A needle punching method for improving mechanical properties of needle punched fabrics

Abstract

The present invention relates to a needle punching method for improving the mechanical properties of needle-punched fabrics, comprising the following steps: S1 preparing an ultra-thin carbon fiber web; S2 measuring the thickness of a unit layer; S3 calculating the needle punching step amount; S4 calculating the number of needle punching rows and columns; S5 setting the knife of a needle punching robot; S6 cutting and weighing the raw materials required for the unit layer; S7 pre-punching and laying; S8 covering with a film; S9 generating a robot pre-punching execution program; S10 performing pre-punching; S11 main puncturing and laying; S12 generating a robot main puncturing execution program; S13 performing in-situ main puncturing; S14 measuring the thickness of the fabric online; S15 cyclic needling. The present invention adopts a needling forming method of pre-punching / main puncturing coordination, and pre-punching generates prefabricated holes, which is beneficial for the needle to bring short fibers into the thickness direction to form a needle-punched fiber bundle during the main puncturing process, thereby improving the interlayer peeling performance of the needle-punched fabric; adopting in-situ needling, that is, the X-axis coordinates and the Y-axis coordinates of the trajectory coordinate points of the main puncturing and pre-puncturing coincide, effectively reducing the needling area, thereby reducing the damage of the needle to the base fabric.

Description

Technical Field

[0001] The invention belongs to the technical field of needle-punched preforms, and in particular relates to a needle-punching method for improving the mechanical properties of needle-punched fabrics. Background Art

[0002] The preparation process of three-dimensional needle-punched fabrics has a high degree of automation, a short delivery cycle, and a low production cost. It also overcomes the shortcoming of easy delamination between laminated layers and has been widely used in new energy, rail transit, aerospace, national defense and other fields.

[0003] Domestic and foreign researchers have conducted extensive research on needle-punching damage. In the paper "Study on Fiber Transfer and Damage in Needle-punched Carbon Cloth / Mesh Composite Fabrics", researchers prepared carbon cloth / mesh-punched needle-punched fabrics and studied the transfer effect and damage mechanism of needle-punching on fibers by scanning electron microscopy. It was found that the needle-punched fiber bundles were transferred along the z direction to form a quasi-three-dimensional structure with the flat fabric as a "pin". Needling caused the in-plane tensile strength to decrease rapidly and the fibers damaged in this process basically did not produce the Z-direction transfer enhancement effect. The paper "Effect of Needle Punching Parameters on Damage and Entanglement of PAN Pre-oxidized Fibers" found through conventional experimental tests and Hough transform analysis that with the increase of needle-punching frequency, needle-punching depth and needle-punching times, the fiber length decreased and the fiber damage intensified. The paper "Damage evaluation of quartz woven fabrics during needle punching process" reported the relationship between the damage morphology and tensile properties of woven fabrics in the warp and weft directions in three-dimensional needle-punched composite preforms with different needle-punching densities. It was found that the needle-punching density was 25 needles / cm 2 The mechanical property damage rate of the fabric reaches 60% to 80% when the needle punching density is high. Therefore, the mechanical properties of the needle-punched fabric prepared by the existing needle-punching process are relatively weak, which limits its application in high-end fields such as the antenna cover, cabin section and brake disc of high-speed rail trains of the new generation of hypersonic aircraft. It is necessary to improve the current conventional needle-punching method of fabrics. Summary of the invention

[0004] The present invention provides a needle punching method for improving the mechanical properties of needle-punched fabrics to solve the technical problems existing in the known technology. The needle punching density is reduced by pre-punching / main-punching coordination and in-situ needling, thereby improving the mechanical properties of the fabric.

[0005] The present invention includes the following technical solutions: A needle punching method for improving the mechanical properties of needle punched fabrics, comprising the following steps:

[0006] S1. Preparing an ultra-thin carbon fiber web: cutting the carbon fiber yarn into short yarns of equal length, further opening and combing, stacking and laying, and pre-puncturing to form an ultra-thin carbon fiber web;

[0007] S2. Calculate the thickness of the unit layer: Use a fabric thickness measuring instrument to calculate the thickness of the unit layer based on the thickness test standard;

[0008] S3. Calculation of acupuncture stepping amount: According to the number of needles on the needle board of the acupuncture robot and the acupuncture density (needles / cm 2 ), calculate the acupuncture row step amount; the number of needles on the needle board is N, and the acupuncture density is M (needles / cm 2 ), the step size is S (cm), and S 2 =N / M;

