A method for ply conversion of composite beams

Abstract

This invention discloses a layup conversion method for composite beams. S1. The sheet of the first layup group (1) is laid on the lower mold (5) and compacted under vacuum at room temperature; S2. The sheet of the second layup group (2) is laid sequentially on the first layup group (1) which has been compacted under vacuum at room temperature, and compacted under vacuum at room temperature; during laying, the edge strip areas between the sheets of the second layup group (2) and between the first layer sheet of the second layup group (2) and the first layup group (1) are isolated with a release film or the backing material of the sheet itself; S3. After the second layup group (2) is laid and compacted, the upper mold (6) is... S4. After closing the mold, remove the release film or backing from the edge strip area of ​​each sheet of the second layup group (2) and wrap it back onto the upper mold (6) in sequence, and perform vacuum compaction at room temperature; S5. Fill the corner of the first and second layup groups with twist strips (9); after filling, continue to lay the third layup group (3) and the fourth layup group (4) on the side mold body A (7) and the side mold body B (8), and perform vacuum compaction at room temperature; then close the two molds; S6. After the two molds are closed, perform vacuum curing. This invention can effectively control the wrinkles in the fabric between the first and second layup groups in the L-shaped flange area of ​​the web.

Description

Technical Field

[0001] This invention belongs to the field of composite material molding technology, and specifically relates to a method for ply conversion of composite material beams. Background Technology

[0002] With the rapid application of composite materials in modern aviation, helicopter vertical tail main load-bearing beams have also begun to use all-composite material parts.

[0003] The tail boom is a solid high-temperature carbon fiber component with a T-shaped cross-section. The T-shaped flange connects to the tail boom skin. At the base of the tail boom is a square opening with an L-shaped flange. Cable supports are riveted to this flange, which also serves to increase the component's strength. (See...) Figure 1 Its structure includes T-shaped flange I at the edge of the I-beam and L-shaped flange II with a square opening at the root.

[0004] The tail beam ply is divided into 4 groups, following the traditional typical I-beam ply pattern (see...). Figure 2 First, lay the first layup group on the lower mold body; then lay the second layup group on the upper mold body; then close the upper and lower mold bodies together. Lay the third and fourth layup groups on the two side mold bodies respectively, and then close the two side mold bodies together.

[0005] Prepreg fabric has a certain thickness ratio before and after curing, generally between 1.2 and 1.5. That is, at room temperature, the layup thickness is higher than the layup thickness after curing. As the part cures, under the influence of pressure and temperature, the interlayer voids decrease and interlayer resin overflows, the gaps between the upper mold, lower mold, and side molds gradually decrease, and the layup gradually thins until it reaches a stable state that forms the thickness of the part after curing. Therefore, the traditional layup process can complete the layup of a typical I-beam (I-beam with no flange on the web). However, when the web has an L-shaped flange, during the mold closing process of the upper and lower molds, the sum of the fabric thicknesses of the first and second layup groups at the L-shaped flange position of the I-beam web is much higher than the gap between the upper and lower mold cavities, causing fabric interference and preventing the molding tooling from closing properly; at the same time, severe wrinkles will appear in the fabric between the first and second layup groups in the L-shaped flange area of ​​the I-beam web (see...). Figure 3 ). Summary of the Invention

[0006] The purpose of this invention is to provide a method for ply conversion in composite beams. This invention can effectively control wrinkles in the fabric between the first and second ply groups in the L-shaped flange region of the web.

[0007] The technical solution of this invention is: a method for ply conversion of composite beams, comprising the following steps:

[0008] S1. Lay the sheet of the first layup group on the lower mold and compact it under vacuum at room temperature;

[0009] S2. The sheets of the second layup group are laid sequentially on the first layup group which has been vacuum-compacted at room temperature, and then vacuum-compacted at room temperature. During laying, the edge strip areas between the sheets of the second layup group and between the first layer of the second layup group and the first layup group are separated by a release film or the backing provided with the sheets.

[0010] S3. After the second layer is laid and compacted, the upper and lower molds are closed.

