Foam sandwich co-curing mouth-shaped beam forming mold and method
Through mold design and process improvements, the quality problem of large-size foam sandwich co-cured orifice beams was solved, achieving improvements in thickness uniformity and internal quality, and reducing production costs.
Patent Information
- Application Number
- CN202511504224.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-21
- Publication Date
- 2026-01-20
AI Technical Summary
When molding large-size foam sandwich co-cured orifice beams, there are quality problems such as uneven pressure, dimensional deviation, difficulty in gas venting, fiber wrinkles and loose delamination, resulting in poor precision and stability of composite material parts after curing.
The design employs a mold with sealing grooves and sealing rubber, combined with vacuum degassing and segmented mold pressing processes. By tilting the parts and pre-curing, the supporting rigidity and stress uniformity of the foam core are improved, mold gaps and gas discharge are controlled, and delamination and loosening are prevented.
It improves the thickness uniformity and internal quality of foam sandwich co-cured orifice beams, reduces fiber wrinkles and delamination problems, enhances the curing accuracy and stability of parts, and reduces production costs.
Smart Images
Figure CN121361224A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to a foam sandwich co-curing mouth beam forming die and method, belonging to the field of composite material forming technology. BACKGROUND
[0002] With the gradual reduction of the price of domestic carbon fiber, the gradual stability of the performance, and the characteristics of light weight and high strength and designability, it is more and more widely used in aerospace products to meet the requirements of low cost and high performance. The composite mouth beam has better stability and torsional stiffness than the traditional C-shaped and I-shaped beam. The molding process has cost advantage compared with the autoclave molding process. The molding process of the mouth beam can reduce the production cost of the part, ensure the shape of the part through the mold cavity, better control the shape precision of the product, and ensure the subsequent bonding assembly of the mouth beam.
[0003] The foam sandwich co-cured mouth beam (as shown in Figure 1 ) is formed by directly laying carbon fiber prepreg on the foam core with a good shape and co-curing under heat and pressure. The low-density foam can provide support for the laying of prepreg and internal support and pressure transmission during curing without significantly increasing the overall weight of the part, reducing tooling investment, and further reducing production cost.
[0004] When the large-size foam sandwich co-cured mouth beam is formed, the overall pressure is uneven due to the difficulty of pressing the web surface, the small molecule gas is difficult to exhaust due to the thickness of the large-size part, the foam processing has size deviation and deformation, the foam will creep and shrink under high temperature and high pressure, and the fiber in the closed structure cannot be expanded during the pressing process. The quality problems such as delamination of the panel, fiber wrinkle and poor thickness uniformity of the part after final curing are prone to occur. SUMMARY
[0005] The purpose of the present application is to provide a foam sandwich co-cured mouth beam forming die and method, which uses a low-cost molding co-curing process to form a low-density foam sandwich mouth beam, and improves the quality problems such as internal loose layering, fiber wrinkle and poor thickness uniformity that are prone to occur during the curing process.
[0006] In order to achieve the above purpose, the present application adopts the following technical scheme: a foam sandwich co-cured mouth beam forming die, comprising an upper die and a lower die, a sealing groove is formed on the bonding surface of the lower die and the upper die, the sealing groove is arranged around the lower die cavity, sealing rubber is placed in the sealing groove, and the thickness of the sealing rubber is greater than the depth of the sealing groove at room temperature; after the upper die and the lower die are closed, the cavity containing the mouth beam is in an inclined state.
[0007] Preferably, a vacuum pipe inlet is left outside the excess area at both ends of the die, the vacuum pipe is connected to a vacuum passage, and is used to exhaust small molecule gas during the curing process.
[0008] A foamed sandwich co-curing mouth beam forming method, using the forming mold as described above, comprising the following steps, (1) preparing PMI foam, carbon fiber prepreg, epoxy film and surface glass cloth prepreg required for forming; (2) using a machining device on a numerical control machine tool to process the foam core, and sealing and storing the foam core after processing; before use, the foam core is subjected to high-temperature dehumidification; (3) coating a layer of film on the surface of the foam core for pre-curing, and sealing and packaging in a bag form; (4) on the foam core after pre-curing, according to the design requirements of the layer, the film and the prepreg are sequentially laid; according to the laying area and the number of layers, the vacuum pre-compaction operation is set; (5) after laying, a layer of peelable cloth is coated on the surface of the mouth beam, and the part is placed in the lower mold cavity of the mold, and the upper mold is closed; (6) the mold is placed in the press, and the upper and lower heating plates are pressed and heated; the segmented mold closing and pressing mode is adopted in the heating process, and the mold closing pressure is gradually increased until the mold gap meets the gap requirement; (7) the peelable cloth on the surface of the part is torn off, the remaining part is cut off, and the internal non-destructive quality, weight, thickness and appearance of the part are detected according to the manufacturing acceptance requirements.
