A method of forming a composite material case flange

Abstract

A composite material casing flange edge forming method, according to the target structure of the composite material casing flange edge, a forming die with an R area forming surface is provided, according to the composite material thickness and the formability of the prepreg, the minimum radius that the prepreg layer can reach in the R area is determined; a laying cover plate not less than the minimum radius of the outer convex surface of the R area is provided, the prepreg twist strip is filled between the laying cover plate and the forming surface and preformed to obtain an R area preformed part, the laying cover plate is removed and the prepreg is laid on the surface of the R area preformed part and the R area forming surface to obtain a composite material preform, curing forming is carried out, the R area preformed part and the composite material preform are connected to become a whole, and a finished part is obtained.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of composite materials, and particularly relates to a forming method for a flange of a composite material casing. BACKGROUND

[0002] Composite materials have the advantages of light weight and high strength, and have been increasingly widely applied in the manufacturing of advanced aero-engines. A composite material casing is a typical application. The composite material casing surrounds the fan blades of an aero-fan engine, and improves the aerodynamic efficiency of the fan blades through the effect of the duct, and can contain fragments when the blades are damaged without damaging the engine and other flight structures. Due to the limitation of the connecting process of the composite material, the flange edge of the composite material casing usually needs to be connected with the front and rear mounting structures, and the flange edge of the casing needs to bear the dynamic load and aerodynamic load transmitted by the front and rear mounting structures, so the forming quality of the flange edge is crucial to the overall performance of the composite material casing. The manufacturing process of the composite material casing usually adopts the method of laying up prepreg on a mold to realize forming, but the R region of the flange edge (the geometric transition region formed by the bending of the flange edge relative to the body of the casing) is affected by factors such as thermal stress, uneven distribution of forming pressure, and elasticity and tension of the prepreg itself, and the dimensional accuracy is difficult to control in the forming process, and forming defects are easily generated, which has an adverse effect on the overall strength of the composite material casing. Therefore, it is of high practical value to provide a forming method capable of improving the forming quality of the R region of the flange edge, for improving the reliability of the composite material casing. SUMMARY

[0003] The present application aims to provide a forming method for a flange edge of a composite material casing, which can improve the forming quality of the R region of the flange edge.

[0004] According to an embodiment of the present application, a forming method for a flange edge of a composite material casing is provided, comprising the following steps: providing a forming mold for the flange edge of the composite material casing, the forming mold having an R region forming surface for forming the profile of the convex side of the R region of the flange edge of the composite material casing; determining the minimum radius R1 that can be reached by the prepreg layup on the concave side of the R region and the minimum radius R2 that can be reached by the prepreg layup on the convex side according to the thickness h of the composite material and the formability of the prepreg; providing a layup cover plate with a radius not less than R2 to cover the R region forming surface, and filling a prepreg twist strip between the layup cover plate and the R region forming surface to form an R region filling structure; pre-forming the R region filling structure to obtain an R region pre-formed part; removing the layup cover plate, and laying up the prepreg on the surface of the forming mold and the R region pre-formed part to form a composite material preform, curing to connect the R region pre-formed part and the composite material preform into a whole, and demolding to obtain a finished part.

[0005] The twist strip filled in the corner position of the mold can effectively eliminate the bridging defects or R corner size deviation caused by the insufficient pressure or the improper laying of the prepreg, and avoid the wrinkles of the prepreg laid in the corner.

[0006] Further, in some embodiments, before filling the twist strip of the prepreg, the step of laying the glass fabric prepreg on the R area forming surface is further included. The glass fabric can improve the corrosion resistance of the casing.

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

[0008] Further, in some embodiments, the central angle of the laid cover plate is 90°.

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

[0010] Further, in some embodiments, the preforming process includes the following steps: laying the release cloth and air-permeable felt on the laid cover plate in turn, sealing with a vacuum bag, vacuumizing to at least-0.095MPa for at least 20min, and compacting the twist strip of the prepreg to complete the preforming.

[0011] Further, in some embodiments, the twist strip of the prepreg uses NY9200GB / T800 prepreg.

[0012] Further, in some embodiments, the composite material preform uses NY9200GB / T700 prepreg.

