Simulation Method and System for Assembly Damage of Composite Laminated Structure Considering Errors and External Loads

Abstract

The present invention discloses a simulation method and system for assembly damage of a composite material laminated structure considering errors and external loads. The method includes: calibrating the material properties of the composite material laminated structure after hole making, and quantitatively characterizing the contact characteristics of the hole wall connection interface of the composite material laminated structure after hole making; establishing a geometric and force collaborative pin connection simulation model according to the material properties and contact characteristics; establishing a geometric and force collaborative tensile load simulation model according to the geometric and force collaborative pin connection simulation model; performing stress analysis on the tensile process of the composite material laminated structure according to the geometric and force collaborative tensile load simulation model, and predicting the damage state and tensile strength during the assembly process. The present invention can improve the accuracy of the prediction results and avoid the problem of damaging the composite material laminated structure during the assembly process.

Description

Technical Field

[0001] The present invention relates to the field of advanced composite material connections, and particularly to a simulation method and system for assembly damage of composite material laminated structures considering errors and external loads. Background Art

[0002] Bolt connections are widely used in various engineering structures due to their simple structure, easy disassembly, low cost, etc., and still play an important role in the manufacture of modern aircraft using advanced composite materials. Since each mechanical connection hole in the aircraft structure destroys the material integrity, the main factors affecting the service strength of the mechanical connection part are stress concentration at the hole edge, micro-damage to the hole wall, and hole-making accuracy, especially for composite material components. Therefore, the hole-making accuracy and assembly quality of the connection holes are the key factors affecting the connection reliability and service strength of aircraft structural parts.

[0003] CFRP materials are typical difficult-to-machine materials. CFRP laminates are non-homogeneous, anisotropic, and hard non-metallic materials with extremely low interlayer bonding strength. During the cutting process, processing defects such as delamination, splitting, radial extrusion damage, and subsurface damage are likely to occur. The material fracture form is mainly brittle fracture of fibers. The frictional effect of carbon fibers on the tool edge leads to rapid tool edge dulling and short tool life. These characteristics make the hole-making process of CFRP structures extremely difficult, and it is difficult to guarantee the hole-making quality and accuracy. In bolt connection structures, interference fit can multiply the fatigue life of metal connectors and become one of the main methods for extending the life of connection structures. However, before installation, the diameter of the nail rod of the interference bolt is larger than the hole diameter, and mechanical external force is required for installation. Due to the low elongation and non-uniformity of composite materials, the extrusion of the bolt causes varying degrees of damage to the composite material hole wall along the axial and circumferential directions, resulting in premature failure of the connection structure.

[0004] From the research status at home and abroad, it can be seen that the existing research on the assembly process of CFRP interference bolt connection structures mainly focuses on the damage forms and stress distributions of composite materials. The finite element method is a method for predicting the assembly damage and strength of composite material connection structures. However, in the prediction of the bearing strength of relevant composite material connection structures, the hole-making accuracy and the damage caused to the connection part during the hole-making and assembly processes are ignored, resulting in inaccurate assembly contact relationships between the bolt and the hole wall. At the same time, the residual stress field of the composite material hole wall during the hole-making and assembly processes has an important impact on the tensile strength of the connection structure, and the prediction results of the existing models are not accurate enough. Summary of the Invention

[0005] The purpose of the present invention is to provide a simulation method and system for assembly damage of composite material laminated structures considering errors and external loads, so as to solve the problem that the prediction results of existing models have low accuracy, resulting in easy damage to composite material laminated structures during the assembly process.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] A simulation method for assembly damage of a composite laminate structure considering errors and external loads, comprising:

[0008] Calibrate the material properties of the composite laminate structure after standard hole-making, and quantitatively characterize the contact characteristics of the hole wall connection interface of the composite laminate structure after hole-making; the material properties include hole position deviation, hole diameter deviation, and hole perpendicularity deviation; the contact characteristics include damage state and tightening torque;

[0009] Establish a geometric and force collaborative pin connection simulation model of the composite laminate structure according to the material properties and the contact characteristics;

[0010] Establish a geometric and force collaborative tensile load simulation model of the composite laminate structure according to the geometric and force collaborative pin connection simulation model;

[0011] Perform stress analysis on the tensile process of the composite laminate structure according to the geometric and force collaborative tensile load simulation model, and predict the damage state and tensile strength during the assembly process.

