An integral composite material expansion section rtm forming mold and a method of using the same

Abstract

The application discloses a whole composite material expansion section RTM forming die and a use method thereof. The die comprises a bottom die, a lower die installed on the upper surface of the bottom die, and an upper die installed on the upper surface of the lower die. The upper die and the lower die jointly form a hollow chamber which is in communication with the interior of the upper die and the interior of the lower die. An upper core die and a lower core die are installed in the hollow chamber. The lower core die is installed on the bottom die, and the upper core die is installed on the upper surface of the lower core die. Glue injection ports and glue discharge ports are respectively arranged on the upper core die and the bottom die. The upper core die, the lower core die, the upper die, the lower die and the bottom die jointly form a die cavity for accommodating a whole expansion section preform. The glue injection ports are in communication with the die cavity. Symmetrical exhaust passage groups are arranged in the interior of the lower die and located on both sides of the die cavity. Each exhaust passage group comprises a plurality of exhaust passages arranged from bottom to top and in communication with the die cavity, and exhaust holes in communication with the plurality of exhaust passages and the atmosphere. The diameters of the plurality of exhaust passages gradually increase from bottom to top.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of resin-based composite material forming, in particular to a whole composite material expansion section RTM forming die and a using method thereof. BACKGROUND

[0002] Resin-based composite materials have the mechanical performance advantages of high strength and high rigidity, improve the performance of anti-fatigue fracture, light weight, high strength and other characteristics, are widely used in the fields of aerospace, military strategy and the like, are also developed and applied in the fields of wind power generation, automobile manufacturing and the like, and make the performance of products continuously improved.

[0003] The expansion section is an important anti-ablation component in the nozzle of a solid rocket engine. The expansion section needs to have high normal strength to resist the ablation and scouring of high-temperature and high-speed gas flow. At present, the expansion section of a solid rocket engine is mostly prepared by using a tape winding process to prepare a preform, and the finally formed composite material has poor mechanical performance and poor ablation performance, and the prominent problem is poor interlayer performance. The comprehensive performance is not high, and in particular, the interlayer shear performance is low, which is not suitable for the development trend of modern weapons of high supersonic speed, high defense and high precision.

[0004] The RTM (Resin Transfer Molding) forming technology is a composite liquid forming technology, and the process is as follows: under certain temperature and pressure, a resin system of low viscosity resin, curing agent and catalyst is injected into a closed mold in which a reinforcing fiber preform has been placed, the fiber reinforced material is completely impregnated through the flow of the resin, and the advanced resin-based composite material is obtained after curing and demolding. The RTM forming process can manufacture complex components with good surface quality and high precision, has high forming efficiency, and avoids the safety performance problems caused by the contact of workers with raw materials such as resin.

[0005] Due to the high overall strength, excellent anti-ablation scouring performance and other high performance requirements of the whole composite material expansion section, the composite material expansion section prepared by the traditional forming process has poor interlayer performance, high porosity and large ablation rate, and it is difficult to form a complex shape. The RTM forming process can effectively improve the above problems, and the RTM forming process can meet the requirements of the complex structure of the whole composite material expansion section and the high forming precision of the inner surface, so a RTM forming die for preparing a whole composite material expansion section with high precision and high performance is needed. SUMMARY

[0006] The present application provides a whole composite material expansion section RTM forming die and a using method thereof for preparing a whole composite material expansion section with high precision and high performance.

[0007] Technical solution: To solve the above problems, the application adopts a whole composite material expansion section RTM forming mold, which comprises a bottom mold, a lower mold installed on the upper surface of the bottom mold, and an upper mold installed on the upper surface of the lower mold, the upper mold and the lower mold jointly form a hollow chamber which communicates the inside of the upper mold with the inside of the lower mold, the upper core mold and the lower core mold are installed in the hollow chamber, the lower core mold is installed on the bottom mold, and the upper core mold is installed on the upper surface of the lower core mold, the upper core mold is also provided with a glue injection port for injecting materials, and the bottom mold is provided with a plurality of glue outlet ports for injecting materials; the upper core mold, the lower core mold, the upper mold, the lower mold and the bottom mold form a mold cavity for accommodating the whole expansion section preform, and the glue injection port is in communication with the mold cavity.

