A method for co-curing a longitudinal and transverse integrated hollow cap type rib

Abstract

The present application relates to the technical field of composite material forming, and provides a longitudinal and transverse integrated hollow cap-shaped rib co-curing forming method, which comprises the following steps: providing a core mold assembly, wherein the core mold assembly comprises a hard core mold and a water-insoluble and flexible isolation layer continuously coated on the surface of the hard core mold; laying a skin prepreg on a forming mold and positioning and installing the core mold assembly on the skin prepreg; filling a preformed fiber filling body into a root area where the core mold assembly and the skin prepreg intersect after the preformed fiber filling body is heated and softened, and pre-compacting; laying a rib prepreg on the core mold assembly and the skin prepreg, bagging and co-curing forming; dissolving the hard core mold and extracting the isolation layer to complete demolding. The present application realizes the co-curing forming of the hollow cap-shaped rib, improves the rigidity and strength of the component, and reduces the production cost.

Description

Technical Field

[0001] This invention relates to the field of composite material molding technology, specifically to a method for co-curing and molding a longitudinally and transversely integrated hollow cap-shaped rib. Background Technology

[0002] Currently, in the manufacturing of high-end equipment such as aerospace, hollow reinforced composite material panels are typically formed using "dry reinforcement with wet skin" co-bonding, "dry skin with wet reinforcement" co-bonding, or secondary bonding processes. However, in these processes, the longitudinal and transverse ribs are often formed independently before assembly, resulting in poor overall structure integrity and limited stiffness and strength. Furthermore, multiple curing processes easily introduce internal stress deformation, requiring additional positioning fixtures to ensure assembly accuracy, leading to high production costs and long production cycles. In addition, for hollow cap-shaped ribs with complex topologies such as crisscrossing, existing technologies often use rubber airbags as internal pressure support media. However, airbags are difficult to adapt to complex intersecting node shapes, have short service life, and high overall costs. Moreover, porosity defects are easily generated in the root junction area during co-curing, affecting the mechanical properties of the component. Therefore, there is an urgent need for a molding method that can achieve integrated co-curing molding of complex intersecting hollow reinforced structures, balancing high quality and low cost. Summary of the Invention

[0003] To address the problem that existing technologies struggle to achieve high-quality integrated co-curing molding of complex, interlocking, hollow, reinforced composite material components, this application proposes a co-curing molding method for longitudinally and transversely integrated hollow cap-shaped ribs, achieving high rigidity, low internal stress deformation, and efficient, low-cost manufacturing of the components.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A method for co-curing and molding a hollow cap-shaped rib with integrated longitudinal and transverse cross-sections, characterized in that it includes: S1. Provide a core mold assembly, the core mold assembly including a water-soluble rigid core mold and an isolation layer continuously covering the surface of the rigid core mold; S2. Lay the skin prepreg on the molding die and position and install the core mold assembly on the skin prepreg; S3. After heating and softening the pre-formed fiber filler, fill it in sections into the root area where the core mold assembly and the skin prepreg meet, and pre-compact it. S4. Lay reinforced prepreg on the core mold assembly and the skin prepreg, make a bag and co-cur it to obtain a semi-finished composite material component. S5. Dissolve the hard core mold and remove the residual material by pulling out the isolation layer to complete the demolding.

[0005] Furthermore, the rigid core mold is formed by mixing and curing a water-soluble matrix with reinforcing aggregate; the isolation layer is continuously wrapped around the surface of the rigid core mold to form a complete release sleeve.

[0006] Furthermore, the water-soluble matrix includes a potassium carbonate solution, the reinforcing aggregate includes sand particles and chopped glass fibers; the insulating layer includes a BOPP film or a heat-shrinkable film, with a continuous winding overlap width of 3 mm to 5 mm.

[0007] Furthermore, step S3 also includes: S30. Cut the heated and softened fiber filler into filler segments of a preset length and fill them sequentially into the root region. S31. After filling, cover with a release liner and vacuum to compact.

[0008] Furthermore, the temperature range for the heating and softening process is 50°C to 60°C, and the preset length is 10mm to 15mm. The filling amount of the unidirectional fiber prepreg Calculate using the following formula: in, The filler width of the unidirectional fiber prepreg is in mm. The radius of the bottom arc of the hollow reinforced structure, in mm; Pi; This is the porosity correction factor for the material during the curing process; The thickness of a single layer of unidirectional fiber prepreg is in mm. This represents the fill factor.

