Dot matrix reinforced preform and method of forming

Abstract

The application discloses a kind of dot array reinforced preform and its forming method, belong to composite material reinforcing technical field;Dot array reinforced preform includes matrix preform and multidirectional dot array unit, the matrix preform includes at least one unit layer, the multidirectional dot array unit is distributed in the unit layer of the matrix preform in the form of dot array on the outer surface of the development surface, and provides skeleton reinforcement for the matrix preform by implanting into the radial stick of the matrix preform.The application combines the method of preform and dot array structure, has the advantages of needle punching, layer preform and dot array, and obtains preform with good comprehensive performance.

Description

Technical Field

[0001] This invention belongs to the field of composite material reinforcement technology, and in particular relates to a lattice-reinforced preform and its molding method. Background Technology

[0002] High-performance fiber-reinforced composite materials possess advantages such as light weight, high strength, and good thermal conductivity, and are widely used in aerospace thermal protection and thermal structures. The fiber preform, as the reinforcement of the composite material, directly affects its performance. With the development of aerospace technology, there are increasing demands for composite materials to be lighter, more designable, and have superior thermal conductivity.

[0003] Preforms formed using needle punching and layup processes have advantages such as high forming efficiency, low cost, and good product density and uniformity. However, their Z-direction performance is somewhat inferior to orthogonal triaxial or 2.5D structures, making it difficult to achieve Z-direction directional transmission and strong shear resistance. Z-Pin technology is a new interlaminar reinforcement technology for laminated composite materials developed in the 1990s. Z-pins can improve interlaminar shear strength. For example, Chinese patent CN201310221587.4 discloses a planar two-dimensional composite material Z-pin method, which prepares carbon fiber preforms through pultrusion and then embeds carbon rods through drilling in different directions; Chinese patent CN201510237415.5 discloses a nozzle preform forming method, in which carbon rods are first pre-set on a mold at a certain spacing, and then fibers are continuously wound along the generatrix direction to form the preform.

[0004] In the above-mentioned molding methods, whether the carbon rod is pre-wound or embedded after drilling, there will be gaps at the contact point between the preform and the carbon rod, resulting in insufficient tightness of the connection between the carbon rod and the preform, which affects the final performance of the finished product. In addition, the carbon rod has low designability and it is difficult to obtain a preform with directional properties.

[0005] Lattice structures are characterized by their lightweight, high designability, and high specific strength. By combining needle-punching and ply-lay structures with lattice structures, using the lattice structure as the reinforcement of the preform and the needle-punching and ply-lay structures as the matrix, a thermodynamically designed preform structure with comprehensive performance can be obtained through lattice reinforcement structure design. Therefore, this invention proposes a lattice-reinforced preform combining a preform and a lattice structure, as well as a molding method therefor. Summary of the Invention

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A lattice-reinforced preform includes a matrix preform and multi-directional lattice units. The matrix preform includes at least one unit layer. The multi-directional lattice units are distributed in a dotted array on the outer surface of the unfolded surface of the unit layer of the matrix preform, and provide a skeleton reinforcement for the matrix preform through radial rods implanted in the matrix preform. The multi-directional lattice units are a lattice combination formed in space by main radial rods and / or multi-directional reinforcing rods.

[0007] Furthermore, the unit layer is formed by stacking at least one layer of mesh and at least one layer of woven fabric; the woven fabric is unidirectional fabric, plain weave fabric or satin weave fabric; the unit layers of the substrate preform are connected by adhesive or needle punching, or are connected by the multidirectional lattice units.

[0008] Furthermore, the structural shape of the substrate preform is either a body of revolution or a plate shape. The body of revolution is a closed cavity or an open cavity, and the plate shape is a flat plate or an irregularly shaped curved plate.

[0009] Furthermore, the main radial rod is implanted along the normal direction of the curved surface of the substrate preform, and the multi-directional reinforcing rod is distributed around the main radial rod and has a certain angle with the main radial rod in space.

