Method for preventing deformation of a longeron end skin and method for forming an end pad

Abstract

The application discloses a kind of preventing long string end head skin deformation method and end head gasket forming method in the technical field of composite material manufacturing process, comprising the following steps: long string is placed in the forming recess in the upper surface of forming curing tool;Place core mold;End head gasket is placed in the gasket groove in the upper surface of forming curing tool, and the gasket groove is vertically communicated with forming recess, and the end head gasket ballast is fixed above core mold;Skin is laid on the upper surface of forming curing tool, and the end of the skin is on end head gasket;Curing is carried out.The application carries out vertical rigid support to skin by end head gasket, not only can reduce the influence of uneven pressure on skin, thereby preventing skin deformation, but also simple operation, strong practicality.

Description

Technical Field

[0001] This invention relates to the field of composite material manufacturing technology, specifically to a method for preventing deformation of the end skin of a stringer and a method for forming end gaskets. Background Technology

[0002] The rear fuselage panel of the wide-body commercial aircraft is a stiffened structure, and the stringers terminate early at the skin edge, such as... Figure 4 As shown, the rear fuselage process uses a co-curing female mold forming method, but there is no stringer at the cut-off position. After the skin is laid and cured, deformation will occur at this position. Under normal circumstances, uneven pressure distribution on the skin will lead to skin deformation, which will affect the overall performance and life of the parts. Therefore, methods to improve skin deformation have always been a research hotspot in the fields of mechanical engineering and manufacturing processes.

[0003] Many solutions have been proposed to address the problem of skin deformation, such as changing the stress distribution, adjusting the mandrel structure, and modifying the material of the filling twist strip. These solutions can distribute pressure evenly on the skin, thus preventing deformation. However, adjusting variables such as the mandrel structure or the amount of filling twist strip is not only time-consuming and costly to implement, but also difficult to operate, resulting in low practicality and hindering mass production.

[0004] Therefore, how to improve the practicality of methods to prevent skin deformation has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a method for preventing deformation of the end skin of a stringer, so as to solve the technical problem of low practicality of existing methods for preventing skin deformation.

[0006] The technical solution adopted in this invention is: a method for preventing deformation of the end skin of a stringer, the method comprising the following steps:

[0007] S10: Place the stringer into the molding groove on the upper surface of the molding and curing fixture;

[0008] S20: Placement of core mold;

[0009] S30: Place the end gasket in the gasket groove on the upper surface of the molding and curing fixture, and the gasket groove is vertically connected to the molding groove. The end gasket is fixed above the core mold under pressure.

[0010] S40: The skin is laid on the upper surface of the molding and curing fixture, and the end of the skin is located on the end gasket;

[0011] S50: Curing.

[0012] Preferably, the end gasket includes a transverse plate and longitudinal ribs, the number of longitudinal ribs is even, and the longitudinal ribs are vertically fixed to the lower surface of the transverse plate. The cross-section of the longitudinal ribs is adapted to the cavity shape between the core mold and the forming groove.

[0013] Preferably, the transverse plate includes alternating layers of unidirectional carbon fiber prepreg and twill-woven carbon fiber prepreg.

[0014] Preferably, the thickness of the transverse plate is 1.5mm to 2.5mm.

[0015] Preferably, the upper surface of the transverse plate is provided with an isolation film.

[0016] Preferably, the transverse plate is filled with resin obtained by impregnating prepreg with acetone.

[0017] A second objective of this invention is to provide a method for forming an end gasket to prevent deformation of the end skin of a stringer, the method comprising the following steps:

[0018] S100: The core mold is placed in the molding groove on the upper surface of the molding and curing fixture, and the two ends of the core mold are located on both sides of the gasket groove on the upper surface of the molding and curing fixture.

[0019] S200: Fill the space between the core mold and the forming groove with a twist strip;

[0020] S300: Place the gasket material into the gasket groove;

[0021] S400: Ballast cover plate above the gasket material;

[0022] S500: Curing.

[0023] Preferably, in S300, unidirectional carbon fiber prepreg and twill-woven carbon fiber prepreg are placed alternately in the gasket groove.

