CN116770507A

CN116770507A - Carbon fiber composite material diversion medium and preparation method thereof

Info

Publication number: CN116770507A
Application number: CN202310685730.9A
Authority: CN
Inventors: 闫超; 王天立; 田亦瑶; 苏霞; 武凯
Original assignee: AVIC Xian Aircraft Industry Group Co Ltd
Current assignee: AVIC Xian Aircraft Industry Group Co Ltd
Priority date: 2023-06-09
Filing date: 2023-06-09
Publication date: 2023-09-19

Abstract

The invention discloses a carbon fiber composite material flow guiding medium and a preparation method thereof, wherein the flow guiding medium is a net-shaped structure formed by fibers and provided with holes, the fibers are mutually intertwined and crossed, and no specific orientation arrangement exists. The diversion medium fiber comprises a skin layer and a core layer, wherein the core layer is made of aromatic polyamide, the skin layer is made of thermoplastic elastomer, and a thermoplastic elastomer molecular chain comprises a hard segment and a soft segment. The technical scheme provided by the invention is applied to the composite material liquid forming process, is beneficial to uniformly distributing the resin diversion effect in each layer of the preformed body, and solves the problems of sufficient preformed body with large thickness and sandwich structure and low defect infiltration. Compared with the traditional diversion medium, the composite material has the shaping, reinforcing and toughening effects, and is used as an internal component of the composite material, so that surface indentation caused by the traditional diversion net is avoided.

Description

Carbon fiber composite material diversion medium and preparation method thereof

Technical Field

The invention belongs to the field of resin-based carbon fiber composite materials, and in particular relates to a diversion medium in a composite material liquid forming process and a preparation method thereof.

Background

With the continuous development of composite material manufacturing technology, composite materials are increasingly widely applied in the aerospace field, and the use amount of the composite materials becomes a large index for measuring the advancement of aircrafts. Compared with autoclave molding methods, liquid molding technologies represented by VARI (vacuum assisted resin infiltration) and RTM (resin transfer molding) have the advantages of low manufacturing cost, high manufacturing efficiency, high size, high surface precision and the like, and have wide application prospects in composite material molding technologies.

The liquid forming VARI process is to lay dry fiber fabric, unidirectional tape, etc. to form prefabricated body, lay auxiliary material and then lay resin in and out flow channel. The preform is then encapsulated using a vacuum bag or closed mold, and the resin is pressed into the vacuum bag or closed mold under vacuum conditions to thoroughly infiltrate the preform. And then closing the glue injection and glue outlet, heating to solidify the resin, and cooling to obtain the composite material part.

The preparation of the composite material by adopting the liquid forming process at the present stage has the following two outstanding problems:

1. because the carbon fibers are in an in-plane orientation arrangement structure, the interlayer toughness is not ideal, which is a great difficulty in restricting the development and application of the carbon fiber composite material, and various interlayer reinforcing and toughening technologies such as Z-PIN reinforcing, stitching and the like are developed in the industry. For the liquid forming process, the surface of the carbon fiber is smooth and non-sticky, the adhesion between the layers is difficult in the paving process, and in engineering application, the paving is assisted by adding a sizing agent between the layers, wherein the sizing agent is usually oligomer powder or solution, and the sizing agent has viscosity after heating. Traditional sizing agents exhibit low strength and brittleness, remain between the plies, and adversely affect the interlayer bond toughness of the composite.

2. The control of the resin infiltration process obviously affects the molding quality of the liquid molding process, and the carbon fibers are orderly arranged in the fabric or the unidirectional tape, so that the fibers in the prepared preform are tightly piled, and the carbon fibers have smooth surfaces and are chemically inert. Therefore, the resin permeates slowly in the preform, and for large-size and complex structures, the defects that the resin permeation time exceeds a process window, the permeation quality difference of the injection riser is obvious and the like are easily caused. In order to solve the problem, a diversion medium auxiliary permeation method is commonly adopted in engineering application. The diversion medium is usually a braided fabric of polyethylene, nylon and other materials, is usually laid on the surface of the preform in combination with a demolding medium, and is peeled off and discarded after the material is solidified and molded. The traditional diversion medium has the following defects:

1. the back surface of the molded product is left with an indentation, which affects the surface quality of the product.

