A unidirectional fiber reinforced ceramic matrix composite mechanical property multi-scale calculation method and system

Abstract

The application provides a unidirectional fiber reinforced ceramic matrix composite mechanical property multiscale calculation method and system. The method adopts a sequential multiscale method, obtains surface energy of a matrix material at a nanoscale through molecular dynamics, and based on periodic damage characteristics of the material at a microscale, proposes a molecular dynamics-discrete element coupling unidirectional fiber reinforced ceramic matrix composite multiscale calculation method and system. Compared with the prior art, the application fully considers nanoscale damage behavior and microcrack aggregation characteristics of the ceramic matrix composite matrix, and significantly improves the calculation accuracy of the microscale result. The application is suitable for component design, structure optimization and mechanical property prediction of the ceramic matrix composite in the field of aerospace.

Description

Technical Field

[0001] This invention belongs to the field of mechanical technology of ceramic matrix composites, and in particular, it relates to a multi-scale calculation method and system for the mechanical properties of unidirectional fiber reinforced ceramic matrix composites. Background Technology

[0002] Fiber-reinforced ceramic matrix composites (CMCs) have become ideal multifunctional materials due to their low density, high fracture toughness, and excellent thermal stability, and have been widely used in aerospace and other fields. However, the small size of the fiber filaments (several orders of magnitude smaller than the experimental sample size) and the unclear mechanical properties of the matrix make numerical calculations of the mechanical properties of CMCs very difficult, which is also a hot topic in the current research field of CMCs.

[0003] Several papers have proposed different numerical calculation methods based on the finite element method for the tensile fracture behavior of unidirectional CMC materials. These methods share the common feature of treating the matrix as a brittle material with randomly distributed tensile strength, and employing elasto-brittle constitutive relations or failure criteria to describe the matrix-fiber relationship, while using a cohesive constitutive model for the interface layer. However, the results obtained using these methods differ significantly from experimental results, especially in the tensile curves, which lack the progressive damage segment characteristic of classical tensile curves. This may be due to the lack of detailed description of the mechanical behavior of the matrix material at the nanoscale.

[0004] Molecular dynamics is considered an effective tool for investigating the mechanical behavior of materials at the nanoscale, and multi-scale computational methods based on molecular dynamics and the finite element method (FEM) have provided new insights for the development of this field. Molecular dynamics can extract the relationship between the opening displacement of interfacial crack tips and the traction force, and combined with the FEM, the mechanical responses of materials at the microscopic level, such as tension, compression, bending, and shear, can be obtained. However, this method is applicable to continuous media such as epoxy resins and metals. For materials with internally rich microcracks and discontinuous medium characteristics (such as ceramics and rocks), the FEM fails to accurately capture the stress concentration phenomenon at the internal microcracks, leading to significant deviations between the fracture mechanical response and the actual situation, and resulting in lower computational accuracy. Therefore, further research and improvement of related computational methods are urgently needed. Summary of the Invention

[0005] The purpose of this invention is to provide a multi-scale calculation method and system for the mechanical properties of unidirectional fiber-reinforced ceramic matrix composites. This method considers the nanoscale damage behavior and microcrack enrichment characteristics of the CMC material matrix, thereby improving the accuracy of the microscopic results calculation. In addition, this method is implemented using the commercial molecular dynamics software LAMMPS and the discrete element software PFC, which has strong versatility and can solve large-scale engineering problems.

[0006] The technical solution to achieve the purpose of this invention is as follows:

[0007] A multi-scale calculation method for the mechanical properties of unidirectional fiber-reinforced ceramic matrix composites includes:

[0008] S1: Based on unidirectional fiber-reinforced ceramic matrix composite samples, obtain the macroscopic mechanical parameters, microstructural parameters, and nanostructural parameters of the samples, and determine the matrix composition; the macroscopic mechanical parameters include the elastic modulus and tensile strength of the fibers, the elastic modulus and tensile strength of the matrix, and the shear modulus and shear strength of the interface layer; the microstructural parameters include the fiber diameter and the average length ratio of the periodic damaged area to the undamaged area; the nanostructural parameter is the interplanar spacing of the matrix.

[0009] S2: Establish a discrete element representative volume unit model;

[0010] S3: Based on the macroscopic mechanical parameters obtained in S1, the particle bonding parameters of the fiber, matrix, and interface are independently calibrated to determine the optimal combination of particle bonding parameters of the matrix; the particle bonding parameters include fiber bonding elastic modulus, fiber bonding tensile strength, matrix bonding elastic modulus, and matrix bonding tensile strength.

[0011] S4: Determine the bonding elastic modulus and bonding shear strength of the interface to determine the optimal combination of particle bonding parameters of the interface layer;

[0012] S5: Based on the matrix composition, establish a surface energy calculation model for the corresponding crystal, including selecting the types of atoms, establishing the molecular structure, inputting the atomic potential function, and setting periodic boundary conditions;

[0013] S6: An optimal combination of particle bonding parameters obtained from S3-S5, including the bonding elastic modulus and bonding tensile strength of the fiber, the bonding elastic modulus, bonding tensile strength and bonding softening coefficient of the matrix, and the bonding elastic modulus and bonding shear strength of the interface layer.

