WO2002002298A1

WO2002002298A1 - Method of manufacturing a seamless thin-walled tubular body from fiber-reinforced plastic material, thin-walled tubular body thus obtained and device for carrying out said method

Info

Publication number: WO2002002298A1
Application number: PCT/NL2001/000500
Authority: WO
Inventors: Joris Kamiel Maria Van Raemdonck; Johanna Cecile Joris Karoline Emile Van Raemdonck; Karst Jan Van Weperen; Norbertus Franciscus Jacobus Elemans; Thomas Maria Jonkers
Original assignee: Stork Screens B.V.
Priority date: 2000-07-04
Filing date: 2001-07-02
Publication date: 2002-01-10
Also published as: AU2001271130A1

Abstract

A method of manufacturing a thin-walled seamless tubular body (3) from fibre-reinforced plastic material, which method comprises the steps of a) applying fibre-reinforced plastic material to a dinensionally stable tubular inner mould (1); b) positioning the inner mould (1) with fibre-reinforced plastic material in a seamless, dimensionally stable tubular outer mould (2) by relative displacement with respect to one another in the longitudinal direction, leaving clear a space (4) which is substantially present between the surface of the fibre-reinforced pastic material and the inner surface of the outer mould (2); c) reducing the size of the space (4) by relative displacement of the outer mould (2) and the inner mould (1) with fibre-reinforced plastic material with respect to one another in such a manner that the fibre-reinforced plastic material is subjected to pressure and is brought into contact with the inner mould (1) and the outer mould (2); d) causing the plastic material to flow; e) hardening the plastic material in the pressurized state; f) relieving the pressure; and g) removing the seamless thin-walled tubular body (3) which has been manufactured by relative displacement in the longitudinal direction with respect to the inner mould (1) and outer mould (2). The invention also relates to a seamless thin-walled tubular body (3), obtained in accordance with the invention, and to a device for manufacturing this body.

Description

Method of manufacturing a seamless thin-walled tubular body from fiber-reinforced plastic material, thin-walled tubular body thus obtained and device for carrying out said method.

The present invention relates first of all to a method of manufacturing a thin-walled seamless tubular body from fibre- reinforced plastic material.

A method for producing seamless tubular bodies from fibre- reinforced plastic material with a wall thickness of greater than 1 mm is known from US patent US-A-5, 071, 506. In this known method, a fibre-reinforced plastic material is applied to an inflatable inner bellows, after which the latter is introduced into a single-part outer mould. The bellows is pressurized with the aid of a suitable fluid, so that this bellows expands. As a result, the fibre- reinforced plastic material is pressed against the inner wall of the outer mould and is then hardened in this state. Tubular bodies produced in this way are intended, for example, for use in space travel, and if desired may be protected with an outer coating layer of aluminium.

This method has the drawback, in particular for the manufacture of thin-walled tubular bodies, that inflatable inner bellows made from a relatively elastic and flexible material, for example from silicone rubber, are used. It has been found that it is difficult to control the expansion of inner bellows of this type at elevated temperature, resulting in wall thicknesses and diameters of the tubular bodies thus manufactured varying constantly over the length and circumference. In other words, the reproducibility and repeatability of this known method leaves something to be desired. Furthermore, the inflatable bellows are susceptible to ageing of the material, which also has an adverse affect on the product quality of the tubular bodies. In particular, this leads to an uneven, for example ribbed, surface on the tubular bodies, in particular on their inner sides. It should be noted at this point that DE-A1-39 23 415 and US-A- 3,165,569 have disclosed methods and devices for manufacturing tubular bodies in which an inner mould covered with fibre-reinforced material is placed into a two-part outer mould. A mould assembly of this type is unsuitable for the production of tubular bodies of low thickness, for example of less than 1 mm. This is because the two- part outer mould causes two longitudinal seams to be produced on the outer side of the manufactured product, and these seams can only be removed by remachining., Remachining of this type is virtually impossible on thin-walled products, owing to the lack of strength of the body. Moreover, remachining of this type increases production costs. Furthermore, in the method described in DE-A1-39 23 415, which is only intended for thermoplastics, the inner mould has to be plastically deformable, since otherwise the pressure required is not maintained during the cooling phase. This means that a new inner mould is required for each new product.

The primary object of the present invention is to provide an expedient method and device for manufacturing tubular bodies, which bodies are seamless and have a low thickness. It is a further object of the invention to at least partially eliminate the abovementioned drawbacks which would arise with the production of seamless and/or thin-walled tubular bodies using the processes according to the prior art, in particular to improve the reproducibility and repeatability, resulting in more uniform products.

