GB2184053A

GB2184053A - Method of manufacturing an article from a fibre reinforced composite material

Info

Publication number: GB2184053A
Application number: GB08530629A
Authority: GB
Inventors: Geoffrey Elliott
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1985-12-12
Filing date: 1985-12-12
Publication date: 1987-06-17
Also published as: GB2184053B; GB8530629D0

Abstract

A method of manufacturing a flanged composite material article is described in which resin impregnated layers of reinforcing fibre (16) are laid up on an appropriately shaped former (10) and are autoclave moulded to the former (10) shape. An annular array of segmental member (17) corresponding in shape with the former are movably positioned on the laid-up layers (16) to form the flange shape. Guides (23) located on the former (10) ensure that all portions of each of the members (17) which correspond in configuration with the former (10) are maintained substantially equidistant from the former (10) during motion of the members (17) inwardly from the broken line to the full line position. This is achieved by cooperating inclined surfaces (21, 22) of the members (17, 23) respectively. <IMAGE>

Description

SPECIFICATION Method of manufacturing an article form a fibre reinforced composite material This invention relates to a method of manufacturing an article from a fibre reinforced composite material.

One particularly common method of manufacturing an article from a composite material is to lay up several layers of reinforcing fibres which have been impregnated with a resin matrix material on a suitably shaped former and exert pressure upon the layers whilst at the same time heating them so as to consolidate the layers and cause them to conform to the shape of the former. Pressure may be exerted upon the laid-up fibre/resin layers by the use of the well-known autoclave moulding technique. In that technique, a layer of porous release material is laid over the laid-up layer and is then covered itself by a layer of flexible impervious material. The impervious material is sealed around its edges to the former and the volume enclosed thereby is evacuated, causing the elevated pressure within the autoclave to exert a moulding force upon the laid-up laye, > s.

Difficulty is sometimes encountered in manufacturing articles by this technique if the articles concerned incorporate flanged portions.

Thus, for instance, it is particularly difficult to manufacture generally cylindrically shaped articles which are provided with radially outwardly extending flanges to facilitate the attachment of the article to another similarly shaped article. A typical article of this type is a by-pass duct for a gas turbine propulsion engine. The usual method of forming the flange is to use a former which defines one surface of the flange, the other surface of the flange being defined by a plurality of segmental generally triangular shaped cross-section members which are interposed between the laid-up layers and the impervious material.The intention is that when the volume enclosed by the impervious material is evacuated, the segmental members are urged by the elevated autoclave pressure exerted upon the impervious material to exert pressure upon the laid up layers and thereby consolidate them and form them into the flange shape. In practice, however, it has been found that the segmental members become positionally unstable to the extent that the resultant flanges tend to be tapered.

It is an object of the present invention to provide a method of manufacturing an article from a fibre reinforced composite material in which the above problem is substantially avoided.

According to the present invention, a method of manufacturing an article from a fibre reinforced composite material comprises the steps of laying up a plurality of resin impregnated fibre layers on a former so configured as to define two surfaces angularly disposed with respect to each other, placing a member having surfaces corresponding in configuration with said two former surfaces and which are similarly angularly disposed with respect to each other over said laid-up layers and exerting pressure on said member to urge said laid-up layers into the shape so defined by said member and said laid-up layers into the shape so defined by said member and said former, said former being associated with means which constrains said member under the influence of said pressure exerted thereon to maintain all portions of each of said surfaces of said member generally equidistant from the corresponding portions of said former surfaces.

The invention will now be described, by way of example, with reference to the accompanying drawing which is a sectioned side view of apparatus for use in the method of the present invention.

With reference to the drawing, a cylindrical former 10 is provided with two portions 11 and 12 of differing diameters. The smaller diameter portion 11 defines a cylindrical surface 13 while the larger diameter portion 12 defines an annular surface 14. The former surfaces 13 and 14 are perpendicular to each other and are interconnected by an annular, radiused surface portion 15.

The former surfaces 14 and 15 together define the inner surface of a flanged ring to be manufactured in accordance with the method of the present invention. The flanged ring is constructed from a plurality of laid-up layers of uncured epoxy resin impregnated carbon fibres which are laid-up on the former surfaces 13 and 14 so that they generally conform with the shape defined by the former surfaces 13 and 14. A annular array of similar segmental members, one of which 17 can be seen in the drawing, are then placed over the laid-up layers 16 in the manner shown in the drawing. Each segmental member 17 is provided with surfaces 18 and 19 which are perpendicuiar to each other and respectively correspond in configuration with the portions of the former surfaces 13 and 14 which they overlie.

Thus the segmental surface 19 is flat while the segmental surface 18 is curved.

Each segmental member 17 is of generally triangular shape cross-section. However, the radially outermost portion 20 thereof is modified so as to define an inclined surface 21 which cooperates in sliding engagement with a corresponding surface 22 provided on a segmental member 23 bolted to the radially outer surface 24 of the larger diameter former portion 12. The segmental member 23 is one of a number of similar segmental members 23 bolted to the former portion 12 to define an annular array thereof which cooperate with the annular array of segmental members 17.

Finally, the laid-up layers 16 and the seg mental members 17 are enclosed by a porous sheet 24 and a gas impervious sheet 24a.

