A hot-pressing tank forming process for ring frame composite structural parts

Abstract

The present invention discloses an autoclave forming process for a ring-frame composite material structural component. The process extracts the area where the non-expandable surface of the structural component is located based on a digital model of the ring-frame composite material structural component. Starting from a prepreg sheet cutting method, the plies whose prepreg fiber direction is consistent with the arc direction of the non-expandable surface are defined as 0° direction plies, and the plies whose prepreg fiber direction is at a certain angle to the arc direction of the surface are defined as non-0° direction plies. The plies are designed and cut respectively so that the angular deviation between the fiber direction of the sheet and the structural design direction meets the design requirements, thereby realizing the autoclave forming of the ring-frame composite material structural component and ensuring the mechanical properties of the formed parts. Moreover, the method is applicable to the forming of ring-frame composite material structural components with various cross-sectional forms, realizing the autoclave forming of various forms of ring-frame composite material structures, ensuring the forming quality of the ring-frame structural components, ensuring the safety of the aircraft structure, and having good practical value and promotion prospects.

Description

Technical Field

[0001] The invention relates to a molding method of a ring frame type composite material structural part, and in particular to a ring frame type composite material structural part. Background Art

[0002] With the expansion of composite material applications in aircraft, various reinforcement frames, from secondary to primary load-bearing structures, are increasingly being constructed from composite materials. Compared to traditional metal materials, carbon fiber composites offer high specific modulus, high specific strength, and the ability to be molded as a single piece. Through integrated structural molding, they effectively reduce the number of parts assembled and minimize weight while meeting structural performance requirements. Ring-frame composite structural components, serving as the annular members of the fuselage, are crucial primary load-bearing structures, supporting the fuselage, distributing concentrated loads, and providing damage protection.

[0003] Currently, ring-frame composite structural components are primarily manufactured using RTM (resin transfer molding) processes, including 3D weaving / RTM and NCF (non-continuous fiber) fabric / RTM processes. However, parts molded using these processes present several challenges: 1) Dry spots and dry areas: These are prone to occur due to local permeability variations and flow channel effects; 2) Bubble stratification: Air leaks, incomplete resin degassing, and small molecule volatilization can lead to internal bubbles and stratification; and 3) Uneven fiber volume content: Pressure gradients during the molding process can lead to uneven fiber volume content within the product. Overall, the current RTM molding technology for ring-frame structural components presents challenges in quality consistency, making it difficult to guarantee aircraft structural safety.

[0004] Autoclave molding is a common composite manufacturing process suitable for producing high-performance composite products, effectively addressing the challenges associated with the aforementioned processes. However, autoclave molding is not a common process for forming ring-frame composite structural components. One key reason for this is that these components are typically subjected to combined bending and axial shear loads, with bending failure being the primary failure mode. The fiber orientation design within the component determines the strength and performance of the structure. The autoclave molding process requires prepregs to be stacked in a mold according to the designed sequence and layers, followed by hot pressing and curing. However, the ring structure of ring-frame composite components is a non-developable curved surface, and its fiber angles vary with the structural form. This makes it difficult to precisely control the fiber orientation and distribution at all layup angles, leading to misalignment between the fiber orientation and the designed structural orientation, thus compromising the mechanical properties of the part. Therefore, ring-frame composite structural components are not suitable for autoclave molding.

