Variable stiffness composite material component compression molding device and method

Abstract

The invention provides a compression molding device and method for a variable-stiffness composite material component. The device comprises an upper mold, a lower mold and a blank holder located between the upper mold and the lower mold. The blank holder comprises an upper blank holder and a lower blank holder, at least one side of the upper blank holder is provided with a blank pressing rib, the width of the blank pressing rib is gradually increased from one end to the other end, and the lower blank holder is provided with a blank pressing groove matched with the blank pressing rib. By means of the device, customized design of the fiber yarn included angle and rigidity performance of the composite material component can be obtained, and preparation of the variable-rigidity composite material component is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of composite material forming, and specifically to a molding device and method for variable stiffness composite material components by compression molding. Background Art

[0002] As a new material formed macroscopically by physical or chemical methods from two or more materials with different properties, composite materials have been widely used in many industrial fields due to their unique performance advantages, such as high strength, high toughness, lightweight, corrosion resistance, high temperature resistance, etc. For fields such as aerospace, automotive, and rail transit, lightweighting is one of the powerful measures to improve product performance, reduce R & D costs, and achieve energy conservation and emission reduction. Composite materials, especially continuous fiber reinforced resin matrix composite materials, have become an important means of lightweighting in these fields due to their excellent mechanical properties and lightweighting effects. For example, in the aerospace field, carbon fiber composite materials are widely used in the manufacture of aircraft structural components and skins, significantly reducing the weight of the aircraft and improving flight efficiency and fuel economy. In the automotive field, in recent years, with the rapid development of manufacturing technology and the continuous reduction of raw material costs, carbon fiber composite materials have begun to be used in the production of new generation automotive parts, such as body structural components and chassis parts, making important contributions to the lightweight development of automobiles.

[0003] There are various preparation processes for carbon fiber composite material components. Among them, the prepreg compression molding technology has advantages such as high automation degree, excellent mechanical properties, and good repeatability, and is suitable for batch production of automotive carbon fiber composite material parts. The prepreg compression molding process mainly includes the following four steps: (1) Laying: Lay the prepreg in the mold. This step requires ensuring uniform material distribution and removing air bubbles to ensure the quality of the finished product; (2) Hot pressing: Put the mold with the prepreg into a hot press and perform hot pressing molding at a certain temperature and pressure. This step is the key to forming the composite material, and the control of temperature and pressure directly affects the performance of the finished product; (3) Cooling: After hot pressing is completed, the product needs to be cooled to room temperature for subsequent processing; (4) Demolding: After cooling, take out the product from the mold and perform quality inspection and necessary trimming. It should be noted that due to the extremely small bending stiffness of fiber yarns, for complex carbon fiber composite material components, in order to avoid wrinkling defects caused by extrusion of fiber yarns during molding, a certain edge pressing force needs to be applied around the prepreg to induce shear deformation of the fiber yarns, so that they can smoothly fit the surface of the female mold during the mold closing process, avoiding wrinkling deformation of the fiber yarns and improving the molding quality of the product.

[0004] In the past, the hot molding devices for composite components often provided the required pre-tension force for the prepreg through a spring assembly or a blank-holder rib structure. By arranging spring assemblies with different stiffnesses around the prepreg, the pre-tension force in different regions can be controlled more flexibly. However, the spring connection operation is relatively cumbersome and the degree of automation is low. In contrast, the processing technology of the blank-holder rib structure is simpler, the operation is more convenient, and it can provide a greater pre-tension force for multi-layer prepregs. However, the blank-holder ribs in traditional hot molding devices for composite components often adopt an equal-width groove design. Although it can successfully induce shear deformation of fiber yarns to effectively suppress the wrinkling defect, it cannot achieve customized design of the shear angle of fiber yarns, so variable stiffness composite components cannot be prepared. Summary of the Invention

[0005] In order to solve the above problems of the prior art, the present invention provides a molding device and method for variable stiffness composite components, which can obtain customized design of the included angle and stiffness performance of the fiber yarns of the composite component and realize the preparation of variable stiffness composite components.