[0010] Multidirectional lattice units are lattice combinations of bars arranged in space at different angles to form a multidirectional reinforcing structure, and their materials are not limited to carbon materials.

[0011] Furthermore, the angle between the multi-directional reinforcing rod and the main radial rod is ±15°, ±30°, ±45°, or ±60°.

[0012] The thermodynamic properties of the preform can be directionally adjusted by the number, spatial distribution, thickness, and angle of the radial rods of the multi-directional lattice unit.

[0013] Furthermore, both the main radial bar and the multi-directional reinforcing bar can be a radial bar unit formed by one bar or multiple bars stranded together. The radial bar unit formed by multiple bars is pre-compressed and then implanted as a whole during implantation.

[0014] Furthermore, the main radial rod and the multi-directional reinforcing rod penetrate through the thickness direction of the substrate preform, and their roots are connected inside the substrate preform, with their heads protruding from the outer surface of the substrate preform by a certain margin, the margin being 10-15% of the thickness of the substrate preform.

[0015] Furthermore, the radial rods and multi-directional reinforcing rods of two adjacent multi-directional lattice units implanted in the matrix preform are connected at the head and / or the middle to form lattice nodes.

[0016] The molding method of any of the above-mentioned lattice-reinforced preforms includes the following steps: Step 1: Cut the woven fabric and mesh into the planar unfolded shape of the base prefabricated unit layer; Step 2: Lay the cut materials layer by layer on the surface of the molding mold according to the unit layer composition order; Step 3: Adhere or needle-punch the above unit layers to form interlayer connections; Step 4: Repeat steps 2-3 until the substrate preform preparation is complete; Step 5: Based on the performance requirements of the precast body, design the number, diameter, implantation angle and spatial distribution of the main radial rods and multi-directional reinforcing rods, and cut the rods into predetermined lengths according to the thickness of the precast body, and cut wedge-shaped cuts at their roots. Step 6: Insert the bars one by one into the precast matrix according to their primary and secondary relationships and the set spacing and angle; Step 7: After implantation, demold and unmold the sample.

[0017] The matrix prefabrication utilizes the combined effect of the radial binding force formed by the rebound of fibers inserted into each unit layer and the reaction force formed by the expansion of multi-strand rod units to form a stable structure and prevent axial detachment.

[0018] Furthermore, in step 6, the order of inserting the bar stock follows these steps: First, assume that the preform material for the implanted matrix has N rows and M columns, where N and M are both natural numbers greater than 1; (1) First, along the generatrix direction of the rotary matrix preform or the X-axis direction of the plate matrix preform, insert the main radial rods at intervals of several rows; (2) Then, along the circumferential direction of the rotary matrix preform or the Y-axis direction of the plate matrix preform, several columns of discrete main radial rods are implanted at intervals; (3) Re-implant all remaining main radial rods; (4) Multi-directional reinforcing rods are implanted in accordance with the same pattern as the main radial rods, and the multi-directional reinforcing rods are implanted in batches according to the different spatial arrangement directions of the main radial rods.

[0019] The carbon rods are implanted in the following order: first, the main radial rods that are evenly distributed and discrete are implanted; then, the remaining main radial rods are implanted; and finally, the multi-directional reinforcing rods are implanted. The multi-directional reinforcing rods are implanted in batches according to their different directional angles with the main radial rods to ensure that the precast structure is subjected to uniform stress and does not deform.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) The method of combining precast bodies with lattice structures combines the advantages of needle-punched and ply-lay precast bodies with lattice structures, and can obtain precast bodies with good comprehensive performance. 2) By directly inserting the radii from different angles, the bar stock can be implanted and molded in one go, improving the molding efficiency of the preform; by utilizing the springback characteristics of the preform after insertion, the tightness of the connection between the preform and the radii can be improved, thereby improving the structural stability and overall performance of the preform. 3) By utilizing the strong designability of the lattice structure, the performance of the prefabricated body can be directionally designed, thereby obtaining a prefabricated body with directional properties.

