A method of forming a large aspect ratio composite structure with controlled distortion

Abstract

The application discloses a forming method for controlling deformation of a large-length-thickness-ratio composite structure, and belongs to the technical field of forming of composite structures. The application firstly determines a verification test object for process simulation of thermal autoclave forming-curing deformation coupling of multiple physical fields, so as to reduce the cycle and cost of the verification test; for the verification test object, the reliability of the process simulation result is determined by using the verification test result, the simulation material parameters are determined, the curing deformation of the composite structure is estimated, the applicable bonding forming process is determined, and finally the composite structure meeting the design requirements is formed. For the components with uneven thickness, the application adopts a tooling forming of a multi-zone independent temperature control structure, so that the curing deformation of the components can be effectively controlled. Compared with the traditional forming method, the application not only can effectively solve the problem of curing deformation of the large-length-thickness-ratio composite structure exceeding the range, but also greatly reduces the trial production cost and shortens the trial production cycle.

Description

Technical Field

[0001] This invention belongs to the field of composite material structural component molding technology, and specifically relates to a molding method for controlling the deformation of composite material structural components with large length-to-thickness ratio. Background Technology

[0002] High aspect ratio fiber-reinforced thermosetting resin matrix composite structural components are composite material parts whose length is much greater than their thickness (typically ≥10, and even exceeding 100), and are widely used in aerospace, automotive, and shipbuilding industries. Traditional processes for preparing high aspect ratio fiber-reinforced thermosetting resin matrix composite structural components include autoclave molding, compression molding, hand lay-up molding, and filament winding. However, due to significant deformation during curing caused by factors such as resin shrinkage, temperature gradients, mold deformation, and fiber-matrix interface stress, it is often necessary to control this deformation when using traditional methods to prepare high aspect ratio fiber-reinforced thermosetting resin matrix composite structural components.

[0003] Traditional methods for controlling deformation of fiber-reinforced thermosetting resin matrix composite structural components rely on empirical mold design or static process parameter adjustments. These methods struggle to address the multi-physics coupling effects of complex structures, making it difficult to achieve comprehensive deformation control for large-sized components. Furthermore, they result in long product prototyping cycles and high prototyping costs. Therefore, a highly efficient and low-cost integrated solution is urgently needed. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a molding method for controlling the deformation of composite material structural parts with large length-to-thickness ratio, so as to reduce the deformation of composite material structural parts with large length-to-thickness ratio, improve the molding quality, shorten the product trial production cycle, and reduce the trial production cost.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: First, the verification test object is determined. Under the same process conditions, simulation analysis and verification tests of autoclave molding-curing deformation process with integrated thermal-structure-fluid coupling algorithm are carried out. The reliability of the simulation results is determined by using the test results, and the simulation material parameters are determined accordingly. A suitable composite material product is selected, and the process parameters and tooling structure are optimized by using autoclave molding-curing deformation process simulation analysis technology and surface compensation technology. Finally, the curing deformation of the composite material structural component is predicted. The applicable adhesive bonding molding process is determined based on the criterion that the predicted curing deformation of the composite material structural component does not exceed the product deformation requirements. Based on the determined adhesive bonding molding process, the composite material structural component is molded, thereby achieving the purpose of the present invention.

[0006] This invention relates to a molding method for controlling the deformation of composite material structural parts with large length-to-thickness ratios, characterized by the following steps:

[0007] (1) Selection of adhesive bonding molding process

[0008] A combination of autoclave molding-curing deformation process simulation and experimental verification technology was adopted, and the adhesive bonding molding process for composite material structural components was selected. The autoclave molding-curing deformation process simulation is a multiphysics coupling simulation technology that integrates thermal-structural-fluid algorithms.

[0009] 1) Determine the test subjects for verification

[0010] Based on the length of composite material structural components, the original or scaled-down components are used as the verification test objects.

[0011] 2) Reliability assessment of simulation results

[0012] For the verification test object, under the same process conditions, simulation analysis and verification tests of the autoclave molding-curing deformation process were carried out respectively. The reliability of the simulation results was determined by the test results. When determining the reliability of the simulation results, a relative simulation error of no more than 15% was used as the criterion. The relative simulation error was determined according to the following formula:

[0013]

[0014] In the formula, It is the simulation relative error. These are the values ​​from the curing deformation experiment. These are the simulation values ​​of solidification deformation;

[0015] 3) Determination of simulation material parameters

[0016] When the simulation results are deemed reliable, the simulation material parameters are the same as those input when conducting the simulation analysis of the autoclave molding-curing deformation process; when the results are deemed unreliable, the simulation material parameters are corrected based on the verification test results and using the autoclave molding-curing deformation process simulation technology.

[0017] 4) Predict the curing deformation of composite material structural components

[0018] Based on the simulation results, the curing deformation of the composite material structural parts is initially estimated. When the initial estimated curing deformation of the composite material structural parts exceeds the product design requirements, based on the determined material parameters, the process parameters and tooling structure are optimized with the goal of controlling the curing deformation of the composite material products by using autoclave molding-curing deformation process simulation technology. The curing deformation of the composite material structural parts is then estimated.

