A honeycomb sandwich structure splicing method based on stiffness matching control and a composite material component

Abstract

The application discloses a honeycomb sandwich structure splicing method based on stiffness matching control and a composite material component, and belongs to the technical field of composite material manufacturing. The splicing method comprises the following steps: firstly, full-thickness splicing and curing of the honeycomb core material is carried out by using a first adhesive, a groove is processed at the top of the splicing joint, a second adhesive with higher hardness is filled and partially pre-cured to form a rigid support layer, the adhesive film and the prepreg panel are laid and pasted after polishing, and the composite material component is obtained through autoclave co-curing forming treatment. By constructing the gradient structure of the low-density connecting layer and the rigid support layer, the pre-cured rigid layer is used as an in-situ mold to resist the forming pressure, the surface collapse and the fax imprint defect of the traditional foam glue splicing are solved, the defect of the large weight increase caused by full-thickness filling is avoided, the whole process is stable and does not need post-repair, and the surface quality and the manufacturing efficiency of the large composite material component are significantly improved.

Description

Technical Field

[0001] This application belongs to the field of composite material manufacturing technology, specifically, it relates to a method for splicing honeycomb sandwich structures based on stiffness matching control and composite material components. Background Technology

[0002] Honeycomb sandwich composite materials possess high specific strength, high specific stiffness, and excellent vibration damping and sound insulation properties, and have been widely used in the aerospace field for primary and secondary load-bearing structures such as fuselage panels, fairings, and doors. In the manufacturing of large components, the honeycomb core material is limited by the width and variable thickness design, necessitating splicing.

[0003] Current honeycomb core material splicing processes have significant technical defects. For example, when using expanded foam for splicing, its low stiffness and high coefficient of thermal expansion after curing make it unable to effectively support the skin under the high temperature and pressure of an autoclave. This easily leads to surface collapse, raised marks, and "convex in the middle and concave on both sides" appearance defects in the splicing area, seriously affecting the aerodynamic shape and surface quality of the component. Furthermore, while using high-density foam or potting materials for full-thickness filling can improve support performance, it also significantly increases the weight of the structure, violating the lightweight design principles of aerospace composite materials. In addition, post-molding repairs require sanding and filling with putty, which not only increases the number of processes and costs but also reduces structural reliability and production efficiency.

[0004] Therefore, there is an urgent need for a honeycomb sandwich structure splicing technology that can simultaneously solve surface defects, control weight increase, and eliminate the need for subsequent repairs. Summary of the Invention

[0005] The purpose of this application is to provide a honeycomb sandwich structure splicing method and composite material components based on stiffness matching control. By slotting the upper part of the foam splicing layer and filling it with high-hardness colloid, a rigid support layer is formed after pre-curing. This solves the surface collapse and fax imprint defects of traditional foam splicing, and avoids the defects of significant weight increase from full-thickness potting. The entire process is stable and requires no post-repair, which significantly improves the surface quality and manufacturing efficiency of large composite material components.

[0006] To achieve the above objectives, this application provides a method for splicing a honeycomb sandwich structure based on stiffness matching control, comprising the following steps: splicing two honeycomb core materials to be spliced ​​together with a first adhesive at full thickness and completing curing to form a honeycomb core splice; processing a groove along the splicing direction in the first adhesive area at the top of the splice seam; filling the groove with a second adhesive and performing local heating pre-curing treatment to form a rigid support layer, and grinding it until it is flush with the upper surface of the honeycomb core material; wherein, the curing hardness of the second adhesive is higher than that of the first adhesive; applying an adhesive film and a prepreg panel to the surface of the honeycomb core splice and the rigid support layer, and then co-curing and molding the material in an autoclave under heat and pressure to obtain a spliced ​​composite material component.

[0007] Furthermore, the first adhesive is epoxy resin foam or phenolic resin foam, which forms a low-density bonding layer after curing.

[0008] Furthermore, the curing temperature of the first adhesive is 110℃~130℃, and the curing time is 30min~90min.

[0009] Furthermore, the second adhesive includes at least one of a high-hardness liquid film, a room-temperature curing potting compound, and a modified epoxy resin liquid. The Shore hardness (Shore D) of the cured second adhesive is greater than 70, forming a rigid support layer.

[0010] Furthermore, the depth of the groove is 5% to 15% of the total height of the honeycomb core material, and the width of the groove is 3mm to 5mm.

[0011] Furthermore, the difference between the filling height of the second adhesive and the height of the upper surface of the honeycomb core material is 0mm~0.2mm, and after pre-curing treatment, it is sanded until completely flush.

[0012] Furthermore, the pre-curing temperature of the second adhesive is 120℃~150℃, and the pre-curing time is 20min~40min.

