Corner filling preform forming mold and forming method for improving corner quality of composite material

Abstract

The invention discloses a forming mold of a corner filling prefabricated body and a forming method for improving the quality of a composite material corner. The forming mold comprises a male mold provided with a step and a female mold provided with an arc surface. And the male die and the female die are detachably and fixedly connected and buckled, so that the step and the cambered surface limit a cavity for preparing the corner filling prefabricated body. Therefore, the male film mold and the female film mold are matched in a detachable buckling manner, so that the layering operation is facilitated, and the sealing performance of the cavity after buckling can be ensured. By means of the cavity formed through precise matching of the step and the arc face, the structure of the prefabricated body can be completely matched with a product cavity, the filling effectiveness is effectively improved, uneven stress caused by filling dislocation is reduced, and then the internal defect risk is reduced.

Description

Technical Field

[0001] This application belongs to the field of composite material molding technology, and in particular relates to a corner filling preform molding die and a molding method for improving the corner quality of composite materials. Background Technology

[0002] Carbon fiber composites are widely used in critical fields such as aerospace due to their excellent specific strength, corrosion resistance, and designability. In this field, structural components requiring mating, such as V-shaped and L-shaped parts, often have front and rear flanges. Their corner areas are typically designed with right-angle transitions, and a specific radius (R-angle) transition exists between the skin surface and the end flange. To ensure continuous fiber layup and avoid stress concentration, a small inner radius is used in this transition area. However, the fixed thickness of the composite layer results in a significantly larger cumulative thickness at the corner than adjacent parallel areas, creating unavoidable "voids." Filling these "voids" usually relies on using prepreg during the layup process. Common filling methods easily lead to defects such as porosity, polymer buildup, bridging, and delamination in the composite corner area, severely affecting the reliability and consistency of the composite corner quality. Summary of the Invention

[0003] This application aims to at least partially reduce the risk of defects such as porosity, polymer buildup, bridging, and delamination that are prone to occur in the corner areas of composite materials, thereby improving the reliability and consistency of composite material corner quality. To this end, this application provides a corner-filling preform molding die and a molding method for improving the corner quality of composite materials.

[0004] In a first aspect, an embodiment of this application provides a molding die for a corner-filling preform, comprising: a positive mold, the positive mold having a step; and a negative mold, the negative mold having an arc surface; wherein the positive mold and the negative mold are detachably fixedly connected and fastened together, so that the step and the arc surface restrict a cavity for preparing the corner-filling preform.

[0005] Therefore, the detachable interlocking mechanism of the positive and negative molds facilitates the layup process and ensures the sealing of the cavity after interlocking. The cavity formed by the precise fit of the steps and curved surfaces allows the structure of the preform to perfectly match the product's voids, effectively improving filling efficiency, reducing stress unevenness caused by filling misalignment, and thus reducing the risk of internal defects.

[0006] In some possible implementations, the molding die includes a release template, the anodizing die has an opening, and the release template is installed in the opening. Thus, the arrangement of the opening and the release template enables uniform force distribution during demolding of the corner-filled preform, ensuring smooth release from the cavity and effectively protecting the structural integrity of the corner-filled preform.

[0007] In some possible implementations, the molding die includes screws. The male mold has a first mounting hole, and the female mold has a second mounting hole. The screw passes through the first and second mounting holes to fix and engage the male and female molds. This precise alignment of the first and second mounting holes ensures accurate engagement between the male and female molds during screw connection, preventing cavity deformation due to misalignment and guaranteeing the dimensional accuracy of the corner filling preform. The screw connection provides a stable and uniform tightening force, which is transmitted through the mold cavity wall to all parts of the corner filling preform, particularly effectively acting on the corner filling area to improve its density. The detachable screw connection facilitates mold disassembly and maintenance, maintains connection stability even after multiple uses, offers high flexibility, adapts to the production needs of different batches, improves production efficiency, and ensures consistent product quality.

[0008] In some possible implementations, there are two steps, namely a first step and a second step, which are continuously arranged. The first step and the arc surface define the cavity for preparing the corner filling preform. Therefore, the arrangement of the first and second steps facilitates the positioning of the corner filling preform, enabling it to be formed in one step, reducing subsequent trimming, improving production efficiency. Simultaneously, the shape of the formed corner filling preform perfectly matches the product cavity, allowing for a tight fit during subsequent assembly.