[0024] The beneficial effects of this invention are:

[0025] The present invention has an end gasket fixedly installed on the molding and curing fixture below the skin of the stringer cut-off area. The end gasket can provide vertical rigid support for the skin, effectively reducing the impact of uneven pressure on the skin. It can not only prevent the skin from deforming, but also is simple to operate and highly practical. Attached Figure Description

[0026] Figure 1 This is a reference diagram showing the usage status of the molding and curing tooling;

[0027] Figure 2 This is a schematic diagram of the molding and curing tooling.

[0028] Figure 3 This is a schematic diagram of the end gasket structure;

[0029] Figure 4 This is a schematic diagram showing the connection between the stringer and the skin.

[0030] Explanation of the reference numerals in the figure:

[0031] 10. Long beam;

[0032] 20. Molding and curing fixtures;

[0033] 21. Molding groove; 22. Gasket groove;

[0034] 30. Core mold;

[0035] 40. End gasket;

[0036] 41. Transverse slab; 42. Longitudinal reinforcement;

[0037] 50. Skin;

[0038] 60. Twisted strips. Detailed Implementation

[0039] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0040] In the description of this invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0041] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0042] Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0043] Examples, such as Figures 1-4 As shown, a method for preventing deformation of the end skin of a stringer is provided. This method is used to prevent deformation of the skin in the stringer termination area; the method includes the following steps:

[0044] S10: Place the stringer 10 into the molding groove 21 on the upper surface of the molding and curing fixture 20.

[0045] S20: Place the core mold 30 and the twist strip 60.

[0046] S30: Place the two end gaskets 40 one by one into the gasket grooves 22 at both ends of the upper surface of the molding and curing fixture 20, and the gasket grooves 22 are vertically connected to the molding groove 21. The end gaskets 40 are fixed on the top of the core mold 30.

[0047] S40: The skin 50 is laid on the upper surface of the molding and curing fixture 20, and the two ends of the skin 50 are located on the two end pads 40 respectively.

[0048] S50: Curing and molding.

[0049] This application has an end gasket 40 fixedly installed on the molding and curing fixture 20 below the skin 50 in the cut-off area of ​​the stringer 10. The end gasket 40 can provide vertical rigid support for the skin 50, effectively reducing the impact of uneven pressure on the skin. It can not only prevent the skin 50 from deforming, but also is simple to operate and highly practical.

[0050] In one specific embodiment, such as Figure 2 , Figure 3 As shown, the end gasket 40 includes a transverse plate 41 and a longitudinal rib 42; wherein, the transverse plate 41 is made of a material with high rigidity after curing, and the transverse plate 41 is adapted to the gasket groove 22 on the molding and curing fixture 20 so that the transverse plate 41 can be accurately reinstalled into the gasket groove 22.

[0051] The number of longitudinal ribs 42 is even, and multiple longitudinal ribs 42 are arranged sequentially along the transverse direction. Each longitudinal rib 42 is vertically fixed to the lower surface of the transverse plate 41. The cross-section of the longitudinal rib 42 is adapted to the cavity shape (triangular area) between the core mold 30 and the molding groove 21, so that after the transverse plate 41 is reinstalled into the gasket groove 22, the longitudinal rib 42 can fill the triangular area between the core mold 30 and the molding and curing fixture 20.

[0052] This design is because: longitudinal ribs 42 are fixedly connected to the lower surface of the transverse plate 41, which can improve the rigidity of the end gasket 40 and help prevent the skin 50 from deforming.

[0053] In one specific embodiment, the transverse plate 41 includes alternating layers of unidirectional carbon fiber prepreg and twill-woven carbon fiber prepreg.

[0054] This design is because the end gasket 40 is used to provide vertical support for the skin 50, thereby offsetting the effect of uneven pressure on the skin 50. Therefore, the end gasket 40 needs to have a certain rigidity, and only materials with high rigidity after curing can be selected. In addition, the material should have good pressure resistance and high rigidity.

