A method for predicting cure distortion and residual stresses in large complex composite structures

Abstract

The application relates to a method for predicting curing deformation and residual stress of a large and complex composite component, and relates to a method for predicting curing deformation and residual stress of a component. In order to solve the problem of poor reliability of a traditional curing simulation method, the application comprises the following steps: step one, measuring intrinsic strain during curing; step two, measuring mechanical parameters; step three, establishing a shell model of the large and complex composite component; step four, predicting the curing deformation through thermal-mechanical coupling numerical calculation; step five, manufacturing a large and complex composite component in a reduced scale; step six, detecting a profile; and step seven, error analysis. The application belongs to the field of composite material processing and manufacturing.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for predicting curing deformation and residual stress of a component, and belongs to the field of composite material processing and manufacturing. BACKGROUND

[0002] Resin matrix composite material is a high performance composite material developed to meet the needs of high-tech fields such as aviation and aerospace, and has superior performance such as light weight, high strength and designability. Autoclave molding process is one of the main methods for manufacturing high-quality resin matrix composite components, and has the characteristics of uniform heating temperature and curing pressure distribution, almost no limitation on the geometric shape of the component, and wide application range.

[0003] However, when using an autoclave to manufacture a resin matrix composite component, after the composite material component undergoes high-temperature curing and cooling processes, due to the thermal expansion and contraction effect of the composite material prepreg, the chemical reaction shrinkage effect of the matrix resin, and the significant difference in thermal expansion coefficient between the composite material and the mold material used for molding, the mismatch of this deformation will cause the formation of residual stress, and there will be a certain degree of inconsistency between the free shape at room temperature and the expected ideal shape, i.e. the curing deformation of the component, which will have a very adverse effect on the part shape accuracy and the connection matching between components.

[0004] In actual production, we often encounter composite components with irregular shapes (irregular component shapes), complex layups (more than 50 layers of layup and complex angle arrangement of layup), missing layers (each layer of layup has inconsistent shape), and mixed layup of multiple materials (containing both fabric and unidirectional tape prepreg). This type of composite component is collectively referred to as a large complex composite component. Large complex composite components are often not symmetrical in terms of layup and geometric form, so their curing deformation and residual stress cannot be ignored. The curing simulation of large complex composite components is often very difficult, because the current curing simulation method requires the establishment of an accurate three-dimensional geometric model (including layup) of the component to be predicted. For large complex composite components, it is almost impossible to establish a three-dimensional model including layup, which brings great difficulty to the curing simulation.

[0005] The intrinsic strain method has great advantages in predicting the curing deformation and residual stress of large complex composite components. A large number of literature studies show that the residual stress in the manufacturing process is caused by intrinsic strain. The intrinsic strain of each layer of prepreg is the same under the same process, so before the resin-based composite component is actually manufactured by using a hot press tank, only the intrinsic strain of the prepreg after curing needs to be measured, so that the curing process specification of the component and the surface of the mold used for part forming can be adjusted and modified repeatedly according to the prediction results, so as to control the degree of deformation or offset the influence of deformation.

[0006] The main method for predicting the curing deformation and residual stress of composite materials at present is to calculate the thermal-chemical-force coupling multi-physical field in the curing process through finite element simulation, or to use the traditional multiple tests of samples, scale-down components and verification components. The results of these methods have great instability and uncertainty, low prediction efficiency and high cost. Therefore, it is increasingly important to develop the intrinsic strain method to efficiently, quickly and accurately predict the curing deformation and residual stress of large complex composite components. SUMMARY

[0007] The present application is to solve the problem of poor reliability of traditional curing simulation method, and further proposes a method for predicting the curing deformation and residual stress of large complex composite components.

[0008] The technical solution adopted by the present application to solve the above problems is that the steps of the present application are:

[0009] Step one, measuring the intrinsic strain after curing;

[0010] Step two, measuring the mechanical parameters;

[0011] Step three, establishing a shell model of a large complex composite component;

[0012] Step four, predicting the curing deformation through thermal-mechanical coupling numerical calculation;

[0013] Step five, manufacturing a large complex composite scale-down component;

[0014] Step six, surface detection;

[0015] Step seven, error analysis.

[0016] Further, the process of measuring the intrinsic strain after curing in step one is to manufacture a standard plate, and to inversely calculate the intrinsic strain of the unidirectional tape and fabric during the curing process according to the mid-surface strain and curvature after curing.

