1. A design method for ultimate failure load of a ceramic matrix composite and high-temperature alloy mechanical connection structure under a high-temperature thermal mismatch condition is characterized by comprising the following steps:

s100, according to geometric parameters, initial assembly parameters and environmental temperature of the ceramic matrix composite and the high-temperature alloy raised head or the countersunk head bolt fastener, establishing a three-dimensional finite element analysis model of the ceramic matrix composite and the high-temperature alloy raised head or the countersunk head bolt fastener under a high-temperature uniaxial tensile loading condition by using ABAQUS software;

s200, selecting a ceramic matrix compositeEstablishing a progressive damage analysis model of the C/SiC composite material structure, carrying out stress analysis, and starting to adjust the stress sigma of the unit integration point in the k-th increment step^k；

S300, substituting stress of the integration points of the ceramic matrix composite material unit into a Tsai-Wu failure criterion for judgment, if the failure criterion is met, the material unit point fails, and performing material rigidity degradation according to a degradation model; if the failure criterion is not met, the material is not damaged, and the rigidity of the material is not changed C^k+1＝C^kUpdate the stress σ^k+1＝σ^k+C^k+1·Δε^k，Δε^kIs the strain increment;

s400, judging whether damage in the composite material structure causes structural damage or not; if the structure is not damaged, increasing the increment of the mechanical load, and returning to S200; if the structure is damaged, the structure loses bearing capacity, analysis is stopped, residual pretightening force and assembly clearance of the C/SiC ceramic matrix composite and the high-temperature alloy bolt fastener are obtained, and failure load at corresponding environmental temperature is obtained;

s500, modifying the environment temperature, and repeating S200 to S400 to obtain the ultimate failure load of the C/SiC ceramic matrix composite and the high-temperature alloy bolt fastener in the corresponding environment temperature range under the high-temperature thermal mismatch condition and the corresponding initial and final assembly pretightening force and clearance thereof.

2. The method for designing the ultimate failure load of the ceramic matrix composite and superalloy mechanical connection structure under the high-temperature thermal mismatch condition according to claim 1, wherein in S100, the step of establishing the three-dimensional finite element analysis model comprises:

s110, according to the geometric parameters of the ceramic matrix composite and the high-temperature alloy raised head or the countersunk head bolt fastener, establishing a three-dimensional geometric model of the ceramic matrix composite and the high-temperature alloy countersunk head bolt fastener by using ABAQUS software;

s120, adopting an eight-node linear reduction integral hexahedron unit C3D8R and setting an enhanced hourglass control to perform structured grid division on the structure;

s130, defining 5 groups of contact pairs in ABAQUS according to the contact relation among the high-temperature alloy plate, the composite material plate and the bolt, and adding friction coefficients to each contact surface in the interaction property;

s140, directly applying axial pretightening force on the cross section of the bolt rod by using a Boltload command in ABAQUS, applying the clearance amount of the nail holes by setting the assembly value of a contact pair between the nail holes, ensuring that the pretightening force is not reduced to be below 0N at high temperature, and applying uniform high-temperature load to the whole connecting structure;

s150, applying solid support constraint to all directions of the end part of the high-temperature alloy plate, applying mechanical load to the X direction of the end part of the ceramic matrix composite plate, and constraining the displacement in the other two directions.

3. The method for designing the ultimate failure load of the ceramic matrix composite and superalloy mechanical connection structure under the high-temperature thermal mismatch condition according to claim 1, wherein in S300, the implementation process for predicting the composite failure state by applying the ceramic matrix composite failure criterion is as follows:

s301, reading unit integral point stress sigma of composite plate with ceramic matrix composite and high-temperature alloy countersunk head bolt connecting structure^k；

S302, substituting the stress value into an improved three-dimensional Hashin failure criterion and a Ye layering failure criterion to perform progressive damage analysis to judge the failure of the C/SiC composite material unit point, wherein the specific form of the strength criterion is as follows:

(1) matrix tensile failure (σ)₂₂＞0)：

(σ₂₂/Y_T)²+(σ₁₂/S₁₂)²+(σ₂₃/S₂₃)²≥1 (1)

(2) Matrix compression fracture failure (σ)₂₂＜0)：

(σ₂₂/Y_C)²+(σ₁₂/S₁₂)²+(σ₂₃/S₂₃)²≥1 (2)

(3) Fiber tensile failure (σ)₁₁＞0)：

(σ₁₁/X_T)²+(σ₁₂/S₁₂)²+(σ₁₃/S₁₃)²≥1 (3)