[0014] S7: Input the optimal combination of determined particle bonding parameters into the discrete element representative solid model, input the bonding tensile strength of the matrix particle contact pair in the undamaged region; set periodic boundary conditions; apply tensile load to stretch the model along the fiber length direction, and solve the tensile stress-strain curve of the unidirectional fiber reinforced ceramic matrix composite.

[0015] A multi-scale calculation system for the mechanical properties of unidirectional fiber-reinforced ceramic matrix composites includes:

[0016] Macroscopic mechanical parameter acquisition module: used to acquire the macroscopic mechanical parameters of the sample, including the elastic modulus and tensile strength of the fiber, the elastic modulus and tensile strength of the matrix, and the shear modulus and shear strength of the interface layer;

[0017] Microstructure parameter acquisition module: used to acquire the microstructure of the sample cross section, measure and calculate the fiber diameter and the average length ratio of the periodic damaged area to the non-damaged area in the sample microstructure parameters;

[0018] Nanostructure parameter acquisition module: used to acquire the nanostructure of the matrix, calculate the interplanar spacing of the matrix using the fast Fourier transform method, and determine the matrix composition;

[0019] Discrete Element Representative Unit Modeling Module: Used to build discrete element representative unit models;

[0020] Particle bonding parameter calibration module: This module is used to independently calibrate the particle bonding parameters of fibers, matrix, and interface based on the macroscopic mechanical parameters obtained by the macroscopic mechanical parameter acquisition module, and to determine the optimal combination of particle bonding parameters of the matrix. The particle bonding parameters include the bonding elastic modulus and bonding tensile strength of fibers and matrix, and the bonding elastic modulus and bonding shear strength of interface.

[0021] Surface energy and adhesion softening coefficient calculation module: Based on the matrix nanostructure parameters obtained from the nanostructure parameter module, a molecular dynamics model of the matrix is ​​established, and the surface energy and adhesion softening coefficient of the matrix are obtained based on first principles.

[0022] Mechanical property calculation module: This module is used to input the particle bonding parameters determined by the particle bonding parameter calibration module and the surface energy and bonding softening coefficient calculation module into the discrete element representative body modeling module; input the bonding tensile strength of the matrix particle contact pair in the non-destructive region; set periodic boundary conditions; apply tensile load to stretch the model along the fiber length direction; and solve the tensile stress-strain curve of the unidirectional fiber reinforced ceramic matrix composite material.

[0023] The significant advantages of this invention compared to existing technologies are:

[0024] (1) By combining molecular dynamics and discrete element method, the nano-micro transmission of damage evolution process in ceramic matrix composite matrix was realized.

[0025] (2) By considering the damage evolution characteristics of the matrix at the nanoscale and the periodic damage characteristics of the material at the microscale, the accuracy of multi-scale calculation of the tensile mechanical properties of unidirectional ceramic matrix composites is improved. Attached Figure Description

[0026] Figure 1 This is a flowchart of Embodiment 1 of the present invention.

[0027] Figure 2 This is a schematic diagram of the system composition of Embodiment 2 of the present invention. Detailed Implementation

[0028] To enable those skilled in the art to have a clearer understanding of the present invention, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described below are merely for illustrative purposes and to facilitate understanding. The technical solutions provided by the present invention are not limited to those provided in the following embodiments, nor should they limit the scope of protection of the present invention.

[0029] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the shape, quantity and proportion of each component can be regarded as an arbitrary change, and the layout of the components may also be more complex.

[0030] Example 1

[0031] like Figure 1 As shown in the figure, this embodiment provides a multi-scale calculation method for the mechanical properties of unidirectional fiber reinforced ceramic matrix composites. The design principle of this method is as follows: This method considers the nanoscale damage behavior and microcrack enrichment characteristics of the unidirectional fiber reinforced ceramic matrix composite matrix. Compared with the traditional multi-scale calculation method combining macroscopic mechanical test and finite element method, its calculation results are more accurate.

[0032] In this embodiment, the specific steps of a multi-scale calculation method for the mechanical properties of unidirectional fiber-reinforced ceramic matrix composites are as follows:

[0033] S1: Based on unidirectional fiber-reinforced ceramic matrix composite samples, obtain the macroscopic mechanical parameters, microstructural parameters, and nanostructural parameters of the samples; the macroscopic mechanical parameters include the elastic modulus and tensile strength of the fibers, the elastic modulus and tensile strength of the matrix, and the shear modulus and shear strength of the interface layer; the microstructural parameters include the fiber diameter and the average length ratio of the periodically damaged region to the undamaged region; the nanostructural parameter is the interplanar spacing of the matrix; the specific steps include:

[0034] S1.1. Based on the tensile specimen of unidirectional fiber-reinforced ceramic matrix composite, the tensile stress-strain curve of the sample is obtained through tensile testing; the elastic modulus and tensile strength of the fiber in the sample are identified based on the slope of the second linear segment of the curve; the elastic modulus and tensile strength of the matrix in the sample are identified based on the slope of the first linear segment of the curve and the preset fiber volume fraction.

[0035] S1.2. Based on the unidirectional fiber-reinforced ceramic matrix composite sheet sample, the indenter reaction force-displacement curve of the nanoindenter is obtained through fiber push-out experiment; the shear modulus of the interface layer is identified based on the slope of the first linear segment; and the shear strength of the interface layer is identified through the peak value of the reaction force.

