A method of blending porous ultra-fine fiber toughened carbon fiber epoxy resin composites

Abstract

The application discloses a method for blending porous superfine fiber toughened carbon fiber epoxy resin composite material, and belongs to the field of interlaminar toughening modification of carbon fiber epoxy resin composite material. The thermoplastic high-performance fiber is prepared by blending a high-melting-point thermoplastic polymer as a matrix and a low-melting-point thermoplastic fiber as a filler in an organic solvent to obtain a uniform spinning solution. The uniform spinning solution is prepared into superfine fibers by using an electrostatic spinning technology, and then is added to the interlaminar part of a carbon fiber epoxy resin prepreg for heat pressing and curing to obtain a carbon fiber epoxy resin composite laminate which is toughened by the thermoplastic fiber. The interlaminar toughening superfine fiber film can realize interlaminar toughening of the carbon fiber epoxy resin composite material while keeping the original form of the carbon fiber epoxy resin composite material, and can significantly improve the impact strength, interlaminar shear performance and bending performance of the laminate.

Description

Technical Field

[0001] This invention relates to a method for blending porous ultrafine fibers to toughen carbon fiber epoxy resin composites, belonging to the field of interlaminar toughening technology for carbon fiber epoxy resin composites. Background Technology

[0002] Carbon fiber epoxy resin composites possess excellent properties such as high strength, high modulus, light weight, and fatigue resistance, making them widely used in critical structural components in aerospace, rail transportation, and wind turbine blades. However, because epoxy resin, after curing into a three-dimensional cross-linked network, is brittle, it is prone to delamination damage between layers upon impact, ultimately leading to the failure of carbon fiber epoxy resin composite components. Therefore, finding methods to improve the toughness of carbon fiber epoxy resin composites is extremely important.

[0003] Currently, numerous researchers both domestically and internationally have adopted methods such as improving the surface structure of carbon fibers, adding "flexible segments" to the cross-linked network formed by epoxy resin, and Z-axis splicing to improve the tendency of carbon fiber-epoxy resin composites to delaminate after curing, thus achieving interlayer toughening of carbon fiber-epoxy resin composites. However, these methods will lead to adverse results such as increased manufacturing costs, more complex processing technology, or decreased in-plane mechanical properties of carbon fiber-epoxy resin composites. Summary of the Invention

[0004] The main technical problem solved by this invention is to increase the impact strength, interlaminar shear performance, and flexural performance of carbon fiber epoxy resin composite laminates by improving the interfacial strength of the composite material without increasing the preparation cost of carbon fiber epoxy resin composites, without changing the processing technology of carbon fiber epoxy resin composites, and without reducing the in-plane mechanical properties of carbon fiber epoxy resin composites.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] S1. Preparation of electrospun fiber membrane, the preparation process includes...

[0007] S11, the high glass transition temperature thermoplastic polymer is selected from one or more of polyaryletheronitrile, polyetherimide, polybenzimidazole, polyetherketone, and polyethersulfone ketone;

[0008] S12, the low glass transition temperature polymer is selected from one or more of polycaprolactone, polyvinyl alcohol, polyvinyl butyral, and polymethyl methacrylate;

[0009] S13. Using a high glass transition temperature thermoplastic polymer as the matrix and a low glass transition temperature thermoplastic polymer as the filler, dissolve both in an organic solvent and stir for 3-12 hours to prepare a blend spinning solution with a concentration of 10-30%; wherein the mass fraction of the low glass transition temperature polymer is 5%-30% of the total mass of the blend spinning solution.

[0010] S14. The obtained homogeneous blend spinning solution is used to prepare ultrafine fibers by electrospinning. By controlling the spinning time, a blend fiber membrane with the required areal density is prepared. The areal density of the fiber membrane ranges from 4 to 25 g / m³. 2 ;

[0011] S2, the preparation of carbon fiber epoxy resin composite material, the preparation process includes:

[0012] S21. A dried blended fiber membrane is laid between the layers of the prepared carbon fiber epoxy resin prepreg, for a total of 16 layers of carbon fiber epoxy resin prepreg and 15 layers of blended fiber membrane.

[0013] S22. The prepreg and blended fiber membrane composite material are hot-pressed above the glass transition temperature of the low glass transition temperature polymer, and then cured by increasing the temperature according to the curing process.

[0014] 2. Wherein, the organic solvent in step S13 includes one or more of acetone, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone.

[0015] 3. The electrospinning conditions described in step S14 are: flow rate of 0.1-9 ml / h, voltage of 15-30 kV, spinning distance of 15-22 cm, temperature of 20-25℃, and ambient humidity of 20%-50%.

[0016] 4. In step S14, the diameter of the blended fiber is 0.7 to 1.2 μm.

