Integrated weaving forming method for throat liner / diffusion section composite material preform

Abstract

The invention discloses an integrated weaving forming method for a throat liner / diffusion section composite material preform. The method comprises the following steps that 1, a throat liner / diffusion section profiling core mold is unfolded; the core mold comprises a throat liner area and a diffusion section area; 2, yarn increasing knitting, yarn decreasing knitting and constant yarn knitting are sequentially conducted on the throat liner area, and a throat liner main body structure is formed; step 3, performing yarn-reducing weaving along the tail end of the throat liner main body structure to form an inner concave area; 4, constant-forming-thickness weaving is conducted along the tail end of the inwards-concave area to the tail end of the diffusion section area of the core mold, and a diffusion section base layer is formed; 5, laying a net tire on the diffusion section base layer, and performing pre-needling to fix the net tire on the upper layer of the diffusion section base layer; the net tire covers the whole diffusion section base layer; step 6, continuously weaving in the reverse direction along the diffusion section area to wrap the net tire, and continuously weaving to the starting point of the concave area to form a diffusion section surface layer; and 7, main needling is conducted on the net tire in the diffusion section so that the net tire can vertically penetrate into the diffusion section base layer and the diffusion section surface layer.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of composite material forming, in particular to a throat liner / diffuser section composite material preform integrated weaving forming method. BACKGROUND

[0002] Advanced composite materials have the advantages of high specific strength, high specific stiffness, fatigue resistance, corrosion resistance and strong designability, and have been widely used in aerospace, automobile and ship, rail transportation and other fields. In the field of solid rocket engine nozzle manufacturing, carbon-carbon composite materials are widely used in throat liners and diffusers due to their excellent high-temperature performance. Because the woven process cannot form the overall shape of the throat liner and the diffuser section at one time, the current throat liner 1' and diffuser section 2' are formed by weaving process respectively, and the shape is woven into a square first, then cut into the expected shape, and finally connected into a whole by mechanical connection, as shown in the left structure. This method has the following problems: stress concentration occurs at the interface between the throat liner and the diffuser section, which is easy to delaminate under high temperature environment; the throat liner variable cross-section needs subsequent machining, which destroys the continuity of the fibers and weakens the mechanical properties. Figure 4 SUMMARY

[0003] The present application provides a throat liner / diffuser section composite material preform integrated weaving forming method, which integrates the throat liner / diffuser section forming, eliminates the connection surface, fundamentally avoids the stress concentration and delamination on the connection surface, and improves the mechanical strength of the preform.

[0004] Technical scheme: In order to solve the above problems, the present application adopts a throat liner / diffuser section composite material preform integrated weaving forming method, which comprises the following steps:

[0005] Step 1, unfolding the throat liner / diffuser section profiled core mold; the core mold comprises a throat liner area and a diffuser section area;

[0006] Step 2, sequentially performing increased yarn weaving, decreased yarn weaving and constant yarn weaving on the throat liner area to form the throat liner main structure;

[0007] Step 3, performing decreased yarn weaving along the end of the throat liner main structure to form an inner recess area;

[0008] Step 4, performing constant forming thickness weaving along the end of the inner recess area to the end of the diffuser section area of the core mold to form a diffuser section base layer;

[0009] Step 5, laying a web on the diffuser section base layer and pre-needling to fix the web on the upper layer of the diffuser section base layer; the web covers the entire diffuser section base layer;

[0010] ​Step 6, continue to weave in the reverse direction along the diffusion section area to wrap the web tire, continue to weave to the starting point of the inner recess area, forming the diffusion section surface layer;

[0011] Step 7, the web tire in the diffusion section is main needled to make the web tire vertically penetrate the diffusion section base layer and the diffusion section surface layer.

[0012] Further, the throat liner section area and the diffusion section area are both smooth curved surfaces; the radius of the end of the throat liner area away from the diffusion section area is greater than the radius of the end of the throat liner area connected to the diffusion section area; the radius of the diffusion section area gradually increases from the side connected to the throat liner area to the end of the diffusion section.

[0013] Further, the upper section of the core mold throat liner area is a collapsible structure.

[0014] Further, the weaving angle of the increased yarn weaving of step 2 is 25°, the curvature radius of the forming area gradually increases, the cross-sectional diameter gradually increases, and the forming thickness gradually increases.

[0015] Further, the weaving angle of the decreased yarn weaving of step 2 is 30°, the curvature radius of the forming area gradually decreases, the cross-sectional diameter gradually decreases, and the forming thickness gradually decreases.

[0016] Further, the weaving angle of the constant yarn weaving of step 2 is 30°, the curvature radius of the forming area is constant, and the cross-sectional diameter is constant.

[0017] Further, the weaving angle of the decreased yarn weaving of step 3 is 30°, the curvature radius of the forming area is infinite, the cross-sectional diameter gradually decreases, and the forming thickness gradually decreases.