2. The flow guiding direction is single, the flow guiding effect is only generated in the surface in-plane direction, the influence on the penetration in the thickness direction is very limited, the difference of the penetration effects of the upper surface and the lower surface is easy to cause, and the resin infiltration of the bottom layer pre-formed body is poor.

3. For the sandwich and embedded insert structure, the guide medium only has an improvement effect on the resin permeation of the upper preformed body, the resin permeation of the lower preformed body is difficult, and the dry spot defect is easy to form.

Disclosure of Invention

Aiming at the problems that a dry fiber preform is difficult to permeate, the traditional diversion medium has an unsatisfactory application effect, a sizing agent affects the interlayer performance of a material and the like, the invention discloses a carbon fiber composite diversion medium and a preparation method thereof, and the technical scheme of the invention is as follows:

the carbon fiber composite material flow guiding medium is arranged between carbon fiber fabrics, the flow guiding medium is a net-shaped structure formed by fibers and provided with holes, and the fibers are mutually intertwined and crossed without specific orientation arrangement. The diversion medium fiber comprises a skin layer and a core layer, wherein the chemical structure of the core layer is aromatic polyamide, the diversion medium fiber is prepared by taking aromatic diamine monomer and aromatic diacid chloride monomer as raw materials through polymerization reaction, the skin layer material is thermoplastic elastomer, and a thermoplastic elastomer molecular chain comprises a hard segment and a soft segment.

Preference is given to scheme 1: the skin material is one of the following: styrene-butadiene block copolymers, styrene-isoprene-butadiene block copolymers, acrylonitrile-butadiene-propylene block copolymers, toluene diisocyanate-polyether glycol-1, 4-butanediol block copolymers, block copolymers of polybutylene terephthalate and aliphatic polyethers.

Preference is given to scheme 2: the mass fraction of the hard segment in the thermoplastic elastomer of the skin layer is 30-45%.

Preference is given to scheme 3: the degree of polymerization of the skin thermoplastic elastomer is 1000-1500.

Preference scheme 4: the sheath layer accounts for 8% -15% of the total mass of the sheath-core structure fiber.

The method for preparing the carbon fiber composite diversion medium comprises the following steps:

(1) Preparing a core polymer solution, namely synthesizing a polyamide solution in an organic solvent by adopting an aromatic diamine monomer and an aromatic diacid chloride monomer.

(2) Preparing core layer fibers: spinning by using the diversion component polymer solution in the step (1), and drying to remove residual solvent to obtain the core layer fiber.

(3) Preparation of a cortical polymer solution: dissolving one of the following thermoplastic elastomer materials in an organic solvent to prepare a cortical polymer solution with a solid content of 8% -12%: styrene-butadiene block copolymers, styrene-isoprene-butadiene block copolymers, acrylonitrile-butadiene-propylene block copolymers, toluene diisocyanate-polyether glycol-1, 4-butanediol block copolymers, block copolymers of polybutylene terephthalate and aliphatic polyethers.

(4) Preparing a sheath-core structural fiber: immersing the cortical fiber prepared in the step (2) into the cortical polymer solution prepared in the step (3) through a guiding device, winding through a collecting device, drying residual solvent in the fiber, and repeating the steps of immersing the obtained fiber into the cortical polymer solution, winding and drying to obtain the sheath-core structural fiber.

(5) And (3) feeding the skin-core structural fibers obtained in the step (4) into carding equipment, carding the skin-core structural fibers in parallel and decomposing the skin-core structural fibers into single fiber states, and preparing the fibers into uniform and disordered fiber webs by using a disordered mechanism to obtain the diversion medium.

The technical scheme of the invention has the following advantages:

1. compared with the technical scheme provided by the invention, the resin diversion effect can be uniformly distributed in each layer of the preformed body, and the preformed body with a large thickness and a sandwich structure is facilitated to be fully soaked with low defects.