(4) Matrix tensile failure (σ)₁₁＜0)：

(σ₁₁/X_C)²≥1 (4)

(5) Fiber-matrix shear failure (σ)₁₁＜0)：

(σ₁₁/X_C)²+(σ₁₂/S₁₂)²+(σ₁₃/S₁₃)²≥1 (5)

(6) Fiber-matrix tensile delamination failure (σ)₃₃＞0)：

(σ₃₃/Z_T)²+(σ₁₃/S₁₃)²+(σ₂₃/S₂₃)²≥1 (6)

(7) Fiber-matrix compressive delamination failure (σ)₃₃＜0)：

(σ₃₃/Z_C)²+(σ₁₃/S₁₃)²+(σ₂₃/S₂₃)²In the formula ≧ 1 (7), σ_ij(i, j ═ 1,2,3) is the structure is stressed in the 1,2,3 direction, X_T，X_C，Y_T，Y_C，Z_T，Z_C，S₁₂，S₁₃，S₂₃X, Y, Z represents tensile or compressive strength in the 1,2,3 directions, S represents shear strength, subscript T represents tensile, subscript C represents compression, for material strength parameters;

and S303, updating the unit failure state variable.

4. The method for designing the ultimate failure load of the ceramic matrix composite and superalloy mechanical connection structure under the high-temperature thermal mismatch condition according to claim 1, wherein in S300, the process for performing material stiffness degradation on the failure material according to the degradation model comprises:

s311, after the material unit is judged to be invalid, the rigidity value of the material unit in each direction is determined to be degraded, and the degraded rigidity is as follows:

(1) failure of the substrate at tensile break:

E′₂₂＝0.2·E₂₂，G′₁₂＝0.2·G₁₂,G′₂₃＝0.2·G₂₃ (8)

(2) matrix compression fracture failure (σ)₂₂＜0)：

E′₂₂＝0.4·E₂₂，G′₁₂＝0.4·G₁₂,G′₂₃＝0.4·G₂₃ (9)

(3) Fiber tensile failure (σ)₁₁＞0)：

E′₁₁＝0.07·E₁₁ (10)

(4) Matrix tensile failure (σ)₁₁＜0)：

E′₁₁＝0.07·E₁₁ (11)

(5) Fiber-matrix shear failure (σ)₁₁＜0)：

G′₁₂＝0，ν′₁₂＝0 (12)

(6) Fiber-matrix tensile delamination failure (σ)₃₃＞0)：

E′₃₃＝0，G′₂₃＝0，G′₁₃＝0，ν′₁₃＝0，ν′₂₃＝0 (13)

(7) Fiber-matrix compressive delamination failure (σ)₃₃＜0)：

E′₃₃＝0，G′₂₃＝0，G′₁₃＝0，ν′₁₃＝0，ν′₂₃＝0 (14)

S312, updating the rigidity matrix of the material, C^k+1＝C^dWherein C represents post-damage material stiffness and the superscript d represents damage;

s313, updating stress sigma of damaged material^k+1＝C^k+1·(ε^k+Δε^k) Wherein, epsilon^kStrain, Δ ε, in the kth incremental step^kIs the strain increment;

s314, go to S500.

Background

The C/SiC ceramic matrix composite has the characteristics of high specific strength, high specific modulus, low density, moderate fracture toughness, excellent oxidation resistance, high temperature resistance and the like, is widely applied to novel high-Mach aircraft thermal protection systems and propulsion system components, and has incomparable advantages compared with the traditional thermal protection metal material. Due to the limitation of the weaving process, the manufacturing of large and complex ceramic matrix composite structural members is difficult and expensive, and how to realize the connection between the composite material and the small metal material parts becomes a key problem to be solved urgently. Mechanical joining techniques have attracted considerable attention for their simplicity, high load transfer capability and reliability, and economy. When the C/SiC composite material bolt connection structure is in a high-temperature service state, the thermal stress concentration around the bolt hole is aggravated due to the fact that the coefficient of thermal expansion of the ceramic matrix composite material is not matched with that of the metal, the initial assembly parameters (bolt pretightening force, bolt hole matching precision and the like) of the connection structure are changed, and then the bearing capacity and the damage mode of the bolt connection structure are influenced. Therefore, the bearing capacity design of the C/SiC composite material hybrid bolt connecting structure under the high-temperature thermal mismatch condition has important significance for optimizing the design form of the connecting structure, relieving the thermal stress level and improving the connecting strength. From the current research situation and literature retrieval situation at home and abroad, most researches on the influence of bolt fasteners on the mechanical property of the connecting structure are concentrated on the fiber reinforced resin matrix composite material mechanical connecting structure, and related researches on the mechanical behavior and failure mode of the ceramic matrix composite material bolt connecting structure under the high-temperature thermal mismatch condition are deficient. The traditional experimental research on the high-temperature mechanical property of the ceramic matrix composite connecting structure needs to consume a large amount of capital and is limited by experimental equipment and experimental technology. Therefore, the design of the bearing capacity of the ceramic matrix composite material hybrid mechanical connection structure under the high-temperature thermal mismatch condition through finite element simulation has important engineering practical significance for improving the bearing efficiency of the structure and guaranteeing the service safety of the connection structure.