[0036] S1.3. The cross-sectional microstructure of the sample was obtained by scanning electron microscopy. The fiber diameter in the microstructure parameters of the sample was measured according to the scale of the scanning electron microscope image, and the average length ratio of the periodically damaged area to the undamaged area was calculated.

[0037] S1.4. The nanostructure of the matrix was obtained by transmission electron microscopy, and the interplanar spacing of the matrix was calculated by fast Fourier transform to determine the matrix composition.

[0038] S2: Based on the discrete element method software PFC (Particle Flow Code), establish a discrete element representative volumetric model, specifically including:

[0039] S2.1. Based on the fiber diameter R obtained in S1.3 and the preset fiber volume fraction V f The side length l of the discrete element representative solid element model is calculated as follows:

[0040]

[0041] Particle radius r:

[0042]

[0043] S2.2. Based on the side length l and particle radius r, a homogeneous particle group cube model with side length l is established using the ball distribute command; based on the fiber diameter R, the particle model is divided into fiber particle group and matrix particle group using the ball group command.

[0044] S2.3. Within the fiber particle group, create fiber particle contact pairs using the cmat apply command; within the matrix particle group, create matrix particle contact pairs using the cmat apply command; between the fiber particle group and the matrix particle group, create interface layer particle contact pairs using the cmat apply command; divide the matrix particle contact pairs into 0.5l1:l2:0.5l1 non-damaged-damaged regions along the fiber length direction according to the damage region length ratio l1:l2 obtained in step S1.3, where l1 is the average length of the non-damaged region and l2 is the average length of the damaged region;

[0045] S3: Based on the macroscopic mechanical parameters obtained in S1, independently calibrate the particle bonding parameters of the fiber, matrix, and interface; the particle bonding parameters include fiber bonding elastic modulus, fiber bonding tensile strength, matrix bonding elastic modulus, and matrix bonding tensile strength. Specific steps include:

[0046] S3.1. Set the adhesive elastic modulus of the fiber particle contact pair to the fiber elastic modulus in S1.1, and the adhesive tensile strength to the fiber tensile strength in S1.1; set the required adhesive parameters for both the matrix particle group and the interface particle group to 10. -9 Periodic boundary conditions are set, and tensile loading is applied to obtain the tensile stress-strain curve of the fiber.

[0047] S3.2. Based on the tensile stress-strain curve of the fiber, identify the slope of the curve as the micro-elastic modulus parameter of the fiber, and identify the stress peak value as the micro-tensile strength of the fiber; compare the micro-elastic modulus and micro-tensile strength of the fiber with the fiber elastic modulus and tensile strength in S1.1 respectively; adjust the bonding elastic modulus and bonding tensile strength of the fiber until the error between the obtained micro-elastic modulus and tensile strength and the comparison result in S1.1 is within 1%, and determine the optimal combination of fiber particle bonding parameters;

[0048] S3.3. Set the adhesive elastic modulus of the matrix particle contact pair to the matrix elastic modulus in S1.1, and the adhesive tensile strength to the matrix tensile strength in S1.1; set the bonding parameters of the fiber particle group and the interface particle group to 10. -9 Set a periodic boundary condition (model domain condition periodic), apply tensile loading, and obtain the tensile stress-strain curve of the fiber.

[0049] S3.4. Based on the tensile stress-strain curve of the matrix, calculate the slope of the curve as the micro-elastic modulus parameter of the matrix, and calculate the peak stress as the micro-tensile strength of the matrix; compare the micro-elastic modulus and micro-tensile strength of the matrix with the matrix elastic modulus and tensile strength in S1.1 respectively; adjust the bond elastic modulus and bond tensile strength of the matrix until the error between the obtained micro-elastic modulus and tensile strength and the comparison result in S1.1 is within 1%, and determine the optimal combination of particle bonding parameters of the matrix;

[0050] S4: Determine the adhesive elastic modulus and adhesive shear strength of the interface, specifically including:

[0051] S4.1. Based on the discrete element representative solid model of S2.3, and referring to the thickness of the thin sheet sample used in the fiber ejection experiment, modify the model size in the fiber length direction; refer to the actual indenter shape, establish an indenter model and perform downward loading to obtain the simulated reaction force-displacement curve of the indenter;

[0052] S4.2. Based on the simulated reaction force-displacement curve of the indenter, identify the peak reaction force, the displacement when the reaction force reaches the peak value, and the peak displacement value; adjust the bonding elastic modulus and bonding shear strength of the interface layer until the error of the comparison result with the fiber push-out experiment in S1.2 is within 1%, and determine the optimal combination of particle bonding parameters of the interface layer.

[0053] S5: Based on the matrix nanostructure parameters obtained in S1.4, a molecular dynamics model of the matrix is ​​established, and based on first-principles calculations, the surface energy and the matrix's adhesion softening coefficient ξ are obtained, specifically including:

[0054] S5.1. Based on the matrix composition determined in S1.4, establish a surface energy calculation model for the corresponding crystal in the molecular dynamics software Lammps, including selecting the types of atoms, establishing the molecular structure, inputting the atomic potential function, and setting periodic boundary conditions;

[0055] S5.2. Based on the conjugate gradient method min_style cg, the energy of the model is minimized to obtain the total energy E of the model. bulk A vacuum layer is inserted in the middle of the model, and energy minimization is performed again to obtain the total energy E of the model with the vacuum layer. cut ;

[0056] S5.3. Calculate the surface energy γ of the sample matrix based on first principles:

[0057]

[0058] Where A is the cross-sectional area of ​​the vacuum layer.

