Partition combination forming method of box-shaped fiber preform

Abstract

The invention discloses a partition combination forming method of a box-shaped fiber preform, which comprises the following steps of: respectively attaching four pre-formed element box piece semi-finished products to the inner sides of four areas of a cross-shaped element, sequentially sewing and fixing the side walls of the element box piece semi-finished products in two symmetrical areas and the intersection of the four areas, and forming the cross-shaped element box piece semi-finished products in the cross-shaped element box piece semi-finished products in the cross-shaped element box piece semi-finished products in the cross-shaped element box piece semi-finished products. The element box piece semi-finished product in each area is sewed and formed, so that the problem of seaming and forming in a semi-closed limit space is solved, and the forming precision and the overall performance of the prefabricated body are ensured; the flanging design is adopted, so that the overall stability and bearing capacity of the prefabricated body are improved; due to the design of the thickening layer, the folding area cloth layers are connected into a whole, and continuity and uniformity of force transmission under the action of external force are guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of fiber preform molding, and in particular to a partitioned combination molding method for a box-shaped fiber preform. Background Art

[0002] Composite materials have the advantages of high specific strength, high specific stiffness, and strong designability. In recent years, they have been widely used in various aerospace structural parts. Among them, box-shaped composite materials are the most common, and are often used in computer cases, wing boxes, cover plates, satellite frames and other components. Fiber preforms, as reinforcing materials for composite materials, determine the overall performance of composite materials. In order to ensure the overall performance of composite materials, the most ideal way is "zero processing" or "micro processing" to ensure the continuity of fibers in composite materials. This puts extremely high demands on the molding accuracy and surface control of composite preforms, and requires net size or near net size molding.

[0003] Since the box-shaped fiber preform belongs to a semi-enclosed extreme space, the ply sewing is limited by space, position and sewing angle, resulting in poor corner forming effect of conventional ply sewing technology, poor dimensional stability after sewing, and it is difficult to ensure the high dimensional accuracy of the box-shaped fiber preform, and there is a bottleneck in practical application. The invention patent with application publication number CN113846431A discloses a preparation method of a box-shaped reinforced three-dimensional fabric preform, which adopts the method of "sewing the bottom surface-inserting the inner and outer molds-overall sewing and forming". After laying four small boxes, their edges are spliced ​​relative to form a large box, and a certain amount of fiber bundles are placed in the gap at the splicing to ensure the mechanical properties of the preform. Then, the fiber cloth is coated on the large box, and the bottom and side box reinforcement ribs of the preform are sewn. After that, the four small boxes and the large box are taken out, and the corners and the connection between the reinforcement ribs and the cloth surface are sewn, which solves the problems of poor corner forming effect and low dimensional accuracy of the preform in the prior art to a certain extent. However, the method of placing a certain amount of fiber bundles in the gaps at the joints to ensure the mechanical properties of the preform is very likely to cause misalignment of the fiber bundle plies during actual operation, thus affecting the molding accuracy and performance of the preform.

[0004] Therefore, it is necessary to provide a partitioned combination molding method for a box-shaped fiber preform through research to solve the above problems. Summary of the invention

[0005] The first object of the present invention is to provide a method for zoning and combining the molding of a box-shaped fiber preform, by placing four pre-molded elementary box semi-finished products respectively in contact with the inner sides of four regions of a cross-shaped basic component, and then sewing and fixing the side walls of the elementary box semi-finished products of two symmetrical regions and the intersections of the four regions in turn, and then sewing and molding the elementary box semi-finished products of each region, thereby solving the problem of sewing molding in a semi-enclosed extreme space and ensuring the molding accuracy and overall performance of the preform.

[0006] Another object of the present invention is to provide a box-shaped fiber preform made by the above-mentioned molding method.

[0007] To achieve the above object, the present invention provides the following solutions:

[0008] A first aspect of the present invention provides a partitioned assembly molding method for a box-shaped fiber preform, comprising the following preparation steps:

[0009] S1. Preparation of semi-finished products of elementary boxes

[0010] Cut the through-layer cloth according to the design size of the elementary box, pre-shape the bottom of the elementary box and the areas where the four side walls are located, and then stand two adjacent side walls upright and sew them together to obtain a three-sided open elementary box semi-finished product; repeat the above process until the preparation of four elementary box semi-finished products is completed;

