A method for preparing a foam core composite material component

Abstract

The invention discloses a method for preparing a foam core composite material component, and relates to the technical field of composite material component preparation. The foam core composite material component consists of two parts: foam and a composite material outer skin. The preparation method proposed by the invention comprises the following steps: firstly laying a layer of foam film on the foam, and then laying the outer skin. Common composite material forming processes such as molding, autoclave, and bag pressing can be adopted. In the preparation method of the invention, the foam film is not affected by the shape of the foam core composite material component and the mold structure during the forming process, and can provide internal expansion force, reduce the influence of the prepreg glue content, surface weight, etc. on the thickness difference of the blank; reduce the foam processing size error and the influence of the mold processing size; reduce the influence of high temperature creep during the foam forming process; reduce the influence of mold temperature unevenness, pressure unevenness, and thermal expansion coefficient difference; and greatly improve the reliability of the internal quality of the sandwich composite material component.

Description

Technical Field

[0001] The invention relates to the technical field of composite material component preparation, and in particular to a method for preparing a foam core composite material component. Background Art

[0002] Composite materials have become an important lightweight structural material in the aerospace field and one of the important indicators for measuring the advancement of aircraft. Sandwich structures have the advantages of light weight, high bending stiffness and strength, strong anti-unbalance ability, and sound absorption, which can optimize the structural performance of composite materials. PMI foam is a foam plastic with high specific strength and specific modulus. Using PMI foam to make composite sandwich structures can significantly improve strength, rigidity, and reduce weight, so it is widely used.

[0003] The main problem with special-shaped parts of foam sandwich composite materials is the interface problem between the foam and the outer skin. Debonding between the core layer and the outer skin is the most common defect in sandwich structures. Non-destructive testing can be used to intuitively judge whether the interface bonding is good.

[0004] The traditional molding process is to directly lay a layer of J-47A film on the foam interlayer and then lay the outer skin prepreg, or to lay the J-47A film and the outer skin prepreg after curing. The molding process is not limited to molding, autoclave, oven, etc.

[0005] The components obtained by the traditional molding method have been verified by a large number of trial products, and there are problems such as foam stratification, debonding, looseness, and polyadhesion at the interface that are unqualified in non-destructive testing; after analysis and evaluation, the traditional molding process has the following disadvantages: a) There are differences in ply thickness The quality of prepreg is unstable and contains volatiles. At the same time, the layering process is affected by the vacuum time and vacuum degree, resulting in errors between the thickness of the blank after layering and the actual thickness. During the pressing process, the difference between the actual thickness and the theoretical thickness leads to uneven force, and the foam and skin interface is prone to non-destructive problems.

[0006] b) PMI foam processing dimensional error There are deviations in the shape of the PMI foam processing digital model, and some local positions are lower than the theoretical value. The interface between the foam and the skin is prone to lossless failure.

[0007] c) Limited mold structure and mold processing accuracy Common mold structures Figure 1 and Figure 2One is that the parting surface is parallel to the bottom plane, and the other is that the parting surface is at a certain angle to the bottom plane. The first structural mold has the problem that the web position is difficult to be subjected to pressure, which leads to the problem of lossless failure at the interface between the foam and the skin; the second structural mold has the problem of unbalanced force, and there is a risk of collapse for low-density foam, which leads to the problem of lossless failure at the interface between the foam and the skin.

[0008] At the same time, it is difficult to ensure that the processing accuracy of the mold is consistent with that of the product during the mold processing process. If there is a gap between the mold and the product, it is very easy to cause lossless failure at the interface between the foam and the skin.

[0009] d) Differences in thermal expansion coefficients between composite materials, PMI foam, and molds The thermal expansion coefficient of the PMI foam used is -0.5×10-6 / K, the linear expansion coefficient of carbon fiber is -0.7×10-6 / K, the metal aluminum is 23×10-6 / K, and the steel is 10~13×10-6 / K. Regardless of whether the mold is made of steel or aluminum, the difference in thermal expansion coefficients of the two different types of materials, metal and composite, seriously affects the internal quality.

[0010] e) Difficult to ensure mold temperature consistency and control the pressure point The compression mold is usually divided into an upper mold and a lower mold. The heating system is located in the lower mold. It is difficult to ensure that the temperature of each position of the upper and lower molds is consistent. The prepreg is heated unevenly, the flow state is inconsistent, and the pressure is uneven, which leads to the problem of non-destructive failure at the interface between the foam and the skin. On the other hand, it is difficult to control the consistency of the gap each time the pressure is applied, and the uneven pressure leads to the problem of non-destructive failure at the interface between the foam and the skin.

