CORROSION RESISTANT STEEL (CRES) BLADDER

Abstract

The disclosure concerns an out-of-autoclave thermoplastic consolidation apparatus and method comprising a metallic bladder which is biased against a lower part of a tool during a consolidation process to form a composite component.

Claims

1.-20. (canceled)

21. An out-of-autoclave thermoplastic consolidation apparatus comprising: an upper forming tool; a lower forming tool opposing the upper forming tool, the upper forming tool and lower forming tools defining a space therebetween for forming a part; a caul plate arranged between the upper forming tool and the lower forming tool, the caul plate being removable from the space and configured to contact a surface of the part; and an expandable bladder arranged between the caul plate and the upper tool, the expandable bladder extending across the caul plate and including a pair of opposing flexible surfaces and a peripherally extending seal.

22. The apparatus of claim 21, wherein the expandable bladder includes two opposing layers defining an expansion chamber therebetween and a port in fluid communication with the expansion chamber.

23. The apparatus of claim 22, wherein the two opposing layers are metallic layers.

24. The apparatus of claim 23, wherein the metallic layers are formed of a material selected from stainless steel, Steel, Plated steel, Invar steel or Titanium.

25. The apparatus of claim 22, wherein the peripherally extending seal is a weld and seals the expansion chamber.

26. The apparatus of claim 25, wherein peripherally extending seal extends around a perimeter of the port.

27. The apparatus of claim 22, wherein the port is a pressure coupling extending laterally from the pair of flexible surfaces, the pressure coupling including a fluid pressure connection arranged perpendicularly to a plane of the pair of flexible surfaces.

28. The apparatus of claim 21, wherein the flexible surfaces are between 0.3 mm to 0.5 in thickness.

29. The apparatus of claim 21, wherein the flexible surfaces are of dissimilar thicknesses.

30. The apparatus of claim 21, wherein the lower forming tool has a geometry corresponding to at least part of a required geometry of the part.

31. The apparatus of claim 21, wherein the caul plate includes a first face corresponding to a required geometry of the part and an opposing compression face arranged to abut the expandable bladder.

32. The apparatus of claim 21, wherein one of the lower forming tool and the upper forming tool is arranged to receive a plurality of sub-parts to be co-consolidated together.

33. The apparatus of claim 21, wherein at least one of the upper forming tool and the lower tool include an internal conduit to receive at least one of a cooling fluid, a heating fluid, an electrical element, and an inductive element so as to allow for the control of the temperature of the at least one of the upper forming tool and the lower tool.

34. The apparatus of claim 21, wherein at least one of the upper forming tool and the lower tool include a recess on a non-part facing side of the respective tool.

35. The apparatus of claim 21, wherein the at least one of the upper forming tool and the lower tool contacts a press platen at locations around the recess.

36. An out-of-autoclave method of consolidating a thermoplastic part, comprising: laying a plurality of thermoplastic containing plies onto a lower forming tool to form a stack; positioning a caul plate onto the stack so that the stack is between the caul plate and the lower forming tool; positioning an expandable bladder onto the caul plate so that the caul plate is between the stack and the expandable bladder, wherein the expandable bladder extends across the caul plate and includes a pair of opposing flexible surfaces and a peripherally extending seal; positioning an upper forming tool onto the expandable bladder so that the expandable bladder is between the caul plate and the upper forming tool; selectively heating and cooling at least one of the upper forming tool and the lower forming tool; and simultaneously selectively applying pressure to the expandable bladder to bias the caul plate against the stack according to a predetermined temperature and pressure sequence.

37. The method of claim 36, wherein the predetermined temperature and pressure sequence includes: increasing a tool temperature continuously to a predetermined temperature; maintaining the tool temperature at a maximum temperature for a predetermined period; and terminating heating at the end of the predetermined period; the method further comprising: applying a first pressure to the expandable bladder during a first consolidation time, applying a second expandable bladder pressure during a second consolidation time; and applying a third expandable bladder pressure during a third consolidation time.

38. The method of claim 37, wherein the first pressure is applied prior to a temperature of the part reaching a glass transition temperature of the part, and the second pressure is applied upon the temperature of the part reaching the glass transition temperature of the part.

