Molding device and molding method

Abstract

To eliminate a need for an autoclave and a vacuum bagging.SOLUTION: The present invention relates to an apparatus and method for molding out-of-autoclave thermoplastic materials that includes a metallic bladder that is forced against a bottom of a mold during a molding process to form a composite part.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a system and method for co-molding thermoplastic materials. In particular, the apparatus and methods described herein enable the co-molding of reinforced skins of thermoplastic materials, for example, but not limited to, for use in aerodynamic structures. [Background technology]

[0002] Co-molding thermoplastic skins and reinforcements is a process that bonds the skins and reinforcing ribs together in a single step. This is traditionally done by placing the components to be bonded together in an autoclave, which heats the components and causes the resin in the pre-impregnated material to bond them together, and the process uses a vacuum bagging apparatus in which the parts are placed. During use, the vacuum bag creates an even pressure on the parts, ensuring good molding and a high quality finished product. Vacuum bagging is labor intensive to apply, remove, and generate waste material as it is discarded after use, but is an essential part of existing manufacturing techniques required to form high performance components such as those used in aerospace. Summary of the Invention [Means for solving the problem]

[0003] The present inventors have established an alternative approach to component co-molding that eliminates the need for autoclave and vacuum bagging equipment. Specifically, the present inventors have devised an arrangement that allows the use of heated press dies. Traditional heated press dies do not allow for the even pressure distribution traditionally achieved in vacuum bagging processes. However, the present inventors have established equipment and techniques that eliminate the need for autoclave and vacuum bagging arrangements while maintaining a high quality product.

[0004] Additionally, the apparatus and methods described herein advantageously reduce energy consumption and waste generation. Additionally, the processes and apparatus described herein can significantly reduce process cycle times, thereby making the process suitable for high speed production.

[0005] Aspects of the invention are set out in the accompanying claims.

[0006] Viewed from a first aspect of the invention described herein, there is provided an out-of-autoclave (OOA) thermoplastic molding apparatus comprising an upper mold and a lower mold opposed to the upper mold, the upper and lower molds defining a space between them for forming a part, the molding apparatus comprising: (i) a removable cowl plate which, in use, is placed between the upper and lower mold dies and contacts the surface of the part to be molded; (ii) an inflatable bladder disposed in use between the removable cowl plate and the upper mold; The inflatable bladder extends across the cowl plate and includes a pair of opposing flexible surfaces and a circumferentially extending seal.

[0007] The term out-of-autoclave (OOA) is a term understood by those skilled in the art and refers to a process for molding thermoplastic parts without the use of an autoclave. Using an autoclave to mold thermoplastic parts is expensive and time consuming due to the thermal inertia of the large autoclaves used. Loading and unloading the autoclave is also labor intensive and time consuming.

[0008] The apparatus and methods described herein provide a simple and reliable co-molding apparatus that is easier to load with integrated pre-impregnated materials, uses less energy, advantageously reduces the thermal inertia of the molding apparatus, and importantly, provides faster cycle times.

[0009] The acronym CRES is known in the industry as an indication of corrosion resistant steel.

[0010] In accordance with the apparatus and methods described herein, a heated press is used in combination with an inflatable bladder, a Cress bladder, to create a bias pressure during the molding process to achieve the same effect of gas pressure achieved in an autoclave. Advantageously, the inflatable bladder described herein is reusable, reduces waste, and includes a high pressure integral seal (as described below) that allows a variable pressure to be applied to the part during heating and molding.

[0011] Specifically, a pair of opposing flexible surfaces and peripherally extending seals allow for near hydrostatic pressure to be applied to the upper surface of a removable cowl plate. The flexibility of the inflatable bladder means that the bladder and upper surface of the cowl plate do not need to be manufactured to very tight tolerances, reducing mold manufacturing costs and allowing for uniform pressure to be applied throughout the mold and the part being molded.

[0012] Advantageously, a removable cowl plate (a rigid or semi-rigid member that is placed over the part being molded and used to apply pressure and geometry to the part being molded) allows the layers and subcomponents that form the desired part to be laid down (laying down is also called "placed" in the art) onto the lower tool surface. The inflatable bladder means that only the geometry of the side of the cowl plate that contacts the part requires high precision.