[0021] To more clearly illustrate the functional characteristics and structural parameters of the present invention, further explanation is provided below in conjunction with the accompanying drawings and specific embodiments. Attached Figure Description

[0022] Figure 1 This is an isometric view of the lattice-reinforced preform of Embodiment 1 of the present invention.

[0023] Figure 2 This is a structural diagram of a multi-directional lattice unit in Embodiment 1 of the present invention.

[0024] Figure 3 for Figure 2 A magnified view of a portion at point A.

[0025] Figure 4 This is a schematic diagram of the unfolded prefabricated unit layer of Embodiment 1 of the present invention.

[0026] Figure 5 This is a dot distribution diagram of the multi-directional dot matrix unit on the unfolded diagram of the preform surface unit layer in Embodiment 1 of the present invention.

[0027] Figure 6 This is a schematic diagram of the spatial combination structure of the main radial bar and the multidirectional reinforcing bar of the multidirectional lattice unit of the present invention.

[0028] Figure 7 This is a schematic diagram of the connection structure of the main radial rod and multi-directional reinforcing rod of two adjacent multi-directional lattice units in the preform of the present invention.

[0029] Figure 8 This is an isometric view of the lattice-reinforced preform of Embodiment 2 of the present invention.

[0030] Figure 9 This is an isometric view of the lattice-reinforced preform of Embodiment 3 of the present invention.

[0031] Figure 10 Axonometric view of the lattice-reinforced preform of Embodiment 4 of the present invention.

[0032] Explanation of reference numerals in the attached figures: 1. Matrix preform; 11. Unit layer; 2. Multi-directional lattice element; 21. Main radial rod; 22. Multi-directional reinforcing rod; 221. First multi-directional reinforcing rod; 222. Second multi-directional reinforcing rod; 223. Third multi-directional reinforcing rod; 224. Fourth multi-directional reinforcing rod. Detailed Implementation

[0033] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0034] like Figures 1-5 As shown, the present invention provides a lattice-reinforced preform, which mainly includes a matrix preform 1 and multi-directional lattice units 2. The matrix preform 1 has a multi-layer structure. In this embodiment, its shape is an open cone. In other embodiments, its shape may also be a closed cone, a ring, a flat plate, an irregular curved surface, or other shapes.

[0035] In this embodiment, the substrate preform 1 includes a unit layer 11. The unit layer 11 is made of unidirectional fabric, plain weave fabric, satin fabric and mesh, and the interlayer connection is formed by needle punching.

[0036] In this embodiment, as Figure 1 and Figure 2 As shown, the multidirectional lattice unit 2 includes one main radial rod 21 and four multidirectional reinforcing rods 22. The four multidirectional reinforcing rods 22 are implanted into the matrix preform 1 from different directions, serving as the skeleton reinforcement of the preform. The radial binding force formed by the in-plane fiber rebound of the preform unit layer 11 ensures that the radial rods are tightly connected to the preform. The multidirectional reinforcing rods 22 implanted into the matrix preform 1 and the main radial rod 21 penetrate the entire thickness of the preform and are connected at their roots. The length of the head protruding from the outer surface of the matrix preform unit layer is 10% to 15% of the thickness of the matrix preform 1, in order to achieve better directional conduction and shear resistance.

[0037] In this embodiment, the main radial rod 21 and the multi-directional reinforcing rod 22 are carbon rods. In other embodiments, they may also be made of other materials such as metal or plastic.

[0038] In other embodiments, such as Figure 6As shown, the main radial rod 21 and the multi-directional reinforcing rod 22 are combined at different angles in space to form a spatial lattice structure. The main radial rod 21 is parallel to the normal of the outer surface of the substrate preform 1. For a single multi-directional lattice unit 2, with the main radial rod 21 as the center, the multi-directional reinforcing rods 22 are distributed around the main radial rod 21 in different numbers and arrangements, forming a certain angle with the main radial rod 21 in space. The multi-directional lattice units 2 are uniformly distributed in a point-like pattern on the surface development plane of the outermost unit layer 11 of the substrate preform 1. By adjusting the number, spatial distribution, thickness, and angle of the main radial rods 21 and multi-directional reinforcing rods 22 of the multi-directional lattice unit 2, the thermodynamic properties of the preform can be directionally adjusted.

