Method for machining R angle of cylindrical interlayer composite part

Abstract

The invention belongs to a composite material part forming technology, and particularly relates to a method for machining an R angle of a cylindrical interlayer composite material part. Due to uncontrollability of pressure transmission and prepreg resin overflow, layering defects of different degrees exist in a large-curvature R corner area. According to the method, the honeycomb I-shaped high-pressure molding splicing is adopted, so that the matching degree of the shape of the honeycomb can be ensured, the local rigidity of the honeycomb is greatly improved, and the honeycomb spliced I-shaped structure can effectively transfer pressure when a part is pressurized and cured, so that the pressure can be smoothly transferred to a hardened area on the lower surface from the upper surface of the honeycomb along a splicing seam; and a good transfer channel is formed. Meanwhile, honeycomb springback caused by gradual change of the angle can be reduced, pressure attenuation is counteracted, and the transmission efficiency is improved. The advantages of the filling layer with the multi-material gradient layout and the closed hole complement each other. The space area is reduced, the effects of the cloth layer and the adhesive film are more obvious, and therefore the purposes of the minimum using amount, the minimum weight increment and the most obvious effect are achieved.

Description

Technical Field

[0001] The present invention belongs to the composite material parts forming technology, and specifically relates to a method for processing the R angle of a cylindrical sandwich composite part, which adopts a new internal structure design form of expanding adhesive film combined with prepreg cloth layer filling to fill the R angle area gap of the cylindrical sandwich component, thereby eliminating the delamination defect of the part after curing. Background Art

[0002] The large-sized and large-curvature cylindrical composite sandwich components are the main structural form of the current helicopter tail boom. The integrated composite component design reduces both assembly and weight of the entire helicopter tail boom, which can be said to kill two birds with one stone. The combination of integrated structural design and integrated molding process makes the molding process of the cylindrical composite sandwich components very complex, the process flow is cumbersome, the process parameters are high and difficult to effectively control, resulting in frequent quality problems in the manufactured parts, and the quality stability needs to be improved.

[0003] The molding process currently used is to form a semi-cylindrical structure by honeycomb splicing, and then form a complete cylindrical structure by combining two half molds. Due to the uncontrollability of pressure transmission and prepreg resin overflow, the outstanding problem of the products manufactured by this process is that there are different degrees of delamination defects in the large curvature R corner area, which makes the repair volume of parts large and even has the risk of overall scrapping, which has a significant adverse impact on the production progress and cost control of parts, greatly increasing the manufacturing cost of the entire helicopter and reducing production efficiency.

[0004] In view of this, a new process method is needed to effectively eliminate the delamination defects in the large curvature R corner area, which is easy to operate, controllable process, and will not affect the subsequent parts assembly and functional use, reduce the loss of manpower, material resources and time caused by the repair process, and improve product quality and quality stability. Summary of the invention

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

[0006] The present invention provides a method for processing the R angle of a cylindrical sandwich composite part, the method comprising the following steps:

[0007] S1. Laying a carrier adhesive film on the R corner area of ​​the honeycomb preforming mold;

[0008] S2, laying the lower layer of the I-shaped film before curing in the area with the carrier film;

[0009] S3, cutting the honeycomb before molding in the direction of the normal line of the center of the R angle area, so that the honeycomb section satisfies the condition that the honeycomb is butted on the lower layer of the adhesive film in the R angle area to form an arc honeycomb state without stress;

[0010] S4, inserting the middle film of the I-shaped film before curing between the honeycomb sections, and then laying the upper film of the I-shaped film before curing on the upper side of the honeycomb sections;

[0011] S5, curing the whole body under high temperature and high pressure to obtain a formed honeycomb;

[0012] S6. Laying the parts layer on the forming die, including the filling prepreg cloth layer, the filling expansion film, the forming honeycomb and the upper layer from bottom to top in the R corner area;

[0013] S7, solidify under high temperature and high pressure.

[0014] Advantageously, the width of the carrier film in S1 is 40 mm on both sides of the R corner.

[0015] Advantageously, in S3, the pre-molded honeycomb is placed in a honeycomb pre-molding mold for cutting or is placed in a honeycomb pre-molding mold after being cut in advance.

[0016] Advantageously, the honeycombs on both sides are connected as one by curing the I-shaped adhesive film.

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

[0018] Advantageously, in S6, three layers of prepreg cloth for filling are first laid in a gradient decreasing manner, and laid along the butt joint; then the expanded adhesive film for filling is laid, and laid along the butt joint; finally, the formed honeycomb is placed in place, and the upper layer of the formed honeycomb is continued to be laid until completion.

[0019] Advantageously, the fiber direction of the filling prepreg cloth layer is 45°, the width of the first layer is 30 mm on both sides of the butt joint, the width of the second layer is 20 mm on both sides of the butt joint, and the width of the third layer is 15 mm on both sides of the butt joint.

[0020] Advantageously, the laying width of the filling expansion film is 10 mm on both sides of the joint.

[0021] The high-pressure plastic splicing of the honeycomb I-shaped in this method can not only ensure the matching degree of the honeycomb shape, but also greatly improve the local rigidity of the honeycomb. The I-shaped structure of the honeycomb splicing can effectively transmit pressure when the parts are pressurized and solidified, so that the pressure can be smoothly transmitted 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 rebound caused by the gradual change of the angle, offset the pressure attenuation, and improve the transmission efficiency.