[0005] Therefore, how to solve the problem of inconsistency between the fiber direction and the structural design direction in the non-expandable curved surface ply in the ring frame structure, and make the ring frame-type structural parts adapt to the autoclave molding process to obtain products with stable quality has become an urgent problem to be solved. Summary of the Invention

[0006] Aiming at the problem that the above-mentioned ring frame type composite material structural parts have non-expandable surfaces, and the fiber direction at each layup angle is consistent with the structural design direction, which is difficult to adapt to the autoclave molding process, the present invention proposes a ring frame type composite material structural part autoclave molding process, which extracts the area where the non-expandable surface of the structural part is located based on the digital model of the ring frame type composite material structural part, and starts from the prepreg sheet cutting method. The layup with the prepreg fiber direction consistent with the arc direction of the non-expandable surface is defined as the 0° direction layup, and the layup with the prepreg fiber direction at a certain angle to the arc direction of the surface is non-0° direction layup. The cutting is designed separately so that the angle deviation between the fiber direction of the sheet and the structural design direction meets the design requirements, thereby realizing the autoclave molding of the ring frame type composite material structural parts and ensuring the mechanical properties of the molded parts. The specific technical scheme is as follows:

[0007] A process for forming a ring frame composite material structure in an autoclave, comprising the following steps:

[0008] 1) Design of non-0° ply blanking templates: Based on the structural form of the ring-frame composite structural component, the target surface area is extracted from the digital model. Based on the ply angle, the corresponding angle line is drawn based on the tangent line of the inner edge of the target surface. The target surface is then divided sequentially by rotating the tangent line and the corresponding angle line according to the angle of the allowable deviation between the fiber direction and the structural design direction. The cutting boundary and fiber direction of each ply blanking template are obtained.

[0009] 2) Design of a 0° ply blanking template: Based on the concept of calculus, the target surface area is bisected along the width direction, and the target surface is circumferentially divided into several narrow rings or arcs to construct a 0° ply blanking template.

[0010] 3) Design of ply blanking template for the interface area: Based on the principle of circumferential overlap, draw the ply blanking template for the interface area according to the arc length of the target surface and the width of the structure connected to the target surface;

[0011] 4) Sheet cutting: Use an automatic blanking machine to cut the prepreg sheets for each layer according to the design of steps 1) to 3);

[0012] 5) Sheet laying: Use a laser positioning device to locate the sheet direction, and lay the cut layers of prepreg sheets layer by layer in the mold cavity according to the designed prepreg layer information to ensure that the sheet direction is consistent with the predetermined direction;

[0013] 6) Encapsulation and curing: After the lamination is completed, the mold and material are encapsulated as a whole and then sent into the autoclave for curing and molding.

[0014] The aforementioned autoclave forming process for ring-frame composite structural parts includes ring-frame composite structural parts with various forms of full rings, partial ring segments or variable curvature rings, including L-shaped, Z-shaped, C-shaped, I-shaped, and T-shaped cross-sections.

[0015] In the aforementioned autoclave forming process for ring frame composite structural parts, in step 1), the non-0° direction of ply laying includes angles of 90°, +45°, and -45°.

[0016] In the aforementioned autoclave forming process for ring frame composite structural parts, in step 1), the non-0° direction layup blanking template is designed, and the specific process is as follows:

[0017] Step 1: Pick any point on the inner edge of the extracted target surface as the tangent point, and draw the tangent line of the inner edge of the target surface based on the tangent point;

[0018] Step 2: Based on the angle information of a certain ply, draw a corresponding angle line of the tangent line based on the tangent point in step 1, and the corresponding angle line intersects with the outer edge line of the target curved surface;

[0019] Step 3: Copy the tangent line made in step 2, rotate it a certain angle, and then make it tangent to the inner edge of the target surface;

[0020] Step 4: Repeat step 2, draw the corresponding angle line of the tangent line based on the tangent point of the copied and rotated tangent line, and intersect it with the outer edge line of the target surface;

[0021] Step 5: Repeat steps 3 and 4 to sequentially segment the target surface to obtain multiple corresponding angle lines that intersect with the outer edge lines of the target surface; use one of the angle lines as the fiber direction line, and the angle lines adjacent to the fiber direction line on both sides as the cutting edges to obtain the cutting boundary and fiber direction of the ply blanking sample;

[0022] Step 6: Design the cutting boundaries and fiber directions of the remaining ply blanking samples in accordance with the methods described in steps 1 to 5 in preparation for cutting and laying.

