A fiber-oriented composite material and its preparation method and application

Abstract

The present invention provides a composite material with directional fiber arrangement, and a preparation method and application thereof, belonging to the field of functional material technology. The present invention adopts thermal conductive fibers with a diameter of micrometer level as fillers, which has low cost. At the same time, the present invention utilizes a stretchable substrate to drive the dispersed movement of fiber bundles while ensuring the parallel arrangement of the thermal conductive fibers. On this basis, by pouring the matrix material, a composite material with directional arrangement of thermal conductive fibers along the height (thickness) direction can be prepared. The method of the present invention facilitates the regulation of the volume fraction of the thermal conductive fibers, and it is easy to obtain a composite material with a high volume fraction of thermal conductive fibers, which has excellent thermal conductivity, avoids the problem that nanomaterials have a large specific surface area and are difficult to obtain composite materials with a high content of thermal conductive fillers, and avoids the problem that the contact thermal resistance between nanomaterials affects the heat transfer efficiency of the composite material. The method provided by the present invention is simple to operate and has broad application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of functional materials, and in particular to a fiber-oriented composite material and a preparation method and application thereof. Background Art

[0002] As electronic device integration and power density continue to increase, heat dissipation issues are becoming increasingly serious. Thermal interface materials (TIMs), which offer lightweight, high thermal conductivity, have become a crucial component of advanced thermal management systems. Furthermore, traditional resin-based composites have low thermal conductivity, leading researchers to focus on developing fiber-based heat transfer pathways to improve their thermal conductivity.

[0003] Taking thermal interface materials as an example, thermally conductive gaskets are placed between the heating element and the heat sink, completing the heat transfer between the heating and heat dissipation parts, thereby achieving rapid heat dissipation of the device. Traditional thermally conductive gaskets are usually made by combining inorganic thermal conductive powders with a matrix. Inorganic thermal conductive powders include aluminum oxide, aluminum nitride, and boron nitride, and their thermal conductivity is generally below 300W / (m·K). Thermally conductive gaskets made with inorganic thermal conductive powders generally have a thermal conductivity of no more than 10W / (m·K).

[0004] Currently, high-thermal-conductivity composite materials can be obtained by using nanomaterials such as carbon nanotubes and graphene as one- or two-dimensional thermally conductive fillers. By manipulating the orientation of the fillers through ice templating or stretching methods, these materials can be oriented. However, these nanomaterials are expensive and have large specific surface areas. Using these methods, the thermally conductive filler content typically does not exceed 5%, making it difficult to obtain composite materials with high thermal-conductivity filler content. Summary of the Invention

[0005] The purpose of the present invention is to provide a fiber-oriented composite material and its preparation method and application. The present invention uses thermally conductive fibers with a diameter of microns as fillers, which has low cost. The method of the present invention facilitates the regulation of the volume fraction of the thermally conductive fibers, and it is easy to obtain a composite material with a high volume fraction of thermally conductive fibers, which has excellent thermal conductivity.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing a composite material with oriented fiber arrangement, comprising the following steps:

[0008] Providing a fiber bundle, wherein the fiber bundle is formed by arranging a plurality of heat-conducting fibers with a diameter of micrometers in parallel along the axis of the fiber bundle;

[0009] vertically adhering the fiber bundle to the surface of a stretchable substrate, and stretching the stretchable substrate to disperse the heat-conducting fibers in the fiber bundle on the surface of the stretchable substrate to obtain a dispersed fiber bundle;

[0010] The dispersed fiber bundle is placed in a mold, a matrix material is poured into the mold containing the dispersed fiber bundle, and the mold is demoulded after solidification and molding to obtain a fiber-oriented composite material.

[0011] Preferably, the fiber bundle is cylindrical as a whole, has a diameter of 8 to 12 mm, and a height of 2 to 10 mm; and the volume fraction of the thermally conductive fibers in the fiber bundle is ≥60%.

[0012] Preferably, the thermally conductive fibers include carbon fibers, silicon nitride fibers or alumina fibers.

[0013] Preferably, the surface of the thermal conductive fiber has a protective film; and before the adhering, the step further includes: removing the protective film on the surface of the thermal conductive fiber in the fiber bundle.

[0014] Preferably, the stretchable substrate comprises a rubber film or an stretchable sponge.