[0011] f) Shape of digital model Due to the special digital model of the product's appearance, the expansion coefficients of the component side faces are also different. Each section is subjected to uneven stress at high temperature, and the internal quality of each composite skin is also different, resulting in increased defects.

[0012] Based on the above technical problems, the present invention proposes a method for preparing a foam sandwich composite material component, aiming to improve the non-destructive qualified rate of internal quality and ensure its internal quality and non-destructive testing are qualified. Summary of the invention

[0013] The invention provides a reliable preparation method for foam core composite material components with high internal quality requirements, especially components with special-shaped structures, aiming to improve the non-destructive qualification rate of internal quality and ensure that the internal quality and non-destructive testing thereof are qualified.

[0014] The scheme used in the present invention is: A method for preparing a foam core composite material component, wherein the foam core composite material component is composed of two parts, foam and composite material outer skin, and may also include other parts such as metal parts, and may adopt common composite material molding processes such as molding, autoclave, bag pressing, etc.; the preparation steps are as follows: N10: Foam shape processing, select foam with moderate compression strength, surface porosity and density, and process it according to the inner cavity size of the special-shaped parts. The dimensional tolerance can be implemented according to the aviation standard HB7741; N20: Laying: Wrap a layer of foam film on the foam; then lay a layer of high temperature resistant structural film on the outer surface of the foam film to improve the bonding strength between the foam and the skin; N30: Vacuum assisted compression molding, the curing system and molding pressure are selected according to the type of prepreg material; N40: Demolding and machining. After the product is demoulded, it is processed on a lathe according to the mold line to obtain the product's dimensions; N50: Non-destructive testing: Inspection shall be carried out according to the design requirements and non-destructive testing standards.

[0015] Preferably, the foam core composite material component is a foam core layer U-shaped beam, which is a foam sandwich structure, including upper and lower flanges, left and right webs, and adopts a variable thickness design; the main beam length is 1500mm, the width is 90-100mm, and the height is 20-30mm; the skin thickness is 1-10mm.

[0016] Preferably, the preparation method of the foam core layer cross beam is as follows: Step 1: Select a density of 52kg / cm 3 PMI foam, the foam film is F40s high-multiple epoxy foam film, and the prepreg is UC125 / 9A16 carbon fiber unidirectional prepreg; Step 2: Laying, PMI foam is used as a process support, the main beam is laid on the PMI foam, a layer of EF80 foam film is laid on the foam, and then a layer of J-47A film is laid, and the prepreg and release fabric are laid in sequence according to the laying table, and vacuum is drawn; Step 3: Vacuum assisted compression molding. Set and operate the curing molding temperature according to the designed molding temperature and pressure. When the mold temperature drops below 50°C, the mold can be removed. When removing the mold, the mold clearance is ≤0.10mm. Step 4: Demolding and machining. After the product is demoulded, it is processed according to the main beam dimensions; Step 5: Non-destructive testing: According to the design requirements, the main beam is non-destructively tested.

[0017] Preferably, the foam core composite material component is a wing, which is a foam sandwich structure, mainly including foam, outer skin, and metal joints; the skin adopts a variable thickness design of 2 to 5 mm, and the thickness of the middle skin rib is 10 mm.

[0018] Preferably, the wing preparation method is as follows: Step 1: Select a density of 52kg / cm 3 PMI foam, the foam film is F40s high-multiple epoxy foam film, and the prepreg is UC125 / 9A16 carbon fiber unidirectional prepreg; Step 2: Laying the wing design on the PMI foam. First, lay a layer of EF80 foam film on the foam, then lay a layer of J-47A film, lay the prepreg and release fabric in the order of the layup table, and then vacuum it. Step 3: Vacuum assisted compression molding. Set and operate the curing molding temperature according to the designed molding temperature and pressure. When the mold temperature drops below 50°C, the mold can be removed. When removing the mold, the mold clearance is ≤0.10mm. Step 4: Demolding and machining. After the product is demoulded, the rear edge is machined according to the elastic wing die line; Step 5: Non-destructive testing: According to the design requirements, the wing is non-destructively tested.

[0019] Compared with the prior art, the present invention has the following beneficial effects: During the molding process, the foam film is not affected by the shape of the foam core composite material component and the mold structure, and can expand freely above 100°C to provide internal expansion force; reduce the influence of bubbles and other impurities between prepregs on the thickness difference of the blank; the foam film can expand freely to fill the inner cavity gap, reduce the foam processing size error and the influence of mold processing size; reduce the influence of high temperature creep during foam molding; the foam film provides internal expansion force, adapts to various types of molds, and reduces the influence of uneven mold temperature, uneven pressure and thermal expansion coefficient differences; the process is simple and the cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of a common compression mold structure.

[0021] Figure 2 Schematic diagram of the molding die structure.

