A method for processing the radius (R) of cylindrical sandwich composite parts

Abstract

This invention pertains to composite material part molding technology, specifically a method for processing the radius (R) of cylindrical sandwich composite parts. Due to the uncontrollable nature of pressure transmission and prepreg resin overflow, varying degrees of delamination defects exist in areas with large curvature (R) corners. In this method, the honeycomb I-shaped high-pressure plastic molding splicing ensures both the matching degree of the honeycomb shape and significantly improves the local rigidity of the honeycomb. The I-shaped structure of the honeycomb splicing effectively transmits pressure during part curing, allowing pressure to be smoothly transferred from the upper surface of the honeycomb along the splice seam to the hardened area on the lower surface, forming a good transmission channel. Simultaneously, it reduces honeycomb springback caused by gradual angle changes, offsetting pressure attenuation and improving transmission efficiency. The complementary advantages of the multi-material gradient layout of the filling layer and the closed pores reduce the space required, making the effects of the fabric layers and adhesive film more pronounced, thus achieving minimal usage, minimal weight gain, and maximum effect.

Description

Technical Field

[0001] This invention pertains to composite material parts molding technology, specifically involving a method for processing the R-angle of cylindrical sandwich composite parts. A novel internal structural design is employed, using an expanding adhesive film combined with prepreg fabric layers to fill the gaps in the R-angle area of ​​the cylindrical sandwich component, thereby eliminating delamination defects after the parts have cured. Background Technology

[0002] Large-sized, high-curvature cylindrical composite sandwich components are currently the main structural form of helicopter tail booms. The integrated composite component design reduces both assembly and weight, achieving multiple benefits. However, the combination of integrated structural design and one-piece molding process makes the molding process of cylindrical composite sandwich components extremely complex, with cumbersome procedures, high requirements for process parameters, and difficulty in effective control. This leads to frequent quality problems in the manufactured parts, and the quality stability still needs to be improved.

[0003] The current molding process uses a honeycomb splicing method to form a semi-cylindrical structure, and then the two semi-molds are joined together to form a complete cylindrical structure. Due to the uncontrollable nature of pressure transmission and prepreg resin overflow, a prominent problem with products manufactured using this process is the presence of varying degrees of delamination defects in areas with large curvature radius (R-angle). This results in significant repair work on the parts, and even the risk of complete scrapping, severely impacting production schedules and cost control, greatly increasing the overall manufacturing cost of the helicopter, and reducing production efficiency.

[0004] In view of this, a new process is needed that can effectively eliminate delamination defects in areas with large curvature R-angles, that is, easy to operate, controllable in process, and will not affect subsequent parts assembly and functional use, reduce the loss of manpower, material resources and time in the repair process, and improve product quality and stability. Summary of the Invention

[0005] The purpose of this invention is to provide a method for processing the R-corner of cylindrical sandwich composite parts, which can effectively fill the interlayer gaps caused by resin overflow and fabric slippage during the curing process, ensure effective pressure transmission, and achieve the purpose of eliminating R-corner delamination defects. This method can effectively improve the overall quality of the parts, reduce changes in structural properties and additional repairs. The method has the characteristics of low manufacturing cost, easy implementation and good quality stability.

[0006] This invention proposes a method for processing the radius (R) of cylindrical sandwich composite parts, the method comprising the following steps:

[0007] S1. Lay a carrier-supported adhesive film on the R-corner area of ​​the honeycomb preform mold;

[0008] S2. Place the lower layer of the pre-cured I-shaped adhesive film in the area with the carrier adhesive film.

[0009] S3. Cut the honeycomb before molding according to the center normal direction of the R-corner area, so that the honeycomb cut surface satisfies the requirement that the honeycomb is joined on the lower layer of adhesive film in the R-corner area to form an arc honeycomb state when there is no stress.

[0010] S4. Insert the middle layer of the pre-cured I-shaped adhesive film between the honeycomb cross-sections, and then lay the upper layer of the pre-cured I-shaped adhesive film on the upper side of the honeycomb cross-sections.

[0011] S5. The entire structure is cured under high temperature and high pressure to obtain the molded honeycomb.

[0012] S6. Lay the part layup on the molding die, including, from bottom to top, a prepreg fabric layer for filling, an expanded rubber film for filling, a molded honeycomb and an upper layup in the R-corner area;

[0013] S7. Curing under high temperature and pressure.

[0014] Advantageously, the width of the carrier film in S1 is 40mm on each side of the R-angle.

[0015] Advantageously, in S3, the honeycomb cells are placed in the honeycomb preforming mold for cutting before molding, or they are cut in advance and then placed in the honeycomb preforming mold.

