A method of forming a composite wing spar
By using inverted male mold forming and digital sheet design, combined with vacuuming and cold compaction processes, the problems of wrinkles, non-destructive radius corners, and fiber discontinuity in the forming of composite main beams were solved, achieving efficient and low-cost forming of composite main beams.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CORTEX (CHINA) COMPOSITE MATERIALS CO LTD
- Filing Date
- 2026-02-28
- Publication Date
- 2026-06-09
AI Technical Summary
Existing composite material main beam molding processes cannot meet the requirements of large size, overall design, high thickness, and irregular bending shape, and have problems such as wrinkles, damage to R-angles, fiber discontinuity, and high cost.
The method of inverted molding with a positive mold is adopted. The sheet material of different thicknesses is designed by CATIA and CAD software. Combined with vacuuming and autoclave cold compaction process, the sheet material is laid layer by layer and the adhesive film is laid in the transition area to solve the problems of fiber continuity and thickness transition.
It effectively eliminates the problems of wrinkles and R-angle damage after molding, reduces process costs, improves fiber continuity and laying efficiency, and enhances fatigue resistance.
Smart Images
Figure CN122165672A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of composite material manufacturing technology, and specifically to a method for forming a composite material main spar for an airfoil. Background Technology
[0002] In electric vertical takeoff and landing aircraft, the composite material main spar of the wing serves as the main load-bearing structure. The thickness is generally less than 5mm. The design of composite material main spar has gradually developed into features such as large size, integral design, high-thickness flanges, small radius angle, narrow delamination area, and irregular curved shape.
[0003] However, existing composite main beam molding technologies are no longer sufficient to meet the requirements. Current molding processes typically use female molds to ensure the bonding surface is the molded surface, which has the following drawbacks: ① The thickness flange of the composite main beam is prone to wrinkling after molding; ② The small radius (R-angle) easily leads to internal non-destructive quality issues; ③ Fiber discontinuity or large angle deviations occur during the laying process; ④ Existing molding processes require one-time auxiliary pressure materials such as pressure strips, rubber, and silicone at corners and other bends in the mold, resulting in high costs per process. Similar structures to composite main beams include fuselage C-shaped keel beams and tail fin C-shaped load-bearing beams, all of which suffer from the above-mentioned defects during molding. Therefore, a new process method is urgently needed to solve these problems. Summary of the Invention
[0004] The purpose of this invention is to provide a new method for forming composite material main beams for airfoils, aiming to solve the problems existing in the current composite material main beam forming process.
[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: This invention provides a method for forming a composite material main beam for an airfoil. The main beam has a curved structure with a large curvature in the middle region and a small curvature at both ends. The main beam is integrally formed by a web of unequal thickness and vertical edge strips of unequal thickness formed on both sides of the web. The forming method of the main beam includes the following steps: S1. Mold Design: Design the molding mold; S2, 0° Material Design: Based on the required 3D model of the main beam, the length and width of the vertical edge strip in the main beam are measured using CATIA software, and the vertical edge strip material is designed into several long rectangular narrow strips with a first width; the curved contour of the web is extracted using CATIA software and unfolded or segmented to obtain the web planar contour drawing; then, the web contour is split into several curved narrow strips with a second width by offsetting the narrow strip width using CAD software, and the curve contour length of the curved narrow strips is measured to convert all the curved narrow strips included in the web into long rectangular narrow strips; S3, 45° sheet design: The web planar outline is offset outward by the width of a vertical edge strip using CAD software, and then rotated 45° to obtain the 45° unfolded planar outline of the main beam. The 45° unfolded planar outline is divided into blocks according to the shape, curvature and material width limit of the main beam to obtain the narrow strip outline of the 45° sheet. The vertical edge strip and the web are on the same 45° sheet. S4. Part Laying: On the laying surface of the forming mold, the whole layer and local layer of the part are laid layer by layer according to the layup design requirements using narrow strips of material at 0° and 45°. During the laying process, vacuum compaction is required every few layers, and cold compaction is required every few layers in a hot autoclave. All local transition layers are laid in a gradually outward manner during the laying process. S5. Vacuum bag making and vacuuming: After the parts are laid out, vacuum bags are made, vacuum is drawn, and the parts are placed in an autoclave for curing. Then, the parts are demolded to obtain the composite material main beam.