[0023] In the aforementioned autoclave forming process for ring-frame composite structural parts, in step three, the tangent line is rotated by a certain angle and then tangent to the inner edge of the target curved surface. The angle of rotation is not greater than the allowable deviation angle between the fiber direction and the structural design direction.

[0024] Preferably, the allowable deviation angle between the fiber direction and the structural design direction is within ±5°.

[0025] In the aforementioned autoclave forming process for ring-frame composite structural components, in step 2), the 0° direction ply blanking template design is specifically as follows: measuring the width of the target curved surface and the maximum arc length of the target curved surface, dividing the width of the target curved surface into several even segments, using the width of each segment as the width of the prepreg sheet, and using the maximum arc length of the target curved surface as the length of the prepreg sheet, dividing the 0° direction ply prepreg into several narrow long sheets; the width of each sheet is 5 to 10 mm.

[0026] In the aforementioned autoclave forming process for the ring-frame composite structural component, in step 3), the circumferential overlap principle is that the overlap width is 15 to 30 mm.

[0027] In the aforementioned autoclave forming process for ring frame composite structural parts, in step 5), the sheet is laid, and a vacuum pre-compaction operation is performed once every four layers during the laying process, with a vacuum pressure of not less than 85 kPa and a pre-compaction time of not less than 10 minutes.

[0028] In the aforementioned autoclave forming process for ring-frame composite structural parts, in step 6), the specific operation of sending the parts into the autoclave for curing and forming is as follows: pressurizing the part into the autoclave to 0.175 MPa, maintaining it for 5 minutes, testing the vacuum state, and releasing the vacuum to the atmosphere after passing the test, and then continuing to pressurize it to 0.6-0.8 MPa and maintaining it for 5 minutes. When there is no vacuum leakage, the temperature is increased under pressure to enter the curing process; during the curing process, the entire pressure is 0.6-0.8 MPa, and during curing, the temperature is increased to 110°C at a rate of 1-3°C / min and maintained for 2 hours; then the temperature is continued to be increased to 180°C and maintained for 4 hours; then the temperature is cooled to room temperature at a rate of 1-3°C / min before the parts are opened and taken out of the autoclave.

[0029] Beneficial effects of the present invention:

[0030] 1) The present invention extracts the non-developable surfaces of the ring-frame composite structural component based on the digital model of the structural component, divides it in a special way, and obtains the cutting boundaries and fiber directions of the blanking template. Based on this, the prepreg used to prepare the ring-frame composite structural component is cut, and the fiber direction at each layup angle of the ring-frame composite structural component is consistent with the structural design direction. This makes the ring-frame composite structural component suitable for the autoclave molding process, obtains the ring-frame composite structural component with stable performance, and ensures the safety of the aircraft structure.

[0031] 2) In the process of the present invention, a point is randomly selected from the inner edge of the curved surface on the blanking drawing, and a tangent line to the inner edge line is drawn along the point. A corresponding angle line of the tangent line is drawn along the tangent point and intersected with the outer edge line. The tangent line is then copied and rotated by a certain angle and then tangent to the inner web surface again to obtain a cutting edge line and a fiber direction line. This effectively unfolds the curved surface of the ring-frame composite structural part, achieves consistency between the fiber direction at various angles of the fiber layup and the structural design direction, enables precise control of the fiber direction and distribution during the autoclave molding process, and ensures that the fiber direction of the prepreg and the structural design fiber direction remain within the requirements of the composite material manual, thereby ensuring the mechanical properties of the parts molded by the autoclave molding process.