[0015] Preferably, the stretching is mechanical stretching; the stretching rate is 3-5 mm / min.

[0016] Preferably, the stretching method includes circular stretching or unidirectional stretching.

[0017] Preferably, the side wall of the fiber bundle has a restraining band for fixing the thermally conductive fibers; and before the stretching, the method further comprises: removing the restraining band on the side wall of the fiber bundle.

[0018] The present invention provides a fiber-oriented composite material prepared by the preparation method described in the above technical solution, comprising a matrix and a fiber reinforcement dispersed in the matrix, wherein the fiber reinforcement is formed by a plurality of thermally conductive fibers with a diameter of micrometers being oriented and arranged along the out-of-plane direction of the fiber-oriented composite material; the volume fraction of the thermally conductive fibers in the fiber-oriented composite material is 10 to 50%.

[0019] The present invention provides the use of the fiber-oriented composite material described in the above technical solution in the preparation of a thermally conductive gasket or a shielding box shell of an electronic device.

[0020] The present invention provides a method for preparing a composite material with oriented fiber arrangement, comprising the following steps: providing a fiber bundle, wherein the fiber bundle is formed by a plurality of heat-conducting fibers with a diameter of micrometers being arranged in parallel along the axis of the fiber bundle; vertically adhering the fiber bundle to the surface of a stretchable substrate, stretching the stretchable substrate to disperse the heat-conducting fibers in the fiber bundle on the surface of the stretchable substrate, and obtaining a dispersed fiber bundle; placing the dispersed fiber bundle in a mold, pouring a matrix material into the mold containing the dispersed fiber bundle, and demolding after solidification to obtain a composite material with oriented fiber arrangement. The present invention uses heat-conducting fibers with a diameter of micrometers as fillers, which is relatively low in cost. At the same time, the present invention utilizes a stretchable substrate to drive the dispersed movement of the fiber bundle while ensuring the parallel arrangement of the heat-conducting fibers. On this basis, by pouring the matrix material, a composite material with heat-conducting fibers oriented along the height (thickness) direction can be prepared. The method of the present invention facilitates control of the volume fraction of thermally conductive fibers, making it easy to obtain composite materials with a high volume fraction of thermally conductive fibers and excellent thermal conductivity. This method avoids the difficulty of obtaining composite materials with high thermally conductive filler content due to the large specific surface area of ​​nanomaterials. Furthermore, it avoids the problem of contact thermal resistance between nanomaterials that affects the heat transfer efficiency of composite materials. The method provided by the present invention is simple to operate and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a flow chart for preparing a fiber-oriented composite material in the present invention;

[0022] Figure 2 This is a physical picture of the rod-shaped aggregate and cylindrical fiber bundle in Example 1;

[0023] Figure 3 1 is a comparison diagram of the dispersed fiber bundles (drafted 2 times and 8 times, respectively) and the fiber bundles (i.e., undrafted) prepared by unidirectional drafting in Examples 1 and 2;

[0024] Figure 4 is a side view of the dispersed fiber bundle obtained after drawing in Example 2;

[0025] Figure 5 3 is a comparison diagram of the dispersed fiber bundles (drafted 4 times and 8 times, respectively) and the fiber bundles (i.e., undrafted) prepared by the annular drafting method in Examples 3 and 4;

[0026] Figure 6 Graph showing the thermal conductivity test results of the composite materials prepared in Examples 1 to 4, as well as silicone rubber and epoxy resin. DETAILED DESCRIPTION

[0027] The present invention provides a method for preparing a composite material with oriented fiber arrangement, comprising the following steps:

[0028] Providing a fiber bundle, wherein the fiber bundle is formed by arranging a plurality of heat-conducting fibers with a diameter of micrometers in parallel along the axis of the fiber bundle;

[0029] vertically adhering the fiber bundle to the surface of a stretchable substrate, and stretching the stretchable substrate to disperse the heat-conducting fibers in the fiber bundle on the surface of the stretchable substrate to obtain a dispersed fiber bundle;

[0030] The dispersed fiber bundle is placed in a mold, a matrix material is poured into the mold containing the dispersed fiber bundle, and the mold is demoulded after solidification and molding to obtain a fiber-oriented composite material.

[0031] In the present invention, unless otherwise specified, the raw materials used are commercially available products well known to those skilled in the art.

