CN115345059A - A method and system for predicting the strength of a rubber-screw hybrid connection considering nail damage - Google Patents

Abstract

The invention relates to a method and a system for predicting mixed glue and screw connection strength considering the damage of an inserted pin, which relate to the field of CFRP (carbon fiber reinforced plastics) connection, wherein the method comprises the steps of constructing a three-dimensional finite element model of the interference inserted pin of a mixed glue and screw connection structure made of a carbon fiber reinforced composite material according to tensile strength, shearing strength, the structure size, contact attributes, load and boundary conditions of the connection structure; based on the model, the type I fracture energy and the type II fracture energy, carrying out damage analysis according to contact stress among the interference bolt, the glue layer and the hole wall of the carbon fiber reinforced composite material, and determining a damage distribution and rigidity reduction model; constructing a tensile damage model of the carbon fiber reinforced composite material rubber-spiral mixed connection structure according to damage distribution; and carrying out stress analysis on the steel plate according to failure criteria and a rigidity reduction model to determine the tensile strength. The invention effectively analyzes and predicts the tensile strength of the CFRP rubber-screw mixed connection structure, and reduces the material cost and the preparation period of the test method.

Description

A method and system for predicting the strength of a rubber-screw hybrid connection considering nail damage

technical field

The invention relates to the field of CFRP connections, in particular to a method and system for predicting the strength of a rubber-screw hybrid connection in consideration of nail insertion damage.

Background technique

The rubber-screw hybrid connection structure is usually used in the assembly process of the overall composite structure. In recent years, the performance of composite materials has been studied in depth, and it is found that the interference connection can not only improve the fatigue performance of the connection structure, but also effectively improve the rubber-screw hybrid connection structure. The problem of low bolt bearing efficiency. However, the diameter of the shank of the interference bolt is larger than the diameter of the hole before installation, and it needs to be installed with the help of mechanical external force. Due to the low elongation and non-uniformity of the composite material, the extrusion of the bolt causes different degrees of damage to the composite hole wall in the axial and circumferential directions, resulting in a substantial change in the contact relationship between the bolt and the hole wall; The friction force and radial extrusion force also make the stress concentration of the adhesive layer in the interference area high, and the cohesive damage inside the adhesive layer accelerates the initiation and propagation of cracks under the action of the applied load, resulting in premature failure of the connection structure.

From the research status at home and abroad, it can be seen that the existing research on the installation process of interference bolted joint structures mainly focuses on the damage form and stress distribution of composite materials, and most of the research is mainly based on test methods, while the research on the interference caused by the adhesive layer after curing Research on performance degradation and its impact on the bearing strength of connected structures is relatively scarce. The finite element method is a method for studying the strength of the carbon fiber reinforced polymer (Carbon Fiber Reinforced Polymer/Plastic, CFRP) glue-screw hybrid connection structure. However, in the prediction of the bearing strength of the related composite connection structure, the installation of fasteners is ignored. The damage caused to the connection part during the process, especially the stress concentration and cohesive damage of the height of the adhesive layer, leads to inaccurate assembly contact relationship between the bolt, the adhesive layer and the hole wall, and the stress of the adhesive layer and the hole wall of the composite material The contact relationship between the field and the assembly has an important influence on the tensile strength of the connected structure, and the existing prediction results are not accurate enough.

Contents of the invention

The purpose of the present invention is to provide a method and system for predicting the strength of a rubber-screw hybrid connection considering nail damage, to effectively analyze and predict the tensile strength of a carbon fiber reinforced composite material rubber-screw hybrid connection structure, and to reduce the material cost and cost of the test method Prep cycle.

To achieve the above object, the present invention provides the following scheme:

A method for predicting the strength of glue-screw hybrid connections considering the damage of screw insertion, including:

Obtain the tensile strength, shear strength, mode I fracture energy and mode II fracture energy of the adhesive layer;

According to the tensile strength, the shear strength, the structural size of the connection structure, the contact properties of the connection structure, the load of the connection structure and the boundary conditions of the connection structure, the three-dimensional finite interference of the interfering nail of the carbon fiber reinforced composite glue-screw hybrid connection structure is constructed. a metamodel; the connection structure includes carbon fiber reinforced composite material, the adhesive layer and interference bolts; the contact properties include a coefficient of friction;

Based on the three-dimensional finite element model of the carbon fiber reinforced composite glue-screw hybrid connection structure interference insertion nail, the I-mode fracture energy and the II-mode fracture energy, according to the interference bolt, the adhesive layer and the carbon fiber reinforced composite material hole The contact stress between the walls is used for damage analysis, and the damage distribution and stiffness reduction model are determined;

According to the damage distribution, the tensile damage model of the carbon fiber reinforced composite rubber-screw hybrid connection structure is constructed;

Stress analysis is performed on the tensile damage model of the carbon fiber reinforced composite rubber-screw hybrid connection structure according to the failure criterion and the stiffness reduction model to determine the tensile strength.

Optionally, said obtaining the tensile strength, shear strength, type I fracture energy and type II fracture energy of the adhesive layer specifically includes:

Carrying out tensile test to described adhesive layer obtains tensile strength;

Carrying out a shear test to the adhesive layer to obtain the shear strength;

Carry out double cantilever beam test to described adhesive layer and obtain I mode fracture energy;

A three-point bending test was performed on the adhesive layer to obtain the mode II fracture energy.

Optionally, the carbon fiber reinforced composite glue-screw hybrid connection is constructed according to the tensile strength, the shear strength, the structural size of the connecting structure, the contact properties of the connecting structure, the load of the connecting structure and the boundary conditions of the connecting structure Three-dimensional finite element model of structural interference nails, including:

Constructing a three-dimensional geometric model according to the structural dimensions of the connection structure, the contact properties of the connection structure, and the boundary conditions of the connection structure;

determining the displacement of the interfering nails according to the load of the connecting structure;

determining the stress-strain constitutive relationship of the carbon fiber reinforced composite material according to the tensile strength and the shear strength;

According to the three-dimensional geometric model, the displacement of the interfering nails, and the stress-strain constitutive relationship of the carbon fiber reinforced composite materials, a three-dimensional finite element model of the interfering nails of the carbon fiber reinforced composite glue-screw hybrid connection structure is constructed.

