Multi-stage hot-press forming mold for pultrusion of C-shaped composite material and use method of multi-stage hot-press forming mold

Abstract

The invention relates to the technical field of molds, and discloses a multi-stage hot-press forming mold for pultrusion of a C-shaped composite material and a using method of the multi-stage hot-press forming mold for pultrusion of the C-shaped composite material, the multi-stage hot-press forming mold for pultrusion of the C-shaped composite material comprises a heating and pressurizing unit, and first sections and second sections are alternately arranged; each section comprises a bottom die, a side die and an upper die; the upper dies and the side dies are of two types, and in the first section, the upper dies and the bottom die enclose to form the top and the corner part of the C-shaped cavity. In the second section, the side die and the bottom die are enclosed to form a corner part and a web part; and heating elements are arranged in the bottom die, the side dies and the upper die. According to the multi-stage hot press forming mold for pultrusion of the C-shaped composite material, through the multiple independent and controllable heating and pressurizing sections, segmented and sequential regulation and control in the sectional material curing process are achieved, and multi-section temperature-pressure curves matched with curing characteristics are conveniently executed; and by alternately applying pressure to the corner part, the resin distribution and fiber wettability of the corner part are improved, and the porosity is reduced.

Description

Technical Field

[0001] This invention relates to the field of mold technology, specifically to a multi-stage hot pressing mold for C-shaped composite material pultrusion and its application method. Background Technology

[0002] Fiber-reinforced composite C-profiles are widely used in high-end equipment manufacturing fields such as aerospace, rail transportation, and new energy vehicles. Advanced pultrusion technology is currently the mainstream manufacturing process for longer C-profiles, offering advantages such as high automation, high efficiency, stable product quality, and low cost.

[0003] However, existing thermoforming molds mostly adopt integral or simple segmented structures, which have the following limitations: First, the pressure application method is singular, usually only applying unidirectional pressure to the corner area of ​​the C-profile, which easily leads to uneven resin distribution, poor fiber wetting, and increased porosity in this area, seriously affecting the overall mechanical properties; Second, the process adaptability is insufficient, unable to accurately execute multi-segment temperature-pressure curves that match the material curing characteristics, and lacks the ability to control the timing of resin flow and curing state at different locations of the profile, thus restricting further improvement of product performance. Summary of the Invention

[0004] In view of this, the present invention provides a multi-stage hot pressing mold for pultrusion of C-type composite materials and its application method, in order to solve the problems of uneven resin distribution, poor fiber impregnation, and increased porosity in the corner areas of C-type profiles due to the single pressing method, as well as insufficient process adaptability, inability to accurately execute multi-segment temperature-pressure curves that match the curing characteristics of materials, and lack of ability to control the timing of resin flow and curing state at different positions of the profile, which restricts further improvement of product performance.

[0005] In a first aspect, the present invention provides a multi-stage hot pressing mold for C-type composite material pultrusion, comprising:

[0006] At least one set of heating and pressurizing units, each set of heating and pressurizing units includes a first section and a second section that are sequentially spliced ​​along a first direction. When there are multiple heating and pressurizing units, multiple first sections and multiple second sections are alternately arranged along the first direction.

[0007] Both the first section and the second section include a bottom mold, side molds and an upper mold arranged symmetrically on the left and right sides. Multiple bottom molds, multiple side molds and multiple upper molds are adapted to enclose and form a continuous C-shaped cavity. The C-shaped cavity extends along the first direction and is adapted to accommodate the preform.

[0008] Both the upper mold and the side mold have two structural forms. In the first section, the upper mold and the bottom mold enclose the top and corner of the C-shaped cavity, and the side mold and the bottom mold enclose the web of the C-shaped cavity. In the second section, the upper mold and the bottom mold enclose the top of the C-shaped cavity, and the side mold and the bottom mold enclose the corner and web of the C-shaped cavity.

[0009] Heating elements are installed inside the bottom mold, side mold, and top mold.

[0010] In one alternative embodiment, the bottom mold is fixed, the upper mold is adapted to move vertically, and the side molds are adapted to move horizontally to apply pressure to the preform.

[0011] In one optional embodiment, multiple heating elements are electrically connected to a temperature control system; temperature sensors are respectively installed in the bottom mold, side mold, and top mold, and the multiple temperature sensors are electrically connected to the temperature control system.

