A composite material interlaminar toughened short-cut fiber web, its preparation method, web-forming device and application

Abstract

This invention proposes a composite material interlaminar toughened chopped fiber web, its preparation method, web-forming device, and applications, belonging to the field of composite materials and high-performance fibers. It solves the problem of poor interlaminar toughness in composite materials. A web-forming device is used to prepare a moist chopped fiber web by uniformly dispersing a solution of chopped fibers. The web-forming device includes a forming filter, a support net, a material cylinder, a pressurizer, a filtrate tank, and a washing mechanism. The forming filter is placed on top of the support net, and the material cylinder is positioned above the support net. A support frame is connected below the material cylinder, and the filtrate tank is positioned below the material cylinder. The material cylinder has an inlet and a pressure gauge is connected to it. The pressurizer is connected to the pressure gauge, and the washing position of the washing mechanism corresponds to the position of the forming filter. It is mainly used for the preparation of composite material interlaminar toughened chopped fiber webs.

Description

Technical Field

[0001] This invention belongs to the field of composite materials and high-performance fibers, and in particular relates to a composite material interlaminar toughened short-cut fiber web, its preparation method, web-forming device and application. Background Technology

[0002] Carbon fiber composites are highly designable, easy to process, and have good formability. With increasingly mature related theories, carbon fiber composites have received widespread attention and development. With carbon fiber as the reinforcing phase, carbon fiber composites fully utilize their advantages such as high strength and high modulus, low density, high temperature resistance, low temperature resistance, corrosion resistance, radiation protection, and good electrical conductivity. As a result, they are highly favored in aerospace, defense, shipbuilding, rail transportation, wind power generation, automotive industry, new energy batteries, sporting goods and other fields.

[0003] In the molding and fabrication process of composite components, there is generally no fiber reinforcement between the layers; the matrix resin plays a role in bonding and load transfer. Therefore, the strength along the thickness direction and between layers is relatively low. Simultaneously, due to the mismatch of Poisson's ratio between layers and the anisotropy of the coefficient of thermal expansion, high-level interlaminar stress concentration zones are generated at geometric discontinuities such as free edges, varying thickness regions, and hole edges, as well as at mechanical connections. This high stress combined with weak interlaminar properties makes composite components susceptible to structural damage after being subjected to impacts from external objects during service. Under external load impact, interlaminar properties deteriorate rapidly, easily leading to delamination failure, resulting in reduced overall performance and limiting its application scenarios. Typically, medium- or high-energy impacts cause intrusion or penetration of composite structures; these damages are easily detected and repaired. However, low-energy impacts cause matrix cracks and delamination damage within the composite component structure. This type of damage often has very small surface damage, difficult to observe with the naked eye, but during subsequent use, internal delamination continues to expand, causing a severe decrease in the structural strength and stiffness of the composite component, leading to premature failure due to insufficient structural performance. Therefore, as the requirements for the performance of advanced composite materials continue to increase both domestically and internationally, it is particularly important to give full play to the excellent properties of carbon fiber and improve the interlaminar properties of composite materials. It is necessary to find ways to improve impact resistance, inhibit delamination, enhance interlaminar delamination resistance, and improve interlaminar toughness.

[0004] Therefore, it is of great significance to develop a short-cut fiber web that is practically controllable, has a simple process, low production cost, and improves fiber dispersion for interlaminar toughening of composite materials. Summary of the Invention

[0005] In view of this, the present invention aims to provide a composite material interlaminar toughened short-cut fiber web, its preparation method, web-forming device and application, in order to solve the problem of poor interlaminar properties of composite materials.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing interlaminar toughened short-cut fiber mesh of composite materials, comprising the following steps:

[0007] Step 1: Determine the fiber size, then cut it to obtain short fibers of uniform size;

[0008] Step 2: Pre-treat the chopped fibers in a vacuum environment to improve their dispersibility in the dispersion liquid;

[0009] Step 3: Add the dispersant to deionized water to completely disperse the dispersant in the deionized water, thus obtaining a dispersant solution;

[0010] Step 4: Add the pretreated chopped fibers to a uniformly mixed dispersant solution, and disperse the chopped fibers under ultrasonic conditions to obtain a uniform mixture of chopped fibers.

