RU2390417C2 - Method and hardware for production of composite circular frames - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: method is intended for manufacturing of composite circular frames for aviation hulls with the help of RTM technology application for moulding of two stocks with C-shaped and L-shaped profiles made with application of two devices. At first material is prepared for stocks in the form of pieces cut in compliance with specified template. Then hot moulding of rectangular flaky material is carried out by placement of material pieces layers onto the first device in specified position and amount, and their exposure to pressure and temperature, so that pieces of material stick to each other at local sections. Then hot moulding of rectangular profile flaky material is carried out from segments of flat flaky material produced by means of cutting on part of stock with rectangular profile on the first device with placement on upper side of part intended for flange of stocks with C-shaped and L-shaped section, holding one longitudinal edge on the first device and leaving the other one free. Then elastic membrane is placed on device, and heat and vacuum is cyclically applied. Hot moulding of stocks with giving them C-shaped and L-shaped form is carried out at the second curvilinear device by means of deformation of specified flaky material with rectangular profile on it. Besides specified deformation includes, in case of C-shaped stocks, bending of the second flange and cyclic application of heat and vacuum. Devices are also proposed, which are used in specified method.

EFFECT: inventions provide for the possibility to reduce duration of process of circular frames manufacturing with complex geometric structure and combined circular frames making with more accurate dimensions.

4 cl, 11 dwg

Description

FIELD OF THE INVENTION

The present invention relates to a method for manufacturing composite annular frames for aircraft fuselages using RTM technology (transfer molding of plastics) and, in particular, to the operations of this process, in which workpieces are prepared that undergo a final injection of resin mixture.

BACKGROUND OF THE INVENTION

In the aviation industry, the ratio of strength to weight is of key importance, and for this reason there is a tendency to abandon metal structures and switch to the use of structures made of composites or optimized for their use.

In the process of optimizing all types of aircraft structures, they strive to minimize weight and integrate the largest number of parts in order to reduce the duration of the assembly process and the handling of small components.

The manufacture of annular frames in a known manner is carried out on the basis of machined metal structures or stamped sheet metal structures with reinforcement of the most load-bearing part by machined parts. In the case of stamped sheet metal, a normally used profile is obtained from two parts: on the one hand, a Z-shaped profile is made, and on the other hand, a corner or babbetes is made, which are screwed to the previous profile (see Fig. 1a).

The disadvantage of this method is that it requires a lot of time for assembly and leads to excess weight in the manufacture of the same profile in a complex way.

The aim of the present invention is to propose a method that eliminates the disadvantages inherent in existing technical solutions.

SUMMARY OF THE INVENTION

The present invention provides a method for manufacturing composite annular frames for aircraft fuselages using RTM technology to form two blanks with C-shaped and L-shaped profiles, characterized in that the said blanks are made using the first and second devices during the following operations:

- preparation of material for blanks in the form of pieces of material cut in accordance with a given pattern;

- hot molding of a rectangular layered material by placing layers of pieces of material on the first device in a predetermined position and quantity and exposing them to pressure and temperature, so that pieces of material stick together only locally, that is, not over their entire surface, but only along the longitudinal strip where unidirectional tape reinforcing elements are placed;

- hot molding of a layered material of a rectangular profile from segments of said flat layered materials of established dimensions obtained by cutting onto a part after the first device with a rectangular profile, with the part intended for the flange, the blanks with a C-shaped or L-shaped being placed on its upper side section, holding one longitudinal edge on the device and leaving the other edge free; placing an elastic membrane on the device and cyclic application of heat and vacuum;

- hot forming of the workpieces with giving them a C-shaped and L-shaped on the second curvilinear device by deforming on it the specified layered materials with a rectangular profile, and this deformation includes, in the case of C-shaped workpieces, bending of the second flange and cyclical application of heat and vacuum.

The present invention also relates to the two devices mentioned.

The first device is formed by a central module and two side modules, which are joined together so as to prepare laminated material for workpieces, as well as to perform longitudinal joining of pieces of material by mutual overlap, and separated to perform the operation of hot forming of a laminated material with a rectangular profile and heating heads designed to apply pressure and temperature during the hot forming of flat layered materials.

The central module contains heating elements, suction devices and a mounting plate with a pneumatic actuator located on the central module for hot forming laminated materials with a rectangular profile.

The second device comprises a curved male module with a recess for accommodating flanges and flanges of L-shaped or C-shaped laminated materials, respectively, and a plurality of elastic strips for holding the laminated materials during the hot forming process.