[0006] Specifically, the wing's composite material main spars are curved structures, with the vertical edge strips and webs having unequal thicknesses, typically less than 3.0 mm at the thinnest point and more than 6.0 mm at the thickest.
[0007] The core of step S2 in the molding method of this invention lies in the fact that, during the design and splitting of the sheet material, the edge strip and the web are drawn separately, and the web is further divided into narrow strips according to the curvature of the web contour curve; the edge strip is designed into a narrow strip rectangular sheet by measuring the length and width of the edge strip using CATIA; the web is extracted with the curved surface contour by CATIA and unfolded to obtain a planar contour drawing, and then the web contour is split into multiple narrow strip sheets by offsetting the width of the narrow strips in CAD, measuring the curve contour length of the rectangular sheet, and converting all the narrow strip sheets of the web into narrow strip rectangular sheets. This method unfolds and normalizes the three-dimensional curved surface into two-dimensional narrow strip sheets, accurately solving the core problem in the pre-processing of complex curved surface components.
[0008] In step S3, for other angled sheets (45° sheets), the edge strip and the web are on the same sheet to ensure fiber continuity and small angle deviation. The curved contour extracted by CATIA is unfolded or segmented to obtain the web planar contour. Then, the edge strip width is measured by CATIA. The web contour is then offset outward by CAD to the edge strip width value measured in step S2. The angle is rotated to obtain the 45° unfolded planar contour of the main beam. The 45° unfolded planar contour is divided into blocks according to the shape of the main beam and the material width limit to obtain the 45° narrow strip contour. Narrow strip laying can prevent wrinkles and angle deviation caused by full-surface laying in curved shapes. This method effectively solves the problem of achieving continuous fiber laying on complex curved surfaces while avoiding wrinkles and angular deviations. The core advantage of this method lies in prioritizing the continuity and precise control of fiber orientation. Through the design of "the edge strip and the web being made of the same sheet" and precise digital unfolding, offsetting, and rotating, it ensures a natural transition and continuous force transmission of fibers from the web to the edge strip, avoiding the structural weaknesses and additional weight caused by splicing edge strips separately. At the same time, narrow strip laying effectively solves the wrinkle problem on complex curved surfaces. By breaking down the whole process into parts, this method significantly improves laying quality and efficiency.
[0009] In step S4 of the molding method of the present invention, the local transition layup sheet is also designed: all the layup sheets in the transition area are designed to gradually face outward (vacuum bag side), that is, the size of the local layer sheet decreases layer by layer; the larger the size beam thickness, the more layup layers there are. During the process of vacuum bag pressure being transferred to the part, the curing pressure on the part thickness section is constant, and the closer to the molding surface ( Figure 5 The smaller the actual pressure transmitted to surface A in the thickness transition area, the more the transition layer is distributed in the middle of the thickness beam, and the layer is laid in a gradual manner; if the gradual layer is laid inward (i.e. towards the formwork surface (surface A)). Figure 6 If the pressure is transmitted from the surface to each ply step position (side A), then more layers are needed, which means that less pressure is transmitted to the ply step position and it is easier to cause non-destructive problems. However, the gradient outward (vacuum bag side (side B)) adopted in this application. Figure 5 In the case of the B side, the pressure is transmitted to the ply step position through the same number of ply layers, ensuring that the part is more likely to pass the test after curing without damage, and solving the problem that the existing process is prone to internal non-destructive quality failure.
[0010] Furthermore, a method for forming a composite material main beam for an airfoil: in step S2, the first width is set to 40-50 mm, and the second width is set to 40-50 mm.