[0013] Furthermore, the co-curing molding process involves a pressure of 0.2 MPa to 0.4 MPa, a temperature of 120°C to 180°C, and a holding time of 1 hour to 3 hours.

[0014] Furthermore, the honeycomb core material is aluminum honeycomb core material or aramid paper honeycomb core material, and the core material height is 10mm~25mm.

[0015] This application also provides a composite material component, which is prepared by a honeycomb sandwich structure splicing method based on stiffness matching control. The composite material component is obtained by splicing honeycomb core materials. A gradient stiffness composite structure is provided in the splicing seam area of ​​adjacent honeycomb core materials. The gradient stiffness composite structure includes, from top to bottom, a rigid support layer and a low-density connecting layer. The rigid support layer is composed of a cured second adhesive, and the low-density connecting layer is composed of a cured first adhesive.

[0016] Furthermore, the surface of the composite component is covered with an adhesive film and a prepreg panel, which are then co-cured to form a skin.

[0017] Furthermore, the weight gain per meter of the splicing seam area shall not exceed 35g, the maximum height deviation of the surface flatness shall not exceed 0.05mm, and there shall be no defects such as collapse, protrusion, or marks on the appearance.

[0018] In summary, this application has the following beneficial effects: (1) The present application provides a honeycomb sandwich structure splicing method based on stiffness matching control. A pre-cured high-hardness rigid support layer is pre-placed on the surface of the splicing seam, which can effectively overcome the "concave in the middle and concave on both sides" defects caused by traditional foam splicing. The rigid support layer can play the role of an in-situ mold, significantly improving the surface flatness and appearance qualification rate of the parts.

[0019] (2) The splicing method of this application adopts a composite structure of low-density soft bottom layer and high-rigidity hard surface layer in the splicing seam area. Under the premise of ensuring the surface rigidity of the splicing area, high-hardness adhesive is used only in the shallow depth of the surface layer. The main connection still uses lightweight foam adhesive, which significantly reduces the weight increase compared with the full-thickness high-density potting solution and fully retains the lightweight advantage of honeycomb sandwich structure.

[0020] (3) The splicing method of this application has formed a stable and flat rigid support surface before the skin is laid, which can avoid uncontrollable deformation caused by the difference in the fluidity of the adhesive layer during the co-curing process, and eliminate the need for post-demolding repair processes such as sanding and applying putty, which significantly improves the stability of the process and manufacturing efficiency, and reduces the production and manufacturing cost.

[0021] (4) Composite material components prepared by the splicing method of this application have higher local compressive strength and load transfer efficiency in the splicing area, which can effectively reduce the risk of stress concentration at the splicing point of the skin, and have stronger structural reliability. They can meet the manufacturing and use requirements of components with high aerodynamic shape requirements such as aircraft wings, tail wings, and fuselage panels. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a cross-sectional view of the composite material component proposed in this application.

[0024] Figure 2 It is an optical photograph of the filling film on the foam after the honeycomb splicing.

[0025] Explanation of reference numerals in the attached drawings: 1-skin; 2-rigid support layer; 3-honeycomb core material; 4-low-density bonding layer. Detailed Implementation

[0026] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0027] Currently, the splicing of honeycomb core material 3 mostly adopts foam bonding technology. This technology utilizes the expansion of foam to fill the splicing gaps to achieve the connection of the core materials, and has the advantages of mature technology and light weight. However, when co-curing with the skin 1, because the compressive modulus of the foam after curing is much lower than that of the honeycomb core material 3 after curing, there will be a significant stiffness mismatch between the splicing area and the honeycomb body. Under the high temperature and pressure of the autoclave, it cannot effectively support the skin 1, which can easily cause local collapse in the splicing area. At the same time, the foam has a large coefficient of thermal expansion, and after curing and cooling, the surface of the part is prone to wavy marks with a bulge in the middle and a depression on both sides, which seriously affects the aerodynamic shape and surface quality of the component. In order to improve the support performance of the splicing area, high-density filler material can be used to fill the splicing seam with full thickness. This method can improve the surface flatness to a certain extent and avoid collapse and mark defects, but it will also significantly increase the overall weight of the component, which violates the lightweight design requirements of aerospace structures.

[0028] Currently, the common method for repairing the aforementioned surface defects is manual sanding and puttying after curing. However, this method not only increases production processes and manufacturing costs, but also poses a risk of detachment due to performance mismatch between the repair material and the component itself, thus reducing the reliability of the honeycomb core material component. Based on this, this application proposes a honeycomb sandwich structure splicing method and composite material component based on stiffness matching control. The method involves initial splicing with foam adhesive across the entire thickness, followed by slotting and filling the top of the splicing area with high-hardness adhesive and pre-curing. This forms a composite structure with a low-density soft underlayer and a high-rigidity hard surface layer, thus solving the problem of surface collapse / protrusion defects in traditional foam adhesive splicing. It also avoids the significant weight increase caused by full-thickness potting, achieving both lightweight and high surface quality. Furthermore, it eliminates the need for any post-repair work and can be used in the manufacture of high-precision aerodynamic components such as aircraft panels.