Disclosure of Invention

The invention aims to provide a design method of ultimate failure load of a ceramic matrix composite and high-temperature alloy mechanical connection structure under a high-temperature thermal mismatch condition, so as to solve the problems in the prior art.

A design method for ultimate failure load of a ceramic matrix composite and superalloy mechanical connection structure under a high-temperature thermal mismatch condition comprises the following steps:

s100, according to geometric parameters, initial assembly parameters and environmental temperature of the ceramic matrix composite and the high-temperature alloy raised head or the countersunk head bolt fastener, establishing a three-dimensional finite element analysis model of the ceramic matrix composite and the high-temperature alloy raised head or the countersunk head bolt fastener under a high-temperature uniaxial tensile loading condition by using ABAQUS software;

s200, selecting a bilinear or nonlinear constitutive model, a failure criterion and a degradation model of the ceramic matrix composite, establishing a progressive damage analysis model of the C/SiC composite structure, performing stress analysis, and starting to call the stress sigma of the unit integration point in the kth increment step^k；

S300, substituting stress of the integration points of the ceramic matrix composite material unit into a Tsai-Wu failure criterion for judgment, if the failure criterion is met, the material unit point fails, and performing material rigidity degradation according to a degradation model; if the failure criterion is not met, the material is not damaged, and the rigidity of the material is not changed C^k+1＝C^kUpdate the stress σ^k+1＝σ^k+C^k+1·Δε^k；

S400, judging whether damage in the composite material structure causes structural damage or not; if the structure is not damaged, increasing the increment of the mechanical load, and returning to S200; if the structure is damaged, the structure loses the bearing capacity, the analysis is stopped, the residual pretightening force and the assembly clearance of the C/SiC ceramic matrix composite and the high-temperature alloy bolt fastener are obtained, and the failure load at the corresponding environment temperature (such as 1000 ℃) is obtained;

s500, modifying the environment temperature, and repeating S200 to S400 to obtain the ultimate failure load of the C/SiC ceramic matrix composite and the high-temperature alloy bolt fastener in the corresponding environment temperature range under the high-temperature thermal mismatch condition and the corresponding initial and final assembly pretightening force and clearance thereof.

Further, in S100, the step of establishing a three-dimensional finite element analysis model includes:

s110, according to the geometric parameters of the ceramic matrix composite and the high-temperature alloy raised head or the countersunk head bolt fastener, establishing a three-dimensional geometric model of the ceramic matrix composite and the high-temperature alloy countersunk head bolt fastener by using ABAQUS software;

s120, adopting an eight-node linear reduction integral hexahedron unit C3D8R and setting an enhanced hourglass control to perform structured grid division on the structure;

s130, defining 5 groups of contact pairs in ABAQUS according to the contact relation among the high-temperature alloy plate, the composite material plate and the bolt, and adding friction coefficients to each contact surface in the interaction property;

s140, directly applying axial pretightening force on the cross section of the Bolt rod by using a Bolt load command in ABAQUS, applying the clearance amount of the nail holes by setting the assembly value of a contact pair between the nail holes, ensuring that the pretightening force is not reduced to be below 0N at high temperature, and applying uniform high-temperature load to the whole connecting structure;

s150, applying solid support constraint to all directions of the end part of the high-temperature alloy plate, applying mechanical load to the X direction of the end part of the ceramic matrix composite plate, and constraining the displacement in the other two directions.