[0013] Advantageously, irregularities in bladder manufacturing, such as welds in the case of large bladders, or accidental dents in the thin sheets of the bladder, are not transferred into the product because the product surface is created by the removable semi-rigid cowl plate.

[0014] The inflatable bladder is advantageously positioned to overlap the edge of the cowl plate and terminate between the peripheral regions of the upper and lower dies, i.e., so that the upper and lower dies meet around the central region where the part is formed. This advantageously ensures that the entire cowl plate is subjected to the biasing pressure caused by the expansion of the inflatable bladder. Additionally, the compressive force of the molds together secures the bladder and prevents movement of the bladder and cowl plate during the molding process.

[0015] Advantageously, the inflatable bladder may be in the form of two opposing layers defining a space or chamber into which a gas or fluid can be introduced. Introducing a gas or fluid into the space causes the two surfaces to move apart. This exerts pressure on the upper mold on one side and on the cowl plate on the other side. As the two molds are coupled together, this increase in pressure within the chamber urges the cowl plate against the lower mold.

[0016] The inflatable bladder can be pressurized to cause a biasing effect by introducing a gas or fluid through an inlet / outlet port that is in gas or fluid communication with the chamber to be inflated. The gas or fluid can then enter or leave the chamber. The gas or fluid itself can be any suitable medium that can withstand high temperatures. Advantageously, compressed air can be used from a gas bottle compressor system, as it can be quickly connected and disconnected without leakage.

[0017] The layers forming the inflatable bladder may be formed from any suitable material. For molding requiring a heated mold, the layers may be advantageously formed from a metal such as stainless steel. The steel may have a thickness of about 0.05 mm to about 1 mm, which allows for flexibility when the chamber between the two layers is pressurized.

[0018] Other suitable materials include durable, weldable metal sheets such as steel, plated steel, Invar steel, or titanium.

[0019] The expandable chamber may be formed by sealing the perimeter of the two flexible layers (or the area around two opposing surfaces). Since metal may be used, the seal may advantageously be formed using a weld bead. The weld may advantageously be formed using a laser welding technique that allows thin flexible layers to be welded together. Furthermore, laser welding allows for shallow weld beads to be formed so as not to interfere with the surfaces of the upper and lower molds as they are assembled on the expandable bladder.

[0020] The welds may be placed at the very perimeter of the inflatable bladder or within the peripheral area of ​​two opposing flexible surfaces. Thus, the bladder can be pierced to create a localized non-pressurized area through which a thermocouple sensor or cowl plate hanging rod can pass. If a large cowl plate is to be lifted from the product, a cowl plate hanging rod can be used. In that case, the cowl plate is connected to the upper mold by a hanging rod across the bladder.

[0021] Inlet and outlet ports are provided for introducing and removing pressure from the chamber of the inflatable bladder. Advantageously, the inlet / outlet ports may be in the form of pressure couplings extending laterally from a pair of flexible surfaces. In effect, portions of the two surfaces extend laterally outward from the standard mating surface to form extended tabs which may act as coupling areas for the inlet / outlet ports. The provision of such extended tabs allows the two flexible surfaces to remain in close proximity to one another across the contact area of ​​the cowl plate, i.e., there is no interruption in contact that would otherwise be required to accommodate the fluid inlet / outlet ports. This advantageously allows the inflatable bladder to be placed between the cowl plate and the mold and to communicate gas or fluid with a pressurized system remote from the bladder via the pressure couplings.

[0022] The pressure coupling itself may comprise a gas or fluid pressure connection disposed perpendicular to the plane of the pair of flexible surfaces. In effect, the pressure connection extends in the plane of the two flexible surfaces forming the bladder, and the connection may advantageously be disposed at approximately 90 degrees to that plane. This allows for the lowest bladder height while still allowing for gas or fluid connections to allow gas or fluid in and out.

[0023] Advantageously, the sealing weld may be a continuous weld extending around the periphery of the bladder and may be a pressure connection to surround the connection through which the pressurized gas or fluid is introduced.

