GB2404612A

GB2404612A - Sectional mould

Info

Publication number: GB2404612A
Application number: GB0416454A
Authority: GB
Inventors: Ebrahim Gharvam Shahidi; David John Liversage; Clive Ronald Bennett
Original assignee: Advanced Composites Group Ltd
Current assignee: Cytec Industrial Materials Derby Ltd
Priority date: 2003-07-25
Filing date: 2004-07-23
Publication date: 2005-02-09
Anticipated expiration: 2024-07-23
Also published as: GB0416454D0; GB2404612B; GB0317390D0

Abstract

Mould apparatus (10, figure 1) for moulding material M, comprising a mould 12 having at least two parts 14,16 locatable together to form a mould surface (18 figure 1) and means 20 to bridge the sections 14,16 to hold them relative to one another. The means 20 comprises a strip of elastomer laminate having a central ply of relatively stiff material (22 figure 2) sandwiched between two plies (24a, 24b figure 2) of relatively flexible, high tear strength material. The construction of the means 20 enables it to act to resist undesirable distortion of the mould about the join region (5 figure 3) between the sections 14,16, particularly thermal distortion during curing of material within the apparatus (10 figure 1). The mould may be used for large composite bodies such as aircraft wings and turbine blades. A vacuum bag (28 figure 1) may be sealed to the mould sections to allow air to be withdrawn to facilitate the moulding of material on the mould. Also included is a method of joining two sections of a mould by locating means, to bridge a join region between the two sections.

Description

Moulding Materials The present invention relates to moulding materials and particularly but not exclusively to a method of moulding large composite bodies. The requirement for large composite bodies is increasing. For instance components such as aircraft wings and wind turbine blades with lengths in excess of thirty metres are increasingly being demanded and there are many advantages in such components being moulded from reinforced composite materials. Further, the physical and mechanical characteristics required of such components means that it is preferred, and sometimes essential, that at least the main structure thereof is moulded as a unitary body. To manufacture such bodies requires moulds of equal or greater length. To produce such moulds requires a master model to be prepared over which the moulds can be formed. The necessary precision required in such moulds means that typically the master models are cut using CNC cutting apparatus and the overall size of the master models that can be produced has generally been governed by the size of suitable CNC machines. Moulds comprising a number of sections have been produced but these have proven problematic. The provision of a number of sections give such moulds quite different physical characteristics compared to similar unitary moulds and it is found that this can adversely affect the quality and characteristics of articles moulded therein. In this specification the term "mould" is used to refer to moulds and tools in, over and/or around which a body can be moulded. According to the present invention there is provided mould apparatus for moulding material, the apparatus comprising a mould comprising at least two sections and means to bridge the sections to hold the sections relative to one another. Preferably the means is locatable over the sections and desirably over, and more desirably along, a join region between two sections. The means is preferably attached, in use, to one or more sections. Preferably the means imparts strength over the join region and thereby provides the mould with sufficient overall strength to ensure satisfactory performance of the mould, including resistance to distortion of the mould over the join region particularly during use of the apparatus during moulding of an article therein. Preferably the means is semi-rigid and provides a semi-rigid bridge between the join region. Preferably the means provides a seal across the join region, which seal may be substantially air tight. Preferably the sections locate together to form a mould surface. Preferably the means does not extend onto the mould surface and is desirably remote therefrom. The means may be located around the join region over which the sections locate together, and is preferably located externally of the sections. The means preferably has some limited flexibility to ensure integrity thereof during limited relative movement between the sections. However, preferably the means has good resistance to thermal expansion. The means may comprise elastomeric material. The means may comprise a plurality of layers of material. At least one of said layers may comprise a relatively flexible elastomer, desirably having relatively high tear resistance characteristics. At least one other of said layers preferably comprises a relatively stiff material, which preferably has a low expansion coefficient and which may be an elastomer. In a preferred construction of means the layer of relatively stiff or rigid material is located between layers of relatively flexible elastomer. A layer of relatively flexible elastomer preferably locates over the join region, which layer generally provides the seal. Said layer may have a larger surface area than the layer of relatively stiff material attached thereto, which in turn may have a relatively larger area than the further layer of relatively flexible layer attached thereto. Preferably the relatively flexible layer comprises fluoro-elastomers, silicone rubber or other elastomeric material with generally similar flexibility characteristics. The layer of relatively stiff material may comprise a carbon prepreg, or other relatively stiff elastomer. An adhesion promoter, such as an adhesive material, may also be provided to facilitate adhesion of the means over the said join region.

