Composite undercarriage forming process

Abstract

The invention relates to the technical field of composite material forming, in particular to a composite material undercarriage forming process which comprises the steps that S1, a mold is designed and manufactured; s2, an inner container is manufactured and solidified; s3, reinforcing ribs are manufactured and solidified; s4, placing reinforcing ribs; s5, paving and curing the outer skin; and S6, post-treatment and performance detection are conducted on the formed undercarriage. Through the step-by-step composite structure of the inner container, the reinforcing ribs and the outer skin, hollow reinforcing rib integrated forming is achieved, the rigidity, the strength and the impact resistance of the undercarriage are remarkably improved, and the stress concentration and cracking risks are effectively avoided; the inner container serves as a reference body, accurate positioning and glue joint of the reinforcing ribs are facilitated, then the outer skin and the inner container are co-cured through mold pressing, the overall combination is firm, the technological process is more stable and controllable, and repeatability is better.

Description

Technical Field

[0001] This application relates to the field of composite material molding technology, and in particular to a composite material landing gear molding process. Background Technology

[0002] Composite materials, with their core properties such as high specific strength, high specific modulus, strong fatigue resistance, outstanding fracture resistance, and excellent vibration damping performance, while also possessing advantages such as light weight, good corrosion resistance, high processing flexibility, and structural diversity, have been widely used in various fields such as aerospace, automotive, construction, electronics, and medical devices. Among them, the aerospace field has the most stringent requirements for material performance, and composite materials are widely used in the manufacture of key components of aircraft, spacecraft, and missiles (such as fuselages, wings, and tail fins), which can effectively reduce the weight of equipment and improve fuel efficiency and flight performance.

[0003] Landing gear is a crucial component of helicopters. During landing, it absorbs the energy generated by the helicopter's impact with the ground, acting as a buffer to protect the entire airframe structure. Helicopter landing gear is mainly divided into skid-type and wheeled landing gear. Traditional skid-type landing gear is mostly made of high-strength aluminum alloy, but it still suffers from problems such as susceptibility to corrosion and short lifespan. In recent years, composite material landing gear has gradually been put into use due to its advantages such as light weight, corrosion resistance, and high design flexibility, but its molding process still faces challenges.

[0004] In existing technologies, skid-type composite landing gear is mostly manufactured using hollow structure air-blowing molding or PMI foam filling method, among which: Hollow structure blowing molding method: The upper and lower skins are laid on the mold respectively, and the whole is formed by individual layer overlap. This method is prone to fiber discontinuity, which cannot effectively distribute the load and is difficult to add reinforcing ribs. The structure is not strong enough and is prone to cracking. PMI foam filling method: PMI foam needs to be carved and spliced ​​first, and then prepreg is laid and cured. However, the foam has poor impact load resistance and is easy to debond from the carbon fiber. It is costly and heavy.

[0005] These methods all suffer from problems such as complex molding processes, high costs, and poor structural stability and durability. Therefore, developing a new molding process to achieve continuous fiber, reinforced, and simple composite material landing gear manufacturing is of significant application value. Summary of the Invention

[0006] This application provides a composite material landing gear molding process to solve the problems of complex molding process, high cost, poor structural stability and durability of traditional composite material landing gear molding processes in the prior art.

[0007] This application provides a composite material landing gear molding process, including the following steps: Step S1, mold design and fabrication: Based on the landing gear structure, manufacture the inner liner mold, reinforcing rib mold, and outer skin mold respectively. Step S2, Inner liner fabrication and curing: Composite material prepreg is laid in the inner liner mold to form two halves of the inner liner, and then cured by vacuum bag pressing process; Step S3, Reinforcing Rib Fabrication and Curing: Composite material prepreg is laid in the reinforcing rib mold to form a reinforcing rib, which is then cured by vacuum bag pressing and demolded for finishing. Step S4, placing the reinforcing rib: place the reinforcing rib in any of the cured half of the inner liner, apply structural adhesive to the contact surface, and then mold the other half of the inner liner to it, so that the two halves of the inner liner and the reinforcing rib are glued together as a whole. Step S5, outer skin laying and curing: composite material prepreg is continuously laid on the outer surface of the overall inner liner, and the outer skin and inner liner are bonded together by molding and co-curing to form a complete landing gear structure. Step S6 involves post-processing and performance testing of the formed landing gear to ensure that it meets design requirements and usage standards.

