Potting processing method of foam core board

Abstract

The invention relates to an encapsulation processing method of a foam core board, which comprises the following steps of: fully injecting a curing glue solution into an encapsulation hole, so that the curing glue solution is cured into a rigid body in a normal-temperature environment, and ensuring that heat generated by curing is completely released; the foam board is integrally heated, so that the rigid body is heated for secondary curing, and the adhesive film is heated to expand; the heating temperature ranges from 120 DEG C to 190 DEG C, the heat preservation time ranges from 90 min to 120 min, and then natural cooling is conducted. The surface of the expansion adhesive film is a non-smooth surface, fluid pouring sealant can be in full contact with the surface of the expansion adhesive film when being injected and filled, uneven positions of the surface of the expansion adhesive film can be filled, the contact area of a bonding interface with the expansion adhesive film is further increased, the bonding force of the pouring sealant and the expansion adhesive film is improved, and cracking of the bonding interface is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of composite material foam core processing, in particular to a potting processing method for a foam core board. Background Art

[0002] Composite foam sandwich structures have unique advantages such as specific strength, specific modulus, bending resistance, and high stiffness. They have been widely used in the aerospace field. When foam sandwich composite structural parts are assembled in the foam area, due to the low stiffness of the foam material, the support capacity of the composite skin is weak and cannot meet the large load requirements. In order to prevent damage to the foam sandwich structural parts and improve the mechanical properties of the parts, it is necessary to perform hole potting on the fastener assembly area of ​​the foam. Due to the different thermal expansion coefficients of the potting glue and the foam, during the potting curing and subsequent co-curing of the foam and the skin, as the temperature changes, cracking is prone to occur at the interface between the potting glue and the foam glue, affecting the internal quality of the foam sandwich structural parts and the subsequent assembly strength.

[0003] Recent inventions for preventing potting cracking are as follows:

[0004] 1) An internal plate to prevent the potting glue of a potted transformer from cracking (authorization number CN207752846U): This patent designs an internal plate to prevent the potting glue of a potted transformer from cracking. It is used in conjunction with a housing containing a transformer coil. When the potting glue cannot be replaced, the potting glue cracking problem will not occur in the potted product. Placing an internal plate in the potting glue increases the weight of the potting glue, and does not meet the subsequent potting operation that requires the fastener hole assembly in the potting area.

[0005] 2) A capacitor structure that prevents potting glue from cracking (authorization number: CN208834908U): This patent proposes a capacitor structure that prevents potting glue from cracking, including a metal shell, a capacitor core, an insulating edging and a potting glue. The plastic insulating edging is fixed to the periphery of the opening end of the metal shell and is coated on the inner wall of the opening end of the metal shell. The difference in linear expansion coefficient between the plastic insulating edging and the potting glue is small to prevent the metal shell and the potting glue from separating. This patent uses plastic insulating edging to solve the problem of inconsistent expansion coefficients between the metal shell and the potting glue, which causes cracking of the potting glue and the metal shell.

[0006] 3) A method for forming a honeycomb sandwich part with a potting glue (application number: CN115352101A): the potting glue is evenly injected into the core cells of the honeycomb sandwich raw material, and processed into a filling module after curing. A potting hole is opened on the honeycomb according to the shape of the potting area, and the filling module is wrapped with a compensation glue layer and placed in the honeycomb potting hole to realize the manufacture of the honeycomb potting part. After the potting module is formed, the module is cured and processed, and then the compensation glue layer is used for bonding. The manufacturing cost is high, the efficiency is low, and there is a problem of incomplete filling of the compensation glue layer.

[0007] In addition, in the prior art, the expansion film is laid first and then the parts are inserted. Since the gap is originally very small and the film is sticky, it is easy to be squeezed or moved, causing the film to accumulate, fall off or shift, resulting in incomplete bonding.

[0008] Furthermore, during machining, since the material in the potting hole and the foam core board have different hardnesses, using the same milling parameters will also bring about the risk of cracking.