Further, in S300, the implementation process of predicting the composite failure state by applying the ceramic matrix composite failure criterion is as follows:

s301, reading unit integral point stress sigma of composite plate with ceramic matrix composite and high-temperature alloy countersunk head bolt connecting structure^k；

S302, substituting the stress value into an improved three-dimensional Hashin failure criterion and a Ye layering failure criterion to perform progressive damage analysis to judge the failure of the C/SiC composite material unit point, wherein the specific form of the strength criterion is as follows:

(1) matrix tensile failure (σ)₂₂＞0)：

(σ₂₂/Y_T)²+(σ₁₂/S₁₂)²+(σ₂₃/S₂₃)²≥1 (1)

(2) Matrix compression fracture failure (σ)₂₂＜0)：

(σ₂₂/Y_C)²+(σ₁₂/S₁₂)²+(σ₂₃/S₂₃)²≥1 (2)

(3) Fiber tensile failure (σ)₁₁＞0)：

(σ₁₁/X_T)²+(σ₁₂/S₁₂)²+(σ₁₃/S₁₃)²≥1 (3)

(4) Matrix tensile failure (σ)₁₁＜0)：

(σ₁₁/X_C)²≥1 (4)

(5) Fiber-matrix shear failure (σ)₁₁＜0)：

(σ₁₁/X_C)²+(σ₁₂/S₁₂)²+(σ₁₃/S₁₃)²≥1 (5)

(6) Fiber-matrix tensile delamination failure (σ)₃₃＞0)：

(σ₃₃/Z_T)²+(σ₁₃/S₁₃)²+(σ₂₃/S₂₃)²≥1 (6)

(7) Fiber-matrix compressive delamination failure (σ)₃₃＜0)：

(σ₃₃/Z_C)²+(σ₁₃/S₁₃)²+(σ₂₃/S₂₃)²≥1 (7)

In the formula, σ_ij(i, j-1, 2,3) is the stress to which the structure is subjected, X_T，X_C，Y_T，Y_C，Z_T，Z_C，S₁₂，S₁₃，S₂₃X, Y, Z represents tensile or compressive strength in the 1,2,3 directions, S represents shear strength, subscript T represents tensile, subscript C represents compression, for material strength parameters;

and S303, updating the unit failure state variable.

Further, in S300, the implementation process of performing material stiffness degradation on the failed material according to the degradation model includes:

s311, after the material unit is judged to be invalid, the rigidity value of the material unit in each direction is determined to be degraded, and the degraded rigidity is as follows:

(1) failure of the substrate at tensile break:

E'₂₂＝0.2·E₂₂，G'₁₂＝0.2·G₁₂,G'₂₃＝0.2·G₂₃ (8)

(2) matrix compression fracture failure (σ)₂₂＜0)：

E'₂₂＝0.4·E₂₂，G'₁₂＝0.4·G₁₂,G'₂₃＝0.4·G₂₃ (9)

(3) Fiber tensile failure (σ)₁₁＞0)：

E'₁₁＝0.07·E₁₁ (10)

(4) Matrix tensile failure (σ)₁₁＜0)：

E'₁₁＝0.07·E₁₁ (11)

(5) Fiber-matrix shear failure (σ)₁₁＜0)：

G'₁₂＝0，ν'₁₂＝0 (12)

(6) Fiber-matrix tensile delamination failure (σ)₃₃＞0)：

E'₃₃＝0，G'₂₃＝0，G'₁₃＝0，ν'₁₃＝0，ν'₂₃＝0 (13)

(7) Fiber-matrix compressive delamination failure (σ)₃₃＜0)：

E'₃₃＝0，G'₂₃＝0，G'₁₃＝0，ν'₁₃＝0，ν'₂₃＝0 (14)

S312, updating the rigidity matrix of the material, C^k+1＝C^dWherein C represents the post-injury material stiffness;

s313, updating stress sigma of damaged material^k+1＝C^k+1·(ε^k+Δε^k) Wherein, epsilon^kStrain, Δ ε, in the kth incremental step^kIs the strain increment;

s314, go to S500.

The invention has the beneficial effects that: the invention provides a design method for ultimate failure load of a mechanical connection structure of a ceramic-based composite material and a high-temperature alloy under a high-temperature thermal mismatch condition, which is characterized in that a Fortran language is adopted to write a nonlinear constitutive model, a failure criterion and a material degradation model into a user subprogram UMAT file, and the user subprogram UMAT file is embedded into ABAQUS finite element software to realize progressive damage analysis of the ceramic-based composite material and the high-temperature alloy countersunk head bolt fastener under a high-temperature stretching condition, so that ultimate failure load, corresponding initial and final assembly pretightening force and gap of the C/SiC ceramic-based composite material and the high-temperature alloy bolt fastener under the high-temperature thermal mismatch condition are obtained. Compared with the existing ceramic matrix composite material connecting structure experiment characterization means, the prediction method is quick and efficient, can obviously save test time consumption and cost, gets rid of the restriction of expensive test equipment and complex test links, has certain universality, provides important technical support for the structure design and strength prediction of the hypersonic aircraft ceramic matrix composite material mechanical connecting structure, and can be popularized and applied to various technical fields of aerospace, military and national defense, energy and chemical engineering and the like.