[0024] It may be advantageous to make the layers of the bladder as thin as possible to create pressures close to hydrostatic pressure. The lower limit is determined by the possibility of making a strong weld around the circumference and the handling and durability of the bladder. If the sheets of the bladder are too thin, welding will be difficult and the bladder will be too brittle to be reused. In one example, sheets of about 0.3 mm to about 0.5 mm can be used. Thinner sheets can also be used. In another configuration, sheets of combined thicknesses may be used. For example, a bladder with about 0.3 mm sheets contacting the cowl plate and about 0.5 mm sheets contacting the top mold can be advantageously used. The thicker sheets provide handling of the bladder and the thinner sheets provide hydrostatic pressure.

[0025] The lower forming tool may have a geometry and / or recess that corresponds to at least a portion of the required formed part geometry. For example, in a process for co-molding stringers and aerospace surfaces, the lower tool may consist of a recess that corresponds to the shape of the stringer and a smooth upper surface that corresponds to the shape of the desired aerospace surface. When molded together, the two subcomponents can then be molded together to form a single molded part formed from the two molded subparts. It will be appreciated that the lower mold (and indeed the upper mold) can be adapted in any suitable manner to form the desired final component shape.

[0026] The cowl plate acts to transmit pressure and force to the stack of thermoplastic layers to be molded. The cowl plate may comprise a first surface corresponding to the required geometric shape of the part and an opposing compression surface (e.g., upper surface) that is arranged in use to abut against the inflatable bladder. Advantageously, using the combination of cowl plate and inflatable bladder in this way allows the use of cowl plates made by galvanic deposition of nickel, since the back side of the cowl plate does not need to be very precise in geometry. This is particularly attractive for doubly curved aerospace surfaces. Only the lower surface that abuts the stack to be molded needs a specific shape corresponding to the desired part shape.

[0027] It will be appreciated by those skilled in the art that the lower mold or upper mold may be advantageously arranged to receive multiple sub-parts that are molded together using various mold blocks, recesses, etc. to form the desired shape.

[0028] The upper and / or lower molds may further comprise one or more internal conduits for receiving cooling and / or heating fluids, electrical or inductive heating elements, allowing control of the temperature of the upper and / or lower molds. Thus, the co-molding process can be controlled with respect to temperature and pressure over a given molding time. Temperature and pressure can be varied over the molding time according to instantaneous feedback and / or predetermined temperature and pressure profiles.

[0029] To optimize the thermal inertia of the mold, each mold can be provided with one or more recesses or cavities on the side not facing the mold part. In practice, a number of pockets are provided on the rear face of each mold. This advantageously reduces the thermal inertia that would occur in the case of a solid mold. This advantageously allows the mold to heat and cool more quickly for a given heating and cooling power. In one configuration, the recesses can form a grid or matrix of recesses with intermediate walls to maintain rigidity.

[0030] In one configuration, the bladder and cowl plate can be connected to the top mold to form one package or assembly. Thus, when the top mold is lifted off the part, both the bladder and cowl plate are lifted at the same time. To do so, the cowl plate can include suspension rods or the like to connect it to the top mold through holes in the bladder.

[0031] In another configuration, the inflatable bladder may be formed with multiple chambers, each connected to an independent pressure joint, so that different pressures can be applied at different times at different locations across the cowl plate. In yet another configuration, multiple independent inflatable bladders may be provided in close proximity to one another, so that complex shapes and complex molded profiles in terms of temperature, pressure, and location across the part can be achieved.

[0032] Viewed from another aspect, there is provided a de-autoclave method for molding a thermoplastic part using a molding apparatus, the molding apparatus including an upper molding die and a lower molding die opposing the upper molding die, the upper and lower molding dies defining a space therebetween for forming the part; (i) a removable cowl plate which, in use, is positioned between the upper and lower mold dies and contacts the surface of the part being molded; (ii) an inflatable bladder disposed in use between a removable cowl plate and the upper mold and extending across the cowl plate and including a pair of opposing flexible surfaces and a seal extending therearound; and the method further comprises: (A) placing a plurality of thermoplastic-containing layers onto a lower mold to form a laminate; (B) positioning a cowl plate on the upper surface of the laminate; (C) positioning an inflatable bladder on an upper surface of the cowl plate; (D) positioning an upper mold over a top surface of the inflatable bladder; (E) selectively heating and cooling the upper mold and / or the lower mold while selectively applying pressure to the expandable bladder to urge the cowl plate against the laminate in accordance with a predetermined temperature and pressure regime.