[0055] In this embodiment, the transverse plate 41 is made of unidirectional carbon fiber prepreg and twill-woven carbon fiber prepreg. The combination of the two can provide sufficient stiffness to resist the deformation of the skin 50 caused by pressure difference. The thickness of each layer of unidirectional carbon fiber prepreg is 0.187 mm, and the thickness of each layer of twill-woven carbon fiber prepreg is 0.2 mm. In the design of the layup, the two materials are laid in staggered layers to reduce surface ripples caused by the difference in thermal expansion of the materials.

[0056] Preferably, the thickness of the transverse plate 41 is 1.5mm to 2.5mm.

[0057] This design is based on the fact that during curing, the upper surface of the end shim 40 needs to be coplanar with the upper surface of the curing fixture 20. Therefore, thickness compensation is required in the shim groove 22 of the curing fixture 20. When the thickness of the end shim 40 is 2.5mm, it can meet the deformation requirements of a 6mm skin. To meet the needs of skin parts with different thicknesses, the thickness of the end shim 40 is adjusted to meet different requirements. For example, for thinner skin 50, we can use end shims 40 with fewer layers to support deformation, that is, use 1.5mm end shims 40 for skin parts with a thickness of less than 3mm; for thicker skin 50, we can use thicker end shims 40 to provide better support and resistance to skin deformation, and use 2.5mm end shims 40 for skin 50 with a thickness between 3mm and 7mm.

[0058] Meanwhile, in order to ensure that the end gasket 40 and the skin 50 can be fully returned to the gasket groove 22 of the molding and curing tooling 20 for effective fit, the edge of the gasket groove 22 should be designed to be 90 degrees to avoid poor fit caused by the slope.

[0059] More preferably, the upper surface of the transverse plate 41 is provided with an isolation film.

[0060] This design is because: the release liner is single-sided adhesive and a contactable material; the adhesive side contacts the end gasket 40 and then cures together, resulting in a smooth and high-quality surface after demolding. When using the end gasket 40 with the release liner for product mounting, the part surface also exhibits better surface quality. Furthermore, the release liner eliminates the need for applying release agent to the end gasket 40, significantly saving time. It also provides excellent demolding properties and extends the service life of the end gasket 40. Previously, uneven application of release agent often caused damage during demolding of the end gasket 40. Alternatively, the transverse plate 41 is filled with resin obtained by impregnating prepreg with acetone.

[0061] This design is because adding fillers, such as resin obtained by soaking prepreg in acetone, to the end gasket 40 increases the material density and rigidity by increasing the resin content, thereby improving the rigidity and stability of the end gasket 40, and thus achieving higher compressive strength and the ability to prevent skin deformation.

[0062] An embodiment provides a method for forming an end gasket to prevent deformation of the end skin of a stringer. The method includes the following steps:

[0063] S100: Place the core mold 30 in the molding groove 21 on the upper surface of the molding and curing fixture 20, and the two ends of the core mold 30 are located on both sides of the gasket groove 22 on the upper surface of the molding and curing fixture 20.

[0064] S200: Fill the triangular area between the core mold 30 and the forming groove 21 with twist strips 60.

[0065] S300: Place the gasket material into the gasket groove 22.

[0066] S400: Ballast cover plate above the gasket material.

[0067] S500: Curing is performed to ensure that the end gasket 40 can obtain a good aerodynamic shape. By being correctly placed inside the gasket groove 22, the cured end gasket 40 can ensure molding accuracy and consistency, reducing manufacturing costs and cycle time.

[0068] In one specific embodiment, in S300, unidirectional carbon fiber prepreg and twill braided carbon fiber prepreg are placed alternately in the gasket groove 22.

[0069] This setup is because, when designing the layup, laying the two materials in staggered layers can reduce surface ripples caused by differences in thermal expansion of the materials.

[0070] The working principle of the method for preventing deformation of the end skin of the girder in this application is as follows:

[0071] 1. Lay a layer of end gasket on the underside surface of the skin. The end gasket is made of a material with high rigidity after curing, which can provide rigidity to resist stress deformation caused by uneven pressure.

