A method of integrally manufacturing a composite boarding stair

Abstract

The application discloses a kind of composite boarding ladder integral manufacturing method, comprising: according to the internal structure of boarding ladder, the shape matching soluble mandrel is prepared, and the surface is covered with vacuum air bag, and the shape of the combination formed is consistent with the shape of boarding ladder inner cavity;With the combination of soluble mandrel and vacuum air bag as male die, the pre-impregnated material piece of boarding ladder column and step is alternately laid on its surface, and the boarding ladder preform is obtained after laying is completed;Boarding ladder preform is transferred to boarding ladder forming mould together with male die, heated and pressurized, and boarding ladder curing forming is carried out, and after forming, mold is opened and soluble mandrel is dissolved, and composite boarding ladder is obtained.The application effectively reduces tooling mold cost, manufacturing cycle and part weight, improves the structural strength of boarding ladder, and has strong designability.Compared with the existing boarding ladder manufacturing process, it has the advantages of high efficiency, low cost and light weight.

Description

Technical Field

[0001] This invention relates to the field of aerospace composite material molding, and specifically to a method for integral manufacturing of a composite material boarding ladder. Background Technology

[0002] As a crucial piece of equipment in aircraft ground support systems, boarding stairs play a vital role in ensuring the safe and efficient boarding and disembarking of pilots and ground maintenance personnel. Currently, aircraft boarding stairs are primarily manufactured using metal materials or traditional composite materials. Metal boarding stairs suffer from drawbacks such as heavy weight and susceptibility to corrosion. Traditional composite material manufacturing methods often employ a modular molding and assembly process, which presents technical challenges including numerous molds, high costs, difficulty in ensuring assembly precision, stress concentration at joints affecting structural strength, difficulties in demolding traditional male molds, and challenges in guaranteeing the molding quality of complex curved surfaces. For example, Chinese patents with publication numbers CN113581486A and CN222522861U both propose a composite material boarding stairs. While the main body of the boarding stairs is made of composite materials, effectively reducing weight, the steps and columns are molded separately and mechanically connected, resulting in cumbersome manufacturing and underutilization of the composite material's performance.

[0003] Therefore, how to achieve integral molding of composite material parts with complex curved surface structures, such as boarding stairs, while ensuring the dimensional accuracy, mechanical properties, and manufacturability of the parts, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0004] The purpose of this invention is to provide a method for manufacturing a composite material boarding ladder as a whole, so as to solve the problems existing in the prior art.

[0005] To achieve the above objectives, the present invention employs the following technical solution: A method for manufacturing a composite boarding ladder includes: preparing a soluble mandrel with a shape matching the internal structure of the boarding ladder; covering its surface with a vacuum bladder, forming an assembly whose shape is consistent with the inner cavity shape of the boarding ladder; using the assembly of the soluble mandrel and the vacuum bladder as a male mold, alternately laying prepreg pieces of boarding ladder columns and steps on its surface, obtaining a boarding ladder preform after the laying is completed; transferring the boarding ladder preform together with the male mold into a boarding ladder molding mold, heating and pressurizing to cure and mold the boarding ladder; after molding, opening the mold and dissolving the soluble mandrel to obtain the composite boarding ladder.

[0006] Furthermore, the soluble mandrel is designed with the dimensions of a vacuum air bladder in mind; the soluble mandrel is made of a soluble material and can be removed by adding a suitable solvent after molding; the soluble mandrel is used to provide surface support during pre-forming; the vacuum air bladder is made of a flexible composite material and undergoes an airtightness test before use.

[0007] Furthermore, the soluble mandrel is designed with a honeycomb-shaped through-hole structure to increase the solvent contact surface; a release film is sprayed onto the surface of the soluble mandrel.

[0008] Furthermore, carbon fiber prepreg is used as the prepreg; when laying the ladder columns, the axial direction of the ladder columns is defined as 0°, the prepreg pieces are flush with the soluble mandrel, and are attached along the ladder columns on both sides of the ladder. In the tread area, the prepreg pieces are cut and attached, and the inner sides of the overlapping joints of all the prepreg pieces are staggered. When laying the treads, define the axial direction of the treads as 0°, center the prepreg piece and attach it to the male mold at the position of the tread, and cut the two ends of the prepreg piece at the junction with the ladder column and attach them to both sides of the ladder.

