A method for repairing a composite workpiece
By using vacuum compaction components and gradient porous isolation membranes, the problems of uneven porosity and adhesive layer thickness in the repair of composite workpieces were solved, thereby improving repair quality and structural strength.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHENYANG NORTHERN AIRCRAFT MAINTENANCE CO LTD
- Filing Date
- 2024-03-26
- Publication Date
- 2026-07-21
AI Technical Summary
Existing layup repair methods for composite material workpieces suffer from poor porosity control and uneven adhesive layer thickness, which affect repair quality and structural strength.
The system employs a vacuum compaction assembly and a gradient porous release membrane. Repair layers are laid layer by layer and then rolled and compacted. Combined with vacuum suction and preheating, the porosity and adhesive layer thickness of the repair layers are controlled, and the resin distribution is controlled using a gradient porous release membrane.
Effective control of the porosity and adhesive layer thickness of the repair layup improves the structural strength and repair quality of composite workpieces, and avoids structural damage caused by weak bonding and porosity.
Smart Images
Figure CN118124177B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of aircraft maintenance technology, and in particular to a repair method for composite material workpieces. Background Technology
[0002] Currently, composite materials, as a new type of material, are widely used in the aerospace industry due to their excellent performance. However, during aviation use, damage can occur due to accidents or other reasons, requiring repair of composite component parts. There are various repair methods for aerospace composite materials. For resin-based composite materials, layup repair is one of the commonly used methods. Layup repair refers to a repair method that involves removing the damage, applying wet layup or prepreg, encapsulating the wet layup or prepreg, and then curing it.
[0003] For the ply repair method, defects in the patch bonding during the adhesive repair process, such as weak bonding and uneven adhesive layer thickness, will reduce the bonding strength of the patch, causing premature detachment of the patch, damage to the internal structure, and may also seriously affect the service life of the composite material structure. In the prior art: (1) the porosity control of the repair ply is poor, affecting the repair quality. (2) the adhesive layer thickness during repair cannot be guaranteed, affecting the sustainability of the repair process after repair. Summary of the Invention
[0004] The purpose of this invention is to provide a repair method for composite material workpieces that can control the porosity of the repair pavement and ensure the thickness of the adhesive layer during repair, thereby guaranteeing its structural strength.
[0005] To achieve the above objectives, the present invention provides a repair method for composite material workpieces, employing a vacuum compaction assembly, the vacuum compaction assembly comprising a frame and a vacuum bag disposed on the inner peripheral wall of the frame, characterized by comprising the following steps:
[0006] S1. Grind the damaged gaps in the composite material workpiece;
[0007] S2, Prepare and repair the ply layer;
[0008] S3. The repair layer is laid from bottom to top at the damaged gap, and the area of the repair layer gradually increases from bottom to top. Each layer of the repair layer is rolled and compacted when it is laid. Multiple repair layers are stacked to form a repair block.
[0009] S4. A gradient porous isolation membrane, an adhesive-absorbing layer, a non-porous isolation membrane, and a pressure equalizing plate are laid sequentially on top of the repair block.
[0010] S5. The frame is bonded to the composite material workpiece, the vacuum bag is located above the damaged notch, the vacuum bag abuts against the pressure equalizing plate, and the vacuum bag is vacuumed and compacted.
[0011] The gradient porous isolation membrane has several overflow holes with a gradually decreasing diameter from the inside to the outside.
[0012] Furthermore, in S2, the repair layer is prepared with resin, and step S2 includes a mixing operation in which the resin is stirred at a uniform speed and in the same direction.
[0013] Furthermore, in S3, one side of the repair ply is first laid on the composite material workpiece, and a roller is rolled and placed on the laid side of the repair ply. While laying the remaining part of the repair ply, the roller is used to roll and compact it.
[0014] Furthermore, in S3 and S4, when the number of repair layers is 1-4 layers, the area of the repair layer is 80-100 cm². 2 In this case, the adhesive-absorbing layer includes a first glass fiber, the area of which is larger than the area of the repair layer located on the topmost layer.
[0015] Furthermore, in S3 and S4, when the number of repair layers is 5-8 layers, the area of the repair layer is 100-150 cm². 2 In this case, the adhesive-absorbing layer includes a second glass fiber and a first glass fiber stacked sequentially from bottom to top. The area of the second glass fiber is larger than the area of the repair layup located on the topmost layer, and the area of the first glass fiber is equal to the area of the repair layup located on the first layer.