For this purpose the method of manufacturing a thin-walled seamless tubular body from fibre-reinforced plastic material according to the invention comprises the steps of a) applying fibre-reinforced plastic material to a dimensionally stable tubular inner mould; b) positioning the inner mould with fibre-reinforced plastic material in a seamless, dimensionally stable tubular outer mould by relative displacement with respect to one another in the longitudinal direction, leaving clear a space which is substantially present between the surface of the fibre- reinforced plastic material and the inner surface of the outer mould; c) reducing the size of the space by relative displacement of the outer mould and the inner mould with fibre-reinforced plastic material with respect to one another in such a manner that the fibre-reinforced plastic material is subjected to pressure and is brought into contact with the inner mould and the outer mould; d) causing the plastic material to flow; e) hardening the plastic material in the pressurized state; f) relieving the pressure; and g) removing the seamless thin-walled tubular body which has been manufactured by relative displacement in the longitudinal direction with respect to the inner mould and outer mould. In the method according to the invention, the fibre-reinforced plastic material from which the thin-walled tubular body is manufactured is applied to a tubular inner mould, which inner mould is dimensionally stable. This means an inner mould which is made from a material which has a fixed, stable form at ambient temperature and which retains its shape, although the size may vary slightly, in the event of expansion, either under pressure from a fluid or as a result of a change in temperature. After the fibre-reinforced plastic material has been applied to the dimensionally stable inner mould, this inner mould together with fibre-reinforced plastic material is introduced into a seamless outer mould, which is likewise dimensionally stable, for example by pushing the inner mould axially into an outer mould arranged in a fixed position. Such a position may, for example, be horizontally or vertically oriented. In this case, a space which lies substantially around the fibre-reinforced plastic material on the inner mould and on the other side is delimited by the inner wall of the outer mould remains present. In a next step, the space defined above is reduced in size, so that a pressure is applied to the fibre-reinforced plastic material and the latter comes into contact with the outer mould as well. This reduction in size may be effected either by changing the temperature, applying pressure to the inner mould and/or outer mould or by a combination of these measures, as will be explained in more detail below. Increasing the temperature causes the viscosity of the plastic material to fall, and the material starts to flow as a result of the pressure. In the case of thermoplastics, the viscosity is increased again by lowering the temperature; for thermosetting plastics, this is achieved by the passage of time. Then, the plastic material is hardened in this state. By way of example, for a thermosetting plastic material the temperature will be increased. For a thermoplastic, hardening takes place after the temperature has been reduced. After the pressure has been relieved, the inner mould, depending on the situation possibly also with the thin-walled tubular body which has been formed, is removed from the outer mould, and then, once again depending on the situation, the body is separated from the outer mould or from the inner mould. By using a dimensionally stable inner mould and dimensionally stable outer mould, as defined above, the expansion and/or contraction thereof can be controlled more successfully, for example in the expansion steps which are carried out at elevated temperature. The expansion of the material of a dimensionally stable inner mould of this type when the temperature rises and/or the pressure rises takes place constantly and uniformly through the entire volume of the inner mould. Consequently, the shape is retained, although the outer circumference increases. When the inner mould is being shrunk, for example as a result of a reduction in temperature and/or pressure, the reverse situation occurs. The use of a seamless outer mould means that there are no seams on the outer circumference of the tubular body. A smooth outer surface is favourable or even required for the intended application of the product. If the inner surface is also to be a seamless, it is preferable to use a seamless, dimensionally stable inner mould. The result of the method according to the invention is that seamless thin-walled tubular bodies whose wall thickness is constant over the entire circumference are always obtained. The use of dimensionally stable moulds also means that these moulds are less susceptible to ageing of the material.

The thin-walled and seamless tubular body manufactured has a wall thickness in particular in the range from 0.005 to 1 mm, and the wall thickness is more preferably in the range from 0.005 to 0.7 mm. The seamless thin-walled tubular bodies made from fibre-reinforced plastic material which are produced with the aid of the method according to the invention can be used for numerous purposes. A non- restrictive list includes, for example, perforated cylinders as used , in rotary screen-printing technology, in which free-flowing compositions, for example printing ink or ink paste, adhesive and the like, are applied, via the perforations in the cylinder, to a substrate which is to be coated, specific examples including printing screens, stencils or plastic galvanos, in which only printing openings which define an image to be printed are present; perforated cylinders used for the sorting, screening or filtering of solid particles from a gas, liquid, solid or combinations thereof; perforated cylinders for the perforation of thin plastic films; unperforated cylinders used as exchangeable surfaces for rollers, as used, for example, in graphic applications, including flexographic, offset and intaglio printing; unperforated seamless cylinders used as self-supporting, lightweight rollers in mechanical engineering applications; optionally perforated seamless cylinders which are used as conveyor and/or guide belts in machines; and optionally perforated cylinders used in solar cells. In the case of the thin-walled tubular bodies made from fibre-reinforced plastic material which have been manufactured in accordance with the invention, the perforations can easily be applied with the aid, for example, of a laser.

