A stepped composite material part co-curing mold and method

Abstract

This invention provides a co-curing mold and method for stepped composite material parts. The stepped composite material part includes a skin layer and a step layer. The mold includes a molding frame, a molding surface, a thickness control strip, a backing plate, and a target positioning hole. The molding surface is positioned above the molding frame and is stepped, matching the surface of the stepped composite material part. When laying the step layer, a target head of a laser projector is installed in the target positioning hole, a thickness control strip is installed on the step surface, and a backing plate is installed on the higher step of the molding surface near the step surface. When the thickness of the stepped layer after hot compaction is flush with the higher step of the molding surface, the thickness control strip and the backing plate are removed, and the skin layer can be laid. This is used to achieve a smooth aerodynamic shape with no overlapping steps after the aircraft's separation surfaces meet.

Description

Technical Field

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[0001] The present invention relates to the field of composite part manufacturing, and particularly to a co-curing forming die and method for stepped composite parts. Background Art

[0002] As the application of composite parts in aircraft expands from secondary load-bearing structures to primary load-bearing structures, the outer wing panels and central wing panels of aircraft composites are the best manifestations of the application of primary load-bearing structures. The butt joints of the roots of the outer wing panels and the central wing panels are generally achieved through the design of process separation surfaces.

[0003] In traditional separation surface designs, for example, the T-shaped stiffened panel of the A350 aircraft transfers loads through a "丄"-shaped structure and a butt joint strip structure. The I-shaped stiffened panel of the B787 aircraft transfers loads through a "土"-shaped structure and a stringer butt joint structure.

[0004] Whether it is a "丄"-shaped structure or a "土"-shaped structure, a small butt joint step will be generated at the butt joint external profile surface of the wing panel and the central wing panel, affecting the smooth aerodynamic profile of the aircraft. Summary of the Invention

[0005] The present invention provides a co-curing forming die and method for stepped composite parts, which are used to achieve a smooth aerodynamic profile without lap steps after the butt joint of the aircraft separation surface.

[0006] The present invention provides a co-curing forming die for stepped composite parts. The stepped composite part includes a skin layer and a stepped layer. The die includes a forming die frame, a forming profile, a thickness control strip, a backing plate, and a target positioning hole.

[0007] The forming profile is arranged above the forming die frame. The forming profile is stepped and matches the profile of the stepped composite part.

[0008] When laying the stepped layer, the target head of a laser projector is arranged in the target positioning hole, the thickness control strip is arranged on the stepped vertical surface, and the backing plate is arranged near the stepped vertical surface on the higher step of the forming profile. When the thickness after hot compaction of the stepped layer is flush with the higher step of the forming profile, the thickness control strip and the backing plate are removed, and then the skin layer can be laid.

[0009] Optionally, it further includes a uniform pressing plate, a uniform pressing plate forming die, a uniform pressing plate positioning hole, and a positioning pin.

[0010] The profile of the uniform pressing plate forming die is consistent with the profile of the stepped layer and is used to generate a uniform pressing plate. The profile of the uniform pressing plate matches the profile of the stepped layer.

[0011] Both ends of the equalizing plate and both ends of the lower step of the forming surface are provided with equalizing plate positioning holes. During the hot pressing of the step layer, the equalizing plate is fixed on the lower step of the forming surface by positioning pins.

[0012] Optional features also include: a flat pad;

[0013] A wedge-shaped pad plate is provided at both ends of the lower step of the molded surface;

[0014] The sum of the width of the end pads and the width of the step layer is the same as the width of the lower step of the shaped surface;

[0015] The length of the slab should not be less than the length of the step layer.

[0016] Optionally, the thickness control strip is made of multiple layers of soft material that can be bonded to the mold and contact the prepreg, and the thickness of the thickness control strip is within 0.5mm to 0.8mm.

[0017] Optionally, the thickness of the pressure plate is within 2mm to 2.5mm.

[0018] Optionally, the backplate is made of aluminum, and its thickness is 10% of the sum of the thickness of the pressure plate and the maximum thickness of the step layer.

[0019] A second aspect of the present invention provides a method for co-curing and molding stepped composite material parts, using a mold for co-curing and molding stepped composite material parts as described in any one of the first aspects, the molding method comprising the following steps:

[0020] S1. Before paving, a thickness control strip with a certain thickness is formed by bonding multiple layers of soft material on the vertical surface of the molded surface step. The backing board is then placed and positioned on the molded surface step.

[0021] S2. Place the target head on the target positioning hole to form the laser projection line. Lay the prepreg on the lower part of the step of the molded surface according to the projection line. Perform cold compaction once every 3 layers and pre-compact once for each preset thickness.

[0022] S3. After the prepreg of the step layer is laid, remove the thickness control strips that are bonded to the vertical surface of the step forming mold.

