CN115109281B - Carbon nanotube reinforced co-curing damping composite material and preparation method thereof - Google Patents

Abstract

The application provides a carbon nanotube reinforced co-curing damping composite material and a preparation method thereof. The method firstly proposes that hydrogenated carboxyl nitrile rubber is used as a viscoelastic damping sandwich material to be embedded into the composite material, and the hydrogenated carboxyl nitrile rubber viscoelastic material can form an interpenetrating network structure with an epoxy resin matrix through physical fusion and chemical crosslinking in the co-curing process, so that the composite material has excellent interlayer bonding performance. In addition, the carbon nanotubes are introduced into the surface of the carbon fiber, and the epoxy resin-based carbon fiber prepreg with different carbon nanotube contents can form a composite material in functional gradient distribution through superposition and curing. Compared with the traditional composite material, the structure can greatly improve the interface bonding strength and reduce the residual stress and the thermal stress; eliminating the stress singularity of the interface cross point and the stress free end point in the connecting material; the joint strength is enhanced, and the crack driving force is reduced, so that the overall mechanical property of the co-curing damping composite material is improved.

Description

A carbon nanotube reinforced co-cured damping composite material and preparation method thereof

technical field

The invention relates to the technical field of structural functional composite materials, in particular to a carbon nanotube reinforced co-cured damping composite material and a preparation method thereof.

Background technique

Because composite materials have many advantages such as high specific strength, high specific stiffness, high specific modulus and fatigue resistance, they have gradually replaced wood and metal alloy materials, and are widely used in aerospace, automotive, electrical and electronic, construction and fitness equipment and other fields. Among them, the matrix of non-metallic composite materials mainly includes synthetic resin, rubber, ceramics, graphite, carbon, etc., and the reinforcing materials mainly include glass fiber, carbon fiber, boron fiber, aramid fiber, silicon carbide fiber, asbestos fiber, whisker, metal, etc. .

In order to further improve the damping performance of non-metallic composite materials, on the basis of traditional resin-based fiber-reinforced composite materials, the damping material can be embedded into the composite material by co-curing with resin. At present, the commonly used damping material is vulcanized rubber, which has low surface molecular activity, poor aging resistance and adhesive mechanical properties, which makes the interfacial bonding performance and overall mechanical properties of the composite material decrease significantly, and is prone to aging and falling off during use. The composite structure loses its bearing capacity, which seriously limits its application.

Contents of the invention

Aiming at the deficiencies in the prior art, the invention provides a carbon nanotube reinforced co-cured damping composite material and a preparation method thereof.

In a first aspect, the present invention provides a method for preparing a carbon nanotube reinforced co-cured damping composite material, comprising the following steps:

Step 1: grow carbon nanotubes on the surface of carbon fibers, combine the carbon fibers grown with carbon nanotubes with epoxy resin to prepare carbon nanotube-modified epoxy resin-based carbon fiber prepregs, and combine the carbon nanotubes with different carbon nanotube contents. Epoxy resin-based carbon fiber prepregs are laid in gradient order to form composite material preforms with functional gradient distribution;

Step 2: masticating and kneading the cut hydrogenated carboxylated nitrile rubber to obtain evenly kneaded raw rubber;

Step 3: dissolving the homogeneously mixed original gum in an easily-dissolved organic solvent to form a glue, and uniformly coating the glue on the substrate to make a viscoelastic damping film;

Step 4: Embedding the viscoelastic damping film as an intermediate layer between two composite material preforms through an autoclave co-curing process.

Preferably, said growing carbon nanotubes on the surface of carbon fibers also includes the following steps:

Carry out heat treatment to carbon fiber in _N2 atmosphere, obtain desizing carbon fiber;

Adding the desizing carbon fiber to 5 wt% NH ₄ H ₂ PO ₄ aqueous solution for electrolysis to obtain modified carbon fiber;

The modified carbon fiber is immersed in an ethanol solution with different catalyst precursors to obtain a carbon fiber with a precursor coating, wherein the different catalysts include: iron nitrate nonahydrate, nickel nitrate hexahydrate, cobalt nitrate hexahydrate;

The carbon fiber with precursor coating was heated to 440°C under the protection of N ₂ and kept for 20 minutes, then H ₂ was passed through to raise the temperature to 460°C, and then kept warm, and finally C ₂ H ₂ was passed through.