[0039] like Figure 6 As shown, the number of main radial rods 21 is 1 or 0, and the number of peripheral multi-directional reinforcing rods 22 is 0, 3, 4, 6, or 8; in addition, any other combination of radial rods that satisfies the present invention to provide skeleton reinforcement for the matrix preform is applicable to the present invention.

[0040] In this embodiment, the angle α between the multi-directional reinforcing rod 22 and the main radial rod 21 is ±45°, such as... Figure 6 As shown, in other embodiments, the included angle α can also be ±15°, ±30° or ±60°, or other combinations thereof; The diameters of the main radial rod 21 and the multi-directional reinforcing rod 22 can be selected within the range of 0.5mm to 2mm respectively; The number of radial bars in the main radial bar 21 and the multi-directional reinforcing bar 22 can be selected from 1, 3, 4, 7, 9, and 12 bars, respectively. Figure 2 and Figure 3 As shown, in this embodiment, both the main radial rod 21 and the multi-directional reinforcing rod 22 have 7 strands. When the multi-strand carbon rods are twisted together, they are subjected to a certain pre-compression force. After the whole structure is implanted, the pre-compression is released, and the expansion of the radial rods generates a reaction force. This force, together with the radial binding force formed by the rebound of the fibers in the unit layer 11 of the matrix preform 1, forms a tight connection.

[0041] In this embodiment, as Figure 7 As shown, the main radial rods 21 and multi-directional reinforcing rods 22 of two adjacent multi-directional lattice units 2 implanted in the matrix preform 1, or the multi-directional reinforcing rods 22 of two adjacent multi-directional lattice units 2, form lattice nodes at the head and / or middle, which can further improve the directional conduction and shear resistance of the preform.

[0042] The molding method of the lattice-reinforced preform described in Example 1 includes the following steps: Step 1: Cut unidirectional fabric, plain weave fabric, satin fabric, and mesh fabric into the unfolded shape of the matrix prefabricated laminated unit layer; Step 2: Lay the cut fabric layer by layer on the surface of the forming mold according to the unit layer composition order; Step 3: Needle-punch the winding unit layer to form interlayer connections; Step 4: Repeat steps 2-3 until the substrate preform preparation is complete; Step 5: Based on the performance requirements of the precast body, design the number, diameter, implantation angle and spatial distribution of the main radial rods and multi-directional reinforcing rods, and cut the rods into predetermined lengths according to the thickness of the precast body, and cut wedge-shaped cuts at their roots. Step 6: Insert the carbon rods one by one into the substrate precast according to the designed spacing and angle; specifically... (1) First, insert the main radial rods at intervals of several rows along the generatrix direction of the rotary matrix prefabricated body; (2) Then, along the circumferential direction of the rotary matrix preform, several rows of discrete main radial rods are implanted; (3) Implant all remaining main radial rods; (4) Multi-directional reinforcing rods are implanted according to the same pattern as the main radial rods, and the multi-directional reinforcing rods are implanted in batches according to their different spatial arrangement directions from the main radial rods. For example Figure 2 As shown, the first multi-directional reinforcing rod 221, the second multi-directional reinforcing rod 222, the third multi-directional reinforcing rod 223 and the fourth multi-directional reinforcing rod 224, which are located in different spatial positions, are implanted in batches in sequence. When performing step 6, a main radial bar and a multi-directional reinforcing bar can also be added to the large end of the cone segment to ensure that the lattice distribution of the outer curved surface is uniform. Step 7: After all the diameter rods have been implanted, demold and unmold the sample. Example 2

