Composite sandwich panel with fire-retardant and sound insulation functions, and preparation method and application thereof

Abstract

This invention relates to a composite sandwich panel with flame-retardant and sound-insulating functions, its preparation method, and its applications. A slurry is prepared by uniformly mixing phenolic resin, a flame retardant, and a solvent. This slurry is then uniformly coated onto the surface of a woven fabric and dried to obtain a prepreg. The prepreg is pressed to obtain a panel. The panel undergoes pretreatment such as sanding and roughening, and cleaning. Then, an adhesive is used to bond the core material between two panels to obtain a blank. The blank is then placed in a vacuum bag and cured to obtain a composite sandwich panel for bulkhead use. This invention enhances the strength and flame retardancy of the carbon fiber composite panel by introducing modified phenolic resin, ensuring good structural support and fire safety. The organic combination of the foam core material and the damping layer not only significantly reduces the overall weight but also improves the bending stiffness of the panel and effectively enhances its sound insulation performance. This composite sandwich panel can be used as a bulkhead material and has good market prospects in many fields such as shipbuilding.

Description

Technical Field

[0001] This invention relates to the field of composite materials and shipbuilding technology, specifically to a composite sandwich panel with flame-retardant and sound-insulating functions, its preparation method, and its application. Background Technology

[0002] During ship operation, noise from machinery, engines, and the marine environment negatively impacts the living and working environment of crew and passengers. Furthermore, bulkheads must possess excellent flame retardancy to address the risk of fire on board, prevent the spread of fire between different compartments, and ensure the safety of the hull structure and personnel. Therefore, the sound insulation and flame retardant properties of bulkheads are crucial in ship design. Effective sound insulation and flame retardant design not only meet safety regulations but also extend the service life of ship equipment, ensuring the overall safety and reliability of operations.

[0003] In modern shipbuilding, composite sandwich panels, due to their combination of lightweight and excellent mechanical properties, have gradually replaced traditional metal sheet materials and are widely used in the construction of ship bulkheads. These composite sandwich panels typically consist of two layers of high-strength surface materials (such as glass fiber reinforced plastics or carbon fiber composites) and a lightweight core material sandwiched in between (such as foam, honeycomb structure, or cork). The surface materials significantly improve sound insulation and structural strength while maintaining lightweight properties, while the core material provides sound absorption and damping effects. The combination of these materials provides sound insulation and flame retardancy to a certain extent, meeting the basic requirements for ship operation.

[0004] Nevertheless, existing bulkhead materials still have the following problems in practical applications: (1) Traditional composite material panels are difficult to meet the International Maritime Organization's standard IMO FTPC 2010 Part 2 regarding the flame retardant performance of ship materials; (2) Relying solely on the lightweight core material in the middle is insufficient to achieve the ideal sound insulation effect. In summary, although existing composite sandwich panels are lightweight and durable, the balance between sound insulation and flame retardant performance has not yet reached the ideal standard, making it difficult to simultaneously meet the dual requirements of ships for high sound insulation and high flame retardancy. Summary of the Invention

[0005] The main objective of this invention is to address the practical problem that existing composite sandwich panels for bulkheads cannot simultaneously meet application requirements in terms of sound insulation and flame retardancy. By introducing modified phenolic resin to enhance the strength and flame retardancy of the carbon fiber composite panel, good structural support and fire safety are ensured. Furthermore, by organically combining the foam core material with a damping layer, an acoustic / structural composite core material is developed, which not only significantly reduces the overall weight but also improves the bending stiffness of the panel and effectively enhances its sound insulation performance. The novel composite sandwich panel for bulkheads provided by this invention achieves excellent weight-to-strength ratio while enhancing overall stability, and its preparation method is simple and low-cost, showing promising market prospects.

[0006] To achieve the above objectives, the composite sandwich panel for bulkheads provided by the present invention has a structure of at least three layers, including opposingly arranged panels and a core material filled between the panels. For composite sandwich panels for bulkheads with more than three layers, a functional layer, such as a decorative layer, can also be provided on the outer surface of the panels.

