Woven preform preparation method based on resin powder filling and obtained preform

Abstract

According to the preparation method of the woven preform based on resin powder filling, thermoplastic resin powder is heated to a semi-molten state through a resistance wire in the three-dimensional weaving process, so that the thermoplastic resin powder is attached to the surface of a yarn bundle, and hot-pressing curing can be directly carried out after the preform is formed; compared with the traditional process, the method has the advantages that the near-net forming advantage of the weaving process is reserved, the resin impregnation process can be avoided, the production efficiency is improved, the rapid forming is realized, the problems of non-uniform resin impregnation, large pore volume, glue shortage and the like caused by poor resin fluidity can be avoided, the quality of the woven composite material product is improved, and the mechanical property of the finished product is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of composite material molding, and in particular to a method for preparing a braided preform based on resin powder filling. Background Art

[0002] Composite weaving technology is a composite preform forming process that weaves reinforcing fibers together in a specific structure and direction. The automated weaving process has higher preform forming efficiency and near-net-shape advantages, and by controlling the orientation and density of the reinforcing fibers, better in-plane and interlayer performance can be obtained. It has broad application prospects in aerospace, rail transportation, wind power generation and other fields.

[0003] The traditional molding process of woven composite materials first forms a fiber preform, and then uses processes such as resin transfer molding, resin film infiltration or autoclave curing to cure it. These curing methods all require the preform to be impregnated with resin first, which is a complicated process. In addition, the molding quality is restricted by the low fluidity of the resin, which can easily cause defects such as uneven resin distribution, large porosity, and lack of glue.

[0004] Therefore, a new technical solution is needed to solve the above problems. Summary of the invention

[0005] Purpose of the invention: In view of the fact that the woven composite material preform in the prior art needs to be impregnated with resin and then cured and formed, the process is complicated and easily causes problems such as uneven resin distribution, large pores, and lack of glue. The present invention provides a method for preparing a woven preform based on resin powder filling.

[0006] The present invention also provides a preform obtained by the above-mentioned method for preparing a braided preform based on resin powder filling.

[0007] To achieve the above-mentioned purpose, the technical solution of the method for preparing a braided preform based on resin powder filling provided by the present invention is as follows:

[0008] A method for preparing a braided preform based on resin powder filling comprises the following steps:

[0009] Step 1, the yarn is led out from the braiding machine and wrapped in thermoplastic resin powder;

[0010] Step 2, starting to heat the thermoplastic resin powder to a semi-molten state;

[0011] Step 3, start the knitting machine to complete a knitting step;

[0012] Step 4: start the lifting mechanism to pull the formed fiber preform;

[0013] Step 5, repeating steps 3 and 4 until a braided preform of a predetermined length is obtained.

[0014] Step six, taking out the braided preform formed in step five, putting it into a pressure mold and placing it in an oven for hot pressing and curing, and demoulding to obtain a fiber braided reinforced thermoplastic composite material.

[0015] Furthermore, in step one, a resin powder box is provided; the resin powder box is provided with a receiving chamber for accommodating resin powder, a water bath layer surrounding the receiving chamber, and a resistance wire located below the water bath layer, and the bottom and top of the resin powder box are provided with a plurality of holes for passing the yarn bundle.

[0016] Furthermore, the resin powder box is arranged below a lifting mechanism for lifting the yarn, and the yarn passes through the resin powder box and is wrapped by semi-molten thermoplastic resin powder in the resin powder box.

[0017] Furthermore, the thermoplastic resin powder is one or more of thermoplastic phenolic resin powder, polyetheretherketone powder, and polyimide powder.

[0018] Furthermore, the fiber braid is prepared by a three-dimensional rotary braiding machine, the braided yarn is one or more of carbon fiber tow, glass fiber tow, and aramid fiber tow, the braiding angle is 15-45°, the cross-sectional size is 6mm×6mm, and the density is 0.5g / cm 3 .

