Density gradient carbon fiber reinforced phenolic composite material and preparation method thereof

Abstract

The invention discloses a density gradient carbon fiber reinforced phenolic composite material and a preparation method thereof, and belongs to the technical field of composite materials. By adopting the gradient design of the carbon fiber fabric and the gradient effect of the drying process, a novel method for preparing the density gradient carbon fiber reinforced phenolic composite material is expanded.

Description

Technical Field

[0001] The present invention relates to a density gradient carbon fiber reinforced phenolic composite material and a preparation method thereof, belonging to the technical field of composite materials. Background Art

[0002] Thermal protection materials are the barriers for re-entry aerospace vehicles to resist the aerodynamic heat environment, providing surface thermal protection for components of various aircraft serving in high-temperature environments to avoid burning or overheating. Traditional carbon fiber fabric reinforced phenolic composite materials have low thermal conductivity, high porosity, and excellent heat insulation performance, and are applied to aerospace frontier fields such as interstellar exploration aircraft. However, the currently used carbon fiber reinforced phenolic composite materials have relatively uniform density, and there is a temperature gradient along the thickness direction during the use of the materials, resulting in thermal stress inside the materials. Density gradient materials can effectively relieve the thermal stress inside the materials. In addition, according to the differences in the stress environment of the materials, density gradient materials can gradually establish a buffer layer to improve the material utilization rate.

[0003] Therefore, it is very necessary to provide a new type of density gradient carbon fiber reinforced phenolic composite material and a preparation method thereof. Summary of the Invention

[0004] In order to solve the above-mentioned existing technical problems, the present invention provides a density gradient carbon fiber reinforced phenolic composite material and a preparation method thereof.

[0005] A density gradient carbon fiber reinforced phenolic composite material and a preparation method thereof, the method comprising the following steps:

[0006] Step 1, preparing a density gradient fabric with an increasing fiber volume density from top to bottom along the thickness direction by using carbon fibers;

[0007] Step 2, impregnating the density gradient fabric with a phenolic solution, and then performing gradient drying; the gradient drying is to wrap and seal the upper surface and side surfaces of the gradient fabric with a film, and then dry and cure by blowing air;

[0008] Step 3, performing solvent replacement on the blank to obtain a density gradient carbon fiber reinforced phenolic composite material;

[0009] Preferably, the fiber volume density of the density gradient fabric varies in the range of 0.1-0.8 g / cm 3 ;

[0010] Preferably, the mass fraction of the phenolic solution is 20%-30%;

[0011] Preferably, the impregnation time is 24-48 h;

[0012] Preferably, the drying temperature is 80 - 120 °C and the drying time is 4 - 12 h;

[0013] Preferably, the film is a plastic food wrap;

[0014] Preferably, the density gradient fabric is a flat fabric, and the flat fabric has 3 - 6 increasing fiber volume density values from top to bottom in the thickness direction, and the fabric thickness corresponding to each fiber volume density value is 3 - 8 mm;

[0015] Preferably, the solvent used for solvent replacement is alcohol, the replacement time is 8 h, and the number of replacement times is 5 times.

[0016] Advantages of the present invention compared with the prior art:

[0017] (1) In the drying and curing process of the present invention, the bottom layer with a high fiber volume density of the density gradient fabric is in direct contact with the outside. Since only the lower surface is the drying channel, under the capillary action, the phenolic solution in the upper layer of the fabric tends to migrate downward, making the density of phenolic in the fabric show a gradually increasing trend from top to bottom; the present invention finds that the superposition of this density gradient of the phenolic solution and the density gradient of the fabric can make the carbon fiber / phenolic composite material show a significant density gradient in the thickness direction from top to bottom;

[0018] (2) The present invention develops a new method for preparing a density gradient carbon fiber reinforced phenolic composite material through the superposition of the double gradient effects of the density gradient fabric and the drying gradient process;

[0019] (3) The present invention is simple in operation, low in cost, and high in preparation efficiency, which is beneficial to preparing a carbon fiber reinforced phenolic composite material with a significant density gradient. Detailed implementation mode

[0020] The present invention will be described in detail below with specific examples.

