Carbon fiber composite material flow guide medium and preparation method thereof

Abstract

The application discloses a kind of carbon fiber composite material flow guide medium and preparation method, flow guide medium is by the net structure of fiber, with hole, fiber is intertwined across each other, without specific orientation arrangement.Flow guide medium fiber includes skin layer and core layer, core layer material is aromatic polyamide, skin layer material is thermoplastic elastomer, thermoplastic elastomer molecular chain includes hard segment and soft segment.The technical scheme provided by the application is applied to composite material liquid forming process, it is helpful that resin flow guide effect is evenly distributed in each layer of preform, solve large thickness, sandwich structure preform is fully, low defect infiltration.Compared with traditional flow guide medium, it has the effect of setting, strengthening and toughening simultaneously, as the internal component of composite material, avoid surface indentation caused by traditional flow guide net.

Description

Technical Field

[0001] This invention belongs to the field of resin-based carbon fiber composite materials, and more specifically, this invention relates to the guiding medium and preparation method in the liquid molding process of composite materials. Background Technology

[0002] With the continuous development of composite material manufacturing technology, composite materials are increasingly widely used in the aerospace field, and their usage has become a major indicator of the advancement of aircraft. Compared with autoclave molding methods, liquid molding technologies, represented by VARI (vacuum-assisted resin infiltration) and RTM (resin transfer molding), have advantages such as low manufacturing cost, high manufacturing efficiency, and high dimensional and surface precision, and have broad application prospects in composite material molding technology.

[0003] The VARI liquid molding process involves laying down dry fiber fabrics, unidirectional tapes, etc., to form a preform. After adding auxiliary materials, resin inlet and outlet channels are laid. The preform is then sealed in a vacuum bag or closed mold, and resin is forced into the vacuum bag or mold under vacuum pressure to fully impregnate the preform. After closing the injection and outlet ports, the resin is heated to cure, and after cooling, the composite material part is obtained.

[0004] Currently, there are two prominent challenges in preparing composite materials using liquid molding processes:

[0005] 1. Due to the in-plane orientation of carbon fibers, unsatisfactory interlayer toughness is a major challenge restricting the development and application of carbon fiber composites. To address this issue, the industry has developed various interlayer reinforcement and toughening technologies, such as Z-PIN reinforcement and stitching. For liquid molding processes, the smooth, non-adhesive surface of carbon fibers makes it difficult for the layers to adhere during the layup process. In engineering applications, a setting agent is added between the layers to assist in the layup. This setting agent is typically an oligomer powder or solution that becomes viscous after heating. Traditional setting agents exhibit low strength and brittleness, remaining between the layers and negatively impacting the interlayer bonding toughness of the composite material.

[0006] 2. Resin impregnation process control significantly affects the molding quality of liquid molding. Because carbon fibers are arranged in an orderly manner within the fabric or unidirectional tape, the fibers in the prepared preform are tightly packed, and the carbon fiber surface is smooth and chemically inert. Therefore, resin penetration into the preform is very slow. For large-size and complex structures, this can easily lead to resin penetration times exceeding the process window, resulting in significant differences in penetration quality at the injection and riser points. To address this issue, a flow-guided medium-assisted penetration method is commonly used in engineering applications. The flow-guided medium is usually a woven fabric made of materials such as polyethylene or nylon, typically used in conjunction with a release medium and laid on the surface of the preform. After the material has cured, it is peeled off and discarded. Traditional flow-guided media have the following drawbacks:

[0007] 1. Indentations are left on the surface of the molded product, affecting the surface quality of the product.

[0008] 2. The flow direction is singular, only producing a flow effect in the direction within the surface layer. The impact on the penetration in the thickness direction is very limited, which can easily cause differences in the penetration effect between the upper and lower surfaces, resulting in poor resin wetting of the bottom preform.

