Preparation method of flexible pin and preparation method of Z-pin reinforced composite material

Abstract

The invention belongs to the technical field of Z-pin reinforced composite materials, and particularly relates to a preparation method of a flexible pin and a preparation method of a Z-pin reinforced composite material. The method comprises the following steps: firstly, preparing a pre-impregnated blank according to a designed layering mode, heating the pre-impregnated blank to a proper temperature, driving a needle head with a proper outer diameter to vertically pierce into a laminated plate on the pre-impregnated blank by adopting a fixed mold to generate prefabricated holes, and implanting the prepared flexible pins into the prefabricated holes one by one until the flexible pins are completely implanted; the needle head with the appropriate diameter can reduce damage to in-plane fibers as much as possible, meanwhile, the fixed mold assists the needle head to be inserted into the pre-impregnated blank to ensure that the flexible Pin needle can be vertically implanted into the pre-impregnated blank, then the Z-pin and the pre-impregnated blank are co-cured, the influence of buckling deformation and the like of the in-plane fibers when the pin needle is implanted is reduced, and the comprehensive heat conduction performance of the composite material is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of Z-pin reinforced composite materials, and in particular relates to a method for preparing a flexible pin needle and a method for preparing a Z-pin reinforced composite material. Background Art

[0002] Carbon fiber reinforced resin-based composites have excellent properties such as light weight, high strength, and strong designability. They have been widely used in many fields such as aerospace, electronic devices, etc. However, the heat generated by electronic devices during operation will seriously reduce the working efficiency and service life of the equipment; heat conduction in carbon fiber reinforced resin-based composites mainly occurs along the fiber direction. The traditional laminated carbon fiber reinforced resin-based composites lack a continuous heat conduction path in the thickness direction, which results in the thermal conductivity in the thickness direction being much lower than that in the surface.

[0003] At present, scholars have studied a variety of technologies to improve the thermal conductivity of carbon fiber reinforced resin-based composites in the thickness direction, including fiber surface modification, 3D weaving, hybridization, Z-pin reinforcement technology, etc. Among them, the Z-pin reinforcement technology borrows the method of discontinuous suturing, inserts the pin needle into the uncured prepreg along the thickness direction for curing and molding, and then constructs a continuous thermal conductive path in the thickness direction. At present, the preparation of Z-pin reinforced composites is mainly through pultrusion to prepare impregnated fiber bundles, which will cause relatively serious damage to the high thermal conductivity intermediate phase asphalt-based carbon fibers, which is not conducive to the high thermal conductivity.

[0004] Therefore, how to prepare Z-pins with a certain fiber volume fraction and prepare thickness-enhanced thermally conductive composite materials without damaging the fibers as much as possible has become an urgent problem to be solved by technicians in this field. Summary of the invention

[0005] In view of this, the present invention provides a method for preparing a flexible pin needle and a method for preparing a Z-pin reinforced composite material. During the preparation of the Z-pin reinforced composite material according to the preparation method provided by the present invention, no damage will be caused to the fiber, which is beneficial to improving the thermal conductivity of the composite material.

[0006] In order to solve the above technical problems, the present invention provides a method for preparing a flexible pin needle, comprising the following steps:

[0007] Measure the single layer thickness of the prepreg used to prepare the flexible pin needle, recorded as h;

[0008] Calculate the radius R of the flexible pin according to formula 1:

[0009]

[0010] Among them, V pis the volume ratio of the total volume of the flexible pin needles to be implanted to the volume of the prepreg blank, S is the upper surface area of ​​the prepreg blank into which the flexible pin needles are to be implanted, and N is the number of flexible pin needles to be implanted in the area where the flexible pin needles are to be implanted;

[0011] The width L of the prepreg for preparing the flexible pin is calculated according to Formula 2:

[0012]

[0013] The prepreg with a width of L is cut along the direction perpendicular to the fiber, and rolled along the direction perpendicular to the fiber to form a flexible pin.

[0014] Preferably, the fibers in the prepreg for preparing the flexible pin needle are mesophase pitch-based carbon fibers.