[0011] Furthermore, a method for forming a composite material main beam for an airfoil: in step S3, the length of the 45° narrow strip material to be laid in the middle area with large curvature on the main beam is 100-300mm; the length of the 45° narrow strip material to be laid in the areas with small curvature at both ends can exceed 500mm.
[0012] Furthermore, a method for forming a composite material main beam for an airfoil: during the laying process in step S4, vacuum compaction is performed every 1 to 3 layers, and autoclave cold compaction is performed every 5 to 8 layers.
[0013] Furthermore, a method for forming a composite material main beam for an airfoil: in step S4, the pressure for vacuum compaction is -0.095 to -0.08 MPa, and the compaction time is 10 to 30 minutes; in step S4, the pressure for cold compaction in the autoclave is 0.3 to 1.0 MPa, and the compaction time is 1 to 3 hours.
[0014] Furthermore, a method for forming a composite material main beam for an airfoil: in step S4, the gradient of the local transition layup is ≤3.0mm.
[0015] Furthermore, a method for forming a composite material main beam for an airfoil includes step S4: after the local transition layup is completed, an adhesive film is applied to the layup surface in the transition area.
[0016] Specifically, for transition layups with a gradient of less than 3.0 mm, it is preferable to apply an adhesive film to the surface of the layup in the transition area to enhance the interfacial structure. By applying the adhesive film, it can melt and flow during curing, thereby filling the microscopic voids at the gradient step and forming a resin-rich, tough transition zone. This not only transfers and disperses stress but also effectively inhibits delamination, significantly improving the fatigue resistance of the area and achieving local reinforcement.
[0017] Furthermore, a method for forming a composite material main beam for an airfoil: in step S4, a carrier-free epoxy resin film with a basis weight of <200 gsm is used.
[0018] The beneficial effects of this invention are: The molding method of this invention abandons the traditional female mold molding method that uses the bonding assembly surface as the mold surface. Instead, it uses a male mold for inverted molding of the thick-sized wing composite main beam. It cleverly solves the molding wrinkling problem of the thick vertical edge strip of the main beam by utilizing the effect of gravity. In the traditional process of molding with a female mold, the thickness of the vertical edge strip is relatively thick during the curing process. The prepreg material softens, and with the addition of gravity, the edge strip ply softens and slides downward. The pressure transmission of the vacuum bag cannot completely fix the thick edge strip on the edge strip, which leads to wrinkles on the vertical edge and R-corner of the molded part. However, the method of this invention inverts the main beam for molding. The thick edge strip softens and sags due to gravity. Its edge strip ply extends to the R-corner and web side and is vertically fixed by the vacuum bag pressure. The sag of the vertical edge can naturally flatten the surface of the thick edge strip and prevent wrinkles from forming on the vertical edge of the part.
[0019] The molding method of this invention uses an inverted male mold for main beam molding. The mold is in the form of a punch, which makes it easier to lay the parts at corners and other corners, ensuring that the parts are laid firmly and in place. Under the premise of ensuring no damage to the quality, there is no need for pressure strips, rubber, silicone and other disposable auxiliary pressure materials, which reduces the process cost. It can mold similar parts with an inner R-angle as small as R3 (micro R-angle, radius 3mm), which is more advantageous compared with the traditional female mold molding method.
[0020] In the molding method of the present invention, when all local layer sheets are laid in a layer-by-layer (gradual) manner, the size decreases layer by layer, and the gradual layers face outward (towards the vacuum bag surface). The method of laying the sheets with the gradual layers facing outward solves the problem of non-destructive treatment in the thickness transition area of the main beam with a large thickness.
[0021] The molding method of this invention also employs film application in the gradient area, which solves the problem of non-destructive application in narrow gradient areas. Narrow areas with missing layers may have gradients of 1-2 mm per layer. Manual application and positioning can lead to some deviations, causing layers to overlap and preventing the complete application of steps. Subsequent layers may then create cavities at the steps, potentially resulting in resin loss and thus non-destructive application. In the application process, for narrow areas with missing layers, film application is performed after application. The film softens and flows upon curing, filling the gaps in the steps and solving the non-destructive application problem.