[0009] Preferably, in step (2), the initial processing state of the foam is that the edge strip and the web face are enlarged by 0.2mm, and the two ends in the spanwise direction are enlarged by 1mm.
[0010] Preferably, in step (3), the film is J-47A film, and the thickness is 0.06mm.
[0011] Preferably, in step (3), the sealing auxiliary material is peelable cloth, non-porous isolation film, air-permeable felt and vacuum bag placed in sequence.
[0012] Preferably, in step (4), the vacuum pre-compaction operation process is that vacuum pre-compaction is performed every 2-3 layers of laying, the vacuum pressure should be not less than-0.08Mpa, and the vacuum pressure is maintained for at least 15min.
[0013] Preferably, in step (6), the segmented mold closing and pressing mode comprises the following steps, Step one, keep the vacuum open state, and heat to 80-85℃ in the mold contact pressure state, and keep warm for 15-20min; Step two, after keeping warm, start heating and increase the mold closing pressure, and press in 3 segments in the temperature range of 80-90℃, each time the temperature interval is 3℃, and each time the pressure is 2MPa, until the mold gap is as small as 0-0.15mm, at which point the vacuum is stopped; Step three, continue to warm up to the highest curing temperature and keep it for curing.
[0014] Compared with the prior art, the present application has the following advantages: 1. By adjusting the size of the foam and reinforcing pretreatment, the support rigidity of the foam core can be improved while reducing the weight increase and shape deviation of the part, reducing the creep shrinkage, better controlling the curing thickness of the mouth-shaped beam, and improving the non-destructive quality of curing; 2. The part is placed at an inclined angle during curing, which can increase the stress on the two sides of the web of the mouth-shaped beam, improve the stress uniformity, and reduce the non-destructive problems; 3. The expanded sealing rubber embedded around the tool can gradually expand as the temperature rises. The initial stage of temperature rise is beneficial to the degassing and gas guiding of the material during the temperature rise process. When the temperature rises above 80℃, the expanded sealing rubber gradually expands to close the gap of the mold, providing air tightness for vacuum. At the same time, small molecule gases generated during the curing process are removed through vacuum extraction in the excess area at both ends, preventing the aggregation of small molecule gases during the curing process and improving the problems of loose and layered parts; 4. By segmenting the mold and pressurizing during the heating process, the part is gradually pressurized when the resin fluidity reaches the optimal state, controlling the exhaust and flow of the prepreg, and improving the loose and layered problems of the carbon fiber panel. BRIEF DESCRIPTION OF DRAWINGS
[0015] Figure 1 is a schematic diagram of the foam sandwich co-curing mouth-shaped beam structure in the embodiment of the present application; Figure 2 is a schematic diagram of the mold structure in the embodiment of the present application; Figure 1 In the above, 1, carbon fiber mouth-shaped beam; 2, low-density foam core; Figure 2 In the above, 3, upper mold; 4, sealing groove; 5, lower mold; 6, vacuum gas guiding hole; 7, mouth-shaped beam. DETAILED DESCRIPTION
[0016] The present scheme uses low-density PMI foam (center density 50 kg / m3), carbon fiber prepreg and adhesive film are all medium-temperature epoxy curing system (maximum curing temperature 130℃), and the prepreg and epoxy adhesive film are directly laid on the processed foam core and cured to form.
