Composite material casing flange edge forming method

Abstract

The invention relates to a composite casing flange edge forming method, which comprises the following steps of: providing a forming mold with an R-region forming surface according to a target structure of a composite casing flange edge, and determining the minimum radius of a prepreg paving layer in an R region according to the thickness of a composite material and the formability of a prepreg; providing a paving cover plate which is not smaller than the minimum radius of the outer convex surface of the R area, filling prepreg rhodomyrtus tomentosa strips between the paving cover plate and the forming surface, performing preforming to obtain an R area preformed part, moving out the paving cover plate, paving prepreg on the surfaces of the R area preformed part and the R area forming surface to obtain a composite material preform, and performing curing forming to obtain the composite material. And connecting the R-region preform and the composite material preform into a whole to obtain a finished part.

Description

Technical Field

[0001] The invention belongs to the field of composite materials, and in particular relates to a composite material casing flange forming method. Background Art

[0002] Composite materials have the advantages of light weight and high strength, and have been increasingly widely used in the manufacture of advanced aircraft engines. Composite casings are a typical application. Composite casings surround the fan blades of aviation turbofan engines, improve the aerodynamic efficiency of fan blades through the duct effect, and contain fragments when blades are damaged without damaging the engine and other flight structures. Due to the limitations of the connection process of composite materials, composite casings usually need to be connected to the front and rear mounting structures using flange edges. Therefore, the flange edges of the casing also need to bear the maneuvering loads and aerodynamic loads transmitted by the front and rear mounting structures. Therefore, the molding quality of the flange edges is crucial to the overall performance of the composite casing. The manufacturing process of composite casings usually uses prepregs to be laid on the mold to achieve molding, but the R zone of the flange edge (the geometric transition zone formed by the flange edge bending relative to the casing body) is affected by factors such as thermal stress, uneven distribution of molding pressure, and the elasticity and tension of the prepreg itself. During the molding process, the dimensional accuracy is difficult to control, and molding defects are prone to occur, which has an adverse effect on the overall strength of the composite casing. Therefore, providing a molding method that can improve the molding quality of the R zone of the flange edge has a high practical value for improving the reliability of the composite casing. Summary of the invention

[0003] The object of the present invention is to provide a composite material casing flange edge forming method, which can improve the forming quality of the flange edge R zone.

[0004] According to an embodiment of the present invention, a composite material casing flange molding method is provided, comprising the following steps: providing a molding die for the composite material casing flange, the molding die having an R-zone molding surface, the R-zone molding surface being used to form a profile on the convex side of the R-zone of the composite material casing flange; determining the minimum radius R1 that the prepreg layer can reach on the concave side of the R-zone and the minimum radius R2 that the prepreg layer can reach on the convex side according to the thickness h of the composite material and the moldability of the prepreg; providing a paving cover plate with a radius not less than R2 to cover the R-zone molding surface, filling prepreg twist strips between the paving cover plate and the R-zone molding surface to form an R-zone filling structure; preforming the R-zone filling structure to obtain an R-zone preform; removing the paving cover plate, paving the prepreg on the surface of the molding die and the R-zone preform to form a composite material preform, curing to connect the R-zone preform and the composite material preform into a whole, and demolding to obtain a finished part.

[0005] Filling the corners of the mold with twist strips can effectively eliminate bridging defects or R-angle size deviations caused by inadequate prepreg laying or insufficient pressure, and avoid wrinkles in the prepreg laying at the corners.

[0006] Furthermore, in some embodiments, before filling the prepreg twist strips, a step of covering the R-zone molding surface with glass fiber fabric prepreg is also included. Glass fiber fabric can improve the anti-corrosion performance of the casing.

[0007] Furthermore, in some embodiments, the glass fiber fabric prepreg is configured as an E-class glass fiber plain weave two-dimensional fabric prepreg.

[0008] Furthermore, in some embodiments, the central angle corresponding to the paving cover plate is 90°.

[0009] Furthermore, in some embodiments, the arc length of the paving cover plate is 0.5π(R1+h).

