Background

The current invention relates to the manufacture of composite materials and in particular manufacturing processes to improve the speed of manufacture.

Composite materials are formed of a thermosetting matrix material reinforced with fibres. For example, a thermosetting polymer matrix may be reinforced with carbon fibres. Composite materials are utilised extensively for the manufacture of high-performance components, for example in the aircraft industry, due to their strength and weight properties.

Composite components are manufactured by curing the matrix material, typically a thermosetting plastic, comprising the reinforcing fibres at elevated temperatures and pressures. For example, typical temperatures are in the region of 80 to 180°C and pressures are in the region of 0.276MPa to

0.55MPa. The cure time required is typically 15 to 180 minutes.

Manufacture times of 15 to 180 minutes are incompatible with the high production rates of the mass-market automotive industry which requires components to have a manufacture time of the order of 1 minute. This incompatibility has prevented composite materials being widely utilised in automotive manufacture. Increased temperatures may provide a faster cure of the component, but the higher temperature leads to degradation of the matrix material properties. It is common to include a proportion of

thermoplastic material in the matrix to act as a toughening agent. A particular problem occurs with such matrices when they are cured using conventional processes but at higher temperatures as phase inversion occurs between the thermosetting and thermoplastic components. A process to increase the speed of production of composite components, with acceptable degradation of the material, may enable the use of composite materials in the automotive industry. Summary

Aspects of the invention are set out in the claims.

Description of the drawings Embodiments of the present invention will now be further described, by way of example, with reference to the drawings, wherein :-

Figure 1 shows an apparatus for forming composite components; and

Figure 2 shows a flow chart of a process for forming composite components.

Detailed description

The detailed description provided below in connection with the appended drawings is intended as a description of the present examples and is not intended to represent the only forms in which the present example may be constructed or utilized. The description sets forth the functions of the example and the sequence of steps for constructing and operating the example.

However, the same or equivalent functions and sequences may be

accomplished by different examples.

Figure 1 shows an apparatus 10 for fabricating composite components. Top and bottom mould tools 1 1 , 12 are provided with mould faces 13, 14 shaped to form a composite material into the required component shape. The mould tools are mounted in a press 15 configured to move the mould tools together and apply pressure to a component formed in the mould. The top and/or bottom mould tools are provided with temperature control systems to maintain an elevated temperature during pressing . For example, a temperature in the range 150°C and 250°C with an accuracy of ±2°C. The curing process may include an exothermic reaction and accordingly the temperature control system may require a cooling system as well as a heating system.

The press is capable of creating a pressure of 5 to 60 MPa in the component being formed. In an embodiment a 58 tonne press may be utilised to create a pressure of 57MPa in the component. The press is configured to increase the pressure rapidly, in contrast to the typical slow increase usually utilised for forming composite components. For example, the pressure may increase to the required level over a period of 200 to 400ms.

The mould tools are formed of a material sufficiently strong to maintain their shape and apply the required loads to the component, while also maintaining the required temperatures. Steel or Aluminium may be appropriate. The mould tool faces are configured to enable the component to release from the mould, for example the mould faces may be polished and coated with a suitable release agent. The mould tool is optionally configured to constrain the size of the component, but there is only minimal flow of the materials during cure. Stops are not necessary, but may be incorporated to control component thickness providing the tool configuration ensures application of full pressure to the component. Figure 2 shows a flow-chart of an embodiment of a process for rapid formation of composite components. At block 20 pre-preg fibres are laid up in the required configuration. At block 21 the mould surfaces are pre-heated. At block 22 the component is placed on the lower mould surface and the top mould surface is lowered to bring it close to the component, but not apply pressure, such that the component is heated. At block 23 the press is activated and the applied load is increased rapidly over the defined period to the required level. At block 24 the pressure is maintained and the

temperature controlled at the required level . At block 25 the pressure is relieved and the component removed. In an example a sample component was prepared of 4 layers of twill weave carbon fibre pre-preg weighing 350gsm impregnated in a black pigmented, flame retardant, toughened epoxy resin system designated MTM58FRB supplied by Advanced Composites Group. The mould surfaces were preheated to 160°C and the sample placed on the lower mould surface. The upper surface was brought into close proximity to the sample and maintained for 40±5 seconds. Full load of 58 tonnes was applied to the sample in 350±10 milliseconds to give a sample pressure of 57MPa. The pressure and temperature were maintained for 1 minute ±30 seconds which was sufficient to wholly cure the component.

The high pressure and rapid application of pressure induces a high rate of cure without degrading the material as occurs with existing techniques when cure rates are accelerated using high temperatures. The apparatus and/or process described herein therefore allows the fabrication of composite components in timescales compatible with the requirements of the automotive industry.

It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. It will further be understood that reference to 'an' item refers to one or more of those items.

The steps of the methods described herein may be carried out in any suitable order, or simultaneously where appropriate. Additionally, individual blocks may be deleted from any of the methods without departing from the spirit and scope of the subject matter described herein. Aspects of any of the examples described above may be combined with aspects of any of the other examples described to form further examples without losing the effect sought.

It will be understood that the above description of a preferred embodiment is given by way of example only and that various modifications may be made by those skilled in the art. The above specification, examples and data provide a complete description of the structure and use of exemplary embodiments of the invention. Although various embodiments of the invention have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this invention.