[0022] The molding method of this invention adopts a narrow strip form that simulates "automatic tape laying" to split the layers at different angles into strips, which are then laid into long rectangular strips. This solves the problem of fiber discontinuity or large angle deviation in the laying process of curved main beams.
[0023] The large number of layers in a thick composite main beam leads to accumulated gaps between the layers, resulting in a larger overall beam profile. During curing and pressurization, the thick prepreg softens and the profile tightens under pressure. Vacuum bag compression can easily create wrinkles on the surface of the thick prepreg layer. The molding method of this invention effectively reduces the gaps between the layers by introducing a "vacuuming + cold compaction" process during the laying process. This makes the laid profile closely resemble the cured profile, solving the wrinkling problem of the vacuum bag surface when using a male mold and addressing the issue of large tolerances in the molded profile caused by the vacuum bag surface being the bonding surface, which could affect bonding and positioning. Attached Figure Description
[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0025] Figure 1 This is a schematic diagram of the main beam of the composite material wing formed in Example 1; Figure 2 This is a schematic diagram of the edge strip and sheet design in Example 1; Figure 3 This is a schematic diagram of the web and sheet design in Example 1; Figure 4 This is the outline diagram of the 45° narrow strip material sheet laying in Example 1; Figure 5 This is a schematic diagram of the gradient outward-facing sheet design in Example 1; Figure 6 A schematic diagram of the design for a gradient inward-facing sheet material. Figure 5 and 6 Side A is the mold side, and side B is the vacuum bag side; Figure 7 This is a cross-sectional view of the paving mold in Example 1.
[0026] The markings in the image are as follows: 1-Edge strip, 2-Body plate, 3-Forming mold. Detailed Implementation
[0027] 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 some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.
[0028] In the description of this invention, it should be understood that the terms "upper," "lower," "left," "right," "top," and "bottom," etc., indicating orientation or positional relationships, are merely for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" and "second" may explicitly or implicitly include one or more of that feature. Moreover, the terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein.
[0029] Example 1
[0030] like Figures 1-7 As shown, this embodiment 1 provides a method for forming a composite material main beam for an airfoil. The main beam has a curved arc structure with a large curvature in the middle region and a small curvature at both ends. The main beam is integrally formed by a web plate 2 of unequal thickness and vertical edge strips 1 of unequal thickness formed on both sides of the web plate 2. The main beam is also characterized by a larger thickness, a smaller outer radius (R), an inner radius (R3) or greater (a rounded corner with a radius of 3 mm), and the thickness of the vertical edge strips is 2 times or more than that of the web plate. Furthermore, the web plate is thicker than that of a typical aircraft main beam, meaning that there are more layers. The forming method of the main beam includes the following steps: S1. Mold Design: Design a forming mold 3 with a "convex" shaped cross section. The mold is a male mold and is inverted to form the main beam. S2, 0° material sheet design: Based on the required three-dimensional model of the main beam, the length and width of the vertical edge strip in the main beam are measured using CATIA software, and the vertical edge strip material sheet is designed into several long rectangular narrow strip material sheets with a first width (40mm); The curved contour of the web is extracted and unfolded using CATIA software to obtain a web planar contour drawing. Then, the web contour is split into several curved narrow strip pieces with a second width (50mm) by offsetting the narrow strip width using CAD software. The length of the curved contour of the curved narrow strip pieces is measured to convert all the curved narrow strip pieces included in the web into long rectangular narrow strip pieces with a width of 50mm. S3, 45° sheet design: The edge strip and web are on the same 45° sheet. The web planar outline is offset outward by the width of the edge strip (i.e., 40mm) using CAD software, and then rotated 45° to obtain the 45° unfolded planar outline of the main beam. According to the shape, curvature and material width limit of the main beam, the 45° unfolded planar outline is divided into blocks to obtain the narrow strip outline of the 45° sheet. The