[0006] The present invention is realized through the following technical solutions: In a first aspect, the present invention provides a molding device for variable stiffness composite components, including: an upper mold, a lower mold, and a blank-holder ring located between the upper mold and the lower mold; the blank-holder ring includes an upper blank-holder ring and a lower blank-holder ring. At least one side of the upper blank-holder ring is provided with a blank-holder rib, and the width of the blank-holder rib gradually increases from one end to the other end. A blank-holder groove matching the blank-holder rib is provided on the lower blank-holder ring.

[0007] Preferably, the blank-holder rib is trapezoidal.

[0008] Preferably, blank-holder ribs are provided on both opposite sides of the upper blank-holder ring, and blank-holder grooves matching the blank-holder ribs are provided on both opposite sides of the lower blank-holder ring.

[0009] Preferably, when in use, the upper blank-holder ring and the lower blank-holder ring are connected by bolts.

[0010] Furthermore, an outward upper convex part is provided on the side of the upper blank-holder ring where the blank-holder rib is provided, and an outward lower convex part is provided on the side of the lower blank-holder ring where the blank-holder groove is provided; when in use, the upper convex part and the lower convex part are connected by bolts.

[0011] Preferably, feet are provided on the lower surface of the lower blank-holder ring.

[0012] Preferably, the upper mold includes a punch and an upper mounting member connected to the punch; the lower mold includes a die and a lower mounting member connected to the die; the punch cooperates with the die. Guide rods are provided on the lower mounting member, and guide holes matching the guide rods are provided on the upper mounting member; holes for the guide rods to pass through are provided on the upper blank-holder ring and the lower blank-holder ring.

[0013] In a second aspect, the present invention provides a molding method for a variable stiffness composite member, based on the molding device for a variable stiffness composite member described above, including: S1. Connect the upper mold to the upper plate of the hot press, and connect the lower mold to the lower plate of the hot press. S2. Place the lower blank holder on the lower mold, lay the composite prepreg on the lower blank holder, place the upper blank holder on the upper surface of the composite prepreg and connect it to the lower blank holder; start the hot press, close the upper mold and the lower mold, and wait for the hot press to finish working, then the variable stiffness composite member is prepared.

[0014] Preferably, in S2, lay polyimide films on the upper and lower surfaces of the composite prepreg, and then lay the composite prepreg on the lower blank holder.

[0015] Preferably, the upper mold includes a punch and an upper mounting member connected to the punch; the lower mold includes a die and a lower mounting member connected to the die; the punch cooperates with the die, a guide rod is provided on the lower mounting member, and a guide hole cooperating with the guide rod is provided on the upper mounting member; holes for the guide rod to pass through are provided on the upper blank holder and the lower blank holder. Before S2 and after S1, it further includes: move the upper mold downward, adjust the position of the lower mold until the guide post on the lower mounting member can pass through the guide hole on the upper mounting member, then the position of the lower mold is determined, and then move the upper mold upward. Specifically, S2 is: place the lower blank holder on the lower mold, the guide rod of the lower mounting member passes through the hole on the lower blank holder for the guide rod to pass through, lay the composite prepreg on the lower blank holder, place the upper blank holder on the upper surface of the composite prepreg, the guide rod of the lower mounting member passes through the hole on the upper blank holder for the guide rod to pass through, and connect the upper blank holder to the lower blank holder; start the hot press, close the upper mold and the lower mold, and wait for the hot press to finish working, then the variable stiffness composite member is prepared.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The device of the present invention can provide a horizontal pre-tensioning force for the composite prepreg by introducing a blank-holder rib structure, thereby effectively suppressing the wrinkling defect during the compression molding of the composite prepreg. At the same time, by adjusting the geometric characteristics of the blank-holder rib, the magnitude of the peripheral pre-tensioning force of the composite prepreg is controlled. The area corresponding to the narrower end of the blank-holder rib is smaller, and the pre-tensioning force borne by the composite prepreg inside this area is also smaller, and the corresponding fiber shear angle is smaller. On the contrary, more materials are constrained inside the wider end of the blank-holder rib, and the composite prepreg inside this area will bear a greater pre-tensioning force, resulting in more significant shear deformation of the composite prepreg and a larger shear angle, thereby realizing the gradient distribution of the peripheral pre-tensioning force of the composite prepreg, and further inducing different degrees of shear deformation of the fiber yarns at different positions of the composite component, realizing the gradient change of the shear angle of the fiber yarns, and finally successfully preparing a composite component with variable stiffness distribution characteristics. The variable stiffness composite component used as a vehicle body anti-collision structure can further improve its deformation mode and enhance its energy absorption level, and has broad application prospects in the field of automotive lightweight. The device of the present invention has the advantages of simple structure, easy processing, convenient operation, low cost, etc., and can be used for unidirectional fiber-reinforced composites, fabric-reinforced composites, thermoplastic composites, and thermosetting composites.

