CN117328188A

CN117328188A - Method for facilitating densification of internal quality of ceramic matrix composite

Info

Publication number: CN117328188A
Application number: CN202311183956.5A
Authority: CN
Inventors: 水佑裕; 李涛
Original assignee: Chengdu Chengwei Precision Machinery Manufacturing Co ltd
Current assignee: Chengdu Chengwei Precision Machinery Manufacturing Co ltd
Priority date: 2023-09-14
Filing date: 2023-09-14
Publication date: 2024-01-02

Abstract

The invention discloses a method for facilitating densification of internal quality of a ceramic matrix composite, which is formed by weaving a fiber preform in the following weaving mode: the warp direction of the outer layer is at least 2 strands of warps, the warp direction of the inner layer is 1 strand of warps, and the weft directions of the outer layer and the inner layer are all 1 strand of wefts. The preform formed by the invention has larger outer layer clearance and smaller inner layer clearance, and perfectly solves the problems of matrix filling rate and internal gap formation.

Description

Method for facilitating densification of internal quality of ceramic matrix composite

Technical Field

The invention relates to the field of ceramic matrix composite production, in particular to a method for facilitating densification of internal quality of a ceramic matrix composite and a preparation method of the ceramic matrix composite.

Background

Silicon carbide ceramic matrix composites are generally composed of three parts, namely reinforcing fibers, an interface layer and a ceramic matrix, wherein the reinforcing fibers are used as the main bearing part of the composite, and have a decisive effect on the performance of the composite, and the influencing factors include: the fiber model, the volume content of the fiber, the braiding method of the fiber and the like, wherein if the fibers of the same model adopt different modes, the fibers have great influence significance on the subsequent interface deposition and matrix filling, and in the production of ceramic matrix composites, most braiding modes are divided into single-strand braiding and double-strand braiding. The warp and weft directions are formed by single-stranded one-twist knitting, namely single-stranded knitting (as shown in fig. 1-2, fig. 1 is a single-stranded knitting mode, fig. 2 is another single-stranded knitting mode), and the warp and weft directions are formed by double-stranded one-twist knitting, namely double-stranded knitting (as shown in fig. 3-4, fig. 3 is a double-stranded knitting mode, and fig. 4 is another double-stranded knitting mode). The single-strand woven preform is characterized in that strand gaps formed by weaving among strands are small, the internal gaps of the preform belong to small channels, the filling rate of the gaps to the internal gaps of the thin-wall part is high, but the filling speed of the gaps to the internal gaps of the thin-wall part is high, and the phenomenon of slow filling and unfilled matrix exists in single-strand woven pores when the thickness of the part is more than 1.8 mm. The double-strand woven preform is characterized in that strand gaps formed by weaving among strands are larger, the gaps inside the preform belong to large channels, the gaps can be densely filled inside a component matrix with the thickness of more than 1.8mm, but due to the large channels, the matrix can be slowly filled, so that the process benefit is reduced, and the cost is increased.

The above background is for the convenience of understanding the present invention and is not a known art which has been disclosed to the general public before the application of the present invention.

Disclosure of Invention

Aiming at the defects, the invention provides a method for facilitating the densification of the internal quality of a ceramic matrix composite material, and the method forms a preform with larger outer-layer clearance and smaller inner-layer clearance, thereby perfectly solving the problems of matrix filling rate and internal void formation.

The technical proposal is as follows: a method for facilitating densification of the internal quality of a ceramic matrix composite is characterized in that the method is formed by weaving a fiber preform in the following weaving mode:

the warp direction of the outer layer is at least 2 strands of warps, the warp direction of the inner layer is 1 strand of warps, and the weft directions of the outer layer and the inner layer are all 1 strand of wefts.

Further, the outer layer is a double-stranded warp.

Further, the braiding is shallow cross-linked braiding.

Further, the fiber preform has five layers, wherein the first layer and the fifth layer are outer layers, and the second layer, the third layer and the fourth layer are inner layers.

Further, the fiber preform has seven layers, wherein the first layer and the seventh layer are outer layers, and the second layer, the third layer, the fourth layer, the fifth layer and the sixth layer are inner layers.

Further, the fiber preform has seven layers, wherein the first layer, the second layer, the seventh layer and the eighth layer are outer layers, and the third layer, the fourth layer and the fifth layer are inner layers.

On the other hand, the invention also provides a preparation method of the ceramic matrix composite.

The technical proposal is as follows: the preparation method of the ceramic matrix composite material adopts the method which is favorable for densification of the internal quality of the ceramic matrix composite material to prepare the fiber preform.

