High-performance aramid honeycomb composite sandwich structure and preparation process thereof

Abstract

The application discloses a kind of high-performance aramid honeycomb composite sandwich structure and preparation process thereof, belong to honeycomb paper technical field, this kind of high-performance aramid honeycomb composite sandwich structure, including honeycomb structure, recess is respectively provided in each cell top of the honeycomb structure inside, a plurality of filling blocks are respectively arranged in each cell of the honeycomb structure inside, a plurality of the filling block is respectively filled with C strip paper between two two, the middle portion of the C strip paper is engaged with recess, the surface layer is attached to the two honeycomb surfaces of the honeycomb structure.Collaborative reinforcement system of the application is innovatively set in the honeycomb cell, and a three-dimensional interlocking microstructure is constructed, the filling block significantly improves the flatness and shear resistance, and the C strip paper forms anchoring in the filling block through the diamond block, greatly enhances the interfacial peel strength, impact resistance and damage tolerance, realizes the significant improvement of light weight and bearing efficiency.

Description

Technical Field

[0001] This invention belongs to the field of honeycomb paper technology, specifically relating to a high-performance aramid honeycomb composite sandwich structure and its preparation process. Background Technology

[0002] High-performance aramid honeycomb composites are lightweight, high-strength structures made by co-curing aramid paper honeycomb as the core and fiber-reinforced resin surface layers as the skin, using a high-toughness adhesive film. Their high performance is reflected in their multi-functional compatibility, including specific strength, specific stiffness, flame retardancy, environmental resistance, fatigue resistance, wave transmission, and wave absorption. They have been widely used in aviation, low-altitude aircraft, high-speed rail, and shipbuilding. The core of the manufacturing process is a three-step method involving honeycomb core manufacturing, surface layer preparation, and co-curing, which can be further developed into upgraded methods such as functionalized filling, ultra-thin cores, and thermoplastic welding.

[0003] Existing technologies still face several prominent challenges. First, traditional homogeneous filling strategies often sacrifice the overall lightweight advantage, and the interfacial bonding strength between the filler and the honeycomb wall is insufficient, making it prone to failure under complex loads. Second, the most critical interface between the surface layer and the core material remains the weakest link in the entire structure, and it is prone to debonding failure under impact, vibration, and fatigue loads, which restricts further improvement in structural reliability. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a high-performance aramid honeycomb composite sandwich structure.

[0005] The technical solution adopted to solve the above technical problems is: a high-performance aramid honeycomb composite sandwich structure, including a honeycomb structure, wherein each cell inside the honeycomb structure is provided with a groove at the top, and each cell inside the honeycomb structure is provided with a plurality of filling blocks, which are arranged in an array at intervals. C strips of paper are filled between each pair of filling blocks, and the middle of the C strips of paper engages with the grooves. A surface layer is attached to the two honeycomb-shaped surfaces of the honeycomb structure.

[0006] Furthermore, the two end surfaces of several of the filling blocks and the middle surface of the C strip paper are respectively bonded to the surface layer.

[0007] Through the above technical solution, the fully bonded interface formed by the filler block and C-strip paper with the surface layer significantly improves the performance of the sandwich structure. This design innovates the traditional binary interface between the surface layer and the honeycomb into a three-dimensional interlocking reinforced interface of the surface layer, filler block, C-strip paper, and honeycomb.

[0008] Furthermore, the surface layer is composed of a high-strength composite material skin and an adhesive layer that are stacked and bonded together in an alternating manner.

[0009] Through the above technical solution, the surface layer is composed of high-strength composite material skin and adhesive layer stacked and bonded together. This design realizes the leap from the traditional three-layer structure to the gradient functional interface. Through the material and structural design at the micro level, this architecture systematically solves the key technical bottlenecks of interface stress concentration and interlayer performance mismatch that have long existed in high-performance sandwich structures.

[0010] Furthermore, the honeycomb structure, filling block, and C-strip paper are respectively bonded to the high-strength composite material skin through an adhesive layer.