[0033] Thus, according to the described method, the molding process is provided in a specific sequence of steps using the molding apparatus described above. In particular, the inflatable bladder is advantageously selectively controlled in combination with a temperature profile to optimize the molding or co-molding process.

[0034] Expansion of the inflatable bladder against the cowl plate in a predetermined manner allows for replication of the molding process in an autoclave in terms of temperature and pressure. Additionally, uniform pressure may be applied in a controlled manner across the cowl plate, which creates a uniform and controlled molding pressure on the parts or sub-parts that form the part.

[0035] The predetermined temperature and pressure regime may, for example, include the following steps: (A) Set the mold temperature to a specified temperature T max and (B) maintaining the mold temperature at the maximum temperature Tmax for a predetermined time (TmaxP); (C) terminating the heating at the end of the predetermined time TmaxP; Furthermore, (D) applying a first pressure P1 to the inflatable bladder during a molding time T0 to T1, applying a second pressure P2 to the inflatable bladder during a molding time T1 to T2, and applying a third pressure P3 to the inflatable bladder during a molding time T2 to T3.

[0036] In effect, a graduated profile of pressure is provided to the molded part while simultaneously increasing the mold temperature through the heated mold.

[0037] Specifically, bladder pressure is applied when the temperature of the molding material reaches the glass transition temperature (Tg) of the particular material, i.e., when the material begins to soften and become more plastic (e.g., PEKK, which is above 158° C.) Advantageously, the cowl plate can be pressed against the molded part by the inflatable bladder without deformation or dents being formed in the cowl plate.

[0038] Upon cooling, when the product reaches the crystallization temperature (eg, for PEKK, this is 240° C.), the pressure in the expandable bladder is released.

[0039] The mold contacts the heating / cooling press platen at a location directly above the heating elements and cooling channels in the press platen, thus optimizing heat flow to the mold.

[0040] Advantageously, after depressurizing the bladder, the mold can be removed from the press and cooled to room temperature by suitable means such as ambient air, a blower, or a cooling plate system. This reduces press run times by over 30%, allowing more dies to be processed in a given time.

[0041] To completely shrink the bladder after depressurization, a vacuum pressure is applied inside the bladder to create the same initial bladder shape for all products. If the bladder remains partially inflated, unintended high pressure may be created in the next product when the upper mold is closed.

[0042] The methods described herein can be used for a variety of components, including but not limited to the following, which form other aspects of the invention described herein: Unreinforced flat or curved parts, Reinforcement components having (lattice) butt joint reinforcement or formed laminate reinforcement; Flat, single and double curved aircraft surfaces, with or without integral stiffeners, ribs, spars and frames; I, C or Z beams, ribs, frames with or without stiffeners.

[0043] PEKK prepregs (pre-impregnated) are produced by several manufacturers such as Solvay, Toray, Hexcel, Barday™, etc. Typical high performance thermoplastic matrices that we use are PEKK, PEEK, LMPAEK and PPS, however any thermoplastic material with any fiber can be used.

[0044] Viewed from a further aspect, there is provided a method for co-molding multiple thermoplastic parts, the method using an apparatus including an upper molding die and a lower molding die opposing the upper molding die, the upper and lower molding dies defining a space therebetween for forming multiple thermoplastic parts, the apparatus comprising: (i) a removable cowl plate which, in use, is positioned between the upper and lower mold dies and contacts the surface of the part being molded; (ii) an inflatable bladder disposed in use between a removable cowl plate and the upper mold and extending across the cowl plate, the inflatable bladder including a pair of opposing flexible surfaces and a seal extending therearound; The method of molding together is as follows: (A) laying or positioning a layer of thermoplastic material on a first mold and / or within a recess in the first mold, the layer defining a first subcomponent; (B) placing a plurality of thermoplastic-containing layers against the layers forming the first subcomponent and onto the lower mold to form an unformed multi-thermoplastic part stack; (C) positioning the cowl plate on an upper surface of the stack; (D) positioning the inflatable bladder on an upper surface of a cowl plate; (E) positioning an upper mold on a top surface of the inflatable bladder; (F) selectively heating and cooling the upper mold and / or the lower mold while selectively applying pressure to an expandable bladder to urge a cowl plate against the laminate in accordance with a predetermined temperature and pressure regime.