Drawings

FIG. 1 is a schematic view of the ceramic matrix composite material and superalloy lug bolt connection;

FIG. 2 is a schematic view of the ceramic matrix composite and superalloy countersunk head bolt connection;

FIG. 3 is a flow chart of progressive damage analysis of a ceramic matrix composite and superalloy bolt-on-bolt joint.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

A design method for ultimate failure load of a ceramic matrix composite and superalloy mechanical connection structure under a high-temperature thermal mismatch condition comprises the following steps:

s100, according to geometric parameters, initial assembly parameters and environmental temperature of the ceramic matrix composite and the high-temperature alloy raised head or the countersunk head bolt fastener, establishing a three-dimensional finite element analysis model of the ceramic matrix composite and the high-temperature alloy raised head or the countersunk head bolt fastener under a high-temperature uniaxial tensile loading condition by using ABAQUS software;

s200, selecting a bilinear or nonlinear constitutive model, a failure criterion and a degradation model of the ceramic matrix composite, establishing a progressive damage analysis model of the C/SiC composite structure, performing stress analysis, and starting to call the stress sigma of the unit integration point in the kth increment step^k；

S300, because the yield strength of the high-temperature alloy is far higher than that of the ceramic matrix composite, the failure process of the screw connection structure is mainly determined by the performance of the composite, so that the plasticity and the damage of the high-temperature alloy are not considered in finite element analysis, and the material is in an elastic deformation stage. Substituting the stress of the integration point of the ceramic matrix composite material unit into a Tsai-Wu failure criterion for judgment, if the failure criterion is met, the material unit point fails, and performing material rigidity degradation according to a degradation model; if the failure criterion is not met, the material is not damaged, and the rigidity of the material is not changed C^k+1＝C^kUpdate the stress σ^k+1＝σ^k+C^k+1·Δε^k；

S400, judging whether damage in the composite material structure causes structural damage or not; if the structure is not damaged, increasing the increment of the mechanical load, and returning to S200; if the structure is damaged, the structure loses bearing capacity, analysis is stopped, residual pretightening force and assembly clearance of the C/SiC ceramic matrix composite and the high-temperature alloy bolt fastener are obtained, and failure load at corresponding environmental temperature is obtained;

s500, modifying the environment temperature, and repeating S200 to S400 to obtain the ultimate failure load of the C/SiC ceramic matrix composite and the high-temperature alloy bolt fastener in the corresponding environment temperature range under the high-temperature thermal mismatch condition and the corresponding initial and final assembly pretightening force and clearance thereof.

Further, in S100, the step of establishing a three-dimensional finite element analysis model includes:

s110, according to the geometric parameters of the ceramic matrix composite and the high-temperature alloy raised head or the countersunk head bolt fastener, establishing a three-dimensional geometric model of the ceramic matrix composite and the high-temperature alloy countersunk head bolt fastener by using ABAQUS software;

s120, adopting an eight-node linear reduction integral hexahedron unit C3D8R and setting an enhanced hourglass control to perform structured grid division on the structure;

s130, defining 5 groups of contact pairs in ABAQUS according to the contact relation among the high-temperature alloy plate, the composite material plate and the bolt, and adding friction coefficients to each contact surface in the interaction property;

s140, directly applying axial pretightening force on the cross section of the bolt rod by using a Boltload command in ABAQUS, applying the clearance amount of the nail holes by setting the assembly value of a contact pair between the nail holes, ensuring that the pretightening force is not reduced to be below 0N at high temperature, and applying uniform high-temperature load to the whole connecting structure;

s150, applying solid support constraint to all directions of the end part of the high-temperature alloy plate, applying mechanical load to the X direction of the end part of the ceramic matrix composite plate, and constraining the displacement in the other two directions.