[0017] 5. The curing conditions for step S22 are: hot pressing at room temperature to 80°C for 30 min at 1-2 MPa, followed by curing at 125°C for 90 min.

[0018] This invention involves adding a blended fiber membrane, using a high glass transition temperature thermoplastic polymer as the matrix and a low glass transition temperature thermoplastic polymer as the filler, to the interlayer regions of the easily damaged carbon fiber epoxy resin prepreg through solution electrospinning. This method can more effectively improve the performance of the laminate without changing the original curing process. This invention utilizes the characteristics of the low glass transition temperature polymer in the blended fibers and the large specific surface area and high porosity of the blended ultrafine fibers, allowing the epoxy resin to fully fill the interlayer voids during hot pressing while simultaneously creating a good interfacial interaction with the thermoplastic fibers. This is a novel and effective method for interlayer toughening modification.

[0019] In addition, the porous ultrafine fiber membrane prepared by this invention is not only inexpensive, but also possesses excellent chemical stability, high specific surface area, and large porosity. The method for preparing interlayer toughened carbon fiber epoxy resin composite laminates described in this invention is simple, controllable, safe, and pollution-free. Attached Figure Description

[0020] Figure 1 Here is a SEM image of the ultrafine fibers prepared in the embodiments of the present invention;

[0021] Figure 2 The image shows the impact performance of the carbon fiber epoxy resin composite material prepared in the embodiments of the present invention.

[0022] Figure 3 This is a diagram showing the interlaminar shear properties of the carbon fiber epoxy resin composite material prepared in the embodiments of the present invention;

[0023] Figure 4 The diagram shows the flexural properties of the carbon fiber epoxy resin composite material prepared in the embodiments of the present invention.

[0024] Figure 5 Scanning electron microscope image of the fracture surface of carbon fiber epoxy resin composite material without interlayer toughening;

[0025] Figure 6 A scanning electron microscope image of the fracture surface of the carbon fiber epoxy resin composite material with interlayer toughening of PEN-PCL blended fiber membrane prepared in the embodiment of the present invention.

[0026] Figure 7 The "microsphere" structure at the fracture surface of the carbon fiber epoxy resin composite material with interlayer toughening of PEN-PCL blended fiber membrane prepared in the embodiments of the present invention. Detailed Implementation

[0027] Example:

[0028] 1. Preparation of blended fiber membranes by electrospinning

[0029] A certain amount of polyarylene ether nitrile (PEN) and 20% polycaprolactone (PCL) of PEN were weighed and added to N,N-dimethylformamide. The mixture was stirred at room temperature for 8 hours to prepare a homogeneous blending spinning solution with a solid content of 22%. The blending spinning solution was then placed in a syringe, and electrospinning was performed under the following conditions: a flow rate of 8.8 ml / h, a +30 kV voltage at the filament outlet, a -5 kV voltage at the roller, an ambient temperature of 25°C, and a relative humidity of 20%. The electrospinning time was controlled to achieve an areal density of 8 g / m³ for the PEN-PCL blended fiber membrane. 2 .

[0030] 2. Preparation of carbon fiber epoxy resin composite laminate

[0031] Sixteen sheets of carbon fiber epoxy resin prepreg with a monofilament diameter of 7μm, epoxy resin grade WP-H1650, epoxy resin content of 32%, and a yield of 150g per square meter were cut. An 8g / m² layer was then laid between each of the 16 prepreg sheets. 2 The PEN-PCL blended fiber membrane was then placed in a hot press and cured at 1 MPa to obtain a carbon fiber epoxy resin composite laminate toughened with the PEN-PCL blended fiber membrane. The curing conditions were: room temperature to 80℃, hot pressing at 80℃ for 30 min, then 80℃ to 125℃, and curing at 125℃ for 90 min. The heating rate was 6℃ / min.

[0032] Impact strength tests were conducted on laminated slabs using a pendulum impact tester, and the results were as follows: Figure 2 The bar chart shown illustrates the impact performance of the untoughened carbon fiber epoxy resin composite, the PEN microfiber membrane-toughened carbon fiber epoxy resin composite, and the PEN-PCL blend membrane-toughened carbon fiber epoxy resin composite. The results indicate that the impact strength of the PEN microfiber membrane-toughened carbon fiber epoxy resin composite is 88.13 kJ / m². 2 The toughening effect of the PEN-PCL blended fiber membrane-toughened carbon fiber epoxy resin composite material is 6.35% higher than that of the untoughened carbon fiber epoxy resin composite material; the impact strength of the PEN-PCL blended fiber membrane-toughened carbon fiber epoxy resin composite material is 185.38 kJ / m. 2 It improves upon the untoughened carbon fiber epoxy resin composite material by 123.67%.

