High-temperature-resistant foam sandwich structure and manufacturing method thereof

Abstract

The invention relates to a high-temperature-resistant foam sandwich structure and a manufacturing method thereof, and belongs to the technical field of high-temperature-resistant composite materials. The high-temperature-resistant foam sandwich structure comprises a foam layer and panels arranged on the upper surface and the lower surface of the foam layer, the foam layer is made of fiber-reinforced polyimide foam, the panels are made of polyimide composite materials, and the foam layer and the panels are bonded through polyimide adhesive films. The high-temperature-resistant foam sandwich structure provided by the invention has the characteristic of light weight and excellent high-temperature mechanical bearing performance.

Description

Technical Field

[0001] The invention relates to the technical field of high temperature resistant composite materials, and in particular to a high temperature resistant foam sandwich structure and a manufacturing method thereof. Background Art

[0002] At present, with the development of aerospace vehicles, future aircraft are facing the requirements of higher cruising altitude and higher maneuvering speed, which not only require extreme lightweight, but also face higher service temperature. Composite materials are widely used in the aerospace field due to their high specific strength, high specific stiffness and excellent lightweight properties. However, traditional composite materials have poor mechanical properties and durability in high temperature environments, and it is difficult to meet the requirements of modern aircraft for higher service temperatures.

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

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

[0005] In a first aspect, the present invention provides a high temperature resistant foam sandwich structure, comprising a foam layer and panels arranged 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 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 in the fiber-reinforced polyimide foam accounts for 5-6.25 wt%.

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

[0010] The thickness of the panel is no more 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 according to the first aspect, comprising the following steps:

[0013] After the polyimide prepreg, the polyimide adhesive film and the fiber-reinforced polyimide foam are layered, they are cured and formed in an autoclave to obtain a high-temperature resistant foam sandwich structure;

[0014] After laying, the layers include, from bottom to top, a polyimide prepreg layer, a polyimide adhesive film, a fiber-reinforced polyimide foam, a polyimide adhesive film and a polyimide prepreg layer.

[0015] Preferably, the polyimide prepreg in the polyimide prepreg layer is laid in a quasi-isotropic laying order 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 comprises: (i) mixing polyimide, a foaming agent and a solvent to obtain a mixed solution; (ii) immersing fibers in the mixed solution and curing the mixed solution to obtain the fiber-reinforced polyimide foam.

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

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

[0019] The mass ratio of the solvent to the 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°C and the pressure is 2-3MPa; preferably, the curing is to first raise the temperature to 350°C and keep it for 1-2h, then raise it to 360°C and keep it for 1-2h, and finally raise it to 370-380°C, apply 2-3MPa pressure and keep it for 1-2h.

[0021] Preferably, the autoclave curing molding is performed at a heating rate of 3-5°C / min, first raising the temperature to 240-250°C and keeping it warm for 1-2h, then raising the temperature to 300-320°C and keeping it warm for 0.5-1h, then raising the temperature to 330-340°C and applying a pressure of 0.4-0.5MPa, and finally raising the temperature to 350-380°C and keeping it warm for 3-4h.

[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 the present invention uses a polyimide composite material as a panel, a fiber reinforced polyimide foam as an intermediate foam layer, and a polyimide adhesive film is used to bond the panel and the foam layer. Each layer adopts a high temperature resistant polyimide resin system, which has good matching and high temperature resistance. The use of fiber reinforced polyimide foam with lightweight characteristics and high high temperature compression strength and polyimide composite panel composite can improve the bending stiffness and high temperature resistance of the foam sandwich structure, and solve the problem of large thickness and high cost of existing composite materials. The high temperature resistant foam sandwich structure provided by the present invention has lightweight characteristics and excellent high temperature mechanical bearing performance, which can effectively solve the problem that it is difficult for existing composite material structures to take into account both lightweight characteristics and mechanical bearing performance at high temperatures.