[0018] Further, the weaving angle of step 4 is 45°, the curvature radius of the forming area is infinite, the cross-sectional diameter gradually increases, and the forming thickness remains unchanged.

[0019] Further, the pre-needling direction of step 5 is parallel to the normal of the fabric plane, and the needling density is 15 needles / cm 2 .

[0020] Further, the main needling density of step 7 is 25 needles / cm 2 , and the penetration depth is 8±0.3mm.

[0021] Beneficial Effects: Compared with the prior art, the present invention has the significant advantage of weaving a concave area between the throat liner and the diffuser, first forming the throat liner main structure and the diffuser base layer to achieve an integrated connection between the throat liner and the diffuser, and then concave to reserve space for the mesh and the diffuser surface, then weaving and wrapping the mesh, and performing acupuncture to strengthen the structure, ultimately achieving the throat liner / diffuser integrated forming, eliminating the connection surface, fundamentally avoiding the shortcomings of stress concentration and easy delamination on the connection surface, and improving the mechanical strength of the prefabricated body. At the same time, since the connection surface is eliminated, there is no need to process the connection assembly structure of the connection surface, which can further reduce the structural weight and processing accuracy of the rocket engine, improve production efficiency, and reduce production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the overall process of the forming method of the present invention;

[0023] Figure 2 This is a schematic diagram of the core mold structure of the present invention;

[0024] Figure 3 Schematic diagram of each node in the weaving process of the present invention;

[0025] Figure 4 It is a comparison diagram of the existing split forming method and the integrated forming structure of the present invention. DETAILED DESCRIPTION

[0026] like Figure 1 As shown, a method for weaving an integrated throat liner / diffuser section composite preform in this embodiment provides a weaving machine, an automatic web laying device, and an automatic needling device, including the following steps:

[0027] Step 1: Expand the throat lining / diffuser section profiling core mold. Design the throat lining / diffuser section profiling core mold of the corresponding size according to the required preform size. The outer shape of the throat lining / diffuser section profiling core mold is the same as the inner shape of the preform. The shape of the throat lining / diffuser section profiling core mold in this embodiment is as follows: Figure 2 As shown, the upper section is the throat lining area 5, and the lower section is the diffuser area 6. Both the throat lining area and the diffuser area have smooth curved surfaces. The radius of the throat lining area 5 at the end away from the diffuser area 6 is larger than the radius at the end where the throat lining area 5 connects to the diffuser area 6. The radius of the diffuser area 6 gradually increases from the side connected to the throat lining area 5 to the end of the diffuser area 6. The upper section of the throat lining area 5 is a retractable structure, which expands during preform forming and contracts after preform forming is completed to facilitate demolding.

[0028] Step 2: Perform yarn increase knitting, yarn reduction knitting, and constant yarn knitting on the throat lining area in sequence to form the main structure of the throat lining. Figure 3As shown, from the top of the throat insert area of the core mold, first use the braiding machine to increase the yarn braiding from the starting point 1, the braiding angle is 25°, the curvature radius of the obtained forming area gradually increases, the cross-sectional diameter gradually increases, the forming thickness gradually increases, and the braiding is carried out to the preset yarn reducing point 2. From the yarn reducing point 2, the yarn reducing braiding is carried out, the braiding angle is 30°, the curvature radius of the obtained forming area gradually decreases, the cross-sectional diameter gradually decreases, the forming thickness gradually decreases, and the braiding is carried out to the constant yarn braiding point 3. From the constant yarn braiding point 3, the constant yarn braiding is carried out, the braiding angle is 30°, the curvature radius of the obtained forming area is constant, the cross-sectional diameter is constant, the braided outer shape is a cylindrical surface, and the braiding is carried out to the preset concave point 4. From the starting point 1 to the preset concave point 4, the throat insert main body structure 3' is formed.

[0029] Step 3, yarn reducing braiding is carried out along the end of the throat insert main body structure to form a concave area. From the preset concave point 4, the yarn reducing braiding is carried out, the braiding angle is 30°, the curvature radius of the obtained forming area is infinite, the cross-sectional diameter gradually decreases, and the forming thickness gradually decreases to form the concave area.

[0030] Step 4, constant forming thickness braiding is carried out along the end of the concave area to the end of the diffusion section of the core mold, the braiding angle is 45°, the curvature radius of the forming area is infinite, the cross-sectional diameter gradually increases, and the forming thickness remains unchanged to form the diffusion section base layer. After the diffusion section base layer braiding is completed, the braiding machine is temporarily stopped and waits at the end of the diffusion section.