[0021] Example 1:

[0022] Step 1, weave a density gradient flat fabric, and the fiber volume density from top to bottom in the thickness direction is 0.15 g / cm 3 , 0.30 g / cm 3 , 0.45 g / cm 3 , and the weaving thickness corresponding to each fiber volume density is 5 mm;

[0023] Step 2, under vacuum, fill a sealed container containing the density gradient fabric with a phenolic resin solution with a mass fraction of 20%. After impregnation for 24 hours, take out the fabric. Wrap the upper surface and sides of the impregnated fabric with plastic wrap, then place it on the stainless steel mesh of a forced-air drying oven. The lower surface of the fabric is directly exposed to the air, and dry and cure it at 120 °C for 8 hours;

[0024] Step 3, place the above blank in an alcohol solution for solvent replacement. The alcohol solution should cover the blank, and replace the alcohol solution every 8 hours. Repeat 5 times to obtain a density gradient carbon fiber reinforced phenolic composite;

[0025] Take samples of the density gradient carbon fiber reinforced phenolic composite prepared in this example at intervals of 5 mm along the thickness direction to test the density. The densities from top to bottom are 0.33 g / cm 3 , 0.56 g / cm 3 , 0.76 g / cm 3 ; The density gradient carbon fiber reinforced phenolic composite prepared in this example has a significant density gradient, with a difference of more than 0.20 g / cm between every two adjacent density values. Its density gradient characteristics are more significant than those of the original density gradient fabric. 3 Take samples of the density gradient carbon fiber reinforced phenolic composite prepared in this example at intervals of 5 mm along the thickness direction to test the compressive strength. The compressive strengths from top to bottom are 3.5 MPa, 6.2 MPa, and 7.3 MPa;

[0026] Take samples of the density gradient carbon fiber reinforced phenolic composite prepared in this example at intervals of 5 mm along the thickness direction to test the tensile strength. The tensile strengths from top to bottom are 7.4 MPa, 10.8 MPa, and 11.6 MPa.

[0027] Example 2:

[0028] Step 1, weave a density gradient flat fabric. The fiber volume densities from top to bottom along the thickness direction are 0.20 g / cm

[0029] , 0.40 g / cm 3 , 0.60 g / cm 3 , 0.60 g / cm 3 , and the weaving thickness corresponding to each fiber volume density is 5 mm;

[0030] Step 2, under vacuum, fill a sealed container containing the density gradient fabric with a phenolic resin solution with a mass fraction of 20%. After impregnation for 24 hours, take out the fabric. Wrap the upper surface and sides of the impregnated fabric with plastic wrap, then place it on the stainless steel mesh of a forced-air drying oven. The lower surface of the fabric is directly exposed to the air, and dry and cure it at 120 °C for 8 hours;

[0031] Step 3: Place the above blank in an alcohol solution for solvent replacement. The alcohol solution should cover the blank, and the alcohol solution is replaced every 8 h and repeated 5 times to obtain a density gradient carbon fiber reinforced phenolic composite material;

[0032] The density gradient carbon fiber reinforced phenolic composite material prepared in this example is sampled and tested for density every 5 mm along the thickness direction. The densities from top to bottom are 0.42 g / cm 3 , 0.65 g / cm 3 , 0.89 g / cm 3 ; The density gradient carbon fiber reinforced phenolic composite material prepared in this example has a significant density gradient, and the difference between every two adjacent density values is more than 0.23 g / cm 3 . Its density gradient characteristics are more significant than those of the original density gradient fabric.

[0033] The density gradient carbon fiber reinforced phenolic composite material prepared in this example is sampled and tested for compressive strength every 5 mm along the thickness direction. The compressive strengths from top to bottom are 4.5 MPa, 6.8 MPa, and 8.2 MPa;

[0034] The density gradient carbon fiber reinforced phenolic composite material prepared in this example is sampled and tested for tensile strength every 5 mm along the thickness direction. The tensile strengths from top to bottom are 8.3 MPa, 11.2 MPa, and 12.3 MPa.

