Composite board and preparation method and application thereof

Abstract

This invention discloses a composite panel, its preparation method, and its application, belonging to the field of building panel technology. The composite panel comprises, from the outside to the inside, a decorative layer, an anti-warping reinforcement layer, a foamed core layer, and a balancing layer, with a thermal expansion release structure at the edge. The anti-warping reinforcement layer uses a high-modulus glass fiber mesh to improve the panel's stiffness and suppress bending deformation; the balancing layer and decorative layer form a symmetrical structure to offset bending stress caused by temperature gradients; the thermal expansion release structure allows for micro-displacement of the panel to release thermal stress. This invention, through the synergy of the anti-warping reinforcement layer, the balancing layer, and the thermal expansion release structure, can effectively reduce the warping deformation of exterior wall cladding under thermal cycling conditions, while also possessing advantages such as weather resistance, thermal insulation, lightweight, and environmental friendliness. The preparation process is simple, suitable for large-scale production, and can be widely applied to composite imitation stone exterior wall cladding.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a composite board, its preparation method, and its application. Background Technology

[0002] Prefabricated building exterior wall panels are usually made of weather-resistant resin and foam materials to achieve decoration and heat insulation. However, during long-term outdoor use, the surface of the panel is heated by solar radiation, while the temperature of the back is relatively lower than that of the panel surface, forming a temperature gradient. When the temperature changes, the mismatch in the thermal expansion coefficients of the different layers of the panel generates bending stress, which can easily lead to warping and deformation.

[0003] At the same time, conventional installation methods impose rigid constraints on the panels, and the stress generated by thermal expansion and contraction cannot be effectively released, which can also easily lead to panel deformation.

[0004] It is evident that existing technologies still need improvement and enhancement. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a composite plate with stable structure, resistance to thermal cycling warping, and the ability to release thermal expansion stress, as well as its preparation method and application.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A composite panel includes, from the outside to the inside, a decorative layer, an anti-warping reinforcement layer, a foamed core layer, and a balancing layer; the anti-warping reinforcement layer is a first glass fiber mesh, used to improve the in-plane stiffness of the composite panel and suppress inward bending deformation of the composite panel; the balancing layer is a second glass fiber mesh, used in conjunction with the decorative layer to counteract the bending stress formed by the temperature gradient; the composite panel also includes a thermal expansion release structure disposed on the edge of the panel, the thermal expansion release structure being used to allow the composite panel to undergo micro-displacement when the temperature changes in order to release thermal expansion stress.

[0007] The composite board wherein the modulus of the first glass fiber mesh is 10-20 GPa.

[0008] In the composite board, the thickness of the anti-warping reinforcement layer is 1.1-1.3 mm.

[0009] The composite panel, wherein the decorative layer is an ASA weather-resistant decorative layer with a thickness of 0.7-0.9 mm.

[0010] In the composite board, the thickness ratio of the balancing layer to the decorative layer is 1:1.

[0011] The composite board, wherein the foamed core layer is a polyurethane foam structural layer with a thickness of 28-32mm.

[0012] The composite board, wherein the polyurethane foam structural layer contains a composite filler composed of oyster shell powder and waste glass powder; the particle size of the composite filler is 50-300 mesh.

[0013] The composite board, wherein the thermal expansion release structure is a strip-shaped sliding mounting hole and a locking screw that mates with the strip-shaped sliding mounting hole; the length direction of the strip-shaped sliding mounting hole is consistent with the main direction of thermal expansion of the composite board.

[0014] A method for preparing a composite board includes the following steps: heating and pressing a sheet to form a decorative layer; attaching an anti-warping reinforcement layer to the inner side of the decorative layer; foaming the inner side of the anti-warping reinforcement layer to form a foamed core layer; attaching a balancing layer to the inner side of the foamed core layer before it cures to form a main structure; and forming a thermal expansion release structure on the edge of the main structure to obtain the composite board described above.

[0015] An application of a composite panel, wherein the above-mentioned composite panel is applied to a composite imitation stone exterior wall panel.

