Polygonal stepped opening forming method and forming die for composite part

Abstract

The invention belongs to the technical field of composite material manufacturing, and discloses a forming method and a forming die for a polygonal stepped opening of a composite material part, and a preformed core die sheet is adopted to occupy positions in a layering manner in the paving process, so that the stepped opening is reserved and formed. The technical problem that an existing polygonal step type opening is difficult to machine and form through numerical control is solved. Precise forming of the polygonal step type opening in the composite material stiffened wall plate can be achieved, the requirement for the assembly precision of the opening is met, and skin laying forming and integrated forming of the polygonal step type opening structure are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite material parts / assemblies manufacturing, and specifically relates to a polygonal stepped opening forming method and a forming die for a composite material part. Background Art

[0002] With the increasing use of composite materials in the aerospace field, composite wing stiffened panels and beams of the main load-bearing structure have been widely used in aircraft. The internal space of the wing box section is used as an integral fuel tank, which can increase the aircraft's fuel storage capacity, increase flight time, and improve flight performance. The inspection cover is generally opened on the lower wall panel. It is a channel for box section assembly, integral fuel tank sealing and maintenance, and is also an indispensable part of the overall structure of the wing stiffened panel.

[0003] In recent years, with the demand for large aircraft, the size of wing panels has increased, the number of inspection cover openings has increased, and the structure has become more and more complex. The polygonal stepped opening on the reinforced wall panel described in the present application is a complex structure cover opening. According to traditional manufacturing methods, in order to ensure the manufacturing accuracy of the assembly at the wall panel opening, CNC machining is used to form the composite material wall panel after it is cured. However, this processing and forming method can only be used for simple openings. For complex polygonal stepped openings, it is extremely difficult or even impossible to use CNC machining to form them. The present application scheme can achieve precise forming of polygonal stepped openings on composite reinforced wall panels, meet the assembly accuracy requirements at the openings, and realize the integrated forming of skin layer forming and polygonal stepped opening structure, without the need for CNC machining after the wall panel is cured. Summary of the invention

[0004] The present invention aims to solve the problem that polygonal stepped openings on composite reinforced wall panels are difficult to be formed by numerical control machining, and proposes a method and a mold that can simultaneously realize the forming of polygonal stepped openings during the composite skin forming process.

[0005] In order to achieve the above invention objectives, the technical solutions adopted in this application are as follows:

[0006] A method for forming a polygonal stepped opening of a composite material part comprises the following steps:

[0007] Step 1: Lay several layers of prepreg on the overall surface of the skin, place a preformed core mold sheet at the corresponding position of the opening, and cut off the prepreg at the position along the edge of the preformed core mold sheet;

[0008] Step 2: Continue to lay the skin prepreg, the number of laying layers is equivalent to that in step 1, cut off the prepreg laid later along the edge of the preformed core mold sheet in step 1, and stack the second preformed core mold sheet on the first preformed core mold sheet, and so on, and repeat this step until the polygonal step opening is completed with laying and preforming;

[0009] Step 3: Take out the preformed core mold composed of several preformed core mold sheets from the polygonal step opening of the preformed skin, replace it with the forming core mold, and use the core mold positioning pin to complete the positioning of the forming core mold through the positioning hole;

[0010] Step 4: Continue laying the remaining layers until all layers of the skin are laid and compacted;

[0011] Step 5: Use a laser projector to determine the position of the elliptical opening above the polygonal step opening, remove the prepreg in the ellipse, put in the annular molding mold, and put a breathable core mold in the annular molding mold;

[0012] Step 6: Assemble the long skin, place auxiliary materials, make bags and package, and autoclave to obtain a part with a polygonal stepped opening.

[0013] As a further solution of the present invention: the preformed core mold sheet is processed and formed in the shape of a polygonal stepped opening, and its thickness is equivalent to the thickness of several layers laid in step 1.

[0014] As a further solution of the present invention: the thickness of the preformed core mold sheet is generally controlled to be 0.5 mm to 1.0 mm, and according to the theoretical thickness of the prepreg, 3 to 6 layers of ply need to be completed each time.

[0015] A composite material part polygonal stepped opening forming die, used in the above forming method, comprising:

[0016] A preformed core mold, which is composed of a plurality of preformed core mold sheets stacked together;

[0017] A forming core mold, which has the same size and shape as the preforming core mold;

[0018] An annular forming die is placed on the forming core die, and its outer contour matches the elliptical opening;

[0019] The air-permeable core mold is placed in the annular forming mold, the outer contour of which is matched with the inner ring of the annular forming mold, and the air-permeable core mold is flush with the upper surface of the annular forming mold.

[0020] As a further solution of the present invention: it also includes an overall profile for skin paving, the preformed core mold or the molding core mold is located on the overall profile for skin paving, the preformed core mold is placed when the polygonal opening is formed, and the molding core mold is placed after paving is completed until curing is completed.

[0021] As a further solution of the present invention: positioning holes are provided on the overall surface of the skin paving, and the forming core mold is fixed on the overall surface of the skin paving by core mold positioning pins.

