stage, a predetermined volume of molten thermoplastic material is inj ected under a pressure of 1500 bar through the inj ection gate to substantially fill the partially open zone between the recess and the first wall and the formation on the second wall, for encapsulation and impregnation ofthe preform fibre core. Once the predetermined volume of matrix material had been injected into the partially open zone, the needle grippers were retracted into the first wall, from securing contact with the preform fibre core. In this example, the movement ofthe needle grippers is not considered to be a part ofthe first injection moulding stage, or subsequent injection moulding stages.

As the needle grippers were retracted, a second injection moulding stage was simultaneously commenced. In this second stage, the inj ection pressure is maintained, and the mould tool is gradually compressed to its fully closed position, with the two opposing walls brought into contact with one another. This second stage is referred to as inj ection compression moulding, whereby the volume of material injected in the first stage is forced into and around the preform fibre core.

The first and second stages are sequential, and a constant inj ection pressure is maintained at all times. The volume of material injected in the first stage, ie prior to the compression ofthe tool walls into the fully closed position, is predetenriined to prevent loss of material from the tool cavity as the second stage is carried out. When the tool is in the fully closed position, the inj ecting pressure is maintained until the thermoplastic matrix material has cooled and solidified sufficiently to enable the tool to be opened.

The maintenance ofthe inj ection pressure in this manner is a third sequential stage ofthe inj ection motύding process, known as the after pressure stage, hi tins third stage, as the themioplastic matrix material begins to cool, shrinkage occurs as well as a loss of volume ofthe preform fibre core, as a result ofthe inj ection pressure. The after pressure is maintained thereby inj ecting more material into the tool cavity, as the shrinkage occurs, thus minimising voids in the final moulded component. Hence, the third stage continues to force the thermoplastic material into and around the fibre core, to promote optimum impregnation and wetting out ofthe thermoplastic with the preform fibre core.

The melt flow value ofthe thennoplastic material at its optimum temperature enables the polymer to impregnate and adhere to the dense fibre tows ofthe preform fibre core. The moulded composite has at least 90% by weight ofthe fibres retained in the preform fibre core longer than 10mm. The high level of impregnation and wetting out achieved by the thennoplastic having ahigh melt flow volume, in combination with the high percentage by weight of fibres retained in the moulded composite of over 10mm, results in a final component with high mechanical properties.

To produce a composite moulding having an overmoulded surface finish, a fourth inj ection moulding stage is carried out in a second mould tool. The second mould tool has a construction conesponding to the first mould tool, having apair of walls which define a tool cavity corresponding to the desired shape ofthe final toecap.

The first mould tool cavity is opened and the moulded component is removed by the robotic arm and positioned in the recess ofthe first wall ofthe second mould tool. The second mould tool includes a second inj ection gate in the recess in its first wall, and external locating features for securably locating the moulded component in the position in the recess.

A tough polypropylene resin is then inj ected under pressure through the two inj ection gates in the second tool and injection compression moulded around the moulded composite, substantially as described above, to form ahigh quality surface finish. The finished composite moulding is then removed from the second cavity by the robotic arm.

It will be appreciated that the above inj ection processes can be carried out in multiple tool cavities in a continuous production cycle, as required, to manufacture aplurality of high surface quality finished composite inj ection mouldings in accordance with the invention. Furthennore, it will be appreciated that only the first inj ection moulding stage is essential, in the production of a composite moulding in accordance with the invention. The second, third and forurth stages are preferable, to provide a composite moulding having higher mechanical properties than a composite moulding produced using only the first stage.

Claims

1. A composite inj ection moulding comprising a preform fibre core and a thermoplastic matrix, characterised in that at least 90%o by weight ofthe fibres which comprise the preform fibre core are longer than 2 mm, and in that the thennoplastic material which forms the thermoplastic matrix has a melt flow volume greater than 50 dg/min.

2. A composite injection moulding according to claim 1, characterised in that the thennoplastic material which forms the thermoplastic matrix has amelt flow volume greater than 100 dg/min, 200 dg/min, 500 dg/min or 800 dg/min.

3. A composite inj ection moulding according to claims 1 or 2, characterised in that at least 90%) by weight ofthe fibres which comprise the prefonn fibre core are longer than 5 mm,

10 mm or 20 mm.

4. A process for manufacturing a composite inj ection moulding comprising the steps of positioning a prefomi fibre core in a mould tool, and injection moulding a thennoplastic into and around the preform fibre core to foi n a thermoplastic matrix, characterised in that at least 90% by weight ofthe fibres which comprise the preform fibre core are longer than

2 mm, and in that the thermoplastic material which fonns the thermoplastic matrix has a melt flow volume greater than 50 dg/min.

5. A process according to claim 4, characterised by a further step of inj ection compression moulding the thermoplastic into and around the preform fibre core.

6. Aprocess according to claim4or 5, characterised by a further step of induction heating ofthe mould tool prior to positioning the preform fibre core in the mould tool and injecting the thermoplastic.

7. A process according to claim 6, characterised in that the mould tool is heated using an induction coil positioned in the mould tool.

8. A process according to claims 6 or 7, characterised in that the mould tool is induction heated to a temperature of between 200 degrees centigrade and 245 degrees centigrade.

9. A process according to any one of claims 6 to 8, characterised in that the mould tool is induction heated to a temperature of 220 degrees centigrade.

10. Aprocess accordingto any one of claims 6 to 9, characterised in that the thermoplastic material which forms the thermoplastic matrix has a melt flow volume greater than 100 dg/min, 200 dg/min, 500 dg/min or 800 dg/min.

11. Aprocess according to any one of claims 9 to 10, characterised in that at least 90%> by weight ofthe fibres which comprise the prefonn fibre core are longer than 5 mm, 10 mm or 20 mm.

12. A process for manufacturing a composite injection moulding comprising the steps of positioning a fibre preform in amould tool, and inj ection moulding a thermoplastic into and around the preform to form a thermoplastic matrix, characterised in that at least 90%> by weight ofthe fibres which comprise the preform fibre core are longer than 10 mm, and in that the thermoplastic material which forms the thermoplastic matrix has amelt flow volume greater than 100 dg/min.

13. A process as claimed in claim 12, characterised by a further step of inj ection compression moulding the thermoplastic into and around the preform fibre core.

14. A process as claimed in claim 12 or 13 , characterised by a further step of induction heating of the mould tool prior to positioning the preform fibre core in the mould tool and inj ecting the thermoplastic.