[0016] Beneficial effects: This invention provides a composite board, its preparation method, and its application. The composite board utilizes the synergistic effect of an anti-warping reinforcement layer, a balancing layer, and a thermal expansion release structure. The balancing layer prevents the decorative layer from bending inward after heating, while the anti-warping reinforcement layer and the balancing layer form rigid layers on the upper and lower sides to counteract the bending moment generated during heating, thereby suppressing thermal cycle warping deformation and improving the dimensional stability of the composite board. In addition, the thermal expansion release structure allows the composite board to undergo slight displacement during thermal expansion and contraction, releasing the internal stress of the board and further reducing warping deformation under long-term thermal cycling conditions. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the layered structure of a composite plate.

[0018] Figure 2 This is a schematic diagram of a thermal expansion release structure for a composite panel located on its edge.

[0019] Explanation of main component symbols: 1-Decorative layer, 2-Anti-warping reinforcement layer, 3-Foamed core layer, 4-Balancing layer, 5-Board edge, 6-Strip sliding mounting hole, 7-Locking screw, 8-Washer. Detailed Implementation

[0020] This invention provides a composite board, its preparation method, and its application. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the scope of protection of the invention.

[0021] Please see Figure 1 and Figure 2 This invention provides a composite panel comprising, from the outside to the inside, a decorative layer 1, an anti-warping reinforcement layer 2, a foamed core layer 3, and a balancing layer 4; the anti-warping reinforcement layer 2 is a high-modulus first glass fiber mesh, used to improve the in-plane stiffness of the composite panel and suppress inward bending deformation of the composite panel; the balancing layer 4 is a second glass fiber mesh, used to form a symmetrical or approximately symmetrical structure with the decorative layer 1 to offset the bending stress caused by the temperature gradient; the composite panel also includes a thermal expansion release structure disposed on the edge 5 of the panel, the thermal expansion release structure being used to allow the composite panel to undergo micro-displacement when the temperature changes in order to release thermal expansion stress.

[0022] The anti-warping reinforcement layer 2 of this invention uses a high-modulus first glass fiber mesh, which can improve the in-plane stiffness of the composite board and enhance the board's ability to resist bending deformation, thereby weakening the bending driving force caused by the temperature gradient and suppressing the board's inward bending deformation. The balancing layer 4 uses a second glass fiber mesh, forming a symmetrical or nearly symmetrical laminated structure with the outer decorative layer 1, so that the bending stress generated by the decorative layer 1 and the balancing layer 4 in the temperature field cancels each other out, keeping the neutral axis of the board in the center, eliminating the warping driving force caused by the temperature gradient from the structural mechanics level, and reducing the tendency of bending deformation. At the same time, the thermal expansion release structure set on the board edge 5 allows the composite board to undergo controllable small displacement along the main direction of thermal expansion (the length direction of the composite board) when the temperature changes and causes thermal expansion and contraction, avoiding the accumulation of internal thermal stress caused by rigid installation constraints, thereby continuously releasing thermal expansion stress, further preventing the board from warping, cracking and other problems due to stress concentration, so that the composite board still maintains good dimensional stability and reliability under long-term repeated thermal cycling conditions.

[0023] In some embodiments, the flexural modulus of the first fiberglass mesh is 10-20 GPa. This modulus range provides sufficient and stable in-plane flexural stiffness for the composite panel, effectively resisting bending deformation under outdoor temperature gradients. It avoids insufficient anti-warping ability due to excessively low modulus, resulting in significant inward bending and warping of the panel. Simultaneously, it prevents increased brittleness of the fiberglass mesh due to excessively high modulus, leading to decreased adhesion with the decorative layer 1 and foamed core layer 3, and consequently, delamination, wrinkling, or localized stress concentration. The 10-20 GPa modulus range allows the first fiberglass mesh to maintain high rigidity while possessing toughness and bonding strength matching the composite system. It can stably play its primary role in suppressing bending deformation and improving overall dimensional stability, while also being compatible with the integrated calendering, molding, and foaming processes, ensuring strong interlayer bonding and preventing delamination during long-term use. Ultimately, this allows the composite panel to remain flat, warp-free, and crack-free under long-term thermal cycling conditions.

