A unit layer mat for preparing a carbon fiber crucible preform, a carbon fiber crucible preform, and a method of preparing the same

Abstract

The application relates to the technical field of carbon fiber composite materials, and particularly discloses a unit layer base cloth for preparing a carbon fiber crucible preform, the carbon fiber crucible preform and a preparation method thereof. The unit layer base cloth disclosed by the application is integrally composed of an upper part of a rectangular structure layer and a lower part composed of n same petal-shaped structure layers connected in sequence, the petal-shaped structure layer comprises four arc segments; the lower part is formed by head-to-tail splicing in the weft direction to form an R angle and a bottom of the carbon fiber crucible preform, and the arc lines of two adjacent petal-shaped structure layers completely coincide at the junction. The application further provides a preparation method of the unit layer base cloth and a carbon fiber crucible preform prepared by using the unit layer base cloth. When the unit layer base cloth is used to prepare the carbon fiber crucible preform, the operation is simple, practical and safe, the phenomenon of ribbing at gaps and poor needling effect is greatly reduced, the hoop strength of the R bottom of the preform, the stability of the interlayer structure and the overall performance of the needling of the layers are ensured.

Description

Technical Field

[0001] This application relates to the technical field of carbon fiber composite materials, specifically to a unit layer preform for preparing carbon fiber crucible preforms, a carbon fiber crucible preform, and a method for preparing the same. Background Technology

[0002] Carbon / carbon composite crucibles, as a type of carbon protective vessel with high design flexibility and excellent performance, represent an important technological direction for manufacturing large-size graphite crucibles. Carbon fiber crucible preforms serve as the skeleton material for carbon / carbon composite crucibles.

[0003] Currently, carbon fiber crucible preforms are generally produced by cutting the unit layers on a mold or by continuously laying and cutting the entire fabric into segments. However, the cutting method and the R-corner seam are consistent with the needle direction of the needle punch, which can easily cause ridges and pits, making it very easy for the crucible product to not meet the requirements in terms of shape and for the unit layers to be misaligned. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, this application provides a unit layer fabric for preparing carbon fiber crucible preforms, a carbon fiber crucible preform, and a method for preparing the same.

[0005] In a first aspect, this application provides a unit layer blank for preparing carbon fiber crucible preforms, characterized in that the unit layer is integrally composed of an upper part (4) and a lower part (5);

[0006] The upper part is a rectangular structure layer; the upper part is seamlessly and flatly overlapped after being spliced ​​end to end in the latitudinal direction to form the crucible straight section unit layer (1) of the carbon fiber crucible preform;

[0007] The lower part is composed of n identical petal-shaped structural layers (51) connected in sequence, where n = 5 or 6. The petal-shaped structural layer includes a first arc segment (51), a second arc segment (52), a third arc segment (53), and a fourth arc segment (54). The radii of the first arc segment and the fourth arc segment are the radii corresponding to the R-angle region of the carbon fiber crucible preform, and the corresponding central angle is 5-30°. The chord length of the second arc segment and the third arc segment is the radius corresponding to the bottom region of the carbon fiber crucible preform, and the corresponding central angle is 30-150°.

[0008] The lower part is seamlessly and smoothly overlapped after being spliced ​​together in the latitudinal direction to form the crucible R-angle (2) and crucible bottom (3) of the carbon fiber crucible preform, and the arc junctions of two adjacent petal-shaped structural layers completely overlap.

[0009] Wherein, the weft direction of the unit layer fabric is the axial direction of the carbon fiber crucible preform, and the warp direction of the unit layer fabric is the direction around the ply circumference of the carbon fiber crucible preform.

[0010] The advantages of the unit layer fabric for preparing carbon fiber crucible preforms provided in this application are that an arc-shaped seam is formed between the unit layer petals during the needle punching process. The seam is needle punched point by point, avoiding the phenomenon in the prior art where long strips are needled simultaneously, causing ridges at the seams and poor needle punching effect. Then, a thickening layer is used to enhance the circumferential strength at the bottom of the R-corner, compensating for the defects of the bottom petals of the unit layer R-corner. The staggered plywood needle punching reinforcement effect is even better.

[0011] Preferably, the central angles corresponding to the second arc segment and the third arc segment are 30-120°.

[0012] In one specific embodiment, the angle corresponding to the arc can be 30°, 60°, 90°, 120°, or 150°.

[0013] In some specific embodiments, the angle corresponding to the arc can also be 30-60°, 30-90°, 30-120°, 60-90°, 60-120°, 60-150°, 90-120°, 90-150°, or 120-150°.

[0014] When the angle corresponding to the arc is 60°, the dividing line is an arc drawn with the circumference of the equally divided circumference as the center and the circumference of the bottom surface of the carbon fiber crucible preform as the radius.