[0007] In the above scheme, the panel is specifically a flame-retardant woven fabric reinforced phenolic resin panel, and the core material is composed of rigid foam (such as polyimide) and damping layer (such as silicone rubber, EPDM rubber, aluminum foam, etc.) alternately combined.

[0008] In the above scheme, the content of phenolic resin in the panel is not less than 30%, preferably 30%-40%.

[0009] The second objective of this invention is to provide a method for preparing the above-mentioned composite sandwich panel for bulkheads, comprising the following steps: (a) preparing a panel using modified flame-retardant phenolic resin and woven fabric; (b) filling the core material between two panels and then vacuum curing to obtain the composite sandwich panel for bulkheads.

[0010] In the above scheme, the panel preparation process in step (a) specifically includes: mixing phenolic resin, flame retardant and solvent evenly to obtain a slurry, applying the slurry to the surface of the woven fabric, drying it to obtain a prepreg, and pressing the prepreg in a mold to obtain a panel.

[0011] In the above scheme, the raw material ratio by weight when preparing the panel is: 55-70 parts phenolic resin, 20-30 parts flame retardant, and 5-15 parts organic solvent.

[0012] In the above scheme, the flame retardant is selected from at least one of aluminum hydroxide, magnesium hydroxide, expanded graphite, and melamine polyphosphate.

[0013] As a preferred embodiment, the flame retardant is specifically a mixture of aluminum hydroxide and expanded graphite, with a mass ratio of 0.5-2:1, wherein the particle size of aluminum hydroxide is D50=1-1.5μm and the particle size of expanded graphite is D50=150-200μm.

[0014] Aluminum hydroxide is an excellent flame retardant. When heated, it absorbs heat and releases water vapor, effectively reducing the surface temperature of materials and diluting flammable gases. Expanded graphite is also a good flame retardant; it rapidly expands at high temperatures to form a dense, porous carbon layer, providing multiple flame-retardant effects such as heat insulation and oxygen barrier. Compared to using aluminum hydroxide or expanded graphite alone as flame retardants, the combined use of the two achieves a dual flame-retardant effect of "gas phase-condensed phase," significantly improving the flame retardant rating and fire spread resistance of the panel.

[0015] Regarding the particle size of flame retardants, micron-sized aluminum hydroxide (D50 = 1-1.5 μm) is beneficial for its uniform dispersion in phenolic resin systems, effectively improving the filling rate and flame retardant efficiency; while medium-sized expanded graphite (D50 = 150-200 μm) ensures sufficient expansion under thermal shock, forming a continuous and stable expanded char layer. Furthermore, this combination or combination of flame retardants' particle sizes makes them less prone to sedimentation during processing, helping to maintain the stability of the slurry and forming a uniform flame-retardant network after curing.

[0016] Compared to other single flame retardants or other compound flame retardant systems, the aluminum hydroxide + expanded graphite flame retardant selected in this invention exhibits better flame retardant performance at the same addition amount, such as a higher limiting oxygen index, a lower heat release rate and smoke density, and has less impact on the mechanical properties of the material. It is especially suitable for ship bulkhead materials with strict requirements for lightweight and high flame retardancy.

[0017] In the above scheme, the solvent is selected from at least one of ethanol and acetone, preferably ethanol.

[0018] In the above scheme, the woven fabric is selected from at least one of carbon fiber fabric, glass fiber fabric, aramid fiber fabric, and basalt fiber fabric, preferably carbon fiber fabric.

[0019] In the above scheme, the mass ratio of slurry to woven fabric in the preparation of the panel is 1:1-5, preferably 1:1.2-1.5.

[0020] In the above scheme, the process of preparing the panel using prepreg is as follows: First, one or more pieces (two or more pieces) of prepreg are laid flat in a molding machine and preheated at 100-110℃ for 15-20 minutes. During the preheating process, the pressure is increased to 3-5 MPa every 3-5 minutes and held for 0.5-1 minutes. Then, the temperature is raised to 110-120℃ and the pressure is held at 5-10 MPa for 10-15 minutes. Then, the temperature is raised to 150-160℃ and the pressure is held at 5-10 MPa for 50-70 minutes. Finally, the heating is stopped, the pressure is kept constant, and the panel is cooled to room temperature. After depressurization, the panel is demolded.