[0009] 3. For sandwich and embedded insert structures, the flow medium only improves the resin penetration of the upper part of the preform, while the resin of the lower part is difficult to wet and is prone to dry spot defects. Summary of the Invention

[0010] To address the problems of difficult permeation of dry fiber preforms, unsatisfactory application effects of traditional flow-guiding media, and the impact of sizing agents on interlayer properties of materials, this invention discloses a carbon fiber composite flow-guiding medium and its preparation method. The technical solution of this invention is as follows:

[0011] A carbon fiber composite fluid guiding medium is disposed between carbon fiber fabrics. The fluid guiding medium has a mesh structure composed of fibers with pores, and the fibers are intertwined and cross-linked without a specific orientation. The fluid guiding medium fibers include a skin layer and a core layer. The core layer has an aromatic polyamide chemical structure, which is prepared by polymerization reaction using aromatic diamine monomers and aromatic diacyl chloride monomers as raw materials. The skin layer material is a thermoplastic elastomer, and the thermoplastic elastomer molecular chain contains hard segments and soft segments.

[0012] • Preferred Option 1: The skin material is one of the following: styrene-butadiene block copolymer, styrene-isoprene block copolymer, styrene-isoprene-butadiene block copolymer, acrylonitrile-butadiene-propylene block copolymer, toluene diisocyanate-polyether diol-1,4-butanediol block copolymer, and a block copolymer of polybutylene terephthalate and aliphatic polyether.

[0013] • Preferred Option 2: The mass fraction of the hard segment in the skin thermoplastic elastomer is 30%-45%.

[0014] • Preferred option 3: The degree of polymerization of the thermoplastic elastomer in the skin layer is 1000-1500.

[0015] • Preferred option 4: The cortex accounts for 8%-15% of the total mass of the cortex-core structure fibers.

[0016] The method for preparing the above-mentioned carbon fiber composite fluid guiding medium includes the following steps:

[0017] (1) Preparation of core polymer solution: Aromatic diamine monomer and aromatic diacyl chloride monomer are used to synthesize polyamide solution in organic solvent.

[0018] (2) Preparation of core fiber: Spinning is carried out using the polymer solution of the flow-conducting component in step (1), and the residual solvent is removed by drying to obtain core fiber.

[0019] (3) Preparation of skin polymer solution: Dissolve one of the following thermoplastic elastomer materials in an organic solvent to prepare a skin polymer solution with a solid content of 8%-12%: styrene-butadiene block copolymer, styrene-isoprene block copolymer, styrene-isoprene-butadiene block copolymer, acrylonitrile-butadiene-propylene block copolymer, toluene diisocyanate-polyether diol-1,4-butanediol block copolymer, and block copolymer of polybutylene terephthalate and aliphatic polyether.

[0020] (4) Preparation of sheath-core structure fiber: The sheath fiber prepared in step (2) is immersed in the sheath polymer solution prepared in step (3) through a guiding device, and then wound up through a collecting device. The residual solvent in the fiber is then dried. The obtained fiber is then immersed in the sheath polymer solution, wound up and dried repeatedly to obtain sheath-core structure fiber.

[0021] (5) The core-sheath structure fiber obtained in step (4) is fed into a carding device, which combs it parallel and decomposes it into a single fiber state. Then, the randomized mechanism makes the fiber into a uniform and randomly arranged fiber web to obtain the flow medium.

[0022] The technical solution of this invention has the following advantages:

[0023] 1. Traditional flow guiding nets only affect the surface carbon fiber. In contrast, the resin flow guiding effect of the technical solution provided by this invention can be evenly distributed in each layer of the preform, which helps to fully and with low defects in thick sandwich structure preforms.

[0024] 2. Traditional flow guide nets are used as auxiliary materials and are peeled off and discarded after product molding. Their mesh structure easily causes indentations on the product surface, affecting surface quality. The flow guide medium provided by this invention is a component of the composite material and does not affect the product surface quality.