[0015] Preferably, the length of the flexible pin needle is 5 to 10 cm, and the length of the prepreg material for preparing the flexible pin needle along the fiber direction is greater than or equal to the length of the flexible pin needle.

[0016] The present invention also provides a method for preparing a Z-pin reinforced composite material, comprising the following steps:

[0017] After preheating the prepreg blank, a prefabricated hole is formed by using a hole-forming component; the hole-forming component includes a needle tube 1 and a fixed mold 2 mounted outside the needle tube; one end of the needle tube has a needle head capable of piercing the prepreg blank; the needle tube 1 is slidably connected to the fixed mold 2, and the height of the needle tube 1 is greater than the height of the fixed mold 2;

[0018] Implanting the flexible pin needle prepared by the preparation method described in the above technical solution into the prefabricated hole;

[0019] The steps of forming prefabricated holes and implanting flexible pins are repeated and then cured to obtain a Z-pin reinforced composite material.

[0020] Preferably, the hole-forming component further comprises a limiting ring 3 fixed to the outside of the needle tube; the limiting ring 3 is located above the fixed mold 2 .

[0021] Preferably, the outer diameter d of the needle o and the diameter d of the flexible pin Pin Satisfaction:d Pin <d o ≤1.2d Pin .

[0022] Preferably, before forming the prefabricated holes by using the hole-forming component, the method further includes arranging a foam layer at the bottom of the prepreg blank.

[0023] Preferably, the distance X between the lower end of the limiting ring (3) and the needle is calculated according to Formula 3:

[0024] X=h m +h p +h f +h a Formula 3;

[0025] Among them, h m is the height of the fixed mold (2), h p is the thickness of the prepreg, h f is the thickness of the foam layer, h a is the total thickness of auxiliary materials.

[0026] Preferably, the curing is pressurized curing.

[0027] Preferably, the fibers in the prepreg are mesophase pitch-based carbon fibers.

[0028] Compared with the prior art, the present invention has achieved the following technical effects: the method for preparing a flexible pin needle of the present invention is convenient and quick to operate, and only needs to cut the prepreg of the required width and manually roll it, and the size of the flexible pin needle can be controlled by adjusting the width of the cut prepreg; at the same time, the fibers in the prepreg are arranged in parallel along the same direction, avoiding the problem of local fiber orientation difference caused by fiber twisting in the process of preparing pin needles using bundled wires, and is more conducive to exerting the axial thermal conductivity of the pin needle; in addition, the method can minimize the damage to the intermediate phase asphalt-based carbon fiber that is easy to break, retain the high thermal conductivity of the fiber, and at the same time, the prepreg resin is lightly cross-linked, and the flexible pin needle has a certain deformation ability. Therefore, compared with the rigid Pin needle, it is easier to control the size of the fisheye area during the molding process, reduce the defects in the laminate (Z-pin reinforced composite material), and the laminate density is better.

[0029] The present invention also provides a method for preparing a Z-pin reinforced composite material. First, a prepreg is prepared according to a designed layering method, the prepreg is heated to an appropriate temperature, a fixed mold is used to drive a needle with a suitable outer diameter to vertically penetrate the laminate on the prepreg, that is, a prefabricated hole is generated, and the prepared flexible pin needles are implanted into the prefabricated holes one by one until the implantation is completed. The needle with a suitable diameter can minimize the damage to the fibers on the surface. At the same time, the fixed mold assists the needle to be inserted into the prepreg to ensure that the flexible pin needle can be vertically implanted into the prepreg. Then the Z-pin and the prepreg are co-cured to reduce the influence of the pin needle implantation on the bending deformation of the fibers on the surface, thereby improving the comprehensive thermal conductivity of the composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic diagram of forming a flexible pin by rolling prepreg;

[0031] Figure 2Schematic diagram of the prepared flexible pin;

[0032] Figure 3 Schematic diagram of the structure of the hole-forming component, wherein 1 is a needle tube, 2 is a fixed mold, and 3 is a limiting ring;

[0033] Figure 4 It is a structural schematic diagram of a fixed mold;

[0034] Figure 5 Schematic diagram of forming prefabricated holes and implanting flexible pins. From left to right, the four steps are needle insertion into prepreg, prefabricated hole formation, flexible pin implantation, and flexible pin trimming. 1 is the needle, 2 is the fixed mold, 3 is the limiting ring, 4 is the prepreg, 5 is the foam layer, and 6 is the flexible pin.