[0009] Furthermore, step S1 also includes a method for manufacturing the hard core mold: S10. Mix the water-soluble matrix solution with the reinforcing aggregate to obtain a wet sand mixture; S11. Fill the wet sand mixture into a core mold forming mold with an interlaced grid cavity and tamp it down to remove air. S12. After the mold is closed and tightened, it is sent into an oven for heating and curing. After cooling, it is demolded to obtain the water-soluble hard core mold.

[0010] Furthermore, step S2 also includes: S20. Lay the skin prepreg on the molding die and pre-compact it at room temperature; S21. Install the core mold positioning block, place the core mold assembly on the skin prepreg and fix it by the core mold positioning block; S22. Vacuum the core mold assembly to make it adhere tightly to the surface of the skin prepreg, maintain it for a preset time, check the gap, and add prepreg to areas that exceed the preset gap threshold.

[0011] Furthermore, step S4 also includes: S41. Lay the reinforced prepreg layer by layer, with the overlap seams of adjacent layers staggered by a preset distance; S42. The semi-finished composite material component after bag making is sent into a hot autoclave, vacuumed throughout the process, heated and pressurized according to the step temperature rise curve, and then cooled and depressurized.

[0012] Furthermore, step S5 also includes: S51. Break the water-insoluble and flexible isolation layer from the reinforced opening; S52. Inject water through the opening to dissolve the water-soluble hard core mold, allowing the core mold material to flow out with the water; S53. The water-insoluble and flexible isolation layer is extracted as a whole from the reinforced cavity.

[0013] Furthermore, the outer surface of the isolation layer is coated with a release agent, which includes release wax.

[0014] Beneficial effects: This invention achieves co-curing and molding of a hollow cap-shaped rib with integrated longitudinal and transverse reinforcement through the synergistic design of a water-soluble rigid core mold and a water-insoluble and flexible isolation layer. The water-soluble rigid core mold provides rigid support that adapts to the staggered topology, overcoming the deficiency of insufficient support at nodes in traditional airbags; while the water-insoluble and flexible isolation layer forms a complete extraction channel, allowing the demolding process to proceed without damaging the component body, solving the problem of cleaning slag from complex cavities. The combination of these two elements enables the skin and longitudinal and transverse reinforcement to be molded simultaneously in a single curing cycle, reducing the number of curing cycles, minimizing internal stress deformation, and improving the overall rigidity and dimensional stability of the component.

[0015] Meanwhile, by heating and softening the preformed fiber filler and then filling it in sections to the root junction area and applying vacuum pre-compaction, the wettability of the prepreg and the fiber adhesion in this area are significantly improved, effectively eliminating root pores and delamination defects common in traditional processes, and enhancing the structural load-bearing efficiency and fatigue life.

[0016] In addition, the entire process does not require special airbags or their maintenance and replacement, the core mold material is inexpensive and can be mass-produced, and the demolding operation is simple and efficient, significantly reducing production costs and manufacturing cycle. Attached Figure Description

[0017] Figure 1 This is an overall process flow diagram of an embodiment of the present invention; Figure 2This is a schematic diagram of the curing curve of an embodiment of the present invention; Figure 3 This is a measurement diagram of the processed thickness data according to an embodiment of the present invention; Figure 4 This is a process flow diagram of the demolding process according to an embodiment of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the present invention clearer, 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.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0020] Example 1 like Figures 1 to 3 As shown, this embodiment provides a method for co-curing and molding a hollow cap-shaped rib with integrated longitudinal and transverse structures. This method achieves high-quality integrated molding of complex interwoven structures through specific core mold component design and process combination. Specifically, the co-curing and molding method includes the following steps: Step S1, providing a core mold assembly, the core mold assembly including a water-soluble rigid core mold and a water-insoluble and flexible isolation layer continuously covering the surface of the water-soluble rigid core mold.