In one embodiment, the inner mould is a hollow or solid cylindrical body with a coefficient of thermal expansion which is greater than the coefficient of thermal expansion of the outer mould. Metals, such as for example aluminium, are suitable for this purpose. Obviously, it will be possible for the diameter of the inner mould to vary as a function of the diameter of the desired thin-walled cylindrical bodies which are to be manufactured. By way of example, a hollow inner mould may have an external diameter of 204 mm with a wall thickness of 2.54 cm. If desired, there may be chambers which are filled with a liquid with a good coefficient of thermal conduction, for example heat-transfer oils or water, provided in a solid inner mould. For the outer mould, a material with a lower coefficient of (thermal) expansion than the coefficient of (thermal) expansion of the inner mould is selected. If, by way of example, the inner mould is made from aluminium, the outer mould may be made, for example, from steel. Numerous other materials which have a low or even negative expansion coefficient are known from the literature. The dimensionally stable and seamless outer mould preferably has a negative coefficient of thermal expansion, which ensures that it is possible to produce seamless and thin-walled products. A suitable example of this is an outer mould made from oriented carbon fibres which are wound around a metal, for example nickel, sleeve. The orientation of the fibres determines the expansion coefficient.

According to another embodiment, the dimensionally stable outer mould is made from fibre-reinforced plastic material, more particularly from an epoxy matrix containing carbon fibres, which even more preferably has a negative expansion coefficient. The latter can be achieved by suitably selecting and in particular orienting the corresponding carbon fibres in the plastic matrix. Cf . for example US-A-5, 071, 506. It is also possible to use a roller comprising fibre- reinforced carbon with a hard cylindrical casing. In this roller, the orientation of the carbon fibres determines whether the roller expands or shrinks in the event of an increase in temperature. The hard casing may, for example, be made from aluminium, nickel, stainless steel or a dispersion of hard particles. It is preferable to use an outer mould which shrinks in the event of an increase in temperature and an inner mould which expands during an increase in temperature. One example of an inner mould of this type is a relatively thick carbon fibre roller with a relatively thin nickel sleeve or nickel layer attached to it. In the event of an increase in temperature, the overall assembly will expand; the expansion of the carbon-fibre roller is greater than that of the nickel sleeve. A relatively thick-walled carbon fibre roller which shrinks in the event of a temperature rise may be selected for the outer mould, with a relatively thin nickel sleeve or nickel layer present on the inner side. In that case, the overall assembly will shrink when the temperature rises, since the carbon fibre roller overcomes the nickel sleeve. A thin metal outer mould, for example made from aluminium, which is placed under pressure from the outer side and therefore shrinks, can also be used. This ensures that, in the event of an increase in temperature during which the inner mould expands uniformly, the outer mould contracts uniformly, with the result that the fibre-reinforced plastic material which has been applied to the inner mould is compressed.

If use is made, for example, of a metal inner mould, for example made from aluminium, and an outer mould made from epoxy reinforced with carbon fibres, a smooth and seamless thin-walled tubular body is obtained. The method according to the invention can advantageously be used for manufacturing tubular thin-walled bodies with a diameter which is between 15 and 400 mm (deviation ± 0.03%) and a length which may be from less than 1 metre to more than 5 metres, the wall thickness lying between 5 and 1000, preferably 5 and 700 micrometers (deviation ± 5%) . The difference in fibre content per m² is less than ± 5% over an average of 10 mm². The surface roughness on the outer side of the tubular bodies obtained in this way is advantageously less than 0.3 Ra. Smooth tubular bodies of this type are particularly suitable as premoulds for printing formes for use in printing techniques, as already described above. If desired, greater roughness is possible.

Advantageously, a vacuum is substantially applied to the space between the inner mould with fibre-reinforced plastic material and the outer mould, with the result that there can be little or no inclusion of gas, for example air, oxygen, nitrogen or water vapour, in the resulting tubular body, which could otherwise lead to a reduced quality of the tubular body manufactured in this way.