Further, in S300, the implementation process of predicting the composite failure state by applying the ceramic matrix composite failure criterion is as follows:

s301, reading unit integral point stress sigma of composite plate with ceramic matrix composite and high-temperature alloy countersunk head bolt connecting structure^k；

S302, substituting the stress value into an improved three-dimensional Hashin failure criterion and a Ye layering failure criterion to perform progressive damage analysis to judge the failure of the C/SiC composite material unit point, wherein the specific form of the strength criterion is as follows:

(1) matrix tensile failure (σ)₂₂＞0)：

(σ₂₂/Y_T)²+(σ₁₂/S₁₂)²+(σ₂₃/S₂₃)²≥1 (1)

(2) Matrix compression fracture failure (σ)₂₂＜0)：

(σ₂₂/Y_C)²+(σ₁₂/S₁₂)²+(σ₂₃/S₂₃)²≥1 (2)

(3) Fiber tensile failure (σ)₁₁＞0)：

(σ₁₁/X_T)²+(σ₁₂/S₁₂)²+(σ₁₃/S₁₃)²≥1 (3)

(4) Matrix tensile failure (σ)₁₁＜0)：

(σ₁₁/X_C)²≥1 (4)

(5) Fiber-matrix shear failure (σ)₁₁＜0)：

(σ₁₁/X_C)²+(σ₁₂/S₁₂)²+(σ₁₃/S₁₃)²≥1 (5)

(6) Fiber-matrix tensile delamination failure (σ)₃₃＞0)：

(σ₃₃/Z_T)²+(σ₁₃/S₁₃)²+(σ₂₃/S₂₃)²≥1 (6)

(7) Fiber-matrix compressive delamination failure (σ)₃₃＜0)：

(σ₃₃/Z_C)²+(σ₁₃/S₁₃)²+(σ₂₃/S₂₃)²≥1 (7)

In the formula, σ_ij(i, j-1, 2,3) is the stress to which the structure is subjected, X_T，X_C，Y_T，Y_C，Z_T，Z_C，S₁₂，S₁₃，S₂₃X, Y, Z represents tensile or compressive strength in the 1,2,3 directions, S represents shear strength, subscript T represents tensile, subscript C represents compression, for material strength parameters;

and S303, updating the unit failure state variable.

Further, in S300, the implementation process of performing material stiffness degradation on the failed material according to the degradation model includes:

s311, after the material unit is judged to be invalid, the rigidity value of the material unit in each direction is determined to be degraded, and the degraded rigidity is as follows:

(1) failure of the substrate at tensile break:

E'₂₂＝0.2·E₂₂，G'₁₂＝0.2·G₁₂,G'₂₃＝0.2·G₂₃ (8)

(2) matrix compression fracture failure (σ)₂₂＜0)：

E'₂₂＝0.4·E₂₂，G'₁₂＝0.4·G₁₂,G'₂₃＝0.4·G₂₃ (9)

(3) Fiber tensile failure (σ)₁₁＞0)：

E'₁₁＝0.07·E₁₁ (10)

(4) Matrix tensile failure (σ)₁₁＜0)：

E'₁₁＝0.07·E₁₁ (11)

(5) Fiber-matrix shear failure (σ)₁₁＜0)：

G'₁₂＝0，ν'₁₂＝0 (12)

(6) Fiber-matrix tensile delamination failure (σ)₃₃＞0)：

E'₃₃＝0，G'₂₃＝0，G'₁₃＝0，ν'₁₃＝0，ν'₂₃＝0 (13)

(7) Fiber-matrix compressive delamination failure (σ)₃₃＜0)：

E'₃₃＝0，G'₂₃＝0，G'₁₃＝0，ν'₁₃＝0，ν'₂₃＝0 (14)

S312, updating the rigidity matrix of the material, C^k+1＝C^dWherein C represents the post-injury material stiffness;

s313, updating stress sigma of damaged material^k+1＝C^k+1·(ε^k+Δε^k) Wherein, epsilon^kStrain, Δ ε, in the kth incremental step^kIs the strain increment;

s314, go to S500.

The above description is only a preferred embodiment of the ultimate failure load design method of the ceramic matrix composite and superalloy mechanical connection structure under the high temperature thermal mismatch condition, and the protection range of the ultimate failure load design method of the ceramic matrix composite and superalloy mechanical connection structure under the high temperature thermal mismatch condition is not limited to the above embodiments, and all technical schemes belonging to the idea belong to the protection range of the present invention. It should be noted that several improvements and changes may be made by those skilled in the art without departing from the principle of the present invention, and such changes, modifications, substitutions and alterations should also be considered as the protection scope of the present invention.