[0024] In some embodiments, the thickness of the anti-warping reinforcement layer 2 is 1.1-1.3 mm. This thickness range allows the first glass fiber mesh to fully exert its high-modulus rigid support function, ensuring sufficient structural strength and in-plane stiffness, and effectively suppressing bending and warping deformation caused by temperature gradients. If the thickness is too thin, the anti-warping reinforcement layer 2 will have insufficient continuity and reduced reinforcement effect, making it unable to stably resist thermal cycling stress. If the thickness is too thick, it will increase the overall weight of the board and increase material costs. At the same time, it is easy to form a clear interface between the decorative layer 1 and the foamed core layer 3, reducing interlayer adhesion and causing delamination, wrinkling, or local debonding problems. The thickness of 1.1-1.3 mm can ensure that the anti-warping reinforcement layer 2 is continuous and flat, without wrinkles or curling edges, and tightly adheres to the decorative layer 1 and the foamed core layer 3. It can also match the overall structure of the exterior wall panel, without affecting the foaming molding and the composite process of the balancing layer 4, so that the composite board achieves a balance between lightweight, structural strength, and long-term dimensional stability.

[0025] In some embodiments, the decorative layer 1 is an ASA weather-resistant decorative layer with a thickness of 0.7-0.9 mm. This thickness range allows the ASA weather-resistant decorative layer to possess sufficient weather resistance, UV resistance, and stone-like texture, meeting the aging resistance requirements under long-term outdoor exposure to sunlight, rain, and temperature fluctuations. It avoids insufficient weather resistance, yellowing, fading, or cracking due to excessive thickness, while also preventing material waste, increased costs, and increased interlayer stress caused by excessive thickness. Furthermore, this thickness range is more suitable for calendering and molding processes, resulting in a smooth surface and clear texture after molding. It adheres tightly to the anti-warping reinforcement layer 2 without voids, ensuring the overall appearance quality and dimensional stability of the composite panel, and synergistically combining decorative, weather-resistant, and structural anti-warping functions.

[0026] In some embodiments, the thickness ratio of the balancing layer 4 to the decorative layer 1 is 1:1. When used outdoors, the surface of the composite board is exposed to solar radiation, creating a temperature difference. Due to the different coefficients of thermal expansion, the decorative layer 1 and the foamed core layer 3 will generate bending moments. The 1:1 thickness ratio allows the balancing layer 4 and the ASA weather-resistant decorative layer 1 to form a completely symmetrical layered structure in terms of elastic modulus, thermal expansion response, and structural stiffness. This allows the bending stress generated on the upper and lower surfaces of the board in the temperature field to cancel each other out, causing the neutral axis of the board to return to the center, thus eliminating the fundamental driving force of warping from a mechanical perspective. At the same time, this ratio ensures that the shrinkage and expansion of the composite board remain consistent during repeated thermal cycles of heating and cooling, avoiding unidirectional warping and wave deformation caused by uneven thickness leading to excessive stress on one side. Combined with the anti-warping reinforcement layer 2, it can further improve the overall dimensional stability, ensuring that the board remains flat, does not warp, and does not crack during long-term use.

[0027] In some embodiments, the foamed core layer 3 is a polyurethane foam structural layer with a thickness of 28-32mm. This thickness range provides the composite panel with sufficient thermal insulation, sound insulation, and structural support capabilities, meeting the requirements of exterior wall cladding in terms of building energy conservation and mechanical load-bearing capacity. Too thin a layer results in insufficient insulation and weak overall rigidity, making it unable to effectively resist external impacts and temperature deformation. Too thick a layer increases the panel's weight, raw material consumption, and installation difficulty, and is also prone to uneven internal cell structure and shrinkage deformation during the foaming process. The 28-32mm thickness of the foamed core layer 3 forms a stable and matched interlayer ratio with the 0.7-0.9mm thick ASA weather-resistant decorative layer and the 1.1-1.3mm thick anti-warping reinforcing layer 2, resulting in a moderate overall panel thickness, facilitating transportation and installation, effectively improving the compressive strength and dimensional stability of the foamed core layer 3, and achieving a balance between thermal insulation, lightweight, high strength, and resistance to thermal cycling deformation, making it suitable for long-term outdoor use of prefabricated exterior wall cladding.

[0028] In some embodiments, a composite filler composed of oyster shell powder and waste glass powder is added to the polyurethane foam structural layer. Oyster shell powder and waste glass powder are widely available and inexpensive. Their combined use can fully fill the micropores naturally formed during the polyurethane foaming process, improving the uniformity of the cell structure and reducing problems such as low strength and easy shrinkage deformation caused by pore defects. This improves the compressive strength, elastic modulus, and structural durability of the polyurethane foam structural layer. The two inorganic fillers themselves have low coefficients of thermal expansion and good dimensional stability. Their addition reduces the overall coefficient of thermal expansion of the polyurethane foam structural layer, decreasing the difference in thermal expansion between the polyurethane foam structural layer and the surface layer (ASA weather-resistant decorative layer 1) and the anti-warping reinforcement layer 2. This further alleviates the internal stress caused by the temperature gradient, and together with the symmetrical structure and the anti-warping reinforcement layer 2, enhances the composite board's resistance to thermal cycling deformation. Furthermore, the resource utilization of waste oyster shells and waste glass meets the requirements of green building materials and energy conservation and environmental protection, achieving performance improvement and environmental benefits without significantly increasing the weight and cost of the board.