[0059] S5.4: Based on the tensile strength of the matrix obtained in S1, the surface energy γ obtained in S5.3, and the particle radius r in S2.1, calculate the adhesion softening coefficient ξ of the matrix contact pair:

[0060]

[0061] Among them, E m The matrix elastic modulus determined by S1, σ m t1 is the matrix tensile strength determined by S1, t1 is the contact pair particle spacing 2r, r is the particle radius calculated by S2.1, and t2 is the width of the crystal crack statistical zone 6nm.

[0062] S6: An optimal combination of particle bonding parameters obtained from S3-S5, including the bonding elastic modulus and bonding tensile strength of the fiber, the bonding elastic modulus, bonding tensile strength and bonding softening coefficient of the matrix, and the bonding elastic modulus and bonding shear strength of the interface layer.

[0063] S7: Input the optimal combination of particle bonding parameters determined in S6 into the discrete element representative solid model established in S2.3, wherein the bonding tensile strength of the matrix particle contact pair in the undamaged region is input as 10. 9 GPa; Set periodic boundary conditions; Apply tensile load to stretch the model along the fiber length direction, and solve for the tensile stress-strain curve of the unidirectional fiber-reinforced ceramic matrix composite.

[0064] Example 2

[0065] like Figure 2 As shown, this embodiment provides a multi-scale calculation system for the mechanical properties of unidirectional fiber-reinforced ceramic matrix composites. The design principle of this method is as follows: This method considers the nanoscale damage behavior and microcrack enrichment characteristics of the unidirectional fiber-reinforced ceramic matrix composite matrix. Compared with the traditional multi-scale calculation method combining macroscopic mechanical testing and the finite element method, its calculation results have higher accuracy; specifically including:

[0066] Macroscopic mechanical parameter acquisition module: Based on unidirectional fiber-reinforced ceramic matrix composite samples, this module acquires the macroscopic mechanical parameters of the samples, including the elastic modulus and tensile strength of the fibers, the elastic modulus and tensile strength of the matrix, and the shear modulus and shear strength of the interface layer. Specific steps include:

[0067] S1.1 Based on the experimental results of the tensile test of unidirectional fiber-reinforced ceramic matrix composites, obtain the tensile stress-strain curve of the sample; based on the slope of the second linear segment of the curve, identify the elastic modulus and tensile strength of the fiber in the sample; based on the slope of the first linear segment of the curve, identify the elastic modulus and tensile strength of the matrix in the sample.

[0068] S1.2. Based on the experimental results of the fiber ejection experiment of unidirectional fiber reinforced ceramic matrix composite material, obtain the indenter reaction force-displacement curve of the nanoindenter; identify the shear modulus of the interface layer based on the slope of the first linear segment; identify the shear strength of the interface layer through the peak value of the reaction force.

[0069] Microstructure parameter acquisition module: The microstructure of the sample cross section is obtained through scanning electron microscopy experimental results. The fiber diameter in the microstructure parameters of the sample is measured according to the scale length of the scanning electron microscope image, and the average length ratio of the periodic non-damaged area to the damaged area is calculated.

[0070] Nanostructure parameter acquisition module: The nanostructure of the matrix is ​​obtained through transmission electron microscopy experimental results. The interplanar spacing of the matrix is ​​calculated according to the fast Fourier transform method to determine the matrix composition.

[0071] Discrete Element Representative Unit Modeling Module: Based on the discrete element software PFC (Particle Flow Code), this module establishes discrete element representative unit models, specifically including:

[0072] S2.1. Fiber diameter R and preset fiber volume fraction V obtained based on the microstructure parameter module. f The side length l of the discrete element representative solid element model is calculated as follows:

[0073]

[0074] Particle radius r:

[0075]

[0076] S2.2. Based on the side length l and particle radius r, a homogeneous particle group model with side length l is established using the ball distribute command; based on the fiber diameter R, the particle model is divided into fiber particle group and matrix particle group using the ball group command.

[0077] S2.3. Within the fiber particle group, create fiber particle contact pairs using the cmat apply command; within the matrix particle group, create matrix particle contact pairs using the cmat apply command; between the fiber particle group and the matrix particle group, create interface layer particle contact pairs using the cmat apply command; divide the matrix particle contact pairs into 0.5l1:l2:0.5l1 non-damaged-damaged regions along the fiber length direction according to the damage region length ratio l1:l2 obtained in step S1.3, where l1 is the average length of the non-damaged region and l2 is the average length of the damaged region;

[0078] Particle bonding parameter calibration module: Based on the macroscopic mechanical parameters obtained by the macroscopic mechanical parameter acquisition module, the particle bonding parameters of the fiber, matrix, and interface are independently calibrated; the particle bonding parameters include the bonding elastic modulus and bonding tensile strength of the fiber and matrix, and the bonding elastic modulus and bonding shear strength of the interface. Specific steps include:

[0079] S3.1. Set the adhesive elastic modulus of the fiber particle contact pair to the fiber elastic modulus in the macroscopic mechanical parameter acquisition module, and the adhesive tensile strength to the fiber tensile strength in the macroscopic mechanical parameter acquisition module; set the required adhesive parameters for both the matrix particle group and the interface particle group to 10. -9 Periodic boundary conditions are set, and tensile loading is applied to obtain the tensile stress-strain curve of the fiber.