Preferably, said step 2 also includes the following steps:

Add the cut hydrogenated carboxylated nitrile rubber into the open mixer and masticate for 2-3 minutes;

Add anti-aging agent p, p-dicumyl diphenylamine, reinforcing agent N330 carbon black to the hydrogenated carboxylated nitrile rubber after mastication and knead for 5-7min, then add cross-linking agent BIBP, vulcanization assistant γ - Aminopropyltriethoxysilane and accelerator ZnO-80 were mixed for 3-4min to obtain pre-vulcanized hydrogenated carboxylated nitrile rubber;

Add the tackifier RS into the pre-vulcanized hydrogenated carboxylated nitrile rubber and knead for 4-5 minutes, then calender to obtain a uniformly kneaded raw rubber.

Preferably, the hydrogenated carboxylated nitrile rubber, the antioxidant p-, p-dicumyl diphenylamine, the reinforcing agent N330 carbon black, the crosslinking agent BIBP, the vulcanization aid γ- The mass ratio of aminopropyltriethoxysilane to the accelerator ZnO-80 is 100:1.5:60:2:1:6.

Preferably, said step 3 also includes the following steps:

Dissolving the uniformly mixed original gum in THF to form a glue, the ratio of the original gum to THF is 1g:4ml;

The glue is dripped on the high-speed rotating substrate, and the glue is made into a viscoelastic damping film by centrifugal force.

Preferably, said step 4 also includes the following steps:

placing the viscoelastic damping film between the two composite material preforms, and pressurizing to 2-3 MPa;

Raise the temperature to 70°C-90°C at a heating rate of 1-2°C/min and keep it for 30-60 minutes, then raise it to 120°C, 150°C and 180°C and keep it for 30-60 minutes, then cool down at a rate of 1-2°C/min Bring to room temperature.

Preferably, the flows of C ₂ H ₂ , H ₂ and N ₂ are 5 L/min, 5 L/min and 10 L/min respectively.

In a second aspect, the present invention also provides a carbon nanotube-reinforced co-cured damping composite material, and the carbon nanotube-reinforced co-cured damping composite material is prepared by any one of the above methods.

The beneficial effects of the application are as follows:

This application proposes for the first time to use hydrogenated carboxylated nitrile rubber as a viscoelastic damping sandwich material embedded in the composite material. The hydrogenated carboxylated nitrile rubber viscoelastic material can be formed by physical fusion and chemical crosslinking with the epoxy resin matrix during the co-curing process. The interpenetrating network structure makes the composite material have excellent interlayer bonding performance. In addition, the present application introduces carbon nanotubes on the surface of carbon fibers, and epoxy resin-based carbon fiber prepregs with different carbon nanotube contents can be superimposed and cured to form a composite material with a functional gradient distribution. Compared with traditional composite materials, the carbon nanotube-reinforced co-cured damping composite structure has the following advantages: 1) The functionally graded composite material is used as an interface layer to connect two incompatible materials, which can greatly improve the interface bonding strength; 2) Using functionally graded composites as interface layers can reduce residual stress and thermal stress; 3) using functionally graded composites as interface layers can eliminate stress singularities at interface intersections and stress free endpoints in connecting materials; 4) using functional The gradient carbon nanotube reinforced co-cured damping composite structure replaces the traditional composite material, which can not only enhance the connection strength but also reduce the crack driving force, thereby improving the overall mechanical properties of the co-cured damping composite material. Under the joint action of carbon nanotubes with functional gradient distribution and chemical bonds of interface molecules, this material has the advantages of designable mechanical properties, high damping, strong interface bonding performance, large overall bending stiffness, and aging resistance. It is used in aerospace, high-speed rail, Lightweight, vibration and noise reduction fields such as automobile manufacturing, household appliances and fan blades have broad application prospects.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, for those skilled in the art, Other drawings can also be obtained from these drawings without any creative effort.

