Molding device and molding method of thermoplastic composite material honeycomb sandwich structure

Abstract

The invention provides a forming device and a forming method for a thermoplastic composite honeycomb sandwich structure, and belongs to the technical field of composite forming. The problems that in an existing compression molding technology, the temperature resistance and pressure supply capacity of a mold are insufficient, and the prepreg positioning process is complex and tedious are solved. The forming device comprises a mold body and an electromagnetic base, the mold body comprises an upper panel, a core mold, four limiting blocks, a lower bottom plate and sliding blocks, the lower bottom plate is arranged on the electromagnetic base, the four limiting blocks are arranged on the lower bottom plate and surround in the circumferential direction, and the sliding blocks are placed on the inner wall sides of the limiting blocks. A plurality of core molds are arranged on the inner sides of the sliding blocks in an array mode, thermoplastic composite prepreg is placed between the sliding blocks and the core molds and between the adjacent core molds, the outer walls of the limiting blocks are inclined planes, inclined plane grooves matched with the inclined planes in angle are formed in the lower portion of the upper panel, and the lower bottom plate is covered with the upper panel. The method is mainly used for forming the thermoplastic composite honeycomb sandwich structure.

Description

Technical Field

[0001] This invention belongs to the field of composite material molding technology, and in particular relates to a molding device and molding method for a thermoplastic composite honeycomb sandwich structure. Background Technology

[0002] Thermoplastic composites have become key materials in the field of lightweight structures due to their excellent specific strength, impact resistance, and recyclability. Material systems using high-performance thermoplastic resins such as polyetheretherketone (PEEK) and polyphenylene sulfide (PPS) as the matrix and carbon fiber or glass fiber as the reinforcing phase exhibit outstanding advantages in temperature resistance, toughness, and reproducibility. However, molding these materials faces unique challenges: the materials have a certain degree of hardness at room temperature, making it difficult to achieve precise fitting and positioning with complex core molds; furthermore, their high softening temperature (typically ≥250℃) and high melt viscosity make them prone to thermo-oxidative aging at high temperatures, further affecting resin fluidity and the molding effect of sandwich structures.

[0003] In mass production, compression molding is a common process for preparing cores for composite sandwich structures. This process involves placing prepreg or preforms into a mold, heating and pressurizing them, venting and heat preservation, and then cooling and shaping. This method is characterized by its simplicity, high efficiency, low energy loss, and low cost of equipment and molds. However, for thermoplastic honeycomb sandwich structures, which have high molding requirements and complex porous geometries, traditional compression molding faces significant challenges in temperature control, pressurization, and prepreg placement. Current honeycomb core mold designs are mostly designed for thermosetting composites, which have low softening and molding temperatures. Mold designs not only struggle to overcome the extremely high temperatures involved in thermoplastic honeycomb core preparation but also rely on manual or vacuum bag pressurization, failing to meet the pressure requirements of thermoplastic composite molding. Furthermore, the high softening temperature of thermoplastic composites makes traditional placement methods ineffective. All these factors severely restrict the structural consistency and production efficiency of high-performance thermoplastic honeycomb cores. Therefore, there is an urgent need for a dedicated mold and molding method designed for thermoplastic honeycomb cores to achieve high-quality, high-efficiency integrated manufacturing. Summary of the Invention

[0004] In view of this, the present invention aims to provide a molding device and molding method for a thermoplastic composite honeycomb sandwich structure, so as to solve the problems of insufficient mold temperature resistance and pressure supply capacity, and complex and cumbersome prepreg positioning process in the existing compression molding process.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a molding device for a thermoplastic composite honeycomb sandwich structure, comprising a mold body and an electromagnetic base. The mold body includes an upper panel, a core mold, a limiting block, a lower base plate, and a sliding block. The lower base plate is mounted on the electromagnetic base. Four limiting blocks are arranged on the lower base plate, surrounding the structure circumferentially. Several sliding blocks are placed on the inner wall of the limiting blocks. Several core molds are arranged in an array on the inner side of the sliding blocks. The core molds, limiting blocks, and sliding blocks are all magnetically attracted. Thermoplastic composite prepreg is placed between the sliding blocks and the core molds, as well as between adjacent core molds. The outer wall of the limiting block is an inclined surface. A sloping groove matching the angle of the sloping surface is opened at the lower part of the upper panel. The upper panel covers the lower base plate, and the sloping groove abuts against the sloping surface.

[0006] Furthermore, the thermoplastic composite prepreg is a thermoplastic plain weave strip prepreg.

[0007] Furthermore, the upper panel and the lower base plate are connected by positioning pins.