[0023] S4. Place and fix the pressure plate on the stepped layer after the prepreg has been laid;

[0024] S5. After completing the bag making and sealing of the stepped layer, the bag is put into the autoclave for hot compaction of the stepped layer prepreg. The hot compaction temperature is controlled within 80℃~90℃.

[0025] S6. After hot compaction, remove the equalizing plate and the backing plate, and check the flushness between the prepreg blank and the higher step of the forming surface; if flush, proceed to S7; if higher than the higher step, execute S5 again; if lower than the higher step, compensate the prepreg by the amount of the difference, and execute S5 again.

[0026] S7. Lay out the skin layer prepreg and form the composite material parts.

[0027] Optional, the preset thickness is 5mm to 6mm.

[0028] This invention provides a co-curing molding die and method for stepped composite material parts, which has the following advantages: 1) The molding die has a simple structure, readily available materials, and strong processability; 2) Low investment cost, and can realize the integrated co-curing molding of single-step or multi-step composite material parts; 3) Low technical risk, and by controlling key parameters and technologies, internal quality that meets document requirements can be achieved; 4) The stepped exterior panel manufactured by this method can achieve an aerodynamic shape with no overlapping steps after the aircraft's separation surfaces are joined, and the whole surface has a smooth transition. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of a molding die for a stepped surface.

[0030] Figure 2 This is a side view of the molding die with a stepped surface.

[0031] Figure 3 This is a schematic diagram of a uniform pressure plate forming mold;

[0032] Figure 4 This is a schematic diagram of the wall panel separation surface mating that can be achieved by the present invention;

[0033] Explanation of reference numerals in the attached figures:

[0034] 1-Forming mold frame, 2-Forming surface, 3-Plate pad, 4-Thickness control strip, 5-Equalizing pressure plate, 7-Backing plate, 8-Target positioning hole, 9-Equalizing pressure plate positioning hole, 11-Step surface, 12-Diameter strip, 13-Wall panel skin, 14-Beam. Detailed Implementation

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of the present invention.

[0036] like Figure 1-4As shown, the present invention provides a stepped composite material part co-curing molding mold, including: a molding mold frame, a molding surface, a pad plate, a thickness control strip, a pressure equalizing plate, a pressure equalizing plate molding mold, a backing plate, a target positioning hole, a pressure equalizing plate positioning hole, a positioning pin, and a stepped surface.

[0037] The forming surface is typically a metal mold, situated on a forming mold frame. A shim plate, target positioning holes, and pressure plate positioning holes are installed in the allowance area of ​​the forming surface. After the stepped area is laid, the shim plate is used to eliminate the steps in the mold's allowance area, facilitating subsequent automatic part placement. Thickness control strips, pressure plates, and backing plates are used to achieve the forming of the stepped surface. The target positioning holes and pressure plate positioning holes are used for positioning during the laying process and for positioning the pressure plate, respectively.

[0038] The thickness control strip is composed of multiple layers of soft material that can be bonded to the mold and contact the prepreg. It is bonded to the stepped surface of the mold before the prepreg is laid, ensuring a 0.5mm–0.8mm gap between the prepreg layers and the mold. This prevents wrinkles from forming on the stepped surface. The thickness control strip is removed after the stepped surface is laid.

[0039] The uniform pressing plate forming mold is generally a metal mold used to form a uniform pressing plate covering the stepped surface after it has been laid. The mold surface of the uniform pressing plate forming mold is consistent with the inner surface of the step. After a certain thickness of prepreg is laid on the uniform pressing plate forming mold and cured in an autoclave, a composite laminate is formed. The thickness of the uniform pressing plate is controlled between 2mm and 2.5mm, and it should not be too thick. The uniform pressing plate is positioned and connected to the formed surface through positioning holes and positioning pins to ensure that the prepreg is flat, dense, and wrinkle-free during the heating and pre-compaction process in the stepped area, which facilitates subsequent laying. If the stepped surface is flat, a steel plate is used instead of a uniform pressing plate, and the uniform pressing plate forming mold is no longer needed.

[0040] The backing plate is placed on the step and flush with the edge of the step. It is used to assist in the shaping of the step surface and prevent the precast part that is higher than the step from collapsing and forming wrinkles during the compaction process. Since the backing plate is not used for curing with the parts in the can, it is generally made of aluminum. The thickness of the backing plate is 10% of the sum of the thickness of the uniform pressure plate and the maximum thickness at the step.

[0041] This invention also provides a method for co-curing and molding stepped composite material parts, comprising the following steps:

[0042] 1. Before paving, a thickness control strip with a certain thickness is formed by bonding multiple layers of soft material on the vertical surface of the molded surface step. The backing board is then placed and positioned on the molded surface step.

