A method of bonding a complex honeycomb sandwich leading edge structure

Abstract

This invention belongs to the technical field of composite material bonding, specifically relating to a method for bonding a complex honeycomb sandwich front edge structure. The method includes: placing the rear beam on a fixture and bonding the honeycomb core recess to the rear beam side plate profile; then fixing the end ribs to the end rib limiting device; placing the entire structure in an oven for verification; compensating the bonding joints with expanding foam based on the verification results; curing the compensated bonding joints of the skeleton structure at high temperature in the oven; placing a second skin on the skeleton; vacuum-sealing the skeleton structure and performing a second bonding verification in an autoclave; placing a third skin on the skeleton structure, adding auxiliary materials, and placing it in an autoclave for curing; finally, demolding. The advantages of this invention are that, compared to existing technologies, it solves the problem of positioning the relative positions of various parts during bonding, greatly reducing bonding errors and improving bonding accuracy.

Description

Technical Field

[0001] This invention belongs to the technical field of composite material bonding, specifically relating to a method for bonding the leading edge structure of a complex honeycomb sandwich structure. Background Technology

[0002] Fixed-wing aircraft typically feature complex honeycomb sandwich leading-edge structures with high aspect ratios. These structures consist of beams, honeycomb structural components with different functions, end ribs on both sides, and a skin. The fabrication process for this type of structure mainly includes two parts: skeleton structure fabrication and bonding of the skin to the skeleton structure. Skeleton structure fabrication includes bonding between different honeycomb core segments, bonding the honeycomb core to the beams, and bonding the honeycomb core to the end ribs on both sides. Current methods for fabricating complex honeycomb sandwich structures with high aspect ratios often involve bonding excess honeycomb cores to other sub-components to form a skeleton, followed by CNC milling. This method has disadvantages such as long fabrication cycle, high cost, complex tooling design and manufacturing, and the inability to share splicing and bonding tooling.

[0003] If a honeycomb core with net dimensions is used for bonding, the integrated design of splicing and bonding tooling allows for precise positioning of each component, enabling efficient and low-cost manufacturing of honeycomb sandwich structures with large aspect ratios. However, the core of this manufacturing method lies in two aspects: first, how to achieve accurate bonding between different components; and second, how to accurately bond the skeleton structure to the skin. In the bonding process of this type of structure, the following difficulties exist: it is difficult to accurately match the components in the skeleton structure; the honeycomb core is prone to shrinkage under pressure during foam bonding of the skeleton; and the leading edge R area is difficult to accurately bond during the secondary bonding of the skeleton structure and the skin.

[0004] For example, a Chinese patent, application number 201910050717.X, application date January 20, 2019, entitled "A Method for Bonding and Positioning Composite Aircraft Control Surfaces with Multiple Joints," describes a method for bonding and positioning composite aircraft control surfaces with multiple joints. The method comprises the following steps: S1 Pre-assembly of parts on an assembly jig, with process lug positioning holes provided on the jig; S2 Positioning of the molded surface skin: the molded surface skin is positioned using process lugs; S3 Positioning of the control surface skeleton: the honeycomb core and ribs are fitted together; S4 Positioning of the non-molded surface skin: the non-molded surface skin is positioned according to the process positioning holes; S5 Sealing in a vacuum bag; S6 Autoclave bonding: the parts are placed in an autoclave for bonding; S7 Demolding: the vacuum bag is removed from the autoclave, and the control surface is taken out.

[0005] While the method described in the aforementioned patent can achieve the bonding and positioning of aircraft control surfaces, the patented technology has the following two drawbacks: First, the technical solution only uses detachable limiting blocks on the bonding fixture and beams, ribs, and rear edge strip axes on the bonding fixture to solve the problem of positioning each part on the bonding fixture and positioning the relative positions of each part during control surface pre-assembly. However, relying solely on detachable limiting blocks and beams, ribs, and rear edge strip axes cannot provide precise positioning and results in certain errors. Second, the use of autoclave bonding in the technical solution leads to the problem of honeycomb shrinkage at high temperatures. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention employs a recessed platform design for the net-size honeycomb core, enabling precise bonding and reducing the risk of honeycomb core shrinkage through mechanical pressure, thus providing a method for bonding complex honeycomb sandwich front edge structures.