[0008] Furthermore, a spiral groove is provided on the lower base plate, the inner side of the spiral groove is a boss structure, a groove is provided on the limiting block, the bottom of the limiting block is located in the spiral groove, and the boss and the groove are positioned correspondingly.

[0009] Furthermore, recessed platforms are provided at the four corners of the lower base plate.

[0010] Furthermore, the top plate is provided with threaded holes, which correspond to the position of the countersunk platform.

[0011] Furthermore, a pin opening is provided at the center of the core mold.

[0012] Furthermore, the angle between the inclined surface and the horizontal plane is 60°.

[0013] Furthermore, the core mold is a straight-walled hexahedral structure or a curved-walled hexahedral structure.

[0014] This invention also provides a molding method for a molding device for a thermoplastic composite honeycomb sandwich structure, specifically: cutting thermoplastic composite prepreg into strips, coating a release agent on the molding surface of the mold body, adsorbing the lower base plate onto the electromagnetic base, placing two limiting blocks vertically with their inner walls forming two right-angled sides, placing sliding blocks sequentially against the inner walls of the two limiting blocks, laying strip-shaped thermoplastic composite prepreg on the side of the sliding blocks, placing the core mold so that the core mold aligns with the side of the sliding block, laying strip-shaped thermoplastic composite prepreg on the other side of the core mold, and then sequentially placing the core mold and strip-shaped thermoplastic composite prepreg. After all core molds are placed, a core array is formed. Sliding blocks are placed on the other two sides of the core array, and two limiting blocks are placed outside the sliding blocks. The upper panel is covered on the lower base plate so that the inclined groove abuts against the inclined surface. The electromagnetic base is closed, the mold body is removed, and the mold body is placed in a preheated hot press for pressure curing.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention provides a molding device and molding method for a thermoplastic composite honeycomb sandwich structure. By specifically designing to address the difficulties in the preparation of traditional honeycomb sandwich structures, it achieves systematic improvements in mold temperature resistance and deformation resistance, pressure distribution control, layup positioning efficiency, and overall process feasibility. This invention significantly enhances the thermal rigidity and dimensional stability of the mold under high-temperature forming conditions by using integral mold steel processing, effectively overcoming the problem of uneven honeycomb cell structure caused by easy deformation of traditional molds. Through a limiting block with a 60° inclined surface, combined with a sloping groove of the same angle on the top panel, the unidirectional vertical pressure of the hot press is converted into triaxial multi-directional pressure, achieving full compaction of the honeycomb node area and directional resin flow, improving the interlayer bonding strength and mechanical consistency of the core. By setting an electromagnetic base to adsorb the mold body, rapid, precise, and non-contact positioning and fixing of the rigid thermoplastic plain weave composite material is achieved, completely solving the problems of cumbersome, misaligned, and wrinkled traditional layup processes. Simultaneously, the integrated and optimized demolding structure of the mold makes the assembly, molding, and demolding processes integrated and repeatable, significantly reducing operational complexity and production cycle. This solution not only effectively addresses the process challenges under high temperature and high pressure, but also provides a reliable and flexible solution for the high-quality, high-efficiency, and large-scale manufacturing of complex three-dimensional honeycomb sandwich structures. Attached Figure Description

[0016] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the molding device for a thermoplastic composite honeycomb sandwich structure according to the present invention; Figure 2 This is a schematic diagram of the lower base plate structure described in this invention; Figure 3 This is a schematic diagram of the limiting block structure described in this invention; Figure 4 This is a schematic cross-sectional view of the upper panel structure described in this invention; Figure 5 This is a schematic diagram of the core mold structure described in this invention; Figure 6 This is a schematic diagram of the straight-walled hexahedral honeycomb structure described in this invention; Figure 7 This is a schematic diagram of the curved wall hexahedral honeycomb structure described in this invention.

[0017] In the picture: 1-Top panel, 2-Core mold, 3-Limiting block, 4-Lower base plate, 5-Electromagnetic base, 6-Sliding block, 7-Positioning pin, 8-U-shaped groove, 9-Boss, 10-Sunken platform, 11-Groove, 12-Inclined surface, 13-Inclined groove, 14-Pin opening. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other, and the described embodiments are only some embodiments of the present invention, not all embodiments.