[0012] In one alternative implementation, the temperature sensor is spaced 3 mm to 8 mm from the C-cavity.

[0013] In one alternative embodiment, the bottom mold is provided with a groove, and the side mold is provided with a protrusion corresponding to the groove, the groove being adapted to abut against the protrusion to limit the side mold in the horizontal direction.

[0014] In one alternative embodiment, the inner surfaces of the bottom mold, side mold, and top mold are provided with a polytetrafluoroethylene (PTFE) anti-stick coating.

[0015] Secondly, the present invention also provides a method for using a multi-stage hot pressing mold for C-shaped composite material pultrusion, comprising the following steps:

[0016] The number of heating and pressurizing units, as well as the length ratio of the first section and the second section, are configured according to process requirements; the heating element is activated to heat the C-shaped cavity, and the temperature is detected by a temperature sensor. After reaching the preset temperature, the temperature is kept stable by a temperature control system; the preform is inserted into the C-shaped cavity in a stepping manner from one end; the side mold first approaches the preform with a first preset pressure, and then extrudes the preform with a second preset pressure greater than the first preset pressure;

[0017] In one alternative implementation, the temperature of the C-cavity of each heating and pressurizing unit is set individually according to process requirements.

[0018] The technical solution of this invention has the following advantages:

[0019] 1. The multi-stage hot-press molding die for C-type composite material pultrusion provided by the present invention is composed of independent first and second sections assembled sequentially, with heating elements provided in each section. This transforms the traditional single-cavity mold into multiple independent and controllable heating and pressurizing sections, facilitating segmented and sequential control during the profile curing process. It also provides a structural basis for executing multi-segment temperature-pressure curves that match the material curing characteristics during the profile curing process, thereby enhancing the mold's process adaptability. Furthermore, by alternately applying pressure to the corners of the C-type profile in different sections and directions, it helps improve resin distribution and fiber wettability in the corner areas, reduces porosity, and enhances the overall mechanical property consistency of the profile.

[0020] 2. The multi-stage hot pressing mold for C-type composite material pultrusion provided by the present invention, by independently setting heating elements and temperature sensors in each section and connecting them to a temperature control system located outside the mold, can achieve independent and precise control of the temperature of each section. This is beneficial to eliminating the inherent temperature field gradient of large molds, ensuring synchronous curing of each structural part of the C-type composite material profile, and giving the molding mold the ability to execute complex multi-segment temperature process curves.

[0021] 3. The multi-stage hot pressing mold for C-type composite material pultrusion provided by the present invention uses protrusions and grooves to form a mechanical limiting structure to limit the range of movement of the side, thereby avoiding overload during the pressurization process.

[0022] 4. The multi-stage hot pressing mold for C-type composite material pultrusion provided by the present invention, by setting a polytetrafluoroethylene anti-stick coating, is used to prevent resin from adhering to the mold surface during the molding process and to facilitate the demolding of the composite material profile after curing, thereby ensuring the surface quality and demolding efficiency of the product.

[0023] 5. The method of using the multi-stage hot pressing mold for C-type composite material pultrusion provided by the present invention allows the side mold to approach the preform with a lower pressure first, and then extrude the preform with a higher pressure, so as to achieve positioning before high pressure, prevent profile size deviation or mold damage caused by excessive pressure or overtravel, and help ensure the stability of the molding process and the consistency of product size. Attached Figure Description

[0024] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the structure of a multi-stage hot pressing mold for pultrusion forming of C-type composite materials according to an embodiment of the present invention;

[0026] Figure 2 for Figure 1 A cross-sectional schematic diagram of the first section shown;

[0027] Figure 3 for Figure 1 A cross-sectional schematic diagram of the second section is shown.

[0028] Explanation of reference numerals in the attached figures:

[0029] 1. Bottom mold; 2. Side mold; 3. Top mold; 4. C-shaped cavity; 5. Groove; 6. Protrusion. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] The following is combined Figures 1 to 3 The following describes embodiments of the present invention.

[0032] According to an embodiment of the present invention, in one aspect, a multi-stage hot pressing die for pultruding C-type composite materials is provided, comprising:

[0033] At least one set of heating and pressurizing units, each set of heating and pressurizing units includes a first section and a second section that are sequentially spliced ​​along a first direction. When there are multiple heating and pressurizing units, multiple first sections and multiple second sections are alternately arranged along the first direction.