[0021] In this embodiment, the water-soluble rigid core mold can withstand external pressure and maintain cavity stability during the co-curing process. Simultaneously, continuously coating the surface of the water-soluble rigid core mold with a water-insoluble and flexible isolation layer is a crucial prerequisite for successful demolding. This isolation layer isolates the prepreg from the core mold body during curing; during the demolding stage, when the internal rigid core mold is dissolved, this isolation layer forms a continuous extraction channel or envelope, capable of carrying away any residual reinforcing aggregate or incompletely discharged particles from the cavity, avoiding the residue retention problem that may occur with simple water flushing, thereby ensuring the smoothness and dimensional accuracy of the component's inner wall.

[0022] Step S2: Lay the skin prepreg on the molding die and position and install the core mold assembly on the skin prepreg.

[0023] Specifically, the skin prepreg is laid layer by layer onto the base of the panel forming mold according to the designed lay-up angle. Then, a dedicated core mold positioning block is used to precisely fix the prepared core mold assembly to the predetermined position of the skin prepreg. This step not only establishes the relative positional relationship between the stiffening structure and the skin, but also restricts the displacement of the core mold during subsequent vacuum compaction and curing processes through the positioning block, providing a reliable assembly benchmark for integrated molding.

[0024] Step S3: After heating and softening the pre-formed fiber filler, fill it in sections to the root area where the core mold assembly and the skin prepreg meet, and then pre-compact it.

[0025] The fiber filler is pultruded from unidirectional fiber prepreg, exhibiting high fiber volume content and density. Pre-filling heating softens the prepreg to reduce its viscosity and improve fiber bundle flexibility, allowing it to better conform to the complex curved surface at the junction of the mandrel and skin. Segmented filling is employed to prevent wrinkles or gaps in the root region where long strip fillers have small bending radii. After each segment is filled, pre-compaction is immediately performed, using external force to force the fiber filler to adhere tightly to the mold and mandrel surfaces, expelling air from between layers and interfaces. This combined process of "heat softening + segmented filling + pre-compaction" eliminates the risk of insufficient prepreg and porosity in the root triangular area due to poor prepreg flow or fiber springback, ensuring density in critical load-bearing areas.

[0026] Step S4: Lay reinforced prepreg on the core mold assembly and skin prepreg, make bags and co-cur them to obtain semi-finished composite material components.

[0027] After the root filling is completed, the reinforcing prepreg is layered onto the core mold assembly and skin surface to form a complete reinforced prefabricated structure. Subsequently, breathable felt, vacuum bags, and other auxiliary materials are laid and sealed. In an autoclave, the skin, root filler, and reinforcing structure simultaneously undergo prepreg impregnation, flow, and curing reactions under high temperature and pressure, forming an integrated composite material component semi-finished product. Compared to secondary bonding or co-bonding processes, this co-curing method eliminates heterogeneous bonding interfaces, significantly improving the overall stiffness and strength of the component and reducing internal stress deformation caused by repeated thermal cycles.

[0028] Step S5: Dissolve the water-soluble hard core mold, and remove the residual material by pulling out the water-insoluble and flexible isolation layer to complete the demolding.

[0029] After curing, the water-soluble matrix in the rigid core mold is first dissolved by injecting water, causing it to lose its structural strength. At this point, the space originally occupied by the core mold becomes a cavity filled with liquid, while the water-insoluble and flexible release layer retains its complete tubular or sleeve-like shape. The operator can pull the release layer from the reinforced opening to remove it, along with any residual aggregate and debris attached to its inner side, from the narrow and interlaced cavity as a whole. This demolding mechanism cleverly utilizes the sacrificial nature of the rigid core mold and the continuity of the flexible release layer. It overcomes the problem of rigid core molds being unable to be removed from undercut or interlaced structures, and avoids the drawback of traditional water-soluble core molds where residue is difficult to remove completely when directly washed with water, achieving efficient and non-destructive demolding of complex hollow components.

[0030] It should be understood that although this embodiment uses a crisscrossing cap-shaped rib as an example, the above process is also applicable to T-shaped ribs, I-shaped ribs or other hollow reinforced structures with interlaced topological features. As long as they adopt a water-soluble hard core mold combined with a flexible isolation layer demolding mechanism and a root heating segmented pre-compaction process, they should all be covered within the protection scope of this invention.