The means may comprise a strip locatable along the said join region. Securing means may be provided to secure location of ends of the means to one or more of the sections. The securing means may comprise a fluoroelastomeric material, desirably in sheet form. Preferably the mould apparatus further comprises means to seal or further seal the mould and enable air to be drawn from therewithin whereby to facilitate moulding of material on the mould. The means may comprise a flexible member locatable over the sections, which member may be a vacuum bag. The member may comprise an opening connectable to further means operable to draw air from within the mould. Preferably the flexible member is sealingly located over the said sections so that as air is drawn from within the mould the air pressure therein reduces, with the means acting to prevent undesirable movement and distortion between the sections about the join region and to preferably maintain the thermal profile of the mould, particularly during curing of material in the mould, as well as preventing undesirable ingress of air through the said join region. The flexible member is preferably sealed over the fluoro-elastomeric material. Tape or other suitably adhesive material may be used to sealingly locate the flexible member on the mould. The invention further provides a method of joining two sections of a mould by locating means to bridge a join region between the sections to hold the sections relative to one another. Prefereably the method involves the use of mould apparatus and means as described in any of the preceding paragraphs. The invention still further provides a mould substantially as described in any of the preceding paragraphs. According to a further aspect of the present invention there is provided means substantially as described in any of the preceding paragraphs. According to a still further aspect of the present invention there is provided a method of moulding a body comprising locating moulding material within mould apparatus substantially as described above, and drawing air from within the apparatus as the material is cured to reduce the pressure within the mould to facilitate the release of air from within the moulding material. Preferred embodiments of the present invention will now be described by way of example only, with reference to the accompanying drawings in which:- Fig. 1 is a diagrammatic cross-sectional view of mould apparatus according to the present invention; Fig. 2 is an enlarged cross-sectional view of the region 11 in Fig. 1; Fig. 3 is a plan view of the apparatus of Fig. 1; Fig. 4 is a perspective view of the exterior of two connected sections of a mould according to the present invention; Fig. 5 is a perspective view from the inside of the section of Fig. 4; and Fig. 6 is an enlarged view of the region VI of Fig. 5. Referring to the drawings there is provided mould apparatus 10 for moulding material M, the apparatus comprising a mould 12 having at least two sections 14, 16 (Figs. 3 to 6) locatable together to form a mould surface 18 and means 20 to bridge the said sections 14, 16 to hold them relative to one another. In more detail, the mould apparatus 10 is described in this particular embodiment as having two sections 14, 16 sealingly located together to define a mould surface 18. Each section 14, 16 has a base surface 11 from which two upstanding side surfaces 13 extend to define the generally 'U'-shaped mould surface 18. An end surface 15 extends between edges of the side and base surfaces 11, 13 of each section 14, 16 so that when the sections 14, 16 are located together they define a hollow defining at least in part the mould surface 18. In Figs. 4 and 5 the end surface 15 are removed for clarity. Referring particularly to Figs. 2, 4 and 6, the means 20 comprises a strip of elastomer laminate having a central ply of relatively stiff material 22 sandwiched between two plies 24a and 24b of relatively flexible, high tear strength material. The construction of the means 20 enables the means 20 to act to resist undesirable distortion of the mould about the join region J between the sections 14, 16, particularly thermal distortion during curing of material within the apparatus 10, as will be described. The central ply 22 comprises a semi-rigid material, such as a carbon pre- preg or other elastomeric material. This provides the means 20 with relative rigidity and resistance to distortion. The upper and lower plies 24a, 24b comprise relatively flexible materials such as fluoro-elastomeric material, silicone rubber or other elastomeric material of suitable character. The lower ply 24b which lies in contact with the section 14, 16 provides a seal, which is preferably air tight, over the join region J. The surface area of the ply 24b is greater than that of the other two plies 24a, 22 to facilitate provision of a seal over the join region J. The surface area of the central ply 22 is greater than that of the upper ply 24a. This construction has proven to give the means 20 physical characteristics which help to ensure the mould functions substantially as though it were unitary, in particular acting to resist thermal and mechanical distortion of the mould about the join region J.Prior to location of the means 20 over the join region J an adhesion promoter can be applied to assist location of the means 20. As can be seen from the drawings, a single length of means 20 extends over the, in use, exterior of the sections 14, 16 to provide a seal remote from the mould surface 18. This ensures that the means 20 does not adversely affect the quality of the surface of the body moulded on the mould surface 18. It will be appreciated that whilst it is preferable for a single strip of seal means 20 to extend around the join region J, a plurality of strips may be used to provide a substantially airtight seal