[0007] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0008] A method for bonding the leading edge structure of a complex honeycomb sandwich structure includes the following steps:

[0009] Step 1: Place the rear beam on the tooling and glue the honeycomb core recess to the rear beam side plate profile. Then fix the end ribs to the end rib limiting device. Then place the first isolation film, the second isolation film and the first skin on the skeleton structure in sequence.

[0010] Step 2: Rotate the top holding device wheel until the first skin is in contact with the top of the skeleton structure, and then rotate the side shaping device wheel to make the first skin in contact with the side of the skeleton structure.

[0011] Step 3: Place the entire assembly in an oven for verification. After verification, compensate for the expansion foam at the joints based on the verification results.

[0012] Step 4: Repeat step 2, and finally cure the glued joints of the skeleton structure at high temperature in the oven.

[0013] Step 5: Place the adhesive film, the first isolation film and the second isolation film on the honeycomb core of the skeleton structure in sequence. Place foam and adhesive film on the end ribs and the end rib limiting device at the bonding points with the honeycomb core and the rear beam respectively, and separate the bonding points with the second isolation film. Finally, place the second skin on the skeleton, and then vacuum seal the skeleton structure and perform a second bonding verification in a thermostatic tank.

[0014] Step Six: Based on the verification results of the secondary adhesive bonding test, make compensation, place the third skin on the skeleton structure, then place the auxiliary materials, and finally put it into the autoclave for curing. After curing, remove the auxiliary materials, top holding device, and end rib limiting device to complete demolding.

[0015] Furthermore, in step one, the honeycomb core recess and the rear beam side plate are matched and bonded by applying expanding foam, and each bonded surface is isolated by a non-porous release film; the honeycomb core recess and the rear beam side plate are matched and positioned by aligning the positioning holes on the tooling with the positioning holes on the rear beam lugs, and then inserting positioning pins into the positioning holes.

[0016] Furthermore, in step one, the end rib includes a wing root side end rib and a wingtip side end rib, and the end rib limiting device includes a wing root side end rib limiting device and a wingtip side end rib limiting device; both the wing root side end rib limiting device and the wingtip side end rib limiting device are installed on the tooling, and the wing root side end rib limiting device is fixedly connected to the wing root side end rib, and the wingtip side end rib limiting device is fixedly connected to the wingtip side end rib.

[0017] Furthermore, the first isolation membrane, the second isolation membrane, the first skin, the second skin, and the third skin are all positioned and installed through positioning holes on the rear beam.

[0018] Furthermore, in step one, the depth of the honeycomb core recesses milled from the honeycomb core is 2.5~3.5 mm.

[0019] Furthermore, the skeleton structure includes a rear beam, a honeycomb core, and end ribs; both ends of the rear beam are connected to the end ribs.

[0020] Furthermore, the first isolation membrane is a porous isolation membrane; the second isolation membrane is a non-porous isolation membrane; the first skin is a process skin; the second skin is an adhesive skin; and the third skin is a cured skin.

[0021] Furthermore, after the process skin is fitted to the side of the skeleton structure, a feeler gauge is used to check the gap.

[0022] Furthermore, in step two, the lateral shaping device includes a lateral shaping device pressure plate and a lateral shaping device base, and the lateral shaping device pressure plate is installed on the lateral shaping device base; the lateral shaping device base is positioned on the tooling by positioning inserts installed on both sides of the tooling; the lateral shaping device pressure plate is installed on both sides of the skeleton structure.

[0023] Furthermore, the verification parameters in step three are: heating to 60~65 ℃ at a heating rate of no more than 1 ℃ / min, holding at that temperature for 60~65 min; and then cooling down after the holding time is completed.

[0024] Furthermore, after the verification is completed in step three, the lateral shaping device, the top holding device, and the first skin need to be removed before the verification results are checked.

[0025] Furthermore, before repeating step two in step four, the lateral support device and the top holding device need to be reinstalled.

[0026] Furthermore, after repeating the second step, the lateral support device is removed again.

[0027] Furthermore, in step four, the oven is used for high-temperature curing. The curing parameters for the foamed adhesive are as follows: the temperature is increased to 150~155 ℃ at a rate not exceeding 1 ℃ / min, and the temperature is kept constant from 150 ℃ for 4~4.5 h. After the temperature is kept constant, the temperature is lowered. During the cooling process from 150 ℃ to 130 ℃, the cooling rate should not exceed 1 ℃ / min. After 130 ℃, the cooling rate should not exceed 0.3 ℃ / min. The pre-foaming process ends when the temperature drops to 60 ℃.