[0029] In some embodiments, the particle size of the composite filler is 50-300 mesh. This particle size range allows the oyster shell powder and waste glass powder to form a good gradation, which can fully fill the tiny voids generated by polyurethane foaming, improving the core layer density, compressive strength, and dimensional stability, without damaging the cell structure due to excessively coarse particles, leading to uneven foaming, local cracking, or reduced interlayer bonding. At the same time, it can avoid problems such as agglomeration, poor dispersibility, increased system viscosity, and reduced foaming flowability caused by excessively fine particles. The 50-300 mesh particle size range is highly matched with the polyurethane foaming process, allowing the filler to be uniformly dispersed in the foaming system, stably playing its role in reinforcement, shrinkage reduction, and thermal stress reduction, further improving the overall durability and anti-warping performance of the composite board.

[0030] In some embodiments, the thermal expansion release structure is a strip-shaped sliding mounting hole 6 and a locking screw 7 that mates with the strip-shaped sliding mounting hole 6; the length direction of the strip-shaped sliding mounting hole 6 is consistent with the main direction of thermal expansion of the composite board. Specifically, the locking screw 7 can be used in conjunction with a washer 8 during installation. More specifically, the length of the strip-shaped sliding mounting hole 6 is 8-15mm, meaning that the maximum allowable micro-displacement of the composite board is 8-15mm. Under long-term thermal cycling conditions, the composite board will undergo regular elongation and contraction with temperature changes. The length direction of the strip-shaped sliding mounting hole 6 is consistent with the main direction of thermal expansion, which can ensure smooth displacement along the preset path when the board expands and contracts. The locking screw 7 used in conjunction with the gasket 8 can not only achieve reliable installation and fixation, but also reduce friction damage between the screw and the board surface. The maximum micro-displacement is controlled within 8-15mm, which can fully meet the thermal deformation release requirements of ASA-PU composite board within the normal outdoor temperature difference range. It will not cause stress failure due to insufficient displacement space, resulting in warping and cracking, nor will it cause installation loosening and falling off due to excessive displacement. Thus, a balance is achieved between structural safety constraints and free release of thermal stress, solving problems such as deformation and cracking caused by rigid fixation from the installation end.

[0031] This invention provides a method for preparing a composite board, comprising the following steps: Forming of ASA weather-resistant decorative layer: ASA sheet is heated to the softening temperature range of 180℃-220℃, and the surface decorative layer is obtained by calendering or molding, and then it is bonded to the surface of the subsequent composite structure.

[0032] Laying the anti-warping reinforcement layer: The anti-warping reinforcement layer is attached to the inside of the ASA weather-resistant decorative layer, so that it is basically attached to the ASA weather-resistant decorative layer and remains flat, without wrinkles or curling edges.

[0033] Molding of polyurethane foam structural layer: Using conventional foaming process, A material (polyol combination material, including polyether polyol, cyclopentane / water foaming agent, amine catalyst, organosilicon foam stabilizer) and B material (isocyanate, polymethylene polyphenyl isocyanate, crude MDI) are mixed in a mass ratio of (1-1.2):1 and injected into the mold for foaming. Oyster shell and waste glass powder (the ratio is determined according to the strength and density requirements of the PU foam structural layer (1-3): (3-1)) composite filler are added to A material.

[0034] Composite of the balancing layer: Before the polyurethane foam structural layer is cured, a balancing layer is attached to its inner side to form the main structure.

[0035] Processing of the edge thermal expansion release structure: After the main structure of the composite board is formed, the edge (tongue / clasp) is processed to form a thermal expansion release structure. Specifically, a strip-shaped sliding mounting hole is formed by stamping, with its long axis aligned with the main thermal expansion direction of the board. The hole width is 5.5-7.0mm; the hole length is 8-15mm.