[0011] Through the above technical solution, when external loads are applied to the surface layer, the force can be effectively transmitted and distributed within this network through the adhesive layer. The pressure is mainly borne by the filler blocks, the shear force is jointly borne by the honeycomb wall and C-strip paper, and the bending stress is resisted by the entire system in a coordinated manner. This achieves a load-bearing effect of 1+1+1>3.

[0012] Furthermore, the honeycomb structure has a standard hexagonal grid shape, and the honeycomb structure is made of meta-aramid paper material.

[0013] Through the above technical solution, meta-aramid paper itself is made of high-strength, high-modulus aramid fibers. The honeycomb core formed by it has extremely high specific strength, and the regular hexagonal grid allows the load to be uniformly transferred and distributed along the honeycomb wall, effectively avoiding stress concentration corners that are prone to occur in triangular or rectangular cells. At the same time, its structure exhibits quasi-isotropic properties, which means that it can provide a consistent and predictable mechanical response in all directions, which is crucial for coping with complex and ever-changing actual working conditions.

[0014] Furthermore, the filler block is made of epoxy-based expanded polystyrene, and the filler block is formed by filling the pores with expanded polystyrene.

[0015] Through the above technical solution, the epoxy-based foam cures in situ within the pores, forming rigid micropillars. These regularly arranged micropillars are tightly bonded to the honeycomb wall, together constituting a three-dimensional spatial support framework. This is equivalent to adding vertical reinforcing fibers to a traditional two-dimensional honeycomb network, enabling the core material to simultaneously and efficiently resist out-of-plane compression and in-plane shear. The foam itself is a low-density material, and through selective filling in a spaced array manner, it adds minimal weight only at critical locations, achieving an optimal balance between lightweight effect and mechanical properties.

[0016] Furthermore, the C strip is made of aramid material, and diamond-shaped blocks are cut and set at the two bottom ends of the C strip, with the diamond-shaped blocks located inside the filling block.

[0017] By employing the aforementioned technical solution, aramid fiber was selected as the material for the C-strip, ensuring a high degree of matching between its thermal expansion coefficient and that of the meta-aramid honeycomb core. When the ambient temperature changes, they can expand or contract synergistically, avoiding significant internal stress at the interface due to thermal mismatch. This guarantees the long-term reliability of the structure under harsh environments. After being encapsulated with foam, the diamond-shaped blocks form a strong mechanical interlock within the filler blocks. Simultaneously, the C-strip design indirectly increases the contact area between the surface layer and the honeycomb structure. When the surface layer is subjected to shear stress, the force is transferred to the C-strip through the adhesive layer, and then further transferred to the surrounding foam and honeycomb walls through the diamond-shaped blocks at its bottom via pulling and squeezing, achieving a three-dimensional force flow transmission network. This significantly improves the shear resistance and delamination resistance of the sandwich structure.

[0018] Furthermore, the high-strength composite material skin is made of epoxy fiberglass prepreg.

[0019] Through the above technical solutions, epoxy fiberglass prepreg is known for its excellent strength-to-weight ratio and stiffness-to-weight ratio. As a skin, it can efficiently withstand the tensile and compressive stresses generated by the sandwich structure under bending loads, ensuring that the structure remains intact under extreme loads. It is the key to achieving the overall goal of lightweight and high strength.

[0020] Furthermore, the adhesive layer is composed of epoxy resin and adhesive mixed in a certain proportion.

[0021] Through the above technical solutions, the base epoxy resin ensures perfect chemical compatibility and co-curing capability with the epoxy fiberglass prepreg skin matrix; while the specially designed epoxy adhesive introduces higher bonding strength, toughness and fluidity. During the curing process, the softening and flow stages of the mixed adhesive layer allow the adhesive layer to be pressed into and locked onto all micro-rough surfaces, achieving a tighter and more uniform interfacial bond.

[0022] The preparation process of the high-performance aramid honeycomb composite sandwich structure includes the following specific steps: S1. Using a CNC milling machine or a gantry milling machine, precisely cut the meta-aramid paper honeycomb structure into the required structural shape and thickness.

[0023] S2. At the location where the filler block needs to be installed, use a micro-machining tool to create grooves in the inner wall of the hole. This step is designed to enhance the mechanical interlock.