[0032] 3) The process of the present invention realizes that the fiber direction of the unidirectional prepreg laid on the non-developable surface is consistent with the structural design direction by designing the block sheets, and is applicable to various cross-section ring frames and ring frame structures with arbitrary arc length and radian, including L-type, Z-type, C-type, I-type, T-type and other cross-sectional forms of full ring, partial ring segment or variable curvature ring-shaped composite material structures. The autoclave process is used to realize the molding of various complex cross-section ring frame parts, improve product performance, and has good practical value and promotion prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic structural diagram of an L-shaped composite material ring frame in Example 2 of the present invention;

[0034] Figure 2 Schematic diagram of the web surface of the L-shaped composite material ring frame in Example 2 of the present invention;

[0035] Figure 3 Schematic diagram of the tangent line of the inner edge line and the boundary points of the outer edge line of the web surface in Example 2 of the present invention;

[0036] Figure 4 Schematic diagram of the cutting edge lines and fiber direction lines in Example 2 of the present invention;

[0037] Figure 5 Schematic diagram of web plate section cutting in Example 2 of the present invention;

[0038] Figure 6 Schematic diagram of a -45° sheet in Example 2 of the present invention;

[0039] Figure 7 This is a schematic diagram of the material in the 0° direction in Example 2 of the present invention. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments and drawings.

[0041] Example 1

[0042] The present embodiment is a hot-pressing molding process for ring-frame composite structural parts. Based on the digital model of the ring-frame composite structural parts, the area where the non-expandable surface of the structural parts is located is extracted. Starting from the prepreg sheet cutting method, the plies whose prepreg fiber direction is consistent with the arc direction of the non-expandable surface are defined as 0° direction plies, and the plies whose prepreg fiber direction is at a certain angle to the arc direction of the surface are non-0° direction plies. They are designed and cut separately to realize the laying molding of unidirectional prepreg on the non-expandable surface, ensure that the angular deviation between the fiber direction and the structural design direction meets the deviation range of less than or equal to ±5°, and guarantee the mechanical properties of the parts. This method can be applied to the molding of ring-frame composite structures with various cross-sectional forms including L-type, Z-type, C-type, I-type, T-type, etc., including full ring, partial ring segment or variable curvature ring, to realize the prepreg cutting, laying, packaging, hot-pressing molding and curing process of various forms of ring-frame structures. The specific method steps are as follows:

[0043] 1) First, the design of the ply blanking template in the non-0° direction. There is a certain angle between the fiber direction of the ply in the non-0° direction and the direction of the curved arc of the surface. How to ensure that the angle is consistent with the design direction. This embodiment adopts a unique segmentation method: first, based on the structural form of the ring-frame composite structural part, the regional surface where the target surface is located is extracted from its digital model; then, based on the ply angle, the corresponding angle line is made based on the tangent of the inner edge of the target surface, and the tangent and the corresponding angle line are rotated according to the angle of the allowable deviation between the fiber direction and the structural design direction to sequentially segment the target surface, and obtain the cutting boundary and fiber direction of each ply blanking template. The specific segmentation process is as follows:

[0044] The first step is to select an arbitrary point on the inner edge of the extracted target surface as the tangent point, and draw a tangent line to the inner edge of the target surface based on the tangent point;

[0045] Step 2: Based on the angle information of a certain ply, draw a corresponding angle line of the tangent line based on the tangent point in step 1, and intersect the corresponding angle line with the outer edge line of the target curved surface;

[0046] Step 3: Copy the tangent line created in Step 2, rotate it a certain angle, and then make it tangent to the inner edge of the target surface. For example, for plies with 90°, +45°, and -45° angles, with a design tolerance of ±5°, the angles between the angle line and the tangent line are 90°, +45°, or -45°. The tangent line is rotated 5° in sequence and then made tangent to the inner edge of the target surface. Then, create another angle line with the tangent line at 90°, +45°, or -45°.

[0047] Step 4. Repeat step 2 and draw the corresponding angle line of the tangent based on the tangent point of the copied and rotated tangent (the angle between the angle line and the tangent is 90°, +45° or -45°), and intersect it with the outer edge line of the target surface.