[0036] This invention provides an application of a composite panel, specifically a composite imitation stone exterior wall cladding. Composite imitation stone exterior wall cladding is constantly exposed to sun and rain, as well as alternating hot and cold temperatures, making it prone to warping, cracking, and aging and peeling of the decorative layer. The composite panel provided by this invention, through the synergistic effect of a symmetrical balanced structure, a high-modulus glass fiber reinforcement layer, and a sliding thermal expansion release structure, can suppress temperature gradient deformation and release thermal stress, ensuring the long-term flatness and stability of the imitation stone appearance. The ASA weather-resistant decorative layer stably presents the texture and color of imitation stone, possessing excellent UV resistance and aging resistance, meeting the aesthetic and durability requirements of exterior wall decoration. The polyurethane foam core layer combines thermal insulation and lightweight properties, adapting to the development needs of efficient installation and energy conservation in prefabricated buildings. Furthermore, the addition of solid waste composite fillers to the polyurethane foam core layer enhances structural strength and meets the requirements of green building materials. By limiting its application to composite imitation stone exterior wall cladding, it achieves an integrated system of five functions: decoration, insulation, structure, weather resistance, and environmental protection.

[0037] To further illustrate the composite plate, its preparation method, and its application provided by the present invention, the following embodiments are provided.

[0038] Example 1 A composite panel includes, from the outside to the inside, the following layers arranged sequentially: an ASA weather-resistant decorative layer, an anti-warping reinforcement layer, a polyurethane foam structural layer, and a balancing layer. The ASA weather-resistant decorative layer is 0.8 mm thick; the anti-warping reinforcement layer is 1.2 mm thick, uses a first glass fiber mesh, and has a flexural modulus of 15 GPa; the balancing layer is 0.8 mm thick, with a thickness ratio of 1:1 to the decorative layer; the polyurethane foam structural layer is 30 mm thick, with a composite filler of oyster shell powder and waste glass powder added in a 1:1 mass ratio, and the filler particle size is 100 mesh; the panel edge is 30 mm thick and 30 mm wide; the thermal expansion release structure consists of strip-shaped sliding mounting holes, 10 mm long and 6.0 mm wide, with the hole length direction aligned with the main direction of thermal expansion of the composite panel, used in conjunction with locking screws with washers.

[0039] The preparation method is as follows: ASA sheet is heated to 200℃ and calendered to obtain an ASA weather-resistant decorative layer; an anti-warping reinforcement layer is laid flat on the inner side of the ASA weather-resistant decorative layer to ensure no wrinkles or curling edges; oyster shell powder and waste glass powder are added to polyurethane component A (polyol combination material, containing polyether polyol, cyclopentane / water foaming agent, amine catalyst, and organosilicon foam stabilizer) and mixed evenly, and then fully mixed with component B (isocyanate, polymethylene polyphenyl isocyanate, crude MDI) at a mass ratio of 1:1 and injected into a mold for foaming to obtain a polyurethane foam structure layer; before the foam structure layer is fully cured, a balancing layer is tightly attached to its inner side to form the main structure of the composite board; strip-shaped sliding mounting holes are processed on the edge of the main structure board by stamping to obtain the finished composite board.

[0040] Example 2 A composite board with a structure basically the same as that in Example 1, differing only in that: the composite filler added to the polyurethane foam structural layer has a particle size of 200 mesh, and the mass ratio of oyster shell powder to waste glass powder is 1:2; the strip-shaped sliding mounting holes in the thermal expansion release structure have a length of 12 mm and a width of 5.5 mm. The remaining structure, materials, thickness, modulus, and preparation steps are consistent with Example 1.

[0041] Comparative Example 1 Compared with Example 1, no anti-warping reinforcement layer and balancing layer are provided, while the other materials, thicknesses and preparation processes are the same.

[0042] Comparative Example 2 Compared with Example 1, no thermal expansion release structure is provided, and a conventional circular fixing hole is used. The rest of the structure, materials and processes are the same.

[0043] Comparative Example 3 Compared with Example 1, the polyurethane foam core layer does not contain oyster shell powder and waste glass powder composite filler, while the rest of the structure, materials and processes are the same.