[0029] Specifically, in the first aspect, this application provides a method for splicing honeycomb sandwich structures based on stiffness matching control, including the following steps: S1. The two honeycomb core materials 3 to be spliced ​​are spliced ​​together with the first adhesive to achieve full thickness splicing and curing, forming a honeycomb core splice.

[0030] In the above scheme, the first adhesive is used to splice the two honeycomb core materials 3 to be spliced ​​together with full thickness and fully cure them. The foamed lightweight adhesive achieves complete filling and reliable connection of the sidewalls of the honeycomb core material 3. While ensuring splicing strength, it retains the inherent lightweight characteristics of the honeycomb sandwich structure to the maximum extent, providing a stable and flat bottom foundation for the subsequent construction of the surface rigid support layer 2, and avoiding the overall structural instability caused by poor splicing or incomplete curing.

[0031] In a specific embodiment, the honeycomb core material 3 is an aluminum honeycomb core material or an aramid paper honeycomb core material, and the core material height is 10mm~25mm. The honeycomb core material 3 of this application can be flexibly selected according to the component load-bearing requirements, the usage environment, and the lightweight index.

[0032] In a specific embodiment, the first adhesive is epoxy resin foam or phenolic resin foam, which, after curing, forms a low-density bonding layer 4. The curing temperature of the first adhesive is 110℃~130℃, and the curing time is 30min~90min. In this application, to ensure that the formed low-density bonding layer 4 meets both the structural bonding strength requirements and minimizes weight, the first adhesive must meet the following performance requirements: the density after curing is within the range of 0.1g / cm³. 3 ~0.5g / cm 3 Furthermore, the room temperature shear strength is ≥1.5MPa. This application selects epoxy resin foam or phenolic resin foam as the first adhesive. After curing, this type of foam can form a low-density bonding layer 4, achieving reliable bonding of the honeycomb core material 3 while minimizing the weight of the splicing area, fully meeting the lightweight design requirements of aerospace composite materials. Controlling the curing temperature of the first adhesive at 110℃~130℃ and the curing time at 30min~90min ensures the foam is fully cured and stably foamed, guaranteeing a dense and uniform low-density bonding layer 4 with stable mechanical properties. This avoids incomplete curing and insufficient bonding strength due to excessively low temperature or time, and also prevents aging of the adhesive layer or damage to the core material due to excessively high temperature or time, providing a stable and reliable underlying foundation for subsequent grooving, filling of rigid layers, and co-curing molding.

[0033] S2. A groove is machined along the splicing direction in the first adhesive area at the top of the splice seam.

[0034] In a specific embodiment, the depth of the groove is 5% to 15% of the total height of the honeycomb core material 3, and the width of the groove is 3mm to 5mm.

[0035] S3. Fill the groove with a second adhesive and perform local heating pre-curing treatment to form a rigid support layer 2, and grind it until it is flush with the upper surface of the honeycomb core material 3; wherein, the curing hardness of the second adhesive is higher than that of the first adhesive.

[0036] The filling and pre-curing treatment in step S3 of this application can construct a stable, high-strength rigid support structure on the surface of the splice joint, creating a stiffness gradient distribution in the splicing area that is softer at the bottom and harder at the top. The pre-curing treatment allows the second adhesive to form a high-hardness solid in advance, acting as an in-situ mold during subsequent co-curing, effectively withstanding autoclave pressure and suppressing the thermal expansion and deformation of the underlying foam, thus fundamentally preventing skin collapse and surface defects. Simultaneously, using high-hardness adhesive only within the surface grooves minimizes weight gain, balancing support stiffness with structural lightweighting.

[0037] In a specific embodiment, the second adhesive includes at least one of a high-hardness liquid film, a room-temperature curing potting compound, and a modified epoxy resin liquid. The high-hardness liquid film is a modified epoxy high-hardness film, a bismaleimide film, or a cyanate ester film; the room-temperature curing potting compound is a high-hardness epoxy potting compound or a high-hardness polyurethane potting compound; and the modified epoxy resin liquid is a rubber-toughened epoxy liquid, a thermoplastic resin-toughened epoxy liquid, or an inorganic nanoparticle-filled modified epoxy liquid. The second adhesive, after curing, has a Shore hardness greater than 70, forming a rigid support layer 2. This application selects a second adhesive with a Shore hardness D > 70. Its high hardness allows the rigid support layer 2 to effectively resist molding pressure under the high temperature and high pressure environment of an autoclave, preventing the lower foam layer from deforming under pressure and causing the skin 1 to collapse. Simultaneously, it can suppress surface protrusions caused by the thermal expansion of the foam, ensuring a smooth component surface.