[0024] S3. Cut the aramid paper into strips, pre-press the middle 90° to form C strip paper, and make an interference fit between the folded ridge and the groove; die-cut the bottom end into diamond-shaped blocks, and the bottom end with the diamond-shaped blocks will hang over the center of the grid.

[0025] S4. Using a metered injection device, epoxy-based expanding foam is precisely injected into the designated honeycomb cells. The injection volume is determined by the designed filler block volume. The diamond-shaped blocks of the C-strip paper are wrapped in the expanding foam, forming a mechanical anchor.

[0026] S5. Cut the high-strength composite skin made of epoxy fiberglass prepreg according to the designed layup direction and sequence, and mix the epoxy resin and adhesive in proportion.

[0027] S6 applies an adhesive layer to each bonding surface.

[0028] S7. Lay the following layers on the mold in sequence: lower high-strength composite skin, adhesive layer, treated honeycomb structure, adhesive layer, upper high-strength composite skin. Ensure that the filler blocks of the honeycomb structure and the top of the C-strip paper are in full contact with the adhesive layer of the high-strength composite skin.

[0029] S8. The assembled components are vacuum-sealed and placed in an autoclave to remove air and volatiles. Curing is then carried out according to a strict curing cycle, with the temperature increased at a program-controlled rate. At specific temperature points, pressure is applied in the autoclave to ensure complete curing of the prepreg on the surface layer, and the adhesive in the bonding layer melts, flows, and cures.

[0030] The beneficial effects of this invention are as follows: 1. This invention constructs a three-dimensional interlocking microstructure by innovatively setting epoxy foam filler blocks and aramid C-strip paper with rhomboid blocks within the honeycomb lattice. The filler blocks, acting as micropillars, significantly improve the compressive and shear resistance of the core, while the C-strip paper, through its rhomboid blocks, forms an anchor within the filler blocks, upgrading traditional surface bonding to volume anchoring. The inclusion of the C-strip paper also indirectly increases the contact area between the surface layer and the honeycomb structure, improving adhesive strength and greatly enhancing interfacial peel strength, impact resistance, and damage tolerance, achieving a significant improvement in lightweighting and load-bearing efficiency.

[0031] 2. This invention employs a highly compatible material combination based on an epoxy resin system, including epoxy fiberglass skin, epoxy-based foam, epoxy-based adhesive layer, and aramid core material. This ensures that all components form molecular-level chemical bonds and interpenetrating networks during co-curing. This not only endows the structure with excellent environmental durability but also optimizes the process window through the inherent consistency of the material system, improving the robustness of the manufacturing process and the consistency of finished product quality. Ultimately, it achieves a reliable and highly designable organic monolithic structure. Attached Figure Description

[0032] Figure 1 This is a three-dimensional schematic diagram of the overall structure of the present invention; Figure 2 for Figure 1 Enlarged view of point A in the middle; Figure 3 This is a three-dimensional schematic diagram of the internal honeycomb structure of the present invention; Figure 4 This is a three-dimensional schematic diagram of the combined structure of the filling block and the C-strip paper of the present invention.

[0033] Reference numerals: 1. Honeycomb structure; 2. Groove; 3. Filler block; 4. C strip paper; 5. Surface layer; 6. High-strength composite material skin; 7. Adhesive layer; 8. Rhomboid block. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0035] like Figures 1 to 4 As shown, this embodiment of a high-performance aramid honeycomb composite sandwich structure includes a honeycomb structure 1. Each cell within the honeycomb structure 1 has a groove 2 at its top. Each cell within the honeycomb structure 1 contains a plurality of filling blocks 3 arranged in an array at intervals. C-strips of paper 4 are filled between each pair of filling blocks 3, with the middle of the C-strips engaging with the groove 2. A surface layer 5 is bonded to the two honeycomb surfaces of the honeycomb structure 1. The gradient interface of the skin and adhesive layers 7, stacked alternately, works synergistically with the three-dimensional mechanical interlocking network of the core, solving the weakest interface problem in the high-performance sandwich structure. This not only significantly improves the peel strength and fatigue resistance of the interface but also effectively suppresses the initiation and propagation of interface cracks under complex loads, significantly enhancing the damage tolerance and reliability of the structure during long-term service.