[0009] S4. Calculation of the number of needling rows and columns: Calculate the number of needling rows and columns according to the stepping amount and the length and width of the fabric; the needling stepping amount is S (cm), the length and width of the fabric are A cm and B cm respectively, then the number of needling rows and columns is A / S and B / S respectively;

[0010] S5. Acupuncture robot knife alignment: On the acupuncture work platform, mark the acupuncture starting point with red tape; move the acupuncture robot so that the acupuncture actuator is aligned with the acupuncture starting point, and record the position information of the acupuncture starting point;

[0011] S6. Cutting and weighing the raw materials required for the unit layer: cutting the base cloth and the mesh with a cutting table, and weighing the mesh to ensure that the weight of the mesh in the unit layer meets the requirements; the mesh has two layers, one for pre-puncture and the other for main puncture;

[0012] S7, pre-needling layer: first lay the base fabric, then lay the web layer; one corner of the layer material is at the starting point of the needling procedure;

[0013] S8, covering with film: covering the upper surface of the pre-needled layer completed in S7 with a layer of film, and sticking the four corners of the film to the bottom felt foam on the needle-punching platform with transparent tape;

[0014] S9, generating a robot pre-needling execution program: inputting the stepping amount, number of rows and columns, position information of the starting point of acupuncture, and the thickness value of the current fabric obtained in S3-S5 into the parametric programming software of the acupuncture robot running in the host computer to generate a robot pre-needling execution program;

[0015] S10, performing pre-needling: importing the pre-needling execution program generated in S9 into the robot controller, and starting the acupuncture robot to start pre-needling;

[0016] S11, main thorn laying: peel off the tape fixed around the film, peel off the fixed film, ensure that the position of the needle-punched fabric remains unchanged, lay the net tire required for the main thorn on the surface of the fabric pre-punctured in S10, ensure that the laying position is aligned, cover the fabric with the film again and fix it with tape;

[0017] S12, generating the robot main needle execution program: modifying the current fabric thickness value in the host computer, running the acupuncture robot parameterized programming software again, and generating the robot main needle execution program;

[0018] S13, performing in-situ main acupuncture: importing the main acupuncture execution program generated in S12 into the robot controller, moving the robot so that the acupuncture actuator approaches the acupuncture starting point, and starting the acupuncture robot to start the main acupuncture; the X-axis coordinates and Y-axis coordinates of the trajectory coordinate points of the main acupuncture and the pre-acupuncture coincide, that is, the in-situ main acupuncture;

[0019] S14. Online measurement of fabric thickness: insert a steel ruler into the bottom surface of the fabric, place a thickness measuring weight on the top surface of the fabric, use a thickness measuring needle with a length mark to penetrate the fabric along the edge of the weight until it reaches the top surface of the steel ruler inserted along the bottom surface of the fabric, use another steel ruler to measure the length of the steel needle left outside the fabric, and calculate the thickness of the fabric;

[0020] S15, cyclic needling: after the needling of the first unit layer is completed, S7 to S14 are cyclically repeated until the needling reaches the target thickness of the preform.

[0021] Furthermore, the density of pre-needling needles does not exceed 3 to 5 needles / cm 2 The pre-puncture needle has a conventional barb spacing; the pre-puncture-formed ultra-thin carbon fiber mesh has a tread density of about 20 to 30 g / m 2 .

[0022] Furthermore, the thickness measuring instrument used in S2 is the JIGAO YG141D digital fabric thickness gauge; the test standard is ISO 9073.2:1995 "Textiles - Test methods for nonwovens - Part 2: Determination of thickness".

[0023] Furthermore, in S3, two red tapes are perpendicularly pasted on the needle punching platform, and the end point of the angle is the starting point of the needle punching; when laying the needle punched fabric, the end point of the fabric coincides with the starting point of the needle punching, and the long side and the wide side of the fabric are laid in parallel directions along the two tapes.

[0024] Furthermore, the S6 includes S6-1 designing a cutting program; S6-2 cutting; and S6-3 weighing raw materials.

[0025] Furthermore, the S6-2 includes placing the base cloth to be cut on the Lectra cutting table, ensuring that the warp and weft yarns of the fiber cloth are respectively parallel to the X and Y coordinate axes of the cutting table, and loading the cutting program file; setting the cutting speed, starting the cutting table, and the cutting table drives the cutter to cut the base cloth according to the designed cutting trajectory; placing the ultra-thin carbon fiber mesh on the Lectra cutting table, setting the cutting speed, starting the cutting table, and the cutting table cuts the ultra-thin carbon fiber mesh according to the predetermined cutting program.

