Pultrusion Die and Preparation Process for Producing Hybrid Fiber Reinforced Polymer Rods

Abstract

The present invention belongs to the technical field of composite material processing, and particularly relates to a pultrusion die and a preparation process for producing hybrid fiber reinforced polymer rods. The pultrusion die includes a yarn bobbin placement rack, an impregnation device, a preforming device, a preheating device, a secondary forming device, a winding device, a high-temperature curing and forming device, a cooling device, a traction device, and a cutting device connected in sequence; the preforming device is used to extrude the fiber bundles impregnated with resin and distributed in an array to form an array of hybrid fiber sub-rods; the preheating device is used to heat-treat the hybrid fiber sub-rods output by the preforming device, with the inlet connected to the preforming device through a glue scraping device and the outlet connected to the secondary forming device through a glue scraping device; the secondary forming device is used to extrude multiple preheated hybrid fiber sub-rods to form a main rod. The present invention can solve the problem that low-strain fibers cannot be uniformly dispersed in the cross-section of the HFRP rod in a preset manner during the production of HFRP rods.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite material processing, and particularly relates to a pultrusion die and a preparation process for producing hybrid fiber reinforced polymer rods. Background Art

[0002] Steel bars, anchor rods, steel strands, etc. are widely used in the engineering field. For example, steel bars are used as reinforcement materials in combination with concrete, greatly improving the overall performance of reinforced concrete. However, the corrosion of steel bars greatly affects the mechanical properties of reinforced concrete load-bearing members or the durability of structures, often causing structures or components still within the service life to prematurely exit the normal service limit state. Such situations as the corrosion of steel bars are also common in engineering practice for anchor rods and steel strands.

[0003] Fiber Reinforced Polymer (FRP) materials, as a new type of composite material, have the advantages of light weight, high strength, corrosion resistance, fatigue resistance, and strong plasticity. Therefore, it is a very effective method to replace steel bars, anchor rods, and steel strands with FRP bars (including FRP bars, FRP anchor rods, and FRP strands).

[0004] In engineering practice applications, very strict requirements are imposed on the mechanical properties of FRP rods (including FRP bars, FRP anchor rods, and FRP strands). For example, the ductility of FRP rods, that is, FRP rods should have obvious plastic deformation and failure omens before failure. However, the failure type of single fiber reinforced polymer materials during tension is mainly brittle failure, that is, there is no plastic deformation and obvious warning before failure. Hybrid Fiber Reinforced Polymer (HFRP) can solve this problem. HFRP refers to a new type of material formed by adding two or more long fibers as the reinforcing phase into a resin-based material and curing at high temperature through various forming methods. Commonly used fibers include carbon fibers, glass fibers, aramid fibers, long synthetic fibers, and steel strands, etc. Commonly used resins include epoxy resins, vinyl resins, and unsaturated polyester resins, etc. Commonly used fiber hybridization methods include in-layer hybridization and inter-layer hybridization. Taking an HFRP laminate as an example, in-layer hybridization means that a thin layer contains multiple fibers, and inter-layer hybridization means that a single layer contains only one type of fiber while the fiber types in adjacent layers are different.

[0005] In existing fiber production technologies, it is impossible to include multiple types of fibers in the same fiber tow simultaneously. Therefore, most fibers on the market exist in the form of single-fiber tows, and the number of individual filaments in a single tow of different types of fibers also varies. Taking carbon fibers as an example, the number of carbon fiber filaments in a single tow can be 1K, 3K, 6K, 12K, 24K, 48K, etc. Therefore, the form of fiber existence determines the distribution pattern of fibers on the cross-section of a hybrid HFRP rod during production. Taking the production of a hybrid HFRP rod as an example, low-strain fiber tows (mainly carbon fibers) are often evenly distributed in a dispersed manner on the cross-section of the HFRP rod or centered.

[0006] The preparation process of the HFRP rod mainly uses pultrusion technology. However, the existing molds that play an extrusion role cannot evenly disperse the low-strain fiber tows on the cross-section of the HFRP rod in a preset manner, and agglomeration often occurs. The degree of dispersion of the low-strain fiber tows on the cross-section determines the superiority of the mechanical properties of the HFRP rod. Summary of the Invention

[0007] Aiming at the problems existing in the prior art, the present invention proposes a pultrusion mold and preparation process for producing hybrid fiber-reinforced polymer rods, which can solve the problem that low-strain fibers cannot be evenly dispersed on the cross-section of the HFRP rod in a preset manner during the production of HFRP rods.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] The present invention provides a pultrusion mold for producing hybrid fiber-reinforced polymer rods, including a yarn bobbin placement rack, an impregnation device, a preforming device, a preheating device, a secondary forming device, a winding device, a high-temperature curing and forming device, a cooling device, a traction device, and a cutting device connected in sequence;