[0015] The inventors of this application discovered that when drawing a segmentation diagram based on the bottom surface of the carbon fiber crucible preform, and controlling the angle corresponding to the arc to be within the aforementioned range, the drawn arc serves as the segmentation line. The unfolded diagram of the unit layer fabric is obtained by expanding along the new segmentation line. In the subsequent needle-punching process, the unit layer fabric cut from the unfolded diagram obtained by this method exhibits a more regular arc shape along the weft direction at the bottom of the R-angle segment connection. Needling will gradually complete the gap needle-punching along the straight section and the R-angle node, thus largely avoiding material lifting and needle-punching edge formation caused by needle-punching along the gap. This also makes the needle-punching process simpler and safer.

[0016] Preferably, the petal-shaped structure layer further includes a fifth arc segment (55), the two ends of which are connected to the second arc segment and the third arc segment respectively. After the fifth arc segment is spliced ​​end to end in the latitudinal direction, it seamlessly and smoothly overlaps to form a circular opening (6) at the bottom of the crucible of the carbon fiber crucible preform, and the arcs of two adjacent petal-shaped structure layers completely overlap.

[0017] When the bottom of the carbon fiber crucible preform has a circular opening, it can be prepared using the aforementioned unit layer fabric including the fifth arc segment.

[0018] Preferably, the unit layer fabric is cut from carbon fiber composite fabric, and the specific method for preparing the carbon fiber composite fabric is as follows:

[0019] Carbon fibers are woven into carbon fiber cloth; short-cut carbon fibers are spun into a mesh; then a single layer of the mesh is laid on a single layer of the carbon fiber cloth, and composite pre-needling is performed to form the carbon fiber composite cloth.

[0020] Preferably, in the method for preparing the carbon fiber composite fabric:

[0021] The carbon fiber has the following specifications: 12K; the carbon fiber cloth has the following specifications: 2-4 yarns / cm in the radial direction and 2-4 yarns / cm in the weft direction.

[0022] The chopped carbon fiber has a diameter of 60-70mm, and the mesh has a diameter of 55-85g / m². 2 ;

[0023] The density ratio of the carbon fiber fabric to the mesh in the carbon fiber composite fabric is 3:1, and the pre-needling process parameters are: pre-needling depth 5-12mm, pre-needling density 4-10 needles / cm. 2 .

[0024] Secondly, this application provides a method for preparing the aforementioned unit layer fabric, specifically including the following steps:

[0025] The fabric is obtained by cutting using the layup pattern of the unit layer fabric.

[0026] The layup development diagram of the unit layer fabric is obtained by taking the bottom and R-angle of the carbon fiber crucible preform as the reference, and drawing an arc as the dividing line with the center point of the bottom and the circumference of the R-angle as the starting point and the ending point. The layup development diagram of the unit layer fabric is obtained by unfolding along the dividing line.

[0027] The number of points dividing the circumference of the R-angle is 5 or 6; the layup development diagram of the unit layer fabric divides the R-angle unit layer and the bottom unit layer of the carbon fiber crucible preform into 5-6 segments; the size of each unit layer fabric increases layer by layer.

[0028] The method for preparing unit layer fabric for carbon fiber crucible preforms provided in this application is simple, practical, and safe. It converts the layup diagram of the carbon fiber crucible preform into a three-dimensional diagram to create a layup unfolded diagram. The design of the layup unfolded diagram is based on the bottom surface of the carbon fiber crucible preform, which is used to draw a segmentation diagram. Then, based on the layup unfolded diagram obtained by segmentation, a unique cutting technique is used to cut the unit layer fabric, which greatly reduces the phenomenon of edge raising at the gaps and poor needle punching effect. It ensures the circumferential strength of the bottom of the preform R, the stability of the interlayer structure, and the overall performance of layup needle punching, and meets the shape standard.

[0029] Thirdly, this application provides a carbon fiber crucible preform prepared using the above-mentioned unit layer fabric.

[0030] Preferably, the carbon fiber crucible preform further includes a thickening layer of fabric, which is obtained by cutting the aforementioned carbon fiber composite fabric, specifically including the following steps:

[0031] The carbon fiber composite fabric is cut into strips for thickening, and adjusted and optimized to form an arc shape; the size of each layer of the thickened fabric is gradually increased, and the fabric is rolled up layer by layer after cutting.

[0032] The thickened layer cut in this application is an arc-shaped strip with strong continuity, which helps to enhance the circumferential strength at the bottom of the R-corner and compensate for the defect of the bottom of the R-corner of the unit layer being segmented.

