Design method of interlayer composite material structure forming equipment for forming process simulation

Abstract

The invention belongs to a composite material manufacturing technology, and relates to a design method of interlayer composite material structure forming equipment for forming process simulation, which comprises the following steps: step 1, initial design of a tool, including initial design of a tool template and a tool fixture; 2, performing molding process simulation on the composite material structure under the conditions of molding parameters in an initial tool and autoclave equipment, solving temperature distribution in an autoclave and deformation of the composite material structure, and analyzing whether the composite material structure meets acceptance standards or not; 3, a tool design scheme is determined; according to the method, a final tool design method is determined by simulating the molding process of the composite autoclave and comparing and analyzing the temperature distribution and the final structural deformation effect of the composite material in the molding process under different tool materials, tool templates and tool fixture schemes, and through a parameterized modeling scheme, a final tool design method is established. And rapid modeling of the sandwich composite material structure is realized.

Description

Technical Field

[0001] The invention belongs to composite material manufacturing technology and relates to a sandwich composite material structure forming equipment design method for forming process simulation. Background Art

[0002] Aircraft composite structures have the characteristic that material forming and structural forming are completed simultaneously. When the composite structure is formed, the prepreg and sandwich materials are first laid on the forming tooling, and then the material and the tooling are subjected to high temperature and high pressure as well as cooling and pressure reduction to complete the composite structure forming.

[0003] Composite material molding tooling is generally composed of a template and a template frame. The template mainly provides a molding surface for the composite material structure molding, and is also distributed with holes such as reference holes, positioning holes, thermocouple holes, etc.; the template frame provides support for the molding surface on the one hand, and on the other hand, ventilation holes are opened on each side of the template to facilitate the flow of hot air during molding.

[0004] The final quality of the composite structure is closely related to the molding tooling. The difference in thermal expansion coefficients between the tooling material and the composite material directly affects the residual stress and curing deformation of the composite structure after molding. The molding tooling template determines the contour of the final molding shape of the composite structure. The distribution of the molding tooling template determines the stiffness of the tooling. The size and distribution of the vent holes on the template frame determine the temperature distribution of the tooling surface during the molding process, which in turn affects the temperature distribution on the surface during the composite material molding process, affects the stress distribution of the composite structure, and affects the final shape of the composite structure.

[0005] Traditional composite molding tooling design generally uses the composite structural surface as the tooling template surface. For example, based on the three-dimensional composite structure digital model, the structural surface is extracted as the tooling template surface. The location design of the thermocouple holes on the surface is generally based on experience. The design of the mold frame is mostly based on experience to determine the distance between each surface, the size and spacing of the holes on the surface, etc. The molding tooling materials are generally steel and aluminum, and the material selection is generally selected based on the complexity of the composite structure combined with experience. Therefore, the composite molding tooling and its impact on the final composite structure mostly rely on the experience of the tooling designer, and the effect of the composite molding cannot be estimated and evaluated during the tooling design stage.

[0006] With the development and application of computer technology, many domestic and foreign enterprises and research institutions have carried out research on composite material design, analysis and manufacturing process based on digital simulation technology. Most of the existing domestic research focuses on the heat transfer and deformation of the composite material structure itself during the molding process, and there are few studies on the influence of tooling structure optimization on the final composite material structure deformation. There are few engineering applications that use simulation methods to study the interaction between composite material structure and tooling to guide tooling optimization design. Summary of the invention

[0007] The technical problem solved by the present invention is that the design method of the traditional aircraft composite material structure forming tooling is mainly based on the original shape of the aircraft components, and relies on the designer's experience to design the forming tooling. The final tooling quality and the quality of the finished composite material structure are difficult to predict, and the controllability and efficiency are low. The present invention proposes a sandwich composite material structure forming equipment design method based on forming process simulation. By simulating the composite autoclave forming process, the temperature distribution of the composite material during the forming process and the final structural deformation effect under different tooling materials, tooling templates, and tooling jig schemes are compared and analyzed to determine the final tooling design method, and through the parametric modeling scheme, the rapid modeling of the sandwich composite material structure is realized. This method can realize the collaborative design of products and processes in the early stage of development, reduce development costs, improve development efficiency, and increase the one-time forming pass rate of aircraft composite material structures.