[0035] Example 3:

[0036] Step 1: Weave a density gradient flat fabric. The fiber volume densities from top to bottom along the thickness direction are 0.15 g / cm 3 , 0.30 g / cm 3 , 0.45 g / cm 3 , 0.60 g / cm 3 , and the weaving thickness corresponding to each fiber volume density is 5 mm;

[0037] Step 2: Under vacuum, fill a sealed container containing the density gradient fabric with a phenolic resin solution with a mass fraction of 20%. After impregnation for 24 h, take out the fabric; wrap the upper surface and side surfaces of the impregnated fabric with plastic wrap, place it on the stainless steel mesh of a blast drying oven, the lower surface of the fabric is directly exposed to the air, and dry and cure at 120 °C for 8 h;

[0038] Step 3: Place the above blank in an alcohol solution for solvent replacement. The alcohol solution should cover the blank, and the alcohol solution is replaced every 8 h and repeated 5 times to obtain a density gradient carbon fiber reinforced phenolic composite material;

[0039] The density gradient carbon fiber reinforced phenolic composite material prepared in this example was sampled every 5 mm along the thickness direction to test the density. The density from top to bottom was 0.34 g / cm 3 , 0.55g / cm 3 , 0.74g / cm 3 , 0.90g / cm 3 The density gradient carbon fiber reinforced phenolic composite material prepared in this embodiment has a significant density gradient, and the difference between each two adjacent density values is 0.16g / cm 3 As mentioned above, its density gradient characteristics are more significant than those of the original density gradient fabric.

[0040] The density gradient carbon fiber reinforced phenolic composite material prepared in this embodiment was sampled every 5 mm along the thickness direction to test the compressive strength. The compressive strengths from top to bottom were 3.5 MPa, 6.0 MPa, 7.1 MPa, and 8.4 MPa, respectively.

[0041] The density gradient carbon fiber reinforced phenolic composite material prepared in this example was sampled every 5 mm along the thickness direction to test the tensile strength. The tensile strengths from top to bottom were 7.5 MPa, 10.5 MPa, 11.3 MPa, and 12.5 MPa, respectively.

[0042] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A density gradient carbon fiber reinforced phenolic composite material and a preparation method thereof, characterized in that, The method comprises the following steps: Step 1: Prepare a density gradient fabric with an increasing fiber volume density from top to bottom in the thickness direction using carbon fiber; Step 2: Impregnate the density gradient fabric with a phenolic solution and then perform gradient drying; the gradient drying is to wrap and seal the upper surface and side surfaces of the gradient fabric with a film and then dry and cure it by blowing air; Step 3: Replace the solvent of the blank to obtain a density gradient carbon fiber reinforced phenolic composite material.

2. The density gradient carbon fiber reinforced phenolic composite material according to claim 1 and its preparation method are characterized in that, The fiber volume density of the density gradient fabric varies in the range of 0.1-0.8 g / cm3 in the thickness direction.

3. A density gradient carbon fiber reinforced phenolic composite material according to claim 1 and its preparation method, characterized in that, The mass fraction of the phenolic solution is 20%-30%.

4. A density gradient carbon fiber reinforced phenolic composite material and a preparation method thereof according to claim 1, characterized in that, The impregnation time is 24-48 h; the drying temperature is 80-120 °C, and the drying time is 4-12 h.

5. A density gradient carbon fiber reinforced phenolic composite material and a preparation method thereof according to claim 1, characterized in that, The film is a plastic cling film.

6. The density gradient carbon fiber reinforced phenolic composite material according to claim 1 and its preparation method are characterized in that, The density gradient fabric is a flat fabric, and the flat fabric has 3-6 increasing fiber volume density values from top to bottom in the thickness direction, and the fabric thickness corresponding to each fiber volume density value is 3-8 mm.

7. A density gradient carbon fiber reinforced phenolic composite material according to claim 1 and a preparation method thereof, characterized in that, The solvent used for solvent replacement is alcohol, the replacement time is 8 h, and the number of replacement times is 5 times.