A forming process for a hollow composite wing with winglets

Abstract

The present invention relates to the technical field of composite wing forming processes, and specifically discloses a hollow composite wing forming process with winglets, comprising: a short fiber composite inner mold, wherein the short fiber composite inner mold is used for segmented molding of a carbon fiber hollow inner mold; the short fiber composite inner mold and a carbon fiber prepreg ply are placed in a vacuum bag, and a non-porous isolation membrane is placed between the short fiber composite inner mold and the carbon fiber prepreg ply; the inner mold of the main wing portion of the wing of the present invention is quickly processed using an additive manufacturing process, the short fiber composite material is easy to print and can withstand the high temperature during the curing of the carbon fiber prepreg, the short fiber composite inner mold is reusable, the polyurethane foam inner mold of the winglet portion is low in cost, the hollow composite wing surface obtained by manufacturing is obtained by integral molding, the mechanical properties at the leading and trailing edges of the wing are better than those of the upper and lower mold clamping process, and can withstand a greater load.

Description

Technical Field

[0001] The invention belongs to the technical field of composite material wing forming technology, and in particular relates to a forming technology of a hollow composite material wing with a winglet. Background Art

[0002] Composite materials are widely used in aerospace due to their high specific strength, specific stiffness, corrosion resistance, and fatigue resistance. With the development of aviation materials, the use of lightweight, high-strength composite load-bearing structural components has become a mainstream trend in aircraft structural design. For small civilian fixed-wing drones, the use of lightweight, high-strength composite wings can help increase the drone's maximum takeoff weight and enhance its carrying capacity, meeting the current development needs of cargo drones.

[0003] At present, the main load-bearing components of aircraft wings are mainly made of thermosetting composite materials, among which thermosetting carbon fiber reinforced composite materials are the main ones; the curing process is divided into prepreg hot pressing curing process and resin induction curing process. The molding method of the prepreg hot pressing curing process mainly relies on the outer mold and internal core mold to maintain the wing shape, and maintain the mold pressure at the curing temperature for molding.

[0004] Composite wings need to take into account the space reserved for internal wire tubes and rudder rods. Therefore, in the process of hot pressing and curing of prepregs, grooves or holes need to be set in the internal mold, or after curing is completed, the mold inside the closed wing skin needs to be destroyed and removed. The traditional manufacturing process of hollow wings adopts the form of curing the upper and lower wing surfaces separately, and then closing the mold for secondary curing. The quality of the wing surface connection is poor, and the vibration generated during the cutting of the pressure edge parts at the leading and trailing edges will cause the separation of part of the matrix, affecting the final molding quality.

[0005] In order to solve the problem of overall molding quality in the curing molding process of hollow composite wings, and taking into account the reusability of the inner mold to meet the design goals of light weight and high strength, a technical invention of a low-cost hollow composite wing molding process is proposed.

[0006] To solve this problem, the inventors proposed a hollow composite wing forming process with winglets to solve the above problems. Summary of the Invention

[0007] The object of the present invention is to provide a process for forming a hollow composite wing with a winglet, so as to solve the problems raised in the above background technology.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A hollow composite wing with winglets, comprising:

[0010] A short fiber composite material inner mold, wherein the short fiber composite material inner mold is used for segmented molding of a carbon fiber hollow inner mold;

[0011] The short fiber composite material inner mold and the carbon fiber prepreg ply are placed in a vacuum bag, and the non-porous isolation membrane is placed between the short fiber composite material inner mold and the carbon fiber prepreg ply to facilitate demoulding. The vacuum bag is connected to a vacuum pump.

[0012] Preferably, the carbon fiber hollow inner mold is cured to form the main wing surface part.

[0013] Preferably, a thermal cycle oven is used to provide a heating environment during the vacuum bag curing process, and the oven is equipped with a fan to ensure uniform temperature distribution inside the oven.

[0014] Preferably, a polyurethane foam inner mould is used to cure the winglet portion of the wing.

[0015] Preferably, the polyurethane foam inner mold and the carbon fiber hollow inner mold obtained by vacuum bag curing are assembled to obtain the inner mold of the entire wing.