[0022] Figure 3 This is a schematic diagram of the cross-sectional structure of the first common typical foam core composite material component.

[0023] Figure 4 This is a schematic diagram of the cross-sectional structure of the second most common typical foam core composite material component.

[0024] Figure 5This is a schematic diagram of the cross-sectional structure of the third most common typical foam core composite material component.

[0025] Figure 6 This is a schematic diagram of the cross-sectional structure of the fourth most common typical foam core composite material component.

[0026] Figure 7 This is a schematic diagram of the main beam structure.

[0027] Figure 8 Schematic diagram of the wing structure.

[0028] Reference numerals: 1. Foam; 2. Outer skin. DETAILED DESCRIPTION

[0029] The following is combined with Figure 1-8 The present invention is specifically described: The foam core composite material component proposed in this embodiment is composed of two parts: foam 1 and composite material outer skin 2, and may also include other parts such as metal parts. The cross-sectional structure of a common typical foam core composite material component is as follows: Figure 3-6 As shown; in order to ensure that the airfoil parts after forming are qualified in non-destructive testing and the internal quality meets the technical requirements, a new preparation method is adopted. A layer of foam film is first laid on the foam, and then the outer skin is laid. Common composite material forming processes such as molding, autoclave, and bag pressing can be used.

[0030] The advantages of this new process are as follows: During the molding process, the foam film is not affected by the shape of the foam core composite material component and the mold structure, and can expand freely above 100°C to provide internal expansion force, reducing the impact of bubbles and other impurities between prepregs on the thickness difference of the blank; the foam film can expand freely to fill the inner cavity gap, reducing the foam processing size error and the impact of mold processing size; reducing the impact of high temperature creep during foam molding; the foam film provides internal expansion force, which is suitable for various types of molds, reducing the impact of uneven mold temperature, uneven pressure and thermal expansion coefficient differences; the process is simple and the cost is low.

[0031] The foam core composite material component is composed of two parts, foam 1 and outer skin 2, and may also include other parts such as metal parts. Common composite material molding processes such as molding, autoclave, and bag pressing can be used. The preparation steps are as follows: N10: Foam shape processing, select foam with moderate compression strength, surface porosity and density, and process it according to the inner cavity size of the special-shaped parts. The dimensional tolerance can be implemented according to the aviation standard HB7741; N20: Laying: Wrap a layer of foam film on the foam; then lay a layer of high temperature resistant structural film on the outer surface of the foam film to improve the bonding strength between the foam and the skin; N30: Vacuum assisted compression molding, the curing system and molding pressure are selected according to the type of prepreg material; N40: Demolding and machining. After the product is demoulded, it is processed on a lathe according to the mold line to obtain the product's dimensions; N50: Non-destructive testing, according to the design requirements, the inspection is carried out according to the non-destructive testing standards; the preparation method of foam core composite material special-shaped parts adopted has been verified by experiments that the non-destructive testing pass rate can reach more than 95%, the molding process is mature, and it has excellent cost performance.

[0032] The main beam of this embodiment is a foam core layer beam, which is a foam sandwich structure, including upper and lower flanges, left and right webs, and adopts a variable thickness design; the main beam length is 1500mm, the width is 90-100mm, and the height is 20-30mm; the skin thickness is 1-10mm, such as Figure 7 As shown: The preparation method of the foam core layer cross beam is as follows: Step 1: Select a density of 52kg / cm 3 PMI foam, the foam film is F40s high-multiple epoxy foam film, and the prepreg is UC125 / 9A16 carbon fiber unidirectional prepreg; Step 2: Laying, PMI foam is used as a process support, the main beam is laid on the PMI foam, a layer of EF80 foam film is laid on the foam, and then a layer of J-47A film is laid, and the prepreg and release fabric are laid in sequence according to the laying table, and vacuum is drawn; Step 3: Vacuum assisted compression molding. Set and operate the curing molding temperature according to the designed molding temperature and pressure. When the mold temperature drops below 50°C, the mold can be removed. When removing the mold, the mold clearance is ≤0.10mm. Step 4: Demolding and machining. After the product is demoulded, it is processed according to the main beam dimensions; Step 5: Non-destructive testing. According to the design requirements, the main beam is tested non-destructively. After multiple verifications, the internal quality of the trial-produced main beam is qualified after non-destructive testing. At the same time, the product obtained by the traditional preparation method of non-foamed film is tested non-destructively, and the qualified rate is less than 50%.