Further, the fiber preform has large channels in the outer layer that facilitate the bulk of the gas flow and matrix into the inner layer, which has small channels for interface deposition and matrix densification filling after the gas flow or matrix is entered.

Compared with the prior art, the invention has the beneficial effects that:

the invention adopts outer layer double-strand braiding and inner layer single-strand braiding, the gap between the outer layer and the inner layer of the formed preform is larger, the gap between the inner layer is smaller, and the problems of filling rate of the matrix and formation of internal gaps are perfectly solved.

According to the invention, as the inner layer is woven in a warp direction and a single strand, the formed microscopic pores are smaller, the densification filling of the inner layer is faster, and the inner layer can be filled more compactly because no external space is blocked. The outer layer is double-stranded braided, the formed channel is large, the air flow and the matrix are not easy to be blocked on the surface layer, and when the deposition and PIP working procedures are carried out, the air flow and the matrix can largely pass through the outer layer to realize the filling of the internal pores. According to the invention, after the internal pores of the prefabricated member are filled in the follow-up process, the small channels are filled and compacted, and then the large channels are closed piece by piece, so that the internal pores are reduced after the composite material is formed, the diameter of the formed pores is less than 50 mu m, the tensile and compressive properties of the material are improved by 150-200 MPa, and the performance is stable.

According to the invention, through weft single-ply weaving, inner-layer warp single-ply weaving and outer-layer warp double-ply weaving, the operation time of the ceramic matrix composite member in a CVI (chemical vapor deposition) process and a PIP (picture in picture) process is shortened by 200h.

Drawings

FIG. 1 is a schematic diagram of a background art structure;

FIG. 2 is a schematic diagram of another prior art structure;

FIG. 3 is a schematic diagram of another prior art structure;

FIG. 4 is a schematic diagram of another prior art structure;

FIG. 5 is a schematic view of the overall structure of a fiber preform according to the present invention;

FIG. 6 is a schematic view of the overall structure of another fiber preform according to the present invention;

FIG. 7 is a schematic representation of the microstructure variation of the size channel of the composite semifinished product (after PIP twice) according to the invention;

FIG. 8 is a composite view of the present invention;

in the figure: 1. the first prefabricated layer, 2, the second prefabricated layer, 3, the third prefabricated layer, 4, the fourth prefabricated layer, 5, the fifth prefabricated layer, 6, the sixth prefabricated layer, 7, the seventh prefabricated layer, 8, the weft fiber group, 9, the warp fiber group, 10, the large channel, 11, the small channel.

Detailed Description

The invention will be further described with reference to the accompanying drawings.

A method for facilitating densification of the internal quality of a ceramic matrix composite is characterized in that the method is formed by weaving a fiber preform in the following weaving mode:

Further, the outer layer is a double-stranded warp.

Further, the braiding is shallow cross-linked braiding.

The preparation method of the ceramic matrix composite material adopts the method which is favorable for densification of the internal quality of the ceramic matrix composite material to prepare the fiber preform.

Example 1

Referring to fig. 5, fig. 5 is a schematic view showing the overall structure of a fiber preform according to the present invention.

A fiber preform is formed by shallow cross-knitting of a weft fiber group 8 and a warp fiber group 9, and sequentially comprises a first layer preform layer 1, a second layer preform layer 2, a third layer preform layer 3, a fourth layer preform layer 4, a fifth layer preform layer 5, a sixth layer preform layer 6 and a seventh layer preform layer 7 from top to bottom, wherein the first layer preform layer 1, the second layer preform layer 2, the sixth layer preform layer 6 and the seventh layer preform layer 7 are outer layers, the third layer preform layer 3, the fourth layer preform layer 4 and the fifth layer preform layer 5 are inner layers, each weft fiber forming the weft fiber group 8 is formed by one strand, among warp fibers forming the warp fiber group 9, the warp fibers completely located in the outer layers are formed by two strands, and the rest of the warp fibers are formed by one strand.

The fiber preform shown in fig. 5, by employing single weft strands, double warp strands in the outer layers of the outer layers, thus forms a large channel 10. The inner layer is single in weft and warp, so that small channels 11 are formed, in the subsequent preparation of the composite material, the matrix is fast in densification and filling in the inner layer, and can be filled more densely because no external space is blocked, the channels formed in the outer layer are large, the air flow and the matrix are not easy to block in the surface layer, and the air flow and the matrix can be largely filled in the inner pores through the outer layer during the deposition and PIP working procedures. After the internal pores of the prefabricated member are filled in the follow-up process, after the small channels are filled and compacted, the large channels are closed one by one, so that the internal pores are reduced after the composite material is formed, the diameter of the formed pores is less than 50 mu m, the tensile and compressive properties of the material are improved by 150-200 MPa, and the performance is stable.

