A delamination resistant composite joint forming die and method

Abstract

The application discloses a layered-preventing composite material joint forming die and forming method. The device part comprises a die, a composite material lining and a pressing plate. The wedge is linked with the outer die through a screw. The screw is removed after the die pressing is completed and before curing, so that the wedge can freely move during the curing process without affecting the joint and causing layered defects of the joint. Meanwhile, the wedge is always in contact with the outer die during the curing process, plays a role in heat transfer and improves the curing efficiency. The expansion coefficient of the composite material lining is the same as that of the composite material joint. During the curing process, the composite material lining will not generate force on the joint due to different deformation amounts, so as to cause layered phenomenon. Meanwhile, the composite material lining has good mechanical properties and can resist the stress of the joint caused by the deformation of the die during the curing process, so as to avoid the deformation of the die and layered phenomenon of the joint. The top block on the inner die can push out the inner die and the composite material joint during demolding, so as to realize rapid demolding.

Description

Technical Field

[0001] This invention relates to the field of molding die technology, and in particular to a molding die and molding method for an anti-delamination composite material joint. Background Technology

[0002] The joint is a major component of the solid rocket motor casing. As a primary load-bearing part within the casing, it is subjected to complex load conditions, thus requiring high mechanical properties and dimensional accuracy. Traditional solid rocket motor casing joints are typically made of aerospace-grade aluminum alloys, titanium alloys, and high-strength structural steel, with the total mass of the metal joint accounting for approximately 10-15% of the casing's weight. The application of carbon fiber composite material joints can reduce the weight of similar metal joints by 30%-50% while maintaining the same load-bearing capacity.

[0003] High-performance fiber-reinforced resin matrix composites possess high specific strength, high specific stiffness, strong design flexibility, and excellent high-temperature resistance and erosion resistance. They are gradually becoming important structural materials for high-end applications in aerospace, aviation, and energy storage, and represent the mainstream development direction for high-performance solid rocket casings and joints worldwide. Using composite materials can effectively reduce the structural mass of solid rocket motor casing joints, improve payload capacity, and achieve both economic and military benefits. Therefore, selecting lightweight, high-strength composite materials for casing joint fabrication is a crucial approach to promoting solid rocket motor technology development and a key determinant of rocket motor performance improvement. However, during the curing process of composite material joints, delamination defects are prone to occur due to the difference in expansion coefficients between the molding die and the composite material during curing, posing a significant problem in the composite material joint molding process.

[0004] Furthermore, existing composite material joint molding dies typically consist of an upper and lower mold, or an upper mold, an inner mold, and an outer mold. These dies often present difficulties in demolding. The components of existing composite material joint molding dies are usually solid or internally hollowed-out. Since the composite material joint molding process requires heating and curing, solid structures, due to the difference in thermal expansion coefficients between the mold material and the composite material, are prone to localized stress concentrations during curing due to different deformation amounts, leading to delamination defects in the composite material joint. Simultaneously, hollow structures suffer from poor heat transfer and low curing efficiency during the curing process. Summary of the Invention

[0005] The purpose of this invention is to provide a molding die and molding method for anti-delamination composite material joints to solve the problems existing in the prior art, avoid delamination of composite material joints during curing, and at the same time take into account the problems of different deformation during curing, poor heat transfer, low curing efficiency, and difficulty in demolding after molding. This invention improves curing efficiency, enhances cooling efficiency, and achieves rapid demolding.

[0006] To achieve the above objectives, the present invention provides the following solution: The present invention provides a molding die for an anti-delamination composite material joint, comprising...

[0007] A mold, comprising an outer mold and an inner mold, the inner mold being installed inside the outer mold, and the outer mold having a wedge groove circumferentially formed therein, wherein a wedge is detachably inserted into the wedge groove; and

[0008] The composite material liner has the same coefficient of thermal expansion as the composite material joint. The composite material liner is fitted into the cavity formed by the connection between the inner mold and the outer mold. A release cloth is attached to the inner surface of the composite material liner, and prepreg is laid on the composite material liner.

[0009] A pressure plate is provided on the top of the mold, and the pressure plate is used to apply pressure to compact the prepreg.