[0016] Preferably, the inner mold of the winglet portion of the wing and the inner mold of the entire wing are located between a metal lower mold and a metal upper mold, and the metal lower mold and the metal upper mold are placed in an autoclave.

[0017] Preferably, the composite hollow wing structure is a symmetrical airfoil with two reinforcing beams.

[0018] Preferably, the two reinforcing beams are divided into beam No. 1 and beam No. 2, the cross-sectional shape of beam No. 1 is I-shaped, and the cross-sectional shape of beam No. 2 is C-shaped.

[0019] A forming process for a hollow composite wing with winglets comprises the following steps:

[0020] S1. Partition the wing and print the short fiber composite inner mold using additive manufacturing technology;

[0021] S2. Lay a non-porous barrier film on the surface of the outer contour of the mold, and lay carbon fiber prepreg on the outer surface of the non-porous barrier film. The number of plies of carbon fiber hollow inner mold is relatively small, and the remaining plies are laid when the wing is cured as a whole. After that, lay a non-porous barrier film on the surface of the carbon fiber prepreg.

[0022] S3. Place the completed wing into a vacuum bag, with different parts of the wing separated by a certain distance; place the vacuum nozzle of the vacuum pump into the vacuum bag, with the vacuum nozzle positioned in the middle of the wing length to ensure uniform pressure distribution on the mold surface;

[0023] S4. After the vacuum bag is sealed, a vacuum pump extracts the air inside the vacuum bag. Under the action of air pressure, the surface of the vacuum bag is tightly attached to the outer surface of the wing. After reaching the required curing pressure conditions, the vacuum bag is placed in a heat circulation oven. The curing temperature is set, and the fan inside the oven is turned on to wait for the carbon fiber hollow wing inner mold to cure and form.

[0024] S5. Open the vacuum bag, take out all the internal structures of the vacuum bag, remove the surface non-porous isolation film, the internal short fiber composite material inner mold and the internal non-porous isolation film to obtain a carbon fiber hollow inner mold;

[0025] S6. Assemble the carbon fiber hollow wing inner mold obtained in step S5 with the polyurethane foam inner mold, lay the remaining wing surface layers on the surface, and place the entire mold into the metal lower mold portion. After adding the metal upper mold, tighten the bolts and pressurize the mold to form the metal outer mold;

[0026] S7. Place the outer metal mold in an autoclave, set the pressure and temperature curve required for curing the carbon fiber prepreg, and after curing, open the outer metal mold and remove the integral wing with winglets;

[0027] S8. Remove the polyurethane foam inner mold of the winglet part, cut off and polish the cloth pressing parts of the leading and trailing edges of the wing, and obtain a hollow composite material wing with winglets.

[0028] Preferably, the curing temperature in step S7 is 120-135° C., and the curing time is 2-3 hours.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The inner mold of the main wing portion of the wing of the present invention is quickly processed using an additive manufacturing process. The short fiber composite material is easy to print and can withstand the high temperature during the curing of the carbon fiber prepreg. The short fiber composite material inner mold is reusable. The polyurethane foam inner mold of the winglet portion is low in cost, which effectively reduces the manufacturing cost.

[0031] (2) The hollow composite wing surface manufactured by the present invention is obtained by integral molding. The mechanical properties at the leading and trailing edges of the wing are better than those of the upper and lower mold-joining process, and it can withstand a greater load. The carbon fiber hollow inner mold used is manufactured in sections, and has strong designability. It can be adaptively adjusted according to the specific load borne by the wing and the installation position of the engine. By adopting different section positions and layer designs on the wing surface, the obtained composite hollow inner mold, the installation position of the internal reinforcement structure and the cross-sectional shape of the beam are highly designable, which is conducive to adding reinforcement beams inside the hollow inner mold, so that the wing can withstand a greater aerodynamic load. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1A schematic diagram of the wing shape and the arrangement of segmented areas and internal reinforcement beams of the present invention;

[0033] Figure 2 This is a schematic diagram of the cross-sectional structure of the carbon fiber hollow inner mold of the wing area A and the No. 1 beam after pressurization inside the vacuum bag of the present invention;

