Airflow denudation behavior analysis method for 2.5 D woven C / C composite material

Abstract

The invention discloses a 2.5 D woven C / C composite material airflow denudation behavior analysis method, and relates to the field of structural damage identification, and the method comprises the steps: constructing a 2.5 D woven C / C composite material geometric model; constructing an airflow denudation analysis geometric model based on the 2.5 D woven C / C composite material geometric model; analyzing the mechanical response of the 2.5 D woven C / C composite material under the action of the aerodynamic load based on a mesomechanics and damage mechanics method; applying an aerodynamic load acting force and a fixed constraint boundary condition to the airflow denudation analysis geometric model; judging the failure state of the 2.5 D woven C / C composite material according to the mechanical response of the 2.5 D woven C / C composite material under the action of the aerodynamic load; and when the 2.5 D woven C / C composite material is completely invalid, the pneumatic load at the moment is defined as the limit pneumatic load value when the 2.5 D woven C / C composite material is subjected to airflow denudation. According to the method, the 2.5 D woven C / C composite material airflow denudation analysis geometric model is constructed, so that the 2.5 D woven C / C composite material airflow denudation behavior is simulated, and the mechanism of 2.5 D woven C / C composite material airflow denudation is effectively revealed.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of structural damage identification, and particularly relates to a 2.5D woven C / C composite material airflow ablation behavior analysis method. BACKGROUND

[0002] C / C composite material has the characteristics of low density, ablation resistance and excellent thermodynamic performance, and is widely used in industrial manufacturing. 2.5D woven C / C composite material is first woven into a fabric (preform) according to a certain interweaving rule by using weaving technology, and then deposited by a matrix to form a composite material. 2.5D woven composite material has the advantages of strong anti-delamination ability, simple process, low production cost, high mechanical performance and strong designability, and is one of the most potential thermal protection candidate materials. In a high-speed airflow environment, C / C composite material first suffers from serious airflow heat effect, and a series of thermochemical ablation reactions such as carbon-oxygen reaction, carbon-nitrogen reaction and carbon sublimation occur on the surface of the material, and the heat on the surface of the aircraft is taken away through the mass loss of the material, thereby achieving the effect of thermal protection. Due to the difference in ablation rate of the components of the C / C composite material and the influence of the microstructure characteristics, the surface roughness phenomenon will occur on the surface of the material during the thermochemical ablation process. Then, the rough surface will undergo airflow ablation under the action of high-speed airflow, thereby causing a large amount of material loss and greatly reducing the thermal protection effect.

[0003] In the past research on the thermal protection performance of 2.5D woven C / C composite material, the thermochemical ablation performance of the material is analyzed and evaluated, but the analysis of the airflow ablation behavior is usually simplified or replaced by a semi-empirical formula, which leads to a certain deviation in the evaluation of the thermal protection performance of 2.5D woven C / C composite material, and cannot reveal the mechanism of airflow ablation, which brings great trouble to the actual application. SUMMARY

[0004] In view of the above problems in the prior art, the 2.5D woven C / C composite material airflow ablation behavior analysis method provided by the present application solves the problem that the prior art cannot accurately analyze the airflow ablation behavior of 2.5D woven C / C composite material and has high test cost.

[0005] In order to achieve the above-mentioned application purposes, the technical scheme adopted by the present application is as follows: a 2.5D woven C / C composite material airflow ablation behavior analysis method, comprising: constructing a 2.5D woven C / C composite material geometric model; constructing an airflow ablation analysis geometric model based on the 2.5D woven C / C composite material geometric model; analyzing the mechanical response of 2.5D woven C / C composite material under the action of aerodynamic load based on the methods of micromechanics and damage mechanics; Applying aerodynamic load action force and fixed constraint boundary conditions to the gas flow ablation analysis geometric model; According to the mechanical response of the 2.5D woven C / C composite material under the action of the aerodynamic load, the failure state of the 2.5D woven C / C composite material is determined. When the 2.5D woven C / C composite material is completely failed, the aerodynamic load at this time is defined as the limit aerodynamic load value when the 2.5D woven C / C composite material occurs gas flow ablation.

[0006] Further: the gas flow ablation analysis geometric model is constructed based on the local region of the 2.5D woven C / C composite material geometric model; the 2.5D woven C / C composite material includes yarns and matrix at the mesoscale, and the cross section and path of the yarns in the 2.5D woven C / C composite material are morphologically equivalent during the construction of the gas flow ablation analysis geometric model.