According to a further preferred embodiment of the method according to the invention, step c) comprises the operation of subjecting one or both moulds to a temperature change, provided that the coefficient of thermal expansion of the inner mould is greater than the coefficient of thermal expansion of the outer mould. In a simple embodiment of this, step c) comprises the operation of subjecting one or both moulds to an increase in temperature. In the preferred combination of a metal inner mould and an outer mould made from epoxy reinforced with carbon fibres and with a negative expansion coefficient which has already been referred to above, this leads, in a simple manner, i.e. by means of a temperature increase, to' the space being simultaneously reduced in size through expansion of the inner mould and contraction of the outer mould and to the fibre-reinforced plastic material situated on the inner mould being compressed and hardened in this state. If a thermosetting plastic matrix is used as starting material for the manufacture of the tubular bodies, in this case steps c) and d) of the method according to the invention take place simultaneously. With thermosetting plastic materials, the temperature will be increased at least to the hardening temperature of the thermosetting plastic material. If a thermoplastic is being used as matrix for the fibre-reinforced plastic material from which the thin-walled tubular body is manufactured with the aid of the method according to the inventions, step d) involves solidifying the plastic material in the pressurized state.

According to another embodiment, step c) comprises the operation of subjecting the dimensionally stable inner mould to an increase in pressure, if desired in combination with a change in temperature .

Obviously, it is also possible for the outer mould to be heated prior to the introduction of the inner mould with fibre-reinforced plastic material and to be expanded in this way, and then for the outer mould to be cooled and therefore contracted after the introduction of the inner mould together with reinforced plastic material, a process which likewise results in the desired reduction in the volume of the space between outer mould and fibre-reinforced plastic material. In cross section, the inner mould and outer mould are advantageously round in shape, and more preferably are cylinders. If desired, the moulds may be conical cylinders, for example for the production of thin conveyor belts for a bend or curve. Preferably, the moulds are cylinders of constant diameter. The walls of the inner mould and outer mould, in particular the outer wall of the inner mould and the inner wall of the outer mould, are smooth and seamless. In this way, a thin-walled, smooth and seamless tubular body is obtained using the invention.

If desired, the thin-walled tubular body which has been manufactured can be released from the outer mould (and, if necessary, the inner mould) by using compressed air.

According to a second aspect, the invention relates to a seamless thin-walled tubular body made from fibre-reinforced plastic material which is obtained using the method according to the invention. The wall thickness of the tubular body according to the invention is preferably 0.005 to 1 mm, more preferably 0.005 to 0.7 mm.

The matrix material for the fibre-reinforced plastic material from which the tubular body according to the invention is produced will be selected on the basis of the intended application of the tubular body produced. Examples include thermoplastics, such as polyester and polypropylene, and thermosetting polymers, such as epoxy, and elastomers, and ceramic materials. Examples of more heat- resistant matrix materials include, inter alia, polyether ether ketone (PEEK) , polyimide (PI) , polyether imide (PEI) , polyphenylene sulphide (PPS) and, to a slightly lesser extent, epoxy resin. Examples of fibres which can be used in the plastic material include fibres made from plastic, metal, ceramic, glass, carbon and natural fibres such as flax, cellulose and cotton. Unidirectional fibres are preferred, since these in principle are able to achieve the highest rigidity of the tubular body. The fibre content is preferably greater than 50% by volume, in particular greater than 55% by volume. The combination of carbon fibres and epoxy matrix is preferred, on account of the excellent ratio of cost to rigidity. The fibre-reinforced plastic materials are advantageously prepreg materials, such as unidirectional carbon-fibre-containing prepreg materials with the carbon fibres oriented in one direction. These prepreg materials may comprise a fibre weight of 5 g/m² - 700 g/m². Depending on the plastic material selected, the hardening step d) will be carried out by means of solidifying or hardening by increasing the temperature.

The hardening temperature is dependent on the type of matrix material used in the fibre-reinforced plastic material. The invention also relates to a device for the manufacture of a thin-walled tubular body from fibre-reinforced plastic material using the method according to the invention, which device comprises an assembly of a seamless, dimensionally stable tubular outer mould and a dimensionally stable inner mould which can be positioned coaxially, the internal diameter of the outer mould being greater than the external diameter of the inner mould, and means for reducing the size of a space between the two moulds. The distance between the external diameter of the inner mould and the internal diameter of the outer mould is equal to 0.1 to 2 mm plus the thickness of the fibre- reinforced plastic material (in mm) . Therefore, a distance of from

0.1 to 2 mm is present in order to form the assembly. In general, the clearance is only a few tenths of a millimetre. The coefficient of thermal expansion of the inner mould is preferably greater than that of the outer mould, and the device preferably also comprises heating means for heating the mould assembly.