[0036] like Figures 1 to 2 As shown, the high-strength composite skin 6 is made of epoxy fiberglass prepreg, which can efficiently withstand the tensile and compressive stresses generated by the sandwich structure under bending loads, ensuring that the structure remains intact under extreme loads.

[0037] like Figures 1 to 2 As shown, the adhesive layer 7 is composed of epoxy resin and adhesive mixed in a certain proportion.

[0038] like Figures 1 to 2 As shown, the surface layer 5 is composed of high-strength composite material skin 6 and adhesive layer 7 stacked and bonded together. The honeycomb structure 1, filling block 3, and C strip paper 4 are bonded to the high-strength composite material skin 6 through adhesive layer 7. During the curing process, the softening and flow stage of the mixed adhesive layer 7 can make the adhesive layer 7 press into and lock onto all the micro-rough surfaces, achieving a tighter and more uniform interface bond.

[0039] like Figure 3As shown, the honeycomb structure 1 has a standard hexagonal cell shape. The regular hexagonal grid allows the load to be evenly transferred and distributed along the honeycomb wall, effectively avoiding stress concentration corners that are prone to occur in triangular or rectangular cells. The honeycomb structure 1 is made of meta-aramid paper material, which is made of high-strength, high-modulus aramid fibers. The honeycomb core it forms has extremely high specific strength.

[0040] like Figures 3 to 4 As shown, filler block 3 is made of epoxy-based foam. Filler block 3 is formed by filling the pores with foam. After the epoxy-based foam cures in situ within the pores, it forms rigid micropillars. These regularly arranged micropillars are tightly bonded to the honeycomb wall, together forming a three-dimensional spatial support skeleton. The two end surfaces of several filler blocks 3 and the middle surface of C strip paper 4 are respectively bonded to the surface layer 5, increasing the vertical reinforcing fibers, enabling the core material to simultaneously and efficiently resist out-of-plane compression and in-plane shear.

[0041] like Figures 3 to 4 As shown, the C strip 4 is made of aramid material, ensuring a high degree of matching with the meta-aramid honeycomb core in terms of thermal expansion coefficient. The two bottom ends of the C strip 4 are cut with diamond-shaped blocks 8. After being wrapped with foam inside the filling block 3, the diamond-shaped blocks 8 form a strong mechanical interlock inside the filling block 3. At the same time, the setting of the C strip 4 also indirectly increases the contact area between the surface layer 5 and the honeycomb structure 1. When the surface layer 5 is subjected to shear stress, the force is transmitted to the C strip 4 and the honeycomb structure 1 through the adhesive layer 7, and then transmitted to the surrounding foam and honeycomb wall through the diamond-shaped blocks 8 at its bottom in a pulling and squeezing manner, realizing a three-dimensional force flow transmission network, which greatly improves the shear resistance and delamination resistance of the sandwich structure.

[0042] The working principle of this embodiment is as follows: Using a CNC milling machine or a gantry milling machine, the meta-aramid paper honeycomb structure 1 is precisely cut into the required structural shape and thickness.

[0043] At the location where the filling block 3 needs to be set, a groove 2 is created on the inner wall of the hole using a micro-machining tool. This step is intended to enhance the mechanical interlock.

[0044] Aramid paper is cut into strips, and the middle is pre-pressed at 90° to form strip C 4. The folded ridge position is interference-fitted with the groove 2. The bottom end is die-cut into a diamond-shaped block 8, and the bottom end with the diamond-shaped block 8 will hang over the center of the grid.

[0045] Using a metered injection device, epoxy-based expanding foam is precisely injected into the designated honeycomb cells. The injection volume is determined by the designed volume of the filler block 3. The diamond-shaped blocks 8 of the C strip paper 4 are encased in the expanding foam, forming a mechanical anchor.

[0046] The high-strength composite skin 6, made of epoxy fiberglass prepreg, is cut according to the designed layup direction and sequence, and the epoxy resin and adhesive are mixed in proportion.

[0047] Apply an adhesive layer 7 to each bonding surface.