[0033] Preferably, depending on the size and model of the carbon fiber crucible preform, the thickness of the thickening layer of the carbon fiber crucible preform is less than the thickness of the unit layer of the carbon fiber crucible preform.

[0034] Fourthly, this application provides a method for preparing the aforementioned carbon fiber crucible preform, specifically including the following steps:

[0035] The unit layer fabric and the thickened layer fabric are interleaved and needle-punched on a preform mold using a continuous lay-up method to form the carbon fiber crucible preform.

[0036] After the upper weft ends of the unit layer fabric are spliced ​​together, they are seamlessly and smoothly overlapped to form the crucible straight section unit of the carbon fiber crucible preform. After the lower part of the unit layer fabric is spliced ​​together, it is seamlessly and smoothly overlapped to form the crucible R-corner and crucible bottom of the carbon fiber crucible preform. The arc intersections of two adjacent petal-shaped structural layers completely overlap.

[0037] Preferably, the process parameters for the layer-by-layer needle punching are: needle punching depth 8-20 mm, needle punching density 20-40 needles / cm². 2 The unit layer density is 10-15 layers / cm.

[0038] Preferably, the continuous layup method includes the following steps:

[0039] The complete needle-punching process for a single unit layer is as follows: The unit layer fabric is neatly laid on the precast mold, and manually needle-punched to fix it. The mold is rotated one revolution to complete the laying of the entire unit layer fabric. The bottom of the R-corners is neatly spliced, and excess fabric is trimmed. Needling is then performed. After needle-punching, each layer is wound with carbon fiber using a grid, cross, or circumferential winding method to maintain the overall strength of the precast body. After the wire is wound, a layer of carbon fiber mesh is laid flat and needle-punched. This process of laying the unit layer fabric, needle-punching, wire winding, laying the mesh, and needle-punching is repeated continuously.

[0040] The complete needle-punching process of a thickening layer: After completing the needle-punching of the third unit layer, the thickening layer fabric is laid circumferentially at the designated position. First, it is manually needle-punched to fix it. Then, the mold is rotated one turn to complete the laying of the entire thickening layer fabric.

[0041] Then, the next unit layer, the next thickening layer, and needle punching are laid, so that the thickening layer fabric and the unit layer fabric are interleaved and needle punched until the size of the carbon fiber crucible preform meets the requirements.

[0042] In the specific implementation of staggered ply needle punching, during the needle punching of the bottom of the R-corner, because the bottom of the R-corner is connected by a segment in an arc along the latitudinal direction, the needle punching will gradually complete the gap needle punching along the straight section and the R-corner node, instead of directly needle punching along the gap, which would cause material lifting and needle punching edge phenomena.

[0043] The complete needle-punching process for a single unit layer in this application is as follows: laying the unit layer fabric, needle-punching, winding, laying the carbon fiber mesh, and needle-punching again. The design of laying a layer of carbon fiber mesh after laying the unit layer fabric compensates for the poor fiber continuity and weak bottom strength caused by the multi-lobed wrapping of the structural unit, and avoids cracking at the bottom of the crucible. At the same time, it helps to reduce the damage to the fibers caused by the needle-punching process, ensure the overall structural strength of the carbon fiber crucible preform, improve the quality of subsequent crucible products, and enhance the thermal insulation effect of the crucible.

[0044] After the third unit layer is laid and needled, a thickening layer of fabric is laid and needled, followed by the next unit layer of fabric, the thickening layer of fabric, and needled again. This process uses the thickening layer of fabric to reinforce the curved surface, ensuring sufficient strength in the weak points of the carbon fiber crucible preform and preventing deformation under high loads and expansion stress. Furthermore, the thickening layer effectively connects the straight sections, radius corners, and bottom of the crucible, ensuring shape stability under high strength and expansion stress. Therefore, the crucible prepared in this application ensures high strength, maintains excellent shape stability, and meets the requirements for use.

[0045] Preferably, the carbon fiber mesh has a specification of 45-65 g / m². 2 .

[0046] Furthermore, the specifications of the carbon fiber mesh are: 55±5g / m². 2 .

[0047] Experimental analysis shows that controlling the specifications of the carbon fiber mesh within the above-mentioned range in this application is beneficial to further enhance the overall structural strength of the preform and improve the quality of the crucible product.

[0048] In summary, the technical solution of this application has the following effects:

[0049] This application employs a unique cutting technique to cut the unit layer fabric, creating an arc-shaped seam between the unit layer petals during the needle punching process. The seam is needle punched point by point, greatly reducing the phenomenon of edge lifting and poor needle punching effect at the seam. This ensures the circumferential strength of the bottom of the precast body R, the stability of the interlayer structure, and the overall performance of the layup needle punching, while also meeting the shape standards.