Fig. 1 is a flowchart of a method for preparing a carbon nanotube-reinforced co-cured damping composite material provided by an embodiment of the present invention;

Fig. 2 is a schematic structural diagram of a carbon nanotube-reinforced co-cured damping composite material provided by an embodiment of the present invention;

Figure 3 is a scanning electron microscope image of a composite material containing a viscoelastic damping film;

Figure 4 is a scanning electron microscope image of a composite material containing carbon nanotubes;

Figure 5 is the vulcanization curve of HXNBR after mixing at 180°C;

Figure 6 is the variation curve of the damping loss factor of HXNBR with temperature;

Fig. 7 is a schematic diagram of the tensile strength of specimen 1 to specimen 7;

Fig. 8 is a schematic diagram of the bending strength of specimen 1 to specimen 7;

Fig. 9 is the free vibration attenuation curve of specimen 1;

Fig. 10 is the free vibration attenuation curve of specimen 4;

Figure 11 shows the distribution pattern of functional gradient of carbon nanotubes.

Detailed ways

In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention. rather than all examples. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts shall belong to the protection scope of the present invention.

Aiming at the deficiencies of the prior art, this proposal provides a carbon nanotube reinforced co-cured damping composite material and a preparation method thereof. Please refer to FIG. 1 , which shows a flowchart of a method for preparing a carbon nanotube-reinforced co-cured damping composite material according to an embodiment of the present invention. As can be seen from Figure 1, the method comprises the following steps:

Step S1: growing carbon nanotubes on the surface of carbon fibers, combining the carbon fibers grown with carbon nanotubes with epoxy resin to prepare carbon nanotube-modified epoxy resin-based carbon fiber prepregs, and combining the carbon nanotubes with different carbon nanotube contents. Epoxy resin-based carbon fiber prepregs are laid in gradient order to form composite material preforms with functional gradient distribution;

Step S2: masticating and kneading the tailored hydrogenated carboxylated nitrile rubber to obtain evenly kneaded raw rubber;

Step S3: dissolving the homogeneously mixed original gum in an easy-to-release organic solvent to form a glue, and uniformly coating the glue on the substrate to make a viscoelastic damping film;

Step S4: Embedding the viscoelastic damping film as an intermediate layer between two composite material preforms through an autoclave co-curing process.

Please refer to FIG. 2 , which is a schematic structural diagram of a carbon nanotube-reinforced co-cured damping composite material provided by an embodiment of the present invention. It can be seen from Fig. 2 that the carbon nanotube-reinforced co-cured damping composite material is composed of a viscoelastic damping film and a composite material preform that are laminated alternately. Wherein, the composite material preform can be formed by laying epoxy resin-based carbon fiber prepregs with different carbon nanotube contents in gradient order. The lamination sequence of the viscoelastic damping film and the composite material preform can be [0 ₄ d0 ₄ ], where 0 represents that the carbon fiber direction is 0 degrees, d represents the viscoelastic damping film as the middle layer, and 4 represents the viscoelastic damping film Both the upper and lower composite material preforms are composed of 4 layers of epoxy resin-based carbon fiber prepreg.

The matrix material used in the present invention is epoxy resin-based carbon fiber prepreg. The main component of viscoelastic damping material is polymer hydrogenated carboxylated nitrile rubber HXNBR. HXNBR is a terpolymer formed by copolymerization of conjugated diene, acrylonitrile and unsaturated carboxylic acid, and then it is made by selective hydrogenation. The carboxyl groups in HXNBR are largely unhydrogenated and distributed randomly along the backbone. The carboxylic acid group can be used as an active point to form a chemical bond by itself or with the matrix, which can supplement the formation of carbon-carbon crosslinks in the peroxide curing system. HXNBR has excellent mechanical properties, wear resistance and adhesion properties. When HXNBR transforms from a glassy state to a highly elastic state, the polymer can exhibit higher damping performance. Therefore, HXNBR is the best choice for the damping layer of co-cured composites due to its own excellent mechanical properties. In addition to maintaining mechanical properties and aging resistance, HXNBR also has fast vulcanization speed, fast reaction speed, and better heat resistance. The epoxy group of epoxy resin can undergo etherification reaction with hydroxyl group (as shown in reaction formula (1)), and the epoxy group of epoxy resin can undergo esterification reaction with carboxyl group (as shown in reaction formula (2) ), forming an IPN structure, and these chemical crosslinking reactions are the theoretical basis for the co-curing of carbon nanotube-reinforced co-curing damping composites.