[0011] S4. After the mold is closed, remove the release film or backing from the edge area of ​​each sheet of the second layup group and wrap it back onto the upper mold in sequence, and then perform vacuum compaction at room temperature.

[0012] S5. Fill the corners of the first and second ply groups with twist strips; after filling, continue to lay the third and fourth ply groups on side mold body A and side mold body B, and perform vacuum compaction at room temperature; then close the two molds together.

[0013] S6. After the molds on both sides are closed, vacuum curing is performed.

[0014] In the aforementioned method for converting composite beams into layers, the room temperature vacuum compaction method is as follows: after laying the first layer of material, the first layer of material is compacted at room temperature for 30 to 40 minutes in an environment with a negative pressure of not less than 0.07 MPa; thereafter, after laying every 3 to 4 layers of material, the same method is used for compaction.

[0015] In the aforementioned method for converting the ply of composite beams, in step S1, after the first ply group is laid, hot compaction is performed. The hot compaction parameters are: after heating to 60℃, heat preservation for 30 minutes, negative pressure not less than 0.07MPa, positive pressure 0.6±0.02MPa, heating and cooling rate 0.5~2℃ / min, and pressurization rate 0.02~0.025MPa / min.

[0016] In the aforementioned method for converting the ply of composite beams, in step S3, after mold closing, compaction is performed under a negative pressure of not less than 0.09 MPa at room temperature.

[0017] In the aforementioned method for converting the ply of composite beams, the gap between the upper mold and the topmost sheet after compaction is less than 0.5 mm.

[0018] In the aforementioned method for converting the ply of composite beams, in step S5, the mold closing gap of the side mold body is ≤0.2mm.

[0019] In the aforementioned method for converting composite beams into layers, the vacuum degree detection during vacuum curing in step S6 is as follows: the vacuum degree of the vacuum bag reaches 0.09 MPa until the vacuum degree stabilizes, the vacuum source is turned off or shut off after 15 minutes, and the vacuum gauge reading drops by no more than 0.017 MPa within 5 minutes.

[0020] In the aforementioned method for converting the ply of composite beams, when laying the sheets of each ply group, the sheets are stretched straight, tightened, and all air bubbles are expelled.

[0021] The advantages of this invention are:

[0022] This invention can avoid wrinkles caused by the relative movement between the first and second ply groups in the L-shaped flange area of ​​the web during the mold closing process, while ensuring that the mold closing is in place.

[0023] This invention employs a method of transferring the first layup group of the upper mold to the lower mold, while simultaneously adding hot compaction during the layup process to reduce the prepreg thickness ratio; the relative movement between the fabric layers in the original mold closing process is transformed into the relative movement between the fabric layer and the tooling, see [link to related documentation]. Figure 4 This method offers the following advantages:

[0024] 1) Ensure precise mold closing in the L-shaped flange area of ​​the web;

[0025] 2) Eliminate wrinkles;

[0026] 3) Reduce the difficulty of joining the upper and lower mold bodies;

[0027] 4) Improve the internal quality of the product. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the vertical tail beam;

[0029] Figure 2 This is a simplified diagram of the traditional I-beam ply laying process;

[0030] Figure 3 This is a simplified diagram of an I-beam with an L-shaped flange on the web, laid according to the traditional I-beam layering process.

[0031] Figure 4 This is a schematic diagram of the operation process of the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of 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, 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 protection of the present invention.

[0033] The features and illustrative embodiments of various aspects of the present invention will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific setups and methods set forth below, but covers any improvements, substitutions, and modifications to structures, methods, and devices without departing from the spirit of the invention. Well-known structures and techniques are not shown in the drawings and the following description to avoid unnecessarily obscuring the invention.

[0034] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited in each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0035] Example 1. A method for ply conversion of composite beams, see [link to example]. Figure 4 The process includes the following steps: Step 1: Tooling preparation

[0036] (1) Tooling collection: Collect tooling according to tooling drawing number and check tooling certificate of conformity;

[0037] (2) Tooling inspection: Visual inspection of the tooling, including whether the tooling surface is worn or corroded, and whether the tooling surface is dented, scratched or corroded.