[0021] As a preferred option, multiple prepregs are stacked and pressed into a panel. The prepregs can be stacked and pressed in the same direction or stacked and pressed in a crisscross pattern to improve the strength of the panel.

[0022] In the above scheme, the specific process of step (b) is as follows: the pressed panel is pre-treated by grinding, roughening and cleaning, and then the core material is bonded between the two panels with adhesive to obtain a blank. The blank is put into a vacuum bag for curing and molding to obtain a composite sandwich panel for the bulkhead.

[0023] In the above scheme, the core material is made of alternating bonding of rigid polyimide foam and damping layer (such as silicone rubber, EPDM rubber, aluminum foam, etc.).

[0024] Furthermore, the adhesive used to bond the various layers of the core material and the panel to the core material is selected from epoxy adhesives, phenolic adhesives, polyurethane adhesives, and acrylic adhesives, and its dosage is 450-600 g / m². 2 .

[0025] In the above scheme, the vacuum curing molding of the slab includes two stages: the first stage is to put the bonded slab into a vacuum bag, vacuum and compact it, and then cure it at room temperature for 12-24 hours; the second stage is to take the slab out of the vacuum bag, place it in an environment of 50-70℃ and let it stand for curing for 2-5 hours, and finally let it cool naturally to room temperature.

[0026] The third objective of this invention is to provide applications of the above-mentioned composite sandwich panels in shipbuilding (such as bulkheads), high-speed trains (such as roof panels and side panels), civil aircraft (such as cargo hold floors), and building construction (such as space partitions).

[0027] This invention significantly improves the flame retardant and sound insulation performance of sandwich panels through the synergistic effects of material selection, structural design, and process innovation. The sandwich panel uses modified phenolic resin as the matrix, which possesses excellent high-temperature resistance and self-extinguishing properties. By compounding aluminum hydroxide and expanded graphite as flame retardants, a synergistic "gas-phase-condensed-phase" flame retardant mechanism is constructed, ensuring that the panel meets stringent marine flame retardant standards. The core material of the sandwich panel is high-performance flame-retardant polyimide foam, which not only has a high limiting oxygen index but also chars without dripping upon contact with fire, forming a fire-resistant barrier together with the panel.

[0028] Furthermore, this invention utilizes alternating bonding of polyimide foam and damping layers (such as silicone rubber or aluminum foam) to form an acoustic / structural composite core material. The polyimide foam provides structural support and forms a sound wave reflection interface, while the damping layer, with its high loss factor, maximizes the conversion of sound wave vibration energy passing through the panel into heat energy. This multi-layered alternating structure effectively disrupts and attenuates the propagation path and energy of sound waves in different media, significantly improving sound insulation performance, especially for low- and mid-frequency noises such as structural noise and mechanical equipment noise commonly found in ships.

[0029] Compared with existing similar products or technologies, the beneficial effects of this invention are mainly reflected in the following aspects: (1) The raw materials are cheap and readily available, the preparation process is simple and easy to implement, and it can be industrialized on a large scale, which helps to reduce the production and use costs of the board.

[0030] (2) The composite sandwich panel has excellent performance, with a vertical combustion rating of V-0 and key indicators such as smoke density that meet or even exceed the stringent requirements of the International Maritime Organization, such as IMO FTPC 2010 Part 2, for bulkhead materials.

[0031] (3) Through the unique composite core material design, the average sound insulation of the board is significantly improved, reaching up to 39dB or more. Compared with traditional single foam core material or simple sandwich structure bulkheads (sound insulation of about 25-30dB), the sound insulation performance of the composite sandwich panel of the present invention is improved by about 30% or more, which can effectively improve the acoustic environment of the ship cabin and is very suitable for the manufacture of ship bulkheads.