[0025] 3. The fiber-skin-core structure design provides shaping effect, while the core layer plays a guiding role. Furthermore, the thermoplastic elastomer material of the skin layer has the characteristics of high elasticity at low temperature and plasticity at high temperature, enabling the skin layer components to play a role in shaping at high temperature and toughening at room temperature, thus solving the problem of traditional shaping agents affecting interlayer toughness. Attached Figure Description

[0026] Figure 1 -Schematic diagram of the flow guiding medium structure

[0027] Figure 2 - Schematic diagram of the preparation process of the flow guiding medium

[0028] Numbering in the diagram: 1-Flow guiding medium; 2-Sheath; 3-Core; 4-Hard segment; 5-Soft segment; 6-Sheath polymer solution; 7-Guiding device; 8-Collection device; 9-Cardizing equipment; 10-Carbon fiber fabric; 11-Sheath-core structure fiber Detailed Implementation

[0029] like Figure 1 As shown, a carbon fiber composite material flow medium is disposed between carbon fiber fabrics 10. The flow medium 1 is a mesh structure composed of fibers with pores. The fibers are intertwined and cross each other without a specific orientation. The fibers include a skin layer 2 and a core layer 3. The core layer 3 is made of aromatic polyamide, which is prepared by polymerization reaction using aromatic diamine monomers and aromatic diacyl chloride monomers as raw materials. The skin layer 2 is made of thermoplastic elastomer, and the thermoplastic elastomer molecular chain contains hard segments 4 and soft segments 5.

[0030] The skin layer 2 material is any one of the following: styrene-butadiene block copolymer, styrene-isoprene block copolymer, styrene-isoprene-butadiene block copolymer, acrylonitrile-butadiene-propylene block copolymer, toluene diisocyanate-polyether diol-1,4-butanediol block copolymer, and block copolymer of polybutylene terephthalate and aliphatic polyether.

[0031] The hard segment 4 in the thermoplastic elastomer skin layer 2 accounts for 30%-45% of the mass of skin layer 2.

[0032] The degree of polymerization of the skin layer 2 thermoplastic elastomer material is 1000-1500.

[0033] The weight of the cortex 2 accounts for 8%-15% of the total weight of the fiber in the flow medium 1.

[0034] The method for preparing the above-mentioned carbon fiber composite fluid guiding medium 1 includes the following steps:

[0035] 1. Preparation of the core layer 3 polymer solution: A polyamide solution was synthesized in an organic solvent using aromatic diamine monomers and aromatic diacyl chloride monomers;

[0036] 2. Preparation of core layer 3 fibers: Spinning is performed using the polyamide solution from step 1, followed by drying to remove residual solvent;

[0037] 3. Preparation of skin polymer solution 6: Dissolve one of the following thermoplastic elastomer materials in an organic solvent. The thermoplastic elastomer materials include: styrene-butadiene block copolymer, styrene-isoprene block copolymer, styrene-isoprene-butadiene block copolymer, acrylonitrile-butadiene-propylene block copolymer, toluene diisocyanate-polyether diol-1,4-butanediol block copolymer, and block copolymer of polybutylene terephthalate and aliphatic polyether. Prepare a skin polymer solution 6 with a solid content of 8%-12% using any one of the above thermoplastic elastomer materials.

[0038] 4. Preparation of core-sheath structure fiber: The core layer 3 fiber prepared in step 2 is immersed in the sheath polymer solution 6 prepared in step 3 through the guiding device 7, and then wound up through the collecting device 8. The residual solvent in the fiber is then dried. The obtained fiber is then subjected to the above steps of immersion in sheath polymer solution 6, winding up and drying to obtain core-sheath structure fiber.

[0039] 5. The core-sheath structure fibers obtained in step 4 are fed into the carding equipment 9, where they are combed parallel and broken down into single fibers. Then, the randomizing mechanism forms the fibers into a uniformly and randomly arranged fiber web.

[0040] The present invention is illustrated by the following three embodiments.

[0041] Example 1:

[0042] Component structure: J-shaped reinforced wall panel with laminated structure, skin size 1000mm*400mm, rib size 280mm*120mm*30mm, skin ply is 30 layers of carbon fiber fabric, vertical rib ply is 6 layers of carbon fiber fabric.

[0043] The preparation process of the flow guiding medium 1 is as follows:

[0044] (1) Preparation of core layer 3 polymer solution: A polyamide solution was synthesized in an organic solvent using the aromatic diamine monomer biphenyl diamine and the aromatic diacyl chloride monomer terephthaloyl chloride.

[0045] (2) Preparation of core layer 3 fiber: Spinning is performed using the polyamide solution in step (1), and the residual solvent inside the fiber is removed by drying to obtain core layer 3 fiber.