[0013] Further, in some embodiments, the curing process of the composite material preform includes the following steps: laying the release cloth, adhesive absorbing cloth, isolation film and air-permeable felt on the surface layer of the composite material preform, sealing with a vacuum bag; vacuumizing and performing airtightness inspection in a hot press tank; heating at a speed of 1-2℃ / min to 145±5℃, and keeping warm for 30-60min; pressurizing to 0.5-0.6MPa, heating to 175-180℃ for 2.5h-3h; after the heat preservation is completed, cooling to below 60℃ in the furnace, and releasing the pressure to obtain the finished part.

[0014] Further, in some embodiments, after the finished part is obtained by demolding, the step of grinding the R area of the finished part is further included. BRIEF DESCRIPTION OF DRAWINGS

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

[0016] Figure 2Figure 1 is a schematic view of a structure for filling the R region in an embodiment;

[0017] Figure 3 Figure 2 is a schematic view of a structure of a composite preform in an embodiment.

[0018] The above drawings are intended to provide a detailed description of the present application so that those skilled in the art can understand the technical concept of the present application, and are not intended to limit the present application. For the sake of brevity, the above drawings only schematically show the structures related to the technical features of the present application, and do not strictly show the complete structures and all details according to the actual proportions. DETAILED DESCRIPTION

[0019] The present application will be further described in detail below with reference to specific embodiments in conjunction with the drawings.

[0020] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present application. The appearances of the phrase that the phrase in various places in the specification are not necessarily referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of one another. Those skilled in the art will appreciate that an embodiment of the present application can be combined with another embodiment in a manner not specifically stated in the description.

[0021] In the description herein, unless otherwise explicitly specified and limited, the technical terms "mounting", "connection", "connecting", and the like should be interpreted in a broad sense. In the description herein, unless otherwise explicitly specified and limited, the technical terms "mounting", "connection", "connecting", and the like should be interpreted in a broad sense. In the description herein, the meaning of "a plurality of" is at least two.

[0022] Due to the constraints of the performance and manufacturing process of the resin-based composite material, large structural parts of the engine case made of the resin-based composite material cannot be connected by welding or other methods. Usually, flanges are provided on the parts, holes are opened on the flanges, and the parts are connected and fixed by bolts. As shown in Figure 1 The composite material case is bent to form a flange 1, and the transition between the flange 1 and the case body is an R region, which includes an outer convex surface 2 and an inner concave surface 3. The R angle radius R3 of the outer convex surface 2 is limited to a small value due to the assembly requirements, so that the composite material case can meet the design requirements when assembled with the front and rear parts. However, the pre-impregnated material itself has a certain elasticity and tension during the manufacturing process of the composite material case, and when the pre-impregnated material is stacked thick, the pre-impregnated material in the R angle region of the flange is difficult to completely fit the mold, as shown in Figure 1As shown, the minimum bending radius achievable by the prepreg closest to the concave surface 3 is R1, but the minimum bending radius achievable by the prepreg layer closest to the convex surface 2 is R2, which is significantly larger than the designed R-angle radius R3. When the bending radius is less than R2, the prepreg layer is prone to wrinkles or bridging at corners, which leads to the formation of a defect area 5 between the actual prepreg surface and the designed R-area contour surface, resulting in the flange edge R-angle dimension not meeting the requirements. The specific values ​​of R1 and R2 can be determined by preparing test specimens with different R-angles and measuring their microstructure and mechanical properties. The minimum radius at which the test specimens do not exhibit wrinkles, bridging, delamination, or strength reduction after curing is also determined.

[0023] To address the aforementioned problems, embodiments of the present invention provide a method for forming a composite material casing flange edge, which can effectively perform flange edge R-zone forming processing.

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

[0025] Next, release cloth and breathable felt are arranged sequentially on the cover plate 8. The composite material casing molding mold is placed into a vacuum bag and sealed. The vacuum is drawn to at least -0.095MPa (in terms of relative vacuum degree) and held for more than 20 minutes. The R-zone filling structure is compacted and pre-formed to obtain the R-zone preform.

[0026] Then, remove the vacuum bag and the cover plate, such as Figure 3 As shown, the prepreg 9 of the composite preform is laid sequentially on the mold and the surface of the R-zone preform according to the lay-up reduction position lines pre-cut on the composite casing molding mold according to the casing structure design. In an optional embodiment, the prepreg 9 is NY9200GB / T700 prepreg.