[0009] Secondly, embodiments of this application also provide a molding method for improving the corner quality of composite materials, using the molding die described in any of the above claims, comprising the following steps: S1. Mold design and manufacturing: Based on the corner structure characteristics and radius (R) size of the product, design and manufacture the corresponding molding mold; S2. Corner filling preform molding: Lay a layer of carbon fiber prepreg on the positive mold. After the layup is completed, fasten the negative mold and the positive mold together with screws, place them in an oven for heating, and tighten the screws after the molding mold reaches a certain temperature; S3. Corner filling preform assembly: After the molding mold cools to room temperature, begin demolding, remove the corner filling preform, and assemble the corner filling preform in the corner area of ​​the product. Before assembly, use fabric prepreg for base layering; S4. Continuous skin layup and pre-pressing: Based on the product size, thickness, and layup... According to requirements such as layer sequence, the prepreg material to be laid on the skin is cut and laid in the corresponding layer sequence to form a composite material component; S5. Overall co-curing: The composite material component is completely vacuum-sealed using vacuum sealing material, and vacuum pre-pressed at room temperature for 30~60 minutes. The composite material component is cured in an autoclave. The curing temperature regime is determined according to the resin system, and the process is carried out in stages with temperature increase and heat preservation; S6. Demolding and inspection: The vacuum sealing material is removed to obtain a composite material with good corner quality. After grinding and cleaning the burrs, internal quality inspection is performed.

[0010] In some possible implementations, prior to step S2, adhesive release cloth is adhered to the surfaces of the male mold and the female mold.

[0011] In some possible implementations, in step S2, during the process of laying the carbon fiber prepreg, a layer of the fabric prepreg is first used as a base layer, the fabric prepreg is used to wrap the surface of the corner filling preform, then the parallel carbon fiber layup is performed, and finally the corner filling layup is performed.

[0012] In some possible implementations, in step S2, the temperature of the molding die is controlled between 60°C and 120°C, depending on the resin system.

[0013] In some possible implementations, during the continuous fiber layup of the skin in step S4, each layer must ensure that the prepreg adheres to the corner filler preform to avoid artificial gaps. During the layup process, a vacuum pre-compression at room temperature is performed for 20 to 30 minutes every 4 to 8 layers, and a heating and pressurizing pre-compression is performed every 1 to 3 mm of layup to ensure the density of the skin layup.

[0014] In some possible implementations, in step S5, the curing temperature is 100~250℃, the pressure is 0.3~0.6MPa, and the vacuum pressure is -0.07MPa to -0.1MPa.

[0015] Therefore, in response to the problem of corner defects such as corner bridging, voids, polyurethane, and delamination that easily occur when using loose fibers to fill the "void" at the corners during the layup process for the inner rounded corner transition and the outer right-angle corner structure, the method provided in this application embodiment effectively reduces the risk of corner defects and improves the reliability and consistency of corner quality. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the structure of a molding die provided in an embodiment of this application; Figure 2 This is a cross-sectional view of a molding die provided in an embodiment of this application; Figure 3 This is a schematic diagram of a corner filling preform forming method provided in an embodiment of this application; Figure 4 This is a structural schematic diagram of an inward and outward flange column structure provided in an embodiment of this application.