[0046] (3) Preparation of skin polymer solution 6: The styrene-butadiene block copolymer is dissolved in an organic solvent to prepare a skin polymer solution 6 with a solid content of 8%. The degree of polymerization of the above styrene-butadiene polymer is 1200, and the mass fraction of hard segment styrene is 30%.

[0047] (4) Preparation of sheath-core structure fiber: The sheath 2 fiber prepared in step (2) is immersed in the sheath polymer solution 6 prepared in step (3) through the guiding device 7, and then wound up through the collecting device 8. The residual solvent in the fiber is then dried to obtain the sheath-core structure fiber.

[0048] (5) The core-sheath structure fiber obtained in step (4) is fed into the carding device 9, which combs it parallel and decomposes it into a single fiber state. Then, the random mechanism makes the fiber into a uniform and randomly arranged fiber web to obtain the flow medium 1.

[0049] The process of molding composite materials using the guiding medium 1 is as follows:

[0050] (1) A preform is prepared by laying carbon fiber fabric 10. During the laying process, a flow medium 1 is laid on top of every 5 layers of carbon fiber fabric 10. The outermost layer of the preform is carbon fiber fabric 10.

[0051] (2) After laying the flow guiding medium 1 and a layer of carbon fiber fabric 10 on it, the flow guiding medium 1 is shaped at 110°C using a shaping device to melt the skin layer 2 component in the flow guiding medium 1. After the skin layer 2 cools, it is bonded and shaped.

[0052] (3) Arrange resin channels along both sides of the length of the preform and along the upper edge of the ribs. After sealing with a vacuum bag, introduce the resin into the preform through the channels to impregnate it. After the preform is completely impregnated with resin, close the resin channels.

[0053] (4) Heat to 190℃ and cure for 2 hours. After cooling to room temperature, demold to obtain composite material product.

[0054] In this embodiment, the preform was prepared using the flow guiding medium 1, and the shaping effect was good, with no fiber wrinkles, slippage, or deformation. Table 1 records the resin penetration distance of the preform in this embodiment. The penetration of the upper and lower layers of the skin was relatively uniform, and no resin flow front convergence was observed. Due to the small size and thickness, the penetration of the ribs was slightly slower than that of the skin, but the overall penetration was uniform and controllable.

[0055] C-scan testing of the J-shaped stiffened wall panel revealed no abnormal signals, indicating that the introduction of the guiding medium did not adversely affect the molding quality of the composite material.

[0056] Table 1 Resin penetration distance in Example 1

[0057] Time / s 282 421 769 976 1536 Penetration distance / mm (upper layer of skin) 61 110 253 318 400 Penetration distance / mm (lower layer of skin) 62 109 250 304 393 Penetration distance / mm (rib) 0 42 79 109 120

[0058] To evaluate the effect of the guiding medium 1 on the mechanical properties of the composite material, drop hammer impact tests were conducted on the reinforced wall panel furnace test plate and the blank control sample without the guiding medium at energies of 5J, 10J, 15J, 20J, and 30J. The results are shown in Table 2. Under the same energy, the impact damage of the blank sample was relatively greater, indicating that the introduction of the guiding medium has a certain toughening effect.

[0059] Table 2 Results of the drop hammer test for Example 1 and blank control samples

[0060] Energy / J Pit depth (Example 1) / mm Pit depth (blank control) / mm 5 0.04 0.05 10 0.07 0.09 15 0.13 0.19 20 0.20 0.31 30 2.10 2.12

[0061] Example 2:

[0062] Styrene-isoprene block copolymers with different hard segment mass fractions and degrees of polymerization were selected as the skin layer 2 material. The degree of polymerization of the styrene-isoprene polymer ranged from 600 to 2000, with the styrene hard segment mass fraction accounting for 10%-60% of the thermoplastic elastomer. The melting temperature of the above thermoplastic elastomer materials was characterized by DSC endothermic peaks, and the results are shown in Table 3. When the degree of polymerization is in the range of 1000-1500 and the hard segment mass fraction is in the range of 30%-45%, the melting temperature of the thermoplastic elastomer can be guaranteed to be in the range of 110℃-130℃, which meets the operating temperature range of existing shaping equipment.