[0031] Example 2 like Figures 1 to 3 As shown, in Example 2, the material composition, coating process, and surface treatment of the mandrel assembly provided in Example 1 are further defined. Specifically, the water-soluble rigid mandrel is formed by mixing and curing a water-soluble matrix with reinforcing aggregate. The water-soluble matrix includes a potassium carbonate solution, and the reinforcing aggregate includes sand particles and chopped glass fibers. The sand particles (e.g., 100-mesh quartz sand) serve as the main rigid filler, are inexpensive, and have a controllable coefficient of thermal expansion, effectively suppressing the thermal deformation of the mandrel. The chopped glass fibers (e.g., 10mm in length) play a toughening role in the mixture, significantly improving the bending strength and impact resistance of the mandrel, preventing the mandrel from generating debris due to brittle fracture during handling, laying, or vacuum compaction, thereby avoiding debris piercing the isolation layer or remaining on the inner wall of the component. It should be understood that although this embodiment lists a specific combination of potassium carbonate, sand particles, and glass fibers, other water-soluble salts, ceramic particles, or organic fibers can also be used in other embodiments, as long as the functional requirements of rigid support and water-soluble demolding are met.

[0032] After the mandrel is prepared, a water-insoluble and flexible release layer is continuously wound around the surface of the water-soluble rigid mandrel to form a complete release sleeve. Due to the complex internal cavity topology of the interlaced hollow stiffened component, with multiple undercuts and intersections, if the release layer has breaks or unsealed seams, it is prone to tearing during demolding. This can cause part of the release film to remain deep within the cavity and be impossible to remove, or allow the dissolved mandrel slurry to leak and contaminate the inner wall of the component. The seamless tubular sleeve formed by continuous winding creates a closed barrier interface, preventing the prepreg from penetrating into the mandrel and providing a continuous force path during demolding. This allows the operator to pull out the entire release sleeve along with any remaining material by pulling one end.

[0033] Specifically, the water-insoluble and flexible release layer includes BOPP film or heat-shrinkable film, with an overlap width of 3mm to 5mm for continuous winding. BOPP film has excellent mechanical strength and dimensional stability, making it suitable for most co-curing processes; heat-shrinkable film can be pre-shrinked by heating to adhere more tightly to the mandrel surface, reducing wrinkles. The overlap width is controlled between 3mm and 5mm. Furthermore, constant tension should be maintained during the winding process to ensure the film layer adheres tightly to the mandrel surface without air bubbles.

[0034] To further optimize the demolding effect, a release agent is coated on the outer surface of the water-insoluble and flexible isolation layer. In this embodiment, the release agent is preferably release wax. Although the isolation layer itself has certain low surface energy characteristics, under high temperature and high pressure curing conditions, the prepreg may still adhere slightly to the film surface. Applying release wax can form a lubricating surface between the isolation layer and the reinforced prepreg, significantly reducing the coefficient of friction and adhesion between the two. This not only greatly reduces the extraction resistance during demolding, preventing the isolation layer from breaking due to excessive force, but also ensures the smoothness of the inner wall of the component, reducing subsequent grinding and finishing processes.

[0035] Example 3 like Figures 1 to 3 As shown, this embodiment 3, based on embodiment 1, further specifies the filling process and filling amount control of the root junction area in step S3. Specifically, the preformed fiber filler is obtained by pultrusion preforming of unidirectional fiber prepreg. During the filling operation, segmented filling includes: S30. Cut the heated and softened fiber filler into filler segments of a preset length and fill them sequentially to the root area.

[0036] In a preferred embodiment, the heating and softening temperature range is 50°C to 60°C, and the preset length is 10mm to 15mm. This process parameter setting is based on a dual consideration of the rheological properties and geometric adaptability of the prepreg. Within the temperature window of 50°C to 60°C, the viscosity of the prepreg is significantly reduced but a rapid cross-linking reaction has not yet occurred, giving the fiber bundle excellent flexibility and conformability, enabling it to closely conform to the complex curved surface formed by the mandrel and skin. If the temperature is too low, the prepreg viscosity is too high, causing severe rebound of the filler and making it difficult to compact; if the temperature is too high, it may cause premature gelation or flow loss of the prepreg. Simultaneously, cutting the filler into short segments of 10mm to 15mm is to accommodate the rapidly changing radii of curvature at intersecting nodes. If a long strip of integral filler is used, it is very easy to create gaps or wrinkles when passing through intersections, forming internal defects; while the segmented filler strategy allows each small segment of filler to independently conform to the local surface, fundamentally eliminating the risk of gaps caused by geometric mismatch.