[0010] Preferably, the bottom of the inner mold is provided with a plurality of top blocks, and the connecting plate of the outer mold is provided with a plurality of top block holes corresponding to the top blocks, and the top blocks are inserted into the corresponding top block holes.

[0011] Preferably, the inner mold and the outer mold are connected by screws.

[0012] Preferably, both the outer periphery of the inner mold and the outer periphery of the outer mold are provided with multiple overflow grooves, from which excess resin overflows.

[0013] Preferably, the top surface of the pressure plate is the upper heating surface of the forming mold, and the bottom surface of the outer mold is the lower heating surface of the forming mold.

[0014] Preferably, eye bolt holes are provided on the outer side of the wedge and the top surface of the pressure plate.

[0015] The present invention also provides a method for molding an anti-delamination composite material joint, applied to the above-mentioned anti-delamination composite material joint molding die, comprising the following steps:

[0016] Step 1: First, connect the inner mold and the outer mold with screws. Insert the composite material liner into the cavity between the inner mold and the outer mold. Apply a release cloth to the inner surface of the composite material liner and then lay the prepreg. After laying, embed the wedge into the wedge slot and connect the wedge to the outer mold with screws. Then, cover with the pressure plate and apply pressure to compact the prepreg. Excess resin overflows from the overflow groove.

[0017] Step 2: Place the mold into the curing oven. Select a suitable curing regime according to the resin characteristics. Remove the screws before curing to make the wedge movable during curing. Heat the mold through the upper heating surface and the lower heating surface.

[0018] Step 3: After curing, cool down by removing the wedge using the eye bolts to increase cooling efficiency;

[0019] Step 4: First, remove the pressure plate using the eye bolts, then use the top block to push the inner mold and composite material joint out of the outer mold, and tear off the release cloth to complete the demolding.

[0020] The present invention achieves the following beneficial technical effects compared to the prior art:

[0021] The present invention relates to a molding die and molding method for anti-delamination composite material joints. The device includes a mold, a composite material liner, and a pressure plate. A wedge is connected to the outer mold by screws. After molding and before curing, the screws are removed so that the wedge can move freely during curing without affecting the joint and causing delamination defects. Simultaneously, the wedge remains in contact with the outer mold during curing, transferring heat and improving curing efficiency. The composite material liner has the same coefficient of thermal expansion as the composite material joint, preventing different deformation amounts from exerting forces on the joint during curing and thus avoiding delamination. Furthermore, the composite material liner possesses excellent mechanical properties, resisting stress on the joint caused by mold deformation during curing and preventing mold deformation leading to delamination. A top block on the inner mold ejects the inner mold and composite material joint during demolding, enabling rapid demolding. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the assembly of the anti-delamination composite material joint molding die in an embodiment of the present invention;

[0024] Figure 2 A schematic diagram showing the disassembly of a mold for forming composite material joints to prevent delamination;

[0025] Figure 3 This is a schematic diagram showing the connection method between the inner mold and the outer mold;

[0026] Figure 4 This is a breakdown diagram of the structural components of the outer mold;

[0027] The components are as follows: 1. Pressure plate; 2. Composite material liner; 3. Inner mold; 4. Outer mold; 5. Wedge block; 6. Screw one; 7. Screw two; 8. Screw three; 11. Screw hole one; 12. Upper heating surface; 31. Glue overflow groove; 32. Screw hole two; 33. Top block; 41. Glue overflow groove; 42. Screw hole three; 43. Top block hole; 44. Screw hole four; 45. Wedge block groove; 46. Lower heating surface; 51. Screw hole five; 52. Lifting eye screw hole. Detailed Implementation

[0028] 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, 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 protection of the present invention.

[0029] The purpose of this invention is to provide a molding die and molding method for anti-delamination composite material joints to solve the problems existing in the prior art, avoid delamination of composite material joints during curing, and at the same time take into account the problems of different deformation during curing, poor heat transfer, low curing efficiency, and difficulty in demolding after molding. It improves curing efficiency, enhances cooling efficiency, and achieves rapid demolding.

