Microscopic modeling calculation analysis method for woven composite material

Abstract

The invention discloses a braided composite material microcosmic modeling calculation analysis method, which belongs to the technical field of analogue simulation calculation, and comprises the following steps: carrying out simulation modeling on a braided composite material through a finite element analysis method to obtain a finite element model of the composite material; performing volume fraction calculation on the fiber bundles in the finite element model, and obtaining performance parameters through a rigidity and strength theoretical model according to a volume fraction calculation result; based on a failure starting criterion, whether a damage mode occurs is judged according to the performance parameters, and the failure starting criterion is a failure criterion; when a damage mode appears, evolving the damage mode through a three-dimensional progressive damage model, and smoothing the evolutionary process through a regularization model to obtain a damage evolution coefficient analogue simulation result of the woven composite material, so as to realize effective and accurate modeling analysis calculation on failure and damage evolution of the composite woven material.

Description

Technical Field

[0001] The invention belongs to the technical field of simulation and computational techniques, and in particular relates to a microscopic modeling and computational analysis method for braided composite materials. Background Art

[0002] Braided composite structures have been widely used in aerospace, aviation, shipbuilding, special engineering machinery and other fields. The use of simulation methods to predict the structural properties of braided composite materials is a common technical means in the field of design and manufacturing, which can effectively reduce costs and optimize design schemes. Among them, 2.5D woven composite materials are new advanced composite materials with high specific strength, high specific modulus, good structural integrity and performance designability. 2.5D braided composite materials have the advantages of high specific strength, high specific modulus, good fatigue resistance and low thermal expansion coefficient of laminated composite materials and three-dimensional braided composite materials. They can also overcome the delamination failure problem caused by poor interlayer bonding strength of laminated composite materials and the inherent defects of the complex braiding process of three-dimensional braided composite materials. Therefore, since its appearance, 2.5D braided composite materials have been highly valued by the composite engineering and mechanics communities, and in-depth research has been carried out on their experimental preparation, performance testing, damage and fracture mechanisms, and rich results have been achieved.

[0003] Generally, the mesomechanical finite element method is used to study the mechanical response of 2.5D braided composites and analyze their fracture failure mechanism. The mesomechanical finite element method establishes a representative volume unit cell (RVE) model of the composite material, applies periodic boundary conditions to calculate the mesoscopic stress and strain field, and then uses the homogenization method to calculate the macroscopic stress-strain response. Its advantage is that it can simultaneously obtain the mesoscopic stress-strain field and macroscopic mechanical response characteristics of the composite material, and can quantitatively analyze the influence of the performance changes of the component materials on the macroscopic properties (modulus, strength, etc.). Therefore, the mesomechanical finite element method is used to study the damage evolution and fracture mechanical behavior of the internal component materials and their interfaces when 2.5D braided composites are loaded, and then the relationship between its macroscopic mechanical properties and the properties of each component and the mesoscopic structural parameters is obtained, which can provide a theoretical basis for achieving its high-performance preparation through component properties and mesoscopic structural design.

[0004] However, the prior art does not have any relevant micromechanical finite element method modeling and analysis method for composite braided materials, and it is impossible to perform effective and accurate modeling, analysis and calculation of the failure and damage evolution of composite braided materials. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes a microscopic modeling calculation and analysis method for woven composite materials to solve the problems existing in the above prior art.

[0006] To achieve the above object, the present invention provides a microscopic modeling and calculation analysis method for a braided composite material, comprising:

[0007] The braided composite material is simulated and modeled by the finite element analysis method to obtain a finite element model of the composite material;

[0008] Calculating the volume fraction of the fiber bundle in the finite element model, and obtaining performance parameters through a stiffness and strength theoretical model based on the volume fraction calculation result;

[0009] Based on the failure initiation criterion, judging whether a damage mode occurs according to the performance parameter, wherein the failure initiation criterion is a failure criterion;

[0010] When a damage mode appears, the damage mode is evolved through a three-dimensional progressive damage model, and the evolution process is smoothed through a regularization model to obtain the simulation results of the damage evolution coefficient of the braided composite material.