[0008] The lower mold is provided with a symmetrical exhaust passage group located on both sides of the mold cavity, the exhaust passage group comprises a plurality of exhaust passages arranged from bottom to top and respectively in communication with the mold cavity, and an exhaust hole for communicating the plurality of exhaust passages with the outside atmosphere, and the diameter of the plurality of exhaust passages gradually increases from bottom to top.

[0009] Further, the upper core mold comprises an upper cylinder and a lower cylinder connected with the upper cylinder, the upper cylinder and the lower cylinder are coaxially arranged, and the diameter of the lower cylinder is smaller than that of the upper cylinder; the upper cylinder is provided with a plurality of glue injection ports, the lower cylinder is provided with a plurality of screw holes and an upper positioning hole located at the center of the upper core mold, and the upper screw hole and the upper positioning hole both penetrate the upper core mold and the axis is parallel to the axis of the upper core mold.

[0010] Further, one end of the lower core mold is cylindrical, and the other end is circular truncated cone, the cylindrical end is provided with a lower positioning hole corresponding to the position of the upper positioning hole and a lower screw hole corresponding to the position of the upper screw hole, a positioning pin shaft is installed in the upper positioning hole and the lower positioning hole to fix the relative position of the upper core mold and the lower core mold, and a bolt is installed in the upper screw hole and the lower screw hole to fixedly connect the upper core mold and the lower core mold.

[0011] Further, the upper mold comprises two upper mold units, the upper mold units are both provided with upper bosses on both sides, the upper bosses are provided with screw holes, and the screw holes are provided with bolts to fixedly connect the two upper mold units; the upper mold units are also provided with notches for connecting with the lower mold.

[0012] Further, the lower mold comprises two lower mold units, the lower mold units are both provided with lower bosses on both sides, the lower bosses are provided with screw holes, and the screw holes are provided with bolts to fixedly connect the two lower mold units; the lower mold units are also provided with screw holes for connecting with the upper mold, and the bolts are installed in the notches of the upper mold units and the screw holes of the lower mold units to fixedly connect the upper mold and the lower mold.

[0013] Further, the bottom die is provided with a groove, and the lower die is installed on the groove; a circular boss with a diameter larger than the outer diameter of the bottom surface of the integral expansion section prefabricated body is arranged in the middle of the groove, and the circular boss is coaxially arranged with the circular boss through bolted fixation.

[0014] Further, the bottom surface of the lower die unit is provided with a semicircular annular glue outlet channel, and a plurality of radial connecting channels are arranged on the inner side of the glue outlet channel; the glue outlet is arranged on the circular boss, and the material is injected from the glue injection port and then flows out from the glue outlet through the mold cavity, the connecting channel and the glue outlet channel.

[0015] Further, a sealing gasket with the same shape as the groove is arranged between the lower die and the bottom die, and the circular boss penetrates the middle of the sealing gasket.

[0016] Further, the application further comprises an integral expansion section prefabricated body, which is installed in the mold cavity, and the material injected from the glue injection port enters the integral expansion section prefabricated body.

[0017] The application also provides a use method of the integral composite expansion section RTM forming mold, which comprises the following steps:

[0018] Step 1, uniformly coating release agent on the surface of the mold inner surface and the mold closing surface for multiple times;

[0019] Step 2, fixedly connecting the lower core die and the bottom die, and placing the integral expansion section prefabricated body on the bottom die;

[0020] Step 3, fixedly connecting the lower die and the bottom die, and placing the integral expansion section prefabricated body in the gap between the lower die, the lower core die and the bottom die;

[0021] Step 4, fixedly connecting the upper core die and the lower core die;

[0022] Step 5, fixedly connecting the upper die and the lower die, and integrally accommodating the integral expansion section prefabricated body in the hollow cavity;

[0023] Step 6, injecting the material from the glue injection port to infiltrate the integral expansion section prefabricated body;

[0024] Step 7, placing for a period of time until the material solidifies, and then sequentially disassembling the upper core die, the upper die and the lower die to take out the infiltrated integral expansion section prefabricated body.