[0011] Step 5: The chopped fiber uniform mixture is mechanically stirred under a mechanical stirrer to achieve uniform dispersion and obtain a chopped fiber uniform dispersion solution;

[0012] Step 6: Add the chopped fiber uniform dispersion solution to the web forming device, lay the forming filter screen flat on the support screen, pour the chopped fiber uniform dispersion solution into the feed cylinder through the inlet, turn on the pressure, and the chopped fiber uniform dispersion solution in the feed cylinder is subjected to positive pressure and passes through the forming filter screen and the support screen. Excess filtrate is collected in the filtrate tank. After the chopped fibers are completely received by the forming filter screen, turn off the pressure and remove the feed cylinder. Use deionized water to rinse the chopped fiber web on the forming filter screen through the rinsing mechanism. After rinsing is completed, remove the forming filter screen and obtain the wet chopped fiber web from the forming filter screen.

[0013] Step 7: Vacuum dry the moist chopped fiber web to finally obtain the chopped fiber web.

[0014] Furthermore, in step 1, the fiber is T300 carbon fiber with a diameter of 5-11 μm and an orientation degree of >92%, and is cut into 3 mm short-cut fibers.

[0015] Furthermore, in step 2, the pretreatment of the chopped fibers is carried out in a vacuum environment at a temperature of 300°C for 1.5 hours.

[0016] Furthermore, in step 3, the dispersant is hydroxyethyl cellulose and polyvinyl alcohol, the mass ratio of hydroxyethyl cellulose to chopped fiber is 12:1, and the mass ratio of polyvinyl alcohol to chopped fiber is 1:1000. The hydroxyethyl cellulose and polyvinyl alcohol are uniformly dissolved by magnetic stirring at a speed of 500 rpm for 2 hours.

[0017] Furthermore, in step 4, an ultrasonic cell disruptor is used to sonicate the short-cut fibers at 900W power for 50 minutes to disperse them into the dispersant solution.

[0018] Furthermore, in step 5, the mechanical stirrer is maintained at 500 rpm for 1 hour.

[0019] Furthermore, in step 6, the pressurizing pressure of the pressurizer is 100 kPa and maintained for 30 minutes, the spray flow rate of the rinsing mechanism is 0.1 L / min, and the spraying duration is 30 minutes.

[0020] In step 7, a vacuum drying oven is used for vacuum drying, maintaining a temperature of 80°C for 1.5 hours.

[0021] This invention also provides a web-forming device for preparing interlaminar toughening chopped fiber webs of composite materials. The web-forming device prepares a moist chopped fiber web by uniformly dispersing a solution of chopped fibers. The web-forming device includes a forming filter screen, a support screen, a material cylinder, a pressure device, a filtrate tank, and a rinsing mechanism. The forming filter screen is placed on top of the support screen. A material cylinder is arranged above the support screen. A support frame is connected to the bottom of the material cylinder. The filtrate tank is arranged below the material cylinder. The material cylinder has an inlet and a pressure gauge is connected to the material cylinder. The pressure device is connected to the pressure gauge. The rinsing position of the rinsing mechanism corresponds to the position of the forming filter screen.

[0022] Furthermore, the pressure regulator is equipped with a pressure regulator switch and a pressure regulator controller. The pressure regulator switch is used to turn the pressure regulator on and off, and the pressure regulator controller is used to regulate the pressure.

[0023] Furthermore, the rinsing mechanism includes a universal nozzle, a spray controller, and a water tank. The water tank stores deionized water and is connected to the spray controller. The spray controller is connected to the universal nozzle, and the position of the universal nozzle corresponds to the position of the shaped filter screen.

[0024] The present invention also provides a composite material interlaminar toughened short-cut fiber mesh, which is prepared using the above-described preparation method.

[0025] The present invention also utilizes an interlaminar toughened short-cut fiber mesh of composite material, which is used as an interlaminar reinforcing phase of the composite material.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention uses fine denier, highly oriented high-performance fiber filaments as raw materials, and prepares fiber webs of different sizes and weights through processes such as fixed-size cutting, ultrasonic dispersion, mechanical stirring dispersion, uniform and rapid fiber web formation and vacuum drying. This achieves precise control of the size and areal density of the fiber web. The areal density of the short-cut fiber web can be as low as 5 gsm, which makes it effective in the integrated molding of composite material structures.

[0027] The method and apparatus for preparing interlayer toughened short-cut fiber webs of composite materials described in this invention can be used not only for single fiber applications such as carbon fiber or aramid fiber, but also for all chemical industrial grade fibers. This invention has a wide range of applications and good forming effect.