[0010] The preforming device is used to extrude the fiber tows impregnated with resin and distributed in an array to form an array of hybrid fiber sub-rods, including a preforming mold. A plurality of yarn extrusion holes are arranged in an array on the inlet end face of the preforming mold, and an equal number of hybrid fiber sub-rod outlets as the number of yarn extrusion holes are provided on the outlet end face;

[0011] The preheating device is used to heat-treat the hybrid fiber sub-rods output by the preforming device. The inlet is connected to the preforming device through a glue scraping device, and the outlet is connected to the secondary forming device through a glue scraping device;

[0012] The secondary forming device is used to extrude multiple preheated hybrid fiber sub-rods to form a main rod, including a secondary forming mold.

[0013] Further, the preforming die is a three - section stepped cylinder; a plurality of yarn extrusion holes are arrayed in a polygonal or circular pattern on the inlet end face of the preforming die.

[0014] Further, the yarn distribution mode of each yarn extrusion hole is as follows: the center is a low - elongation fiber bundle impregnated with resin, and the periphery is wrapped with a high - elongation fiber bundle impregnated with resin.

[0015] Further, the preheating device includes a preheating chamber and a pipeline chamber located below the preheating chamber; a preheating chamber door is provided on the front of the preheating chamber, and a display screen is provided on the front of the pipeline chamber.

[0016] Further, the preheating device further includes a heating device arranged on the top of the preheating chamber. The heating device includes a heat - driving fan and a heater. The heat - driving fan is used to evenly disperse the heat generated by the heater into the preheating chamber, and the heater is used to provide heat to the preheating chamber.

[0017] Further, the sizing device includes a cap, a sizing film, and a connecting piece. The cap includes an orifice, a fixing bolt, and a sizing film fixing groove. The sizing film is placed in the sizing film fixing groove, and the fixing bolt fixes the cap on the connecting piece. The end of the connecting piece presses the sizing film in the sizing film fixing groove.

[0018] Further, two annular card slots are provided on the outside of the connecting piece, and spring clips are locked in the card slots. One spring clip is stuck inside one side of the preforming device box body or inside one side of the secondary forming device box body, and the other spring clip is stuck inside the preheating chamber.

[0019] Further, the secondary forming die is a three - section stepped cylinder; one yarn inlet hole and one yarn outlet hole are respectively provided on both end faces of the secondary forming die.

[0020] Further, a chamfered passivation slope is provided at the yarn extrusion holes of the preforming die, the orifice of the cap, and the yarn inlet hole of the secondary forming die.

[0021] The present invention also provides a preparation process using the above - mentioned pultrusion die for producing hybrid fiber - reinforced polymer rods, which includes the following steps:

[0022] Determine the parameters of the target hybrid fiber - reinforced polymer rod;

[0023] Regularly place fiber yarn clusters on the yarn cluster placement rack according to the yarn distribution mode of the yarn extrusion holes;

[0024] The fiber bundle is impregnated with resin through the impregnation device;

[0025] The fiber bundle impregnated with resin is driven by a traction device into a preforming device. A plurality of yarn squeezing holes are arrayed on the inlet end face of the preforming die. The fiber bundle impregnated with resin enters the corresponding yarn squeezing holes in a manner that the high elongation rate fiber bundle wraps the low elongation rate fiber bundle;

[0026] The arrayed hybrid fiber sub-rods formed by extrusion through the preforming device are driven by a traction device into a preheating device for heating;

[0027] The preheated hybrid fiber sub-rods are driven by a traction device into a secondary forming device, and the secondary forming die squeezes the arrayed hybrid fiber sub-rods together to form a main rod;

[0028] The hybrid fiber reinforced polymer rod after being extruded by the secondary forming die is further wound by a winding device to bind the hybrid fiber reinforced polymer rod and generate winding ribs on the surface of the hybrid fiber reinforced polymer rod;

[0029] The hybrid fiber reinforced polymer rod with winding ribs is pulled into a high-temperature curing and forming device, the resin is cured by heat to form a hybrid fiber reinforced polymer rod, and then it undergoes temperature reduction treatment by a cooling device and fixed-length cutting by a cutting device.