[0038] Step 2: Material Preparation

[0039] (1) Collect materials;

[0040] (2) Low-temperature materials are thawed in an air-conditioned room. During the thawing process, the materials are kept sealed. Before opening the seal, ensure that no moisture is formed inside or outside the bag.

[0041] (3) The pre-made materials are not allowed to be folded. They can be laid flat or rolled up with support for storage.

[0042] Step 3: Material preparation

[0043] (1) Press the material sheet and the corresponding program to use the correct prepreg CNC cutting. The cut material sheet should be marked with: product drawing number, layup number, angle, and fiber direction of the fabric.

[0044] (2) Lay the sheets flat in the order of the sheet pages, and check the integrity of the sheets and the clarity and completeness of the markings.

[0045] Step 4: Laying out layers

[0046] (1) Lay the first layer of material sheet in the first layer group 1 on the lower mold according to the projection program. When laying the material sheet, pull it straight, tighten it, and remove all air bubbles.

[0047] (2) Vacuum compaction at room temperature. Use a non-porous isolation membrane during the vacuuming process. Start timing after the vacuum bag reaches the pressure value. The negative pressure should not be lower than 0.07MPa and the time should be 30 to 40 minutes.

[0048] (3) After laying the first layer, lay the remaining material sheets according to the projection procedure. After laying 3 to 4 layers of material sheets, vacuum compaction is performed once, in the same way as step 2, until the last layer of material sheets in the first layer group 1 is laid.

[0049] (4) After all the sheets in the first layer group 1 are laid in the lower mold 5, hot compaction is carried out. The hot compaction parameters are: after heating to 60℃, keep warm for 30 minutes, negative pressure is not less than 0.07MPa, positive pressure is 0.6±0.02MPa, heating and cooling rate is 0.5~2℃ / min, and pressurization rate is 0.02~0.025MPa / min.

[0050] (5) After the lower mold 5 is hot-pressed and cooled to room temperature, the sheet material originally laid in the second ply group 2 of the upper mold 6 is transferred to the lower mold 5. First, according to the projection program, the outermost sheet material of the second ply group 2 is laid on the lower mold 5. At this time, the outermost sheet material of the second ply group 2 is only in contact with the last sheet material of the first ply group 1 in the web area, and the edge strip area is separated by a release film or the backing material itself.

[0051] (6) After laying the outermost layer of the second layer group 2, vacuum compact it at room temperature, using the same method as step 2;

[0052] (7) After laying the outermost layer of the second ply group 2, lay the remaining layers of the second ply group 2 in sequence according to the projection procedure, wherein all the layers are isolated in the edge strip area by a release film or the backing provided with the layer itself.

[0053] (8) After laying 3 to 4 layers of the remaining sheet material in the second layup group 2, compact it once, in the same way as step 2. During this process, provide support and protection in the transition area where the sheet material is isolated to prevent wrinkles that cannot be eliminated after solidification from appearing in the transition area where the sheet material is isolated by the isolation film or backing during the vacuum compaction process.

[0054] (9) After all the sheets in the second layup group 2 are laid on the lower mold 5, the mold is closed. At this time, there are no sheets on the upper mold 6, and all the sheets in the first layup group 1 and the second layup group 2 have been laid on the lower mold 5.

[0055] (10) Make vacuum bags, vacuum and compact them at room temperature. Start timing after the vacuum bag reaches the pressure value. The negative pressure should not be lower than 0.09MPa. Stop when the gap between the upper mold 6 and the prepreg is less than 0.5mm.

[0056] (11) After removing the vacuum bag, wrap all the fabric layers of the edge strip of the second layup group 2 separated by the isolation film back onto the upper mold 6. During the wrapping process, pull the sheet flat, tighten it, and expel all air bubbles.

[0057] (12) After the repacking process is completed, vacuum and compact the material, using the same method as step 2;

[0058] (13) Fill the corners where the upper and lower molds are joined with twist strips 9. After filling, continue to lay all the fabric layers in the third ply group 3 and the fourth ply group 4 of the side mold body A7 and the side mold body B8 according to the projection program. Compact the fabric after laying 3 to 4 layers, in the same way as step 2.