[0012] Optionally, calibrating the material properties of the composite laminate structure after standard hole-making and quantitatively characterizing the contact characteristics of the hole wall connection interface of the composite laminate structure after hole-making specifically includes:

[0013] Calibrate the damage range of the hole perimeter area of the composite laminate structure after hole-making;

[0014] Slice the composite laminate structure within the damage range at equal distances along the direction perpendicular to the fiber normal, and calibrate the fiber volume fraction and porosity coefficient of each sliced area;

[0015] Establish a microscopic representative volume element with pores according to the fiber volume fraction and porosity coefficient;

[0016] Perform unidirectional loading in six degrees of freedom on the microscopic representative volume element with pores, homogenize and calculate the equivalent material properties with hole-making damage, and establish a constitutive model considering in-layer damage and inter-layer damage;

[0017] Determine the material properties of the composite laminate structure after hole-making according to the constitutive model;

[0018] Divide the composite laminate structure after hole-making into 4 pieces, and conduct friction coefficient calibration experiments on each divided composite laminate structure to quantitatively characterize the contact characteristics of the hole wall connection interface of the composite laminate structure after hole-making.

[0019] Optionally, establishing the geometric and force collaborative pin connection simulation model of the composite material laminated structure according to the material properties and the contact characteristics specifically includes:

[0020] Establish a three-dimensional geometric model of the bolt, and establish a three-dimensional geometric model of the composite material laminated structure according to the material properties;

[0021] During the assembly process, the laminates of the composite material laminated structure are in surface contact with each other. The hole wall area is divided into four parts. A friction relationship is established between the bolt and each area of the composite material hole wall, and the friction relationship is added to the contact characteristics;

[0022] Restrict the degrees of freedom of the three translational directions and the three rotational directions of the composite material laminated structure and the base, restrict the five degrees of freedom of the bolt moving in the horizontal and vertical directions, set the displacement of the bolt along the hole axis, establish an interference pin load constraint, and under the above restrictions, establish a composite material stress-strain constitutive relationship according to the equivalent material properties with hole-making damage;

[0023] Determine the contact stress between the bolt and the composite material hole wall area according to the composite material stress-strain constitutive relationship and the contact characteristics with the added friction relationship;

[0024] Based on the three-dimensional geometric model of the bolt and the three-dimensional geometric model of the composite material laminated structure, according to the contact stress, perform damage analysis on the composite material laminated structure by using the maximum stress criterion and the three-dimensional Hashin failure criterion, and establish the geometric and force collaborative pin connection simulation model.

[0025] Optionally, establishing the geometric and force collaborative tensile load simulation model of the composite material laminated structure according to the geometric and force collaborative pin connection simulation model specifically includes:

[0026] Read the pin connection simulation result file and output the residual stress field and damage field during the pin connection process; the pin connection simulation result file is the result file obtained by the geometric and force collaborative pin connection simulation model;

[0027] According to the pin connection simulation result file, establish a moving coupling reference point for the upper and lower laminates in the composite material laminated structure, restrict the degrees of freedom of the upper and lower laminates, add a static tensile position to the upper laminate, apply the bolt pre-tightening force, and set the upper and lower laminates in the composite material laminated structure as a predefined field to complete the setting operation;

[0028] Based on the above-mentioned setting operations, select the results of the last analysis step in the geometric and force collaborative pin connection simulation model, import the stress state and damage distribution brought during the pinning process, establish a three-dimensional tensile model inheriting the pinning force field, and complete the dynamic transfer and evolution process of the force field;

[0029] Perform stress analysis on the three-dimensional tensile model according to the failure criterion and stiffness reduction model, and establish the geometric and force collaborative tensile load simulation model.

[0030] A composite laminate structure assembly damage simulation system considering errors and external loads, comprising:

[0031] A material property and contact characteristic determination module, used to calibrate the material properties of the composite laminate structure after hole making, and quantitatively characterize the contact characteristics of the hole wall connection interface of the composite laminate structure after hole making; the material properties include hole position deviation, hole diameter deviation, and hole perpendicularity deviation; the contact characteristics include damage state and tightening torque;

[0032] A geometric and force collaborative pin connection simulation model establishment module, used to establish a geometric and force collaborative pin connection simulation model of the composite laminate structure according to the material properties and the contact characteristics;

[0033] A geometric and force collaborative tensile load simulation model establishment module, used to establish a geometric and force collaborative tensile load simulation model of the composite laminate structure according to the geometric and force collaborative pin connection simulation model;

[0034] A damage state and tensile strength determination module, used to perform stress analysis on the tensile process of the composite laminate structure according to the geometric and force collaborative tensile load simulation model, and predict the damage state and tensile strength during the assembly process.