[0018] Figure label: Molding mold-1; Positive mold-10; Step-110; First step-111; Second step-112; Opening-120; First mounting hole-130; Third mounting hole-140; Negative mold-20; Curved surface-210; Second mounting hole-220; Fourth mounting hole-230; Demolding template-30; Screw-40; Corner filling preform-101; Outward flange thickening and corner filling ply preform-1011; Inward flange thickening and corner filling ply preform-1012; Loose fiber prepreg-102; Fabric prepreg-103; Skin continuous fiber-104; Parallel zone continuous carbon fiber-105; Transition zone continuous fiber-106. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] It should be noted that all directional indications in the embodiments of this invention are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indication will also change accordingly. In this invention, unless otherwise explicitly specified and limited, the terms "connection" and "fixed" should be interpreted broadly. For example, "fixed" can be a fixed connection, a detachable connection, or an integral part; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two components or the interaction relationship between two components, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances. In addition, the descriptions involving "first," "second," etc., in this invention are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0021] Because the thickness of each layer in a carbon fiber layup is fixed, the thickness at corners is greater than that of the parallel areas on both sides, inevitably resulting in "voids" at the corners. The process typically involves filling these "voids" with prepreg during the layup process. There are two common filling methods. One common approach is to fill the voids dispersedly between continuous fiber layups. While this method allows the filler to integrate well into the continuous layers, it can easily cause the continuous layup to be suspended at the corners, introducing porosity defects. Furthermore, the process is cumbersome, inefficient, and challenges the reliability and controllability of the quality. Another approach is to fill the voids centrally, either before or after the continuous layup begins. While this method is relatively independent, its bonding with the main fiber is weak, making it prone to fraying. More importantly, the lack of an effective reference makes it difficult to precisely control the filler amount, and the filler's placement profile does not easily match the "void" shape. Additionally, the filler itself lacks density. This prevents the pressure from subsequent layups and preloading from being effectively transferred to this area, posing a risk of loosening or localized resin accumulation, severely affecting the overall quality consistency.

[0022] This application provides a corner filling preform molding die and a molding method for improving the corner quality of composite materials, which can at least reduce the risk of defects such as porosity, polyurethane, bridging, and delamination that are prone to occur in the corner area of ​​composite materials, and improve the reliability and consistency of the corner quality of composite materials.

[0023] This application is described below with reference to the accompanying drawings and specific embodiments: Please see Figure 1 and Figure 2 , Figure 1 This is a schematic diagram of the structure of a molding die provided in an embodiment of this application. Figure 2 This is a cross-sectional view of a molding die provided in an embodiment of this application. This embodiment of the application provides a molding die 1 for a corner-filling preform 101, comprising: a positive mold 10, the positive mold 10 having a step 110; and a negative mold 20, the negative mold 20 having an arc surface 210. The positive mold 10 and the negative mold 20 are detachably fixedly connected and fastened together, so that the step 110 and the arc surface 210 define a cavity for preparing the corner-filling preform 101.

[0024] In one possible embodiment, both the male mold 10 and the female mold 20 are annular structures. The step 110 is continuously arranged along the circumference of the male mold 10, and the arc surface 210 is continuously arranged along the circumference of the female mold 20. It is understood that the male mold 10 and the female mold 20 may also be of other shapes, which can be adjusted according to the actual situation, and the embodiments of this application do not specifically limit them.

[0025] In some possible embodiments, the positive mold 10 is the main body for the layup of the corner filling preform 101, and the negative mold 20 is a segmented design. The segmented negative mold 20 helps to ensure the external dimensions of the corner filling preform 101.

[0026] In one possible embodiment, the molding die 1 is designed for a composite material shell structure with a front-end outward-turning and a rear-end inward-turning flange column. The positive mold 10 is an L-shaped structure adapted to the corner of the product; the negative mold 20 has an arc surface 210 that matches the inner corner of the product, and the edge of the arc surface 210 matches the edge of the step 110. The positive mold 10 and the negative mold 20 are fastened together in a detachable and fixed manner. After fastening, the step 110 of the positive mold 10 and the arc surface 210 of the negative mold 20 are precisely aligned, jointly defining a cavity for preparing the corner-filling preform 101. The shape and size of this cavity match the void in the corner area of ​​the product.

[0027] Therefore, the detachable interlocking mechanism of the positive mold 10 and the negative mold 20 facilitates the layup operation and ensures the sealing of the cavity after interlocking. The cavity formed by the precise fit between the step 110 and the arc surface 210 allows the structure of the preform to be perfectly matched with the product voids, effectively improving the filling efficiency, reducing stress unevenness caused by filling misalignment, and thus reducing the risk of internal defects.

[0028] Please see Figure 2 In this embodiment of the application, the molding die 1 includes a release template 30, the anodizing die 10 is provided with an opening 120, and the release template 30 is installed in the opening 120.