[0032] (4) Through structural innovation, a balance between performance and lightweighting of composite sandwich panels is achieved. By organically combining high-strength flame-retardant panels with acoustic / structural composite core materials, the overall weight is significantly reduced while ensuring high bending stiffness and strength of the panels. This also breaks through the bottleneck of traditional sandwich panels where sound insulation and structural performance are difficult to balance. The panels produced according to the method of this invention all have excellent weight-to-strength ratios and are particularly suitable for transportation fields such as shipbuilding and high-speed rail, where weight control and multifunctionality are extremely important. Attached Figure Description

[0033] Figure 1 This is a process flow diagram for the preparation of the composite sandwich panel for the bulkhead described in this invention. Detailed Implementation

[0034] To enable those skilled in the art to fully understand the purpose, technical solution, and beneficial effects of this invention, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be emphasized that the illustrative embodiments and descriptions listed herein are for illustrative purposes only and do not constitute any limitation on the invention.

[0035] It should also be noted that, to avoid obscuring the invention with unnecessary details, the accompanying drawings only show structures and / or method steps closely related to the technical solutions of the invention, while omitting some irrelevant details. The term "comprising / including" herein indicates the presence of a feature, element, step, or component, but does not exclude the presence or addition of one or more other features, elements, steps, or components. Unless otherwise specified, the terms "connected" or "linked" can refer not only to a direct connection but also to an indirect connection or wireless connection involving an intermediary.

[0036] Unless otherwise stated, the descriptions of orientation or positional relationships in this invention, such as "upper," "lower," "left," "right," "front," and "rear," are based on the orientation or positional relationships shown in the accompanying drawings and are used only for the purpose of facilitating the description of this invention and simplifying the description. They are not intended to indicate or imply that the product or equipment referred to must have a specific orientation or be constructed or operated in a specific orientation, and should not be construed as limiting the technical solution of this invention.

[0037] The manufacturing process of the composite sandwich panel for bulkheads with flame-retardant and sound-insulating functions provided by this invention is as follows: Figure 1 As shown, it includes the following steps: (1) Mix 55-70 parts of phenolic resin and 20-30 parts of flame retardant (such as aluminum hydroxide + expanded graphite) evenly to obtain modified phenolic resin, then add 5-15 parts of alcohol with a concentration of 99.5% (volume percentage) or higher, mix evenly to obtain slurry.

[0038] (2) Cut the woven fabric (such as carbon fiber) to the target size and weigh it. After it passes the test, apply the slurry evenly to each surface of the woven fabric and let it air dry to obtain the prepreg.

[0039] (3) Lay one or more pieces of prepreg flat on a molding press to obtain a panel. The molding is carried out in stages. First, the prepreg is preheated at 100-110℃ for 15-20 minutes. During the preheating process, the pressure is increased to 3-5 MPa every 3-5 minutes and held for 0.5-1 minutes. Then, the temperature is raised to 110-120℃ and held for 10-15 minutes at 5-10 MPa. Then, the temperature is raised to 150-160℃ and held for 50-70 minutes at 5-10 MPa. Finally, the heating is stopped, the pressure is kept constant and cooled to room temperature, and the pressure is released to demold the panel.

[0040] (4) Take two panels of the same size and sand them. Then apply the adhesive to the core material and the panel surface to be bonded. Put the bonded blanks into a vacuum bag, vacuum and compact them, and then cure them at room temperature. Then take out the blanks and transfer them to an oven. Heat them at 50-70℃ and let them stand for 2-5 hours to cure. After natural cooling, you will get a composite sandwich panel for the bulkhead.

[0041] Example 1 (1) Using a mixer (speed 1000r / min, mixing time 30min), 65 parts of phenolic resin, 25 parts of flame retardant (aluminum hydroxide, D50=1μm, expanded graphite, D50=150μm, the mass ratio of the two is 2:1), and 10 parts of anhydrous ethanol were mixed evenly and allowed to stand for 24h to naturally degas, resulting in a modified phenolic resin slurry with a total weight of about 5kg.

[0042] (2) Cut the carbon fiber cloth into 1270mm*1300mm squares, weigh them and record the weight as W. f The weighing is equivalent to 1.226 times W. f The modified phenolic resin slurry of a certain weight is evenly applied to both sides of the carbon fiber cloth using a scraper to ensure that the slurry evenly wets the carbon fiber cloth. After standing for 24 hours to dry, the prepreg is obtained for later use.