[0072] 2. The end gasket and the molding and curing fixture are formed in one step, which can ensure the precise fit and consistency of the end gasket after it is returned to the molding and curing fixture.

[0073] 3. The selection of gasket materials should meet the requirements of sufficient rigidity, good pressure resistance, and moderate cost. When appropriate, a reinforced structure can be used to achieve the required rigidity.

[0074] Compared with the prior art, this application has at least the following beneficial technical effects:

[0075] (1) This application only requires laying a layer of material with high rigidity after curing on the lower surface of the skin, and forming it with the molding tooling in one step. Compared with the prior art, which requires adjusting the core mold structure and filling twist strips, this application is simple and easy to implement.

[0076] (2) The implementation cost of this application is relatively low. It only requires adding a layer of material with greater rigidity and can be molded in one step with the molding and curing tooling. There is no need to conduct a lot of tests and adjustments. Compared with the existing technical solutions, which require consideration of multiple variables and have higher test cycles and costs, the cost of this application is lower.

[0077] (3) The end gasket in this application is made of a material with high rigidity after curing, which can effectively resist the deformation of the skin caused by pressure difference, thereby improving the overall performance and life of the part. Compared with the existing technical solution which requires consideration of multiple variables, the effect of this application is more stable and reliable.

[0078] In summary, this application has the advantages of simple implementation, low cost, and excellent results. It can not only effectively solve the problem of skin deformation, but also has high practical and economic value.

[0079] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A method for preventing deformation of the end skin of a stringer, characterized in that, The method includes the following steps: S10: Place the stringer (10) in the molding groove (21) on the upper surface of the molding and curing fixture (20); S20: Place the core mold (30); S30: Place the end gasket (40) in the gasket groove (22) on the upper surface of the molding and curing fixture (20), and the gasket groove (22) is vertically connected to the molding groove (21), and the end gasket (40) is fixed above the core mold (30). S40: The skin (50) is laid on the upper surface of the molding and curing fixture (20), and the end of the skin (50) is located on the end gasket (40); S50: Curing.

2. The method for preventing deformation of the end skin of a stringer according to claim 1, characterized in that, The end gasket (40) includes a transverse plate (41) and longitudinal ribs (42). The number of longitudinal ribs (42) is even, and the longitudinal ribs (42) are vertically fixed to the lower surface of the transverse plate (41). The cross-section of the longitudinal ribs (42) is adapted to the cavity shape between the core mold (30) and the forming groove (21).

3. The method for preventing deformation of the end skin of a stringer according to claim 2, characterized in that, The transverse plate (41) includes alternating layers of unidirectional carbon fiber prepreg and twill woven carbon fiber prepreg.

4. A method for preventing deformation of the end skin of a stringer according to claim 2, characterized in that, The thickness of the transverse plate (41) is 1.5mm to 2.5mm.

5. A method for preventing deformation of the end skin of a stringer according to claim 2, characterized in that, The upper surface of the transverse plate (41) is provided with an isolation membrane.

6. A method for preventing deformation of the end skin of a stringer according to claim 2, characterized in that, The transverse plate (41) is filled with resin obtained by soaking prepreg in acetone.

7. A method for forming an end gasket to prevent deformation of the end skin of a stringer, wherein the end gasket is used to be installed on a forming and curing fixture and located below the skin of the stringer's cut-off area, characterized in that, The method includes the following steps: S100: Place the core mold (30) in the molding groove (21) on the upper surface of the molding and curing fixture (20). The upper surface of the molding and curing fixture (20) is provided with a gasket groove (22) that is perpendicularly connected to the molding groove (21), and the two ends of the core mold (30) are located on both sides of the gasket groove (22) on the upper surface of the molding and curing fixture (20). S200: Fill the space between the core mold (30) and the forming groove (21) with a twist strip (60); S300: Place the gasket material into the gasket groove (22); S400: Ballast cover plate above the gasket material; S500: Curing.

8. The method for forming end gaskets to prevent deformation of the end skin of a stringer according to claim 7, characterized in that, In S300, unidirectional carbon fiber prepreg and twill braided carbon fiber prepreg are placed alternately in the gasket groove (22).

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