[0029] In some possible embodiments, the demolding template 30 is made of a high-temperature resistant metal material, and its size is adapted to the opening 120 at the bottom of the positive mold 10. The opening 120 is located on the side of the positive mold 10 away from the step 110. After the corner filling preform 101 is formed, during demolding, the corner filling preform 101 can be smoothly ejected from the cavity by inserting a support rod into the demolding template 30 through the opening 120. During the ejection process, the shape of the corner filling preform 101 will not be damaged, especially the arc surface structure of the corner area and the layup flatness of the parallel area will not be damaged.

[0030] Therefore, the setting of opening 120 and demolding template 30 can achieve uniform force distribution when corner filling preform 101 is demolded, smoothly detach from the cavity, and effectively protect the structural integrity of corner filling preform 101.

[0031] Please see Figure 2 In this embodiment of the application, the molding die 1 includes a screw 40, the positive mold 10 is provided with a first mounting hole 130, and the negative mold 20 is provided with a second mounting hole 220. The screw 40 is used to pass through the first mounting hole 130 and the second mounting hole 220 to fix and fasten the positive mold 10 and the negative mold 20.

[0032] Specifically, there are multiple screws 40, and correspondingly, there are also multiple first mounting holes 130 and second mounting holes 220. The first mounting holes 130 are arranged at equal intervals along the circumference of the male mold 10, and the first mounting holes 130 penetrate the male mold 10 along the axial direction. The second mounting holes 220 are arranged at equal intervals along the circumference of the female mold 20, and the second mounting holes 220 penetrate the female mold 20 along the axial direction.

[0033] In some possible embodiments, the male membrane mold 10 is provided with a third mounting hole 140, and the female membrane mold 20 is provided with a fourth mounting hole 230. Screws 40 are used to pass through the third mounting holes 140 and 230 to fix and engage the male membrane mold 10 and the female membrane mold 20. The plurality of third mounting holes 140 are arranged equidistantly along the circumference of the male membrane mold 10, and the third mounting holes 140 penetrate the male membrane mold 10 radially. Similarly, the plurality of fourth mounting holes 230 are arranged equidistantly along the circumference of the female membrane mold 20, and the fourth mounting holes 230 penetrate the female membrane mold 20 radially.

[0034] Therefore, on the one hand, the precise alignment and cooperation of the first mounting hole 130 and the second mounting hole 220 ensures accurate engagement between the male mold 10 and the female mold 20 when the screw 40 is connected, avoiding cavity deformation caused by misalignment and thus guaranteeing the dimensional accuracy of the corner filling preform 101. On the other hand, the screw 40 connection provides a stable and uniform tightening force, which is transmitted through the cavity wall of the molding mold 1 to all parts of the corner filling preform 101, especially effectively acting on the corner filling area to improve the density of the corner filling preform 101. Furthermore, the detachable connection of the screw 40 facilitates the disassembly and maintenance of the molding mold 1, and maintains connection stability even after multiple uses. Its high flexibility allows it to adapt to the production needs of different batches of products, improving production efficiency and ensuring consistent product quality.

[0035] Please see Figure 2 In this embodiment of the application, there are two steps 110, namely a first step 111 and a second step 112. The first step 111 and the second step 112 are continuously arranged. The first step 111 and the arc surface 210 define the cavity for preparing the corner filling preform 101.

[0036] Therefore, the setting of the first step 111 and the second step 112 is beneficial to the limiting of the corner filling preform 101, which enables the corner filling preform 101 to be formed in one step, reducing subsequent trimming and improving production efficiency. At the same time, the shape of the formed corner filling preform 101 is completely matched with the product cavity, and it can fit tightly during subsequent assembly.

[0037] Please see Figure 2 , Figure 3 and Figure 4 , Figure 3 This is a schematic diagram of a corner filling preform forming method provided in an embodiment of this application. Figure 4 This is a structural schematic diagram of an inward and outward flange column segment structural component provided in an embodiment of this application. Based on the same inventive concept, this application also provides a molding method for improving the corner quality of composite materials, using any of the molding molds 1 in the above embodiments, including the following steps: S1. Mold design and manufacturing: Based on the corner structure characteristics and R-angle size of the product, design and manufacture the corresponding forming mold 1.