Further, the fibers are SiC fibers.

Referring to fig. 6, fig. 6 is a schematic view showing the overall structure of another fiber preform according to the present invention.

Example 2

The fiber preform used in this example was the same as that of fig. 6 in example 1.

(1) The fiber preform of example 1 was placed in a chemical vapor deposition furnace to prepare a pyrolytic carbon interface layer, the precursors being: propane, deposition temperature: 1000 ℃, and the heat preservation time is as follows: 10h, the pressure in the furnace: 1.2kPa, the propane interface thickness is: 100nm;

(2) preparing a polycarbosilane precursor solution (the solvent is dimethylbenzene) into impregnating slurry, and controlling the viscosity to be 80 mPa.s;

(3) placing the fiber preform into a vacuum high-pressure impregnation tank, injecting the impregnation liquid in the step (2) to submerge the fiber preform, vacuumizing to-0.09 MPa, keeping the vacuum for 3 hours, pressurizing to 4MPa, and maintaining the pressure for 2 hours;

(4) taking out the fiber preform, draining the surface impregnating solution of the mold, and putting the fiber preform into a high-pressure curing furnace for curing at the temperature: 300 ℃, curing pressure: 3MPa, curing time: 6h;

(5) putting the fiber preform into a high-temperature cracking furnace for cracking, heating to 1200 ℃ at a heating rate of 5 ℃/min in nitrogen atmosphere, preserving heat for 120min, and naturally cooling to room temperature;

(6) repeating the steps (3) - (5) until the weight change of the preform is less than 1%, and completing the preparation of the composite material.

Comparative example 1 (Single strand)

Comparative example 1 was identical to example 1 except that the fiber preform of the structure of fig. 2 was used (i.e., both the inner and outer layers were woven in a single strand), as compared to example 1.

Comparative example 2

Comparative example 1 was identical to example 1 except that the fiber preform of the structure of fig. 4 was used (i.e., both the inner and outer warps were doubled and the wefts were doubled), as compared with example 1.

Example 3

1. Comparative tests were carried out on the composites prepared in example 2, comparative example 1 and comparative example 2, respectively, and the results are shown in Table 1 below.

TABLE 1

2. The microstructure of the fiber preform obtained in the process of the embodiment 2 after the CVI interface deposition process and the two PIP matrix filling processes was observed, as can be seen from fig. 7, the large channel formed by the double-strand layer and the small channel formed by the single-strand layer are in a state that the channel is gradually closed after the CVI interface deposition process and the two PIP matrix filling processes, the middle small channel tends to be closed, and the large channel gap on both sides is larger than the middle small channel gap, but also tends to be closed.

3. The composite material prepared in the example 2 is taken for dissection, and an anatomic graph is shown as figure 8, which shows that along with the end of the final procedure, the internal gaps of the sample are densely filled, no obvious holes are formed under observation under a high-power electron microscope, and the compactness is good.

The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for facilitating densification of the internal quality of a ceramic matrix composite is characterized in that the method is formed by weaving a fiber preform in the following weaving mode:

2. The method of facilitating densification of an internal mass of a ceramic matrix composite according to claim 1, wherein the outer layer is a bifilar warp.

3. The method of facilitating densification of an internal mass of a ceramic matrix composite according to any one of claims 1-2, wherein the weave is a shallow cross-linked weave.

4. The method of claim 3, wherein the fiber preform comprises five layers, wherein the first layer and the fifth layer comprise outer layers, and the second layer, the third layer, and the fourth layer comprise inner layers.

5. The method of claim 3, wherein the fiber preform is seven layers, wherein the first layer and the seventh layer are exterior layers, and the second layer, the third layer, the fourth layer, the fifth layer, and the sixth layer are interior layers.

6. The method of claim 3, wherein the fiber preform is seven layers, wherein the first, second, seventh, and eighth layers are exterior layers, and the third, fourth, and fifth layers are interior layers.

7. A method for preparing a ceramic matrix composite, characterized in that the method for preparing the ceramic matrix composite adopts the method for facilitating densification of the internal quality of the ceramic matrix composite according to any one of claims 1 to 6 to prepare a fiber preform.

8. The method of preparing a ceramic matrix composite according to claim 7, wherein: the fiber preform has large channels on the outer layer for facilitating the flow of air and the matrix to enter the inner layer in large quantity, and the inner layer has small channels for performing interface deposition and matrix densification filling after the flow of air or the matrix enters.