[0044] The samples obtained from Examples 1-2 and Comparative Examples 1-3 were subjected to performance tests. The test environment temperature was (23±2)℃, and the relative humidity was (50±5)%. The sample size was 300mm×300mm, and three samples were tested in each group. The average value was taken. The test items, methods, and results are as follows: Thermal cycling warpage: The test conditions are to place the sample horizontally and cycle it 100 times at -30℃ to 80℃. The maximum deflection of the midpoint of the long side of the sample relative to the connection of the two ends is measured, and the warpage is calculated in mm / m. Warpage ≤ 1.0 mm / m is considered acceptable.

[0045] Compressive strength: Tested according to GB / T 8813-2008 "Test Method for Compression Properties of Rigid Foamed Plastics", unit is MPa.

[0046] Dimensional stability: Refer to GB / T 8811-2021 "Test method for dimensional stability of rigid foamed plastics", place at 70℃ for 48h and test the dimensional change rate, in %; among which, dimensional change rate ≤0.2% is excellent.

[0047] Thermal expansion stress relief performance: The sample was heated in an 80℃ oven for 2 hours, and the presence of cracks, bulges, hole edge damage, warping deformation, etc. was observed and recorded.

[0048] The test results are shown in the table below: Results Analysis: The thermal cycling warpage of Examples 1 and 2 of this invention is lower than that of the comparative groups, indicating superior dimensional stability. The addition of the anti-warpage reinforcement layer and the balancing layer can offset the bending stress generated by the temperature gradient and suppress warpage deformation. The thermal expansion release structure can effectively release thermal stress, preventing the board from cracking and bulging. The addition of composite fillers made from oyster shell powder and waste glass powder can improve the compressive strength and dimensional stability of the foamed core layer. Overall, this invention, through the synergistic design of structure and materials, improves the composite board in terms of thermal cycling warpage resistance, thermal stress release, mechanical properties, and durability, making it particularly suitable for long-term outdoor use as a composite imitation stone exterior wall panel.

[0049] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0050] Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first," "second," or "third" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0051] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows for communication; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0052] It is understood that those skilled in the art can make equivalent substitutions or changes to the technical solution and inventive concept of the present invention, and all such changes or substitutions should fall within the protection scope of the present invention.

Claims

1. A composite board, characterized by, The composite panel comprises, from the outside to the inside, a decorative layer, an anti-warping reinforcement layer, a foamed core layer, and a balancing layer. The anti-warping reinforcement layer is a first glass fiber mesh, used to improve the in-plane stiffness of the composite panel and suppress inward bending deformation. The balancing layer is a second glass fiber mesh, used in conjunction with the decorative layer to counteract the bending stress caused by the temperature gradient. The composite panel also includes a thermal expansion release structure disposed on the edge of the panel, which allows the composite panel to undergo micro-displacement when the temperature changes in order to release thermal expansion stress.

2. The composite sheet according to claim 1, characterized by The modulus of the first glass fiber mesh is 10-20 GPa.

3. The composite sheet of claim 1, wherein The thickness of the anti-warping reinforcement layer is 1.1-1.3 mm.

4. The composite sheet of claim 1, wherein The decorative layer is an ASA weather-resistant decorative layer with a thickness of 0.7-0.9 mm.

5. The composite sheet according to claim 4, wherein The thickness ratio of the balancing layer to the decorative layer is 1:

1.

6. The composite sheet of claim 1, wherein The foamed core layer is a polyurethane foam structure layer with a thickness of 28-32mm.

7. The composite board according to claim 6, characterized in that, The polyurethane foam structural layer contains a composite filler composed of oyster shell powder and waste glass powder; the particle size of the composite filler is 50-300 mesh.

8. The composite board according to claim 1, characterized in that, The thermal expansion release structure consists of a strip-shaped sliding mounting hole and a locking screw that mates with the strip-shaped sliding mounting hole; the length direction of the strip-shaped sliding mounting hole is consistent with the main direction of thermal expansion of the composite plate.

9. A method for preparing a composite plate according to any one of claims 1-8, characterized in that, The process includes the following steps: heating and pressing a sheet to form a decorative layer; attaching an anti-warping reinforcement layer to the inner side of the decorative layer; foaming the inner side of the anti-warping reinforcement layer to form a foamed core layer; attaching a balancing layer to the inner side of the foamed core layer before it cures to form a main structure; and processing the edge of the main structure to form a thermal expansion release structure to obtain the composite board.

10. An application of the composite panel as described in any one of claims 1-8, characterized in that, The composite board is applied to composite imitation stone exterior wall cladding.

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