[0028] Unlike existing negative pressure molding methods, the preparation method and web-forming device provided by this invention use positive pressure molding to prepare a moist chopped fiber web from a uniformly dispersed solution of short fibers. This allows for more thorough filtrate discharge, ensuring molding quality. Furthermore, the positive pressure method facilitates rinsing of the chopped fiber web, ensuring good air permeability and resin impregnation after drying, thus achieving a good bond between the chopped fiber web and the composite material layer.

[0029] The prepared composite interlaminar toughened chopped fiber web is composed of interlaced fibers that are interconnected, resulting in high porosity. Its basis weight can be adjusted according to actual needs.

[0030] The prepared interlaminar toughened short-cut fiber mesh is used as an interlaminar reinforcing phase in composite materials. It can be widely used in the field of composite materials, effectively improving impact resistance, inhibiting delamination, enhancing interlaminar delamination resistance, improving interlaminar fracture toughness, and increasing the load limit of composite materials when damaged.

[0031] This invention provides a new approach to preparing high-performance composite materials, solves the problem of poor interlayer toughness in composite materials, and eliminates the need for complex and costly instruments and equipment. The process is simple, energy-efficient, and can be mass-produced. Attached Figure Description

[0032] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0033] Figure 1 This is a schematic diagram of a web-forming device for preparing interlaminar toughened short-cut fiber webs of composite materials according to the present invention;

[0034] Figure 2This is a macroscopic view of the 3mm 10gsm short-cut carbon fiber mesh of Embodiment 1 of the present invention;

[0035] Figure 3 This is a macroscopic view of the 3mm 8gsm short-cut carbon fiber mesh of Embodiment 2 of the present invention;

[0036] Figure 4 This is a macroscopic view of the 3mm 5gsm short-cut carbon fiber mesh of Embodiment 3 of the present invention;

[0037] Figure 5 This is a macroscopic view of the 3mm 6gsm chopped aramid fiber web of Example 4 of the present invention;

[0038] Figure 6 This is a standard sample image of the interlayer toughened short-cut carbon fiber mesh carbon fiber composite material described in this invention.

[0039] In the picture:

[0040] 1-Formed filter screen, 2-Support screen, 3-Cylinder, 4-First flange, 5-Second flange, 6-Pressure gauge, 7-Pressure pressurizer, 8-Inlet, 9-Pressure pressurizer switch, 10-Pressure pressurizer controller, 11-Filtration tank, 12-Universal nozzle, 13-Spray controller, 14-Support frame, 15-Water storage tank, 16-Shear test specimen, 17-Bending test specimen, 18-Tension test specimen. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other, and the described embodiments are only some embodiments of the present invention, not all embodiments.

[0042] See Figure 1-6 This embodiment describes a method for preparing a composite material interlaminar toughened short-cut fiber mesh, which includes the following steps:

[0043] Step 1: Determine the fiber size, then cut it to obtain short fibers of uniform size;

[0044] Step 2: Pre-treat the chopped fibers in a vacuum environment. Pre-treating the chopped fibers can improve their dispersibility in the dispersion solution. If using unsizing fibers, this step can be skipped.

[0045] Step 3: Add the dispersant to the deionized water to ensure that the dispersant is completely dispersed in the deionized water, and obtain the dispersant solution;

[0046] Step 4: Add the pretreated chopped fibers to a uniformly mixed dispersant solution, and disperse the chopped fibers under ultrasonic conditions to obtain a uniform mixture of chopped fibers.

[0047] Step 5: The chopped fiber uniform mixture is mechanically stirred under a mechanical stirrer to achieve uniform dispersion and obtain a chopped fiber uniform dispersion solution;

[0048] Step 6: Add the chopped fiber uniform dispersion solution to the web forming device. First, lay the selected forming filter 1 flat on the support net 2. Connect the material cylinder 3 and the support frame 14. Connect the pressure gauge 6 to the pressure injector 7. Pour the chopped fiber uniform dispersion solution into the material cylinder 3 through the feed port 8. Turn on the pressure injector switch 9 and use the pressure injector controller 10 to adjust the pressure. Observe the pressure of the pressure gauge 6. The chopped fiber uniform dispersion solution in the material cylinder 3 is subjected to positive pressure and passes through the forming filter 1 and the support net 2. The excess filtrate is collected by the filtrate tank 11. After the chopped fibers are completely received by the forming filter 1, turn off the pressure injector switch 9, remove the material cylinder 3, aim the universal nozzle 12 directly above the forming filter 1, adjust the spray controller 13, and use deionized water to rinse the chopped fiber web on the forming filter 1. After rinsing, remove the forming filter 1 and obtain the wet chopped fiber web from the forming filter 1.