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] The pultrusion die and preparation process for producing hybrid fiber reinforced polymer rods of the present invention. This preparation process combines the improvement of the preforming device with the secondary forming device. Through a two-step forming method, the low elongation rate fibers can be evenly distributed on the cross-section of the target hybrid fiber reinforced polymer rod, that is, the low elongation rate fibers are evenly dispersed on the cross-section. Adopting the idea that a large-diameter rod is composed of small-diameter rods, the target hybrid fiber reinforced polymer rod is divided into multiple arrayed hybrid fiber sub-rods. And in the hybrid fiber sub-rods, a fiber layer distribution is adopted, that is, the middle is a low elongation rate fiber core and the periphery is a high elongation rate fiber layer. Then, the arrayed hybrid fiber sub-rods are integrated into a main rod by a secondary forming die, so as to achieve the preset method of evenly distributing the low strain fibers on the cross-section of the hybrid fiber reinforced polymer rod, and solve the problem of the aggregation of low elongation rate fibers on the cross-section of the HFRP rod during the mixing in the traditional preparation process; By heating the air in the high-temperature chamber, the preheating device and the high-temperature curing and forming device under online real-time control are in a constant temperature state, avoiding the problem of uneven heating of the HFRP rod; This preparation process can make the resin redistribute between the fibers multiple times, greatly increasing the uniformity and wettability of the resin distribution between the fibers; The preparation process of the present invention is simple, reasonable in design, convenient to operate, and the preparation target can be truly presented according to the preset plan, breaking the way that only numerical simulation can accurately generate the fiber distribution on the cross-section in the existing methods. Description of the Drawings

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0033] Figure 1 is a schematic cross-sectional structure diagram of a pultrusion die for producing hybrid fiber-reinforced polymer rods according to an embodiment of the present invention;

[0034] Figure 2 is a connection schematic diagram of a preforming die, a preheating device, and a secondary forming die according to an embodiment of the present invention;

[0035] Figure 3 is a schematic structure diagram of a preforming die according to an embodiment of the present invention;

[0036] Figure 4 is a schematic structure diagram of the inlet end face of the preforming die;

[0037] Figure 5 is Figure 3 the sectional view taken along line 1-1 of

[0038] Figure 6 is Figure 3 the sectional view taken along line 2-2 of

[0039] Figure 7 is a schematic structure diagram of the preheating device;

[0040] Figure 8 is a schematic structure diagram of the heating device;

[0041] Figure 9 is one of the schematic structure diagrams of the cap;

[0042] Figure 10 is another schematic structure diagram of the cap;

[0043] Figure 11 is a schematic structure diagram of the scraping film;

[0044] Figure 12 is a connection schematic diagram of the spring clip and the card slot;

[0045] Figure 13 is a schematic external structure diagram of the connecting member;

[0046] Figure 14 is a schematic structure diagram of the secondary forming device;

[0047] Figure 15 is Figure 14 the sectional view taken along line 3-3 of

[0048] Figure 16 It is a schematic diagram of carbon fiber bundles, as low-elongation materials, being uniformly dispersed onto the cross-section of HFRP bars according to five fiber distribution patterns.

[0049] The meanings represented by the serial numbers in the figure are as follows:

[0050] 1. Yarn bobbin placement rack, 2. Impregnation device, 3. Preforming device, 301. Preforming die, 302. Yarn extrusion hole, 303. Inclined surface of the inverted table for passivation, 304. Low-elongation fiber bundles impregnated with resin, 305. High-elongation fiber bundles impregnated with resin, 306. Resin, 307. Hybrid fiber secondary rod, 308. Low-elongation fiber core, 309. High-elongation fiber layer, 310. Resin layer, 4. Preheating device, 401. Preheating chamber, 402. Pipeline chamber, 403. Door of the preheating chamber box, 404. Display screen, 405. Heat-driving fan, 406. Heater, 407. Cap, 408. Scraping film, 409. Connecting piece, 410. Scraping device, 411. Entrance, 413. Heating device, 414. Fixed groove for scraping film, 415. Fixed bolt, 416. Orifice, 417. Card slot, 418. Spring clip, 5. Secondary forming device, 501. Secondary forming die, 502. Yarn inlet hole, 6. Winding device, 7. High-temperature curing and forming device, 8. Cooling device, 9. Traction device, 10. Cutting device, 11. Carbon fiber bundles and resin, 12. Glass fiber bundles and resin. Specific implementation manners

[0051] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0052] Embodiment 1

[0053] The pultrusion die for producing hybrid fiber-reinforced polymer rods in this embodiment is applicable not only to the preparation of hybrid fiber-reinforced polymer rods (including HFRP bars, HFRP anchor bolts, and HFRP strands), but also to the preparation of single-fiber-reinforced polymer strands and cables. The reinforcing phase materials for preparing hybrid fiber-reinforced polymer rods can be composed of two or more reinforcing phases such as carbon fiber, glass fiber, aramid fiber, long synthetic fiber, and steel strand, etc. The reinforcing phase materials for preparing single-fiber-reinforced polymer strands and cables can be carbon fiber, glass fiber, aramid fiber, long synthetic fiber, and steel strand, etc.; the matrix phase materials for preparing hybrid fiber-reinforced polymer rods can be epoxy resin, vinyl resin, unsaturated polyester resin, etc.