[0008] Technical solution of the present invention

[0009] The method for designing sandwich composite material structure forming equipment based on forming process simulation includes the following steps:

[0010] Step 1: Initial design of tooling, including the initial design of tooling template and tooling frame;

[0011] Step 2: Simulate the molding process of the composite material structure under the initial tooling and molding parameter conditions in the autoclave equipment, solve the temperature distribution in the autoclave and the deformation of the composite material structure, and analyze whether the composite material structure meets the acceptance criteria;

[0012] Step 3: Determine the tooling design plan.

[0013] Furthermore, step 1 of the preliminary design of tooling specifically includes:

[0014] 1.1 Based on the original model of the composite material structure, the tooling template is preliminarily preset, and steel material is used as the initial template material;

[0015] 1.2 Analyze the original model of the composite material structure and determine the windward surface of the composite material structure during molding based on the curvature of the original model;

[0016] 1.3 No openings are set on the template surface, including thermocouple holes;

[0017] 1.4 According to the length and width of the frame, the templates that make up the frame are initially designed to be distributed at a spacing of 300mm;

[0018] 1.5 The air circulation holes on the template are designed according to the following parameters: the initial radius of the upper semicircular hole is 40mm, the spacing is 50mm, and the square ventilation holes are evenly distributed in the template, with a minimum distance of 100mm from the edge of the template and a minimum distance of 70mm between holes.

[0019] Furthermore, the windward side determined in 1.2, that is, the placement direction in the autoclave, is combined with the original model, and the vertical wind direction of the composite material structure boundary is used as the length direction of the jig, and the downwind direction is used as the width direction of the jig, or the downwind direction of the composite material structure boundary is used as the length direction of the jig, and the vertical wind direction is used as the width direction of the jig. The specific length and width directions are determined according to the size of the composite material structure. The length direction boundary and width direction boundary of the tooling jig are preliminarily preset according to the original model boundary.

[0020] Further, step 2 includes the following steps:

[0021] Step 2.1 Establish a temperature field analysis model of the autoclave, molding tooling and composite material structure, establish a CAE mesh model based on the CAD model, and set up sharing of mesh nodes for the contact surfaces between the air in the autoclave, the composite material structure and the molding tooling;

[0022] Step 2.2: Set the temperature and pressure boundary conditions according to the molding parameters of the composite autoclave, perform temperature-airflow coupling simulation of the molding process of the autoclave, molding tooling and composite structure, and solve the temperature distribution of the molding tooling and composite structure. If the temperature difference of the composite structure is controlled within 5°C during the process, design the air circulation holes on the plate with the parameters in 1.5. If the temperature difference exceeds 5°C, execute step 2.3.

[0023] Step 2.3: Based on the temperature distribution of the composite material structure in step 2.2, the size of the air circulation hole corresponding to the template with poor air circulation is increased, and the process returns to step 2.1 until the temperature difference of the composite material structure is controlled within 5°C;

[0024] Step 2.4 establishes a composite material structure curing deformation analysis model, and uses the obtained temperature distribution and preset pressure as boundary conditions to solve the deformation result of the composite material structure after forming; if the deformation result meets the acceptance criteria, the original model data of the composite material structure in 1.1 is used as the basis for the design of the tooling template; if the deformation result exceeds the acceptance criteria, execute step 2.5;

[0025] Step 2.5: Solve the composite material structure forming process model based on the composite material structure deformation results:

