Use of variable density carbon fiber needle-punched preform in preparing carbon-carbon composite material

Abstract

The present invention discloses the use of a variable-density carbon fiber needle-punched preform in the preparation of a carbon-carbon composite material, including: a carbon fiber needle-punched layer having at least three layers, the carbon fiber needle-punched layer including a carbon fiber needle-punched edge layer and a carbon fiber needle-punched intermediate layer; a first weight per unit area unit with a cyclic ply is provided in the carbon fiber needle-punched edge layer, and a second weight per unit area unit with a cyclic ply is provided in the carbon fiber needle-punched intermediate layer; both the first weight per unit area unit and the second weight per unit area unit are composed of a web and a carbon cloth, and the weight of the web is 40-200 gsm. During the gas-phase deposition densification process of the carbon fiber needle-punched preform prepared by the present invention, the surface of the product is not easily blocked by carbon deposition in the holes, so that the density of different parts of the product is relatively uniform, effectively improving the densification rate and reducing the number of densification times.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon fiber needle-punched preforms, and particularly relates to the use of variable-density carbon fiber needle-punched preforms in the preparation of carbon-carbon composites. Background Art

[0002] Carbon-carbon composites have advantages such as low density, high strength, oxidation resistance, and high temperature resistance. In recent years, with the continuous in-depth research, carbon-carbon composites have gradually developed from military and aerospace application fields to civilian industrial fields such as photovoltaic, automobile manufacturing, and medical treatment. Their demand is also steadily increasing. Therefore, a stable preparation method suitable for large-scale production is needed.

[0003] Carbon fiber needle-punched preform is a quasi-three-dimensional structure. By using barbed needles, the web fibers are inserted into the carbon cloth in the Z-axis direction, and a three-dimensional network structure is formed inside the preform, which improves the interlayer shear force and interlayer thermal conductivity of the product, enables it to have the performance of 3D woven preforms, and overcomes the disadvantages of complex 3D weaving process and high cost. This carbon fiber needle-punched preform has advantages such as wear resistance, high temperature resistance, simple preparation process, low cost, and can greatly improve mechanical properties. Currently, it has been widely used in products such as crucibles, brake discs, and rocket nozzles.

[0004] The existing carbon fiber needle-punched preform technology uses the method of layer-by-layer laying and needling of web and non-woven cloth. The web used in this method has a fixed gram weight, and the non-woven cloth is laid at 0° / 90° with a fixed gram weight. During the preparation of carbon-carbon composites, since the gas flow direction during chemical vapor deposition is from outside to inside, it will cause the surface densification rate of the product to be fast. When the surface density of the product reaches a certain level, the internal densification of the product will stop. Only by multiple carbonization and impregnation densification can the density of the internal area of the product be increased to make the density uniform, wasting time and cost. Therefore, there is an urgent need to develop a carbon-carbon preform that can reduce the production cycle and improve the densification efficiency. Summary of the Invention

[0005] The purpose of the present invention is to provide the use of variable-density carbon fiber needle-punched preforms in the preparation of carbon-carbon composites, so as to solve the problem that after the carbon-carbon preform is impregnated, densified, and carbonized, the surface part of the product is blocked by more residual carbon deposits in the internal pores, resulting in uneven internal density distribution of the product, thus generating stress concentration and being prone to delamination and peeling phenomena, affecting the product quality, and causing poor impregnation effect in the next time, and requiring manual grinding of the surface carbon deposits, which prolongs the product production cycle.

[0006] To solve the above technical problems, the present invention specifically provides the following technical solutions:

[0007] A carbon-carbon composite material, comprising: using a variable-density carbon fiber needle-punched preform as a matrix, and performing resin sizing impregnation and carbonization on the matrix to form a carbon-carbon composite material;

[0008] The resin sizing agent includes a thermosetting resin and a functional agent mixed in the thermosetting resin.

[0009] A carbon fiber needled preform with a density gradient change includes:

[0010] A carbon fiber needled layer with at least 3 layers, the carbon fiber needled layer includes a carbon fiber needled edge layer and a carbon fiber needled intermediate layer; the carbon fiber needled edge layer has a first weight per unit area unit with a cyclic laying, and the carbon fiber needled intermediate layer has a second weight per unit area unit with a cyclic laying; both the first weight per unit area unit and the second weight per unit area unit are composed of a web and a carbon cloth, and the weight of the web is 40 - 200 gsm.

[0011] Preferably, the density of the second weight per unit area unit is greater than or equal to the density of the first weight per unit area unit; or, the web is formed by carding chopped carbon fibers or modified chopped carbon fibers; or, the weight of the carbon cloth is 200 - 400 gsm; or, the carbon cloth is located above the web in the weight per unit area unit; or, the web is located on the outside in the weight per unit area unit; or, the average length of the chopped carbon fibers or modified chopped carbon fibers is 40 - 80 mm. The chopped carbon fibers are modified to increase the surface roughness of the carbon fibers, and the above-mentioned web and carbon cloth are cross - stacked and needled to prepare the needled preform. During the impregnation densification and carbonization treatment process of the needled preform, the impregnation effect is good, the density increment is large, the purpose of efficient impregnation is achieved, and the mechanical properties and thermal properties of the prepared carbon - carbon composite material can be improved.

