Solid triangular prism special-shaped prefabricated body and paving and compacting method thereof

Abstract

The invention relates to a solid triangular prism special-shaped prefabricated body and a laying and compacting method thereof. The method comprises the steps that a split type metal tool matched with the prefabricated body in shape is manufactured; selecting a continuous one-way SiC fiber prepreg tape, and cutting the prepreg tape according to the size of the preform; the 90-degree prepreg tape and the 0-degree prepreg tape are sequentially and continuously laid in the circumferential direction of the prism in a V-shaped path; a plurality of 0-degree continuous fiber bundles are inserted into the sharp corner area of the triangular prism in the thickness direction, and every time the fiber bundles with the thickness ranging from 0.1 mm to 0.3 mm are filled in a cumulative mode, the filled fiber bundles are manually compacted; and the prefabricated body is subjected to overall mechanical compaction through the tool, then the tool and the prefabricated body are put into a drying oven together to be cured, and cooling and demolding are conducted after curing is completed. According to the method, the core technical problems that when the triangular prism solid prefabricated body is prepared through a traditional technology, the density of fibers in a sharp corner area is insufficient, and pores are prone to gathering are effectively solved through the synergistic effect of the three-dimensional forming technology of a layering mode, sharp corner reinforcement and a compaction technology.

Description

Technical Field

[0001] This invention relates to the field of ceramic matrix composite preform preparation technology, and more specifically to a solid triangular prism irregular preform and its layup and compaction method. Background Technology

[0002] Ceramic matrix composites (CMCs) have become the preferred material for thermal structural components in extreme environments such as hypersonic vehicles, rocket engines, and nuclear reactors due to their excellent properties of high specific strength, high temperature resistance, oxidation resistance, and thermal shock resistance. Triangular prism-shaped solid preforms, as core blanks, are widely used in high-temperature load-bearing parts with uniform cross-section structures, such as turbines, rudder shafts, nozzle support ribs, and combustion chamber guide vane tail sections in the aforementioned equipment. These components need to maintain structural strength in 1800°C-level gas environments, placing stringent requirements on the density and pore uniformity of the preforms. In particular, the preforms must achieve overall high density, with no pore accumulation in sharp corner areas.

[0003] However, the preparation of solid triangular prism preforms presents three major technical challenges: sharp corners, uniform thickness, and solidity. Traditional lay-up or weaving processes cannot effectively solve the densification problem in the sharp corner areas. Defects such as pore aggregation, delamination, and fiber buckling are prone to occur at the sharp corners, resulting in a high overall porosity of the preforms. This leads to uneven penetration and local defects during subsequent ceramicization processes, significantly increasing the ceramicization failure rate. Ultimately, the performance of the finished components is highly variable, failing to meet the requirements for high-temperature load-bearing components in extreme environments such as hypersonic vehicle engines.

[0004] Currently, the fabrication processes for triangular prism preforms are mainly divided into two categories. One is the 3D weaving method, such as the multi-layer interlacing process on a three-dimensional loom disclosed in US5085252. Although this method can achieve near-net-shape forming of the preform, it is limited by the fixed weaving angle, and the problem of insufficient fiber density in the sharp corner areas cannot be solved, resulting in a porosity of preforms generally higher than 3.5%. At the same time, the equipment required for this process is expensive and the manufacturing cycle is long, making it difficult to meet the needs of mass production. Patent US6129122 proposes a multi-axis 3D circular weaving process based on this, but it is only applicable to the preparation of annular cross-section preforms and cannot be adapted to triangular prism structures. Furthermore, it does not include a segmented compaction process, and the porosity of the resulting product is still not less than 3%, failing to fundamentally solve the problem of density.

[0005] The second method is the rectangular layup cutting and splicing method, such as the rectangular film overlapping layup process used in CN109291459A. The overlapping area is prone to forming through pores, and no reinforcement scheme is designed for the sharp corner area of ​​the triangular prism. The overall porosity of the preform is greater than 3%. The small piece prepreg splicing + pulse molding process proposed in CN104260368A still requires a lot of cutting and splicing. The pore aggregation phenomenon at the splicing part is obvious, and it cannot achieve the requirement of high density preform preparation with an overall porosity of ≤1%. Summary of the Invention

[0006] To address the problem of pore accumulation in the solid apical region of a triangular prism in the prior art, this invention aims to provide a solid triangular prism irregular precast body and its layup and compaction method.

