A method for manufacturing a flexible pin needle, a method for manufacturing a z-pin reinforced composite material

Abstract

The present application belongs to the technical field of Z-pin reinforced composite materials, and particularly relates to a preparation method of a flexible pin needle and a preparation method of a Z-pin reinforced composite material. First, a prepreg is prepared according to a designed layup mode, the prepreg is heated to an appropriate temperature, a needle head with a suitable outer diameter is driven by a fixed mold to vertically pierce into the prepreg, a preformed hole is formed, the prepared flexible pin needle is implanted into the preformed hole one by one until the implantation is completed, the needle head with a suitable diameter can minimize the damage to the in-plane fibers, and the fixed mold assists the insertion of the needle head into the prepreg to ensure that the flexible pin needle can be vertically implanted into the prepreg, and then the Z-pin is co-cured with the prepreg, the influence of the pin needle implantation on the buckling deformation of the in-plane fibers is reduced, and the comprehensive thermal conductivity of the composite material is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of Z-pin reinforced composite materials, and particularly relates to a preparation method of a flexible pin needle and a preparation method of a Z-pin reinforced composite material. BACKGROUND

[0002] Carbon fiber reinforced resin matrix composite materials have excellent properties such as light weight, high strength and strong designability, and are widely used in many fields such as aerospace and electronic devices. However, the heat generated by electronic devices during operation can seriously reduce the working efficiency and service life of the equipment. In carbon fiber reinforced resin matrix composite materials, heat conduction mainly occurs along the fiber direction. The traditional carbon fiber reinforced resin matrix composite material lacks continuous heat conduction channels in the thickness direction, which results in that the heat conduction performance in the thickness direction is much lower than that in the plane.

[0003] At present, scholars have studied many technologies for improving the heat conduction performance of carbon fiber reinforced resin matrix composite materials in the thickness direction, including fiber surface modification, 3D weaving, hybridization and Z-pin reinforcement technology. Among them, the Z-pin reinforcement technology draws lessons from the method of discontinuous stitching, inserts the pin needle into the uncured prepreg along the thickness direction for curing and molding, and then builds a continuous heat conduction channel in the thickness direction. At present, Z-pin reinforced composite materials are mainly prepared by pultrusion molding to prepare impregnated fiber bundles. For high-thermal-conductivity mesophase pitch-based carbon fibers, the fibers will be seriously damaged, which is not conducive to the development of high-thermal-conductivity performance.

[0004] Therefore, how to prepare Z-pin with a certain fiber volume fraction without damaging the fibers as much as possible and prepare thickness-enhanced thermal conduction composite materials has become a problem to be solved by those skilled in the art. SUMMARY

[0005] Therefore, the application provides a preparation method of a flexible pin needle and a preparation method of a Z-pin reinforced composite material. The preparation method provided by the application does not damage the fibers during the preparation of the Z-pin reinforced composite material, and is conducive to improving the heat conduction performance of the composite material.

[0006] To solve the above technical problems, the application provides a preparation method of a flexible pin needle, which comprises the following steps:

[0007] The single-layer thickness of the prepreg for preparing the flexible pin needle is measured and recorded as h;

[0008] The radius R of the flexible pin needle is calculated according to formula 1:

[0009]

[0010] V pThe volume ratio of the total volume of the flexible pin needle to be implanted and the volume of the prepreg, S is the upper surface area of the prepreg of the flexible pin needle to be implanted, and N is the number of flexible pin needles to be implanted in the area to be implanted with flexible pin needles;

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

[0012]

[0013] The prepreg with a width of L is cut along the vertical fiber direction, and the flexible pin needle is formed by rolling along the vertical fiber direction.