[0032] The present invention provides a fiber bundle, which is formed by multiple thermally conductive fibers with micron-sized diameters arranged in parallel along the axial direction of the fiber bundle. In the present invention, the fiber bundle is preferably cylindrical as a whole; the diameter of the fiber bundle is preferably 8-12 mm, more preferably 9-11 mm. A larger diameter may cause the thermally conductive fibers to become loose during subsequent processing, while a smaller diameter may result in low processing efficiency and may cause the thermally conductive fibers to bend and be damaged. The height of the fiber bundle is preferably 2-10 mm, more preferably 4-6 mm. The volume fraction of the thermally conductive fibers in the fiber bundle is preferably ≥60%, more preferably 60-65%.

[0033] In the present invention, the thermally conductive fibers preferably include carbon fibers, silicon nitride fibers, or alumina fibers. The carbon fibers preferably include mesophase pitch-based carbon fibers and / or polyacrylonitrile-based carbon fibers, more preferably one or more of XN-90 mesophase pitch-based carbon fibers, K13C6U mesophase pitch-based carbon fibers, and M65J polyacrylonitrile-based carbon fibers. In an embodiment of the present invention, the mesophase pitch-based carbon fibers used are specifically TC-HC-800 fibers. In the present invention, the diameter of the thermally conductive fibers is in the micron range, preferably 5 to 11 μm. The thermal conductivity of the thermally conductive fibers is preferably 100 to 500 W / (m·K). In the present invention, the thermally conductive fibers have a high aspect ratio and a micron-level diameter, which avoids the problem that nanomaterials have a large specific surface area and are difficult to obtain composite materials with high thermal conductive filler content, and also avoids the problem that the contact thermal resistance between nanomaterials affects the heat transfer efficiency of the composite materials. The present invention preferably uses the above-mentioned types of thermally conductive fibers, which have excellent axial thermal conductivity. For example, the thermal conductivity of carbon fibers with different microstructures can be varied from 1W / (m·K) to 1000W / (m·K). By controlling the directional arrangement of the thermally conductive fibers, composite materials can be prepared to obtain thermal interface materials or resin-based thermally conductive composite materials with different thermal conductivities.

[0034] In the present invention, the side wall of the fiber bundle preferably has a restraining band for fixing the thermal conductive fibers, that is, the thermal conductive fibers are bundled and fixed by the restraining band to form a fiber bundle; specifically, the preparation method of the fiber bundle preferably includes the following steps: using a restraining band to bundle thermal conductive fibers of a predetermined length and a predetermined number into a dense rod shape to obtain a rod-shaped aggregate; the rod-shaped aggregate is cut and polished in sequence to obtain a fiber bundle.

[0035] In the present invention, the length of the thermal conductive fiber is preferably 8 to 15 cm, more preferably 10 cm. In the present invention, the number of the thermal conductive fibers is calculated according to the formula shown in formula I:

[0036] n=(V1×S2) / S1 Formula I;

[0037] In formula I, n is the number of thermal conductive fibers in the fiber bundle, V1 is the volume fraction of the thermal conductive fibers in the fiber bundle, S1 is the cross-sectional area of ​​a single thermal conductive fiber in the fiber bundle, and S2 is the cross-sectional area of ​​the fiber bundle.

[0038] In the present invention, the restraining belt can specifically be an adhesive tape, and the width of the adhesive tape is preferably 1.5 to 2.5 cm, more preferably 2 cm. In the present invention, the thermal conductive fibers should be prevented from bending during the bundling process. In the present invention, the cutting is preferably performed by using a blade to cut the fiber bundle obtained after bundling into a number of cylinders with a height of 3 to 12 mm along the vertical axial direction. In the present invention, the polishing is preferably performed by using 100 to 800 mesh sandpaper to polish the upper and lower surfaces of the cylinder obtained after cutting until the upper and lower surfaces are smooth and flat, and finally a fiber bundle with a height of 2 to 10 mm is obtained.