The manufacture of blanks of the annular frame, which will be further used in the RTM process, is facilitated by the application of the method according to the present invention, which has the following advantages:

- it is possible to produce ring frames of complex geometric shapes and combined ring frames in accordance with the requirements for any design;

- the problem of finishing only one surface is solved by adding high accuracy in size without reducing the radius due to the refusal to use the autoclave;

- the thickness control is improved (reaching tolerances ≤0.2 mm) regardless of what the thickness may be, due to which good mating between the flange of the annular frames and the overlapping layer and the stringer is achieved;

- the process is periodically repeated with a short duration of cycles, which reduces the duration of the manufacturing process.

Other features and advantages of the present invention will become apparent from the following detailed description, given by way of illustration of an embodiment of its object with reference to the accompanying drawings.

Brief Description of the Drawings

Fig. 1a shows a section through an annular frame made of metal, and Fig. 1b shows a section through an annular frame made from a composite made by the method that is the subject of the present invention;

on figa shows a perspective view of the first device used in the method, which is the subject of the present invention;

on fig.2b schematically shows the components of the first device used in the method, which is the subject of the present invention;

figure 3 schematically shows the various phases of the operation of hot forming flat layered materials in a manner that is the subject of the present invention;

figure 4 schematically shows cutouts made in a flat layered material so as to obtain layered materials with the dimensions required for blanks with a C-shaped and L-shaped profiles;

figure 5 schematically shows the various phases of the operation of forming flat layered materials in a manner that is the subject of the present invention;

6 schematically shows the various phases of the operation of hot forming preforms with C-shaped and L-shaped profiles in a manner that is the subject of the present invention;

7 schematically shows a sectional view of a second device used in the method that is the subject of the present invention;

on Fig and 9 schematically shows in section a central module of the first device.

DETAILED DESCRIPTION OF THE INVENTION

The following describes an embodiment of the method according to the invention, intended for the manufacture of blanks of the annular frame of the aircraft fuselage using composites.

The profile intended for production is formed by a C-shaped profile 11 and an L-shaped corner 13 made of fabric and reinforced with a unidirectional tape on the lower flange 15 in order to increase the moment of inertia and, therefore, stiffness. With this invention ring frames up to 8 m long with a radius of curvature of up to 250 mm can be obtained.

The process begins with the preparation of the material required for the manufacture of the layered material: models of a certain shape obtained during the cutting operation are made in groups with the same geometric shape, so that the cutting machine operates only once, producing the model required in each case. Identification of each of the parts, according to this process, is not required, but it is only required to gradually select the required number of pieces of the desired geometric shape for the manufacture of the layered material.

For its part, a device 21 is proposed for the manufacture of layered material in the form of C-shaped and L-shaped blanks, connecting the side modules 23 with the central module 25. The longitudinal clamping strips 27 are placed on the side modules 23 in the area where the lamination is carried out (suitable for this either of the two side modules 23).

To begin manufacturing the laminated material 41, the mounting plate 29 is removed from the upper part of the device 21. Then, rectangular pieces of material 30 are placed at an angle of +/- 45 ° between the central module 25 and the pressure bars 27 of the side module 23 selected for manufacture, with pieces overlapping each other friend in the longitudinal direction. Contour dimensions, as well as offset, cut, and overlap markings provided here, are carried out using a laser projector. To combine the reinforcing elements and mutually overlapping pieces of material 30, until the full profile of the annular frame is obtained, the temperature and pressure are applied by means of the heating head 31, which can be moved along the guides located on the sides of the table 33. The heating head 31 lowered over the laminate 41 by means of a manually controlled pneumatic actuator. The heater can rotate + 45 °, + 90 °, -90 °, -45 ° around the Z axis in order to be able to fasten the reinforcing element in the form of a unidirectional tape or a point of mutual overlap, depending on the circumstances. After the manufacture of the layered material is completed, it is cut in the marked areas, designating each of the parts and axes of symmetry with a white marker so that it is obvious that the four ring frames 43, 45, 47, 49 are made simultaneously from the same laminate.