[0080] S3.2. Based on the tensile stress-strain curve of the fiber, calculate the slope of the curve as the micro-elastic modulus parameter of the fiber, and calculate the peak stress as the micro-tensile strength of the fiber; compare the micro-elastic modulus and micro-tensile strength of the fiber with the fiber elastic modulus and tensile strength in the macro-mechanical parameter acquisition module respectively; adjust the fiber's bonding elastic modulus and bonding tensile strength until the error between the obtained micro-elastic modulus and tensile strength and the comparison result in the macro-mechanical parameter acquisition module is within 1%, and determine the optimal combination of fiber particle bonding parameters;

[0081] S3.3. Set the adhesive elastic modulus of the matrix particle contact pair to the fiber elastic modulus in the macroscopic mechanical parameter acquisition module, and the adhesive tensile strength to the fiber tensile strength in the macroscopic mechanical parameter acquisition module; set the adhesive parameters of the fiber particle group and the interface particle group to 10. -9 Set a periodic boundary condition (model domainconditionperiodic), apply tensile loading, and obtain the tensile stress-strain curve of the fiber.

[0082] S3.4. Based on the tensile stress-strain curve of the matrix, calculate the slope of the curve as the micro-elastic modulus parameter of the matrix, and calculate the peak stress as the micro-tensile strength of the matrix; compare the micro-elastic modulus and micro-tensile strength of the matrix with the matrix elastic modulus and tensile strength in the macro-mechanical parameter acquisition module respectively; adjust the bond elastic modulus and bond tensile strength of the matrix until the error between the obtained micro-elastic modulus and tensile strength and the comparison result in the macro-mechanical parameter acquisition module is within 1%, and determine the optimal combination of particle bonding parameters of the matrix;

[0083] S3.5. Based on the discrete element representative unit modeling module, refer to the thickness of the thin sheet sample used in the fiber ejection experiment and modify the model size in the fiber length direction; refer to the actual indenter shape, establish an indenter model and apply downward pressure to obtain the simulated reaction force-displacement curve of the indenter;

[0084] S3.6. Based on the simulated reaction force-displacement curve of the pressure head, identify the peak reaction force, the displacement when the reaction force reaches the peak value, and the peak displacement value; adjust the bonding elastic modulus and bonding shear strength of the interface layer until the error of the comparison result with the fiber push-out experiment of the macroscopic mechanical parameter acquisition module is within 1%, and determine the optimal combination of particle bonding parameters of the interface layer.

[0085] Surface Energy and Bond Softening Coefficient Calculation Module: Based on the matrix nanostructure parameters obtained from the nanostructure parameter module, a molecular dynamics model of the matrix is ​​established. Then, based on first-principles calculations, the surface energy and bond softening coefficient ξ of the matrix are obtained, specifically including:

[0086] S4.1. Based on the matrix composition determined by the nanostructure parameter module, establish the surface energy calculation model of the corresponding crystal in the molecular dynamics software Lammps, including selecting the types of atoms, establishing the molecular structure, inputting the atomic potential function, and setting periodic boundary conditions;

[0087] S4.2. Based on the conjugate gradient method min_style cg, the total energy E of the model in the energy minimization state is obtained. bulk A vacuum layer is inserted in the middle of the model, and energy minimization is performed again to obtain the total energy E of the model with the vacuum layer. cut ;

[0088] S4.3. Calculate the surface energy γ of the sample matrix based on first principles:

[0089]

[0090] Where A is the cross-sectional area of ​​the vacuum layer.

[0091] S4.4: Based on the tensile strength of the matrix obtained from the macroscopic mechanical parameters module, the surface energy γ obtained from S4.3, and the particle radius r from the discrete element representative unit modeling module, calculate the bonding softening coefficient ξ of the matrix.

[0092]

[0093] Among them, E m The matrix elastic modulus determined by S1, σ m S1 represents the matrix tensile strength, t1 represents the particle spacing of the contact pair, and t2 represents the width of the statistical region of crystal cracks (6 nm).

[0094] Mechanical property calculation module: Inputs the particle bonding parameters determined by the particle bonding parameter calibration module and the surface energy and softening coefficient calculation module into the model established by the discrete element representative element modeling module, and replaces the bonding tensile strength of the matrix particle contact pair in the undamaged region with 10. 9 GPa; Set periodic boundary conditions; Apply tensile load to stretch the model along the fiber length direction, and solve for the tensile stress-strain curve of the unidirectional fiber-reinforced ceramic matrix composite.

[0095] It should be noted that the division of modules in the above system represents only a logical functional division; in actual implementation, these modules can be fully or partially integrated into a single physical entity, or implemented separately. They can be invoked in software by processing elements, or implemented entirely in hardware; for example, a module can exist as an independent processing unit, or be integrated into a chip within the device. Furthermore, program code can also be stored in the device's memory, invoked and executed by a processing element, and other modules are implemented in a similar manner. These modules can be fully or partially integrated, or operate independently; the processing elements mentioned here can be integrated circuits with signal processing capabilities. In the implementation process, the steps or modules of the above methods can be completed through the logic circuits or software instructions of the processor and related hardware.