[0011] Optionally, the volume fraction calculation process includes:

[0012] In the finite element model, the volume V of the fiber bundle is Fib Perform the calculation:

[0013]

[0014] Where R is the radius of the carbon fiber, K is the number of fibers contained in each bundle of yarn, and D is the total length of the fiber bundle in a unit cell. A single fiber bundle is composed of the superposition of the minimum structure, and the volume V is obtained by superimposing the volume of the minimum structure. Ele , the volume fraction of the fiber bundle V f for:

[0015] .

[0016] Optionally, the failure onset criterion is a Hashin failure criterion combined with a Hou failure criterion, and the damage modes corresponding to the failure onset criterion include fiber tensile failure, fiber compression failure, matrix tensile failure and matrix compression failure.

[0017] Optionally, the failure initiation criteria corresponding to different damage modes are:

[0018] Fiber tensile failure

[0019]

[0020] Fiber compression failure

[0021]

[0022] Matrix tensile failure

[0023]

[0024] Matrix compression failure

[0025]

[0026] Among them, e ft , e fc , e mt and e mc is the damage index corresponding to the damage modes of fiber tensile failure, fiber compression failure, matrix tensile failure and matrix compression failure, F 1t , F 1c , F 2t , F 2c , F ls and F ts They represent the axial tensile strength, axial compressive strength, transverse tensile strength, transverse compressive strength, longitudinal shear strength and transverse shear strength of the fiber bundle material respectively. α is the coefficient used to describe the effect of shear stress on the fiber tensile failure of the material. σ ab It represents the stress tensor generated in the b direction when stress is applied in the a direction.

[0027] Optionally, a three-dimensional progressive damage model is constructed based on the Murakami-Ohno damage model, and the damage mode is evolved through the three-dimensional progressive damage model.

[0028] Optionally, the process of obtaining the damage evolution coefficient of the braided composite material includes:

[0029]

[0030] Where: d i represents the damage evolution coefficient under the corresponding failure mode, i represents the corresponding failure mode; represents the equivalent failure displacement under the corresponding failure mode; represents the equivalent damage initiation displacement of the corresponding failure mode; It represents the real-time equivalent displacement of the corresponding failure mode.

[0031] Optionally, the equivalent failure displacement is based on the fracture energy The equivalent stress at failure is calculated; the fracture energy for:

[0032] ;

[0033] in: and are the equivalent failure strength and equivalent failure strain, respectively. is the element characteristic length.

[0034] Optionally, the yarn material parameters in the finite element model include: fiber volume fraction, elastic modulus and shear modulus in different directions, tensile strength, compressive strength and shear strength in different directions.

[0035] Optionally, the larger the value of the damage evolution coefficient is, the higher the failure degree of the braided composite material is; wherein, when the damage evolution coefficient is 0, it indicates that the braided composite material is intact, and when the damage evolution coefficient is 1, it indicates that the braided composite material has completely failed.

[0036] Optionally, the woven composite material is a 2.5D woven composite material.

[0037] Compared with the prior art, the present invention has the following advantages and technical effects:

[0038] The present invention establishes a macro- and micro-integrated simulation and analysis method for woven composite materials, which can effectively simulate the failure judgment and damage evolution process of composite woven materials, and can effectively generate accurate damage evolution simulation results of woven composite materials. The present invention analyzes the macro- and micro-mechanical behaviors and failure modes of woven composite material structures, establishes a composite material structure mechanical model and failure assessment criteria, develops a multi-scale failure prediction method and analysis system for composite material structures, reduces the cost of composite material physical testing, accelerates structure selection and verification speed, and provides a multi-scale simulation method for mechanical property analysis and structural design of woven composite material structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0040] Figure 1 Defining warp and weft yarn properties for the Texgen software of an embodiment of the present invention;