[0039] After obtaining the fiber bundle, the present invention vertically adheres the fiber bundle to the surface of a stretchable substrate, stretches the stretchable substrate, and disperses the heat-conducting fibers in the fiber bundle on the surface of the stretchable substrate to obtain a dispersed fiber bundle. In the present invention, the surface of the heat-conducting fiber has a protective film. Taking the carbon fiber as an example, there is a protective film formed by a sizing agent on the surface of the carbon fiber. The protective film can prevent the carbon fiber from being worn, fuzzing, and other problems during transportation and storage. When the surface of the heat-conducting fiber has a protective film, the adhesion preferably further includes: removing the protective film on the surface of the heat-conducting fiber in the fiber bundle. In the present invention, the method for removing the protective film on the surface of the heat-conducting fiber is preferably to soak the fiber bundle in an organic solvent; the organic solvent is preferably acetone; the soaking is preferably carried out under stirring; the soaking can also preferably be assisted by ultrasound. When ultrasound is used, a rigid ring is preferably provided on the side wall of the fiber bundle. The inner diameter of the rigid ring is preferably equal to the diameter of the fiber bundle to avoid vibration of the fiber bundle. In the present invention, the organic solvent is preferably replaced every hour during the soaking process; the soaking time is based on the complete removal of the protective film. In the present invention, soaking the fiber bundle in an organic solvent not only removes the protective film on the fiber surface, but also cleans and removes debris remaining from the cutting and polishing processes. After soaking, the fiber bundle is preferably dried; the drying temperature is preferably 50°C and the drying time is preferably 30 minutes.

[0040] After removing the protective film on the surface of the heat-conducting fibers in the fiber bundle, the present invention vertically adheres the obtained fiber bundle to the surface of a stretchable substrate, stretches the stretchable substrate, and disperses the heat-conducting fibers in the fiber bundle on the surface of the stretchable substrate to obtain a dispersed fiber bundle. In the present invention, the stretchable substrate preferably includes a rubber film or an extensible sponge; the stretching ratio of the stretchable substrate is preferably ≥10 times; the stretching ratio is specifically the area growth ratio after stretching. The present invention preferably uses an adhesive to adhere the fiber bundle to the surface of the stretchable substrate, specifically by atomizing and spraying the adhesive on the surface of the stretchable substrate, and then vertically placing the fiber bundle on the surface of the stretchable substrate coated with the adhesive to bond the two together; the specific type of the adhesive is preferably a spray-type quick-drying glue, and the adhesive preferably does not undergo an obvious curing reaction within 20 minutes to ensure that it does not affect the stretching properties of the stretchable substrate.

[0041] In the present invention, when the side wall of the fiber bundle has a restraining band for fixing the thermally conductive fiber, the stretching preferably further includes: removing the restraining band on the side wall of the fiber bundle. In the present invention, the stretching is preferably mechanical stretching; the stretching rate is preferably 3 to 5 mm / min, more preferably 4 to 5 mm / min. In the present invention, the stretching ratio is preferably determined according to the volume fraction of the thermally conductive fibers in the final fiber-oriented composite material (denoted as the target volume fraction) before stretching, and the stretching is based on satisfying the stretching ratio. Specifically, the volume fraction of the thermally conductive fibers in the fiber bundle / stretching ratio = target volume fraction. In the present invention, the stretching method preferably includes annular stretching or unidirectional stretching; the annular stretching is specifically stretching in the same proportion in all directions within the plane; the unidirectional stretching is specifically stretching in a single direction under the condition of fixing the size in a certain direction. The principle of the present invention is to first prepare a fiber bundle with a high thermal conductivity fiber volume fraction, adhere the fiber bundle to the surface of a stretchable substrate, and under the action of stretching, the deformation of the stretchable substrate drives the thermal conductive fibers in the fiber bundle to disperse without destroying the orientation of the thermal conductive fibers. Subsequently, through operations such as pouring the matrix material and curing and molding, a fiber-oriented composite material can be obtained.

[0042] After obtaining the dispersed fiber bundles, the present invention places the dispersed fiber bundles in a mold, pours the matrix material into the mold containing the dispersed fiber bundles, and demolds after curing and molding to obtain a fiber-oriented composite material. The present invention preferably places a mold around the dispersed fiber bundles on its surface while keeping the stretchable substrate in an elongated state, and then pours the matrix material along the edge of the mold until all the dispersed fiber bundles are immersed in the matrix material, and then performs curing and molding, and obtains a fiber-oriented composite material after demolding. In the present invention, the matrix material preferably includes a thermosetting resin or rubber; the thermosetting resin preferably includes an epoxy resin, a phenolic resin, an unsaturated polyester resin or a bismaleimide resin; the rubber preferably includes natural rubber or silicone rubber. In an embodiment of the present invention, the silicone rubber specifically uses polydimethylsiloxane (PDMS).