[0035] Figure 6 The thermal infrared imaging images of the upper and lower surfaces at the same time when the same power heating sheets are placed on the lower surfaces of the thermal conductive materials prepared in Comparative Example 1 and Example 1, respectively, wherein the left one is the thermal infrared imaging image of Comparative Example 1, and the right one is the thermal infrared imaging image of Example 1;

[0036] Figure 7 This is a cross-sectional metallographic image of the Z-pin reinforced PMI foam sandwich unidirectional laminate composite material prepared in Example 4. DETAILED DESCRIPTION

[0037] The present invention provides a method for preparing a flexible pin, comprising the following steps:

[0038] Measure the single layer thickness of the prepreg used to prepare the flexible pin needle, recorded as h;

[0039] Calculate the radius R of the flexible pin according to formula 1:

[0040]

[0041] Among them, V p is the volume ratio of the total volume of the flexible pin needles to be implanted to the volume of the prepreg blank, S is the upper surface area of ​​the prepreg blank into which the flexible pin needles are to be implanted, and N is the number of flexible pin needles to be implanted in the area where the flexible pin needles are to be implanted;

[0042] The width L of the prepreg for preparing the flexible pin is calculated according to Formula 2:

[0043]

[0044] The prepreg with a width of L is cut along the direction perpendicular to the fiber, and rolled along the direction perpendicular to the fiber to form a flexible pin.

[0045] As a specific embodiment of the present invention, the fiber in the prepreg for preparing a flexible pin needle can be an intermediate phase asphalt-based carbon fiber; the length of the flexible pin needle can be 5 to 10 cm, specifically 6 cm, 7 cm, 8 cm or 9 cm; the length of the prepreg for preparing a flexible pin needle along the fiber direction is greater than or equal to the length of the flexible pin needle.

[0046] Figure 1 A schematic diagram of forming a flexible pin by rolling prepreg; Figure 2 Schematic diagram of the prepared flexible pin needle.

[0047] The present invention also provides a method for preparing a Z-pin reinforced composite material, comprising the following steps:

[0048] After preheating the prepreg blank, a prefabricated hole is formed by using a hole-forming component; the hole-forming component includes a needle tube 1 and a fixed mold 2 mounted outside the needle tube; one end of the needle tube has a needle head capable of piercing the prepreg blank; the needle tube 1 is slidably connected to the fixed mold 2, and the height of the needle tube 1 is greater than the height of the fixed mold 2;

[0049] Implanting the flexible pin needle prepared by the preparation method described in the above technical solution into the prefabricated hole;

[0050] The steps of forming prefabricated holes and implanting flexible pins are repeated and then cured to obtain a Z-pin reinforced composite material.

[0051] The present invention has no special requirements for the prepreg, and the prepreg can be obtained by laying it in a conventional laying method in the art; in order to fill the fisheye area formed by the implantation of the pin needle, each time a layer of prepreg is laid, a layer of resin film (the composition corresponds to the resin used in the prepreg) can be laid on its upper surface. If the density of the laminate is to be further reduced, PMI foam or asphalt-based carbon foam can also be used as an interlayer. As a specific embodiment of the present invention, the fiber in the prepreg can be a mesophase asphalt-based carbon fiber.

[0052] The present invention has no special requirements for the preheating temperature, as long as the prepreg can remain soft and facilitate the implantation of the flexible pin. As a specific embodiment of the present invention, the preheating temperature can be 40-50°C, specifically 40°C, 45°C or 50°C.