[0026] Step 2.6: Use the composite material structure forming process model obtained in step 2.5 as the design basis for the forming tool template, redesign the tool template, and then establish the temperature field analysis model of the autoclave, forming tool and composite material structure. Then, set the temperature and pressure boundary conditions according to the composite material autoclave forming parameters, perform the temperature-airflow coupling simulation of the forming process of the autoclave, forming tool and composite material structure, solve the temperature distribution of the forming tool and composite material structure, and then return to step 2.4 until the composite material structure forming effect meets the acceptance criteria;

[0027] Step 2.7 Comprehensively analyze the strength of the tooling template and tooling frame. After the composite material structure forming process, the structural strength of the tooling template and tooling frame should meet the maximum Mises stress within the allowable stress range of the material. If it does not meet the requirements, adjust the tooling template and tooling design plan.

[0028] Further, step 2.5 is specifically as follows: the deformation result of the composite material structure is a point cloud numerical model containing multiple grid nodes. When solving the composite material structure forming process model, the displacement of each grid node is negative and multiplied by the compensation coefficient and added to the original composite material structure three-dimensional data node. The compensation coefficient is initially set to 1.5, and the composite material structure three-dimensional process model is formed through CAD software.

[0029] Furthermore, in step 2.7, the tooling template and tooling design are adjusted, including: ① replacing the tooling template material with aluminum material; ② changing the size of the vent holes of the tooling frame; ③ increasing the number of templates in the supporting frame, and repeating the above simulation analysis until the deformation of the composite material structure and the tooling strength meet the requirements.

[0030] Further, the tooling design scheme of step 3 includes:

[0031] 3.1 The tooling template material should be selected in combination with the structural strength of the molding tooling and the deformation results of the composite material structure;

[0032] 3.2 The tooling template should meet the requirements of the acceptance standards for composite material structures. The tooling template design should be based on the original data of the composite material structure, or on the molding process model obtained by simulation iteration;

[0033] 3.3 The thermocouple holes on the tooling template should be arranged at the corresponding positions of the template according to the coordinates of the characteristic points on the die surface of the composite material structure in the simulated autoclave and the thermocouple holes;

[0034] 3.4 The material of the tooling frame should be steel;

[0035] 3.5 The forklift pipe position should be set on the windward side of the tooling frame placed in the autoclave;

[0036] 3.6 The design of the air circulation holes on the jig should be determined based on the uniformity of the temperature distribution of the composite material structure during the autoclave molding process.

[0037] Furthermore, the characteristic points in 3.3 include: a temperature leading point, a temperature lagging point and a temperature intermediate point.

[0038] Beneficial Effects

[0039] The present invention proposes a sandwich composite material structure forming equipment design method based on forming process simulation. Through numerical simulation technology, the special process of aircraft thermosetting resin-based honeycomb sandwich composite material structure autoclave forming can be effectively displayed in intuitive images and numerical forms, and the influence of forming tooling design on product design can be displayed in intuitive forms such as numerical values ​​and cloud maps. At the beginning of tooling design, the influence of different tooling materials, tooling templates and tooling plate frame vent sizes on the temperature distribution and final deformation of the composite material structure during the autoclave forming process can be effectively simulated, and the deformation results can be converted into tooling template profiles through digital deformation compensation methods. Through the present invention, the dependence of honeycomb sandwich composite material structure forming tooling design on the experience of designers can be effectively reduced, reliable predictability and controllability can be provided for tooling design, and the repetitive engineering tests and tooling modeling of new aircraft-based honeycomb sandwich composite material structures can be reduced, the product development cost can be reduced, the development rate of new materials, new structures and new aircraft can be improved, and technical guarantees can be provided for the independent control of composite material structures of my country's aircraft equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a schematic diagram of initial design parameters of a plate rack according to an embodiment of the present invention;

[0041] Figure 2 It is a diagram of the grid model of the tooling, the composite structure and the grid model of the autoclave according to the embodiment of the present invention;

[0042] Figure 3 This is a schematic diagram of the temperature distribution of the composite material structure and the tooling die surface at 50 minutes in the embodiment of the present invention;

[0043] Figure 4 A schematic diagram of changing the parameters of the vent holes of the tooling template according to an embodiment of the present invention;

[0044] Figure 5 This is a diagram showing the curing deformation simulation results of an embodiment of the present invention;

[0045] Figure 6 It is a three-dimensional process model of the composite material structure and a deformation result diagram of the composite material structure according to an embodiment of the present invention.