[0037] To ensure the stability and repeatability of the filling quality, the filling amount W of the unidirectional fiber prepreg is calculated according to the following formula: Where W is the unidirectional fiber prepreg filling width in mm; R is the bottom arc radius of the hollow reinforcement in mm. Pi; This is the porosity correction factor for the material during the curing process; The thickness of a single layer of unidirectional fiber prepreg is in mm; k is the filler ratio. Parameters This reflects the volume change of the prepreg during hot-press curing due to prepreg flow, volatile matter release, and fiber rearrangement. Its value is usually calibrated through process experiments to compensate for the difference between the theoretical geometric volume and the actual cured volume. The parameter k is the filler ratio, typically greater than 1, designed to introduce an appropriate amount of interference filler to offset curing shrinkage and establish interfacial contact pressure, preventing root debonding. R and... This links the macroscopic geometric features of the components with their microscopic material properties, enabling dynamic binding of process parameters and design dimensions.

[0038] The engineering value of this calculation formula lies in establishing a quantitative control standard for root filling quality. In actual production, if the filling amount is too large (i.e., the W value exceeds the reasonable range), it will lead to prepreg enrichment in the root area, which not only increases the weight of the component but may also cause thermal stress cracks due to the concentrated heat release during prepreg curing. Conversely, if the filling amount is too small, it will not be able to completely fill the voids in the triangular area, forming pores or delamination defects, which will seriously weaken the load-bearing efficiency of the structure. By accurately calculating the filling width using the above formula and combining it with a heated segmented pre-compaction process, the optimal ratio of fiber to prepreg in the root area can be achieved, ensuring the density and integrity of the co-cured interface.

[0039] S31. After completing the segmented filling, pre-compaction is carried out, specifically including: covering with a release liner and vacuuming for compaction after filling.

[0040] This step utilizes atmospheric pressure to force the softened infill to further embed itself into the root dead corner, expelling air trapped between layers and ensuring good initial adhesion between the infill surface and the subsequently laid reinforcing prepreg. Vacuum precompaction not only reinforces the effect of segmented filling but also creates favorable boundary conditions for the uniform flow of prepreg during the subsequent co-curing process, serving as the final line of defense against root porosity defects.

[0041] Example 4 like Figures 1 to 3 As shown, this Example 4, based on Examples 1 to 3, further presents the specific implementation parameters and quality control closed loop of the entire process from core mold preparation to final demolding, to support the requirement of full disclosure and demonstrate the reproducibility of the process. Specifically, providing the core mold assembly includes providing a water-soluble rigid core mold, which includes the following steps: S10. Mix the water-soluble matrix solution with the reinforcing aggregate to obtain a wet sand mixture; S11. Fill the wet sand mixture into the core mold forming mold with interlaced grid cavities and tamp it down to remove air. S12. After the mold is closed and tightened, it is sent into an oven for heating and curing. After cooling, it is demolded to obtain a water-soluble hard core mold.

[0042] When preparing water-soluble rigid mandrels, the tamping and venting operation aims to eliminate air between the particles of the wet sand mixture, preventing porous defects inside the cured mandrel and thus avoiding local collapse or deformation under the high pressure of the subsequent autoclave. During mold clamping, the gap between the mold joints must be strictly controlled to be below 0.05mm. This precision directly determines the accuracy of the mandrel's external dimensions, thus affecting the dimensional tolerances of the internal cavities of the final reinforced component. The preferred heat curing regime is 150℃ for 4 hours. This combination of temperature and time ensures sufficient bonding strength between the water-soluble matrix and the reinforcing aggregate, allowing the mandrel to maintain structural integrity under co-curing pressure. Furthermore, cooling to room temperature before demolding effectively prevents cracking of the mandrel due to thermal stress.

[0043] Laying the skin prepreg onto the molding die and positioning and installing the core mold assembly onto the skin prepreg includes the following steps: S20. Lay the skin prepreg on the molding die and pre-compact it at room temperature; S21. Install the core mold positioning block, place the core mold assembly on the skin prepreg and fix it with the core mold positioning block; S22. Vacuum the core mold assembly to make it adhere tightly to the surface of the skin prepreg, maintain it for a preset time, check the gap, and add prepreg to areas that exceed the preset gap threshold.

