Anti-deformation composite wing surface sandwich foam structure and preparation method thereof

Abstract

The present invention relates to an anti-deformation composite wing sandwich foam structure and a preparation method thereof, and belongs to the technical field of composite material design and molding. The anti-deformation composite wing sandwich foam structure includes at least two arched foam units, each foam unit is tightly fitted, and the gaps between each foam unit are filled with fiber strips along the span direction of the wing surface. The anti-deformation composite wing surface includes an upper foam, a lower foam, a fiber-reinforced base plate arranged between the upper foam and the lower foam, and a skin; wherein the upper foam and the lower foam each include at least two arched foam units, each foam unit is tightly fitted, and the gaps between each foam unit are filled with fiber strips along the span direction of the wing surface. The present invention can significantly reduce the deformation of the foam when it is under pressure, make the orientation of the skin fibers on the foam surface closer to the theoretical design direction, and improve the consistency and reliability of the wing surface product quality.

Description

Technical Field

[0001] The invention relates to an anti-deformation composite material wing surface sandwich foam structure and a preparation method thereof, belonging to the technical field of composite material design and molding. Background Art

[0002] Aircraft weight is closely related to performance and economy, and reducing the weight of aircraft structures is one of the main goals in aircraft development. Composite wing surfaces have excellent mechanical properties such as high specific stiffness and strength, good fatigue resistance and corrosion resistance, and have been widely used in aviation and aerospace structures.

[0003] In order to further reduce the structural weight of the composite wing surface, the wing surface can be designed into a "sandwich" structure of fiber panel foam sandwich, and the foam can be polymethacrylimide foam, phenolic resin foam or rigid polyurethane foam. However, due to the limited compression strength of the foam, and its compression performance will further decrease with the increase of temperature, the foam will be greatly deformed during the preparation of the composite wing surface, affecting the alignment of the foam surface fiber, thereby affecting the stiffness and strength of the wing surface product, which is not conducive to the reliability of the aircraft during flight. Summary of the invention

[0004] The object of the present invention is to provide a deformation-resistant composite wing sandwich foam structure and a preparation method thereof. The structural design of the foam can transfer the vertical pressure exerted on the foam to both sides and the bottom, thereby improving the deformation resistance of the foam.

[0005] The technical solution of the present invention:

[0006] In a first aspect, the present invention provides a deformation-resistant composite wing sandwich foam structure, which includes at least two arched foam units, each foam unit is tightly fitted, and the gaps between the foam units are filled with fiber strips along the span direction of the wing.

[0007] Preferably, the foam in the sandwich foam structure is polymethacrylimide foam or phenolic resin foam or polyurethane foam, which is pre-machined into the required shape; the cross-section of the foam unit can be a part of a semicircle or a circle, or a part of a parabola or an ellipse.

[0008] Optionally, the foam units are closely fitted, which can be achieved by directly closely fitting different single foams together and bonding them with adhesives, or by combining / bonding a single foam block with a certain number of layers of fibers, which is equivalent to combining multiple foam return beams.

[0009] Optionally, in the sandwich foam structure, the external dimensions of different foam units may be the same, or the height dimension of the foam unit in the middle area of ​​the wing surface may be greater than that of the foam units on both sides.

[0010] Preferably, the sandwich foam structure is divided into an upper foam and a lower foam, each of which is composed of at least two foam units, and the gaps between the foam units are filled with fiber strips along the span direction of the wing surface.

[0011] Preferably, the edges of the single foam block need to be rounded with a radius of 1 to 3 mm, so that the strength of the skin fiber covering the outside of the foam can be retained to the maximum extent after the composite wing surface is made of the single foam block.