Optionally, based on the three-dimensional finite element model of the interfering stud, the mode I fracture energy and the mode II fracture energy based on the carbon fiber reinforced composite glue-screw hybrid connection structure, according to the interference bolt, the adhesive layer As well as the contact stress between the hole walls of carbon fiber reinforced composite materials, the damage analysis is carried out to determine the damage distribution and stiffness reduction model, including:

According to the adhesive layer in the three-dimensional finite element model of the carbon fiber-reinforced composite glue-screw hybrid connection structure interference inserting nails, the secondary stress failure criterion is used for stress analysis to determine the damage of the adhesive layer; the damage includes occurrence of damage and No damage occurred;

When the damage condition of the adhesive layer is damage, the adhesive layer stiffness reduction in the stiffness reduction model is determined according to the damage variable and the displacement of the adhesive layer;

determining a damage distribution based on said Mode I fracture energy and said Mode II fracture energy;

According to the carbon fiber reinforced composite material in the three-dimensional finite element model of the interfering nail-screw hybrid connection structure of the carbon fiber reinforced composite material, the maximum stress criterion and the three-dimensional Hassing failure criterion are used for stress analysis to determine the damage of the carbon fiber reinforced composite material;

When the damage condition of the carbon fiber reinforced composite material is damage, the stiffness reduction of the carbon fiber reinforced composite material in the damage stiffness reduction model is determined according to the damage stiffness matrix.

A system for predicting the strength of glue-screw hybrid joints considering nail damage, including:

An acquisition module, configured to acquire the tensile strength, shear strength, type I fracture energy and type II fracture energy of the adhesive layer;

The three-dimensional finite element model building block of the carbon fiber reinforced composite glue-screw hybrid connection structure interference inserting nails is used to calculate the tensile strength, the shear strength, the structural size of the connection structure, the contact properties of the connection structure, and the load of the connection structure and the boundary conditions of the connection structure to construct a three-dimensional finite element model of the interfering screw of the carbon fiber reinforced composite glue screw hybrid connection structure; the connection structure includes the carbon fiber reinforced composite material, the adhesive layer and the interference bolt; the contact properties include the coefficient of friction;

The damage analysis module is used to, based on the three-dimensional finite element model of the interfering stud of the carbon fiber-reinforced composite glue-screw hybrid connection structure, the I-mode fracture energy and the II-mode fracture energy, according to the interference bolt, the adhesive layer And the contact stress between the carbon fiber reinforced composite material hole wall is used for damage analysis, and the damage distribution and stiffness reduction model are determined;

A tensile damage model building block for a carbon fiber reinforced composite material rubber-screw hybrid connection structure, used to construct a carbon fiber reinforced composite material rubber-screw hybrid connection structure tensile damage model according to the damage distribution;

The stress analysis module is used to perform stress analysis on the tensile damage model of the carbon fiber reinforced composite rubber-screw hybrid connection structure according to the failure criterion and the stiffness reduction model, and determine the tensile strength.

Optionally, the acquisition module specifically includes:

a tensile strength acquisition unit, configured to perform a tensile test on the adhesive layer to obtain the tensile strength;

a shear strength acquisition unit, configured to perform a shear test on the adhesive layer to obtain the shear strength;

A type I fracture energy acquisition unit, configured to perform a double cantilever beam test on the adhesive layer to obtain a type I fracture energy;

The type II fracture energy acquisition unit is used to perform a three-point bending test on the adhesive layer to obtain the type II fracture energy.

Optionally, the construction module of the three-dimensional finite element model of the carbon fiber-reinforced composite glue-screw hybrid connection structure interference inserting nails specifically includes:

A three-dimensional geometric model construction unit, configured to construct a three-dimensional geometric model according to the structural dimensions of the connection structure, the contact properties of the connection structure and the boundary conditions of the connection structure;

An interference nail displacement determining unit, configured to determine the interference nail displacement according to the load of the connecting structure;

A carbon fiber reinforced composite material stress-strain constitutive relationship determination unit, used to determine the carbon fiber reinforced composite material stress-strain constitutive relationship according to the tensile strength and the shear strength;

The construction unit of the three-dimensional finite element model model of the interfering screw of the carbon fiber reinforced composite glue-screw hybrid connection structure is used to construct the carbon fiber reinforced composite material according to the three-dimensional geometric model, the displacement of the interfering pin and the stress-strain constitutive relationship of the carbon fiber reinforced composite material. Three-dimensional finite element model of interfering nails in composite rubber-screw hybrid connection structure.

Optionally, the damage analysis module specifically includes:

The damage determination unit of the adhesive layer is used to perform stress analysis on the adhesive layer in the three-dimensional finite element model of the carbon fiber reinforced composite glue-screw hybrid connection structure interference insertion nail using the secondary stress failure criterion to determine the damage of the adhesive layer situation; the damage situation includes occurrence of damage and non-injury;

The glue line stiffness reduction determination unit is used to determine the glue line stiffness reduction in the stiffness reduction model according to the damage variable and the displacement of the glue line when the damage condition of the glue line is damage;

a damage distribution determination unit configured to determine a damage distribution based on the mode I fracture energy and the mode II fracture energy;

The damage determination unit of the carbon fiber reinforced composite material is used for stress analysis using the maximum stress criterion and the three-dimensional Hasing failure criterion according to the carbon fiber reinforced composite material in the three-dimensional finite element model of the carbon fiber reinforced composite material rubber-screw hybrid connection structure interference insertion nail , determining the damage condition of the carbon fiber reinforced composite material;

The carbon fiber reinforced composite material stiffness reduction determination unit is used to determine the carbon fiber reinforced composite material stiffness reduction in the damage stiffness reduction model according to the damage stiffness matrix when the damage condition of the carbon fiber reinforced composite material is damage.

According to the specific embodiments provided by the invention, the invention discloses the following technical effects:

The present invention obtains the tensile strength, shear strength, type I fracture energy and type II fracture energy of the adhesive layer; according to the tensile strength, the shear strength, the structural size of the connection structure, the contact property of the connection structure, the The load of the structure and the boundary condition of the connection structure construct the three-dimensional finite element model of the interfering nail of the mixed connection structure of carbon fiber reinforced composite glue and screw; Type II fracture energy and the Type II fracture energy, according to the contact stress between the interference bolts, the adhesive layer and the carbon fiber reinforced composite hole wall, the damage analysis is carried out to determine the damage distribution and stiffness reduction model; according to the damage Distributed construction of the tensile damage model of the carbon fiber-reinforced composite rubber-screw hybrid connection structure; according to the failure criterion and the stiffness reduction model, the stress analysis of the tensile damage model of the carbon fiber-reinforced composite rubber-screw hybrid connection structure is carried out to determine the tension strength. Effectively analyze and predict the tensile strength of the carbon fiber reinforced composite rubber-screw hybrid connection structure, and reduce the material cost and preparation period of the test method.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the embodiments. Obviously, the accompanying drawings in the following description are only some of the present invention. Embodiments, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without paying creative labor.