[0017] The following will be described in detail with reference to the accompanying drawings Figures 1-2 The present application is further described in detail: a foam sandwich co-curing mouth-shaped beam forming method for forming a carbon fiber mouth-shaped beam 1, comprising the following steps: 1. Obtain the PMI foam, carbon fiber prepreg, epoxy adhesive film and surface glass cloth prepreg required for forming; the adhesive film is divided into two specifications of 0.35mm and 0.06mm thickness; 2、In the numerical control machine tool with machining equipment, processing low density foam core 2, in order to offset the shrinkage of foam in the forming process, the initial processing state of foam is required to be enlarged by 0.2mm on the edge strip and the web surface, and enlarged by 1mm on both ends in the span direction; The foam is sealed after processing; 3、Before using the foam core, high temperature dehumidification is carried out, and after dehumidification, it is sealed and stored and put into moisture-proof agent until it is unpacked and unpacked before use.
[0018] 4、A layer of 0.06mm thick J-47A adhesive film is coated on the surface of the low density foam core 2 for pre-curing, and is sealed and packaged in the form of bagging, and the auxiliary materials are placed in the order of peelable cloth, non-porous isolation film, air-permeable felt and vacuum bag; After curing according to the curing temperature of the adhesive film, take out and clean the surface; 5、On the low density foam core 2 treated by pre-curing, according to the FiberSIM layer design requirements of the part, the adhesive film and the prepreg are pasted in turn. According to the pasting area and the number of layers, the vacuum pre-compaction operation process is set to ensure the compaction of the prepreg layers and prevent R area bridging and interlayer porosity. It is required to pre-compaction by vacuum every 2~3 layers, the vacuum pressure should be not less than-0.08Mpa, and the vacuum pressure should be maintained for at least 15min; 6、After the material is pasted, a layer of peelable cloth is coated on the surface of the mouth beam 7, and the part is put into the mold lower die 5 mold cavity, and is positioned by the positioning block and the ladder mark in the mold; 7、Put the sealing rubber into the sealing groove 4 on one side of the lower die 5 of the mold, insert the vacuum pipe into the vacuum air guide hole 6 at both ends, and seal by sealing rubber, close the upper die 3; 8、Put the mold into the press, and press and heat by the upper and lower heating plates. The temperature rising process adopts segmented pressure increasing mode, keeps the vacuum open state, and rises to 80℃-85℃ in the mode of mold contact pressure, and keeps warm for 15min~20min; After the heat preservation is finished, start to rise temperature and increase the closing pressure, increase the closing pressure by 2MPa every time in 3℃ temperature interval in 80℃ to 90℃ temperature section, until the closing gap is less than 0~0.15mm, at this time stop vacuumizing; Continue to rise to the highest curing temperature and keep warm and curing; 9、The part is cooled to 60℃ and the mold is removed, the peelable cloth on the surface of the part is torn off, the remaining amount is cut off, and the internal non-destructive quality, weight, thickness and appearance of the part are detected according to the manufacturing acceptance requirements.
[0019] Design principle: Considering the creep shrinkage of foam in the compaction process and providing the necessary support in the pre-preg curing process, the foam blank is enlarged on the basis of the original part shape during numerical control machining, and the increase is adjusted according to the boundary conditions such as foam density, foam creep performance, part size and heating temperature. The precision of the foam shape is detected on the detection tool after numerical control machining to meet the tolerance requirements.
[0020] The foam core is dehumidified at high temperature before use. In order to control the uniformity of the foam in temperature rise and reduce deformation, a heat preservation platform is set at 85-90°C, and then the temperature is raised to the highest dehumidification temperature for dehumidification. The heating parameters can be adjusted according to the exposure time and size of the foam core material.
[0021] In order to improve the rigidity of low-density foam, control the deformation of foam during the main beam laying process and the deformation during the curing process, the foam core is pretreated before the prepreg laying, and a thin glue film or prepreg is cured on the surface of the foam core to reinforce it. In this application, a glue film with a theoretical thickness of 0.06mm is used for pre-curing treatment, which can fill the pores on the surface of the foam, stabilize the part, reduce the weight and shape deviation of the part, provide sufficient internal support for the prepreg curing, and help to control the thickness tolerance of the composite material layer.