[0016] Furthermore, in S3 and S4, when the number of repair layers is 9-16 layers, the area of the repair layer is 150-200 cm². 2 In this case, the adhesive-absorbing layer includes a second glass fiber and two layers of first glass fiber stacked sequentially from bottom to top. The area of the second glass fiber in the first layer is larger than the area of the repair layer in the topmost layer. The area of the first glass fiber in the second layer is equal to the area of the repair layer in the first layer. The area of the first glass fiber in the third layer is equal to the area of the repair layer in the eighth layer.
[0017] Furthermore, in S3 and S4, when the number of repair layers is 16-28 layers, the area of the repair layer is 200-400 cm². 2In this case, the adhesive-absorbing layer includes a second layer of glass fiber and three layers of first glass fiber stacked sequentially from bottom to top. The area of the second glass fiber in the first layer is larger than the area of the repair layer in the topmost layer. The area of the first glass fiber in the second layer is equal to the area of the repair layer in the first layer. The area of the first glass fiber in the third layer is equal to the area of the repair layer in the eighth layer. The area of the first glass fiber in the fourth layer is equal to the area of the repair layer in the fourteenth layer.
[0018] Furthermore, the first glass fiber has a fiber diameter of 10-14 μm, and the second glass fiber has a fiber diameter of 16-20 μm.
[0019] Furthermore, in S4, the equalizing plate is made of a flexible material.
[0020] Furthermore, in S5, during vacuum pressing, the repair layer is preheated to 28-32°C.
[0021] Compared with existing technologies, the repair method for composite material workpieces according to this invention has the following advantages: During the application of repair layers, each repair layer is rolled and compacted, ensuring tight adhesion between layers and eliminating gaps, thus controlling the porosity between repair layers. A gradient porous release membrane is laid on top of the repair block. This membrane has overflow holes with gradually decreasing pore size from the inside to the outside. Multiple experiments have shown that the repair block has the highest structural strength when its thickness is 0.16-0.24 mm. Since the resin thickness is greater closer to the inner side of the repair block, more resin needs to overflow to reduce the adhesive layer thickness. Conversely, the adhesive layer thickness is smaller closer to the outer side of the repair block, so a small amount of overflowing resin is needed to maintain the thickness of the repair block and increase its structural strength. Attached Figure Description
[0022] Figure 1 This is a flowchart of a repair method for composite material workpieces according to an embodiment of the present invention;
[0023] Figure 2 This is a schematic diagram of the repair method for composite material workpieces according to an embodiment of the present invention;
[0024] Figure 3 This is a structural schematic diagram from another angle of the repair method for composite material workpieces according to an embodiment of the present invention;
[0025] Figure 4 This is a schematic diagram of the mixing of adhesives in step S2 of the repair method for composite material workpieces according to an embodiment of the present invention;
[0026] Figure 5This is a schematic diagram of the laying and repairing layer in S3 of the repair method for composite material workpieces according to an embodiment of the present invention;
[0027] Figure 6 This is a schematic diagram of the progressive porous isolation membrane in the repair method for composite material workpieces according to an embodiment of the present invention;
[0028] Figure 7 This is a table showing the relationship between the number and area of repair layers and the adhesive absorption layer in S3 and S4 of the repair method for composite material workpieces according to an embodiment of the present invention.
[0029] In the diagram, 1 is a composite material workpiece;
[0030] 2. Repair the pavement blocks; 201. Repair the pavement layers;
[0031] 3. Vacuum compaction assembly; 301. Frame; 302. Vacuum bag;
[0032] 4. Gradient-type porous separator membrane; 401. Overflow hole;
[0033] 5. Adhesive-absorbing layer;
[0034] 6. Non-porous separator membrane;
[0035] 7. Pressure equalizing plate. Detailed Implementation
[0036] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.
[0037] In the description of this invention, the terms "upper," "lower," "left," "right," "front," "rear," "inner," "outer," "lateral," and "longitudinal," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are used only for the convenience of describing the invention and simplifying the description. They are not intended to limit the indicated devices, elements, or components to having a specific orientation, or to be constructed and operated in a specific orientation, and therefore should not be construed as limiting this utility model. Those skilled in the art can understand the specific meaning of these terms in this invention according to the specific circumstances.