2. The traditional diversion net is used as an auxiliary material, the product is stripped and discarded after being molded, and the grid structure of the traditional diversion net is easy to cause indentation on the surface of the product, so that the surface quality is affected. The diversion medium provided by the invention becomes a composite material component, and the surface quality of a product is not affected.

3. The fiber sheath-core structure design has the advantages that the sheath layer provides a shaping effect, the core layer plays a role in guiding flow, and the thermoplastic elastomer material of the sheath layer has the characteristics of low temperature high elasticity and high temperature plasticity, so that the sheath layer component plays a role in shaping at high temperature and toughening at room temperature, and the problem that the traditional shaping agent influences interlayer toughness is solved.

Drawings

FIG. 1-schematic diagram of a flow guiding medium structure

FIG. 2-schematic illustration of a process for preparing a diversion medium

The numbering in the figures illustrates: 1-a diversion medium; 2-cortex; 3-core layer; 4-hard segments; 5-soft segments; 6-cortical polymer solution; 7-guiding means; 8-a collection device; 9-carding equipment; 10; a carbon fiber fabric; 11; sheath-core structural fiber

Detailed Description

As shown in fig. 1, a carbon fiber composite material flow guiding medium is arranged between carbon fiber fabrics 10, the flow guiding medium 1 is a net structure formed by fibers, the fibers are provided with holes, the fibers are intertwined and crossed with each other, no specific orientation arrangement exists, the fibers comprise a skin layer 2 and a core layer 3, wherein the core layer 3 is made of aromatic polyamide by taking aromatic diamine monomers and aromatic diacid chloride monomers as raw materials through polymerization reaction, the skin layer 2 is thermoplastic elastomer, and a thermoplastic elastomer molecular chain comprises a hard segment 4 and a soft segment 5.

The cortex 2 material is any one of the following: styrene-butadiene block copolymers, styrene-isoprene-butadiene block copolymers, acrylonitrile-butadiene-propylene block copolymers, toluene diisocyanate-polyether glycol-1, 4-butanediol block copolymers, block copolymers of polybutylene terephthalate and aliphatic polyethers.

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

The thermoplastic elastomer material of skin layer 2 has a degree of polymerization of 1000 to 1500.

The mass of the cortex 2 accounts for 8% -15% of the total mass of the fibers of the diversion medium 1.

The method for preparing the carbon fiber composite material diversion medium 1 comprises the following steps:

1 preparing a core layer 3 polymer solution, namely synthesizing a polyamide solution in an organic solvent by adopting an aromatic diamine monomer and an aromatic diacid chloride monomer;

2 preparing core layer 3 fiber: spinning by using the polyamide solution in the step 1, and drying to remove residual solvent;

3 preparation of cortical polymer solution 6: dissolving one of the following thermoplastic elastomer materials in an organic solvent, the thermoplastic elastomer material comprising: styrene-butadiene block copolymer, styrene-isoprene-butadiene block copolymer, acrylonitrile-butadiene-propylene block copolymer, toluene diisocyanate-polyether glycol-1, 4-butanediol block copolymer, polybutylene terephthalate-aliphatic polyether block copolymer, and preparing a cortical polymer solution 6 with a solid content of 8% -12% from any one of the above thermoplastic elastomer materials;

4, preparing a sheath-core structural fiber: immersing the core layer 3 fiber prepared in the step 2 into the sheath polymer solution 6 prepared in the step 3 through a guiding device 7, winding through a collecting device 8, drying residual solvent in the fiber, and repeating the steps of immersing the obtained fiber into the sheath polymer solution 6, winding and drying to obtain the sheath-core structure fiber;

5 feeding the sheath-core structure fiber obtained in step 4 into carding equipment 9, carding and decomposing the sheath-core structure fiber into single fiber state, and preparing the fiber into uniform and disordered fiber web by using a disordered mechanism

The invention is illustrated by the following 3 examples.

Example 1:

part structure: the laminated structure J-shaped reinforced wallboard is characterized in that a skin layer is 30 layers of carbon fiber fabrics, a rib layer is 6 layers of carbon fiber fabrics, and the skin size is 1000mm x 400mm, the rib size is 280mm x 120mm x 30 mm.