[0022] In order to improve the uniformity of the force on each surface of the part during the curing process and guide the small molecule gas to be discharged in time, improve the non-destructive quality of the co-cured beam part, according to the size and characteristics of the beam structure, a mold forming tool with vacuum passage function is designed, and the stress uniformity of the side web is increased by adjusting the part placement posture. As shown in Figure 2 , the upper and lower molds are pressed together, and the part is placed in an inclined posture to increase the lateral pressure of the web. The mold can provide airtightness for vacuum after the mold is closed, and the sealing rubber is slightly lower than the sealing groove at room temperature, which does not affect the closing of the mold. When the mold is gradually heated to a certain temperature, the sealing rubber can gradually expand to close the gap, maintaining the vacuum environment. The two ends of the excess area are provided with vacuum pipe inlets connected to the vacuum passage to discharge small molecule gas during the curing process.
[0023] During the curing of the part, in order to control the exhaust and flow of the prepreg, and reduce the loose layering of the carbon fiber panel, a segmented mold pressing method is used during the heating process, and the mold pressing force is gradually increased until the mold gap meets the gap requirements. The part pressing point needs to find the optimal correspondence between flowability and pressing point according to the heating parameters of the selected prepreg and the viscosity-temperature curve of the resin.
Claims
1. A foam sandwich co-cured mouthpiece forming mold comprising an upper mold, a lower mold, characterized in that: A sealing groove is formed on the joint surface of the lower mold and the upper mold, the sealing groove is arranged around the cavity of the lower mold, sealing rubber is placed in the sealing groove, the thickness of the sealing rubber is greater than the depth of the sealing groove at room temperature, and the cavity accommodating the beam is in an inclined state after the upper mold and the lower mold are closed.
2. The foam sandwich co-curing mouth beam forming mold of claim 1, wherein: Vacuum pipe inlets are left outside the excess area of the mold, the vacuum pipes are connected to a vacuum passage, and the vacuum passage is used to discharge small molecule gases during the curing process.
3. A method of forming a foam cored co-cured sandwich jaw beam, the method comprising: The molding mold is used, The method comprises the following steps, (1) preparing PMI foam, carbon fiber prepreg, epoxy film, and surface glass cloth prepreg required for molding; (2) processing the foam core on a numerical control machine tool by using a machining device, and sealing and storing the foam core after processing; before use, the foam core is subjected to high-temperature dehumidification; (3) coating the foam core with a layer of film for pre-curing, and sealing and packaging the foam core in a bag form; (4) according to the lamination design requirements, the film and the prepreg are sequentially laminated on the foam core subjected to the pre-curing treatment; according to the lamination area and the number of laminations, a vacuum pre-compaction operation is performed; (5) after the lamination is completed, a layer of peelable cloth is coated on the surface of the beam, and the part is placed in the lower mold cavity of the mold, and the upper mold is closed; (6) the mold is placed in a press, and pressure and heat are applied by upper and lower heating plates; In the heating process, the mold is closed in stages, the closing pressure is gradually increased, and the gap of the closed joint is less than 0-0.15 mm. (7) the peelable cloth on the surface of the part is torn off, the excess part is cut off, and the internal non-destructive quality, weight, thickness, and appearance of the part are detected according to the manufacturing acceptance requirements.
4. The method of claim 3, wherein: In step (2), the initial processing state of the foam is that the edge strip and the web are enlarged by 0.2 mm, and the two ends in the spanwise direction are enlarged by 1 mm.
5. The method of claim 3, wherein: In step (3), the thickness of the film is 0.06 mm.
6. The method of claim 3, wherein: In step (3), the sealing auxiliary materials are peelable cloth, non-porous isolation film, air-permeable felt, and vacuum bag arranged in sequence.
7. The method of claim 3, wherein: In step (4), the vacuum pre-compaction operation process is that vacuum pre-compaction is performed every 2-3 layers of lamination, the vacuum pressure should be greater than or equal to -0.08 MPa, and the vacuum pressure is maintained for at least 15 min.
8. The method of claim 3, wherein: In step (6), the segmented mold closing and pressurizing method comprises the following steps, Step one, keep the vacuum open state, and heat to 80-85℃ in the mold contact pressure state, and keep warm for 15-20 min; Step two, after the warm-keeping is completed, heat and increase the closing pressure, and pressurize in three stages at a temperature of 80-90℃, the temperature interval is 3℃ each time, the pressurizing is 2 MPa each time, until the joint gap is less than 0-0.15 mm, at this time, the vacuum is stopped; Step three, continue to heat to the highest curing temperature and keep warm for curing.