[0017] Further, the process of measuring the mechanical parameters in step two is to test the elastic modulus, Poisson's ratio and shear modulus of the unidirectional tape and fabric according to the national standard test method.

[0018] Further, the process of establishing the shell model of the large complex composite component in step three is: according to the shape of the large complex composite component, a shell element model of the large complex composite component is established.

[0019] Further, the process of predicting the curing deformation through thermal coupling numerical calculation in step four is: the experimentally measured intrinsic strain is input into the simulation model of the complex component as the thermal expansion coefficient, and other mechanical material parameters are input; thermal coupling numerical calculation is performed to obtain the curing deformation and residual stress field of the complex composite component under the same process.

[0020] Further, the process of manufacturing the large complex composite component in step five is: according to the equal reduction of the original model, a scaled component is manufactured, and is cured and formed in a heat press tank.

[0021] Further, the process of surface detection in step six is: the point coordinates of the surface of the scaled component after curing are accurately obtained through ultrasonic scanning measurement tools.

[0022] Further, the process of error analysis in step seven is: the curing deformation of the scaled component is calculated by using the method of step four, and is compared with the detection result of the surface detection to verify the correctness of the prediction result.

[0023] The beneficial effects of the present application are: compared with the existing curing simulation technology and experimental method, the intrinsic strain method is used to predict the curing deformation and residual stress of the large complex composite component, which can be used to numerically simulate the curing deformation and residual stress of any shape and any layer of the laminated plate made of the same material under the same process. First, the complex composite component with irregular shape, complex layer, missing layer and mixed material can be quickly and accurately predicted; second, this method is simple to operate, only needs the shell element model of the outer shape of the composite component, and has low simulation modeling requirements, without the need to establish a complex three-dimensional solid model, which greatly improves the simulation convergence and meets the demand of low-cost and rapid and accurate prediction of the curing deformation and residual stress of any composite component; then, compared with the existing curing simulation technology, this method has higher accuracy because the prediction data is derived from experimental testing, avoiding the inherent error caused by theoretical assumptions. Finally, this method uses experimental methods instead of curing mechanism research, omits the curing material parameter testing, greatly simplifies the prediction process of the curing deformation and residual stress, and greatly reduces the cost of predicting the curing of the large complex composite component. DETAILED DESCRIPTION

[0024] Detailed implementation one: the method for predicting the curing deformation and residual stress of the large complex composite component is realized through the following steps:

[0025] Step one, measure the intrinsic strain of curing;

[0026] Step two, measure the mechanical parameters;

[0027] Step three, establish a large complex composite component shell model;

[0028] Step four, predict the curing deformation by thermal-mechanical coupling numerical calculation;

[0029] Step five, make a large complex composite material scale-down component;

[0030] Step six, surface detection;

[0031] Step seven, error analysis.

[0032] Specific implementation method two: the process of measuring the intrinsic strain of curing in step one of the method for predicting the curing deformation and residual stress of unidirectional tape laminated plate according to the embodiment is: making a standard plate, and inversely calculating the intrinsic strain of unidirectional tape and fabric generated in the curing process according to the middle surface strain and curvature after curing.

[0033] Specific implementation method three: the process of measuring the mechanical parameters in step two of the method for predicting the curing deformation and residual stress of unidirectional tape laminated plate according to the embodiment is: according to the national standard test method, performing test, testing the elastic modulus, Poisson's ratio and shear modulus of unidirectional tape and fabric.

[0034] Specific implementation method four: the process of establishing a large complex composite component shell model in step three of the method for predicting the curing deformation and residual stress of unidirectional tape laminated plate according to the embodiment is: establishing a large complex composite component shell element model according to the shape of the large complex composite component.

[0035] Specific implementation method five: the process of predicting the curing deformation by thermal-mechanical coupling numerical calculation in step four of the method for predicting the curing deformation and residual stress of unidirectional tape laminated plate according to the embodiment is: inputting the experimentally measured intrinsic strain of curing as the thermal expansion coefficient into the simulation model of the complex component, inputting other mechanical material parameters; performing thermal-mechanical coupling numerical calculation to obtain the curing deformation and residual stress field of the complex composite component under the same process.