[0019] The optimization of the tooling structure adopts the surface compensation technology: based on the tooling and composite material product model, with the help of autoclave molding-curing deformation process simulation technology, the deformation of the composite material product after curing is estimated, the tooling structure is redesigned, the deformation deviation of the composite material product is compensated in reverse, and the molding process simulation is carried out again; the above operation is repeated until the curing deformation of the composite material product reaches the minimum.

[0020] 5) Determine the applicable adhesive bonding process

[0021] The applicable adhesive bonding process is determined based on the criterion that the estimated curing deformation of the composite material structural component does not exceed the product deformation requirements.

[0022] (2) Molded composite material structural parts

[0023] Based on the selected adhesive bonding process, optimized process parameters, and tooling structure, composite material structural components are formed.

[0024] Preferably, when determining the verification test object in step (1) 1), if the length of the composite material structural part is not greater than 1 meter, the original part is used as the verification test object; otherwise, a scaled-down part is used as the verification test object.

[0025] Preferably, the autoclave molding-curing deformation process simulation includes heat transfer simulation analysis, curing kinetics simulation analysis, and structural deformation simulation analysis; the heat transfer simulation analysis is used to simulate the dynamic interaction between the heat release during resin curing and the temperature field of the solid component and tooling, the curing kinetics simulation analysis is used to calculate the change in the degree of resin crosslinking over time, and the structural deformation simulation analysis is used to predict the shrinkage of the simulated object and the deformation caused by residual stress.

[0026] Preferably, in step (1) 4), the composite material product includes a composite structural component, a scaled-down component, and components made of fiber-reinforced thermosetting resin-based composite material.

[0027] More preferably, when the component made of fiber-reinforced thermosetting resin matrix composite material has uneven thickness, the molding tooling adopts a multi-zone independent temperature control structure, which can perform segmented temperature control for different thickness areas.

[0028] More preferably, the temperature segmented control includes segmented control of the heating rate and the holding time.

[0029] More preferably, the composite material product is a scaled-down version of a composite material structural component. When estimating the curing deformation of the composite material structural component, the curing deformation of the scaled-down component is first estimated based on the optimized process parameters and tooling structure. Then, the deformation amount of the composite material structural component is estimated according to the following formula:

[0030]

[0031] in It is the deformation of composite material structural components. K is the deformation amount of the scaled-down part, and K is the scaling ratio.

[0032] Preferably, in step (1) 5), when both co-bonding and secondary bonding molding processes meet the judgment criteria, co-bonding molding process is preferred.

[0033] Preferably, when it is determined that the secondary adhesive bonding molding process is applicable to the adhesive bonding molding process of composite material structural parts, before molding the components of the composite material structural parts in step 2), the molding process parameters or tooling structure of each component are further optimized by using the secondary adhesive autoclave molding-curing deformation process simulation technology.

[0034] This invention relates to a molding method for controlling the deformation of composite material structural parts with large length-to-thickness ratios. First, based on the length of the composite material structural part, a simulation verification test object for the multi-physics field coupled autoclave molding-curing deformation process is determined, using either the original or a scaled-down version, to reduce the cycle and cost of the verification test. For the verification test object, the reliability of the autoclave molding-curing deformation process simulation results is determined using the verification test results, and the simulation material parameters are corrected and determined accordingly. This lays the foundation for optimizing the molding process parameters and tooling structure of the original composite material structural part, the scaled-down version, and components made of fiber-reinforced thermosetting resin-based composite materials using autoclave molding-curing deformation process simulation analysis technology. Finally, the curing deformation of the composite material structural part is predicted. Based on the predicted curing deformation of the composite material structural part, an applicable adhesive bonding molding process is determined. Finally, based on the determined adhesive bonding molding process, optimized process parameters, and tooling structure, the composite material structural part is molded. For composite structural components made of fiber-reinforced thermosetting resin matrix composites with uneven thickness, this invention employs a multi-zone independent temperature control fixture for molding. This allows for segmented temperature control of different thickness areas, using varying heating rates and holding times to avoid thermal stress concentration. This enables simultaneous segmented curing of the components, effectively controlling curing deformation. By innovatively integrating multiphysics simulation and segmented curing technology, this invention provides a scientific and intelligent solution for high-precision manufacturing of aspect ratio composite structural components, significantly improving process reliability and production efficiency. Compared to traditional molding methods, using this invention to mold large aspect ratio composite structural components not only effectively solves the problem of excessive curing deformation but also reduces trial production costs by more than 50% and shortens the molding cycle by more than 120%. Detailed Implementation

[0035] To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the following examples provide a more detailed description of the invention. It should be noted that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention.

[0036] Example 1

[0037] The composite material structural component in this embodiment is a C-shaped structure, 3000mm long, 500mm high, and 200mm wide at the bottom opening. It consists of a main beam, a front cover, a rear cover, a honeycomb core, and a C-shaped skin.