[0038] In a specific embodiment, the difference between the filling height of the second adhesive and the height of the upper surface of the honeycomb core material 3 is 0mm to 0.2mm, and after pre-curing, it is sanded until completely flush. This application reserves a certain height of the second adhesive, which can ensure that the groove is fully filled without voids or material shortages, and also reserve a reasonable sanding allowance to avoid discontinuity of the rigid support layer 2 due to insufficient filling or excessive subsequent sanding due to excessive filling.

[0039] In a specific embodiment, the pre-curing temperature of the second adhesive is 120℃~150℃, and the pre-curing time is 20min~40min. Pre-curing in this application allows the high-hardness adhesive to fully complete the pre-curing reaction, forming a solid support layer with sufficient strength and rigidity. This ensures that it does not flow or deform during subsequent co-curing, can stably withstand the pressure of the autoclave, and will not cause the adhesive layer to become too brittle or develop internal defects due to excessively high temperatures or prolonged curing times.

[0040] S4. An adhesive film and a prepreg panel are laid on the surface of the honeycomb core splice and the rigid support layer 2. After being heated and pressurized in a hot autoclave, the spliced ​​composite material component is obtained.

[0041] Step S4 of this application employs an autoclave co-curing molding process, which enables the skin 1 (prepreg panel), adhesive film, rigid support layer 2, and honeycomb core material 3 to form a complete integrated structure within the same curing cycle, ensuring interlayer bonding strength and structural integrity. In this process, the rigid support layer 2 acts as an in-situ rigid mold, effectively resisting molding pressure, inhibiting deformation of the underlying foam, eliminating surface collapse and fingerprints at the joints, and obtaining a high-flatness, high-appearance-quality composite material component in a single molding process. This eliminates subsequent repair procedures, significantly improving manufacturing efficiency and product qualification rate.

[0042] In a specific embodiment, the co-curing molding process involves a pressure of 0.2 MPa to 0.4 MPa, a temperature of 120°C to 180°C, and a holding time of 1 hour to 3 hours. The co-curing molding process parameters in this application are mainly adjusted based on the curing requirements of the prepreg system. It is necessary to ensure that the resin can flow, wet, and cross-link to cure fully, thereby ensuring the density and mechanical properties of the skin 1.

[0043] In summary, based on the principle of stiffness matching, this application constructs a high-hardness rigid support layer 2 above the soft foam bonding layer by employing a groove-fill-pre-curing process on the surface of the honeycomb splice seam, forming a stiffness gradient composite structure and achieving precise control over the molding quality. The pre-cured rigid support layer 2 plays a core role in the co-curing process: firstly, as a mechanical barrier layer, it can directly withstand the molding pressure of the autoclave and vacuum bag, preventing the low-density foam below from deforming under pressure and preventing the skin 1 from collapsing; secondly, as a thermal expansion shielding layer, it can suppress the thermal expansion of the foam due to its high hardness and low flowability, eliminating surface "push-out" defects; thirdly, as an in-situ molding tooling, it can provide a continuous and flat laying reference surface, ensuring the dimensional accuracy and surface consistency of the skin 1. This application combines lightweight connection with high-rigidity support through the above mechanism, fundamentally solving the surface quality problem of honeycomb splicing co-curing molding without significantly increasing weight, and ultimately producing composite material components that combine lightweight and appearance precision.

[0044] This application also provides a composite material component, which is prepared using a honeycomb sandwich structure splicing method based on stiffness matching control. The composite material component is obtained by splicing honeycomb core material 3, such as... Figure 1As shown, a gradient stiffness composite structure is provided in the splicing area of ​​adjacent honeycomb core materials 3. The gradient stiffness composite structure includes, from top to bottom, a rigid support layer 2 and a low-density connecting layer 4. The rigid support layer 2 is composed of a cured second adhesive, and the low-density connecting layer 4 is composed of a cured first adhesive. An adhesive film and a prepreg panel are sequentially laid on the surface of the composite material component. After co-curing, the prepreg panel forms the skin 1 structure. In this application, the low-density connecting layer 4 is used to connect the sidewalls of adjacent honeycomb core materials 3. The rigid support layer 2 is disposed above the low-density connecting layer 4, and its upper surface is flush with the upper surface of the honeycomb core material 3, serving to support the skin 1 on the surface.

[0045] The technical solutions described above in this application will be explained in detail below with reference to specific embodiments.