[0038] In the description of this invention, the terms "provided with," "set up," "connected," and "placed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, elements, or components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.
[0039] Furthermore, the terms "first," "second," etc., are primarily used to distinguish different devices, elements, or components (which may be the same or different in specific type and construction), and are not intended to indicate or imply the relative importance or quantity of the indicated devices, elements, or components. Unless otherwise stated, "a plurality of" means two or more.
[0040] The technical solution of the present invention will be further described below with reference to the embodiments and accompanying drawings.
[0041] like Figure 1 , 2 As shown in Figure 6, a repair method for a composite material workpiece 1 according to an embodiment of the present invention employs a vacuum compaction assembly 3. The vacuum compaction assembly 3 includes a frame 301 and a vacuum bag 302 disposed on the inner peripheral wall of the frame 301. The method is characterized by including the following steps:
[0042] S1. Grind the damaged notch of composite material workpiece 1;
[0043] S2, Prepare repair layer 201;
[0044] S3. Repair ply 201 is laid layer by layer from bottom to top at the damaged gap. The area of repair ply 201 gradually increases from bottom to top. Each layer of repair ply 201 is rolled and compacted during laying. Multiple repair ply 201 are stacked to form repair ply block 2.
[0045] S4. Lay the gradient porous isolation membrane 4, adhesive absorption layer 5, non-porous isolation membrane 6 and pressure equalization plate 7 in sequence above the repair block 2.
[0046] S5. Frame 301 is bonded to composite material workpiece 1. Vacuum bag 302 is located above the damaged notch. Vacuum bag 302 abuts against pressure equalization plate 7. Vacuum bag 302 is vacuumed and compacted.
[0047] The gradient porous isolation membrane 4 has several overflow holes 401 whose diameter gradually decreases from the inside to the outside.
[0048] Based on the above technical solution, during the application of the repair layer 201, each repair layer 201 is rolled and compacted to ensure tight adhesion between each repair layer 201, eliminating gaps between layers and controlling the porosity between the repair layers 201. A gradient porous release membrane 4 is laid on top of the repair block 2. The gradient porous release membrane 4 has overflow holes 401 with gradually decreasing pore size from the inside to the outside. After multiple tests, it was found that the repair block 2 has the highest structural strength when its thickness is 0.16-0.24mm. Since the resin thickness of the repair block 2 increases closer to the inside, more resin needs to overflow. To reduce the thickness of the adhesive layer, the closer the repair ply 2 is to the outer side, the thinner its adhesive layer. Therefore, a small amount of overflowing resin is needed to ensure the thickness of the repair ply 2 and increase its structural strength. When the amount of overflowing resin is too large, it will lead to a resin shortage phenomenon at the repair interface, resulting in weak bonding, significantly reducing the bonding strength, and causing the repair ply 201 to detach prematurely. On the other hand, when the amount of overflowing resin is too small, it will lead to an excessively thick adhesive layer, which will cause the pores to increase continuously during the bonding process, and the porosity between the repair ply 201 will increase. The presence of pores will have an adverse effect on the modulus, strength, and fatigue performance of the composite material, reducing the safety and reliability of the composite material structure.
[0049] Preferably, such as Figure 4 As shown, in step S2, the repair layup 201 is prepared using resin. Step S2 includes a mixing operation, in which the resin is stirred at a uniform speed and in the same direction. During mixing, the resin is stirred at a uniform speed and in the same direction to minimize air entrainment into the resin, ensuring the porosity of each repair layup 201 during the repair process.
[0050] Preferably, such as Figure 5 As shown, in step S3, one side of the repair ply 201 is first laid onto the composite material workpiece 1. A roller is then rolled and placed on the laid side of the repair ply 201. While laying the remaining portion of the repair ply 201, the roller is used to compact it. Rolling in the same direction while laying the repair ply 201 removes air between adjacent repair plies 201, ensuring that the repair plies 201 adhere to each other without gaps.