[0028] Furthermore, in step five, after placing the second skin on the skeleton, putty strips are laid on the side of the top holding device, and the top holding device and the skeleton structure are vacuum sealed together and subjected to secondary bonding verification in a thermostatic precipitator.

[0029] Furthermore, the auxiliary materials in step six include a non-porous isolation membrane, a porous isolation membrane, a breathable felt, a vacuum bag, and putty strips, and are placed in the order of non-porous isolation membrane, porous isolation membrane, breathable felt, vacuum bag, and putty strips. Finally, the vacuum bag is vacuumed and leak checked.

[0030] Furthermore, the curing parameters in the autoclave during step six are as follows: Vacuuming begins, with a vacuum level of -0.027 MPa to -0.033 MPa, and the negative pressure inside the vacuum bag does not exceed -0.034 MPa throughout the process; external pressure is increased to 0.08 to 0.1 MPa at a rate of 20 to 30 kPa / min, and maintained for 10 to 30 minutes; then atmospheric venting is performed, with the venting rate not exceeding 1 kPa / min; after atmospheric venting, the pressure is increased to 0.18 to 0.20 MPa, and this pressure is maintained until the curing process ends; after pressurization, heating begins, increasing to 150 to 155 °C at a rate of 1 to 1.5 °C / min, and maintained at this temperature for 4 hours; subsequently, heating is increased to 175 to 180 °C at a rate of 0.5 °C / min, and maintained at this temperature for 2 hours; after completion, cooling is performed at a rate not exceeding 0.3 °C / min, at a rate of 20 to 30 kPa / min. Release the pressure from the tank at a certain rate, and stop curing when the pressure is released and the temperature drops to 60 ℃.

[0031] Furthermore, the tooling includes a tooling assembly, and positioning inserts are mounted on both sides of the tooling assembly.

[0032] According to the above technical solution, the beneficial effects of the present invention are as follows:

[0033] 1. Compared with the prior art, the method adopted in this invention solves the problem of positioning the relative positions of each part during gluing, greatly reducing gluing errors and improving the accuracy of gluing.

[0034] 2. The method of the present invention uses a net-size honeycomb core. Compared with the prior art that uses a spare honeycomb core, the preparation of a complex honeycomb sandwich structure with a large aspect ratio using a spare honeycomb core requires three CNC machining operations. However, using a net-size honeycomb core for bonding only requires one CNC machining operation, which reduces the number of CNC machining operations in the preparation of structural parts and greatly improves production efficiency.

[0035] 3. The method of the present invention employs positioning holes, honeycomb core recesses, wing root side rib limiting devices, and wingtip side rib limiting devices, and achieves precise positioning of sub-components through the above positioning measures.

[0036] 4. The method of the present invention uses a top holding device for mechanical pressure, and the top holding device and the honeycomb sandwich leading edge structure component are vacuum sealed together during assembly. By using a weak vacuum, a low vacuum atmospheric replacement rate, and a slow heating rate during curing, accurate bonding of the leading edge R area is achieved during the secondary bonding of the skeleton structure and the skin.

[0037] 5. The wing root side rib limiting device and wing tip side rib limiting device used in the method of the present invention achieve accurate positioning of the wing root side rib and wing tip side rib with the honeycomb core adhesive surface, while preventing the rear beam from warping and deforming during the thermal process, thus improving the accuracy of the skeleton adhesive bonding.

[0038] 6. In the method of the present invention, the skeleton structure is placed in an oven for curing, and foaming is performed by heating without vacuuming.

[0039] The adhesive is cured, which avoids the problem of lateral shrinkage of the honeycomb core under high temperature. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the honeycomb core recess design of the present invention.

[0041] Figure 2 This is a schematic diagram of the positioning of the lateral support device and the top holding device of the present invention.

[0042] Figure 3 This is a schematic diagram of the skeleton forming and assembly of the present invention.

[0043] Figure 4 This is a schematic diagram of the adhesive bonding assembly of the skin and skeleton of the present invention.

[0044] Figure 5 This is a schematic diagram of the leading edge R region of the present invention.