[0041] Figure 2 This is a unit cell model of a braided composite material RVE established by Texgen software and abaqus software in an embodiment of the present invention. DETAILED DESCRIPTION

[0042] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0043] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0044] The present invention provides a microscopic modeling and calculation analysis method for woven composite materials, which belongs to the field of simulation and calculation methods. At present, woven composite materials have been widely used in various advanced equipment. In view of the multi-mode, multi-scale, mutual coupling and other characteristics of damage and failure of woven composite materials under load, the present invention establishes a macro-micro integrated simulation and analysis method for woven composite materials, analyzes the macro-micro mechanical behavior and failure mode of woven composite material structures, aims to establish a composite material structure mechanical model and failure assessment criteria, develop a composite material structure multi-scale failure prediction method and analysis system, reduce the cost of composite material physical testing, accelerate the structure selection and verification speed, and provide a multi-scale simulation method for mechanical performance analysis and structural design of woven composite material structures.

[0045] The present invention proposes a multi-scale simulation analysis method for composite structures with micro-macro integration. In terms of micromechanics, if fiber fluctuations are not considered, woven composite materials can be regarded as isotropic materials in the transverse direction, and the 1 direction represents the axial direction of its fiber bundle, which is defined as a unidirectional composite material. When judging its failure behavior, the above definition becomes particularly important, and Hooke's law is also applicable to fiber bundle composite materials. On this basis, four damage modes applicable to fiber bundles are predicted by combining the Hashin criterion with the Hou criterion. In terms of damage evolution, it is believed that when the stress state of a unit in the model satisfies the damage initiation criterion equation, the unit is damaged. The destruction of the predefined material is not based on the occurrence of damage as a criterion, and the default material gradually loses its bearing capacity. The damage evolution part in the three-dimensional progressive damage model is established according to the Murakami-Ohno damage theory. Through the above scheme, the damage of the composite woven material can be effectively judged, and the damage evolution coefficient describing the stiffness degradation during the damage evolution process is analyzed and calculated to characterize its evolution process. Multi-scale simulation of the macro- and micro-mechanical responses and failure modes of braided composites under loads has been achieved, providing an effective tool for predicting the structural performance of braided composites.

[0046] The above technical solution of the present invention is described in detail in combination with relevant parameters:

[0047] The present invention mainly aims at the multi-mode, multi-scale, and mutual coupling characteristics of damage failure of woven composite materials under load, and establishes a macro-micro integrated simulation analysis system for woven composite materials to analyze the macro-micro mechanical behavior and failure mode of woven composite materials. It aims to establish a composite material structure mechanical model and failure assessment criteria, develop a multi-scale failure prediction method and analysis system for composite material structures, reduce the cost of composite material physical testing, accelerate the speed of structure selection and verification, and provide a multi-scale simulation method for mechanical performance analysis and structural design of woven composite materials. A woven composite material micro-modeling method, the method specifically includes the following steps:

[0048] 1. Micromechanical model establishment

[0049] The warp yarn layer and the bias yarn layer in the multi-scale finite element model are equivalent to the warp yarn fibers, and the weft yarn layer is equivalent to the weft yarn fibers. The fiber bundle of the 2.5D woven composite material is composed of carbon fiber filaments and epoxy matrix. The cross-section is isotropic in the plane. Therefore, without considering the fluctuation of the fiber bundle, it is regarded as a transversely isotropic material. The axial direction of the fiber bundle is specified as 1, and the transverse directions are 2 and 3 respectively, which is defined as a unidirectional composite material.