[0053] As a specific embodiment of the present invention, the hole-forming component may further include a limiting ring 3 fixed to the outside of the needle tube; the limiting ring 3 is located above the fixed mold 2; the fixed mold 2 is located between the needle head and the limiting ring 3. As a specific embodiment of the present invention, the limiting ring 3 is detachably connected to the needle tube 1 and the connection position between the two can be adjusted; the pillow in the needle tube 1 is beveled; the needle head formed by the beveled treatment can reduce the movement resistance of the needle tube 1, thereby allowing the needle tube 1 to be smoothly implanted into the prepreg blank. As a specific embodiment of the present invention, the fixed mold 2 is a hollow cylindrical shape; the fixed mold is made of a transparent material. In order to ensure that the needle tube 1 does not tilt at an angle during the insertion of the prepreg blank, which causes the implantation angle of the flexible Pin needle 6 to change, the inner diameter of the fixed mold 2 should be slightly larger than the outer diameter d of the needle tube 1. o If there is a large gap, tape can be used to wrap the needle tube 1 to achieve an approximate match.

[0054] In the present invention, the setting of the limiting ring 3 is convenient for positioning the depth of the needle inserted into the prepreg, so as to ensure that the preformed hole penetrates the prepreg body. When the limiting ring 3 abuts against the fixed mold 2, it means that the needle insertion reaches the predetermined position; the limiting ring 3 is detachably connected to the needle tube 1 and the connection position of the two can be adjusted. The position of the limiting ring 3 is changed according to the different prepregs, which improves the flexibility and adaptability of the hole-forming component. In the present invention, the fixed mold 2 abuts against the prepreg, which can limit the movement direction of the needle tube 1, thereby improving the accuracy of the implantation of the flexible pin needle. The cylindrical fixed mold 2 abuts against the prepreg, so that the needle tube 1 can be inserted into the prepreg in a direction perpendicular to the prepreg, avoiding the needle tube 1 from tilting during the insertion process of the prepreg and affecting the implantation angle of the flexible Pin needle; in addition, the fixed mold 2 is made of a transparent material, which is convenient for observing the working process of the needle tube 1 and provides convenience for the operator; the fixed mold 2 can keep the needle inserted vertically into the prepreg body to ensure that the preformed hole remains vertical, so that the flexible pin needle is vertically implanted into the prepreg. Figure 3 It is a schematic diagram of the structure of the hole-forming component, wherein 1 is a needle tube, 2 is a fixed mold, and 3 is a limiting ring. Figure 4 It is a schematic diagram of the structure of the fixed mold.

[0055] As a specific embodiment of the present invention, the outer diameter d of the needle o and the diameter d of the flexible pin Pin Can satisfy:d Pin <d o ≤1.2d Pin .

[0056] As a specific embodiment of the present invention, before forming the prefabricated hole using the hole-forming component, a foam layer may be provided at the bottom of the prepreg. The foam layer provided at the bottom of the prepreg can ensure that the prepreg is completely penetrated in the thickness direction. As a specific embodiment of the present invention, the distance X between the lower end of the limiting ring 3 and the needle head can be calculated according to Formula 3:

[0057] X=h m +h p +h f +h a Formula 3;

[0058] Among them, h m is the height of the fixed mold 2, h p is the thickness of the prepreg, h f is the thickness of the foam layer, h a is the total thickness of the auxiliary material; the auxiliary material may be coordinate paper.

[0059] As a specific implementation of the present invention, the curing may be pressurized curing. The present invention has no special requirements on the condition parameters of the pressurized curing, and conventional methods in the art may be used.

[0060] As a specific implementation of the present invention, after curing, sandpaper can be used to remove the foam layer on the lower surface of the composite material.

[0061] Figure 5 Schematic diagram of forming a prefabricated hole and implanting a flexible pin needle, wherein 1 is a needle head, 2 is a fixed mold, 3 is a limiting ring, 4 is a prepreg blank, 5 is a foam layer, and 6 is a flexible pin needle.