[0054] AsFigure 1 and Figure 2 As shown in Figure 2 , the pultrusion die includes a yarn bobbin rack 1, a resin impregnation device 2, a preforming device 3, a preheating device 4, a secondary forming device 5, a winding device 6, a high-temperature curing and forming device 7, a cooling device 8, a traction device 9, and a cutting device 10 that are sequentially connected.

[0055] The preforming device 3 is used to extrude the fiber bundles impregnated with resin and distributed in an array to form an array of hybrid fiber sub-rods 307; as Figure 3 and Figure 4 shown in Figure 4 , the preforming device 3 includes a preforming die 301. A plurality of yarn extrusion holes 302 are arrayed on the inlet end face of the preforming die 301, and hybrid fiber sub-rod outlets equal in number to the yarn extrusion holes 302 are provided on the outlet end face; preferably, the preforming die 301 is a three-section variable-diameter cylinder, aiming to facilitate reliable installation and fixation of the die on the equipment and achieve good pultrusion effect; the arrayed yarn extrusion holes 302 can be arrayed in a polygonal manner or in a circular manner, and the diameter of the yarn extrusion holes 302 is determined according to the total cross-sectional area of the fiber bundles expected to pass through the holes and the fiber volume fraction. The yarn extrusion holes 302 are provided with a stepped passivation slope 303. The stepped passivation makes the yarn extrusion holes 302 have a certain slope, preventing the fibers from breaking due to friction with the edges of the yarn extrusion holes 302 and enabling the extruded resin to flow back into the resin impregnation pool along the slope outside the yarn extrusion holes 302. As Figure 5 shown in Figure 5 , the yarn laying method for each yarn extrusion hole 302 is as follows: the center is a low-elongation fiber bundle 304 impregnated with resin, and the periphery is wrapped with a high-elongation fiber bundle 305 impregnated with resin. As Figure 6 shown in Figure 6 , the preforming die 301 can array multiple hybrid fiber sub-rods 307 at one time according to the target hybrid fiber-reinforced polymer rod, and the fiber distribution type of the hybrid fiber sub-rods 307 is interlayer distribution.

[0056] The preheating device 4 is used to heat-treat the hybrid fiber sub-rods 307 output by the preforming device 3, thereby increasing the fluidity and wettability of the resin between the fibers; as Figure 7 shown in Figure 7 , the preheating device 4 includes an inlet 411, an outlet, a preheating chamber 401, a pipeline chamber 402, a heating device 413, a preheating chamber door 403, and a display screen 404. The inlet 411 of the preheating device 4 is connected to the preforming device 3 through a scraping device 410, and the outlet is connected to the secondary forming device 5 through a scraping device 410.

[0057] The scraping device 410 includes a cap 407, a scraping film 408, and a connecting member 409, as Figure 9 and Figure 10As shown, the cap 407 includes an orifice 416 with a stepped passivation slope 303, a fixing bolt 415, and a wiper blade fixing groove 414. The orifice 416 with the stepped passivation slope 303 is to prevent the fibers from breaking due to friction with the edge of the orifice 416, and to allow the scraped resin to flow along the stepped slope into the waste glue collection container below the glue scraping device 410, while preventing the scraped resin from accumulating at the orifice 416 and infiltrating into the interior of the glue scraping device 410. First, place the wiper blade 408 in the wiper blade fixing groove 414, and then firmly fix the cap 407 with the wiper blade 408 on the connector 409 through the fixing bolt 415. The end of the connector 409 tightly presses the wiper blade 408 in the wiper blade fixing groove 414 to prevent it from shaking up, down, left, or right during operation, resulting in imperfect glue scraping. Preferably, as Figure 11 shown, the material of the wiper blade 408 is made of wear-resistant rubber. According to the different diameters of the prepared HFRP rods, the specifications of the holes on the wiper blade 408 should correspond one by one. The connector 409 is made by boring a hole in the center of a solid cylinder with a relatively large rigidity, as Figure 12 and Figure 13 shown, two annular clamping grooves 417 are provided on the outside of the connector 409, and the spring clip 418 is locked in the clamping groove 417 so that the spring clip 418 is always in its original position. One of the spring clips 418 is clamped inside one side of the box body of the preforming device 4 or inside one side of the box body of the secondary forming device 5, and the other spring clip 418 is clamped inside the preheating chamber 401. The spring clip 418 prevents the connector 409 from having a large displacement in the fiber traveling direction, so that the preforming device 3, the preheating device 4, and the secondary forming device 5 connected by the connector 409 are stably connected together.