[0012] Preferably, the modified chopped carbon fibers include chopped carbon fibers and their amino - modified structures.

[0013] Preferably, the web includes a low - weight web and a high - weight web; the weight of the low - weight web is 40 - 100 gsm; the weight of the high - weight web is 110 - 200 gsm.

[0014] Preferably, the carbon fiber needled preform has a carbon fiber needled layer with 3 layers; or, the carbon fiber needled preform has a carbon fiber needled layer with 5 layers, and there are 3 weight per unit area units with different densities in the carbon fiber needled intermediate layer; or, the thickness of the carbon fiber needled edge layer is 1 - 8 mm; or, the thickness of the carbon fiber needled intermediate layer is 1.5 - 10 mm.

[0015] Preferably, the bulk density of the carbon fiber needled edge layer is 0.35 - 0.55 g / cm 3 ; the bulk density of the carbon fiber needled intermediate layer is 0.45 - 0.65 g / cm 3 .

[0016] Preferably, in the preparation of the modified chopped carbon fibers, the chopped carbon fibers are desized and then reacted with isobutyl 4 - aminobenzoate to obtain the modified chopped carbon fibers.

[0017] The present invention discloses a method for preparing the above-mentioned carbon fiber needle-punched preform, including:

[0018] Taking a web and carbon cloth as a gram weight unit, needle-punching the laid gram weight unit and then needle-punching again; sequentially laying the gram weight units layer by layer, and performing needle-punching layer by layer during the process of laying layer by layer to obtain a carbon fiber needle-punched preform; having at least 3 layers of carbon fiber needle-punched layers, and the carbon fiber needle-punched layers are divided according to different densities of the gram weight units therein, and the gram weight units are divided into the first to the Nth gram weight units according to different densities.

[0019] Preferably, the density of the carbon fiber needle-punched preform is 0.3 - 0.6 g / cm 3 .

[0020] The present invention discloses the use of the above-mentioned carbon fiber needle-punched preform in the preparation of carbon-carbon composites.

[0021] The present invention discloses a carbon-carbon composite material, including: the above-mentioned carbon fiber needle-punched preform and resin carbon.

[0022] Preferably, the average length of the chopped carbon fiber is 40 - 80 mm.

[0023] Preferably, the gram weight of the carbon cloth is 200 - 400 gsm.

[0024] Preferably, the gram weight of the low-gram-weight web is 40 - 100 gsm.

[0025] Preferably, the gram weight of the high-gram-weight web is 110 - 200 gsm.

[0026] Preferably, the preparation method of the modified chopped carbon fiber includes: subjecting the chopped carbon fiber to desizing treatment, and then reacting with isobutyl 4-aminobenzoate to obtain the modified chopped carbon fiber. The desizing treatment of the chopped carbon fiber exposes the active groups on the carbon fiber surface, and then isobutyl 4-aminobenzoate modifies and modifies the carbon fiber surface, improving the interfacial bonding performance between the carbon fiber and the resin matrix, and further improving the performance of the carbon-carbon composite material.

[0027] The present invention also provides the application of any one of the above-mentioned carbon fiber needle-punched preforms in the preparation of carbon-carbon composites.

[0028] The present invention also provides a carbon-carbon composite material, which is prepared by subjecting any one of the above-mentioned carbon fiber needle-punched preforms to vacuum impregnation, curing, carbonization and high-pressure liquid phase impregnation. Using a web with a larger gram weight in the middle layer of the structural unit of the carbon fiber needle-punched preform and using webs with smaller gram weights in the lower layer and the upper layer can prevent the product surface from being blocked by carbon deposition in the holes during the gas-phase deposition densification process, make the density of different parts of the product more uniform, effectively improve the densification rate, reduce the number of densification times, and the product is not prone to quality problems such as delamination.

[0029] In one embodiment, in the preparation of the carbon felt, carbon fiber rovings of Toray T700-12K with a carbon content of ≥95% are provided, cut into short carbon fibers, added to acetone, refluxed at 40-60 °C for 36-60 h, taken out, washed, and dried to obtain desized short carbon fibers; after the desized short carbon fibers are carded into tow by a carding machine, a carbon felt is prepared.

[0030] Preferably, the average length of the short carbon fibers is 40-80 mm; the usage amount of the short carbon fibers is 20-40 wt% of acetone.

[0031] Preferably, in the preparation of the carbon fiber needle-punched preform, the needle punching density is 20-40 needles / cm 3 , the penetration depth is 2-7 mm, the thickness of the carbon fiber needle-punched preform is 8-12 mm, and the density of the carbon fiber needle-punched preform is 0.3-0.6 g / cm 3 .

[0032] Preferably, in the preparation of the resin sizing, an additive is added to the resin to prepare the resin sizing.

[0033] Preferably, the resin is a thermosetting resin; the additive is KH550 silane coupling agent, and the usage amount of KH550 silane coupling agent in the resin sizing is 0.02-0.04 wt% of the phenolic resin.

[0034] Preferably, the resin sizing can also be furfural resin.