The invention will be explained below with reference to the appended drawing, in which:

Fig. 1 shows an axial section through an embodiment of a device according to the invention; and Figs. 2 and 3 show cross-sectional views of an assembly of inner mould and outer mould with thin-walled tubular body as shown in Fig. 1.

A fibre-reinforced plastic material is applied to a single- part, dimensionally stable and smooth cylindrical inner mould 1, which is made, for example, from aluminium. The application of a material of this type, as a so-called "prepreg material", to an inner mould may take place in various ways which are known in the art per se. Examples are the manual laying of strips of fibre-reinforced plastic material, filament winding, the application of a braided material, extrusion, winding of tape or fibre. As has already been described above, the preferred fibre-reinforced plastic material is a composite of carbon fibres in epoxy. The use of the prepreg materials allows the carbon fibres to be applied to the inner mould 1 in any desired direction and with any desired thickness. A seamless, dimensionally stable outer mould 2 made from a single part is then pushed axially over the inner mould 1 which has been covered in this way. At ambient temperature, the outer mould 2 has a larger internal diameter than the external diameter of the inner mould 1, so that a space, which is denoted overall by reference numeral 4, is enclosed between the inner mould 1 and the outer mould 2 with the fibre- reinforced plastic material. During operation, this space 4 is preferably evacuated by means of a vacuum device 5 before the solidification of a thermoplastic, or the hardening by an increase in temperature of a thermosetting plastic, is carried out. When the assembly is arranged in a furnace 6, the situation illustrated in Fig. 2 will prevail at the beginning of the hardening process. The fibre-reinforced plastic material bears against the outer surface of the inner mould 1. After an increase in temperature, for example to 140 °C or 270 °C or even higher, selected in particular according to the matrix material of the fibre-reinforced plastic material, if the inner mould 1 is produced from a material with higher coefficient of thermal expansion than the outer mould 2, the fibre-reinforced plastic material will, over the course of time, come into contact with the inner wall of the outer mould 2, and will thereby be compressed between the inner mould and outer mould.

After sufficient hardening time, the assembly is cooled again to room temperature, so that the configuration illustrated in Fig. 3 is obtained, in which a tubular body 3 made from fibre-reinforced plastic material is bearing against the inner wall of the outer mould 2 and there is now a space between the outer wall of the inner mould 1 and the body 3 of fibre-reinforced plastic material. Consequently, the inner mould 1 can easily be removed by being pushed axially out of the outer mould. The tubular body 3 can easily be removed from the outer mould 2 by blowing compressed air in between them. It will be understood that the dimensions indicated in Figs. 2 and 3, in particular the size of the intervening space 4, are exaggerated. This space is usually as small as possible, for example less than 1 mm, more preferably less than 0.3 mm. A smaller space offers the advantage that, firstly, the space is easier to evacuate, and, secondly, a quicker process time is achieved. A few examples are given below.

For the manufacture of thin-walled cylinders which are particularly suitable for use in the abovementioned rotary screen- printing techniques, respectively two layers of prepreg material and five layers of prepreg material are hardened in accordance with the invention. The orientation of the fibres in these multilayer products differs, so that the tubular end product has anisotropic properties. By way of example, for a sleeve two layers of 70 g/m² carbon-fibre- containing prepreg material are used, the fibres being oriented in a direction of +70° and -70° with respect to the axis of the inner mould. For production of a stencil, it is possible, for example, to use five layers of a material comprising prepreg material containing unidirectional carbon fibres, with a carbon content of 30 g/m², which are oriented in different directions, for example of ±45°, 0°, ±45°, or ±60°, 0, ±60°. An alternating layer system of this type offers good rigidity in particular for stencils.

With a view to economic considerations, the process time, i.e. the heating and cooling time, should be as short as possible. Forced heating and cooling may be provided for this purpose. Forced cooling of this type may, for example, be brought about by the heated assembly of inner mould, outer mould and cylindrical body being immersed in a cold water bath. An alternative is for cooling elements to be fitted in one or both moulds .