[0046] Figure 7 This is the tooling design effect of the embodiment of the present invention. DETAILED DESCRIPTION

[0047] The features and illustrative embodiments of various aspects of the present invention will be described in detail below. In the detailed description below, many specific details are proposed to provide a comprehensive understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without the need for some of these specific details. The following description of the embodiments is only to provide a better understanding of the present invention by illustrating examples of the present invention. The present invention is by no means limited to any specific settings and methods proposed below, but covers any improvements, replacements and modifications of structures, methods, devices without departing from the spirit of the present invention. In the accompanying drawings and the following description, known structures and technologies are not shown to avoid unnecessary ambiguity in the present invention.

[0048] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other, and the embodiments can refer to and quote each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0049] One embodiment of the present invention is to provide a method for designing sandwich composite material structure forming equipment based on forming process simulation, comprising the following steps:

[0050] Step 1: Initial design of tooling, including the initial design of tooling templates and tooling jigs; the initial design of tooling specifically includes:

[0051] 1.1 Based on the original model of the composite material structure, the tooling template is preliminarily preset, and steel material is used as the initial template material;

[0052] 1.2 Analyze the original model of the composite material structure, determine the windward side of the composite material structure during molding according to the curvature of the original model, that is, the placement direction in the autoclave, combine the placement direction with the original model, take the vertical wind direction of the composite material structure boundary as the length direction of the jig, and take the downwind direction as the width direction of the jig, or take the downwind direction of the composite material structure boundary as the length direction of the jig, and take the vertical wind direction as the width direction of the jig. The specific length and width directions are determined according to the size of the composite material structure; preliminarily preset the length and width boundaries of the tooling jig according to the boundaries of the original model.

[0053] 1.3 No openings are set on the template surface, including thermocouple holes;

[0054] 1.4 According to the length and width of the frame, the templates that make up the frame are initially designed to be distributed at a spacing of 300mm;

[0055] 1.5 The air circulation holes on the template are designed according to the following parameters: the initial radius of the upper semicircular hole is 40mm, the spacing is 50mm, and the square ventilation holes are evenly distributed in the template, with a minimum distance of 100mm from the edge of the template and a minimum distance of 70mm between holes.

[0056] Step 2: Simulate the molding process of the composite material structure under the initial tooling and molding parameter conditions in the autoclave equipment, solve the temperature distribution in the autoclave and the deformation of the composite material structure, and analyze whether the composite material structure meets the acceptance criteria;

[0057] The following steps are involved:

[0058] Step 2.1 Establish a temperature field analysis model of the autoclave, molding tooling and composite material structure, establish a CAE mesh model based on the CAD model, and set up sharing of mesh nodes for the contact surfaces between the air in the autoclave, the composite material structure and the molding tooling;

[0059] Step 2.2: Set the temperature and pressure boundary conditions according to the molding parameters of the composite autoclave, perform temperature-airflow coupling simulation of the molding process of the autoclave, molding tooling and composite structure, and solve the temperature distribution of the molding tooling and composite structure. If the temperature difference of the composite structure is controlled within 5°C during the process, design the air circulation holes on the plate with the parameters in 1.5. If the temperature difference exceeds 5°C, execute step 2.3.

