A high temperature resistant foam sandwich structure and method of manufacturing the same

Abstract

The present application relates to a kind of high-temperature-resistant foam sandwich structure and its manufacturing method, belong to high-temperature-resistant composite material technical field.The high-temperature-resistant foam sandwich structure includes foam layer and the panel arranged on the upper and lower surfaces of the foam layer, the foam layer is fiber reinforced polyimide foam, the panel is polyimide composite material, the foam layer and the panel are bonded by polyimide adhesive film.The high-temperature-resistant foam sandwich structure provided by the present application has lightweight characteristics and excellent high-temperature mechanical bearing performance.

Description

Technical Field

[0001] This invention relates to the field of high-temperature resistant composite materials technology, and in particular to a high-temperature resistant foam sandwich structure and its manufacturing method. Background Technology

[0002] Currently, with the development of aerospace vehicles, future aircraft face the demands of higher cruising altitudes and higher maneuvering speeds, requiring not only extreme lightweighting but also higher service temperatures. Composite material structures, due to their high specific strength, high specific stiffness, and excellent lightweight properties, are widely used in the aerospace field. However, traditional composite materials exhibit poor mechanical properties and durability at high temperatures, making it difficult to meet the higher service temperature requirements of modern aircraft.

[0003] Therefore, there is an urgent need to provide a composite material with excellent temperature resistance to meet the higher service temperature requirements of modern aircraft. Summary of the Invention

[0004] To address one or more technical problems existing in the prior art, the present invention provides a high-temperature resistant foam sandwich structure and its manufacturing method. The high-temperature resistant foam sandwich structure provided by the present invention has lightweight characteristics and excellent high-temperature mechanical load-bearing performance, which can effectively solve the problem that existing composite material structures are difficult to balance lightweight characteristics and high-temperature mechanical load-bearing performance.

[0005] The present invention provides a high-temperature resistant foam sandwich structure in a first aspect, comprising a foam layer and a panel disposed on the upper and lower surfaces of the foam layer, wherein the foam layer is fiber-reinforced polyimide foam, the panel is a polyimide composite material, and the foam layer and the panel are bonded together by a polyimide adhesive film.

[0006] Preferably, the fiber-reinforced polyimide foam is quartz fiber-reinforced polyimide foam; and / or

[0007] The polyimide composite material is a carbon fiber reinforced polyimide composite material.

[0008] Preferably, the fiber-reinforced polyimide foam contains 5 to 6.25 wt% fiber.

[0009] Preferably, the thickness of the foam layer is not less than 8 mm;

[0010] The thickness of the panel is no greater than 1.5 mm; and / or

[0011] The thickness of the polyimide film is 0.15–0.25 mm.

[0012] In a second aspect, the present invention provides a method for manufacturing the high-temperature resistant foam sandwich structure described in the first aspect, comprising the following steps:

[0013] After laying out polyimide prepreg, polyimide film and fiber-reinforced polyimide foam, the mixture is cured in an autoclave to obtain a high-temperature resistant foam sandwich structure.

[0014] After layup, the layers consist of, from bottom to top, a polyimide prepreg layer, a polyimide film, a fiber-reinforced polyimide foam, a polyimide film, and a polyimide prepreg layer.

[0015] Preferably, the polyimide prepreg layer is laid in a quasi-isotropic layup sequence of (0 / 45 / 90 / -45 / -45 / 90 / 45 / 0); preferably, the thickness of the polyimide prepreg layer is not greater than 1.5 mm.

[0016] Preferably, the method for preparing the fiber-reinforced polyimide foam includes: (i) mixing polyimide, foaming agent and solvent to obtain a mixture; (ii) impregnating fibers in the mixture and curing them to obtain fiber-reinforced polyimide foam.

[0017] Preferably, the mass ratio of the fiber to polyimide is 1:15 to 19;

[0018] The mass ratio of the foaming agent to polyimide is 1:5 to 10. Preferably, the foaming agent includes, but is not limited to, one or more of azodicarbonamide, amino-based foaming agents, and organic peroxides; and / or

[0019] The mass ratio of the solvent to polyimide is 4 to 10:1. Preferably, the solvent includes, but is not limited to, one or more of N,N-dimethylformamide (DMF) and dimethyl sulfoxide.