[0016] Advantageously, the two honeycomb structures on both sides are connected as one by using the pre-cured I-shaped adhesive film.

[0017] Advantageously, the cured I-shaped adhesive film in S5 becomes a rigid body after curing, and the carrier adhesive film forms an isolation layer on the honeycomb surface.

[0018] Advantageously, in S6, three layers of prepreg fabric for filling are first laid in a gradient decreasing manner along the joint; then, an expansion film for filling is laid along the joint; finally, the shaped honeycomb is placed in place, and layers are laid on top of the shaped honeycomb until the end.

[0019] Advantageously, the fiber orientation of the prepreg filling layers is 45°, the width of the first layer is 30 mm on each side of the butt joint, the width of the second layer is 20 mm on each side of the butt joint, and the width of the third layer is 15 mm on each side of the butt joint.

[0020] Advantageously, the width of the expansion membrane used for filling is 10mm on each side of the butt joint.

[0021] In this method, the honeycomb I-shaped high-pressure plastic molding splicing not only ensures the matching degree of the honeycomb shape but also greatly improves the local rigidity of the honeycomb. The I-shaped structure of the honeycomb splicing can effectively transmit pressure during the pressure curing of the parts, allowing the pressure to be smoothly transferred from the upper surface of the honeycomb along the splicing seam to the hardened area on the lower surface, forming a good transmission channel. At the same time, it can also reduce the honeycomb springback caused by gradual changes in angle, offset the pressure attenuation, and improve the transmission efficiency.

[0022] This method leverages the complementary advantages of a multi-material gradient layout for the filling layer and the sealing of the pores. The prepreg fabric filling effectively compensates for gaps caused by resin overflow during heating, while the expanded adhesive film effectively compensates for gaps formed between the honeycomb and the fabric layer due to stress. The gradient layout effectively reduces the triangular spaces formed at the boundary intersections of the fabric layer and the adhesive film. Sealing the honeycomb pores maximizes the compensation efficiency, preventing resin and adhesive film from penetrating into the honeycomb cells during heating, reducing the space required, and making the effects of the fabric layer and adhesive film more pronounced. This results in minimal material usage, minimal weight gain, and maximum effectiveness.

[0023] Beneficial effects:

[0024] 1. Increased rigidity in the honeycomb R-corner area allows for effective pressure transmission, improving the overall compaction effect of the parts and greatly reducing the probability of defects.

[0025] 2. The process flow was not changed, the process parameters were not adjusted, and no new materials were introduced. It maintained a high degree of consistency with the original system, with minimal increase in cost and weight, and low systemic risk.

[0026] 3. This method optimizes the part internally without changing its external shape, offering high controllability and ensuring the part's aerodynamic performance. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of a honeycomb splicing pattern;

[0028] Figure 2 A schematic diagram showing the laying of the I-shaped expandable film and the carrier-supported film;

[0029] Figure 3 This is a schematic diagram of the cured honeycomb structure.

[0030] Figure 4 This is a schematic diagram of the layer gradient layout.

[0031] 1. Honeycomb preform mold; 2. Honeycomb before molding; 3. Honeycomb cross-section; 4. I-shaped adhesive film before curing; 5. Carrier-supported adhesive film; 6. Expanded adhesive film for filling; 7. Prepreg fabric layer for filling; 8. Molded honeycomb; 9. I-shaped adhesive film after curing. Detailed Implementation

[0032] For a detailed implementation of the method for processing the radius (R) of cylindrical sandwich composite parts according to the present invention, please refer to [link to specific implementation details]. Figure 1-4 , including the following steps:

[0033] Step 1: Lay a carrier-supported adhesive film 5, 40mm wide on each side of the rounded corner of the honeycomb preform mold 1, to seal the honeycomb holes. Figure 2 As shown.

[0034] Step 2: Place the lower layer of the pre-cured I-shaped adhesive film 4 in the area of ​​the carrier adhesive film 5.

[0035] Step 3: After placing the pre-formed honeycomb 2 onto the honeycomb pre-forming mold 1, cut the pre-formed honeycomb 2 along the normal direction of the center of the R-corner area. This allows the honeycomb cut surface 3 to allow the honeycombs to align on the lower layer of adhesive film in the R-corner area without stress, forming an arc-shaped honeycomb. Figure 1 As shown.

[0036] Step 4: Insert the middle adhesive film of the pre-cured I-shaped adhesive film 4 between the honeycomb cut surfaces 3, and then lay the upper adhesive film of the pre-cured I-shaped adhesive film 4 on the upper side of the honeycomb cut surface 3 to form an I-shaped structure, connecting the two honeycomb pieces into one.