Fig. 1 is the flow chart of the method for predicting the strength of the rubber-screw hybrid connection considering the nail damage provided by the present invention in practical application;

Fig. 2 is a structural schematic diagram of an interference nail provided by the present invention;

Fig. 3 is the schematic diagram of the three-dimensional finite element model of the interference nail provided by the present invention;

Fig. 4 is a schematic diagram of the nail pressing force-displacement curve in the interference nail insertion process provided by the present invention;

Fig. 5 is a schematic diagram of a tensile finite element model of a carbon fiber reinforced composite material glue-screw hybrid connection structure considering nail insertion damage provided by the present invention;

Fig. 6 is the schematic diagram of tensile load-displacement curve provided by the present invention;

Fig. 7 is a flow chart of the method for predicting the strength of the glue-screw hybrid joint considering the damage of the inserted nail provided by the present invention.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The purpose of the present invention is to provide a method and system for predicting the strength of a rubber-screw hybrid connection considering nail damage, to effectively analyze and predict the tensile strength of a carbon fiber reinforced composite material rubber-screw hybrid connection structure, and to reduce the material cost and cost of the test method Prep cycle.

In order to make the above objects, features and advantages of the present invention more comprehensible, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

As shown in Figure 7, the present invention provides a method for predicting the strength of a rubber-screw hybrid connection considering nail damage, including:

Step 701: Obtain the tensile strength, shear strength, mode I fracture energy and mode II fracture energy of the adhesive layer.

Step 701 specifically includes: performing a tensile test on the adhesive layer to obtain the tensile strength; performing a shear test on the adhesive layer to obtain the shear strength; performing a double cantilever beam test on the adhesive layer to obtain the mode I fracture energy;

A three-point bending test was performed on the adhesive layer to obtain the mode II fracture energy.

Step 702: Construct a carbon fiber reinforced composite glue-screw hybrid connection structure interference interpolation according to the tensile strength, the shear strength, the structural size of the connection structure, the contact properties of the connection structure, the load of the connection structure, and the boundary conditions of the connection structure A three-dimensional finite element model of a nail; the connection structure includes carbon fiber reinforced composite materials, the adhesive layer and interference bolts; the contact properties include a friction coefficient.

Step 702 specifically includes:

Construct a three-dimensional geometric model according to the structural dimensions of the connection structure, the contact properties of the connection structure and the boundary conditions of the connection structure; determine the interfering nail displacement according to the load of the connection structure; according to the elongation and the The shear strength determines the stress-strain constitutive relationship of carbon fiber reinforced composite materials; according to the three-dimensional geometric model, the displacement of the interfering pins and the stress-strain constitutive relationship of carbon fiber reinforced composite materials, the construction of carbon fiber reinforced composite material glue-screw hybrid connection Three-dimensional finite element model of structural interference pins.

Step 703: Based on the three-dimensional finite element model of the interfering stud of the carbon fiber-reinforced composite glue-screw hybrid connection structure, the mode I fracture energy and the mode II fracture energy, according to the interference bolt, the adhesive layer and the carbon fiber reinforcement The contact stress between the composite hole walls is analyzed for damage, and the damage distribution and stiffness reduction model are determined.

Step 703 specifically includes:

According to the adhesive layer in the three-dimensional finite element model of the carbon fiber-reinforced composite glue-screw hybrid connection structure interference inserting nails, the secondary stress failure criterion is used for stress analysis to determine the damage of the adhesive layer; the damage includes occurrence of damage and No damage occurred.

When the damage condition of the adhesive layer is damage, the adhesive layer stiffness reduction in the stiffness reduction model is determined according to the damage variable and the displacement of the adhesive layer.

Damage distribution is determined from the Mode I fracture energy and the Mode II fracture energy.

According to the carbon fiber reinforced composite material in the three-dimensional finite element model of the interfering screw-and-screw hybrid connection structure of the carbon fiber reinforced composite material, the maximum stress criterion and the three-dimensional Hassing failure criterion are used for stress analysis to determine the damage of the carbon fiber reinforced composite material.

When the damage condition of the carbon fiber reinforced composite material is damage, the stiffness reduction of the carbon fiber reinforced composite material in the damage stiffness reduction model is determined according to the damage stiffness matrix.

Step 704: Construct a tensile damage model of the carbon fiber reinforced composite rubber-screw hybrid connection structure according to the damage distribution.

Step 705: Perform stress analysis on the tensile damage model of the carbon fiber reinforced composite rubber-screw hybrid connection structure according to the failure criterion and the stiffness reduction model to determine the tensile strength.

In order to overcome the fact that the existing prediction method ignores the real stress state and damage distribution of the adhesive layer after the interference bolt is installed, and cannot establish an accurate contact relationship between the bolt, the adhesive layer and the composite material hole wall, the present invention provides a consideration Considering the nail damage, the method of predicting the strength of the glue-screw hybrid connection with nail damage is the specific processing process in practical application. This method can effectively analyze and predict the tensile strength of the carbon fiber reinforced composite glue-screw hybrid connection structure, reducing the The material cost and preparation period of the test method are used to optimize the assembly process and promote the development of advanced connection technology.

As shown in Figure 1, this embodiment takes ERGO7200 structural adhesive, T700/TED-85 carbon fiber reinforced composite material (layer sequence is [0/45/-45/90] _3s ) and Ti6Al4V bolt material as examples, and provides a A method for predicting the strength of a glue-screw hybrid connection considering nail damage, comprising the following steps:

1. Conduct tensile test, shear test, double cantilever beam test, and three-point bending test on the adhesive layer samples to obtain the tensile strength, shear strength, type I and II fracture toughness of the adhesive layer, and on this basis A bilinear cohesive constitutive model of the adhesive layer was established on the

具体为设计长40mm，宽13mm的试样，对中胶接，胶层厚度为12mm，进行拉伸试验，得到极限载荷为1248N，因此胶层的拉伸强度

为8MPa。1.1 According to the requirements in ASTM-D2095, perform a tensile test to obtain the tensile strength in the normal direction

Specifically, a sample with a length of 40mm and a width of 13mm is designed, glued in the center, and the thickness of the glue layer is 12mm. The tensile test is carried out, and the ultimate load is 1248N. Therefore, the tensile strength of the glue layer

is 8MPa.