[0062] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0063] Example 1

[0064] Preparation of flexible pin needle volume fraction V p The Z-pin reinforced thermal conductive composite material is 13.85% (the upper surface area S of the reinforced thermal conductive composite material is 100cm 2 ), the specific steps are as follows:

[0065] a. The thickness of the unidirectional mesophase pitch-based carbon fiber prepreg TPC60 was measured multiple times and the average value was calculated. The average thickness h was 0.17 mm;

[0066] b. According to the size of the implant area and the implant spacing of 3.3 mm, the number of flexible pin needles to be implanted is calculated to be 900. According to formula 1, the radius of the flexible pin needle is 0.7 mm and the diameter is 1.4 mm;

[0067] c. According to formula 2, the required prepreg width L along the vertical fiber direction is 9 mm;

[0068] d. Cut a 9mm wide prepreg along the vertical fiber direction and a 5cm long prepreg along the fiber direction, heat and soften it on a hot plate at 40℃, and manually roll it into a flexible pin;

[0069] e. Use mesophase asphalt based carbon fiber prepreg according to [0 / 90] 12 The prepreg is laid on the mold in a manner of paving. After each layer of prepreg is laid, a layer of resin film is laid on the upper surface to make a prepreg blank with a thickness of about 3mm. The Z-pin reinforced laminate structure drawing is drawn according to the required implantation density. The drawing is fixed on the prepreg blank with porous PTFE cloth on the upper and lower surfaces to assist in positioning. In order to ensure a completely penetrating heat conduction path in the thickness direction, a 1mm thick PMI foam layer is laid on the lower surface of the blank;

[0070] f. Due to the diameter d of the flexible pin Pin 1.4mm, choose a 17G needle (17G corresponds to the outer diameter d o 1.48mm) to meet d Pin <d o ≤1.2d Pin ; The corresponding material is PMMA organic glass, and the fixed mold with an inner diameter of 1.5 mm is selected. After calculating X according to formula 3, mark it on the needle tube, wrap it with wide tape, and the wide tape covers the mark to play an approximate matching role. Wrap it with fine tape, and the fine tape is located above the mark to play a limiting role. The prepreg is placed on a 45°C hot table for preheating. The fixed mold is used to drive the needle to vertically penetrate the laminate on the prepreg to generate a prefabricated hole;

[0071] g. Implant the prepared flexible pin into the prefabricated hole and trim the flexible pin that protrudes beyond the surface of the prepreg blank with flat-nose pliers.

[0072] h. Repeat steps f and g until the designed structure is implanted, peel off the drawing on the surface of the prepreg, pressurize and cure the prepreg with the flexible pin needle implanted, and then use 800-grit sandpaper to polish and remove the foam layer on the lower surface of the composite material to obtain a Z-pin reinforced composite material.

[0073] Example 2

[0074] The Z-pin reinforced composite material was prepared according to the method of Example 1, except that the volume fraction of the flexible pin needle in the Z-pin reinforced thermal conductive composite material is V p The upper surface area S of the enhanced thermal conductive composite material is 100 cm 2 , the specific steps are as follows:

[0075] a. The average thickness of the unidirectional mesophase pitch-based carbon fiber prepreg TPC60 was calculated by measuring the thickness multiple times, and the average thickness h was 0.17 mm;

[0076] b. According to the size of the implant area and the implant spacing of 3.3 mm, the number of flexible pin needles to be implanted is calculated to be 900. According to Formula 1, the radius of the flexible pin needle is 0.5 mm and the diameter is 1 mm;

[0077] c. According to formula 2, the required prepreg width L along the vertical fiber direction is 4.6 mm;

[0078] d. Cut a prepreg with a width of 4.6 mm and a length of 5 cm along the fiber direction in the prepreg, heat and soften it on a hot plate at 40°C, and roll it into a flexible pin manually;

[0079] e. Use mesophase asphalt based carbon fiber prepreg according to [0 / 90] 12 The prepreg is laid on the mold in a manner of paving. After each layer of prepreg is laid, a layer of resin film is laid on the upper surface to make a prepreg blank with a thickness of about 3mm. The Z-pin reinforced laminate structure drawing is drawn according to the required implantation density. The drawing is fixed on the prepreg blank with porous PTFE cloth on the upper and lower surfaces to assist in positioning. In order to ensure a completely penetrating heat conduction path in the thickness direction, a 1mm thick PMI foam layer is laid on the lower surface of the blank;

