A forming die and method for a surface-stiffened thermoplastic composite

Abstract

The application discloses a forming die and a preparation method of a surface-reinforced thermoplastic composite material, and belongs to the field of high-performance thermoplastic composite material manufacturing. The forming die comprises an upper die, a lower die and a frame. The bottom of the upper die is provided with a planar boss, and a reinforcing rib boss is detachably arranged at the bottom of the planar boss. The two are respectively provided with transverse lugs for being locked by a locking mechanism on two sides. The upper die is matched with the lower die through the frame, and the side surface of the lower die is provided with a temperature detection hole for placing a thermocouple. The surface-reinforced thermoplastic composite material prepared by the application has excellent interface performance, size stability and impact resistance, can have excellent mechanical properties of continuous fiber reinforced composite materials and manufacturing flexibility of long fiber reinforced composite materials, and has a relatively wide application scene.

Description

Technical Field

[0001] This invention belongs to the field of high-performance thermoplastic composite material manufacturing, specifically relating to a molding die and preparation method for a surface-reinforced thermoplastic composite material. Background Technology

[0002] Thermoplastic composites, with their high strength-to-weight ratio, lightweight advantages, and recyclability, have shown broad application prospects in high-end manufacturing fields such as aerospace structural components, lightweight rail transit components, and key components for new energy vehicles. To meet the stringent requirements for impact resistance and structural integrity under dynamic loads, the development of thermoplastic composite products with surface-integrated stiffeners is increasingly urgent. The efficient production of such products relies heavily on specialized molding equipment with multi-form switching capabilities. Among these, the mold locking mechanism, as a core component, directly affects production cycle control and the stability of finished product quality.

[0003] Currently, molding dies used in the market for preparing surface-reinforced thermoplastic composites are generally equipped with dual working modes to adapt to different process stages. However, the locking mechanisms of these dies often adopt a non-separable, integral structure. During mode-changing operations, the movement trajectory of the mechanism can easily conflict with the mold cavity contour or the already placed preform, resulting in a lengthy switching process that requires repeated adjustments. This operational delay causes the preform to continuously dissipate heat during the conversion, and the temperature may drop below the glass transition temperature threshold of the thermoplastic resin, hindering molecular diffusion at the interlayer interface and significantly weakening the bonding strength. At the same time, some locking mechanisms have design flaws in the force transmission path when applying clamping force, transmitting pressure that is not required by the process to the pressing area, causing an imbalance in the internal stress distribution of the composite material, resulting in quality defects such as thickness deviation or surface ripples in the product. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art in that the locking mechanism is prone to spatial conflict with the cavity when the mold shape is changed, and the additional pressure causes the stress distribution of the composite material to be unbalanced. The present invention provides a molding die and preparation method for surface-reinforced thermoplastic composite material that can quickly switch working modes and has uniform locking force.

[0005] The technical solution adopted by the present invention to achieve the above objectives is as follows:

[0006] A molding die for a surface-reinforced thermoplastic composite material includes an upper die, a lower die, and a frame; the bottom of the upper die has a flat boss, and the bottom of the flat boss is detachably provided with a reinforcing rib boss, and both have transverse lugs on their sides for being locked by a locking mechanism; the upper die and the lower die are fitted together by the frame, and the side of the lower die has a temperature sensing hole for placing a thermocouple.

[0007] Preferably, the molding die has two working states: F1 state, in which the bottom of the upper die only has a flat boss and no reinforcing rib boss is installed, which is used to prepare a preform with a flat surface; F2 state, in which the bottom of the flat boss is equipped with a reinforcing rib boss through a locking mechanism, which is used to prepare a thermoplastic composite material with a reinforcing rib structure.

[0008] Preferably, a method for preparing a surface-reinforced thermoplastic composite material, using the above-mentioned molding die, includes the following steps:

[0009] S1. Using an ultrasonic spot welding machine, the cut continuous fiber reinforced thermoplastic resin prepreg is laid up and spot welded according to the preset layup method P to form a preform A1.

[0010] S2. Place the preform A1 into the mold of shape F1, and press it into preform A2 using process strategy M1.

[0011] S3. Weigh the long fiber prepreg sheet with an aspect ratio of R according to the required weight W1, put it into the mold of shape F1, and then press it into preform A3 using process strategy M2.

[0012] S4. The preform is placed into the mold of shape F2 with A3 on top and A2 on the bottom, and then pressed into a surface-reinforced thermoplastic composite material with dimensional stability and impact resistance using process strategy M3.

[0013] Preferably, the thermoplastic composite material is prepared from a prepreg, and its reinforcing fibers include carbon fiber and glass fiber, and the thermoplastic resin matrix is ​​selected from one or more of polyetheretherketone, polyaryletherketone, and polyphenylene sulfide.

[0014] Preferably, the pre-laid method P of the preform A1 in step S1 includes orthogonal layup and quasi-isotropic layup, and the number of layups depends on the thickness of the continuous fiber composite material in the target part; the weight of the long fiber prepreg weighed in the molding step S3 is 1.05-1.15 times the product of the volume of the long fiber composite material and the density of the prepreg, the aspect ratio of the long fiber prepreg is 2≤R≤5, and its width range is 3-10mm.

[0015] Preferably, process strategy M1 has a temperature 20°C to 30°C above the glass transition temperature of the thermoplastic resin, a pressure of 3MPa to 6MPa, and a holding time of 20min to 40min; process strategy M2 has a temperature 30°C to 50°C below the melting temperature of the thermoplastic resin, a pressure of 6MPa to 9MPa, a holding time of 25min to 35min, and venting ≥ 5 times; process strategy M3 has a temperature 30°C to 50°C above the melting temperature of the thermoplastic resin, a pressure of 1MPa to 3MPa, and a holding time of 40min to 50min.

[0016] Preferably, the locking mechanism is a split L-shaped structure, including an upper L-shaped structure that is connected to the upper mold and can rotate axially, and a lower L-shaped structure that can be raised and lowered relative to the upper L-shaped structure. The two are connected by a control structure. The upper L-shaped structure and the lower L-shaped structure each have a horizontally protruding end for clamping the transverse lugs on the same side.

[0017] Preferably, the upper L-shaped structure is connected to the protruding part at the top of the upper mold via a rotating shaft, with a rotation angle range of 0~90°. When the upper L-shaped structure rotates, it drives the lower L-shaped structure to rotate synchronously, thereby enabling the locking mechanism to switch between the working position and the avoidance position.