[0037] Step 5: The entire structure is cured under high temperature and pressure. After curing, the honeycomb structure has formed a rounded corner. The I-shaped adhesive film 4 before curing becomes the cured I-shaped adhesive film 9, which is a rigid body. The carrier adhesive film 5 has formed an isolation layer on the honeycomb surface, completely sealing the honeycomb pores to obtain the formed honeycomb 8. Figure 3 As shown.

[0038] Step 6: In the part layup stage, first lay three layers of prepreg fabric 7 (not shown) as filler in a gradient decreasing manner, with the fiber direction at 45°, along the butt joint. The width of the first layer is 30mm on each side of the butt joint, the width of the second layer is 20mm on each side of the butt joint, and the width of the third layer is 15mm on each side of the butt joint. Then lay the expanding film 6 as filler, along the butt joint, with a width of 10mm on each side of the butt joint. Finally, place the molded honeycomb 8 in place, as shown. Figure 4 As shown. Continue layering on top of the formed honeycomb 8 until completion.

[0039] Step 7: During high-temperature and high-pressure curing, the pressure can be transmitted through the molded honeycomb 8 along the cured I-shaped adhesive film 9. Due to its high rigidity, the pressure transmission effect is good. It forms a good pressure effect on the filling expansion film 6 and the filling prepreg cloth layer 7, effectively filling the gaps formed during the curing process, ensuring that the R-corner area forms a dense structure, and the molding effect is good.

Claims

1. A method for processing the radius (R) of a cylindrical sandwich composite part, characterized in that, The method includes the following steps: S1. Lay a carrier-supported adhesive film (5) on the R-corner area of ​​the honeycomb preform mold (1); S2. Place the lower layer of the pre-cured I-shaped adhesive film (4) in the area of ​​the carrier adhesive film (5); S3. Cut the honeycomb (2) before molding according to the center normal direction of the R-corner area so that the honeycomb cut surface (3) satisfies the requirement that the honeycomb is joined to the lower layer of adhesive film in the R-corner area in an arc-shaped honeycomb state without stress. S4. Insert the middle film of the I-shaped adhesive film 4 before curing into the honeycomb cross-section (3), and then lay the upper layer of the I-shaped adhesive film (4) before curing on the upper side of the honeycomb cross-section (3). S5. The whole structure is cured under high temperature and high pressure to obtain the molded honeycomb (8); S6. Lay the part layup on the molding die, including, from bottom to top, a prepreg fabric layer for filling (7), an expanded rubber film for filling (6), a molded honeycomb (8) and an upper layup in the R-corner area; S7. Curing under high temperature and pressure.

2. The method for processing the radius (R) of a cylindrical sandwich composite part according to claim 1, characterized in that: The width of the carrier film (5) in S1 is 40mm on each side of the R-angle.

3. The method for processing the radius (R) of a cylindrical sandwich composite part according to claim 1, characterized in that: In S3, the honeycomb (2) before molding is placed in the honeycomb preforming mold (1) for cutting, or it is cut in advance and then placed in the honeycomb preforming mold (1).

4. The method for processing the radius (R) of a cylindrical sandwich composite part according to claim 1, characterized in that: The honeycomb on both sides is connected as one unit by the pre-cured I-shaped adhesive film (4).

5. The method for processing the radius (R) of a cylindrical sandwich composite part according to claim 1, characterized in that: After curing in S5, the I-shaped adhesive film (4) before curing becomes a rigid cured I-shaped adhesive film (9), and the carrier adhesive film (5) forms an isolation layer on the honeycomb surface.

6. The method for processing the radius (R) of a cylindrical sandwich composite part according to claim 1, characterized in that: In S6, three layers of prepreg fabric (7) for filling are laid in a gradient decreasing manner along the joint; then the expansion film (6) for filling is laid along the joint; finally, the shaped honeycomb (8) is placed in place, and the layers on top of the shaped honeycomb (8) are continued until the end.

7. The method for processing the radius (R) of a cylindrical sandwich composite part according to claim 6, characterized in that: The fiber direction of the prepreg fabric layer (7) for filling is 45°. The width of the first layer is 30 mm on each side of the butt joint, the width of the second layer is 20 mm on each side of the butt joint, and the width of the third layer is 15 mm on each side of the butt joint.

8. The method for processing the radius (R) of a cylindrical sandwich composite part according to claim 7, characterized in that: The width of the expansion film (6) used for filling is 10mm on each side of the joint.

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