[0036] Specific implementation method six: the process of making a large complex composite material scale-down component in step five of the method for predicting the curing deformation and residual stress of unidirectional tape laminated plate according to the embodiment is: according to the equal ratio reduction of the original model, making a scale-down component, and curing and forming in a heat press tank.

[0037] Specific embodiment seven: the process of the step six of the method for predicting the curing deformation and residual stress of the unidirectional tape laminated plate is that the coordinates of the profile of the reduced scale component after curing are accurately obtained by the ultrasonic scanning measurement tool.

[0038] Specific embodiment eight: the process of the step seven of the method for predicting the curing deformation and residual stress of the unidirectional tape laminated plate is that the curing deformation of the reduced scale component is calculated by using the method of the step four, and the correctness of the prediction result is verified by comparing with the detection result of the profile detection.

[0039] Working principle

[0040] Firstly, the shell element model is established according to the outer shape of the large and complex composite component; and finally, the curing intrinsic strain is substituted into the thermal-mechanical coupling simulation, and the curing deformation and residual stress field of the unidirectional tape / fabric / hybrid laminated plate with any shape and any layer made of the same material under the same process are simulated.

[0041] Principle of calculating the curing deformation of the composite component by using the intrinsic strain method:

[0042] Mura firstly proposed that the residual stress is caused by the non-coordinated strain in the solid, and this strain is called "intrinsic strain" or "inherent strain", which is the sum of all non-elastic and non-recoverable strains in the solid. The intrinsic strain mainly includes the strain caused by the change of the external physical field (acoustic, optical, electromagnetic, thermal, etc.), plastic strain, phase change strain, etc.

[0043] The mismatch of the interlaminar intrinsic strain will cause the change of the curvature of the inhomogeneous laminated thin structure, and the curing deformation of the laminated plate can be considered to be caused by the intrinsic strain generated in the curing process. The curing intrinsic strain mainly includes the thermal strain and the resin shrinkage strain caused by the process. Since the intrinsic strain is only affected by the process, the intrinsic strain of the same type of prepreg is the same under the same process. The curing intrinsic strain of the standard component can be tested, and then the curing deformation and residual stress field of the composite component with any layer and any shape made of the same prepreg under the same process can be calculated according to the intrinsic strain.

[0044] The above merely describes preferred embodiments of the present application, and is not intended to limit the present application in any form. Although the present application has been disclosed with preferred embodiments as above, it is not intended to limit the present application. Any person skilled in the art, without departing from the technical solution of the present application, can make some changes or modifications to the above disclosed technical content to obtain equivalent embodiments with equivalent changes. However, as long as it does not deviate from the technical solution of the present application, and is within the spirit and principle of the present application, any simple modification, equivalent replacement and improvement of the above embodiments are still within the protection scope of the technical solution of the present application.

Claims

1. A method for predicting the curing deformation and residual stress of large, complex composite material components, characterized in that: The method for predicting the curing deformation and residual stress of large and complex composite material components is achieved through the following steps: Step 1: Measure the intrinsic strain during curing; fabricate a standard plate and invert the intrinsic strain of the unidirectional tape and fabric during the curing process based on the mid-surface strain and curvature after curing. Step 2: Measure mechanical parameters; The process of measuring mechanical parameters is as follows: According to the national standard test methods, conduct experiments to test the elastic modulus, Poisson's ratio, and shear modulus of the unidirectional belt and fabric. Step 3: Establish a shell model for large and complex composite material components; Based on the shape of the large and complex composite material components, establish a shell element model for the large and complex composite material components. Step 4: Predict curing deformation through thermo-mechanical coupling numerical calculation; The experimentally measured intrinsic strain of the cured material is used as the coefficient of thermal expansion and input into the simulation model of the complex component, along with other mechanical material parameters. Thermo-mechanical coupling numerical calculations were performed to obtain the curing deformation and residual stress field of complex composite material components under the same process; Step 5: Fabricate large, complex composite material scaled-down components; scale down the original model proportionally to fabricate scaled-down components and cure them in an autoclave. Step Six: Surface Inspection; The surface inspection process involves accurately obtaining the location coordinates of the scaled-down component surface after curing using an ultrasonic scanning measuring tool. Step 7, Error Analysis; The error analysis process is as follows: Use the method in Step 4 to calculate the curing deformation of the scaled-down component using thermo-coupling numerical simulation, and compare it with the detection results of the surface inspection to verify the correctness of the prediction results.