[0018] Preferably, the control structure is an electrically controlled telescopic rod or a manual gear transmission mechanism, which can drive the lower L-shaped structure to rise and fall axially to adjust the distance between the two protruding ends of the same locking mechanism.

[0019] Preferably, the outer top surface of the upper L-shaped structure maintains a fixed gap with the top protrusion of the upper mold, and the outer bottom surface of the lower L-shaped structure maintains a movable gap with the upper surface of the frame, so as to avoid the locking mechanism transmitting additional pressure and affecting the uniformity of material pressing.

[0020] Compared with the prior art, this invention has the following advantages: The mold shape conversion process is simplified, avoiding spatial conflicts between the mechanism and the cavity or preform, reducing heat dissipation from the preform, and improving interlayer bonding strength; detachable reinforcing ribs and bosses facilitate replacement, reducing operational complexity, minimizing fiber arrangement disturbance, and improving molding efficiency and product quality stability; two working modes significantly improve mold versatility and utilization, avoiding the high costs of frequent mold changes and facilitating maintenance and cleaning; phased and refined process control ensures optimal resin flow and wetting, significantly improving composite material performance; the split L-shaped locking mechanism enables rapid position switching, allows precise adjustment of clamping distance, avoids additional pressure affecting pressing uniformity, has strong versatility, reduces maintenance costs and mold changeover time, and makes operation safer. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the molding die in state F2.

[0022] Figure 2 This is a schematic diagram of the overall disassembled structure of the molding die;

[0023] Figure 3 A schematic diagram of the layered structure of a surface-reinforced thermoplastic composite material;

[0024] Figure 4 This is a schematic diagram of the molding die in state F1.

[0025] Figure 5 This is a schematic diagram of the locking mechanism structure in Embodiment 3 of the present invention;

[0026] Figure 6 This is a schematic diagram of the internal workings of the locking mechanism in Embodiment 3;

[0027] Figure 7 This is a schematic diagram of the locking mechanism in the avoidance position;

[0028] Figure 8 This is a schematic diagram of the locking mechanism in its working position.

[0029] Reference numerals: 1. Upper mold; 2. Flat boss; 3. Reinforcing rib boss; 4. Frame; 5. Lower mold; 6. Horizontal ear piece; 61. Upper ear piece; 62. Lower ear piece; 7. Surface-reinforced composite material; 71. Lower layer material; 72. Upper layer material; 8. Locking mechanism; 9. Temperature probe hole; 10. Threaded hole; 81. Upper L-shaped structure; 810. Upper pressing surface; 82. Lower L-shaped structure; 820. Lower pressing surface; 83. Control structure; 84. Rotating shaft; 85. Guide structure. Detailed Implementation

[0030] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings:

[0031] Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0032] Example 1:

[0033] See Figures 1-4 A molding die for a surface-reinforced thermoplastic composite material includes an upper die 1, a lower die 5, and a frame 4. The upper die 1 has a flat boss 2 at its bottom, and a reinforcing rib boss 3 is detachably provided at the bottom of the flat boss 2. Both of them have transverse lugs 6 on their sides for locking by a locking mechanism 8. The upper die 1 and the lower die 5 are connected by the frame 4. The lower die 5 has a temperature sensing hole 9 on its side for placing a thermocouple. The upper die 1 and the lower die 5 are respectively provided with threaded holes 10 for fixing to a press. The transverse lugs 6 on both sides of the flat boss 2 are upper lugs 61, and the transverse lugs 6 on both sides of the reinforcing rib boss 3 are lower lugs 62, which are arranged correspondingly.

[0034] This application aims to solve the problems of low mold shape conversion efficiency, insufficient product quality stability, and inconvenience in replacing reinforcing ribs and bosses in the prior art through the above structure.

[0035] Upper mold 1 refers to the upper part of the mold, whose internal or bottom structure is used to form the upper surface or a specific shape of the composite material product. During the molding process, upper mold 1 moves downward and applies pressure to the material.

[0036] The lower mold 5 refers to the lower half of the mold, whose internal or bottom structure is used to support the composite material and form the lower surface or specific shape of the article. The lower mold 5 is usually kept fixed or moves relative to the upper mold 1.

[0037] The frame 4 forms a closed cavity between the upper mold 1 and the lower mold 5 to restrict material flow and ensure the dimensional accuracy and edge integrity of the molded product. The frame 4 fits tightly with the upper mold 1 and the lower mold 5 when the mold is closed. The upper end of the lower mold 5 has a planar protrusion structure that mates with the inside of the frame 4 to allow the frame 4 to be mounted on the lower mold 5.

[0038] The planar boss 2 is a planar protrusion at the bottom of the upper mold 1. Its main function is to press the preform with a flat surface when the mold is in the F1 position. The planar boss 2 is set to cooperate with the inner side of the frame to ensure that the planar boss 2 and the lower mold 5 press the material within the frame when the mold is closed.

[0039] The reinforcing rib boss 3 is a raised structure that can be detachably set at the bottom of the planar boss 2. Its function is to form a reinforcing rib structure on the surface of the composite material product when the mold is in the F2 state, so as to improve the impact resistance and structural rigidity of the product.

[0040] The locking mechanism 8 is used to firmly fix the flat boss 2 and the reinforcing rib boss 3 together during the molding process to withstand the pressing force and maintain the alignment accuracy of the mold.

[0041] The transverse lugs 6 are protruding parts located on both sides of the planar boss 2 and the reinforcing rib boss 3, used to cooperate with the locking mechanism 8 to achieve quick positioning and locking of the components. The planar boss 2 has transverse lugs 6 only on its opposite sides, and the reinforcing rib boss 3 has transverse lugs 6 only on its corresponding opposite sides, to ensure that the planar boss 2 and the reinforcing rib boss 3 can be pressed together by the locking mechanism 8 through the transverse lugs 6 on the same side, achieving a firm connection.

[0042] Temperature sensing hole 9 is a hole located on the side of the lower mold 5, used to insert temperature sensors such as thermocouples to monitor the temperature inside the mold in real time, ensuring that the molding process is carried out within a preset temperature range. The depth and diameter of temperature sensing hole 9 should match the size of the thermocouple used. Temperature sensing hole 9 can be designed as a straight hole or an angled hole to facilitate the insertion and fixation of the thermocouple, and to ensure that its sensing end is located at a critical temperature monitoring point inside the mold, thereby achieving accurate monitoring of the molding temperature.