[0050] This application utilizes a thickened layer to enhance the circumferential strength at the bottom of the radius corner, compensating for the defect of the bottom lobe of the radius corner of the unit layer, and employs staggered plying and needle punching to achieve a better reinforcement effect.

[0051] This application further optimizes the angle corresponding to the arc dividing line to optimize the cutting method of the unit layer fabric and the specific steps of the staggered layup needle punching, which further makes up for the shortcomings of poor fiber continuity and weak bottom strength caused by the multi-lobed wrapping of structural units, and avoids cracking at the bottom of the crucible; at the same time, it helps to reduce the damage to the fibers caused by the needle punching process, ensure the overall structural strength of the carbon fiber crucible preform, and improve the quality of subsequent crucible products. Attached Figure Description

[0052] Figure 1 This is a layup diagram of the carbon fiber crucible preform of this application; where 1 represents the straight section of the crucible, 2 represents the radius (R) of the crucible, and 3 represents the bottom of the crucible.

[0053] Figure 2 This is a cutting diagram of the unit layer blank fabric for the carbon fiber crucible preform of this application; wherein, Figure 2-1 This is a cutting pattern for a single-layer fabric unit without an opening at the bottom of the crucible. Figure 2-2 4 represents the cutting diagram of the unit layer fabric with a circular opening at the bottom of the crucible; 4 represents the upper part, which is the overall rectangular unfolded diagram of the unit layer based on the three-dimensional graphic of the straight section of the crucible; 5 represents the lower part, which is the 6-petal unfolded diagram of the crucible's R-corner and bottom based on the three-dimensional graphic; 51-first arc segment, 52-second arc segment, 53-third arc segment, 54-fourth arc segment, 55-fifth arc segment; A is the perimeter of the unit layer, and B is the width.

[0054] Figure 3 The blank fabric for the thickening layer of the carbon fiber crucible preform in this application is cut according to the three-dimensional graphic, and then adjusted and optimized to form an arc shape; A is the perimeter of the unit layer, and B is the width.

[0055] Figure 4 This is a design drawing of the unfolded dividing line in Embodiment 3 of this application, which divides the material into 6 petals.

[0056] Figure 5 This is a rendering of the unit layer material layout effect for this application; wherein, Figure 5-1 This is an illustration of the effect of layered material placement in a crucible without an opening at the bottom. Figure 5-2This is a diagram showing the effect of a unit layer with a circular opening at the bottom of the crucible; 6 indicates the connection point of the straight section, 7 indicates the bottom surface of the unit layer divided into 6 petals, and 8 indicates the needle placement position on the needle plate. Detailed Implementation

[0057] The present application will be further described in detail below with reference to embodiments, comparative examples and performance test results. These embodiments should not be construed as limiting the scope of protection claimed in this application.

[0058] Example

[0059] Example 1

[0060] This embodiment provides a method for preparing a carbon fiber crucible preform.

[0061] The specific steps for preparing the carbon fiber crucible preform in this embodiment are as follows:

[0062] S1: Cut the carbon fiber composite fabric into unit layer blanks and thickened layer blanks respectively.

[0063] S1.1: Preparation of carbon fiber composite fabric

[0064] S1.1.1: Carbon fiber with a specification of 12K is woven into carbon fiber cloth with a specification of 3 radial yarns / cm and 3 weft yarns / cm through a weaving process.

[0065] S1.1.2: Short-cut carbon fibers with a specification of 60-70mm are spun into fibers with a specification of 70g / m². 2 The mesh tire.

[0066] S1.1.3: Lay a single layer of mesh on a single layer of carbon fiber cloth, with a carbon fiber cloth to mesh density ratio of 3:1, a pre-needle-punching depth of 8mm, and a pre-needle-punching density of 7 needles / cm. 2 The parameters are used for composite pre-needling to form carbon fiber composite fabric;

[0067] S1.2: Place the carbon fiber composite fabric on the feeding rack of the CNC cutting equipment, and cut out the unit layer fabric and the thickened layer fabric according to the layup diagram.

[0068] S1.2.1: The layup pattern of the unit layer fabric is obtained through the following steps.

[0069] Through such Figure 1 The layup diagram of the carbon fiber crucible preform shown is converted into a 3D model to create a 3D model. Figure 2 The layup diagram of the unit layer fabric shown is as follows:

[0070] like Figure 4As shown in the diagram (the design of the unfolding dividing line in Example 3, which is divided into 6 petals with a central angle of 60°), the layup unfolding diagram is made based on the bottom and R-corner of the carbon fiber crucible preform. Taking the center point of the bottom and the circumference of the R-corner as the starting and ending points, an arc with a corresponding central angle of 15° is drawn as the dividing line. The bottom and R-corner of the unit layer of the carbon fiber crucible preform are divided into 5-6 petals. The layup unfolding diagram of the unit layer fabric is obtained by unfolding along the new dividing line. The designed arc dividing line makes the connecting gaps and the needle direction of the needle punching fabric misaligned and do not coincide.