反应式（1）

Reaction formula (1)

反应式（2）

Reaction formula (2)

Please refer to FIG. 3 and FIG. 4 , which are the scanning electron micrographs of the composite material containing the viscoelastic damping film and the scanning electron micrograph of the composite material containing carbon nanotubes, respectively. It can be seen from Figure 3 and Figure 4 that the viscoelastic material and the resin matrix and the carbon nanotubes and the resin matrix are tightly combined, there is no obvious interface between the two, and a stable transitional crosslinking structure is formed between different phases. On the microscopic level, it shows good physical compatibility. At the same time, on the one hand, it shows that HXNBR has excellent compatibility with the matrix epoxy resin, and on the other hand, it proves that the excellent interlayer mechanical properties of the co-cured damping composite structure come from the physical and chemical interactions between different materials.

In this application, co-curing refers to the matching of the vulcanization time and temperature of the embedded viscoelastic material HXNBR with the curing time and temperature of the matrix epoxy resin. A microscopic interpenetrating network structure is formed on the bonding interface to ensure that the composite material has a high interlayer bonding strength, so that the material has both excellent structural stiffness and damping properties. The present invention adopts epoxy resin-based carbon fiber prepreg with a curing temperature of 180° C., which has the advantages of good mechanical properties, high temperature resistance and the like.

(1) The damping mechanism of the co-cured damping composite structure is as follows: the loss factor of HXNBR is related to the melting and glass transition of nitrile rubber. When the HXNBR is in a viscous flow state near the glass transition temperature, its internal viscosity is relatively large, and the rubber When the molecules move, they will be hindered by the internal chain segments of the rubber, causing the strain to lag behind the stress and resulting in hysteresis loss. At this time, the friction inside the rubber molecules reaches the maximum, so the loss factor near the glass transition temperature is the largest. In addition, the internal friction between the reinforcing agent and the reinforcing agent or between the HXNBR molecular chain and the reinforcing agent can cause strong damping loss.

(2) The principle that functional gradient distribution can improve the mechanical properties of traditional co-cured damping composite structures: Compared with traditional composite materials, carbon nanotube-reinforced co-cured damping composite materials have the following advantages: 1) Functionally graded materials are used as interface layers to connect Two incompatible materials can greatly improve the interface bonding strength; 2) Using functionally graded materials as interface layers can reduce residual stress and thermal stress; 3) Using functionally graded materials as interface layers can eliminate the Stress singularity at interface intersections and stress-free endpoints; 4) Replacing traditional composites with functionally graded carbon nanotube-reinforced co-cured damping composite structures, which can both enhance the connection strength and reduce the crack driving force.

The specific preparation method of this material is illustrated below with specific examples.

Step 1: Preparation of composite material preform with functional gradient distribution:

First place the carbon fiber in a vertical CVD furnace, and heat-treat it in _N2 atmosphere for 2 hours to remove the sizing agent to obtain desized carbon fiber. The heat treatment temperature is 400°C. Subsequently, the carbon fiber surface was modified by selective electrochemical anodization, using 5 wt% NH ₄ H ₂ PO ₄ aqueous solution as the electrolyte, the current intensity was 0.4A, and the modification time was 90 s. The modified carbon fibers were immersed in ethanol solutions with different catalyst precursors for 9 min, and a uniform coating of catalyst precursors was obtained on the surface of the carbon fibers. Then put the carbon fiber coated with the catalyst precursor on the sample holder, raise the furnace temperature to 440°C for 20min under the protection of _N2 , feed _H2 to convert the catalyst precursor into metal nanoparticles, and then raise the furnace temperature to 460°C and heat preservation, feed carbon source to grow carbon nanotubes directly on the surface of carbon fiber. Among them, the flow rates of H ₂ and N ₂ in the reducing atmosphere were set to 5L/min and 10L/min, respectively, and the flow rates of C ₂ H ₂ , H ₂ and N ₂ in the growth atmosphere were set to 5L/min, 5L/min and 10L/min, respectively. /min. During the preparation process, _N2 is continuously used for gas seal protection to ensure that the gas in the tube furnace is isolated from the air, and the wire speed is adjusted to control the growth time, thereby controlling the growth rate of carbon nanotubes. In addition, this example adopts hand lay-up method to combine carbon fiber with carbon nanotubes and epoxy resin to prepare carbon nanotube-modified epoxy resin-based carbon fiber prepreg. Hand lay-up method is a common method in this field. Here No longer. The epoxy resin-based carbon fiber prepregs with different carbon nanotube contents are laid according to gradient sequence to form a composite material preform with functional gradient distribution. In other embodiments of the present application, the layering sequence may also be [0 ₃ d0 ₃ ] and so on.

Step 2: Preparation of HXNBR Raw Gum:

(1) Cropping of HXNBR. Firstly, 100 copies of HXNBR were cut into rubber strips of 100 mm×20 mm×20 mm, so that they could be placed in the mill more easily, and finally the volume fraction of HXNBR rubber accounted for more than 80% of the capacity of the mill;

(2) Plasticizing of HXNBR. Due to the high hardness of HXNBR, firstly adjust the roller distance of the open mill to 2mm for HXNBR calendering, then gradually adjust the roller distance according to the hardness change of HXNBR, plasticize it for 2-3 minutes, and finally carry out HXNBR thin pass 4 -6 times;

(3) Mixing of HXNBR. Control the temperature of the mill roller at 50°C-60°C by water cooling method, first add 1.5 parts of anti-aging agent 445 (p, p-dicumyl diphenylamine) and 60 parts of reinforcing agent N330 carbon black to HXNBR Neutralize and knead for 5-7 minutes, so that the N330 carbon black is completely absorbed by the rubber; then add 2 parts of crosslinking agent BIBP, 1 part of vulcanization aid KH550 (γ-aminopropyltriethoxysilane), 6 parts of accelerator Add ZnO-80 into HXNBR and knead for 3-4min to complete the pre-vulcanization of HXNBR; then add the tackifier RS (a blend of resorcinol and stearic acid) into the compound and knead for 4- 5min to enhance the adhesive performance of HXNBR; then, calender the pre-mixed HXNBR, adjust the roller distance to the minimum and make triangle bag 5-6 times, and then adjust the roller distance to 1.2-1.5 mm to roll the rubber The air bubbles inside are removed to obtain uniformly mixed HXNBR, and finally the damping material has excellent mechanical properties and damping properties through the mixing process. In this embodiment, the addition amount of each material is in parts by mass, and the ratio is the best ratio obtained through testing the designed material components and related mechanical properties and damping properties.

The present invention selects an organic peroxide curing system to vulcanize HXNBR, and the crosslinking agent of HXNBR can be sulfur or peroxide. HXNBR sulfur vulcanized has higher tensile strength and elongation at break, and has excellent comprehensive mechanical properties, but it is suitable for medium and low temperature vulcanization; HXNBR vulcanized by peroxide has a high crosslinking temperature and better resistance to compression set. By comparison, the vulcanization temperature of the peroxide system is more suitable than that of the sulfur vulcanization system, which is conducive to better mutual infiltration between the epoxy resin matrix and HXNBR during curing molding, and at the same time helps to form interpenetration between the two phases. The network structure can improve the interfacial bonding strength of the epoxy resin-based co-cured damping composite structure. Therefore, this application uses BIBP as the cross-linking agent of HXNBR. BIBP vulcanizes HXNBR. When HXNBR is vulcanized by peroxide, BIBP will decompose under the action of high temperature and high pressure to generate free radicals, which capture free radicals from HXNBR molecules. Atoms form polymer groups.