[0017] Furthermore, the present invention is provided with blank-holder ribs on both opposite sides of the upper blank-holder ring, which can more effectively induce the shear deformation of the fiber yarns and suppress the generation of wrinkling defects during the compression molding of the composite prepreg.

[0018] Furthermore, the present invention is provided with an outward upper convex part on the side of the upper blank-holder ring where the blank-holder rib is provided, and an outward lower convex part on the side of the lower blank-holder ring where the blank-holder groove is provided; during use, the upper convex part and the lower convex part are connected by bolts; compared with only connecting bolts at the four corners, the connection of the upper convex part and the lower convex part by bolts provides a greater pressing force for the middle area of the blank-holder ring, ensuring that the fiber yarns are pressed tightly.

[0019] Furthermore, the present invention is provided with guide rods on the lower mounting part and matching guide holes on the upper mounting part, so as to realize the positioning of the upper die and the lower die. At the same time, holes for the guide rods to pass through are provided on the upper blank-holder ring and the lower blank-holder ring, and the guide rods can be used to position the upper blank-holder ring and the lower blank-holder ring.

[0020] The molding method of the variable stiffness composite component of the present invention uses a blank holder to press the side edges of the composite prepreg into the internal blank holder grooves, causing a certain degree of horizontal pre-tension force to be borne on both sides of the composite prepreg, thereby inducing shear deformation of the fiber yarns during molding and effectively suppressing the generation of wrinkling defects. At the same time, since the widths of both ends of the blank holder ribs are different, the magnitudes of the peripheral pre-tension forces of the composite prepreg are different, and the corresponding fiber shear angles are different, and finally the prepared composite component has the characteristic of variable stiffness distribution.

[0021] Furthermore, the present invention uses a polyimide film when laying the composite prepreg to solve the problem of demolding of the component after molding. Brief Description of the Drawings

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0023] Figure 1 Isometric view of the appearance of the device of the present invention; Figure 2 Schematic diagram of the structure of the device of the present invention; Figure 3 Side view schematic diagram of the structure of the device of the present invention; Figure 4 Cross-sectional view schematic diagram of the structure of the device of the present invention; Figure 5 Front view schematic diagram of the blank holder of the device of the present invention; Figure 6 Side view schematic diagram of the blank holder of the device of the present invention; Figure 7 Front view schematic diagram of the lower blank holder of the device of the present invention; Figure 8 Schematic diagram of the mounting part on the device of the present invention; Figure 9 Schematic diagram of the lower mounting part of the device of the present invention; Figure 10 Schematic diagram of the change of the internal fiber angle of the component prepared by the device; Figure 11 Stress-strain curve diagram of three different angle laminates; Illustration serial number: 1—Punch, 15—Die; 2—Upper mounting part, 10—Lower mounting part; 6—Upper blank holder, 9—Lower blank holder; 7—Polyimide film; 8—Composite prepreg; 14—Floor feet. Detailed implementation manners

[0024] The following describes the implementation manners of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0025] It should be noted that the process equipment or devices not specifically noted in the following embodiments are all conventional equipment or devices in the art.