[0012] In a second aspect, the present invention provides a method for preparing the above-mentioned anti-deformation composite wing surface sandwich foam structure, comprising the following steps:

[0013] 1) Foam preparation: The foam sheet machine is formed into multiple arched foam units;

[0014] 2) Foam drying: clean the debris on the surface of the foam unit and dry the foam unit;

[0015] 3) Foam docking and filling with fiber prepreg: Each foam unit is evenly pasted with adhesive film and then docked. The gaps between the foam units naturally formed due to the arched shape are filled with fiber strips along the span direction of the wing surface.

[0016] Preferably, the drying treatment in step 2) is to dry the foam unit in an oven at 130°C ± 5°C for 3 hours.

[0017] Preferably, in step 3), the fiber strips filled in the gaps between the foam units have a plying direction of [90 / 45 / 0 / -45], wherein the 0-degree plying direction is parallel to the airfoil span direction.

[0018] Optionally, the fiber prepreg in step 3) may include carbon fiber, glass fiber, quartz fiber, or the like.

[0019] In a third aspect, the present invention provides an anti-deformation composite wing surface, which includes an upper foam, a lower foam, a fiber-reinforced base plate arranged between the upper foam and the lower foam, and a skin; wherein the upper foam and the lower foam each include at least two arched foam units, each foam unit is tightly fitted, and the gaps between the foam units are filled with fiber strips along the span direction of the wing surface.

[0020] In the anti-deformation composite wing surface, the upper foam and the lower foam transfer the load to the sides and downward to the web (the web refers to the side wall of the wing surface, connecting the upper and lower skin parts) and the internal fiber-reinforced bottom plate. In addition, the fiber strips along the span direction of the wing surface filled in the gaps between the arched foam units can further improve the structural strength.

[0021] Preferably, the skin is divided into an upper and lower skin, which is prepared by fiber and resin under a certain temperature and pressure, and can be formed by molding, autoclave or RTM. The fiber can be carbon fiber, glass fiber or quartz fiber, and the resin can be medium temperature or high temperature epoxy resin, or phenolic resin.

[0022] Preferably, the fiber reinforced base plate is pre-cured with the same fiber and resin material as the skin. The fiber reinforced base plate is placed between the upper foam and the lower foam, is usually rectangular, and has an outer envelope size that is the same as or slightly larger than the size of the foam combination. The thickness of the fiber reinforced base plate is usually 2~10mm.

[0023] In a fourth aspect, the present invention provides a method for preparing the above-mentioned anti-deformation composite wing surface, comprising the following steps:

[0024] 1) The fiber prepreg is laid and placed in a flat mold, and a hot press is used for compression molding to obtain a fiber-reinforced base plate;

[0025] 2) forming the foam sheet into a foam unit with an arched cross section;

[0026] 3) Clean the debris on the surface of the foam unit and dry the foam unit;

[0027] 4) Evenly adhere each foam unit with adhesive film and then butt them together. Fill the gaps between the foam units with fiber strips along the span direction of the wing surface.

[0028] 5) The fiber unidirectional prepreg is integrally coated on the surface of each assembled foam unit;

[0029] 6) Load each foam unit coated with prepreg into a foam molding tool, and put the tool into an oven for curing and strengthening treatment;

[0030] 7) Demolding and grinding each solidified foam unit, then evenly sticking a layer of adhesive film, and then covering the whole with fiber prepreg to obtain a covered wing surface;

[0031] 8) Place the paved wing surface into a compression molding mold, use a hot press to solidify the wing surface, and demold it after natural cooling.

[0032] Preferably, in step 1), the fiber prepreg is prepared according to [45 / -45 / 0 / 0 / 90 / 45 / 0 / -45 / 0 / 0 / 45] s The laying is carried out in the laying direction.

[0033] Preferably, in step 4), the fiber strips filled in the gaps between the foam units have a plying direction of [90 / 45 / 0 / -45], wherein the 0-degree plying direction is parallel to the airfoil span direction.

[0034] Preferably, in step 5), the laying direction of the fiber unidirectional prepreg is [90 / 90 / 0 / 90 / / 45 / 0 / -45 / 90 / ] s .