[0027] Finally, after the completion of laying, a release cloth, a glue absorbing cloth, an isolation film and a breather fabric are arranged on the surface of the composite preform in sequence, the composite preform and the composite case mold are integrally put into a vacuum bag for sealing, are put into a hot pressing furnace for vacuumizing and air tightness checking, after the air tightness checking is qualified, heating is performed at a speed of 1-2℃ / min to 145±5℃ for 30-60min, after the heat preservation is completed, pressurizing is performed at 0.5-0.6MPa and heating is performed to 175℃-180℃ for 2.5h-3h, after the heat preservation is completed, furnace cooling is performed to below 60℃, and the composite case product is obtained after demolding.

[0028] In optional embodiments, after demolding, the R area of the composite case can be polished to round, and the R angle is polished to the composite design requirement. Since the convex surface part of the R area is formed by the twist rod, mechanical polishing will not damage the fiber continuity of the prepreg, and will not have a negative impact on the overall mechanical properties of the case.

[0029] In preferred embodiments, the central angle of the laying cover plate 8 is set to 90°, so that it can be tangent to the two planes perpendicular to the forming surface 6 of the R area respectively, and thus the arc length of the laying cover plate 8 section can be calculated as 0.5π(R1+h). In other embodiments, the laying cover plate 8 can also be set to a central angle less than 90°, so that the edges of the laying cover plate 8 are in intersecting relationship with the two planes perpendicular to the forming surface 6, and assuming that the corresponding central angle of the laying cover plate 8 is θ° at this time, the arc length of the laying cover plate 8 is 2π(θ / 360)(R1+h).

[0030] Through the method provided in the above embodiments, the flange edge of the composite case is formed, the forming tool can not need to consider the R angle size requirement of the flange edge assembly surface, and is simple to design and manufacture; meanwhile, the forming precision of the R area of the flange edge can be effectively improved, defects and size out-of-tolerance caused by laying out of position or insufficient compaction can be avoided, and the forming quality and mechanical properties of the R area are further improved; and since small angle laying is avoided, the laying direction of the prepreg is more natural, and the wrinkle defect of the R area can also be avoided.

[0031] The above embodiments are intended to make further detailed description of the present application in combination with the drawings, so that those skilled in the art can understand the technical concept of the present application. Within the scope of the present application, optimization or equivalent replacement of the method steps involved, and combination of the embodiments in different embodiments without structural and principle conflicts, all fall within the protection scope of the present application.

Claims

1. A method for forming a composite material casing flange edge, characterized in that, Includes the following steps: A molding die is provided for the flange edge of the composite material casing, the molding die having an R-zone molding surface, the R-zone molding surface being used to form a profile on the outwardly convex side of the R-zone of the flange edge of the composite material casing; The minimum radius R1 that the prepreg layup can achieve on the concave side and the minimum radius R2 that can be achieved on the convex side of the R region are determined based on the thickness h of the composite material and the formability of the prepreg. A cover plate with a radius not less than R2 is provided to cover the R-zone molding surface, and prepreg twist strips are filled between the cover plate and the R-zone molding surface to form an R-zone filling structure; The R-region filling structure is pre-formed to obtain an R-region preform; Remove the cover plate, cover the mold and the R-zone preform surface with the prepreg to form a composite material preform, cure to connect the R-zone preform and the composite material preform into a whole, and demold to obtain the finished part.

2. The method for forming the flange edge of a composite material casing according to claim 1, characterized in that, Before filling the prepreg twist strip, the process also includes the step of laying fiberglass fabric prepreg on the R-zone molding surface.

3. The method for forming the flange edge of a composite material casing 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 method for forming the flange edge of a composite material casing according to claim 1 or 2, characterized in that, The center angle corresponding to the cover plate is 90°.

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

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

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

8. The method for forming the flange edge of a composite material casing according to claim 1 or 2, characterized in that, The composite material preform uses NY9200GB / T700 prepreg.

9. The method for forming the flange edge of a composite material casing according to claim 8, characterized in that, The curing process of the composite material preform includes the following steps: a release cloth, absorbent cloth, release film, and breathable felt are arranged on the surface of the composite material preform in one step, and sealed with a vacuum bag; the preform is placed in an autoclave, vacuumed, and its airtightness is checked; the temperature is increased to 145±5℃ at a rate of 1-2℃ / min and held for 30-60min; pressure is applied at 0.5-0.6MPa, and the temperature is increased to 175-180℃ and held for 2.5-3h; after the holding period, the preform is cooled to below 60℃ in the furnace, and the pressure is released to demold the finished part.

10. The method for forming the flange edge of a composite material casing according to claim 1 or 2, characterized in that, After demolding to obtain the finished part, the process also includes a step of grinding the R-zone of the finished part.

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