Direct hot forming of C-shaped and L-shaped blanks is carried out on the device for lamination 21 after the operations shown in figure 5. First, a release film 53 is placed so that the starting laminate 51 (with the dimensions required for hot forming the provided C-shaped or L-shaped preform) does not adhere to the elastic membrane 55 and does not contaminate the material. Then, a mounting plate 29 is installed, which is fastened with a pneumatic actuator to the protrusion of the central module 25, the console of which overlaps the longitudinal strip of the laminate 41 by only 10 mm and presses it to a degree sufficient to prevent it from being drawn by the elastic membrane 55 Since the laminate 51 has in the region intended for heating longitudinal reinforcing elements of different thicknesses, the mounting plate 29 must be non-continuous in order to connect with different Noah’s height. After installing the mounting plate 29 in place, the side models 23 are carefully removed so as not to pull the laminate 41 obtained before, and an annular frame with an elastic membrane 55 is placed in their place. The elastic silicone membrane is deformed in a vacuum and can withstand temperatures of 120 ° C. as the operating temperature with a relative elongation of about 400%. After assembling all the elements, the operation of hot forming (temperature + vacuum) is performed. Thermal action is carried out using the hot forming device 21. The central module 25 contains built-in resistors 61 designed to heat the laminate 51. During hot forming, these resistors heat the horizontal section on which the laminate 51 and 5 mm (at most) of the vertical zone are supported . To prevent heating of the vertical zone on the device in this zone is placed the material FV 63, which serves as a heat insulator. The local temperature is usually brought up to 100 ° C (with a tolerance of ± 5 ° C) for a period of 20 minutes. A vacuum is created through the table 33 of the device 21, made as an aluminum panel of a honeycomb shape, and the suction devices are located under the central module 25, which has a longitudinal recess with transverse bypass channels 67.

To perform a second hot forming cycle, a curved hot forming device is used. To obtain C- and L-profiles, the layered material 51 in the form of a rectangular profile obtained in the previous operation is placed on the hot forming component corresponding to the C-shaped and L-shaped workpieces, deforming them manually to attach to the covered part 57 without occurrence folds, first placing the flanges formed during the previous operation in the recesses 59 followed by the application of the rest of the laminate to the device, which in the case of C-shaped blanks means that in addition to curvilinear deformation ave to be carried deformation required for hot-forming the other flange, using for this purpose the recesses 60.

Then, a separating film is laid on the blanks, which makes it necessary to make cuts for its precise application, and everything is held by elastic bands 71 and fastening clamps 73, preventing wrinkles in radius and web. On each of the blanks, control thermocouples will be placed, inserted to a depth of about 5 mm in the middle of the flanges obtained during the first cycle of direct hot molding. In conclusion, the device formed by the aluminum sheet 75 on the base metal sheet 77, also of aluminum, will be introduced into the hot forming apparatus (cyclic application of heat and vacuum).

After profiling blanks, excess parts are cut off.

If it is necessary to connect the outer flange of the annular frame with a flat support, such as the top layer, it is possible to make wedge-shaped devices that are placed on the annular frames, connecting them to the flanges by heating with a contact heater.

The workpieces are now ready for use in the manufacture of an annular frame with a fully integrated profile using a method known as RTM injection.

Any modifications that fall within the scope defined by the following claims may be added to the preferred embodiment described above.

Claims (4)

1. A method of manufacturing a composite annular frame for the aircraft fuselage through the RTM process for forming two blanks with a C-shaped and L-shaped profiles, characterized in that these blanks are made using the first (21) and second device in the following operations:
a) preparation of material for blanks in the form of pieces of material (30), cut in accordance with a given pattern;
b) hot forming a rectangular layered material (41) by placing the layers of pieces of material (30) on the first device (21) in a predetermined position and quantity and exposing them to pressure and temperature, so that the pieces of material (30) stick together in local areas ;
c) hot molding of rectangular layered material (51) from segments of flat layered material (41) of established dimensions obtained by cutting onto a part of the obtained workpiece with a rectangular profile on the first device (21) with placement on the upper side of the part intended for the workpiece flange with a C-shaped or L-shaped section, holding one longitudinal edge on the first device (21) and leaving the other free; placing an elastic membrane on the device (55) and cyclic application of heat and vacuum;
d) hot forming of the workpieces with giving them a C-shaped (11) and L-shaped (13) shapes on a second curved device by deformation of said laminated material with a rectangular profile (51) on it, and this deformation includes in the case of C- shaped bending of the second flange and the cyclical application of heat and vacuum. 2. The method according to claim 1, characterized in that the predetermined shape of the pieces of material (30) includes a rectangular shape at +/- 45 ° and a unidirectional reinforcing tape for the flange. 3. A device (21) for performing operations b) and c) in the method according to any one of claims 1 and 2, characterized in that it comprises a central module (25) and two side modules (23) that are connected together to step b) and are separated for step (c), and heating heads (31) for applying pressure and temperature during step b), wherein the central module (25) contains inside the heating elements (61), suction devices for performing operations (c) and a mounting plate (29) with pneumatic perform lnym mechanism disposed on the central module (25) for holding the laminates (51) during step c). 4. A device for performing step d) of the method according to claims 1 and 2, characterized in that it comprises a curved male module (57) with recesses (59, 60) for accommodating the flange and flanges of the segments of the L-shaped or C-shaped layered material (51) respectively, and a plurality of elastic strips (71) for holding the laminate segments during the hot forming process.

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