[0020] Preferably, the curing temperature is 350-380℃ and the pressure is 2-3MPa; more preferably, the curing is performed by first raising the temperature to 350℃ and holding it for 1-2 hours, then raising it to 360℃ and holding it for 1-2 hours, and finally raising it to 370-380℃, applying a pressure of 2-3MPa, and holding it for 1-2 hours.

[0021] Preferably, the autoclave curing process involves raising the temperature to 240–250°C at a rate of 3–5°C / min and holding it for 1–2 hours, then raising it to 300–320°C and holding it for 0.5–1 hour, then raising it to 330–340°C and applying a pressure of 0.4–0.5 MPa, and finally raising it to 350–380°C and holding it for 3–4 hours.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects:

[0023] The high-temperature resistant foam sandwich structure provided by this invention uses a polyimide composite material as the face panel and fiber-reinforced polyimide foam as the intermediate foam layer, with a polyimide adhesive film bonding the face panel and the foam layer. Each layer uses a high-temperature resistant polyimide resin system, exhibiting good compatibility and high-temperature resistance. By combining lightweight, high-temperature compressive strength fiber-reinforced polyimide foam with a polyimide composite material face panel, the flexural stiffness and high-temperature resistance of the foam sandwich structure can be improved, solving the problems of large thickness and high cost of existing composite materials. The high-temperature resistant foam sandwich structure provided by this invention possesses lightweight characteristics and excellent high-temperature mechanical load-bearing capacity, effectively solving the problem that existing composite material structures struggle to balance lightweight characteristics and high-temperature mechanical load-bearing capacity.

[0024] This invention employs a layering process involving polyimide prepreg, polyimide film, and fiber-reinforced polyimide foam to create a sandwich structure comprising, from bottom to top, a polyimide prepreg layer, a polyimide film, fiber-reinforced polyimide foam, another polyimide film, and a polyimide prepreg layer. An autoclave curing process is then used to ensure that the fiber-reinforced polyimide foam structure is not damaged, allowing the polyimide prepreg layer to cure and form a high-temperature resistant foam sandwich structure with an integrated polyimide composite panel and fiber-reinforced polyimide foam. The autoclave curing process used in this invention avoids the problem of foam layer collapse that can occur with compression molding, which requires applying significant pressure to ensure proper compaction of the mold. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the high-temperature resistant foam sandwich structure provided by the present invention.

[0027] Figure reference numerals: 11-foam layer; 12-polyimide film; 13-panel. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0029] The present invention provides a high-temperature resistant foam sandwich structure in a first aspect, comprising a foam layer and a panel disposed on the upper and lower surfaces of the foam layer, wherein the foam layer is fiber-reinforced polyimide foam, the panel is a polyimide composite material, and the foam layer and the panel are bonded together by a polyimide adhesive film.

[0030] The high-temperature resistant foam sandwich structure provided by this invention uses a polyimide composite material as the face panel and fiber-reinforced polyimide foam as the intermediate foam layer, with a polyimide adhesive film bonding the face panel and the foam layer. Each layer uses a high-temperature resistant polyimide resin system, exhibiting good compatibility and high-temperature resistance. By combining lightweight, high-temperature compressive strength fiber-reinforced polyimide foam with a polyimide composite material face panel, the flexural stiffness and high-temperature resistance of the foam sandwich structure can be improved, solving the problems of large thickness and high cost of existing composite materials. The high-temperature resistant foam sandwich structure provided by this invention possesses lightweight characteristics and excellent high-temperature mechanical load-bearing capacity, effectively solving the problem that existing composite material structures struggle to balance lightweight characteristics and high-temperature mechanical load-bearing capacity.

[0031] According to some preferred embodiments, the fiber-reinforced polyimide foam is quartz fiber-reinforced polyimide foam.

[0032] According to some preferred embodiments, the polyimide composite material is a carbon fiber reinforced polyimide composite material.

[0033] According to some preferred embodiments, the fiber-reinforced polyimide foam contains 5 to 6.25 wt% fibers.

[0034] According to some preferred embodiments, the thickness of the foam layer is not less than 8 mm.

[0035] According to some preferred embodiments, the thickness of the panel is no more than 1.5 mm.

[0036] According to some preferred embodiments, the thickness of the polyimide film is 0.15 to 0.25 mm.

[0037] In a second aspect, the present invention provides a method for manufacturing the high-temperature resistant foam sandwich structure described in the first aspect, comprising the following steps:

[0038] After laying out polyimide prepreg, polyimide film and fiber-reinforced polyimide foam, the mixture is cured in an autoclave to obtain a high-temperature resistant foam sandwich structure.

