Method for improving size and appearance precision stability of machined honeycomb sandwich

Abstract

The invention discloses a method for improving size and appearance precision stability of a honeycomb sandwich after machining, and relates to the field of composite material preparation.A closed mold cavity is adopted for carrying out supporting fabric adhesive film curing reinforcement treatment on the honeycomb sandwich, and fixing and protection of the size and the molded surface of the honeycomb sandwich are achieved; and in the transferring, storing and curing forming processes of the honeycomb sandwich, the honeycomb sandwich is used as an integral structure restrained by a cured adhesive film, so that the dimensional stability and the structural integrity of the honeycomb sandwich are guaranteed, and a guarantee is provided for improving the forming quality of the subsequent honeycomb sandwich structure.

Description

Technical Field

[0001] The invention relates to the field of composite material preparation, and in particular to a method for improving the stability of the size and shape accuracy of a honeycomb core after machining. Background Art

[0002] Honeycomb sandwich composite materials are a common structural form of secondary load-bearing structures in aircraft structures. They can greatly improve structural stiffness and have a very significant weight reduction effect, and the honeycomb core is the key to achieving the improvement of sandwich structure rigidity. In order to achieve the change of structural curvature and gradual change of stiffness in the sandwich structure to eliminate the problem of stress concentration, the honeycomb core in the structure is usually processed with stress to obtain the theoretical size and shape of the honeycomb core because the honeycomb core has weak compressive strength in the W direction and is difficult to trim manually. After machining, the honeycomb core will deform and the size will be difficult to maintain in an unconstrained state. In engineering applications, honeycomb cores are usually processed and machined in batches, but the production of actual structures cannot be carried out synchronously due to the production cycle of composite materials. As a result, the honeycomb core is very likely to change in shape and size without protection during storage, transportation, and use of the core after machining, and the edge thickness gradient area will be damaged, which brings great risks to the molding size accuracy and molding quality assurance of the honeycomb sandwich structure, and it is difficult to meet application requirements. Therefore, it is necessary to optimize and improve the preparation method based on the molding quality problems of honeycomb sandwich structures in actual engineering applications, so as to further improve the application reliability of honeycomb sandwich structure composite materials. Summary of the invention

[0003] The purpose of the present invention is to address the problem that the machining of the honeycomb core and the curing and molding of the sandwich structure are not synchronized in the current preparation process of the honeycomb sandwich structure, and that the honeycomb core after machining is prone to size changes and core edge crushing damage during transportation, storage and curing molding of the honeycomb core. By optimizing the molding technical route, a closed mold cavity is used to perform a curing and strengthening treatment of the honeycomb core with a supporting fabric film, thereby achieving the fixation and protection of the size and profile of the honeycomb core. During the transportation, storage and curing molding of the honeycomb core, it exists as an integral structure constrained by a cured film, thereby ensuring the dimensional stability and structural integrity of the honeycomb core, and providing a guarantee for the improvement of the subsequent molding quality of the honeycomb sandwich structure.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for improving the stability of the size and shape accuracy of a honeycomb core after machining, comprising the following steps:

[0006] 1) According to the theoretical profile of the honeycomb sandwich structure after machining, a sandwich reinforcement mold is processed, and the sandwich reinforcement mold is divided into an upper module and a lower module, the lower module contains a cavity matching the profile of the honeycomb sandwich, and the upper module contains a profile matching the other side of the honeycomb sandwich;

[0007] 2) Lay a layer of isolation film or peelable cloth on the surface of the cavity of the lower module;

[0008] 3) Lay a layer of adhesive film with supporting fabric on the surface of the laid isolation film or peelable cloth;

[0009] 4) Positioning and placing the honeycomb core made by machining into the cavity of the lower module and fitting it tightly with the adhesive film;

[0010] 5) Laying a layer of adhesive film with supporting fabric on the upper surface of the honeycomb core;

[0011] 6) Place another layer of isolation film or peelable cloth on the upper surface of the film laid in the previous step;

[0012] 7) Place the upper module on the isolation film or peelable cloth placed in the previous step, align the mold closing position of the upper module and the lower module, and fix the upper module and the lower module with bolts;

[0013] 8) The entire sandwich reinforcement mold is heated by a hot press, and the film is cured according to the selected film curing process;

[0014] 9) After curing, the core reinforcement mold is disassembled and demoulded to obtain the reinforced honeycomb core.

[0015] Preferably, the material of the sandwich reinforcement mold in step 1) is metal, specifically mold steel or aluminum alloy.