[0035] Preferably, in step 7), the ply direction of the fiber prepreg is [45,0,-45,0,0,0,90,0,45,0,-45,0] s .

[0036] Beneficial effects of the present invention:

[0037] Through the sectioning and CT detection of the wing test piece, the deformation of the wing core foam of the embodiment of the present invention is no more than 1mm, while the compression deformation of the foam of the traditional wing product is more than 3mm. In the present invention, the foam transfers the load to the web and the internal fiber-reinforced bottom plate to the sides and downwards, and the fiber strips along the wing span filled in the gap between the arched foam units can further improve the structural strength, so that the deformation of the foam when under pressure can be significantly reduced, and the orientation of the skin fiber on the foam surface is closer to the theoretical design direction, thereby improving the consistency and reliability of the wing product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of three foam units of the anti-deformation composite material wing sandwich foam structure in one embodiment of the present invention.

[0039] Figure 2 It is a schematic diagram of fiber strips filled between foam units of the anti-deformation composite wing sandwich foam structure in one embodiment of the present invention.

[0040] Figure 3 Schematic diagram of a sandwich foam structure composed of upper foam and lower foam in one embodiment of the present invention.

[0041] Figure 4 It is a schematic diagram of an upper foam, a lower foam and a fiber-reinforced bottom plate of an anti-deformation composite wing surface in one embodiment of the present invention.

[0042] Figure 5 It is a schematic diagram of fiber strips filled between foam units of an anti-deformation composite wing surface in one embodiment of the present invention.

[0043] 1-Filling fiber strips; 2-Sandwich foam; 3-Fiber reinforced base plate. DETAILED DESCRIPTION

[0044] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below through specific embodiments and drawings.

[0045] In one embodiment of the present invention, a deformation-resistant composite wing sandwich foam structure is provided, such as Figure 1 As shown, it includes a plurality of arched foam units, and this embodiment includes three arched foam units. Each foam unit is closely fitted, and the gaps between each foam unit are filled with fiber strips along the span direction of the wing surface, such as Figure 2 shown.

[0046] Preferably, the foam in the sandwich foam structure is polymethacrylimide foam or phenolic resin foam or polyurethane foam, which is pre-machined into the required shape; the cross-section of the foam unit can be a part of a semicircle or a circle, or a part of a parabola or an ellipse.

[0047] Optionally, the foam units are closely fitted, which can be achieved by directly closely fitting different single foams together and bonding them with adhesives, or by combining a single foam with a certain number of layers of fibers, which is equivalent to combining multiple foam return beams.

[0048] Optionally, in the sandwich foam structure, the external dimensions of different foam units may be the same, or the height dimension of the foam unit in the middle area of ​​the wing surface may be greater than that of the foam units on both sides.

[0049] In one embodiment of the present invention, a deformation-resistant composite wing sandwich foam structure is provided, such as Figure 3 As shown, the sandwich foam structure is divided into an upper foam and a lower foam, and the upper foam and the lower foam are both composed of at least two of the foam units, each of which is tightly fitted, and the gaps between each foam unit are filled with fiber strips along the span direction of the wing surface. Wherein, the foam is polymethacrylimide foam or phenolic resin foam or polyurethane foam, which is pre-machined into the required shape; the cross-section of the outer shape of the foam unit can be a part of a semicircle or a circle, or a part of a parabola or an ellipse. Wherein, each foam unit is tightly fitted, which can be directly and tightly fitted between different single foams, bonded by adhesives, or a single foam can be coated with a certain number of layers of fibers and then combined, which is equivalent to combining multiple foam return beams. Wherein, the outer dimensions of different foam units can be the same, or the height dimension of the foam unit in the middle area of ​​the wing surface can be larger than that of the foam units on both sides.

[0050] In one embodiment of the present invention, a method for preparing a deformation-resistant composite wing sandwich foam structure is provided, comprising the following steps:

[0051] 1) Foam preparation.