[0025] Beneficial effects: relative to the prior art, the present application has the following advantages: (1) the integral composite material expansion section product made by using the mold of the present application has high dimensional accuracy and excellent inner and outer surface quality, the entire product is integrally solidified and formed, the demolding process is simple, and the manufacturing cost of the integral composite material expansion section is effectively reduced; at the same time, the interlaminar performance of the composite material is effectively improved, the overall strength and comprehensive performance of the composite material are improved, and the harm of chemical products such as resin to people and the environment is reduced; (2) the plurality of evenly arranged glue injection ports and glue discharge ports are arranged, so as to ensure the uniformity of the impregnation of the thermosetting resin to the reinforcing fabric; (3) the exhaust channel is arranged, so as to effectively exhaust the small molecules such as water continuously generated in the chemical reaction of the resin during the solidification process, thereby reducing the porosity of the product and improving the mechanical properties of the product; and since the upper part of the mold is subjected to greater pressure than the lower part, the diameters of the exhaust holes are arranged in a stepped manner, the diameters of the connecting ports of the exhaust channels gradually increase from the lower part to the upper part, and the exhaust process is more smooth. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 It is a schematic diagram of the overall structure of the RTM forming mold of the present application;

[0027] Figure 2 It is a schematic diagram of the overall structure of the RTM forming mold of the present application from a top view;

[0028] Figure 3 It is a schematic diagram of the structure of the RTM forming mold of the present application along a section;

[0029] Figure 4 It is a schematic diagram of the structure of the RTM forming mold of the present application along another section;

[0030] Figure 5 It is a schematic diagram of the section of the RTM forming mold of the present application;

[0031] Figure 6 It is a schematic diagram of the structure of the upper core mold of the RTM forming mold of the present application;

[0032] Figure 7 It is a schematic diagram of the structure of the lower core mold of the RTM forming mold of the present application;

[0033] Figure 8 It is a schematic diagram of the structure of the upper mold of the RTM forming mold of the present application from a top view;

[0034] Figure 9 It is a schematic diagram of the structure of the lower right mold of the RTM forming mold of the present application from a top view;

[0035] Figure 10 It is a schematic diagram of the structure of the bottom mold of the RTM forming mold of the present application. DETAILED DESCRIPTION

[0036] As Figures 1 to 5As shown, the RTM forming mold of the integral composite expansion section in the embodiment includes an upper core mold 1, an upper mold, a lower mold, a bottom mold 6, a lower core mold 7, and an integral expansion section preform 8. The length of the integral structure is 350 mm, the width is 250 mm, and the height is 360 mm. Each part of the mold is made of Cr12 steel. The bottom mold 6 is located at the bottom, the lower mold is installed on the upper surface of the bottom mold, and the upper mold is installed on the upper surface of the lower mold. The upper mold and the lower mold have a hollow chamber passing through the upper and lower molds. The upper core mold 1 and the lower core mold 7 are installed in the hollow chamber, the lower core mold 7 is installed on the bottom mold 6, the upper core mold 1 is installed on the upper surface of the lower core mold 7, and the upper surface of the upper core mold 1 is flush with the upper surface of the upper mold. The upper core mold 1, the lower core mold 7, the upper mold, the lower mold, and the bottom mold 6 form a mold cavity with the same size as the integral expansion section preform 8.

[0037] As shown in Figure 6 The upper core mold 1 includes an upper cylinder 105 and a lower cylinder 102 arranged coaxially. The upper cylinder 105 and the lower cylinder 102 are integrally formed, and the diameter of the lower cylinder 102 is smaller than that of the upper cylinder 105. The upper cylinder 105 is provided with a sealing groove 104 on the side surface, and a sealing ring is installed in the sealing groove 104. The upper cylinder 105 is provided with four glue injection ports 103 distributed in a circle on the upper surface, and the diameter of the glue injection port 103 is 9 mm. The lower cylinder 102 is provided with three upper screw holes 106 and an upper positioning hole 101 located at the center of the lower cylinder 102. The upper screw holes 106 and the upper positioning hole 101 penetrate the upper core mold 1 and have an axis parallel to the axis of the upper core mold 1.

[0038] As shown in Figure 7 The lower core mold 7 has a cylindrical shape at one end and a circular truncated cone shape at the other end. The cylindrical end is provided with a lower positioning hole 702 corresponding to the position of the upper positioning hole 101 and a lower screw hole 701 corresponding to the position of the upper screw hole 106. A positioning pin shaft is installed in the upper positioning hole 101 and the lower positioning hole 702 to fix the relative position of the upper core mold 1 and the lower core mold 7. A bolt is installed in the upper screw hole 106 and the lower screw hole 701 to fixedly connect the upper core mold 1 and the lower core mold 7.