[0009] In summary, the above-mentioned core material potting method can realize the foam potting operation. Adding built-in plates or adding edging materials in the potting glue requires design structure changes, which cannot meet the stiffness requirements of the potting area of ​​the foam sandwich structure. The method of manufacturing the potting block and then bonding the glue layer to the foam is not suitable for foam potting, and there is a situation where the glue film is incompletely filled. The existing foam potting method cannot meet the potting requirements of the assembly area of ​​the foam sandwich structure. Summary of the invention

[0010] The purpose of the present invention is: the present invention proposes a method for preventing foam potting cracking, which effectively solves the problem of different thermal expansion coefficients and hardnesses of foam and potting glue during processing (including potting and machining), resulting in cracking of potting glue and foam during subsequent co-curing of skin and foam and cracking during machining, can improve the bonding quality of foam and potting glue, realize high-quality and efficient foam potting operation, and can be widely applicable to potting operations of foam holes of different sizes.

[0011] The technical solution of the present invention is:

[0012] A method for potting a foam core board is provided, comprising the following steps:

[0013] Step 1: obtaining a foam core board, and making the foam core board have a processing allowance in thickness, and opening a potting hole in the foam core board;

[0014] Step 2, affixing a film on the inner wall of the potting hole, wherein the film is a heat-expandable film;

[0015] Step 3, filling the potting hole with curing glue, so that the curing glue is cured into a rigid body at room temperature, and ensuring that the heat generated by curing is completely released;

[0016] Step 4, heating the foam board as a whole, so that the rigid body is heated for secondary curing, and the adhesive film is heated for expansion; the heating temperature is 120° C. to 190° C., the heat preservation time is 90 to 120 minutes, and then naturally cooled;

[0017] Step 5: Milling the upper and lower surfaces of the foam board to remove the excess so that the solidified rigid body in the potting hole forms an integral plane with the foam board to obtain a potted foam core board.

[0018] Furthermore, the foam core board is made of PMI foam.

[0019] Furthermore, the potting glue is a two-component epoxy resin glue, preferably with a grade of CG1305A / B.

[0020] Furthermore, the expanded adhesive film is a foamed adhesive, and the preferred grades are FM490A, J-297B or J-490B.

[0021] Furthermore, in step 3, the total time for curing and heat dissipation of the potting glue at room temperature is at least 24 hours.

[0022] Furthermore, during the curing process of the potting glue at room temperature, the curing is carried out in a vacuum environment, preferably in a vacuum bag.

[0023] Furthermore, the potting glue heating temperature is preferably 120°C, and the heating time is preferably 90 minutes;

[0024] Furthermore, the foam core board obtained in step 1 is a dried foam core board. Furthermore, the drying process parameters are a drying temperature of at least 180° C. and a drying time of at least 180 minutes.

[0025] Furthermore, the potting holes of the foam board after potting in step 5 are first milled, and then the foam is diffusely milled from the potting holes to the surrounding areas. Preferably, when the potting holes are milled, the milling cutter speed is not less than 6000r / min. Preferably, when the foam core board is diffusely milled from the potting holes, the milling cutter speed is not higher than 4000r / min.

[0026] The invention has the advantages that the method for preventing foam potting cracking is applicable to foam potting operations of different sizes and shapes, and the potting operation is simple, the potting cost is low, the rate is fast, and the cracking problem of foam and potting glue can be solved.

[0027] Compared with the contact between rigid parts and the film in the prior art, the surface of the expanded film in the present invention is a non-smooth surface. When the fluid potting glue is injected for filling, it will fully contact the surface of the expanded film and fill the uneven positions on its surface, further increasing the contact area of ​​the bonding interface with the expanded film, improving the bonding strength between the potting glue and the expanded film, and helping to reduce cracking of the bonding interface.

[0028] The glue injection of the present invention will not cause damage or destruction to the laid glue film, and the integrity is good.

[0029] In this method, processing is performed in two ways, and the motion trajectory of the tool head is planned to prevent processing cracks. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of foam potting;

[0031] Among them: 1-support tooling, 2-tape, 3-foam, 4-film, 5-potting glue. DETAILED DESCRIPTION

[0032] The disclosed examples will be more fully described with reference to the accompanying drawings, in which some (but not all) of the disclosed examples are shown. In fact, many different examples may be described and these examples should not be construed as limited to the examples set forth herein. Instead, these examples are described so that this disclosure will be thorough and complete and will fully convey the scope of the disclosure to those skilled in the art.