[0010] Furthermore, in some embodiments, the preforming process includes the following steps: laying a release cloth and a breathable felt on the paving cover in sequence, sealing with a vacuum bag, evacuating to at least -0.095 MPa and maintaining for at least 20 minutes, and compacting the prepreg twist strips to complete the preforming.

[0011] Furthermore, in some embodiments, the prepreg twist strips are made of NY9200GB / T800 prepreg.

[0012] Furthermore, in some embodiments, the composite material preform is made of NY9200GB / T700 prepreg.

[0013] Furthermore, in some embodiments, the curing process of the composite material preform includes the following steps: arranging a demoulding cloth, an adhesive tape, an isolation film, and a breathable felt on the surface of the composite material preform at one time, and sealing it with a vacuum bag; placing it in an autoclave, evacuating the air, and performing an air tightness check; heating to 145±5°C at a rate of 1-2°C / min, and keeping warm for 30-60min; pressurizing to 0.5-0.6MPa, heating to 175-180°C, and keeping warm for 2.5h-3h; after the insulation is completed, cooling it to below 60°C with the furnace, releasing the pressure and demolding to obtain the finished parts.

[0014] Furthermore, in some embodiments, after demolding to obtain the finished part, a step of grinding the R zone of the finished part is also included. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the local structure of the composite material casing R area in one embodiment;

[0016] Figure 2This is a schematic diagram of the R region filling structure in one embodiment;

[0017] Figure 3 Schematic diagram of the composite material preform structure in one embodiment.

[0018] The purpose of the above drawings is to explain the present invention in detail so that those skilled in the art can understand the technical concept of the present invention, but it is not intended to limit the present invention. For the sake of simplicity, the above drawings only schematically illustrate the structures related to the technical features of the present invention, and do not strictly follow the actual scale to draw the complete structure and all details. DETAILED DESCRIPTION

[0019] The present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings.

[0020] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The phrase appearing in various locations in the specification does not necessarily refer to the same embodiment, nor is it limited to mutually exclusive independent or alternative embodiments. Those skilled in the art should be able to understand that the embodiments herein may be combined with other embodiments without causing structural conflicts.

[0021] In the description of this article, unless otherwise clearly specified and limited, the technical terms "install", "connect", "connect", etc. should be understood in a broad sense. In the description of this article, unless otherwise clearly specified and limited, the technical terms "install", "connect", "connect", etc. should be understood in a broad sense. In the description of this article, "multiple" means at least two.

[0022] Due to the limitations of the performance and manufacturing process of resin-based composite materials, large structural parts of engine casings made of resin-based composite materials cannot be connected by welding or other methods. Usually, flanges are set on the parts, holes are opened on the flanges, and bolts are used to connect and fix them. Figure 1 As shown, the composite material receiver is bent to form a flange edge 1. The transition between the flange edge 1 and the receiver body is the R zone. The R zone includes an outer convex surface 2 and an inner concave surface 3. The outer convex surface 2 extends to the surface of the flange edge 1 to form a mating interface 4. Restricted by assembly requirements, the R corner radius R3 of the outer convex surface 2 is limited to a smaller value so that the composite material receiver can meet the design requirements when assembled with the front and rear end parts. However, in the manufacturing process of the composite material receiver, multiple layers of prepreg need to be laid layer by layer on the mold and pressurized. The prepreg itself has certain elasticity and tension. When the prepreg is stacked thicker, the prepreg in areas such as the flange edge R corner is difficult to fully fit the mold. Figure 1As shown, the minimum bending radius that can be achieved by the prepreg closest to the inner concave surface 3 is R1, but the minimum bending radius that can be achieved by the prepreg layer closest to the outer convex surface 2 is R2, which is significantly larger than the R angle radius R3 required by the design. When the bending radius is less than R2, the prepreg layer is very likely to have wrinkles or form bridges at the corners, which leads to the formation of defective areas 5 between the actual paving surface of the prepreg and the R zone design contour surface, resulting in the flange edge R angle size not meeting the requirements. Among them, the specific values ​​of R1 and R2 can be determined by preparing test pieces by paving prepregs, measuring the organization and mechanical properties of test pieces with different R angles, and the minimum radius at which no wrinkles, bridges, delamination or strength reduction occurs after the test pieces are cured.