[0030] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] like Figures 1-4 As shown, the present invention provides a molding die for an anti-delamination composite material joint, comprising:

[0032] The mold includes an outer mold 4 and an inner mold 3. The inner mold 3 is installed inside the outer mold 4. A wedge groove 45 is formed on the outer circumference of the outer mold 4, and a wedge 5 is detachably inserted into the wedge groove 45.

[0033] The composite material liner 2 has the same coefficient of expansion as the composite material joint. The composite material liner 2 is fitted into the cavity formed by the connection between the inner mold 3 and the outer mold 4. The inner surface of the composite material liner 2 is covered with a release cloth, and the prepreg is laid on the composite material liner 2.

[0034] Pressure plate 1: A pressure plate 1 is provided on the top of the mold. The pressure plate 1 is used to apply pressure to compact the prepreg.

[0035] In one embodiment, in order to achieve the positioning and installation of the inner mold 3 and the outer mold 4, the bottom of the inner mold 3 is provided with a plurality of top blocks 33, and the connecting plate of the outer mold 4 is provided with a plurality of top block holes 43 corresponding to the top blocks 33. The top blocks 33 are inserted into the corresponding top block holes 43 to achieve the positioning of the inner mold 3 and the outer mold 4; then the inner mold 3 and the outer mold 4 are connected by screws 6.

[0036] In one embodiment, multiple overflow grooves are provided on the outer periphery of the inner mold 3 and the outer periphery of the outer mold 4, and excess resin overflows from the overflow grooves.

[0037] In one embodiment, the top surface of the pressure plate 1 is the upper heating surface 12 of the forming mold, and the bottom surface of the outer mold 4 is the lower heating surface 46 of the forming mold.

[0038] In one embodiment, in order to facilitate the disassembly or transportation of the mold, the mold has multiple eye bolt holes 52, such as the outer side of the wedge block 5 and the top surface of the pressure plate 1.

[0039] The present invention also provides a method for forming a composite material joint to prevent delamination, comprising the following steps:

[0040] 1) First, connect the inner mold 3 and the outer mold 4 with screw 6, and pass the top block 33 through the top block hole 43. Fit the composite material liner 2 into the cavity formed by connecting the inner mold and the outer mold 4. Apply a release cloth to the inner surface of the composite material liner 2, and then lay the prepreg. After laying, insert the wedge 5 into the wedge groove 45, connect the wedge 5 to the outer mold 4 with screw 7, and then cover with the pressure plate 1 to apply pressure to compact the prepreg, squeezing out excess resin from the overflow tank to increase the relative fiber content.

[0041] 2) Curing of composite material joints. Place the mold into the curing oven, select a suitable curing regime according to the resin characteristics, remove screw 7 before curing to make wedge 5 movable during curing, and heat it through the upper heating surface 12 and the lower heating surface 46.

[0042] 3) Cooling down. When cooling down after curing is complete, wedge 5 is pulled out using screw 38 to increase cooling efficiency.

[0043] 4) Demolding of the finished product. First, remove the pressure plate 1 using screw 38, then remove screw 16, and use the top block 33 to push the inner mold 3 and the composite material joint out of the outer mold. Tear off the demolding cloth to complete the demolding.

[0044] This invention proposes a molding die for anti-delamination composite material joints. This structure primarily addresses the problem of delamination during the curing of composite material joints, while also considering issues such as different deformation during curing, poor heat transfer, low curing efficiency, and difficulty in demolding after molding. The die consists of an upper mold (pressure plate 1), an inner mold 3, an outer mold 4, a wedge block 5, a composite material liner 2, and screws. The wedge block 5 is connected to the outer mold 4 via screw 7. After molding and before curing, screw 7 can be removed, allowing the wedge block 5 to move freely during curing without affecting the joint and causing delamination defects. Simultaneously, the wedge block 5 remains in contact with the outer mold 4 throughout the curing process, effectively transferring heat and improving curing efficiency. During joint cooling, the wedge block 5 can be removed via screw 8, increasing the contact area between the mold and air and improving cooling efficiency. The composite material liner 2 has the same coefficient of thermal expansion as the composite material joint, preventing different deformation during curing from exerting forces on the joint and causing delamination. Meanwhile, the composite material liner 2 has excellent mechanical properties, which can resist the stress on the joint caused by the deformation of the mold during the curing process, and avoid delamination of the joint due to mold deformation. The top block 33 on the inner mold 3 can push the inner mold 3 and the composite material joint out during demolding, so as to achieve rapid demolding.