[0043] 2. Place the target head on the target positioning hole to form the laser projection line for application. Apply the prepreg material on the molded surface according to the projection line, and compact it with cold oil every 3 layers to ensure the density between layers.

[0044] 3. Select the number of pre-compaction times during the laying process according to the height of the step. Generally, pre-compact once every 5mm to 6mm to ensure the density between the prepreg layers and to get as close as possible to the cured state.

[0045] 4. Based on the actual cured thickness of the prepreg, the theoretical number of layers needs to be adjusted during the application process. For prepregs with a cured thickness exceeding the theoretical upper limit, reduce the number of layers according to the thickness deviation; conversely, increase the number of layers. This process avoids step differences between the prepreg and the molded surface at the stepped areas, which could lead to internal fiber wrinkles in the parts.

[0046] 5. After the prepreg material for the stepped surface is laid, remove the thickness control strips that are bonded to the vertical surface of the stepped forming mold.

[0047] 6. On the stepped surface where the prepreg has been laid, place a composite pressure plate or steel pressure plate that has been pre-cured using a pressure plate forming mold, and position and connect the composite pressure plate or steel pressure plate through the positioning holes and positioning pins in the excess area of ​​the stepped surface.

[0048] 7. After completing the bag making and sealing of the shaped surface, the bag is put into the autoclave for hot compaction of the stepped surface prepreg. The hot compaction temperature is controlled at 80℃~90℃.

[0049] 8. After hot compaction, remove the equalizing plate and the backing plate, and check the flushness between the prepreg blank and the molding surface. If it is higher than the molding surface, repeat step 7 for hot compaction. If it is lower than the molding surface, compensate the prepreg by the amount of material that is lower until it is flush with the molding surface.

[0050] 9. Place a pad in the allowance area of ​​the molding surface to enable automatic placement of the prepreg until the bonding is complete. Subsequent processes can then be carried out according to the general process for molding composite parts.

[0051] For example, in a specific embodiment, the stepped composite material part co-curing molding die provided by the present invention includes: a molding die frame 1, a molding surface 2, a pad plate 3, a thickness control strip 4, a pressure equalizing plate 5, a pressure equalizing plate molding die, a backing plate 7, a target positioning hole 8, a pressure equalizing plate positioning hole 9, a positioning pin, and a stepped surface 11.

[0052] The forming surface 2 is generally a metal mold, located on the forming mold frame 1. A pad plate 3, target positioning holes 8, and pressure plate positioning holes 9 are provided in the allowance area of ​​the forming surface 2. After the stepped area is laid, the pad plate 3 is used to eliminate the steps in the mold allowance area, facilitating subsequent automatic placement of parts. The thickness control strip 4, pressure plate 5, and backing plate 7 are used to form the stepped surface 11. The target positioning holes 8 and pressure plate positioning holes 9 are used for positioning during the laying process and for placing and positioning the pressure plate 5, respectively.

[0053] The thickness control strip 4 is made of 6 layers of release fabric. The thickness control strip 4 is bonded to the step surface of the molded surface 2 before the prepreg is laid on the step surface 11 to prevent the prepreg from forming wrinkles on the step surface.

[0054] The pressure equalizing plate forming mold is a metal mold used to form the pressure equalizing plate 5 covering the completed stepped surface 11. The surface of the pressure equalizing plate forming mold is consistent with the inner surface of the step. The prepreg with a thickness of 2.5mm after laying and curing is cured in a hot autoclave to complete the manufacturing of the pressure equalizing plate 5.

[0055] The backing plate 7 is made of aluminum and is 2mm thick. It is placed on the step and flush with the edge of the step. It is used to assist in the forming of the step surface 11 and to prevent the precast body that is higher than the step from collapsing and forming wrinkles during the compaction process.

[0056] The co-curing molding method for stepped composite wall panels is as follows:

[0057] 1. Before laying, 6 layers of release cloth are bonded to the vertical surface of the stepped surface 11 to form a thickness control strip 4, and a backing plate 7 is placed and positioned on the step of the stepped surface 11.

[0058] 2. Place the target head on the target positioning hole 8 to form the laser projection line for laying. Lay the prepreg on the molded surface 2 according to the projection line, and perform cold pressing and compaction every 3 layers to ensure the density between layers.

[0059] 3. Perform pre-compacting every 5mm to 6mm to ensure the density between prepreg layers and to bring them as close to the cured state as possible;

[0060] 4. Based on the actual cured thickness of the prepreg, the theoretical number of layers needs to be adjusted during the application process. Because the cured thickness of the prepreg used in this embodiment is slightly different from the top, three layers of prepreg were reduced during the application process. This operation avoids the occurrence of step differences between the prepreg and the molding surface at the step, which could lead to internal fiber wrinkles in the part.