[0011] S2. Preparation of cross-shaped base element

[0012] According to the design size of the cross-shaped base element, one longitudinal fiber-reinforced cloth and two transverse fiber-reinforced cloths are cut and pre-shaped, wherein a pair of overlapping edges are reserved on one side of the two transverse fiber-reinforced cloths, and the two transverse fiber-reinforced cloths are symmetrically sewn to the two sides of the middle section of the longitudinal fiber-reinforced cloth through their overlapping edges to obtain a cross-shaped base element;

[0013] S3. Combination molding of box-shaped fiber preforms

[0014] The four elementary box parts semi-finished products made in step S1 are respectively placed in the four areas of the cross-shaped basic element made in step S2, and the two side walls of the elementary box parts semi-finished products in each area are completely fitted to the inner side of the area, and the side walls of the elementary box parts semi-finished products of two adjacent areas are sequentially pierced and sewn, and the intersections of the four areas are sewed and fixed, and then the other two side walls of the elementary box parts semi-finished products in each area are sewed and fixed to the adjacent side walls to form a complete elementary box part, and finally a box-shaped fiber preform is obtained.

[0015] Furthermore, in step S1, the through-layer fabric is formed by laying and sewing a plurality of structural unit layers, with an interlayer density of (28-46) layers / 10 mm and a sewing spacing of (4-7) mm×(4-7) mm.

[0016] Furthermore, the structural unit layer is a fiber cloth layer composited with a fiber mesh winding layer.

[0017] Furthermore, the fiber cloth and the fiber mesh are made of one or a mixture of two or more of carbon fiber, glass fiber, quartz fiber, mullite fiber, alumina fiber, silicon carbide fiber and silicon nitride fiber.

[0018] Furthermore, in step S2, the material of the longitudinal fiber reinforcement cloth and the transverse fiber reinforcement cloth is consistent with the material of the fiber cloth.

[0019] Furthermore, the transverse fiber reinforced cloth is formed by overlapping and sewing two single-layer cloths, and the pair of overlapping edges reserved therefor are respectively extended sections of the corresponding single-layer cloths.

[0020] Furthermore, the length of the overlapping edge is 1 / 8 to 1 / 2 of the length of the longitudinal fiber reinforced cloth.

[0021] Furthermore, the upper ends of the two upright side walls of the elementary box semi-finished product described in step S1 are respectively reserved with a first flange and a second flange; the upper end of the transverse fiber reinforced cloth described in step S2 is reserved with a first transverse flange and a second transverse flange; the first transverse flange and the second transverse flange respectively overlap with the first flange and the second flange adjacent to them and are pre-formed and then folded to the top of the elementary box where the first flange and the second flange are located and sewn and fixed thereto.

[0022] Furthermore, the widths of the first flange, the second flange, the first transverse flange, and the second transverse flange are consistent, which are 1 / 6 to 1 / 4 of the width of the top of the basic box.

[0023] Furthermore, the upper ends of the elementary boxes described in step S3 are provided with thickening layers, and the two ends of the thickening layers are sequentially sewn and connected with the corresponding folding area fabric layers.

[0024] Furthermore, the material and thickness of the thickened layer are consistent with the material and thickness of the folded area fabric layer.

[0025] Furthermore, the outer surface of the box-shaped fiber preform obtained in step S3 is wrapped with a layer of continuous fiber reinforcement cloth, and the material of the continuous fiber reinforcement cloth is consistent with the material of the transverse fiber reinforcement cloth or the longitudinal fiber reinforcement cloth.

[0026] Another aspect of the present invention is to prepare a box-shaped fiber preform by the above-mentioned molding method, wherein the box-shaped fiber preform comprises a cross-shaped base element and four elementary boxes arranged in four areas of the cross-shaped base element, and the four elementary boxes are all designed to be opened at the top.

[0027] The advantages and obvious technical features of the present invention compared with the prior art are:

[0028] (1) The partition combination molding method of the present invention adopts a three-sided open elementary box semi-finished product and a cross-shaped elementary component to partition and combine the elementary box semi-finished products in each zone, and then stitches the elementary box semi-finished products in each zone to form, thereby solving the problem of stitching molding in a semi-enclosed extreme space and ensuring the molding accuracy and overall performance of the preform;

[0029] (2) The design of the first flange, the second flange, the first transverse flange, and the second transverse flange of the present invention improves the overall stability and load-bearing capacity of the preform;

[0030] (3) The design of the thickening layer of the present invention connects the fabric layers in each folding area into a whole, thereby ensuring the continuity and uniformity of force transmission under the action of external force, and further improving the overall stability and bearing capacity of the box-shaped fiber preform. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the semi-finished structure of the elementary box component of Example 1 of the present invention.

[0032] Figure 2 This is a schematic structural diagram of a box-shaped fiber preform according to Example 1 of the present invention.