[0050] After homogenization, the volume of each part of the sub-unit cell model must have changed significantly, so it is necessary to recalculate the fiber volume fraction in the minimum structure including warp and weft yarns. Fib Calculated by the following formula:

[0051] (1)

[0052] R is the radius of the carbon fiber, K is the number of fibers contained in each bundle of yarn, and D is the total length of the fiber bundle in a unit cell. In this multi-dimensional model, a single fiber bundle is composed of the superposition of the minimum structure, and the volume obtained by superimposing the volume of the minimum structure is V Ele It is easy to obtain that the volume fraction of the fiber bundle in the model is:

[0053] (2)

[0054] After obtaining the fiber volume fractions of the warp and weft yarns respectively, their stiffness and strength parameters were calculated using Huang's bridging model.

[0055] Axial tensile strength:

[0056]

[0057] Axial compressive strength:

[0058]

[0059] Transverse tensile strength:

[0060]

[0061] Transverse compression strength:

[0062]

[0063] In-plane shear strength:

[0064]

[0065] Where: and is the volume fraction of fiber and matrix; , , are the longitudinal, transverse and shear moduli of the fiber; is the elastic modulus of the matrix; , , , , They are the tensile and compressive strength of the fiber, and the tensile, compressive, and shear strength of the matrix; and are the transverse tensile stress concentration factor and the transverse compressive stress concentration factor of the substrate respectively; α is a bridging parameter, which can generally be taken between 0.4 and 0.5, and is taken as 0.45 in the present invention.

[0066] Table 1 shows the material parameters of the multi-scale model yarn.

[0067] Table 1

[0068]

[0069] 2. Establishment of fiber bundle injury model

[0070] When using a microscopic finite element model to analyze the failure behavior of a woven composite material, the fiber bundle can usually be regarded as a transversely isotropic unidirectional composite material. The stress-strain relationship of the fiber bundle composite material satisfies the three-dimensional orthotropic Hooke's law. On this basis, the progressive damage model is used to describe the damage initiation and damage evolution process in the fiber bundle. The composite failure initiation criterion used in the present invention is the Hashin failure criterion combined with the Hou failure criterion, which can predict four different modes of damage behavior that may occur in the fiber bundle, including fiber tensile damage, fiber compression damage, matrix tensile damage and matrix compression damage. The damage initiation criterion for each damage mode is shown in formulas (3) to (6).

[0071] (1) Fiber tensile failure

[0072] (3)

[0073] (2) Fiber compression failure

[0074] (4)

[0075] (3) Matrix tensile failure

[0076] (5)

[0077] (4) Matrix compression failure

[0078] (6)

[0079] In the above formula, e ft , e fc , e mt and e mc are the damage indices corresponding to the four different damage modes. 1t , F 1c , F 2t , F 2c , F ls and F ts They represent the axial tensile strength, axial compressive strength, transverse tensile strength, transverse compressive strength, longitudinal shear strength and transverse shear strength of the fiber bundle material respectively. The coefficient α in formula (3) is used to describe the influence of shear stress on the fiber tensile failure of the material. The larger α is, the greater the influence of shear stress on the fiber tensile failure of the material. σ ab It represents the stress tensor generated in the b direction when a load per unit area, i.e. stress, is applied in the a direction.

[0080] 3. Damage evolution definition

[0081] When the stress state at a certain point in the fiber bundle (a certain unit in the model) satisfies any damage initiation criterion equation, it is considered that the corresponding mode of damage has occurred at that point (the unit). After damage occurs, the material will not be destroyed immediately, but will gradually lose its bearing capacity. This process is implemented in the numerical model through a progressive damage model, that is, the damage evolution coefficient d is used to characterize the degree of degradation of the stiffness matrix of the damaged unit. This damage evolution coefficient can be used to characterize the degree of damage of the unit, and the damage evolution coefficient is strongly related to the real-time stress state of the unit. In order to predict the stiffness degradation process of the material after damage occurs, the present invention establishes the damage evolution part in the three-dimensional progressive damage model based on the Murakami-Ohno damage theory, as shown in Table 2, which is the calculation formula for the equivalent displacement and equivalent stress corresponding to the four damage modes.