[0060] Step 2.3: Based on the temperature distribution of the composite material structure in step 2.2, the size of the air circulation hole corresponding to the template with poor air circulation is increased, and the process returns to step 2.1 until the temperature difference of the composite material structure is controlled within 5°C;

[0061] Step 2.4 establishes a composite material structure curing deformation analysis model, and uses the obtained temperature distribution and preset pressure as boundary conditions to solve the deformation result of the composite material structure after forming; if the deformation result meets the acceptance criteria, the original model data of the composite material structure in 1.1 is used as the basis for the design of the tooling template; if the deformation result exceeds the acceptance criteria, execute step 2.5;

[0062] Step 2.5 solves the composite material structure forming process model according to the composite material structure deformation result. Specifically, the composite material structure deformation result is a point cloud numerical model containing multiple grid nodes. When solving the composite material structure forming process model, the displacement of each grid node is negative and multiplied by the compensation coefficient and added to the original composite material structure three-dimensional data node. The compensation coefficient is initially set to 1.5, and the composite material structure three-dimensional process model is formed through CAD software.

[0063] Step 2.6: Use the composite material structure forming process model obtained in step 2.5 as the design basis for the forming tool template, redesign the tool template, and then establish the temperature field analysis model of the autoclave, forming tool and composite material structure. Then, set the temperature and pressure boundary conditions according to the composite material autoclave forming parameters, perform the temperature-airflow coupling simulation of the forming process of the autoclave, forming tool and composite material structure, solve the temperature distribution of the forming tool and composite material structure, and then return to step 2.4 until the composite material structure forming effect meets the acceptance criteria;

[0064] Step 2.7 Comprehensively analyze the strength of the tooling template and the tooling jig. After the composite material structure forming process, the structural strength of the tooling template and the tooling jig should meet the maximum Mises stress within the allowable stress range of the material. If it does not meet the requirements, adjust the tooling template and the jig design plan; adjust the tooling template and the jig design plan, including: ① Replace the tooling template material with aluminum material; ② Change the size of the vent holes of the jig; ③ Increase the number of templates in the supporting jig, and repeat the above simulation analysis until the composite material structure deformation and the tooling strength meet the requirements.

[0065] Step 3: Determine the tooling design plan; the tooling design plan includes:

[0066] 3.1 The tooling template material should be selected in combination with the structural strength of the molding tooling and the deformation results of the composite material structure;

[0067] 3.2 The tooling template should meet the requirements of the acceptance standards for composite material structures. The tooling template design should be based on the original data of the composite material structure, or on the molding process model obtained by simulation iteration;

[0068] 3.3 The thermocouple holes on the tooling template should be arranged at the corresponding positions of the template according to the coordinates of the characteristic points on the die surface of the composite material structure in the simulated autoclave and the thermocouple holes; the characteristic points include: temperature leading point, temperature lagging point and temperature intermediate point;

[0069] 3.4 The material of the tooling frame should be steel;

[0070] 3.5 The forklift pipe position should be set on the windward side of the tooling frame placed in the autoclave;

[0071] 3.6 The design of the air circulation holes on the jig should be determined based on the uniformity of the temperature distribution of the composite material structure during the autoclave molding process.

[0072] The second embodiment of the present invention is to provide a method for designing sandwich composite material structure forming equipment based on forming process simulation, taking the design of a certain fairing forming tooling as an example, comprising the following steps:

[0073] Step 1: Initial design of tooling, including the initial design of tooling templates and tooling jigs:

[0074] 1.1 Based on the original model of the center-reduced fairing, the tooling template surface is preliminarily preset, and steel material is used as the initial template material;

[0075] 1.2 Analyze the original model of the mid-range fairing, determine the windward side of the composite material structure during molding according to the curvature of the original model, that is, the placement direction in the autoclave, combine the placement direction with the original model, take the vertical wind direction of the composite material structure boundary as the length direction of the jig, and take the downwind direction as the width direction of the jig;

[0076] 1.3 No openings are set on the template surface, including thermocouple holes;

[0077] 1.4 According to the length and width of the frame, the templates that make up the frame are initially designed to be distributed at a spacing of 300mm;

[0078] 1.5 The air circulation holes on the plate are designed according to the following parameters: the radius of the semicircular holes at the upper end is initially set to be 40mm, the spacing is 50mm, and the square ventilation holes are evenly distributed in the plate, with a minimum distance of 100mm from the upper edge of the plate and a minimum distance of 70mm between holes. Figure 1 .