Claims

C L A I M S

1. Method of manufacturing a thin-walled seamless tubular body (3) from fibre-reinforced plastic material, which method comprises the steps of a) applying fibre-reinforced plastic material to a dimensionally stable tubular inner mould (1) ; b) positioning the inner mould (1) with fibre-reinforced plastic material in a seamless, dimensionally stable tubular outer mould (2) by relative displacement with respect to one another in the longitudinal direction, leaving clear a space (4) which is substantially present between the surface of the fibre-reinforced plastic material and the inner surface of the outer mould (2) ; c) reducing the size of the space (4) by relative displacement of the outer mould (2) and the inner mould (1) with fibre-reinforced plastic material with respect to one another in such a manner that the fibre-reinforced plastic material is subjected to pressure and is brought into contact with the inner mould (1) and the outer mould (2); d) causing the plastic material to flow; e) hardening the plastic material in the pressurized state; f) relieving the pressure; and g) removing the seamless thin-walled tubular body (3) which has been manufactured by relative displacement in the longitudinal direction with respect to the inner mould (1) and outer mould (2) .

2. Method according to claim 1, characterized in that the seamless thin-walled tubular body (3) which has been produced has a wall thickness in the range from 0.005 to 1 mm.

3. Method according to claim 2, characterized in that the wall thickness lies in the range from 0.005 to 0.7 mm.

4. Method according to one of the preceding claims, characterized in that the inner mould (1) is made from metal.

5. Method according to claim 4, characterized in that the metal is aluminium.

6. Method according to one of the preceding claims , characterized in that the outer mould (2) has a negative coefficient of thermal expansion .

7. Method according to one of the preceding claims, characterized in that the outer mould (2) is made from a fibre-reinforced plastic material .

8. Method according to claim 7, characterized in that the fibre- reinforced plastic material comprises carbon fibres in an epoxy matrix.

9. Method according to one of the preceding claims, characterized in that the space (4) between the inner mould (1) with fibre- reinforced plastic material and the outer mould (2) is evacuated substantially.

10. Method according to one of the preceding claims, characterized in that step c) comprises the operation of subjecting one or both moulds (1, 2) to a temperature change, the coefficient of thermal expansion of the inner mould (1) being greater than the coefficient of thermal expansion of the outer mould (2) .

11. Method according to claim 10, characterized in that step c) comprises the operation of subjecting one or both moulds (1, 2) to an increase in temperature.

12. Method according to claim 11, characterized in that the temperature is increased to at least the hardening temperature of a thermosetting fibre-reinforced plastic material.

13. Method according to claim 11, characterized in that the temperature is increased to at least the softening temperature of a thermoplastic fibre-reinforced plastic material and is then reduced to the hardening temperature .

14. Method according to one of the preceding claims, characterized in that step c) involves subjecting the inner mould (1) and/or the outer mould (2) to an increase in pressure.

15. Method according to one of the preceding claims, characterized in that the inner mould (1) and outer mould (2) , in cross section, are of a round shape, more preferably are cylinders, and even more preferably are cylinders of constant diameter.

16. Seamless thin-walled tubular body (3) made from fibre- reinforced plastic material, obtained using the method according to one of the preceding claims.

17. Tubular body according to claim 16, characterized in that the wall thickness is 0.005 to 1 mm and more preferably 0.005 to 0.7 mm.

18. Tubular body according to claim 16 or 17, characterized in that the fibre-reinforced plastic material comprises carbon fibres in an epoxy matrix.

19. Device for producing a thin-walled tubular body (3) from fibre- reinforced plastic material according to one of claims 1 - 15, comprising an assembly of a seamless, dimensionally stable tubular outer mould (2) and a dimensionally stable, tubular inner mould (1) which can be positioned coaxially, the internal diameter of the outer mould (2) being greater than the external diameter of the inner mould (1) , and means for reducing^' the size of a space (4) between the two moulds (1, 2) .

20. Device according to claim 17, characterized in that the coefficient of thermal expansion of the inner mould (1) is greater than that of the outer mould (2) , and the device also comprises heating means (6) for heating the assembly.

21. Device according to claim 19 or 20, characterized in that the dimensionally stable inner mould (1) is made from a metal, more preferably aluminium.

22. Device according to one of the preceding claims 19 - 21, characterized in that the dimensionally stable outer mould (2) is made from a fibre-reinforced plastic material, more preferably an epoxy matrix containing carbon fibres, and even more preferably with a negative expansion coefficient.

23. Device according to one of the preceding claims 19 - 22, characterized in that the inner mould (1) and outer mould (2) , in cross section, have a circular outer and inner surface, more preferably are hollow cylinders.