[0051] Preferably, such as Figure 7 As shown, in S3 and S4, when the number of repair layers 201 is 1-4 layers and the area of the repair layer 201 is 80-100, the adhesive-absorbing layer 5 includes a first glass fiber, and the area of the first glass fiber is larger than the area of the uppermost repair layer 201.
[0052] Preferably, in S3 and S4, when the number of repair layers 201 is 5-8 layers and the area of the repair layer 201 is 100-150, the adhesive-absorbing layer 5 includes a second glass fiber and a first glass fiber stacked sequentially from bottom to top. The area of the second glass fiber is larger than the area of the repair layer 201 located on the top layer, and the area of the first glass fiber is equal to the area of the repair layer 201 located on the first layer.
[0053] Preferably, in S3 and S4, when the number of repair layers 201 is 9-16 layers and the area of the repair layer 201 is 150-200, the adhesive-absorbing layer 5 includes a second glass fiber and two layers of first glass fiber stacked sequentially from bottom to top. The area of the second glass fiber in the first layer is greater than the area of the repair layer 201 in the top layer, the area of the first glass fiber in the second layer is equal to the area of the repair layer 201 in the first layer, and the area of the first glass fiber in the third layer is equal to the area of the repair layer 201 in the eighth layer.
[0054] Preferably, in S3 and S4, when the number of repair layers 201 is 16-28 and the area of the repair layers 201 is 200-400, the adhesive-absorbing layer 5 includes a second glass fiber and three layers of first glass fiber stacked sequentially from bottom to top. The area of the second glass fiber in the first layer is greater than the area of the repair layer 201 in the topmost layer. The area of the first glass fiber in the second layer is equal to the area of the repair layer 201 in the first layer. The area of the first glass fiber in the third layer is equal to the area of the repair layer 201 in the eighth layer. The area of the first glass fiber in the fourth layer is equal to the area of the repair layer 201 in the fourteenth layer.
[0055] More preferably, the first glass fiber has a fiber diameter of 10-14 μm, and the second glass fiber has a fiber diameter of 16-20 μm.
[0056] The above technical solution is based on multiple experiments and the number, size and diameter of glass fiber in the adhesive absorption layer 5 are determined according to the number and area of the repair ply 201. This solution can limit the thickness of the repair ply 2 to a certain extent and ensure the structural strength of the repair ply 2.
[0057] It should be noted that the appendix Figure 7 The term "full size" refers to the fact that each edge of the glass fiber is 125.4 mm larger than the largest repair layer 201.
[0058] Preferably, such as Figure 3As shown, the equalizing plate 7 is made of a flexible material. The material used for the equalizing plate 7 is preferably a rubber sheet or a pure aluminum sheet with a thickness of 0.012 in-0.016 in. Since the area of the repair ply 201 adjacent to and above the first repair ply 201 is larger than that of the first repair ply 201, and the area of the repair ply 201 adjacent to and below the first repair ply 201 is smaller than that of the first repair ply 201, the outer edges of several repair plies 201 together define an interlayer bridging. If a rigid equalizing plate 7 is used for compaction, the applied pressure is not uniform enough, and the interlayer bridging may deform due to excessive pressure, resulting in pores between the repair plies 201. Using a flexible equalizing plate 7 ensures uniform pressure applied to the repair plies 201, the interlayer bridging hardly deforms, has good adhesion, and is beneficial for controlling porosity.
[0059] Preferably, in S5, during vacuum pressing, the repair layup 201 is preheated to 28-32°C. Preheating improves the fluidity of the resin, further mixes the resin, reduces air that may be present in the repair layup 201, controls porosity, and increases the structural strength of the repair layup 201.
[0060] In summary, this invention provides a repair method for composite material workpieces. During the application of the repair layer 201, each repair layer 201 is rolled and compacted to ensure tight adhesion between layers, eliminating gaps and controlling porosity. A gradient porous release membrane 4 is laid above the repair block 2. The gradient porous release membrane 4 has overflow holes 401 with gradually decreasing pore size from the inside to the outside. Since the resin thickness is greater closer to the inside of the repair block 2, more resin needs to overflow to reduce the thickness of the adhesive layer. Conversely, the adhesive layer thickness is smaller closer to the outside of the repair block 2, requiring only a small amount of overflowing resin to maintain the thickness of the repair block 2. Furthermore, the reduced thickness of the repair block 2 also reduces its porosity, thereby ensuring its structural strength.