[0071] For odd-numbered layers, the bottom of the R-corner of the unit layer fabric segment is cut into 5 pieces, and for even-numbered layers, the bottom of the R-corner of the unit layer fabric segment is cut into 6 pieces to avoid overlapping gaps at the R-corner between layers. The weft direction of the unit layer fabric is the axis of the carbon fiber crucible preform, and the warp direction of the unit layer fabric is the direction around the circumference of the carbon fiber crucible preform layup. The size of each unit layer fabric increases layer by layer according to the unfolded diagram, and the cutting is completed by winding layer by layer.

[0072] S1.2.2: The layup development diagram of the thickened layer fabric is obtained through the following steps:

[0073] Through such Figure 1 The layup diagram of the carbon fiber crucible preform shown is converted into a 3D model to create a 3D model. Figure 3 The layup diagram of the thickened fabric shown is as follows:

[0074] Based on the unfolded 3D graphic, the thickened fabric layer is a strip thickened layer, which is then adjusted and optimized to form an arc shape. The weft direction of the thickened fabric layer is the axis of the preform, and the radial direction of the thickened fabric layer is the direction around the perimeter of the preform's layup. The size of each layer of the thickened fabric layer increases layer by layer according to the unfolded drawing, and after cutting, each layer is rolled up.

[0075] Depending on the size and model of the carbon fiber crucible preform, the thickness of the thickening layer of the carbon fiber crucible preform is less than the thickness of the unit layer of the carbon fiber crucible preform.

[0076] S2: As Figure 5 The diagram shown illustrates the effect of unit layer layup. The precast structure's layup is based on the density specifications of the carbon fiber cloth and mesh used. By controlling the needle-punching depth and unit layer thickness, the required unit layer density is achieved. To ensure the bonding performance between the layers of the precast structure, a continuous layup method is used, where the unit layer fabric and the thickening layer fabric are staggered and needle-punched on the precast structure mold to form a structure as shown. Figure 1 The carbon fiber crucible preform shown is fabricated using the following specific steps:

[0077] S2.1: Complete needle-punching process for laying a single unit layer: The unit layer fabric is neatly laid on the precast mold, manually needle-punched to fix it, the mold is rotated one revolution to complete the laying of the entire unit layer fabric, the bottom of the R-corners is neatly spliced, and excess fabric is trimmed; needle-punching is then performed, and after needle-punching, each layer is wound with carbon fiber in a grid, cross, or circumferential manner to maintain the overall strength of the precast; after the winding is completed, a layer of 55g / m² is laid flat. 2 The carbon fiber mesh is needle-punched; in this manner, the unit layer fabric is continuously laid, needle-punched, wound, laid, and needle-punched.

[0078] S2.2: Complete needle-punching process for laying a thickened layer: After completing the needle-punching of the third unit layer, lay the thickened layer fabric in a circumferential manner at the designated position. First, manually needle-punch it to fix it, then rotate the mold one revolution to complete the laying of the entire thickened layer fabric.

[0079] Then, the next unit layer and the next thickening layer are laid and needled, so that the thickening layer fabric and the unit layer fabric are laid and needled alternately until the size of the carbon fiber crucible preform meets the requirements.

[0080] The process parameters for layered needle punching are: needle depth 14mm, needle density 30 needles / cm². 2 The unit layer density is 13 layers / cm.

[0081] Examples 2-7

[0082] Examples 2-7 provide a method for preparing a carbon fiber crucible preform.

[0083] The difference between the above embodiments and Embodiment 1 is that the angles corresponding to the arcs are different during the fabrication of the unit layer fabric layup unfolding diagram, as shown in Table 1.

[0084] Table 1. Angles corresponding to the arcs

[0085]

[0086] Example 8

[0087] This embodiment provides a method for preparing a carbon fiber crucible preform.

[0088] The difference between this embodiment and embodiment 3 is that in step S2.1, when laying the unit layer, a carbon fiber mesh was not laid. Specifically:

[0089] S2.1: Complete laying and needle punching process of a unit layer: Lay the unit layer fabric neatly on the precast mold, manually needle punch it to fix it, rotate the mold one round to complete the laying of the entire unit layer fabric, splice the bottom of the R corner neatly, and trim the excess fabric; then needle punch it again. After needle punching, each layer is wrapped with carbon fiber in a grid, star, or circumferential winding method to maintain the overall strength of the precast body; continue to lay unit layer fabric, needle punch, and wrap the fiber in this way.