[0033] The interlaminar shear properties of laminated plate strips were tested using a universal testing machine, and the results were as follows: Figure 3The bar chart shown illustrates the interlaminar shear properties of the untoughened carbon fiber epoxy resin composite, the PEN microfiber membrane-toughened carbon fiber epoxy resin composite, and the PEN-PCL blend membrane-toughened carbon fiber epoxy resin composite, respectively. The test results indicate that the interlaminar shear strength of the PEN microfiber membrane-toughened carbon fiber epoxy resin composite is 73.77 kJ / m. 2 The toughening effect was improved by 11.73% compared to the untoughened carbon fiber epoxy resin composite; the interlaminar shear strength of the PEN-PCL blended fiber membrane-toughened carbon fiber epoxy resin composite was 78.94 kJ / m. 2 This represents an increase of 19.57%.

[0034] The bending properties of laminated plate strips were tested using a universal testing machine, and the results were as follows: Figure 4 The bar charts shown represent the flexural properties of the untoughened carbon fiber epoxy resin composite, the PEN microfiber membrane-toughened carbon fiber epoxy resin composite, and the PEN-PCL blend membrane-toughened carbon fiber epoxy resin composite, respectively. The results show that the flexural strength and modulus of the PEN microfiber membrane-toughened carbon fiber epoxy resin composite are 1152.67 MPa and 111.19 GPa, respectively, representing decreases of 12.74% and 6.46% compared to the untoughened carbon fiber epoxy resin composite. However, the flexural strength and modulus of the PEN-PCL microfiber membrane-toughened carbon fiber epoxy resin composite are 1720.26 MPa and 149.24 GPa, respectively, representing increases of 30.23% and 25.55%.

[0035] Figure 6 Scanning electron microscope (SEM) image of the fracture surface of carbon fiber epoxy resin composite material with interlayer toughening of PEN-PCL blended fiber membrane. The PEN-PCL blended thermoplastic fibers and epoxy resin interdiffusion at the fracture surface, forming a "microsphere" structure after hot-pressing curing. Figure 7 This structure greatly enhances the interfacial interaction, which is closely related to the significant improvement in the mechanical properties of carbon fiber epoxy resin composites toughened between PEN-PCL blended fiber membrane layers.

[0036] The above description is only one specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a blended porous ultrafine fiber toughened carbon fiber epoxy resin composite material, characterized in that, Includes the following steps: S1. Preparation of electrospun blended fiber membrane, the preparation process includes S11, the high glass transition temperature thermoplastic polymer is selected from polyarylether nitrile; S12, low glass transition temperature thermoplastic polymer is selected from polycaprolactone; S13. Using a high glass transition temperature thermoplastic polymer as the matrix and a low glass transition temperature thermoplastic polymer as the filler, dissolve both in an organic solvent and stir for 3-12 hours to prepare a homogeneous blend spinning solution with a concentration of 10-30%; wherein the mass fraction of the low glass transition temperature polymer is 5%-30% of the total mass of the blend spinning solution. S14. The obtained blend spinning solution is used to prepare ultrafine fibers by electrospinning. By controlling the spinning time, a blend fiber membrane with the required areal density is prepared. The areal density of the blend fiber membrane ranges from 4 to 25 g / m³. 2 ; S2, the preparation of carbon fiber epoxy resin composite material, the preparation process includes: S21 involves laying dried blended fiber membranes between the layers of the prepared carbon fiber epoxy resin prepreg, with a total of 16 layers of prepreg and 15 layers of blended fiber membranes. S22 involves hot-pressing the prepreg and blended fiber membrane composite material above the glass transition temperature of the low glass transition temperature polymer, and then curing it by increasing the temperature according to the curing process conditions.

2. The method for preparing a blended porous ultrafine fiber toughened carbon fiber epoxy resin composite material according to claim 1, characterized in that, The organic solvent mentioned in step S13 includes one or more of acetone, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

3. The method for preparing a blended porous ultrafine fiber toughened carbon fiber epoxy resin composite material according to claim 1, characterized in that, In step S14, the electrospinning conditions are a flow rate of 0.1–9 ml / h. The voltage is 15-30kV, the spinning distance is 15-22cm, the temperature is 20-25℃, and the ambient humidity is 20%-50%.

4. The method for preparing a blended porous ultrafine fiber toughened carbon fiber epoxy resin composite material according to claim 1, characterized in that, The diameter of the blended fibers in step S14 is 0.7 to 1.2 μm.

5. The method for preparing a blended porous ultrafine fiber toughened carbon fiber epoxy resin composite material according to claim 1, characterized in that, The curing process conditions for step S22 are as follows: hot pressing at room temperature to 80°C for 30 minutes at 1-2 MPa, followed by curing at 125°C for 90 minutes.

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