[0044] Specifically, room temperature pre-compaction typically lasts 10 to 15 minutes to initially remove air between skin layers and improve layup density. Subsequently, a sand core mold positioning block is used to precisely position the water-soluble rigid core mold. Pins are first inserted for pre-positioning, and then bolts are tightened for rigid fixation, ensuring the core mold does not shift during subsequent operations. A crucial quality control step is vacuum bonding: after covering with a vacuum bag, a 100% vacuum is drawn and maintained for 2 to 3 hours. Atmospheric pressure allows the rigid core mold to self-adaptively and tightly bond with the skin surface. After maintaining the preset time, the vacuum is released, and the assembly gap between the two is checked. If a local gap exceeds the preset threshold of 0.2 mm, an additional layer of epoxy carbon fiber prepreg must be laid in that area. Through vacuum bonding, gap detection, and dynamic replenishment, root suspension problems caused by core mold manufacturing errors or uneven skin layup are eliminated. Excessive prepreg accumulation at gaps during co-curing, forming prepreg-rich areas, or porosity due to uncompacted fibers are avoided.

[0045] Laying reinforced prepreg on the core mold assembly and skin prepreg includes the following steps: S41. Lay the reinforced prepreg layer by layer, with the overlaps of adjacent layers staggered by a preset distance; S42. Co-curing molding includes: sending the semi-finished composite material components after bag making into an autoclave, evacuating the entire process, heating and pressurizing according to a stepped temperature rise curve, and then cooling and depressurizing.

[0046] In this embodiment, the laying of the reinforced prepreg strictly follows the staggered joint principle, with the overlap of adjacent layers staggered by at least 20mm. This design effectively disperses stress concentration at the joints between layers, avoids the formation of through weak surfaces, and significantly improves the overall load-bearing capacity of the reinforced structure.

[0047] The co-curing process employs a stepped heating curve: first, the temperature is raised to 80°C at a rate not exceeding 2°C / min and held for 30 minutes. This stage represents the prepreg flow and wetting window; the lower heating rate and holding plateau allow the prepreg to fully fill the fiber gaps and root triangular areas while simultaneously releasing volatiles. Subsequently, the temperature is raised to 130°C at the same rate and held for 120 minutes. This is the main reaction zone for prepreg cross-linking and curing, ensuring complete curing and achieving the desired mechanical properties. Finally, the temperature is lowered to 60°C at a rate not exceeding 2°C / min, and then the prepreg is depressurized and removed from the container. Maintaining 100% vacuum throughout the process not only facilitates the continuous removal of volatiles but also further improves the internal density of the component through negative pressure-assisted compaction. This stepped curing regime is precisely matched to the rheological properties and reaction kinetics of the prepreg, effectively preventing prepreg bursting, flowing, or internal defects caused by excessively rapid heating. It is a core process parameter for achieving high-quality co-curing.

[0048] Dissolving a water-soluble rigid core mold and removing residual material by extracting a water-insoluble and flexible insulating layer includes the following steps: S51. Break through the water-insoluble and flexible isolation layer from the reinforced opening; S52. Inject water through the opening to dissolve the water-soluble hard core mold, allowing the core mold material to flow out with the water; S53. The water-insoluble and flexible isolation layer is extracted as a whole from the reinforced cavity.

[0049] Specifically, firstly, a water-insoluble and flexible isolation layer is carefully broken at the opening end of the reinforced structure to form a water injection channel. Then, warm or room temperature water is injected through the break. Water molecules penetrate into the core mold, causing the water-soluble matrix, such as potassium carbonate, which acts as the binder, to dissolve rapidly. The reinforcing aggregates (sand, fiberglass) that have lost structural strength are then suspended in the water and discharged from the cavity with the water flow. After the core mold material is mostly removed, the operator pulls the water-insoluble and flexible isolation layer from the same break, extracting it as a whole from the complex, crisscrossing cavity. Because the isolation layer maintains its integrity and water insolubility during curing and forms a continuous extraction sleeve during encapsulation, it removes trace amounts of residual aggregate, debris, or incompletely flushed particles adhering to its inner wall during extraction. This completely solves the problems of difficult-to-clean residue and easy scratching of the component's inner wall after demolding with traditional water-soluble core molds.