[0039] After layup, the layers consist of, from bottom to top, a polyimide prepreg layer, a polyimide film, a fiber-reinforced polyimide foam, a polyimide film, and a polyimide prepreg layer.

[0040] This invention employs a layering process involving polyimide prepreg, polyimide film, and fiber-reinforced polyimide foam to create a sandwich structure comprising, from bottom to top, a polyimide prepreg layer, a polyimide film, fiber-reinforced polyimide foam, another polyimide film, and a polyimide prepreg layer. An autoclave curing process is then used to ensure that the fiber-reinforced polyimide foam structure is not damaged, allowing the polyimide prepreg layer to cure and form a high-temperature resistant foam sandwich structure with an integrated polyimide composite panel and fiber-reinforced polyimide foam. The autoclave curing process used in this invention avoids the problem of foam layer collapse that can occur with compression molding, which requires applying significant pressure to ensure proper compaction of the mold.

[0041] The manufacturing method of the high-temperature resistant foam sandwich structure of the present invention is simple and low-cost, and solves the problem of complex manufacturing process of existing composite materials.

[0042] According to some preferred embodiments, the polyimide prepreg in the polyimide prepreg layer is laid in a quasi-isotropic layup sequence of (0 / 45 / 90 / -45 / -45 / 90 / 45 / 0); preferably, the thickness of the polyimide prepreg layer is no greater than 1.5 mm. It should be noted that when the thickness of the polyimide prepreg layer is controlled within the above range, applying a pressure of 0.4–0.5 MPa during autoclave curing ensures a panel with a complete structure and excellent performance, without damaging the structure of the fiber-reinforced polyimide foam. The inventors have found that if the thickness is too large, greater pressure is required during autoclave curing to ensure the polyimide prepreg cures to obtain a panel with a complete structure and excellent performance; however, greater pressure can cause the fiber-reinforced polyimide foam layer to collapse, resulting in structural damage.

[0043] According to some preferred embodiments, the method for preparing the fiber-reinforced polyimide foam includes: (i) mixing polyimide, foaming agent and solvent to obtain a mixture; (ii) impregnating fibers in the mixture and curing them to obtain fiber-reinforced polyimide foam.

[0044] According to some preferred embodiments, the mass ratio of the fiber to polyimide is 1:15 to 19.

[0045] According to some preferred embodiments, the mass ratio of the foaming agent to polyimide is 1:5 to 10. Preferably, the foaming agent includes, but is not limited to, one or more of azodicarbonamide, amino-based foaming agents, and organic peroxides. The present invention preferably uses the above-mentioned chemical foaming agent, which decomposes at high temperatures to produce gases such as nitrogen and carbon dioxide.

[0046] According to some preferred embodiments, the mass ratio of the solvent to polyimide is 4 to 10:1. Preferably, the solvent includes, but is not limited to, one or more of N,N-dimethylformamide (DMF) and dimethyl sulfoxide.

[0047] According to some preferred embodiments, the curing temperature is 350–380°C (e.g., 350°C, 355°C, 360°C, 365°C, 370°C, 375°C, or 380°C), and the pressure is 2–3 MPa. Preferably, the curing involves first raising the temperature to 350°C and holding it at that temperature for 1–2 hours, then raising it to 360°C and holding it at that temperature for 1–2 hours, and finally raising it to 370–380°C, applying a pressure of 2–3 MPa, and holding it at that temperature for 1–2 hours. In this invention, the temperature is first raised to 350°C to allow the polyamide to undergo initial cross-linking, initiating the formation of the foam structure. Then, the temperature is raised to 360°C to accelerate the cross-linking reaction, gradually generating gas and expanding the cell structure. Finally, the temperature is raised to 370°C–380°C and a pressure of 2–3 MPa is applied to completely cure the polyimide, controlling the cell structure and foam density, thus stabilizing the foam structure and improving the material strength. After curing, the foam is slowly cooled to room temperature at a rate of 2–5 °C / min to prevent the foam structure from shrinking or generating internal stress due to rapid cooling.

[0048] According to some preferred embodiments, the autoclave curing process involves raising the temperature to 240-250°C at a heating rate of 3-5°C / min and holding it for 1-2 hours, then raising it to 300-320°C and holding it for 0.5-1 hours, then raising it to 330-340°C and applying a pressure of 0.4-0.5 MPa, and finally raising it to 350-380°C and holding it for 3-4 hours.