[0026] Furthermore, S6-3 includes weighing the cut raw materials in S6-2 and comparing them with the theoretical weight, and replacing the ultra-thin fiber mesh with excessive weight difference so that its weight meets the theoretical requirement; the theoretical weight is the product of the surface density of the ultra-thin carbon fiber mesh and the size of the carbon fiber mesh required for actual needle punching.

[0027] Furthermore, the size of the film in S8 is larger than the puncture area; the film is made of polyethylene and has a thickness of about 0.01 mm; when fixing the film, the ply is first pressed to a certain extent through the film, so that after the film is fixed, it can generate a certain tension on the ply, thereby better fixing the position of the ply.

[0028] Furthermore, after the acupuncture robot returns to the acupuncture starting point in S10, the acupuncture robot is manipulated so that the acupuncture actuator is raised a certain distance in the vertical direction to facilitate the laying of the main acupuncture layer.

[0029] Furthermore, the X and Y coordinates of the main puncture point in the in-situ main puncture in S13 are the same as the X and Y coordinates of the pre-puncture point, and only the thickness direction is different. When observed from the horizontal direction, the two puncture trajectories are exactly the same.

[0030] The present invention has the advantages and positive effects:

[0031] 1. The present invention adopts a pre-punching / main-punching coordinated needle punching forming method. Pre-punching generates prefabricated holes, which is beneficial for the needle to bring short fibers into the thickness direction to form needle-punched fiber bundles during the main puncture process, thereby improving the interlayer peeling performance of the needle-punched fabric.

[0032] 2. The present invention adopts in-situ needling, that is, the X-axis coordinates and Y-axis coordinates of the trajectory coordinate points of the main needling and the pre-needling coincide, which effectively reduces the needling area, thereby reducing the damage of the needling needle to the base fabric and improving the in-plane tensile properties of the needling fabric.

[0033] 3. The present invention uses a fabric thickness measuring instrument to measure the thickness of the unit layer material and obtain accurate unit layer thickness data, which is conducive to the accurate cumulative calculation of the fabric thickness, thereby accurately setting the position height of the stripping plate to avoid excessive squeezing of the stripping plate on the needle-punched fabric, resulting in interlayer damage and stratification.

[0034] 4. The present invention adopts a cutting table to cut the ultra-thin mesh and weighs the mesh to ensure that the weight of the mesh in the unit layer meets the requirements, thereby improving the stability of the needle punching forming process.

[0035] 5. The present invention covers the upper surface of the paving layer with a layer of film, and the four corners of the film are adhered to the bottom felt foam on the needle punching platform with transparent tape. The fixed film has a certain tension, which has a compacting and densifying effect on the web layer, which is beneficial for the needles to hook more short fibers to form needle punched fiber bundles during the needle punching process. At the same time, the film also plays an efficient web stripping role to prevent the needle punched fiber bundles from being brought out by the needles. The combination of the two effectively improves the molding effect of the needle punched fiber bundles, thereby improving the interlayer performance of the fabric.

[0036] 6. The traditional flat-plate needling machine only feeds and needles in one direction, resulting in the in-plane mechanical properties of the fabric in the direction of movement being weaker than the properties perpendicular to the direction of movement, and the in-plane mechanical properties of the fabric being uneven. This method proposes the use of a matrix dot-matrix needling trajectory, which can eliminate the influence of the movement direction on the fabric properties, and the fabric can obtain uniform in-plane mechanical properties.

[0037] 7. The present invention adopts online measurement of fabric thickness, which is beneficial to real-time monitoring of fabric volume density and ensures the volume fraction and overall mechanical properties of the needle-punched fabric.

[0038] 8. The present invention adopts a host computer to edit, modify and download the acupuncture robot program, and controls acupuncture through the pre-puncture execution program and the main acupuncture execution program respectively, which is fast and convenient and improves efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic structural diagram of a needle-punched fabric based on pre- / main-punch synergy in the present invention;

[0040] Figure 2 is a flow chart of acupuncture process of the present invention;

[0041] Figure 3 This is a schematic diagram of the knife setting of the acupuncture robot in the present invention;

[0042] Figure 4 It is a schematic diagram of the pre-needling / main-needling coordinated acupuncture trajectory in the present invention;

[0043] Figure 5 It is a schematic diagram of online measurement of fabric thickness.

[0044] In the figure, 1-pre-needle net layer; 2-main needle net layer; 3-needle point; 4-needle fiber bundle; 5-base cloth; 6-needle platform; 7-needle starting point; 8-needle actuator; 9-first steel ruler; 10-second steel ruler; 11-weight. DETAILED DESCRIPTION

[0045] In order to further disclose the content, features and effects of the present invention, the following examples are given and described in detail with reference to the accompanying drawings.