[0079] Step 2: Simulate the molding process of the composite material structure under the initial tooling and molding parameter conditions in the autoclave equipment, solve the temperature distribution in the autoclave and the deformation of the composite material structure, and analyze whether the composite material structure meets the acceptance criteria, which specifically includes the following steps:

[0080] Step 2.1, establish the temperature field analysis model of the autoclave, molding tooling and composite material structure, establish the CAE mesh model based on the CAD model, and set the shared mesh nodes of the contact surfaces between the air in the autoclave, the composite material structure and the molding tooling.

[0081] Generate surface grid units based on the autoclave tank size, molding tool template surface, composite material structure die surface and honeycomb surface; form the molding tool body domain, composite material structure solid domain and fluid domain based on the relationship between the molding tool template surface, honeycomb surface molding and tooling frame template surface, and establish three-dimensional space grid units in each calculation domain. The grid model is as follows: Figure 2 .

[0082] Step 2.2 Set the temperature and pressure boundary conditions according to the composite autoclave molding parameters, perform temperature-airflow coupling simulation on the autoclave, molding tooling and composite structure during the molding process, and solve the temperature distribution of the molding tooling and composite structure. Take the temperature distribution at 50 minutes as an example. Figure 3 . Analyze the entire process, the temperature difference of the composite material structure is controlled to exceed 5℃, and execute step 2.3

[0083] Step 2.3: Based on the temperature distribution of the composite material structure in 2.2, increase the size of the air circulation holes at the corresponding air circulation holes of the template with poor air circulation, and return to step 2.1 until the temperature difference of the composite material structure is controlled within 5°C.

[0084] Step 2.4 establishes a deformation analysis model for the curing of the mid-range fairing, and uses the obtained temperature distribution and the preset pressure as boundary conditions to solve the deformation results of the composite material structure after molding. The maximum deformation result is about 8.24mm, which does not meet the requirements. Go to step 2.5.

[0085] Step 2.5 solves the composite material structure forming process model based on the composite material structure deformation result. The composite material structure deformation result is a point cloud numerical model containing multiple grid nodes. When solving the composite material structure forming process model, the displacement of each grid node is negative and multiplied by the compensation coefficient and added to the original composite material structure three-dimensional data node. The compensation coefficient is initially set to 1.5, and the composite material structure three-dimensional process model is formed through CAD software.

[0086] Step 2.6 uses the composite material structure forming process model obtained in step 2.5 as the design basis for the forming tooling template, redesigns the tooling template, and then establishes the temperature field analysis model of the autoclave, forming tooling and composite material structure. Then, according to the composite material autoclave forming parameters, the temperature and pressure boundary conditions are set, and the temperature-airflow coupling simulation of the forming process of the autoclave, forming tooling and composite material structure is performed to solve the temperature distribution of the forming tooling and composite material structure, and then returns to step 2.4 until the composite material structure forming effect meets the acceptance criteria.

[0087] Step 2.7 Comprehensively analyze the strength of the tooling template and tooling jig. After the composite material structure forming process, the structural strength of the tooling template and tooling jig should meet the maximum Mises stress within the allowable stress range of the material.

[0088] Step 3. Determine the tooling design plan, including the following:

[0089] 3.1 The material of tooling template is steel;

[0090] 3.2 The tooling template profile is based on the process profile obtained by simulation;

[0091] 3.3 The thermocouple holes on the tooling template are arranged at the corresponding positions of the template according to the coordinates of the characteristic points such as the leading point, the lagging point and the intermediate point on the die surface temperature of the composite material structure in the simulated autoclave;

[0092] 3.4 The material of the tooling frame is steel;

[0093] 3.5 The forklift pipe position should be set on the windward side of the tooling frame placed in the autoclave;

[0094] 3.6 Set the ventilation holes on the tooling frame according to step 2.3.