[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 5-10 cm, and the length of the prepreg 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 application also provides a method for preparing a Z-pin reinforced composite material, comprising the following steps:

[0017] The prepreg is preheated and a preformed hole is formed by using a hole forming member; the hole forming member comprises a needle tube 1 and a fixed mold 2 sleeved outside the needle tube; one end of the needle tube has a needle head capable of penetrating the prepreg; the needle tube 1 and the fixed mold 2 are in sliding connection, and the height of the needle tube 1 is greater than the height of the fixed mold 2;

[0018] The flexible pin needle prepared by the preparation method is implanted into the preformed hole;

[0019] After repeating the steps of forming the preformed hole and implanting the flexible pin needle, curing is performed to obtain a Z-pin reinforced composite material.

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

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

[0022] Preferably, before forming the preformed hole by using the hole forming member, a foam layer is further arranged at the bottom of the prepreg.

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

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

[0025] Wherein, 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.

[0026] Preferably, the curing is pressure curing.

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

[0028] The present application has the following technical effects relative to the prior art: the method for preparing the flexible pin needle of the present application is convenient and fast to operate, only needs to cut the prepreg of the required width and manually roll to form the flexible pin needle, and can control the size of the flexible pin needle by adjusting the width of the cut prepreg; meanwhile, the fibers in the prepreg are arranged in parallel in the same direction, avoiding the problem of poor local fiber orientation caused by fiber twisting in the process of preparing the pin needle by using a bundle of fibers, and being more conducive to exerting the axial heat conduction performance of the pin needle; in addition, the method can minimize the damage to the mesophase pitch-based carbon fibers which are prone to breakage, and retain the high heat conduction performance of the fibers, and meanwhile, the prepreg resin is lightly crosslinked, and the flexible pin needle has a certain deformation capacity, so that compared with the rigid pin needle, the size of the fish eye area is easier to control in the molding process, the defects in the laminate (Z-pin reinforced composite material) are reduced, and the laminate is more compact.

[0029] The present application also provides a method for preparing a Z-pin reinforced composite material, first preparing a prepreg according to a designed layup method, heating the prepreg to an appropriate temperature, using a fixed mold to drive a needle with a suitable outer diameter to vertically penetrate into the laminate on the prepreg, i.e. to generate a preformed hole, and then implanting the prepared flexible pin needle into the preformed hole one by one until the implantation is completed, so that the needle with a suitable diameter can minimize the damage to the in-plane fibers, and meanwhile, the fixed mold can assist the needle to penetrate into the prepreg to ensure that the flexible pin needle can be vertically implanted into the prepreg, and then the Z-pin is co-cured with the prepreg to reduce the influence of the pin needle implantation on the bending deformation of the in-plane fibers, and improve the comprehensive heat conduction performance of the composite material. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 Schematic diagram of rolling the prepreg to form a flexible pin needle;

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

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

[0033] Figure 4 Schematic diagram of the structure of the fixed mold;

[0034] Figure 5 Schematic diagram of the formation of a preformed hole and the implantation of a flexible pin needle, from left to right, the four steps are respectively needle head piercing into pre-impregnated blank, preformed hole formation, flexible pin needle implantation and trimming of the flexible pin needle, wherein 1 is a needle head, 2 is a fixed mold, 3 is a limiting ring, 4 is a pre-impregnated blank, 5 is a foam layer, and 6 is a flexible pin needle;

[0035] Figure 6 Thermal infrared imaging diagram of the upper surface at the same time under the lower surface of the heat sheet of the same power prepared from the heat-conducting material of Comparative Example 1 and Example 1, respectively, wherein the left is the thermal infrared imaging diagram of Comparative Example 1, and the right is the thermal infrared imaging diagram of Example 1;

[0036] Figure 7 Cross-sectional metallographic diagram of the Z-pin reinforced PMI foam sandwich unidirectional laminate composite prepared in Example 4. DETAILED DESCRIPTION

[0037] The present application provides a preparation method of a flexible pin needle, comprising the following steps:

[0038] The single-layer thickness of the pre-impregnated material for preparing the flexible pin needle is measured, denoted as h;

[0039] The radius R of the flexible pin needle is calculated according to Formula 1:

[0040]

[0041] wherein, V p is the volume ratio of the total volume of the flexible pin needle to be implanted to the volume of the pre-impregnated blank, S is the upper surface area of the pre-impregnated blank of the flexible pin needle to be implanted, and N is the number of flexible pin needles to be implanted in the area to be implanted with the flexible pin needle;

[0042] The width L of the pre-impregnated material for preparing the flexible pin needle is calculated according to Formula 2:

[0043]

[0044] The pre-impregnated material with a width of L is cut along the vertical fiber direction, and the flexible pin needle is formed by rolling along the vertical fiber direction.

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

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

[0047] The present application also provides a preparation method of a Z-pin reinforced composite material, comprising the following steps:

[0048] After preheating the prepreg blank, a preformed hole is formed by using a hole forming member; the hole forming member comprises a needle tube 1 and a fixed mold 2 sleeved outside the needle tube; one end of the needle tube has a needle head capable of penetrating into the prepreg blank; the needle tube 1 is in sliding connection with the fixed mold 2, and the height of the needle tube 1 is greater than the height of the fixed mold 2;

[0049] The flexible pin needle prepared by the preparation method according to the above technical solution is implanted into the preformed hole;

[0050] After repeating the steps of forming the preformed hole and implanting the flexible pin needle, curing is performed to obtain a Z-pin reinforced composite material.

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

[0052] The present application has no special requirements for the preheating temperature, as long as the prepreg blank can be kept soft to facilitate the implantation of the flexible pin needle. As a specific embodiment of the present application, the preheating temperature can be 40-50℃, which can be specifically 40℃, 45℃ or 50℃.

[0053] As a specific embodiment of the present application, the hole-forming component can further comprise 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 application, the limiting ring 3 is detachably connected with the needle tube 1 and the connecting position of the two can be adjusted; the pillow in the needle tube 1 is obliquely cut; the needle head formed by the oblique cutting process can reduce the movement resistance of the needle tube 1, thereby enabling the needle tube 1 to be smoothly implanted into the pre-impregnated blank. As a specific embodiment of the present application, the fixed mold 2 is hollow cylindrical; the fixed mold is made of transparent material. In order to ensure that the needle tube 1 does not occur angle tilt during the process of inserting into the pre-impregnated blank, thereby causing the implantation angle of the flexible pin 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 larger gap, adhesive tape can be wound around the needle tube 1 to achieve approximate matching.

[0054] In the present application, the limiting ring 3 is provided to facilitate positioning the depth of the needle head inserted into the pre-impregnated blank, thereby ensuring that the pre-prepared hole penetrates the pre-impregnated blank body; when the limiting ring 3 abuts against the fixed mold 2, it indicates that the needle head has reached the predetermined position; the limiting ring 3 is detachably connected with the needle tube 1 and the connecting position of the two can be adjusted, the position of the limiting ring 3 is changed according to the different pre-impregnated blanks, thereby improving the flexible adaptability of the hole-forming component. In the present application, the fixed mold 2 abuts against the pre-impregnated blank, which can limit the movement direction of the needle tube 1, thereby improving the accuracy of the implantation of the flexible pin; the cylindrical fixed mold 2 abuts against the pre-impregnated blank, so that the needle tube 1 can be inserted into the pre-impregnated blank in a direction perpendicular to the pre-impregnated blank, thereby avoiding the needle tube 1 from being tilted during the process of inserting into the pre-impregnated blank, which affects the implantation angle of the flexible pin; in addition, the fixed mold 2 is made of transparent material, which facilitates the observation of the working process of the needle tube 1 and provides convenience for the operator; the fixed mold 2 can keep the needle head vertically inserted into the pre-impregnated blank to ensure that the pre-prepared hole remains vertical, thereby enabling the flexible pin to be vertically implanted into the pre-impregnated blank. Figure 3 It is a structural diagram 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 structural diagram of the fixed mold.