[0058] The preheating chamber 401 is similar to a box-type high-temperature furnace, surrounded by heat-insulating materials with good heat preservation performance; the pipeline chamber 402 is located below the preheating chamber 401 and is separated from the preheating chamber 401. The temperature of the pipeline chamber 402 is normal room temperature, and signal transmission lines, power supply lines, electrical components, and waste gas collection pipes all pass through it.

[0059] As Figure 8 shown, the heating device 413 is installed on the top of the preheating chamber 401, including a heat-driving fan 405 and a heater 406. The heat-driving fan 405 evenly diffuses the heat dynamically generated by the heater 406 into the preheating chamber 401 to prevent uneven temperature in the chamber; the heater 406 can change the power to provide heat to the preheating chamber 401. When the temperature of the preheating chamber 401 is relatively low, the heater 406 can work at full power to quickly increase the indoor temperature. When the temperature of the preheating chamber 401 approaches the specified temperature, the heater 406 can work at low power to gradually make the indoor temperature approach the specified temperature; during the preparation process of the HFRP rod, the temperature in the preheating chamber 401 is adjusted in real time and online by the heater 406 to keep it at a constant temperature state.

[0060] The preheating chamber door 403 is arranged on the front of the preheating chamber 401. When the initial production heating device 413 heats up the preheating chamber 401, there may be an excessive heating rate, causing the internal temperature of the chamber to exceed the command temperature. It can be quickly cooled by opening the preheating chamber door 403. After the production task is completed, the preheating chamber door 403 can be opened to clean the waste resin inside. The display screen 404 is arranged on the front of the pipeline chamber 402. Through the display screen 404, the internal temperature of the preheating chamber 401 and the fault identification of the preheating device 4 can be monitored in real time, and the preheating device 4 can also be manually adjusted through the display screen 404 for human-machine interaction.

[0061] The secondary forming device 5 is used to extrude multiple preheated hybrid fiber sub-rods 307 into a main rod. As Figure 14 shown, the secondary forming device 5 includes a secondary forming die 501. The secondary forming die 501 is a three-section variable-diameter cylinder, which is convenient for installation and disassembly and has a good extrusion effect. An inlet yarn hole 502 and an outlet yarn hole are respectively arranged on both end faces of the secondary forming die 501. It is used in cooperation with the preforming device 3 to extrude the array of hybrid fiber sub-rods 307 formed in the preforming device 3 together to form a main rod. After being extruded by the secondary forming die 501, as Figure 15 shown, the fiber distribution on the cross-section of the formed HFRP main rod is the same as the preset fiber distribution pattern. Preferably, the inlet yarn hole 502 is provided with an inverted table passivation slope 303. The inverted table passivation makes the inlet yarn hole 502 have a certain slope, preventing the fibers from breaking due to friction with the edge of the inlet yarn hole 502, and making the extruded resin flow back to the lower waste glue container along the outer slope.

[0062] The present invention uses a combination of a preforming die 301 with an array of yarn extrusion holes 302 and a secondary forming die 501 to produce HFRP rods, solving the problem that the original single die cannot evenly disperse the hybrid fibers into the cross-section of the HFRP rod according to the preset method, and online real-time controlling the temperature in the preheating chamber 401 of the preheating device 4 and the high-temperature curing and forming device 7 to be in a constant temperature state, avoiding the problem of uneven heating of the HFRP rod.

[0063] Embodiment 2

[0064] Corresponding to the above pultrusion die for producing hybrid fiber reinforced polymer rods, this embodiment provides a preparation process for hybrid fiber reinforced polymer rods, including the following steps:

[0065] Step S21, determining the parameters of the target hybrid fiber reinforced polymer rod: the diameter D of the HFRP rod, the total fiber volume ratio V f , the hybrid fiber volume ratio V L ∶V H (VL represents the volume of low - elongation fibers, V H represents the volume of high - elongation fibers), the cross - sectional area of a single bundle of low - strain fibers is S L , and the cross - sectional area of a single bundle of high - strain fibers is S H , the fiber distribution pattern and other corresponding equipment control parameters.

[0066] The following calculations are required to prepare the above - mentioned target HFRP rod:

[0067] The total number of bundles of low - strain fibers required:

[0068] The total number of bundles of high - strain fibers required:

[0069] Determine the yarn - laying method through the yarn - extrusion holes 302 of the pre - forming die 301 according to the preset distribution pattern of low - strain fibers on the cross - section of the target HFRP rod, and calculate the number of fiber bundles in a single hole of the yarn - extrusion hole 302 based on the diameter r of a single yarn - extrusion hole 302.

[0070] Step S22: Regularly place the fiber yarn balls on the yarn - ball placement rack 1 according to the yarn - laying method of the yarn - extrusion holes 302, and lead the fibers out from the yarn balls through the first yarn - collecting plate to avoid the fibers crossing when passing through the first yarn - collecting plate.