[0033] Figure 3 This is a schematic diagram of the semi-finished structure of the elementary box component of Example 2 of the present invention. Figure 4 This is a schematic structural diagram of a box-shaped fiber preform according to Example 2 of the present invention. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] The partition combination molding method of a box-shaped fiber preform described in the present invention comprises the following steps:

[0036] S1. Preparation of semi-finished products of elementary boxes

[0037] Cut the through-layer cloth according to the design size of the elementary box, pre-shape the bottom of the elementary box and the areas where the four side walls are located, and then stand two adjacent side walls upright and sew them together to obtain a three-sided open elementary box semi-finished product; repeat the above process until the preparation of four elementary box semi-finished products is completed;

[0038] The through-layer fabric is formed by laying and sewing a plurality of structural unit layers, with an interlayer density of (28-46) layers / 10 mm and a sewing spacing of (4-7) mm×(4-7) mm.

[0039] The structural unit layer is a fiber cloth layer composited with a fiber grid winding layer, and the fiber material used is one or a mixture of two or more of carbon fiber, glass fiber, quartz fiber, mullite fiber, alumina fiber, silicon carbide fiber, and silicon nitride fiber.

[0040] S2. Preparation of cross-shaped base element

[0041] According to the design size of the cross-shaped base element, one longitudinal fiber-reinforced cloth and two transverse fiber-reinforced cloths are cut and pre-shaped, wherein a pair of overlapping edges are reserved on one side of the two transverse fiber-reinforced cloths, and the two transverse fiber-reinforced cloths are symmetrically sewn to the two sides of the middle section of the longitudinal fiber-reinforced cloth through their overlapping edges to obtain a cross-shaped base element;

[0042] The material used for the longitudinal fiber reinforcement cloth and the transverse fiber reinforcement cloth is consistent with the material of the fiber cloth.

[0043] The transverse fiber reinforced cloth is formed by overlapping and sewing two single-layer cloths, and a pair of overlapping edges reserved therefor are respectively extended sections of the corresponding single-layer cloths.

[0044] The length of the overlapping edge is 1 / 8 to 1 / 2 of the length of the longitudinal fiber reinforced cloth.

[0045] S3. Combination molding of box-shaped fiber preforms

[0046] The four elementary box parts semi-finished products made in step S1 are respectively placed in the four areas of the cross-shaped basic element made in step S2, and the two side walls of the elementary box parts semi-finished products in each area are completely fitted to the inner side of the area, and the side walls of the elementary box parts semi-finished products of two adjacent areas are sequentially pierced and sewn, and the intersections of the four areas are sewed and fixed, and then the other two side walls of the elementary box parts semi-finished products in each area are sewed and fixed to the adjacent side walls to form a complete elementary box part, and finally a box-shaped fiber preform is obtained.

[0047] In order to prevent the upper joint of the box-shaped fiber preform from twisting or fiber breakage when subjected to force, thereby affecting the overall stability and load-bearing capacity of the preform, the upper ends of the two upright side walls of the elementary box semi-finished product described in step S1 are respectively reserved with a first flange and a second flange; the upper ends of the transverse fiber reinforcement cloth corresponding to the two upright side walls of the elementary box semi-finished product are reserved with a first transverse flange and a second transverse flange; the first transverse flange and the second transverse flange respectively overlap with the first flange and the second flange adjacent to them, and are pre-formed and then folded to the top of the elementary box where the first flange and the second flange are located and sewn and fixed thereto.

[0048] The widths of the first flange, the second flange, the first transverse flange and the second transverse flange are consistent, which are 1 / 6 to 1 / 4 of the width of the top of the basic box.

[0049] The present invention also provides a thickening layer at the upper end of each elementary box, and the two ends of the thickening layer are sequentially sewn and connected with the corresponding folding area cloth layer, and the material and thickness of the thickening layer are consistent with the material and thickness of the folding area cloth layer. Such a design connects the folding area cloth layers into a whole, ensures the continuity and uniformity of force transmission under the action of external force, and further improves the overall stability and bearing capacity of the box-shaped fiber preform.

[0050] Example 1

[0051] The method of the present invention is used to prepare a box-shaped carbon fiber preform with a bottom size of 100 mm×100 mm.

[0052] The through-layer cloth used in this embodiment is composed of two layers of carbon fiber satin cloth and one layer of carbon fiber grid winding layer.

[0053] The longitudinal fiber reinforcement cloth and the transverse fiber reinforcement cloth used in this embodiment are carbon fiber satin cloth.