[0080] f. Due to the diameter d of the flexible pin Pin 1mm, choose a 19G needle (19G corresponds to an outer diameter d o 1.06mm) to meet d Pin <d o ≤1.2d Pin , the corresponding material is PMMA organic glass, the inner diameter of the fixed mold is 1.1mm, after calculating X according to formula 3, mark it on the needle tube, wrap it with wide tape, the wide tape covers the mark to play an approximate matching role, wrap it with fine tape, the fine tape is located above the mark to play a limiting role, place the prepreg on a 45℃ hot table for preheating, use the fixed mold to drive the needle to vertically penetrate the laminate on the prepreg to generate a prefabricated hole;

[0081] g. The prepared flexible pin needle is implanted into the preformed hole, and the flexible pin needle that exceeds the surface of the prepreg blank is trimmed with flat-nose pliers;

[0082] h. Repeat steps f and g until the designed structure is implanted, peel off the drawing on the surface of the prepreg, pressurize and cure the prepreg with the flexible pin needle implanted, and then use 800-grit sandpaper to polish and remove the foam on the lower surface of the composite material to obtain a Z-pin reinforced composite material.

[0083] Example 3

[0084] The Z-pin reinforced composite material was prepared according to the method of Example 1, except that a 0.5 mm thick PMI foam was used as an interlayer in the prepreg. 2s The prepregs of orthogonal symmetrical plies are used as upper and lower panels, and the upper surface area S of the enhanced thermal conductive composite material is 100cm 2 , the specific steps are as follows:

[0085] a. The average thickness of the unidirectional mesophase pitch-based carbon fiber prepreg TPC60 was calculated by measuring the thickness multiple times, and the average thickness h was 0.17 mm;

[0086] b. According to the size of the implant area and the implant spacing of 3.3 mm, the number of flexible pin needles to be implanted is calculated to be 900. According to formula 1, the radius of the flexible pin needle is 0.7 mm and the diameter is 1.4 mm;

[0087] c. According to formula 2, the required prepreg width L along the vertical fiber direction is 9 mm;

[0088] d. Cut a 9mm wide prepreg along the vertical fiber direction and a 5cm long prepreg along the fiber direction, heat and soften it on a hot plate at 40℃, and manually roll it into a flexible pin;

[0089] e. Use mesophase asphalt based carbon fiber prepreg according to [0 / 90] 2s The upper and lower panels as the layer board are laid on the mold in a manner. After each layer of prepreg is laid, a layer of resin film is laid on the upper surface. A 0.5mm thick PMI foam is used as an interlayer to make a prepreg blank with a thickness of about 2.5mm. The Z-pin reinforced laminate structure drawing is drawn according to the required implantation density. The drawing is fixed on the prepreg blank with porous PTFE cloth on the upper and lower surfaces to assist in positioning. In order to ensure a completely penetrating heat conduction path in the thickness direction, a 1mm thick PMI foam layer is laid on the lower surface of the blank;

[0090] f. Due to the diameter d of the flexible pin Pin 1.4mm, choose a 17G needle (17G corresponds to the outer diameter d o1.48mm) to meet d Pin <d o ≤1.2d Pin ; The corresponding material is PMMA organic glass, and the fixed mold with an inner diameter of 1.5 mm is selected. After calculating X according to formula 3, mark it on the needle tube, wrap it with wide tape, and the wide tape covers the mark to play an approximate matching role. Wrap it with fine tape, and the fine tape is located above the mark to play a limiting role. The prepreg is placed on a 45°C hot table for preheating. The fixed mold is used to drive the needle to vertically penetrate the laminate on the prepreg to generate a prefabricated hole;

[0091] g. Implant the prepared flexible pin into the prefabricated hole and trim the flexible pin that protrudes beyond the surface of the prepreg blank with flat-nose pliers.

[0092] h. Repeat steps f and g until the designed structure is implanted, peel off the drawing on the surface of the prepreg, pressurize and cure the prepreg with the flexible pin needle implanted, and then use 800-grit sandpaper to polish and remove the foam layer on the lower surface of the composite material to obtain a Z-pin reinforced composite material.

