A method for controlling curing distortion of composite material based on curing gradient effect

Abstract

The application belongs to the technical field of composite material forming simulation, and particularly relates to a composite material curing deformation control method based on a curing gradient effect. U i The displacement changes of each node of the component relative to a design model are simulated by establishing a finite element simulation model of the component and the mold, the compensation displacement of each node is calculated, the mold surface is non-uniformly compensated based on the initial mold surface, the finite element simulation model of the component and the mold is re-established and simulated according to the mold surface compensated according to the design, and the component region whose surface precision does not meet the requirements is corrected until all regions of the component surface meet the precision requirements.

Description

Technical Field

[0001] This invention belongs to the field of composite material molding simulation technology, specifically relating to a method for controlling the curing deformation of composite materials based on the curing gradient effect. Background Technology

[0002] Fiber-reinforced resin matrix composites are widely used in various industrial fields due to their excellent properties such as high specific strength, high specific modulus, and strong design flexibility. The proportion of composite materials used in aircraft is gradually increasing, and their application range is gradually shifting from simple, small-sized components to large-sized, complex components with high curvature. Currently, the aerospace field mainly uses autoclave equipment to cure composite components. After the curing process, the components are demolded, resulting in curing deformation. For general composite components, the main factors causing curing deformation include the inconsistency of the thermal expansion coefficients of the resin and fiber, the chemical shrinkage of the resin, and the interaction between the component and the mold. Curing deformation not only affects the quality of composite components but also subsequent assembly.

[0003] To reduce curing deformation of composite components, traditional methods rely on experiments and employ a uniform springback angle or scaling factor to perform reverse compensation correction on the molding die. However, these methods ignore the gradient effects of curing degree evolution, temperature history, and stress accumulation in different regions of the component due to thickness, curvature, and layup. Even after die surface compensation, the component deformation still exceeds acceptable limits. Traditional methods depend on experiments and require repeated die modifications based on actual deformation, resulting in low efficiency and high trial-and-error iteration costs. Summary of the Invention

[0004] Purpose of the invention: This paper provides a method for controlling the curing deformation of composite materials based on the curing gradient effect, which controls the curing deformation of composite material components and reduces the cycle and cost in the component development process.

[0005] Technical solution: A method for controlling the curing deformation of composite materials based on the curing gradient effect, comprising: S1: Based on the design model of the composite component and the mold design model, establish the finite element simulation model of the component and the mold, and assign the curing kinetic parameters of the composite resin matrix to the finite element simulation model of the component and the mold, including the elastic modulus, shear modulus, thermal conductivity and thermal expansion coefficient of the composite material under different states, as well as the elastic modulus, thermal conductivity and thermal expansion coefficient of the mold material. S2: Extract the geometric features of each node of the composite material component in the finite element simulation model of the component and mold, and take each node as the point to be compensated. S3: Input the curing regime of the component into the finite element simulation model of the component and mold, and perform finite element simulation to simulate the temperature, degree of curing, stress and displacement of each node during the curing process. Finally, output the displacement changes of each node of the component relative to the design model. U i ; S4: Determine the compensation factor for each node in different feature regions. β i ； S5: Calculate the initial compensation displacement of each node. C i ， Add compensation displacement to the coordinates of each node of the initial mold design surface to reconstruct the mold surface; S6: Based on the compensated mold surface, re-establish the finite element simulation models of the component and the mold, and output the displacement changes of each node of the component relative to the design model of the composite material component through finite element simulation. U j According to displacement changes U j Confirm Certainly Does all areas of the profile meet the accuracy requirements? For component areas where the surface accuracy does not meet the requirements, corrections are made until all areas of the component surface meet the accuracy requirements.

[0006] Furthermore, in S1, the curing kinetic parameters of the composite resin matrix are obtained through dynamic differential scanning calorimetry.

[0007] Furthermore, in S1, the elastic modulus, shear modulus, thermal conductivity, and coefficient of thermal expansion of the composite material under different states are obtained by testing the mechanical and thermal properties of the composite material.

[0008] Furthermore, in S4, the feature regions include: flat plate region, transition region, and corner region.

[0009] Furthermore, in S4, the compensation factor for the flat plate region is 1.0, and the compensation factor for the transition region is 1.2.