[0054] S1. Preparation of semi-finished products of elementary boxes

[0055] Cut 4 pieces of 180mm×180mm through-layer fabric, select a 50mm×50mm area in the center of each piece of through-layer fabric for sewing and pre-forming, determine and cut out the areas where the 4 side walls are located through a mold for sewing and pre-forming, and place 2 adjacent side walls upright and sew them to obtain 4 semi-finished elementary box pieces with three sides open;

[0056] S2. Preparation of cross-shaped base element

[0057] A longitudinal fiber reinforced cloth and two transverse fiber reinforced cloths were cut and pre-shaped, wherein a pair of 50 mm long overlapping edges were reserved on one side of the two transverse fiber reinforced cloths, and the two transverse fiber reinforced cloths were symmetrically sewn to both sides of the middle section of the longitudinal fiber reinforced cloth through their overlapping edges to obtain a cross-shaped base element with a longitudinal thickness of 1.5 mm and a transverse thickness of 1 mm. The length and width of the cross-shaped base element were 100 mm and the height was 50 mm.

[0058] S3. Combination molding of box-shaped fiber preforms

[0059] The four elementary box parts semi-finished products made in step S1 are placed in the four areas of the cross-shaped basic element made in step S2 respectively, and the two side walls of the elementary box parts semi-finished products in each area are completely fitted with the inner side of the area, the side walls of the elementary box parts semi-finished products in two adjacent areas are pierced and sewn in turn, and the intersections of the four areas are sewed and fixed, and then the other two side walls of the elementary box parts semi-finished products in each area are sewed and fixed with the adjacent side walls to form a complete elementary box part, and the excess part is subtracted to obtain the box-shaped fiber preform.

[0060] Example 2

[0061] The method of the present invention is used to prepare a box-shaped carbon fiber preform with a bottom size of 100 mm×100 mm.

[0062] The through-layer cloth used in this embodiment is a layer of carbon fiber satin cloth composited with a layer of carbon fiber grid winding layer.

[0063] The longitudinal fiber reinforcement cloth and the transverse fiber reinforcement cloth used in this embodiment are carbon fiber satin cloth.

[0064] S1. Preparation of semi-finished products of elementary boxes

[0065] Cut 4 pieces of 200mm×200mm through-layer fabrics, select a 50mm×50mm area in the center of each piece of through-layer fabric for sewing and pre-forming, and then use a mold to determine and cut out the areas where the 4 side walls are located for sewing and pre-forming, wherein 10mm long flanges are reserved for 2 adjacent side walls, namely the first flange and the second flange, and the 2 adjacent side walls are placed upright and sewn and fixed, thereby obtaining 4 semi-finished elementary box pieces with three sides open;

[0066] S2. Preparation of cross-shaped base element

[0067] Cut a longitudinal fiber reinforced cloth with a size of 100×50mm and two transverse fiber reinforced cloths with a size of 100mm×60mm and pre-shape them. The upper ends of the two transverse fiber reinforced cloths are reserved with a transverse flange of 10mm, that is, corresponding to each semi-finished unit box, a first transverse flange and a second transverse flange are set, corresponding to the first flange and the second flange respectively. The two transverse fiber reinforced cloths are symmetrically sewn on both sides of the middle section of the longitudinal fiber reinforced cloth through their overlapping edges to obtain a cross-shaped unit element with a longitudinal thickness of 1.5mm and a transverse thickness of 1mm;

[0068] S3. Combination molding of box-shaped fiber preforms

[0069] The four elementary box semi-finished products made in step S1 are placed in the four areas of the cross-shaped base element made in step S2 respectively, and the two side walls of the elementary box semi-finished products in each area are completely fitted with the inner side of the area, the side walls of the elementary box semi-finished products of two adjacent areas are pierced and sewn in turn, and the intersections of the four areas are sewed and fixed, and then the other two side walls of the elementary box semi-finished products in each area are sewed and fixed with their adjacent side walls to form a complete elementary box. At the same time, the first transverse flange and the first flange, the second transverse flange and the second flange are folded to the corresponding upper end of the elementary box and sewed and fixed thereto. In order to further improve the overall stability and bearing capacity of the box-shaped fiber preform, carbon fiber satin cloth is used for thickening design at the insufficient thickness of the upper end of each elementary box, so that it is connected with the cloth layer of each folded area to form a whole, thereby obtaining the box-shaped fiber preform described in Example 2.