[0022] As a further solution of the present invention: the preformed core mold sheet is made of non-metallic polymer material, and its contour tolerance is 0.5-1.0 mm.

[0023] As a further solution of the present invention: the molding core mold is made of a metal material with a thermal expansion coefficient close to that of the composite material, and its thickness is determined according to the step thickness. At the same time, according to the thickness change of the composite material before and after curing, the thickness tolerance of the molding core mold is between 0 and 0.2 mm.

[0024] As a further solution of the present invention: the annular forming mold is formed by curing prepreg + rubber and is machined into an annular structure, and its thickness is generally consistent with the thickness of the elliptical prepreg above the polygonal step.

[0025] As a further solution of the present invention: the air-permeable core mold is made of honeycomb material, and its thickness is consistent with the thickness of the annular forming mold.

[0026] Compared with the prior art, the beneficial effects of this application are:

[0027] 1. Use a core mold with a simple structure to achieve integrated molding of the skin and polygonal stepped opening.

[0028] 2. The preforming / forming core mold used for polygonal stepped opening forming has a simple structure, is easy to manufacture, and has readily available materials.

[0029] 3. The polygonal stepped opening formed by this method has high forming accuracy and meets the assembly accuracy requirements of the cover. At the same time, it combines the manufacturing processes, improves production efficiency, and achieves the purpose of saving costs in the manufacturing of composite parts.

[0030] The present application is further described below in conjunction with the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0032] In the attached picture:

[0033] Figure 1 This is a schematic diagram of the polygonal stepped opening forming mold of this application;

[0034] Figure 2 This is a schematic diagram of a polygonal stepped opening preforming die for this application;

[0035] Figure 3 This is a three-dimensional schematic diagram of the polygonal stepped opening of this application;

[0036] Figure 4 These are the bottom and top views of the polygonal stepped opening of this application.

[0037] Explanation of the reference numerals in the figure: 1-paving the overall surface, 2-preforming core mold, 3-preforming core mold sheet, 4-forming core mold, 5-annular forming mold, 6-breathable core mold, 7-positioning hole, 8-core mold positioning pin, 9-polygonal step opening, 10-elliptical opening. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0039] This scheme takes the polygonal stepped opening of the composite material reinforced wall panel structure as an example. Figure 1 As shown, in the first aspect, a composite material part step-type opening forming mold is provided, which includes a part paving overall profile 1, a preforming core mold 2, a preforming core mold sheet 3, a forming core mold 4, an annular forming mold 5, a breathable core mold 6, a positioning hole 7, and a core mold positioning pin 8. Positioning holes 7 are arranged on the overall profile of the skin paving, and a plurality of preforming core mold sheets 3 or a forming core mold 4 are positioned by the core mold positioning pin 8. The preforming core mold 2 is composed of a plurality of preforming core mold sheets 3 that can be separated and combined, and the material is a non-metallic polymer. The thickness of the preforming core mold sheet 3 is determined according to the thickness of a single layer of paving, and the general thickness is controlled at 0.5mm to 1.0mm. The contour tolerance of the preforming core mold sheet 3 is 0.5mm to 1.0mm, which is used for the preforming of polygonal steps during the skin paving process.

[0040] The preforming core mold 2 or the forming core mold 4 is located on the integral part paving surface 1. The preforming core mold 2 is placed when the polygonal step opening 9 is formed, and the forming core mold 4 is placed after the paving is completed until the curing is completed. The annular forming mold 5 is placed on the forming core mold 4 for the forming of the elliptical opening 10. The breathable core mold 6 is placed on the forming core mold 4, in the middle of the annular forming mold 5, to prevent bag bridging and balance the thermal uniformity during the curing process.

[0041] The forming core mold 4 replaces the preforming core mold 2 after the polygonal step opening 9 is laid, and enters the tank for curing along with the preformed part. The forming core mold 4 is made of a metal material with a thermal expansion coefficient close to that of the composite material, and the thickness is determined according to the step thickness. At the same time, according to the thickness change before and after the material is cured, the thickness tolerance of the forming core mold 4 is between 0 and 0.2 mm.

[0042] The annular forming mold 5 is made of composite material prepreg + silicone rubber cured and machined into an annular structure. The thickness is generally consistent with the thickness of the elliptical prepreg above the polygonal step opening 9, and is placed on the forming core mold 4 for forming the elliptical opening 10. The air-permeable core mold 6 is a honeycomb material with the same thickness as the annular forming mold 5 or slightly thinner, which is used to fill the space in the middle of the annular forming mold 5 to prevent bag bridging, and at the same time helps to balance the thermal uniformity during the curing process of the thick opening area of ​​the wall panel.

[0043] like Figure 2-4 As shown, in a second aspect, a method for forming a polygonal stepped opening of a composite material part is provided, which comprises the following steps:

[0044] 1. Lay the prepreg layer on the overall skin paving surface 1. After completing 3 to 6 layers of ply according to the theoretical thickness of the material, place a preformed core mold sheet 3 at the corresponding position of the opening, and cut off the prepreg at the position according to the boundary of the preformed core mold sheet 3.