[0095] Specific tooling effects such as Figure 7 .

[0096] The present invention can effectively present the special process of hot-pressing molding of aircraft thermosetting resin-based honeycomb sandwich composite material structure in the form of intuitive images and numerical values ​​through numerical simulation technology, and can display the influence of molding tool design on product design in the form of intuitive values ​​and cloud maps. At the beginning of tool design, the influence of different tool materials, tool templates, and tool plate frame vent sizes on the temperature distribution and final deformation of the composite material structure during the autoclave molding process can be effectively simulated, and the deformation results can be converted into tool template profiles through digital deformation compensation methods. The present invention can effectively reduce the dependence of the design of the tooling for the molding of the honeycomb sandwich composite material structure on the experience of designers, provide reliable predictability and controllability for tool design, reduce the repetitive engineering tests and tooling modeling of the honeycomb sandwich composite material structure of the new aircraft base, reduce product development costs, and increase the development rate of new materials, new structures, and new aircraft, providing technical guarantees for the independent control of composite material structures of my country's aircraft equipment.

[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the field can easily think of various equivalent modifications or substitutions within the technical scope disclosed by the present invention, and these modifications or substitutions should all be covered within the protection scope of the present invention.

Claims

1. A sandwich composite material structure forming equipment design method based on forming process simulation, characterized in that: The following steps are involved: Step 1: Initial design of tooling, including the initial design of tooling template and tooling jig; Step 2: Simulate the molding process of the composite material structure under the initial tooling and molding parameter conditions in the autoclave equipment, solve the temperature distribution in the autoclave and the deformation of the composite material structure, and analyze whether the composite material structure meets the acceptance criteria; Step 3: Determine the tooling design plan.

2. The method for designing sandwich composite material structure forming equipment based on forming process simulation according to claim 1, characterized in that: Step 1: Preliminary design of tooling includes: 1.1 Based on the original model of the composite material structure, the tooling template is preliminarily preset, and steel material is used as the initial template material; 1.2 Analyze the original model of the composite material structure and determine the windward surface of the composite material structure during molding based on the curvature of the original model; 1.3 No openings are set on the template surface, including thermocouple holes; 1.4 According to the length and width of the frame, the templates that make up the frame are initially designed to be distributed at a spacing of 300mm; 1.5 The air circulation holes on the template are designed according to the following parameters: the initial radius of the upper semicircular hole is 40mm, the spacing is 50mm, and the square ventilation holes are evenly distributed in the template, with a minimum distance of 100mm from the edge of the template and a minimum distance of 70mm between holes.

3. The method for designing sandwich composite material structure forming equipment based on forming process simulation according to claim 2, characterized in that: 1.2 Determine the windward side, that is, the placement direction in the autoclave, combine the placement direction with the original model, take the vertical wind direction of the composite material structure boundary as the length direction of the jig, and take the downwind direction as the width direction of the jig, or take the downwind direction of the composite material structure boundary as the length direction of the jig, and take the vertical wind direction as the width direction of the jig. The specific length and width directions are determined according to the size of the composite material structure; preliminarily preset the length and width boundaries of the tooling jig according to the boundaries of the original model.

4. The method for designing sandwich composite material structure forming equipment based on forming process simulation according to claim 3, characterized in that: Step 2 includes the following steps: Step 2.1 Establish a temperature field analysis model of the autoclave, molding tooling and composite material structure, establish a CAE mesh model based on the CAD model, and set up sharing of mesh nodes for the contact surfaces between the air in the autoclave, the composite material structure and the molding tooling; Step 2.2: Set the temperature and pressure boundary conditions according to the molding parameters of the composite autoclave, perform temperature-airflow coupling simulation of the molding process of the autoclave, molding tooling and composite structure, and solve the temperature distribution of the molding tooling and composite structure. If the temperature difference of the composite structure is controlled within 5°C during the process, design the air circulation holes on the plate with the parameters in 1.