[0052] The polymethacrylimide foam or other foam sheets are machined into a plurality of semicircular foam blocks, namely, foam units.

[0053] 2) Foam drying process.

[0054] Use a hair dryer to clean the debris on the foam surface and dry the foam in an oven at 130℃±5℃.

[0055] 3) Foam butt joint and filled with carbon fiber prepreg.

[0056] After J-47A film is evenly pasted on each foam block, they are butt-jointed. The butt joints naturally formed between the foams due to the arched shape are filled with T700 / 8522 ​​carbon fiber strips. The laying direction of the carbon fiber strips is a quasi-isotropic layup of [90 / 45 / 0 / -45], where the 0-degree laying direction is parallel to the span direction of the wing surface.

[0057] In one embodiment of the present invention, a deformation-resistant composite wing surface is provided, such as Figure 4 As shown, it includes an upper foam, a lower foam, a fiber-reinforced bottom plate disposed between the upper foam and the lower foam, and a skin ( Figure 4 The upper foam and the lower foam each include at least two arched foam units, each foam unit is closely fitted, and the gaps between the foam units are filled with fiber strips along the span direction of the wing surface, such as Figure 5 The upper foam and the lower foam transfer the loads to the sides and downwards to the web and the internal fiber-reinforced bottom plate. In addition, the fiber strips along the span direction of the wing surface filled in the gaps between the arched foam units can further improve the structural strength.

[0058] Preferably, the skin is divided into an upper skin and a lower skin, which are prepared by fibers and resins at a certain temperature and pressure, and can be formed by molding, autoclave or RTM. The fibers can be carbon fibers, glass fibers or quartz fibers, and the resin can be medium-temperature or high-temperature epoxy resin, or phenolic resin.

[0059] Preferably, the fiber reinforced base plate is pre-cured with the same fiber and resin material as the skin. The fiber reinforced base plate is placed between the upper foam and the lower foam, is usually rectangular, and has an outer envelope size that is the same as or slightly larger than the size of the foam combination. The thickness of the fiber reinforced base plate is usually 2~10mm.

[0060] In one embodiment of the present invention, a method for preparing a deformation-resistant composite wing surface is provided, comprising the following steps:

[0061] The first step is to prepare the carbon fiber reinforced base plate. The carbon fiber prepreg is laid in the set ply direction and placed in a flat mold, and then molded and cured using a hot press.

[0062] The second step is to prepare the sandwich foam. The foam sheet is machined into a foam block with a semicircular cross section.

[0063] The third step is to dry the foam. Use a hair dryer to clean the debris on the foam surface and dry the foam in an oven.

[0064] The fourth step is to butt the foams and fill them with carbon fiber prepreg. After evenly sticking the adhesive film on each piece of foam, butt them together. The butt joints formed naturally by the arched shape between the foams are filled with carbon fiber strips.

[0065] The fifth step is to wrap the carbon fiber prepreg with foam. The surface of the assembled foam is entirely covered with carbon fiber unidirectional prepreg.

[0066] Step 6: Foam pre-curing and strengthening treatment: The foam coated with prepreg is loaded into the foam molding tool, and the tool is placed in the oven for pre-curing and strengthening treatment.

[0067] Step 7: Laying the wing surface. The solidified foam is demoulded and polished, and then a layer of adhesive film is evenly applied, and then the whole is covered with carbon fiber prepreg.

[0068] Step 8: The wing surface is solidified and formed.

[0069] Place the paved wing surface into the compression molding mold, and check that the hot press and temperature probe are working properly. Use a crane to lift the mold onto the press table, and the upper panel of the press is in contact with the upper mold. Use the hot press to solidify and mold the wing surface.

[0070] Step 9: De-mould the wing surface. Allow the mould to cool naturally before demoulding.

