Method and system for producing a panel member for an airframe

Abstract

A method of producing a composite panel member, especially a composite panel member having a foam core sandwich structure for an airframe of an aircraft or spacecraft, including: providing at least one fiber reinforcement layer in a panel molding tool; moving or transferring the molding tool to an infusion station that is pre-heated to an infusion temperature and infusing the fiber reinforcement layer in the molding tool with a polymer resin; moving or transferring the molding tool to a curing station that is pre-heated to a curing temperature and curing the at least one resin-infused fiber reinforcement layer in the molding tool to form a composite panel member; and moving or transferring the molding tool to a cooling station that is provided at a cooling temperature and cooling the composite panel member in the molding tool.

Claims

1. A system for producing a composite panel member with a sandwich structure, the system comprising: a molding tool for receiving at least one fiber reinforcement layer and for molding a panel; an infusion station for infusing the at least one fiber reinforcement layer in the molding tool with a polymer resin, wherein the infusion station is adapted to be heated to an infusion temperature; a curing station for curing the at least one resin-infused fiber reinforcement layer in the molding tool to form a composite panel member, wherein the curing station is configured to be heated to a curing temperature; a cooling station for cooling the composite panel member in the molding tool, wherein the cooling station is configured to be provided at or heated to a cooling temperature; and a transfer mechanism for moving or transferring the molding tool from the infusion station to the curing station and from the curing station to the cooling station; wherein the infusion station, the curing station, and the cooling station are arranged in series adjacent to one another and are provided as distinct regions of a single heating apparatus.

2. The system according to claim 1, wherein the transfer mechanism includes a sliding or rolling transport device arranged to transport the molding tool between the infusion station, the curing station, and the cooling station.

3. The system according to claim 1, wherein the molding tool has at least two mold parts which together define a mold cavity for accommodating the at least one fiber reinforcement layer and for molding the panel, wherein the mold parts are configured to hold or clamp the panel member against thermal expansion when the molding tool is closed; and wherein the system further comprises a digital controller for controlling or regulating a temperature in the infusion station and/or in the curing station and/or in the cooling station.

4. The system according to claim 2, wherein the transfer mechanism includes a lay-up station for placement of the at least one fiber reinforcement layer in the molding tool.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) For a more complete understanding of the present invention and the advantages thereof, exemplary embodiments of the invention are explained in more detail in the following description with reference to the accompanying drawings, in which like reference characters designate like parts and in which:

(2) FIG. 1(a) is a perspective view of a system for producing a composite panel member for a tail or wing of an aircraft according to an embodiment;

(3) FIG. 1(b) is a perspective view the system shown in FIG. 1(a) in a transparent representation;

(4) FIG. 1(c) is an end view of the molding tool assembly of the system in FIGS. 1(a) and 1(b) taken in the direction of arrow D;

(5) FIG. 2 is a schematic side view of resin infusion, curing and cooling stations for producing a panel member by a method according to a further embodiment of the invention;

(6) FIG. 3 is a perspective view of the system for producing a panel member according to a further embodiment of the invention;

(7) FIG. 4 is a diagram illustrating temperature progression of an exemplary MVI production process compared with the ZZ process;

(8) FIG. 5 is a flow diagram which schematically illustrates a method according to another embodiment of the invention; and

(9) FIG. 6 is a schematic illustration of an aircraft in which one or more panel member according to another embodiment of the invention is installed.

(10) The accompanying drawings are included to provide a further understanding of the present invention and are incorporated in and constitute a part of this specification. The drawings illustrate particular embodiments of the invention and together with the description serve to explain the principles of the invention. Other embodiments of the invention and many of the attendant advantages of the invention will be readily appreciated as they become better understood with reference to the following detailed description.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(11) It will be appreciated that common and well understood elements that may be useful or necessary in a commercially feasible embodiment are not necessarily depicted in order to facilitate a more abstracted view of the embodiments. The elements of the drawings are not necessarily illustrated to scale relative to each other. It will further be appreciated that certain actions and/or steps in an embodiment of a method may be described or depicted in a particular order of occurrences while those skilled in the art will understand that such specificity with respect to sequence is not necessarily required. It will also be understood that the terms and expressions used in the present specification have the ordinary meaning as is accorded to such terms and expressions with respect to their corresponding respective areas of inquiry and study, except where specific meanings have otherwise been set forth herein.

(12) With reference firstly to FIGS. 1(a) to 1(c) of the drawings, the components of a system 1 for producing or manufacturing a composite panel member 2 for an empennage or wing of an aircraft is illustrated. As will be appreciated by persons skilled in the art, both the vertical tail plane (VTP) and wings of an aircraft are often formed having a central box structure typically comprising a number of spars and ribs which are then covered with panel members 2 to provide an outer or aerodynamic skin. With the current manufacturing trends, the panel members 2 are often fabricated from fiber-reinforced polymer (FRP) composites and preferably in a foam core sandwich construction. Furthermore, in light of recent design developments, the panel members 2 to be mounted on the box structures of the tail and the wings have a lens shape or lenticular form in cross-section. The benefits of the lenticular panel form are described, for example, in the published International Patent Application WO 2012/028263 A1, the entire contents of which are to be incorporated herein by reference.