[0008] Preferably, in step S1, the inner mold is a two-part female mold, and the parting surface of the two-part female mold is provided with positioning pin holes.

[0009] Preferably, in step S1, the reinforcing rib mold is a molding mold, and the reinforcing rib is an I-shaped structure.

[0010] Preferably, in step S2, the thickness of the inner liner is 2-3 layers of composite prepreg, and the inner liner is not demolded after curing, but is molded after the reinforcing ribs are placed.

[0011] Preferably, in step S5, the outer skin is laid using a combination of spiral winding and cross-layout, with the same layer of fibers laid continuously and different layer interfaces staggered.

[0012] Preferably, the composite prepreg is made of carbon fiber or glass fiber composite material.

[0013] Preferably, the post-processing includes sanding and painting the formed landing gear; The performance testing includes mechanical performance testing, abrasion resistance testing, and corrosion resistance testing of the landing gear.

[0014] Preferably, the performance testing further includes non-destructive testing, which includes ultrasonic scanning and X-ray flaw detection.

[0015] This application also provides a composite landing gear manufactured based on the composite landing gear molding process described in any one of the above claims, comprising an inner liner, reinforcing ribs, and an outer skin, wherein: The inner liner has a hollow structure; The reinforcing rib is disposed inside the inner liner, and at least one reinforcing rib is provided. The outer skin covers the outside of the inner liner, and the inner liner, reinforcing ribs and outer skin are bonded and co-cured to form an integrated load-bearing structure.

[0016] Preferably, the composite material prepreg used for the inner liner is made of carbon fiber composite material or glass fiber composite material, and the composite material prepreg used for the outer skin and reinforcing ribs is made of carbon fiber composite material.

[0017] The beneficial effects of this application are as follows: The composite material landing gear molding process of this application achieves hollow and reinforced integrated molding through a step-by-step composite structure of "inner liner-reinforcing rib-outer skin", which significantly improves the rigidity, strength and impact resistance of the landing gear and effectively avoids stress concentration and cracking risks. Furthermore, by using the inner liner as a reference body, it is easier to accurately position and bond the reinforcing ribs. The outer skin is then molded and co-cured with the inner liner, making the overall bond strong and the process more stable, controllable, and repeatable. At the same time, by adopting a hollow reinforced structure, extreme lightweighting is achieved while ensuring the overall performance of the landing gear. Compared with the traditional production process that uses heavy PMI foam for carving and splicing, this simplifies the continuous production process, reduces material waste, and lowers production costs. In particular, by using continuous fiber lay-up or winding to form the outer skin, the continuity of fibers on the main load-bearing path is ensured, so that the load can be evenly distributed, which greatly improves the structural load-bearing efficiency and durability. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 A flowchart illustrating the steps of the composite material landing gear molding process provided in this application embodiment; Figure 2 This is a schematic diagram of the overall structure of the inner liner mold in this application; Figure 3 This is a schematic diagram of the overall structure of the reinforcing rib mold in this application; Figure 4 This is a schematic diagram of the overall structure of the inner liner during mold closing in this application; Figure 5 This is a schematic diagram of the overall structure of the outer skin mold in this application. Figure 6 This is a schematic diagram of the overall structure of the composite material landing gear in this application. Figure 7 for Figure 6 Schematic diagram of the cross section at point AA; Figure 8 This is a schematic diagram of the overall structure of the inner liner in this application; Figure 9 This is a schematic diagram of the overall structure of the reinforcing rib in this application; Figure 10 for Figure 9 A cross-sectional view of section BB.

[0020] Figure label: 100. Landing gear structure; 1. Inner liner; 11. Semi-inner liner; 2. Reinforcing rib; 21. Reinforcing rib blank; 3. Outer skin; 4. Inner liner mold; 41. First inner liner mold; 42. Second inner liner mold; 5. Reinforcing rib mold; 51. First reinforcing rib mold; 52. Second reinforcing rib mold; 6. Outer skin mold; 61. First outer skin mold; 62. Second outer skin mold. Detailed Implementation

[0021] The technical solutions of this application will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] The following is combined Figure 1-10 This describes the composite material landing gear molding process provided in the embodiments of this application.

