Ceramic matrix composite matrix crack density calculation method

Abstract

The invention discloses a method for calculating the crack density of a ceramic matrix composite matrix. The method comprises the following steps: calculating the saturated crack density of the ceramic matrix composite matrix in different temperature environments; based on the saturated crack density of the ceramic matrix composite matrix in different temperature environments, fitting to obtain a relational expression of the saturated crack density and the temperature; analyzing the interface debonding conditions of the ceramic matrix composite material under different stress conditions, and fitting the interface debonding conditions to a relational expression of an interface debonding coefficient and stress; and correcting the Weibull distribution model based on the relational expression of the saturated crack density and the temperature and the relational expression of the interface debonding coefficient and the stress according to the change condition of the interface debonding, constructing a relation model of the change of the crack density of the ceramic-based composite material along with the stress and the temperature, and calculating the crack density of the ceramic-based composite material matrix. The method can accurately calculate the matrix crack density of the ceramic matrix composite material in different high-temperature load environments.

Description

Technical Field

[0001] The present invention relates to the technical field of mechanical property calculation of ceramic matrix composite materials, and in particular to a method for calculating matrix crack density of ceramic matrix composite materials. Background Art

[0002] Continuous fiber-reinforced ceramic matrix composites (CMCs) have become the material of choice for next-generation aircraft engine hot-end components due to their high specific strength, high specific modulus, and high-temperature resistance. As brittle materials, cracks and their propagation in CMCs affect various mechanical properties. Therefore, studying the evolution of CMC crack characteristics is crucial. Accurately calculating the matrix crack density of CMCs under service conditions is a key technology for simulating their mechanical properties.

[0003] Critical strain energy criteria and probabilistic statistical methods are currently commonly used to predict matrix cracking in ceramic matrix composites. However, the critical strain energy criterion cannot accurately predict the initial matrix cracking process, and the selection of load steps has a significant impact on the prediction results of probabilistic statistical methods. Moreover, the hysteresis effect of interface debonding on matrix cracking is not considered. In addition, the invention with publication number CN114943148B proposes a method for predicting the interface properties of fiber-reinforced ceramic matrix composites using tangent modulus, and discloses the application of an improved Weibull distribution model to cracks and stress. However, in this invention, the Weibull distribution model only considers the probability of matrix cracking. However, during the cracking process, both the original Weibull distribution model and the improved Weibull distribution model assume that the cracking probability is only related to stress. In fact, during the tensile process, debonding occurs between the fiber and matrix interface, and the degree of debonding has a significant impact on the cracking probability. For example, interface debonding hinders the continued cracking of the matrix, reducing the probability of matrix cracking. Therefore, the existing Weibull distribution model is difficult to accurately simulate the matrix cracking situation.

[0004] At the same time, under high-temperature service conditions, ceramic matrix composites (CMCs) gradually lose mechanical properties due to oxidation, affecting their strength and, in severe cases, even causing structural failure. The dual effects of high temperature and stress, as well as the complex mechanism of interfacial debonding on matrix cracking, have made it difficult for researchers to develop a fast, accurate, and widely applicable method for calculating matrix crack density in CMCs. Accurately simulating the crack density of CMCs under high-temperature loading is crucial for exploring their oxidation mechanical properties. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for calculating the matrix crack density of ceramic matrix composite materials, which can accurately calculate the matrix crack density of ceramic matrix composite materials under different high temperature load environments, is convenient and fast to calculate, and has wide application.

[0006] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0007] A method for calculating the crack density of a ceramic matrix composite material, the method comprising the following steps:

[0008] S1, calculate the saturated crack density of the ceramic matrix composite matrix under different temperature environments;

[0009] S2, based on the saturated crack density of the ceramic matrix composite matrix under different temperature environments, the relationship between the saturated crack density and temperature is fitted;

[0010] S3, analyze the interface debonding of ceramic matrix composites under different stress conditions and fit the relationship between interface debonding coefficient and stress;

[0011] S4. According to the changes in interface debonding, the Weibull distribution model is modified based on the relationship between saturated crack density and temperature and the relationship between interface debonding coefficient and stress. A model for the relationship between the crack density of ceramic matrix composites and stress and temperature is constructed to calculate the crack density of the ceramic matrix composite material.

[0012] Step S1 further comprises:

[0013] By counting the matrix cracks of the ceramic matrix composite after fracture, the saturated crack density of the ceramic matrix composite matrix at room temperature and different high temperature conditions is calculated.

[0014] Furthermore, in step S2, the relationship between the saturated crack density and temperature is:

[0015] n sat，T =0.000756T+n sat0

[0016] Where T is temperature, n sat，T is the saturated crack density at temperature T, n sat0 is the saturated crack density of the ceramic matrix composite matrix at room temperature.