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

[0056] In one specific embodiment of the present invention, a foam layer may be provided at the bottom of the prepreg blank before forming the pre-drilled hole using the hole-forming component. The foam layer at the bottom of the prepreg blank ensures that the prepreg blank is completely penetrated in the thickness direction. In another specific embodiment of the present invention, the distance X from the lower end of the limiting ring 3 to the needle tip can be calculated according to formula 3:

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

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

[0059] In one specific embodiment of the present invention, the curing can be pressure curing; the present invention has no special requirements for the conditions and parameters of the pressure curing, and conventional methods in the art can be used.

[0060] As a specific embodiment of the present invention, the foam layer on the lower surface of the composite material can be removed by sanding after curing.

[0061] Figure 5 This diagram illustrates the formation of pre-drilled holes and the implantation of flexible pins, where 1 is the needle tip, 2 is the fixing mold, 3 is the limiting ring, 4 is the prepreg blank, 5 is the foam layer, and 6 is the flexible pin.

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

[0063] Example 1

[0064] Preparation of flexible pin volume fraction V p The thermally conductive composite material contains 13.85% Z-pin reinforcement (the upper surface area S of the reinforced thermally conductive composite material is 100 cm²). 2 The specific steps are as follows:

[0065] a. The thickness of 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. The number of flexible pins to be implanted N is 900 according to the size of the pin area and the implantation interval of 3.3 mm, and the radius of the flexible pin is 0.7 mm and the diameter is 1.4 mm according to formula 1;

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

[0068] d. A prepreg with a width of 9 mm along the vertical fiber direction and a length of 5 cm along the fiber direction is cut, heated and softened on a hot table at 40°C, and manually rolled into a flexible pin;

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

[0070] f. Since the diameter d Pin of the flexible pin is 1.4 mm, a needle with a specification of 17G (17G corresponds to an outer diameter d o of 1.48 mm) is selected to meet d Pin <d o ≤1.2d Pin ; and the corresponding material is PMMA organic glass with an inner diameter of 1.5 mm. According to formula 3, X is calculated and marked on the needle tube, wrapped with wide tape, wrapped with fine tape, and the prepreg blank is placed on a 45°C hot table for preheating. The fixed mold drives the needle to vertically penetrate the laminate on the prepreg blank to generate a pre-prepared hole;

[0071] g. The prepared flexible pin is implanted into the pre-prepared hole, and the flat pliers are used to trim the flexible pin that exceeds the surface of the prepreg blank.

[0072] h. Repeat steps f and g until the designed structure is implanted, remove the drawing paper on the surface of the prepreg blank, and polish the foam layer on the lower surface of the prepreg blank after implanting the flexible pin using 800 mesh sandpaper to obtain a Z-pin reinforced composite material.

[0073] Example 2

[0074] The Z-pin reinforced composite was prepared according to the method of Example 1, except that the flexible pin needles accounted for a volume fraction V of the Z-pin reinforced thermally conductive composite p was 7.07%, and the upper surface area S of the reinforced thermally conductive composite was 100 cm 2 , and the specific steps were as follows:

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

[0076] b. According to the pin implantation area size and the implantation interval of 3.3 mm, the number N of flexible pin needles to be implanted was calculated to be 900, and the radius of the flexible pin needle was calculated to be 0.5 mm according to formula 1, and the diameter was 1 mm;

[0077] c. The width L of the prepreg required along the vertical fiber direction was calculated to be 4.6 mm according to formula 2;

[0078] d. A 4.6 mm wide and 5 cm long prepreg along the fiber direction was cut, and the prepreg was heated and softened on a hot table at 40°C, and was manually rolled into a flexible pin needle;

[0079] e. The mesophase pitch-based carbon fiber prepreg was laid on the mold in the manner of [0 / 90] 12 , and a layer of resin film was laid on the upper surface of each layer of prepreg to make a prepreg blank with a thickness of about 3 mm. A structure drawing of the Z-pin reinforced laminate was drawn according to the required implantation density, and the drawing was fixed on the prepreg blank with a hole-containing Teflon cloth on the upper and lower surfaces to assist positioning. In order to ensure the complete penetration of the thermally conductive path in the thickness direction, a 1 mm thick PMI foam layer was laid on the lower surface of the blank;