[0023] Reference Figure 1-6 As shown, the composite material landing gear molding process provided in this application includes the following steps: Step S1, mold design and manufacturing: Based on the landing gear structure, manufacture the inner liner mold 4, the reinforcing rib mold 5, and the outer skin mold 6 respectively. Specifically, based on the required structural parameters and layup requirements of the skid-type composite landing gear, special inner liner mold 4, reinforcing rib mold 5, and outer skin mold 6 are manufactured respectively. Among them, the inner liner mold 4 is a two-part female mold used to form the landing gear inner liner 1, and the mold surface is provided with positioning pin holes to ensure the forming accuracy of the inner liner 1 and the alignment of the mold. The reinforcing rib mold 5 is a molding mold adapted to the structural design of the reinforcing rib 2, and the reinforcing rib 2 is an I-shaped structure to improve the rigidity and bending resistance of the landing gear. The outer skin mold 6 is a split structure, and its inner wall curve fits the outer curve of the landing gear outer skin 3, and a layup operation space is reserved. Step S2, Inner liner 1 fabrication and curing: Composite material prepreg is laid in inner liner mold 4 to form two halves of inner liner 11, and cured by vacuum bag pressing process. Specifically, after cleaning and applying a release agent to the inner walls of the two halves of the inner liner 11 mold, 2-3 layers of composite prepreg are laid on each half. The composite prepreg is made of carbon fiber or glass fiber composite material. After the laying is completed, a vacuum bag is covered and the mold is cured using a vacuum bag pressing process. The curing temperature is controlled at 120-150℃ and the curing time is 2-4 hours. After curing, the half inner liner 11 is kept in contact with the mold and is not demolded for the time being. Step S3, Reinforcing Rib 2 fabrication and curing: Composite material prepreg is laid in reinforcing rib mold 5 to form reinforcing rib 2, and then demolded and trimmed after being cured by vacuum bag pressing. Specifically, based on the common stress analysis results of the landing gear, an I-shaped cross-section stiffener 2 structure is designed. After the inner wall of the stiffener mold 5 is coated with a release agent, a composite material prepreg made of carbon fiber composite material is laid in the layup sequence. During the laying process, the fiber direction is kept consistent with the stress direction of the stiffener 2, and a vacuum bag pressing process is used for curing. The curing parameters are the same as those of the inner liner 1. After curing, the mold is removed, and the edges of the stiffener 2 are trimmed and polished to ensure its surface flatness, thus obtaining the I-shaped stiffener 2.

[0024] Step S4, placing the reinforcing rib 2: Place the reinforcing rib 2 in any of the cured half of the inner liner 11, and after applying structural adhesive to the contact surface, mold the other half of the inner liner 11 with it, so that the two halves of the inner liner 11 and the reinforcing rib 2 are glued together to form a whole. Specifically, the reinforcing rib 2 prepared in step S3 is placed on the surface of one half of the cured inner liner 1. After the contact surface between the reinforcing rib 2 and the inner liner 1 is sanded and activated, structural adhesive is evenly applied. The structural adhesive is an epoxy-based high-temperature resistant structural adhesive, and the thickness of the adhesive is controlled at 0.1-0.3 mm. The other half of the inner liner 11 is then molded by positioning pin holes on the inner liner mold 4. A mold closing pressure of 0.5-1 MPa is applied and the pressure is maintained for 2-3 hours to bond the reinforcing rib 2 to the two halves of the inner liner 11 to form a complete inner liner 1 structure. Then, the mold is demolded. Step S5, outer skin 3 laying and curing: composite material prepreg is continuously laid on the outer surface of the overall inner liner 1, and the outer skin 3 is bonded to the inner liner 1 by molding co-curing to form a complete landing gear structure 100. Specifically, the surface of the integral inner liner 1 obtained in step S4 is polished and activated to remove surface impurities and oxide layers. Then, according to the landing gear outer skin 3 ply design, a composite prepreg made of carbon fiber composite material is laid and wound for reinforcement. The fibers in the same ply are kept continuous, and the interfaces of different plies are staggered to enhance fiber continuity and load distribution capability. After that, the ply-laid inner liner 1-outer skin 3 combined structure is placed into the preheated outer skin mold 6 and cured by compression molding at a curing temperature of 130-160℃ and a curing pressure of 0.5-1MPa for 2-5 hours. Compression molding co-curing is performed to make the outer skin 3 and the inner liner 1 tightly bonded to form the final landing gear structure 100. The outer skin mold 6 is composed of a first outer skin mold 61 and a second outer skin mold 62 whose inner wall curves fit the outer shape curve of the landing gear. Step S6: Perform post-processing and performance testing on the formed landing gear to ensure that it meets design requirements and usage standards; Specifically, the solidified landing gear is demolded, and post-processing procedures such as surface grinding, defect repair, and anti-corrosion painting are completed in sequence. After confirming that there are no defects through non-destructive testing such as ultrasonic testing, mechanical property tests such as tensile strength, bending strength, impact toughness, wear resistance, and corrosion resistance are performed to ensure that its various performance indicators meet the design requirements.