[0048] Step 5: Repeat steps 3 and 4 to sequentially segment the target surface, obtaining multiple corresponding angle lines that intersect the outer edge of the target surface. Use one of these angle lines as the fiber direction line, and the adjacent angle lines on either side of it as the cutting edges to obtain the cutting boundary and fiber direction of the ply blanking template.

[0049] Step 6. Design the blanking templates for the remaining non-0° plies according to the methods described in steps 1 to 5. That is, the tangent lines are used as references to their corresponding tangent points, and the angles of the remaining plies are rotated (including 90°, +45°, and -45°). The corresponding angle lines are also rotated accordingly, thereby obtaining the cutting boundaries and fiber directions of the remaining plies.

[0050] 2) Secondly, the design of the 0° ply blanking template is required. The fiber orientation of the 0° ply should align with the arc direction of the curved surface. However, due to the width of the sheet, the inner diameter is smaller than the outer diameter during placement, which inevitably leads to folding and stacking of the sheet, making it difficult to accurately ensure the fiber orientation. Based on this, and in accordance with the principle of segmentation based on calculus, the width of the target surface is measured and evenly divided into several segments. This is to say, the target surface is circumferentially divided into several narrow rings or arcs to construct the 0° ply blanking template. The 0° ply blanking template is drawn using the width of each segment as the width of the prepreg sheet and the maximum arc length of the target surface as the length of the prepreg sheet. To facilitate placement and ensure the accuracy of fiber orientation, the width of each segment along the width of the target surface is preferably 5-10 mm. The resulting 0° ply blanking template is a narrow strip with a length equal to the maximum arc length of the target surface and a width of 5-10 mm.

[0051] 3) Design of ply blanking template for the joint area: Based on the principle of 15-30mm circumferential overlap, draw the ply blanking template for the joint area according to the arc length of the target surface and the width of the structure connected to the target surface, so as to ensure the overlap between the target surface and the structure connected to it.

[0052] 4) Sheet cutting: Use an automatic blanking machine to complete the cutting of each layer of prepreg sheets according to the design of steps 1) to 3).

[0053] 5) Sheet Laying: After the prepreg sheets are cut, a laser locator is used to determine the sheet orientation. The cut prepreg sheets are then manually laid layer by layer in the mold cavity according to the designed prepreg layup information, ensuring that the sheet orientation is consistent with the predetermined direction. During the laying process, vacuum pre-compaction is performed once every four layers, with a vacuum pressure of no less than 85kPa and a pre-compaction time of no less than 10 minutes.

[0054] 6) Encapsulation and Curing: After the layers are laid, the mold and material are encapsulated as a whole and then sent to the autoclave for curing and molding. The specific operation of sending the autoclave for curing and molding is as follows: enter the tank and pressurize to 0.175MPa, maintain for 5 minutes, test the vacuum state, and if the test is qualified, release the vacuum to the atmosphere, continue to pressurize to 0.6-0.8MPa, maintain for 5 minutes, and then start the curing process under pressure with no leakage. During the curing process, the entire pressure is 0.6-0.8MPa. During the curing process, the temperature is raised to 110℃ at a rate of 1-3℃ / min and maintained for 2 hours; then the temperature is continued to rise to 180℃ and maintained for 4 hours; then the temperature is lowered to room temperature at a rate of 1-3℃ / min before opening the tank and taking out.

[0055] Example 2

[0056] This embodiment takes an L-shaped composite material ring frame as an example, and its structure is as follows: Figure 1 As shown, it includes a web surface and flanges. This embodiment uses the method described in Example 1 to achieve autoclave molding of the L-shaped composite ring frame. In this embodiment, the L-shaped composite ring frame is designed with four typical layup angles: 0°, 90°, +45°, and -45°. The specific prepreg cutting, laying, packaging, and curing process are as follows:

[0057] First, the cutting design of the plies in the 90°, +45° and -45° directions is as follows:

[0058] The first step is to extract the surface of the web surface in the digital model according to the structural form of the L-shaped ring frame, such as Figure 2 As shown;