[0039] As shown in Figure 8 The upper mold includes two upper mold units, namely an upper left mold 2 and an upper right mold 3, which have the same structure. The upper mold unit is provided with an upper boss 302 on both sides, and a bolt through hole 301 is provided on the upper boss 302. A bolt is installed in the bolt through hole 301 to fixedly connect the two upper mold units. The upper mold unit is also provided with two upper mold long straight grooves 304 penetrating the upper and lower surfaces of the upper mold unit and an upper mold short straight groove 303 located between the two long straight grooves 304.

[0040] As shown in Figure 9As shown, the lower mold includes a lower left mold 4 and a lower right mold 5, both of which are provided with lower bosses on both sides, the lower bosses are provided with bolt through holes 501, and bolts are installed in the bolt through holes 501 to fixedly connect the lower left mold 4 and the lower right mold 5. The lower bosses are also provided with long sealing grooves 502, and sealing strips are installed in the long sealing grooves 502 to sealingly connect the lower left mold 4 and the lower right mold 5. The upper end surfaces of the lower left mold 4 and the lower right mold 5 are also provided with screw holes for connecting with the upper mold, and bolts are installed in the notches of the upper mold unit and the screw holes of the lower mold unit to fixedly connect the upper mold and the lower mold. The bottom surfaces of the lower left mold 4 and the lower right mold 5 are both provided with a semicircular annular glue outlet channel 505, and a plurality of connection channels 506 are arranged on the inner side of the glue outlet channel 505. The side surface of the lower right mold 5 is also provided with an exhaust channel 503, one end of which is in communication with the mold cavity, and the other end is in communication with the atmosphere through an exhaust hole 504. After the composite material is injected, the reaction in the mold cavity produces gas, which is discharged in time to prevent the gas from affecting the molding process. Since the pressure at the upper part of the mold is greater than that at the lower part, the diameters of the exhaust holes are arranged in a stepped manner, the diameters of the connection ports of the exhaust channel gradually increase from bottom to top, and the diameter of the connection port of the exhaust channel 503 connected with the mold cavity is 0.1 mm at the maximum and 0.03 mm at the minimum.

[0041] As shown in Figure 10 The bottom mold 6 is provided with a groove 601, the vertical distance between the bottom surface of the groove 601 and the upper surface of the bottom mold 6 is 1.5 mm, and a sealing gasket 608 with a thickness of 2 mm is arranged in the groove 601. The groove 601 is provided with four bottom mold long straight notches 605, bottom mold short straight notches 604 and bolt through holes 606, and the lower mold is installed on the groove 601 through bolts. The middle part of the groove 601 is provided with a circular boss 602 with a diameter greater than the outer diameter of the bottom surface of the integral expansion section preform 8, the circular boss 602 penetrates the middle part of the sealing gasket 608, and the upper surface of the circular boss 602 is flush with the upper surface of the bottom mold 6. The circular boss 602 is provided with four bolt holes 607 arranged in a circumferential manner and one bolt hole located at the center, and the circular boss 602 is fixedly installed on the circular boss 602 through bolts. The axis of the lower core mold 7 is coaxially arranged with the circular boss 602. The circular boss 602 is provided with four glue outlets 603 close to the outer circumference, the glue outlets 603 are arranged in a circumferential manner and have a diameter of 6 mm, and the material is injected from the glue injection port 103, and then flows out through the integral expansion section preform 8, the connection channel 506, the glue outlet channel 505 and the glue outlet 603 in sequence.

[0042] The method for preparing the integral composite material expansion section product of the present application is as follows:

[0043] Step 1, wipe the surfaces of each part of the mold clean, so that there is no any adhering matter on the surfaces, then uniformly coat the mold inner surface and the mold closing surface with release agent for 3 times, when coating, the second layer should be coated after the first layer is dried to form a film, and the interval time between each layer is not less than 15 min.

[0044] Step 2, the lower core mold 7 is placed on the bottom mold 6, and the two are fastened by bolts. The large-diameter end of the integral expansion section preform 8 is placed on the center cylindrical boss 602 of the bottom mold 6, and the sealing gasket 608 is placed in the groove 601 of the bottom mold 6.