[0043] The molding die of this application features a detachable reinforcing rib boss 3 at the bottom of the upper die 1, and a locking mechanism 8 to lock the upper die 1, the planar boss 2, and the transverse lugs 6 of the reinforcing rib boss 3. Simultaneously, the upper die 1 and the lower die 5 are connected by a frame 4, and the lower die 5 has a temperature sensing hole 9 on its side. This simplifies the die shape conversion process, avoids spatial conflicts between the locking mechanism 8 and the die cavity or preform, reduces continuous heat dissipation of the preform during conversion, and helps improve interlayer bonding strength. Furthermore, the detachable reinforcing rib boss 3 facilitates replacement, reduces operational complexity, and minimizes disturbance to the fiber arrangement of the preform, thereby improving the molding efficiency and product quality stability of the impact-resistant surface-reinforced thermoplastic composite material. This effectively solves the problems of low die shape conversion efficiency, unstable product quality, and inconvenient replacement of reinforcing rib bosses in existing technologies.

[0044] The molding die has two working modes:

[0045] F1 form is a state in which the bottom of the upper mold 1 only has a flat boss 2 and no reinforcing rib boss 3 is installed, which is used to prepare a preform with a flat surface;

[0046] The F2 form is a state in which the bottom of the planar boss 2 is fitted with a reinforcing rib boss 3 via a locking mechanism 8, and is used to prepare thermoplastic composite materials with reinforcing rib structures.

[0047] Specifically, "two working modes" refers to the molding die being designed to operate in two different configurations to accommodate the molding requirements of stacked materials. "F1 mode" refers to a specific configuration of the molding die in which the bottom of the upper die 1 retains only the flat boss 2, while the reinforcing rib boss 3 is not installed. In this state, the molding surface of the die is flat, without any protrusions or depressions. More specifically, "the state where the bottom of the upper die 1 only has flat boss 2 and no reinforcing rib boss 3" means that in F1 mode, the bottom of the upper die 1 only presents the flat surface of the flat boss 2, and the reinforcing rib boss 3, originally used to form the reinforcing rib structure, is removed or not installed. This configuration allows the die to uniformly planar press the material, thereby producing a preform with a smooth surface and no rib structure. Therefore, the main use of F1 mode is to produce preforms without reinforcing ribs. These preforms are often used as the base layer for subsequent composite material structures, or in some applications directly as the final product, characterized by a flat surface and uniform thickness.

[0048] On the other hand, "F2 configuration" refers to another configuration of the molding die, in which the reinforcing rib boss 3 is securely mounted on the bottom of the flat boss 2 via the locking mechanism 8. This configuration allows the die to form composite materials with specific reinforcing rib structures. Specifically, "the state in which the reinforcing rib boss 3 is mounted on the bottom of the flat boss 2 via the locking mechanism 8" means that in the F2 configuration, the reinforcing rib boss 3 is precisely positioned and fixed below the flat boss 2. The locking mechanism 8 plays a crucial role here, ensuring that the reinforcing rib boss 3 does not shift during the pressing process, thereby guaranteeing the precise forming of the reinforcing rib structure. The main application of the F2 configuration is the production of thermoplastic composite materials with reinforcing rib structures. The reinforcing rib structure can significantly improve the stiffness, strength, and impact resistance of composite materials and is often used in components with high structural performance requirements. With this configuration, complex reinforcing rib geometries can be directly formed in a single molding process, avoiding subsequent secondary processing.

[0049] Through the above technical solution, the molding die of this application can flexibly switch working modes according to production needs, effectively solving the problem that a single die cannot accommodate the molding of different product structures. When a preform with a flat surface needs to be prepared, the die can be configured in F1 mode. In this case, the bottom of the upper die 1 only has a flat boss 2, ensuring that the surface of the pressed preform is smooth and without ribs, simplifying the production process. When a thermoplastic composite material with a reinforcing rib structure needs to be prepared, the die can be quickly switched to F2 mode. The reinforcing rib boss 3 is installed at the bottom of the flat boss 2 through the locking mechanism 8, thereby directly forming a precise reinforcing rib structure in one pressing process. This switchable working mode design greatly improves the versatility and utilization of the die, avoiding the cumbersome and costly process of manufacturing or frequently changing the entire set of dies for different product structures, and significantly improving production efficiency and economic benefits. At the same time, due to the detachability of the reinforcing rib boss 3, it is also convenient for the maintenance, cleaning, and replacement of different rib structures of the die, further enhancing the adaptability of the die.

[0050] This application discloses a method for preparing an impact-resistant surface-reinforced thermoplastic composite material, which includes the following steps:

[0051] S1. Fix the upper mold 1 and lower mold 5 to the press table through the threaded hole 10. Then, fit the frame 4 onto the planar protrusion structure of the lower mold 5. Insert one end of the thermocouple sensor into the temperature detection hole 9 of the mold and connect the other end to the temperature display. Finally, apply a release agent to the surface of the mold cavity and set it aside. Use an ultrasonic spot welding machine to lay and spot weld the cut continuous fiber reinforced thermoplastic resin prepreg according to the preset layup method P to form a preform A1.

[0052] S2. Place the preform A1 into the mold of shape F1, and press it into preform A2 using process strategy M1. After pressing, take out the preform A2 for later use.

[0053] S3. Weigh the long fiber prepreg sheet with an aspect ratio of R according to the required weight W1, put it into the mold of shape F1, and then press it into a preform A3 using process strategy M2. The aspect ratio R is defined as the ratio of the length to the width of the prepreg sheet, i.e. R=L / W.

[0054] S4. The reinforcing rib boss 3 is fixed to the plane boss 2 below the upper mold 1 by the locking mechanism 8, so that the mold changes to the F2 shape. The preform is put into the mold of the F2 shape with A3 on top and A2 on the bottom. Then, the process strategy M3 is used to press it into a surface-reinforced thermoplastic composite material with dimensional stability and impact resistance.

[0055] The cooling steps after S4 are as follows: the mold is cooled to below the glass transition temperature of the composite material, the composite material is removed, and the burrs are trimmed to form a surface-reinforced thermoplastic composite part with dimensional stability and impact resistance.

[0056] Among them, the surface-reinforced thermoplastic composite material in S4 is called surface-reinforced composite material 7, which includes an upper material 72 located on the upper layer and having reinforcing ribs on the surface, and a lower material 71.