[0080] f. Since the diameter d Pin of the flexible pin needle was 1 mm, a needle with a specification of 19G (19G corresponds to an outer diameter d o of 1.06 mm) was selected to satisfy d Pin <d o ≤1.2d Pin , and the corresponding material was PMMA organic glass with an inner diameter of 1.1 mm. X was calculated according to formula 3, and marks were made on the needle tube. Wide tape was wrapped around, and the wide tape covered the mark to approximately match. Fine tape was wrapped around, and the fine tape was located above the mark to limit the position. The prepreg blank was placed on a hot table at 45°C for preheating, and the fixed mold was used to drive the needle to vertically penetrate the laminate on the prepreg blank to generate a preformed hole;

[0081] g. The prepared flexible pin needle is implanted into the pre-prepared hole, and the flat pliers are used to trim the flexible pin needle that exceeds the surface of the prepreg;

[0082] h. Steps f and g are repeated until the designed structure is implanted, the drawing paper on the surface of the prepreg is removed, and the prepreg implanted with the flexible pin needle is pressed and cured. After that, the foam on the lower surface of the composite material is polished and removed using 800 mesh sandpaper to obtain a Z-pin reinforced composite material.

[0083] Example 3

[0084] The Z-pin reinforced composite material is prepared according to the method of Example 1, except that 0.5 mm thick PMI foam is used as the interlayer in the prepreg, [0 / 90] 2s The prepreg with orthogonal symmetric layers is used as the upper and lower panels, and the upper surface area S of the reinforced thermal conductive composite material is 100 cm 2 The specific steps are as follows:

[0085] a. The thickness of the unidirectional mesophase pitch-based carbon fiber prepreg TPC60 is measured multiple times to calculate the average value, and the average thickness h is 0.17 mm;

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

[0087] c. The required prepreg width L along the perpendicular fiber direction is calculated to be 9 mm according to formula 2;

[0088] d. The prepreg with a width of 9 mm along the perpendicular fiber direction and a length of 5 cm along the fiber direction is cut, heated and softened on a hot table at 40°C, and manually rolled into a flexible pin needle;

[0089] e. The mesophase pitch-based carbon fiber prepreg is laid on the mold according to the way of [0 / 90] 2s , and the upper and lower panels of the laminate are prepared. After laying each layer of prepreg, a layer of resin film is laid on its upper surface, and 0.5 mm thick PMI foam is used as the interlayer to make a prepreg with a thickness of about 2.5 mm. According to the required implantation density, a Z-pin reinforced laminate structure drawing is drawn, and the drawing is fixed on the prepreg with a hole four fluorine cloth on the upper and lower surfaces to assist positioning. In order to ensure the complete penetration of the thermal conductive path in the thickness direction, a 1 mm thick PMI foam layer is laid on the lower surface of the prepreg;

[0090] f. Since the diameter d Pin of the flexible pin needle is 1.4 mm, a needle with a specification of 17G is selected (17G corresponds to an outer diameter d oto meet d Pin <d o ≤1.2d Pin ; the corresponding selected material is PMMA organic glass, the fixed mold with an inner diameter of 1.5 mm, X is calculated according to formula 3, and a mark is made on the needle tube, a wide adhesive tape is wound, the wide adhesive tape covers the mark to play an approximate matching role, a thin adhesive tape is wound, the thin adhesive tape is located above the mark to play a limiting role, the pre-impregnated blank is placed on a 45°C hot table for preheating, the needle is vertically inserted into the laminate by the fixed mold, and a preformed hole is generated;

[0091] g. The flexible pin needle prepared is implanted into the preformed hole, and flat pliers are used to trim the flexible pin needle that exceeds the surface of the pre-impregnated blank.