(13) Referring to FIGS. 1(a), 1(b) and 1(c), the system 1 includes a large heating apparatus or oven O, within which a molding tool 3 having a lower mold part 4 and an upper mold part 5 is employed to form the panel member 2. Frame members 6, each having an inverted U-shape, stand over and span the molding tool 3 within the oven O to form a support frame 7 for supporting a resin feed assembly 8. The resin feed assembly 8 comprises a resin reservoir 9 and a resin distributor 10 that includes a network of resin feed lines or feed conduits 11 in connection with the upper mold part 5 for introducing the liquid resin into a mold cavity in the molding tool 3. In this regard, the positioning of the resin feed assembly 8, and especially the resin reservoir 9 (e.g., tanks), at an elevated position above the molding tool 3 generates a pressure head in the resin supply. This can help avoid or counteract difficulties in the permeability of the reinforcement fiber fabric layer/s during the production of panels having a foam core sandwich structure, especially in a constant volume procedure, where pressure is applied to maintain a substantially constant core volume.

(14) The upper mold part 5 essentially forms a lid or closure for the mold cavity and is movably supported on cross-beams 12 connected to vertical legs of the frame members 6 to move up and down for opening and closing the molding tool 3. A number of stiffening ribs 13 is provided across the upper mold part 5 for a strong and rigid connection with cross-beams 12 at weld points 14. This strength and rigidity is important when the upper mold part 5 is driven down and clamped to the lower mold part 4 against sealing beads 15 via bolts 16 to close and seal the mold cavity under pressure, e.g., 2 bar of pressure. As is apparent from FIGS. 1(a) and 1(b), the lower mold part 4 includes a base 17 and at least partially defines a cavity 18 that is laid up with layers L of fiber reinforcement, such as woven as well as non-woven fabric (NCF) sheets, and a hard foam core C. In FIG. 1(c), the molding tool 3 can be seen with the upper and lower mold parts 4, 5 clamped via bolts 16 in the closed position. In this way, the semi-finished product formed by the foam core C covered by the layers L of fiber reinforcement is clamped in the cavity 18 of the molding tool 3 under pressure to limit or substantially prevent volume change via thermal expansion.

(15) Turning now to FIG. 2 of the drawings, a series of production stations S1, S2, S3 in the system 1 for manufacturing or producing the composite panel 2 according to a preferred embodiment of the invention is shown schematically. The first of these is an infusion station S1 for infusing the fiber reinforcement layers L around the core C in the molding tool 3 with a polymer resin from the reservoir 9. In other words, the closed molding tool 3 with the support frame 7 and the resin feed assembly 8 are provided in infusion station S1, which forms a part or region of the large heating apparatus O and is heated to a predetermined infusion temperature T1 of about 120 C. The resin is then introduced into the molding tool 3 via the resin feed assembly 8, the reservoir 9 and distributor 10. After the resin has been infused into the molding tool 3 at the infusion temperature T1 to impregnate the fiber reinforcement layers L in the mold cavity 18, a transport device R is controlled to move or transfer molding tool 3 to a curing station S2 for curing the now resin-infused fiber reinforcement layers L in the molding tool 3 to form the composite panel member 2. To this end, the curing station S2 also forms a part or region of heating apparatus O and is heated step-wise via the ZZ-process to a predetermined curing temperature T2 of about 180 C. After the curing of the polymer resin has been completed (e.g., after a predetermined curing time or period) the transport device R, which may for example include rails for rolling and/or sliding movement of the molding tool 3, is employed to transfer molding tool 3 to the next adjacent production station, namely to cooling station S3. As apparent from the name, the cooling station S3 is designed to provide controlled cooling of the composite panel member 2 in the molding tool 3. To this end, the cooling station S3 also forms a part or region of the heating apparatus or oven O at a cooling temperature T3. This allows a controlled cooling of the panel member 2 from the curing temperature T2.

(16) It will be noted that the transport mechanism R provides two transport paths, namely a lower path RL, which corresponds to the transport path of the lower mold part 4, and an upper path RU, which corresponds to the transport path of the upper mold part 5. From the infusion station S1 to the cooling station S3 these lower and upper paths RL, RU run together because the upper and lower mold parts 4, 5 of the molding tool 3 are clamped closed. In the cooling station S3 in the course of the cooling phase, however, the molding tool 3 is opened such that the upper mold part 5 is lifted away from the lower mold part 4, which contains the newly formed panel member 2. In this manner, upper mold part 5 together with the support frame 7 and resin feed assembly 8 are transported back along upper path RU to the infusion station S1. As such, the upper mold part 5 remains within the heating apparatus O for the next panel production. The lower mold part 4 with the panel member 2, on the other hand, cools at the cooling station S3 then is transported along the lower path RL out of the heating apparatus O to a lay-up station S4. At the lay-up station S4 the newly formed panel member 2 is removed from the lower mold part 4 and the lower mold part 4 can then be prepared for the next panel production, i.e., by placement of fiber reinforcement layers L and the foam core C into the mold cavity 18 (e.g., manually at room temperature).