[0082] Table 2

[0083]

[0084] Among them, ε ab It represents the strain tensor generated in the b direction when stress is applied in the a direction; Represents the unit characteristic length; , , , They represent the equivalent displacements corresponding to fiber tensile damage, fiber compression damage, matrix tensile damage, and matrix compression damage, respectively. , , , They represent the equivalent stresses corresponding to fiber tensile damage, fiber compression damage, matrix tensile damage, and matrix compression damage, respectively.

[0085] Once a certain damage meets its failure criterion, continued loading will cause the material stiffness to decrease. In the damage evolution expression of this model, by introducing the characteristic element length (the cube root of the solid unit volume), the fracture energy of the unit can be calculated. :

[0086]

[0087] in: and are the equivalent failure strength and equivalent failure strain respectively; is the unit characteristic length. Based on the fracture energy and the equivalent stress at failure, the corresponding equivalent failure displacement can be obtained, and the evolution of the damage variable of the unit can be obtained based on the linear relationship of the equivalent failure displacement:

[0088]

[0089] Where: d i represents the damage evolution coefficient under the corresponding failure mode, i represents the corresponding failure mode, i.e., damage mode, including fiber tensile damage, fiber compression damage, matrix tensile damage, matrix compression damage: ft, fc, mt, mc; represents the equivalent failure displacement under the corresponding failure mode; represents the equivalent damage initiation displacement of the corresponding failure mode; It represents the real-time equivalent displacement of the corresponding failure mode.

[0090] After the damage starts, the progressive degradation of the composite material properties can be described by a second-order symmetric tensor matrix containing the damage variables, where =0 means the material is intact, =1 means that the material has completely failed. The software implementation of the above simulation calculation scheme of the present invention is:

[0091] like Figure 1 As shown in the figure, first, the mesoscopic model and damage evolution definition are oriented to 2.5D woven composites. The mesoscopic RVE model of 2.5D woven composites can be directly modeled by Texgen software, which is specially designed for micro-structure modeling of woven composites and has high interface compatibility with the subsequent finite element calculation and analysis software abaqus. The .inp file corresponding to the model can be directly exported for abaqus to read.

[0092] The micro-model was established in Texgen software and imported into abaqus in the subsequent calculation and analysis process. Through the wizard modeling method, the cross-sectional shape, number and distance of the warp and weft yarns can be defined. In this step, the Texgen tool is used to draw the braided fiber model. When defining the warp and weft yarn properties, the relevant parameters are set and the weft yarn data is input: Yarn number: 4; Number of Yarns Layers: 4; Yarn Spacing: 1; Yarn width: 0.8; Yarn height: 0.1; Ellipse Section Power: 0.6; Input bonding yarn data: Yarn width: 0.4; Yarn height: 0.05; Yarn Spacing: 0.5; Gap size: 0.0; Number of Binder Yarns Layers: 4; Ellipse Section Power: 0.6; and the number of layers through which the weft yarn passes and the weaving order of each layer can be defined by dragging and dropping, and finally the expected braided structure model is obtained as shown in the figure. Figure 2 The display of the RVE model of the braided composite material in Texgen software and abaqus software is shown as follows. Figure 2 As shown in (a) and (b).

[0093] Secondly, this method can be used to define the damage evolution in the ABAQUS software through user subroutines. The initial damage judgment criteria and damage evolution criteria of the fiber and matrix can be defined through the umat (implicit calculation) / vumat (explicit calculation) material subroutines provided by the ABAQUS software. Among them, the required yarn material parameters are provided by Table 1, the damage evolution mode is provided by Table 2, and the initial damage judgment criteria are provided by formulas (3)-(6).

[0094] Then, through finite element mesh node pairing, the nodes of the opposite end faces of the input unit cell finite element mesh model are paired to obtain a paired node group, and the reference node degrees of freedom for defining boundary conditions are created to achieve the periodic boundary condition definition of the RVE model. In the case of a large number of unit cells, it is necessary to use the Python program to locate the unit cell boundary nodes in the .inp file and give periodic boundary condition constraints.