main beam is curved, and the curvature in the middle area is large, so it needs to be divided into smaller sheets. The length of each sheet is controlled between 100 and 300 mm. The curvature at both ends is small and close to a straight line, so it does not need to be divided into multiple segments. The sheet size can be controlled above 500 mm. S4. Component Laying: The whole layer and partial layer sheets are pre-processed and cut according to the above design method. On the laying surface of the laying mold 3, the whole layer and partial layer of the component are laid layer by layer using narrow strip sheets of 0° and 45° according to the lay design requirements. During the laying process, vacuum compaction is required every 2 layers (vacuum pressure -0.08MPa, compaction time 15 minutes) and autoclave cold compaction is required every 5 layers (pressure 0.6MPa, time 1 hour). During the laying process, all local transition layers are laid in a gradient outward manner, with the size decreasing layer by layer. The gradient size is 2mm. After the local transition layer is laid, a layer of carrier-free epoxy resin film with a weight of 146gsm is laid on the surface of the transition area layer (gradient layer). S5. Bag making and vacuuming: After the parts are laid out, a non-porous release film and breathable felt are laid out, thermocouples / vacuum nozzles are arranged, vacuum bags are made, vacuuming is performed, airtightness is tested, and the parts are placed in an autoclave for curing according to the process curve. Then, the parts are demolded, cut, and inspected to obtain the composite material main beam.
[0031] Specifically, the molding method provided in Embodiment 1 above employs the following technical means: ① Inverted molding using a male mold: The male mold helps ensure the smoothness of the outer surface of the part, and inverted molding facilitates the laying operation; ② Digital processing of the material sheet: The three-dimensional curved surface is unfolded and normalized into a two-dimensional narrow strip material sheet. CATIA is used to extract and unfold the curved surface contour. In CAD, it is offset and divided according to the design width and converted into rectangular material sheets. This provides accurate data for automatic feeding and laying, which is conducive to the elimination of wrinkles; ③ Layer-by-layer laying and compaction: The material sheets are laid and compacted on the mold in sequence. Combined with intermittent vacuuming and autoclave cold compaction processes, interlayer air is effectively eliminated, resin residue is reduced, and the layup structure is stabilized; ④ Local transition zone treatment: A smooth transition in thickness areas is achieved by using a gradual (dropped layer) laying method. Each layer is rolled back inward by 2mm. After laying, a layer of carrier-free epoxy resin film is added to the surface of the transition zone to fill the micro gaps and enhance the interface strength; ⑤ Curing and post-treatment: The resin is cured and the part is post-treated.
[0032] The present invention provides a method for forming a composite material main beam for an airfoil: the complex spatial curved surface is flattened into a regular two-dimensional rectangular sheet. This not only improves the accuracy of fiber sheet orientation and avoids the problem of wrinkles caused by the inability to eliminate material excess when laying the whole sheet, but also the regular sheet shape is very suitable for automated feeding equipment and automated tape laying equipment, which can significantly improve the material utilization rate and production efficiency.
[0033] The molding method of this invention also employs a combined process of "vacuuming + cold compaction." Vacuuming can promptly remove interlayer gas and prevent the formation of large-area bubbles; while cold compaction (applying high pressure at a temperature before the resin undergoes a violent chemical reaction) can further compact the layers, reduce interlayer gaps, and provide a stable preform for the subsequent high-temperature curing stage, effectively reducing curing deformation. The molding method of this invention also applies a layer of adhesive film to the surface of the layers in the transition region. This is because in areas of abrupt thickness change (gradient layers), the interface structure is relatively weak. By applying a carrier-free epoxy resin film, this invention allows the film to melt and flow during curing, thereby filling the microscopic voids at the gradient (delamination) steps and forming a resin-rich, tough transition zone. This not only transfers and disperses stress, avoiding stress concentration, but also effectively inhibits delamination, significantly improving the fatigue resistance of this area and achieving a localized reinforcement effect.