[0046] Example 1 This embodiment employs a honeycomb sandwich structure splicing method based on stiffness matching control to prepare composite material components, including the following steps: (1) Preliminary splicing Select aluminum honeycomb core material with a height of 20mm and align the edges of two pieces to be spliced. Use a first adhesive to fill and splice the core material; the first adhesive is epoxy resin foam (SY-P9 from Beijing Institute of Aeronautical Materials, China Aero Engine Corporation, with a foaming ratio of 2.0). Then, place the core material in an oven and cure it at 120℃ for 60 minutes to form a honeycomb core splice.

[0047] (2) Grooving Sand down any excess expanding foam that has cured at the joint until it is flush with the surface of the honeycomb core material 3. Then, using a grooving tool, create a groove along the joint direction on the first adhesive layer formed by the curing of the first adhesive at the top of the joint. The groove should be 2mm deep (10% of the honeycomb height) and 4mm wide.

[0048] (3) Fill A second adhesive was filled into the groove. The second adhesive was a high-hardness epoxy resin potting compound (HT-6128 produced by Hubei Huitian New Materials Co., Ltd.), which has a Shore hardness D of 85 after curing. The filling height was slightly higher than the honeycomb surface by 0.1mm. The image after filling is shown below. Figure 2 As shown.

[0049] (4) Rigid support layer 2 pre-curing The second adhesive is heated using a local heating device and cured at 120°C for 30 minutes to form a high-hardness rigid support layer 2. After cooling, the surface is polished smooth to make it completely flush with the upper surface of the honeycomb core material 3.

[0050] (5) Co-curing molding An epoxy resin film (Heishi Chemical J-154) and carbon fiber prepreg (Hengshen EM103 / HF10A / 34, 8 layers of prepreg) were sequentially laid on the surfaces of the honeycomb core material 3 and the rigid support layer 2. The mixture was then placed in an autoclave and cured for 2 hours at 0.3 MPa pressure and 130°C to obtain the composite material component. Unless otherwise specified in the following examples, the parts are consistent with those in Example 1, such as the selection of materials.

[0051] Example 2 This embodiment employs a honeycomb sandwich structure splicing method based on stiffness matching control to prepare composite material components, including the following steps: (1) Preliminary splicing Select a honeycomb core material 3 with a height of 20mm and align the edges of the two core materials to be spliced. Use the first adhesive to fill and splice the core material; the first adhesive is epoxy resin foam (expansion ratio 2.0). Then place it in an oven and cure at 120℃ for 60 minutes to form a honeycomb core material splice.

[0052] (2) Grooving Sand down any excess expanding foam that has cured at the joint until it is flush with the surface of the honeycomb core material 3. Then, use a grooving tool to create a groove on the first adhesive layer at the top of the joint. The groove should be 1 mm deep (5% of the honeycomb height) and 4 mm wide.

[0053] (3) Fill A second adhesive is filled into the groove. The second adhesive is a high-hardness liquid adhesive film (Black Petrochemical J-96), which has a Shore hardness D of 80 after curing. The filling height is slightly higher than the honeycomb surface by 0.1mm.

[0054] (4) Rigid support layer 2 pre-curing The second adhesive is heated using a local heating device and cured at 120°C for 30 minutes to form a high-hardness rigid support layer 2. After cooling, the surface is polished smooth to make it completely flush with the upper surface of the honeycomb core material 3.

[0055] (5) Co-curing molding An epoxy resin film and a carbon fiber prepreg panel (8 layers) are sequentially laid on the surface of the honeycomb core material 3 and the rigid support layer 2. The mixture is placed in an autoclave and cured for 2 hours at a pressure of 0.3 MPa and a temperature of 130°C to obtain a composite material component.

[0056] Example 3 This embodiment employs a honeycomb sandwich structure splicing method based on stiffness matching control to prepare composite material components, including the following steps: (1) Preliminary splicing Select a honeycomb core material 3 with a height of 20mm and align the edges of the two core materials to be spliced. Use the first adhesive to fill and splice the core material; the first adhesive is epoxy resin foam (expansion ratio 2.0). Then place it in an oven and cure at 120℃ for 60 minutes to form a honeycomb core material splice.

[0057] (2) Grooving Sand down any excess expanding foam that has cured at the joint until it is flush with the surface of the honeycomb core material 3. Then, use a grooving tool to create a groove along the joint direction on the first adhesive layer at the top of the joint. The groove should be 3mm deep (15% of the honeycomb height) and 4mm wide.

[0058] (3) Fill A second adhesive is filled into the groove. The second adhesive is a modified epoxy resin structural adhesive (Heishi Chemical HY-JG120), which has a Shore hardness D of 90 after curing, and the filling height is slightly higher than the honeycomb surface by 0.1 mm.