[0050] Example 5 This embodiment provides a hollow reinforced composite material component, which is prepared using the co-curing molding method described in any one of Embodiments 1 to 4 above. As a product embodiment, its structural features directly reflect the technological advantages of the aforementioned molding method, and together with the method embodiments, constitute a complete technical solution protection system.

[0051] Specifically, the prototype material for this hollow reinforced composite material component is: Carbon fiber epoxy plain weave fabric prepreg JD2626A / JDW70200T / 42 / 1000, carbon fiber epoxy unidirectional prepreg JD2626 / SYT49C / 150 / 35 / 1000; The fiber filler is prepared by cutting carbon fiber epoxy unidirectional prepreg JD2626 / SYT49C / 150 / 35 / 1000 into a shape with R=6.5mm, a single layer thickness Δt=0.15mm, a filling ratio k=105%, and a filling width W=127mm. A hollow reinforced composite material component is prepared using the co-curing molding method described in any one of Examples 1 to 4 above. After processing, the thickness is measured using a digital caliper. Specific data are as follows: Figure 4 As shown; the curing temperature curve during the trial production process is as follows: Figure 3 As shown.

[0052] The hollow reinforced composite material component exhibits a macroscopic structure where the skin and the interwoven hollow reinforcing structure are integrally co-cured. After co-curing in an autoclave, the skin prepreg and the reinforcing prepreg undergo a cross-linking reaction to form a continuous chemical bond interface, eliminating the heterogeneous adhesive layers commonly found in traditional secondary or co-bonding processes. This integrated structure eliminates weak bonding surfaces, allowing for efficient load transfer between the skin and the reinforcing structure, significantly improving the overall stiffness and strength of the component, while avoiding internal stress deformation problems caused by differences in the thermal history of multiple curing processes. It should be understood that although this embodiment uses an interwoven cap-shaped rib as an example, this integral co-curing connection feature is also applicable to T-shaped, I-shaped, or other reinforced structures with interwoven topological features.

[0053] Regarding the quality of the internal cavity, the reinforced internal cavity surface of this component is smooth, intact, and free of residue. This structural feature is a direct result of the aforementioned water-soluble rigid core mold and the water-insoluble and flexible isolation layer working together for demolding. Because the flexible isolation layer maintains its physical integrity and water insolubility during curing and acts as a continuous extraction sleeve during demolding to remove the dissolved core mold residue as a whole, the inner wall of the component does not develop scratches, pits, or embedded debris as in traditional rigid core mold mechanical breakage, nor does it retain aggregate particles in dead corners as in simple water washing processes. This highly intact inner wall surface not only meets the stringent requirements of aerospace and other fields for fluid or cable channels but also avoids the risk of stress concentration caused by surface defects.

[0054] In critical stress areas, the component exhibits a continuous, dense, and non-porous microstructure at the root triangle where the stiffened structure meets the skin. This is thanks to the segmented filling and vacuum pre-compaction process using heated softening of the fiber filler employed in the aforementioned embodiments. Within this region, unidirectional fibers are continuously arranged along the root curved surface, without fiber breakage, gaps, or wrinkles caused by improper filling; the prepreg fully impregnates the fiber gaps, and no visible pores or resin-deficient areas are observed. This dense root structure effectively solves the industry problem of molding defects easily occurring at complex, intersecting nodes, ensuring that the stiffened structure does not experience early root failure under compressive or shear loads, significantly improving the component's fatigue life and structural reliability.

[0055] In summary, the hollow stiffened composite material component provided in this embodiment achieves excellent structural integrity and internal quality through a specific molding method. This product is particularly suitable for aircraft stiffened panels, fuselage frames, or wing spars and ribs, where extremely high requirements are placed on weight reduction, rigidity, and manufacturing precision. However, its application is not limited to the aviation field; it can also be extended to scenarios requiring high-performance composite material structures, such as rail transportation, new energy vehicles, and high-end equipment.