In order to speed up the formation process of polymer radicals, this protocol also added ZnO-80 to promote the decomposition of BIBP radicals and the formation of cross-linked polymers. In addition, as a vulcanization aid, KH550 can increase the cross-linking degree of HXNBR and prevent rubber from scorching. Anti-aging agent 445 is used to prevent the aging of damping materials, and can also improve the high temperature resistance and corrosion resistance of rubber. Tackifier RS can further increase its interlayer bonding force, and N330 carbon black is an excellent reinforcing agent.

In the present embodiment, the physical performance of HXNBR is tested:

The vulcanization characteristics were tested according to the standard ASTM-D-2084-07, and the vulcanization test results showed that the HXNBR with this mass fraction component met the 180°C high-temperature co-curing process requirements. Please refer to Figure 5, which shows the vulcanization curve of HXNBR after kneading at 180°C. It can be seen from Figure 5 that the scorch time of the vulcanized rubber is 0.35 min, the vulcanization time to reach 50% torque is 3.6 min, and the time to 90% vulcanization is 33 min. The aging resistance is good; the maximum torque is 52N.m; the torque fluctuation range is 6.5 N.m-52N.m, which can meet the high temperature co-curing requirements of co-curing large damping composite materials used in aerospace.

Vulcanize the mixed raw rubber with a flat vulcanizer for 60 minutes at 180°C to obtain a 2mm thick strength test piece, and then cut the test piece into a standard tensile test piece with a special cutting knife. Put the HXNBR after one-step vulcanization into a hot air aging box for two-step vulcanization. The vulcanization temperature is 180 °C, the vulcanization pressure is normal pressure, and the vulcanization time is 1 h. The storage modulus represents the ability of HXNBR to store elastic deformation energy. The loss modulus refers to the energy dissipated by HXNBR through internal friction and heat generation by its own viscoelasticity. The loss factor determines the damping performance of HXNBR. Please refer to Figure 6, which shows the change curve of damping loss factor of HXNBR with temperature. It can be seen from Figure 6 that in the glass transition temperature region, the loss factor of HXNBR is relatively large, while the loss factor is relatively small in the glass state and high elastic state; in addition, the temperature corresponding to the peak loss factor of the damping material is 5 ° C, which is consistent with The melting of HXNBR is related to the glass transition. The peak loss factor of HXNBR in the present invention is 0.73, the effective damping temperature range is -10-20°C, and more importantly, its peak temperature is close to the ambient temperature. In addition, the loss factor peak of HXNBR is asymmetrical, which is caused by the local dynamic change of HXNBR in the glass transition range. The above analysis shows that HXNBR has excellent damping performance.

Step 3: Preparation of viscoelastic damping film:

(1) Mix uniformly mixed HXNBR original rubber fragments and tetrahydrofuran organic solvent according to the ratio of 1g: 4ml to prepare a glue;

(2) Drop the glue on the high-speed rotating substrate, and use the centrifugal force to make the glue dripped on the substrate evenly coated on the substrate to make a viscoelastic damping film. The thickness of the viscoelastic damping film can be controlled by the rotation speed and rotation time of the substrate, and is also related to the viscosity coefficient between the glue and the substrate. In other embodiments of the present application, tetrahydrofuran can also be replaced by ethyl acetate, acetone and formaldehyde.

Step 4: Preparation of carbon nanotube-reinforced co-cured damping composite:

Place the viscoelastic damping film between the carbon nanotube prepregs distributed in a functional gradient, and pressurize to 2-3MPa;

Raise the temperature to 70°C-90°C at a heating rate of 1-2°C/min and keep it for 30-60 minutes, then raise it to 120°C, 150°C and 180°C and keep it for 30-60 minutes, then cool down at a rate of 1-2°C/min Bring to room temperature.