[0043] (3) Cut the prepreg into four small squares with a size of 635mm*650mm (i.e., four equal parts). Stack three of the cut prepreg pieces together neatly and wrap them with release paper. Make a few small cuts on the top and bottom surfaces with a knife to facilitate air release.

[0044] (4) Preheat the molding machine to 100°C in advance, and then put the wrapped prepreg and gasket into the mold for molding. The curing process is as follows: First, preheat at 100°C for 20 min, press up to 4MPa every 5 min and hold for about 1 min; then heat up to 110°C and press for 10 min at a pressure of 10MPa; then continue to heat up to 150°C and keep the pressure unchanged (i.e., 10MPa) and continue to press for 60 min; finally, stop heating, keep the pressure unchanged and cool naturally to room temperature, and release the pressure to obtain the panel.

[0045] (5) Roughen the surface of the panel by sanding with 80-grit sandpaper, then clean it with alcohol and set aside. Mix the A and B components of epoxy MF1305 adhesive evenly at a mass ratio of A:B=3:1, and then apply it evenly to the bonding surface of the panel, with a coating amount of approximately 450g / m² on each side. 2 The core material (composed of 6mm thick polyimide foam, 5mm thick aluminum foam, and 6mm thick polyimide foam bonded together from top to bottom) is arranged between the two panels, ensuring the edges are aligned. After pressing, excess adhesive is wiped clean to obtain the blank. The blank is placed in a vacuum bag, vacuum-pressed, and cured at room temperature for 24 hours. Then, the vacuum bag is removed, and the blank is transferred to a 60℃ environment for static curing for 2 hours. After naturally cooling to room temperature, the composite sandwich panel is obtained.

[0046] Example 2 (1) Using a mixer (speed 1000r / min, mixing time 30min), 65 parts of phenolic resin, 25 parts of flame retardant (aluminum hydroxide, D50=1μm, expanded graphite, D50=150μm, the mass ratio of the two is 2:1), and 10 parts of anhydrous ethanol were mixed evenly, and then allowed to stand for 24h to naturally degas, to obtain a modified phenolic resin slurry with a total weight of about 5kg.

[0047] (2) Cut the carbon fiber cloth into 1270mm*1300mm squares, weigh them and record the weight as W. f The weighing is equivalent to 1.226 times W. f The modified phenolic resin slurry of a certain weight is evenly applied to both sides of the carbon fiber cloth using a scraper to ensure that the slurry evenly wets the carbon fiber cloth. After standing for 24 hours to dry, the prepreg is obtained for later use.

[0048] (3) Cut the prepreg into four small squares with a size of 635mm*650mm (i.e., four equal parts). Stack three of the cut prepreg pieces together neatly and wrap them with release paper. Make a few small cuts on the top and bottom surfaces with a knife to facilitate air release.

[0049] (4) Preheat the molding machine to 100°C in advance, and then put the wrapped prepreg and gasket into the mold for molding. The curing process is as follows: First, preheat at 100°C for 20 min, press up to 4MPa every 5 min and hold for about 1 min; then heat up to 110°C and press for 10 min at a pressure of 10MPa; then continue to heat up to 150°C and press for 60 min while keeping the pressure constant; finally, stop heating, keep the pressure constant and cool naturally to room temperature, and demold after depressurization to obtain the panel.

[0050] (5) Roughen the surface of the panel by sanding with 80-grit sandpaper, then clean it with alcohol and set aside. Mix the A and B components of epoxy MF1305 adhesive evenly at a mass ratio of A:B=3:1, and then apply it evenly to the bonding surface of the panel, with a coating amount of approximately 450g / m² on each side. 2 The core material (composed of four layers of polyimide foam, two layers of silicone rubber, two layers of polyimide foam, two layers of silicone rubber, and two layers of polyimide foam bonded together) is arranged between the two panels, ensuring the edges are aligned. After pressing, excess adhesive is wiped clean to obtain the blank. The blank is placed in a vacuum bag, vacuum-pressed, and cured at room temperature for 24 hours. Then, the vacuum bag is removed, and the blank is transferred to a 60°C environment for static curing for 2 hours. Finally, it is allowed to cool naturally to room temperature to obtain the composite sandwich panel.