[0007] The method for laying and compacting a solid triangular prism irregular preform according to the present invention includes the following steps: (1) determining the shape of the preform: the preform to be prepared is a triangular prism with a uniform cross-section, the cross-section of which is a near-isosceles triangle; (2) providing tooling: fabricating a split metal tooling adapted to the shape of the preform; (3) cutting the prepreg tape: selecting a continuous unidirectional SiC fiber prepreg tape, cutting the prepreg tape according to the size of the preform, and cutting at least two pieces each of 90° prepreg tape and 0° prepreg tape; (4) V-shaped path layup: laying the 90° prepreg tape and 0° prepreg tape together. ° Prepreg tape is laid continuously along the circumference of the prism in a V-shaped path; (5) Filling and segmented compaction of the sharp corner area: Insert multiple 0° continuous SiC fiber bundles along the thickness direction in the sharp corner area of ​​the triangular prism. After each fiber bundle with a cumulative thickness of 0.1-0.3mm is filled, manually compact the filled fiber bundles; (6) Overall compaction and curing demolding: After the fiber bundles are filled to the design height of the preform cross section which is similar to an isosceles triangle, the preform is mechanically compacted as a whole by the tooling. Then the tooling and the preform are placed in the oven for curing. After curing, the preform is cooled and demolded.

[0008] In a preferred embodiment, in step (1), the base length of the cross-sectional triangle is 10-30mm, the height of the triangle is 40-60mm, and the height of the prism is 80-120mm.

[0009] In a preferred embodiment, in step (2), the split metal fixture includes a frame with a triangular prism shape of equal cross section and an irregularly shaped top cover plate, the irregularly shaped top cover plate being fixed to the top of the frame by screws.

[0010] In a preferred embodiment, in step (3), the fiber direction of the 90° prepreg tape is perpendicular to the height of the prism, and the fiber direction of the 0° prepreg tape is parallel to the height of the prism.

[0011] In a preferred embodiment, in step (3), the thickness of the prepreg tape is 0.1-0.25 mm.

[0012] In a preferred embodiment, in step (4), the circumferential direction is the plane containing the two sides of the triangle and the axis of the prism.

[0013] In a preferred embodiment, in step (4), the included angle of the V-shaped bonding structure formed after the two 90° prepreg tapes are laid is 20-35°.

[0014] In a preferred embodiment, in step (5), when manually pressing the fiber bundle, the applied pressure is ≥100N.

[0015] In a preferred embodiment, in step (6), the curing temperature of the oven is 70-120℃ and the heat preservation time is ≥60min.

[0016] The solid triangular prism preform obtained by the above-mentioned layer-laying and compaction method is wherein the preform is a triangular prism with a uniform cross-section, the cross-section being a near-isosceles triangle, and the overall porosity is ≤1%.

[0017] The layup and compaction method for solid triangular prism preforms according to the present invention, by matching a suitable split-type metal tooling to the uniform cross-section triangular prism preform, combining a V-shaped path circumferential continuous layup of prepreg tape, and a structural design for directional filling of fiber bundles in the sharp corner areas, and then through a segmented compaction process of manual compaction after each accumulation of a certain thickness of fiber bundles, and subsequent overall mechanical compaction and oven curing and demolding operations, forms a synergistic effect from three dimensions: layup method, sharp corner reinforcement, and compaction process. This effectively solves the core technical problems of insufficient fiber density and easy pore aggregation in the sharp corner areas when preparing solid triangular prism preforms using traditional processes. Simultaneously, it eliminates the pressure gradient in the thickness direction of the preform, allowing for a uniform distribution of porosity within the preform, successfully controlling the overall porosity of the preform stably below 1%. This method significantly improves upon the problem of excessively high overall porosity in preforms under traditional processes, and avoids issues such as uneven penetration and local defects caused by uneven porosity during subsequent ceramization. It also greatly reduces the ceramization defect rate. Furthermore, this method relies entirely on existing tooling and equipment, requiring no additional specialized equipment, and exhibits excellent process compatibility. While improving the preform molding quality and structural consistency, it effectively reduces equipment investment costs and increases production efficiency. This enables low-cost, mass production of high-density triangular prism-shaped preforms. The resulting preforms can meet the manufacturing requirements of high-temperature load-bearing components such as the tail section of the guide vane in the combustion chamber of hypersonic vehicle engines. It effectively solves the industry problem of the controllable preparation of high-density triangular prism solid preforms, which is difficult to achieve with traditional technologies, providing reliable technical support for the engineering application of ceramic matrix composite preforms. Attached Figure Description