[0043] like Figure 8 As shown, this embodiment of a lattice-reinforced preform differs from Embodiment 1 in that the multi-directional lattice unit 2 is composed of a single radial rod 21, and its preparation method includes the following steps: Step 1: Cut unidirectional fabric, plain weave or satin weave fabric and mesh fabric into a fan shape that is unfolded into a single layer; Step 2: Wrap the cut fabric layer by layer around the surface of the forming mold according to the unit layer composition order; Step 3: Needle-punch the winding unit layer to form interlayer connections; Step 4: Repeat steps 2-3 until the substrate preform preparation is complete; Step 5: Based on the performance requirements of the precast body, design the number, diameter and spatial distribution of the main radial bars, and cut the bars into predetermined lengths according to the thickness of the precast body, and cut wedge-shaped cuts at their roots. Step 6: Insert the main radial rods one by one into the precast substrate according to the designed spacing and angle; specifically... (1) First, insert the main radial rods at intervals of several rows along the generatrix direction of the rotary matrix prefabricated body; (2) Then, along the circumferential direction of the rotary matrix preform, several rows of discrete main radial rods are implanted; (3) Implant all remaining main radial rods; Add a main radial bar at the large end of the cone section to ensure uniform distribution of the lattice on the outer curved surface; Step 7: Demold and cut sample. Example 3

[0044] like Figure 9 As shown, this embodiment of a lattice-reinforced preform differs from Embodiment 1 in that the matrix preform 1 has a flat plate shape, and the unit layer 11 unfolds into a square shape. Its preparation method includes the following steps: Step 1: Cut unidirectional fabric, plain weave or satin weave fabric and mesh fabric into rectangles; Step 2: Lay the cut fabric layer by layer on the surface of the forming mold according to the unit layer composition order; Step 3: Needle-punch the metalayer to form interlayer connections; Step 4: Repeat steps 2-3 until the substrate preform preparation is complete; Step 5: Based on the performance requirements of the precast body, design the number, diameter and spatial distribution of the main radial bars, and cut the bars into predetermined lengths according to the thickness of the precast body, and cut wedge-shaped cuts at their roots. Step 6: First, implant the main radial bars at intervals of several rows along the x-axis, then at intervals of several columns along the y-axis, and finally implant all remaining main radial bars. Based on their spatial distribution direction, multi-directional reinforcing rods are first implanted in batches along the x-axis at intervals of several spaces, then implanted along the y-axis at intervals of several columns, followed by the implantation of the remaining multi-directional reinforcing rods in this direction. Finally, multi-directional reinforcing rods from other batches in other directions are implanted sequentially until all are completed. Step 7: Demold and cut sample. Example 4

[0045] like Figure 10 As shown, this embodiment of the lattice-reinforced preform differs from Embodiment 1 in that the matrix preform 1 has an irregular curved flat plate structure, and its preparation method includes the following steps: Step 1: Cut the unidirectional fabric, plain weave or satin weave fabric and mesh fabric into an unfolded flat surface and then cut it. Step 2: Lay the cut fabric layer by layer on the surface of the forming mold according to the unit layer composition order; Step 3: Needle-punch the unit layer to form interlayer connections; Step 4: Repeat steps 2-3 until the substrate preform preparation is complete; Step 5: Based on the performance requirements of the precast body, design the number, diameter and spatial distribution of the main radial bars, and cut the bars into predetermined lengths according to the thickness of the precast body, and cut wedge-shaped cuts at their roots. Step 6: First, implant the main radial bars according to the x-axis trajectory of the irregular curved surface at intervals of several rows, then implant them according to the y-axis trajectory at intervals of several columns, and finally implant all the remaining main radial bars. Based on their spatial distribution direction, the multi-directional reinforcing rods are first implanted in batches along the x-axis trajectory of the irregular curved surface at intervals of several spaces, then implanted along the y-axis trajectory at intervals of several columns, followed by the implantation of the remaining multi-directional reinforcing rods in this direction, and finally implanted in other batches in sequence until all are completed. Step 7: Demold and cut sample.