The preparation process of the diversion medium 1 is as follows:

(1) The preparation of the core layer 3 polymer solution comprises the steps of adopting aromatic diamine monomer biphenyl diamine and aromatic diacid chloride monomer terephthaloyl chloride to synthesize polyamide solution in an organic solvent.

(2) Preparing core layer 3 fiber: spinning by using the polyamide solution in the step (1), and drying to remove residual solvent in the fiber to obtain the fiber with the core layer 3.

(3) Preparation of cortical polymer solution 6: the styrene-butadiene block copolymer was dissolved in an organic solvent to prepare a skin polymer solution 6 having a solid content of 8%, the polymerization degree of the above styrene-butadiene polymer being 1200, wherein the mass fraction of hard segment styrene was 30%.

(4) Preparing a sheath-core structural fiber: immersing the sheath layer 2 fiber prepared in the step (2) into the sheath polymer solution 6 prepared in the step (3) through a guiding device 7, rolling through a collecting device 8, and drying residual solvent in the fiber to obtain the sheath-core structural fiber.

(5) And (3) feeding the skin-core structural fibers obtained in the step (4) into carding equipment 9, carding the skin-core structural fibers in parallel and decomposing the skin-core structural fibers into single fiber states, and preparing the fibers into uniform and disordered fiber webs by using a disordered mechanism to obtain the diversion medium 1.

The process of forming the composite material using the flow guiding medium 1 is as follows:

(1) The carbon fiber fabric 10 is paved to prepare a preformed body, 1 layer of diversion medium 1 is paved above every 5 layers of carbon fiber fabric 10 in the paving process, and the outermost layer of the preformed body is the carbon fiber fabric 10.

(2) After laying the diversion medium 1 and a layer of carbon fiber fabric 10 thereon, shaping at 110 ℃ by shaping equipment, melting the component of the cortex 2 in the diversion medium 1, cooling the cortex 2, and bonding and shaping.

(3) Resin runners are arranged along the two sides of the length direction of the prepared preform and the upper edges of the ribs, and after the resin runners are packaged by a vacuum bag, the resin is introduced into the preform from the runners to infiltrate the preform. After the preform is completely impregnated with resin, the resin flow path is closed.

(4) And (3) heating to 190 ℃ for curing for 2 hours, cooling to room temperature, and demoulding to obtain the composite material product.

In the embodiment, the flow guiding medium 1 is used for preparing the preformed body, the shaping effect is good, and fiber wrinkles, slippage and deformation are avoided. Table 1 records the resin penetration distance of the preform in the examples, the penetration of the upper and lower layers of the skin is uniform, no resin flow front is found to be converged, and the penetration of the ribs is slightly slower than the penetration of the skin due to the smaller size and thickness, but the overall penetration is uniform and controllable.

C scanning detection is carried out on the J-shaped reinforced wallboard, no abnormal signal is found, and the introduction of the diversion medium does not adversely affect the molding quality of the composite material.

TABLE 1 example 1 resin penetration distance

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

In order to evaluate the influence of the diversion medium 1 on the mechanical properties of the composite material, 5J, 10J, 15J, 20J and 30J energy is selected for the test, and the drop hammer impact test is carried out on the reinforced wallboard along with the furnace test board and the blank control sample without the diversion medium. The results are shown in Table 2. Under the same energy, the impact damage of the blank sample is relatively larger, and the introduction of the diversion medium has a certain toughening effect.

Table 2 example 1 and blank drop hammer test results

energy/J	Pit depth (example 1)/mm	Pit depth (blank)/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

Example 2:

styrene-isoprene block copolymers with different mass fractions of hard segments and different polymerization degrees are selected as the material of the skin layer 2, the polymerization degree of the styrene-isoprene polymer is 600-2000, wherein the mass fraction of the hard segment styrene accounts for 10% -60% of that of the thermoplastic elastomer, the melting temperature of the thermoplastic elastomer material is represented by DSC endothermic peaks, and the results are shown in Table 3. When the polymerization degree is 1000-1500 and the mass fraction of the hard segment is 30% -45%, the melting temperature of the thermoplastic elastomer can be ensured to be 110-130 ℃, and the working temperature range of the existing shaping equipment is satisfied.