[0019] Furthermore, when the resistance wire water bath heats the thermoplastic resin powder in step 2, the relationship between the temperature T of the thermoplastic resin powder and the time t satisfies the following conditions:

[0020]

[0021] Where T0 is the initial temperature, r is the heat transfer efficiency, m r is the mass of resin powder, c r is the specific heat of resin powder, V is the rated power of resistance wire, and R is the resistance value of resistance wire.

[0022] Furthermore, when the resistance wire water bath heats the thermoplastic resin powder in step 2, the relationship between the heat Q required for melting the resin powder and the temperature T satisfies the curve Q=F(T), which is obtained by calibrating and measuring the actual melting process of the corresponding resin.

[0023] Furthermore, the specific operation of removing the formed preform and placing it into the pressure mold described in step six is: placing a release cloth, a preform, a release cloth, an isolation film, and a guide net in the pressure mold in sequence, pressing a cover plate and placing it in an oven.

[0024] Furthermore, step six adopts staged hot pressing curing: the first stage is the melting processing stage, the temperature is 80-120°C, the pressure is 10-50MPa, and the processing time is 0.5-1h; the second stage is the molding curing stage, maintaining the pressure in the oven at 10-50MPa until it returns to room temperature, so that the thermoplastic resin is cooled and cured.

[0025] Furthermore, it comprises 40-50% by mass of thermoplastic resin powder and 50-60% by mass of fiber braid, the thermoplastic resin powder has a particle size of 160-300 meshes, and the fiber braid is a two-dimensional braid and / or a three-dimensional braid.

[0026] Beneficial effects:

[0027] The composite material forming process of the present invention heats the thermoplastic resin powder to a semi-molten state through a resistance wire during the weaving process, so that the resin powder adheres to the surface of the yarn bundle, and the resin powder is directly introduced into the fiber braid. After the preform is formed, it can be directly put into the oven for staged heating and curing. This method has the advantage of near-net forming of the composite material braiding process. Compared with the traditional preform curing processes such as resin transfer molding, resin film penetration or autoclave curing, it improves production efficiency, avoids the resin impregnation process, can realize the rapid prototyping of fiber braided reinforced thermoplastic composite materials, can reduce the defects such as uneven impregnation, large pore volume and lack of glue caused by poor resin fluidity, and improve the quality of composite material braiding products. At the same time, because the resin powder is attached to the surface of the yarn bundle during the weaving process, compared with the traditional weaving process, it can reduce the problems of fuzzing and breakage caused by friction between yarns, reduce the friction damage of yarns during the weaving process, and improve the quality of component forming. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a flow chart of forming and curing a braided preform based on resin powder filling in the present invention;

[0029] Figure 2 Schematic diagram of the structure of the thermoplastic resin powder box of the present invention;

[0030] Figure 3 It is a schematic diagram of the relationship curve Q=F(T) between the heat Q required for melting the thermoplastic resin powder and the temperature T in the present invention;

[0031] Figure 4 A schematic diagram of a three-dimensional rotary braiding machine used in the present invention;

[0032] Figure 5 It is a schematic diagram of the curing and molding process of the braided preform based on resin powder filling in the present invention. DETAILED DESCRIPTION

[0033] Embodiment 1

[0034] like Figure 1 As shown, this embodiment provides a method for preparing a braided preform based on resin powder filling, comprising the following steps:

[0035] Step 1: Lead the yarn out of the braiding machine and pass it through a resin powder box containing thermoplastic resin powder fixed to a lifting mechanism. Figure 2 As shown, it includes a resistance wire, a water bath layer and a thermoplastic resin powder layer. The bottom surface has 80 round holes with a diameter of 2 mm. Ceramic eyes are installed in the holes to reduce the friction between the yarn and the plastic box. The resin powder box contains thermoplastic resin powder with a particle size of 160-300 mesh. After completing this step, you can directly start the next step, or you can adjust the parameters such as yarn tension, forming plane height, and lifting mechanism feed amount to obtain a braided fabric with a specific structure.