[0057] In this invention, by adjusting the mold shape using the above method, two types of composite material preforms are prepared. Then, through integral compression molding, a composite material with one side in the form of continuous fibers and the other in the form of long fibers is produced. During the molding process, the processing flexibility of the long-fiber composite material is utilized to form the reinforcing ribs of the desired configuration. This method does not directly form reinforcing ribs on the surface of the continuous-fiber composite material, but rather utilizes the flowability of the long-fiber composite material to form raised reinforcing ribs under the constraint of the mold. This produces composite material parts with excellent interfacial properties, dimensional stability, and impact resistance. Furthermore, by changing the bosses of the compression molding mold, low-cost and rapid preparation of surface-reinforced composite materials with different configurations can be achieved.

[0058] Thermoplastic composites are made from prepregs, and their reinforcing fibers include carbon fiber and glass fiber. The thermoplastic resin matrix is ​​selected from one or more of polyetheretherketone, polyaryletherketone, and polyphenylene sulfide.

[0059] In molding step S1, the layup method P of preform A1 includes orthogonal layup and quasi-isotropic layup. The number of layups depends on the thickness of the continuous fiber composite material in the target part. In molding step S3, the weight of the long fiber prepreg is 1.05-1.15 times the product of the volume of the long fiber composite material and the density of the prepreg. The aspect ratio of the long fiber prepreg is 2≤R≤5, its length ranges from 6 to 50 mm, and its width ranges from 3 to 10 mm. Based on the range of aspect ratio R and width W, the length L of the prepreg sheet can be calculated to be in the range of 6 mm to 50 mm.

[0060] Orthogonal layup enables composite materials to exhibit excellent strength and stiffness in two main directions, making it suitable for structural components primarily subjected to unidirectional or bidirectional orthogonal loads. Quasi-isotropic layup aims to make composite materials exhibit approximately isotropic mechanical properties in a plane, meaning they have similar strength and stiffness in different directions, making it suitable for structural components subjected to complex multidirectional loads. The number of layups is determined based on the final thickness of the continuous fiber composite material required for the target part, ensuring that the material usage matches the design requirements and avoiding performance defects caused by material waste or insufficient thickness. Furthermore, when preparing preform A3, the weight of the long fiber prepreg is precisely controlled, set to 1.05-1.15 times the product of the long fiber composite volume and the prepreg density. This ensures that the mold cavity is fully filled while reserving a certain margin to compensate for material flow and compaction during the pressing process, effectively avoiding excessive porosity due to insufficient material or overflow waste due to excessive material. The aspect ratio R of the long fiber prepreg is limited to 2 ≤ R ≤ 5, and its width ranges from 3 to 10 mm. This setting helps optimize the flow and distribution behavior of the long fibers within the mold. Appropriate aspect ratio and width can prevent excessive entanglement or localized accumulation of fibers during pressing, ensuring that the long fibers are uniformly dispersed, thereby forming a uniform reinforcing structure in the final composite material.

[0061] The temperature of process strategy M1 is set to 20°C to 30°C above the glass transition temperature of the thermoplastic resin, the pressure is 3MPa to 6MPa, and the holding time is 20min to 40min.

[0062] The temperature is controlled within a range of 20°C to 30°C above the glass transition temperature of the thermoplastic resin. This aims to bring the thermoplastic resin in preform A1 to a moderately softened state, enabling it to deform. Under pressure, the layers of prepreg are tightly bonded together, eliminating trapped gas. Applying a pressure of 3MPa to 6MPa helps to fully compact the fiber bundles inside preform A1, reducing porosity and promoting uniform resin distribution between fibers, thereby effectively removing air from preform A1 and improving the material's density. A holding time of 20 to 40 minutes ensures that the set temperature and pressure are maintained, and that the stress inside preform A1 is released, resulting in a structurally stable and dimensionally accurate preform A2.

[0063] In process strategy M2, the temperature is set to 30°C–50°C below the melt temperature of the thermoplastic resin, the pressure to be 6 MPa–9 MPa, the holding time to be 25–35 minutes, and the number of venting operations to be ≥5. Controlling the temperature within the range of 30°C–50°C below the melt temperature of the thermoplastic resin allows for the compaction of the prepreg in a softened state, eliminating air inclusions and contributing to the formation of a dense and defect-free preform A3. Applying a higher pressure of 6 MPa–9 MPa further compacts the long-fiber prepreg sheets, removing residual air and volatiles, and promoting uniform resin penetration and flow between the long fibers, thereby improving the density and mechanical properties of preform A3. The holding time of 25–35 minutes ensures the formation of a uniform preform A3 under high temperature and high pressure, and allows for sufficient relaxation of internal stress. In addition, by performing ≥5 venting operations, air and volatile substances inside the mold cavity and material can be effectively removed, significantly reducing the porosity in the final product and improving the material's density and mechanical properties, especially its impact resistance.

[0064] In process strategy M3, the temperature is set to 30°C–50°C above the melt temperature of the thermoplastic resin, the pressure is 1 MPa–3 MPa, and the holding time is 40–50 minutes. Pressing within this temperature range ensures that the thermoplastic resin in preforms A3 and A2 is in a molten state, allowing for thorough fusion and tight fit with the cavity formed by the reinforcing rib boss 3. The lower pressure of 1 MPa–3 MPa is used in the final molding step primarily to ensure sufficient material fusion and filling of the mold cavity while avoiding excessive compression or damage to the preforms, especially for complex shapes with reinforcing ribs, thus helping to maintain the dimensional accuracy and surface quality of the final product. The longer holding time of 40–50 minutes ensures that preforms A3 and A2 are fully fused at the lower pressure, with the resin evenly distributed throughout the composite material and completely filling the reinforcing rib structure, resulting in a final product with good dimensional stability and excellent impact resistance.

[0065] By precisely defining the temperature, pressure, holding time, and number of venting cycles in process strategies M1, M2, and M3, this application ensures that the thermoplastic resin achieves optimal flowability and wetting at each stage of preparing the impact-resistant surface-reinforced thermoplastic composite. Specifically, process strategy M1 involves pressing the thermoplastic resin at temperatures above its glass transition temperature, causing the preform A1 to soften and densify initially, laying the foundation for subsequent molding. Process strategy M2, using higher pressure and multiple venting cycles at temperatures below the melting temperature of the thermoplastic resin, effectively promotes the venting of the long fiber prepreg sheet, significantly reducing porosity and improving the density of the preform A3. Process strategy M3, using moderate pressure and a longer holding time at temperatures above the melting temperature of the thermoplastic resin, ensures that preforms A3 and A2 are fully fused and accurately replicates the mold cavity, forming a surface-reinforced structure with high dimensional accuracy and excellent impact resistance. This phased and refined process parameter control effectively solves the material defect problem caused by improper parameters in traditional methods, and significantly improves the overall performance and reliability of the final composite material.