[0090] Example 9

[0091] This embodiment provides a method for preparing a carbon fiber crucible preform.

[0092] The difference between this embodiment and embodiment 3 is that the specifications of the carbon fiber mesh are different in step S2.1 when laying the unit layer. Specifically, the specifications of the carbon fiber mesh are 45g / m. 2 .

[0093] Example 10

[0094] This embodiment provides a method for preparing a carbon fiber crucible preform.

[0095] The difference between this embodiment and embodiment 3 is that the specifications of the carbon fiber mesh are different in step S2.1 when laying the unit layer. Specifically, the specifications of the carbon fiber mesh are 65g / m. 2 .

[0096] Example 11

[0097] This embodiment provides a method for preparing a carbon fiber crucible preform.

[0098] The difference between this embodiment and embodiment 3 is that step S2 is different, specifically:

[0099] S2.1: Complete needle-punching process for laying a single unit layer: The unit layer fabric is neatly laid on the precast mold, manually needle-punched to fix it, the mold is rotated one revolution to complete the laying of the entire unit layer fabric, the bottom of the R-corners is neatly spliced, and excess fabric is trimmed; needle-punching is then performed, and after needle-punching, each layer is wound with carbon fiber in a grid, cross, or circumferential manner to maintain the overall strength of the precast; after the winding is completed, a layer of 55g / m² is laid flat. 2 The carbon fiber mesh is needle-punched; in this manner, the unit layer fabric is continuously laid, needle-punched, wound, laid, and needle-punched.

[0100] S2.2: Complete needle-punching process for laying a thickened layer: After completing the needle-punching of the first unit layer, lay the thickened layer fabric in a circumferential manner at the designated position. First, manually needle-punch it to fix it, then rotate the mold one revolution to complete the laying of the entire thickened layer fabric.

[0101] Then, the next unit layer and the next thickening layer are laid and needled, so that the thickening layer fabric and the unit layer fabric are laid and needled alternately until the size of the carbon fiber crucible preform meets the requirements.

[0102] The process parameters for layered needle punching are: needle depth 14mm, needle density 30 needles / cm². 2 The unit layer density is 13 layers / cm.

[0103] Example 12

[0104] This embodiment provides a method for preparing a carbon fiber crucible preform.

[0105] The difference between this embodiment and embodiment 3 is that step S2 is different, specifically:

[0106] S2.1: Complete needle-punching process for laying a single unit layer: The unit layer fabric is neatly laid on the precast mold, manually needle-punched to fix it, the mold is rotated one revolution to complete the laying of the entire unit layer fabric, the bottom of the R-corners is neatly spliced, and excess fabric is trimmed; needle-punching is then performed, and after needle-punching, each layer is wound with carbon fiber in a grid, cross, or circumferential manner to maintain the overall strength of the precast; after the winding is completed, a layer of 55g / m² is laid flat. 2 The carbon fiber mesh is needle-punched; in this manner, the unit layer fabric is continuously laid, needle-punched, wound, laid, and needle-punched.

[0107] S2.2: Complete needle-punching process for laying a thickened layer: After completing the needle-punching of the second unit layer, lay the thickened layer fabric in a circumferential manner at the designated position. First, manually needle-punch it to fix it, then rotate the mold one revolution to complete the laying of the entire thickened layer fabric.

[0108] Then, the next unit layer and the next thickening layer are laid and needled, so that the thickening layer fabric and the unit layer fabric are laid and needled alternately until the size of the carbon fiber crucible preform meets the requirements.

[0109] The process parameters for layered needle punching are: needle depth 14mm, needle density 30 needles / cm². 2 The unit layer density is 13 layers / cm.

[0110] Example 13

[0111] This embodiment provides a method for preparing a carbon fiber crucible preform.

[0112] The difference between this embodiment and embodiment 3 is that step S2 is different, specifically:

[0113] S2.1: Complete needle-punching process for laying a single unit layer: The unit layer fabric is neatly laid on the precast mold, manually needle-punched to fix it, the mold is rotated one revolution to complete the laying of the entire unit layer fabric, the bottom of the R-corners is neatly spliced, and excess fabric is trimmed; needle-punching is then performed, and after needle-punching, each layer is wound with carbon fiber in a grid, cross, or circumferential manner to maintain the overall strength of the precast; after the winding is completed, a layer of 55g / m² is laid flat. 2 The carbon fiber mesh is needle-punched; in this manner, the unit layer fabric is continuously laid, needle-punched, wound, laid, and needle-punched.

[0114] S2.2: Complete needle-punching process for laying a thickened layer: After completing the needle-punching of the fourth unit layer, lay the thickened layer fabric in a circumferential manner at the designated position. First, manually needle-punch it to fix it, then rotate the mold one revolution to complete the laying of the entire thickened layer fabric.