[0009] Furthermore, multiple layers of prepreg fabric pieces are overlapped and laid together on the tread surface for local reinforcement; finally, carbon felt prepreg is laid on the surface of the stair posts and the tread surface to ensure a smooth outer surface.

[0010] Furthermore, the boarding ladder molding mold is a self-limiting molding mold made of steel, consisting of an upper mold and a lower mold, used in conjunction with a soluble mandrel and a vacuum bladder; after the mold is closed, the mold can maintain the shape of the boarding ladder parts; during the curing process, curing pressure is provided by blowing air into the vacuum bladder.

[0011] Furthermore, during hot-press curing, the curing temperature is set to 120-160℃, air is supplied into the vacuum chamber and pressurized to 2-3MPa, and a vacuum system is used to evacuate the vacuum, maintaining a vacuum level above -0.095MPa throughout the process, with a curing time of 2-3 hours.

[0012] Furthermore, after curing, the pressure of the vacuum bag is released, the mold is cooled to below 70°C, the mold is separated, and the boarding ladder parts are removed; a solvent is added to dissolve the soluble mandrel, the vacuum bag is removed, and a complete composite material boarding ladder is obtained.

[0013] Further, first lay the stair columns, then lay the prepreg in the order of [0° / 0° / 90° / 0° / 0°], with the inner sides of all prepreg pieces staggered, and the overlap length of the pieces is 10-15mm; then lay the treads, each tread in the order of [0° / 0° / 90° / 0° / 0°], with each layer of prepreg pieces staggered by 5mm; alternately lay the stair columns and treads multiple times, and before the last lay, use multiple layers of prepreg pieces [0° / 90° / 0°] to overlap and reinforce the tread surface locally.

[0014] Further, the boarding ladder molding mold is preheated to 60℃; a release agent is sprayed onto the cavity surface of the mold, and the preformed boarding ladder body, along with the male mold, is transferred to the boarding ladder molding mold and closed, and then heated and pressurized; first, it is heated to 120℃ at 2℃ / min and held for 30min, then heated to 160℃ at 1℃ / min and held for 90min; the external oil pressure of the mold is maintained at 150±20kg / cm², while air is supplied to the vacuum bladder and pressurized, gradually increasing the pressure to 2MPa, maintaining a vacuum degree above -0.095MPa throughout the process, and curing is performed; after curing, the vacuum bladder pressure is released, the mold is cooled to 60℃ and then opened, the boarding ladder parts are removed, immersed in a dissolving system at 60±2℃ to dissolve the soluble mandrel, the vacuum bladder is removed and dried with hot air.

[0015] Compared with the prior art, the present invention has the following technical features: This invention provides a method for integrally manufacturing composite boarding stairs. It utilizes a combination of a soluble mandrel and a vacuum chamber-type male mold, solving the problem of difficult demolding with traditional male molds. Combined with a self-limiting molding die, the method employs flexible pressure from the vacuum chamber for internal expansion molding, ensuring the quality of the boarding stairs and achieving integral manufacturing. This reduces the number of molds and connectors in the boarding stairs manufacturing process, significantly lowering tooling costs, manufacturing cycle, and component weight. Simultaneously, this method fully utilizes the properties of the reinforcing fibers, improving the structural strength of the boarding stairs and offering strong design flexibility. Compared with existing boarding stairs manufacturing processes, it offers advantages such as high efficiency, low cost, and lightweight design. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the boarding ladder structure in an embodiment of the present invention; Figure 2 This is a schematic diagram of the prepreg stacking of the ladder column in an embodiment of the present invention; Figure 3 This is a schematic diagram of the prepreg layering for the pedals in an embodiment of the present invention; Figure 4 This is a schematic diagram of the local reinforcement of the pedal in an embodiment of the present invention.

[0017] Wherein: 1-ladder post, 2-tread plate, 3-prepreg fabric piece, 4-intersection area of ​​ladder post and tread plate, 5-prepreg fabric piece, 6-intersection area of ​​ladder post, 7-overlapping prepreg fabric pieces. Detailed Implementation