The present application makes specimen 2, specimen 3, specimen 4, specimen 5, specimen 6 and specimen 7 according to the above-mentioned preparation method, wherein, the carbon nanometers of the composite material preform in specimen 4 to specimen 7 The tubes were prepared in an O-shaped functional gradient distribution mode (as shown in Figure 11). Specimen 4 to Specimen 7 were all modified and optimized by carbon nanotubes, and the thickness of the damping film gradually increased from 0.1mm to 0.4mm. The composite material preform contains 4 layers of epoxy resin-based carbon fiber prepreg, and the mass fractions of carbon nanotubes in the 4 layers of epoxy resin-based carbon fiber prepreg are 4%, 3%, 2%, and 1%, respectively, in a gradient decrease. The application also provides three kinds of comparison pieces, which are test piece 1, test piece 2 and test piece 3 respectively. Carbon nanotubes with O-type functional gradient distribution were added, but no viscoelastic damping film intermediate layer was added; Specimen 3 was a 0.1mm thick viscoelastic damping film intermediate layer, but no carbon nanotube optimization Contrast pieces. The total thicknesses of specimens 1 to 7 are 2mm, 2mm, 2.1mm, 2.1mm, 2.2mm, 2.3mm and 2.4mm respectively, and the viscoelastic damping film thicknesses of specimens 1 to 7 are 0mm, 0mm, 0.1mm, 0.1mm, 0.2mm, 0.3mm and 0.4mm.

In order to further illustrate the performance of the carbon nanotube-reinforced co-cured damping composite material, in this embodiment, the static mechanical performance test and the damping performance test were respectively carried out on the specimens 1 to 5.

1. Static mechanical performance test:

Please refer to FIG. 7 and FIG. 8 , which are schematic diagrams of tensile strength of specimens 1 to 7 and schematic diagrams of bending strength of specimens 1 to 7 respectively. It can be seen from Figure 7 and Figure 8 that the tensile strength and bending strength of specimen 2 to specimen 7 have been improved to varying degrees compared with specimen 1. When the embedded viscoelastic damping film is 0.3mm, the static mechanical properties achieve the best. This is because the tensile properties and bending properties of the co-cured damping composite structure are not only related to the resin and fiber content in the composite material, but also the interfacial bonding performance of the composite material and the carbon nanotubes with functional gradient distribution. The HXNBR viscoelastic damping films embedded in specimens 3 to 7 not only have high hardness and rigidity, but also have excellent interfacial bonding properties with epoxy resin, and epoxy resin and HXNBR can form a tight microscopic cross-linked structure; in addition , the functionally graded structure can enhance the overall mechanical strength of the composite. Therefore, the tensile properties and bending properties of the functionally graded carbon nanotube-reinforced co-cured damping composite structure specimens have been improved.

2. Damping performance test:

According to the standard ASTM E756-05, the relative damping coefficients of specimens 1 to 7 were tested by free vibration attenuation experiments, and then the loss factor of the material was obtained. Please refer to FIG. 9 and FIG. 10 , which show the free vibration attenuation curve of specimen 1 and the free vibration attenuation curve of specimen 4 respectively. It can be seen from Figures 9 and 10 that the embedding of the viscoelastic damping film can greatly increase the amplitude attenuation rate of the carbon nanotube-reinforced co-cured damping composite. The loss factors of specimen 1 to specimen 7 are 1.98%, 1.76%, 2.91%, 2.87%, 3.56%, 4.12% and 4.34%, respectively, and the loss factor of specimen 2 is 12.5% lower than that of specimen 1. It is caused by the addition of carbon nanotubes to increase the overall stiffness of the composite structure; the loss factors of specimens 4 to 7 are respectively increased by 44.95%, 79.80%, 108.10% and 119.20% compared with specimen 1, showing that the viscoelastic The embedding of materials greatly improves the damping performance of composite materials. It can be seen that the carbon nanotube reinforced co-cured damping composite material designed in the present invention with high temperature resistance and high mechanical properties has excellent damping performance and has high utilization value.

In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention. rather than all examples. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts shall belong to the protection scope of the present invention.