[0045] In the attached diagram: 1-Honeycomb core recess; 2-Positioning insert; 3-Tooling assembly; 4-Tooling surface; 5-Lateral shaping device base hole; 6-Top holding device hole; 7-Wing root side rib limiting device; 8-Wing root side rib; 9-Rear beam; 10-Honeycomb core; 11-Process skin; 12-Non-porous isolation membrane; 13-Porous isolation membrane; 14-Wingtip side rib; 15-Wingtip side rib limiting device; 16-Lateral shaping device pressure plate; 17-Lateral shaping device base; 18-Tooling; 19-Top holding device; 20-Positioning hole; 21-Foaming adhesive; 22-Adhesive film; 23-Skin; 24-Breathable felt; 25-Rear beam side plate profile; 26-Rear beam lug; 27-End rib limiting device hole; 28-Leading edge R area; 29-Vacuum bag. Detailed Implementation

[0046] The objectives, technical solutions, and advantages of the embodiments of this application will become clearer. The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of this application, but not all embodiments.

[0047] Example 1

[0048] A method for bonding the leading edge structure of a complex honeycomb sandwich structure includes the following steps:

[0049] Step 1: As Figure 1 and Figure 3 As shown, the rear beam 9 is placed on the tooling 18, and the honeycomb core recess 1 is matched and glued to the rear beam side plate profile 25. Then the end ribs are fixed to the end rib limiting device, and then the first isolation film, the second isolation film and the first skin are placed on the skeleton structure in sequence.

[0050] Step Two: As Figure 3 As shown, the first skin is attached to the top of the skeleton structure by rotating the top holding device 19 until it fits against the top of the skeleton structure, and then the side shaping device is rotated to make the first skin fit against the side of the skeleton structure.

[0051] Step 3: Place the whole assembly in an oven for verification. After verification, compensate with expanding foam 21 at the joints based on the verification results.

[0052] Step 4: Repeat step 2, and finally cure the glued joints of the skeleton structure at high temperature in the oven.

[0053] Step 5: Next, place the adhesive film 22, the first isolation film and the second isolation film on the honeycomb core 10 of the skeleton structure in sequence. On the end ribs and the end rib limiting device, place the foam adhesive 21 and adhesive film 22 at the bonding points with the honeycomb core 10 and the rear beam 9 respectively, and separate the bonding points with the second isolation film. Finally, place the second skin on the skeleton, and then vacuum seal the skeleton structure and perform a second bonding verification in a thermostatic tank.

[0054] Step 6: Based on the verification results of the secondary adhesive bonding test, make compensation, place the third skin on the skeleton structure, then place the auxiliary materials, and finally put it into the autoclave for curing. After curing, remove the auxiliary materials, the top holding device 19, and the end rib limiting device to complete the demolding.

[0055] The first isolation membrane is a porous isolation membrane 13; the second isolation membrane is a non-porous isolation membrane 12; the first skin is a process skin 11; the second skin is an adhesive skin; and the third skin is a cured skin. The porous isolation membrane 13 serves to guide gas, allowing small molecule components generated during the curing process to escape and preventing the aggregation of small molecule gases. The non-porous isolation membrane 12 serves to isolate the skin and adhesive film 22 during the verification process, preventing the inability to check the verification effect after bonding. The process skin 11 has the same function as the pressure equalizing plate in the autoclave molding process, maintaining the shape of the skeleton structure during the skeleton structure splicing verification process, and obtaining the optimal amount of foam adhesive 21 during the skeleton structure foaming verification process. The adhesive skin and the cured skin are both formal skins, used for verification when the skin is bonded to the skeleton structure and for curing the skin to the skeleton structure, respectively.

[0056] Example 2

[0057] A method for bonding the leading edge structure of a complex honeycomb sandwich structure includes the following steps:

[0058] Step 1: As Figure 1 and Figure 3 As shown, the rear beam 9 is placed on the tooling 18, and the honeycomb core recess 1 is matched and glued to the side plate profile 25 of the rear beam 9. Then the end ribs are fixed to the end rib limiting device, and then the first isolation film, the second isolation film and the first skin are placed on the skeleton structure in sequence.

[0059] Step 2: Rotate the top holding device 19 until the first skin is in contact with the top of the skeleton structure, and then rotate the side shaping device to make the first skin in contact with the side of the skeleton structure; Step 2 uses mechanical pressure to make the first skin completely fit the skeleton structure.