[0048] Lay the following layers on the mold in sequence: lower high-strength composite skin 6, adhesive layer 7, treated honeycomb structure 1, adhesive layer 7, and upper high-strength composite skin 6. Ensure that the tops of the filler blocks 3 and C strips 4 of the honeycomb structure 1 are in full contact with the adhesive layer 7 of the high-strength composite skin 6.

[0049] The assembled components are vacuum-sealed and placed in an autoclave to remove air and volatiles. Curing is then carried out according to a strict curing cycle, with the temperature increased at a programmed rate. At specific temperature points, pressure is applied in the autoclave to ensure that the prepreg of the top layer 5 is fully cured, and the adhesive of the bonding layer 7 melts, flows, and cures.

[0050] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention.

Claims

1. A high-performance aramid honeycomb composite sandwich structure, comprising a honeycomb structure (1), characterized in that: The honeycomb structure (1) has filling blocks (3) selected in each cell. The top of each cell located at the position of the filling block (3) is provided with a groove (2). Several filling blocks (3) are arranged in an array at intervals. C strips of paper (4) are filled between each pair of filling blocks (3). The middle part of the C strips of paper (4) engages with the groove (2). The two honeycomb surfaces of the honeycomb structure (1) are attached with a surface layer (5). The two end surfaces of several filler blocks (3) and the middle surface of C strip paper (4) are respectively bonded to the surface layer (5); The surface layer (5) is composed of a high-strength composite material skin (6) and an adhesive layer (7) that are stacked and bonded together in an alternating manner; The honeycomb structure (1), filling block (3), and C strip paper (4) are bonded to the high-strength composite material skin (6) through the adhesive layer (7); The honeycomb structure (1) has a standard hexagonal grid shape and is made of meta-aramid paper material. The filler block (3) is made of epoxy-based foam material, and the filler block (3) is formed by filling the pores with foam. The C strip paper (4) is made of aramid material. The two bottom ends of the C strip paper (4) are cut with diamond-shaped blocks (8), which are located inside the filling block (3). The high-strength composite material skin (6) is made of epoxy fiberglass prepreg.

2. The high-performance aramid honeycomb composite sandwich structure according to claim 1, characterized in that, The adhesive layer (7) is composed of epoxy resin and adhesive mixed in a certain proportion.

3. The preparation process of the high-performance aramid honeycomb composite sandwich structure according to any one of claims 1-2, characterized in that, The specific steps include the following: S1. Using a CNC milling machine or a gantry milling machine, the meta-aramid paper honeycomb structure (1) is precisely cut into the required structural shape and thickness; S2. At the location where the filling block (3) needs to be set, a groove (2) is made in the inner wall of the hole using a micro-machining tool. This step is intended to enhance the mechanical interlock. S3. Cut the aramid paper into strips, pre-press the middle 90° to form C strip paper (4), and make an interference fit between the folded ridge and the groove (2); die-cut out the diamond-shaped block (8) at the bottom, and the bottom end with the diamond-shaped block (8) will hang in the center of the grid. S4. Using a quantitative injection device, epoxy-based foam is precisely injected into the designated honeycomb cells. The injection volume is determined by the volume of the designed filler block (3). The diamond-shaped blocks (8) of the C strip paper (4) are wrapped in the foam to form a mechanical anchor. S5. Cut the high-strength composite skin (6) made of epoxy fiberglass prepreg according to the designed layup direction and sequence, and mix the epoxy resin and adhesive in proportion; S6. Apply an adhesive layer to each bonding surface (7); S7. Lay the following layers on the mold in sequence: bottom layer, adhesive layer (7), treated honeycomb structure (1), adhesive layer (7), top layer, and ensure that the top of the filling block (3) and C strip paper (4) of the honeycomb structure (1) are in full contact with the adhesive layer (7) of the high-strength composite skin (6); S8. The assembled components are vacuum-sealed and sent to an autoclave to remove air and volatiles. The components are cured according to a strict curing cycle, with the temperature increased at a program-controlled rate. At a specific temperature point, the autoclave applies pressure to ensure that the prepreg of the surface layer is completely cured, and the adhesive of the bonding layer (7) melts, flows and cures.

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