[0043] In the present invention, the curing molding includes standing, evacuating bubbles and curing in sequence. In the present invention, the standing time is preferably 15 minutes, and the purpose of the standing is to provide sufficient time for the bubbles to be eliminated. In the present invention, after the standing, the mold containing the dispersed fiber bundle and the matrix material is preferably placed in a vacuum oven as a whole for evacuating bubbles and curing; the evacuation of bubbles is preferably carried out under -0.05MPa and -0.1MPa conditions for 15 minutes respectively to eliminate bubbles in the system; the specific conditions of the curing are preferably selected according to the type of the matrix material. Specifically, when the thermosetting resin is an epoxy resin, the curing conditions of the epoxy resin preferably include: pre-curing at 80°C for 30 minutes, then heating to 120°C and further curing for 2 hours; when the rubber is polydimethylsiloxane, the curing conditions of the polydimethylsiloxane preferably include: pre-curing at 60°C for 1 hour, then heating to 100°C and further curing for 1 hour.

[0044] In the present invention, after demoulding, the material surface is preferably polished to directly obtain a fiber-oriented composite material with a height of 2 to 10 mm; if a fiber-oriented composite material with a height of 0.5 to 2 mm is required, it is preferably processed to the required thickness by mechanical processing methods, and the present invention has no special restrictions on this.

[0045] Figure 1 The flow chart of the preparation of fiber-oriented composite materials in the present invention is as follows: for example, a rubber film is used as a stretchable substrate, and dispersed fiber bundles are prepared by a circular stretching method, and then an epoxy resin is used as a matrix material to prepare a fiber-oriented composite material; another example is using an extensible sponge as a stretchable substrate, and dispersed fiber bundles are prepared by a unidirectional stretching method, and then a fiber-oriented composite material is prepared by using silicone rubber as a matrix material.

[0046] The present invention provides a fiber-oriented composite material prepared by the preparation method described in the above technical solution, comprising a matrix and a fiber reinforcement dispersed in the matrix. The fiber reinforcement is formed by a plurality of thermally conductive fibers with micron-sized diameters aligned outward from the plane of the fiber-oriented composite material. The volume fraction of the thermally conductive fibers in the fiber-oriented composite material is 10 to 50%, preferably 11 to 32%, more preferably 13 to 25%, and even more preferably 18 to 20%. In the present invention, the thermally conductive fibers in the fiber-oriented composite material are uniformly distributed, and the fiber-oriented composite material as a whole has no obvious pore defects. The height can be controlled within the range of 0.5 to 10 mm through pre-treatment or post-processing as needed. According to the present invention, the thermal conductivity of the fiber-oriented composite material can be controlled within the range of 1 to 200 W / (m·K), specifically 15 to 191 W / (m·K), or even 39 to 102 W / (m·K), depending on the types of thermally conductive fibers and matrix materials selected, as well as the volume fraction of the thermally conductive fibers. Specifically, considering that the thermal conductivity of the matrix is ​​extremely low, the matrix thermal conductivity is ignored, and the fiber type and fiber volume fraction are selected and estimated according to the law of mixing. That is, the thermal conductivity of the final fiber-oriented composite material is approximately equal to the fiber thermal conductivity multiplied by the volume fraction of the thermally conductive fibers.

[0047] The present invention provides the use of the fiber-oriented composite material described in the above technical solution in the preparation of a thermally conductive gasket or a shielding box shell of an electronic device.

[0048] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0049] In the present invention, the thermal conductivity of each composite material is measured according to ASTM D5470, a standard test method for thermal conductivity of thermally conductive electrical insulating materials.

[0050] The TC-HC-800 fibers used in the following examples were provided by Shaanxi Tiance New Materials Technology Co., Ltd.

[0051] PDMS was purchased from Dow Corning, USA;

[0052] Epoxy resin was purchased from Nantong Xingchen Synthetic Materials Co., Ltd.

[0053] The stretchable sponge is a common commercially available compressed sponge;

[0054] The rubber membrane was purchased from Changzhou Baling Future Intelligent Technology Co., Ltd.