[0038] The main beam is made of steel and is 10mm thick.

[0039] The front cover, rear cover, and C-shaped skin are made of glass fiber reinforced epoxy resin-based composite material. The front cover and rear cover are 5mm thick, and the C-shaped skin is divided into three sections along its length: the front and rear sections are 900mm long and 5mm thick, and the middle section is 1200mm long and 8mm thick.

[0040] In this embodiment, the composite material structural component has a front cover and a rear cover located at both ends of a C-shaped skin, with the main beam and honeycomb core located inside the C-shaped skin. The honeycomb core fills the space between the C-shaped skin and the main beam. The design requirements for the composite material structural component are: maximum deformation in the length direction not exceeding 8mm and maximum deformation in the height direction not exceeding 1mm.

[0041] When molding the composite material structural component of this embodiment, the following steps are included:

[0042] (1) Selection of adhesive bonding molding process

[0043] Composite material bonding processes include co-bonding and secondary bonding processes.

[0044] To reduce costs and shorten time, a scaled-down version of the composite material structural component was used as the verification test object when selecting the molding process. The scaling ratio between the scaled-down component and the original component was 1:5.

[0045] 1) Co-bonding process molding

[0046] Based on the structural dimensions of the composite material structural components and scaled-down tooling parts, a three-dimensional finite element model was constructed to conduct simulation analysis of the autoclave molding-curing deformation process. Autoclave molding-curing deformation process simulation is a multiphysics coupled simulation technology integrating heat, structure, and fluid algorithms, including heat transfer simulation analysis, curing kinetics simulation analysis, and structural deformation simulation analysis. Heat transfer simulation analysis is used to simulate the dynamic interaction between the heat release during resin curing and the temperature fields of the honeycomb core, main beam, and tooling. Curing kinetics simulation analysis is used to calculate the change in resin crosslinking degree over time. Structural deformation simulation analysis is used to predict the shrinkage of the scaled-down parts and the deformation caused by residual stress. The multiphysics coupled simulation results for the deformation of the scaled-down parts are: a maximum deformation of 2.05 mm along the length direction and a maximum deformation of 0.25 mm along the height direction.

[0047] Experimental verification of the autoclave molding process of scaled-down parts: Under the same process conditions, the prepregs of the C-shaped skin, front cover and rear cover of the scaled-down parts were combined with the main beam and honeycomb core on the tooling and placed in the autoclave for curing.

[0048] Taking the maximum deformation in the length and height directions of the scaled-down part as the object, the simulation relative error is determined according to equation (1):

[0049] (1)

[0050] In the formula, It is the simulation relative error. These are the values ​​from the curing deformation experiment. These are the simulation values ​​of solidification deformation.

[0051] When the relative error of the simulation is no more than 15%, the simulation results are considered reliable.

[0052] In this embodiment, the simulation relative error in the length direction of the scaled part formed by the autoclave / co-bonding process is about 9.83%, and the relative error in the height direction is about 8.61%, indicating that the simulation results are reliable.

[0053] The deformation of the composite material structure can be estimated according to equation (2):

[0054] (2)

[0055] in, It is the deformation of the composite material structural component. K is the deformation amount of the scaled-down part, and K is the scaling ratio.

[0056] Based on the autoclave / co-bonding molding process, the estimated maximum deformation in the length direction of the composite structural component is 10.25 mm, exceeding the curing deformation requirement in the length direction by 28.1%; the estimated maximum deformation in the height direction is 1.25 mm, exceeding the curing deformation requirement in the height direction by 25%. This does not meet the design requirements for the composite structural component.

[0057] Using autoclave molding-curing deformation process simulation technology, this study aims to control the deformation of scaled-down parts. It involves optimizing process parameters, optimizing tooling structure, and predicting curing deformation. For tooling structure optimization, surface compensation technology is employed: a three-dimensional finite element model of the tooling and scaled-down parts is constructed. The deformation of the scaled-down parts after curing is predicted using autoclave molding-curing deformation simulation technology. Based on the deformation after curing, the tooling structure is redesigned to compensate for the deformation deviation of the scaled-down parts, and the molding process simulation is repeated. This process is repeated multiple times—predicting curing deformation, redesigning tooling geometry, and repeating simulation—until the maximum deformation of the scaled-down parts is minimized. Finally, based on the optimized molding process parameters and tooling structure, the curing deformation of the scaled-down parts is: a maximum deformation of 1.86 mm in the length direction and a maximum deformation of 0.21 mm in the height direction.

[0058] According to formula (2), the estimated maximum deformation in the length direction of the composite material structural component is 9.3 mm, which exceeds the curing deformation requirement of 16.3% in the length direction; the estimated maximum deformation in the height direction is 1.05 mm, which exceeds the curing deformation requirement of 5% in the height direction. Therefore, the design requirements for the composite material structural component are still not met.