TABLE 3 styrene-isoprene Block copolymer melting temperatures for different hard segment mass fractions and degrees of polymerization

Example 3:

the composition ratio of the skin and the core layer has obvious influence on the diversion medium effect, the skin layer is too much in proportion, so that the carbon fiber fabrics are tightly bonded, resin permeation is hindered, the diversion effect of the core layer is influenced, and the shaping effect is poor due to too low skin layer proportion. According to the use experience of the traditional sizing agent powder, the optimal dosage of the sizing agent is below 5 percent, and the sizing agent is uniformly distributed among the carbon fiber fabric layers in a punctiform manner. Example 3 compares the performance differences of the diversion media with different proportions of the sheath component and the core component, and provides a reference for determining the proportions of the sheath component and the core component. The preparation process of the diversion medium 1 is as follows:

(2) Preparing core layer 3 fiber: spinning by using the diversion component polymer solution in the step (1), drying to remove residual solvent, obtaining the core layer 3 fiber, weighing and recording the weight.

(3) Preparation of cortical polymer solution 6: the styrene-butadiene block copolymer was dissolved in an organic solvent to prepare a cortical polymer solution having a solid content of 8%, the polymerization degree of the styrene-butadiene polymer was 1500, wherein the mass fraction of hard segment styrene was 40%.

(4) Preparing sheath-core structural fibers with different sheath-core component ratios: immersing the fibers of the core layer 3 prepared in the step (2) into the sheath polymer solution 6 prepared in the step (3) through a guiding device 7, rolling through a collecting device 8, drying residual solvents in the fibers, respectively immersing the fibers into the sheath polymer solution 6, rolling, drying the fibers for 1, 2, 3 and 4 times to obtain the fibers of the sheath-core structure diversion medium 1 with different sheath and core component ratios, weighing, and recording weight changes before and after the weight step (4).

(5) And (3) feeding the fibers of the diversion medium 1 with the skin-core structure obtained in the step (4) into carding equipment 9, carding the fibers in parallel and decomposing the fibers into single fiber states, and preparing the fibers into fiber webs which are uniformly and randomly arranged by a messy mechanism to obtain the diversion medium 1.

And calculating the mass fraction of the cortex 2 according to the weighing result, and calculating the content of the cortex 2 in matrix resin according to the fiber volume fraction of the composite material. A layer of carbon fiber fabric 10 is respectively paved on the upper part and the lower part of the diversion medium 1, and the shaping treatment is carried out at 120 ℃ by means of shaping equipment. The carbon fiber fabric 10 was then peeled off, and the morphology of the sheath 2 component was observed with a microscope apparatus, and the results are shown in Table 4. When the mass fraction of the skin layer component is 8% -15%, the skin layer component is within 5% of the matrix resin, and most of the skin layer is island-shaped after shaping and is distributed at the fiber crossing position.

TABLE 4 Performance of flow guiding Medium with different sheath/core composition ratios

The principle of the invention is as follows:

the diversion medium provided by the invention consists of the skin-core structural fibers, the skin is made of thermoplastic elastomer materials, the molecular chain comprises a hard segment and a soft segment, and the diversion medium has plasticity at a certain temperature and plays a role in shaping the bonded carbon fiber layer. After the skin layer component flows through heating, the skin layer component is converged into liquid drops, the core layer component is exposed, the chemical structure of the core layer component is aromatic polyamide, the amide bond has stronger polarity, and hydrogen bond interaction can be formed between the core layer component and the epoxy resin prepolymer. And the carding machine is used for carding to form a network which is arranged in a disordered way, and the internal pores are more. The medium formed by the core fiber can promote the resin to flow in the carbon fiber preform.

After curing and forming, the diversion medium provided by the invention is used as an internal component of the composite material. Wherein, the thermoplastic elastomer of the skin layer is distributed among the layers of the composite material in an island shape due to lower content. Under the room temperature service environment, the thermoplastic elastomer has high elasticity and plays a role in interlayer toughening. The aromatic polyamide core layer fiber has the characteristics of high strength and high modulus, and can play a role of a reinforcing material.