[0055] Example 1

[0056] In this embodiment, mesophase pitch-based carbon fibers (TC-HC-800 fibers, 11 μm in diameter) and silicone rubber PDMS (polydimethylsiloxane) are used to prepare a composite material (denoted as TC-HC-800 fiber / PDMS thermal conductive composite material) in the following steps:

[0057] The carbon fibers were cut into 10 cm long fibers, and the required number of fibers was calculated according to formula I, and then stacked in parallel; all the fibers were bundled into dense rods using a 2 cm wide tape, and the fibers were prevented from bending during the bundling process to obtain a rod-shaped aggregate with a diameter of 10 mm (such as Figure 2 shown);

[0058] The rod-shaped aggregate was cut into several 6 mm high cylinders along the vertical axial direction using a blade, and then the upper and lower surfaces were polished with 100-800 grit sandpaper until the upper and lower surfaces were smooth and flat, obtaining a fiber bundle with a height of 4 mm and a fiber volume fraction of about 65%, in which the fibers were arranged parallel to the axial direction (such as Figure 2 shown);

[0059] A rigid ring is provided on the side wall of the fiber bundle, and the inner diameter of the rigid ring is equal to the diameter of the fiber bundle. The fiber bundle is then immersed in acetone, mechanically stirred and assisted by ultrasound. The acetone is replaced once every 1 hour during the immersion process until the sizing agent on the fiber surface of the fiber bundle is completely removed. The fiber bundle is then dried in an oven at 50° C. for 30 minutes to obtain a pretreated fiber bundle.

[0060] An extensible sponge was used as a substrate, and an adhesive (spray-type quick-drying adhesive) was sprayed on the surface of the substrate in an atomized manner. Then, the pretreated fiber bundle was placed vertically on the surface of the substrate coated with the adhesive to bond the two together. After that, the rigid ring and the tape on the side wall of the pretreated fiber bundle were removed, and the substrate was mechanically stretched. The mechanical stretching method was unidirectional stretching, the stretching ratio was 2 times (that is, the area stretching of the substrate increased by 2 times), and the stretching rate was 5 mm / min to obtain a dispersed fiber bundle (such as Figure 3 shown);

[0061] The substrate was kept in an elongated state, a mold was placed around the dispersed fiber bundles on the surface of the substrate, and then PDMS was poured along the edge of the mold until all the dispersed fiber bundles were immersed in the PDMS. After standing for 15 minutes, the mold containing the dispersed fiber bundles and PDMS was placed in a vacuum oven and treated at -0.05 MPa and -0.1 MPa for 15 minutes respectively to eliminate bubbles in the system. After that, it was heated and cured according to the curing system of the PDMS (specifically, pre-curing at 60°C for 1 hour, and then heating to 120°C for further curing for 1 hour). After demolding, the surface of the obtained cured molding material was polished to obtain a composite material with a thickness of 4 mm, a fiber volume fraction of approximately 31.8%, and a thermal conductivity of 190.9 W / (m·K).

[0062] Example 2

[0063] A composite material was prepared according to the method of Example 1, except that the draft ratio of the extensible sponge was 8 times; the side view of the dispersed fiber bundle obtained after drafting is as shown in FIG. Figure 4 As shown, the fibers are well oriented; the actual picture of the dispersed fiber bundles obtained after drawing is as shown in Figure 3 As shown; the final composite material with a thickness of 4 mm, a fiber volume fraction of about 8.2%, and a thermal conductivity of 42.0 W / (m·K) was obtained.

[0064] Example 3

[0065] A composite material was prepared according to the method of Example 1, except that a rubber film was used as the substrate, the draft ratio of the rubber film was 4 times, the mechanical drafting method was circular drafting, and the matrix material was epoxy resin. The curing conditions were as follows: after keeping the temperature at 80°C for 30 minutes, the temperature was raised to 120°C and cured for 2 hours; the actual picture of the dispersed fiber bundle obtained after drafting is shown in FIG. Figure 5 As shown; the final composite material with a thickness of 4 mm, a fiber volume fraction of about 16.5%, and a thermal conductivity of 102.0 W / (m·K) was obtained.