[0007] Further: the damage-containing constitutive relationship of the yarns and the matrix under the action of the aerodynamic load is:

[0008]

[0009] wherein, is the stress tensor of the yarns, is the damage-containing variable stiffness matrix of the yarns, is the damage variable of the yarns, is the strain tensor of the yarns, is the stress tensor of the matrix, is the damage-containing variable stiffness matrix of the matrix, is the damage variable of the matrix of the yarns, is the strain tensor of the matrix.

[0010] Further: the specific method of applying the aerodynamic load action force to the gas flow ablation analysis geometric model is to apply the aerodynamic load action force to the side surface of the warp yarns in the gas flow ablation analysis geometric model.

[0011] Further: the specific method of applying the fixed constraint boundary conditions to the gas flow ablation analysis geometric model is to apply the periodic displacement boundary conditions to the four side surfaces of the gas flow ablation analysis geometric model; for a pair of corresponding boundary surfaces of the local region of the 2.5D woven C / C composite material, the expression of the periodic displacement boundary conditions is:

[0012]

[0013] wherein, and are the displacement components along the x and y directions respectively. Xj displacement of the axis in the positive and negative directions, is the average strain, and is the periodic displacement along X j coordinates of the axis at the interface between the positive and negative directions, is the correction amount of the periodic displacement.

[0014] The beneficial effects of the present application are: 1. The present application realizes the simulation of the gas flow ablation behavior of 2.5D woven C / C composite materials by constructing a 2.5D woven C / C composite material gas flow ablation analysis geometric model. Based on advanced geometric modeling techniques and numerical analysis methods, this model can accurately simulate the complex process of the interaction between the gas flow and the surface of the composite material, including the gas flow velocity, pressure distribution, and the ablation response of the material surface. Through this simulation, researchers can adjust and optimize different gas flow parameters (such as flow rate, temperature, pressure) and material properties (such as fiber arrangement, matrix density) in a virtual environment, thereby predicting the impact of gas flow ablation on material performance.

[0015] 2. Compared with traditional high-cost experimental methods, the simulation technology of the present application has significant advantages. It not only saves a lot of time and resources, but also can provide more comprehensive and detailed analysis results. Through simulation, researchers can quickly evaluate the impact of different design parameters on the thermal protection performance of 2.5D woven C / C composite materials, thereby providing strong support for the optimized design of materials. In addition, this model can effectively reveal the micro-mechanism of 2.5D woven C / C composite materials in the process of gas flow ablation, helping researchers better understand the failure mode and damage evolution law of materials in extreme environments.

[0016] 3. The implementation of the present application not only improves the thermal protection performance evaluation capability of 2.5D woven C / C composite materials, but also provides important technical support for high-tech fields such as aerospace, national defense, etc. Through in-depth research on gas flow ablation phenomena, the structure design of composite materials can be further optimized, and their service life and reliability in high-temperature, high-speed airflow environments can be improved. In addition, this technology can also be popularized to the research of other composite materials, providing reference and reference for the technical progress of related fields. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 A flowchart of a 2.5D woven C / C composite material gas flow ablation behavior analysis method provided for an embodiment; Figure 2 A 2.5D woven C / C composite material geometric model constructed; Figure 3 A gas flow ablation analysis geometric model; Figure 4Schematic diagram for applying aerodynamic load force and fixing constraint boundary condition; Figure 5 Damage and failure cloud atlas of 2.5D woven C / C composite under aerodynamic load. DETAILED DESCRIPTION

[0018] The specific embodiments of the present application are described below to facilitate the understanding of the present application for those skilled in the art, but it should be clear that the present application is not limited to the scope of the specific embodiments, and for those skilled in the art, any changes within the spirit and scope of the present application defined and determined by the appended claims are obvious, and all the inventions utilizing the concept of the present application are within the scope of protection.

[0019] As shown in the drawings, Figure 1 In one embodiment of the present application, a 2.5D woven C / C composite airflow ablation behavior analysis method includes the following steps: S1, constructing a 2.5D woven C / C composite geometric model in Texgen software.