[0092] h. Steps f and g are repeated until the designed structure is implanted, the drawing paper on the surface of the pre-impregnated blank is removed, the pre-impregnated blank after implanting the flexible pin needle is pressurized and solidified, and the foam layer on the lower surface of the composite material is polished and removed by using 800-mesh sandpaper to obtain a Z-pin reinforced composite material.

[0093] Example 4

[0094] The Z-pin reinforced composite material is prepared according to the method of Example 3, except that the unidirectional pre-impregnated material is used on the upper and lower panels in the pre-impregnated blank, and the upper surface area S of the heat-conducting composite material is 100 cm 2 , and the specific steps are as follows:

[0095] a. The thickness of the unidirectional mesophase pitch-based carbon fiber pre-impregnated material TPC60 is measured multiple times to calculate the average value, and the average thickness h is 0.17 mm;

[0096] b. The number N of flexible pin needles to be implanted is calculated as 900 according to the size of the Pin implantation area and the implantation interval of 3.3 mm, and the radius of the flexible pin needle is calculated as 0.7 mm and the diameter is calculated as 1.4 mm according to formula 1;

[0097] c. The pre-impregnated material width L required along the vertical fiber direction is calculated as 9 mm according to formula 2;

[0098] d. The pre-impregnated material with a width of 9 mm and a length of 5 cm along the fiber direction is cut, heated and softened on a 40°C hot table, and manually rolled into a flexible pin needle;

[0099] e. The intermediate phase pitch-based carbon fiber prepreg is laid on the mold as the upper and lower panels of the laminate in a unidirectional manner. After laying each layer of prepreg, a layer of resin film is laid on the upper surface. A 0.5mm thick PMI foam is used as the interlayer to make a prepreg with a thickness of about 2.5mm. The Z-pin reinforced laminate structure diagram is drawn according to the required implantation density. The diagram is fixed on the prepreg with a hole-containing Teflon cloth on the upper and lower surfaces to assist positioning. In order to ensure the complete penetration of the heat conduction path in the thickness direction, a 1mm thick PMI foam layer is laid on the lower surface of the prepreg;

[0100] f. Since the diameter d Pin of the flexible pin needle is 1.4mm, a needle with a specification of 17G (17G corresponds to an outer diameter d o of 1.48mm) is selected to meet d Pin <d o ≤1.2d Pin ; and the corresponding selected material is PMMA organic glass with an inner diameter of 1.5mm. X is calculated according to formula 3 and marked on the needle tube. Wide tape is wrapped around the mark to approximate matching, and thin tape is wrapped above the mark to limit the position. The prepreg is placed on a 45℃ hot table for preheating, and the needle is vertically inserted into the laminate on the prepreg by using the fixed mold to drive the needle, to generate a preformed hole;

[0101] g. The flexible pin needle prepared is implanted into the preformed hole, and the flexible pin needle protruding from the surface of the prepreg is trimmed with flat pliers.

[0102] h. Steps f and g are repeated until the designed structure is implanted. The drawing on the surface of the prepreg is removed, and the prepreg with implanted flexible pin needles is pressurized and cured. The foam layer on the lower surface of the composite material is polished and removed using 800 mesh sandpaper to obtain a Z-pin reinforced composite material.

[0103] Comparative Example 1

[0104] The intermediate phase pitch-based carbon fiber prepreg with a thermal conductivity of 600W / m·K is laid on the mold in a [0 / 90] 12 manner. After the prepreg with a thickness of 3mm is prepared, it is pressurized and cured to obtain a heat conducting material.

[0105] The heat conducting materials prepared in Examples 1-3 and Comparative Example 1 are tested for thermal conductivity by laser flash method. The results of the thermal conductivity of the composite laminate in the thickness direction and the thermal conductivity of the laminate in the 0° direction are shown in Table 1.