[0061] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.
Claims
1. A repair method for composite material workpieces, employing a vacuum compaction assembly (3), the vacuum compaction assembly (3) comprising a frame (301) and a vacuum bag (302) disposed on the inner peripheral wall of the frame (301), characterized in that, Includes the following steps: S1. Grind the damaged gaps of the composite material workpiece (1); S2, Prepare the repair layer (201); S3. The repair layer (201) is laid layer by layer from bottom to top at the damaged gap. The area of the repair layer (201) gradually increases from bottom to top. Each layer of the repair layer (201) is rolled and compacted when it is laid. Multiple repair layers (201) are stacked to form a repair block (2). S4. A gradient porous isolation membrane (4), an adhesive-absorbing layer (5), a non-porous isolation membrane (6), and a pressure equalizing plate (7) are laid sequentially on top of the repair block (2). S5. The frame (301) is bonded to the composite material workpiece (1), the vacuum bag (302) is located above the damage gap, the vacuum bag (302) abuts against the pressure equalizing plate (7), and the vacuum bag (302) is vacuumed and vacuum compacted. The gradient porous isolation membrane (4) has several overflow holes (401) with gradually decreasing diameters from the inside to the outside.
2. The repair method for composite material workpieces according to claim 1, characterized in that, In S2, the repair layer (201) is made of resin. Step S2 includes a mixing operation in which the resin is stirred at a uniform speed and in the same direction.
3. The repair method for composite material workpieces according to claim 1, characterized in that, In S3, one side of the repair layer (201) is first laid on the composite material workpiece (1), and a roller is rolled and placed on the laid side of the repair layer (201). While laying the remaining part of the repair layer (201), the roller is used to roll and compact it.
4. The repair method for composite material workpieces according to claim 1, characterized in that, In S3 and S4, when the number of repair layers (201) is 1-4 layers, the area of the repair layer (201) is 80-100, and the adhesive-absorbing layer (5) includes a first glass fiber, the area of which is larger than the area of the uppermost repair layer (201).
5. The repair method for composite material workpieces according to claim 1, characterized in that, In S3 and S4, when the number of repair layers (201) is 5-8 layers, the area of the repair layer (201) is 100-150. The adhesive-absorbing layer (5) includes a second glass fiber and a first glass fiber stacked sequentially from bottom to top. The area of the second glass fiber is greater than the area of the repair layer (201) located on the top layer, and the area of the first glass fiber is equal to the area of the repair layer (201) located on the first layer.
6. The repair method for composite material workpieces according to claim 1, characterized in that, In S3 and S4, when the number of repair layers (201) is 9-16 layers, the area of the repair layer (201) is 150-200. The adhesive-absorbing layer (5) includes a second glass fiber and two layers of first glass fiber stacked sequentially from bottom to top. The area of the second glass fiber in the first layer is greater than the area of the repair layer (201) in the top layer. The area of the first glass fiber in the second layer is equal to the area of the repair layer (201) in the first layer. The area of the first glass fiber in the third layer is equal to the area of the repair layer (201) in the eighth layer.
7. The repair method for composite material workpieces according to claim 1, characterized in that, In S3 and S4, when the number of repair layers (201) is 16-28 layers, the area of the repair layer (201) is 200-400. The adhesive-absorbing layer (5) includes a second glass fiber and three layers of first glass fiber stacked sequentially from bottom to top. The area of the second glass fiber in the first layer is greater than the area of the repair layer (201) in the topmost layer. The area of the first glass fiber in the second layer is equal to the area of the repair layer (201) in the first layer. The area of the first glass fiber in the third layer is equal to the area of the repair layer (201) in the eighth layer. The area of the first glass fiber in the fourth layer is equal to the area of the repair layer (201) in the fourteenth layer.
8. The repair method for composite material workpieces according to any one of claims 4-7, characterized in that, The first glass fiber has a diameter of 10-14 μm, and the second glass fiber has a diameter of 16-20 μm.
9. The repair method for composite material workpieces according to claim 1, characterized in that, In S4, the equalizing plate (7) is made of a flexible material.
10. The repair method for composite material workpieces according to claim 1, characterized in that, In S5, during vacuum pressing, the repair layer (201) is preheated to 28-32°C.