[0022] The advantages of the filling layer and hole closure of the multi-material gradient layout of this method complement each other. The filling of the prepreg cloth layer can effectively compensate for the gap formed by the resin overflow during the heating process of the parts, and the expansion film can effectively compensate for the gap between the honeycomb and the cloth layer due to stress. The gradient layout effectively reduces the triangular space formed by the cloth layer and the film at the boundary intersection area. The closure of the honeycomb holes maximizes the efficiency of compensation, so that the resin and the film will not penetrate into the honeycomb grid during the heating process, reducing the space area, making the role of the cloth layer and the film more obvious, thereby achieving the minimum usage, the lowest weight gain, and the most obvious effect.

[0023] Beneficial effects:

[0024] 1. The rigidity of the honeycomb R corner area is improved, the pressure can be effectively transmitted, the overall compaction effect of the parts is improved, and the probability of defects is greatly reduced;

[0025] 2. No changes to the process flow, no adjustment to the process parameters, no introduction of new materials, and a high degree of consistency with the original system, with little increase in cost and weight, and low systemic risk;

[0026] 3. This method optimizes the inside of the part without changing the appearance of the part. It has high controllability and ensures the aerodynamic performance of the part. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0028] Figure 2 It is a schematic diagram of laying out the I-shaped expansion film and the film with carrier;

[0029] Figure 3 is a schematic diagram of the molded honeycomb state after curing;

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

[0031] 1. Honeycomb preforming mold, 2. Honeycomb before forming, 3. Honeycomb section, 4. I-shaped film before curing, 5. Film with carrier, 6. Expanded film for filling, 7. Prepreg cloth layer for filling, 8. Formed honeycomb, 9. I-shaped film after curing DETAILED DESCRIPTION

[0032] For a specific implementation of the method for processing the R angle of a cylindrical sandwich composite part of the present invention, see Figure 1-4 , including the following steps:

[0033] Step 1: Lay a carrier adhesive film 5 on the R corner area of ​​the honeycomb preforming mold 1, with a width of 40 mm on both sides of the R corner, to block the honeycomb holes, such as Figure 2 shown.

[0034] Step 2: Lay the lower layer of the I-shaped adhesive film 4 before curing in the area with the carrier adhesive film 5.

[0035] Step 3: After placing the pre-molded honeycomb 2 on the honeycomb pre-molding mold 1, the pre-molded honeycomb 2 is cut along the normal direction of the center of the R angle area, so that the honeycomb cut surface 3 can make the honeycomb butt on the lower layer of the adhesive film in the R angle area without stress, forming an arc honeycomb state. Figure 1 shown.

[0036] Step 4: insert the middle film of the I-shaped film 4 before curing between the honeycomb sections 3, and then lay the upper film of the I-shaped film 4 before curing on the upper side of the honeycomb section 3 to form an I-shaped structure and connect the two honeycombs into one.

[0037] Step 5: The whole is cured under high temperature and high pressure. The honeycomb state after curing is that the R-angle shape has been formed, and the I-shaped adhesive film 4 before curing has become the I-shaped adhesive film 9 after curing. It is a rigid body, and the carrier adhesive film 5 has formed an isolation layer on the honeycomb surface, and the honeycomb holes have been completely closed to obtain a formed honeycomb 8, such as Figure 3 shown.

[0038] Step 6: At the part laying stage, first lay three layers of filling prepreg cloth 7 on the molding die (not shown) in a gradient decreasing manner, with the fiber direction at 45°, laid along the butt joint, the width of the first layer is 30mm on both sides of the butt joint, the width of the second layer is 20mm on both sides of the butt joint, and the width of the third layer is 15mm on both sides of the butt joint. Then lay the filling expansion film 6, lay it along the butt joint, with a width of 10mm on both sides of the butt joint. Finally, put the formed honeycomb 8 in place, as shown in the figure. Figure 4 Continue laying layers on the upper layer of the formed honeycomb 8 until it is completed.

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

Claims

1. A method for processing the R angle of a cylindrical sandwich composite part, characterized in that: The method comprises the following steps: S1, laying a carrier adhesive film (5) on the R corner area of ​​the honeycomb preforming mold (1); S2, laying the lower layer of the I-shaped adhesive film (4) before curing in the area with the carrier adhesive film (5); S3, cutting the honeycomb (2) before molding in the direction of the normal line of the center of the R-angle region, so that the honeycomb cut surface (3) satisfies the condition that the honeycomb is butted on the lower layer of adhesive film in the R-angle region to form an arc-shaped honeycomb in the absence of stress; S4, inserting the middle film of the I-shaped film 4 before curing between the honeycomb cut surfaces (3), and then laying the upper film of the I-shaped film (4) before curing on the upper side of the honeycomb cut surfaces (3); S5, curing the whole at high temperature and high pressure to obtain a formed honeycomb (8); S6, laying the parts layer on the forming mold, including the filling prepreg cloth layer (7), the filling expansion film (6), the forming honeycomb (8) and the upper layer from bottom to top in the R corner area; S7, solidify under high temperature and high pressure.

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

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

4. The method for processing the R angle of a cylindrical sandwich composite part according to claim 1, characterized in that: The honeycombs on both sides are connected as one by curing the I-shaped adhesive film (4).

5. The method for processing the R angle of a cylindrical sandwich composite part according to claim 1, characterized in that: After curing in S5, the pre-cured I-shaped adhesive film (4) becomes a rigid cured I-shaped adhesive film (9), and the carrier adhesive film (6) forms an isolation layer on the honeycomb surface.

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

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

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

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