[0063] Table 3 Melting temperatures of styrene-isoprene block copolymers with different hard segment mass fractions and degrees of polymerization.

[0064]

[0065] Example 3:

[0066] The ratio of skin to core components significantly affects the performance of the flow medium. An excessive skin layer leads to tight adhesion between carbon fiber fabrics, hindering resin penetration and affecting the flow performance of the core layer. Conversely, an insufficient skin layer ratio results in poor setting performance. Based on traditional experience with setting agent powders, the optimal amount of setting agent is below 5%, and it should be evenly distributed in a dotted pattern between the carbon fiber fabric layers. Example 3 compares the performance differences of flow media with different skin to core component ratios, providing a reference for determining the skin to core component ratio. The preparation process of flow medium 1 is as follows:

[0067] (1) Preparation of core layer 3 polymer solution: A polyamide solution was synthesized in an organic solvent using the aromatic diamine monomer biphenyl diamine and the aromatic diacyl chloride monomer terephthaloyl chloride.

[0068] (2) Preparation of core layer 3 fiber: Spinning is carried out using the polymer solution of the guiding component in step (1), the residual solvent is removed by drying, core layer 3 fiber is obtained, weighed and recorded.

[0069] (3) Preparation of skin polymer solution 6: The styrene-butadiene block copolymer is dissolved in an organic solvent to prepare a skin polymer solution with a solid content of 8%. The degree of polymerization of the above styrene-butadiene polymer is 1500, of which the mass fraction of hard segment styrene is 40%.

[0070] (4) Preparation of core-shell structure fibers with different ratios of core and sheath components: The core layer 3 fiber prepared in step (2) is immersed in the sheath polymer solution 6 prepared in step (3) through the guiding device 7, and then wound up through the collecting device 8. The residual solvent in the fiber is then dried. Steps 1, 2, 3 and 4 of immersion in the sheath polymer solution 6, winding and drying are performed respectively to obtain core-shell structure flow medium 1 fibers with different ratios of core and sheath components. The weight is weighed and the weight change before and after step (4) is recorded.

[0071] (5) The core-shell structure flow medium 1 fiber obtained in step (4) is fed into the carding device 9, which combs it parallel and decomposes it into a single fiber state. Then, the random mechanism makes the fiber into a uniform and randomly arranged fiber web to obtain the flow medium 1.

[0072] The mass fraction of the skin layer 2 was calculated based on the weighing results, and the content of the skin layer 2 in the matrix resin was calculated based on the volume fraction of the composite fiber. A layer of carbon fiber fabric 10 was laid on both the top and bottom of the aforementioned flow medium 1, and then shaped at 120°C using a shaping device. Subsequently, the carbon fiber fabric 10 was peeled off, and the morphology of the skin layer 2 components was observed using a microscope. The results are shown in Table 4. When the mass fraction of the skin layer component is 8%-15%, the content of the skin layer component in the matrix resin is less than 5%, and after shaping, the skin layer is mostly island-shaped, distributed at the fiber intersections.

[0073] Table 4 Performance of fluid guiding media with different ratios of skin and core components

[0074]

[0075]

[0076] The principle of this invention is as follows:

[0077] The flow-guiding medium proposed in this invention is composed of a core-skin structure fiber. The skin layer is a thermoplastic elastomer material with molecular chains including hard and soft segments. It exhibits plasticity at certain temperatures, serving to bond and shape the carbon fiber layup. After heating and flowing, the skin layer components converge into droplets, exposing the core layer components. The core layer has an aromatic polyamide chemical structure with strong polarity in the amide bonds, which can form hydrogen bonds with the epoxy resin prepolymer. Furthermore, after being carded, it forms a randomly arranged network with numerous internal pores. Therefore, the medium formed by the core layer fibers promotes the flow of resin within the carbon fiber preform.

[0078] After curing, the flow-guiding medium proposed in this invention serves as an internal component of the composite material. The thermoplastic elastomer in the outer layer, due to its low content, is distributed in an "island" pattern between the composite layers. Under room temperature service conditions, the thermoplastic elastomer exhibits high elasticity, acting as an interlayer toughening agent. The aromatic polyamide core fiber possesses high strength and high modulus, thus functioning as a reinforcing material.