[0026] It should be noted that the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices. Moreover, unless otherwise specified, the numbers of the method steps are only convenient tools for identifying the method steps, rather than limiting the arrangement order of the method steps or the scope in which the present invention can be implemented. The change or adjustment of their relative relationship, without substantially changing the technical content, should also be regarded as the scope in which the present invention can be implemented.

[0027] Generally speaking, the device of the present invention mainly includes three parts, namely an upper mold, a blank holder ring and a lower mold. As Figures 1 to 4 shown, the blank holder ring is located between the upper mold and the lower mold; the blank holder ring includes an upper blank holder ring 6 and a lower blank holder ring 9. At least one side of the upper blank holder ring 6 is provided with blank holding ribs, and the width of the blank holding ribs gradually increases from one end to the other end. A blank holding groove matching the blank holding ribs is provided on the lower blank holder ring 9.

[0028] During use, the material on at least one side of the composite material prepreg 8 is pressed into the blank holding groove of the lower blank holder ring 9 by the blank holding ribs of the upper blank holder ring 6 to fix the composite material prepreg 8. When the upper mold moves downward, a certain degree of horizontal pre-tensioning force is applied to both sides of the composite material prepreg 8, effectively inducing the fiber yarns to undergo shear deformation and inhibiting the generation of fiber yarn wrinkling. Since the area corresponding to the narrower end of the blank holding ribs is smaller, the pre-tensioning force borne by the composite material prepreg 8 inside this area is also smaller, resulting in a weaker shear deformation degree of the fiber yarns in the composite material prepreg 8 during molding and a smaller corresponding fiber shear angle. On the contrary, more material is constrained inside the wider end of the blank holding ribs, and the composite material prepreg 8 inside this area will bear a greater pre-tensioning force, causing a more significant shear deformation of the composite material prepreg 8 and a larger shear angle, as Figure 10 shown. As Figure 11As shown, the larger the angle of the fiber, the smaller the stiffness of the composite member made therefrom, and the greater the toughness compared to the composite member with a smaller fiber angle. As the fiber angle increases, the stiffness of the composite member made at this location also gradually decreases. Therefore, by using the device of the present invention to change the fiber angle of the composite prepreg at different positions, the preparation of a variable-stiffness composite member can be achieved.

[0029] In some embodiments of the present invention, the blank holding rib is trapezoidal, such as a right trapezoid.

[0030] In some embodiments of the present invention, blank holding ribs are provided on both opposite sides of the upper blank holding ring 6. Similarly, blank holding grooves that cooperate with the blank holding ribs are provided on both opposite sides of the lower blank holding ring 9. By providing blank holding ribs on both sides of the upper blank holding ring, the shearing deformation of the fiber yarn can be more effectively induced and the generation of wrinkling defects during the compression molding of the composite prepreg 8 can be inhibited.

[0031] In some embodiments of the present invention, as Figures 5 to 7 shown, bolt holes are provided around the upper blank holding ring 6 and the lower blank holding ring 9. During use, the upper blank holding ring 6 and the lower blank holding ring 9 are connected by bolts. More preferably, an outward upper convex portion is provided on the side of the upper blank holding ring 6 where the blank holding rib is provided, and an outward lower convex portion is provided on the side of the lower blank holding ring 9 where the blank holding groove is provided; bolt holes are provided on the upper convex portion and the lower convex portion. During use, the upper convex portion and the lower convex portion are connected by bolts. Specifically, two bolt holes are provided on each of the upper convex portion and the lower convex portion, and bolt holes are provided at the four corners of the upper blank holding ring 6 and the lower blank holding ring 9, so that the upper blank holding ring 6 and the lower blank holding ring 9 are connected and fixed by eight bolts.