[0025] Through a step-by-step composite structure of "inner liner-reinforcing ribs-outer skin," hollow reinforcement is integrated into a single molding process, significantly improving the rigidity, strength, and impact resistance of the landing gear and effectively avoiding stress concentration and cracking risks. By using the inner liner as a reference body, it is easy to accurately position and bond the reinforcing ribs. The outer skin is then molded and co-cured with the inner liner, resulting in a strong overall bond and making the process more stable, controllable, and repeatable. At the same time, the hollow reinforcement structure achieves extreme lightweighting while ensuring the overall performance of the landing gear. Compared with the traditional production process that uses heavy PMI foam for carving and splicing, this simplifies the continuous production process, reduces material waste, and lowers production costs.

[0026] In some specific embodiments, in step S1, the inner liner mold 4 is a two-part female mold, specifically a first inner liner mold 41 and a second inner liner mold 42, and high-precision positioning pin holes are machined at the parting surface of the first inner liner mold 41 and the second inner liner mold 42 to ensure the molding accuracy of the inner liner 1 and the alignment of the mold.

[0027] In some specific embodiments, in step S1, the reinforcing rib mold 5 is a molding mold, which includes a first reinforcing rib mold 51 and a second reinforcing rib mold 52. The reinforcing rib blank 21 is placed between the first reinforcing rib mold 51 and the second reinforcing rib mold 52 and molded to form an I-shaped structure, so as to improve the rigidity and bending resistance of the landing gear.

[0028] In some specific embodiments, in step S2, the thickness of the inner liner 1 is 2-3 layers of composite prepreg, and the inner liner 1 is not demolded after curing, so that the mold can be closed after the reinforcing ribs 2 are placed.

[0029] In some specific embodiments, in step S5, when the outer skin 3 is laid, the composite prepreg is laid using a winding process. The fibers of the same layer are laid continuously, and the interfaces of different layers are staggered to enhance fiber continuity and load distribution capability, ensuring the service life of the landing gear in harsh environments.

[0030] In some specific embodiments, the composite prepreg is made of carbon fiber or glass fiber composite material.

[0031] In some specific embodiments, post-processing includes sanding and painting the shaped landing gear to improve its appearance quality and corrosion resistance. Performance testing includes mechanical performance testing, abrasion resistance testing, and corrosion resistance testing of the landing gear to ensure that it meets aerospace standards.

[0032] In some specific embodiments, performance testing also includes non-destructive testing, including ultrasonic scanning and X-ray flaw detection, to assess the presence of defects and the quality of internal bonding.

[0033] Please continue reading. Figure 6-10 In some specific embodiments, this application also provides a composite landing gear manufactured based on the composite landing gear molding process of any of the above, comprising an inner liner 1, reinforcing ribs 2, and an outer skin 3, wherein: The inner liner 1 has a hollow structure, and the hollow inner liner 1 is formed by gluing together two half inner liners 11. The reinforcing rib 2 is provided inside the inner liner 1, and at least one reinforcing rib 2 is provided; The outer skin 3 covers the outside of the inner liner 1. The inner liner 1, the reinforcing rib 2, and the outer skin 3 are bonded together and co-cured to form an integrated load-bearing structure.

[0034] In the specific implementation process, on the one hand, a sawtooth or wave-shaped interlocking structure can be set on the adhesive surface of the reinforcing rib 2 and the inner liner 1 to enhance the interface shear strength and anti-peeling ability. On the other hand, polyurethane microbubble material with a volume ratio not exceeding 15% can be filled into the hollow interior of the inner liner 1 to improve the damping performance and impact resistance of the structure.

[0035] In some specific embodiments, the composite material prepreg used for the inner liner 1 is made of carbon fiber composite material or glass fiber composite material, and the composite material prepreg used for the outer skin 3 and the reinforcing rib 2 is made of carbon fiber composite material.