[0020] As shown in the drawings, Figure 2 The constructed 2.5D woven C / C composite geometric model contains two parts of yarn and matrix at the mesoscale, the yarn is divided into two types of warp and weft, the yarn along the Y direction and parallel to the material surface is weft, the yarn along the X direction and interlaced with different layers of weft is warp, the warp has a certain distribution in the thickness Z direction, which plays a certain anti-delamination shear role for the weft. The cross section of the yarn is elliptical, and the cross section shape and size of all warps and wefts are consistent.

[0021] S2, constructing an airflow ablation analysis geometric model based on the 2.5D woven C / C composite geometric model.

[0022] In the ablation process of C / C composite, the ablation resistance of the matrix is weaker than that of the yarn, resulting in a faster surface recession rate of the matrix than that of the yarn. Therefore, ablation will make the surface of the C / C composite rough, and the rough surface will be ablated under the action of airflow shear. The geometric model for airflow ablation analysis needs to be established on the basis of the micro-thermal chemical ablation morphology.

[0023] Therefore, the following factors need to be considered when establishing the airflow ablation analysis geometric model: (1) the ablation resistance of the matrix is weaker than that of the yarn, so the surface recession of the matrix is faster than that of the yarn; (2) since the weft is parallel to the material surface, without the constraint of the warp, the weft has little anti-ablation ability; (3) at the microscale, the yarn is composed of fibers and matrix, without the constraint of the warp, the part of the weft higher than the matrix will be directly ablated by the airflow in the ablation process.

[0024] In summary, the airflow ablation analysis of 2.5D woven composite material is mainly to analyze the stress state of warp yarn under the action of aerodynamic load.

[0025] Based on the microstructure characteristics and micro-surface ablation behavior of 2.5D woven composite material, the airflow ablation analysis geometric model is established as shown in Figure 3 Figure 3 Fig. 1 is a schematic diagram of the position of the airflow ablation analysis geometric model in the 2.5D woven C / C composite material geometric model, Fig. 1(b) is the airflow ablation analysis geometric model, Fig. 1(c) is the geometric model of the yarn in the airflow ablation analysis geometric model, and Fig. 1(d) is the geometric model of the matrix in the airflow ablation analysis geometric model. In order to simplify the airflow ablation analysis, the cross section and path of the yarn are subjected to morphological equivalent treatment, which is convenient for the construction and meshing of the geometric model.

[0026] S3, based on the method of micromechanics and damage mechanics, the mechanical response of 2.5D woven C / C composite material under the action of aerodynamic load is analyzed.

[0027] According to the theory of micromechanics and damage mechanics, the yarn is regarded as a transversely isotropic homogeneous body, and the matrix is regarded as an isotropic homogeneous body. The yarn and the matrix both adopt linear elastic constitutive relation. The damage-containing constitutive relation of the yarn and the matrix under the action of aerodynamic load is:

[0028]

[0029] wherein, is the stress tensor of the yarn, is the damage-containing stiffness matrix of the yarn, is the damage variable of the yarn, is the strain tensor of the yarn, is the stress tensor of the matrix, is the damage-containing stiffness matrix of the matrix, is the damage variable of the matrix, is the strain tensor of the matrix.

[0030] S4, the aerodynamic load and the fixed constraint boundary condition are applied to the airflow ablation analysis geometric model.

[0031] as shown in Figure 4 ​As shown, aerodynamic loads are applied to the sides of the warp yarns at the top of the geometric model for airflow erosion analysis, and fixed constraint boundary conditions are applied to the bottom surface of the model. Since the geometric model for airflow erosion analysis is taken from a local region of a 2.5D woven C / C composite material, periodic displacement boundary conditions are applied to the four sides of the model to ensure the continuity of displacement and stress. The expression for the periodic displacement of a pair of corresponding boundary surfaces in a local region of the composite material is as follows:

[0032]

[0033] in, and For along X j Displacement in the positive and negative directions of the axis. For average strain, and For along X j The coordinates of the boundary surfaces in the positive and negative directions of the axis. This is the correction amount for periodic displacement.

[0034] Due to the corresponding surface They are the same; the unknown can be eliminated by subtracting the two calculations above. :

[0035] This represents the distance between the corresponding faces.

[0036] S5. Determine the failure state of 2.5D woven C / C composite material based on the mechanical response of 2.5D woven C / C composite material under aerodynamic load.