[0051] Example 3 (1) Using a mixer (speed 1000r / min, mixing time 30min), 65 parts of phenolic resin, 25 parts of flame retardant (aluminum hydroxide, D50=1μm, expanded graphite, D50=150μm, the mass ratio of the two is 2:1), and 10 parts of anhydrous ethanol were mixed evenly, and then allowed to stand for 24h to naturally degas, to obtain a modified phenolic resin slurry with a total weight of about 5kg.

[0052] (2) Cut the carbon fiber cloth into 1270mm*1300mm squares, weigh them and record the weight as W. f The weighing is equivalent to 1.226 times W. f The modified phenolic resin slurry of a certain weight is evenly applied to both sides of the carbon fiber cloth using a scraper to ensure that the slurry evenly wets the carbon fiber cloth. After standing for 24 hours to dry, the prepreg is obtained for later use.

[0053] (3) Cut the prepreg into four small squares with a size of 635mm*650mm (i.e., four equal parts). Stack three of the cut prepreg pieces together neatly and wrap them with release paper. Make a few small cuts on the top and bottom surfaces with a knife to facilitate air release.

[0054] (4) Preheat the molding machine to 100°C in advance, and then put the wrapped prepreg and gasket into the mold for molding. The curing process is as follows: First, preheat at 100°C for 20 min, press up to 4MPa every 5 min and keep it for about 1 min; then heat up to 110°C and press for 10 min at a pressure of 10MPa; then continue to heat up to 150°C and keep the pressure unchanged (i.e., 10 MPa) and continue to press for 60 min; finally, stop heating, keep the pressure unchanged and cool naturally to room temperature, and demold after depressurization to obtain the panel.

[0055] (5) Roughen the surface of the panel by sanding with 80-grit sandpaper, then clean it with alcohol and set aside. Mix the A and B components of epoxy MF1305 adhesive evenly at a mass ratio of A:B=3:1, and then apply it evenly to the bonding surface of the panel, with a coating amount of approximately 450g / m² on each side. 2 The core material (composed of four layers of polyimide foam, two layers of EPDM rubber, two layers of polyimide foam, two layers of EPDM rubber, and two layers of polyimide foam bonded together) is arranged between the two panels, ensuring the edges are aligned. After pressing, excess adhesive is wiped clean to obtain the blank. The blank is placed in a vacuum bag, vacuum-pressed, and cured at room temperature for 24 hours. Then, the vacuum bag is removed, and the blank is transferred to a 60°C environment for static curing for 2 hours. Finally, it is allowed to cool naturally to room temperature to obtain the composite sandwich panel.

[0056] Comparative Example 1 This comparative example is basically the same as Example 1, except that all 25 parts of flame retardant are aluminum hydroxide with a D50 of 1 μm.

[0057] Comparative Example 2 This comparative example is basically the same as Example 1, except that all 25 parts of flame retardant are expanded graphite with D50=150μm.

[0058] To fully understand the performance of the composite sandwich panels prepared in Examples 1-3 and Comparative Examples 1-2, samples were taken for tests on flame retardancy, smoke density, sound insulation, etc. The results are shown in Table 1.

[0059] Table 1 Performance test results of the embodiment

[0060] As shown in Table 1, using a mixture of aluminum hydroxide and expanded graphite as a flame retardant, combined with silicone rubber, EPDM rubber, and aluminum foam as an acoustic damping layer, results in a composite sandwich panel with excellent flame retardant properties. This fully meets the smoke density requirements of Part II of the IMO FTPC 2010 International Rules for the Application of Fire Resistance Testing Procedures, and achieves a sound insulation level of over 30 dB. Conversely, when using aluminum hydroxide or expanded graphite alone as a flame retardant, the smoke density exceeds the requirements of Part II of the IMO FTPC 2010 International Rules for the Application of Fire Resistance Testing Procedures, failing to meet the needs of specific application scenarios.

[0061] Example 4 (1) Using a mixer (speed 800 r / min, mixing time 50 min), 70 parts of phenolic resin, 25 parts of flame retardant (aluminum hydroxide, D50=1.5μm, expanded graphite, D50=200μm, the mass ratio of the two is 1:1) and 5 parts of anhydrous ethanol were mixed evenly, and then allowed to stand for 48 h to naturally degas, to obtain a modified phenolic resin slurry with a total weight of about 5 kg.