[0059] The second step is to take any point on the inner edge line of the web surface, make a tangent to the inner edge line along the point, and make the corresponding angle line of the tangent along the tangent point. Taking the -45° direction ply as an example, the angle between the angle line and the tangent line is -45° (45° rotated counterclockwise), and it intersects with the outer edge line of the web surface, such as Figure 3 As shown;

[0060] Step 3: Copy the tangent line made in step 2 and rotate it 5°, then make it tangent to the inner edge of the inner web surface again;

[0061] Step 4. Repeat the operation in step 2. Draw a -45° angle line based on the tangent point of the copied and rotated tangent line, and intersect it with the outer edge line of the web surface.

[0062] Step 5. Repeat steps 3 and 4 to split the web surface in sequence and obtain multiple corresponding angle lines that intersect with the outer edge lines of the web surface, such as Figure 4 As shown. Take one of the angle lines as the fiber direction line and the angle lines on both sides of the fiber direction line as the cutting edge lines to obtain the cutting boundary and fiber direction of the blanking sample of the -45° ply, as shown in Figure 5 and Figure 6 shown.

[0063] Step 6: Refer to the segmentation method described in Steps 1 through 5 to design the cutting boundaries and fiber orientations for the 45° and 90° ply samples. Specifically, draw a tangent line at any point on the inner edge of the web surface. Based on this tangent point, create 45° and 90° angles for this tangent line. Rotate this tangent line to the inner edge of the web surface within a ±5° range to obtain a second tangent point. Based on this second tangent point, create 45° and 90° angles for this tangent line. Repeat this process. This yields the cutting boundaries and fiber orientations for the corresponding 45° and 90° ply samples.

[0064] Secondly, the cutting design of the 0° direction ply is as follows: the width of the web area is measured to be 70mm, and its width is evenly divided into sections with a width of 5mm each. The maximum arc length of the web area is measured to be 3000mm; with a width of 5mm as the sheet width, the 0° direction ply cutting template is drawn into 14 narrow strips with a width of 5mm, such as Figure 7 It should be noted that the principle of a 15-30mm circumferential overlap must be followed during laying (i.e., the overlap between the ends of the narrow prepreg strips cut according to the blanking template after laying into a ring shape should be 15-30mm). Therefore, the overlap dimension must be added to the prepreg length during cutting, i.e., the maximum arc length of the web area plus 15-30mm is the length of the prepreg sheet.

[0065] Then, according to the width of the L-shaped composite material ring frame edge strip, draw the blanking template in the edge strip area in the 0° direction. Since the fiber direction of the sheet in the edge strip area is consistent with its structural form, the sheet in this area is designed as a whole sheet, and also follows the principle of 15 to 30 mm circumferential overlap, such as Figure 7 shown.

[0066] An automatic blanking machine is then used to cut the prepreg sheets for each layer according to the aforementioned design. After cutting, a laser locator is used to determine the direction of the sheet. The cut prepreg sheets are then manually laid layer by layer in the mold cavity according to the designed prepreg layup information, ensuring that the sheet direction is consistent with the predetermined direction. During the laying process, a vacuum pre-compaction operation is performed once every four layers, with a vacuum pressure of no less than 85kPa and a pre-compaction time of no less than 10 minutes. After the layers are laid, the mold and material are encapsulated as a whole and then sent to the autoclave for curing and molding. The specific operation is as follows: Enter the tank and pressurize to 0.175MPa, hold for 5 minutes, test the vacuum state, release the vacuum and vent to the atmosphere, then continue pressurizing to 0.6MPa and hold for 5 minutes. If there is no vacuum leakage, heat up and enter the curing process. During the curing process, the entire pressure is 0.6MPa. During the curing process, the temperature is increased at 2°C / min to 110°C and held for 2 hours. Then, the temperature is continued to rise to 180°C and held for 4 hours. The temperature is then cooled at 2°C / min to room temperature before opening the tank. The cured L-shaped composite ring frame is removed and demolded to obtain the composite ring frame cured in the autoclave.