[0060] Step 3: As Figure 3 As shown, the whole thing is placed in an oven for verification. After the verification is completed, the expanding foam 21 at the joint is compensated according to the verification results.

[0061] Step 4: Repeat step 2, and finally cure the glued joints of the skeleton structure at high temperature in the oven.

[0062] Step 5: As Figure 4 As shown, the honeycomb core 10 of the skeleton structure is then placed with adhesive film 22, first isolation film and second isolation film in sequence. Foaming adhesive 21 and adhesive film 22 are respectively laid on the end ribs and end rib limiting devices at the bonding points with the honeycomb core 10 and the rear beam 9, and the bonding points are separated by the second isolation film. Finally, the second skin is placed on the skeleton structure, and the skeleton structure is vacuum sealed and subjected to secondary bonding verification in a thermostatic tank. The function of adhesive film 22 is to use adhesive film 22 to perform a second bonding between the second skin and the skeleton structure.

[0063] Step Six: Based on the verification results of the secondary bonding test, compensate for any discrepancies. Place the third skin onto the skeleton structure, then add auxiliary materials, and finally place it in an autoclave for curing. After curing, remove the auxiliary materials, top holding device 19, and end rib limiting device to complete demolding. Figure 5 As shown, removing the top retainer 19 requires first rotating the wheel of the top retainer 19 until the retainer leaves the leading edge R region 28 of the component, and then removing the top retainer 19.

[0064] Before performing the above steps, a trial assembly of the honeycomb core 10, rear beam 9, and end ribs can be performed. The specific trial assembly steps are as follows: place the rear beam 9 on the fixture 18, and position it by connecting the positioning holes 20 on the rear beam lugs 26 and the positioning holes 20 on the fixture 18 with positioning pins. Match the honeycomb core 10 with the honeycomb core recess 1 after CNC machining with the side plate profile 25 of the rear beam 9. Then place the end ribs and end rib limiting devices on the fixture 18, and position the end rib limiting devices and the fixture 18 with nuts. The purpose of the trial assembly is to check whether the positioning is standard and qualified, and whether it can be installed normally.

[0065] In step one, the honeycomb core recess 1 and the side plate profile 25 of the rear beam 9 are matched and bonded by applying expanding foam 21, and the bonding surfaces are isolated by a non-porous release film 12; the bonding surfaces between the honeycomb core 10 and the rear beam 9, as well as between the honeycomb cores 10, are also covered with expanding foam 21 and isolated by a non-porous release film 12; the honeycomb core recess 1 and the side plate profile 25 of the rear beam are matched and positioned by aligning the positioning holes 20 on the tooling 18 with the positioning holes 20 on the rear beam ear piece 26, and then inserting a positioning pin into the positioning hole 20.

[0066] In step one, the end ribs include the wing root side end rib 8 and the wingtip side end rib 14. The end rib limiting devices include the wing root side end rib limiting device 7 and the wingtip side end rib 14 limiting device. The wing root side end rib limiting device 7 and the wingtip side end rib 14 limiting device are both installed on the fixture 18, and the wing root side end rib limiting device 7 is fixedly connected to the wing root side end rib 8, and the wingtip side end rib 14 limiting device is fixedly connected to the wingtip side end rib 14. The wing root side end rib limiting device 7 and the wingtip side end rib 14 limiting device are both positioned and installed on the fixture 18 through the end rib limiting device hole 27 on the fixture 18.

[0067] The first isolation membrane, the second isolation membrane, the first skin, the second skin, and the third skin are all positioned and installed through the positioning holes 20 on the rear beam 9; for example Figure 4 As shown, the skin 23 can be a second skin or a third skin; the depth of the honeycomb core recess 1 milled from the honeycomb core 10 in step one is 2.5~3.5 mm; the depth of the honeycomb core recess 1 milled from the honeycomb core 10 can be 2.5 mm, 3.5 mm, or 3 mm.

[0068] The skeleton structure includes a rear beam 9, a honeycomb core 10, and end ribs; the two ends of the rear beam 9 are connected to the end ribs.