[0093] Example 4

[0094] The Z-pin reinforced composite material was prepared according to the method of Example 3, except that the upper and lower panels of the prepreg blank were unidirectionally laminated prepregs, and the upper surface area S of the reinforced thermal conductive composite material was 100 cm 2 , the specific steps are as follows:

[0095] a. The average thickness of the unidirectional mesophase pitch-based carbon fiber prepreg TPC60 was calculated by measuring the thickness multiple times, and the average thickness h was 0.17 mm;

[0096] b. According to the size of the implant area and the implant spacing of 3.3 mm, the number of flexible pin needles to be implanted is calculated to be 900. According to formula 1, the radius of the flexible pin needle is 0.7 mm and the diameter is 1.4 mm;

[0097] c. According to formula 2, the required prepreg width L along the vertical fiber direction is 9 mm;

[0098] d. Cut a 9mm wide prepreg along the vertical fiber direction and a 5cm long prepreg along the fiber direction, heat and soften it on a hot plate at 40℃, and manually roll it into a flexible pin;

[0099] e. Use mesophase pitch-based carbon fiber prepreg to lay on the mold in a unidirectional laying manner as the upper and lower panels of the laminate. After laying each layer of prepreg, lay a layer of resin film on its upper surface. Use 0.5mm thick PMI foam as an interlayer to make a prepreg blank with a thickness of about 2.5mm. Draw a Z-pin reinforced laminate structure drawing according to the required implantation density, and fix the drawing on the prepreg blank with porous PTFE cloth on the upper and lower surfaces to assist in positioning. In order to ensure a completely penetrating heat conduction path in the thickness direction, lay a 1mm thick PMI foam layer on the lower surface of the blank;

[0100] f. Due to the diameter d of the flexible pin Pin 1.4mm, choose a 17G needle (17G corresponds to the outer diameter d o 1.48mm) to meet d Pin <d o ≤1.2d Pin ; The corresponding material is PMMA organic glass, and the fixed mold with an inner diameter of 1.5 mm is selected. After calculating X according to formula 3, mark it on the needle tube, wrap it with wide tape, and the wide tape covers the mark to play an approximate matching role. Wrap it with fine tape, and the fine tape is located above the mark to play a limiting role. The prepreg is placed on a 45°C hot table for preheating. The fixed mold is used to drive the needle to vertically penetrate the laminate on the prepreg to generate a prefabricated hole;

[0101] g. Implant the prepared flexible pin into the prefabricated hole and trim the flexible pin that protrudes beyond the surface of the prepreg blank with flat-nose pliers.

[0102] h. Repeat steps f and g until the designed structure is implanted, peel off the drawing on the surface of the prepreg, pressurize and cure the prepreg with the flexible pin needle implanted, and then use 800-grit sandpaper to polish and remove the foam layer on the lower surface of the composite material to obtain a Z-pin reinforced composite material.

[0103] Comparative Example 1

[0104] Using mesophase pitch-based carbon fiber prepreg with a thermal conductivity of 600W / m·K according to [0 / 90] 12 The prepreg with a thickness of 3 mm is laid on the mold and then pressurized and cured to obtain the thermal conductive material.

[0105] The thermal conductivity of the thermally conductive materials prepared in Examples 1 to 3 and Comparative Example 1 was tested by laser flash method. The results of thermal conductivity in the thickness direction of the composite material layer and thermal conductivity in the 0° direction within the layer plane are listed in Table 1.

[0106] Table 1 Thermal conductivity of thermally conductive materials prepared in Examples 1 to 3 and Comparative Example 1

[0107]

[0108] Figure 6 The thermal infrared imaging images of the upper and lower surfaces of the thermally conductive material prepared in Comparative Example 1 and the Z-pin enhanced thermally conductive composite material prepared in Example 1 at the same time when the same power heating sheet is placed on the lower surface, wherein the left one is the thermal infrared imaging image of Comparative Example 1, and the right one is the thermal infrared imaging image of Example 1; Figure 6 It can be seen that the temperature of the Z-pin part is significantly higher than that of the non-pin-implanted area. At the same time, it can be seen from Table 1 that the Z-pin enhanced thermally conductive composite material prepared according to the preparation method provided by the present invention has good thermal conductivity in both thickness and in-plane directions.