[0045] A further aspect of the invention described herein extends to an aerodynamic component formed according to the methods described herein. [Brief description of the drawings]

[0046] Aspects of the present invention will now be described, by way of example only, with reference to the accompanying drawings. [Figure 1] FIG. 1 illustrates a prior attempt to provide a mold for out-of-autoclave molding. [Diagram 2] FIG. 1 illustrates a prior attempt to provide a mold for out-of-autoclave molding. [Diagram 3] FIG. 1 illustrates a configuration in accordance with the apparatus described herein. [Figure 4] 3 with the addition of a cowl plate located adjacent to the molding. [Figure 5A] FIG. 1 illustrates a cowl plate and an inflatable bladder according to configurations described herein. [Figure 5B] FIG. 5B illustrates a pressure coupling of the inflatable bladder shown in FIG. 5A. [Figure 6] FIG. 2 is an exploded view of the components of the device described herein. [Figure 7] FIG. 13 shows the top surface of the upper die and the thermal mass reduction recess. [Figure 8] 4 shows graphs of temperature, pressure and time for an exemplary molding process using the methods and apparatus described herein. [Figure 9] 1A-1D illustrate components resulting from the methods and apparatus described herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0047] While the invention is susceptible to various modifications and alternative forms, specific embodiments have been 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 invention to the particular forms disclosed, but rather are intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

[0048] Any reference to prior art documents in this specification should not be considered as an admission that such prior art is widely known or forms part of the common general knowledge in the field. As used herein, the words "comprises", "comprising" and similar words should not be interpreted in an exclusive or exhaustive sense. In other words, they are intended to mean "including, but not limited to". The present invention is further described with reference to the following examples. It will be understood that the invention as claimed is not limited in any way by these examples. It will also be recognized that the present invention encompasses not only the individual embodiments but also combinations of the embodiments described herein.

[0049] The various embodiments described herein are presented only to aid in the understanding and teaching of the features of the claims. These embodiments are provided only as representative examples of embodiments and are not exhaustive and / or exclusive. The advantages, embodiments, examples, functions, features, structures, and / or other aspects described herein should not be considered as limitations on the scope of the invention as defined by the claims, or equivalents of the claims, and it is understood that other embodiments may be utilized and modifications may be made without departing from the spirit and scope of the invention as claimed. Various embodiments of the invention may suitably include, consist of, or consist essentially of any suitable combination of the disclosed elements, components, features, parts, steps, means, etc., other than those specifically described herein. In addition, the present disclosure may include other inventions not currently claimed but which may be claimed in the future.

[0050] It will be appreciated that the features of the aspects of the invention described herein may be conveniently and interchangeably used in any suitable combination.

[0051] Detailed Description The apparatus and methods described herein relate to molding thermoplastic materials in a process that does not require an autoclave. This is known in the art as the "out-of-autoclave" or OOA process. Specifically, the apparatus and methods described herein include an improved heated mold and inflatable bladder apparatus that work together to overcome problems with existing systems.

[0052] There are several problems to overcome when transferring the co-molding technique from the autoclave to a heated press. First, when two rigid dies are used for the press, a suboptimal pressure distribution is obtained due to the prepregged material and die tolerances, especially for thin parts. Second, it is difficult to prevent the squeeze-out of the composite material at the edges of the part. The inflatable bladder configuration described below eliminates these problems with existing methods, without the use of hydraulic seals. Specifically, it is the use of two "cress membranes" or layers that are welded at the edges and pressurized with either air or hydraulic fluid to apply the required molding pressure.

[0053] As a reminder, the principle of molding a thermoplastic part in a conventional autoclave is shown in Figure 1. The part 1 is vacuum bagged on an Inner Mould Line (IML) mould 2 with a high temperature resistant foil (commonly Kapton or aluminium-3a) and sealed at the edges with a suitable sealant 3. Both the vacuum bag foil and the sealant are disposable. Pressure is applied by increasing the pressure in the autoclave and remaining gases are vented via the vacuum system. Heat is applied by heating the air or nitrogen in the autoclave.

[0054] The autoclave process has several disadvantages. Large volumes of air need to be compressed and heated to 400°C, which requires a lot of energy. The vacuum bag, sealant and inlet / outlet tubes are disposable and are waste. Thermoplastic molding cycle times are around 6 hours due to heating and cooling requirements, which makes them less suitable for high speed production.