[0067] Testing has shown that the L-shaped composite ring frame molded in this embodiment has no dry spots, dry areas, or bubble stratification, and the fiber volume content in the part is evenly distributed. Mechanical property testing has shown that all indicators meet the design requirements, and the molding quality of the structural part is qualified, ensuring the safety of the aircraft structure.

[0068] In summary, the present invention extracts the non-developable surfaces of the structural parts based on the digital model of the ring-frame type composite material structural parts, divides the cutting boundaries and fiber directions of the blanking template in a special way, and uses this as a basis to cut the prepreg used to prepare the ring-frame type composite material structural parts, so as to achieve the consistency of the fiber direction and the structural design direction at each layup angle of the ring-frame type structural parts, so that the ring-frame type composite material structural parts can adapt to the autoclave molding process, obtain the ring-frame type composite material structural parts with stable performance, ensure the mechanical properties of the parts formed by the autoclave molding process, and ensure the safety of the aircraft structure.

[0069] At the same time, the process of the present invention realizes that the fiber direction of the unidirectional prepreg laid on the non-developable surface is consistent with the structural design direction through the design of the block material, and can be applied to various cross-section ring frames and ring frame structures with arbitrary arc length and radian, including L-type, Z-type, C-type, I-type, T-type and other cross-sectional forms of full ring, partial ring segment or variable curvature ring-shaped composite material structures. The autoclave process is used to realize the molding of various complex cross-section ring frame parts, improve product performance, and have good practical value and promotion prospects.

[0070] In addition, it should be noted that it is obvious to those skilled in the art that the present invention is not limited to the details of the above-mentioned exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. In addition, it should be understood that although this specification is described in terms of implementation methods, it does not contain only one technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in the embodiments can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A process for autoclave forming of ring frame composite structural parts, characterized by: Based on the digital model of the ring-frame composite structural component, the area where the non-developable surface of the structural component is located is extracted. Starting from the prepreg sheet cutting method, the plies of the structural component whose prepreg fiber direction is consistent with the arc direction of the non-developable surface are defined as 0° direction plies, and the plies whose prepreg fiber direction is at a certain angle to the arc direction of the surface are defined as non-0° direction plies. They are designed and cut respectively, and after laying, they are cured in an autoclave to form a shape. The specific steps include: 1) Design of non-0° ply blanking templates: Based on the structural form of the ring-frame composite structural component, the target surface area is extracted from the digital model. Based on the ply angle, the corresponding angle line is drawn based on the tangent line of the inner edge of the target surface. The target surface is then divided sequentially by rotating the tangent line and the corresponding angle line according to the angle of the allowable deviation between the fiber direction and the structural design direction. The cutting boundary and fiber direction of each ply blanking template are obtained. 2) Design of a 0° ply blanking template: Based on the concept of calculus, the target surface area is bisected along the width direction, and the target surface is circumferentially divided into several narrow rings or arcs to construct a 0° ply blanking template. 3) Design of ply blanking template for the interface area: Based on the principle of circumferential overlap, draw the ply blanking template for the interface area according to the arc length of the target surface and the width of the structure connected to the target surface; 4) Sheet cutting: Use an automatic blanking machine to cut the prepreg sheets for each layer according to the design of steps 1) to 3); 5) Sheet laying: Use a laser positioning device to locate the sheet direction, and lay the cut layers of prepreg sheets layer by layer in the mold cavity according to the designed prepreg layer information to ensure that the sheet direction is consistent with the predetermined direction; 6) Encapsulation and curing: After the lamination is completed, the mold and material are encapsulated as a whole and then sent into the autoclave for curing and molding.