[0066] Example 4

[0067] A composite material was prepared according to the method of Example 1, except that a rubber film was used as the substrate, the draft ratio of the rubber film was 8 times, the mechanical drafting method was circular drafting, and the matrix material was epoxy resin. The curing conditions were pre-curing at 80°C for 30 minutes, and then heating to 120°C for further curing for 2 hours. The actual picture of the dispersed fiber bundle obtained after drafting is shown in FIG. Figure 5 As shown; the final composite material with a thickness of 4 mm, a fiber volume fraction of about 8.2%, and a thermal conductivity of 39.2 W / (m·K) was obtained.

[0068] Example 5

[0069] A composite material was prepared according to the method of Example 1, except that the carbon fibers were replaced with silicon nitride fibers, the height of the fiber bundle was 4 mm, and the fiber volume fraction was approximately 68%. The resulting composite material had a thickness of 4 mm, a fiber volume fraction of approximately 34.2%, and a thermal conductivity of 15.5 W / (m·K).

[0070] Test Case

[0071] The composite materials prepared in Examples 1 to 4 were placed on a hot stage with their lower surfaces in contact with the hot stage. An infrared thermal imager was used to observe the temperature variation of the upper surface over time and compare it with silicone rubber and epoxy resin. Figure 6 The thermal conductivity test results of the composite materials prepared in Examples 1 to 4, as well as silicone rubber and epoxy resin are shown in Table 1. Figure 6 As shown in Table 1, the temperature change rates of the composite materials prepared in Examples 1 to 4 are faster than those of the epoxy resin and silicone rubber without thermal conductive fiber reinforcement, and the final equilibrium temperature is higher, which indicates that the orientation of the thermal conductive fibers significantly enhances the thermal conductivity.

[0072] Table 1 Temperature variation data of Examples 1 to 4 and pure silicone rubber and epoxy resin

[0073]

[0074]

[0075] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a fiber-oriented composite material, comprising the following steps: A fiber bundle is provided, wherein the fiber bundle is formed by arranging a plurality of heat-conducting fibers with a diameter of micrometers in parallel along the axis of the fiber bundle; the diameter of the heat-conducting fibers is 5 to 11 μm; the height of the fiber bundle is 2 to 10 mm; the volume fraction of the heat-conducting fibers in the fiber bundle is 60 to 65%; and the heat-conducting fibers are carbon fibers; The fiber bundle is vertically adhered to the surface of a stretchable substrate, and the stretchable substrate is stretched to disperse the heat-conducting fibers in the fiber bundle on the surface of the stretchable substrate to obtain a dispersed fiber bundle; the stretching method is annular stretching, and the stretching rate is 3 to 5 mm / min; The dispersed fiber bundle is placed in a mold, a matrix material is poured into the mold containing the dispersed fiber bundle, and the mold is demoulded after curing and molding to obtain a fiber-oriented composite material; the matrix material is epoxy resin; the volume fraction of the thermal conductive fiber in the fiber-oriented composite material is 13-25%.

2. The preparation method according to claim 1, characterized in that The fiber bundle is cylindrical as a whole, and the diameter of the fiber bundle is 8 to 12 mm.

3. The preparation method according to claim 1, characterized in that The surface of the heat-conducting fiber is provided with a protective film; and before the adhering, the method further comprises: removing the protective film on the surface of the heat-conducting fiber in the fiber bundle.

4. The preparation method according to claim 1, characterized in that The stretchable substrate includes a rubber film or an stretchable sponge.

5. The preparation method according to claim 1, characterized in that The drafting is mechanical drafting.

6. The preparation method according to claim 1 or 5, characterized in that The side wall of the fiber bundle has a restraining band for fixing the heat-conducting fiber; and before the stretching, the method further includes: removing the restraining band on the side wall of the fiber bundle.

7. The fiber-oriented composite material prepared by the preparation method according to any one of claims 1 to 6 comprises a matrix and a fiber reinforcement dispersed in the matrix, wherein the fiber reinforcement is formed by a plurality of thermally conductive fibers with a diameter of micrometers being oriented along the out-of-plane direction of the fiber-oriented composite material; the volume fraction of the thermally conductive fibers in the fiber-oriented composite material is 13 to 25%.

8. Use of the fiber-oriented composite material according to claim 7 in the preparation of thermal conductive gaskets or shielding box shells for electronic devices.

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