[0034] Both the first section and the second section include a bottom mold 1, side molds 2 and an upper mold 3 arranged symmetrically on the left and right sides. Multiple bottom molds 1, multiple side molds 2 and multiple upper molds 3 are adapted to enclose and form a continuous C-shaped cavity 4. The C-shaped cavity 4 extends along the first direction and is adapted to accommodate the preform.

[0035] Both the upper mold 3 and the side mold 2 have two structural forms. In the first section, the upper mold 3 and the bottom mold 1 enclose the top and corner of the C-shaped cavity 4, and the side mold 2 and the bottom mold 1 enclose the web of the C-shaped cavity 4. In the second section, the upper mold 3 and the bottom mold 1 enclose the top of the C-shaped cavity 4, and the side mold 2 and the bottom mold 1 enclose the corner and web of the C-shaped cavity 4.

[0036] Heating elements are installed inside the bottom mold 1, side mold 2 and upper mold 3 respectively.

[0037] The multi-stage hot-press molding die for C-type composite material pultrusion provided in this embodiment is composed of independent first and second sections assembled sequentially, with heating elements installed in each section. This transforms the traditional single-cavity mold into multiple independent and controllable heating and pressurizing sections, facilitating segmented and sequential control during the profile curing process. It also provides a structural basis for executing multi-segment temperature-pressure curves that match the material's curing characteristics during the profile curing process, enhancing the mold's process adaptability. Furthermore, by alternately applying pressure to the corners of the C-type profile in different sections and directions, it improves resin distribution and fiber wettability in the corner areas, reduces porosity, and enhances the overall consistency of the profile's mechanical properties.

[0038] Specifically, the heating and pressurizing unit is elongated, with its length pointing in the first direction. The molding die is arranged horizontally so that the length directions of multiple heating and pressurizing units are parallel to the horizontal direction. The heating elements located in different sections are independent of each other, making the first and second sections independent heating and pressurizing zones. This provides a physical carrier for segmented and time-sequential control of the profile curing process, laying the structural foundation for independent zoned control of the entire mold and the execution of complex process curves.

[0039] Traditional thermoforming molds often employ a single-piece or simple segmented structure with a single pressure application method. They typically apply unidirectional pressure only to the corner areas of the C-profile, which can easily lead to uneven resin distribution, poor fiber impregnation, and increased porosity in these areas, severely impacting the overall mechanical properties of the C-profile. In contrast, the molding die provided in this example features different structures in its first and second sections to achieve alternating pressure in different directions at the corner areas of the C-profile.

[0040] In the first section, the upper mold 3 covers the top and corner portions of the C-profile, while the side mold 2 only covers the side web portion of the C-profile and does not extend to the corner area. This ensures that when pressure is applied in the first section, as the upper mold 3 moves downward to apply pressure, the pressure acts directly and primarily on the two corner areas, meaning the corners mainly bear the vertical pressure from the upper mold 3. In the second section, the upper mold 3 only covers the top of the C-profile, excluding the corner portion, while the side mold 2 covers both the corner portion and the side web portion of the C-profile. This ensures that when the side mold 2 applies horizontal pressure towards the mold center, the pressure acts directly and primarily on the two corner areas, meaning the corners mainly bear the horizontal pressure from the side mold 2. This combined arrangement of the first and second sections allows the corner areas of the C-profile to be subjected to alternating forces in different directions during hot pressing, effectively improving resin distribution and fiber wettability in the corner areas, reducing porosity, and enhancing the overall mechanical property consistency of the profile.

[0041] In one embodiment, combined Figure 1 As shown, the bottom mold 1 is fixedly set, the upper mold 3 is adapted to move in the vertical direction, and the side mold 2 is adapted to move in the horizontal direction to apply pressure to the preform.

[0042] Specifically, the bottom mold 1 is fixedly set to provide a stable molding reference platform. The upper mold 3 can move vertically to apply downward pressure, and the two side molds 2 can move horizontally to apply rightward and leftward pressure respectively. It should be noted that the orientations indicated by "left" and "right" are based on the orientations shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, thereby achieving multi-directional coordinated pressurization.