[0034] Figure 3 Schematic diagram of the cross-sectional structure of the carbon fiber hollow inner mold of the wing region B after pressurization inside the vacuum bag of the present invention;

[0035] Figure 4 Schematic diagram of the cross-sectional structure of the main part of the wing of the present invention in the metal outer mold;

[0036] Figure 5 Schematic diagram of the cross-sectional structure of the winglet portion of the present invention in the metal outer mold;

[0037] Figure 6 A schematic diagram of the metal outer mold used in the present invention;

[0038] Figure 7 This is a flow chart of a molding process of a hollow composite wing with winglets according to the present invention;

[0039] In the figure: 1. Short fiber composite material inner mold; 2. Carbon fiber prepreg; 3. Non-porous isolation membrane; 4. Vacuum bag; 5. Carbon fiber hollow inner mold; 6. Polyurethane foam inner mold; 7. Metal lower mold; 8. Metal upper mold; 9. Beam No. 1; 10. Beam No. 2. DETAILED DESCRIPTION

[0040] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0041] Example 1:

[0042] See also Figures 1 to 7 As shown, a hollow composite wing with winglets, comprising:

[0043] A short fiber composite material inner mold 1, wherein the short fiber composite material inner mold 1 is used for segmented molding of a carbon fiber hollow inner mold 5;

[0044] The short fiber composite material inner mold 1 and the carbon fiber prepreg 2 ply are placed in a vacuum bag 4, and the non-porous isolation membrane 3 is placed between the short fiber composite material inner mold 1 and the carbon fiber prepreg 2 ply to facilitate demoulding. The vacuum bag 4 is connected to a vacuum pump.

[0045] Specifically, the carbon fiber hollow inner mold 5 is cured to form the main wing surface part.

[0046] Specifically, the thermal cycle oven is used to provide a heating environment during the curing process of the vacuum bag 4 , and the oven is equipped with a fan to ensure uniform temperature distribution inside the oven.

[0047] Specifically, the polyurethane foam inner mold 6 is used to solidify the winglet portion of the wing.

[0048] Specifically, the polyurethane foam inner mold 6 and the carbon fiber hollow inner mold 5 obtained by curing the vacuum bag 4 are assembled to obtain the inner mold of the entire wing.

[0049] Specifically, the inner molds of the winglet part of the wing and the entire wing are located between a metal lower mold 7 and a metal upper mold 8, and the metal lower mold 7 and the metal upper mold 8 are placed in an autoclave.

[0050] Specifically, the composite hollow wing structure is a symmetrical airfoil with two reinforcing beams.

[0051] Specifically, the two reinforcement beams are divided into a No. 1 beam 9 and a No. 2 beam 10 . The cross-section of the No. 1 beam 9 is an I-shape, and the cross-section of the No. 2 beam 10 is a C-shape.

[0052] From the above, it can be seen that the hollow composite wing surface manufactured is obtained by integral molding, and the mechanical properties of the leading and trailing edges of the wing are better than those of the upper and lower mold combining process, and can withstand greater loads.

[0053] Example 2:

[0054] refer to Figures 1 to 7 As shown, a forming process of a hollow composite wing with winglets includes the following steps:

[0055] S1. Partition the wing and print a short fiber composite inner mold 1 using an additive manufacturing process;

[0056] S2. Lay a non-porous separator 3 on the surface of the outer contour of the mold, and lay a carbon fiber prepreg 2 on the outer surface of the non-porous separator 3. The number of layers of the carbon fiber hollow inner mold 5 is relatively small, and the remaining layers are laid when the wing is cured as a whole. Then, lay a non-porous separator 3 on the surface of the carbon fiber prepreg 2;

[0057] S3. Place the completed wing into a vacuum bag 4, with different parts of the wing separated by a certain distance; place the vacuum nozzle of the vacuum pump into the vacuum bag 4, with the vacuum nozzle positioned in the middle of the wing length to ensure uniform pressure distribution on the mold surface;

[0058] S4. After the vacuum bag 4 is sealed, the air inside the vacuum bag 4 is extracted by a vacuum pump. Under the action of air pressure, the surface of the vacuum bag 4 is tightly attached to the outer surface of the wing. After reaching the required curing pressure condition, the vacuum bag 4 is placed in a heat circulation oven. The curing temperature is set, and the fan inside the oven is turned on to wait for the carbon fiber hollow wing inner mold to be cured and formed.