[0010] Furthermore, in S5, the initial compensation displacement satisfies: C i =- β i · U i .

[0011] Furthermore, in S6, for component areas where the surface accuracy does not meet the requirements, corrections are made, specifically as follows: For component areas where the surface accuracy does not meet the requirements, return to step 5 and calculate the displacement changes of the component areas that do not meet the requirements. U j Recalculate the compensation displacement C j =- β j · U j Correct the mold surface corresponding to the component area that does not meet the requirements until all areas of the component surface meet the accuracy requirements.

[0012] Furthermore, in S3, the curing regime includes: curing temperature, time, heating rate, cooling rate, and pressure.

[0013] Beneficial effects: This invention establishes a simulation analysis model of the curing deformation of composite material components to predict the springback displacement vector of each node relative to the design surface. Different compensation factors are applied to different characteristic regions of the component, and the compensation displacement vector of each node is calculated. Based on the initial mold surface, a non-uniform compensation design is performed on the mold surface. A simulation model is then established based on the reconstructed mold surface until the component deformation meets the requirements.

[0014] By employing a non-uniform surface compensation design based on node deformation, the deformation of composite components can be controlled. Compared with traditional testing and mold uniform compensation design, the curing deformation results of composite materials can be obtained quickly, reducing the deformation of composite components and lowering the testing cycle and cost. Detailed Implementation

[0015] To control the curing deformation of composite material components and reduce the cycle and cost in the component development process, the curing and molding process of composite material components is simulated and analyzed considering the gradient effect. The simulation results enable the non-uniform compensation design of the mold surface to reduce the deformation of the composite material components and achieve the required surface accuracy after curing.

[0016] A method for controlling the curing deformation of composite materials based on the curing gradient effect, comprising: (1) Curing kinetic parameters of the composite resin matrix were obtained by dynamic differential scanning calorimetry. The elastic modulus, shear modulus, thermal conductivity and coefficient of thermal expansion of the composite material under different states were obtained by testing the mechanical and thermal properties of the composite material. Based on the design model of the composite component and the mold design model, finite element simulation models of the component and the mold were established. The finite element simulation models of the component and the mold were assigned curing kinetic parameters, elastic modulus, shear modulus, thermal conductivity and coefficient of thermal expansion, as well as the elastic modulus, thermal conductivity and coefficient of thermal expansion of the mold material.

[0017] (2) Extract the geometric features of each node of the composite material component in the finite element simulation model of the component and the mold, and take each node as the point to be compensated; (3) Input the curing regime of the component into the finite element simulation model of the component and the mold, and perform finite element simulation to simulate the temperature, degree of curing, stress and displacement of each node during the curing process. Finally, output the displacement changes of each node of the component relative to the design model. U i ; (4) Based on the geometric features extracted in step (2), determine the compensation factors for each node in different feature regions according to engineering experience. β i For example, the compensation factor for the flat plate area can be 1.0, and the compensation factor for the transition area can be 1.2. The characteristic regions include: flat plate area, transition area, and corner area.

[0018] (5) Based on steps (3) and (4), the initial compensation displacement of each node is calculated. C i =- β i · U i Add compensation displacement to the coordinates of each node of the initial mold design surface (perform non-uniform compensation design on the mold surface) to reconstruct the mold surface; (6) Based on the mold surface after compensation design, re-establish the finite element simulation model of the component and the mold, and output the displacement changes of each node of the component relative to the design model of the composite material component through finite element simulation. U j According to displacement changes U j Confirm Certainly Does all areas of the profile meet the accuracy requirements? For component areas where the surface accuracy does not meet the requirements, return to step 5 and calculate the displacement changes of the component areas that do not meet the requirements. U j Recalculate the compensation displacement C j =- β j · U j Correct the mold surface corresponding to the component area that does not meet the requirements until all areas of the component surface meet the accuracy requirements.