[0023] In order to solve the above problems, an embodiment of the present invention provides a composite material casing flange edge forming method, which can effectively perform flange edge R zone forming processing.

[0024] like Figure 2 As shown, the molding surface 6 is a part of the composite casing molding die, which is used to mold the outer convex surface 2 of the flange edge R zone. Before manufacturing the composite casing preform, a paving cover plate 8 with a radius not less than R2 is first provided. The paving cover plate 8 is an arc structure and has a certain rigidity, which can cover the corners of the molding surface 6 and maintain its own surface stability. In a preferred embodiment, the radius of the paving cover plate 8 is R2, and the pore volume between the paving cover plate 8 and the molding surface 6 when the paving cover plate 8 covers the corners of the molding surface 6 is calculated. The twist strip 7 is made of NY9200GB / T800 prepreg and filled in the gap between the paving cover plate 8 and the molding surface 6 to obtain the R zone filling structure. In a preferred embodiment, before filling the twist strip 7, two layers of E-class glass fiber two-dimensional plain fabric prepreg with a single layer thickness of 0.1 mm are first laid on the surface of the molding surface 6. The laying direction of the prepreg is [0 / 90] along the circumference of the casing, and the length range along the axial direction of the casing is 100 mm axially extended after the R angle of the flange is flattened. The glass fiber prepreg is laid as the anti-corrosion layer of the flange.

[0025] Next, release cloth and breathable felt are arranged in sequence on the paving cover plate 8, the composite casing forming mold is placed in a vacuum bag and sealed as a whole, and the vacuum is evacuated to at least -0.095 MPa (in terms of relative vacuum degree) and maintained for more than 20 minutes, and the R zone filling structure is compacted and preformed to obtain the R zone preform.

[0026] Afterwards, remove the vacuum bag and the paving cover. Figure 3 As shown, the prepreg 9 of the composite material preform is laid sequentially on the mold and the surface of the R zone preform according to the ply decreasing position lines pre-engraved on the composite material casing forming mold according to the casing structure design. In an optional embodiment, the prepreg 9 uses NY9200GB / T700 prepreg.

[0027] Finally, after paving is completed, release cloth, adhesive tape, isolation film and breathable felt are arranged on the surface of the composite material preform in sequence, and the composite material preform and the composite material casing mold are put into a vacuum bag as a whole for sealing, and put into a hot press furnace for vacuuming and air tightness inspection. After the air tightness inspection is qualified, the temperature is increased to 145±5℃ at a rate of 1-2℃ / min and kept warm for 30-60min. After the insulation is completed, the pressure is increased by 0.5-0.6MPa and the temperature is increased to 175℃-180℃ and kept warm for 2.5h-3h. After the insulation is completed, it is cooled to below 60℃ with the furnace, and the mold is pressed down to obtain the finished composite material casing.

[0028] In an optional embodiment, the R area of ​​the composite casing can be rounded after demoulding to grind the R angle to the composite design requirements. Since the outer convex surface of the R area is formed by curing the twist strips, mechanical grinding will not destroy the fiber continuity of the prepreg and will not have a negative impact on the overall mechanical properties of the casing.

[0029] In a preferred embodiment, the central angle of the paving cover plate 8 is set to 90°, so that it can be tangent to the two planes perpendicular to the molding surface 6 of the R zone, respectively. From this, it can be calculated that the arc length of the cross section of the paving cover plate 8 is 0.5π(R1+h). In other embodiments, the paving cover plate 8 can also be set to a central angle less than 90°, so that the edge of the paving cover plate 8 intersects with the two planes perpendicular to the molding surface 6. Assuming that the central angle corresponding to the paving cover plate 8 is θ°, the arc length of the paving cover plate 8 is 2π(θ / 360)(R1+h).