[0049] Step 7: Vacuum dry the moist chopped fiber web to finally obtain the chopped fiber web.

[0050] In step 1, the fiber is T300 carbon fiber with a diameter of 5-11 μm and an orientation degree of >92%. Short fibers are obtained by cutting, and the length of the short fibers is preferably 1-8 mm, more preferably 2-7 mm, and even more preferably 3-6 mm.

[0051] In step 2, the pretreatment of the chopped fibers is carried out in a vacuum environment at a temperature preferably 200–400°C, more preferably 250–350°C, and even more preferably 270–330°C; the vacuum holding time is preferably 1–4 h, more preferably 1.5–3.5 h, and even more preferably 1.9–3.1 h.

[0052] In step 3, the dispersant is hydroxyethyl cellulose and polyvinyl alcohol. The mass ratio of hydroxyethyl cellulose to chopped carbon fiber is preferably 20:1, more preferably 16:1, and even more preferably 12:1. The mass ratio of polyvinyl alcohol to chopped carbon fiber is preferably 1:200, more preferably 1:150, and even more preferably 1:100. The hydroxyethyl cellulose and polyvinyl alcohol are uniformly dissolved by magnetic stirring. The stirring speed is preferably 300-800 rpm, more preferably 400-700 rpm, and even more preferably 500-600 rpm. The stirring time is preferably 1.0h-3.0h, more preferably 1.5-2.5h, and even more preferably 1.9-2.1h.

[0053] In step 4, an ultrasonic cell disruptor is used, with an ultrasonic power preferably of 600-1200W, more preferably 700-1100W, and even more preferably 800-1000W; the ultrasonic duration is preferably 30-70min, more preferably 40-60min, and even more preferably 45-55min, so that the chopped fibers are dispersed in the dispersant solution.

[0054] In step 5, the rotation speed of the mechanical stirrer is preferably maintained at 300-800 rpm, more preferably 400-700 rpm, and even more preferably 500-600 rpm. The stirring time is preferably 30-70 min, more preferably 40-60 min, and even more preferably 45-55 min.

[0055] In step 6, the selected forming filter screen 1 is laid flat on the support net 2. The material cylinder 3 and the support frame 14 are connected. The pressure gauge 6 is connected to the pressurizer 7. The uniformly dispersed solution of short-cut fibers is poured into the material cylinder 3 through the feed port 8. The pressurizer switch 9 is turned on, and the pressure is adjusted using the pressurizer controller 10. The loading pressure is preferably 50-150 kPa, more preferably 80-120 kPa, and more preferably 90-110 kPa. The pressurization time is preferably 10-50 min, more preferably 20-40 min, and more preferably 25-35 min. The pressure of the pressure gauge 6 is observed. The uniformly dispersed solution of short-cut fibers in the material cylinder 3 is subjected to positive pressure and passes through the forming filter screen 1 and the support net 2. Excess filtrate is collected by the filtrate tank 11. After the short-cut fibers are completely collected by the forming filter screen 1, the pressurizer switch is turned off. Remove cylinder 3, align the universal nozzle 12 directly above the forming filter screen 1, adjust the spray controller 13, and use deionized water to rinse the chopped fiber mesh on the forming filter screen 1. The flow rate of the rinsing deionized water is preferably 0.05L~0.15L / min, more preferably 0.07~0.12L / min, and more preferably 0.09~0.11L / min. The rinsing time is preferably 10~50min, more preferably 20~40min, and more preferably 25~35min. After rinsing is completed, remove the forming filter screen 1. The damp chopped fiber mesh has been evenly spread on the forming filter screen 1. The forming filter screen 1 is preferably 40~100 mesh, more preferably 60~90 mesh, and more preferably 70~80 mesh. Obtain the damp chopped fiber mesh from the forming filter screen 1.

[0056] In step 7, a vacuum drying oven is used for vacuum drying, and the drying temperature is preferably 60-100℃, more preferably 70-90℃, and even more preferably 75-85℃; the vacuum drying time is preferably 0.5-3h, more preferably 1.0-2.5h, and even more preferably 1.5-2.0h.