[0046] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0047] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A lattice-reinforced preform, characterized in that, The system includes a matrix preform (1) and multi-directional lattice units (2). The matrix preform (1) includes at least one unit layer (11). The multi-directional lattice units (2) are distributed in a dotted array on the outer surface of the unfolded surface of the unit layer (11) of the matrix preform (1), and provide a skeleton reinforcement for the matrix preform (1) through radial rods implanted in the matrix preform (1). The multi-directional lattice units (2) are a lattice combination formed in space by main radial rods (21) and / or multi-directional reinforcing rods (22). The unit layer (11) is formed by at least one layer of mesh and at least one layer of woven fabric; the woven fabric is unidirectional fabric, plain weave fabric or satin fabric; each unit layer of the substrate preform (1) is connected by adhesive or needle punching, or the multidirectional lattice unit (2) is connected by interlayer. The main radial rod (21) is implanted along the curved surface normal of the substrate preform (1), and the multi-directional reinforcing rod (22) is distributed around the main radial rod (21) and has a certain angle with the main radial rod (21) in space.

2. The lattice-reinforced preform according to claim 1, characterized in that, The structure of the substrate preform (1) is either a rotating body or a plate. The rotating body is a closed cavity or an open cavity, and the plate is a flat plate or an irregular curved plate.

3. The lattice-reinforced preform according to claim 1, characterized in that, The angle between the multi-directional reinforcing rod (22) and the main radial rod (21) is ±15°, ±30°, ±45° or ±60°.

4. The lattice-reinforced preform according to claim 1, characterized in that, Both the main radial bar (21) and the multi-directional reinforcing bar (22) can be a radial bar unit formed by one bar or multiple bars. The radial bar unit formed by multiple bars is pre-compressed and then implanted as a whole.

5. A lattice-reinforced preform according to claim 1, characterized in that, The main radial rod (21) and the multi-directional reinforcing rod (22) penetrate the thickness direction of the substrate preform (1), and their roots are connected inside the substrate preform (1), with their heads protruding from the outer surface of the substrate preform (1) by a certain margin, the margin being 10 to 15% of the thickness of the substrate preform (1).

6. A lattice-reinforced preform according to claim 5, characterized in that, The main radial rod (21) and multidirectional reinforcing rod (22) of two adjacent multidirectional lattice units (2) implanted in the matrix preform (1) are connected at the head and / or middle to form a lattice node.

7. A method for forming a lattice-reinforced preform according to any one of claims 1-6, characterized in that, Includes the following steps: Step 1: Cut the woven fabric and mesh into the planar unfolded shape of the base prefabricated unit layer; Step 2: Lay the cut material layer by layer on the surface of the molding mold according to the unit layer composition order; Step 3: Adhere or needle-punch the above unit layers to form interlayer connections; Step 4: Repeat steps 2-3 until the substrate preform preparation is complete; Step 5: Based on the performance requirements of the precast body, design the number, diameter, implantation angle and spatial distribution of the main radial rods and multi-directional reinforcing rods, and cut the rods into predetermined lengths according to the thickness of the precast body, and cut wedge-shaped cuts at their roots. Step 6: Insert the bars one by one into the precast matrix according to their primary and secondary relationships and the set spacing and angle; Step 7: After implantation, demold and unmold the sample.

8. The molding method according to claim 7, characterized in that, In step 6, the order of inserting the bar stock follows these steps: First, assume that the preform material for the implanted matrix has N rows and M columns, where N and M are both natural numbers greater than 1; (1) First, along the generatrix direction of the rotary matrix preform or the X-axis direction of the plate matrix preform, insert the main radial rods at intervals of several rows; (2) Then, along the circumferential direction of the rotary matrix preform or the Y-axis direction of the plate matrix preform, several columns of discrete main radial rods are implanted at intervals; (3) Re-implant all remaining main radial rods; (4) Multi-directional reinforcing rods are implanted in accordance with the same pattern as the main radial rods, and the multi-directional reinforcing rods are implanted in batches according to the different spatial arrangement directions of the main radial rods.

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