Claims (8)

1. A preparation method of a carbon nano tube reinforced co-cured damping composite material is characterized by comprising the following steps:

step 1: growing carbon nanotubes on the surfaces of carbon fibers, combining the carbon fibers on which the carbon nanotubes are grown with epoxy resin to prepare carbon nanotube modified epoxy resin-based carbon fiber prepregs, and paving the epoxy resin-based carbon fiber prepregs with different carbon nanotube contents according to a gradient sequence to form a composite material preformed body in functional gradient distribution;

step 2: plasticating and mixing the cut hydrogenated carboxyl nitrile rubber to obtain uniformly mixed virgin rubber;

and step 3: dissolving the uniformly mixed virgin rubber in an organic solvent which is easy to exert to form rubber cement, and uniformly coating the rubber cement on a substrate to prepare a viscoelastic damping film;

and 4, step 4: and embedding the viscoelastic damping film serving as an intermediate layer between the two composite material preformed bodies through an autoclave co-curing process.

2. The method for preparing carbon nanotubes according to claim 1, wherein the growing of carbon nanotubes on the surface of carbon fibers further comprises the steps of:

adding carbon fiber in N ₂ Carrying out heat treatment in the atmosphere to obtain desized carbon fibers;

adding the desized carbon fiber into 5 wt% NH ₄ H ₂ PO ₄ Electrolyzing in the aqueous solution to obtain modified carbon fibers;

immersing the modified carbon fiber into ethanol solution with different catalyst precursors to obtain the carbon fiber with a precursor coating, wherein the different catalysts comprise: ferric nitrate nonahydrate, nickel nitrate hexahydrate and cobalt nitrate hexahydrate;

subjecting the carbon fiber with the precursor coating to N ₂ Heating to 440 deg.C under protection, maintaining the temperature for 20min, and introducing H ₂ Heating to 460 deg.C, keeping the temperature, and finally introducing C ₂ H ₂ 。

3. The method of claim 1, wherein the step 2 further comprises the steps of:

adding the cut hydrogenated carboxyl nitrile rubber into an open mill for plasticating for 2-3 min;

adding the antioxidant p, p-diisopropylphenyl diphenylamine and the reinforcing agent N330 carbon black into the plasticated hydrogenated carboxylated nitrile rubber, mixing for 5-7min, then adding the crosslinking agent BIBP, the vulcanization aid gamma-aminopropyltriethoxysilane and the accelerator ZnO-80, and mixing for 3-4min to obtain the pre-vulcanized hydrogenated carboxylated nitrile rubber;

adding the tackifier RS into the pre-vulcanized hydrogenated carboxylated nitrile rubber, mixing for 4-5min, and calendering to obtain uniformly mixed virgin rubber.

4. The preparation method according to claim 3, wherein the mass ratio of the hydrogenated carboxylated nitrile rubber, the antioxidant pair, p-diisopropylphenyl diphenylamine, the reinforcing agent N330 carbon black, the crosslinking agent BIBP, the vulcanization aid gamma-aminopropyltriethoxysilane, and the accelerator ZnO-80 is 100:1.5:60:2:1:6.

5. The method of claim 1, wherein the step 3 further comprises the steps of:

dissolving the uniformly mixed virgin rubber in tetrahydrofuran to form rubber cement, wherein the proportion of the virgin rubber to the tetrahydrofuran is 1g;

and dripping the adhesive cement on a substrate rotating at a high speed, and preparing the adhesive cement into a viscoelastic damping film by using centrifugal force.

6. The method for preparing a composite material according to claim 1, wherein the step 4 further comprises the steps of:

placing a viscoelastic damping film between the two composite material preformed bodies, and pressurizing to 2-3 MPa;

heating to 70-90 deg.C at a heating rate of 1-2 deg.C/min, maintaining for 30-60min, heating to 120 deg.C, 150 deg.C and 180 deg.C respectively, maintaining for 30-60min, and cooling to room temperature at a cooling rate of 1-2 deg.C/min.

7. The method of claim 2, wherein C is ₂ H ₂ 、H ₂ And N ₂ The flow rates of (A) are respectively 5L/min, 5L/min and 10L/min.

8. A carbon nanotube reinforced co-cured damping composite, prepared by the method of any one of claims 1-7.

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