[0017] Furthermore, in step S3, the interface debonding of the ceramic matrix composite material under different stress conditions is analyzed by microscopic and tensile curve analysis, and the interface debonding is calculated using a Weibull distribution model; wherein the interface debonding coefficient is between 0 and 1, where 0 indicates no interface debonding and 1 indicates complete interface debonding.

[0018] Furthermore, the relationship between the interface debonding coefficient and stress is:

[0019]

[0020] Wherein, the coefficients m and σ0 are obtained by fitting the interfacial debonding of ceramic matrix composites under different stress conditions, σ is the stress value, and D is the interfacial debonding coefficient, which indicates the degree of bonding between the matrix and the fiber under different stresses. The tighter the interface bonding, the smaller the value of D, and vice versa. sat is the debonding coefficient when the load is maximum.

[0021] Furthermore, in step S4, the crack density n of the ceramic matrix composite material is T，σ The relationship model between stress σ and temperature T is:

[0022]

[0023] Where n sat，T is the saturated crack density at temperature T, D is the interface debonding coefficient, σ is the stress value, and the coefficients m and σ0 are obtained by fitting the interface debonding of ceramic matrix composites under different stress conditions.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The method for calculating the matrix crack density of ceramic-based composite materials of the present invention introduces the influencing factor of interface debonding to modify the Weibull distribution model. At the same time, combined with the relationship between saturated crack density and temperature and the relationship between interface debonding coefficient and stress, a model for the relationship between the crack density of ceramic-based composite materials and stress and temperature is constructed. Therefore, the matrix crack density of ceramic-based composite materials under different high-temperature load environments can be accurately calculated. The calculation is convenient and fast, and the application is wide. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the surface crack morphology of the ceramic matrix composite material after tensile fracture at room temperature;

[0027] Figure 2 Schematic diagram of the surface crack morphology of the ceramic matrix composite material after tensile fracture at 600℃;

[0028] Figure 3 Crack density maps of ceramic matrix composites under different stresses obtained for in situ tests;

[0029] Figure 4 Schematic diagram of the relationship between the simulated crack density and stress;

[0030] Figure 5 Schematic diagram of the relationship between crack density and stress simulated by the Weibull distribution model based on debonding. DETAILED DESCRIPTION

[0031] The embodiments of the present invention are described in further detail below with reference to the accompanying drawings.

[0032] The present invention discloses a method for calculating the crack density of a ceramic matrix composite material, the method comprising the following steps:

[0033] S1, calculate the saturated crack density of the ceramic matrix composite matrix under different temperature environments;

[0034] S2, based on the saturated crack density of the ceramic matrix composite matrix under different temperature environments, the relationship between the saturated crack density and temperature is fitted;

[0035] S3, analyze the interface debonding of ceramic matrix composites under different stress conditions and fit the relationship between interface debonding coefficient and stress;

[0036] S4. According to the changes in interface debonding, the Weibull distribution model is modified based on the relationship between saturated crack density and temperature and the relationship between interface debonding coefficient and stress. A model for the relationship between the crack density of ceramic matrix composites and stress and temperature is constructed to calculate the crack density of the ceramic matrix composite material.

[0037] The following is combined with Figure 1 To the attached Figure 5 The steps of the method for calculating the matrix crack density of the ceramic-based composite material of the present invention are described in detail.

[0038] (1) Calculation of the saturated crack density of the ceramic matrix composite matrix under different temperature environments

[0039] By counting the cracks in the ceramic matrix composite material after fracture, the saturated crack density of the ceramic matrix composite material matrix at room temperature and different high temperature conditions is calculated. In this embodiment, the high temperature condition is not specifically limited and is determined according to the working environment temperature of the ceramic matrix composite material matrix. Figure 1 Schematic diagram of the surface crack morphology of the ceramic matrix composite material after tensile fracture at room temperature; Figure 2 Schematic diagram of the surface crack morphology of the ceramic matrix composite material after tensile fracture at 600℃. Figure 1 and Figure 2 In the figure, the yellow lines indicate the cracks and the corresponding cracking directions.

[0040] (2) Fitting the relationship between saturated crack density and temperature

[0041] In this step, the relationship between saturated crack density and temperature is fitted by the saturated crack density under different temperature environments. The relationship between saturated crack density and temperature is expressed as:

[0042] n sat，T =0.000756T+n sat0

[0043] Where t is temperature, n issat，T is the saturated crack density at temperature T, n sat0 is the saturated crack density of the ceramic matrix composite matrix at room temperature.