[0038] The molding die 1 has the following characteristics: First, it can ensure the external dimensions of the corner filling preform 101, ensuring that the shape of the corner filling preform 101 fully matches the corner "hole" of the product, ensuring effective corner filling, reducing uneven filling, and preventing internal defects caused by uneven stress; Second, the tooling can pressurize the corner filling preform 101 by tightening with screws 40, ensuring the density of the corner filling preform 101 and reducing the internal quality risk of the corner.

[0039] Before step S2, adhesive release cloth is attached to the surfaces of the male mold 10 and the female mold 20. This facilitates subsequent demolding. Release agents are not allowed here to prevent subsequent corner filling preforms 101 from failing to bond with the continuous fibers and causing detachment.

[0040] S2. The corner filling preform 101 is formed. A layer of carbon fiber prepreg is laid on the positive mold 10. After the layup is completed, the negative mold 20 is fastened to the positive mold 10 and connected with screws 40. It is placed in an oven for heating. After the forming mold 1 reaches a certain temperature, the screws 40 are tightened.

[0041] In some possible embodiments, in step S2, during the layup of carbon fiber prepreg, a layer of fabric prepreg 103 is first used as a base layer to wrap the surface of the corner-filling preform 101. Then, continuous carbon fiber 105 is laid up in parallel zones, and finally, the corner carbon fiber prepreg 102 is filled up. Thus, by using continuous carbon fiber 105 in parallel zones to cover the loose fibers in the corner filling, the integrity of the corner-filling preform 101 is improved, and loose fibers are prevented from falling off.

[0042] In some possible embodiments, the loose fiber prepreg used for the corner filling preform 101 is the same as that used in subsequent products. The loose fiber prepreg is laid in a single layer to avoid localized fiber gaps caused by multi-layer overlapping.

[0043] In some possible embodiments, the weight of the loose fiber filler in the corner filling preform 101 needs to be calculated to prevent insufficient filling, loose preform, excessive filling, insufficient resin content, and resin deficiency. The filling amount can be calculated according to the following empirical formula: m=ρ×ν×f, where m represents the weight of the filler, v represents the volume of the structural void, and f is the filling coefficient, which is generally taken as 1.05~1.10.

[0044] In some possible embodiments, in step S2, the temperature of the molding die 1 is controlled between 60°C and 120°C, depending on the resin system. This avoids insufficient resin flow due to excessively low temperatures and premature resin gelation due to excessively high temperatures.

[0045] S3. The corner filling preform 101 is assembled. After the molding mold 1 cools to room temperature, the demolding begins. The corner filling preform 101 is taken out and assembled in the corner area of ​​the product. Before assembly, the prepreg fabric 103 is used for the base layer.

[0046] In some possible embodiments, the resin system of the fabric prepreg 103 is consistent with the unidirectional prepreg of the subsequent lay-up. The purpose of the underlay is to wrap the corner filler preform 101 with the skin continuous fiber 104 to improve the overall integrity of the lay-up.

[0047] S4. Skin continuous fiber 104 layup and pre-compression: According to the product size, thickness and layup sequence requirements, the prepreg to be laid on the skin is cut and laid up in the corresponding layup sequence to form a composite material component.

[0048] In some possible embodiments, during step S4, during the layup of the continuous fiber 104 of the skin, each layup layer must ensure the adhesion between the prepreg and the corner filling preform 101 to avoid artificial gaps. During the layup process, a vacuum pre-compression at room temperature is performed for 20 to 30 minutes after every 4 to 8 layup layers, and a heating and pressurizing pre-compression is performed after every 1 to 3 mm layup layer to ensure the density of the skin layup.

[0049] S5. Overall co-curing: The composite material component is completely vacuum-sealed using vacuum sealing material. Vacuum pre-compression is performed at room temperature for 30-60 minutes. The composite material component is then cured in an autoclave. The curing temperature regime is determined based on the resin system, and the process is carried out using staged heating and heat preservation methods.

[0050] In some possible embodiments, in step S5, the curing temperature is 100~250℃, the pressure is 0.3~0.6MPa, and the vacuum pressure is -0.07MPa to -0.1MPa.

[0051] S6. Demolding and inspection: Remove the vacuum sealing material to obtain a composite material with good corner quality. After grinding and cleaning the burrs, perform internal quality inspection.