5. If the temperature difference exceeds 5°C, execute step 2.

3. Step 2.3: Based on the temperature distribution of the composite material structure in step 2.2, the size of the air circulation hole corresponding to the template with poor air circulation is increased, and the process returns to step 2.1 until the temperature difference of the composite material structure is controlled within 5°C; Step 2.4 establishes a composite material structure curing deformation analysis model, and uses the obtained temperature distribution and preset pressure as boundary conditions to solve the deformation result of the composite material structure after forming; if the deformation result meets the acceptance criteria, the original model data of the composite material structure in 1.1 is used as the basis for the design of the tooling template; if the deformation result exceeds the acceptance criteria, execute step 2.5; Step 2.5: Solve the composite material structure forming process model based on the composite material structure deformation results: Step 2.6: Use the composite material structure forming process model obtained in step 2.5 as the design basis for the forming tool template, redesign the tool template, and then establish the temperature field analysis model of the autoclave, forming tool and composite material structure. Then, set the temperature and pressure boundary conditions according to the composite material autoclave forming parameters, perform the temperature-airflow coupling simulation of the autoclave, forming tool and composite material structure during the forming process, solve the temperature distribution of the forming tool and composite material structure, and then return to step 2.4 until the composite material structure forming effect meets the acceptance criteria; Step 2.7 Comprehensively analyze the strength of the tooling template and tooling frame. After the composite material structure forming process, the structural strength of the tooling template and tooling frame should meet the maximum Mises stress within the allowable stress range of the material. If it does not meet the requirements, adjust the tooling template and tooling design plan.

5. The method for designing sandwich composite material structure forming equipment based on forming process simulation according to claim 4, characterized in that: Step 2.5 is specifically as follows: the deformation result of the composite material structure is a point cloud numerical model containing multiple grid nodes. When solving the composite material structure forming process model, the displacement of each grid node is negative and multiplied by the compensation coefficient and added to the original composite material structure three-dimensional data node. The compensation coefficient is initially set to 1.5, and the composite material structure three-dimensional process model is formed through CAD software.

6. The method for designing sandwich composite material structure forming equipment based on forming process simulation according to claim 5, characterized in that: In step 2.7, the tooling template and tooling design are adjusted, including: ① replacing the tooling template material with aluminum material; ② changing the size of the vent holes of the tooling frame; ③ increasing the number of templates in the supporting frame, and repeating the above simulation analysis until the deformation of the composite material structure and the tooling strength meet the requirements.

7. The method for designing sandwich composite material structure forming equipment based on forming process simulation according to claim 6, characterized in that: Step 3: Tooling design includes: 3.1 The tooling template material should be selected in combination with the structural strength of the molding tooling and the deformation results of the composite material structure; 3.2 The tooling template should meet the requirements of the acceptance standards for composite material structures. The tooling template design should be based on the original data of the composite material structure, or on the molding process model obtained by simulation iteration; 3.3 The thermocouple holes on the tooling template should be arranged at the corresponding positions of the template according to the coordinates of the characteristic points on the die surface of the composite material structure in the simulated autoclave and the thermocouple holes; 3.4 The material of the tooling frame should be steel; 3.5 The forklift pipe position should be set on the windward side of the tooling frame placed in the autoclave; 3.6 The design of the air circulation holes on the jig should be determined based on the uniformity of the temperature distribution of the composite material structure during the autoclave molding process.

8. The method for designing sandwich composite material structure forming equipment based on forming process simulation according to claim 7, characterized in that: The characteristic points in 3.3 include: temperature leading point, temperature lagging point and temperature intermediate point.

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