[0115] Then, the next unit layer and the next thickening layer are laid and needled, so that the thickening layer fabric and the unit layer fabric are laid and needled alternately until the size of the carbon fiber crucible preform meets the requirements.

[0116] The process parameters for layered needle punching are: needle depth 14mm, needle density 30 needles / cm². 2 The unit layer density is 13 layers / cm.

[0117] Comparative Example

[0118] Comparative Example 1

[0119] This comparative example provides a method for preparing a carbon fiber crucible preform.

[0120] The difference between this comparative example and Example 1 is that the dividing line is a line segment. That is, the center point of the bottom surface of the carbon fiber crucible preform and the point where the R-angle circumference is equally divided are taken as the starting point and the ending point. The corresponding straight line segment between the two points is drawn as the dividing line. The bottom of the R-angle of the unit layer of the carbon fiber crucible preform is divided into 5-6 petals. The layer unfolding diagram of the unit layer fabric is obtained by unfolding along the new dividing line.

[0121] Performance testing

[0122] (1) Acupuncture effect

[0123] Observe whether, during the needle punching process, the gaps between the unit layer petals in Examples 1-13 and Comparative Example 1 are prone to fuzzing, material lifting, ridge lifting, and pitting, resulting in poor needle punching effect.

[0124] (2) Bending strength

[0125] The bending properties of the carbon fiber crucible preform samples (average size of the sample is 55×10×4mm) in Examples 1-13 and Comparative Example 1 were tested using a universal testing machine. The bending was performed using a three-point bending method with a span of 45mm, a radius of 5mm for the indenter and support, and a loading speed of 0.5mm / min.

[0126] Bending strength = 3PL / (2bh) 2 P is the maximum load, L is the span, h is the sample height, and b is the sample width.

[0127] (3) Interlaminar shear strength

[0128] According to the standard test method of ASTM D2344, the interlaminar shear strength of the carbon fiber crucible preforms (average specimen size of 25×8×4mm) in Examples 1-13 and Comparative Example 1 were measured using an Instron universal testing machine at a test speed of 1mm / min.

[0129] (4) Antioxidant properties and thermal shock resistance

[0130] The carbon fiber crucible preform samples (average size of the sample is 10×10×4mm) from Examples 1-13 and Comparative Example 1 were oxidized in air at 1500℃ for 10h and then tested and subjected to 10 thermal shock tests. The weight gain (wt%) after treatment was calculated.

[0131] Test results are shown in Table 2.

[0132] Table 2 shows the performance test results of the carbon fiber crucible preforms in Examples 1-13 and Comparative Example 1.

[0133]

[0134]

[0135] Based on Table 2, by comparing the test results of Examples 1-13 with Comparative Example 1, this application uses a unique cutting technique to cut the unit layer fabric, so that an arc-shaped seam is formed between the unit layer petals during the needle punching process. The seam is needle punched point by point, which greatly reduces the phenomenon of ridges and pits at the seam, resulting in poor needle punching effect.

[0136] By comparing the test results of Examples 1-7, when the angle corresponding to the arc is controlled to be 30-150° during the step of drawing the segmentation diagram with the bottom surface of the carbon fiber crucible preform as the reference, the needle will gradually complete the gap needle punching along the straight section and the R-corner node, which avoids the phenomenon of material lifting and needle punching forming edges caused by needle punching along the gap to a greater extent, and at the same time makes the needle punching process simpler and safer.

[0137] Comparing the test results of Examples 3 and 8-10, it was found that when laying the unit layers, the carbon fiber preforms with lower flexural strength and interlaminar shear strength were either not laid with carbon fiber mesh or had smaller carbon fiber mesh dimensions. Conversely, when the carbon fiber mesh dimensions were larger, the carbon fiber preforms had poorer oxidation resistance and thermal shock resistance. Therefore, this application selected 55±5g / m³. 2 Specifications of carbon fiber mesh tires.

[0138] By comparing the test results of Examples 3 and 11-13, it was found that after the first unit layer was needled and then the thickening layer was laid, the flexural strength and interlaminar shear strength of the carbon fiber preform were lower; while after the fourth unit layer was needled and then the thickening layer was laid, the oxidation resistance and thermal shock resistance of the carbon fiber preform were poor. Therefore, this application chooses to lay the thickening layer after the second unit layer is completed or after the second unit layer is needled.