[0024] The present invention uses polyimide prepreg, polyimide film, and fiber-reinforced polyimide foam to lay up a sandwich structure including a polyimide prepreg layer, a polyimide film, a fiber-reinforced polyimide foam, a polyimide film, and a polyimide prepreg layer from bottom to top, and then uses an autoclave curing molding process to ensure that the fiber-reinforced polyimide foam structure is not damaged, and the polyimide prepreg layer is cured to obtain a polyimide composite material panel and a fiber-reinforced polyimide foam composite to form a high-temperature resistant foam sandwich structure with an integrated structure. The present invention uses an autoclave curing molding process to form a high-temperature resistant foam sandwich structure to avoid the problem of applying a large pressure to ensure that the mold is fully compacted and pressed when using a molding process to cause the foam layer structure to collapse. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

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

[0027] Figure numerals: 11 - foam layer; 12 - polyimide film; 13 - panel. DETAILED DESCRIPTION

[0028] In order to make the purpose, 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 part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0029] In a first aspect, the present invention provides a high temperature resistant foam sandwich structure, comprising a foam layer and panels arranged 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 by a polyimide adhesive film.

[0030] The high temperature resistant foam sandwich structure provided by the present invention uses a polyimide composite material as a panel, a fiber reinforced polyimide foam as an intermediate foam layer, and a polyimide adhesive film is used to bond the panel and the foam layer. Each layer adopts a high temperature resistant polyimide resin system, which has good matching and high temperature resistance. The use of fiber reinforced polyimide foam with lightweight characteristics and high high temperature compression strength and polyimide composite panel composite can improve the bending stiffness and high temperature resistance of the foam sandwich structure, and solve the problem of large thickness and high cost of existing composite materials. The high temperature resistant foam sandwich structure provided by the present invention has lightweight characteristics and excellent high temperature mechanical bearing performance, which can effectively solve the problem that it is difficult for existing composite material structures to take into account both lightweight characteristics and mechanical bearing performance at high temperatures.

[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 in the fiber-reinforced polyimide foam accounts for 5 to 6.25 wt %.

[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 greater than 1.5 mm.

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

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

[0038] After the polyimide prepreg, the polyimide adhesive film and the fiber-reinforced polyimide foam are layered, they are cured and formed in an autoclave to obtain a high-temperature resistant foam sandwich structure;

[0039] After laying, the layers include, from bottom to top, a polyimide prepreg layer, a polyimide adhesive film, a fiber-reinforced polyimide foam, a polyimide adhesive film and a polyimide prepreg layer.

[0040] The present invention uses polyimide prepreg, polyimide film, and fiber-reinforced polyimide foam to lay up a sandwich structure including a polyimide prepreg layer, a polyimide film, a fiber-reinforced polyimide foam, a polyimide film, and a polyimide prepreg layer from bottom to top, and then uses an autoclave curing molding process to ensure that the fiber-reinforced polyimide foam structure is not damaged, and the polyimide prepreg layer is cured to obtain a polyimide composite material panel and a fiber-reinforced polyimide foam composite to form a high-temperature resistant foam sandwich structure with an integrated structure. The present invention uses an autoclave curing molding process to form a high-temperature resistant foam sandwich structure to avoid the problem of applying a large pressure to ensure that the mold is fully compacted and pressed when using a molding process to cause the foam layer structure to collapse.

[0041] The manufacturing method of the high temperature resistant foam sandwich structure of the present invention has simple process and low cost, and solves the problem of complicated 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 laying order of (0 / 45 / 90 / -45 / -45 / 90 / 45 / 0); preferably, the thickness of the polyimide prepreg layer is not more than 1.5 mm. It should be noted that when the thickness of the polyimide prepreg layer is controlled within the above range, a pressure of 0.4 to 0.5 MPa can be applied during the autoclave curing process to ensure that the panel has a complete structure and excellent performance, while the structure of the fiber-reinforced polyimide foam is not destroyed. The inventors have found that if the thickness is too large, a greater pressure is required during the autoclave curing process to ensure that the polyimide prepreg is cured to obtain a panel with a complete structure and excellent performance, and a greater pressure will cause the fiber-reinforced polyimide foam layer to collapse, and the structure will be destroyed.