[0046] See attached Figure 1-5, a needle punching method for improving the mechanical properties of needle punched fabrics, comprising the following steps:

[0047] S1. Preparation of ultra-thin carbon fiber web:

[0048] The carbon fiber yarn is cut into short yarns of equal length, and then further loosened, combed, laid in layers, and pre-punctured to form an ultra-thin carbon fiber web;

[0049] Preferably, the length of the short yarn is about 40 mm to 70 mm; the number of layers is four; the tread density of the carbon fiber yarn net during the carding process is 6 to 8 g / m 2 The density of pre-needling should not exceed 3-5 needles / cm 2 The pre-puncture needle has a conventional barb spacing; the pre-puncture-formed ultra-thin carbon fiber mesh has a tread density of about 20 to 30 g / m 2 ;

[0050] S2. Calculate the thickness of the unit layer:

[0051] A fabric thickness measuring instrument is used to measure the thickness of the unit layer based on the thickness test standard. A sample of the raw material required for the experiment is cut and placed on the measuring platform of the fabric thickness measuring instrument. The fabric thickness measuring instrument is started and the instrument measures the thickness of the raw material. Based on the thickness measurement standard, the actual thickness is obtained and the theoretical value of the unit layer thickness is calculated according to different unit layer ply designs.

[0052] The thickness measuring instrument used in S2 is a JIGAO YG141D digital fabric thickness gauge; the test standard is ISO 9073.2:1995 "Textiles - Test methods for nonwovens - Part 2: Determination of thickness";

[0053] S3. Calculation of acupuncture step amount:

[0054] According to the number of needles on the needle board of the needle punching robot and the needle punching density (needles / cm 2 ), calculate the acupuncture row step amount; the number of needles on the needle board is N, and the acupuncture density is M (needles / cm 2 ), the step size is S (cm), and S 2 =N / M;

[0055] S4. Calculation of the number of acupuncture rows and columns:

[0056] The number of needling rows and columns is calculated according to the stepping amount and the length and width of the fabric; the needling stepping amount is S (cm), the length and width of the fabric are A cm and B cm respectively, then the number of needling rows and columns is A / S and B / S respectively;

[0057] S5. Acupuncture robot knife setting:

[0058] On the acupuncture work platform, two red tapes are pasted perpendicularly to each other on the acupuncture platform 6, and the end point of the angle is the acupuncture starting point 7 (such as Figure 3 As shown), when laying the needle-punched fabric, the end point of the fabric coincides with the starting point of the needle-punching, and the long side and the wide side of the fabric are laid along the parallel directions of the two tapes respectively. The needle-punching robot is moved so that the needle-punching actuator 8 is aligned with the needle-punching starting point 7 determined by the red tape, and the posture information of this point is read and recorded; preferably, the needle-punching starting point 7 is a point randomly selected on the needle-punching platform 6, but it is necessary to ensure that the needle-punched fabric can be completely laid on the needle-punching platform 6 along the starting point, and the needle-punched fabric cannot be suspended;

[0059] S6. Cutting and weighing the raw materials required for the unit layer:

[0060] The base cloth and the web are cut by a cutting table, and the web is weighed to ensure that the weight of the web in the unit layer meets the requirements; the web has two layers, one for pre-puncture and the other for main puncture; S6 includes S6-1 designing the cutting program; S6-2 cutting and S6-3 weighing the raw materials;

[0061] The S6-1 uses AUTOCAD software to design the cutting trajectory; according to the size of the base cloth, the cutting area is flexibly designed so that the cutting area covers the entire fiber cloth as much as possible to reduce the waste of raw materials; the cutting trajectory is exported to dwg format in AUTOCAD software, and then the dwg file is opened with DESIGNCONCEPT TECHTEX, a Lectra cutting table design software, and the cutting lines are assigned according to the sketch, and saved as xin files and dat files respectively; the xin files and dat files are loaded and laid out with DIAMINO TECHTEX, a Lectra cutting table layout software, to generate MKX and PLX cutting program files;

[0062] The S6-2 includes placing the base fabric to be cut on the Lectra cutting table, ensuring that the warp and weft of the fiber fabric are parallel to the X and Y coordinate axes of the cutting table respectively, and loading the MKX and PLX cutting program files; setting the cutting speed, starting the cutting table, and the cutting table drives the cutter to cut the base fabric according to the designed cutting trajectory; placing the ultra-thin carbon fiber mesh tire on the Lectra cutting table, setting the cutting speed, starting the cutting table, and the cutting table cuts the ultra-thin carbon fiber mesh tire according to a predetermined cutting program; the cutting speed is 10-15 m / min, and the base fabric is a woven fabric, specifically a satin fabric, a twill fabric or a plain fabric;