[0056] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for co-curing and molding a longitudinally and transversely integrated hollow cap-shaped rib, characterized in that, include: S1. Provide a core mold assembly, the core mold assembly including a water-soluble rigid core mold and an isolation layer continuously covering the surface of the rigid core mold; S2. Lay the skin prepreg on the molding die and position and install the core mold assembly on the skin prepreg; S3. After heating and softening the pre-formed fiber filler, fill it in sections into the root area where the core mold assembly and the skin prepreg meet, and pre-compact it. S4. Lay reinforced prepreg on the core mold assembly and the skin prepreg, make a bag and co-cur it to obtain a semi-finished composite material component. S5. Dissolve the hard core mold and remove the residual material by pulling out the isolation layer to complete the demolding.

2. The method for co-curing and molding a longitudinally and transversely integrated hollow cap-shaped rib according to claim 1, characterized in that: The rigid core mold is formed by mixing and curing a water-soluble matrix with reinforcing aggregate; the isolation layer is continuously wrapped around the surface of the rigid core mold to form a complete release sleeve.

3. The method for co-curing and molding a longitudinally and transversely integrated hollow cap-shaped rib according to claim 2, characterized in that: The water-soluble matrix includes a potassium carbonate solution, and the reinforcing aggregate includes sand and chopped glass fibers; the insulating layer includes a BOPP film or a heat-shrinkable film, with a continuous winding overlap width of 3 mm to 5 mm.

4. The method for co-curing and molding a longitudinally and transversely integrated hollow cap-shaped rib according to claim 1, characterized in that: Step S3 further includes: S30. Cut the heated and softened fiber filler into filler segments of a preset length and fill them sequentially into the root region. S31. After filling, cover with a release liner and vacuum to compact.

5. The method for co-curing and molding a longitudinally and transversely integrated hollow cap-shaped rib according to claim 4, characterized in that: The temperature range for heating and softening is 50°C to 60°C, and the preset length is 10mm to 15mm. The filling amount of the unidirectional fiber prepreg Calculate using the following formula: in, The filler width of the unidirectional fiber prepreg is in mm. The radius of the bottom arc of the hollow reinforced structure, in mm; Pi; This is the porosity correction factor for the material during the curing process; The thickness of a single layer of unidirectional fiber prepreg is in mm. This represents the fill factor.

6. The method for co-curing and molding a longitudinally and transversely integrated hollow cap-shaped rib according to claim 1, characterized in that, Step S1 also includes a method for manufacturing the hard core mold: S10. Mix the water-soluble matrix solution with the reinforcing aggregate to obtain a wet sand mixture; S11. Fill the wet sand mixture into a core mold forming mold with an interlaced grid cavity and tamp it down to remove air. S12. After the mold is closed and tightened, it is sent into an oven for heating and curing. After cooling, it is demolded to obtain the water-soluble hard core mold.

7. The method for co-curing and molding a longitudinally and transversely integrated hollow cap-shaped rib according to claim 1, characterized in that, Step S2 also includes: S20. Lay the skin prepreg on the molding die and pre-compact it at room temperature; S21. Install the core mold positioning block, place the core mold assembly on the skin prepreg and fix it by the core mold positioning block; S22. Vacuum the core mold assembly to make it adhere tightly to the surface of the skin prepreg, maintain it for a preset time, check the gap, and add prepreg to areas that exceed the preset gap threshold.

8. The method for co-curing and molding a longitudinally and transversely integrated hollow cap-shaped rib according to claim 1, characterized in that: Step S4 further includes: S41. Lay the reinforced prepreg layer by layer, with the overlap seams of adjacent layers staggered by a preset distance; S42. The semi-finished composite material component after bag making is sent into a hot autoclave, vacuumed throughout the process, heated and pressurized according to the step temperature rise curve, and then cooled and depressurized.

9. The method for co-curing and molding a longitudinally and transversely integrated hollow cap-shaped rib according to claim 1, characterized in that: Step S5 further includes: S51. Break the water-insoluble and flexible isolation layer from the reinforced opening; S52. Inject water through the opening to dissolve the water-soluble hard core mold, allowing the core mold material to flow out with the water; S53. The water-insoluble and flexible isolation layer is extracted as a whole from the reinforced cavity.

10. The method for co-curing and molding a longitudinally and transversely integrated hollow cap-shaped rib according to claim 1, characterized in that: The outer surface of the isolation layer is coated with a release agent, which includes release wax.

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