[0016] Preferably, the outer shape boundary of the isolation film or the peelable cloth in step 2) is 10-20 mm larger than the size boundary of the adhesive film in step 3).

[0017] Preferably, in steps 2) and 6), wrinkles are evenly eliminated after the isolation film or peelable cloth is placed.

[0018] Preferably, the adhesive film with the supporting fabric in steps 3) and 5) is a medium-temperature curing system or a high-temperature curing system, and the supporting fabric is one of thermoplastic fiber fabric, thin layer glass fiber fabric, and thermoplastic mesh film.

[0019] Preferably, the thickness of the adhesive film in steps 3) and 5) is 0.2-0.5 mm.

[0020] Preferably, in step 3), the size of the adhesive film is 5-10 mm larger than the net size edge of the honeycomb core.

[0021] Preferably, in step 5), the boundary size of the adhesive film is consistent with the size of the honeycomb core.

[0022] Preferably, in step 4), the honeycomb core is accurately positioned and placed in the cavity of the lower module with reference to a laser projector or a scribed line, and is closely fitted to the adhesive film by a pressing roller.

[0023] The advantages of the present invention are as follows:

[0024] 1. The honeycomb core reinforcement treatment measures of the present invention are simple and convenient, and do not change the existing conventional honeycomb sandwich structure molding process method and molding quality control technical approach;

[0025] 2. The processing method of the honeycomb sandwich almost does not increase the weight of the sandwich structure, ensuring the optimized weight distribution state verified by the structural design. At the same time, the surface constraints of the metal rigid mold can meet the size and shape constraints of the complex honeycomb sandwich, ensuring the dimensional accuracy of the processed honeycomb sandwich;

[0026] 3. The honeycomb core reinforced with supporting adhesive film improves the rigidity of the honeycomb core structure, especially the anti-crushing ability of the honeycomb core edge is significantly improved, which can meet the storage and transportation requirements of the industrial application process and ensure the molding quality of the subsequent honeycomb sandwich structure;

[0027] 4. The reinforcement treatment method of the present invention can also be used for the reinforcement treatment of foam sandwich cores, and has a relatively wide range of promotion and application value for the manufacture of sandwich structure composite materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural schematic diagram of the core-reinforced mold in the embodiment.

[0029] Figure 2 Schematic diagram of laying an isolation film or a peelable cloth on the mold surface of the sandwich reinforced lower module in the embodiment.

[0030] Figure 3 It is a schematic diagram of the embodiment in which the supporting fabric adhesive film is laid on the molded surface of the sandwich reinforced lower module.

[0031] Figure 4 It is a schematic diagram of placing the honeycomb core in the lower module cavity in the embodiment.

[0032] Figure 5 Schematic diagram of laying supporting fabric film on the upper surface of the honeycomb core in the embodiment.

[0033] Figure 6 It is a schematic diagram of using an isolation film or a peelable cloth to isolate and protect the adhesive film in the embodiment.

[0034] Figure 7 It is a schematic diagram of the assembly of the upper module of the sandwich reinforcement mold in the embodiment. DETAILED DESCRIPTION

[0035] In order to make the various technical features and advantages or technical effects in the above technical solutions of the present invention more obvious and easy to understand, they are described in detail below with reference to the accompanying drawings.

[0036] This embodiment specifically discloses a method for improving the stability of the size and shape accuracy of a honeycomb core after machining, comprising the following steps:

[0037] Step 1: According to the actual profile of the honeycomb sandwich, a mold for reinforcing the sandwich is designed and processed. The present invention is called a sandwich reinforcing mold, which is divided into a lower module containing a profile groove (i.e., a cavity) matching the profile of the honeycomb sandwich and an upper module matching the profile of the sandwich. The profile of the upper module matches the profile of the honeycomb sandwich, and the cover plate is respectively called the sandwich reinforcing lower module and the sandwich reinforcing upper module, also known as the lower module and the upper module. The mold tooling material is preferably metal, such as mold steel, aluminum alloy, etc. Figure 1 shown.

[0038] Step 2: Lay a layer of isolation film or peelable cloth on the surface of the cavity of the lower module, spread it evenly to eliminate wrinkles, and its outer shape boundary should be 10-20mm larger than the size boundary of the subsequent adhesive film. The isolation film or peelable cloth can prevent the adhesive film from sticking to the lower module, such as Figure 2 shown.

[0039] Step 3: Lay a layer of adhesive film with supporting fabric on the surface of the isolation film or peelable cloth. The size of the film should be 5-10mm larger than the net size edge of the honeycomb core. Figure 3 shown.