[0044] (3) Fitting to the relationship between interface debonding coefficient and stress

[0045] In this step, the interface debonding of the ceramic matrix composite material under different stress conditions is analyzed through microscopic and tensile curves, and the interface debonding is calculated using the Weibull distribution model; wherein the interface debonding coefficient is between 0 and 1, where 0 means no interface debonding and 1 means complete interface debonding. Figure 3 The crack density diagram of ceramic matrix composites under different stresses obtained from in-situ tests. The relationship between the interface debonding coefficient and stress is expressed as:

[0046]

[0047] Where D is the interface debonding coefficient, which ranges from 0 to 1. As stress increases, the more severe the interface debonding becomes, the larger the D value becomes. The relationship between D and stress is expressed using the Weibull distribution model. sat is the debonding coefficient at maximum load, σ is the stress value; the coefficients m and σ0 are obtained by fitting the test data during the in-situ test to adapt to different matrix materials. Figure 3 For example, the fitted m=5,σ0=130MPa. Figure 4 Schematic diagram of the relationship between simulated crack density and stress.

[0048] (IV) Constructing a model for the relationship between crack density of ceramic matrix composites and stress and temperature

[0049] According to the change of interface debonding, a Weibull distribution model for calculating the crack density of ceramic matrix composites is established to calculate the relationship between the crack density of ceramic matrix composites and stress and temperature. T，σ The relationship model between stress σ and temperature T is:

[0050]

[0051] Where: D is the interface debonding coefficient. The smaller D is, the lighter the debonding degree is. The larger D is, the more serious the debonding degree is. In the first linear section under the load, there is basically no debonding at the interface. When entering the second linear section, the interface gradually debonds. As the load increases, the interface debonding reaches saturation. Continuing to increase the load will cause the fiber to break gradually. In this example, due to the debonding coefficient D at the maximum load, sat =1, the value of the interface debonding coefficient D is set to 0-1. Figure 5 Schematic diagram of the relationship between crack density and stress simulated by the Weibull distribution model based on debonding.

[0052] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present application.

[0053] Obviously, those skilled in the art may make various changes and modifications to this application without departing from the spirit and scope of this application. Thus, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalents, this application is intended to include these modifications and variations.

Claims

1. A method for calculating the matrix crack density of a ceramic matrix composite material, characterized in that: The method comprises the following steps: S1, calculate the saturated crack density of the ceramic matrix composite matrix under different temperature environments; S2, based on the saturated crack density of the ceramic matrix composite matrix under different temperature environments, the relationship between the saturated crack density and temperature is fitted; S3, analyze the interface debonding of ceramic matrix composites under different stress conditions and fit the relationship between interface debonding coefficient and stress; S4. According to the changes in interface debonding, the Weibull distribution model is modified based on the relationship between saturated crack density and temperature and the relationship between interface debonding coefficient and stress. A model for the relationship between the crack density of ceramic matrix composites and stress and temperature is constructed to calculate the crack density of the ceramic matrix composite material.

2. The method for calculating the matrix crack density of a ceramic matrix composite material according to claim 1, wherein: Step S1 further comprises: By counting the matrix cracks of the ceramic matrix composite after fracture, the saturated crack density of the ceramic matrix composite matrix at room temperature and different high temperature conditions is calculated.

3. The method for calculating the matrix crack density of ceramic matrix composite materials according to claim 1, characterized in that: In step S2, the relationship between the saturated crack density and temperature is: n sat,T =0.000756T+n sat0 Where T is temperature, n sat,T is the saturated crack density at temperature T, n sat0 is the saturated crack density of the ceramic matrix composite matrix at room temperature.

4. The method for calculating the matrix crack density of a ceramic matrix composite material according to claim 1, wherein: In step S3, the interface debonding of the ceramic matrix composite material under different stress conditions is analyzed by microscopic and tensile curve analysis, and the interface debonding is calculated using a Weibull distribution model; wherein the interface debonding coefficient is between 0 and 1, where 0 indicates no interface debonding and 1 indicates complete interface debonding.

5. The method for calculating the matrix crack density of a ceramic matrix composite material according to claim 1 or 4, characterized in that: The relationship between the interface debonding coefficient and stress is: Wherein, coefficients m and σ0 are obtained by fitting the interface debonding of ceramic matrix composites under different stress conditions, D is the interface debonding coefficient, and D sat is the debonding coefficient when the load is maximum, and σ is the stress value.

6. The method for calculating the matrix crack density of a ceramic matrix composite material according to claim 1 or 4, characterized in that: In step S4, the crack density n of the ceramic matrix composite material is T,σ The relationship model between stress σ and temperature T is: Where n sat,T is the saturated crack density at temperature T, D is the interface debonding coefficient, σ is the stress value, and the coefficients m and σ0 are obtained by fitting the interface debonding of ceramic matrix composites under different stress conditions.

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