[0066] Example 2:

[0067] Based on the molding die for an impact-resistant surface-reinforced thermoplastic composite material disclosed in Embodiment 1 of this invention, this embodiment uses carbon fiber reinforced polyaryletherketone prepreg to prepare a surface-reinforced thermoplastic composite material part. The part is 400mm long, 240mm wide, and approximately 8mm thick. It has four reinforcing ribs along its length and two reinforcing ribs along its width. The surface reinforcing ribs are approximately 4mm high and 2.5mm wide. The prepreg density is approximately 1.58g / cm³. 3 The layup pattern of the continuous carbon fiber reinforced polyaryletherketone thermoplastic composite is [45° / 0° / -45° / 90°]. 2s The long carbon fiber reinforced polyaryletherketone prepreg has an aspect ratio of 5, a width of approximately 5 mm, and a length of approximately 25 mm. [45° / 0° / -45° / 90°] 2s This indicates that the layup sequence is symmetrically repeated twice. The fabrication process of this surface-reinforced thermoplastic composite part is shown below:

[0068] Step 1: Fix the upper mold 1 and lower mold 5 to the press table with M12 hex bolts. Then, put the frame 4 on the boss of the lower mold 5. Insert one end of the J-type thermocouple into the temperature probe hole of the mold and connect the other end to the temperature display. Finally, apply NC770 release agent three times to the surface of the mold cavity, with a 10-minute interval between each application.

[0069] Step 2: Prepare the continuous fiber prepreg unidirectional belt at [45° / 0° / -45° / 90°].2s The prepreg sheets are cut into pieces according to the required angles, dimensions and quantities for the layup, and then an ultrasonic spot welding machine is used to lay the prepreg sheets into a continuous fiber composite preform according to the layup sequence and dimensions.

[0070] Step 3: Place the continuous fiber composite preform into the mold of F1 shape, and press it with a process of 180℃, 5MPa and 30min to form a continuous fiber composite preform with good internal bonding and small air inclusions.

[0071] Step 4: Weigh 312g of long fiber prepreg sheet and put it evenly into the F1 mold. Then press it into a long fiber composite material preform with a smooth surface and a thickness of about 4mm using a process of 300℃, 8MPa, 30min, and 10 degassing cycles.

[0072] Step 5: Fix the reinforcing rib boss to the flat boss 2 of the upper mold 1 using the locking mechanism 8 on both sides of the mold, and apply the release agent 3 times for later use.

[0073] Step 6: Place the two preforms into the F2 mold with the continuous fiber composite preform at the bottom and the long fiber composite preform at the top, and then press them using a process of 360°C, 2MPa, and 45min.

[0074] Step 7: When the mold cools to 100°C, open the press, remove the composite material, trim the burrs, and form a surface-reinforced thermoplastic composite part with dimensional stability and impact resistance.

[0075] The composite material prepared by this method has an interlaminar shear strength of >75MPa between the continuous fiber composite part and the long fiber composite part. After the surface is subjected to an impact of 30J energy from a hemispherical hammer with a diameter of 16mm, the back reinforcing rib does not split, and the overall rigidity is good without twisting deformation.

[0076] Example 3:

[0077] See Figures 5-6 The locking mechanism 8 is a split L-shaped structure, including an upper L-shaped structure 81 that is connected to the upper mold 1 and can rotate axially, and a lower L-shaped structure 82 that can be raised and lowered relative to the upper L-shaped structure 81. The two are connected by a control structure 83. The upper L-shaped structure 81 and the lower L-shaped structure 82 each have a horizontally extended end for clamping the horizontal ear pieces 6 on the same side.

[0078] The upper L-shaped structure 81 and the lower L-shaped structure 82 have an upper clamping surface 810 and a lower clamping surface 820 on their inner sides, respectively. The transverse ear pieces 6 are divided into upper ear pieces 61 and lower ear pieces 62, which are respectively arranged as upper ear pieces 61 and lower ear pieces 62. The upper ear pieces 61 are distributed on two opposite sides of the planar boss 2, and the lower ear pieces 62 are distributed on two opposite sides of the reinforcing rib boss 3 and are arranged corresponding to the two upper ear pieces 61. The horizontally extended end of the upper L-shaped structure 81 has an upper clamping surface 810, which is used to contact and clamp the upper end of the upper ear piece 61. The horizontally extended end of the lower L-shaped structure 82 has a lower clamping surface 820, which is used to contact and clamp the lower end of the lower ear piece 62. By adjusting the relative lifting and lowering of the two L-shaped structures through the control structure 83, the relative position of the two clamping surfaces is adjusted to achieve clamping of the transverse ear pieces 6 arranged on the same side and vertically.

[0079] This split L-shaped structure means that the locking mechanism 8 is not a single fixed L-shaped component, but rather composed of two relatively movable L-shaped components. This design gives the locking mechanism 8 greater flexibility and adjustability, allowing it to adapt to different locking requirements and mold configurations. The upper L-shaped structure 81 is the upper component of the locking mechanism 8, connected to the upper mold 1, and capable of rotating around its own axis. This axial rotation function allows the upper L-shaped structure 81 to switch between a working position (i.e., the locking position) and a non-working position (i.e., the clearance position), thereby facilitating mold loading and unloading and the installation or removal of the reinforcing rib boss 3. The lower L-shaped structure 82 is the lower component of the locking mechanism 8, capable of vertical lifting relative to the upper L-shaped structure 81. This lifting capability is key to achieving precise clamping and adapting to transverse lugs 6 of different thicknesses, ensuring that the locking mechanism 8 can apply a uniform and stable clamping force to the transverse lugs 6. The control structure 83 connects the upper L-shaped structure 81 and the lower L-shaped structure 82, and drives the lower L-shaped structure 82 to move up and down relative to the upper L-shaped structure 81. The function of the control structure 83 is to provide precise and controllable relative movement. The horizontal extensions of the upper L-shaped structure 81 and the lower L-shaped structure 82 constitute the actual clamping surfaces. When the locking mechanism 8 is in operation, these two horizontal extensions simultaneously clamp the transverse lugs 6 on the upper mold 1 or the reinforcing rib boss 3 from above and below, thereby firmly fixing the upper mold 1 and its components within the mold frame, ensuring the stability and positioning accuracy of the mold during the pressing process.