[0032] When fixing the upper blank holding ring 6 and the lower blank holding ring 9 with bolts, it is necessary to ensure that the torque received by each bolt is equal to ensure a uniform vertical load on the entire composite prepreg 8 after fixation. Therefore, when fixing the bolts, it is preferably to use an electronic torque wrench to ensure the consistency of the torque of each bolt.

[0033] In some embodiments of the present invention, the upper mold includes a punch 1 and an upper mounting member 2 connected to the punch 1 ( Figure 8 ); the lower mold includes a die 15 and a lower mounting member 10 connected to the die 15 ( Figure 9); The punch 1 cooperates with the die 15. The lower mounting part 10 is provided with guide rods, and the upper mounting part 2 is provided with guide holes for cooperating with the guide rods. The upper blank-holder 6 and the lower blank-holder 9 are provided with holes for the guide rods to pass through. The guide rods are used for positioning the upper blank-holder 6 and the lower blank-holder 9; at the same time, the position of the lower die is also determined by the guide rods: after installing the upper die, move it downward. When the upper mounting part 2 on the upper die is about to contact the guide rod of the lower mounting part 10, adjust the position of the lower die until the guide rod on the lower mounting part 10 can pass through the upper mounting part 2. At this time, the position of the lower die exactly corresponds to the position of the upper die. The setting of the guide rods can ensure the fixation of the relative positions of the whole device and prevent deviation in the correspondence between the punch and the die.

[0034] In a specific embodiment of the present invention, four upper mounting parts 2 are provided, which are respectively arranged at the four corners of the punch 1. The upper mounting parts 2 and the punch 1 are connected by a plurality of bolts (such as two). When the hot press works, both the punch 1 and the upper mounting parts 2 move downward simultaneously. Four lower mounting parts 10 are provided, which are respectively arranged at the four corners of the die 15 and are connected to the die 15 by bolts. The upper mounting parts 2 and the lower mounting parts 10 correspond one by one, and the guide rods on the lower mounting parts 10 and the guide holes on the upper mounting parts 2 correspond one by one.

[0035] In some embodiments of the present invention, the lower surface of the lower blank-holder 9 is connected with a floor 14 by bolts. The floor 14 serves to support the lower blank-holder 9, thereby ensuring that the upper plane of the lower blank-holder 9 and the upper plane of the die 15 are on the same horizontal plane. Specifically, four floors 14 can be provided, which are respectively arranged at the four corners of the lower blank-holder 9.

[0036] Embodiment Reference Figures 1 to 9 , the device of this embodiment includes three parts, namely the upper die, the blank-holder and the lower die. As Figure 2 and Figures 5 to 7 shown, the upper die includes a punch 1 and four upper mounting parts 2 connected to the punch 1 by bolts; the lower die includes a die 15 and four lower mounting parts 10 connected to the die 15 by bolts; the punch 1 cooperates with the die 15, the upper mounting parts 2 and the lower mounting parts 10 correspond one by one, the lower mounting parts 10 are provided with guide rods, the upper mounting parts 2 are provided with guide holes for cooperating with the guide rods, and the guide rods on the lower mounting parts 10 and the guide holes on the upper mounting parts 2 correspond one by one. The punch 1 and the die 15 are used to form a hat-shaped beam member.

[0037] The blank-holder includes an upper blank-holder 6 and a lower blank-holder 9. Right-angled trapezoidal blank-holding ribs are provided on two opposite sides of the upper blank-holder 6, and right-angled trapezoidal blank-holding grooves for cooperating with the blank-holding ribs are provided on the lower blank-holder 9. The upper blank-holder 6 and the lower blank-holder 9 are provided with holes for the guide rods to pass through.

[0038] On one side of the upper blank-holder ring 6 where the blank-holding ribs are provided, there is an outward upper convex part, and on one side of the lower blank-holder ring 9 where the blank-holding grooves are provided, there is an outward lower convex part; there are two bolt holes on the upper convex part and the lower convex part; bolt holes are provided at the four corners of the upper blank-holder ring 6 and the lower blank-holder ring 9. When in use, the upper blank-holder ring 6 and the lower blank-holder ring 9 are fixedly connected by eight bolts.