[0139] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a carbon fiber crucible preform, characterized in that, Specifically, the following steps are included: The carbon fiber crucible preform is formed by interleaving and needle-punching unit layer fabric and thickened layer fabric on a preform mold using a continuous lay-up method. After the upper part of the unit layer fabric is spliced ​​together in the weft direction, it is seamlessly and flatly overlapped to form the crucible straight section unit of the carbon fiber crucible preform. After the lower part of the unit layer fabric is spliced ​​together in the weft direction, it is seamlessly and flatly overlapped to form the crucible R-corner and crucible bottom of the carbon fiber crucible preform. The arc intersections of two adjacent petal-shaped structural layers completely overlap. The unit layer fabric is composed of an upper part (4) and a lower part (5) as a whole; The upper part is a rectangular structure layer; the upper part is seamlessly and flatly overlapped after being spliced ​​end to end in the latitudinal direction to form the crucible straight section unit layer (1) of the carbon fiber crucible preform. The lower part is composed of n identical petal-shaped structural layers connected in sequence, where n=5 or 6. The petal-shaped structural layer includes a first arc segment (51), a second arc segment (52), a third arc segment (53), and a fourth arc segment (54). The radii of the first arc segment and the fourth arc segment are the radii corresponding to the R-angle region of the carbon fiber crucible preform, and the corresponding central angle is 5-30°. The chord length of the second arc segment and the third arc segment is the radius corresponding to the bottom region of the carbon fiber crucible preform, and the corresponding central angle is 60-90°. The lower part is seamlessly and flatly overlapped after being spliced ​​together in the latitudinal direction to form the crucible R-corner (2) and crucible bottom (3) of the carbon fiber crucible preform, and the arc junctions of two adjacent petal-shaped structural layers completely overlap. The unit layer fabric is cut from carbon fiber composite fabric. The preparation method of the carbon fiber composite fabric is as follows: carbon fiber is made into carbon fiber fabric through weaving process; short carbon fiber is made into mesh through spinning process; then a single layer of the mesh is laid on the single layer of carbon fiber fabric, and composite pre-needling is performed to form the carbon fiber composite fabric. The carbon fiber has the following specifications: 12K; the carbon fiber cloth has the following specifications: 2-4 yarns / cm in the radial direction and 2-4 yarns / cm in the weft direction. The chopped carbon fiber has a diameter of 60-70 mm, and the mesh has a diameter of 55±5 g / m². The density ratio of the carbon fiber fabric to the mesh in the carbon fiber composite fabric is 3:1, and the pre-needling process parameters are: pre-needling depth 5-12mm, pre-needling density 4-10 needles / cm². The thickening layer fabric is cut from the carbon fiber composite fabric, specifically including the following steps: cutting the carbon fiber composite fabric into strips for thickening, adjusting and optimizing to form an arc shape; increasing the size of each layer of the thickening layer fabric layer by layer, and rolling up layer by layer after cutting; The complete needle-punching process for laying a thickening layer is as follows: after completing the needle-punching of the second or third unit layer, the thickening layer fabric is laid circumferentially at the designated position. First, it is manually needle-punched to fix it, and then the mold is rotated one revolution to complete the laying of the entire thickening layer fabric. Then, the next unit layer, the next thickening layer, and needle punching are laid, so that the thickening layer fabric and the unit layer fabric are interleaved and needle punched until the size of the carbon fiber crucible preform meets the requirements.

2. The method for preparing the carbon fiber crucible preform according to claim 1, characterized in that, The petal-shaped structure layer also includes a fifth arc segment (55), the two ends of which are connected to the second arc segment and the third arc segment respectively. After the fifth arc segment is spliced ​​end to end in the latitudinal direction, it seamlessly and smoothly overlaps to form a circular opening (6) at the bottom of the crucible of the carbon fiber crucible preform. The arcs of two adjacent petal-shaped structure layers completely overlap.

3. The method for preparing the carbon fiber crucible preform according to claim 1, characterized in that, The preparation method of the unit layer fabric specifically includes the following steps: The fabric is obtained by cutting using the layup pattern of the unit layer fabric. The layup development diagram of the unit layer fabric is obtained by taking the bottom and R-angle of the carbon fiber crucible preform as the reference, and drawing an arc as the dividing line with the center point of the bottom and the circumference of the R-angle as the starting point and the ending point. The layup development diagram of the unit layer fabric is obtained by unfolding along the dividing line. The number of points dividing the circumference of the R-angle is 5 or 6; the layup development diagram of the unit layer fabric divides the R-angle unit layer and the bottom unit layer of the carbon fiber crucible preform into 5 or 6 segments; the size of each unit layer fabric increases layer by layer.

4. The method for preparing the carbon fiber crucible preform according to claim 1, characterized in that, The process parameters for the layered needle punching are: needle punching depth 8-20mm, needle punching density 20-40 needles / cm², and unit layer density 10-15 layers / cm.

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