[0057] The method for preparing interlaminar toughened chopped fiber webs of composite materials described in this embodiment can be carried out at room temperature. Using fine-denier, highly oriented high-performance fiber precursors as raw materials, fiber webs of varying thicknesses and weights are prepared through processes such as sizing, ultrasonic dispersion, mechanical stirring dispersion, rapid and uniform fiber web formation, and vacuum drying. This allows for precise control of the size and thickness of the fiber webs, with the areal density of the chopped fiber webs reaching as low as 5 gsm, resulting in excellent performance in the integrated molding of composite structures. This provides a new approach to preparing high-performance composite materials, solving the problem of poor interlaminar toughness in composite materials. Furthermore, it eliminates the need for complex and costly equipment, features a simple process, low energy consumption, and enables mass production.

[0058] like Figure 1As shown, this embodiment is a web-forming device for preparing interlaminar toughening chopped fiber webs of composite materials. The web-forming device prepares a moist chopped fiber web by uniformly dispersing a solution of chopped fibers. The web-forming device includes a forming filter screen 1, a support net 2, a material cylinder 3, a pressure device 7, a filtrate tank 11, and a rinsing mechanism. The forming filter screen 1 is laid on top of the support net 2. The material cylinder 3 is arranged on top of the support net 2. A support frame 14 is connected to the bottom of the material cylinder 3. The filtrate tank 11 is arranged below the material cylinder 3. The material cylinder 3 has an inlet 8. A pressure gauge 6 is connected to the material cylinder 3. The pressure device 7 is connected to the pressure gauge 6. The rinsing position of the rinsing mechanism corresponds to the position of the forming filter screen 1.

[0059] The material cylinder 3 is provided with a first flange 4, and the support frame 14 is provided with a second flange 5. The first flange 4 and the second flange 5 are connected to realize the connection between the material cylinder 3 and the support frame 14.

[0060] The pressure booster 7 is equipped with a pressure booster switch 9 and a pressure booster controller 10. The pressure booster switch 9 is used to switch the pressure booster 7 on and off, and the pressure booster controller 10 is used to regulate the pressure.

[0061] The rinsing mechanism includes a universal nozzle 12, a spray controller 13, and a water tank 15. The water tank 15 stores deionized water. The water tank 15 is connected to the spray controller 13, and the spray controller 13 is connected to the universal nozzle 12. The position of the universal nozzle 12 corresponds to the position of the molded filter screen 1.

[0062] Unlike existing negative pressure molding methods, the web-forming device provided in this embodiment uses positive pressure molding to prepare a moist chopped fiber web from a uniformly dispersed solution of short fibers. This allows for more thorough filtrate discharge and ensures molding quality. Furthermore, the positive pressure method facilitates rinsing of the chopped fiber web.

[0063] This embodiment describes a composite material interlaminar toughened chopped fiber mesh, which is prepared using the method described above. The chopped fiber mesh is composed of interlaced fibers, with the fibers overlapping and connected to each other, resulting in high porosity. Its basis weight can be adjusted according to actual needs; the basis weight X / Sgsm corresponds to Xg of chopped carbon fibers, and the filter area used in the mesh is Sm². 2 .

[0064] This embodiment describes the application of interlaminar toughened short-cut fiber mesh in composite materials. The interlaminar toughened short-cut fiber mesh is used as an interlaminar reinforcing phase in composite materials and can be widely used in the field of composite materials.