[0033] The present embodiment also uses a wing, which is a foam sandwich structure, mainly including foam, outer skin, and metal joints; the skin adopts a variable thickness design of 2 to 5 mm, the thickness of the middle skin rib is 10 mm, and the cross-sectional structure is as follows Figure 8 As shown: The wing preparation method is as follows: Step 1: Select a density of 52kg / cm 3 PMI foam, the foam film is F40s high-multiple epoxy foam film, and the prepreg is UC125 / 9A16 carbon fiber unidirectional prepreg; Step 2: Laying the wing design on the PMI foam. First, lay a layer of EF80 foam film on the foam, then lay a layer of J-47A film, lay the prepreg and release fabric in the order of the layup table, and then vacuum it. Step 3: Vacuum assisted compression molding. Set and operate the curing molding temperature according to the designed molding temperature and pressure. When the mold temperature drops below 50°C, the mold can be removed. When removing the mold, the mold clearance is ≤0.10mm. Step 4: Demolding and machining. After the product is demoulded, the rear edge is machined according to the elastic wing die line; Step 5: Non-destructive testing. According to the design requirements, the wing is tested non-destructively. After multiple verifications, the internal quality of the trial-produced wing is all qualified after non-destructive testing. At the same time, the product obtained by the traditional preparation method of non-foamed film has a pass rate of less than 50% after non-destructive testing.

Claims

1. A method for preparing a foam core composite material component, characterized in that: The foam core composite material component is composed of two parts, foam (1) and outer skin (2), and may also include other parts such as metal parts. Common composite material molding processes such as molding, autoclave, and bag pressing can be used. The preparation steps are as follows: N10: Foam shape processing, select foam with moderate compression strength, surface porosity and density, and process it according to the inner cavity size of the special-shaped parts. The dimensional tolerance can be implemented according to the aviation standard HB7741; N20: Laying: Wrap a layer of foam film on the foam; then lay a layer of high-temperature resistant structural film on the outer surface of the foam film to improve the bonding strength between the foam and the skin; N30: Vacuum assisted compression molding, the curing system and molding pressure are selected according to the type of prepreg material; N40: Demolding and machining. After the product is demoulded, it is processed on a lathe according to the mold line to obtain the product's dimensions; N50: Non-destructive testing: Inspection is carried out according to the design requirements and non-destructive testing standards.

2. A method for preparing a foam core composite material component according to claim 1, characterized in that: The foam core composite material component is a foam core layer U-shaped beam, which is a foam sandwich structure, including upper and lower flanges, left and right webs, and adopts a variable thickness design; the main beam has a length of 1500mm, a width of 90-100mm, and a height of 20-30mm; the skin thickness is 1-10mm.

3. A method for preparing a foam core composite material component according to claim 2, characterized in that: The preparation method of the foam core layer cross beam is as follows: Step 1: Select a density of 52kg / cm 3 PMI foam, the foam film is F40s high-multiple epoxy foam film, and the prepreg is UC125 / 9A16 carbon fiber unidirectional prepreg; Step 2: Laying, PMI foam is used as a process support, the main beam is laid on the PMI foam, a layer of EF80 foam film is laid on the foam, and then a layer of J-47A film is laid, and the prepreg and release fabric are laid in sequence according to the laying table, and vacuum is drawn; Step 3: Vacuum assisted compression molding. Set and operate the curing molding temperature according to the designed molding temperature and pressure. When the mold temperature drops below 50°C, the mold can be removed. When removing the mold, the mold clearance is ≤0.10mm. Step 4: Demolding and machining. After the product is demoulded, it is processed according to the main beam dimensions; Step 5: Non-destructive testing: According to the design requirements, the main beam is non-destructively tested.

4. The method for preparing a foam core composite material component according to claim 1, characterized in that: The foam core composite material component is a wing, which is a foam sandwich structure, mainly including foam, outer skin, and metal joints; the skin adopts a variable thickness design of 2 to 5 mm, and the thickness of the middle skin rib is 10 mm.

5. A method for preparing a foam core composite material component according to claim 4, characterized in that: The method for preparing the wing is as follows: Step 1: Select a density of 52kg / cm 3 PMI foam, the foam film is F40s high-multiple epoxy foam film, and the prepreg is UC125 / 9A16 carbon fiber unidirectional prepreg; Step 2: Laying the wing design on the PMI foam. First, lay a layer of EF80 foam film on the foam, then lay a layer of J-47A film, lay the prepreg and release fabric in the order of the layup table, and then vacuum it. Step 3: Vacuum assisted compression molding. Set and operate the curing molding temperature according to the designed molding temperature and pressure. When the mold temperature drops below 50°C, the mold can be removed. When removing the mold, the mold clearance is ≤0.10mm. Step 4: Demolding and machining. After the product is demoulded, the rear edge is machined according to the elastic wing die line; Step 5: Non-destructive testing: According to the design requirements, the wing is non-destructively tested.

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