[0045] Step 3, the lower left mold 4 and the lower right mold 5 are respectively placed on the upper surface of the bottom mold 6 at both ends of the edge, and the lower left mold 4 and the lower right mold 5 are moved horizontally to close, when the gap between the two is very small, the sealing strip is inserted into the long sealing groove 502, and finally the bolts are fastened through the bolt holes on the bosses on both sides of the lower left mold 4 and the lower right mold 5, and then the bolts are inserted through the short straight slot 604, the long straight slot 605 and the bolt through hole 606 of the bottom mold 6 to fasten, realizing the combination and relative position fixation of the bottom mold 6, the lower core mold 7, the lower left mold 4 and the lower right mold 5.

[0046] Step 4, the sealing ring is placed in the sealing groove 104 of the upper core mold 1, the positioning pin shaft is inserted into the upper positioning hole 101, then the positioning pin shaft of the upper core mold 1 is aligned with the lower positioning hole 702 on the upper surface of the lower core mold 7, the lower surface of the upper core mold 1 and the upper surface of the lower core mold 7 are tightly attached, the upper core mold 1 is rotated horizontally, so that the bolts can be fastened through the bolt holes 106 of the upper core mold 1 and the threaded holes 701 of the lower core mold 7.

[0047] Step 5, the sealing gasket is placed on the upper surface of the lower left mold 4 and the lower right mold 5, and then the upper left mold 2 and the upper right mold 3 are respectively placed at both ends of the edge of the sealing gasket, the upper left mold 2 and the upper right mold 3 are moved horizontally to close, and the bolts are inserted through the bolt through holes 301 to fasten, realizing the combination and relative position fixation of the upper left mold 2 and the upper right mold 3. Then fasten through the long straight slot 304 and the short straight slot 303, realize the overall combination and fixation of the upper core mold 1, the upper left mold 2, the upper right mold 3, the lower left mold 4, the lower right mold 5, the bottom mold 6 and the lower core mold 7, and the internal cavity after closing wraps the integral expansion section preform 8.

[0048] Step 6, RTM forming process is adopted, low viscosity liquid forming resin is injected into the mold, the resin flows and infiltrates the preform fiber fabric, under the action of high temperature, the curing of the composite material is completed. Phenolic resin is selected for injection into the mold in this embodiment, the viscosity of the resin is 0.9 Pa·s, the mold can withstand a pressure of 2.5 MPa after closing, can resist 250℃ high temperature, the surface roughness of the sealed cavity is in the range of 0.2-0.4.

[0049] Step 7, all the bolts are removed, the upper core mold 1 is removed first, then the upper left mold 2 and the upper right mold 3 are removed, the sealing gasket is taken off, then the lower left mold 4 and the lower right mold 5 are removed, finally the integral composite material expansion section product is taken out from the mold, which completes the demolding of the integral composite material expansion section product.

[0050] The present application can realize near-net forming of the integral composite material expansion section product, reduces the processing time and cost of the composite material in later period, effectively improves the interlaminar performance of the composite material, improves the overall strength and comprehensive performance of the composite material, and reduces the harm of chemicals such as resin to people and environment.

Claims

1. A one-piece composite material expansion section RTM forming mold characterized by, The bottom die (6), the lower die installed on the upper surface of the bottom die (6), and the upper die installed on the upper surface of the lower die are provided, the upper die and the lower die jointly form a hollow chamber which communicates the interior of the upper die with the interior of the lower die, the upper core die (1) and the lower core die (7) are installed in the hollow chamber, the lower core die (7) is installed on the bottom die (6), the upper core die (1) is installed on the upper surface of the lower core die (7), the upper core die (1) is further provided with a glue injection port (103) for injecting materials, and the bottom die (6) is provided with a plurality of glue outlet ports (603) for the injection materials to flow out; the upper core die (1), the lower core die (7), the upper die, the lower die, and the bottom die (6) jointly form a die cavity for accommodating a whole expansion section prefabricated body (8), and the glue injection port (103) is in communication with the die cavity. The upper core die (1) comprises an upper cylinder (105) and a lower cylinder (102) connected with the upper cylinder (105), the upper cylinder (105) and the lower cylinder (102) are coaxially arranged, and the diameter of the lower cylinder (102) is smaller than that of the upper cylinder (105); the upper cylinder (105) is provided with a plurality of glue injection ports (103), the lower cylinder (102) is provided with a plurality of upper screw holes (106) and an upper positioning hole (101) located at the center of the upper core die (1), and the upper screw holes (106) and the upper positioning hole (101) all penetrate the upper core die (1) and have axes parallel to the axis of the upper core die (1). One end of the lower core die (7) is in a cylindrical shape, and the other end is in a circular truncated cone shape, the cylindrical end is provided with a lower positioning hole (702) corresponding to the position of the upper positioning hole (101) and a lower screw hole (701) corresponding to the position of the upper screw hole (106), a positioning pin shaft is installed in the upper positioning hole (101) and the lower positioning hole (702) to fix the relative positions of the upper core die (1) and the lower core die (7), and a bolt is installed in the upper screw hole (106) and the lower screw hole (701) to fixedly connect the upper core die (1) and the lower core die (7). The lower die is internally provided with a plurality of exhaust passage groups symmetrically arranged on both sides of the die cavity, each exhaust passage group comprises a plurality of exhaust passages (503) arranged from bottom to top and in communication with the die cavity, and an exhaust hole (504) in communication with the atmosphere and the plurality of exhaust passages (503), and the diameters of the plurality of exhaust passages (503) gradually increase from bottom to top.