[0019] See Figure 1-7 This embodiment describes a molding device for a thermoplastic composite honeycomb sandwich structure, comprising a mold body and an electromagnetic base 5. The mold body includes an upper panel 1, a core mold 2, a limiting block 3, a lower base plate 4, and sliding blocks 6. The lower base plate 4 is mounted on the electromagnetic base 5, and four limiting blocks 3 are arranged on the lower base plate 4, forming a circumferential enclosure. Several sliding blocks 6 are placed on the inner wall of each limiting block 3, and several core molds 2 are arranged in an array on the inner side of each sliding block 6. The core molds 2, limiting blocks 3, and sliding blocks 6 are all magnetically attracted. Thermoplastic composite prepreg is placed between the sliding blocks 6 and the core molds 2, as well as between adjacent core molds 2. The outer wall of the limiting block 3 is an inclined surface 12. The lower part of the upper panel 1 has an inclined groove 13 that matches the angle of the inclined surface 12. The upper panel 1 covers the lower base plate 4, and the inclined groove 13 abuts against the inclined surface 12.

[0020] The thermoplastic composite prepreg described in this embodiment is a thermoplastic plain weave strip prepreg. The upper panel 1 and the lower base plate 4 are connected by positioning pins 7.

[0021] To facilitate subsequent mold opening and demolding, a spiral groove 8 is provided on the lower base plate 4. The inner side of the spiral groove 8 has a boss 9 structure, and a groove 11 is provided on the limiting block 3. The bottom of the limiting block 3 is located in the spiral groove 8, and the boss 9 and the groove 11 are positioned correspondingly. By limiting the size, a certain gap is maintained between the limiting block 3 and the lower base plate 4 after the structure is formed. Tools such as pry tools can be inserted into the gap and pried to remove the limiting block 3, facilitating the removal of the core structure.

[0022] To facilitate subsequent mold opening and demolding, recessed platforms 10 are provided at the four corners of the lower base plate 4. A screwdriver or pry tool can be used to perform initial mold movements to separate the upper panel 1 from the lower base plate 4.

[0023] To facilitate subsequent mold opening and demolding, threaded holes are provided on the upper panel 1, and the threaded holes correspond to the positions of the countersunk platform 10. Bolts are screwed into the threaded holes to eject the entire upper panel 1. This method allows for the even lifting of the upper panel 1 using bolts, avoiding structural damage caused by forceful mold opening.

[0024] To facilitate subsequent mold opening and demolding, a pin opening 14 is provided in the center of the core mold 2, which can be used with a pin remover to remove the core mold 2.

[0025] To ensure that the uniaxial vertical pressure of the hot press can be smoothly converted into triaxial multi-directional pressure during hot pressing, the angle between the inclined surface 12 and the horizontal plane is greater than 50°, preferably 60°, and the inclined groove 13 has the same angle as the inclined surface 12 to avoid jamming.

[0026] In this embodiment, the core mold 2 has a straight-walled hexahedral structure, thereby forming a straight-walled hexahedral honeycomb structure, such as... Figure 6 As shown. The core mold 2 can also be a curved-wall hexahedral structure, thereby forming a curved-wall hexahedral honeycomb structure, such as... Figure 7 As shown. The core mold 2 can also be replaced in various ways to achieve the fabrication of honeycomb structures with different unit cell forms.

[0027] This embodiment describes a molding method for a molding device for a thermoplastic composite honeycomb sandwich structure, specifically as follows: The thermoplastic composite prepreg is cut into strips of appropriate size, and a release agent is applied to the molding surface of the mold body to facilitate subsequent demolding. The lower base plate 4 is attached to the electromagnetic base 5, and the magnetic force is adjusted so that the core mold 2 can be properly attached and move without obstruction.

[0028] Two limiting blocks 3 are placed vertically and magnetically attracted. Taking the left limiting block and the front limiting block as an example, the inner walls of the left limiting block and the front limiting block form two right-angled sides. Sliding blocks 6 are placed in sequence close to the inner walls of the left limiting block and the front limiting block, and strip-shaped thermoplastic composite prepreg is laid on the side of the sliding block 6.

[0029] Place the first row of core molds 2 so that the core molds 2 align with the side of the sliding block 6 and adhere tightly to the strip-shaped thermoplastic composite prepreg. Lay the strip-shaped thermoplastic composite prepreg on the other side of the first row of core molds 2. Then, place the core molds 2 and the strip-shaped thermoplastic composite prepreg in sequence. After all the core molds 2 are placed, a core array is formed.

[0030] Place the rear sliding block 6 and the right sliding block 6 on the right side of the core array. Place the rear limiting block 3 and the right limiting block 3 outside the rear sliding block 6 and the right sliding block 6. Insert the positioning pin 7 into the corresponding opening on the lower base plate 4, match the positioning pin 7 with the opening of the upper panel 1, and perform the mold closing operation of the upper panel 1 so that the upper panel 1 covers the lower base plate 4, and the inclined groove 13 abuts against the inclined surface 12.