[0065] Example 1

[0066] A 10 gsm short-cut fiber web was prepared, using a shaped filter screen 1 with an area of ​​0.05 m². 2 Using T300 grade unsizing carbon fiber as raw material, a 3mm size was determined for subsequent chopped carbon fiber cutting. The carbon fiber bundles were uniformly cut to 3mm using electric shears. 0.5g of this 3mm chopped carbon fiber was weighed out and set aside. 6g of hydroxyethyl cellulose and 0.005g of polyvinyl alcohol were also weighed out and set aside. Deionized water was placed in a 500ml beaker, and the two dispersants weighed out were added to the water. The magnetic stirrer was set to 500rpm and stirred for 2 hours to completely dissolve the hydroxyethyl cellulose and polyvinyl alcohol. 0.5g of the weighed 3mm chopped carbon fiber was added to the uniformly dissolved dispersant solution, and the mixture was ultrasonically stirred at 900W for 50 minutes to completely disperse the chopped carbon fiber bundles. The uniformly mixed chopped fiber solution was stirred at 500rpm for 1 hour using a mechanical stirrer. A shaped filter screen 1 was laid flat on a support screen 2, and a material cylinder 3 was connected. A pressure gauge 6 was connected to a pressure injector 7. The chopped fiber... The uniformly dispersed solution of chopped fibers is poured into the feed cylinder 3 through the feed inlet 8; the pressure regulator switch 9 is turned on, and the pressure is adjusted using the pressure regulator controller 10. The pressure is observed on the pressure gauge 6 and controlled at 100 kPa. This pressure value is maintained for 30 minutes. The uniformly dispersed solution of chopped fibers in the feed cylinder 3 is subjected to positive pressure and passes through the forming filter screen 1 and the support screen 2. Excess filtrate is collected by the filtrate tank 11; after the chopped carbon fibers are completely collected by the forming filter screen 1, the pressure regulator switch 9 is turned off, the feed cylinder 3 is removed, and the universal joint is... The nozzle 12 is aimed directly above the molded filter screen 1. The spray controller 13 is adjusted, and deionized water is used to rinse the short-cut fiber mesh on the molded filter screen 1. The flow rate of the rinsing deionized water is controlled at 0.1L / min, and this flow rate is maintained for rinsing for 30 minutes. After rinsing is completed, the molded filter screen 1 is removed, and the wet short-cut carbon fiber mesh is obtained from the molded filter screen 1. The wet short-cut carbon fiber mesh is transferred into a vacuum drying oven and maintained at 80°C for 1.5 hours to obtain a 3mm short-cut carbon fiber mesh with a thickness of 10gsm.

[0067] A macroscopic photograph of the 10gsm 3mm short-cut carbon fiber mesh in this embodiment is shown below. Figure 2 As shown.

[0068] Example 2

[0069] In this embodiment, the chopped carbon fiber mesh is changed from 10gsm to 8gsm, the corresponding amount of 3mm chopped carbon fiber is changed to 0.4g, the amount of hydroxyethyl cellulose is changed to 4.8g, and the amount of polyvinyl alcohol is changed to 0.004g. Other conditions are the same as in Example 1.

[0070] A macroscopic photograph of the carbon fiber mesh in this embodiment is shown below. Figure 3 As shown.

[0071] Example 3

[0072] In this embodiment, the chopped carbon fiber mesh is changed from 10gsm to 5gsm, the corresponding amount of 3mm chopped carbon fiber is changed to 0.25g, the amount of hydroxyethyl cellulose is changed to 3g, and the amount of polyvinyl alcohol is changed to 0.0025g. Other conditions are the same as in Example 1.

[0073] A macroscopic photograph of the carbon fiber mesh in this embodiment is shown below. Figure 4 As shown.

[0074] Example 4

[0075] A 6 gsm chopped aramid fiber web was prepared using a 0.05 m² mesh screen. 2 Using Teijin para-aramid fiber as raw material, a 3mm diameter was determined for subsequent chopped aramid fiber cutting. The aramid fiber bundles were evenly cut to 3mm using electric shears. 0.3g of this 3mm chopped aramid fiber was weighed out and set aside. 4g of hydroxyethyl cellulose and 0.003g of polyvinyl alcohol were also weighed out and set aside. Deionized water was then placed in a 500ml beaker.

[0076] Add the two dispersants weighed above to deionized water, set the magnetic stirring speed to 500 rpm, and stir for 2 hours to completely dissolve the hydroxyethyl cellulose and polyvinyl alcohol. Add 0.5 g of 3 mm chopped aramid fibers to the uniformly dissolved dispersant solution, and use an ultrasonic cell disruptor at 900 W power for 50 minutes to completely disperse the chopped aramid fiber bundles. Place the forming filter screen 1 flat on the support screen 2, connect the material cylinder 3, and connect the pressure gauge 6 to the pressure injector 7. Pour the uniformly dispersed chopped fiber solution into the material cylinder 3 through the feed inlet 8. Turn on the pressure injector switch 9, use the pressure injector controller 10 to adjust the pressure, observe the pressure on the pressure gauge 6, and control the pressure at 100 kPa, maintaining this pressure value for 30 minutes. In the process, the chopped fiber uniformly dispersed solution in the barrel 3 is subjected to positive pressure and passes through the forming filter 1 and the support net 2. Excess filtrate is collected by the filtrate tank 11. After the chopped carbon fibers are completely received by the forming filter 1, the pressure regulator switch 9 is turned off, the barrel 3 is removed, the universal nozzle 12 is aimed directly above the forming filter 1, the spray controller 13 is adjusted, and deionized water is used to rinse the chopped fiber web on the forming filter 1. The flow rate of the rinsing deionized water is controlled at 0.1L / min, and this flow rate is maintained for rinsing for 30 minutes. After rinsing is completed, the forming filter 1 is removed, and the moist chopped aramid fiber web is obtained from the forming filter 1. The moist chopped aramid fiber web is transferred as a whole into a vacuum drying oven and maintained at 80°C for 1.5 hours to obtain a 3mm chopped aramid fiber web with a density of 6gsm.