39. The method of claim 37, wherein the third pressure is applied after a temperature of the part decreases to a crystallization temperature of the part.

40. A co-consolidation method for a multi-component thermoplastic part, comprising: laying a plurality of first thermoplastic plies defining a first sub-component into recesses in a lower forming tool; laying a plurality of second thermoplastic plies against the plies forming the first sub-component and onto the lower tool to form an unconsolidated multi-component stack; positioning a caul plate onto the multi-component stack so that the multi-component stack is arranged between the caul plate and the lower forming tool; positioning an expandable bladder onto the caul plate so that the caul plate is arranged between the expandable bladder and the multi-component stack; positioning an upper forming tool onto the expandable bladder so that the expandable bladder is arranged between the upper forming tool and the caul plate; selectively heating and cooling at least one of the upper forming tool and the lower forming tool; and simultaneously selectively applying pressure to the expandable bladder to bias the caul plate against the multi-component stack according to a predetermined temperature and pressure sequence.

Description

DRAWINGS

[0072] Aspects of the disclosure will now be described, by way of example only, with reference to the accompanying figures in which:

[0073] FIGS. 1 and 2 illustrate conventional attempts to provide tooling for out of autoclave consolidation;

[0074] FIG. 3 illustrates an arrangement according to an exemplary apparatus described herein;

[0075] FIG. 4 corresponds to the arrangement shown in FIG. 3 with the addition of a caul plate located proximate to the consolidation part;

[0076] FIG. 5A shows a caul plate and expandable bladder according to an exemplary arrangement described herein;

[0077] FIG. 5B shows a pressure coupling of the expandable bladder shown in FIG. 5A;

[0078] FIG. 6 shows an exploded view of the components of an exemplary apparatus described herein;

[0079] FIG. 7 shows the upper surface of the upper tool and thermal mass reducing recesses;

[0080] FIG. 8 shows a temperature, pressure and time graph for an example consolidation process using the method and apparatus described herein; and

[0081] FIG. 9 shows a resultant part from a method and apparatus described herein.

[0082] While the disclosure is susceptible to various modifications and alternative forms, specific embodiments are shown by way of example in the drawings and are herein described in detail. It should be understood however that the drawings and detailed description attached hereto are not intended to limit the disclosure to the particular form disclosed but rather the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the claimed invention.

[0083] Any reference to prior art documents in this specification is not to be considered an admission that such prior art is widely known or forms part of the common general knowledge in the field. As used in this specification, the words comprises, comprising, and similar words, are not to be interpreted in an exclusive or exhaustive sense. In other words, they are intended to mean including, but not limited to. The disclosure is further described with reference to the following examples. It will be appreciated that the disclosure as claimed is not intended to be limited in any way by these examples. It will also be recognised that the disclosure covers not only individual embodiments but also combination of the embodiments described herein.

[0084] The various embodiments described herein are presented only to assist in understanding and teaching the claimed features. These embodiments are provided as a representative sample of embodiments only and are not exhaustive and/or exclusive. It is to be understood that advantages, embodiments, examples, functions, features, structures, and/or other aspects described herein are not to be considered limitations on the scope of the disclosure as defined by the claims or limitations on equivalents to the claims, and that other embodiments may be utilised and modifications may be made without departing from the spirit and scope of the claimed invention. Various embodiments of the disclosure may suitably comprise, consist of, or consist essentially of, appropriate combinations of the disclosed elements, components, features, parts, steps, means, etc, other than those specifically described herein. In addition, this disclosure may include other inventions not presently claimed, but which may be claimed in future.

[0085] It will be recognised that the features of the aspects of the disclosure described herein can conveniently and interchangeably be used in any suitable combination.

DETAILED DESCRIPTION

[0086] An apparatus and method described herein are concerned with the consolidation of thermoplastic materials in a process which does not require an autoclave. This is known in the art as an out-of-autoclave or OOA process. Specifically, the apparatus and method described herein involves a modified heated tool and expandable bladder arrangement which function together to overcome the problems with existing systems.