[0035] Preferably, in the preparation of the carbon-carbon composite precursor, the carbon fiber needle-punched preform is subjected to vacuum impregnation. It is placed in a vacuum impregnation tank and evacuated for 20-40 min. The resin sizing is pumped into the preform through a conduit. Under the action of the pressure difference, the resin sizing completely submerges the needle-punched preform, and then evacuated for 10-20 min, kept under pressure for 40-80 min, taken out, placed in a drying oven, and the temperature-rising program of the drying oven is set for curing. After the curing is completed, the carbon-carbon composite precursor is prepared.

[0036] Preferably, the temperature-rising program is set to start from 80-120 °C, maintained for 2-6 h, and then stepwise heated to 180-220 °C, and held for 2-6 h for every 10-30 °C increase.

[0037] Preferably, in the preparation of the carbon-carbon composite, the carbon-carbon composite precursor is subjected to carbonization and high-pressure liquid-phase impregnation cycle treatment, and after the cycle is completed, high-temperature carbonization is carried out to obtain the carbon-carbon composite.

[0038] Preferably, the carbonization temperature is 1200 - 1800 °C, and the time is 1 - 3 h; the temperature of high-pressure liquid-phase impregnation is 120 - 240 °C, the pressure is 1 - 5 MPa, and the time is 1 - 4 h; the number of cycles of carbonization and high-pressure liquid-phase impregnation treatment is 2 - 6 times; the temperature of high-temperature carbonization is 2000 - 3000 °C, and the high-temperature carbonization time is 1 - 3 h.

[0039] In one embodiment, a carbon fiber needle-punched preform with a density gradient change and its use, including: using modified chopped carbon fibers instead of desized chopped carbon fibers.

[0040] Preferably, the preparation method of the modified chopped carbon fibers includes the following steps: providing carbon fiber rovings of Toray T700 - 12K with a carbon content of ≥95%, cutting them into chopped carbon fibers, adding them to acetone, refluxing at 40 - 60 °C for 36 - 60 h, taking them out, washing, and drying to obtain desized chopped carbon fibers; adding the desized chopped carbon fibers to a modified solution, adding a catalyst, treating at 70 - 80 °C for 7 - 12 h, taking them out, washing, and drying to obtain modified chopped carbon fibers.

[0041] Preferably, the average length of the chopped carbon fibers is 40 - 80 mm; the usage amount of the chopped carbon fibers is 20 - 40 wt% of acetone.

[0042] Preferably, the modified solution is a mixed solution of isobutyl 4-aminobenzoate and DMSO, and the modified solution contains 5 - 30 wt% of isobutyl 4-aminobenzoate.

[0043] Preferably, the usage amount of the desized chopped carbon fibers is 40 - 60 wt% of the modified solution.

[0044] Preferably, the catalyst is isoamyl nitrite, and the usage amount of the catalyst is 10 - 20 wt% of the desized chopped carbon fibers.

[0045] In one embodiment, a carbon fiber needle-punched preform with a density gradient change and its use, including:

[0046] Preparation of the resin sizing: adding additives to the resin to prepare the resin sizing.

[0047] Preferably, the resin is a thermosetting resin; the additives are KH550 silane coupling agent and sucrose acetate isobutyrate. The usage amount of KH550 silane coupling agent in the resin sizing is 0.02 - 0.04 wt% of the phenolic resin, and the usage amount of sucrose acetate isobutyrate in the resin sizing is 0.02 - 0.04 wt% of the phenolic resin. During the preparation of the resin sizing, adding KH550 silane coupling agent and sucrose acetate isobutyrate can reduce the number of carbonization densification times of the prepared carbon fiber needle-punched preform, and the prepared carbon-carbon composite material has high mechanical properties and high thermal conductivity.

[0048] The beneficial effects adopted by the present invention are as follows: during the densification process of carbon fiber needle-punched preforms by chemical vapor deposition, the surface of the product is not easily blocked by carbon deposition, so that the density of different parts of the product is relatively uniform, effectively improving the densification rate, reducing the number of densification times, and the product is not prone to quality problems such as delamination. The interlayer bonding is more dense and uniform, reducing anisotropy, making the product performance more stable, having better thermal conductivity, low preparation cost, short preparation cycle, effectively reducing subsequent processes, and being suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only exemplary, and for those of ordinary skill in the art, without creative efforts, other implementation drawings can be obtained according to the provided drawings.

[0050] Figure 1 is a schematic diagram for the preparation of carbon fiber needle-punched preforms;

[0051] Figure 2 is an infrared spectrum diagram of modified carbon fiber;

[0052] Figure 3 is a tensile strength diagram of carbon-carbon composite materials;

[0053] Figure 4 is a thermal conductivity diagram of carbon-carbon composite materials. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0054] The following further describes the present invention in detail in combination with specific embodiments. The given embodiments are only for clarifying the present invention, rather than limiting the scope of the present invention. The following provided embodiments can be used as a guide for those of ordinary skill in the art to further improve, and do not limit the present invention in any way.

[0055] In the present invention, the variable-density carbon fiber needle-punched preform can also be called a carbon fiber needle-punched preform with density gradient change, and sometimes it is simply called a carbon fiber needle-punched preform. Without special instructions, the variable-density carbon fiber needle-punched preform, the carbon fiber needle-punched preform with density gradient change, and the carbon fiber needle-punched preform have the same meaning.