[0071] In one embodiment of the present invention, a method for preparing a deformation-resistant composite wing surface is provided. The steps of the method are substantially the same as those of the above embodiment, except that:

[0072] In the first step, the carbon fiber prepreg is prepared according to [45 / -45 / 0 / 0 / 90 / 45 / 0 / -45 / 0 / 0 / 45] s The ply is laid in the ply direction;

[0073] In the fourth step, the carbon fiber strips are laid in a quasi-isotropic direction of [90 / 45 / 0 / -45], where the 0-degree laying direction is parallel to the span direction of the wing surface;

[0074] In the fifth step, the carbon fiber unidirectional prepreg is coated on the surface of the assembled foam in the direction of [90 / 90 / 0 / 90 / / 45 / 0 / -45 / 90 / ] s ;

[0075] In the seventh step, the ply direction of the coated carbon fiber prepreg is [45,0,-45,0,0,0,90,0,45,0,-45,0] s .

[0076] In one embodiment of the present invention, forming an airfoil product using an anti-deformation foam as a weight-reducing core layer comprises the following steps:

[0077] The first step is to prepare the carbon fiber reinforced base plate.

[0078] T700 / 8522 ​​high temperature epoxy prepreg (prepreg composed of carbon fiber and resin) is prepared according to [45 / -45 / 0 / 0 / 90 / 45 / 0 / -45 / 0 / 0 / 45] s The laminate is laid in the laying direction (the subscript s indicates symmetry), and placed in a 1000mm×1000mm×3mm flat mold for compression molding. The hot press is heated from room temperature to 130℃±5℃ at a rate of (2-5)℃ / min → kept warm for 2h → a pressure of 0.3MPa is applied → the temperature is continued to rise to 185℃±5℃ → kept warm for 2h, and the hot press is turned off.

[0079] The cured carbon fiber reinforced base plate was cut into three pieces along the width direction, each with a size of 1000 mm × 300 mm × 3 mm.

[0080] The second step is sandwich foam preparation.

[0081] The density is 110kg / m 3 The polymethacrylimide foam board machine is added into 3 foam blocks with a semicircular cross-section. The length of the foam block is 1000mm and the width is 100mm.

[0082] The third step is foam drying.

[0083] Use a hair dryer to clean the debris on the foam surface, and dry the foam in an oven at 130°C ± 5°C for 2-4 hours, preferably 3 hours.

[0084] In the fourth step, the foam is butt-jointed and filled with carbon fiber prepreg.

[0085] After J-47A film is evenly pasted on each piece of foam, they are connected. The joints formed naturally due to the arched shape between the foams are filled with T700 / 8522 ​​carbon fiber strips. The laying direction of the carbon fiber strips is a quasi-isotropic layup of [90 / 45 / 0 / -45], among which the 0-degree laying direction is parallel to the span direction of the wing surface.

[0086] Step 4 and 5: Foam winding carbon fiber prepreg.

[0087] The foam and carbon fiber reinforced base are bonded together, and then the surface of the assembled foam is covered with 2mm thick T700 / 8522 ​​carbon fiber unidirectional prepreg, with the ply direction of [90 / 90 / 0 / 90 / / 45 / 0 / -45 / 90 / ] s .

[0088] Step 6: Foam pre-curing and reinforcement treatment.

[0089] Load the foam coated with prepreg into the foam molding tool, put the tool into the oven, heat the oven to 130℃ and keep it warm for 2h, then continue to heat it to 185℃ and keep it warm for 2h, and then turn off the oven.

[0090] Step 7: Wing surface laying.

[0091] The cured foam was demoulded and polished, and then a layer of J-47A film was evenly pasted, and then the whole was covered with 3mm thick T700 / 9368 carbon fiber prepreg, and the ply direction was [45,0,-45,0,0,0,90,0,45,0,-45,0] s .

[0092] Step 8: The wing surface is solidified and formed.