[0018] Figure 1This is a simplified structural diagram of a triangular prism-shaped solid prefabricated body according to the present invention.

[0019] Figure 2 This is a structural schematic diagram of the triangular prism-shaped solid prefabricated body and tooling according to the present invention.

[0020] Figure 3 This is a CT scan of the triangular prism-shaped solid preform according to the present invention.

[0021] Figure 4 It is a CT scan image of a triangular prism preform based on existing technology. Detailed Implementation

[0022] The preferred embodiments of the present invention are given below with reference to the accompanying drawings and described in detail.

[0023] The layup and compaction method for a solid triangular prism irregular precast according to the present invention first includes determining the shape of the precast. The precast to be prepared is a triangular prism with a uniform cross-section. For example... Figure 1 As shown, the solid triangular prism precast body according to the present invention is a triangular prism structure with a uniform cross-section. The left side is the triangular cross-section end of the precast body, which is a quasi-isosceles triangle. The axial extension direction of the precast body is shown from left to right, also referred to as the prism height of the precast body. In a preferred embodiment, the base of the quasi-isosceles triangle is approximately 20 mm long, the side length is approximately 60 mm long, the height is approximately 50 mm, and the prism height is approximately 100 mm. It should be understood that these dimensions can be adjusted according to actual engineering requirements.

[0024] The method for laying and compacting a solid triangular prism-shaped precast according to the present invention further includes providing tooling. Based on the precast shape determined in the above steps, a suitable metal tooling is designed and fabricated. This metal tooling has a split structure, such as... Figure 2 As shown, the metal fixture includes a frame 4 and a top cover plate 5. The frame 4 is a triangular prism with a uniform cross section, and the top cover plate 5 is an irregularly shaped pressure block that can be fixed to the top of the frame 4 with screws, providing support and a compaction foundation for subsequent layering and compaction processes.

[0025] The layup and compaction method for a solid triangular prism-shaped preform according to the present invention further includes cutting a prepreg tape. Here, the prepreg tape refers to a strip-shaped semi-finished product in which a fiber skeleton and a matrix material are combined, the matrix material acting as a binder during the layup and compaction stages and transforming into a SiC ceramic phase during the subsequent ceramization process. In a preferred embodiment, the matrix of the prepreg tape is a polycarbosilane precursor, and the prepreg tape thickness is 0.1-0.25 mm. A continuous unidirectional SiC fiber prepreg tape is selected; the prepreg tape is cut according to the preform dimensions. In a preferred embodiment, the width of the prepreg tape is cut to approximately 100 mm to match the prism height of the preform, and the length of the prepreg tape is cut to approximately 60 mm to match the side length of an isosceles triangle-like cross-section of the preform. Two pieces each of 90° prepreg tape 1 and 0° prepreg tape 2 are cut. The fiber direction of the 90° prepreg tape is perpendicular to the prism height (prism axis), and the fiber direction of the 0° prepreg tape is parallel to the prism height.