和

具体为设计长190.5mm，宽25mm的试样，上下胶接，搭接区域面积为343mm²，进行剪切试验，得到极限载荷为6174N，因此胶层的两个剪切强度

及

为18MPa。步骤1.1和步骤1.2得到的是胶层所允许承受的最大拉伸强度和剪切强度。1.2 According to the requirements in ASTM-D3165, perform a tensile test to obtain the strength in the shear direction

and

Specifically, a sample with a length of 190.5mm and a width of 25mm is designed, the upper and lower parts are glued together, and the overlapping area is 343mm ² . The shear test is carried out, and the ultimate load is 6174N. Therefore, the two shear strengths of the adhesive layer

and

is 18MPa. Step 1.1 and step 1.2 obtain the maximum tensile strength and shear strength that the adhesive layer is allowed to bear.

进行双悬臂梁试验，获取胶层的I型断裂能

进行三点弯曲试验，获取胶层的II型断裂能

计算公式如下：1.3 According to the HB 7402-96 test standard and the HB 7403-96 test standard, the double cantilever beam test and the three-point bending test are carried out, and the formula (1) and formula (2) can be obtained

Perform double cantilever beam test to obtain the mode I fracture energy of the adhesive layer

Perform a three-point bending test to obtain the mode II fracture energy of the adhesive layer

Calculated as follows:

in:

Among them, P _I and P _II are the applied load; a is the crack length of the adhesive layer; χ is the correction coefficient of the crack length; h is the thickness of the adhesive layer; b is the width of the adhesive layer sample; E ₁₁ is the x direction of the adhesive layer The elastic modulus; E ₂₂ is the elastic modulus in the y direction of the adhesive layer; G ₁₃ is the shear modulus in the xoz plane of the adhesive layer, and Γ is the intermediate parameter.

The bilinear stress-strain constitutive model of the adhesive layer satisfies the following expression:

[t _n t _s t _t ] ^T ＝K[δ _n δ _s δ _t ] ^T (5)

Among them, K is the stiffness matrix of the adhesive layer, t _n , t _s , and t _t are the stress components of the adhesive layer in the normal direction and two shear directions respectively; K _n , K _s , K _t are the stress components of the adhesive layer in the normal direction and two The stiffness of the two shearing directions is known, and the two shearing directions are the stiffnesses of the adhesive layer in the 13 direction and the 23 direction; δ _n , δ _s , δ _t are the normal and two shearing directions The relative displacement component of , its parameters are shown in Table 1:

Table 1 Adhesive layer material parameters

无法通过试验得到有效的测量，通常情况下

Type III fracture energy

cannot be effectively measured through experiments, usually

2. According to the structural dimensions, contact properties, loads and boundary conditions of carbon fiber reinforced composite materials, adhesive layers and interference bolts, use ABAQUS finite element software to establish a three-dimensional finite element model of interfering bolts for carbon fiber reinforced composite rubber-screw hybrid connection structures, and build Stress-strain constitutive relationship for carbon fiber reinforced composites. The tensile strength and shear strength obtained in step 1 provide parameter input for the glue layer model in step 2.

2.1 The structure required in ASTM D-5961 is shown in Figure 2, and its dimensional parameters are shown in Table 2. (a) in Figure 2 is a schematic diagram of the adhesive layer structure, and (b) in Figure 2 is a schematic diagram of the interference bolt structure , (c) in Figure 2 is a schematic diagram of the structure of a carbon fiber composite laminate. The three-dimensional geometric model of carbon fiber reinforced composite material, adhesive layer and bolt is established by using ABAQUS software, as shown in Fig. 3. According to the requirements of ASTM D-5961, the three-dimensional geometric models of carbon fiber reinforced composite materials, adhesive layers and bolts were established by using ABAQUS software. Since the length of the polished bolt rod is greater than the thickness of the connecting structure stack, the threaded part is ignored, and the bolt is simplified into a "T"-shaped solid model. The parameters are shown in Table 3, and the identification names of each three-dimensional geometric model are set. Set the identification name of the adhesive layer as ADHESIVE-1; the identification names of carbon fiber reinforced composite materials as PLANE-1 and PLANE-2; the identification name of the bolts as BOLT-1.

Table 2 Dimensional parameters of CFRP rubber-screw hybrid connection structure

L _a , W _a , _{ea , ra are the width, length, distance from the center of the hole to one end and the radius of the adhesive layer, R is the diameter of the bolt, L p , W p , e p , r are} the CFRP laminates The length, width, distance and radius from the center of the hole to one end, in mm.

Table 3 Ti6Al4V bolt material parameters

E is the elastic modulus of the bolt, and V is Poisson's ratio.

2.2 Set the maximum tensile strength, shear strength, and mode I and II fracture energy of the adhesive layer in the attribute module to establish a bilinear stress-strain constitutive model. The adhesive layer adopts the cohesive force unit COH3D8, carbon fiber reinforced composite material and Bolts use reduced integral hexahedral element C3D8R, and set enhanced hourglass control to reduce mesh distortion.

2.3 Surface binding constraints are used between the glue layer and the upper and lower composite laminates in the assembly, the friction relationship is established between the bolts and the glue layer and the carbon fiber reinforced composite material, the main surface and the slave surface are defined, and the friction coefficient and "Hard" contact.

2.4 According to the real test conditions, limit the freedom of carbon fiber reinforced composite material and base in 3 moving directions and 3 rotating directions, and limit the 5 degrees of freedom of bolts except z direction movement; establish interference insertion nail displacement in the load module. Among them, the displacement of the interfering nail is 8.5mm.