[0080] Through the above technical solution, the locking mechanism 8 is designed as a split L-shaped structure, with the upper L-shaped structure 81 capable of axial rotation and the lower L-shaped structure 82 capable of relative lifting and lowering. These are connected and driven by the control structure 83, significantly improving the locking efficiency and ease of operation of the molding die. Specifically, the axial rotation function of the upper L-shaped structure 81 allows the locking mechanism 8 to quickly switch from the working position to the avoidance position, greatly simplifying the installation and disassembly process of the upper die 1 and the reinforcing rib boss 3, and shortening the time required for die configuration conversion. Simultaneously, the relative lifting and lowering capability of the lower L-shaped structure 82, combined with the precise drive of the control structure 83, allows the locking mechanism 8 to be finely adjusted according to the actual position and thickness of the transverse lug 6, ensuring a uniform and stable clamping force on the transverse lug 6, avoiding die deformation or product defects caused by uneven locking. This split, adjustable L-shaped structure design not only ensures high precision and stability of the die during the pressing process but also significantly improves the versatility and production efficiency of the die, enabling it to flexibly adapt to the preparation needs of different product forms.

[0081] See Figures 7-8 The upper L-shaped structure 81 is connected to the top protruding part of the upper mold 1 via a rotating shaft 84, with a rotation angle range of 0~90°. When the upper L-shaped structure 81 rotates, it drives the lower L-shaped structure 82 to rotate synchronously, realizing the switching of the locking mechanism 8 between the working position and the avoidance position. The upper L-shaped structure 81 and the lower L-shaped structure 82 each have a vertical end that is perpendicularly connected to their respective protruding ends. The vertical end is located on the side of the planar boss 2 that does not have the transverse lug 6.

[0082] The working position of the locking mechanism 8 is configured such that the protruding end extends from the vertical end connected to it and is arranged in the direction of extending towards the transverse ear 6 to cover the upper and lower sides of the transverse ear 6; the clearance position of the locking mechanism 8 is configured such that the protruding end extends from the numerical end connected to it and is arranged in the direction of moving away from the transverse ear 6 to allow the reinforcing rib boss 3 to reach below the bottom of the planar boss 2 and fit against it.

[0083] Specifically, the upper L-shaped structure 81 is connected to the top protruding part of the upper mold 1 via a pivot 84. This connection allows the upper L-shaped structure 81 to rotate around the pivot 84. The pivot 84 is typically a cylindrical pin that passes through corresponding holes on the upper L-shaped structure 81 and the top protruding part of the upper mold 1, and can be secured with fasteners to ensure a stable connection. This rotatable connection is the basis for the flexible switching of the locking mechanism 8. The rotation angle range is 0~90°, meaning that the upper L-shaped structure 81 can rotate from a fully locked or working position to a fully open or clearance position. For example, when the locking mechanism 8 is in the working position, the upper L-shaped structure 81 may be parallel to the upper mold 1 or at a specific angle to clamp the transverse lug 6; when switching to the clearance position, the upper L-shaped structure 81 can rotate 90° to completely disengage from the clamping area of ​​the transverse lug 6, thus providing unobstructed space for mold loading / unloading or component replacement. This rotation range is typically precisely controlled by mechanical limiting structures (such as limiting blocks, limiting pins, or machined surfaces on the mold body) to ensure accurate positioning for each operation. Furthermore, the upper L-shaped structure 81, when rotating, drives the lower L-shaped structure 82 to rotate synchronously. This means there is a linkage between the upper L-shaped structure 81 and the lower L-shaped structure 82, ensuring they maintain a consistent rotational direction. This synchronous rotation can be achieved in several ways. The lower L-shaped structure 82 is slidably connected to the upper L-shaped structure 81 via a guide structure 85. The guide structure 85 includes a guide groove on the upper L-shaped structure 81 and a protrusion at a corresponding position on the outer side of the lower L-shaped structure. The protrusion engages within the guide groove to synchronize the lifting, lowering, and rotation of the two L-shaped structures. This synchronous rotation ensures that the entire locking mechanism 8 rotates as a whole, allowing for smooth switching between the working position and the clearance position. In the working position, the horizontally extended end of the locking mechanism 8 effectively clamps the transverse lug 6, providing the required locking force; while in the clearance position, the locking mechanism 8 is completely disengaged, facilitating mold operation.

[0084] By connecting the upper L-shaped structure 81 of the locking mechanism 8 to the upper mold 1 via a rotating shaft 84, and enabling it to rotate within a range of 0-90°, while simultaneously driving the lower L-shaped structure 82 to rotate synchronously, this application achieves rapid and convenient switching between the working position and the clearance position of the locking mechanism 8. This design greatly improves the flexibility and efficiency of mold operation, allowing operators to easily load and unload preforms or replace mold components without cumbersome disassembly and reinstallation, thereby optimizing the convenience of the entire molding process. This rotatable locking mechanism 8 avoids the additional disassembly or adjustment steps that may be required when loading and unloading the mold with traditional fixed locking mechanisms, significantly shortening operation time and improving production efficiency.

[0085] In some embodiments described above, the locking mechanism 8 is designed as a split L-shaped structure. Its upper L-shaped structure 81 and lower L-shaped structure 82 clamp the transverse lugs 6 on the upper mold 1 and the reinforcing rib boss 3 through their horizontally extended ends, thereby achieving mold locking. However, in actual operation, due to factors such as material thickness, pressing process parameters, or mold wear, it may be necessary to precisely adjust the clamping distance of the locking mechanism 8 to ensure uniform pressing effect and stable product quality. Without effective adjustment methods, it is difficult to adapt to different production needs, which may lead to uneven pressing or ineffective locking.

[0086] In this regard, this application further proposes that the control structure 83 is an electrically controlled telescopic rod or a manual gear transmission mechanism, which can drive the lower L-shaped structure 82 to rise and fall axially to adjust the distance between the two extended ends of the same locking mechanism 8.