[0040] Step 4: Perform mechanical processing according to the theoretical size and shape of the honeycomb sandwich core to obtain a honeycomb sandwich core material with precise surface dimensions; accurately position the honeycomb sandwich core with precise surface dimensions in the cavity of the lower module under the reference of a laser projector or a scribed line to ensure that the placement is accurate, and achieve close contact with the film through a pressure roller, such as Figure 4 shown.

[0041] Step 5: Place another layer of adhesive film with supporting fabric on the upper surface of the honeycomb core. The boundary size of the adhesive film is consistent with the size of the honeycomb core, such as Figure 5 shown.

[0042] Step 6: Place another layer of isolation film or peelable cloth on the upper surface of the film and evenly eliminate wrinkles. The isolation film or peelable cloth can prevent the film from adhering to the upper module. Figure 6 shown.

[0043] Step 7: Place the upper module on top of the isolation film or peelable cloth, and ensure the accurate mold closing position through the position restriction measures of the upper and lower modules, and fix the upper and lower modules with bolts, such as Figure 7 shown.

[0044] Step 8: Heat the entire sandwich reinforcement mold through a hot press, and according to the selected film curing process, keep the film warm at the recommended curing process temperature to complete the curing of the film.

[0045] Step 9: After curing, the core reinforcement mold is disassembled and demoulded to obtain the reinforced honeycomb core, and conventional honeycomb core transportation and storage are performed to prepare and shape the subsequent honeycomb sandwich structure.

[0046] Although the present invention has been disclosed as above by way of embodiments, it is not intended to limit the present invention. Appropriate modifications or equivalent substitutions of the technical solutions of the present invention made by ordinary technicians in the field should all be included in the protection scope of the present invention. The protection scope of the present invention shall be based on what is defined in the claims.

Claims

1. A method for improving the stability of the size and shape accuracy of honeycomb core after machining, characterized in that: The following steps are involved: 1) According to the theoretical profile of the honeycomb sandwich structure after machining, a sandwich reinforcement mold is processed, and the sandwich reinforcement mold is divided into an upper module and a lower module, the lower module contains a cavity matching the profile of the honeycomb sandwich, and the upper module contains a profile matching the other side of the honeycomb sandwich; 2) Lay a layer of isolation film or peelable cloth on the surface of the cavity of the lower module; 3) Lay a layer of adhesive film with supporting fabric on the surface of the laid isolation film or peelable cloth; 4) Positioning and placing the honeycomb core made by machining into the cavity of the lower module and fitting it tightly with the adhesive film; 5) Laying a layer of adhesive film with supporting fabric on the upper surface of the honeycomb core; 6) Place another layer of isolation film or peelable cloth on the upper surface of the film laid in the previous step; 7) Place the upper module on the isolation film or peelable cloth placed in the previous step, align the mold closing position of the upper module and the lower module, and fix the upper module and the lower module with bolts; 8) The entire sandwich reinforcement mold is heated by a hot press, and the film is cured according to the selected film curing process; 9) After curing, the core reinforcement mold is disassembled and demoulded to obtain the reinforced honeycomb core.

2. The method according to claim 1, characterized in that In step 1), the material of the sandwich reinforcement mold is metal, specifically mold steel or aluminum alloy.

3. The method according to claim 1, characterized in that In step 2), the outer shape boundary of the isolation film or the peelable cloth is larger than the size boundary of the adhesive film in step 3) by 10-20 mm.

4. The method according to claim 1 or 3, characterized in that After the isolation film or peelable cloth is placed in steps 2) and 6), wrinkles are evenly eliminated.

5. The method according to claim 1, characterized in that The adhesive film with supporting fabric in steps 3) and 5) is a medium temperature curing system or a high temperature curing system, and the supporting fabric is one of thermoplastic fiber fabric, thin layer glass fiber fabric, and thermoplastic mesh film.

6. The method according to claim 1 or 5, characterized in that The thickness of the film in steps 3) and 5) is 0.2-0.5 mm.

7. The method according to claim 1 or 5, characterized in that In step 3), the size of the adhesive film is 5-10 mm larger than the net size edge of the honeycomb core.

8. The method according to claim 1 or 5, characterized in that In step 5), the boundary size of the adhesive film is consistent with the size of the honeycomb core.

9. The method according to claim 1, characterized in that In step 4), the honeycomb core is accurately positioned and placed in the cavity of the lower module with the reference of a laser projector or a scribed line, and is closely fitted with the adhesive film by a pressing roller.

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