[0043] In one embodiment, multiple heating elements are electrically connected to a temperature control system; temperature sensors are respectively provided in the bottom mold 1, side mold 2 and upper mold 3, and multiple temperature sensors are electrically connected to the temperature control system.

[0044] The multi-stage hot pressing mold for C-type composite material pultrusion provided in this embodiment achieves independent and precise temperature control of each section by independently setting heating elements and temperature sensors in each section and connecting them to a temperature control system located outside the mold. This helps to eliminate the inherent temperature field gradient of large molds, ensure synchronous curing of various structural parts of the C-type composite material profile, and endow the molding mold with the ability to execute complex multi-segment temperature process curves.

[0045] Specifically, each section's upper mold 3, bottom mold 1, and side mold 2 are equipped with heating channels, each containing a stainless steel tubular resistance heating rod. Furthermore, the arrangement of the heating rods is optimized using finite element simulation software to ensure uniform surface temperature across the upper mold 3, bottom mold 1, and side mold 2. All heating elements and temperature sensors are electrically connected to a temperature control system, such as a PLC system, to achieve independent closed-loop control.

[0046] In one embodiment, the temperature sensor is spaced 3 mm to 8 mm from the C-cavity 4.

[0047] Specifically, the temperature sensing element of the temperature sensor is spaced 3mm to 8mm from the C-shaped cavity 4. As a feasible implementation, a K-type thermocouple is embedded 5mm from the cavity surface for real-time temperature feedback.

[0048] In one embodiment, as shown in the figure, the bottom mold 1 is provided with a groove 5, and the side mold 2 is provided with a protrusion 6 corresponding to the groove 5. The groove 5 is adapted to abut against the protrusion 6 to limit the side mold 2 in the horizontal direction.

[0049] The multi-stage hot pressing mold for C-type composite material pultrusion provided in this embodiment uses protrusions 6 and grooves 5 to form a mechanical limiting structure, which limits the range of movement on the side, thereby avoiding overload during the pressurization process.

[0050] In one embodiment, the inner surfaces of the bottom mold 1, side mold 2, and upper mold 3 are provided with a polytetrafluoroethylene (PTFE) anti-stick coating.

[0051] The multi-stage hot-press molding die for C-type composite material pultrusion provided in this embodiment is equipped with a polytetrafluoroethylene anti-stick coating to prevent resin from adhering to the mold surface during the molding process and to facilitate demolding of the composite material profile after curing, thereby ensuring product surface quality and demolding efficiency.

[0052] According to an embodiment of the present invention, in another aspect, a method for using a multi-stage hot pressing die for C-shaped composite material pultrusion is also provided. The method using the aforementioned multi-stage hot pressing die for C-shaped composite material pultrusion includes the following steps:

[0053] The number of heating and pressurizing units, as well as the length ratio of the first section and the second section, are configured according to process requirements; the heating element is activated to heat the C-shaped cavity 4, and the temperature is detected by a temperature sensor. After reaching the preset temperature, the temperature is kept stable by a temperature control system; the preform is inserted into the C-shaped cavity 4 in a stepping manner from one end; the side mold 2 first approaches the preform with a first preset pressure, and then extrudes the preform with a second preset pressure greater than the first preset pressure;

[0054] The multi-stage hot pressing mold method for C-type composite material pultrusion provided in this embodiment allows the side mold 2 to approach the preform with a lower pressure first, and then extrude the preform with a higher pressure. This achieves positioning before high pressure, preventing profile dimensional deviations or mold damage caused by excessive pressure or overtravel, and helps ensure stability during the molding process and consistency of product dimensions.

[0055] Specifically, the length of the first and second sections is 350mm to 450mm, and the single step distance of the preform is 8mm to 18mm.

[0056] In one embodiment, the temperature of the C-shaped cavity of each heating and pressurizing unit is set individually according to process requirements, so as to achieve individual temperature control of each temperature zone.

[0057] Specifically, taking a multi-stage hot-press molding die for C-shaped composite material pultrusion as an example, which includes four sections, two first sections and two second sections are alternately spliced ​​together. One end of the C-shaped cavity is the inlet for introducing the preform, and the other end is the outlet for discharging the cured C-shaped composite material profile. Along the direction from the inlet to the outlet, multiple sections are defined as the first section, the second section, the third section, and the fourth section, where each section is 400mm long.