[0109] The Z-pin reinforced composite material prepared in Example 4 was tested using an optical microscope to obtain a metallographic image of the cross section of the laminate. Figure 7 As shown. Figure 7 It can be seen that there are a small amount of pores in the plywood of the Z-pin reinforced PMI foam sandwich unidirectional laminate composite material prepared in Example 4, and the molding quality is good.

[0110] The present invention can reduce the density of the composite material layer by setting the interlayer (Example 1 and Example 3). The density of the Z-pin reinforced composite material prepared in Example 1 is 1.53 g / cm 3 The density of the Z-pin reinforced composite material prepared in Example 3 is 1.26 g / cm 3 .

[0111] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a flexible pin, characterized in that: The following steps are involved: Measure the single layer thickness of the prepreg used to prepare the flexible pin needle, recorded as h; Calculate the radius R of the flexible pin according to formula 1: Among them, V p is the volume ratio of the total volume of the flexible pin needles to be implanted to the volume of the prepreg blank, S is the upper surface area of ​​the prepreg blank into which the flexible pin needles are to be implanted, and N is the number of flexible pin needles to be implanted in the area where the flexible pin needles are to be implanted; The width L of the prepreg for preparing the flexible pin is calculated according to Formula 2: The prepreg with a width of L is cut along the direction perpendicular to the fiber, and rolled along the direction perpendicular to the fiber to form a flexible pin.

2. The method for preparing the flexible pin according to claim 1, characterized in that: The fiber in the prepreg for preparing the flexible pin needle is mesophase pitch-based carbon fiber.

3. The method for preparing the flexible pin according to claim 1, characterized in that: The length of the flexible pin needle is 5 to 10 cm, and the length of the prepreg material for preparing the flexible pin needle along the fiber direction is greater than or equal to the length of the flexible pin needle.

4. A method for preparing a Z-pin reinforced composite material, characterized in that: The following steps are involved: After preheating the prepreg blank, a prefabricated hole is formed using a hole-forming component; the hole-forming component comprises a needle tube (1) which is sleeved on a fixed mold (2) outside the needle tube; one end of the needle tube has a needle head capable of piercing the prepreg blank; the needle tube (1) is slidably connected to the fixed mold (2), and the height of the needle tube (1) is greater than the height of the fixed mold (2); Implanting the flexible pin needle prepared by the preparation method according to any one of claims 1 to 3 into the prefabricated hole; The steps of forming prefabricated holes and implanting flexible pins are repeated and then cured to obtain a Z-pin reinforced composite material.

5. The method for preparing the Z-pin reinforced composite material according to claim 4, characterized in that: The hole-forming component also includes a limiting ring (3) fixed to the outside of the needle tube; the limiting ring (3) is located above the fixed mold (2).

6. The method for preparing the Z-pin reinforced composite material according to claim 4, characterized in that: The outer diameter d of the needle o and the diameter d of the flexible pin Pin Satisfaction:d Pin <d o ≤1.2d Pin .

7. The method for preparing the Z-pin reinforced composite material according to any one of claims 4 to 6, characterized in that: The method further comprises arranging a foam layer at the bottom of the prepreg before forming the prefabricated holes by using the hole-forming component.

8. The method for preparing the Z-pin reinforced composite material according to claim 7, characterized in that: The distance X between the lower end of the limiting ring (3) and the needle is calculated according to Formula 3: X=h m +h p +h f +h a Formula 3; Among them, h m is the height of the fixed mold (2), h p is the thickness of the prepreg, h f is the thickness of the foam layer, h a is the total thickness of auxiliary materials.

9. The method for preparing the Z-pin reinforced composite material according to claim 4, characterized in that: The curing is pressurized curing.

10. The method for preparing the Z-pin reinforced composite material according to claim 4, characterized in that: The fibers in the prepreg are mesophase pitch-based carbon fibers.

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