all around the join region. The ends 21 of the seal means 20 are wrapped around the lips 23 of the sections 14, 16 to ensure sealing around the whole of the length of the join region J. As can be seen particularly in Figs. 2 and 6, the lengths of the strips of the material 22 and 24a, 24b are chosen so that the ends of the respective strips of material 22, 24a and 24b are staggered such that the overlap of 24a around the edge of the sections 14, 16 is less than that of the strip of material 22 which in turn is less than that of the strip of material 24b. Again this structure is found to assist performance of the means 20. A piece of fluoro-elastomeric material 26 is used to secure the means 20 to the sections 14, 16. The fluoro-elastomeric material 26 extends over the join region between the sections 14, 16 and partially over the end of the ply of material 24b. The mould apparatus 10 also comprises means to evacuate air from within the mould 12 whereby to reduce the air pressure within the mould 12 and facilitate removal of air trapped within the moulding material M during curing thereof, as will be explained. The means comprises a vacuum bag 28 sealingly located over the sections 14, 16 and which is attached via an outlet 34 to means for drawing air from within the mould 12, such as vacuum apparatus (not shown). The vacuum bag 28 may be of generally conventional design. The vacuum bag 28 is sealingly secured over the upper surfaces 30, defined in part by the lips 23 and similar lips 25 extending from the edge surfaces 15 by using "tacky tape" in generally conventional manner. Where the vacuum bag 28 extends over ends 21 of the means 20, it is secured to the fluoro-elastomeric material 26 to effectively produce an airtight seal. In this construction, the mould apparatus 10 has a substantially airtight seal around the region J of location between the sections 14, 16 by virtue of the means 20. The sealing location of the vacuum bag 28 around the upper surface 30 of the mould 12, including the regions of overlap over the fluoro-elastomeric material 26, ensure that the inside of the mould is substantially air tight. In use, the apparatus 10 is used to mould moulding material M located on the moulding surface 18. The materials M of particular interest are fibrereinforced composite materials, although the apparatus 10 can be used to mould other suitable types of material. The material M may be located in the form of pre-pregs or may be manually layered in usual manner for moulding composite material. The sections 14, 16 will preferably be located together with means 20 before the moulding material M is applied to the mould surface 18. However it is conceivable that the seal means 20 could be applied thereafter. The vacuum bag 28 would generally be sealingly located on the sections 14, 16 once the material M had been located in the mould 12. Once the means 20 and vacuum bag 28 are in place, the material M can be subjected to appropriate curing processes to form a moulded body. The removal of air from within the mould 12 through the outlet 34 reduces the air pressure within the mould 12 and thereby facilitates the removal of air trapped within the material M, as the material M cures during moulding. In conventional manner heat would be applied during curing. The means 20 acts to resist any distortion that may naturally occur across the join region, particularly thermal distortion as the mould is heated during curing. The physical characteristics of the materials used in the means 20 and the arrangement of these in plies 22, 24a, 24b are important, although it will be appreciated that alternative arrangements may be adopted to act in similar manner.The means 20 also provides a seal across the region J, so that the means 20 acts to maintain the integrity of the mould and the satisfactory performance thereof under different conditions particularly of heat, pressure and vacuum. Once the moulding process is complete, the tacky tape 32 can be removed allowing for release of the vacuum bag 28. Application of the tacky tape 32 to the fluoro-elastomeric material 26 facilitates removal of the tacky tape 32 therefrom without damaging the integrity of the means 20. This enables the mould 12 to be re-used. The moulded body can then be removed from the mould 12. As mentioned hereinbefore, the particular embodiment exemplified in relation to the drawings comprises a mould 12 having two sections 14, 16 joined together. It will be appreciated that any number of sections can be bridged together in accordance with this invention. A particularly useful application of the present invention is to enable the moulding of unitary bodies of large sizes including bodies of great length. It will be appreciated that moulds can be produced in accordance with the invention defining a mould surface essentially of any length by locating any number of sections, whether similar or dissimilar together using means 20.Using the invention, elongate composite bodies such as aircraft wings and wind turbine blades which may be required to be in excess of thirty metres in length, and perhaps up to eighty metres in length, can be produced as a single moulding or unitary body while still maintaining the desired physical characteristics mould and therefore of the moulded articles and ensuring the appropriate removal of air entrapped within the moulding material during curing. Various modifications may be made without departing from the spirit or scope of the present invention. The moulds described above could be used as master models from which moulds for moulding bodies can be produced. Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon. 1. Mould apparatus for moulding material, the apparatus comprising a mould comprising at least two sections and means to bridge the sections to hold the sections relative to one another.