[0058] The heating elements are activated to raise the temperature of each section of the mold to its preset target temperature and maintain it stable. The temperature of the first and second sections is stabilized at 140℃, and the temperature of the third and fourth sections is stabilized at 160℃, with the temperature difference between each section ≤ ±2℃.

[0059] The preform is fed into the molding die from the feed port in a stepping manner, with a single stepping distance of 10 mm.

[0060] In the first stage, the upper mold 3 applies a downward pressure of 1.0 MPa to the preform, while the side mold 2 first moves horizontally to approach the preform under a pressure of 0.8 MPa, and then squeezes the preform under a pressure of 1.0 MPa until the groove 5 abuts against the protrusion 6.

[0061] In the second stage, the side mold 2 first moves horizontally to approach the preform under a pressure of 0.8 MPa, and then squeezes the preform under a pressure of 1.0 MPa until the groove 5 abuts against the protrusion 6. At the same time, the upper mold 3 applies a downward pressure of 0.8 MPa to the preform.

[0062] In the third stage, the upper mold 3 applies a downward pressure of 1.2 MPa to the preform, while the side mold 2 first moves horizontally to approach the preform under a pressure of 1.0 MPa, and then squeezes the preform under a pressure of 1.2 MPa until the groove 5 abuts against the protrusion 6.

[0063] In the fourth stage, the side mold 2 first moves horizontally to approach the preform under a pressure of 1.0 MPa, and then squeezes the preform under a pressure of 1.2 MPa until the groove 5 abuts against the protrusion 6. At the same time, the upper mold 3 applies a downward pressure of 1.0 MPa to the preform.

[0064] As the C-shaped composite material preform moves forward, it undergoes curing reactions at different temperature zones, eventually being drawn out from the outlet as a fully cured, smooth-surfaced C-shaped cross-section composite material.

[0065] Taking a multi-stage hot-press molding die for C-shaped composite material pultrusion as an example, comprising six sections, three first sections and three second sections are alternately spliced ​​together. One end of the C-shaped cavity is the inlet for introducing the preform, and the other end is the outlet for discharging the cured C-shaped composite material profile. Along the direction from the inlet to the outlet, multiple sections are defined as the first, second, third, fourth, fifth, and sixth sections, each with a length of 400 mm.

[0066] The heating elements are activated to raise the temperature of each section of the mold to its preset target temperature and maintain it stable. The temperature of the first and second sections is stabilized at 120℃, the temperature of the third and fourth sections is stabilized at 140℃, and the temperature of the fifth and sixth sections is stabilized at 160℃, with the temperature difference between each section ≤ ±2℃.

[0067] The preform is fed into the molding die from the feed port in a stepping manner, with a single stepping distance of 15 mm.

[0068] In the first stage, the upper mold 3 applies a downward pressure of 0.8 MPa to the preform, while the side mold 2 first moves horizontally to approach the preform under a pressure of 0.6 MPa, and then squeezes the preform under a pressure of 0.8 MPa until the groove 5 abuts against the protrusion 6.

[0069] In the second stage, the side mold 2 first moves horizontally to approach the preform under a pressure of 0.6 MPa, and then squeezes the preform under a pressure of 0.8 MPa until the groove 5 abuts against the protrusion 6. At the same time, the upper mold 3 applies a downward pressure of 0.6 MPa to the preform.

[0070] In the third stage, the upper die 3 applies a downward pressure of 1.0 MPa to the profile, while the side die 2 first moves horizontally to approach the preform under a pressure of 0.8 MPa, and then squeezes the preform under a pressure of 1.0 MPa until the groove 5 abuts against the protrusion 6.

[0071] In the fourth stage, the side mold 2 first moves horizontally to approach the preform under a pressure of 0.8 MPa, and then squeezes the preform under a pressure of 1.0 MPa until the groove 5 and the protrusion 6 abut against each other. At the same time, the upper mold 3 applies a downward pressure of 0.8 MPa to the preform.

[0072] In the fifth section, the upper mold 3 applies a downward pressure of 1.2 MPa to the preform, while the side mold 2 first moves horizontally to approach the preform under a pressure of 1.0 MPa, and then squeezes the preform under a pressure of 1.2 MPa until the groove 5 abuts against the protrusion 6.