[0077] Example 5

[0078] In this embodiment, a vacuum resin infusion molding process is used to integrally mold the short-cut carbon fiber mesh prepared in Examples 1-3 above. The specific molding steps are as follows:

[0079] (1) Clean the mold, grind the mold surface flat, clean the mold simply, and cut the release cloth, guide net, carbon fiber cloth, guide tube and vacuum bag according to the product size and mold size.

[0080] (2) Material Laying: Apply a release agent to the mold on which the carbon fiber prepreg will be laid. Apply sealant around the mold to prevent carbon fiber debris from falling off. Then lay multiple layers of carbon fiber prepreg in a certain order and direction. The first layer should be flat and wrinkle-free. Place the prepared chopped carbon fiber mesh in the middle layer. Then lay the release cloth to facilitate demolding after the part has cured. Then lay the flow guide net to promote resin flow. Lay the resin inlet and outlet guide pipes and PVC vacuum hoses, then lay the breathable felt. Then cover the entire mold with a vacuum bag and place the vacuum bag sealing material on the mold edge to seal it. Finally, install the vacuum valve, vacuum tube, and connect the vacuum pump and resin collector.

[0081] (3) Check the vacuum bag, clamp the guide tube, turn on the vacuum pump power, and perform an overall vacuum tightness check to observe whether the requirements for resin vacuuming are met. Carefully locate any leaks, correct them, and reseal.

[0082] (4) Extract the resin, mix the epoxy resin and curing agent evenly, turn on the vacuum pump to start vacuuming, and at the same time, introduce epoxy resin into the guide tube, so that the resin can be evenly penetrated into the carbon fiber cloth through the guide net. After the epoxy resin is completely introduced, use clamps to clamp the glue inlet tube and the air outlet, and turn off the vacuum pump.

[0083] (5) Curing and demolding: After the epoxy resin has been fully discharged, remove the rubber tube behind the clamp and place the vacuum bag and mold completely in the mold (usually heated to 60-80℃ for three hours, or cured at room temperature for more than 24 hours) to wait for the epoxy resin to fully cure. After complete curing, peel off the release cloth for demolding and post-processing.

[0084] (6) Post-processing: The carbon fiber interlayer toughened composite material obtained after demolding is cut according to the experimental standard size to obtain the experimental standard sample.

[0085] Macroscopic photographs of the standard experimental samples of the short-cut carbon fiber interlaminar toughened short-cut carbon fiber composite material in this embodiment are shown below. Figure 6 As shown, the specimens are shear specimen 16, bending specimen 17, and tensile specimen 18, respectively.

[0086] The preparation method of the present invention can realize the production of short-cut high-performance fiber webs in a low-cost, high-efficiency, large-scale and rapid manner, and can be integrated with the composite material molding process, providing a new design idea for the industrialization of toughened composite materials.