Claims

2. Mould apparatus as claimed in claim 1, in which the means is locatable over the sections.

3. Mould apparatus as claimed in claim 1 or claim 2, in which the means is locatable over a join region between the two sections.

4. Mould apparatus as claimed in claim 3, in which the means is locatable along the join region.

5. Mould apparatus as claimed in any preceding claim, in which the means is attached, in use, to one or more sections.

6. Mould apparatus as claimed in any of claims 3 to 5, in which the means imparts strength over the join region and thereby provides the mould with sufficient overall strength to ensure satisfactory performance of the mould, including resistance to distortion of the mould over the join region particularly during use of the apparatus during moulding of an article therein. 7. Mould apparatus as claimed in any of claims 3 to 6, in which the means is semi-rigid and provides a semi-rigid bridge over the join region.

8. Mould apparatus as claimed in any of claims 3 to 7, in which the means provides a seal across the join region.

9. Mould apparatus as claimed in claim 8, in which the seal in substantially air tight.

10. Mould apparatus as claimed in any preceding claim, in which the sections locate together to form a mould surface.

11. Mould apparatus as claimed in claim 10, in which the means does not extend onto the mould surface.

12. Mould apparatus as claimed in claim 10 or claim 11, in which the means is remote from the mould surface.

13. Mould apparatus as claimed in any of claims 10 to 12, in which the means is located around the join region over which the sections locate together. 14. Mould apparatus as claimed in any preceding claim, in which the means is located externally of the sections.

15. Mould apparatus as claimed in any preceding claim, in which the means has some limited flexibility to ensure integrity thereof during limited relative movement between the sections.

16. Mould apparatus as claimed in any preceding claim, in which the means has good resistance to thermal expansion.

17. Mould apparatus as claimed in any preceding claim, in which the means comprises elastomeric material.

18. Mould apparatus as claimed in any preceding claim, in which the means comprises a plurality of layers of material.

19. Mould apparatus as claimed in claim 18, in which at least one of said layers comprises a relatively flexible elastomer.

20. Mould apparatus as claimed in claim 19, in which the elastomer has relatively high tear resistance characteristics. 21. Mould apparatus as claimed in any of claims 18 to 20, in which at least one other of said layers comprises a relatively stiff material.