[0026] The layup and compaction method for the solid triangular prism precast body according to the present invention further includes laying prepreg tape in a V-shaped path along the circumference of the prism. Here, "circumferential" refers to the plane containing the two sides of the triangle and the axis of the prism; the plane containing the base of the triangle and the axis of the prism is not considered part of the circumferential direction. Figure 2 As shown, firstly, a pre-cut 90° prepreg tape 1 is laid on one inner side of frame 4, and then another 90° prepreg tape 1 is laid on the other inner side of frame 4 in the same manner. After the two 90° prepreg tapes 1 are laid, a V-shaped bonding structure with an included angle of approximately 25° is formed. Subsequently, two 0° prepreg tapes 2 are laid on the inner sides of the two 90° prepreg tapes 1 respectively, completing the V-shaped path layup of the prepreg tapes. It should be understood that the included angle of 25° here is only an example and not a limitation, and it is preferably in the range of 20-35°.

[0027] The layup and compaction method for solid triangular prism-shaped precast bodies according to the present invention further includes axial continuous layup of longitudinal fiber bundles (i.e., 0° fiber bundles) and segmented compaction. For example... Figure 2As shown, after the prepreg tape is laid up, multiple 0° continuous SiC fiber bundles 3 are inserted along the thickness direction in the sharp corner area of ​​the triangular prism to fill and reinforce the sharp corner area. During the process of inserting 0° continuous SiC fiber bundles 3 along the thickness direction in the sharp corner area, a layer-by-layer compaction process is adopted: after each cumulative filling of 0.2mm thick fiber bundles, the filled fiber bundles are manually compacted with a force of ≥100N using tools such as tweezers. After compaction, the next layer of fiber bundles is filled. When the thickness of the fiber bundle filling reaches the height of 50mm of the isosceles triangle of the precast cross section, the top cover plate 5 is installed on the top of the frame 4, the fixing screws are tightened, and the precast body is mechanically compacted by the special-shaped pressure block. In particular, by using a segmented compaction strategy to eliminate the pressure gradient in the thickness direction, the uniform distribution of porosity inside the preform is ensured, with the standard deviation of porosity in the same batch ≤0.15% and the difference in fiber volume fraction between the sharp corner area and the central area ≤3%. This effectively avoids the problem of insufficient fiber density in the sharp corner area in traditional processes and improves the overall quality consistency of the preform.

[0028] The method for laying and compacting the solid triangular prism preform according to the present invention finally includes oven curing and demolding. The tooling and preform, which have been mechanically compacted and assembled, are placed together in an oven for curing. The oven temperature is raised to 70-120°C and held at this temperature for ≥60 minutes. After the curing process is completed, the oven is cooled down. After the temperature drops to room temperature, the fixing screws and the top cover plate of the tooling are removed, and the solid triangular prism preform is demolded from the tooling.

[0029] X-ray CT cross-sectional scanning was performed on the demolded preform for inspection, such as... Figure 3 As shown in the figure, the pore areas inside the precast body are marked in red. The porosity and pore distribution can be directly observed by the distribution and size of the red areas. The results show that the overall porosity of the precast body is ≤1%, there are no continuous pores in the central area, and no stratification phenomenon occurs. There is no pore aggregation problem in the sharp corner area. The density and structural uniformity of the precast body meet the design requirements.

[0030] To further verify the technical effect of the process of this invention, this invention uses the above-mentioned equal-section triangular prism steel mold, but eliminates the V-path prepreg layup process and the directional fiber bundle filling process in the sharp corner area. Instead, it directly fills the mold cavity with SiC fiber rolls of 1mm diameter randomly. These SiC fiber rolls are small clusters / rolls formed by the loose and disordered winding of continuous SiC fibers, which is significantly different from the above-mentioned ordered and oriented continuous SiC fiber bundles. After filling, the SiC fiber rolls in the mold cavity are pressurized from the top to achieve macroscopic compaction. After pressurization, a curing treatment is performed. The prepared solid triangular prism irregular preform of the same size is then subjected to X-ray CT cross-sectional scanning inspection. Figure 4As shown, the fiber orientation inside the product is completely random, with no continuous 0° / 90° fiber bearing paths; obvious pore aggregation occurs in the sharp corner area, and millimeter-level pore channels exist in this area; obvious delamination defects also appear in the central area of ​​the product; the overall porosity of the product is >5%, which is much higher than the porosity of the preform obtained by this invention, and cannot meet the requirements of high-temperature load-bearing components for the density and structural uniformity of the preform.