[0069] The first isolation membrane is a porous isolation membrane 13; the second isolation membrane is a non-porous isolation membrane 12; the first skin is a process skin 11; the second skin is an adhesive skin; and the third skin is a cured skin. The porous isolation membrane 13 serves to guide gas, allowing small molecule components generated during curing to escape and preventing the accumulation of small molecule gases. The non-porous isolation membrane 12 serves to isolate the skin and adhesive film 22 during the verification process, preventing the inability to check the verification effect after bonding. The process skin 11 functions similarly to the pressure equalizing plate in the autoclave molding process, maintaining the shape of the skeleton structure during splicing verification and obtaining the optimal amount of foam adhesive 21 during the foaming verification of the skeleton structure. The adhesive skin and the cured skin are both formal skins used for verification when the skin is bonded to the skeleton structure and for curing the skin to the skeleton structure, respectively. After the process skin 11 is attached to the side of the skeleton structure, a feeler gauge is used to check the gap.

[0070] like Figure 2As shown, in step two, the lateral shaping device includes a lateral shaping device pressure plate 16 and a lateral shaping device base 17, and the lateral shaping device pressure plate 16 is mounted on the lateral shaping device base 17; the lateral shaping device base 17 is positioned on the tooling 18 by positioning inserts 2 mounted on both sides of the tooling 18, and the lateral shaping device base 17 is fixed by installing positioning pins in the lateral shaping device base holes 5 of the positioning inserts 2; the lateral shaping device pressure plate 16 is mounted on both sides of the skeleton structure; the tooling 18 includes a tooling assembly 3, and the positioning inserts 2 are mounted on both sides of the tooling assembly 3, with the positioning inserts 2 close to the tooling surface 4.

[0071] The calibration parameters in step three are: heating to 60~65 ℃ at a heating rate of no more than 1 ℃ / min, holding at that temperature for 60~65 min; and then cooling down after the holding time is completed.

[0072] After the verification is completed in step three, the lateral support device, the top holding device 19 and the first skin need to be removed, and then the verification results need to be checked. The verification results are checked visually, and then the foam 21 at the adhesive joint is compensated according to the verification results.

[0073] Before repeating step two in step four, the lateral support device and top retaining device 19 need to be reinstalled; after repeating step two, the lateral support device should be removed again; as... Figure 2 As shown, the top retaining device 19 is positioned and installed using the top retaining device hole 6.

[0074] In step four, the foam adhesive undergoes high-temperature curing in an oven. The curing parameters for foam adhesive 21 are as follows: the temperature is increased to 150~155 ℃ at a rate not exceeding 1 ℃ / min. When the temperature reaches 150 ℃, the temperature is kept constant for 4~4.5 h. After the temperature is kept constant, the temperature is lowered. During the cooling process from 150 ℃ to 130 ℃, the cooling rate should not exceed 1 ℃ / min. After the temperature reaches 130 ℃, the cooling rate should not exceed 0.3 ℃ / min. The pre-foaming process ends when the temperature drops to 60 ℃.

[0075] In step five, after the second skin is placed on the skeleton structure, putty strips are laid on the side of the top holding device 19, and the top holding device 19 and the skeleton structure are vacuum sealed together and then subjected to secondary bonding verification in a thermostatic precipitator.

[0076] In step six, the auxiliary materials include a non-porous release membrane 12, a porous release membrane 13, a breathable felt 24, a vacuum bag 29, and putty strips. These materials are placed in the following order: non-porous release membrane 12, porous release membrane 13, breathable felt 24, vacuum bag 29, and putty strips. Finally, the vacuum bag 29 is vacuumed and leak-tested. The function of the vacuum bag 29 is to seal and protect the parts, and the function of the putty strips is to adhere the vacuum bag 29 to the tooling 18.

[0077] The curing parameters in the autoclave in step six are as follows: Vacuuming begins, with a vacuum level of -0.027 MPa to -0.033 MPa. Throughout the process, the negative pressure inside the vacuum bag 29 does not exceed -0.034 MPa. External pressure is increased to 0.08 to 0.1 MPa at a rate of 20 to 30 kPa / min, and maintained for 10 to 30 minutes. Then, atmospheric venting is performed, with a venting rate not exceeding 1 kPa / min. After venting, the autoclave pressure is increased to 0.18 to 0.20 MPa, and maintained at this pressure until the curing process ends. After pressurization, the temperature is increased to 150 to 155 °C at a rate of 1 to 1.5 °C / min, and maintained at this temperature for 4 hours. Subsequently, the temperature is increased to 175 to 180 °C at a rate of 0.5 °C / min, and maintained at this temperature for 2 hours. Finally, the temperature is decreased at a rate not exceeding 0.3 °C / min, using a rate of 20 to 30 kPa / min. Release the pressure from the tank at a certain rate, and stop curing when the pressure is released and the temperature drops to 60 ℃.