[0055] To overcome these shortcomings, the present inventors have developed an alternative method and apparatus for molding thermoplastic parts.

[0056] Referring to FIG. 2, another example of conventional molding is shown.

[0057] A flat platen press is used to apply pressure to the unformed laminate stack. The press is fitted with two heating / cooling plates (4, 5). Between these plates is positioned a die set consisting of an IML (inner mold line) 6 and an OML (outer mold line) die 7. Typically, these dies are made of metal and are rigid.

[0058] A temperature cycle is applied by heating / cooling platens that include heating to 375°C, a dwell stage at 375°C, followed by a cooling stage to solidify the part. This press forming method is used to form flat laminates or stacks of layers.

[0059] However, the matching die must be very accurate to get good pressure and thickness distribution within the part. If the part material has local thickness variations (typically + / - 8%), the matching die will compress a thicker part more than a thinner part, which can result in voids and waviness due to lateral shifting of layers (layers moving to areas of lower pressure). Additionally, layers extrude from the laminate stack at the open edges 8 shown in Figure 2. This can be prevented by applying foil to the edges of the laminate, but this is labor intensive.

[0060] The present invention, as illustrated with reference to Figures 3 and 4, aims to overcome the high temperature sealing problems mentioned above.

[0061] Specifically, the membrane consists of two thin stainless steel sheets or membranes 9, 10 that are laser welded 11 at the edges (periphery). This forms a bladder (balloon) that can expand to create pressure on the thermoplastic part. In this way, high temperature sealing of the membrane at the edges is not required. In addition, the closure of the top mold is not critical to ensure the tightness of the bladder. There can be a gap 12 between the top and bottom molds because the laser weld is strong enough to withstand the internal pressure.

[0062] Figure 4 shows the final system used for co-molding the reinforced skin with the apparatus described herein. A cowl plate 13 can be added to have the same pressure distribution and behavior compared to the autoclave bagging procedure.

[0063] 5A and 5B show in greater detail an exemplary arrangement of an inflatable bladder and pressure coupling as shown in FIGS.

[0064] Figure 5A shows an inflatable bladder 14 and a cowl plate 13, with the bladder 14 being formed by the steel membrane 9 and the steel membrane 10 shown in Figure 3. As shown in Figure 5A, the cowl plate is disposed on top of the inflatable bladder, which is larger in area to define a peripheral region 15 surrounding the cowl plate. The inflatable bladder includes laser formed welds 16 in the peripheral region 15, i.e., the welds 16 are not located in the area where the cowl plate will be located.

[0065] 5A also shows bladder pressure coupling 17, i.e., the coupling used to transfer pressurized fluid or gas into or out of the bladder. As shown, a connection is made to the body of the bladder and a conduit is used to communicate fluid or gas from a compressor, pump, bottle, etc. to apply pressure to the bladder.

[0066] 5B shows in more detail an advantageous configuration of the pressure joint. Specifically, the two portions of the membranes 9 and 10 of the bladder extend to the joint or region 18 in the same plane as the two membranes, i.e., the two portions or regions 18 extend outwardly rather than perpendicularly to the membrane surfaces. This ensures that the surface of the bladder can be as flat as possible for insertion into the mold and for alignment with the cowl plate.

[0067] The two portions or regions 18 may include openings to allow for vertical fluid or gas flow into the space between membranes 9 and 10, as indicated by solid and dotted lines 19. The fluid or gas may then flow along lines 19 into cavity 20 within the bladder, allowing the bladder to remain as thin as possible. Returning to Figure 5A, a screw-on valve 21 may be used to connect pipes to the openings to communicate fluid or gas as described above.

[0068] FIG. 6 shows the configuration of the device prior to molding according to the methods and apparatus described herein.

[0069] As shown, the molding apparatus includes an upper mold 22 and an inner mold line mold 23, which is the surface that defines the lower contour of the shape to be formed or molded and against which the stack of thermoplastic layers is placed or laid.