[0030] By using the method provided in the above embodiment to form the flange edge of the composite casing, the forming tooling does not need to consider the R angle dimension requirements of the flange edge assembly surface, and the design and manufacturing are simple; at the same time, it can effectively improve the forming accuracy of the R zone of the flange edge, avoid defects and dimensional deviations caused by inadequate paving or insufficient compaction, and further improve the forming quality and mechanical properties of the R zone; and because small-angle paving is avoided, the prepreg paving direction is more natural, and wrinkle defects in the R zone can also be avoided.

[0031] The purpose of the above embodiments is to further explain the present invention in detail in conjunction with the accompanying drawings so that those skilled in the art can understand the technical concept of the present invention. Within the scope of the present invention, the optimization or equivalent replacement of the method steps involved, and the combination of the implementation methods in different embodiments without conflict of structure and principle, all fall within the protection scope of the present invention.

Claims

1. A composite material casing flange edge forming method, characterized in that: The following steps are involved: Providing a molding die for the composite material casing flange edge, the molding die having an R-zone molding surface, the R-zone molding surface being used to form a molding surface on a convex side of the R-zone of the composite material casing flange edge; Determine the minimum radius R1 that the prepreg layer can reach on the concave side of the R zone and the minimum radius R2 that the prepreg layer can reach on the convex side according to the thickness h of the composite material and the formability of the prepreg; Providing a paving cover plate with a radius not less than R2 to cover the R-zone molding surface, and filling prepreg twist strips between the paving cover plate and the R-zone molding surface to form an R-zone filling structure; Preforming the R-region filling structure to obtain an R-region preform; The paving cover plate is removed, and the prepreg is spread on the surface of the forming mold and the R-zone preform to form a composite material preform. The R-zone preform and the composite material preform are connected as a whole by curing, and the finished part is demoulded to obtain the finished part.

2. The composite material casing flange edge forming method according to claim 1, characterized in that: Before filling the prepreg twist strips, the method further includes the step of laying glass fiber fabric prepreg on the R zone molding surface.

3. The composite casing flange edge forming method according to claim 2, characterized in that: The glass fiber fabric prepreg is configured as an E-grade glass fiber plain weave two-dimensional fabric prepreg.

4. The composite casing flange edge forming method according to claim 1 or 2, characterized in that: The central angle corresponding to the paving cover plate is 90°.

5. The composite material casing flange edge forming method according to claim 4, characterized in that: The arc length of the paving cover plate is 0.5π(R1+h).

6. The composite material casing flange edge forming method according to claim 1 or 2, characterized in that: The preforming process comprises the following steps: laying a release cloth and a breathable felt on the paving cover in sequence, sealing with a vacuum bag, evacuating to at least -0.095 MPa and maintaining for at least 20 minutes, and compacting the prepreg twist strips to complete the preforming.

7. The composite casing flange edge forming method according to claim 1 or 2, characterized in that: The prepreg twist strips are made of NY9200GB / T800 prepreg.

8. The composite material casing flange edge forming method according to claim 1 or 2, characterized in that: The composite material preform is made of NY9200GB / T700 prepreg.

9. The composite material casing flange edge forming method according to claim 8, characterized in that: The curing process of the composite material preform comprises the following steps: arranging a demoulding cloth, an adhesive tape, an isolation film and a breathable felt on the surface of the composite material preform at one time, and sealing it with a vacuum bag; placing it in an autoclave, evacuating the air and performing an air tightness inspection; heating it to 145±5°C at a rate of 1-2°C / min, and keeping it warm for 30-60min; pressurizing it to 0.5-0.6MPa, heating it to 175-180°C and keeping it warm for 2.5h-3h; after the insulation is completed, cooling it to below 60°C with the furnace, releasing the pressure and demoulding it to obtain a finished part.

10. The composite material casing flange edge forming method according to claim 1 or 2, characterized in that: After demoulding to obtain the finished part, the method further includes grinding the R zone of the finished part.

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