[0059] (14) After all the sheets in the third ply group 3 and the fourth ply group 4 are laid, the side mold 1 and the side mold 2 are closed respectively to ensure that the mold closing gap between the side mold 1 and the side mold 2 is less than or equal to 0.2mm;

[0060] Step 5: Make the final vacuum bag;

[0061] ① Check the quality of the vacuum bag sealing and ensure that the vacuum nozzles are placed in the correct position and number;

[0062] ② Vacuum degree detection: The vacuum degree of the vacuum bag reaches 0.09MPa and remains stable. After 15 minutes, the vacuum source is turned off or shut off. The vacuum gauge reading should not drop by more than 0.017MPa within 5 minutes.

[0063] Step 6: Curing

[0064] Curing should be performed according to the corresponding curing parameters;

[0065] Step 7: Unmolding

[0066] Insert the mold release wedge evenly into the gap between the edge of the part and the tooling. After ensuring that the edge of the part has been removed from the tooling, insert the mold release wedge evenly inward around the part. Do not use excessive force during operation.

[0067] Step 8: Mark

[0068] Mark product drawing number, version number, serial number, and other information on the product;

[0069] Step 9: Cutting

[0070] Cut off the portion outside the allowance line along the product's edge.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should be covered within the protection scope of the present invention.

Claims

1. A method for ply conversion of composite beams, characterized in that, Includes the following steps: S1. Place the sheet of the first layup group (1) on the lower mold (5) and perform vacuum compaction at room temperature; S2. The sheets of the second layup group (2) are laid sequentially on the first layup group (1) which has been vacuum-compacted at room temperature, and then vacuum-compacted at room temperature. During the laying, the edge strip areas between the sheets of the second layup group (2) and between the first layer sheet of the second layup group (2) and the first layup group (1) are separated by a release film or the backing provided by the sheet. S3. After the second layer group (2) is laid and compacted, the upper mold (6) and the lower mold (5) are closed. S4. After the mold is closed, remove the release film or backing from the edge strip area of ​​each sheet of the second layup group (2) and wrap it back onto the upper mold (6) in sequence, and then perform vacuum compaction at room temperature; S5. Fill the corners of the first and second ply groups with twist strips (9); after filling, continue to lay the third ply group (3) and the fourth ply group (4) on the side mold body A (7) and the side mold body B (8), and perform vacuum compaction at room temperature; then close the two molds together. S6. After the molds on both sides are closed, vacuum curing is performed.

2. The layup conversion method for composite material beams according to claim 1, characterized in that, The method for vacuum compaction at room temperature is as follows: After laying the first layer of material, compact the first layer of material at room temperature for 30 to 40 minutes in an environment with a negative pressure of not less than 0.07 MPa; then compact it once in the same way after laying every 3 to 4 layers of material.

3. The layup conversion method for composite material beams according to claim 1, characterized in that, In step S1, after the first layer group (1) is laid, hot compaction is carried out. The hot compaction parameters are: after heating to 60℃, keep warm for 30 minutes, negative pressure not less than 0.07MPa, positive pressure 0.6±0.02MPa, heating and cooling rate 0.5~2℃ / min, and pressurization rate 0.02~0.025MPa / min.

4. The layup conversion method for composite material beams according to claim 1, characterized in that, In step S3, after the mold is closed, it is compacted under a negative pressure of not less than 0.09 MPa at room temperature.

5. The layup conversion method for composite material beams according to claim 4, characterized in that, After compaction, the gap between the upper mold and the topmost material sheet is less than 0.5mm.

6. The method for ply conversion of composite beams according to claim 1, characterized in that, In step S5, the mold closing gap of the side mold body is ≤0.2mm.

7. The layup conversion method for composite material beams according to claim 1, characterized in that, The vacuum degree test in step S6 is as follows: the vacuum degree of the vacuum bag reaches 0.09MPa until the vacuum degree stabilizes, and the vacuum source is turned off or shut off after 15 minutes. The vacuum gauge reading drops by no more than 0.017MPa within 5 minutes.

8. The layup conversion method for composite material beams according to claim 1, characterized in that, When laying the sheets of each layer, pull the sheets straight, tighten them, and remove all air bubbles.

Images