2.5 Establish the stress-strain constitutive relationship of carbon fiber reinforced composite materials. The carbon fiber reinforced composite material is modeled as a transversely isotropic material, and its stress-strain constitutive relationship can be expressed as:

in:

C ₁₁ =E ₁₁ (1−v ₂₃ v ₃₂ )/Δ(8)

C ₂₂ =E ₂₂ (1−v ₁₃ v ₃₁ )/Δ(9)

C ₃₃ =E ₃₃ (1−v ₁₂ v ₂₁ )/Δ(10)

C ₁₂ =E ₁₁ (v ₂₁ +v ₃₁ v ₂₃ )/Δ(11)

C ₂₃ =E ₂₂ (v ₃₂ +v ₁₂ v ₃₁ )/Δ(12)

C ₁₃ =E ₁₁ (v ₃₁ +v ₂₁ v ₃₂ )/Δ(13)

C ₄₄ =2G ₁₂ (14)

C ₅₅ =2G ₂₃ (15)

C ₆₆ =2G ₁₃ (16)

Δ=1/(1-v ₁₂ v ₂₁ -v ₂₃ v ₃₂ -v ₁₃ v ₃₁ -2v ₂₁ v ₃₂ v ₁₃ ) (17)

where σ _n and σ _t are the normal stress components (σ ₁₁ , σ ₂₂ , σ ₃₃ ) and shear stress components (σ ₁₂ , σ ₁₃ , σ ₂₃ ) respectively; ε _n and ε _t are the normal strain Components (ε ₁₁ , ε ₂₂ , ε ₃₃ ) and shear strain components (ε ₁₂ , ε ₁₃ , ε ₂₃ ); C _ij =C _ji (i, j=1, 2,...6); and C _ij is the stiffness coefficient.

E ₁ , E ₂ , E ₃ are the elastic modulus of the carbon fiber reinforced composite material, G ₁₂ , G ₁₃ , G ₂₃ are the shear modulus of the carbon fiber reinforced composite material, v12, v13, v23 are the Poisson of the carbon fiber reinforced composite material , where the subscripts 12, 13, and 23 respectively indicate the directions 12, 13, and 23 of carbon fiber reinforced composite materials; and v _ij =v _ji , (i, j=1, 2,...6). Δ is an intermediate parameter.

The parameters of T700/TED-85 carbon fiber reinforced composite materials are shown in Table 4.

Table 4 T700/TED-85 material parameters and strength

X _T is the fiber tensile strength, X _C is the fiber compressive strength, Y _T is the in-plane matrix tensile strength, Y _C is the in-plane matrix compressive strength, Z _T is the out-of-plane matrix tensile strength, Z _C is the out-of-plane matrix Compressive strength, S ₁₂ , S ₁₃ , S ₂₃ are shear strength, the unit is MPa.

3. Combined with the 3D finite element model in step 2, according to the contact stress between the bolt and the adhesive layer and the composite material hole wall, use the corresponding material failure criterion to conduct damage analysis on each adhesive layer and carbon fiber reinforced composite material unit, and judge whether the unit is damaged. If there is damage, use the corresponding stiffness reduction model to reduce the current material stiffness and update the stress; if there is no damage, the element stiffness remains unchanged.

3.1 Carry out stress analysis on the adhesive layer unit, and use the secondary stress failure criterion to judge whether the adhesive layer unit is damaged. The criteria are as follows:

和

分别是胶层的法向拉伸强度及13方向和23方向的剪切强度；t_n、T_s、t_t分别是拉伸载荷下胶层当前的法向应力和13方向和23方向的剪应力。若Fa≥1，胶层单元发生损伤；若F_a＜1，胶层单元未发生损伤。In the formula, the symbols <> are Macaulay brackets, indicating that the compressive load will not cause damage to the adhesive layer.

and

are the normal _tensile strength of the adhesive layer and the _shear strength in the 13-direction and 23 _- direction respectively; stress. If Fa≥1, the subbing layer unit is damaged; if F _a <1, the subbing layer unit is not damaged.

3.2 If the adhesive layer unit is damaged and cracks are generated, the mixed mode B-K criterion based on fracture toughness is used to predict the comprehensive expansion of the three crack forms:

G _T =G _I +G _II (20)

分别为I、II型断裂能；G_I、G_II分别为当前I、II型断裂能；

为总断裂能；G_T是当前总断裂能即胶层材料破坏时当前I、II型断裂能之和；η为经验参数，设η＝1。In the formula,

are I and II fracture energies respectively; G _I and G _II are current I and II fracture energies respectively;

is the total fracture energy; G _T is the current total fracture energy, that is, the sum of the current type I and II fracture energy when the adhesive layer material is damaged; η is an empirical parameter, and η=1.

Apply discounts to the bondline element stiffness:

K _i =(1-D)K (21)

Then the stress-strain constitutive relation of the adhesive layer element after damage is:

in:

为胶层单元发生损伤时的初始位移；

为胶层单元完全失效时的位移；

为胶层单元的实际位移；δ₁、δ₂、δ₃分别是胶层单元的法向位移以及胶层13方向及23方向的位移。In the formula (24), i=n, s, t; D is the damage variable; K _i is the stiffness matrix after the damage of the adhesive layer unit;

is the initial displacement when the adhesive layer unit is damaged;

is the displacement when the adhesive layer unit fails completely;

is the actual displacement of the adhesive layer unit; δ ₁ , δ ₂ , and δ ₃ are the normal displacement of the adhesive layer unit and the displacements in the 13 and 23 directions of the adhesive layer, respectively.

3.3 Considering the shear nonlinear behavior of carbon fiber reinforced composite materials, combined with the maximum stress criterion and the three-dimensional Hasing failure criterion, the stress analysis of the carbon fiber reinforced composite material unit is carried out:

(1) Fiber tensile failure (σ ₁₁ ≥0):

(2) Fiber compression failure (σ ₁₁ <0):

(3) In-plane matrix tensile failure (σ ₂₂ +σ ₃₃ ≥0):

(4) In-plane matrix compression failure (σ ₂₂ +σ ₃₃ <0):

(5) Out-of-plane matrix tensile failure (σ ₃₃ ≥0):

(5) Out-of-plane matrix compression failure ((σ ₃₃ <0):

In the formula, σ ₁₁ , σ ₂₂ , and σ ₃₃ are the principal stresses in the three directions of x, y, and z, respectively; σ ₁₂ , σ ₁₃ , and σ ₂₃ are the in-plane shear stresses in the corresponding directions; X _c , X _t , Y _c , Y _t , Z _c , and Z _t are the tensile and compressive ultimate strengths in the three directions of x, y, and z respectively, the subscript t means tension, and c means compression; S ₁₂ , S ₁₃ , and S ₂₃ are the corresponding directions The shear ultimate strength of ; when F _ft , F _fc , F _mt , F _mc , F _nt , F _nc ≥ 1, the carbon fiber reinforced composite material unit is damaged; otherwise, the unit is not damaged.