[0059] 2) Secondary adhesive bonding molding process

[0060] Based on the structural dimensions of the front cover, rear cover, and tooling of the scaled-down part, a three-dimensional finite element model was constructed, and simulation analysis of the autoclave forming-curing deformation process was carried out. The multiphysics coupling simulation results of the deformation of the front cover and rear cover of the scaled-down part are as follows: along the length and height directions of the scaled-down part, the maximum deformation of the front cover is 0.15 mm and 0.22 mm, respectively, and the maximum deformation of the rear cover is 0.12 mm and 0.21 mm, respectively.

[0061] Experimental verification of the autoclave molding-curing deformation process of the front and rear covers of scaled-down parts: Under the same process conditions, the front and rear covers of scaled-down parts were molded using the autoclave molding process.

[0062] Taking the maximum deformation of the front and rear covers of the scaled-up part along the length and height directions as the object, the simulation relative error along the length direction of the scaled-up part is determined according to formula (1). The simulation relative error of the front cover is about 10.78%, and that of the rear cover is about 8.82%. Along the height direction of the scaled-up part, the simulation relative error of the front cover is about 6.72%, and that of the rear cover is about 5.35%. The simulation results are reliable.

[0063] Based on the C-shaped skin and tooling structure dimensions of the scaled-down part, a three-dimensional finite element model was constructed. Based on the optimized molding process parameters of the co-bonding molding process, a simulation analysis of the autoclave molding-curing deformation process was conducted. The multiphysics coupling simulation results for the C-shaped skin of the scaled-down part are as follows: along the length and height directions of the scaled-down part, the maximum deformation of the C-shaped skin is 1.52 mm and 0.23 mm, respectively.

[0064] Experimental verification of the simulation analysis of the autoclave molding-curing deformation process of the C-shaped skin of the scaled-down part: Under the same process conditions, the C-shaped skin of the scaled-down part was formed using the autoclave molding process.

[0065] Taking the maximum deformation of the C-shaped skin of the scaled part along the length and height directions as the object, the simulation relative error of the C-shaped skin of the scaled part along the length direction is approximately 16.21%, and the simulation relative error along the height direction is 10.85%, according to Equation (1). The simulation results are unreliable.

[0066] For the autoclave molding process of the C-shaped skin of the scaled-down part, the simulation material parameters of the autoclave molding-curing deformation process were corrected. Based on the simulation relative error of the C-shaped skin of the scaled-down part, the simulation input parameters of the autoclave molding-curing deformation process were fine-tuned, and the simulation analysis was carried out again; this operation was repeated until the simulation relative error of the C-shaped skin of the scaled-down part was no more than 15%. In this embodiment, after adjusting the elastic modulus of the glass fiber along the fiber direction to 80 GPa, the simulation relative error of the C-shaped skin of the scaled-down part in the length direction was about 12.5%, and the simulation relative error in the height direction was 9.3%, indicating that the simulation results are reliable.

[0067] According to formula (2), the estimated curing deformation of the composite material structural component is as follows: the maximum deformation in the length direction of the composite material structural component is the estimated value of the sum of the length directions of the front cover, rear cover, and C-shaped skin, which is approximately 8.95 mm, exceeding the curing deformation requirement of the composite material structural component product in the length direction by 11.9%; the maximum deformation in the height direction is the maximum estimated value of the height direction of the front cover, rear cover, or C-shaped skin, which is approximately 1.15 mm, exceeding the curing deformation requirement of the composite material structural component product in the height direction by 15%. Therefore, the design requirements of the composite material structural component product are not met.

[0068] Using autoclave molding-curing deformation process simulation technology, we conducted optimization analysis of the autoclave molding process parameters for the front cover and the rear cover. Finally, based on the optimized molding process parameters, the maximum deformation of the front cover along the length and height directions of the scaled part was 0.11 mm and 0.19 mm, respectively, and the maximum deformation of the rear cover was 0.08 mm and 0.18 mm, respectively.

[0069] Based on the corrected material parameters, this study utilizes autoclave molding-curing deformation process simulation technology to control the curing deformation of the scaled-down C-shaped skin. The analysis includes optimization of molding process parameters, tooling structure, and prediction of curing deformation. The tooling structure optimization simulation analysis is based on the optimized molding process parameters. Ultimately, based on the optimized molding process parameters and tooling structure, the predicted minimum curing deformation of the scaled-down C-shaped skin is as follows: the maximum deformation along the length and height of the scaled-down part is 1.30 mm and 0.19 mm, respectively.

[0070] According to formula (2), the curing deformation of the composite material structural component is estimated as follows: the maximum deformation in the length direction of the composite material structural component is the estimated value of the sum of the length directions of the front cover, the rear cover and the C-shaped skin, which is about 7.45 mm, meeting the product design requirements; the maximum deformation in the height direction is the maximum estimated value in the height direction of the front cover, the rear cover or the C-shaped skin, which is about 0.95 mm, meeting the product design requirements.