[0078] The above description is a detailed description of the preferred embodiments of this application. However, the embodiments are not intended to limit the scope of the patent application of this application. All equivalent changes or modifications made under the technical spirit of this application should fall within the patent scope covered by this application.

Claims

1. A method for bonding the leading edge structure of a complex honeycomb sandwich core, characterized in that, Includes the following steps: Step 1: Place the rear beam (9) on the tooling (18), and glue the honeycomb core recess (1) to the rear beam side plate profile (25). Then fix the end ribs to the end rib limiting device, and then place the first isolation film, the second isolation film and the first skin on the skeleton structure in sequence. Step 2: Rotate the top holding device (19) until the first skin is in contact with the top of the skeleton structure, and then rotate the side shaping device to make the first skin in contact with the side of the skeleton structure. Step 3: Place the whole assembly in an oven for verification. After verification, compensate for the expansion foam (21) at the joints based on the verification results. Step 4: Repeat step 2, and finally cure the glued joints of the skeleton structure at high temperature in the oven. Step 5: Place the adhesive film (22), the first isolation film and the second isolation film on the honeycomb core (10) of the skeleton structure in sequence. Place the foam adhesive (21) and adhesive film (22) on the end ribs and the end rib limiting device at the bonding points with the honeycomb core (10) and the rear beam (9) respectively, and separate the bonding points with the second isolation film. Finally, place the second skin on the skeleton, and then vacuum seal the skeleton structure and perform a second bonding verification in a thermostatic tank. Step 6: Based on the verification results of the secondary adhesive bonding test, make compensation, place the third skin on the skeleton structure, then place the auxiliary materials, and finally put it into the autoclave for curing. After curing, remove the auxiliary materials, the top holding device (19), and the end rib limiting device to complete the demolding.

2. The method for bonding the leading edge structure of a complex honeycomb sandwich structure according to claim 1, characterized in that: In step one, the honeycomb core recess (1) and the rear beam side plate profile (25) are matched and glued by the application of expanding foam (21), and each glued surface is isolated by a non-porous isolation film (12); the honeycomb core recess (1) and the rear beam side plate profile (25) are matched and positioned by the positioning hole (20) on the tooling (18) coinciding with the positioning hole (20) on the rear beam ear piece (26), and then the positioning pin is inserted into the positioning hole (20).

3. The method for bonding the leading edge structure of a complex honeycomb sandwich structure according to claim 1, characterized in that: In step one, the end ribs include the wing root side end rib (8) and the wing tip side end rib (14). The end rib limiting device includes the wing root side end rib limiting device (7) and the wing tip side end rib limiting device (15). The wing root side end rib limiting device (7) and the wing tip side end rib limiting device (15) are both installed on the tooling (18), and the wing root side end rib limiting device (7) is fixedly connected to the wing root side end rib (8), and the wing tip side end rib limiting device (15) is fixedly connected to the wing tip side end rib (14).

4. The method for bonding the leading edge structure of a complex honeycomb sandwich structure according to claim 1, characterized in that: The first isolation membrane, the second isolation membrane, the first skin, the second skin, and the third skin are all positioned and installed through the positioning holes (20) on the rear beam (9).

5. The method for bonding the leading edge structure of a complex honeycomb sandwich structure according to claim 1, characterized in that: In step one, the depth of the honeycomb core recess (1) milled from the honeycomb core (10) is 2.5~3.5 mm.

6. The method for bonding the leading edge structure of a complex honeycomb sandwich structure according to claim 4, characterized in that: The first isolation membrane is a porous isolation membrane (13); the second isolation membrane is a non-porous isolation membrane (12); the first skin is a process skin (11); the second skin is an adhesive skin; and the third skin is a cured skin.

7. The method for bonding the leading edge structure of a complex honeycomb sandwich structure according to claim 6, characterized in that: After the process skin (11) is attached to the side of the skeleton structure, a feeler gauge is used to check the gap.

8. The method for bonding the leading edge structure of a complex honeycomb sandwich structure according to claim 1, characterized in that: The skeleton structure includes a rear beam (9), a honeycomb core (10), and end ribs; the two ends of the rear beam (9) are connected to the end ribs.