[0093] Place the paved wing surface into the compression molding mold, and check that the hot press and temperature probe are working properly. Use a crane to lift the mold onto the press table, and the upper panel of the press is in contact with the upper mold. Heat the hot press from room temperature to 130℃±5℃ at a rate of (2-5)℃ / min → keep warm for 2h → apply a pressure of 0.3MPa → continue to heat to 185℃±5℃ → keep warm for 2h, and turn off the hot press.

[0094] Step 9: Demolding the wing surface. Allow the mold to cool naturally to below 50°C before demolding.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A deformation-resistant composite wing surface, characterized in that: It includes an upper foam, a lower foam, a fiber-reinforced bottom plate arranged between the upper foam and the lower foam, and a skin; wherein the upper foam and the lower foam each include at least two arched foam units, each foam unit is tightly fitted in the horizontal direction, and the gaps between the foam units are filled with fiber strips along the span direction of the wing surface, and the two arched foam units and the fiber strips constitute a sandwich foam structure; in the sandwich foam structure, the outer dimensions of different foam units are the same, or the height dimension of the foam unit in the middle area of ​​the wing surface is larger than that of the foam units on both sides.

2. The anti-deformation composite wing surface according to claim 1, characterized in that: The foam unit is polymethacrylimide foam, phenolic resin foam or polyurethane foam; the cross section of the arched foam unit is a part of a semicircle or a circle, or a part of a parabola or an ellipse.

3. The anti-deformation composite wing surface according to claim 1, characterized in that: The foam units are closely fitted, which means that different single foams are directly closely fitted and bonded by adhesive; or a single foam is covered with a certain number of layers of fibers and then fitted.

4. The anti-deformation composite wing surface according to claim 1, characterized in that: The skin is divided into upper and lower skins, which are prepared by fibers and resin under a certain temperature and pressure; the fibers are carbon fibers, glass fibers or quartz fibers; the resin is medium-temperature or high-temperature epoxy resin, or phenolic resin; the fiber-reinforced base plate is pre-cured with the same fiber and resin materials as the skin.

5. A method for preparing the anti-deformation composite wing surface according to claim 1, characterized in that: The following steps are involved: Step 1) draping the fiber prepreg, placing it in a flat mold, and using a hot press to perform compression molding and curing to obtain a fiber-reinforced base plate; Step 2) forming the foam sheet into a foam unit with an arched cross section; Step 3) Clean the debris on the surface of the foam unit and dry the foam unit; Step 4) each foam unit is evenly bonded with adhesive film, and the gaps between the foam units are filled with fiber strips along the span direction of the wing surface; Step 5) The fiber unidirectional prepreg is entirely coated on the surface of each assembled foam unit; Step 6) loading each foam unit coated with the prepreg into a foam molding tool, and placing the tool into an oven for curing and strengthening treatment; Step 7) demoulding and grinding each solidified foam unit, then evenly sticking a layer of adhesive film, and then covering the whole with fiber prepreg to obtain a covered wing surface; Step 8) Place the paved wing surface into a compression molding mold, use a hot press to solidify the wing surface, and demould it after natural cooling.

6. The preparation method according to claim 5, characterized in that: The drying process is to dry the foam unit in an oven at 130° C.±5° C. for 3 hours.

7. The preparation method according to claim 5, characterized in that Step 1) The layup direction of the fiber prepreg is [45 / -45 / 0 / 0 / 90 / 45 / 0 / -45 / 0 / 0 / 45] s ; In step 4), the laying direction of the fiber strips filled in the gaps between the foam units is [90 / 45 / 0 / -45], where the 0-degree laying direction is parallel to the wing span direction; in step 5), the laying direction of the fiber unidirectional prepreg is [90 / 90 / 0 / 90 / / 45 / 0 / -45 / 90 / ] s ; In step 7), the ply direction of the fiber prepreg is [45,0,-45,0,0,0,90,0,45,0,-45,0] s .

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