[0062] (2) Cut the aramid fiber cloth into 1270mm*1300mm squares, weigh them and record the weight as W. f The weighing is equivalent to 1.45 times W. f The modified phenolic resin slurry of a certain weight is evenly applied to both sides of the carbon fiber cloth using a scraper to ensure that the slurry evenly wets the carbon fiber cloth. After standing for 48 hours to dry, the prepreg is obtained for later use.

[0063] (3) Cut the prepreg into four small squares with a size of 635mm*650mm (i.e., four equal parts). Stack two of the cut prepregs neatly together and wrap them with release paper. Make a few small cuts on the top and bottom surfaces with a knife to facilitate air release.

[0064] (4) Preheat the molding machine to 110°C in advance, and then put the wrapped prepreg and gasket into the mold for molding. The curing process is as follows: First, preheat at 110°C for 15 minutes, pressurize to 3MPa every 3 minutes and maintain it for about 0.5 minutes; then heat up to 120°C and hot press for 15 minutes at a pressure of 8MPa; then continue to heat up to 160°C and keep the pressure constant for 70 minutes; finally, stop heating, keep the pressure constant and cool naturally to room temperature, and release the pressure to obtain the panel.

[0065] (5) Roughen the surface of the panel by sanding with 100-grit sandpaper, then clean it with alcohol and set aside. Apply phenolic adhesive evenly to the bonding surfaces of the panel, with an application rate of approximately 600g / m² on each side. 2 The core material (composed of 6mm thick polyimide foam, 5mm thick aluminum foam, and 6mm thick polyimide foam bonded together from top to bottom) is arranged between the two panels, ensuring the edges are aligned. After pressing, excess adhesive is wiped clean to obtain the blank. The blank is placed in a vacuum bag, vacuum-pressed, and cured at room temperature for 12 hours. Then, the vacuum bag is removed, and the blank is transferred to a 70℃ environment for static curing for 4 hours. Finally, it is allowed to cool naturally to room temperature to obtain the composite sandwich panel.

[0066] Example 5 (1) Using a mixer (speed 800 r / min, mixing time 50 min), 60 parts of phenolic resin, 25 parts of flame retardant (aluminum hydroxide, D50=1.3μm, expanded graphite, D50=180μm, the mass ratio of the two is 1.5:1) and 15 parts of anhydrous ethanol were mixed evenly, and then allowed to stand for 48 h to naturally degas, to obtain a modified phenolic resin slurry with a total weight of about 5 kg.

[0067] (2) Cut the fiberglass cloth into 1270mm*1300mm squares, weigh them and record the weight as W. f The weighing is equivalent to 1.38 times W. f The modified phenolic resin slurry of a certain weight is evenly applied to both sides of the carbon fiber cloth using a scraper to ensure that the slurry evenly wets the carbon fiber cloth. After standing for 48 hours to dry, the prepreg is obtained for later use.

[0068] (3) Cut the prepreg into four small squares with a size of 635mm*650mm (i.e., four equal parts). Stack two of the cut prepregs neatly together and wrap them with release paper. Make a few small cuts on the top and bottom surfaces with a knife to facilitate air release.

[0069] (4) Preheat the molding machine to 110°C in advance, and then put the wrapped prepreg and gasket into the mold for molding. The curing process is as follows: First, preheat at 110°C for 15 minutes, pressurize to 3MPa every 3 minutes and maintain it for about 0.5 minutes; then heat up to 120°C and hot press for 15 minutes at a pressure of 8MPa; then continue to heat up to 160°C and keep the pressure constant for 70 minutes; finally, stop heating, keep the pressure constant and cool naturally to room temperature, and release the pressure to obtain the panel.