[0071] Step S23: The fiber bundles are impregnated with resin through the impregnation device 2. Due to the viscosity of the resin, the fiber bundles bond into groups. Therefore, the fiber - bundle groups need to be separated by the second yarn - collecting plate to keep the single - bundle fibers impregnated with resin moving forward. At the same time, another function of the second yarn - collecting plate is to scrape off the excess resin impregnated on the fibers, and this resin flows back into the impregnation tank for reuse.

[0072] Step S24: The fiber bundles impregnated with resin are driven by the traction device 9 into the pre - forming device 3. The yarn - extrusion holes 302 of the pre - forming die 301 are composed of an array of small holes. The impregnated hybrid fiber bundles enter the corresponding array of yarn - extrusion holes 302 according to the preset scheme (the number of fiber bundles entering each yarn - extrusion hole 302 and the fiber distribution pattern, and this fiber distribution pattern is the way that high - elongation fibers wrap low - elongation fibers).

[0073] After the resin-impregnated fiber passes through the preforming die 301, the array of extrusion holes 302 squeezes out the excess resin impregnated on the fiber, and the excess resin drips down the inverted passivation slope 303 of the extrusion holes 302 and flows back to the resin dipping pool for reuse. After the resin-impregnated fiber passes through the array of extrusion holes 302, the resin is evenly distributed between the fiber filaments to form an array of mixed fiber secondary rods 307. At this time, the mixed fiber secondary rods 307 without any curing reaction of the resin initially have the prototype of a HFRP rod (the middle is a low elongation fiber core 308, and the outer periphery is a high elongation fiber layer 309).

[0074] In step S25, the array mixed fiber secondary rod 307 extruded by the preforming device 3 is driven by the traction device 9 into the preheating device 4, and enters the cavity of the preheating chamber 401 through the inlet 411 of the preheating device 4 through the scraping device 410. The scraping blade 408 built into the scraping device 410 scrapes off the resin glue droplets hanging under the mixed fiber secondary rod 307, and the scraped resin is collected into the waste glue collection container below along the hole 416 with the downturn passivation slope 303 on the cap 407. If the resin used for fiber impregnation is bisphenol A epoxy vinyl resin, the viscosity meter measures that the resin has the best fluidity at 50°C. The temperature inside the preheating chamber 401 is achieved by inputting a command temperature signal to the heating device 413 on the equipment console. By inputting the command temperature of 50°C for the heating device 413 on the equipment console, the heater 406 of the heating device 413 works at full power. The heat generated by the heater 406 is evenly diffused to the entire cavity of the preheating chamber 401 through the heat-driving fan 405. The temperature of the preheating chamber 401 is monitored online in real time. When the temperature of the preheating chamber 401 is close to the command temperature, the heater 406 compensates the heat at low power until the command temperature is reached.

[0075] When the mixed fiber secondary rods 307 of the array enter the preheating chamber 401, the temperature rises and the mixed fiber secondary rods 307 are heated. Due to the principle of heat transfer, after a period of time, the temperature difference between the inner and outer layers of the mixed fiber secondary rods 307 is not large. In this process, the temperature of the resin gradually rises, the corresponding viscosity decreases, and the fluidity of the resin increases, further increasing the uniformity and wettability of the resin distribution between the fibers. The main purpose is to further increase the wettability of the resin on the fiber surface and the uniformity between the fibers and to make the resin on the surface of the mixed fiber secondary rods 307 of the array have a certain degree of fluidity, so that all the mixed fiber secondary rods 307 can be squeezed together by the secondary molding device 5 to form a main rod.

[0076] Step S26, the preheated mixed fiber secondary rod 307 is driven by the traction device 9 to enter the secondary molding device 5. Since the diameter of the yarn inlet hole 502 of the secondary molding die 501 is the same as the diameter of the target HFRP rod, the mixed fiber secondary rods 307 in the array are squeezed together to form a main rod after being extruded by the secondary molding die 501, and the diameter of the main rod is the same as the diameter of the target HFRP rod. After being extruded by the secondary molding die 501, the distribution of fibers on the cross section of the formed HFRP rod is the same as the preset fiber distribution mode.

[0077] When passing through the secondary molding die 501 , the resin inside the mixed fiber secondary rods 307 of the array is squeezed and redistributed, and the excess resin drips down along the inverted passivation slope 303 of the yarn inlet hole 502 and is collected in the waste resin collection container below the yarn inlet hole 502 .

[0078] Step S27, after being extruded by the secondary molding die 501, the HFRP rod is wound by the fiber tape winding device 6, and the pre-tightened winding tape forms winding ribs on the surface of the HFRP rod. During the process of the fiber tape winding the HFRP rod, the winding tape has a certain binding effect on the HFRP rod, which once again promotes the redistribution of the resin inside the HFRP.