22. Mould apparatus as claimed in claim 21, in which the relatively stiff material has a low expansion coefficient.

23. Mould apparatus as claimed in claim 21 or claim 22, in which the material is an elastomer.

24. Mould apparatus as claimed in claim 23, in which the layer of relatively stiff or rigid material is located between layers of relatively flexible elastomer.

25. Mould apparatus as claimed in any of claims 19 to 24, in which a layer of relatively flexible elastomer locates over the join region, which layer generally provides the seal.

26. Mould apparatus as claimed in claim 25, in which said layer has a larger surface area than the layer of relatively stiff material attached thereto. 27. Mould apparatus as claimed in any of claims 24 to 26 in which the layer of relatively stiff material has a larger surface area than the further layer of relatively flexible elastomer attached thereto.

28. Mould apparatus as claimed in any of claims 19 to 27, in which the relatively flexible layer comprises fluoro-elastomers, silicone rubber or other elastomeric material with generally similar flexibility characteristics.

29. Mould apparatus as claimed in any of claims 21 to 28, in which the layer of relatively stiff material comprises a carbon pre-preg, or other relatively stiff elastomer.

30. Mould apparatus as claimed in any of claims 3 to 29, in which an adhesion promoter, such as an adhesive material, is provided to facilitate adhesion of the means over the said join region. 31. Mould apparatus as claimed in any of claims 3 to 30, in which the means comprises a strip locatable along the said join region.

32. Mould apparatus as claimed in any preceding claim, in which securing means is provided to secure location of ends of the means to one or more of the sections.

33. Mould apparatus as claimed in claim 32, in which the securing means may comprise a fluoro-elastomeric material.

34. Mould apparatus as claimed in claim 32 or claim 33, in which the securing means is in sheet form.

35. Mould apparatus as claimed in any preceding claim, in which the mould apparatus further comprises means to seal or further seal the mould and enable air to be drawn from therewithin whereby to facilitate moulding of material on the mould.

36. Mould apparatus as claimed in claim 35, in which the means comprises a flexible member locatable over the sections. 37. Mould apparatus as claimed in claim 36, in which the member may be a vacuum bag.

38. Mould apparatus as claimed in claim 36 or claim 37, in which the member comprises an opening connectable to further means operable to draw air from within the mould.

39. Mould apparatus as claimed in any of claims 36 to 38, in which the flexible member is sealingly located over the said sections so that as air is drawn from within the mould the air pressure therein reduces, with the means acting to prevent undesirable movement and distortion between the sections about the join region.

40. Mould apparatus as claimed in claim 39, in which the means acts to maintain the thermal profile of the mould, particularly during curing of material in the mould, as well as preventing undesirable ingress of air through the said join region. 41. Mould apparatus as claimed in any of claims 36 to 40, in which the flexible member is sealed over the fluoro-elastomeric material.

42. Mould apparatus as claimed in claim 41, in which tape or other suitably adhesive material is used to sealingly locate the flexible member on the mould.

43. A method of joining two sections of a mould by locating means to bridge a join region between the sections to hold the sections relative to one another.

44. A method as claimed in claim 43, in which the method comprises the use of mould apparatus as defined in any of claims 1 to 42.

45. A method as claimed in claim 43 or claim 44, in which the method involves the use of means as defined in any of claims 1 to 42.

46. A mould substantially as defined in any of claims 1 to 42.

47. Means as defined in any of claims 1 to 42. 48. A method of moulding a body comprising locating moulding material within mould apparatus as defined in any of claims 1 to 42, and drawing air from within the apparatus as the material is cured to reduce the pressure within the mould to facilitate the release of air from within the moulding material.

49. Mould apparatus substantially as hereinbefore described with reference to accompanying drawings.

50. A method substantially as hereinbefore described with reference to the accompanying drawings.

51. A mould substantially as hereinbefore described with reference to the accompanying drawings.

52. A method of moulding in body substantially as hereinbefore described with reference to the accompanying drawings.

53. Means substantially as hereinbefore described with reference to the accompanying drawings. 54. Any novel subject matter or combination including novel subject matter disclosed herein, whether or not within the scope of or relating to the same invention as any of the preceding claims.