[0033] A method for potting a foam core board is provided, comprising the following steps:

[0034] Step 1: obtaining a foam core board, and making the foam core board have a processing allowance in thickness, and opening a potting hole in the foam core board;

[0035] Step 2, affixing a film on the inner wall of the potting hole, wherein the film is a heat-expandable film;

[0036] Step 3, filling the potting hole with curing glue, so that the curing glue is cured into a rigid body at room temperature, and ensuring that the heat generated by curing is completely released;

[0037] Step 4, heating the foam board as a whole, so that the rigid body is heated for secondary curing, and the adhesive film is heated for expansion; the heating temperature is 120° C. to 190° C., the heat preservation time is 90 to 120 minutes, and then naturally cooled;

[0038] Step 5: Milling the upper and lower surfaces of the foam board to remove the excess so that the solidified rigid body in the potting hole forms an integral plane with the foam board to obtain a potted foam core board.

[0039] The foam core board is made of PMI foam.

[0040] The potting glue is a two-component epoxy resin glue, and the brand is CG1305A / B.

[0041] The expansion film is foamed rubber, and the brand is FM490A.

[0042] In step 3, the total time for the potting glue to cure at room temperature and dissipate heat is at least 24 hours.

[0043] During the curing process of potting glue at room temperature, it is cured in a vacuum environment and vacuum bagged.

[0044] The heating temperature of the potting glue is 120℃ and the heating time is 90 minutes;

[0045] The foam core board obtained in step 1 is a dried foam core board. The drying process parameters are a drying temperature of at least 180° C. and a drying time of at least 180 minutes.

[0046] The potting holes of the foam board after potting in step 5 are first milled, and then the foam is diffused from the potting holes to the surrounding areas by milling. When the potting holes are milled, the milling cutter speed is not less than 6000r / min. When the foam core board is diffused from the potting holes by milling, the milling cutter speed is not higher than 4000r / min.

[0047] The description of different advantageous arrangements has been presented for purposes of illustration and description, but the description is not intended to be exclusive or limited to examples of the disclosed form. Many modifications and variations will be apparent to those of ordinary skill in the art. Additionally, different advantageous examples may describe different advantages over other advantageous examples. The selected example or examples are chosen and described in order to best illustrate the principles of the examples, the practical application, and to enable those of ordinary skill in the art to understand the disclosure with various examples with various modifications suitable for the particular use contemplated.

Claims

1. A method for potting a foam core board, characterized in that: The steps include: Step 1: obtaining a foam core board, and making the foam core board have a processing allowance in thickness, and opening a potting hole in the foam core board; Step 2, affixing a film on the inner wall of the potting hole, wherein the film is a heat-expandable film; Step 3, filling the potting hole with curing glue, so that the curing glue is cured into a rigid body at room temperature, and ensuring that the heat generated by curing is completely released; Step 4, heating the foam board as a whole, so that the rigid body is heated for secondary curing, and the adhesive film is heated for expansion; the heating temperature is 120° C. to 190° C., the heat preservation time is 90 to 120 minutes, and then naturally cooled; Step 5: Milling the upper and lower surfaces of the foam board to remove the excess so that the solidified rigid body in the potting hole forms an integral plane with the foam board to obtain a potted foam core board.

2. A method for potting a foam core board according to claim 1, characterized in that: The foam core board is made of PMI foam.

3. A method for potting a foam core board according to claim 1, characterized in that: The potting glue is a two-component epoxy resin glue, preferably with a grade of CG1305A / B.

4. A method for potting a foam core board according to claim 1, characterized in that: The expanded film is foamed plastic, and the preferred grades are FM490A, J-297B or J-490B.

5. A method for potting a foam core board according to claim 1, characterized in that: In step 3, the total time for the potting glue to cure at room temperature and dissipate heat is at least 24 hours.

6. A method for potting a foam core board as claimed in claim 1, characterized in that: During the curing process of the potting glue at room temperature, the curing is carried out in a vacuum environment, preferably in a vacuum bag.

7. A method for potting a foam core board as claimed in claim 1, characterized in that: The potting glue heating temperature is preferably 120° C., and the heating time is preferably 90 minutes.

8. The method for potting a foam core board according to claim 1, characterized in that: The foam core board obtained in step 1 is a dried foam core board. Furthermore, the drying process parameters are a drying temperature of at least 180° C. and a drying time of at least 180 minutes.

9. A method for potting a foam core board as claimed in claim 1, characterized in that: After potting in step 5, the potting holes of the foam board are first milled, and then the foam is spread from the potting holes to the surrounding areas by milling.

10. The method for potting a foam core board according to claim 1, characterized in that: When milling the potting holes, the milling cutter speed shall not be less than 6000r / min; when milling the foam core board from the potting holes, the milling cutter speed shall not be higher than 4000r / min.

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