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

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

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

[0046] According to some preferred embodiments, the mass ratio of the solvent to the 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 (for example, 350°C, 355°C, 360°C, 365°C, 370°C, 375°C or 380°C), and the pressure is 2-3MPa. Preferably, the curing is to first raise the temperature to 350°C and keep it warm for 1-2h, then raise it to 360°C and keep it warm for 1-2h, and finally raise it to 370-380°C and apply 2-3MPa pressure and keep it warm for 1-2h. The present invention first raises the temperature to 350°C to make the polyamide initially cross-linked and start the formation of the foam structure, then raises the temperature to 360°C to accelerate the cross-linking reaction, gradually generate gas, expand the pores, and finally raise the temperature to 370°C-380°C and apply 2-3MPa pressure to completely cure the polyimide, control the pore structure and the density of the foam, shape the foam structure and improve the material strength. After curing is completed, slowly cool to room temperature at a cooling rate of 2 to 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 molding is performed at a heating rate of 3 to 5°C / min, first raising the temperature to 240 to 250°C and keeping it warm for 1 to 2 hours, then raising the temperature to 300 to 320°C and keeping it warm for 0.5 to 1 hour, then raising the temperature to 330 to 340°C and applying a pressure of 0.4 to 0.5 MPa, and finally raising the temperature to 350 to 380°C and keeping it warm for 3 to 4 hours.

[0049] In order to ensure the structural integrity of the fiber-reinforced polyimide foam during the molding process, the pressure during the autoclave curing molding process of the present invention is controlled within the above range. The inventors found that during the autoclave curing molding process, the fiber-reinforced polyimide foam has good compressive resistance within the above pressure range; when the pressure reaches 0.6 MPa or above, the fiber-reinforced polyimide foam will begin to collapse.

[0050] Since the polyimide system has stringent curing requirements, problems such as polyimide foam softening and molding auxiliary materials being easily damaged or burned may occur at high temperatures. In order to ensure that a high-temperature resistant foam sandwich structure with an integrated structure having lightweight characteristics and high-temperature mechanical bearing properties is obtained by molding, the present invention preferably uses the above autoclave curing molding process parameters.

[0051] In order to more clearly illustrate the technical solutions and advantages of the present invention, the present invention is further described below in conjunction with the examples. The present invention does not specifically limit the sources of the reagents used in the examples and comparative examples, and the reagents can be directly purchased or synthesized by themselves.

[0052] Example 1

[0053] S1. Mix polyimide resin, azodicarbonamide (foaming agent) and N,N-dimethylformamide to obtain a uniform mixed solution; immerse quartz fiber in the mixed solution to completely absorb the polyimide solution; cure the impregnated quartz fiber, and the curing procedure is as follows: first heat to 350℃ and keep warm for 1h, then keep warm at 360℃ for 1h, and finally apply 3MPa pressure at 380℃ and keep warm and pressurized for 1h. After curing, cool to room temperature at a cooling rate of 3℃ / min to obtain quartz fiber reinforced polyimide foam.

[0054] S2. Polyimide prepreg, polyimide film and quartz fiber reinforced polyimide foam are used for plying. After plying, the layers include, from bottom to top, 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); wherein the polyimide prepreg layer is plyed using polyimide prepreg in a quasi-isotropic plying sequence (0 / 45 / 90 / -45 / -45 / 90 / 45 / 0).

[0055] S3. The sandwich structure after laying is laid in an autoclave placed on a demoulding cloth, and wrapped with breathable cotton, and then a vacuum bag is laid. When laying the vacuum bag, a vacuum pipeline is placed, and the edge of the vacuum bag is sealed with a high-temperature sealant, and the vacuum is evacuated to a vacuum degree of 99%, and finally the autoclave is cured, wherein the autoclave curing procedure is: then at a heating rate of 3°C / min, it is raised to 240°C and kept warm for 1h, then raised to 300°C and kept warm for 0.5h, then raised to 330°C and applied a pressure of 0.4MPa, and finally raised to 380°C and kept warm for 3h, and then dropped to below 60°C to obtain a high temperature resistant foam sandwich structure. The performance data of the quartz fiber reinforced polyimide foam prepared 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] It is basically the same as Example 1, except that the autoclave curing procedure is: then increase the temperature to 240°C at a heating rate of 3°C / min and keep it warm for 1 hour, then increase it to 300°C and keep it warm for 0.5 hour, then increase it to 330°C and apply a pressure of 0.5 MPa, finally increase it to 380°C and keep it warm and pressurized for 3 hours, and then reduce it to below 60°C.