(17) Thereafter, the lower mold part 4 of the molding tool 3 is moved or transferred into the infusion station S1, where it is combined and closed with the upper mold part 5 to perform the infusing step. The continuous but segmented oven system with portal and guidance of the mold parts 4, 5 along the paths RU, RL via the transport device R reduces the overall energy consumption and can be implemented with the standard resin infusion processes. In particular, the fact that upper mold part 5 and parts of support frame 7 remain within the heating apparatus O provides a heat exchange mechanism which transfers and conserves heat energy between the stations S1, S2, S3 to promote the energy efficiency of the system 1.

(18) It will be appreciated that the molding tool 3 need not be opened in the cooling station S3. That is, the cooling may be conducted with the molding tool 3 in the closed state. After cooling in the cooling station S3, the entire molding tool 3 may then be transferred to the lay-up station S4 where it is further cooled and opened to remove the finished or completed panel 2. In this embodiment, however, the support frame 7 and the resin feed assembly 8 will still remain in the heating apparatus or oven O for interconnection with the next laid-up molding tool 3 introduced into the infusion station S1.

(19) FIG. 3 of the drawings shows a perspective view of the system 1 for producing the panel member 2. The molding tool 3 can be seen supported on the transport device R which includes rails or tracks for conveying the molding tool 3 through the stations S1, S2, S3. In addition, the frame members 6 of the support frame 7 for supporting the resin feed assembly 8 with the network of resin feed lines 11 are provided within the infusion station 51 for connection with an upper mold part 5 of the molding tool 3 and at least some components thereof may move with the molding tool 3 via the transport device R between the infusion station 51, the curing station S2 and the cooling station S3.

(20) Referring now to FIG. 5 of the drawings, a flow diagram is shown that schematically illustrates the steps in a method of forming a panel member 1 according to the embodiments of the invention described above with respect to FIGS. 1(a) to 3. In this regard, the first box I of FIG. 5 represents the step of laying-up fiber reinforcement layers L and a foam core C in a lower mold part 4 of the panel molding tool 3. The molding tool 3 is then clamped closed with an upper mold tool part 5 via clamping bolts 16 to hold the volume of the foam core C substantially constant against thermal expansion. The second box II represents the step of then moving or transferring the molding tool 3 to the infusion station S1, which is heated to an infusion temperature T1, and infusing the laid-up fiber reinforcement layers L in the molding tool 3 with the polymer resin. The third box III of FIG. 5 represents the step of moving or transferring the molding tool 3 to the curing station S2, which is then heated stepwise via the ZZ-process to the curing temperature T2, and curing the resin-infused fiber reinforcement layers L in the molding tool 3 to form a composite panel member 2. Then, the fourth box IV in FIG. 5 represents the step of moving or transferring the molding tool 3 to a cooling station S3, which may have been pre-heated to the cooling temperature T3, and cooling the composite panel member 2 in the molding tool 3 at cooling station S3. Thereafter, the newly formed panel 2 may be removed from the mold cavity 18 at the lay-up station S4.

(21) Finally, with reference to FIG. 6, a schematic illustration is shown of an aircraft A having an airframe, including the tail T and wings W as well as the fuselage F, in which one or more panel members 1 formed by a method according to any one of the embodiments of the invention described above, e.g., as described in reference to FIG. 2, FIG. 3, or FIG. 5, is/are included.

(22) Although specific embodiments of the invention have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations exist. It should be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing at least one exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents. Generally, this application is intended to cover any adaptations or variations of the specific embodiments discussed herein.

(23) In this document, the terms comprise, comprising, include, including, contain, containing, have, having, and any variations thereof, are intended to be understood in an inclusive (i.e., non-exclusive) sense, such that the process, method, device, apparatus or system described herein is not limited to those features or parts or elements or steps recited but may include other elements, features, parts or steps not expressly listed or inherent to such process, method, article, or apparatus. Furthermore, the terms a and an used herein are intended to be understood as meaning one or more unless explicitly stated otherwise. Moreover, the terms first, second, third, etc. are used merely as labels, and are not intended to impose numerical requirements on or to establish a certain ranking of importance of their objects.

(24) As is apparent from the foregoing specification, the invention is susceptible of being embodied with various alterations and modifications which may differ particularly from those that have been described in the preceding specification and description. It should be understood that I wish to embody within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of my contribution to the art.