[0059] (4) Rigid support layer 2 pre-curing The second adhesive is heated using a local heating device and cured at 120°C for 30 minutes to form a high-hardness rigid support layer 2. After cooling, the surface is polished smooth to make it completely flush with the upper surface of the honeycomb core material 3.

[0060] (5) Co-curing molding An epoxy resin film and a carbon fiber prepreg panel (8 layers) are sequentially laid on the surface of the honeycomb core material 3 and the rigid support layer 2. The mixture is placed in an autoclave and cured for 2 hours at a pressure of 0.3 MPa and a temperature of 130°C to obtain a composite material component.

[0061] Example 4 This embodiment employs a honeycomb sandwich structure splicing method based on stiffness matching control to prepare composite material components, including the following steps: (1) Preliminary splicing Select aramid paper honeycomb core material with a height of 10mm, and align the edges of two core materials to be spliced. Use a first adhesive, which is phenolic resin foam, to fill and splice the core. Then place it in an oven and cure at 120℃ for 60 minutes to form a honeycomb core splice.

[0062] (2) Grooving Sand down any excess expanding foam that has cured at the joint until it is flush with the surface of the honeycomb core material 3. Then, use a grooving tool to create a groove along the joint direction on the first adhesive layer at the top of the joint. The groove should be 1mm deep (10% of the honeycomb height) and 3mm wide.

[0063] (3) Fill A second adhesive is filled into the groove. The second adhesive is a high-hardness bismaleimide resin adhesive (Black Petrochemical J-188), which has a Shore hardness D of 88 after curing. The filling height is slightly higher than the honeycomb surface by 0.1mm.

[0064] (4) Rigid support layer 2 pre-curing The second adhesive is heated using a local heating device and cured at 150°C for 30 minutes to form a high-hardness rigid support layer 2. After cooling, the surface is polished smooth to make it completely flush with the upper surface of the honeycomb core material 3.

[0065] (5) Co-curing molding Bismale resin film and carbon fiber prepreg panel (8 layers) are sequentially laid on the surface of honeycomb core material 3 and rigid support layer 2, and placed in a hot autoclave. They are cured for 3 hours at 0.3MPa pressure and 180℃ to obtain composite material component.

[0066] Example 5 This embodiment employs a honeycomb sandwich structure splicing method based on stiffness matching control to prepare composite material components, including the following steps: (1) Preliminary splicing Select a honeycomb core material 3 with a height of 25mm and align the edges of the two core materials to be spliced. Use the first adhesive to fill and splice the core material; the first adhesive is epoxy resin foam (expansion ratio 2.0). Then place it in an oven and cure at 120℃ for 60 minutes to form a honeycomb core material splice.

[0067] (2) Grooving Sand down any excess expanding foam that has cured at the joint until it is flush with the surface of the honeycomb core material 3. Then, use a grooving tool to create a groove along the joint direction on the first adhesive layer at the top of the joint. The groove should be 1.5 mm deep (6% of the honeycomb height) and 5 mm wide.

[0068] (3) Fill A second adhesive is filled into the groove. The second adhesive is a reinforced epoxy adhesive (Zhonghang Composite Materials J80N) with added nano alumina filler. After curing, its Shore hardness D is 82, and the filling height is slightly higher than the honeycomb surface by 0.1mm.

[0069] (4) Rigid support layer 2 pre-curing The second adhesive is heated using a local heating device and cured at 120°C for 30 minutes to form a high-hardness rigid support layer 2. After cooling, the surface is polished smooth to make it completely flush with the upper surface of the honeycomb core material 3.

[0070] (5) Co-curing molding An epoxy resin film and a carbon fiber prepreg panel (8 layers) are sequentially laid on the surface of the honeycomb core material 3 and the rigid support layer 2. The mixture is placed in an autoclave and cured for 2 hours at a pressure of 0.3 MPa and a temperature of 130°C to obtain a composite material component.

[0071] Comparative Example 1 This comparative example provides a method for splicing with expanding foam, including the following steps: (1) Select a honeycomb core material 3 with a height of 20mm and align the edges of the two core materials to be spliced; (2) Use the first adhesive to fill and splice. The first adhesive is epoxy resin foam (expansion ratio 2.0). Fill the splice gap with the full thickness and put it in the oven to cure at 120°C for 60 minutes. (3) Sand the excess expanding foam on the surface until it is flush with the honeycomb surface; (4) Epoxy resin film and carbon fiber prepreg panel (8 layers) are directly laid on the surface of the honeycomb core material 3, placed in a hot autoclave, and cured for 2 hours at 0.3MPa pressure and 130℃ temperature to obtain composite material component.