[0052] Therefore, in response to the problem of corner defects such as corner bridging, voids, polyurethane, and delamination that easily occur when using loose fibers to fill the "void" at the corners during the layup process for the inner rounded corner transition and the outer right-angle corner structure, the method provided in this application embodiment effectively reduces the risk of corner defects and improves the reliability and consistency of corner quality.

[0053] Please see Figure 2 , Figure 3 and Figure 4 The product's exterior is described in detail, featuring a composite material shell with an outward-facing front and an inward-facing rear flange column structure, transitioning at an internal corner R1, and maintaining a right angle. The thickness of the continuous fiber 106 layer in the transition zone and the continuous fiber 104 layer in the skin is 6mm, while the thickness of the continuous carbon fiber 105 layer in the end-face thickening parallel zone is 2mm. The material selected is T700 grade carbon fiber, and the resin is bismaleimide resin cured at 230℃. The theoretical thickness of a single layer of prepreg is 0.15mm.

[0054] S1. Mold Design and Manufacturing. The product has two flange structures: inward and outward flared. Two types of corner-filling prefabricated bodies 101 are required: an outward flared flange thickening and corner-filling ply prefabricated body 1011 and an inward flared flange thickening and corner-filling ply prefabricated body 1012. The prefabricated body forming tooling is disassembled, cleaned, and assembled according to the tooling instruction manual. A layer of high-temperature resistant adhesive release cloth is then pasted inside the tooling cavity to facilitate subsequent demolding.

[0055] S2. The corner-filling preform 101 is formed. The amount of loose fiber filling, m, is calculated using the formula ρ×ν×f, where f is taken as 1.05. The corner-filling preform layup is performed in the following order: 1 layer of 3k carbon fiber / bismaleimide resin prepreg as a base layer—2mm thick T700 grade carbon fiber / bismaleimide resin unidirectional prepreg layup—weighing out m units of loose fiber layup. After layup, the tooling mold is installed, connected with screws 40, and placed in an oven. When heated to 80℃~120℃, screws 40 are tightened. The tightening force of screws 40 applies pressure to the corner-filling preform 101 to increase density. After the molding mold 1 cools to room temperature, the corner-filling preform 101 is demolded by reverse ejection.

[0056] S3. Assembly of Corner Filling Preform 101. After the preform is formed, the thickened and corner filling preform 1011 of the outward-facing flange is assembled in the corner area of ​​the outward-facing flange of the product. Before assembly, a prepreg fabric 103 is used to lay a base layer on all areas of the product. The purpose of the base layer is to wrap the corner filling preform 101 with the continuous fibers of each area, thereby improving the overall integrity of the layup. After the corner filling preform 101 is assembled, it is covered with vacuum-assisted material and vacuum-pre-pressed at room temperature for 30-60 minutes to improve the adhesion of the prepreg fabric 103 and the corner filling preform 101 to the molding mold 1.

[0057] S4. Continuous fiber 104 layup and pre-compression for the skin. Based on the thickness of each region and the thickness of a single layer of prepreg, calculate the number of layup layers for each region. Following the designed layup direction (primarily 0°, 90°, ±45°), first complete the continuous fiber 106 layup in the transition zone, followed by the continuous fiber 104 layup for the skin. During the layup process, perform pre-compression at room temperature after every 4-8 layup layers, with a vacuum pressure of -0.09MPa to -0.1MPa and a time of 15-30 minutes. After every 1-3mm layup layer, perform pre-compression at a pressure of -0.1MPa to -0.6MPa, a temperature of 90℃ to 130℃, and a time of 0.5-2 hours.

[0058] After completing the layup and pre-compression of the continuous fiber 106 in the transition zone and the continuous fiber 104 in the skin, the thickened and corner-filled prefabricated body 1012 of the inward flange is installed in the corner area of ​​the inward flange. After installation, vacuum heating and pre-compression are carried out using auxiliary materials. During pre-compression, a certain rigid process skin can be placed on the outer surface of the product or a metal die can be used for shaping to ensure the product's external dimensions. The pre-compression pressure is controlled at -0.1MPa to -0.6MPa, the temperature is 90℃ to 130℃, and the time is 0.5h to 2h.