[0031] Step 5, lay the web on the diffusion section base layer and pre-needling to fix the web on the upper layer of the diffusion section base layer. Use the web automatic laying device to lay the web on the diffusion section base layer at a pressure of 0.3 MPa, the web covers the entire diffusion section base layer, and the automatic needling device is used for pre-needling of the web, the needling direction is parallel to the normal of the fabric plane, and the needling density is 15 needles / cm 2 . The web is completely attached to the diffusion section base layer through the laying of the web and the pre-needling, the target thickness of the diffusion section is achieved through the superposition of layers, and the web is temporarily fixed by being vertically pierced into the woven cloth through the pre-needling of the automatic needling device.

[0032] Step 6, start the braiding machine at the end of the diffusion section again, continue to braid in reverse along the diffusion section area to wrap the web, and continuously braid to the starting point of the concave area, i.e. the preset concave point 4, to realize connection with the throat insert main body structure and form the diffusion section surface layer.

[0033] Step 7, use the automatic needling device to main-needle the web in the diffusion section to vertically pierce the web into the diffusion section base layer and the diffusion section surface layer. The needling density is 25 needles / cm 2 , the piercing depth is 8±0.3 mm, further realizing z-direction reinforcement, thickening weaving to form the required diffusion section 5', and finally forming the integrated formed throat insert / diffusion section structure as shown on the right. Figure 4 ​

[0034] The present invention weaves a concave area between the throat liner and the diffuser, first forming the throat liner main structure and the diffuser base layer to achieve an integrated connection between the throat liner and the diffuser. The concave area is then formed to reserve space for the mesh and the diffuser surface. The mesh is then woven and wrapped, and the structure is reinforced by needling. Ultimately, the throat liner / diffuser is integrated, eliminating the connection surface, fundamentally avoiding the shortcomings of stress concentration and easy delamination on the connection surface, and improving the mechanical strength of the prefabricated body. Furthermore, since the connection surface is eliminated, there is no need to machine the connection assembly structure of the connection surface, which can further reduce the weight and processing accuracy of the rocket engine structure, improve production efficiency, and reduce production costs.

Claims

1. A method for forming an integrated weaving of a throat liner / diffuser section composite material preform, characterized in that: The following steps are involved: Step 1: unfolding a throat liner / diffuser section profiling core mold; the core mold includes a throat liner area and a diffuser section area; Step 2: performing yarn increasing knitting, yarn reducing knitting, and constant yarn knitting in sequence on the throat lining area to form the main structure of the throat lining; Step 3: Weaving with reduced yarn along the end of the throat lining main structure to form a concave area; Step 4: Weaving a constant forming thickness along the end of the concave area to the end of the core mold diffusion section area to form a diffusion section base layer; Step 5: Laying a mesh on the diffusion section base layer and pre-needling the mesh to fix it on the upper layer of the diffusion section base layer; the mesh covers the entire diffusion section base layer; Step 6: Continue weaving in the reverse direction along the diffusion section to wrap the mesh, and continue weaving to the starting point of the concave area to form the surface layer of the diffusion section; Step 7: Perform main needling on the mesh in the diffusion section so that the mesh vertically penetrates the base layer and the surface layer of the diffusion section.

2. The forming method according to claim 1, wherein: The surfaces of the throat lining area and the diffusion section area are both smooth curved surfaces; the radius of the throat lining area away from the diffusion section area is larger than the radius of the end where the throat lining area is connected to the diffusion section area; the radius of the diffusion section area gradually increases from the side connected to the throat lining area to the end of the diffusion section.

3. The forming method according to claim 2, wherein: The upper section of the core mold throat lining area is a retractable structure.

4. The forming method according to claim 1, wherein: The braiding angle of the yarn-increasing braiding in step 2 is 25°, the curvature radius of the forming area gradually increases, the cross-sectional diameter gradually increases, and the forming thickness gradually increases.

5. The forming method according to claim 1, wherein: The braiding angle of the yarn reduction braiding in step 2 is 30°, the curvature radius of the forming area gradually decreases, the cross-sectional diameter gradually decreases, and the forming thickness gradually decreases.

6. The forming method according to claim 1, wherein: The braiding angle of the constant yarn braiding in step 2 is 30°, the curvature radius of the forming area remains unchanged, and the cross-sectional diameter remains unchanged.

7. The forming method according to claim 1, wherein: The braiding angle of the yarn reduction braiding described in step 3 is 30°, the curvature radius of the forming area is infinite, the cross-sectional diameter gradually decreases, and the forming thickness gradually decreases.

8. The forming method according to claim 1, wherein: In step 4, the braiding angle is 45°, the curvature radius of the forming area is infinite, the cross-sectional diameter gradually increases, and the forming thickness remains unchanged.

9. The forming method according to claim 1, wherein: The pre-needling direction of step 5 is parallel to the normal direction of the fabric plane, and the needling density is 15 needles / cm 2 .

10. The forming method according to claim 1, wherein: The main acupuncture density in step 7 is 25 needles / cm 2 The puncture depth is 8±0.3mm.

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