[0031] Turn off electromagnetic base 5, remove the mold body, and place the mold body into a preheated hot press for pressure curing. Specifically: the normal curing temperature of the material is 380℃. During pressure curing, first preheat the hot press to 400℃, place the mold body into the hot press, and perform pre-molding to achieve rapid heating of the mold body. After heat conduction is completed, gradually increase the pressure to enter the heat preservation stage to avoid problems such as wrinkles in the prepreg caused by sudden pressure. After the heat preservation stage is completed, maintain the pressure and cool down to complete the curing process. Then remove the mold and perform mold opening and demolding.

[0032] The specific embodiments of the present invention disclosed above are merely illustrative of the invention. These embodiments do not exhaustively describe all details, nor do they limit the invention to the specific embodiments described. Many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A molding device for a thermoplastic composite honeycomb sandwich structure, characterized in that: It includes a mold body and an electromagnetic base (5). The mold body includes an upper panel (1), a core mold (2), a limiting block (3), a lower base plate (4), and sliding blocks (6). The lower base plate (4) is mounted on the electromagnetic base (5). Four limiting blocks (3) are mounted on the lower base plate (4). The four limiting blocks (3) enclose the lower base plate circumferentially. Several sliding blocks (6) are placed on the inner wall of the limiting blocks (3). Several core molds (2) are arranged in an array on the inner side of the sliding blocks (6). The core mold (2), the limiting block (3) and the sliding block (6) are all magnetically attracted. Thermoplastic composite prepreg is placed between the sliding block (6) and the core mold (2) and between adjacent core molds (2). The outer wall of the limiting block (3) is an inclined surface (12). The lower part of the upper panel (1) is provided with an inclined groove (13) that matches the angle of the inclined surface (12). The upper panel (1) covers the lower bottom plate (4). The inclined groove (13) abuts against the inclined surface (12).

2. The molding device for a thermoplastic composite honeycomb sandwich structure according to claim 1, characterized in that: The thermoplastic composite prepreg is a thermoplastic plain weave strip prepreg.

3. The molding device for a thermoplastic composite honeycomb sandwich structure according to claim 1, characterized in that: The upper panel (1) and the lower base plate (4) are connected by a positioning pin (7).

4. The molding device for a thermoplastic composite honeycomb sandwich structure according to claim 1, characterized in that: The bottom plate (4) has a groove (8) with a boss (9) on the inside. The limiting block (3) has a groove (11) with the bottom of the limiting block (3) located in the groove (8). The boss (9) and the groove (11) are in the same position.

5. The molding device for a thermoplastic composite honeycomb sandwich structure according to claim 1, characterized in that: The bottom plate (4) is provided with recessed platforms (10) at the four corners.

6. The molding device for a thermoplastic composite honeycomb sandwich structure according to claim 5, characterized in that: The upper panel (1) is provided with a threaded hole, which corresponds to the position of the countersunk platform (10).

7. The molding device for a thermoplastic composite honeycomb sandwich structure according to claim 1, characterized in that: The core mold (2) has a pin opening (14) at its center.

8. The molding device for a thermoplastic composite honeycomb sandwich structure according to claim 1, characterized in that: The angle between the inclined surface (12) and the horizontal surface is 60°.

9. The molding device for a thermoplastic composite honeycomb sandwich structure according to claim 1, characterized in that: The core mold (2) is a straight-walled hexahedron structure or a curved-walled hexahedron structure.

10. A molding method for a molding apparatus for a thermoplastic composite honeycomb sandwich structure as described in any one of claims 1-9, characterized in that: Cut the thermoplastic prepreg into strips, apply a release agent to the molding surface of the mold body, attach the bottom plate (4) to the electromagnetic base (5), place the two limiting blocks (3) vertically, with the inner walls of the two limiting blocks (3) forming two right-angled sides, place the sliding blocks (6) in sequence close to the inner walls of the two limiting blocks (3), lay the strip-shaped thermoplastic prepreg on the side of the sliding block (6), place the core mold (2) so that the core mold (2) aligns with the side of the sliding block (6), and lay the core mold (2) on the other side of the core mold (2). After placing the strip-shaped thermoplastic composite prepreg, the core mold (2) and the strip-shaped thermoplastic composite prepreg are placed in sequence. After all the core molds (2) are placed, a core array is formed. Sliding blocks (6) are placed on the other two sides of the core array. Two limiting blocks (3) are placed on the outside of the sliding blocks (6). The upper panel (1) is covered on the lower base plate (4) so ​​that the inclined groove (13) abuts against the inclined surface (12). The electromagnetic base (5) is turned off. The mold body is removed and placed into the preheated hot press for pressure curing.

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