[0087] Specifically, the control structure 83 can be an electrically controlled telescopic rod. An electrically controlled telescopic rod is a device that achieves linear reciprocating motion by driving a lead screw or gear with a motor. Its working principle is generally that the motor drives the lead screw to rotate, and the lead screw nut moves on the lead screw, thereby extending or shortening the telescopic rod. This mechanism can provide precise displacement control and can be remotely operated or automatically controlled via electrical signals to achieve precise setting and adjustment of the lifting position of the lower L-shaped structure 82.

[0088] Alternatively, the control structure 83 can also be a manual gear transmission mechanism. Manual gear transmission mechanisms typically consist of mechanical components such as gears, racks, worm gears, or lead screws and nuts. Rotational motion is converted into linear motion by manually turning a crank or handwheel. For example, turning the handwheel can drive the worm, which in turn drives the worm wheel, which then drives the lower L-shaped structure 82 to move axially up and down via the lead screw and nut mechanism. This mechanism is characterized by its simple structure, intuitive operation, and convenient maintenance, making it suitable for applications requiring manual adjustment.

[0089] The purpose of the axial lifting and lowering of the lower L-shaped structure 82 is to change the vertical distance between its horizontally extended end and the horizontally extended end of the upper L-shaped structure 81, i.e., the clamping gap. This lifting and lowering movement allows the locking mechanism 8 to adapt to clamped parts of different thicknesses. For example, when installing or removing the reinforcing rib boss 3, or when pressing prepregs of different thicknesses, the appropriate clamping force can be ensured by adjusting the position of the lower L-shaped structure 82. Adjusting the gap between the two extended ends of the locking mechanism 8 is key to achieving precise clamping. By precisely adjusting this gap, it can be ensured that the locking mechanism 8 can apply uniform and appropriate pressure when locking the transverse lug 6, avoiding insecure locking due to excessive gap, or excessive compression or even damage to mold components due to insufficient gap. This adjustment capability improves the versatility and adaptability of the mold, enabling it to flexibly meet various molding needs.

[0090] By introducing an electrically controlled telescopic rod or a manual gear transmission mechanism as the control structure 83, this application provides a reliable and controllable axial lifting capability for the lower L-shaped structure 82 of the locking mechanism 8. When using an electrically controlled telescopic rod, automated and high-precision adjustment of the position of the lower L-shaped structure 82 can be achieved. Operators can accurately set the clamping distance through the control system without directly contacting the mold, thereby significantly improving production efficiency and operational safety, and ensuring consistent locking during each pressing process. When using a manual gear transmission mechanism, a simple, intuitive, and easy-to-maintain adjustment method is provided. Operators can manually and precisely adjust the lifting position of the lower L-shaped structure 82 to adapt to different mold configurations or material thicknesses, effectively avoiding uneven pressing or mold damage caused by improper clamping distance. Whether electrically or manually controlled, the locking mechanism 8 can flexibly adapt to different molding requirements, ensuring that the mold provides stable and reliable locking force under various working conditions, thereby guaranteeing the molding quality and dimensional stability of the final product.

[0091] The outer top surface of the upper L-shaped structure 81 maintains a fixed gap with the top protruding part of the upper mold 1, and the outer bottom surface of the lower L-shaped structure 82 maintains a movable gap with the upper surface of the frame 4, so as to avoid the locking mechanism 8 transmitting additional pressure and affecting the uniformity of material pressing.

[0092] Specifically, the outer top surface of the upper L-shaped structure 81 maintains a fixed gap with the top protruding part of the upper mold 1. This is designed to ensure that, in the working state, the top of the upper L-shaped structure 81 does not directly contact or press against the top protruding part of the upper mold 1. This fixed gap can be achieved through precise machining tolerance control, or maintained by setting a shim or limiting structure of predetermined thickness between them. This design allows the main function of the upper L-shaped structure 81 to focus on clamping the transverse lug 6 of the upper mold 1 through its horizontally extended end, without applying additional vertical support or pressure to the upper mold 1, thereby avoiding interference of the locking mechanism 8 with the overall stress state of the upper mold 1.

[0093] Meanwhile, the bottom outer end face of the lower L-shaped structure 82 maintains a movable gap with the upper end face of the frame 4. This means that when the mold is working, there is a non-contact gap between the bottom of the lower L-shaped structure 82 and the upper end face of the frame 4. This movable gap allows the lower L-shaped structure 82 to have a certain degree of freedom during lifting or rotation, and ensures that the lower L-shaped structure 82 will not exert additional support or pressure on the frame 4 due to accidental contact during mold pressing. This gap setting can prevent the locking mechanism 8 from transmitting unintended forces to the mold cavity through the frame 4 during mold pressing, thereby maintaining the structural integrity and force purity of the frame 4 as the boundary of the mold cavity.

[0094] Through the above technical solution, this application effectively isolates the additional stress that the locking mechanism 8 may generate during clamping and pressing. Specifically, the fixed gap between the upper L-shaped structure 81 and the protruding part at the top of the upper mold 1, and the movable gap between the lower L-shaped structure 82 and the upper end face of the frame 4, ensure that the locking mechanism 8 only performs its preset clamping function and does not transmit unnecessary vertical or horizontal forces to the upper mold 1 and the frame 4. This refined gap control fundamentally eliminates the potential interference of the locking mechanism 8 on the internal pressure distribution of the mold, enabling the pressure inside the mold cavity to remain highly uniform during the pressing and molding of composite materials. Therefore, this application can significantly improve the dimensional stability and internal structural uniformity of the final molded material, and effectively enhance its impact resistance, thereby obtaining a higher quality surface-reinforced thermoplastic composite material.

[0095] Taking resin as an example, because the above structure enables rapid assembly of the reinforcing rib boss 3 below the planar boss 2, the temperature range of the M3 process closely matches the residual heat temperature of the lower mold, allowing it to enter the process state without significant heating. That is, by reducing the preform exposure time through the avoidance design of the locking mechanism, when preparing composite materials, maintaining the composite arrangement with A3 on top and A2 on the bottom, the rapid assembly scheme allows the residual heat of the mold to be maintained above 250°C, ensuring the preform temperature does not drop below the glass transition temperature, thus improving the interlaminar shear strength compared to traditional processes. Traditional mold changes result in longer preform heat dissipation time, causing the temperature to drop below the glass transition temperature of the thermoplastic resin, hindering interlaminar molecular diffusion and significantly weakening the bonding strength.