[0072] Comparative Example 2 This comparative example provides a method for splicing full-thickness potting compound, including the following steps: (1) Select a honeycomb core material 3 with a height of 20mm and align the edges of the two core materials to be spliced; (2) Use a second adhesive to fill the splicing. The second adhesive is a high-hardness epoxy resin potting compound (Shore hardness D is 85). Fill the splicing gap with the full thickness and put it in an oven to cure at 120°C for 60 minutes. (3) Grind the excess potting compound on the surface until it is flush with the honeycomb surface; (4) Epoxy resin film and carbon fiber prepreg panel (8 layers) are directly laid on the surface of the honeycomb core material 3, placed in a hot autoclave, and cured for 2 hours at 0.3MPa pressure and 130℃ temperature to obtain composite material component.

[0073] Comparative Example 3 This comparative example provides a method for splicing two layers without pre-curing, including the following steps: (1) Select a honeycomb core material 3 with a height of 20mm and align the edges of the two core materials to be spliced. Use the first adhesive (epoxy resin foam, foaming ratio 2.0) to fill and splice, and place it in an oven to cure at 120℃ for 60 minutes; (2) Smooth out the excess foam at the joint and process a groove with a depth of 2mm and a width of 4mm at the top of the joint. (3) Fill the groove with a second adhesive, which is a high-hardness epoxy resin potting compound. No pre-curing treatment is performed after filling. (4) Epoxy resin film and carbon fiber prepreg panel (8 layers) are laid on the surface of honeycomb core material 3 and uncured second adhesive, and placed in a hot autoclave. They are cured for 2 hours at 0.3 MPa pressure and 130°C to obtain composite material component.

[0074] Comparative Example 4 This comparative example provides a method for splicing low-hardness surface layers, including the following steps: (1) Select a honeycomb core material 3 with a height of 20mm, align the edges of the two core materials to be spliced; use the first adhesive (epoxy resin foam, foaming ratio 2.0) to fill and splice, and put it in an oven to cure at 120℃ for 60 minutes; (2) Smooth out the excess foam at the joint and process a groove with a depth of 2mm and a width of 4mm at the top of the joint. (3) Fill the groove with low-hardness sealant (XM16 from Beijing Institute of Aeronautical Materials, China Aero Engine Corporation), whose Shore hardness D is only 35 after curing. (4) Use a heating device to pre-cure the filled sealant. The process parameters are: heating temperature 80℃, curing time 60min, and sanding smooth after cooling. (5) Epoxy resin film and carbon fiber prepreg panel (8 layers) are laid on the surface of honeycomb core material 3 and cured sealant, and placed in a hot autoclave. They are cured for 2 hours at 0.3MPa pressure and 130℃ to obtain composite material component.

[0075] Comparative Example 5 This comparative example provides a method for post-assembly repair, including the following steps: (1) Select a honeycomb core material 3 with a height of 20mm and use epoxy resin foam (expansion ratio 2.0) to splice the entire thickness; then put it in an oven and cure it at 120℃ for 60 minutes to form a honeycomb core splice body; (2) Epoxy resin film and carbon fiber prepreg panel (8 layers) are sequentially laid on the surface of the honeycomb core splice, and placed in a hot autoclave. The mixture is cured for 2 hours at a pressure of 0.3 MPa and a temperature of 130°C to obtain the composite material component. (3) After demolding, inspect the surface of the parts and fill any depressions or defects at the joints with putty. (4) Manually sand the filled area until the surface flatness meets the requirements.

[0076] The composite material components obtained in Examples 1-5 and Comparative Examples 1-5 were subjected to performance tests, and the test standards and results included: 1) Surface flatness (maximum waviness): The surface of the splicing area was scanned using a laser profilometer, and the maximum height deviation (MaxDeviation) within a 100mm range centered on the splice seam was measured. The results are shown in Table 1.

[0077] 2) Weight gain at splicing seams: The weight gain per meter of splicing seam compared to pure honeycomb core material was calculated, and the results are shown in Table 1.

[0078] 3) Appearance defect rating: Visual inspection, no visible marks are grade A, slightly visible marks are grade B, and obvious dents or bumps are grade C.

[0079] Table 1 Performance test results of each embodiment and comparative example

[0080] As shown in Table 1: (1) Compared with Comparative Example 1, compared with the obvious surface collapse (flatness 0.25mm) caused by splicing with a single foam adhesive, this application optimizes the surface flatness to 0.03mm by constructing a stiffness matching structure with a soft bottom and a hard surface, and improves the appearance rating from C to A, which significantly solves the fax defect.

[0081] (2) Compared with Comparative Example 2, both Example 1 and Comparative Example 2 can achieve excellent surface quality (Grade A), but the weight increase of the splice seam in Example 1 is only 28 g / m, while the weight increase of Comparative Example 2, which uses full-thickness potting, is as high as 180 g / m. This shows that the present application has a significant weight reduction effect compared with the full potting scheme while ensuring surface quality, and retains the lightweight advantage of the honeycomb structure.