[0071] Therefore, the composite material structural component in this embodiment is formed using a two-stage adhesive bonding molding process.

[0072] (2) Fabrication of composite material structural parts using autoclave / secondary bonding molding process

[0073] 1) Preparation of front and back covers

[0074] Based on the optimized molding process parameters of the scaled-down front and rear covers, the molding process parameters and tooling structure of the front and rear covers are further optimized using autoclave molding-curing deformation process simulation technology and surface compensation technology.

[0075] Based on the final optimized molding process parameters and tooling structure, the front and rear covers were fabricated using an autoclave molding process. The maximum deformations of the fabricated front and rear covers were: 0.46 mm and 0.41 mm along the length of the composite material structure, respectively; and 0.83 mm and 0.71 mm along the height of the composite material structure, respectively.

[0076] 2) Preparation of C-type skin

[0077] Based on the optimized molding process parameters and tooling structure of the scaled-down C-shaped skin, further optimization of the molding process parameters and tooling structure was achieved using autoclave molding-curing deformation process simulation technology and surface compensation technology. The tooling adopts a multi-zone independent temperature control structure, including three independent heating / cooling modules, 800mm long at both ends and 1200mm long in the middle, with temperature regulated by a PID controller. These three independent heating / cooling modules are used for heating and cooling the front, middle, and rear sections of the C-shaped skin, respectively. This segmented temperature control of different thickness areas of the C-shaped skin avoids thermal stress concentration. During the resin curing exothermic peak, the independent heating / cooling modules control different heating rates and holding times for the thinner areas at both ends and the thicker area in the middle, suppressing shrinkage stress caused by excessively rapid resin curing in the thinner areas at both ends. This achieves synchronous segmented curing of the C-shaped skin, effectively controlling its curing deformation.

[0078] The C-type skin prepreg is laid on the optimized tooling and placed in an autoclave to produce the C-type skin based on the optimized process parameters.

[0079] The maximum deformation of the final C-shaped skin is 6.1 mm along the length of the composite material structure and 0.85 mm along the height of the composite material structure.

[0080] 3) Molded composite material structural components

[0081] The main beam was fabricated according to the requirements of the original composite structural components.

[0082] Based on optimized molding process parameters and tooling structure, the front cover, rear cover, and C-shaped skin are molded.

[0083] The honeycomb sandwich core is prepared based on the front cover, rear cover, C-shaped skin, and main beam.

[0084] After assembling the formed front cover, rear cover, C-shaped skin, and prepared main beam and honeycomb sandwich, a composite material structural component is formed in an autoclave.

[0085] The maximum deformation of the final molded composite material structural component is 7.02 mm along the length direction and 0.87 mm along the height direction, which meets the product curing deformation requirements.

[0086] Compared with traditional molding methods, the composite material structural parts prepared by the molding method of this embodiment not only effectively solve the problem of excessive curing deformation, but also reduce the trial production cost by more than 60% and shorten the molding cycle by more than 120%.

[0087] Example 2

[0088] The composite material structural component in this embodiment is a C-shaped structure, 1500mm long, 300mm high, and with a bottom opening width of 150mm. It consists of a main beam, a front cover, a rear cover, a honeycomb core, and a C-shaped skin.

[0089] The main beam is made of steel and is 10mm thick.

[0090] The front cover, rear cover, and C-shaped skin are made of carbon fiber reinforced epoxy resin-based composite material. The front cover and rear cover are 3mm thick, and the C-shaped skin transitions from 3mm thick at the top to 6mm thick on both sides at the bottom.

[0091] In this embodiment, the composite material structural component has a front cover and a rear cover located at both ends of a C-shaped skin, with the main beam and honeycomb core located inside the C-shaped skin. The honeycomb core fills the space between the C-shaped skin and the main beam. The deformation requirements for the composite material structural component are: a maximum of 6mm in the length direction and a maximum of 1mm in the height direction.

[0092] (1) Selection of adhesive bonding molding process

[0093] The scaling ratio of the scaled-down part to the original part is 1:5.

[0094] Based on the structural dimensions of the composite material structural parts and the scaled-down tooling parts, a three-dimensional finite element model was constructed to conduct simulation analysis of the autoclave forming-curing deformation process. The simulation results of the scaled-down part deformation are as follows: the maximum deformation along the length direction is 1.22 mm, and the maximum deformation along the height direction is 0.18 mm.

[0095] Experimental verification of the autoclave molding process of scaled-down parts: Under the same process conditions, the C-type skin prepreg, front cover prepreg and rear cover prepreg of the scaled-down parts were combined with the main beam and honeycomb sandwich on the tooling and placed in the autoclave for curing.

[0096] Taking the maximum deformation in the length and height directions of the scaled-up part as the object, the simulation relative error is determined according to formula (1). In this embodiment, the simulation relative error in the length direction of the scaled-up part formed by co-bonding process is about 8.26%, and the relative error in the height direction is about 8.15%, and the simulation results are reliable.