[0070] The above embodiments are only used to help understand the technical solution and core idea of ​​the present invention; at the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for partitioning and combining a box-shaped fiber preform, characterized in that: The steps include: S1. Preparation of semi-finished products of elementary boxes Cut the through-layer cloth according to the design size of the elementary box, pre-shape the bottom of the elementary box and the areas where the four side walls are located, and then stand two adjacent side walls upright and sew them together to obtain a three-sided open elementary box semi-finished product; repeat the above process until the preparation of four elementary box semi-finished products is completed; S2. Preparation of cross-shaped base element According to the design size of the cross-shaped base element, one longitudinal fiber-reinforced cloth and two transverse fiber-reinforced cloths are cut and pre-shaped, wherein a pair of overlapping edges are reserved on one side of the two transverse fiber-reinforced cloths, and the two transverse fiber-reinforced cloths are symmetrically sewn to the two sides of the middle section of the longitudinal fiber-reinforced cloth through their overlapping edges to obtain a cross-shaped base element; S3. Combination molding of box-shaped fiber preforms The four elementary box parts semi-finished products made in step S1 are respectively placed in the four areas of the cross-shaped basic element made in step S2, and the two side walls of the elementary box parts semi-finished products in each area are completely fitted to the inner side of the area, and the side walls of the elementary box parts semi-finished products of two adjacent areas are sequentially pierced and sewn, and the intersections of the four areas are sewed and fixed, and then the other two side walls of the elementary box parts semi-finished products in each area are sewed and fixed to the adjacent side walls to form a complete elementary box part, and finally a box-shaped fiber preform is obtained.

2. The method for partitioning and combining a box-shaped fiber preform according to claim 1, characterized in that: In step S1, the through-layer fabric is formed by laying and sewing a plurality of structural unit layers, with an interlayer density of (28-46) layers / 10 mm and a sewing spacing of (4-7) mm×(4-7) mm.

3. The method for forming a box-shaped fiber preform by partitioning according to claim 2, characterized in that: The structural unit layer is a fiber cloth layer composited with a fiber mesh winding layer, and the fiber cloth and the fiber mesh are made of one or a mixture of two or more of carbon fiber, glass fiber, quartz fiber, mullite fiber, alumina fiber, silicon carbide fiber, and silicon nitride fiber.

4. The method for forming a box-shaped fiber preform by partitioning according to claim 3, characterized in that: In step S2, the material of the longitudinal fiber reinforcement cloth and the transverse fiber reinforcement cloth is consistent with the material of the fiber cloth.

5. The method for forming a box-shaped fiber preform by partitioning according to claim 1, characterized in that: The transverse fiber reinforced cloth is formed by overlapping and sewing two single-layer cloths, and its reserved pair of overlapping edges are respectively extended sections of the corresponding single-layer cloths; the length of the overlapping edges is 1 / 8 to 1 / 2 of the length of the longitudinal fiber reinforced cloth.

6. The method for forming a box-shaped fiber preform by partitioning according to claim 1, characterized in that: The upper ends of the two upright side walls of the elementary box semi-finished product described in step S1 are respectively reserved with a first flange and a second flange; the upper end of the transverse fiber reinforcement cloth described in step S2 is reserved with a first transverse flange and a second transverse flange; the first transverse flange and the second transverse flange respectively overlap with the first flange and the second flange adjacent to them and are pre-formed and then folded to the top of the elementary box where the first flange and the second flange are located and sewn and fixed thereto.

7. The method for forming a box-shaped fiber preform by partitioning according to claim 6, characterized in that: The widths of the first flange, the second flange, the first transverse flange and the second transverse flange are consistent, which are 1 / 6 to 1 / 4 of the width of the top of the basic box.

8. The method for forming a box-shaped fiber preform by partitioning according to claim 1, characterized in that: The upper end of the elementary box described in step S3 is provided with a thickening layer, and the two ends of the thickening layer are sequentially sewn and connected with the corresponding folding area cloth layer; the material and thickness of the thickening layer are consistent with the material and thickness of the folding area cloth layer.

9. The method for forming a box-shaped fiber preform by partitioning and combining according to claim 1, characterized in that: The outer surface of the box-shaped fiber preform obtained in step S3 is wrapped with a layer of continuous fiber reinforcement cloth, and the material of the continuous fiber reinforcement cloth is consistent with the material of the transverse fiber reinforcement cloth or the longitudinal fiber reinforcement cloth.

10. A box-shaped fiber preform prepared by the molding method according to any one of claims 1 to 9, characterized in that: The box-shaped fiber preform comprises a cross-shaped base element and four elementary box parts arranged in four areas of the cross-shaped base element, and the four elementary box parts are all designed to be opened at the top.

Images