[0095] Finally, in the “load module” of abaqus, load is applied to the macroscopic overall structure according to the required loading conditions, and the simulation analysis is submitted to complete the computational analysis.

[0096] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A microscopic modeling and calculation analysis method for braided composite materials, characterized in that: include: The braided composite material is simulated and modeled by the finite element analysis method to obtain a finite element model of the composite material; Calculating the volume fraction of the fiber bundle in the finite element model, and obtaining performance parameters through a stiffness and strength theoretical model based on the volume fraction calculation result; Based on the failure initiation criterion, judging whether a damage mode occurs according to the performance parameter, wherein the failure initiation criterion is a failure criterion; When a damage mode appears, the damage mode is evolved through a three-dimensional progressive damage model, and based on the evolution results, the simulation results of the damage evolution coefficient of the braided composite material are obtained.

2. The method according to claim 1, characterized in that The process of volume fraction calculation includes: In the finite element model, the volume V of the fiber bundle is Fib Perform the calculation: Where R is the radius of the carbon fiber, K is the number of fibers contained in each bundle of yarn, and D is the total length of the fiber bundle in a unit cell. A single fiber bundle is composed of the superposition of the minimum structure, and the volume V is obtained by superimposing the volume of the minimum structure. Ele , the volume fraction of the fiber bundle V f for: 。 3. The method according to claim 1, characterized in that The failure initiation criterion is a combination of the Hashin failure criterion and the Hou failure criterion. The damage modes corresponding to the failure initiation criterion include fiber tensile failure, fiber compression failure, matrix tensile failure and matrix compression failure.

4. The method according to claim 3, characterized in that The failure initiation criteria corresponding to different damage modes are: Fiber tensile failure Fiber compression failure Matrix tensile failure Matrix compression failure Among them, e ft , e fc , e mt and e mc is the damage index corresponding to the damage modes of fiber tensile failure, fiber compression failure, matrix tensile failure and matrix compression failure, F 1t , F 1c , F 2t , F 2c , F ls and F ts They represent the axial tensile strength, axial compressive strength, transverse tensile strength, transverse compressive strength, longitudinal shear strength and transverse shear strength of the fiber bundle material respectively. α is the coefficient used to describe the effect of shear stress on the fiber tensile failure of the material. σ ab It represents the stress tensor generated in the b direction when stress is applied in the a direction.

5. The method according to claim 1, characterized in that A three-dimensional progressive damage model is constructed based on the Murakami-Ohno damage model, and the damage mode is evolved through the three-dimensional progressive damage model.

6. The method according to claim 5, characterized in that The process of obtaining the damage evolution coefficient of braided composite materials includes: Where: d i represents the damage evolution coefficient under the corresponding failure mode, i represents the corresponding failure mode; represents the equivalent failure displacement under the corresponding failure mode; represents the equivalent damage initiation displacement of the corresponding failure mode; It represents the real-time equivalent displacement of the corresponding failure mode.

7. The method according to claim 6, characterized in that Equivalent failure displacement based on fracture energy The equivalent stress at failure is calculated; The fracture energy for: ； in: and are the equivalent failure strength and equivalent failure strain, respectively. is the element characteristic length.

8. The method according to claim 1, characterized in that The yarn material parameters in the finite element model include: fiber volume fraction, elastic modulus and shear modulus in different directions, tensile strength, compressive strength and shear strength in different directions.

9. The method according to claim 1, characterized in that: The larger the value of the damage evolution coefficient is, the higher the failure degree of the braided composite material is; wherein, when the damage evolution coefficient is 0, it indicates that the braided composite material is intact, and when the damage evolution coefficient is 1, it indicates that the braided composite material is completely failed.

10. The method according to claim 1, characterized in that The braided composite material is a 2.5D woven composite material.

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