[0097] According to formula (2), the maximum deformation in the length direction of the composite material structural component is estimated to be 6.1 mm, which exceeds the curing deformation requirement of 1.7% in the length direction of the composite material structural component; the maximum deformation in the height direction is estimated to be 0.9 mm, which meets the curing deformation requirement in the height direction of the composite material structural component.

[0098] This study focuses on composite material structural components, aiming to control their deformation. Based on defined material parameters, it utilizes autoclave molding-curing deformation process simulation technology and surface compensation technology to conduct optimization analysis of autoclave molding process parameters, tooling structure optimization simulation analysis, and curing deformation prediction analysis for composite material structural components. The tooling employs a multi-zone independent temperature control structure, including two independent heating / cooling modules, with temperature regulated by a PID controller. These two independent heating / cooling modules are used for heating and cooling the 3mm thick area above and the 5mm thick areas on both sides below the C-shaped skin, respectively. This segmented temperature control of different thickness areas of the C-shaped skin enables synchronous segmented curing of the C-shaped skin, effectively controlling its curing deformation.

[0099] Ultimately, based on optimized molding process parameters and tooling structure, the minimum curing deformation of the composite material structural parts is: the maximum deformation in the length direction is approximately 5.53 mm, and the maximum deformation in the height direction is approximately 0.72 mm, both of which meet the curing deformation requirements of the composite material structural parts.

[0100] Compared to two-stage bonding molding, co-bonding has the advantages of shorter molding cycle and lower cost, but the disadvantage of larger curing deformation. Therefore, co-bonding molding is preferred when the curing deformation meets the product design requirements. The composite material structural component in this embodiment is formed using co-bonding molding.

[0101] (2) Fabrication of composite structural parts using autoclave / co-bonding molding process

[0102] Based on optimized molding process parameters and tooling structure, composite material structural parts are prepared using autoclave / co-bonding molding process.

[0103] The maximum deformation of the final composite material structural component is 5.86 mm along the length direction and 0.87 mm along the height direction, which meets the product curing deformation requirements.

[0104] Compared with traditional molding methods, the composite material structural parts prepared by the molding method of this embodiment not only effectively solve the problem of excessive curing deformation, but also reduce the trial production cost by more than 80% and shorten the molding cycle by more than 200%.

[0105] Example 3

[0106] The composite material structural component in this embodiment is a C-shaped structure, 1000mm long, 200mm high, and with a bottom opening width of 100mm. It consists of a main beam, a front cover, a rear cover, a honeycomb core, and a C-shaped skin.

[0107] The main beam is made of steel and is 10mm thick.

[0108] The front cover, rear cover, and C-shaped skin are made of carbon fiber reinforced epoxy resin-based composite material with a thickness of 2mm.

[0109] In this embodiment, the composite material structural component has a front cover and a rear cover located at both ends of a C-shaped skin, with the main beam and honeycomb core located inside the C-shaped skin. The honeycomb core fills the space between the C-shaped skin and the main beam. The deformation requirements for the composite material structural component are: a maximum of 5mm in the length direction and a maximum of 0.6mm in the height direction.

[0110] (1) Selection of adhesive bonding molding process

[0111] 1) Co-bonding process molding

[0112] Based on the structural dimensions of the composite material structural components and tooling, a three-dimensional finite element model was constructed, and simulation analysis of the autoclave molding-curing deformation process was conducted. The simulation results of the composite material structural component deformation are: a maximum deformation of 5.5 mm along the length direction and a maximum deformation of 0.63 mm along the height direction. Neither of these results meets the product design requirements for composite material structural components.

[0113] Experimental verification of the autoclave molding process of composite structural parts: Under the same process conditions, the prepregs of C-shaped skin, front cover and rear cover were combined with the main beam and honeycomb core on the tooling and placed in the autoclave for curing.

[0114] Taking the maximum deformation in the length and height directions of the composite material structural component as the object, the simulation relative error is determined according to formula (1). In this embodiment, the simulation relative error in the length direction of the scaled-down part formed by the autoclave / co-bonding process is about 9.83%, and the relative error in the height direction is about 8.61%, and the simulation results are reliable.

[0115] Using autoclave molding-curing deformation process simulation technology, this study aims to control the deformation of composite material structural components. It involves optimizing process parameters, simulating tooling structure optimization, and predicting curing deformation in the autoclave / co-bonding process of scaled-down parts. The tooling structure optimization simulation analysis is based on the optimized molding process parameters. Ultimately, based on the optimized molding process parameters and tooling structure, the minimum curing deformation of the composite material structural component is: a maximum deformation of approximately 5.3 mm in the length direction, exceeding the length direction curing deformation requirement by 6%; and a maximum deformation of approximately 0.61 mm in the height direction, exceeding the height direction curing deformation requirement by 1.7%. This still does not meet the design requirements for the composite material structural component.