[0063] S6-3 includes weighing the cut raw materials in S6-2 and comparing them with the theoretical weight, combing the ultra-thin fiber webs with excessive weight differences to make their weight meet the theoretical requirements; the theoretical weight is the product of the surface density of the ultra-thin carbon fiber web and the size of the carbon fiber web required for actual needle punching;

[0064] S7, Pre-puncture laying:

[0065] The needle-punched raw materials cut in S6 are laid on the needle-punching platform 6 in the order of laying layers. The base cloth 6 is laid first, and the pre-punched mesh layer 1 is laid on the top. It is ensured that each layer is laid with the needle-punching starting point 8 determined in S5 as the origin, and the long and wide sides are parallel to the direction of the red tape attached to the needle-punching platform 6. Each layer should be laid exactly the same as the previous layer to avoid laying misalignment.

[0066] S8, cover with film:

[0067] Cut a piece of film, the size of which should be larger than the needle punching area, and cover the upper surface of the pre-puncture ply completed in S7 with a layer of film, and stick the four corners of the film on the bottom felt foam on the needle punching platform 6 with transparent tape; the film is made of polyethylene and has a thickness of about 0.01 mm; when fixing the film, first press the ply to a certain extent through the film, so that after the film is fixed, it can generate a certain tension on the pre-puncture ply, so as to better fix the position of the pre-puncture ply;

[0068] S9. Generate robot pre-stab execution program:

[0069] Taking the raw material thickness measured in S2 as a reference, the current theoretical value of the ply thickness is calculated according to the actual number of unit layers, and the stepping amount, number of rows and columns, position information of the starting point of acupuncture, and the current thickness value of the fabric obtained in S3-S5 are input into the parametric programming software of the acupuncture robot running in the host computer to generate a robot pre-needling execution program;

[0070] S10, pre-puncture:

[0071] Import the pre-needling execution program generated in S9 into the robot controller, load the program, ensure that the program is loaded normally, the fabric is laid and the film is fixed correctly, and the robot working area is normal. After being able to correctly and safely execute the corresponding program, control the acupuncture robot to perform acupuncture according to the pre-needling execution program. First, perform the single-step acupuncture step to check whether there is any problem with the acupuncture situation. After confirming that it is correct, change it to the automatic acupuncture mode. The robot acupunctures according to the predetermined program. After the acupuncture is completed, the robot will control the acupuncture actuator 8 to return to the acupuncture origin to prepare for the next acupuncture;

[0072] Preferably, after the acupuncture robot returns to the acupuncture origin, the acupuncture robot is manipulated to raise the acupuncture actuator 8 by a certain distance in the vertical direction, so as to facilitate the laying of the main acupuncture layer;

[0073] S11, Main thorn layer:

[0074] Remove the tape fixed around the film, remove the fixed film, ensure that the position of the needle-punched fabric remains unchanged, lay the mesh required for the main needle-punching on the surface of the fabric pre-punctured in S10, ensure that the laying position is aligned, cover the fabric with the film again and fix it with tape;

[0075] S12, generate robot main thorn execution program:

[0076] Calculate the theoretical value of the current layer thickness, modify the current fabric thickness value in the host computer, ensure that the data such as the needling step amount, the number of needling rows and columns, and the needling starting point 7 remain unchanged, and run the needling robot parameter programming software again to generate the robot main needling execution program;

[0077] S13, perform the main puncture in situ:

[0078] The main acupuncture execution program generated in S12 is imported into the robot controller, the robot is moved so that the acupuncture actuator 8 is close to the acupuncture starting point 7, the program is executed, and the acupuncture situation is observed to be normal. After confirmation, the automatic acupuncture mode is executed, and the acupuncture robot is started to start the main acupuncture; the X-axis coordinates and Y-axis coordinates of the trajectory coordinate points of the main acupuncture and the pre-puncture coincide, that is, the in-situ main acupuncture; the in-situ main acupuncture is the main acupuncture point. The X, Y coordinates of the acupuncture point are the same as the X, Y coordinates of the pre-puncture point, and the only difference is the thickness direction. The two acupuncture trajectories are exactly the same when observed from the horizontal direction (such as Figure 4 In-situ acupuncture is adopted, that is, the X-axis coordinates and the Y-axis coordinates of the trajectory coordinate points of the main puncture and the pre-puncture coincide with each other, which effectively reduces the acupuncture area, thereby reducing the damage of the needle to the base fabric and improving the in-plane tensile properties of the acupuncture fabric;