[0036] Step 2: Start the resistance wire water bath to heat the thermoplastic resin powder to make it semi-molten, and the heating temperature is 70-80°C. Figure 3 As shown, the relationship between the heat Q required for melting the thermoplastic resin powder and the temperature T satisfies the curve Q = F (T), which is obtained by calibrating the actual melting process of the corresponding resin. At the same time, the relationship between the resin powder temperature T and the time t satisfies the following conditions:

[0037]

[0038] Where T0 is the initial temperature, r is the heat transfer efficiency, m r is the mass of resin powder, c r is the specific heat of resin powder, V is the rated power of resistance wire, and R is the resistance value of resistance wire.

[0039] Step 3: Start the knitting machine, rotate the angle wheel and the dial in sequence, and drive the yarn to interweave and complete a knitting step. The three-dimensional rotary knitting machine structure used in this embodiment is as follows: Figure 4 As shown, the braiding angle of the formable braid is 15-45°, the cross-sectional size is 6mm×6mm, and the density is 0.5g / cm 3 After completing this step, you can directly proceed to the next step, or you can use a densification device to densify the formed preform.

[0040] Step 4: Start the lifting mechanism to pull the formed preform structure at a pulling speed of 2 mm per weaving cycle, tension the yarn and keep the forming plane at the same height.

[0041] Step 5: Repeat steps 3 and 4 to gradually and alternately form the fiber braid until the predetermined length requirement is reached.

[0042] Step 6: Take out the preform obtained in step 5, such as Figure 5 As shown, the fiber braided reinforced thermoplastic composite material is obtained by performing hot pressing and curing in stages. The demoulding cloth, preform, demoulding cloth, isolation film, and guide net are placed in the pressure mold in sequence, and the cover plate is pressed and placed in the oven. First, the oven is heated to 80-120°C, the pressure is 10-50MPa, and the processing time is 0.5-1h to completely melt the thermoplastic resin powder, and then the mold is cured. The oven stops heating and maintains the pressure at 10-50MPa until it returns to room temperature. Finally, the pressure mold is removed and demoulding is performed to obtain the fiber braided reinforced thermoplastic composite material.

[0043] According to the performance requirements of the composite material, the thermoplastic resin powder can be one or more of thermoplastic phenolic resin powder, polyetheretherketone powder, and polyimide powder, the structure of the fiber braid can be one or more of two-dimensional braid and three-dimensional braid, and the braiding yarn can be one or more of carbon fiber tow, glass fiber tow, and aramid fiber tow. According to the structural requirements of the composite material, the pitch, braiding angle, braiding length and other parameters of the fiber braid are determined.

[0044] Embodiment 2

[0045] This embodiment provides a preform prepared by the method for preparing a braided preform based on resin powder filling in embodiment 1. Since the raw material yarn forming the preform has been wrapped by the resin powder, the preform formed includes 40-50% by mass of thermoplastic resin powder and 50-60% by mass of fiber braid, the particle size of the thermoplastic resin powder is 160-300 mesh, and the fiber braid is one or more of a two-dimensional braid or a three-dimensional braid.

[0046] The composite material forming process of the present invention heats the thermoplastic resin powder to a semi-molten state through a resistance wire during the weaving process, so that the resin powder adheres to the surface of the yarn bundle, and the resin powder is directly introduced into the fiber braid. After the preform is formed, it can be directly put into the oven for staged heating and curing. This method has the advantage of near-net forming of the composite material braiding process. Compared with the traditional preform curing processes such as resin transfer molding, resin film penetration or autoclave curing, it improves production efficiency, avoids the resin impregnation process, can realize the rapid prototyping of fiber braided reinforced thermoplastic composite materials, can reduce the defects such as uneven impregnation, large pore volume and lack of glue caused by poor resin fluidity, and improve the quality of composite material braiding products. At the same time, because the resin powder is attached to the surface of the yarn bundle during the weaving process, compared with the traditional weaving process, it can reduce the problems of fuzzing and breakage caused by friction between yarns, reduce the friction damage of yarns during the weaving process, and improve the quality of component forming.