[0087] There are several problems to overcome when transferring co-consolidation technology from autoclave to a heated press. First, if two hard tools are used in a press, a non-optimal pressure distribution is obtained due to pre-impregnated material and tool tolerances, especially for thin parts. Second, preventing squeeze out of composite material at the part edges is difficult. The configuration of expandable bladder described below removes these issues with existing methods without the use of hydraulic seals. Specifically the use of two CRES membranes' or layers that are welded at the edges and pressurized with either air or hydraulic fluid function to apply the necessary consolidation pressure.

[0088] For completeness the principle of conventional thermoplastic part consolidation in an autoclave is shown in FIG. 1. The part 1 is vacuum bagged on an inner mould line (IML) tool 2 with a high temperature resistant foil (typically Kapton or Aluminium3a) and sealed at the edges with an appropriate sealant 3. Both vacuum bag foil and sealant are disposable. Pressure is applied by raising the pressure in the autoclave and remaining gasses are evacuated via a vacuum system. Heat is applied by heating the air or nitrogen in the autoclave.

[0089] The autoclave process has several disadvantages: [0090] A large volume of air needs to be compressed and heated up to 400? C. This requires a lot of energy; [0091] The vacuum bag, sealants and breathers are disposable and are waste materials; and [0092] The cycle time for thermoplastic consolidation is about 6 hours due to heat up and cool down capability, which is less suited for high rate production.

[0093] To overcome these disadvantages, an alternative method and apparatus for consolidation of thermoplastic parts is described below.

[0094] Referring to FIG. 2, another example of conventional consolidation is shown.

[0095] A flat platen press is used to apply pressure to an unconsolidated laminate stack. In the press two heating/cooling plates (4,5) are mounted. Between these plates a tool set is placed consisting of an IML (inner mould line) 6 and OML (outer mould line) tool 7. Typically, these tools are metallic and rigid.

[0096] A temperature cycle is applied by the heating/cooling platens, comprising: heat up to 375? C., a dwell phase at 375? C. followed by a cool down phase to solidify the part. This press consolidation method is used to consolidate a stack of flat laminates or plies.

[0097] However, the matched metal tools must be very accurate to obtain good pressure and thickness distribution in the part. If the part material has local thickness variations (typically +/?8%), the matched metal tools will compress the thick parts more than the thin parts, possibly leading to areas with voids or in plane waviness due to sideways movement of plies (plies migrate to areas with lower pressure). Furthermore, the plies can be squeezed out of the laminate stack at the open edges 8 shown in FIG. 2. Sometimes this is prevented by applying a foil to the edges of the laminate, but this is labour intensive.

[0098] The present disclosure aims to overcome the high temperature seal problem mentioned above as illustrated with reference to FIGS. 3 and 4.

[0099] Specifically the membrane now consists of two thin stainless steel sheets or membranes 9, 10 that are laser welded 11 at the edges (circumference). This creates a bladder (balloon) that can be inflated to generate pressure to the thermoplastic part. This way there is no need for a high temperature seal of the membrane at the edges. In addition, the closing of the upper tool is not critical to guarantee tightness of the bladder. There can be a gap 12 between upper and lower tool since the laser weld is strong enough to withstand the internal pressure.

[0100] FIG. 4 shows the final system used for co-consolidation of stiffened skins according to an apparatus described herein. A caul plate 13 may be added to have the same pressure distribution and behaviour compared to the autoclave bagging procedure.

[0101] FIGS. 5A and 5B show an example arrangement of expandable bladder as shown in FIGS. 3 and 4 and the pressure coupling in more detail.

[0102] FIG. 5A shows the expandable bladder 14, which is formed by the steel membrane 9 and steel membrane 10 shown in FIG. 3, and the caul plate 13. As shown in FIG. 5A the caul plate 13 is located on top of the expandable bladder 14 with the expandable bladder 14 being larger in area to define a peripheral zone 15 surround the caul plate 13. The expandable bladder 14 comprises a laser formed weld 16 which is located within the peripheral zone 15, i.e., not within the area over which the caul plate 13 is located.

[0103] FIG. 5A also illustrates the bladder pressure coupling 17, i.e., the coupling that is used to communicate pressurised fluid or gas into and out of the bladder 14. As shown, a connection is made with the body of the bladder 14 and a conduit is used to communicate fluid or gas from a compressor, pump, bottle or the like to apply the pressure to the bladder 14.