[0079] S14, online measurement of fabric thickness:

[0080] After the needle punching is completed, ensure that the position of the needle punched fabric remains unchanged, insert the first steel ruler 9 into the gap between the needle punching platform 6 and the needle punched fabric in the horizontal direction, place a weight 11 on the surface of the fabric, take a marked thickness measuring needle, use the second steel ruler 10 to measure the distance from the mark to the tip of the thickness measuring needle and record the data C (mm). After the measurement is completed, insert the thickness measuring needle vertically into the needle punched fabric along the edge of the weight 11 until the tip of the thickness measuring needle touches the first steel ruler 9, and use the second steel ruler 10 to vertically place it on the surface of the fabric (such as Figure 5 As shown in the figure, get close to the thickness gauge needle, measure the distance between the fabric surface and the thickness gauge needle mark point at this time and record the data D (mm); calculate the fabric thickness as CD (mm)

[0081] S15, Circulation Acupuncture:

[0082] After the first unit layer is needled, steps S7 to S14 are repeated in a loop until the needled layer reaches the target thickness of the preform.

[0083] Example 1

[0084] The needle-punched fabric is prepared by the method of the present invention. The needle-punched fabric uses four layers of 0-degree non-wefted fabric and two layers of mesh tires, and the mesh tire surface density is 25g / m 2 , non-woven fabric surface density 237g / m 2 The pre-stab / main stab process is as follows:

[0085] Pre-needling process: lay four layers of 0-degree non-woven fabric and one layer of mesh (the mesh is on the top) for pre-needling, and the pre-needling density is 5 needles / cm 2 , the acupuncture depth is 15mm.

[0086] Main puncture process: lay a layer of mesh on the top of the pre-punctured fabric, and then carry out the main puncture. The main puncture density is 5 needles / cm 2 , the acupuncture depth is 15mm.

[0087] The total number of needling passes is two, and a needle-punched fabric is obtained.

[0088] Comparative Example 1

[0089] The needle-punched fabric is prepared by a traditional needle-punching method. The needle-punched fabric uses four layers of 0-degree non-wefted fabric and one layer of mesh tire. The mesh tire surface density is 50g / m 2 , non-woven fabric surface density 237g / m 2 The acupuncture process is as follows:

[0090] Lay four layers of 0-degree non-woven fabric and one layer of mesh (the mesh is on the top) for acupuncture, with a density of 10 needles / cm 2 , the acupuncture depth is 15mm.

[0091] The total number of needling passes is one time, and a needle-punched fabric is obtained.

[0092] Example 2

[0093] The needle-punched fabric is prepared by the method of the present invention. The needle-punched fabric uses four layers of 0-degree non-wefted fabric and two layers of mesh tires, and the mesh tire surface density is 25g / m 2 , non-woven fabric surface density 237g / m 2 The pre-stab / main stab process is as follows:

[0094] Pre-needling process: lay four layers of 0-degree non-woven fabric and one layer of mesh (the mesh is on the top) for pre-needling, and the pre-needling density is 8 needles / cm 2 , the acupuncture depth is 15mm.

[0095] Main puncture process: lay a layer of mesh on the top of the pre-punctured fabric, and then carry out the main puncture, the main puncture density is 8 needles / cm 2 , the acupuncture depth is 15mm.

[0096] The total number of needling passes is two, and a needle-punched fabric is obtained.

[0097] Comparative Example 2

[0098] The needle-punched fabric is prepared by a traditional needle-punching method. The needle-punched fabric uses four layers of 0-degree non-wefted fabric and one layer of mesh tire. The mesh tire surface density is 50g / m 2 , non-woven fabric surface density 237g / m 2 The acupuncture process is as follows:

[0099] Lay four layers of 0-degree non-woven fabric and one layer of mesh (the mesh is on the top) for acupuncture, with a needle density of 16 needles / cm 2 , the acupuncture depth is 15mm.

[0100] The total number of needling passes is one time, and a needle-punched fabric is obtained.

[0101] Example 3

[0102] The needle-punched fabric is prepared by the method of the present invention. The needle-punched fabric uses four layers of 0-degree non-wefted fabric and two layers of mesh tires, and the mesh tire surface density is 25g / m 2 , non-woven fabric surface density 237g / m 2 The pre-stab / main stab process is as follows:

[0103] Pre-needling process: lay four layers of 0-degree non-woven fabric and one layer of mesh (the mesh is on the top) for pre-needling, and the pre-needling density is 10 needles / cm 2 , the acupuncture depth is 15mm.