[0096] For example, these modules can constitute one or more integrated circuits to perform the above methods, including one or more application-specific integrated circuits, microprocessors, or field-programmable gate arrays; in addition, when a module is implemented in the form of program code by a processing element, the processing element can be a general-purpose processor, such as a central processing unit or other processor capable of calling program code; these modules can also be integrated together in the form of a system-on-a-chip.

Claims

1. A multi-scale calculation method for the mechanical properties of unidirectional fiber-reinforced ceramic matrix composites, characterized in that, include: S1: Based on unidirectional fiber-reinforced ceramic matrix composite samples, obtain the macroscopic mechanical parameters, microstructural parameters, and nanostructural parameters of the samples, and determine the matrix composition. The macroscopic mechanical parameters include the elastic modulus and tensile strength of the fibers, the elastic modulus and tensile strength of the matrix, and the shear modulus and shear strength of the interface layer. The microstructural parameters include the fiber diameter and the average length ratio of the periodic undamaged region to the damaged region. The nanostructural parameter is the interplanar spacing of the matrix. S2: Establish a discrete element representative volume unit model; S3: Based on the macroscopic mechanical parameters obtained in S1, the particle bonding parameters of the fiber, matrix, and interface are independently calibrated to determine the optimal combination of particle bonding parameters of the matrix; the particle bonding parameters include fiber bonding elastic modulus, fiber bonding tensile strength, matrix bonding elastic modulus, and matrix bonding tensile strength. S4: Determine the bonding elastic modulus and bonding shear strength of the interface to determine the optimal combination of particle bonding parameters of the interface layer; S5: Based on the matrix composition, establish a surface energy calculation model for the corresponding crystal, including selecting the types of atoms, establishing the molecular structure, inputting the atomic potential function, and setting periodic boundary conditions; S6: An optimal combination of particle bonding parameters obtained from S3-S5, including the bonding elastic modulus and bonding tensile strength of the fiber, the bonding elastic modulus, bonding tensile strength and bonding softening coefficient of the matrix, and the bonding elastic modulus and bonding shear strength of the interface layer. S7: Input the optimal combination of determined particle bonding parameters into the discrete element representative body model, and input the bonding tensile strength of the matrix particle contact pair in the undamaged region. Set periodic boundary conditions; apply tensile load to stretch the model along the fiber length direction, and solve for the tensile stress-strain curve of the unidirectional fiber-reinforced ceramic matrix composite.

2. The multi-scale calculation method for the mechanical properties of unidirectional fiber-reinforced ceramic matrix composites according to claim 1, characterized in that, S1 specifically includes: S1.

1. Based on the tensile specimen of unidirectional fiber-reinforced ceramic matrix composite, the tensile stress-strain curve of the sample is obtained through tensile testing; the elastic modulus and tensile strength of the fiber in the sample are identified based on the slope of the second linear segment of the curve; the elastic modulus and tensile strength of the matrix in the sample are identified based on the slope of the first linear segment of the curve and the preset fiber volume fraction. S1.

2. Based on the unidirectional fiber-reinforced ceramic matrix composite sheet sample, the indenter reaction force-displacement curve of the nanoindenter is obtained through fiber push-out experiment; the shear modulus of the interface layer is identified based on the slope of the first linear segment; and the shear strength of the interface layer is identified through the peak value of the reaction force. S1.

3. Obtain the microstructure of the sample cross-section, and measure and calculate the fiber diameter and the ratio of the damaged area length in the sample microstructure parameters; S1.

4. The nanostructure of the matrix was obtained by transmission electron microscopy, and the interplanar spacing of the matrix was calculated by fast Fourier transform to determine the matrix composition.

3. The multi-scale calculation method for the mechanical properties of unidirectional fiber-reinforced ceramic matrix composites according to claim 1, characterized in that, S2 specifically includes: S2.

1. Based on the obtained fiber diameter R and the preset fiber volume fraction V f The side length l of the discrete element representative solid element model is calculated as follows: Particle radius r: S2.

2. Based on the side length l and particle radius r, a homogeneous particle group cube model with side length l is established using the ball distribute command; based on the fiber diameter R, the particle model is divided into fiber particle group and matrix particle group using the ball group command. S2.

3. Within the fiber particle group, create fiber particle contact pairs using the `cmat apply` command; within the matrix particle group, create matrix particle contact pairs using the `cmat apply` command; between the fiber particle group and the matrix particle group, create interface layer particle contact pairs using the `cmat apply` command; divide the matrix particle contact pairs into 0.5l1:l2:0.5l1 non-damaged-damaged-non-damaged regions along the fiber length direction according to the obtained damage region length ratio, where l1 is the average length of the non-damaged region and l2 is the average length of the damaged region.

4. The multi-scale calculation method for the mechanical properties of unidirectional fiber-reinforced ceramic matrix composites according to claim 1, characterized in that, S3 specifically includes: S3.

1. Set the adhesive elastic modulus of the fiber particle contact pair to the fiber elastic modulus in S1, and the adhesive tensile strength to the fiber tensile strength in S1; set the required adhesive parameters for the matrix particle group and the interface particle group; set periodic boundary conditions, perform tensile loading, and obtain the tensile stress-strain curve of the fiber. S3.