[0061] 5. After the prepreg material of the stepped surface 11 is laid, remove the thickness control strip 4 that is bonded to the vertical surface of the stepped surface 2;

[0062] 6. On the stepped surface 11 after the prepreg has been laid, place the pressure plate 5, which has been pre-cured by the pressure plate forming mold, and position and connect the pressure plate 5 through the pressure plate positioning holes 9 and positioning pins in the excess area of ​​the stepped surface.

[0063] 7. After completing the bag making and sealing of the molded surface 2, the bag is placed in the autoclave for hot compaction of the prepreg material of the stepped surface 11. The hot compaction temperature is controlled at 80℃~90℃.

[0064] 8. After hot compaction, remove the equalizing plate 5 and the backing plate 7, and check the flushness between the prepreg blank and the higher step of the molding surface 2. If flush, proceed to the next process; if higher, repeat step 7 for hot compaction. If lower, compensate the prepreg by the amount of lower prepreg until flush.

[0065] 9. Place the pad plate 3 in the remaining area of ​​the molded surface 2, and automatically lay the wire for the wall panel skin until the skin is laid.

[0066] 10. Assemble the stringer skin and make bags for sealing. After completion, place the bags in an autoclave for curing and shaping.

[0067] The manufactured wall panel skin 13 and beam 14 are assembled and connected by mating strip 12 to form a... Figure 4 The component structure shown enables an aerodynamic shape that is seamless and has no overlapping steps after the aircraft's surfaces are joined, resulting in a smooth overall transition.

Claims

1. A stepped composite material part co-curing molding die, characterized in that, The stepped composite material part includes: a skin layer and a stepped layer; the mold includes: a molding mold frame, a molding surface, a thickness control strip, a backing plate, and a target positioning hole. The molding surface is set above the molding mold frame. The molding surface is stepped and matches the surface of the stepped composite material part. When laying the step layer, a target head of a laser projector is installed in the target positioning hole, a thickness control strip is installed on the step surface, and a backing plate is installed on the higher step of the shaped surface near the step surface. When the thickness of the step layer after hot compaction is flush with the higher step of the shaped surface, the thickness control strip and backing plate are removed, and the skin layer can be laid. The co-curing molding die for stepped composite material parts also includes: a pressure plate, a pressure plate forming die, a pressure plate positioning hole, and a positioning pin; The profile of the uniform pressure plate forming mold is consistent with the profile of the stepped layer, and is used to generate the uniform pressure plate. The profile of the uniform pressure plate matches the profile of the stepped layer. Both ends of the equalizing plate and both ends of the lower step of the forming surface are provided with equalizing plate positioning holes. During the hot pressing of the step layer, the equalizing plate is fixed on the lower step of the forming surface by positioning pins. The co-curing mold for stepped composite material parts also includes: a pad plate; A wedge-shaped pad plate is provided at both ends of the lower step of the molded surface; The sum of the width of the end pads and the width of the step layer is the same as the width of the lower step of the shaped surface; The length of the slab should not be less than the length of the step layer. The co-curing molding method for stepped composite material parts includes the following steps: S1. Before paving, a thickness control strip with a certain thickness is formed by bonding multiple layers of soft material on the vertical surface of the molded surface step. The backing board is then placed and positioned on the molded surface step. S2. Place the target head on the target positioning hole to form the laser projection line. Lay the prepreg on the lower part of the step of the molded surface according to the projection line. Perform cold compaction once every 3 layers and pre-compact once for each preset thickness. S3. After the prepreg of the step layer is laid, remove the thickness control strips that are bonded to the vertical surface of the step forming mold. S4. Place and fix the pressure plate on the stepped layer after the prepreg has been laid; S5. After completing the bag making and sealing of the stepped layer, the bag is put into the autoclave for hot compaction of the stepped layer prepreg. The hot compaction temperature is controlled within 80℃~90℃. S6. After hot compaction, remove the equalizing plate and the backing plate, and check the flushness between the prepreg blank and the higher step of the forming surface; if flush, proceed to S7; if higher than the higher step, execute S5 again; if lower than the higher step, compensate the prepreg by the amount of the difference, and execute S5 again. S7. Lay out the skin layer prepreg and form composite material parts.

2. The stepped composite material part co-curing molding die according to claim 1, characterized in that, The thickness control strip is made of multiple layers of soft material that can be bonded to the mold and come into contact with the prepreg. The thickness of the thickness control strip is within the range of 0.5mm to 0.8mm.

3. The stepped composite material part co-curing molding die according to claim 1, characterized in that, The thickness of the pressure plate is between 2mm and 2.5mm.

4. The stepped composite material part co-curing molding die according to claim 1, characterized in that, The backrest is made of aluminum, and its thickness is 10% of the sum of the thickness of the pressure plate and the maximum thickness of the step layer.

5. The stepped composite material part co-curing molding die according to claim 1, characterized in that, The preset thickness is 5mm to 6mm.

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