[0049] To ensure the structural integrity of the fiber-reinforced polyimide foam during the molding process, the pressure during the autoclave curing process of this invention is controlled within the aforementioned range. The inventors have discovered that during autoclave curing, the fiber-reinforced polyimide foam exhibits good compressive strength within the aforementioned pressure range; however, when the pressure reaches 0.6 MPa or higher, the fiber-reinforced polyimide foam begins to collapse.

[0050] Because the curing requirements of polyimide systems are stringent, problems such as softening of polyimide foam, damage or combustion of molding auxiliary materials can easily occur at high temperatures. In order to ensure that the molding process yields a high-temperature resistant foam sandwich structure with lightweight characteristics and high-temperature mechanical load-bearing capacity, the present invention preferably uses the above autoclave curing molding process parameters.

[0051] To more clearly illustrate the technical solution and advantages of the present invention, the present invention will be further described below with reference to embodiments. The present invention does not specifically limit the source of the reagents used in the embodiments and comparative examples; they can be directly purchased or synthesized in-house.

[0052] Example 1

[0053] S1. Polyimide resin, azodicarbonamide (foaming agent), and N,N-dimethylformamide are mixed to obtain a homogeneous mixture. Quartz fibers are impregnated in the mixture until they completely absorb the polyimide solution. The impregnated quartz fibers are then cured according to the following procedure: first, the temperature is raised to 350℃ and held for 1 hour, then at 360℃ for 1 hour, and finally, a pressure of 3MPa is applied at 380℃ and held for 1 hour. After curing, the mixture is cooled to room temperature at a rate of 3℃ / min to obtain quartz fiber reinforced polyimide foam.

[0054] S2. The polyimide prepreg, polyimide film, and quartz fiber reinforced polyimide foam are laid up sequentially from bottom to top, including a polyimide prepreg layer (1 mm thick), a polyimide film (0.2 mm thick), a fiber reinforced polyimide foam (8 mm thick), a polyimide film (0.2 mm thick), and a polyimide prepreg layer (1 mm thick). The polyimide prepreg layer is laid up in a quasi-isotropic layup sequence (0 / 45 / 90 / -45 / -45 / 90 / 45 / 0).

[0055] S3. The laminated sandwich structure is placed in an autoclave containing a release cloth and wrapped with breathable cotton. A vacuum bag is then placed on top, with the vacuum tubing positioned correctly. The edges of the vacuum bag are sealed with high-temperature sealant. Vacuuming is performed until a vacuum level of 99% is reached. Finally, autoclave curing is carried out. The autoclave curing procedure is as follows: The temperature is increased to 240°C at a rate of 3°C / min and held for 1 hour; then increased to 300°C and held for 0.5 hours; then increased to 330°C and pressure is applied at 0.4 MPa; finally, the temperature is increased to 380°C and held under pressure for 3 hours, and then reduced to below 60°C to obtain a high-temperature resistant foam sandwich structure. The performance data of the quartz fiber reinforced polyimide foam obtained in this embodiment are shown in Table 1, and the performance data of the high-temperature resistant foam sandwich structure are shown in Table 2.

[0056] Example 2

[0057] The process is basically the same as in Example 1, except that the autoclave curing procedure is as follows: the temperature is increased to 240°C at a rate of 3°C / min and held for 1 hour, then increased to 300°C and held for 0.5 hours, then increased to 330°C and pressure of 0.5 MPa is applied, and finally the temperature is increased to 380°C and held for 3 hours, and then reduced to below 60°C.

[0058] Comparative Example 1

[0059] The process is basically the same as in Example 1, except that polyimide foam is used instead of quartz fiber to reinforce the polyimide foam, that is, no quartz fiber is added in step S1.

[0060] Because no quartz fiber was added, the polyimide foam collapsed significantly under the same molding pressure, and a reliable load-bearing structure was not formed after molding.

[0061] The performance data of the quartz fiber reinforced polyimide foam prepared in this comparative example are shown in Table 1, and the performance data of the high-temperature resistant foam sandwich structure are shown in Table 2.

[0062] Comparative Example 2

[0063] The process is basically the same as in Example 1, except that the autoclave curing procedure is as follows: the temperature is increased to 240°C at a rate of 3°C / min and held for 1 hour, then increased to 300°C and held for 0.5 hours, then increased to 330°C and pressure of 0.6 MPa is applied, and finally the temperature is increased to 380°C and held for 3 hours, and then reduced to below 60°C.