[0087] The embodiments of the present invention disclosed above are merely illustrative of the invention. These embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A method for preparing a composite material interlaminar toughened short-cut fiber mesh, characterized in that: It includes the following steps: Step 1: Determine the fiber size, then cut it to obtain short fibers of uniform size; Step 2: Pre-treat the chopped fibers in a vacuum environment at a temperature of 200-400℃ for 1-4 hours to improve the dispersibility of the chopped fibers in the dispersion liquid. Step 3: Add the dispersant to deionized water to completely disperse the dispersant in the deionized water, thus obtaining a dispersant solution; the dispersant is hydroxyethyl cellulose and polyvinyl alcohol; Step 4: Add the pretreated chopped fibers to a uniformly mixed dispersant solution, and disperse the chopped fibers under ultrasonic conditions to obtain a uniform mixture of chopped fibers. Step 5: The chopped fiber uniform mixture is mechanically stirred under a mechanical stirrer to achieve uniform dispersion and obtain a chopped fiber uniform dispersion solution; Step 6: Add the chopped fiber uniform dispersion solution to the web forming device, lay the forming filter screen (1) flat on the support screen (2), pour the chopped fiber uniform dispersion solution into the feed cylinder (3) through the feed port (8), turn on the pressure regulator (7), the chopped fiber uniform dispersion solution in the feed cylinder is subjected to positive pressure and passes through the forming filter screen and the support screen, the excess filtrate is collected by the filtrate tank (11), after the chopped fiber is completely received by the forming filter screen, turn off the pressure regulator and remove the feed cylinder, use deionized water to rinse the chopped fiber web on the forming filter screen through the rinsing mechanism, after rinsing is completed, remove the forming filter screen and obtain the wet chopped fiber web from the forming filter screen; Step 7: Vacuum dry the moist chopped fiber web to finally obtain the chopped fiber web.

2. The method for preparing a composite material interlaminar toughened short-cut fiber mesh according to claim 1, characterized in that: In step 1, the fibers used in the chopped fiber web are carbon fiber, aramid fiber, glass fiber, or silane fiber.

3. The method for preparing a composite material interlaminar toughened short-cut fiber mesh according to claim 1, characterized in that: In step 3, the mass ratio of hydroxyethyl cellulose to chopped fiber is 12-20:1, and the mass ratio of polyvinyl alcohol to chopped fiber is 1:

100. The hydroxyethyl cellulose and polyvinyl alcohol are uniformly dissolved in deionized water using magnetic stirring at a speed of 300-800 rpm for 1.0-3.0 h.

4. The method for preparing a composite material interlaminar toughened short-cut fiber mesh according to claim 1, characterized in that: In step 4, an ultrasonic cell disruptor is used to sonicate the cells at a power of 600–1200W for 30–70 minutes to uniformly disperse the short-cut fibers in the dispersant solution; in step 5, a mechanical stirrer is used to maintain a speed of 300–800 rpm for 30–70 minutes.

5. The method for preparing a composite material interlaminar toughened short-cut fiber mesh according to claim 1, characterized in that: In step 6, the pressurizing pressure of the pressurizer is 50-150 kPa and maintained for 10-50 min, the spray flow rate of the rinsing mechanism is 0.05 L-0.15 L / min, and the spraying duration is 10-50 min; in step 7, a vacuum drying oven is used for vacuum drying, and the temperature is maintained at 60-100℃ for 0.5-3 h.

6. A web-forming apparatus for preparing interlaminar toughened chopped fiber webs of composite materials according to any one of claims 1-5, wherein the chopped fiber uniformly dispersed solution is used to prepare a moist chopped fiber web, characterized in that: The screen forming device includes a forming filter screen, a support screen, a material cylinder, a pressure device, a filtrate tank, and a rinsing mechanism. The forming filter screen is laid on top of the support screen. A material cylinder is set above the support screen. A support frame (14) is connected to the bottom of the material cylinder. The filtrate tank is set below the material cylinder. An inlet (8) is opened on the material cylinder. A pressure gauge is connected to the material cylinder. The pressure device is connected to the pressure gauge (6). The rinsing position of the rinsing mechanism corresponds to the position of the forming filter screen.

7. The web-forming apparatus for preparing interlaminar toughened short-cut fiber webs of composite materials according to claim 6, characterized in that: The pressurizer is equipped with a pressurizer switch and a pressurizer controller (10). The pressurizer switch (9) is used to switch the pressurizer on and off, and the pressurizer controller is used to regulate the pressure.

8. The web-forming apparatus for preparing interlaminar toughened short-cut fiber webs of composite materials according to claim 6, characterized in that: The rinsing mechanism includes a universal nozzle (12), a spray controller (13), and a water tank (15). The water tank stores deionized water. The water tank is connected to the spray controller, and the spray controller is connected to the universal nozzle. The position of the universal nozzle corresponds to the position of the shaped filter screen.

9. A composite material interlaminar toughened short-cut fiber mesh, characterized in that: The composite material interlayer toughened short-cut fiber mesh is prepared using the preparation method described in any one of claims 1-5.

10. An application of the composite material interlaminar toughened short-cut fiber mesh as described in claim 9, characterized in that: The interlaminar toughened short-cut fiber mesh of the composite material is used as an interlaminar toughening phase of the composite material.

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