[0059] S5, open the vacuum bag 4, take out all the internal structures of the vacuum bag 4, remove the surface non-porous isolation membrane 3, the internal short fiber composite material inner mold 1 and the internal non-porous isolation membrane 3, and obtain the carbon fiber hollow inner mold 5;

[0060] S6, assembling the carbon fiber hollow wing inner mold obtained in step S5 with the polyurethane foam inner mold 6, laying the remaining layers of the wing surface on the surface, and placing the whole into the metal lower mold 7. After adding the metal upper mold 8, tighten the bolts and pressurize the mold to form the metal outer mold;

[0061] S7. Place the outer metal mold in an autoclave, set the pressure and temperature curve required for curing the carbon fiber prepreg 2, and after curing, open the outer metal mold and remove the integral wing with winglets;

[0062] S8. Take out the polyurethane foam inner mold 6 of the winglet part, cut off and polish the cloth pressing part of the leading and trailing edges of the wing, and obtain a hollow composite material wing with a winglet.

[0063] Specifically, the curing temperature in step S7 is 120° C. and the curing time is 3 hours.

[0064] As can be seen from the above, the inner mold of the wing main part is quickly processed using the additive manufacturing process. The short fiber composite material is easy to print and can withstand the high temperature when the carbon fiber prepreg 2 is cured. The short fiber composite inner mold 1 is reusable. The polyurethane foam inner mold 6 of the winglet part is low in cost, which effectively reduces the manufacturing cost.

[0065] The hollow composite wing surface is obtained by integral molding. The mechanical properties of the leading and trailing edges of the wing are better than those of the upper and lower mold processes and can withstand greater loads.

[0066] Example 3:

[0067] refer to Figures 1 to 7 As shown, step 1: using an additive manufacturing process, the material is selected from short carbon fiber polyethylene terephthalate high temperature resistant composite material to manufacture the inner mold of areas A and B;

[0068] Step 2: Divide the inner mold of area A into two parts starting from the position of the leading edge No. 1 beam 9, lay a non-porous isolation film 3 on the surface of the short fiber composite material mold, and then lay carbon fiber prepreg 2 towards the leading and trailing edges respectively to form a C-shaped beam, which is bonded and cured to form a No. 1 I-beam;

[0069] Step 3: Lay the prepreg layer of the carbon fiber hollow inner mold 5 on the surface; lay the non-porous isolation membrane 3 on the surface of the carbon fiber prepreg 2 layer;

[0070] Step 4: Use the same laying method to lay out areas A, B and the second beam 10, put all the laid parts into the vacuum bag 4, heat and cure them in the thermal cycle oven, take out the vacuum bag 4, demould and remove the short fiber composite material inner mold 1 for the next manufacturing use;

[0071] Step 5: Assemble the carbon fiber hollow inner molds 5 in the A and B areas of the main wing together, evenly apply resin adhesive on the surface of the second beam 10, and place it inside the main wing; place the entire structure into the metal outer mold, bolt it and pressurize it, and remove it after curing for 8 hours;

[0072] Step 6: Assemble the carbon fiber hollow inner mold 5 and the polyurethane foam inner mold 6 in area C together, and lay the carbon fiber prepreg 2 on the surface of the wing shape; place the entire wing after laying into the metal lower mold 7, cover it with the metal upper mold 8, close the mold and pressurize it; the curing environment adopts a combination of autoclave process and molding process, the temperature is 135℃, and the time is 2 hours to ensure the secondary curing bonding quality between the carbon fiber hollow inner mold 5 and the remaining layers of the wing skin.

[0073] Step 7: After the predetermined time is reached, the can is opened and the mold is removed, the polyurethane foam inner mold 6 of the winglet part is broken and removed, and the leading and trailing edge pressing parts are cut and polished to obtain a finished hollow composite wing.