3.4 When the carbon fiber reinforced composite material unit is damaged, the material damage stiffness matrix will be activated, and damage variables will be introduced to characterize the damage process. When the material is not damaged, the damage variable is 0; when damage occurs, the damage variable will increase monotonically, and when it reaches 1, it indicates that the material has completely failed. The damage stiffness matrix C _d related to the damage variables is expressed as follows:

Then the stress-strain constitutive relation of the carbon fiber reinforced composite unit after damage is:

in:

b ₁ =1-d _f (33)

b ₂ =1-d _m (34)

b ₃ =1-d _s (35)

Three independent damage variables are considered: d _f , d _m , d _s ; d _f represents degradation along the fiber direction; d _m represents degradation along the direction perpendicular to the fiber; d _s represents the degradation of shear properties parallel to the fiber direction. The relationship is as follows:

d _f ＝1-(1-d _FT )(1-d _FC ) (36)

d _m ＝1-(1-d _MT )(1-d _MC ) (37)

d _s ＝1-(1-d _f )(1-smt×d _MT )(1-smc×d _MC ) (38)

In the formula, d _FT , d _FC are the damage variables in the direction of fiber tension and compression; d _MT , d _MC are damage variables in the direction of matrix tension and compression; smt and smc are the damage caused by matrix tensile and compression Coefficient of shear modulus loss.

4. Combining the interference of the nail insertion displacement in 2.4, judge whether the nail insertion process is over. If the nail insertion process is not over, increase the nail insertion load, return to step 3, and continue the stress analysis; if the nail insertion process is over, the model stops analyzing ;The displacement of the interfering screw is a fixed value set artificially. During the analysis, the model divides the displacement of the screw into several small displacements according to the complexity of the model. If not, continue the analysis until the analysis of several small displacements is completed, and the model will automatically stop the analysis.

5. After the analysis of the three-dimensional finite element model of the carbon fiber reinforced composite rubber-screw hybrid joint structure interference nail insertion is stopped, compare the nail force-displacement curve, as shown in Figure 4, to verify the accuracy of the friction coefficient; the damage distribution of the unit is in the step The third calculation is obtained, and then the equivalent stress of each adhesive layer unit and carbon fiber reinforced composite material unit in the finite element results is extracted.

6. According to the three-dimensional anisotropic progressive damage model in step 3, that is, the criteria in 3.1 and 3.3, inherit the unit equivalent stress and damage distribution extracted in step 5, establish corresponding loads and boundary conditions, and build a carbon fiber reinforced composite The tensile damage model of the material rubber screw hybrid connection structure; as shown in Figure 5. Loads refer to bolt pretension in 6.2; boundary conditions refer to operational settings in 6.4.

6.1 Read the equivalent stress and damage distribution of the adhesive layer and carbon fiber reinforced composite material unit obtained in step 5, and correlate the equivalent stress and damage distribution of the unit in the predefined field according to the identification name of the adhesive layer and carbon fiber reinforced composite material in 2.1. Damage distribution.

6.2 Since the elastic-plastic damage of the bolts is not considered, refer to the structural dimensions of each component in 2.1, establish the "I"-shaped bolt model, replace the "T"-shaped bolt model, and apply the bolt pretightening force in the load module; in order to avoid the bolt section Attribute conflict, set bolt section attribute to default in Mesh module.

6.3 In the contact module, establish the friction properties between the bolt and the adhesive layer that inherits the equivalent stress and damage and the composite hole wall unit, add "hard" contact, and the friction coefficient is 0.1.

6.4 In the load and boundary module, establish the motion coupling reference point of the upper and lower laminates, limit the 6 degrees of freedom of the motion coupling reference point of the lower laminate, limit the 5 degrees of freedom except the x direction of the upper laminate motion coupling reference point, and add Quasi-static tensile displacement. Specifically, in the load and boundary module, the kinematic coupling reference points RP-1 and RP-2 of the upper and lower laminates are established, and the degrees of freedom of the upper and lower laminates are restricted, and a quasi-static tensile displacement of 3.5mm is added to the reference point RP-1 .

7. Combining the failure criterion and the stiffness reduction model in step 3, conduct stress analysis on the tensile damage model of the carbon fiber reinforced composite rubber screw hybrid interference connection structure in step 6, and judge whether each glue layer unit and composite material unit Damage or stiffness reduction. The present invention includes two stages: the interfering bolt insertion process + the stretching process after the nail insertion is completed. These two processes correspond to two different finite element models, so two judgments are required, but the criteria are the same, and the elements in the second tensile model inherit the stress and damage of the first model, and then Stress analysis is performed again under the action of tensile load, and then the damage and stiffness reduction are obtained, and finally the overall failure of the structure is obtained.

8. Determine whether the damage of each adhesive layer unit and composite material unit causes the failure of the connection structure. If the connection structure does not fail, increase the tensile load and return to step 7; if the connection structure fails, the model stops analyzing, and then The tensile load at this time is the tensile strength of the carbon fiber reinforced composite rubber-screw hybrid interference connection structure, and the output tensile load-displacement curve is shown in Figure 6, and the prediction effect is shown in Table 5. For carbon fiber reinforced composite material glue The prediction error of the tensile strength of the screw hybrid interference connection structure is 3.21%. Among them, the judgment of the failure of the connection structure is judged by the iterative calculation of the element stiffness by Abaqus software. When the element is damaged, the stiffness will be reduced, and the normal stiffness will be reduced to 0. However, the element stiffness has a negative value during the stretching process, which makes The software is unable to assemble the element stiffness matrix, and the analysis stops by itself, at which point the connection is considered to have failed.

Table 5 Comparison of tensile test and predicted results

The present invention also provides a system for predicting the strength of a rubber-screw hybrid connection considering nail damage, including:

The acquisition module is used to acquire the tensile strength, shear strength, mode I fracture energy and mode II fracture energy of the adhesive layer.

The three-dimensional finite element model building block of the carbon fiber reinforced composite glue-screw hybrid connection structure interference inserting nails is used to calculate the tensile strength, the shear strength, the structural size of the connection structure, the contact properties of the connection structure, and the load of the connection structure The three-dimensional finite element model of the interfering plug of the carbon fiber-reinforced composite glue-screw hybrid connection structure is constructed with the boundary conditions of the connection structure; the connection structure includes the carbon fiber-reinforced composite material, the adhesive layer and the interference bolt; the contact properties include the friction coefficient.

The damage analysis module is used to, based on the three-dimensional finite element model of the interfering stud of the carbon fiber-reinforced composite glue-screw hybrid connection structure, the I-mode fracture energy and the II-mode fracture energy, according to the interference bolt, the adhesive layer As well as the contact stress between the hole walls of carbon fiber reinforced composite materials, the damage analysis is carried out to determine the damage distribution and stiffness reduction model.