2. Based on the tensile stress-strain curve of the fiber, identify the slope of the curve as the micro-elastic modulus parameter of the fiber, and identify the stress peak value as the micro-tensile strength of the fiber; compare the micro-elastic modulus and micro-tensile strength of the fiber with the fiber elastic modulus and tensile strength in S1 respectively; adjust the bonding elastic modulus and bonding tensile strength of the fiber until the obtained micro-elastic modulus and tensile strength are within the error range compared with the comparison results in S1, and determine the optimal combination of particle bonding parameters of the fiber. S3.

3. Set the adhesive elastic modulus of the matrix particle contact pair to the matrix elastic modulus in S1, and the adhesive tensile strength to the matrix tensile strength in S1; set the adhesive parameters of the fiber particle group and the interface particle group; set periodic boundary conditions, perform tensile loading, and obtain the tensile stress-strain curve of the fiber. S3.

4. Based on the tensile stress-strain curve of the matrix, calculate the slope of the curve as the micro-elastic modulus parameter of the matrix, and calculate the peak stress as the micro-tensile strength of the matrix; compare the micro-elastic modulus and micro-tensile strength of the matrix with the matrix elastic modulus and tensile strength in S1 respectively; adjust the bond elastic modulus and bond tensile strength of the matrix until the obtained micro-elastic modulus and tensile strength are within the error range compared with the comparison results in S1, and determine the optimal combination of particle bonding parameters of the matrix.

5. The multi-scale calculation method for the mechanical properties of unidirectional fiber-reinforced ceramic matrix composites according to claim 1, characterized in that, S4 specifically includes: S4.

1. Based on the discrete element representative body model, and referring to the thickness of the thin sheet sample used in the fiber ejection experiment, the model size in the fiber length direction is modified; referring to the actual indenter shape, an indenter model is established and pressure loading is performed to obtain the simulated reaction force-displacement curve of the indenter; S4.

2. Based on the simulated reaction-displacement curve of the indenter, identify the peak reaction force, the displacement when the reaction force reaches its peak, and the peak displacement; adjust the bonding elastic modulus and bonding shear strength of the interface layer until the error of the comparison results with the fiber ejection experiment is within the range, and determine the optimal combination of particle bonding parameters of the interface layer.

6. The multi-scale calculation method for the mechanical properties of unidirectional fiber-reinforced ceramic matrix composites according to claim 1, characterized in that, S5 specifically includes: S5.

1. Based on the matrix composition, establish a surface energy calculation model for the corresponding crystal in the molecular dynamics software Lammps, including selecting the types of atoms, establishing the molecular structure, inputting the atomic potential function, and setting periodic boundary conditions; S5.

2. Minimize the energy of the model using the conjugate gradient method to obtain the total energy E of the model. bulk A vacuum layer is inserted in the middle of the model, and energy minimization is performed again to obtain the total energy E of the model with the vacuum layer. cut ; S5.

3. Calculate the surface energy γ of the sample matrix based on first principles: Where A is the cross-sectional area of ​​the vacuum layer; S5.4: Calculate the adhesion softening coefficient ξ of the matrix contact pair based on the tensile strength, surface energy γ, and particle radius r of the matrix. Among them, E m σ is the elastic modulus of the matrix. m t1 represents the tensile strength of the matrix, t2 represents the distance between the contact particles, and t2 represents the width of the statistical zone of crystal cracks.

7. A multi-scale calculation system for the mechanical properties of unidirectional fiber-reinforced ceramic matrix composites, characterized in that, include: Macroscopic mechanical parameter acquisition module: used to acquire the macroscopic mechanical parameters of the sample, including the elastic modulus and tensile strength of the fiber, the elastic modulus and tensile strength of the matrix, and the shear modulus and shear strength of the interface layer; Microstructure parameter acquisition module: used to acquire the microstructure of the sample cross section, measure and calculate the fiber diameter and the average length ratio of the periodic non-damaged area to the damaged area in the sample microstructure parameters; Nanostructure parameter acquisition module: used to acquire the nanostructure of the matrix, calculate the interplanar spacing of the matrix using the fast Fourier transform method, and determine the matrix composition; Discrete Element Representative Unit Modeling Module: Used to build discrete element representative unit models; Particle bonding parameter calibration module: This module is used to independently calibrate the particle bonding parameters of fibers, matrix, and interface based on the macroscopic mechanical parameters obtained by the macroscopic mechanical parameter acquisition module, and to determine the optimal combination of particle bonding parameters of the matrix. The particle bonding parameters include the bonding elastic modulus and bonding tensile strength of fibers and matrix, and the bonding elastic modulus and bonding shear strength of interface. Surface energy and adhesion softening coefficient calculation module: Based on the matrix nanostructure parameters obtained from the nanostructure parameter module, a molecular dynamics model of the matrix is ​​established, and the surface energy and adhesion softening coefficient of the matrix are obtained based on first principles. Mechanical property calculation module: Used to input the particle bonding parameters determined by the particle bonding parameter calibration module and the surface energy and softening coefficient calculation module into the model established by the discrete element representative body element modeling module, and input the bonding tensile strength of the matrix particle contact pair in the non-destructive region; Set periodic boundary conditions; apply tensile load to stretch the model along the fiber length direction, and solve for the tensile stress-strain curve of the unidirectional fiber-reinforced ceramic matrix composite.