Claims

1. A method for preparing a braided preform based on resin powder filling, characterized in that: The following steps are involved: Step 1, the yarn is led out from the braiding machine and wrapped in thermoplastic resin powder; Step 2, starting to heat the thermoplastic resin powder to a semi-molten state; Step 3, start the knitting machine to complete a knitting step; Step 4: start the lifting mechanism to pull the formed fiber preform; Step 5, repeating step 3 and step 4 until a braided preform of a predetermined length is obtained; Step six, taking out the braided preform formed in step five, putting it into a pressure mold and placing it in an oven for hot pressing and curing, and demoulding to obtain a fiber braided reinforced thermoplastic composite material.

2. The method for preparing a braided preform based on resin powder filling according to claim 1, characterized in that: In step one, a resin powder box is provided; the resin powder box is provided with a receiving chamber for accommodating resin powder, a water bath layer surrounding the receiving chamber, and a resistance wire located below the water bath layer, and the bottom and top of the resin powder box are provided with a plurality of holes for passing the yarn bundle.

3. The method for preparing a braided preform based on resin powder filling according to claim 2, characterized in that: The resin powder box is arranged below a lifting mechanism for lifting the yarn, and the yarn passes through the resin powder box and is wrapped by semi-molten thermoplastic resin powder in the resin powder box.

4. The method for preparing a braided preform based on resin powder filling according to claim 1, characterized in that: The thermoplastic resin powder is one or more of thermoplastic phenolic resin powder, polyetheretherketone powder and polyimide powder.

5. The method for preparing a braided preform based on resin powder filling according to claim 1 or 4, characterized in that: The fiber braid is prepared by a three-dimensional rotary braiding machine. The braided yarn is one or more of carbon fiber tows, glass fiber tows, and aramid fiber tows. The braiding angle is 15-45°, the cross-sectional size is 6mm×6mm, and the density is 0.5g / cm 3 .

6. The method for preparing a braided preform based on resin powder filling according to claim 1, characterized in that: When the thermoplastic resin powder is heated by the resistance wire water bath in step 2, the relationship between the temperature T of the thermoplastic resin powder and the time t satisfies the following conditions: Where T0 is the initial temperature, r is the heat transfer efficiency, m r is the mass of resin powder, c r is the specific heat of resin powder, V is the rated power of resistance wire, and R is the resistance value of resistance wire.

7. The method for preparing a braided preform based on resin powder filling according to claim 1 or 6, characterized in that: When the resistance wire water bath heats the thermoplastic resin powder in step 2, the relationship between the heat Q required for melting the resin powder and the temperature T satisfies the curve Q=F(T), which is obtained by calibrating and measuring the actual melting process of the corresponding resin.

8. The method for preparing a braided preform based on resin powder filling according to claim 1, characterized in that: The specific operation of removing the formed preform and placing it into the pressure mold described in step 6 is: placing the release cloth, preform, release cloth, isolation film, and guide net in the pressure mold in sequence, pressing the cover plate and placing it in the oven.

9. The method for preparing a braided preform based on resin powder filling according to claim 1 or 8, characterized in that: In step six, hot pressing curing is adopted in stages: the first stage is the melting processing stage, the temperature is 80-120°C, the pressure is 10-50MPa, and the processing time is 0.5-1h; the second stage is the molding curing stage, maintaining the pressure in the oven at 10-50MPa until it returns to room temperature, so that the thermoplastic resin is cooled and cured.

10. A preform obtained according to the method for preparing a braided preform according to any one of claims 1 to 9, characterized in that: The invention comprises 40-50% by mass of thermoplastic resin powder and 50-60% by mass of fiber braid. The particle size of the thermoplastic resin powder is 160-300 meshes. The fiber braid is a two-dimensional braid and / or a three-dimensional braid.

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