[0082] (3) Compared with Comparative Example 3, Comparative Example 3 omitted the pre-curing step, which caused the high-hardness adhesive to have fluidity in the early stage of co-curing and a deviation of 0.12 mm under pressure. This proves that the pre-curing step of the rigid support layer 2 in this application plays a key role, that is, the splicing method of this application needs to form a rigid entity in advance to act as an in-situ mold.

[0083] (4) Compared with Comparative Example 4, although Comparative Example 4 was layered and pre-cured, the surface adhesive had too low hardness (ShoreD 40) and could not effectively resist the pressure of the autoclave, resulting in a 0.18mm indentation on the surface. This shows that the second adhesive must have sufficiently high hardness (preferably ShoreD 70 or higher) to achieve stiffness matching.

[0084] (5) Compared with Comparative Example 5, although Comparative Example 5 can also achieve good flatness through later repairs, its weight gain is higher than that of Example 1 (which was filled with putty), and it also increases the additional repair time. This application achieves the qualified standard in one molding process, which is more efficient.

[0085] In summary, this application solves the problems of seam collapse, obvious marks, and large repair volume during co-curing of honeycomb sandwich structures by constructing a stiffness-matching structure of a low-density soft base layer and a high-stiffness hard surface layer, combined with a process flow of grooving, filling, pre-curing, and co-curing, without significantly increasing the structural weight. It also has the advantages of lightweight, high surface quality, and high manufacturing efficiency. The process is stable and reliable, and the overall technical effect is significantly better than single-material splicing or simple process superposition. It can be widely used in the industrial manufacturing of high-performance honeycomb sandwich composite material components for aerospace.

[0086] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0087] Although preferred embodiments of the present application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are limited to all changes and modifications that include the preferred embodiments and fall within the scope of the embodiments of the present application.

[0088] Finally, it should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes said element.

[0089] This application uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for splicing honeycomb sandwich structures based on stiffness matching control, characterized in that, Includes the following steps: The first adhesive is used to splice the two honeycomb core materials to be spliced ​​together with full thickness and then cured to form a honeycomb core splice body. A groove is machined along the splicing direction in the first adhesive area at the top of the splice seam; A second adhesive is filled into the groove and subjected to localized heating and pre-curing treatment to form a rigid support layer, which is then polished to be flush with the upper surface of the honeycomb core material; wherein, the curing hardness of the second adhesive is higher than that of the first adhesive; After applying adhesive film and prepreg panels to the surfaces of the honeycomb core splice and the rigid support layer, and then co-curing them in an autoclave under heat and pressure, a spliced ​​composite material component is obtained.

2. The method according to claim 1, characterized in that, The first adhesive is epoxy resin foam or phenolic resin foam, which forms a low-density bonding layer after curing.

3. The method according to claim 1 or 2, characterized in that, The curing temperature of the first adhesive is 110℃~130℃, and the curing time is 30min~90min.

4. The method according to claim 1, characterized in that, The second adhesive includes at least one of a high-hardness liquid film, a room-temperature curing potting compound, and a modified epoxy resin liquid. The Shore hardness of the second adhesive after curing is greater than 70, forming a rigid support layer.

5. The method according to claim 1, characterized in that, The depth of the groove is 5% to 15% of the total height of the honeycomb core material, and the width of the groove is 3mm to 5mm.

6. The method according to claim 1, characterized in that, The difference between the filling height of the second adhesive and the height of the upper surface of the honeycomb core material is 0mm~0.2mm, and after pre-curing treatment, it is polished to be completely flush.

7. The method according to claim 1, characterized in that, The pre-curing temperature of the second adhesive is 120℃~150℃, and the pre-curing time is 20min~40min.

8. The method according to claim 1, characterized in that, The co-curing molding pressure is 0.2MPa~0.4MPa, the temperature is 120℃~180℃, and the heat and pressure holding time is 1h~3h.

9. The method according to claim 1, characterized in that, The honeycomb core material is aluminum honeycomb core material or aramid paper honeycomb core material, and the core material height is 10mm~25mm.

10. A composite material component, characterized in that, The composite material component is prepared by the method described in any one of claims 1-9. The composite material component is obtained by splicing honeycomb core materials. A gradient stiffness composite structure is provided in the splicing seam area of ​​adjacent honeycomb core materials. The gradient stiffness composite structure includes, from top to bottom, a rigid support layer and a low-density connecting layer. The rigid support layer is composed of a cured second adhesive, and the low-density bonding layer is composed of a cured first adhesive.

Images