[0059] S5. Overall co-curing: After completing the above pre-compression, inspect the product's appearance quality and repair any missing parts with prepreg. Vacuum sealing material is used to completely encapsulate the product under vacuum; the components are cured in an autoclave at a curing temperature of 230℃, an autoclave pressure of 0.6MPa, and a vacuum pressure not exceeding -0.09MPa.

[0060] S6. Demolding and Inspection. After curing, the vacuum-assisted material is removed, resulting in a composite material component with good corner quality. After the burrs are cleaned, internal quality inspection is performed.

[0061] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0062] Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed in this application.

[0063] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A molding die for a corner filling preform, characterized in that, include: A positive pressure film mold, wherein the positive pressure film mold is provided with steps; An analgesic mold, wherein the analgesic mold has an arc surface; The positive mold and the negative mold are detachably fixedly connected and fastened together, so that the step and the arc surface restrict the cavity for preparing the corner filling preform.

2. The molding die according to claim 1, characterized in that, The forming mold includes a release template, the anodizing mold has an opening, and the release template is installed in the opening.

3. The molding die according to claim 1, characterized in that, The molding die includes screws. The male mold has a first mounting hole and the female mold has a second mounting hole. The screws are used to pass through the first mounting hole and the second mounting hole to fix and fasten the male mold and the female mold together.

4. The molding die according to claim 1, characterized in that, The number of steps is two, namely a first step and a second step. The first step and the second step are arranged continuously. The first step and the arc surface define the cavity for preparing the corner filling preform.

5. A molding method for improving the corner quality of composite materials, using the corner filling preform molding die according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Mold design and manufacturing: Design and manufacture the corresponding forming mold according to the corner structure characteristics and R-angle size of the product; S2. The corner filling preform is formed by laying a layer of carbon fiber prepreg on the positive mold. After the layering is completed, the negative mold and the positive mold are fastened together and connected with screws. The mold is placed in an oven for heating. After the forming mold reaches a certain temperature, the screws are tightened. S3. The corner filling preform is assembled. After the molding mold cools to room temperature, demolding begins. The corner filling preform is taken out and assembled in the corner area of ​​the product. Before assembly, a prepreg fabric is used for base layering. S4. Continuous fiber layup and pre-compression of the skin: According to the product size, thickness and layup sequence requirements, the carbon fiber prepreg to be laid on the skin is cut and laid up in the corresponding layup sequence to form a composite material component. S5. Overall co-curing: The composite material component is completely vacuum-sealed using vacuum sealing material. Vacuum pre-compression is performed at room temperature for 30-60 minutes. The composite material component is then cured in an autoclave. The curing temperature regime is determined based on the resin system. The process is carried out using staged heating and heat preservation. S6. Demolding and inspection: Remove the vacuum sealing material to obtain a composite material with good corner quality. After grinding and cleaning the burrs, perform internal quality inspection.

6. The molding method according to claim 5, characterized in that, Before step S2, adhesive release cloth is attached to the surfaces of the male mold and the female mold.

7. The molding method according to claim 5, characterized in that, In step S2, during the process of laying up carbon fiber prepreg, a layer of the fabric prepreg is first used as a base layer, and the surface of the corner filling preform is wrapped with the fabric prepreg. Then, the parallel area carbon fiber layup is performed, and finally, the corner filling layup is performed.

8. The molding method according to claim 5, characterized in that, In step S2, depending on the resin system, the temperature of the molding die is controlled between 60°C and 120°C.

9. The molding method according to claim 5, characterized in that, In step S4, during the layup of the continuous fiber skin, each layer must ensure the adhesion between the prepreg and the corner filling preform to avoid artificial gaps. During the layup process, a vacuum pre-compression at room temperature is performed for 20 to 30 minutes after every 4 to 8 layers, and a heating and pressurization pre-compression is performed after every 1 mm to 3 mm of layup to ensure the density of the continuous fiber skin layup.

10. The molding method according to claim 5, characterized in that, In step S5, the curing temperature is 100℃~250℃, the pressure is 0.3MPa~0.6MPa, and the vacuum pressure is -0.07MPa~-0.1MPa.

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