[0079] In the field of aerospace composite materials, the curing temperature range of the matrix epoxy resin is 180℃-220℃. In order to fully utilize the effects of the guiding medium in promoting penetration, assisting in shaping, and enhancing toughness, this invention further specifies the technical solution:

[0080] The mass fraction of the hard segment in the skin thermoplastic elastomer is limited to 30%-45%, and the degree of polymerization of the thermoplastic elastomer macromolecules is 1000-1500. Under the above conditions, the skin thermoplastic elastomer exhibits ideal fluidity and viscosity within the temperature range of 110℃-130℃ (the suitable operating temperature range of existing shaping equipment), and the interlayer shaping effect is good (see Example 2).

[0081] The sheath component is limited to 8%-15% of the total mass of the sheath-core structure fibers. Under the above conditions, the content of the sheath component in the matrix resin can be controlled within 5%, and the shaped sheath component is distributed in an "island" shape between the carbon fiber fabric layers. At this time, the negative impact on resin penetration is small, while the interlayer toughening effect can be fully utilized (see Example 3).

Claims

1. A carbon fiber composite fluid guiding medium, characterized in that... The flow medium is a mesh structure made of fibers with pores. The fibers are intertwined and cross each other without a specific orientation. The fibers include a skin layer and a core layer. The core layer material is aromatic polyamide, which is prepared by polymerization reaction using aromatic diamine monomers and aromatic diacyl chloride monomers as raw materials. The skin layer material is thermoplastic elastomer, and the thermoplastic elastomer molecular chain contains hard segments and soft segments.

2. The carbon fiber composite fluid guiding medium according to claim 1, characterized in that, The thermoplastic elastomer material of the skin layer is any one of the following: styrene-butadiene block copolymer, styrene-isoprene block copolymer, styrene-isoprene-butadiene block copolymer, acrylonitrile-butadiene-propylene block copolymer, toluene diisocyanate-polyether diol-1,4-butanediol block copolymer, and block copolymer of polybutylene terephthalate and aliphatic polyether.

3. The carbon fiber composite fluid guiding medium according to claim 1, characterized in that, The hard segment portion of the skin layer thermoplastic elastomer material accounts for 30%-45% of the skin layer mass fraction.

4. The carbon fiber composite fluid guiding medium according to claim 1, characterized in that, The degree of polymerization of the skin thermoplastic elastomer material is 1000-1500.

5. The carbon fiber composite fluid guiding medium according to claim 1, characterized in that, The sheath layer accounts for 8%-15% of the total fiber mass.

6. A method for preparing the carbon fiber composite fluid guiding medium according to any one of claims 1-5, comprising the following steps: 6-1 Preparation of core layer polymer solution: Polyamide solution was synthesized in an organic solvent using aromatic diamine monomer and aromatic diacyl chloride monomer; 6-2 Preparation of core fiber: Spinning is performed using the polyamide solution from step 6-1, followed by drying to remove residual solvent; 6-3 Preparation of the skin polymer solution: Dissolve one of the following thermoplastic elastomer materials in an organic solvent, wherein the thermoplastic elastomer material includes: A skin polymer solution with a solid content of 8%-12% is prepared using any one of the following thermoplastic elastomer materials: styrene-butadiene block copolymer, styrene-isoprene block copolymer, styrene-isoprene-butadiene block copolymer, acrylonitrile-butadiene-propylene block copolymer, toluene diisocyanate-polyether diol-1,4-butanediol block copolymer, and block copolymer of polybutylene terephthalate and aliphatic polyether. 6-4 Preparation of core-sheath structured fibers: The core fibers prepared in step 6-2 are immersed in the sheath polymer solution prepared in step 6-3 through a guiding device, and then wound up through a collecting device. The residual solvent in the fibers is then dried. The obtained fibers are then subjected to the above steps of immersion in the sheath polymer solution, winding up, and drying to obtain core-sheath structured fibers. 6-5 The core-sheath structure fibers obtained in step 6-4 are fed into a carding device to be combed parallel and decomposed into single fibers. Then, a randomizing mechanism is used to make the fibers into a uniform and randomly arranged fiber web to obtain a flow medium.

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