[0104] Main puncture process: lay a layer of mesh on the top of the pre-punctured fabric, and then carry out the main puncture. The main puncture density is 10 needles / cm 2 , the acupuncture depth is 15mm.

[0105] The total number of needling passes is two, and a needle-punched fabric is obtained.

[0106] Comparative Example 3

[0107] The needle-punched fabric is prepared by a traditional needle-punching method. The needle-punched fabric uses four layers of 0-degree non-wefted fabric and one layer of mesh tire. The mesh tire surface density is 50g / m 2 , non-woven fabric surface density 237g / m 2 The acupuncture process is as follows:

[0108] Lay four layers of 0-degree non-woven fabric and one layer of mesh (the mesh is on the top) for acupuncture, with a needle density of 20 needles / cm 2 , the acupuncture depth is 15mm.

[0109] The total number of needling passes is one time, and a needle-punched fabric is obtained.

[0110] The in-plane tensile strength and interlayer peel strength of the prepared needle-punched preform tested according to GJB 1867-64 are shown in Table 1.

[0111] Table 1

[0112] Fabric Source In-plane tensile strength / MPa Interlayer peel strength N / mm Example 1 352.47 0.52 Comparative Example 1 323.94 0.33 Example 2 284.59 0.57 Comparative Example 2 252.55 0.37 Example 3 232.82 0.79 Comparative Example 3 201.30 0.50

[0113] It can be seen from Table 1 that Comparative Examples 1, 2 and 3 adopt the traditional needling method, while Examples 1, 2 and 3 adopt the fabric prepared by the needling preform method for improving the mechanical properties of the fabric introduced in the present invention. Compared with Comparative Example 1, the in-plane tensile strength of Example 1 is increased by 8.8%, and the interlayer peel strength is increased by 58.46%; compared with Comparative Example 2, the in-plane tensile strength of Example 2 is increased by 12.7%, and the interlayer peel strength is increased by 56.16%; compared with Comparative Example 3, the in-plane tensile strength of Example 3 is increased by 15.7%, and the interlayer peel strength is increased by 57.65%.

[0114] Although the preferred embodiments of the present invention are described above, the present invention is not limited to the above specific embodiments, which are merely illustrative and not restrictive. Under the guidance of the present invention, a person skilled in the art can make many forms without departing from the scope of the present invention and the claims. All of these belong to the protection scope of the present invention.

Claims

1. A needle punching method for improving the mechanical properties of needle punched fabrics, characterized in that: The following steps are involved: S1. Preparing an ultra-thin carbon fiber web: cutting the carbon fiber yarn into short yarns of equal length, further opening and combing, stacking and laying, and pre-puncturing to form an ultra-thin carbon fiber web; S2. Calculate the thickness of the unit layer: Use a fabric thickness measuring instrument to calculate the thickness of the unit layer based on the thickness test standard; S3. Calculation of acupuncture stepping amount: Calculate the acupuncture row and column stepping amount according to the number of needles on the needle board of the acupuncture robot and the acupuncture density; S4. Calculation of the number of needle punching rows and columns: Calculate the number of needle punching rows and columns according to the stepping amount and the length and width of the fabric; S5. Acupuncture robot knife alignment: On the acupuncture work platform, mark the acupuncture starting point with red tape; move the acupuncture robot so that the acupuncture actuator is aligned with the acupuncture starting point, and record the position information of the acupuncture starting point; S6. Cutting and weighing the raw materials required for the unit layer: cutting the base cloth and the mesh with a cutting table, and weighing the mesh to ensure that the weight of the mesh in the unit layer meets the requirements; the mesh has two layers, one for pre-puncture and the other for main puncture; S7, pre-needling layer: first lay the base fabric, then lay the web layer; one corner of the layer material is at the starting point of the needling procedure; S8, covering with film: covering the upper surface of the pre-needled layer completed in S7 with a layer of film, and sticking the four corners of the film to the bottom felt foam on the needle-punching platform with transparent tape; S9, generating a robot pre-needling execution program: inputting the stepping amount, number of rows and columns, position information of the starting point of acupuncture, and the thickness value of the current fabric obtained in S3-S5 into the parametric programming software of the acupuncture robot running in the host computer to generate a robot pre-needling execution program; S10, performing pre-needling: importing the pre-needling execution program generated in S9 into the robot controller, and starting the acupuncture robot to start pre-needling; S11, main thorn laying: peel off the tape fixed around the film, peel off the fixed film, ensure that the position of the needle-punched fabric remains unchanged, lay the net tire required for the main thorn on the surface of the fabric pre-punctured in S10, ensure that the laying position is aligned, cover the fabric with the film again and fix it with tape; S12, generating the robot main needle execution program: modifying the current fabric thickness value in the host computer, running the acupuncture robot parameterized programming software again, and generating the robot main needle execution program; S13, performing in-situ main acupuncture: importing the main acupuncture execution program generated in S12 into the robot controller, moving the robot so that the acupuncture actuator approaches the acupuncture starting point, and starting the acupuncture robot to start the main acupuncture; the X-axis coordinates and Y-axis coordinates of the trajectory coordinate points of the main acupuncture and the pre-acupuncture coincide, that is, the in-situ main acupuncture; S14. Online measurement of fabric thickness: insert a steel ruler into the bottom surface of the fabric, place a thickness measuring weight on the top surface of the fabric, use a thickness measuring needle with a length mark to penetrate the fabric along the edge of the weight until it reaches the top surface of the steel ruler inserted along the bottom surface of the fabric, use another steel ruler to measure the length of the steel needle left outside the fabric, and calculate the thickness of the fabric; S15, cyclic needling: after the needling of the first unit layer is completed, S7 to S14 are cyclically repeated until the needling reaches the target thickness of the preform.