[0056] Figure 1 is a schematic diagram for the preparation of carbon fiber needle-punched preforms of the present invention. The experimental methods in the following embodiments are all conventional methods without special instructions. The materials, reagents, etc. used in the following embodiments can all be obtained from commercial channels without special instructions.

[0057] Example 1: A carbon fiber needle-punched preform and its use

[0058] Preparation of low-grammage web tire: Provide carbon fiber raw yarns of Toray T700-12K with a carbon content of ≥95%, cut them into short carbon fibers, add them to acetone, reflux at 50 °C for 48 h, take them out, wash, and dry to obtain desized short carbon fibers; after carding the desized short carbon fibers into wool filaments by a carding machine, prepare a low-grammage web tire, where the average length of the short carbon fibers is 60 mm; the usage amount of the short carbon fibers is 30 wt% of acetone, and the gram weight of the low-grammage web tire is 60 gsm.

[0059] Preparation of carbon fiber needle-punched preform with the same density: Consist of one layer of low-grammage web tire and one layer of carbon cloth to form a low-grammage unit, perform needle punching, and then layer by layer layering with the low-grammage unit, and perform layer-by-layer needle punching during the layer-by-layer layering to prepare a carbon fiber needle-punched preform with the same density; where the needle punching density is 30 needles / cm 3 , the penetration depth is 3 mm, and the carbon cloth is 12K, 300 gsm plain weave carbon cloth. The thickness of the carbon fiber needle-punched preform is 9 mm, and the density of the carbon fiber needle-punched preform is 0.35 g / cm 3 .

[0060] Preparation of resin sizing: Add additives to the resin to prepare resin sizing, where the resin is a thermosetting resin; the additive is KH550 silane coupling agent, and the usage amount of KH550 silane coupling agent in the resin sizing is 0.03wt% of phenolic resin.

[0061] Preparation of carbon-carbon composite precursor: Perform vacuum impregnation on the carbon fiber needle-punched preform, put it into a vacuum impregnation tank and evacuate for 30 min, pump the resin sizing into the preform through a conduit, under the action of the pressure difference, the resin sizing completely submerges the needle-punched preform, continue to evacuate for 15 min, keep the pressure for 60 min, take it out, put it into a drying oven, set the heating program of the drying oven for curing, and obtain the carbon-carbon composite precursor after the curing ends; where the heating program is set to start from 100 °C, maintain for 4 h, and then stepwise heat up to 200 °C, and keep warm for 4 h for every 20 °C increase.

[0062] Preparation of carbon-carbon composite: Perform carbonization and high-pressure liquid phase impregnation cyclic treatment on the carbon-carbon composite precursor, and perform high-temperature carbonization after the cycle ends to obtain the carbon-carbon composite; where the temperature of carbonization is 1600 °C and the time is 2 h; the temperature of high-pressure liquid phase impregnation is 180 °C, the pressure is 2 MPa, and the time is 2 h; the number of times of carbonization and high-pressure liquid phase impregnation cyclic treatment is 4 times; the temperature of high-temperature carbonization is 2000 °C, and the high-temperature carbonization time is 2 h.

[0063] Example 2: A carbon fiber needle-punched preform with density gradient change and its use

[0064] In this embodiment, compared with Embodiment 1, the difference lies in the preparation of the carbon fiber needle-punched preform.

[0065] The preparation steps of the carbon fiber needle-punched preform include the preparation of a low-gram-weight web, the preparation of a high-gram-weight web, and the preparation of the carbon fiber needle-punched preform.

[0066] Preparation of the low-gram-weight web: Provide carbon fiber rovings of Toray T700-12K with a carbon content of ≥95%, cut them into short carbon fibers, add them to acetone, reflux at 50 °C for 48 h, take them out, wash, and dry to obtain desized short carbon fibers; after combing the desized short carbon fibers into tow by a carding machine, prepare a low-gram-weight web, where the average length of the short carbon fibers is 60 mm; the usage amount of the short carbon fibers is 30 wt% of the acetone, and the gram weight of the low-gram-weight web is 60 gsm.

[0067] Preparation of the high-gram-weight web: Provide carbon fiber rovings of Toray T700-12K with a carbon content of ≥95%, cut them into short carbon fibers, add them to acetone, reflux at 50 °C for 48 h, take them out, wash, and dry to obtain desized short carbon fibers; after combing the desized short carbon fibers into tow by a carding machine, prepare a high-gram-weight web, where the average length of the short carbon fibers is 60 mm; the usage amount of the short carbon fibers is 30 wt% of the acetone, and the gram weight of the high-gram-weight web is 150 gsm.