[0070] A stack of thermoplastic layers is placed on an inner mold line tool 23 to form a stack or laminate of thermoplastic layers, and then a cowl plate 24 is placed on top of the stack. The cowl plate has a lower surface that defines the contours of the desired part shape once molded, and the desired part shape is precisely machined or formed into it. The upper surface of the cowl plate does not require precision machining and is positioned to receive pressure from an inflatable bladder or CRES membrane 25. As shown, the CRES membrane or inflatable bladder 25 is connected to a pressure coupling 26.

[0071] The top mold is then placed over the inflatable bladder and the entire formation is placed into a press to lock the individual components shown in FIG. 6 together and in place.

[0072] Figure 7 illustrates the top surface of the top mold 22. As shown in Figure 7, the top mold is placed onto the bottom mold / IML mold 23. Figure 7 illustrates the recesses of the pockets 27 located on the top surface of the top mold. The purpose of the recesses is to improve the heat and cool time of the die by lowering the thermal mass, allowing the part to be removed from the press more quickly and restarted for another cycle, thus maximizing manufacturing throughput.

[0073] The mass of the die is reduced by about 50% by applying the pockets on the back side, so less heating and cooling power is required for the thermal cycle, resulting in lower costs for the heating and cooling system. The pockets are advantageously positioned so that the ribs correspond to the heating and cooling channel positions of the press platen, optimizing the heating and cooling rates.

[0074] FIG. 8 shows an example of a temperature and pressure profile for molding using the apparatus and methods described herein.

[0075] As shown, there are three separate pressures and three separate heating and cooling periods used during the molding cycle.

[0076] The process starts with a certain vacuum evacuation pressure on the bladder, which is applied to completely shrink it. This prevents the cowl plate from being subjected to undue forces resulting from the unformed part, which would cause it to deform permanently. When the mold is heated and the temperature of the part rises above the Tg of the thermoplastic matrix material, the material softens and the pressure in the bladder rises to the molding pressure. This also protects the cowl plate from indentation. Once the part reaches the molding temperature, the temperature is kept constant for the required molding time. The part is then cooled, and once the part temperature is lower than the Tc (crystallization temperature) of the thermoplastic matrix material, the bladder pressure is released and a vacuum pressure is applied, which results in the bladder shrinking. This allows the part to release itself as it cools further due to thermal stresses caused by the differential expansion of the part and the mold. Once the temperature falls below Tc and the bladder pressure is released, the mold can be moved out of the press.

[0077] 9 illustrates a co-molded part using the methods and apparatus described herein. The resulting part has a contoured, smooth aircraft surface 28 with spars 29 and ribs 30 co-molded to the aircraft surface. As shown, complex curved components can be formed using the inflatable bladder and mold apparatus described herein without the need for an autoclave.

Claims

1. 1. An out-of-autoclave thermoplastic molding apparatus comprising an upper mold and an opposing lower mold, the upper and lower molds defining a space therebetween for forming a part, the apparatus comprising: (i) a removable cowl plate which, in use, is positioned between the upper and lower mold dies and contacts the surface of the part being molded; (ii) an inflatable bladder disposed in use between the removable cowl plate and the upper mold; The inflatable bladder extends across the cowl plate and includes a pair of opposing flexible surfaces and a seal extending therearound.

2. 10. The device of claim 1, wherein the inflatable bladder is in the form of two opposing layers defining an expansion chamber therebetween and further comprising inlet / outlet ports in fluid or gas communication with the expansion chamber to allow fluid or gas to enter or exit the expansion chamber.

3. The device of claim 2 , wherein the opposing layers are metal layers.

4. The apparatus of claim 3 , wherein the metal layer is formed from a material selected from stainless steel, steel, plated steel, Invar steel, or titanium.

5. 5. The apparatus of claim 1, wherein the inflatable bladder includes a weld extending around the periphery of the bladder to seal the expansion chamber.

6. 6. The apparatus of claim 5, wherein the weld is a laser formed weld extending around the bladder and the inlet / outlet ports.

7. 7. The apparatus of claim 6, wherein the inlet / outlet ports are in the form of pressure couplings extending laterally from the pair of flexible surfaces, the pressure couplings comprising fluid or gas pressure connections disposed perpendicular to the plane of the pair of flexible surfaces, and the welds extend around the pressure couplings to surround the fluid or gas pressure connections.

8. 5. The device of claim 1, wherein the flexible surface is between about 0.3 mm and about 0.5 mm thick.