[0058] Comparative Example 1

[0059] The method is basically the same as Example 1, except that polyimide foam is used instead of quartz fiber reinforced polyimide foam, that is, quartz fiber is not added in step S1.

[0060] Due to the lack of quartz fiber, the polyimide foam collapsed significantly under the same molding pressure and did not form a reliable load-bearing structure 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] It is basically the same as Example 1, except that the autoclave curing procedure is: then increase the temperature to 240°C at a heating rate of 3°C / min and keep it warm for 1 hour, then increase it to 300°C and keep it warm for 0.5 hour, then increase it to 330°C and apply a pressure of 0.6MPa, finally increase it to 380°C and keep it warm and pressurized for 3 hours, and then reduce it to below 60°C.

[0064] Under the pressure of 0.6 MPa, the quartz fiber reinforced polyimide foam core layer began to collapse slightly 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 the foam layer obtained in the examples of the present invention and the comparative examples

[0067]

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

[0069]

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions 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 panels arranged on the upper and lower surfaces of the foam layer, the foam layer is fiber reinforced polyimide foam, the panel is a polyimide composite material, and the foam layer and the panel are bonded by a polyimide adhesive film.

2. The high temperature resistant foam sandwich structure according to claim 1, characterized in that: The fiber-reinforced polyimide foam is 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 according to claim 1, characterized in that: The fiber in the fiber-reinforced polyimide foam accounts for 5-6.25 wt%.

4. The high temperature resistant foam sandwich structure according to claim 1, characterized in that: The thickness of the foam layer is not less than 8 mm; The thickness of the panel is no more than 1.5 mm; and / or The thickness of the polyimide film is 0.15-0.25 mm.

5. A method for manufacturing a high temperature resistant foam sandwich structure according to any one of claims 1 to 4, characterized in that: The steps include: After the polyimide prepreg, the polyimide adhesive film and the fiber-reinforced polyimide foam are layered, they are cured and formed in an autoclave to obtain a high-temperature resistant foam sandwich structure; After laying, the layers include, from bottom to top, a polyimide prepreg layer, a polyimide adhesive film, a fiber-reinforced polyimide foam, a polyimide adhesive film and a polyimide prepreg layer.

6. The manufacturing method according to claim 5, characterized in that: The polyimide prepreg in the polyimide prepreg layer is laid in a quasi-isotropic laying 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.

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

8. The manufacturing method according to claim 7, characterized in that: The mass ratio of the fiber to the polyimide is 1:15 to 19; The mass ratio of the foaming agent to the polyimide is 1:5-10. Preferably, the foaming agent includes but is not limited to one or more of azodicarbonamide, amino foaming agents, and organic peroxides; and / or The mass ratio of the solvent to the 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.

9. The manufacturing method according to claim 7, characterized in that: The curing temperature is 350-380°C and the pressure is 2-3MPa; preferably, the curing is to first raise the temperature to 350°C and keep it for 1-2h, then raise it to 360°C and keep it for 1-2h, and finally raise it to 370-380°C, apply 2-3MPa pressure and keep it for 1-2h.

10. The manufacturing method according to claim 5, characterized in that: The autoclave curing molding is performed at a heating rate of 3-5°C / min, first raising the temperature to 240-250°C and keeping it warm for 1-2 hours, then raising the temperature to 300-320°C and keeping it warm for 0.5-1 hour, then raising the temperature to 330-340°C and applying a pressure of 0.4-0.5MPa, and finally raising the temperature to 350-380°C and keeping it warm for 3-4 hours.

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