2. A needle punching method for improving the mechanical properties of needle punched fabrics according to claim 1, characterized in that: The density of pre-needling needles should not exceed 3~5 needles / cm 2 The pre-puncture needle has a barb spacing of conventional spacing; the pre-puncture formed ultra-thin carbon fiber mesh tread density is 20-30g / m 2 .

3. A needle punching method for improving the mechanical properties of needle punched fabrics according to claim 1, characterized in that: The thickness measuring instrument used in S2 is a digital fabric thickness meter.

4. A needle punching method for improving the mechanical properties of needle punched fabrics according to claim 1, characterized in that: In S3, two red tapes are perpendicularly pasted on the needle punching platform, and the end point of the angle is the starting point of the needle punching; when laying the needle punched fabric, the end point of the fabric coincides with the starting point of the needle punching, and the long side and the wide side of the fabric are laid along the parallel directions of the two tapes.

5. A needle punching method for improving the mechanical properties of needle punched fabrics according to claim 1, characterized in that: The S6 includes S6-1 designing a cutting program; S6-2 cutting; and S6-3 weighing raw materials.

6. A needle punching method for improving the mechanical properties of needle punched fabrics according to claim 5, characterized in that: The S6-2 includes placing the base cloth to be cut on the Lectra cutting table, ensuring that the warp and weft of the fiber cloth are respectively parallel to the X and Y coordinate axes of the cutting table, and loading the cutting program file; setting the cutting speed, starting the cutting table, and the cutting table drives the cutter to cut the base cloth according to the designed cutting trajectory; placing the ultra-thin carbon fiber mesh tire on the Lectra cutting table, setting the cutting speed, starting the cutting table, and the cutting table cuts the ultra-thin carbon fiber mesh tire according to the predetermined cutting program.

7. A needle punching method for improving the mechanical properties of needle punched fabrics according to claim 6, characterized in that: The S6-3 includes weighing the cut raw materials in S6-2 and comparing them with the theoretical weight, and replacing the ultra-thin fiber mesh tires with excessive weight difference to make their weight meet the theoretical requirements; the theoretical weight is the product of the ultra-thin carbon fiber mesh tire surface density and the carbon fiber mesh tire size actually required for needle punching.

8. A needle punching method for improving the mechanical properties of needle punched fabrics according to claim 1, characterized in that: The size of the film in S8 should be larger than the puncture area; the film material is polyethylene, and the thickness is 0.01 mm; when fixing the film, the layer is first pressed through the film.

9. A needle punching method for improving the mechanical properties of needle punched fabrics according to claim 1, characterized in that: After the acupuncture robot returns to the acupuncture starting point in S10, the acupuncture robot is manipulated to raise the acupuncture actuator by a certain distance in the vertical direction, so as to facilitate the laying of the main acupuncture layer.

10. A needle punching method for improving mechanical properties of needle punched fabric according to claim 1, characterized in that: The in-situ main puncture in S13 is that the X and Y coordinates of the main puncture point are the same as the X and Y coordinates of the pre-puncture point, and only the thickness direction is different. When observed from the horizontal direction, the two puncture trajectories are exactly the same.

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