[0106] Table 1 Thermal conductivity of the heat conducting materials prepared in Examples 1-3 and Comparative Example 1

[0107]

[0108] Figure 6 The images show thermal infrared (TIR) ​​images of the upper surfaces at the same time when heating elements of the same power were placed on the lower surfaces of the thermally conductive material prepared in Comparative Example 1 and the Z-pin reinforced thermally conductive composite material prepared in Example 1, respectively. The left image is the TIR image of Comparative Example 1, and the right image is the TIR 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 unpinned area. At the same time, Table 1 shows that the Z-pin reinforced thermally conductive composite material prepared according to the preparation method provided by the present invention has good thermal conductivity in both the thickness and in-plane directions.

[0109] The Z-pin reinforced composite material prepared in Example 4 was examined using an optical microscope, and metallographic images of the laminate cross-section were obtained, as shown below. Figure 7 As shown. By Figure 7 It can be seen that the Z-pin reinforced PMI foam sandwich unidirectional layup composite material prepared in Example 4 has a small number of pores in the laminate, and the molding quality is good.

[0110] This invention reduces the density of the composite laminate by incorporating sandwich layers (Examples 1 and 3). The density of the Z-pin reinforced composite material prepared in Example 1 is 1.53 g / cm³. 3 The density of the Z-pin reinforced composite material prepared in Example 3 was 1.26 g / cm³. 3 .

[0111] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a Z-pin reinforced composite material, characterized in that, Includes the following steps: The prepreg blank is preheated and then pre-drilled holes are formed using a hole-forming component; the hole-forming component includes a needle tube (1) and a fixed mold (2) fitted outside the needle tube; one end of the needle tube has a needle tip that can pierce 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). Insert the flexible pin into the pre-made hole; After repeating the steps of forming pre-drilled holes and implanting flexible pins, the material is cured to obtain a Z-pin reinforced composite material. The method for preparing the flexible pin includes the following steps: The thickness of a single layer of the prepreg used to prepare flexible pins is measured and denoted as h; Calculate the radius R of the flexible pin according to Formula 1: Among them, V p S is the volume ratio of the total volume of the flexible pin to be implanted to the volume of the prepreg blank, S is the upper surface area of ​​the prepreg blank to be implanted with the flexible pin, and N is the number of flexible pins to be implanted in the area to be implanted with the flexible pin. The width L of the prepreg used to prepare flexible pins is calculated according to Formula 2: A prepreg with a width of L is cut along the direction perpendicular to the fiber, and then rolled along the direction perpendicular to the fiber to form a flexible pin; the length of the flexible pin is 5 to 10 cm, and the length of the prepreg along the fiber direction is greater than or equal to the length of the flexible pin. The fibers used in the prepreg for preparing flexible pins are mesophase pitch-based carbon fibers.

2. The method for preparing the Z-pin reinforced composite material according to claim 1, 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).

3. The method for preparing the Z-pin reinforced composite material according to claim 1, characterized in that, The outer diameter d of the needle o and the diameter d of the flexible pin Pin Satisfy: d Pin <d o ≤1.2d Pin .

4. The method for preparing the Z-pin reinforced composite material according to any one of claims 1 to 3, characterized in that, Before forming pre-drilled holes using the hole-forming component, a foam layer is also provided at the bottom of the prepreg blank.

5. The method for preparing the Z-pin reinforced composite material according to claim 4, characterized in that, Calculate the distance X from the lower end of the limiting ring (3) to the needle tip according to formula 3: X = h m +h p +h f +h a Formula 3; Among them, h m h is the height of the fixed mold (2). p h represents the thickness of the prepreg. f h is the thickness of the foam layer. a This refers to the total thickness of the auxiliary materials.

6. The method for preparing the Z-pin reinforced composite material according to claim 1, characterized in that, The curing process is pressure curing.

7. The method for preparing the Z-pin reinforced composite material according to claim 1, characterized in that, The fibers in the prepreg are mesophase pitch-based carbon fibers.

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