[0031] The preform obtained by the layup and compaction method of the solid triangular prism irregular preform according to the present invention provides a highly uniform and reliable blank for subsequent ceramization, meeting the mass production requirements of high-temperature load-bearing components such as hypersonic aircraft. In a preferred embodiment, the density increases by ≥25% after subsequent ceramization (chemical vapor infiltration CVI / precursor impregnation pyrolysis PIP / melt infiltration MI), with a density deviation of ≤3% at the same cross section. Used for high-temperature load-bearing components such as turbine blades of aircraft engines, it exhibits a high-temperature resistance of ≥1300℃, effectively improving the uniformity of the ceramization process, reducing local defects caused by uneven porosity, and improving the performance and reliability of the final product. Moreover, the present invention requires no new equipment; mass production can be achieved using existing tooling and ovens. It has good process compatibility, reduces equipment investment costs, improves production efficiency, and shortens the single-piece production cycle by 30%, demonstrating good prospects for engineering and mass production.

[0032] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. Various variations can be made to the above embodiments of the present invention. That is, all simple and equivalent changes and modifications made in accordance with the claims and description of this invention fall within the protection scope of the claims. All aspects not described in detail in this invention are conventional technical content.

Claims

1. A method for laying and compacting solid triangular prism-shaped precast bodies, characterized in that, Includes the following steps: (1) Determine the shape of the preform: The preform to be prepared is a triangular prism with a uniform cross section, and its cross section is a quasi-isosceles triangle; (2) Provide tooling: manufacture a split metal tooling that is adapted to the shape of the preform; (3) Cutting the prepreg tape: Select continuous unidirectional SiC fiber prepreg tape, cut the prepreg tape according to the size of the preform, and cut at least 2 pieces of 90° prepreg tape and 0° prepreg tape respectively; (4) V-shaped path layup: The 90° prepreg tape and the 0° prepreg tape are laid up continuously along the circumference of the prism in a V-shaped path; (5) Filling and segmented compaction of the sharp corner area: Insert multiple 0° continuous SiC fiber bundles along the thickness direction in the sharp corner area of ​​the triangular prism. After each fiber bundle with a cumulative thickness of 0.1-0.3 mm is filled, manually compact the filled fiber bundles. (6) Overall compaction and curing demolding: After the fiber bundles are filled to the design height of the preform cross section which is an isosceles triangle, the preform is mechanically compacted as a whole by the tooling. Then the tooling and the preform are placed in an oven for curing. After curing, the preform is cooled and demolded.

2. The layer compaction method according to claim 1, characterized in that, In step (1), the base length of the cross-section triangle is 10-30mm, the height of the triangle is 40-60mm, and the height of the prism is 80-120mm.

3. The layer compaction method according to claim 1, characterized in that, In step (2), the split metal fixture includes a frame with a triangular prism shape of equal cross section and an irregular top cover plate, which is fixed to the top of the frame by screws.

4. The layer compaction method according to claim 1, characterized in that, In step (3), the fiber direction of the 90° prepreg tape is perpendicular to the height of the prism, and the fiber direction of the 0° prepreg tape is parallel to the height of the prism.

5. The layer compaction method according to claim 1, characterized in that, In step (3), the thickness of the prepreg tape is 0.1-0.25 mm.

6. The layer compaction method according to claim 1, characterized in that, In step (4), the circumferential direction is the plane containing the two sides of the triangle and the axis of the prism.

7. The layer compaction method according to claim 1, characterized in that, In step (4), the included angle of the V-shaped bonding structure formed after the two 90° prepreg tapes are laid is 20-35°.

8. The layer compaction method according to claim 1, characterized in that, In step (5), when manually pressing the fiber bundle, the applied pressure is ≥100N.

9. The layer compaction method according to claim 1, characterized in that, In step (6), the curing temperature of the oven is 70-120℃ and the heat preservation time is ≥60min.

10. The solid triangular prism precast body obtained by the layup and compaction method according to any one of claims 1-9, characterized in that, The precast body is a triangular prism with a uniform cross-section, the cross-section being a near-isosceles triangle, and the overall porosity is ≤1%.

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