[0070] (5) Roughen the surface of the panel by sanding with 100-grit sandpaper, then clean it with alcohol and set aside. Apply acrylic adhesive evenly to the bonding surfaces of the panel, with an application rate of approximately 600g / m² on each side. 2 The core material (composed of 6mm thick polyimide foam, 5mm thick aluminum foam, and 6mm thick polyimide foam bonded together from top to bottom) is arranged between the two panels, ensuring the edges are aligned. After pressing, excess adhesive is wiped clean to obtain the blank. The blank is placed in a vacuum bag, vacuum-pressed, and cured at room temperature for 12 hours. Then, the vacuum bag is removed, and the blank is transferred to a 70℃ environment for static curing for 4 hours. Finally, it is allowed to cool naturally to room temperature to obtain the composite sandwich panel.

[0071] Test results show that the composite sandwich panels prepared in Examples 4-5 also have good flame retardant and sound insulation properties and can be used as ship bulkhead materials.

Claims

1. A composite material sandwich panel, characterized in that: The composite sandwich panel has at least three layers, including oppositely arranged panels and a core material filled between the panels. Specifically, the panels are flame-retardant woven fabric reinforced with phenolic resin, and the core material is composed of alternating rigid foam and damping layers.

2. The composite sandwich panel as described in claim 1, characterized in that: The panel contains no less than 30% phenolic resin, and the flame-retardant woven fabric is selected from at least one of carbon fiber cloth, glass fiber cloth, aramid fiber cloth, and basalt fiber cloth.

3. The composite sandwich panel as described in claim 1, characterized in that: The core material has at least three layers, wherein the rigid foam is specifically flame-retardant polyimide rigid foam, and the damping layer is selected from at least one of silicone rubber, EPDM rubber, and aluminum foam.

4. A method for preparing the composite sandwich panel according to any one of claims 1-3, characterized in that... The method includes: preparing panels using modified flame-retardant phenolic resin and flame-retardant woven fabric; filling the core material between two panels and vacuum curing to obtain a composite sandwich panel.

5. The method as described in claim 4, characterized in that... The panel preparation process includes: mixing phenolic resin, flame retardant and solvent evenly to obtain a slurry, applying the slurry evenly to the surface of flame retardant woven fabric, drying it to obtain a prepreg, and pressing the prepreg in a mold to obtain a panel, wherein the mass ratio of slurry to flame retardant woven fabric is 1:1-5.

6. The method as described in claim 5, characterized in that: The raw materials required for preparing the panel are in the following proportions by weight: 55-70 parts of phenolic resin, 20-30 parts of flame retardant, and 5-15 parts of organic solvent. The flame retardant is selected from at least one of aluminum hydroxide, magnesium hydroxide, expanded graphite, and melamine polyphosphate, and the solvent is selected from at least one of ethanol and acetone.

7. The method as described in claim 6, characterized in that: The flame retardant is specifically a mixture of aluminum hydroxide and expanded graphite in a mass ratio of 0.5-2:1, wherein the D50 of aluminum hydroxide is 1-1.5 μm and the D50 of expanded graphite is 150-200 μm; the solvent is ethanol.

8. The method as described in claim 4, characterized in that The process of preparing panels using prepreg includes: placing at least one piece of prepreg flat in a molding press along the same direction or in a crisscross pattern, preheating at 100-110℃ for 15-20 minutes, increasing the pressure to 3-5 MPa every 3-5 minutes during preheating and holding the pressure for 0.5-1 minutes; raising the temperature to 110-120℃ and holding the pressure at 5-10 MPa for 10-15 minutes; continuing to raise the temperature to 150-160℃ and holding the pressure at 5-10 MPa for 50-70 minutes; stopping heating, maintaining the pressure and cooling to room temperature, and demolding to obtain the panel after depressurization.

9. The method as described in claim 4, characterized in that... The process of preparing composite sandwich panels using panels and core materials includes: pre-treatment of the panels, including roughening and cleaning; bonding the core material between the two panels with an adhesive to obtain a blank; placing the blank in a vacuum bag, vacuuming and compacting it, and curing it at room temperature for 12-24 hours; removing the blank from the vacuum bag, placing it at 50-70℃ for static curing for 2-5 hours, and naturally cooling it to room temperature to obtain the composite sandwich panel.

10. The application of the composite sandwich panel according to any one of claims 1-3 in ships, high-speed trains, civil aircraft, and building construction.

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