[0018] This invention provides a method for integrally manufacturing composite boarding stairs. The method uses a combination of a soluble mandrel and a vacuum bladder as a male mold to integrally lay up the boarding stairs, followed by hot-pressing curing to achieve integral molding of the composite boarding stairs. This method achieves efficient, low-cost, lightweight, and high-strength integral molding of composite boarding stairs. Specific steps include: preparing a soluble mandrel with a shape matching the internal structure of the boarding stairs; covering its surface with a vacuum bladder, forming a combination whose shape matches the inner cavity shape of the boarding stairs; using the combination of the soluble mandrel and the vacuum bladder as a male mold, alternately laying up the stair columns and tread prepregs to obtain a preformed boarding stairs; transferring the preformed boarding stairs along with the male mold to a boarding stairs molding mold, heating and pressurizing to cure and mold the boarding stairs; after molding, opening the mold and dissolving the soluble mandrel to obtain the composite boarding stairs. This invention has the characteristics of high molding efficiency, light product weight, low manufacturing cost, and excellent mechanical properties, and is suitable for manufacturing high-performance composite boarding stairs in the aerospace and other fields. The specific steps include: Step 1: Prepare a positive mold combining a soluble mandrel and a vacuum air bladder.

[0019] Based on the internal structure of the boarding ladder, the shape of the soluble mandrel is designed so that the shape of the soluble mandrel and vacuum bladder assembly formed after covering the vacuum bladder matches the shape of the boarding ladder's inner cavity. This means the dimensions of the vacuum bladder are pre-reserved during the design of the soluble mandrel. The soluble mandrel is made of a soluble material and can be removed after molding by adding a suitable solvent. The soluble mandrel provides surface support during preforming and determines the inner cavity shape of the boarding ladder. A vacuum bladder, made of a flexible composite material, is then covered onto the outer surface of the soluble mandrel, forming the soluble mandrel and vacuum bladder assembly, which serves as the male mold for subsequent lay-up molding. The vacuum bladder is used to transmit uniform pressure to the inside of the preform during subsequent curing, achieving internal expansion molding.

[0020] The soluble mandrel can be designed with a honeycomb-like through-hole structure to increase the solvent contact area and improve the dissolution efficiency. A release film is sprayed onto the surface of the soluble mandrel.

[0021] Step 2: Alternately lay the prepreg for the ladder columns and treads.

[0022] Using the soluble mandrel and vacuum airbag assembly prepared in step one as the positive mold, prepreg pieces of ladder columns and treads are alternately laid on its surface to form a preformed boarding ladder. Carbon fiber prepreg is used. Ladder columns and treads are alternately laid to ensure structural strength at the joints. The specific laying method is as follows: When laying the ladder posts, define the axial direction of the ladder posts as 0°, and attach the prepreg pieces flush with the soluble mandrel along both sides of the ladder posts. Cut and attach the prepreg pieces in the tread area, and stagger the inner sides of all the prepreg pieces at the overlapping joints.

[0023] When laying the treads, define the axial direction of the treads as 0°, center the prepreg fabric piece and attach it to the male mold at the position of the tread, and cut the two ends of the prepreg fabric piece at the junction with the ladder column and attach them to both sides of the ladder. At the same time, use multiple layers of overlapping prepreg fabric pieces to locally reinforce the tread surface.

[0024] Finally, carbon felt prepreg is laid on the surfaces of the stair columns and treads to ensure a smooth outer surface.

[0025] Step 3: Hot pressing and curing molding.

[0026] After the preform of the boarding ladder is laid up, it is transferred together with the male mold to the boarding ladder forming mold. This mold is a self-limiting forming mold made of steel, consisting of an upper mold and a lower mold, used in conjunction with a soluble mandrel and a vacuum chamber. After the mold is closed, it can maintain the shape of the boarding ladder parts, ensuring the accuracy of the parts' dimensions. During the curing process, air is blown into the vacuum chamber to provide curing pressure for the parts.

[0027] When performing hot-press curing, set the curing temperature to 120-160℃, pressurize the vacuum chamber to 2-3MPa, and evacuate through the vacuum system to maintain a vacuum level above -0.095MPa throughout the process. The curing time is 2-3 hours.

[0028] Step four: demolding and post-processing.

[0029] After curing, release the pressure from the vacuum chamber, cool the mold to below 70°C, separate the mold, and remove the boarding ladder parts. Add a solvent to dissolve the soluble mandrel, remove the vacuum chamber, and obtain a complete composite material boarding ladder.

[0030] Example: This embodiment uses Figure 1 The above method will be specifically explained using the example of a hollow composite material boarding ladder consisting of ladder column 1 and step 2 shown.