[0104] FIG. 5B illustrates the arrangement of pressure coupling in more detail. Specifically, two portions of the bladder membranes 9 and 10 extending into a couple portion or region 18 in the same plane as the two membranes 9,10, i.e., the portion or region 18 extends outwards and not perpendicular to the membrane surfaces. This ensures that the surfaces of the bladder 14 can be as flat as possible for insert into the tooling and for alignment with the caul plate 13.

[0105] The portion or region 18 may comprise an aperture allowing the flow of fluid or gas in a perpendicular direction into the space between the membranes 9 and 10 as illustrated by the line and dotted line 19. Fluid or gas may then flow along the line 19 and into a cavity 20 within the bladder 14 in such a manner that the bladder 14 can remain as thin as possible. Returning to FIG. 5A, a threaded valve 21 may be used to connect the pipe to the aperture to communicate the fluid or gas as described above.

[0106] FIG. 6 illustrates the configuration of an apparatus before consolidation according to a method and apparatus described herein.

[0107] As shown, the forming apparatus comprises an upper tool 22 and an inner mould line tool 23, the inner mould line tool 23 being the surface defining the lower profile of the shape to be formed or consolidated and against which a stack of thermoplastic plies is arranged or laid.

[0108] A stack of thermoplastic layers are laid onto the inner mould line tool 23 to form a thermoplastic stack or laminate and the caul plate 24 is then positioned on top of the stack. The caul plate 24 has a lower surface that defines the profile of the desire part shape once consolidated and as such is precisely machined or formed. The upper surface of the caul plate 24 does not require precision machining and is arranged to receive pressure from the expandable bladder or cres membrane 25. As shown the cres membrane or expandable bladder 25 is connected to the pressure coupling 26.

[0109] The upper tool 22 is then located on top of the expandable bladder 25 and the entire formation is placed in a press to secure the individual components shown in FIG. 6 together and in position.

[0110] FIG. 7 illustrates an upper surface of the upper tool 22. As shown in FIG. 7, the upper tool 22 is located on the lower tool/IML tool 23. FIG. 7 illustrates the recesses of pockets 27 located in the upper surface of the upper tool 22. The purpose of the recesses is to improve the heating and cooling time of the tool by lowering the thermal mass. This allows the part to be removed from the press more quickly and another cycle restarted. This maximises manufacturing throughput.

[0111] The mass of the tool is lowered by about 50% by applying pockets 27 at the back side. The thermal cycle therefore require less heating and cooling power resulting in a lower cost heating and cooling system. The arrangement of the pockets is such that the ribs correspond to heating and cooling channel locations in the press platens, for optimized heat up and cool down speed.

[0112] FIG. 8 illustrates one example temperature and pressure profile for a consolidation using an apparatus and method described herein.

[0113] As shown there are 3 separate pressures used during the consolidate cycle and a 3 separate heating cooling periods.

[0114] The process starts with a certain vacuum evacuation pressure on the bladder 14, 25, which is applied to fully retract the bladder 14, 25. This prevents excessive forces on the caul plate 13, 24 coming from the unconsolidated part, which can permanently deform the caul plate 13, 24. The tool is heated and once the part temperature is above the Tg of the thermoplastic matrix material, the material softens and the pressure in the bladder 14, 25 is increased to consolidation pressure. This also protects the caul plate 13, 24 from dents. If the part reaches the consolidation temperature, the temperature is kept constant for the required consolidation time. Next, the part is cooled and when the part temperature is lower than the Tc (crystallization temperature) of the thermoplastic matrix material, the bladder 14, 25 pressure is released and vacuum pressure is applied, so the bladder 14, 25 retracts. This allows the part to release itself upon further cool down due to thermal stress created by the expansion difference between part and tool. Once the temperature is below the Tc and bladder pressure is released, the tool can be moved out of the press.

[0115] FIG. 9 illustrates a co-consolidated part using a method and apparatus described herein. The resulting part has a contoured and smooth aero surface 28 with a spar 29 and rib 30 that are co-consolidated to the aero surface. As shown a complex curved component can be formed using the expandable bladder 14, 25 and tooling arrangement described herein without the need for an autoclave.