9. 5. The apparatus of claim 1, wherein the pair of flexible surfaces are of different thicknesses.

10. 5. Apparatus according to any one of claims 1 to 4, wherein the lower mould has a geometry and / or recess corresponding to at least a part of the geometry of the desired moulded part.

11. 5. Apparatus according to any preceding claim, wherein the cowl plate has a first surface corresponding to the required geometry of the part and an opposing pressing surface arranged to abut the inflatable bladder in use.

12. 5. An apparatus according to claim 1, wherein the lower mould or the upper mould is arranged to receive a plurality of sub-parts which are moulded together.

13. 5. Apparatus according to any one of claims 1 to 4, wherein the upper and / or lower moulds are provided with one or more internal conduits for receiving cooling and / or heating fluids, electrical or inductive elements, allowing control of the temperature of the upper and / or lower moulds.

14. 5. The apparatus according to claim 1, wherein the upper and / or lower mould comprises one or more recesses on the side of the mould not facing the part in order to reduce the thermal mass of the mould.

15. 5. The apparatus of claim 1, wherein the mold contacts a heated / cooled press platen at a location directly above the heating element and cooling channels in the press.

16. 1. A de-autoclave method for molding a thermoplastic part using a molding apparatus, the molding apparatus comprising an upper mold and a lower mold opposed to the upper mold, the upper mold and the lower mold defining a space therebetween for forming the part; (i) a removable cowl plate which, in use, is positioned between the upper and lower mold dies and contacts the surface of the part being molded; (ii) an inflatable bladder disposed in use between a removable cowl plate and the upper mold die, the inflatable bladder extending across the cowl plate and having a pair of opposing flexible surfaces and a circumferentially extending seal; and the method further comprising: (A) placing a plurality of thermoplastic-containing layers onto a lower mold to form a laminate; (B) positioning a cowl plate on an upper surface of the stack; (C) positioning an inflatable bladder on the upper surface of the cowl plate; (D) positioning an upper mold over an upper surface of the inflatable bladder; (E) selectively heating and cooling the upper mold and / or the lower mold while selectively applying pressure to the expandable bladder to urge the cowl plate against the laminate in accordance with a predetermined temperature and pressure regime.

17. The predetermined temperature and pressure regime comprises: (A) continuously increasing the mold temperature to a predetermined temperature T; (B) maintaining the mold temperature at the maximum temperature Tmax for a predetermined time (TmaxP); (C) terminating the heating at the end of a predetermined time TmaxP; Furthermore, 17. The method of claim 16, further comprising the steps of: (D) applying a first pressure P1 to the inflatable bladder during a molding time T to T; applying a second pressure P2 to the inflatable bladder during a molding time T to T; and applying a third pressure P3 to the inflatable bladder during a molding time T to T.

18. 18. The method of claim 17, wherein the first pressure P1 is applied when the temperature of the thermoplastic material exceeds a temperature Tg of the thermoplastic material.

19. 19. The method of claim 17 or 18, wherein a third pressure P3 to the inflatable bladder is applied after a molding time T2.

20. 1. A method for molding multiple thermoplastic parts together, the method using an apparatus including an upper molding die and a lower molding die opposing the upper molding die, the upper molding die and the lower molding die defining a space therebetween for forming multiple thermoplastic parts, the apparatus further comprising: (i) a removable cowl plate which, in use, is positioned between the upper and lower mold dies and contacts the surface of the part to be molded; (ii) an inflatable bladder disposed in use between a removable cowl plate and the upper mold and extending across the cowl plate, the inflatable bladder including a pair of opposing flexible surfaces and a seal extending therearound; The method of molding together is as follows: (A) laying or positioning a layer of thermoplastic material on a first mold and / or within a recess in the first mold, the layer defining a first subcomponent; (B) placing a plurality of thermoplastic resin-containing layers against the layers forming the first subcomponent and onto the lower mold to form an unformed multi-piece thermoplastic stack; (C) positioning the cowl plate on an upper surface of the stack; (D) positioning the inflatable bladder on an upper surface of the cowl plate; (E) positioning the upper mold over an upper surface of the inflatable bladder; (F) selectively heating and cooling said upper mold and / or said lower mold while selectively applying pressure to said expandable bladder to urge said cowl plate against said laminate in accordance with a predetermined temperature and pressure regime.

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