The curing temperature range of matrix epoxy resin used in the field of aviation composite materials is 180 ℃ -220 ℃, and in order to fully exert the effects of promoting permeation, assisting shaping, reinforcing and toughening of a diversion medium, the technical scheme is further defined:

the mass fraction of the hard segment part in the thermoplastic elastomer of the skin layer is limited to be 30-45%, and the macromolecular polymerization degree of the thermoplastic elastomer is 1000-1500. Under the above conditions, the thermoplastic elastomer of the skin layer exhibits more ideal fluidity and viscosity in the range of 110 ℃ to 130 ℃ (the range of the proper operating temperature of the existing shaping equipment), and the shaping effect between the layers is better (see example 2).

The sheath component accounts for 8% -15% of the total mass of the sheath-core structural fiber. Under the above conditions, the content of the skin component in the matrix resin can be controlled within 5%, and the skin component after shaping is distributed among the carbon fiber fabric layers in a sea-island shape, so that the negative influence on the resin penetration is small, and the interlayer toughening effect can be fully exerted (see example 3).

Claims

1. A carbon fiber composite material flow guiding medium is characterized in that the flow guiding medium is of a net structure formed by fibers and provided with holes, the fibers are intertangled and crossed without specific orientation arrangement, the fibers comprise a skin layer and a core layer, wherein the core layer is made of aromatic polyamide, aromatic diamine monomers and aromatic diacid chloride monomers are used as raw materials and prepared through polymerization reaction, the skin layer is a thermoplastic elastomer, and a thermoplastic elastomer molecular chain comprises a hard segment and a soft segment.

2. The carbon fiber composite flow medium of claim 1, wherein the cortical thermoplastic elastomer material is any one of: styrene-butadiene block copolymers, styrene-isoprene-butadiene block copolymers, acrylonitrile-butadiene-propylene block copolymers, toluene diisocyanate-polyether glycol-1, 4-butanediol block copolymers, block copolymers of polybutylene terephthalate and aliphatic polyethers.

3. The carbon fiber composite flow medium of claim 1, wherein the hard segment portion of the cortical thermoplastic elastomer material comprises 30% -45% of the cortical mass fraction.

4. The carbon fiber composite flow medium of claim 1, wherein the cortical thermoplastic elastomer material has a degree of polymerization of 1000 to 1500.

5. The carbon fiber composite flow medium of claim 1, wherein the skin mass comprises 8% -15% of the total mass of the fiber.

6. A method of preparing a carbon fiber composite flow medium according to any one of claims 1-5, comprising the steps of:

6-1 preparing a core polymer solution, namely synthesizing a polyamide solution in an organic solvent by adopting an aromatic diamine monomer and an aromatic diacid chloride monomer;

6-2 preparation of core fiber: spinning by using the polyamide solution in the step 6-1, and drying to remove residual solvent;

6-3 preparation of a cortical polymer solution: dissolving one of the following thermoplastic elastomer materials in an organic solvent, said thermoplastic elastomer material comprising: styrene-butadiene block copolymer, styrene-isoprene-butadiene block copolymer, acrylonitrile-butadiene-propylene block copolymer, toluene diisocyanate-polyether glycol-1, 4-butanediol block copolymer, polybutylene terephthalate and aliphatic polyether block copolymer, and preparing a cortical polymer solution with a solid content of 8% -12% by using any one of the above thermoplastic elastomer materials;

6-4 preparation of sheath-core structural fibers: immersing the core layer fiber prepared in the step 6-2 into the sheath polymer solution prepared in the step 6-3 through a guiding device, winding through a collecting device, drying residual solvent in the fiber, and repeating the steps of immersing the obtained fiber into the sheath polymer solution, winding and drying to obtain the sheath-core structure fiber;

6-5, feeding the skin-core structure fibers obtained in the step 6-4 into carding equipment, carding the skin-core structure fibers in parallel and decomposing the skin-core structure fibers into a single fiber state, and preparing the fibers into fiber webs which are uniformly and randomly arranged by a messy mechanism to obtain the diversion medium.