GB2156262A - Trimming fibre-reinforced plastics material - Google Patents

Abstract

In a method of manufacturing a component from a composite material a sheet (12) of fibres in an uncured resin matrix is laid up on an appropriately contoured former. The sheet (12) is then removed from the former and clamped between two support members (14) and (15) which are so configured as to maintain the sheet (12) in the contour of the former. The peripheries of the support members (14), and (15) are aligned and coincide with the desired periphery of the component to be manufactured so that excess sheet (13) material protrudes from between the support members (14) and (15). The excess material is then trimmed off and the sheet (12) removed from between the support members (14) and (15), placed on a second former of the same general configuration as the first former and then subjected to elevated temperature and pressure in order to cure the resin. <IMAGE>

Description

SPECIFICATION Method of Manufacture of Components from Composite Materials This invention relates to the manufacture of components from composite materials.

One common method of manufacturing components from composite materials is to stack layers of resin impregnated fibres on a suitably contoured former to define a sheet which follows the contours of the former. The sheet is then subjected to elevated temperature and pressure in order to cure the resin and mould the sheet to the desired three dimensional configuration. After the resin has been cured, the resultant component is removed from the former and its edges trimmed to the desired shape. Edge trimming is very difficult however if the composite material is one which is very tough such as carbon fibres enclosed in a cured resin matrix. Tungsten carbide rotary burrs have been used forthis purpose. However severe vibration occurs during trimming and this results in excessive noise being generated in the workshop area in which the trimming is carried out.Diamond rotary burrs have also been used for edge trimming but they generally have a short life through clogging with the debris generated during the trimming operation. Both types of rotary burr additionally suffer from the handicap of being high cost items.

An alternative method of trimming is to carry out the trimming operation on the flat layers prior to the resin being cured. This generally entails cutting the layers with scalpels, vibro-saws or shaped cutters similar to those used in the cutting of pastry and like materials. However since the cutting operation is carried out on flat layers, great difficulty is encountered in determining, with any degree of accuracy, the line of cut which defines the component edge when the layers are subsequently stacked on the contoured former.

It is an object of the present invention to provide a method of manufacturing components from composite materials in which such problems in trimming the edges of the components are substantially avoided.

According to the present invention, a method of manufacturing a component from a composite material comprises the steps of laying up a plurality of layers of resin impregnated fibres on the surface of a first contoured former so that said layers define a sheet which follows the contours of said former and has a peripheral extent which extends beyond that of the desired periphery of said component, removing the thus contoured sheet from said contoured former and clamping it between the adjacent surfaces of corresponding support members, said adjacent surfaces being so contoured that said sheet is maintained in the configuration of said first contoured former, and so dimensioned that the peripheries of said adjacent surfaces thereof are aligned and coincide with the desired periphery of said component, cutting off those portions of said sheet which protrude from the peripheries of said adjacent surfaces of said support members, removing said sheet from between said support members, placing said sheet on a second former corresponding in shape with said first former and subjecting said sheet to elevated temperature and pressure in order to mould said sheet to the contour of said second former and cure said resin.

The invention will now be described, by way of example, with reference to the accompanying drawings in which:~ Figure 1 is a sectioned side view of the first contoured former upon which layers of resin impregnated carbon fibre have been laid up.

Figure 2 is a sectioned side view of the laid up sheet of resin impregnated carbon fibre shown in Figure 1 positioned between two support members prior to trimming.

Figure 3 is a sectioned side view of the resin impregnated fibre sheet shown in Figures 1 and 2 after trimming and positioned on a second contoured former prior to vacuum moulding.

With reference to Figure 1 a former 10 has an upper surface 11 which is contoured to define the shape of a component which is to be manufactured from a carbon fibre reinforced composite material.

A number of layers of resin impregnated fibre are laid up on the surface 11 so that they define a sheet 12 which follows the surface contour. The resin is of the epoxy type but it will be appreciated that the method of the present invention is applicable to composite materials which utilise other resins as their matrix materials whether those resins are thermosets or thermoplastics. Likewise fibres other than those of carbon could be used for reinforcing purposes.

The sheet of resin impregnated fibre 12 is so dimensioned and laid up on the former surface 11 that the periphery 13 thereof extends somewhat beyond that of the component which is to be manufactured.

The resin impregnated fibre sheet 12 is then removed from the former 10 and interposed between two glass fibre reinforced resin support members 14 and 15 as shown in Figure 2. The support members 14 and 15 have complementary adjacent surfaces 16 and 17 respectively which are so contoured that the resin impregnated fibre sheet 12 is maintained thereby in the configuration of the contoured surface 11 of the first former 10. The support members 14 and 15 are clamped together by means not shown.

The peripheries 18 and 19 of the support members 14 and 15 respectively are aligned and coincide with the desired periphery of the component which is to be manufactured. Since the periphery 13 of the resin impregnated sheet 12 extends beyond that of the component which is to be manufactured, it protrudes beyond the aligned peripheries 18, 19 of the support members 14 and 15. The protruding portions of the resin impregnated sheet 12 are then cut off by the use of a scalpel, vibro-saw or other suitable tool. Since the resin is in its uncured state, it is comparatively simple to cut without providing accelerated cutter wear or creating excessive noise.