[0068] Preparation of the carbon fiber needle-punched preform: A low-gram-weight unit composed of one layer of low-gram-weight web and one layer of carbon cloth is needled, and then layer-by-layer paving is carried out with the low-gram-weight unit, and layer-by-layer needling is carried out during the layer-by-layer paving to obtain a low-gram-weight layer; then a high-gram-weight unit composed of one layer of high-gram-weight web and one layer of carbon cloth is paved on the low-gram-weight layer, needled, and then layer-by-layer paving is carried out with the high-gram-weight unit, and layer-by-layer needling is carried out during the layer-by-layer paving to obtain a low-gram-weight layer - high-gram-weight layer; then, a low-gram-weight unit composed of one layer of low-gram-weight web and one layer of carbon cloth is paved on the low-gram-weight layer - high-gram-weight layer, needled, and then layer-by-layer paving is carried out with the low-gram-weight unit, and layer-by-layer needling is carried out during the layer-by-layer paving to obtain a low-gram-weight layer - high-gram-weight layer - low-gram-weight layer, that is, the carbon fiber needle-punched preform; where the needling density is 30 needles / cm 3 , the penetration depth is 3 mm, and the carbon cloth is 12K, 300 gsm plain weave carbon cloth. The thickness of the carbon fiber needle-punched preform is 9 mm, where the thicknesses of the low-gram-weight layer - high-gram-weight layer - low-gram-weight layer are 3 mm - 3 mm - 3 mm respectively, and the density of the carbon fiber needle-punched preform is 0.35 g / cm 3 .

[0069] Example 3: A carbon fiber needle-punched preform with a density gradient change and its uses

[0070] This embodiment is different from Embodiment 2 in the preparation of the carbon fiber needle-punched preform.

[0071] Preparation of the carbon fiber needle-punched preform: A high-grammage unit is composed of a layer of high-grammage web and a layer of carbon cloth, and needle punching is carried out. Then, the high-grammage units are laid layer by layer, and needle punching is carried out layer by layer during the layer-by-layer laying to obtain a high-grammage layer. Then, a low-grammage unit is composed of a layer of low-grammage web and a layer of carbon cloth, and the low-grammage unit is laid on the high-grammage layer, and needle punching is carried out. Then, the low-grammage units are laid layer by layer, and needle punching is carried out layer by layer during the layer-by-layer laying to obtain a high-grammage layer - low-grammage layer. Then, a high-grammage unit is composed of a layer of high-grammage web and a layer of carbon cloth, and the high-grammage unit is laid on the high-grammage layer - low-grammage layer, and needle punching is carried out. Then, the high-grammage units are laid layer by layer, and needle punching is carried out layer by layer during the layer-by-layer laying to obtain a high-grammage layer - low-grammage layer - high-grammage layer, that is, the carbon fiber needle-punched preform. Among them, the needle punching density is 30 needles / cm 3 , the needle penetration depth is 3 mm, the carbon cloth is 12K, 300 gsm plain weave carbon cloth. The thickness of the carbon fiber needle-punched preform is 9 mm. Among them, the thicknesses of the high-grammage layer - low-grammage layer - high-grammage layer are 3 mm - 3 mm - 3 mm respectively, and the density of the carbon fiber needle-punched preform is 0.35 g / cm 3 .

[0072] Embodiment 4: A carbon fiber needle-punched preform with a density gradient change and its use

[0073] This embodiment is different from Embodiment 2 in that in the preparation of the web, modified short carbon fibers are used instead of desized short carbon fibers.

[0074] The preparation of the modified short carbon fibers includes the following steps:

[0075] Preparation of the modified short carbon fibers: Provide carbon fiber tows of Toray T700 - 12K with a carbon content ≥ 95%, cut them into short carbon fibers, add them to acetone, reflux at 50 °C for 48 h, take them out, wash, and dry to obtain desized short carbon fibers; add the desized short carbon fibers to the modification solution, add a catalyst, and treat them at 80 °C for 9 h, take them out, wash, and dry to obtain modified short carbon fibers. Among them, the average length of the short carbon fibers is 60 mm; the usage amount of the short carbon fibers is 30 wt% of acetone; the modification solution is a mixed solution of isobutyl 4-aminobenzoate and DMSO, and the modification solution contains 10 wt% of isobutyl 4-aminobenzoate. The usage amount of the desized short carbon fibers is 50 wt% of the modification solution, the catalyst is isoamyl nitrite, and the usage amount of the catalyst is 10 wt% of the desized short carbon fibers.

[0076] Embodiment 5: A carbon fiber needle-punched preform with a density gradient change and its use

[0077] The difference between this example and Example 4 lies in the preparation of modified short carbon fiber

[0078] Preparation of modified short carbon fiber: Provide carbon fiber roving with carbon content ≥ 95% of Toray T700 - 12K, cut it into short carbon fibers, add them to acetone, reflux at 50 °C for 48 h, take out, wash, and dry to obtain desized short carbon fibers; add the desized short carbon fibers to the modification solution, add a catalyst, and treat at 80 °C for 9 h, take out, wash, and dry to obtain modified short carbon fibers; among them, the average length of the short carbon fibers is 60 mm; the usage amount of the short carbon fibers is 30 wt% of acetone; the modification solution is a mixed solution of isobutyl 4 - aminobenzoate and DMSO, the modification solution contains 20 wt% of isobutyl 4 - aminobenzoate, the usage amount of the desized short carbon fibers is 50 wt% of the modification solution, the catalyst is isoamyl nitrite, and the usage amount of the catalyst is 10 wt% of the desized short carbon fibers.

[0079] Example 6: A carbon fiber needle - punched preform with density gradient change and its use

[0080] The difference between this example and Example 4 lies in the preparation of the resin adhesive solution.