[0116] 2) Secondary adhesive bonding molding process

[0117] Based on the structural dimensions of the front and rear covers of the composite material structure, a three-dimensional finite element model was constructed, and simulation analysis of the autoclave molding-curing deformation process was conducted. The simulation results show that the maximum deformation of the front cover is 0.55 mm and 0.59 mm along the length and height directions of the composite material structure, respectively, while the maximum deformation of the rear cover is 0.46 mm and 0.57 mm, respectively.

[0118] Experimental verification of the autoclave molding-curing deformation process of the front and rear covers of composite material structural parts: Under the same process conditions, the front and rear covers of composite material structural parts were molded using the autoclave molding process.

[0119] Taking the maximum deformation of the front and rear covers along the length and height directions of the composite material structure as the object, the simulation relative error was determined according to equation (1). Specifically, along the length direction of the composite material structure, the simulation relative error of the front cover was approximately 9.56%, and that of the rear cover was approximately 8.18%; along the height direction of the composite material structure, the simulation relative error of the front cover was approximately 7.82%, and that of the rear cover was approximately 9.65%. The simulation results are reliable.

[0120] Based on the dimensions of the C-shaped skin and tooling structure of the composite material structural component, a three-dimensional finite element model was constructed. Simulation analysis of the autoclave molding-curing deformation process was conducted using optimized molding process parameters. The simulation results show that the maximum deformation of the C-shaped skin along the length and height of the composite material structural component is 3.95 mm and 0.61 mm, respectively.

[0121] Experimental verification of the C-shaped skin of composite structural parts by autoclaving molding-curing deformation simulation analysis: Under the same process conditions, C-shaped skin of composite structural parts is formed using autoclave molding process.

[0122] Taking the maximum deformation of the C-shaped skin along the length and height directions of the composite material structure as the object, the simulation relative error of the C-shaped skin in the length direction of the composite material structure is determined to be about 9.28% and the simulation relative error in the height direction is 8.68% according to Equation (1), and the simulation results are reliable.

[0123] Therefore, the curing deformation of the composite material structural component is as follows: the maximum deformation in the length direction of the composite material structural component is 4.96 mm for the front cover, rear cover, and C-shaped skin, which meets the design requirements for curing deformation in the length direction of the composite material structural component product; the maximum deformation in the height direction is the maximum value in the height direction of the front cover, rear cover, or C-shaped skin, which is 0.61 mm, exceeding the curing deformation requirement in the height direction of the composite material structural component product by 1.7%. Therefore, it does not meet the design requirements for the composite material structural component product.

[0124] Using autoclave molding-curing deformation process simulation technology and surface compensation technology, we conducted optimization analysis on the autoclave molding process parameters and tooling structure of the front cover and rear cover. Finally, along the length and height directions of the composite material structure, the maximum deformation of the front cover was 0.52 mm and 0.49 mm, respectively, and the maximum deformation of the rear cover was 0.45 mm and 0.43 mm, respectively.

[0125] Using autoclave molding-curing deformation process simulation technology and surface compensation technology, this study aims to control the curing deformation of C-shaped skin in composite structural parts. Molding process parameters and tooling structure optimization analyses were conducted. Ultimately, based on the optimized molding process parameters and tooling structure, the predicted minimum curing deformation of the C-shaped skin is as follows: the maximum deformation along the length and height of the composite structural part is 3.86 mm and 0.52 mm, respectively.

[0126] Therefore, the composite material structural parts prepared by autoclave / secondary bonding molding process have a maximum deformation of about 4.83 mm in the length direction and a maximum deformation of about 0.52 mm in the height direction, which meets the product design requirements.

[0127] After optimizing the molding process parameters and tooling structure using molding process simulation technology, the maximum deformation of the composite material structural parts formed by co-bonding process still cannot meet the product design requirements in the length and height directions, while the secondary bonding molding process meets the product design requirements. Therefore, the composite material structural parts in this embodiment are formed by secondary bonding molding process.

[0128] (2) Fabrication of composite material structural parts using autoclave / secondary bonding molding process

[0129] The main beam was fabricated according to the requirements of the original composite structural components.

[0130] Based on optimized molding process parameters and tooling structure, the front cover, rear cover, and C-shaped skin are molded.

[0131] The honeycomb sandwich core is prepared based on the front cover, rear cover, C-shaped skin, and main beam.

[0132] After assembling the formed front cover, rear cover, C-shaped skin, and prepared main beam and honeycomb sandwich, a composite material structural component is formed in an autoclave.

[0133] The maximum deformation of the final formed composite material structural component is 4.86 mm along the length direction and 0.56 mm along the height direction, which meets the product curing deformation requirements.

[0134] Compared with traditional molding methods, the composite material structural parts prepared by the molding method of this embodiment not only effectively solve the problem of excessive curing deformation, but also reduce the trial production cost by more than 50% and shorten the molding cycle by more than 150%.