The tensile damage model building block of the carbon fiber reinforced composite rubber-screw hybrid connection structure is used for constructing the tensile damage model of the carbon fiber reinforced composite material rubber-screw hybrid connection structure according to the damage distribution.

The stress analysis module is used to perform stress analysis on the tensile damage model of the carbon fiber reinforced composite rubber-screw hybrid connection structure according to the failure criterion and the stiffness reduction model, and determine the tensile strength.

As an optional implementation manner, the acquisition module specifically includes:

The tensile strength obtaining unit is used to perform a tensile test on the adhesive layer to obtain the tensile strength.

The shear strength acquisition unit is configured to perform a shear test on the adhesive layer to obtain the shear strength.

The type I fracture energy acquisition unit is used for performing a double cantilever beam test on the adhesive layer to obtain the type I fracture energy.

The type II fracture energy acquisition unit is used to perform a three-point bending test on the adhesive layer to obtain the type II fracture energy.

As an optional implementation, the construction module of the three-dimensional finite element model of the carbon fiber-reinforced composite glue-screw hybrid connection structure interference inserting nail specifically includes:

A three-dimensional geometric model construction unit is configured to construct a three-dimensional geometric model according to the structural dimensions of the connection structure, the contact properties of the connection structure and the boundary conditions of the connection structure.

The interfering nail displacement determining unit is configured to determine the interfering nail displacement according to the load of the connecting structure.

The carbon fiber reinforced composite material stress-strain constitutive relationship determining unit is used for determining the carbon fiber reinforced composite material stress-strain constitutive relationship according to the tensile strength and the shear strength.

The construction unit of the three-dimensional finite element model model of the interfering screw of the carbon fiber reinforced composite glue-screw hybrid connection structure is used to construct the carbon fiber reinforced composite material according to the three-dimensional geometric model, the displacement of the interfering pin and the stress-strain constitutive relationship of the carbon fiber reinforced composite material. Three-dimensional finite element model of interfering nails in composite rubber-screw hybrid connection structure.

As an optional implementation manner, the damage analysis module specifically includes:

The damage determination unit of the adhesive layer is used to perform stress analysis on the adhesive layer in the three-dimensional finite element model of the carbon fiber reinforced composite glue-screw hybrid connection structure interference insertion nail using the secondary stress failure criterion to determine the damage of the adhesive layer Situation; the injury situation includes occurrence of injury and non-injury.

The glue line stiffness reduction determination unit is configured to determine the glue line stiffness reduction in the stiffness reduction model according to the damage variable and the displacement of the glue line when the damage condition of the glue line is damage.

A damage distribution determining unit configured to determine damage distribution according to the type I fracture energy and the type II fracture energy.

The damage condition determination unit of the carbon fiber reinforced composite material is used to perform stress analysis according to the carbon fiber reinforced composite material in the three-dimensional finite element model of the interfering screw interfering screw mixed connection structure of the carbon fiber reinforced composite material using the maximum stress criterion and the three-dimensional Hasing failure criterion , to determine the damage condition of the carbon fiber reinforced composite material.

The carbon fiber reinforced composite material stiffness reduction determination unit is used to determine the carbon fiber reinforced composite material stiffness reduction in the damage stiffness reduction model according to the damage stiffness matrix when the damage condition of the carbon fiber reinforced composite material is damage.

The invention considers the degradation of the cohesive performance of the adhesive layer after the installation of the interference bolt, the stress state and damage distribution of the hole wall interface of the composite material, and realizes accurate prediction of the tensile strength of the connection structure under quasi-static displacement loading.

Each embodiment in this specification is described in a progressive manner, each embodiment focuses on the difference from other embodiments, and the same and similar parts of each embodiment can be referred to each other. As for the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and for the related information, please refer to the description of the method part.

In this paper, specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; meanwhile, for those of ordinary skill in the art, according to the present invention Thoughts, there will be changes in specific implementation methods and application ranges. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims (8)

1. A method for predicting the mixed connection strength of a rubber bolt by considering the damage of a plug pin is characterized by comprising the following steps:

obtaining the tensile strength, the shear strength, the type I fracture energy and the type II fracture energy of the adhesive layer;

constructing a carbon fiber reinforced composite material rubber-screw mixed connection structure interference plug pin three-dimensional finite element model according to the tensile strength, the shear strength, the structure size of the connection structure, the contact property of the connection structure, the load of the connection structure and the boundary condition of the connection structure; the connecting structure comprises a carbon fiber reinforced composite material, the glue layer and an interference bolt; the contact attribute comprises a coefficient of friction;

based on the interference pin three-dimensional finite element model of the carbon fiber reinforced composite material rubber-screw mixed connection structure, the type I fracture energy and the type II fracture energy, performing damage analysis according to contact stress among the interference bolt, the rubber layer and the hole wall of the carbon fiber reinforced composite material, and determining a damage distribution and rigidity reduction model;

constructing a tensile damage model of the carbon fiber reinforced composite material rubber-spiral mixed connection structure according to the damage distribution;

and carrying out stress analysis on the tensile damage model of the carbon fiber reinforced composite material rubber-screw mixed connection structure according to failure criteria and the rigidity reduction model to determine the tensile strength.

2. The method for predicting the mixed joint strength of the rubber and the screw considering the nail inserting damage according to claim 1, wherein the obtaining of the tensile strength, the shear strength, the type I fracture energy and the type II fracture energy of the rubber layer specifically comprises:

performing a tensile test on the adhesive layer to obtain tensile strength;

carrying out a shear test on the adhesive layer to obtain the shear strength;

performing a double cantilever beam test on the adhesive layer to obtain I-type fracture energy;

and performing a three-point bending test on the adhesive layer to obtain II-type fracture energy.

3. The method for predicting the hybrid rubber-bolt joint strength considering the damage of the plug pin according to claim 1, wherein the constructing of the three-dimensional finite element model of the interference plug pin of the carbon fiber reinforced composite material hybrid rubber-bolt joint structure according to the tensile strength, the shear strength, the structural size of the joint structure, the contact property of the joint structure, the load of the joint structure and the boundary conditions of the joint structure specifically comprises:

constructing a three-dimensional geometric model according to the structure size of the connecting structure, the contact property of the connecting structure and the boundary condition of the connecting structure;

determining the displacement of the interference plug pins according to the load of the connecting structure;

determining the stress-strain constitutive relation of the carbon fiber reinforced composite material according to the tensile strength and the shear strength;

and constructing an interference plug pin three-dimensional finite element model of the carbon fiber reinforced composite material rubber-screw mixed connection structure according to the three-dimensional geometric model, the interference plug pin displacement and the stress-strain constitutive relation of the carbon fiber reinforced composite material.