[0073] In the sixth section, the side mold 2 first moves horizontally to approach the preform under a pressure of 1.0 MPa, and then squeezes the preform under a pressure of 1.2 MPa until the groove 5 abuts against the protrusion 6. At the same time, the upper mold 3 applies a downward pressure of 1.0 MPa to the preform.

[0074] As the C-shaped composite material preform moves forward, it undergoes curing reactions at different temperature zones, ultimately resulting in a fully cured, smooth-surfaced C-shaped cross-section composite material being drawn out of the outlet.

[0075] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Although embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and all such modifications and variations fall within the scope defined by the present invention.

Claims

1. A multi-stage hot pressing mold for pultrusion forming of C-shaped composite materials, characterized in that, include: At least one set of heating and pressurizing units, each set of heating and pressurizing units includes a first section and a second section sequentially spliced ​​along a first direction. When there are multiple heating and pressurizing units, multiple first sections and multiple second sections are alternately arranged along the first direction. Both the first section and the second section include a bottom mold (1), side molds (2) and an upper mold (3) arranged symmetrically on the left and right sides. The multiple bottom molds (1), the multiple side molds (2) and the multiple upper molds (3) are adapted to enclose and form a continuous C-shaped cavity (4). The C-shaped cavity (4) extends along the first direction and is adapted to accommodate the preform. The upper mold (3) and the side mold (2) each have two structural forms. In the first section, the upper mold (3) and the bottom mold (1) enclose the top and corner of the C-shaped cavity (4), and the side mold (2) and the bottom mold (1) enclose the web of the C-shaped cavity (4). In the second section, the upper mold (3) and the bottom mold (1) enclose the top of the C-shaped cavity (4), and the side mold (2) and the bottom mold (1) enclose the corner and web of the C-shaped cavity (4); Heating elements are respectively provided inside the bottom mold (1), the side mold (2) and the upper mold (3).

2. The multi-stage hot pressing mold for C-type composite material pultrusion according to claim 1, characterized in that, The bottom mold (1) is fixedly set, the upper mold (3) is adapted to move in the vertical direction, and the side mold (2) is adapted to move in the horizontal direction to apply pressure to the preform.

3. The multi-stage hot pressing mold for C-type composite material pultrusion according to claim 1, characterized in that, The heating elements are electrically connected to the temperature control system respectively; temperature sensors are respectively provided in the bottom mold (1), the side mold (2) and the upper mold (3), and the temperature sensors are electrically connected to the temperature control system respectively.

4. The multi-stage hot pressing mold for C-type composite material pultrusion according to claim 3, characterized in that, The temperature sensor is spaced 3mm to 8mm from the C-shaped cavity (4).

5. The multi-stage hot pressing mold for C-type composite material pultrusion according to claim 1, characterized in that, The bottom mold (1) is provided with a groove (5), and the side mold (2) is provided with a protrusion (6) corresponding to the groove (5). The groove (5) is adapted to abut against the protrusion (6) to limit the side mold (2) in the horizontal direction.

6. The multi-stage hot pressing mold for C-type composite material pultrusion according to claim 1, characterized in that, The inner surfaces of the bottom mold (1), the side mold (2) and the upper mold (3) are provided with a polytetrafluoroethylene anti-stick coating.

7. A method of using a multi-stage hot pressing mold for C-shaped composite material pultrusion, comprising using the multi-stage hot pressing mold for C-shaped composite material pultrusion as described in any one of claims 1-6, characterized in that, Includes the following steps: The number of heating and pressurizing units, and the length ratio of the first section and the second section are configured according to the process requirements; the heating element is started to heat the C-shaped cavity (4), and the temperature is detected by the temperature sensor. After reaching the preset temperature, the temperature is kept stable by the temperature control system; the preform is inserted into the C-shaped cavity (4) in a stepping manner from one end; the side mold (2) first approaches the preform with the first preset pressure, and then squeezes the preform with the second preset pressure which is greater than the first preset pressure.

8. The method of using the multi-stage hot pressing mold for C-type composite material pultrusion according to claim 7, characterized in that, The temperature of the C-shaped cavity of each of the heating and pressurizing units is set individually according to process requirements.

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