Claims

1. A molding method for controlling the deformation of composite material structural parts with large length-to-thickness ratios, characterized in that the steps include... include: (1) Selection of adhesive bonding molding process The technique combines simulation and experimental verification of autoclave molding-curing deformation process, and selects the adhesive molding process for composite material structural parts; the autoclave molding-curing deformation process simulation is a multi-physics coupling simulation technology that integrates thermal, structural and fluid algorithms; 1) Determine the test subjects for verification Based on the length of composite material structural components, the original or scaled-down components are used as the verification test objects. 2) Reliability assessment of simulation results For the verification test object, under the same process conditions, simulation analysis and verification tests of the autoclave molding-curing deformation process were carried out respectively. The reliability of the simulation results was determined by the test results. When determining the reliability of the simulation results, a relative simulation error of no more than 15% was used as the criterion. The relative simulation error was determined according to the following formula: In the formula, It is the simulation relative error. These are the values ​​from the curing deformation experiment. These are the simulation values ​​of solidification deformation; 3) Determination of simulation material parameters When the simulation results are deemed reliable, the simulation material parameters are the same as those input when conducting the simulation analysis of the autoclave molding-curing deformation process; when the results are deemed unreliable, the simulation material parameters are corrected based on the verification test results and using the autoclave molding-curing deformation process simulation technology. 4) Predict the curing deformation of composite material structural components Preliminary estimates of the curing deformation of composite material structural components are based on simulation results; When the preliminary estimated curing deformation of composite structural components exceeds the product design requirements, based on the determined material parameters, the process parameters and tooling structure are optimized with the aim of controlling the curing deformation of composite products by using autoclave molding-curing deformation process simulation technology, and the curing deformation of composite structural components is estimated. The optimization of the tooling structure adopts the surface compensation technology: based on the tooling and composite material product model, with the help of autoclave molding-curing deformation process simulation technology, the deformation of the composite material product after curing is estimated, the tooling structure is redesigned, the deformation deviation of the composite material product is compensated in reverse, and the molding process simulation is carried out again. Repeat the above steps until the curing deformation of the composite material product reaches its minimum. 5) Determine the applicable adhesive bonding process The applicable adhesive bonding process is determined based on the criterion that the estimated curing deformation of the composite material structural component does not exceed the product deformation requirements. (2) Molded composite material structural parts Based on the selected adhesive bonding process, optimized process parameters, and tooling structure, composite material structural components are formed.

2. The molding method for controlling the deformation of composite material structural parts with large length-to-thickness ratios according to claim 1, characterized in that: When determining the verification test object in step (1) 1), if the length of the composite material structural part is not greater than 1 meter, the original part is used as the verification test object; otherwise, a scaled-down part is used as the verification test object.

3. The molding method for controlling the deformation of composite material structural parts with large length-to-thickness ratios according to claim 1, characterized in that: The simulation of the autoclave molding-curing deformation process includes heat transfer simulation analysis, curing kinetics simulation analysis, and structural deformation simulation analysis. The heat transfer simulation analysis is used to simulate the dynamic interaction between the heat release during resin curing and the temperature field of the solid component and tooling. The curing kinetics simulation analysis is used to calculate the change in the degree of resin crosslinking over time. The structural deformation simulation analysis is used to predict the shrinkage of the simulated object and the deformation caused by residual stress.

4. The molding method for controlling the deformation of composite material structural parts with large length-to-thickness ratios according to claim 1, characterized in that: In step (1) 4), the composite material product includes composite structural parts, scaled-down parts, and components made of fiber-reinforced thermosetting resin-based composite materials.

5. The molding method for controlling the deformation of composite material structural parts with large length-to-thickness ratios according to claim 4, characterized in that: When the thickness of the component made of fiber-reinforced thermosetting resin matrix composite material is uneven, the molding tooling adopts a multi-zone independent temperature control structure, which can control the temperature in segments for different thickness areas.

6. The molding method for controlling the deformation of composite material structural parts with large length-to-thickness ratios according to claim 5, characterized in that: The temperature segmented control includes segmented control of the heating rate and the holding time.

7. The molding method for controlling the deformation of composite material structural parts with large length-to-thickness ratio according to claim 4, characterized in that: The composite material product is a scaled-down version of a composite structural component. When estimating the curing deformation of the composite structural component, the curing deformation of the scaled-down component is first estimated, and then the deformation of the composite structural component is estimated according to the following formula: in It is the deformation of composite material structural components. K is the deformation amount of the scaled-down part, and K is the scaling ratio.

8. The molding method for controlling the deformation of composite material structural parts with large length-to-thickness ratios according to claim 1, characterized in that: In step (1) 5), when both co-bonding and secondary bonding molding processes meet the judgment criteria, co-bonding molding process is preferred.

9. The molding method for controlling the deformation of composite material structural parts with large length-to-thickness ratios according to claim 1, characterized in that: When it is determined that the secondary adhesive bonding molding process is applicable to the adhesive bonding molding process of composite material structural parts, before molding the composite material structural parts in step (2), the molding process parameters and tooling structure of each component are further optimized by using the autoclave molding-curing deformation process simulation technology.

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