4. The method for predicting the mixed glue and screw connection strength considering the damage of the inserted pin according to claim 1, wherein the interference inserted pin three-dimensional finite element model, the type i fracture energy and the type ii fracture energy based on the mixed glue and screw connection structure of the carbon fiber reinforced composite material are subjected to damage analysis according to the contact stress among the interference bolt, the glue layer and the hole wall of the carbon fiber reinforced composite material, and the damage distribution and stiffness reduction model are determined, and specifically comprise:

performing stress analysis by adopting a secondary stress failure criterion according to a glue layer in the interference plug pin three-dimensional finite element model of the carbon fiber reinforced composite material glue and screw mixed connection structure, and determining the damage condition of the glue layer; the damage condition comprises damage and non-damage;

when the damage condition of the glue layer is damage, determining the glue layer rigidity reduction in the rigidity reduction model according to the damage variable and the displacement of the glue layer;

determining damage distribution according to the type I fracture energy and the type II fracture energy;

performing stress analysis on the carbon fiber reinforced composite material in the interference plug pin three-dimensional finite element model of the carbon fiber reinforced composite material rubber-screw mixed connection structure by adopting a maximum stress criterion and a three-dimensional Haxin failure criterion to determine the damage condition of the carbon fiber reinforced composite material;

and when the damage condition of the carbon fiber reinforced composite material is damage, determining the rigidity reduction of the carbon fiber reinforced composite material in the damage rigidity reduction model according to the damage rigidity matrix.

5. A system for predicting the strength of a glue and nut mixed connection in consideration of the damage of a plug pin is characterized by comprising:

the acquisition module is used for acquiring the tensile strength, the shear strength, the type I fracture energy and the type II fracture energy of the adhesive layer;

the interference plug pin three-dimensional finite element model building module of the carbon fiber reinforced composite material rubber and screw mixed connection structure is used for building an interference plug pin three-dimensional finite element model of the carbon fiber reinforced composite material rubber and screw mixed connection structure according to the tensile strength, the shearing strength, the structure size of the connection structure, the contact property of the connection structure, the load of the connection structure and the boundary condition of the connection structure; the connecting structure comprises a carbon fiber reinforced composite material, the glue layer and an interference bolt; the contact attribute comprises a coefficient of friction;

the damage analysis module is used for carrying out damage analysis according to contact stress among the interference bolt, the glue layer and the hole wall of the carbon fiber reinforced composite material based on the interference insert nail three-dimensional finite element model, the type I fracture energy and the type II fracture energy of the carbon fiber reinforced composite material glue and screw mixed connection structure, and determining damage distribution and rigidity reduction models;

the carbon fiber reinforced composite material rubber and screw mixed connection structure tensile damage model building module is used for building a carbon fiber reinforced composite material rubber and screw mixed connection structure tensile damage model according to the damage distribution;

and the stress analysis module is used for carrying out stress analysis on the tensile damage model of the carbon fiber reinforced composite material rubber-screw mixed connection structure according to failure criteria and the rigidity reduction model so as to determine the tensile strength.

6. The system for predicting strength of a glue and screw mixed connection considering the damage of the inserted pin according to claim 5, wherein the obtaining module specifically comprises:

the tensile strength acquisition unit is used for carrying out a tensile test on the adhesive layer to obtain the tensile strength;

the shear strength acquisition unit is used for carrying out a shear test on the adhesive layer to obtain the shear strength;

the I-type fracture energy acquisition unit is used for carrying out a double cantilever beam test on the adhesive layer to obtain I-type fracture energy;

and the II-type fracture energy acquisition unit is used for carrying out a three-point bending test on the adhesive layer to obtain II-type fracture energy.

7. The system for predicting the mixed glue and screw connection strength considering the damage of the plug pin according to claim 5, wherein the interference plug pin three-dimensional finite element model building module of the carbon fiber reinforced composite glue and screw mixed connection structure specifically comprises:

a three-dimensional geometric model construction unit for constructing a three-dimensional geometric model according to the structural size of the connection structure, the contact property of the connection structure, and the boundary condition of the connection structure;

the interference plug pin displacement determining unit is used for determining the interference plug pin displacement according to the load of the connecting structure;

the carbon fiber reinforced composite material stress-strain constitutive relation determining unit is used for determining the carbon fiber reinforced composite material stress-strain constitutive relation according to the tensile strength and the shearing strength;

and the interference insertion nail three-dimensional finite element model construction unit of the carbon fiber reinforced composite material rubber and screw mixed connection structure is used for constructing the interference insertion nail three-dimensional finite element model of the carbon fiber reinforced composite material rubber and screw mixed connection structure according to the three-dimensional geometric model, the interference insertion nail displacement and the stress-strain constitutive relation of the carbon fiber reinforced composite material.

8. The system for predicting strength of a glue and screw hybrid connection considering the damage of a plug pin according to claim 5, wherein the damage analyzing module specifically comprises:

the damage condition determining unit of the glue layer is used for carrying out stress analysis according to a secondary stress failure criterion on the glue layer in the interference plug pin three-dimensional finite element model of the carbon fiber reinforced composite material glue and screw mixed connection structure, and determining the damage condition of the glue layer; the damage condition comprises damage and non-damage;

the glue layer rigidity reduction determining unit is used for determining glue layer rigidity reduction in the rigidity reduction model according to damage variables and glue layer displacement when the damage condition of the glue layer is damage;

a damage distribution determination unit for determining a damage distribution according to the type I fracture energy and the type II fracture energy;

the damage condition determining unit is used for performing stress analysis on the carbon fiber reinforced composite material in the three-dimensional finite element model of the interference plug pin of the glue and screw mixed connection structure of the carbon fiber reinforced composite material by adopting a maximum stress criterion and a three-dimensional Harsin failure criterion to determine the damage condition of the carbon fiber reinforced composite material;

and the carbon fiber reinforced composite material rigidity reduction determining unit is used for determining the rigidity reduction of the carbon fiber reinforced composite material in the damage rigidity reduction model according to the damage rigidity matrix when the damage condition of the carbon fiber reinforced composite material is damage.

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