[0096] Taking resin as an example, the residual heat of the lower mold 5 is used to preferentially heat layer A2, that is, to preferentially heat the continuous fiber layer, which promotes the full wetting of the resin and the long fibers of layer A3. The residual heat of the mold can be maintained above 250°C, and the temperature of the preform does not drop below the glass transition temperature. The interlaminar shear strength is maintained above 75MPa, which is 20% higher than the traditional process. Traditional mold changes cause the preform to dissipate heat for more than 30 minutes, and the temperature drops below the glass transition temperature of the thermoplastic resin. The diffusion of interlaminar molecules is hindered, and the bonding strength is significantly weakened.

[0097] For the overall scheme of Embodiment 3, the locking mechanism can switch between working and avoidance positions by rotating from 0 to 90°. In the avoidance position, the extended end is completely away from the transverse lug, providing an open operating space for the installation of the reinforcing rib boss. The boss can be replaced without disassembling any parts, the heat dissipation time of the preform is shortened, and the interlayer shear strength can be maintained, effectively avoiding the product performance degradation caused by space conflicts in the prior art. The clamping surface of the locking mechanism 8 can be adapted to all reinforcing rib bosses with transverse lugs of the same specifications; by adjusting the lifting distance of the lower L-shaped structure, it can be compatible with bosses of different thicknesses without replacing the locking parts, improving versatility and reducing mold maintenance costs and changeover time. Moreover, the operating space of the locking mechanism 8 is completely open in the avoidance position, eliminating the need to work under the narrow upper mold 1, avoiding the risk of falling from height and damage from falling parts, and improving operational safety.

[0098] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, 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. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A molding die for a surface-reinforced thermoplastic composite material, characterized in that: The mold includes an upper mold (1), a lower mold (5), and a frame (4). The upper mold (1) has a flat boss (2) at the bottom, and the flat boss (2) is detachably provided with a reinforcing rib boss (3) at the bottom. Both of them have transverse lugs (6) on both sides for being locked by a locking mechanism (8). The upper mold (1) and the lower mold (5) are connected by the frame (4). The lower mold (5) has a temperature probe hole (9) on its side for placing a thermocouple. The molding die has two working states: F1 state, in which the upper mold (1) has only a flat boss (2) at the bottom and the reinforcing rib boss (3) is not installed, which is used to prepare a preform with a flat surface; F2 state, in which the flat boss (2) is installed with the reinforcing rib boss (3) at the bottom through the locking mechanism (8), which is used to prepare a thermoplastic composite material with a reinforcing rib structure.

2. The molding die for a surface-reinforced thermoplastic composite material according to claim 1, characterized in that: The locking mechanism (8) is a split L-shaped structure, including an upper L-shaped structure (81) that is axially rotatable and connected to the upper mold (1), and a lower L-shaped structure (82) that can be raised and lowered relative to the upper L-shaped structure (81). The two are connected by a control structure (83). The upper L-shaped structure (81) and the lower L-shaped structure (82) each have a horizontal protruding end for clamping the transverse ear pieces (6) that are on the same side and distributed vertically.

3. The molding die for a surface-reinforced thermoplastic composite material according to claim 2, characterized in that: The upper L-shaped structure (81) is connected to the top protruding part of the upper mold (1) via a rotating shaft (84). The rotation angle range is 0-90°. When the upper L-shaped structure (81) rotates, it drives the lower L-shaped structure (82) to rotate synchronously, thereby enabling the locking mechanism (8) to switch between the working position and the avoidance position.

4. The molding die for a surface-reinforced thermoplastic composite material according to claim 2, characterized in that: The control structure (83) is an electrically controlled telescopic rod or a manual gear transmission mechanism, which can drive the lower L-shaped structure (82) to rise and fall axially to adjust the distance between the two protruding ends of the same locking mechanism (8).

5. The molding die for a surface-reinforced thermoplastic composite material according to claim 2, characterized in that: The outer top surface of the upper L-shaped structure (81) maintains a fixed gap with the top protruding part of the upper mold (1), and the outer bottom surface of the lower L-shaped structure (82) maintains an movable gap with the upper surface of the frame (4) to avoid the locking mechanism (8) transmitting additional pressure and affecting the uniformity of material pressing.

6. A method for preparing a surface-reinforced thermoplastic composite material, using the molding die for the surface-reinforced thermoplastic composite material according to any one of claims 1-5, characterized in that... Includes the following steps: S1. Using an ultrasonic spot welding machine, the cut continuous fiber reinforced thermoplastic resin prepreg is laid up and spot welded according to the preset layup method P to form a preform A1. S2. Place the preform A1 into the mold of shape F1, and press it into preform A2 using process strategy M1. S3. Weigh the long fiber prepreg sheet with an aspect ratio of R according to the required weight W1, put it into the mold of shape F1, and then press it into preform A3 using process strategy M2. S4. The preform is placed into the mold of shape F2 with A3 on top and A2 on the bottom, and then pressed into a surface-reinforced thermoplastic composite material with dimensional stability and impact resistance using process strategy M3.

7. The preparation method according to claim 6, characterized in that: The thermoplastic composite material is prepared from prepreg, and its reinforcing fibers include carbon fiber and glass fiber. The thermoplastic resin matrix is ​​selected from one or more of polyetheretherketone, polyaryletherketone, and polyphenylene sulfide.

8. The preparation method according to claim 6, characterized in that: In step S1, the pre-laid method P of the preform A1 includes orthogonal layup and quasi-isotropic layup. The number of layups depends on the thickness of the continuous fiber composite material in the target part. In the molding step S3, the weight of the long fiber prepreg is 1.05-1.15 times the product of the volume of the long fiber composite material and the density of the prepreg. The aspect ratio of the long fiber prepreg is 2≤R≤5, and its width ranges from 3 to 10 mm.

9. The preparation method according to claim 6, characterized in that: The process strategy M1 has a temperature 20°C to 30°C above the glass transition temperature of the thermoplastic resin, a pressure of 3MPa to 6MPa, and a holding time of 20min to 40min; the process strategy M2 has a temperature 30°C to 50°C below the melting temperature of the thermoplastic resin, a pressure of 6MPa to 9MPa, a holding time of 25min to 35min, and venting ≥ 5 times; the process strategy M3 has a temperature 30°C to 50°C above the melting temperature of the thermoplastic resin, a pressure of 1MPa to 3MPa, and a holding time of 40min to 50min.

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