[0036] In this design, the prepreg used for the inner liner 1 is made of glass fiber composite material, while the prepreg used for the outer skin 3 and reinforcing ribs 2 is made of carbon fiber composite material. This creates a gradient strength structure that is flexible inside and rigid outside. By using higher rigidity carbon fiber composite material for the outermost outer skin 3 and the reinforcing ribs 2 inside the inner liner 1, the inner liner 1 can be provided with more effective outer protection and inner lining support. By using lower rigidity glass fiber composite material for the inner liner 1, it has higher corrosion resistance and a certain degree of deformation buffer, forming a load-bearing structure that is flexible inside and rigid outside between the inner liner 1 and the outer skin 3 and reinforcing ribs 2. When bearing load, the high modulus carbon fiber outer skin 3 and the internal carbon fiber reinforcing ribs 2 act as the main load-bearing frame, providing most of the rigidity and strength, while the relatively flexible glass fiber inner liner 1 plays a role in buffering and stress redistribution, and can effectively inhibit crack propagation, thereby significantly enhancing the overall toughness and damage tolerance of the landing gear and enhancing its overall load-bearing capacity.

[0037] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application 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 this application.

[0038] 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 technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0039] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between components; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0040] In this application, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0041] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A composite landing gear forming process, characterized by, The method comprises the following steps: Step S1, mold design and manufacturing, according to the landing gear structure, the inner container mold, the reinforcing rib mold and the outer skin mold are manufactured respectively; Step S2, inner container manufacturing and curing, laying composite prepreg in the inner container mold to form two half inner containers, and curing by vacuum bag pressing process; Step S3, reinforcing rib manufacturing and curing, laying composite prepreg in the reinforcing rib mold to form reinforcing rib, and curing by vacuum bag pressing and demolding and trimming; Step S4, reinforcing rib placement, placing the reinforcing rib in any cured half inner container, and combining the other half inner container after coating structural adhesive on the contact surface, so that the two half inner containers and the reinforcing rib are glued into a whole; Step S5, outer skin laying and curing, continuously laying composite prepreg on the outer surface of the whole inner container, combining the outer skin and the inner container by mold pressing and co-curing to form a complete landing gear structure; Step S6, post-processing and performance detection of the formed landing gear to ensure that it meets the design requirements and use standards.

2. The composite material landing gear forming process of claim 1, wherein, In the step S1, the inner container mold is a two half female mold, and positioning pin holes are arranged at the parting surface of the two half female mold.

3. The composite landing gear forming process of claim 1, wherein, In the step S1, the reinforcing rib mold is a mold pressing mold, and the reinforcing rib is a I-shaped structure.

4. The composite material landing gear forming process of claim 1, wherein, In the step S2, the thickness of the inner container is 2-3 layers of composite prepreg, and the inner container is not demolded after curing, but combined after the reinforcing rib is placed.

5. The composite material landing gear forming process of claim 1, wherein, In the step S5, the outer skin laying adopts spiral winding and cross layer combination, and the fibers of the same layer are continuously laid, and the interfaces of different layers are staggered.

6. The composite material landing gear forming process of claim 1, wherein, The composite prepreg is made of carbon fiber or glass fiber composite material.

7. The composite material landing gear forming process of claim 1, wherein, The post-processing includes polishing and painting of the formed landing gear; The performance detection includes mechanical property test, wear resistance test and corrosion resistance test of the landing gear.

8. The composite material landing gear forming process of claim 1, wherein, The performance detection also includes nondestructive testing, and the nondestructive testing includes ultrasonic scanning and X-ray detection.

9. A composite landing gear, characterized by, The composite landing gear formed by the forming process of any one of claims 1-8 comprises an inner container, a reinforcing rib and an outer skin, wherein: The inner container is a hollow structure; The reinforcing rib is arranged inside the inner container, and at least one reinforcing rib is arranged; The outer skin is arranged outside the inner container, and the inner container, the reinforcing rib and the outer skin are integrated into a load bearing structure by gluing and co-curing.

10. The composite landing gear of claim 9, wherein, The composite prepreg used in the inner container is made of carbon fiber composite material or glass fiber composite material, and the composite prepreg used in the outer skin and the reinforcing rib is made of carbon fiber composite material.

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