[0079] Step S28, the HFRP rod with the winding ribs is pulled into the high temperature curing molding device 7, and the initial temperature rises sharply, the viscosity of the resin in the HFRP rod decreases and the fluidity increases, which once again promotes the fluidity and wettability of the resin in the HFRP rod to achieve a more uniform distribution. As time goes by, the HFRP rod is heated in the high temperature curing molding device 7, and the ethylene resin undergoes a sufficient polymerization reaction to form a high-density three-dimensional cross-linked polymer. Finally, after the cooling device 8 cools down and the cutting device 10 cuts to a fixed length, the HFRP rod with its cross-sectional fiber distribution in a preset manner is realized.

[0080] The preparation process of the present invention has a simple principle and is easy to operate, and can redistribute the resin among the fibers for multiple times, thereby greatly increasing the uniformity of the distribution of the resin among the fibers.

[0081] Here is a specific example:

[0082] The laboratory used the above preparation process to produce a batch of HFRP bars with a diameter of 16 mm. The reinforcement materials used were carbon fiber bundles and glass fiber bundles. The total fiber volume ratio was 60%, and the volume content ratio of the two fibers was 1:6. The carbon fiber bundle was used as a low elongation material according to the following method: Figure 16The five fiber distribution patterns shown are evenly dispersed across the cross-section of the HFRP bars. The glass fiber bundles are distributed around the carbon fiber bundles as materials with high elongation rates. The matrix material used is bisphenol A epoxy vinyl resin. The parameters related to the tests and the test results are shown in the following table:

[0083]

[0084] Influence of fiber distribution pattern on the performance of HFRP bars:

[0085]

[0086] Therefore, the parameter that can best reflect the influence of the fiber distribution pattern on the cross-section of the HFRP bar on the performance of the HFRP bar is the yield strain of the HFRP bar, that is, the state in which the low-strain fibers in the HFRP bar first reach the ultimate elongation and break and then completely withdraw from work. After that, only the high-strain fibers are stressed alone, which conforms to the characteristics of single fiber stress.

[0087] The analysis method is as follows: By comparing the HFRP bars with five fiber distribution types on the cross-section, when the carbon fiber breaks and fails and completely withdraws from work during the tensile test of the HFRP bar, the ratio of the difference between the yield strain and the ultimate strain measured when the single carbon fiber bar is pulled to fracture to the ultimate strain measured when the single carbon fiber bar is pulled to fracture is observed. By observing the change trend of this ratio, the influence law of the fiber distribution pattern on the performance of the HFRP bar can be obtained.

[0088] Type A:

[0089] Type B:

[0090] Type C:

[0091] Type D:

[0092] Type E:

[0093] Through the analysis of the test results of the five fiber distribution types on the cross-section of the above-mentioned HFRP bars, it can be observed that as the dispersion of the low-strain fibers on the cross-section of the HFRP bars increases, the yield strain of the HFRP bars becomes higher and higher. Taking the E-type fiber distribution method as an example, the yield strain of the HFRP bars is increased by 26.47% compared with the yield strain of the single carbon fiber bars. The phenomenon that the yield strain of the HFRP bars becomes higher and higher as the dispersion of the low-strain fibers on the cross-section of the HFRP bars increases is called the "hybrid effect". This phenomenon is mainly caused by two reasons: 1. Thermal residual stress is formed inside the HFRP bars during high-temperature curing; 2. When the low-strain fibers break, the high-strain fibers around them play a "bridging role", delaying the time when the low-strain fibers break.

[0094] Unless otherwise defined, the technical terms or scientific terms used herein shall have the ordinary meanings understood by those of ordinary skill in the art to which the present invention pertains. Similar terms such as "a" or "an" do not necessarily imply a quantity limitation. Similar terms such as "comprising" or "including" mean that the elements or items appearing before this word cover the elements or items listed after this word and their equivalents, without excluding other elements or items. Similar terms such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. Terms such as "upper", "lower", "left", and "right" are only used to represent relative position relationships. When the absolute position of the object being described changes, the relative position relationship may also change accordingly.

[0095] The exemplary embodiments of the present invention have been described in detail above with reference to the preferred embodiments. However, those skilled in the art can understand that, without departing from the concept of the present invention, various modifications and variations can be made to the above specific embodiments, and various combinations of the technical features and structures proposed by the present invention can be made, without exceeding the protection scope of the present invention. The protection scope of the present invention is determined by the appended claims.