[0039] The lower surface of the lower blank-holder ring 9 is connected with four anchor feet 14 by bolts to ensure that the upper plane of the lower blank-holder ring 9 and the upper plane of the female die 15 are on the same horizontal plane.

[0040] When the device is in use, the specific operation steps are as follows: First, the punch is fixed to the four upper mounting parts 2 with hexagon head bolts to form the upper die, and the upper die is installed on the upper plate of the hot press with six hexagon head bolts to fix the upper die to the upper plate of the hot press without relative movement, ensuring the stability of the upper die during the working process. When installing the lower die, the hat-shaped beam female die is fixed to the four lower mounting parts 10 with bolts and placed on the upper plane of the lower plate of the hot press. Move the upper plate of the hot press downward. When the upper mounting part 2 is about to contact the lower mounting part 10, adjust the position of the lower die until the guide posts on the lower mounting part 10 can pass through the reserved guide holes on the upper mounting part 2, and the position of the lower die is determined.

[0041] Move the upper die upward to reserve enough space for installing the blank-holder ring. First, fix the lower blank-holder ring 9 to the anchor feet 14 with bolts, pass the guide rods of the lower mounting part 10 through the holes reserved near the four corners of the lower blank-holder ring 9 to determine the position of the lower blank-holder ring 9. Lay the polyimide film 7 tightly on the upper and lower surfaces of the composite material prepreg 8, and lay the composite material prepreg 8 with the polyimide film on the upper and lower surfaces flat on the upper surface of the lower blank-holder ring 9 in the direction of +45° / -45°. Fix the upper blank-holder ring 6 to the lower blank-holder ring 9 with eight bolts, and use the blank-holder ring to press the materials on both sides of the composite material prepreg 8 into the blank-holding grooves, so that the materials on both sides of the composite material prepreg 8 bear a certain degree of horizontal pre-tension force, thereby inducing shear deformation of the fiber yarns during molding and effectively suppressing the generation of wrinkling defects. After fixing the upper and lower blank-holder rings, adjust the temperature and displacement speed of the hot press, start closing the die, wait for the hot press to finish working, and the hat-shaped beam component is prepared.

[0042] When laying the prepreg, the device needs to be used in combination with the polyimide film to solve the problem of demolding of the component after molding.

[0043] As Figure 11 shown, the larger the angle of the fiber, the smaller the stiffness of the composite material component made of it, and the toughness is relatively larger than that of the composite material component with a smaller angle. As the fiber angle increases, the stiffness of the composite material component made here also gradually decreases, realizing the preparation of a variable-stiffness composite material component.

[0044] The device has a simple structure and a convenient operation process. It does not require complex processing and only needs one-time molding to prepare variable-stiffness composite components, providing a new solution for the customized design of the stiffness performance of composite parts. The variable-stiffness composite components prepared by using it can be applied to protective structures such as vehicle body anti-collision beams, energy-absorbing boxes, and B-pillars. Compared with ordinary metal body protective components, the variable-stiffness composite thin-walled energy-absorbing components prepared by using the device of the present invention do not need to additionally process crush-induced grooves to achieve the goal of stable deformation and energy absorption; when a vehicle frontal collision accident occurs, the variable-stiffness composite body front-section protective components (such as energy-absorbing boxes, front longitudinal beams, etc.) will undergo progressive crushing deformation from the side with weaker stiffness performance to the side with stronger stiffness performance, so as to achieve the effect of stably absorbing external impact energy, and will significantly reduce the peak load and acceleration at the moment of collision, thereby improving the collision safety performance of the whole vehicle and better protecting the lives of drivers and passengers in the vehicle.