8. The multi-scale calculation system for the mechanical properties of unidirectional fiber-reinforced ceramic matrix composites according to claim 7, characterized in that, Establishing a discrete element representative volumetric model specifically includes: Based on the obtained fiber diameter R and the preset fiber volume fraction V f The side length l of the discrete element representative solid element model is calculated as follows: Particle radius r: Based on the side length l and particle radius r, a homogeneous cubic model of particle group with side length l is established using the ball distribute command; based on the fiber diameter R, the particle model is divided into fiber particle group and matrix particle group using the ball group command. Within the fiber particle group, fiber particle contact pairs are created using the `cmat apply` command; within the matrix particle group, matrix particle contact pairs are created using the `cmat apply` command; between the fiber particle group and the matrix particle group, interface layer particle contact pairs are created using the `cmat apply` command; the matrix particle contact pairs are divided into undamaged-damaged-undamaged regions along the fiber length direction according to the obtained damage region length ratio, with a ratio of 0.5l1:l2:0.5l1, where l1 is the average length of the undamaged region and l2 is the average length of the damaged region.

9. The multi-scale calculation system for the mechanical properties of unidirectional fiber-reinforced ceramic matrix composites according to claim 7, characterized in that, The processing steps of the particle bonding parameter calibration module specifically include: The adhesive elastic modulus of the fiber particle contact pair is set to the fiber elastic modulus in the macroscopic mechanical parameter acquisition module, and the adhesive tensile strength is set to the fiber tensile strength in the macroscopic mechanical parameter acquisition module; the required adhesive parameters of the matrix particle group and the interface particle group are set; periodic boundary conditions are set, tensile loading is performed, and the tensile stress-strain curve of the fiber is obtained. Based on the tensile stress-strain curve of the fiber, the slope of the curve is calculated as the micro-elastic modulus parameter of the fiber, and the peak stress is calculated as the micro-tensile strength of the fiber. The micro-elastic modulus and micro-tensile strength of the fiber are compared with the fiber elastic modulus and tensile strength in the macro-mechanical parameter acquisition module. The bond elastic modulus and bond tensile strength of the fiber are adjusted until the error between the obtained micro-elastic modulus and tensile strength and the comparison results in the macro-mechanical parameter acquisition module is within the range, and the optimal combination of fiber particle bonding parameters is determined. The adhesive elastic modulus of the matrix particle contact pair is set to the fiber elastic modulus in the macroscopic mechanical parameter acquisition module, and the adhesive tensile strength is set to the fiber tensile strength in the macroscopic mechanical parameter acquisition module; the adhesive parameters of the fiber particle group and the interface particle group are set with periodic boundary conditions, and tensile loading is performed to obtain the tensile stress-strain curve of the fiber. Based on the tensile stress-strain curve of the matrix, the slope of the curve is calculated as the micro-elastic modulus parameter of the matrix, and the peak stress is calculated as the micro-tensile strength of the matrix. The micro-elastic modulus and micro-tensile strength of the matrix are compared with the matrix elastic modulus and tensile strength in the macro-mechanical parameter acquisition module. The bond elastic modulus and bond tensile strength of the matrix are adjusted until the error between the obtained micro-elastic modulus and tensile strength and the comparison results in the macro-mechanical parameter acquisition module is within the range, and the optimal combination of particle bonding parameters of the matrix is ​​determined. Based on the discrete element modeling module, the model dimensions along the fiber length direction are modified according to the thickness of the thin sheet sample used in the fiber ejection experiment; the indenter model is established according to the actual indenter shape, and the indenter is subjected to downward loading to obtain the simulated reaction force-displacement curve of the indenter. Based on the simulated reaction-displacement curve of the pressure head, the peak reaction force, the displacement when the reaction force reaches its peak, and the peak displacement are identified. The bonding elastic modulus and bonding shear strength of the interface layer are adjusted until the error between the results and the fiber ejection experiment results obtained from the macroscopic mechanical parameter acquisition module is within the range, and the optimal combination of particle bonding parameters of the interface layer is determined.

10. The multi-scale calculation system for the mechanical properties of unidirectional fiber-reinforced ceramic matrix composites according to claim 7, characterized in that, The surface energy and adhesion softening coefficient calculation module's processing steps specifically include: Based on the matrix composition determined by the nanostructure parameter module, a surface energy calculation model for the corresponding crystal is established, including selecting the types of atoms, establishing the molecular structure, inputting the atomic potential function, and setting periodic boundary conditions. Based on the conjugate gradient method, the total energy E of the model in the energy minimization state is obtained. bulk A vacuum layer is inserted in the middle of the model, and energy minimization is performed again to obtain the total energy E of the model with the vacuum layer. cut ; Based on first principles, the surface energy γ of the sample matrix is ​​calculated: Where A is the cross-sectional area of ​​the vacuum layer; Based on the tensile strength and surface energy γ of the matrix obtained from the macroscopic mechanical parameter module, and the particle radius r from the discrete element representative unit modeling module, the cohesion softening coefficient ξ of the matrix is ​​calculated: Among them, E m σ is the elastic modulus of the matrix. m t1 represents the tensile strength of the matrix, t2 represents the particle spacing of the contact pair, and t2 represents the width of the statistical zone of crystal cracks.

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