[0064] Under a pressure of 0.6 MPa, the quartz fiber reinforced polyimide foam core layer begins to show slight collapse during the molding process.

[0065] The performance data of the quartz fiber reinforced polyimide foam prepared in this comparative example are shown in Table 1, and the performance data of the high-temperature resistant foam sandwich structure are shown in Table 2.

[0066] Table 1. Performance data of foam layers obtained in the embodiments and comparative examples of the present invention.

[0067]

[0068] Table 2. Performance data of the foam sandwich structures prepared in the embodiments and comparative examples of the present invention.

[0069]

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high temperature resistant foam sandwich structure, characterized in that, The high-temperature-resistant foam sandwich structure comprises a foam layer and a panel arranged on the upper and lower surfaces of the foam layer, the foam layer is a fiber-reinforced polyimide foam, and the panel is a polyimide composite material, the foam layer and the panel are bonded by a polyimide adhesive film under a heat-pressure tank curing process; The panel comprises a polyimide prepreg layer, and the polyimide prepreg in the polyimide prepreg layer is laid in a quasi-isotropic lay-up sequence of 0 / 45 / 90 / -45 / -45 / 90 / 45 / 0; the thickness of the polyimide prepreg layer is not greater than 1.5 mm; The thickness of the polyimide adhesive film is 0.15-0.25 mm; The heat-pressure tank curing forming is performed at a temperature increasing rate of 3-5 ℃ / min, the temperature is first increased to 240-250 ℃ and kept for 1-2 h, then increased to 300-320 ℃ and kept for 0.5-1 h, then increased to 330-340 ℃ and a pressure of 0.4-0.5 MPa is applied, and finally increased to 350-380 ℃ and kept for 3-4 h.

2. The high temperature resistant foam sandwich structure of claim 1, wherein, The fiber-reinforced polyimide foam is a quartz fiber-reinforced polyimide foam; and / or The polyimide composite material is a carbon fiber-reinforced polyimide composite material.

3. The high temperature resistant foam sandwich structure of claim 1, wherein, The fibers account for 5-6.25 wt% in the fiber-reinforced polyimide foam.

4. The high temperature resistant foam sandwich structure of claim 1, wherein, The thickness of the foam layer is not less than 8 mm; The thickness of the panel is not greater than 1.5 mm.

5. A method of manufacturing the high temperature resistant foam sandwich structure according to any one of claims 1 to 4, characterized in that, The method comprises the following steps: The polyimide prepreg, the polyimide adhesive film and the fiber-reinforced polyimide foam are laid and then subjected to heat-pressure tank curing forming to obtain the high-temperature-resistant foam sandwich structure; After the laying, the polyimide prepreg layer, the polyimide adhesive film, the fiber-reinforced polyimide foam, the polyimide adhesive film and the polyimide prepreg layer are sequentially arranged from bottom to top.

6. The production method according to claim 5, wherein The polyimide prepreg in the polyimide prepreg layer is laid in a quasi-isotropic lay-up sequence of 0 / 45 / 90 / -45 / -45 / 90 / 45 / 0; the thickness of the polyimide prepreg layer is not greater than 1.5 mm.

7. The production method according to claim 5, wherein The preparation method of the fiber-reinforced polyimide foam comprises: (i) mixing polyimide, a foaming agent and a solvent to obtain a mixed solution; (ii) impregnating fibers in the mixed solution and then subjecting to curing to obtain the fiber-reinforced polyimide foam.

8. The production method according to claim 7, wherein The mass ratio of the fibers to the polyimide is 1:15-19; The mass ratio of the foaming agent to the polyimide is 1:5-10, the foaming agent comprises one or more of azodicarbonamide, amino foaming agent and organic peroxide; and / or The mass ratio of the solvent to the polyimide is 4-10:1, and the solvent comprises one or more of N,N-dimethylformamide (DMF) and dimethyl sulfoxide.

9. The production method according to claim 7, wherein The curing is performed at a temperature of 350-380 ℃ and a pressure of 2-3 MPa, and the curing comprises the following steps: first increasing the temperature to 350 ℃ and keeping for 1-2 h, then increasing the temperature to 360 ℃ and keeping for 1-2 h, and finally increasing the temperature to 370-380 ℃ and applying a pressure of 2-3 MPa and keeping for 1-2 h.

Images