[0037] The entire mechanical response process of the 2.5D woven C / C composite material under aerodynamic loading was performed in Abaqus software. The mechanical property parameters of the component materials, carbon fiber bundles and carbon matrix, were set, and the solution type was set to static analysis. Damage contour maps of the yarn and matrix were generated based on the mechanical response of the 2.5D woven C / C composite material under aerodynamic loading, as shown below. Figure 5 As shown, (a) is the initial damage cloud diagram of the yarn, at which point the aerodynamic load value is 0, and the material is not damaged. Figure 5 As shown in (b), with the increase of aerodynamic load, the material will experience damage and failure, but the entire material has not yet completely failed. Figure 5 As shown in (c), further increasing the aerodynamic load value will cause the material to fail completely when the aerodynamic load increases to a certain value.

[0038] S6, when 2.5D woven C / C composite material is completely failed, define the aerodynamic load at this time as the limit aerodynamic load value when 2.5D woven C / C composite material occurs airflow ablation.

[0039] Figure 5 (d) is the damage and failure cloud of the matrix under the action of aerodynamic load, at this time, the material is completely failed, and the aerodynamic load at this moment is defined as the limit aerodynamic load.

[0040] In summary, the application realizes the simulation of the airflow ablation behavior of the 2.5D woven composite material by constructing the airflow ablation analysis geometric model of the 2.5D woven C / C composite material, does not need to study the airflow ablation phenomenon through high-cost experiments, can improve the thermal protection performance evaluation ability of the 2.5D woven C / C composite material, and effectively reveals the mechanism of the airflow ablation of the 2.5D woven C / C composite material.

Claims

1. A method for analyzing the airflow erosion behavior of 2.5D woven C / C composite materials, characterized in that, include: Construct a 2.5D geometric model of woven C / C composite material; A geometric model for airflow erosion analysis was constructed based on a 2.5D woven C / C composite material geometric model. The mechanical response of 2.5D woven C / C composite material under aerodynamic load was analyzed based on micromechanics and damage mechanics methods. Apply aerodynamic loads and fixed constraint boundary conditions to the geometric model for airflow erosion analysis; The failure state of 2.5D woven C / C composite material is determined based on the mechanical response of 2.5D woven C / C composite material under aerodynamic load. When the 2.5D woven C / C composite material completely fails, the aerodynamic load at this time is defined as the ultimate aerodynamic load value when the 2.5D woven C / C composite material undergoes airflow erosion.

2. The method according to claim 1, characterized in that, The geometric model for airflow erosion analysis is constructed based on a local region of the geometric model of 2.5D woven C / C composite material.

3. The method according to claim 2, characterized in that, The 2.5D woven C / C composite material consists of two parts at the microscale: yarn and matrix. In the process of constructing the geometric model for airflow erosion analysis, the cross-section and path of the yarn in the 2.5D woven C / C composite material are morphologically equivalent.

4. The method according to claim 3, characterized in that, The constitutive relationship of the yarn and matrix under aerodynamic load, including damage, is as follows: in, For the stress tensor of the yarn, Let be the stiffness matrix of the yarn including damage variables. For yarn damage variables, For the strain tensor of the yarn, For the stress tensor of the matrix, Let be the stiffness matrix of the matrix containing damage variables. For the damage variable of the yarn matrix, Let be the strain tensor of the matrix.

5. The method according to claim 1, characterized in that, Applying aerodynamic loads to the airflow erosion analysis geometric model specifically involves applying aerodynamic loads to the side of the warp yarns in the airflow erosion analysis geometric model.

6. The method according to claim 1, characterized in that, Applying fixed constraint boundary conditions to the geometric model for airflow erosion analysis specifically involves applying periodic displacement boundary conditions to the four sides of the geometric model for airflow erosion analysis.

7. The method according to claim 6, characterized in that, For a pair of corresponding boundary surfaces in a local region of a 2.5D woven C / C composite material, the expression for its periodic displacement boundary condition is: in, and For along X j Displacement in the positive and negative directions of the axis. For average strain, and For along X j The coordinates of the boundary surfaces in the positive and negative directions of the axis. This is the correction amount for periodic displacement.

8. The method according to claim 1, characterized in that, The mechanical response process of 2.5D woven C / C composite material under aerodynamic load was studied in Abaqus software.

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