[0045] Compared to existing technologies, the anti-delamination composite material joint molding die of this invention has the following characteristics:

[0046] 1. Existing composite material joint molding molds are prone to delamination during the curing process. The mold of this invention avoids the occurrence of delamination during the curing process.

[0047] 2. Existing composite material joint molding dies use solid or hollow structures, which leads to large deformation or low heat transfer efficiency during the curing process. This invention proposes a freely movable wedge block, which avoids large deformation during the curing process and ensures efficient heat transfer during curing and heat dissipation during cooling.

[0048] 3. The present invention proposes a composite material liner 2 whose coefficient of expansion is the same as that of the composite material joint during the curing process. It will not cause stress to the joint due to the difference in deformation. At the same time, its good mechanical properties can resist the stress on the joint caused by the deformation of the mold during the curing process, and avoid the joint delamination caused by the deformation of the mold.

[0049] 4. The top block 33 on the inner mold 3 of the present invention can push out the inner mold 3 and the composite material joint during demolding, so as to achieve rapid demolding.

[0050] It should be noted that, for those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention, and no reference numerals in the claims should be construed as limiting the scope of the claims.

[0051] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A molding die for an anti-delamination composite material joint, characterized in that: include A mold, comprising an outer mold and an inner mold, the inner mold being installed inside the outer mold, and the outer mold having a wedge groove circumferentially formed therein, wherein a wedge is detachably inserted into the wedge groove; and The composite material liner has the same coefficient of thermal expansion as the composite material joint. The composite material liner is fitted into the cavity formed by the connection between the inner mold and the outer mold. A release cloth is attached to the inner surface of the composite material liner, and prepreg is laid on the release cloth. A pressure plate is provided on the top of the mold, and the pressure plate is used to apply pressure to compact the prepreg.

2. The anti-delamination composite material joint molding die according to claim 1, characterized in that: The bottom of the inner mold is provided with multiple top blocks, and the outer mold is provided with a connecting plate. The connecting plate of the outer mold has multiple top block holes corresponding to the top blocks, and the top blocks are inserted into the corresponding top block holes.

3. The anti-delamination composite material joint molding die according to claim 2, characterized in that: The inner mold and the outer mold are connected by screws.

4. The anti-delamination composite material joint molding die according to claim 3, characterized in that: Multiple overflow grooves are provided on the outer periphery of both the inner mold and the outer periphery of the outer mold, and excess resin overflows from the overflow grooves.

5. The anti-delamination composite material joint molding die according to claim 4, characterized in that: The top surface of the pressure plate is the upper heating surface of the forming mold, and the bottom surface of the outer mold is the lower heating surface of the forming mold.

6. The anti-delamination composite material joint molding die according to claim 5, characterized in that: The outer side of the wedge and the top surface of the pressure plate are provided with eye bolt holes.

7. A method for molding an anti-delamination composite material joint, applied to the anti-delamination composite material joint molding die described in claim 6, characterized in that, Includes the following steps: Step 1: First, connect the inner mold and the outer mold with screws. Place the composite material liner in the cavity between the inner mold and the outer mold. Apply a release cloth to the inner surface of the composite material liner and then lay the prepreg. After laying, embed the wedge into the wedge slot and connect the wedge to the outer mold with screws. Then cover with the pressure plate and apply pressure to compact the prepreg. Excess resin overflows from the overflow tank. Step 2: Place the mold into the curing oven. Select the appropriate curing regime according to the resin characteristics. Remove the screws before curing to make the wedge movable during curing. Heat the mold through the upper heating surface and the lower heating surface. Step 3: After curing, cool down by removing the wedge using the eye bolts to increase cooling efficiency; Step 4: Remove the pressure plate, then use the top block to push the inner mold and composite material joint out of the outer mold, and tear off the release cloth to complete the demolding.

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