[0081] Preparation of the resin adhesive solution: Add additives to the resin to prepare the resin adhesive solution, among which, the resin is a thermosetting resin; the additives are KH550 silane coupling agent and sucrose acetate isobutyrate, the usage amount of KH550 silane coupling agent in the resin adhesive solution is 0.03 wt% of phenolic resin, and the usage amount of sucrose acetate isobutyrate in the resin adhesive solution is 0.02 wt% of phenolic resin.

[0082] Example 7: A carbon fiber needle - punched preform with density gradient change and its use

[0083] The difference between this example and Example 6 is that the usage amount of sucrose acetate isobutyrate in the resin adhesive solution is 0.04 wt% of phenolic resin.

[0084] Test Example 1: Infrared spectrum analysis

[0085] Test samples: Desized short carbon fibers and modified short carbon fibers prepared in Example 4.

[0086] The infrared spectrum characterization is as Figure 2 shown, where a is the desized short carbon fiber, b is the modified short carbon fiber, the desized short carbon fiber has a hydroxyl stretching vibration absorption peak at 3300 - 3400 cm -1 , and by comparison, the modified carbon fiber has an absorption peak of amino group at 3497 cm -1 , indicating that the modified short carbon fiber is successfully obtained.

[0087] Test Example 2:

[0088] The following tests were carried out on the carbon-carbon composites prepared in Examples 1-7:

[0089] 1. Density of carbon-carbon composites

[0090] 1.1 Samples and methods

[0091] Using the Archimedes drainage method, the density of the carbon-carbon composites after each carbonization and high-pressure liquid-phase impregnation cycle treatment was measured: First, the mass of the dry material was measured in air, and the measurement result was recorded as m. Subsequently, the test material was placed in deionized water, and the floating mass was recorded as the wet weight m1. The carbon-carbon composite material that had fully absorbed water in water was fished out and weighed in air, which was recorded as m0; the density calculation formula was: ρ=(m / (m1 - m0))×ρ 水 。

[0092] Table 1 Density of carbon-carbon composites (g / cm 3 )

[0093]

[0094] Table 1 shows the density of the carbon-carbon composites after each cycle of carbonization and high-pressure liquid-phase impregnation treatment using the carbon fiber needled preforms prepared in Examples 1-7. It can be seen that, firstly, among Examples 1-3, the carbon fiber needled preform prepared in Example 2 has the best densification effect, followed by Example 3, and Example 1 has a relatively poor densification effect. During the densification process of the carbon fiber needled preforms prepared in Examples 1-3, carbon fiber needled layers with different densities are set in the carbon fiber needled preforms. The carbon fiber needled preform in Example 1 has 1 layer of carbon fiber needled layer, that is, in Example 1, only a low-gram-weight net tire is used to make a uniform carbon fiber needled preform. Both Example 2 and Example 3 have 3 layers of carbon fiber needled layers. The carbon fiber needled preform prepared in Example 2 is a carbon fiber needled preform with a low-gram-weight layer - high-gram-weight layer - low-gram-weight layer structure, and the carbon fiber needled preform prepared in Example 3 is a carbon fiber needled preform with a high-gram-weight layer - low-gram-weight layer - high-gram-weight layer structure. During densification, it is found that the carbon fiber needled preform with a low-gram-weight layer - high-gram-weight layer - low-gram-weight layer structure has the fastest densification rate. This shows that during the densification process, although the initial density of the carbon fiber needled preform in Example 3 is relatively high, during the densification process, because the net tire with a smaller gram weight is used in the middle layer of the structural unit, and the net tires with a larger gram weight are used in the bottom and upper layers, the pores on the surface of the middle layer are blocked, resulting in a poor internal densification effect, and there is a density difference from the carbon-carbon composites in Examples 1 and 2. And if the surface blockage situation is not manually treated during multiple densification processes, the subsequent densification effect will become worse and worse. While Example 2 can achieve the same densification effect as Examples 1 and 3 after 3 densification treatments, which indicates that using a net tire with a larger gram weight in the middle layer of the structural unit and net tires with a smaller gram weight in the bottom and upper layers can make the prepared carbon fiber needled preform not easily be blocked by carbon deposition in the pores on the product surface during the gas-phase deposition densification process, make the density of different parts of the product more uniform, effectively improve the densification rate, reduce the number of densification times, and the product is not prone to quality problems such as delamination, which can effectively save working hours and reduce production costs. Secondly, the densification efficiency of the carbon fiber needled preform prepared in Example 4 is higher than that in Example 2, which shows that modifying the short carbon fibers can improve the densification efficiency of the carbon fiber needled preform; the densification efficiency of the carbon fiber needled preform prepared in Example 5 is higher than that in Example 4, which shows that increasing the usage amount of isobutyl 4-aminobenzoate can improve the densification efficiency of the carbon fiber needled preform; the densification efficiency of the impregnated carbon fiber needled preform prepared in Example 6 is higher than that in Example 5, which shows that adding sucrose acetate isobutyrate during the preparation of the resin sizing can improve the densification efficiency; the densification efficiency of the impregnated carbon fiber needled preform prepared in Example 7 is higher than that in Example 6, which shows that increasing the addition amount of sucrose acetate isobutyrate in the resin sizing can improve the densification efficiency of the carbon fiber needled preform.