2. The autoclave forming process for ring frame composite structural parts according to claim 1, characterized in that: The ring frame composite material structural member includes ring frame composite material structural members with various forms of full ring, partial ring segment or variable curvature ring shapes including L-shaped, Z-shaped, C-shaped, I-shaped and T-shaped cross sections.

3. The autoclave forming process for ring frame composite structural parts according to claim 1, characterized in that: In step 1), the ply laying in the non-0° direction may have angles of 90°, +45°, and -45°.

4. The autoclave forming process for ring frame composite structural parts according to claim 3, characterized in that: In step 1), the non-0° direction ply blanking sample design is as follows: Step 1: Pick any point on the inner edge of the extracted target surface as the tangent point, and draw a tangent line to the inner edge of the target surface based on the tangent point; Step 2: Based on the angle information of a certain ply, draw a corresponding angle line of the tangent line based on the tangent point in step 1, and the corresponding angle line intersects with the outer edge line of the target curved surface; Step 3: Copy the tangent line made in step 2, rotate it a certain angle, and then make it tangent to the inner edge of the target surface; Step 4: Repeat step 2, draw the corresponding angle line of the tangent line based on the tangent point of the copied and rotated tangent line, and intersect it with the outer edge line of the target surface; Step 5: Repeat steps 3 and 4 to sequentially segment the target surface to obtain multiple corresponding angle lines that intersect with the outer edge lines of the target surface; use one of the angle lines as the fiber direction line, and the angle lines adjacent to the fiber direction line on both sides as the cutting edges to obtain the cutting boundary and fiber direction of the ply blanking sample; Step 6: Design the cutting boundaries and fiber directions of the remaining ply blanking samples in the same manner as described in steps 1 to 5, in preparation for cutting and laying.

5. The autoclave forming process for ring frame composite structural parts according to claim 4, characterized in that: In step three, the tangent line is rotated by a certain angle and then tangent to the inner edge of the target curved surface. The angle of rotation is not greater than the angle of allowable deviation between the fiber direction and the structural design direction.

6. The autoclave forming process for ring frame composite structural parts according to claim 5, characterized in that: The allowable deviation angle between the fiber direction and the structural design direction is within ±5°.

7. The autoclave forming process for ring frame composite structural parts according to claim 1, characterized in that: In step 2), the 0° direction ply blanking template design is specifically as follows: the width of the target curved surface and the maximum arc length of the target curved surface are measured, the width of the target curved surface is evenly divided into several segments, the width of each segment is used as the width of the prepreg sheet, and the maximum arc length of the target curved surface is used as the length of the prepreg sheet. The 0° direction ply prepreg is divided into several narrow and long sheets; the width of each sheet is 5 to 10 mm.

8. The autoclave forming process for ring frame composite structural parts according to claim 1, characterized in that: In step 3), the circumferential overlap principle is that the overlap width is 15 to 30 mm.

9. The autoclave forming process for ring frame composite structural parts according to claim 1, characterized in that: In step 5), the sheet is laid, and a vacuum pre-compaction operation is performed once every four layers of the sheet are laid, with a vacuum pressure of not less than 85 kPa and a pre-compaction time of not less than 10 minutes.

10. The autoclave forming process for ring frame composite structural parts according to claim 1, characterized in that: In step 6), the specific operation of sending the autoclave for curing molding is as follows: pressurizing the autoclave to 0.175 MPa, maintaining it for 5 minutes, testing the vacuum state, releasing the vacuum and venting it to the atmosphere after passing the test, continuing to pressurize it to 0.6-0.8 MPa, maintaining it for 5 minutes, and then heating it under pressure without leakage to enter the curing process; during the curing process, the entire pressure is 0.6-0.8 MPa, and during curing, the temperature is raised to 110°C at a rate of 1-3°C / min to 110°C and kept at this temperature for 2 hours; then the temperature is continued to be raised to 180°C and kept at this temperature for 4 hours; then the temperature is lowered to room temperature at a rate of 1-3°C / min before opening the autoclave and taking it out.

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