2. The integral composite material expansion section RTM molding mold of claim 1, wherein, The upper die comprises two upper die units, each of the upper die units is provided with an upper boss (302), the upper boss (302) is provided with a screw hole, and a bolt is installed in the screw hole to fixedly connect the two upper die units; the upper die unit is further provided with a notch for connecting with the lower die.

3. The integral composite material expansion section RTM molding mold of claim 2, wherein, The lower die comprises two lower die units, each of the lower die units is provided with a lower boss, the lower boss is provided with a screw hole, and a bolt is installed in the screw hole to fixedly connect the two lower die units; the lower die unit is further provided with a screw hole for connecting with the upper die, and a bolt is installed in the notch of the upper die unit and the screw hole of the lower die unit to fixedly connect the upper die and the lower die.

4. The integral composite material expansion section RTM molding mold of claim 3, wherein, The bottom die (6) is provided with a groove (601), and the lower die is installed on the groove (601); the middle part of the groove (601) is provided with a circular boss (602) with a diameter larger than the outer diameter of the bottom surface of the integral expansion section prefabricated body (8), and the circular table-shaped one end of the lower core die (7) is fixedly installed on the circular boss (602) through bolts, and the axis of the lower core die (7) is coaxially arranged with the circular boss (602).

5. The integral composite material expansion section RTM molding mold of claim 4, wherein, The bottom surface of the lower die unit is provided with a semicircular annular glue outlet channel (505), the inner side of the glue outlet channel (505) is provided with a plurality of radially arranged connecting channels (506), and the glue outlet (603) is arranged on the circular boss (602); after the material is injected from the glue injection port (103), the material flows out in sequence through the mold cavity, the connecting channel (506), the glue outlet channel (505) and the glue outlet (603).

6. The integral composite material expansion section RTM molding mold of claim 5, wherein, The lower die and the bottom die (6) are provided with a sealing gasket (608) with the same shape as the groove (601), and the circular boss (602) penetrates from the middle part of the sealing gasket (608).

7. The integral composite material expansion section RTM molding mold of claim 1 wherein, The integral expansion section prefabricated body (8) is also included, which is installed in the mold cavity, and the material injected from the glue injection port (103) enters the integral expansion section prefabricated body (8).

8. A method of using the integral composite material expansion section RTM mould of any one of claims 1 to 7, characterised in that, The method comprises the following steps: Step 1, uniformly coating release agent on the surface of the mold inner surface and the mold closing surface for multiple times; Step 2, fixedly connecting the lower core die (7) and the bottom die (6), and placing the integral expansion section prefabricated body (8) on the bottom die (6); Step 3, fixedly connecting the lower die and the bottom die (6), and the integral expansion section prefabricated body (8) is located in the gap between the lower die, the lower core die (7) and the bottom die (6); Step 4, fixedly connecting the upper core die (1) and the lower core die (7); Step 5, fixedly connecting the upper die and the lower die, and the integral expansion section prefabricated body (8) is entirely accommodated in the hollow cavity; Step 6, injecting the material from the glue injection port (103) to make the material infiltrate the integral expansion section prefabricated body (8); Step 7, placing for a period of time until the material solidifies, and sequentially disassembling the upper core die (1), the upper die, the lower die, and taking out the infiltrated integral expansion section prefabricated body (8).

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