[0095] 2. Mechanical Properties of Carbon-Carbon Composites

[0096] 2.1. Samples and Methods

[0097] The carbon-carbon composite materials prepared in Examples 1-7 were subjected to axial tensile performance tests using a Sansi CMT-5205 universal testing machine. The size of the sample was 100 mm × 10 mm × 3 mm. Aluminum reinforcement sheets were attached to both ends of the tensile test sample to ensure that the sample was not damaged by the fixture of the instrument during the test. Tensile strength The calculation formula is: In the formula, P b Indicates the maximum tensile load, N; F indicates the cross-sectional area of ​​the specimen, cm 2 .

[0098] Figure 3 The tensile strength of the carbon-carbon composite materials prepared in Examples 1-7 can be seen that the tensile strength of the carbon-carbon composite material prepared in Example 3 is higher than that in Example 1, indicating that the tensile strength of the carbon-carbon composite material can be improved by using a mesh tire with a smaller gram weight in the middle layer of the structural unit of the carbon fiber needle-punched preform, and using a mesh tire with a larger gram weight in the bottom layer and the upper layer; the tensile strength of the carbon-carbon composite material prepared in Example 2 is higher than that in Example 3, indicating that the tensile strength of the carbon-carbon composite material can be improved by using a mesh tire with a larger gram weight in the middle layer of the structural unit of the carbon fiber needle-punched preform, and using a mesh tire with a smaller gram weight in the bottom layer and the upper layer; the tensile strength of the carbon-carbon composite material prepared in Example 4 is higher than that in Example 2 The tensile strength of the carbon-carbon composite material prepared in Example 5 is higher than that in Example 4, which means that increasing the amount of 4-aminobenzoic acid isobutyl ester can improve the tensile strength of the carbon-carbon composite material. The tensile strength of the carbon-carbon composite material prepared in Example 6 is higher than that in Example 5, which means that adding sucrose acetate isobutyrate in the process of preparing the resin adhesive can improve the tensile strength of the carbon-carbon composite material. The tensile strength of the carbon-carbon composite material prepared in Example 7 is higher than that in Example 6, which means that increasing the amount of sucrose acetate isobutyrate in the resin adhesive can improve the tensile strength of the carbon-carbon composite material.

[0099] 3. Determination of thermal conductivity of carbon-carbon composite materials

[0100] The thermal diffusion coefficients of the carbon-carbon composite materials prepared in Examples 1-7 were measured using a German NETZSCH LFA457 laser flash analyzer. The sample size was Ø12.5×2.5 mm. 3 The test was carried out under an argon protective atmosphere. Each sample was tested 3 times and the average value was taken. The room temperature thermal conductivity of carbon-carbon composites is calculated as follows: , where is the thermal conductivity of the material, W / m·K; is the thermal diffusivity of the material, m 2 / s; is the bulk density of the material, g / cm3 ; is the specific heat capacity of the material, J / g / K.

[0101] Figure 4 is the thermal conductivity of the carbon-carbon composite material prepared in Examples 1-7. It can be seen that the thermal conductivity of the carbon-carbon composite material prepared in Example 3 is higher than that in Example 1, indicating that using a lighter-weight mesh tire in the middle layer of the structural unit of the carbon fiber needle-punched preform and heavier-weight mesh tires in the bottom and top layers can increase the thermal conductivity of the carbon-carbon composite material; the tensile strength of the carbon-carbon composite material prepared in Example 2 is higher than that in Example 3, indicating that using a heavier-weight mesh tire in the middle layer of the structural unit of the carbon fiber needle-punched preform and lighter-weight mesh tires in the bottom and top layers can increase the thermal conductivity of the carbon-carbon composite material; the tensile strength of the carbon-carbon composite material prepared in Example 4 is higher than that in Example 2, indicating that using modified short-cut carbon fibers can increase the thermal conductivity of the carbon-carbon composite material; the tensile strength of the carbon-carbon composite material prepared in Example 5 is higher than that in Example 4, indicating that increasing the usage amount of isobutyl 4-aminobenzoate can increase the thermal conductivity of the carbon-carbon composite material; the tensile strength of the carbon-carbon composite material prepared in Example 6 is higher than that in Example 5, indicating that adding sucrose acetate isobutyrate during the preparation of the resin sizing can increase the thermal conductivity of the carbon-carbon composite material; the tensile strength of the carbon-carbon composite material prepared in Example 7 is higher than that in Example 6, indicating that increasing the usage amount of sucrose acetate isobutyrate in the resin sizing can increase the thermal conductivity of the carbon-carbon composite material.

[0102] The above-described embodiments and / or implementation manners are only used to illustrate the preferred embodiments and / or implementation manners for implementing the technology of the present invention, and do not impose any formal restrictions on the implementation manners of the technology of the present invention. Any person skilled in the art, without departing from the scope of the technical means disclosed in the content of the present invention, may make some changes or modifications to other equivalent embodiments, but should still be regarded as the same technology or embodiment as the present invention in essence.