[0074] As can be seen from the above, the inner mold of the wing main part is quickly processed using the additive manufacturing process. The short fiber composite material is easy to print and can withstand the high temperature when the carbon fiber prepreg 2 is cured. The short fiber composite inner mold 1 is reusable. The polyurethane foam inner mold 6 of the winglet part is low in cost, which effectively reduces the manufacturing cost.

[0075] The hollow composite wing surface is obtained by integral molding. The mechanical properties of the leading and trailing edges of the wing are better than those of the upper and lower mold processes and can withstand greater loads.

[0076] The carbon fiber hollow inner mold 5 is manufactured in sections, which has strong designability and can be adaptively adjusted according to the specific load borne by the wing and the engine installation position, and adopts different section positions and wing surface layer designs.

[0077] The obtained composite hollow inner mold has a highly designable installation position of the internal reinforcement structure and the cross-sectional shape of the beam, which is conducive to adding reinforcement beams inside the hollow inner mold, so that the wing can withstand greater aerodynamic loads.

[0078] In the description of this specification, the reference terms "one embodiment", "some embodiments", "examples", "specific examples" or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0079] In the drawings of the embodiments disclosed in the present invention, only the structures related to the embodiments disclosed in the present invention are involved. Other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of the present invention can be combined with each other.

[0080] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A process for forming a hollow composite wing with winglets, characterized in that: The following steps are involved: S1. Partition the wing and print a short fiber composite inner mold (1) using an additive manufacturing process; S2, laying a non-porous isolation film (3) on the surface of the outer contour of the mold, laying a carbon fiber prepreg (2) on the outer surface of the non-porous isolation film (3), the number of layers of the carbon fiber hollow inner mold (5) is small, and the remaining layers are laid when the wing is solidified as a whole, and then the non-porous isolation film (3) is laid on the surface of the carbon fiber prepreg (2); S3, placing the entire wing after laying into a vacuum bag (4), with different parts of the wing separated by a certain distance; placing the vacuum nozzle of the vacuum pump into the vacuum bag (4), with the vacuum nozzle placed in the middle of the wing length to ensure that the pressure on the mold surface is evenly distributed; S4. After the vacuum bag (4) is sealed, the air inside the vacuum bag (4) is extracted by a vacuum pump. Under the action of air pressure, the surface of the vacuum bag (4) is tightly attached to the outer surface of the wing. After the required pressure conditions for curing are reached, the vacuum bag (4) is placed in a heat cycle oven, the curing temperature is set, the fan inside the oven is turned on, and the carbon fiber hollow wing inner mold is allowed to cure and form. S5, opening the vacuum bag (4), taking out all the internal structures of the vacuum bag (4), removing the surface non-porous isolation membrane (3), the internal short fiber composite material inner mold (1) and the internal non-porous isolation membrane (3), and obtaining a carbon fiber hollow inner mold (5); S6, assembling the carbon fiber hollow wing inner mold obtained in step S5 and the polyurethane foam inner mold (6) together, laying the remaining layers of the wing surface on the surface, placing the whole into the metal lower mold (7), adding the metal upper mold (8), tightening the bolts and pressurizing the mold to form the metal outer mold; S7, placing the metal outer mold into an autoclave, setting the pressure and temperature curve required for curing the carbon fiber prepreg (2), and after curing, opening the metal outer mold and taking out the integral wing with winglets; S8, destroying and removing the polyurethane foam inner mold (6) of the winglet part, cutting and polishing the cloth pressing part of the leading and trailing edges of the wing, and obtaining a hollow composite material wing with winglets.

2. The forming process of a hollow composite wing with winglets according to claim 1, characterized in that: The curing temperature in step S7 is 120-135° C. and the curing time is 2-3 hours.

3. A hollow composite wing with winglets, characterized by: The wing is prepared by the process described in any one of claims 1-2.

4. The hollow composite wing with winglets according to claim 3, characterized in that: The composite hollow wing structure is a symmetrical airfoil and has a structure with two reinforcing beams.

5. The hollow composite wing with winglets according to claim 4, characterized in that: The two reinforcement beams are divided into a No. 1 beam (9) and a No. 2 beam (10), the No. 1 beam (9) has an I-shaped cross-section, and the No. 2 beam (10) has a C-shaped cross-section.

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