[0031] Positive mold preparation: The soluble mandrel is made of a composite material of 85% PEG-4000 (polyethylene glycol) and 15% nano-kaolin, manufactured by melt deposition modeling. The internal structure of the soluble mandrel is designed with a honeycomb-like through-hole structure to increase the solvent contact area and improve dissolution efficiency. A release film is sprayed onto the surface. The vacuum bladder is made of 0.4mm thick fluororubber, which is wrapped around the soluble mandrel and subjected to airtightness testing. The self-limiting molding die is made of 50# steel, and the corresponding dimensions and shapes are obtained through CNC machining and polished. The dimensions of the vacuum bladder should be reserved during machining. The prepreg is T700 carbon fiber / epoxy resin prepreg.

[0032] Lamination process: Using a soluble mandrel and vacuum bladder assembly as the positive mold, layup is performed on its surface. For example... Figure 2 As shown, first lay the ladder posts, defining the axis of ladder post 1 as the 0° direction of the prepreg. Prepreg pieces 3 are flush with the soluble mandrel and attached along both sides of the ladder posts 1. At the junction area 4 of ladder post 1 and tread 2, prepreg pieces are cut and attached along both sides of the tread. The prepreg is laid in a [0° / 0° / 90° / 0° / 0°] layering sequence, with all prepreg pieces overlapping at the inner edges, and the overlap length is 10-15mm. Then lay the treads, defining the tread axis as the 0° direction of the prepreg, as shown. Figure 3 As shown, prepreg sheet 5 is centered on the tread and fitted with the ladder post. The area 6 where it intersects with the ladder post is cut along the marked line, and the cut prepreg portions are fitted to both sides of the ladder. Each tread is laid in the order of [0° / 0° / 90° / 0° / 0°], with each layer of prepreg sheet staggered by 5mm. The ladder post and treads are alternately laid four times. Before the final layering, three layers of prepreg sheet 7, overlapping each other in a [0° / 90° / 0°] pattern, are used to locally reinforce the tread surface, as shown in the image. Figure 4 As shown. After the laying is completed, carbon felt prepreg is laid on the surface of the ladder column 1 and the tread 2 to ensure the quality of their outer surface.

[0033] Curing and Demolding: Preheat the boarding ladder molding mold to 60℃. Spray a release agent onto the cavity surface of the mold. Transfer the pre-formed boarding ladder along with the male mold into the boarding ladder molding mold and close the mold. Heat and pressurize. First, heat to 120℃ at 2℃ / min and hold for 30 minutes, then heat to 160℃ at 1℃ / min and hold for 90 minutes. Maintain the external oil pressure of the mold at 150±20 kg / cm², while simultaneously supplying air to the vacuum chamber and gradually increasing the pressure to 2 MPa, maintaining a vacuum degree above -0.095 MPa throughout the process for curing. After curing, release the vacuum chamber pressure, cool the mold to 60℃, open the mold, remove the boarding ladder parts, immerse them in a 60±2℃ circulating water dissolution system to dissolve the mandrel, remove the vacuum chamber, and dry with hot air to obtain a complete boarding ladder.

[0034] This invention discloses a method for integrally manufacturing composite material boarding stairs. By employing a combination of a soluble mandrel and a vacuum chamber as the positive mold, and using a whole-body lay-up and curing process, it solves the problems of numerous molds and high manufacturing costs associated with traditional boarding stairs. The multi-axial lay-up design of the stairs and treads enhances the overall load-bearing capacity of the boarding stairs. One-piece molding achieves highly efficient manufacturing of the boarding stairs. The boarding stairs are manufactured without connecting parts, fully utilizing the advantages of composite materials and reducing the weight of the boarding stairs. Compared to traditional boarding stairs manufacturing methods, this invention features high molding efficiency, lightweight product, low manufacturing cost, and excellent mechanical properties, making it suitable for manufacturing high-performance composite material boarding stairs in the aerospace and aviation industries.

[0035] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for integrally manufacturing a composite material boarding ladder, characterized in that, include: A soluble mandrel with a shape matching the internal structure of the boarding ladder is prepared, and a vacuum bladder is wrapped on its surface. The shape of the resulting assembly is consistent with the shape of the inner cavity of the boarding ladder. Using a combination of a soluble mandrel and a vacuum bladder as a male mold, prepreg pieces of boarding ladder columns and treads are alternately laid on its surface to obtain a boarding ladder preform. The boarding ladder preform, together with the male mold, is transferred to a boarding ladder molding mold, heated and pressurized to solidify and mold the boarding ladder. After molding, the mold is opened and the soluble mandrel is dissolved to obtain a composite material boarding ladder.