It will be appreciated that in order to ensure that the cut edge of the resin impregnated fibre sheet 12 is as close as possible to the peripheries 18 and 19 of the glass fibre support members 14 and 15, some contact will be made between the cutter and the support peripheries. Since the support members 14 and 15 are made from glass fibre reinforced resin then some protection of the support member peripheries 18 and 19 is necessary in order to prevent their damage by the cutter. This protection is afforded by a plasma spray applied coating 20 of a nickel aluminium alloy on the support member peripheries 18 and 19. It will be appreciated however that alternative protective coatings such as those of plasma spray applied aluminium, copper or molybdenum could be applied to the support member peripheries 18 and 19 if desired.

After the resin impregnated sheet 12 has had its periphery 13 trimmed, it is removed from between the support members, whilst still maintaining the configuration of the contoured surface 11 of the first former 10. It is then placed on the contoured surface 21 of the second former 22 which generally corresponds in configuration with the contoured surface of the first former 10 as can be seen in Figure 3. It is however, only contoured to the extent that it will accept the trimmed resin impregnated sheet 12 in an appropriately recessed portion 23 of its surface. The depth of the recessed portion 23 is equal to the thickness of the resin impregnated sheet 12 so that when the sheet 12 is in place on the second former 22, it is generally flush with the upper surface of that former 22.This being so it will be seen that the trimmed periphery of the resin impregnated sheet 12 sits against the shoulder 24 which defines the edge of the rcessed portion 23.

The majority of the upper surface of the second former 22, including the whole of the exposed surface of the resin impregnated sheet 12, is covered by an impervious membrane 25. The membrane 25 is sealingly attached at its periphery to the upper surface of the second former 22. A connector 26 is attached to the membrane and provides a communication between the underside of the membrane and a vacuum source (not shown).

After air has been drawn out of the gap between the membrane 25 and the resin impregnated sheets 12 through the connector 26, the former 22 is heated to a temperature at which the resin contained in the sheet 12 cures. The application of a vacuum to the sheet 12 ensures its consolidation by compression and the substantial elimination of porosity therein.

This stage of the method of present invention constitutes the conventional process of vacuum moulding and consequently is not as described in detail since it is a process which is well known to those skilled in the art.

When the sheet 12 has been exposed to compression and elevated temperature for sufficient time for the resin therein to cure, the vacuum is released, the membrane removed and the sheet 12 released from the second former 22.

Since the shoulder 24 on the second former 22 ensures that the sheet 12 does not spread during the vacuum moulding operation, the resultant moulded component is correctly dimensioned so far as its peripheral dimensions are concerned. Indeed all that is required is for small amounts of moulding flash to be removed from the periphery of the sheet 12.

It will be seen therefore that the method of the present invention provides a method of manufacturing composite material components which are of complex configuration without the requirement to trim the periphery of the composite material in its flat uncured state or its cured configured state.

Claims (10)

1. A method of manufacturing a component from a composite material comprising the steps of laying up a plurality of layers of resin impregnated fibres on the surface of a first contoured former so that said layers define a sheet which follows the contours of said former and has a peripheral extent which extends beyond that of the desired periphery of said component, removing the thus contoured sheet from said contoured former and clamping it between the adjacent surfaces of corresponding support members, said adjacent surfaces being so contoured that said sheet is maintained in the configuration of said first contoured former, and so dimensioned that the peripheries of said adjacent surfaces thereof are aligned and coincide with the desired periphery of said component, cutting off those portions of said sheet which protrude from the peripheries of said adjacent surfaces of said support members, removing said sheet from between said support members, placing said sheet on a second former corresponding in shape with said first former and subjecting said sheet to elevated temperature and pressure in order to mould said sheet to the contour of said second former and cure said resin.

2. A method of manufacturing a component from a composite material as claimed in claim 1 wherein said second former is provided with a shoulder on the surface thereof which receives said sheet, said shoulder coinciding with and abutting said sheet periphery so as to fix the peripheral extent of said sheet during the moulding thereof at said elevated temperature and pressure.

3. A method of manufacturing a component from a composite material as claimed in claim 2 wherein said shoulder is defined by the periphery of a recessed area in the surface of said second former which receives said sheet, said recessed area being so contoured as to accept said sheet in engagement therewith.

4. A method of manufacturing a component from a composite material as claimed in any of claims 1 to 3 wherein said peripheries of said support members are provided with a protective coating thereon which coating minimises damage to said support member peripheries during the cutting off of the portions of said sheet which protrude therefrom.

5. A method of manufacturing a componentfrom a composite material as claimed in claim 4 wherein said protective coating is a nickel aluminium alloy applied by plasma spraying.

6. A method of manufacturing a component from a composite material as claimed in claim 4 or claim 5 wherein said support members are formed from a glass fibre reinforced resin.

7. A method of manufacturing a component from a composite material as claimed in any one preceding claim wherein said sheet is subjected to said elevated pressure by vacuum moulding.

8. A method of manufacturing a component from a composite material as claimed in any one preceding claim wherein said fibres are of carbon.

9. A method of manufacturing a component from a composite material as claimed in any one preceding claim wherein said resin is an epoxy resin.

10.A method of manufacturing a component from a composite material substantially as hereinbefore described with reference to the accompanying drawings.