[0034] The core of this invention's method for forming a composite wing main beam lies in: solving the problems of wrinkles in the flange strips and non-destructive delamination of the radius angle after forming the main beam using a simpler method; enabling the formation of smaller radius angle features; and addressing issues such as fiber discontinuity or large angle deviations. This invention utilizes a male mold forming method (inverted main beam forming) to eliminate flange wrinkles by leveraging the downward force of gravity, while also saving on process costs. The material sheet design method of this invention solves the problems of fiber discontinuity or large angle deviations, addresses the issue of non-destructive delamination in the transition area, and improves laying efficiency. The method employs a combination of vacuuming and cold compaction, reducing the gap between layers and eliminating the shape deviation issues that may arise from wrinkles on the vacuum bag surface in the male mold forming method, which could affect assembly.
[0035] The above-described preferred embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of the invention. Any obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.
Claims
1. A method for forming a composite material main sparsity for an airfoil, characterized in that, The main beam has a curved structure with a large curvature in the middle region and a small curvature at both ends. The main beam is integrally formed by webs (2) of unequal thickness and vertical edge strips (1) of unequal thickness formed on both sides of the webs (2). The forming method of the main beam includes the following steps: S1. Mold design: Design the molding mold (3); S2, 0° material sheet design: Based on the required three-dimensional model of the main beam, the length and width of the vertical edge strip (1) in the main beam are measured by CATIA software, and the vertical edge strip material sheet is designed into several long rectangular narrow strip material sheets with a first width; The curved contour of the web (2) is extracted by CATIA software and unfolded or segmented to obtain the web planar contour. Then, the web contour is split into several curved narrow strips with a second width by offsetting the narrow strip width using CAD software. The length of the curved contour of the curved narrow strip is measured to convert all the curved narrow strips included in the web (2) into long rectangular narrow strips. S3, 45° sheet design: The web planar outline is offset outward by the width of a vertical edge strip using CAD software, and then rotated 45° to obtain the 45° unfolded planar outline of the main beam. The 45° unfolded planar outline is divided into blocks according to the shape, curvature and material width limit of the main beam to obtain the narrow strip outline of the 45° sheet. S4. Parts laying: On the laying surface of the forming mold (3), the whole layer and local layer of the parts are laid layer by layer using narrow strips of 0° and 45° according to the layup design requirements. During the laying process, vacuum compaction is performed every few layers, and cold compaction is performed in a hot autoclave every few layers. During the laying process, all local transition layers are laid in a gradually outward manner. S5. Vacuum bag making and vacuuming: After the parts are laid out, vacuum bags are made, vacuum is drawn, and the parts are placed in an autoclave for curing. Then, the parts are demolded to obtain the composite material main beam.
2. The method for forming a composite material main beam for an airfoil according to claim 1, characterized in that, In step S2, the first width is set to 40-50mm, and the second width is set to 40-50mm.
3. The method for forming a composite material main beam for an airfoil according to claim 1, characterized in that, In step S3, the length of the 45° narrow strip material to be laid in the middle area with large curvature on the main beam is 100-300mm; the length of the 45° narrow strip material to be laid in the area with small curvature at both ends can exceed 500mm.
4. The method for forming a composite material main beam for an airfoil according to claim 1, characterized in that, In step S4, vacuum compaction is performed every 1 to 3 layers, and autoclave cold compaction is performed every 5 to 8 layers.
5. A method for forming a composite material main spar for an airfoil according to claim 1 or 4, characterized in that, In step S4, the pressure for vacuum compaction is -0.095 to -0.08 MPa, and the compaction time is 10 to 30 minutes; in step S4, the pressure for cold compaction in the autoclave is 0.3 to 1.0 MPa, and the compaction time is 1 to 3 hours.
6. The method for forming a composite material main beam for an airfoil according to claim 1, characterized in that, In step S4, the gradient of the local transition layup is ≤3.0mm.
7. The method for forming a composite material main beam for an airfoil according to claim 6, characterized in that, Step S4 also includes: after the local transition layer is laid, applying an adhesive film to the surface of the transition area layer.
8. The method for forming a composite material main beam for an airfoil according to claim 1, characterized in that, In step S4, a carrier-free epoxy resin film with a basis weight of <200 gsm is used.