2. The integral manufacturing method of the composite material boarding ladder according to claim 1, characterized in that, The soluble mandrel is designed with the dimensions of the vacuum air bladder reserved; the soluble mandrel is made of soluble material and can be removed by adding the appropriate solvent after molding; the soluble mandrel is used to provide surface support during pre-forming; the vacuum air bladder is made of flexible composite material and undergoes an airtightness test before use.

3. The integral manufacturing method of the composite material boarding ladder according to claim 1, characterized in that, The soluble mandrel has a honeycomb-like through-hole structure inside to increase the solvent contact area; a release film is sprayed onto the surface of the soluble mandrel.

4. The integral manufacturing method of the composite material boarding ladder according to claim 1, characterized in that, The prepreg is made of carbon fiber prepreg. When laying the ladder columns, the axial direction of the ladder columns is defined as 0°. The prepreg pieces are flush with the soluble mandrel and are attached to the ladder columns on both sides. The prepreg pieces are cut and attached in the tread area. The inner sides of the overlapping joints of all the prepreg pieces are staggered. When laying the treads, define the axial direction of the treads as 0°, center the prepreg piece and attach it to the male mold at the position of the tread, and cut the two ends of the prepreg piece at the junction with the ladder column and attach them to both sides of the ladder.

5. The integral manufacturing method of the composite material boarding ladder according to claim 1, characterized in that, The tread surface is locally reinforced by overlapping layers of prepreg pieces; finally, carbon felt prepreg is laid on the surface of the stair posts and the tread surface to ensure a smooth outer surface.

6. The integral manufacturing method of the composite material boarding ladder according to claim 1, characterized in that, The boarding ladder molding mold is a self-limiting molding mold made of steel. It consists of two parts: an upper mold and a lower mold. It is used in conjunction with a soluble mandrel and a vacuum bladder. After the mold is closed, it can maintain the shape of the boarding ladder parts. During the curing process, curing pressure is provided by blowing air into the vacuum bladder.

7. The integral manufacturing method of the composite material boarding ladder according to claim 1, characterized in that, When performing hot-press curing, set the curing temperature to 120-160℃, pressurize the vacuum chamber to 2-3MPa, and evacuate through the vacuum system to maintain a vacuum level above -0.095MPa throughout the process. The curing time is 2-3 hours.

8. The integral manufacturing method of the composite material boarding ladder according to claim 1, characterized in that, After curing, release the pressure of the vacuum bag, cool the mold to below 70°C, separate the mold, and remove the boarding ladder parts; add solvent to dissolve the soluble mandrel, remove the vacuum bag, and obtain a complete composite material boarding ladder.

9. The integral manufacturing method of the composite material boarding ladder according to claim 1, characterized in that, First, lay the stair columns, layering the prepreg in the order of [0° / 0° / 90° / 0° / 0°]. All prepreg pieces should be staggered at the inside, with an overlap length of 10-15mm. Then, lay the treads, layering each tread in the order of [0° / 0° / 90° / 0° / 0°]. Each layer of prepreg pieces should be staggered by 5mm. Alternately lay the stair columns and treads multiple times. Before the last layer, reinforce the tread surface with multiple layers of prepreg pieces overlapping each other in the order of [0° / 90° / 0°].

10. The integral manufacturing method of the composite material boarding ladder according to claim 1, characterized in that, Preheat the boarding ladder molding mold to 60℃; spray the mold cavity surface with release agent, transfer the pre-formed boarding ladder along with the male mold to the boarding ladder molding mold, close the mold, and heat and pressurize; first heat to 120℃ at 2℃ / min, hold for 30min, then heat to 160℃ at 1℃ / min, hold for 90min; maintain the external oil pressure of the mold at 150±20kg / cm², while simultaneously supplying air to the vacuum bladder and gradually increasing the pressure to 2MPa, maintaining a vacuum degree above -0.095MPa throughout the process, and solidify the molding; after solidification, release the vacuum bladder pressure, cool the mold to 60℃, open the mold, remove the boarding ladder parts, immerse them in a dissolving system at 60±2℃ to dissolve the soluble mandrel, remove the vacuum bladder and dry with hot air.

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