[0045] 2. Continue to lay the skin prepreg. After 3 to 6 layers of laying are completed according to the theoretical thickness of the material, the prepreg laid later is cut off according to the boundary of the first preformed core mold sheet 3, and the second preformed core mold sheet 3 is placed in the opening position. And so on, repeat the above contents continuously until the polygonal step opening 9 is completed with laying and preforming.

[0046] 3. Take out the preformed core mold 2 composed of several preformed core mold sheets 3 from the polygonal step opening 9 of the preformed skin, and replace it with the forming core mold 4, and use the core mold positioning pin 8 to complete the positioning of the forming core mold 4 through the positioning hole 7.

[0047] 4. Continue to lay the remaining layers until all the layers of the skin are laid and compacted. Use a laser projector to determine the position of the elliptical opening 10 above the polygonal step opening 9, remove the prepreg in the ellipse, put the annular molding mold 5 in, and put the breathable core mold 6 into the annular molding mold 5 to prevent bag bridging and balance the thermal uniformity during the curing process.

[0048] 5. Carry out long-line skin assembly, auxiliary material placement, bag packaging and autoclave curing to obtain parts with polygonal stepped openings.

[0049] So far, the purpose of the present invention has been achieved.

[0050] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for forming a polygonal stepped opening of a composite material part, characterized in that: The steps include: Step 1: Lay several layers of prepreg on the overall surface of the skin, place a preformed core mold sheet at the corresponding position of the opening, and cut off the prepreg at the position along the edge of the preformed core mold sheet; Step 2: Continue to lay the skin prepreg, the number of laying layers is equivalent to that in step 1, cut off the prepreg laid later along the edge of the preformed core mold sheet in step 1, and stack the second preformed core mold sheet on the first preformed core mold sheet, and so on, and repeat this step until the polygonal step opening is completed with laying and preforming; Step 3: Take out the preformed core mold composed of several preformed core mold sheets from the polygonal step opening of the preformed skin, replace it with the forming core mold, and use the core mold positioning pin to complete the positioning of the forming core mold through the positioning hole; Step 4: Continue laying the remaining layers until all layers of the skin are laid and compacted; Step 5: Use a laser projector to determine the position of the elliptical opening above the polygonal step opening, remove the prepreg in the ellipse, put in the annular molding mold, and put a breathable core mold in the annular molding mold; Step 6: Assemble the long skin, place auxiliary materials, make bags and package, and autoclave to obtain a part with a polygonal stepped opening.

2. A method for forming a polygonal stepped opening of a composite material part according to claim 1, characterized in that: The preformed core mold sheet is processed and formed in the shape of a polygonal stepped opening, and its thickness is equivalent to the thickness of several layers laid in step 1.

3. A method for forming a polygonal stepped opening of a composite material part according to claim 2, characterized in that: The thickness of the preformed core mold sheet is generally controlled to be 0.5 mm to 1.0 mm, and according to the theoretical thickness of the prepreg, 3 to 6 layers of ply need to be completed each time.

4. A composite material part polygonal stepped opening forming die, used in any forming method of claims 1-3, characterized in that: include: A preformed core mold, which is composed of a plurality of preformed core mold sheets stacked together; A forming core mold, which has the same size and shape as the preforming core mold; An annular forming die is placed on the forming core die, and its outer contour matches the elliptical opening; The air-permeable core mold is placed in the annular forming mold, the outer contour of which is matched with the inner ring of the annular forming mold, and the air-permeable core mold is flush with the upper surface of the annular forming mold.

5. A composite material part polygonal stepped opening forming die according to claim 4, characterized in that: It also includes an overall profile for skin paving, wherein the preformed core mold or the molding core mold is located on the overall profile for skin paving, the preformed core mold is placed when the polygonal opening is formed, and the molding core mold is placed after paving is completed until curing is completed.

6. A composite material part polygonal stepped opening forming die according to claim 5, characterized in that: Positioning holes are arranged on the overall surface for skinning, and the forming core mold is fixed on the overall surface for skinning via core mold positioning pins.

7. A composite material part polygonal stepped opening forming die according to any one of claims 4 to 6, characterized in that: The preformed core mold sheet is made of non-metallic polymer material, and its profile tolerance is 0.5-1.0 mm.

8. A composite material part polygonal stepped opening forming die according to any one of claims 4 to 6, characterized in that: The molding core mold is made of a metal material with a thermal expansion coefficient close to that of the composite material, and its thickness is determined according to the step thickness. At the same time, according to the thickness change before and after the composite material is cured, the thickness tolerance of the molding core mold is between 0 and 0.2 mm.

9. A composite material part polygonal stepped opening forming die according to any one of claims 4 to 6, characterized in that: The annular forming mold is formed by curing prepreg + rubber and is machined into an annular structure, and its thickness is generally consistent with the thickness of the elliptical prepreg above the polygonal step.

10. A composite material part polygonal stepped opening forming die according to any one of claims 4 to 6, characterized in that: The air-permeable core mold is made of honeycomb material, and its thickness is consistent with that of the annular forming mold.

Images