Claims

1. A molding device for a variable stiffness composite member, characterized in that Comprising: An upper die, a lower die, and a blank holder located between the upper die and the lower die; the blank holder includes an upper blank holder (6) and a lower blank holder (9), at least one side of the upper blank holder (6) is provided with blank holding ribs, the width of the blank holding ribs gradually increases from one end to the other end, and the lower blank holder (9) is provided with blank holding grooves that cooperate with the blank holding ribs.

2. The molding device for variable stiffness composite components according to claim 1, characterized in that, The blank holding ribs are trapezoidal.

3. The compression molding device for variable stiffness composite components according to claim 1, characterized in that, Both opposite sides of the upper blank holder (6) are provided with blank holding ribs, and both opposite sides of the lower blank holder (9) are provided with blank holding grooves that cooperate with the blank holding ribs.

4. The compression molding device for variable stiffness composite components according to claim 1, characterized in that, During use, the upper blank holder (6) and the lower blank holder (9) are connected by bolts.

5. The variable stiffness composite component compression molding device according to claim 4, characterized in that, One side of the upper blank holder (6) where the blank holding ribs are provided is provided with an outward upper convex part, and one side of the lower blank holder (9) where the blank holding grooves are provided is provided with an outward lower convex part; during use, the upper convex part and the lower convex part are connected by bolts.

6. The compression molding device for variable stiffness composite components according to claim 1, characterized in that The lower surface of the lower blank holder (9) is provided with feet (14).

7. The compression molding device for variable stiffness composite components according to claim 1, characterized in that, The upper die includes a punch (1) and an upper mounting member (2) connected to the punch (1); the lower die includes a die cavity (15) and a lower mounting member (10) connected to the die cavity (15); the punch (1) cooperates with the die cavity (15), the lower mounting member (10) is provided with guide rods, and the upper mounting member (2) is provided with guide holes that cooperate with the guide rods; the upper blank holder (6) and the lower blank holder (9) are provided with holes for the guide rods to pass through.

8. A molding method for a variable stiffness composite component, characterized in that, Based on the variable stiffness composite component molding device according to any one of claims 1 to 7, comprising: S1, Connect the upper die to the upper plate of the hot press, and connect the lower die to the lower plate of the hot press; S2, Place the lower blank holder on the lower die, lay the composite prepreg (8) on the lower blank holder, place the upper blank holder on the upper surface of the composite prepreg (8) and connect it to the lower blank holder; start the hot press, close the upper die and the lower die, wait for the hot press to finish working, and the variable stiffness composite component is prepared.

9. The compression molding method of the variable stiffness composite member according to claim 8, characterized in that In S2, lay the polyimide film (7) on the upper and lower surfaces of the composite prepreg (8), and then lay the composite prepreg (8) on the lower blank holder.

10. The compression molding method of the variable stiffness composite component according to claim 8, characterized in that, The upper die includes a punch (1) and an upper mounting member (2) connected to the punch (1); the lower die includes a die cavity (15) and a lower mounting member (10) connected to the die cavity (15); the punch (1) cooperates with the die cavity (15), the lower mounting member (10) is provided with guide rods, and the upper mounting member (2) is provided with guide holes that cooperate with the guide rods; the upper blank holder (6) and the lower blank holder (9) are provided with holes for the guide rods to pass through; After S1 and before S2, it further includes: Move the upper die downward, adjust the position of the lower die until the guide posts on the lower mounting member can pass through the guide holes on the upper mounting member, complete the determination of the position of the lower die, and then move the upper die upward; Specifically, S2 is as follows: The blank holding ring (9) is placed on the lower die, the guide rods of the lower mounting part (10) pass through the holes in the blank holding ring (9) for the guide rods to pass through, the composite material prepreg (8) is laid on the blank holding ring, the upper blank holding ring (6) is placed on the upper surface of the composite material prepreg (8), the guide rods of the lower mounting part (10) pass through the holes in the upper blank holding ring (6) for the guide rods to pass through, and the upper blank holding ring (6) is connected to the lower blank holding ring (9); Start the hot press, close the upper die and the lower die, wait for the hot press to finish working, and the variable stiffness composite material component is prepared.

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