[0019] Example 1 The following steps are used to reduce the deformation of the variable-thickness V-shaped composite component after curing by designing a non-uniform compensation mold: Step 1: The component is a variable thickness V-shaped component, with two flat plates of 2mm and 4mm thicknesses respectively, forming a 60° angle, and transitioning through a radius of R10 in the middle. Based on the V-shaped component design model, establish finite element simulation models of the component and mold, assigning relevant parameters for material curing kinetics and constitutive models; Step 2: Take each mesh node of the component finite element model as the point to be compensated, and extract the thickness and curvature of each node; Step 3: Based on the coupled thermo-chemical-mechanical multi-field simulation model of the component curing, output the displacement changes of each node of the component relative to the design model. U i ; Step 4: Determine the compensation factor for each node in different characteristic areas based on engineering experience. The compensation factor for the pure flat plate area on both sides of the component is 1.0. The compensation factor for the rounded corner transition area is 1.2 due to stress and strain concentration. The compensation factor for the thickness gradient area linearly transitions from 1.0 to 1.2. Step 5: Based on the displacement change and compensation factor, reconstruct the mold surface according to the initial total model. Use the reconstructed mold surface to establish a simulation model to simulate the deformation of the component. The included angle deviation of the V-shaped component is -0.4°, which meets the design requirements. The angle deviation of uniform compensation is 1.2°.

[0020] The above detailed embodiments are a description of the present invention. It should not be considered that the specific embodiments of the present invention are limited to these descriptions. For those skilled in the art, several simple deductions and substitutions can be made without departing from the concept of the present invention, and all of these should be considered to fall within the protection scope of the present invention.

Claims

1. A method for controlling the cure distortion of a composite material based on the cure gradient effect, characterized in that, include: S1: Based on the design model of the composite component and the mold design model, establish the finite element simulation model of the component and the mold, and assign the curing kinetic parameters of the composite resin matrix to the finite element simulation model of the component and the mold, including the elastic modulus, shear modulus, thermal conductivity and thermal expansion coefficient of the composite material under different states, as well as the elastic modulus, thermal conductivity and thermal expansion coefficient of the mold material. S2: Extract the geometric features of each node of the composite material component in the finite element simulation model of the component and mold, and take each node as the point to be compensated. S3: input the curing schedule of the component into the finite element simulation model of the component and the mold, simulate the temperature, the degree of cure, the stress and the displacement of each node during the curing process by finite element simulation, and finally output the displacement change of each node of the component relative to the design model U i ; S4: determining compensation factors of nodes in different feature regions β i ； S5: calculate the initial compensation displacement of each node C i ， add the compensation displacement to the coordinates of each node of the initial design surface of the mold to reconstruct the mold surface S6: According to the compensated design mold surface, re-establish the finite element simulation model of the component and the mold, and carry out finite element simulation to output the displacement change of each node of the component relative to the design model of the composite component U j ; According to the displacement change U j Sure Whether all regions of the surface meet the accuracy requirements; For component areas where the surface accuracy does not meet the requirements, corrections are made until all areas of the component surface meet the accuracy requirements.

2. The composite cure distortion control method of claim 1, wherein, In S1, the curing kinetic parameters of the composite resin matrix are obtained through dynamic differential scanning calorimetry.

3. The composite cure distortion control method according to claim 1, wherein, In S1, the elastic modulus, shear modulus, thermal conductivity, and coefficient of thermal expansion of the composite material under different states are obtained by testing the mechanical and thermal properties of the composite material.

4. The composite cure distortion control method according to claim 1, wherein, In S4, the feature regions include: flat plate region, transition region, and corner region.

5. The composite cure distortion control method according to claim 1, wherein, In S4, the compensation factor for the flat plate region is 1.0, and the compensation factor for the transition region is 1.

2.

6. The method for controlling the curing deformation of composite materials according to claim 1, characterized in that, In S5, the initial compensation displacement satisfies: C i =- β i · U i .

7. The method for controlling the curing deformation of composite materials according to claim 1, characterized in that, In S6, for component areas where the surface accuracy does not meet the requirements, corrections are made, specifically as follows: For component areas where the surface accuracy does not meet the requirements, return to step 5 and calculate the displacement changes of the component areas that do not meet the requirements. U j Recalculate the compensation displacement C j =- β j · U j Correct the mold surface corresponding to the component area that does not meet the requirements until all areas of the component surface meet the accuracy requirements.

8. The method for controlling the curing deformation of composite materials according to claim 1, characterized in that, In S3, the curing regime includes: curing temperature, time, heating rate, cooling rate, and pressure.