Although in the interests of clarity, the sheets 24 and 24a are shown as being spaced apart from each other and the segmental members 17 and 23, as well as the former 10, they are all in fact in abutting relationship. In addition, the impervious sheet 24a is sealed against gas leakage at its edge contact areas (not shown) with the former 10 in the manner usually employed in the well known technique of autoclave moulding.

In operation, the volume enclosed by the impervious sheet is evacuated and the whole assembly heated in manner usually employed in autoclave moulding. This is done to achieve consolidation of the laid-up layers 16 by the exertion of elevated autoclave pressure upon them as well as the softening and eventual curing of the epoxy resin in the layers 16.

The atmospheric pressure exerted upon the segmental members 17 causes them to translate from the position shown in interrupted lines to that shown in full lines to compress the laid-up layers 16 against the former surfaces 13 and 14. This in turn results in the layers 16 conforming with the flanged ring shape defined by the surfaces 13,14,18 and 19. The cooperating surfaces 21 and 22 of each pair of segmental members 17 and 23 constrain the segmental members 17 to follow a path along which all portions of each of the surfaces 18 and 19 of the segmental members 17 remain generally equidistant from the corresponding portions of the former surfaces 13 and 14. The cooperating surfaces 21 and 22 achieve this objective by being inclined to the axis of the former 10 at an angle of 45 degrees, that is, half the included angle A between former faces 13 and 14.

Although the former 10 has been described as having surfaces 13 and 14 which are perpendicular to each other, the present invention is not specifically restricted to such an arrangement. Thus the surfaces 13 and 14 could be disposed with respect to each other at an angle other than 90 degrees. However, whatever the included angle may be between the surfaces 13 and 14, the cooperating surfaces 21 and 22 must be inclined to the former 10 axis at an angle which is one half of that angle between the surfaces 13 and 14.

It will be seen therefore that the provision of the cooperating surfaces 21 and 22 ensures that there is no tendency for the members 17 to tilt under the influence of the pressure exerted thereon and thereby result in an undesirable tapering of the article formed thereby.

When the resin impregnated fibre layers 16 have been exposed to elevated pressure and temperature for a sufficient time for consolidation of the layers 16 and the curing of the resin to take place, the assembly is cooled to room temperature and the resultant fibre reinforced flanged ring removed therefrom.

Although the present invention has been described with reference to the manufacture of an article on a circular cross-section former 10 it will be appreciated that alternative former configurations could be used if so desired.

Thus the former could, for instance, be flat or alternatively conical. The important constraint however is that corresponding portions of the confronting surfaces of the members 17 and the former 10 remain generally equidistant during the manufacturing operation. This is achieved by ensuring that the angle between the cooperating surfaces 21 and 22 and the former surface 13 is one half of the included angle between the segmental member surfaces 18 and 19.

It will also be appreciated that although the present invention has been described with reference to segmental members 17 which are urged into engagement with the layers 16 by the use of the autoclave moulding technique, other techniques could be employed if so desired. Thus for instance, the segmental members 17 could be so urged by hydraulically actuated means, or by elastomeric expansion moulding techniques or Hydraclaving. Moreover although the present invention has been described with reference to a method of manufacture employing an uncured epoxy resin, a partially cured epoxy resin could be employed if so desired. Indeed, other suitable thermosetting resins or thermoplastic resins could be used in place of the epoxy resin.

Claims

1. A method of manufacturing an article from a fibre reinforced composite material comprising the steps of laying up a plurality of resin impregnated fibre layers on a former so configured as to define two surfaces angularly disposed with respect to each other, placing a member having surfaces corresponding in configuration with said two former surfaces and which are similarly angularly disposed with respect to each other over said laid up layers and exerting pressure on said member to urge said laid-up layers into the shape so defined by said member and said former, said former being associated with means which constrains said member under the influence of said pressure exerted thereon to maintain all portions of each of said surfaces of said member generally equidistant from the corresponding portions of said former surfaces.

2. A method of manufacturing an article as claimed in claim 1 wherein said means which constrains said member under the influence of said pressure comprises a guide means provided on said former, said guide means constraining said member to be urged under the influence of said pressure exerted thereon in a direction which lies in a plane normal to said former surfaces, said direction being at an angle to each of said former surfaces which angle is one half of the angle between said former surfaces.

3. A method of manufacturing an article as claimed in claim 2 wherein said guide means provided on said former comprises a planar surface which cooperates in sliding engagement with a corresponding planar surface on said member.

4. A method of manufacturing an article as claimed in any one preceding claim wherein the pressure exerted upon said member is so exerted by the use of the autoclave moulding technique.

5. A method of manufacturing a moulded article as claimed in any one preceding claim wherein said former faces are substantially perpendicular to each other.

6. A method of manufacturing a moulded article as claimed in any one preceding claim wherein said former is generally cylindrical in shape and is provided with two different diameter portions which portions together define said two angularly disposed surfaces.

7. A method of manufacturing a moulded article as claimed in claim 6 wherein said member is one of a plurality of similar members which are grouped in an annular array around said former.

8. An article made by the method of any one preceding claim.

9. A method of manufacturing a moulded article substantially as hereinbefore described with reference to the accompanying drawing.