9. The method for bonding the leading edge structure of a complex honeycomb sandwich structure according to claim 1, characterized in that: In step two, the lateral shaping device includes a lateral shaping device pressure plate (16) and a lateral shaping device base (17), and the lateral shaping device pressure plate (16) is installed on the lateral shaping device base (17); the lateral shaping device base (17) is positioned on the tooling (18) by positioning inserts (2) installed on both sides of the tooling (18); the lateral shaping device pressure plate (16) is installed on both sides of the skeleton structure.

10. The method for bonding the leading edge structure of a complex honeycomb sandwich structure according to claim 1, characterized in that: The calibration parameters in step three are: heating to 60~65 ℃ at a heating rate of no more than 1 ℃ / min, holding at that temperature for 60~65 min; and then cooling down after the holding time is completed.

11. The method for bonding the leading edge structure of a complex honeycomb sandwich structure according to claim 1, characterized in that: After the verification is completed in step three, the lateral shaping device, the top holding device (19) and the first skin need to be removed before the verification results are checked.

12. The method for bonding the leading edge structure of a complex honeycomb sandwich structure according to claim 1, characterized in that: Before repeating step two in step four, the lateral support device and the top holding device (19) need to be reinstalled.

13. The method for bonding the leading edge structure of a complex honeycomb sandwich structure according to claim 12, characterized in that: After repeating the second step, remove the lateral support device again.

14. The method for bonding the leading edge structure of a complex honeycomb sandwich structure according to claim 1, characterized in that: In step four, the oven is used for high-temperature curing. The curing parameters for the foam adhesive (21) are as follows: the temperature is increased to 150~155℃ at a rate not greater than 1℃ / min. When the temperature reaches 150℃, the constant temperature is started and the constant temperature time is 4~4.5 h. After the constant temperature is finished, the temperature is lowered. During the process of cooling from 150℃ to 130℃, the cooling rate should not be higher than 1℃ / min. During the cooling process after 130℃, the cooling rate should not be higher than 0.3℃ / min. The pre-foaming process ends after the temperature drops to 60℃.

15. The method for bonding the leading edge structure of a complex honeycomb sandwich structure according to claim 1, characterized in that: In step five, after the second skin is placed on the skeleton, putty strips are laid on the side of the top holding device (19), and the top holding device (19) and the skeleton structure are vacuum sealed together and subjected to secondary bonding verification in a hot autoclave.

16. The method for bonding the leading edge structure of a complex honeycomb sandwich structure according to claim 1, characterized in that: The auxiliary materials in step six include a non-porous isolation membrane (12), a porous isolation membrane (13), a breathable felt (24), a vacuum bag (29), and putty strips, and are placed in the order of non-porous isolation membrane (12), porous isolation membrane (13), breathable felt (24), vacuum bag (29), and putty strips. Finally, the vacuum bag (29) is vacuumed and leak checked.

17. The method for bonding the leading edge structure of a complex honeycomb sandwich structure according to claim 1, characterized in that: The curing parameters in the autoclave during step six are as follows: Vacuuming begins with a vacuum of -0.027 MPa to -0.033 MPa, and the negative pressure inside the vacuum bag (29) does not exceed -0.034 MPa throughout the process; external pressure is increased to 0.08 to 0.1 MPa at a rate of 20 to 30 kPa / min, and maintained for 10 to 30 minutes; then atmospheric venting is performed, with a venting rate not exceeding 1 kPa / min; after atmospheric venting, the pressure is increased to 0.18 to 0.20 MPa until the curing process ends; after pressurization, the temperature is increased to 150 to 155 ℃ at a rate of 1 to 1.5 ℃ / min, and maintained at this temperature for 4 hours; subsequently, the temperature is increased to 175 to 180 ℃ at a rate of 0.5 ℃ / min, and maintained at this temperature for 2 hours; after completion, the temperature is decreased at a rate not exceeding 0.3 ℃ / min, at a rate of 20 to 30 kPa / min. Release the pressure from the tank at a certain rate, and stop curing when the pressure is released and the temperature drops to 60 ℃.

18. The method for bonding the leading edge structure of a complex honeycomb sandwich structure according to claim 9, characterized in that: The tooling (18) includes a tooling assembly (3), and positioning inserts (2) are mounted on both sides of the tooling assembly (3).

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