Claims

1. A pultrusion die for producing hybrid fiber reinforced polymer rods, comprising a yarn bobbin rack, a resin impregnation device, a preforming device, a preheating device, a secondary forming device, a winding device, a high-temperature curing and forming device, a cooling device, a traction device, and a cutting device connected in sequence; characterized in that, The preforming device is used to extrude the fiber bundles impregnated with resin and distributed in an array to form an array of hybrid fiber sub-rods. It includes a preforming die. On the inlet end face of the preforming die, there are a plurality of yarn extrusion holes arranged in an array, and on the outlet end face, there are hybrid fiber sub-rod outlets equal in number to the yarn extrusion holes; the yarn distribution method of each yarn extrusion hole is: in the center is a fiber bundle with low elongation rate impregnated with resin, and the periphery is wrapped with a fiber bundle with high elongation rate impregnated with resin; The preheating device is used to heat-treat the hybrid fiber sub-rods output by the preforming device. The inlet is connected to the preforming device through a glue scraping device, and the outlet is connected to the secondary forming device through a glue scraping device; The secondary forming device is used to extrude multiple preheated hybrid fiber sub-rods into a main rod, including a secondary forming die.

2. The pultrusion die for producing the hybrid fiber reinforced polymer rod according to claim 1, characterized in that, The preforming die is a three-section variable-diameter cylinder; on the inlet end face of the preforming die, there are a plurality of yarn extrusion holes arranged in a polygon or circular manner.

3. The pultrusion die for producing hybrid fiber reinforced polymer rods according to claim 1, characterized in that, The preheating device includes a preheating chamber and a pipeline chamber located below the preheating chamber; on the front of the preheating chamber, there is a preheating chamber door, and on the front of the pipeline chamber, there is a display screen.

4. The pultrusion die for producing hybrid fiber reinforced polymer rods according to claim 3, characterized in that, The preheating device further includes a heating device arranged on the top of the preheating chamber. The heating device includes a heat-driving fan and a heater. The heat-driving fan is used to evenly spread the heat generated by the heater into the preheating chamber, and the heater is used to provide heat to the preheating chamber.

5. The pultrusion die for producing a hybrid fiber reinforced polymer rod according to claim 3, characterized in that, The glue scraping device includes a cap, a glue scraping sheet, and a connecting piece. The cap includes an orifice, a fixing bolt, and a glue scraping sheet fixing groove. The glue scraping sheet is placed in the glue scraping sheet fixing groove, and the fixing bolt fixes the cap on the connecting piece. The end of the connecting piece presses the glue scraping sheet in the glue scraping sheet fixing groove.

6. The pultrusion die for producing a hybrid fiber reinforced polymer rod according to claim 5, characterized in that, Two annular clamping grooves are formed on the outside of the connecting piece, and spring clips are locked in the clamping grooves. One spring clip is clamped inside one side of the preforming device box body or inside one side of the secondary forming device box body, and the other spring clip is clamped inside the preheating chamber.

7. The pultrusion die for producing the hybrid fiber reinforced polymer rod according to claim 5, characterized in that, The secondary forming die is a three-section variable-diameter cylinder; on both end faces of the secondary forming die, there is an inlet yarn hole and an outlet yarn hole respectively.

8. The pultrusion die for producing the hybrid fiber reinforced polymer rod according to claim 7, characterized in that, The yarn extrusion holes of the preforming die, the orifices of the caps, and the inlet yarn holes of the secondary forming die are provided with inverted platform passivation slopes.

9. A preparation process of a pultrusion die for producing a hybrid fiber reinforced polymer rod according to any one of claims 1 to 8, characterized in that, It includes the following steps: Determine the parameters of the target hybrid fiber reinforced polymer rod; Regularly place the fiber yarn bobbins on the yarn bobbin rack according to the yarn distribution method of the yarn extrusion holes; The fiber bundles are impregnated with resin through the resin impregnation device; The fiber bundles impregnated with resin are driven by the traction device into the preforming device. On the inlet end face of the preforming die, there are a plurality of yarn extrusion holes arranged in an array, and the fiber bundles impregnated with resin enter the corresponding yarn extrusion holes in the way that the fiber bundles with high elongation rate wrap the fiber bundles with low elongation rate; The array of hybrid fiber sub-rods formed by extrusion through the preforming device is driven by the traction device into the preheating device for heating; The preheated hybrid fiber secondary rods are driven by a traction device into a secondary forming device, and the secondary forming die extrudes the array of hybrid fiber secondary rods together to form a main rod; The hybrid fiber reinforced polymer rod after being extruded by the secondary forming die is further wound by a winding device to bind the hybrid fiber reinforced polymer rod and generate winding ribs on the surface of the hybrid fiber reinforced polymer rod; The hybrid fiber reinforced polymer rod with winding ribs is tractioned into a high-temperature curing and forming device, and the resin is cured by heat to form a hybrid fiber reinforced polymer rod, and then is cooled by a cooling device and cut to a fixed length by a cutting device.

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