Claims

1. A carbon-carbon composite material, comprising: Using a variable-density carbon fiber needled preform as the matrix, impregnating and carbonizing with a resin sizing on the matrix to form a carbon-carbon composite material; The resin sizing includes a thermosetting resin and a functional agent mixed in the thermosetting resin; The variable-density carbon fiber needled preform has 3 layers of carbon fiber needled layers, and the carbon fiber needled layer includes a carbon fiber needled edge layer and a carbon fiber needled intermediate layer; in the carbon fiber needled edge layer, there is a first weight per unit area unit with a circular layup, and in the carbon fiber needled intermediate layer, there is a second weight per unit area unit with a circular layup; both the first weight per unit area unit and the second weight per unit area unit are composed of a web and a carbon cloth, and the web includes a low-weight web and a high-weight web; the weight of the low-weight web is 40-100 gsm; the weight of the high-weight web is 110-200 gsm; the weight of the carbon cloth is 200-400 gsm; The variable-density carbon fiber needled preform is a carbon fiber needled layer with a low-weight layer - high-weight layer - low-weight layer, and the web is formed by carding modified short carbon fibers; the average length of the modified short carbon fibers is 40-80 mm; In the preparation of the modified short carbon fibers, the short carbon fibers are subjected to desizing treatment and then reacted with isobutyl 4-aminobenzoate to obtain modified short carbon fibers; specifically including the following steps: adding the short carbon fibers to acetone, refluxing at 40-60 °C for 36-60 h, taking out, washing, and drying to obtain desized short carbon fibers; adding the desized short carbon fibers to a modification solution, adding a catalyst, treating at 70-80 °C for 7-12 h, taking out, washing, and drying to obtain modified short carbon fibers; the modification solution is a mixed solution of isobutyl 4-aminobenzoate and DMSO, the modification solution contains 5-30 wt% of isobutyl 4-aminobenzoate, the usage amount of the desized short carbon fibers is 40-60 wt% of the modification solution, the catalyst is isoamyl nitrite, and the usage amount of the catalyst is 10-20 wt% of the desized short carbon fibers; The density of the second weight per unit area unit is greater than the density of the first weight per unit area unit; in the weight per unit area unit, the carbon cloth is located above the web; in the weight per unit area unit, the web is located on the outside; The thickness of the carbon fiber needled edge layer is 1-3 mm; the thickness of the carbon fiber needled intermediate layer is 1.5-3 mm; The volume density of the carbon fiber needle-punched edge layer is 0.35 - 0.55 g / cm 3 ; the volume density of the carbon fiber needle-punched intermediate layer is 0.45 - 0.65 g / cm 3 .

2. A preparation method of a carbon fiber needled preform, including: Using a web and a carbon cloth to form a weight per unit area unit, needling and then laying up the weight per unit area unit, and then needling again; Sequentially performing layer-by-layer laying up of the weight per unit area unit, and performing layer-by-layer needling during the layer-by-layer laying up process to obtain a carbon fiber needled preform; The carbon fiber needled preform has 3 layers of carbon fiber needled layers, The carbon fiber needled layer includes a carbon fiber needled edge layer and a carbon fiber needled intermediate layer; in the carbon fiber needled edge layer, there is a first weight per unit area unit with a circular layup, and in the carbon fiber needled intermediate layer, there is a second weight per unit area unit with a circular layup; both the first weight per unit area unit and the second weight per unit area unit are composed of a web and a carbon cloth, and the web includes a low-weight web and a high-weight web; the weight of the low-weight web is 40-100 gsm; the weight of the high-weight web is 110-200 gsm; the weight of the carbon cloth is 200-400 gsm; The web tire is formed by carding modified short carbon fiber; the average length of the modified short carbon fiber is 40 - 80 mm; In the preparation of the modified short carbon fiber, the short carbon fiber is desized and then reacted with isobutyl 4-aminobenzoate to obtain the modified short carbon fiber; specifically, it includes the following steps: adding the short carbon fiber into acetone, refluxing at 40 - 60 °C for 36 - 60 h, taking out, washing, and drying to obtain the desized short carbon fiber; adding the desized short carbon fiber into the modification solution, adding a catalyst, treating at 70 - 80 °C for 7 - 12 h, taking out, washing, and drying to obtain the modified short carbon fiber; the modification solution is a mixed solution of isobutyl 4-aminobenzoate and DMSO, the modification solution contains 5 - 30 wt% of isobutyl 4-aminobenzoate, the usage amount of the desized short carbon fiber is 40 - 60 wt% of the modification solution, the catalyst is isoamyl nitrite, and the usage amount of the catalyst is 10 - 20 wt% of the desized short carbon fiber; The density of the second grammage unit is greater than that of the first grammage unit; in the grammage unit, the carbon cloth is located above the web tire; in the grammage unit, the web tire is located on the outside; The thickness of the carbon fiber needle-punched edge layer is 1 - 8 mm; the thickness of the carbon fiber needle-punched intermediate layer is 1.5 - 10 mm; The volume density of the carbon fiber needle-punched edge layer is 0.35 - 0.55 g / cm 3 ; the volume density of the carbon fiber needle-punched intermediate layer is 0.45 - 0.65 g / cm 3 .

3. The preparation method of the carbon fiber needled preform according to claim 2, characterized in that, The density of the carbon fiber needled preform is 0.3 - 0.6 g / cm 3 .

4. Use of the carbon fiber needle-punched preform prepared by the method according to any one of claims 2 - 3 in the preparation of carbon-carbon composites.

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