[0035] Optionally, the material property and contact characteristic determination module specifically includes:

[0036] A damage range calibration unit, used to calibrate the damage range of the hole circumference area of the composite laminate structure after hole making;

[0037] A fiber volume coefficient and porosity coefficient calibration unit, used to slice the composite laminate structure within the damage range at equal distances along the direction perpendicular to the fiber normal, and calibrate the fiber volume coefficient and porosity coefficient of each slice area;

[0038] A unit for establishing a microscopic representative volume element with pores, used to establish a microscopic representative volume element with pores according to the fiber volume coefficient and porosity coefficient;

[0039] A constitutive model establishment unit considering in - layer damage and inter - layer damage is used to perform unidirectional loading with six degrees of freedom on the micro - representative volume element with pores, homogenize and calculate the equivalent material properties of the composite material with hole - making damage, and establish a constitutive model considering in - layer damage and inter - layer damage;

[0040] A material property determination unit is used to determine the material properties of the composite laminate structure after hole - making according to the constitutive model;

[0041] A contact characteristic determination unit is used to divide the composite laminate structure after hole - making into 4 equal parts, perform a friction coefficient calibration experiment on each equal - divided composite laminate structure, and quantitatively characterize the contact characteristics of the hole - wall connection interface of the composite laminate structure after hole - making.

[0042] Optionally, the geometric - force collaborative pin - connection simulation model establishment module specifically includes:

[0043] A three - dimensional geometric model establishment unit is used to establish a three - dimensional geometric model of the bolt and establish a three - dimensional geometric model of the composite laminate structure according to the material properties;

[0044] A friction relationship establishment unit is used to perform surface - to - surface contact between the laminates of the composite laminate structure during the assembly process, divide the hole - wall area into cross - shaped blocks, establish a friction relationship between the bolt and each block of the composite material hole - wall area, and add the friction relationship to the contact characteristics;

[0045] A composite material stress - strain constitutive relationship establishment unit is used to restrict the degrees of freedom of the three translational directions and the three rotational directions of the composite laminate structure and the base, restrict the five degrees of freedom of the bolt's horizontal and vertical movements, set the bolt's axial displacement along the hole, establish an interference pin - load constraint, and under the above restrictions, establish a composite material stress - strain constitutive relationship according to the equivalent material properties with hole - making damage;

[0046] A contact stress determination unit is used to determine the contact stress between the bolt and the composite material hole - wall area according to the composite material stress - strain constitutive relationship and the contact characteristics with added friction relationship;

[0047] A geometric - force collaborative pin - connection simulation model establishment unit is used to perform damage analysis on the composite laminate structure based on the three - dimensional geometric model of the bolt and the three - dimensional geometric model of the composite laminate structure according to the contact stress, and establish the geometric - force collaborative pin - connection simulation model by using the maximum stress criterion and the three - dimensional Hashin failure criterion.

[0048] Optionally, the geometric - force collaborative tensile - load simulation model establishment module specifically includes:

[0049] The nail connection simulation result file reading unit is used to read the nail connection simulation result file and output the residual stress field and damage field during the nail connection process; the nail connection simulation result file is the result file obtained from the geometric and force collaborative nail connection simulation model;

[0050] The setting operation completion unit is used to establish a moving coupling reference point for the upper and lower laminates in the composite laminate structure according to the nail connection simulation result file, restrict the degrees of freedom of the upper and lower laminates, add a static tensile position to the upper laminate, apply a bolt pre-tightening force, and set a predefined field for the upper and lower laminates in the composite laminate structure to complete the setting operation;

[0051] The tensile three-dimensional model establishment unit inheriting the nail force field is used to, based on the setting operation, select the result of the last analysis step in the geometric and force collaborative nail connection simulation model, import the stress state and damage distribution brought during the nail connection process, and establish a tensile three-dimensional model inheriting the nail force field to complete the dynamic transfer and evolution process of the force field;

[0052] The geometric and force collaborative tensile load simulation model establishment unit is used to perform stress analysis on the tensile three-dimensional model according to the failure criterion and stiffness reduction model, and establish the geometric and force collaborative tensile load simulation model.

[0053] An electronic device includes a memory and a processor. The memory is used to store a computer program, and the processor runs the computer program to enable the electronic device to execute the above-mentioned composite laminate structure assembly damage simulation method considering errors and external loads.

[0054] A computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, it implements the above-mentioned composite laminate structure assembly damage simulation method considering errors and external loads.

[0055] According to the specific embodiments provided by the present invention, the following technical effects are disclosed: The present invention provides a simulation method and system for assembly damage of composite material laminated structures considering errors and external loads. By calibrating the material properties of the composite material laminated structure after hole making and quantitatively characterizing the contact characteristics of the hole wall connection interface of the composite material laminated structure after hole making, a geometric and force collaborative pin connection simulation model of the composite material laminated structure is established based on the material properties and contact characteristics. Finally, a geometric and force collaborative tensile load simulation model is established to predict the damage state and tensile strength during the assembly process. In the prediction of the bearing strength of the composite material laminated structure, the hole making accuracy, the damage caused to the connection part during hole making and assembly, and the influence of the residual stress field of the composite material hole wall during hole making and assembly on the tensile strength of the connection structure are fully considered, thereby improving the accuracy of the model prediction results. Based on the prediction results of the geometric and force collaborative tensile load simulation model, the assembly process is adjusted, and thus the problem of damage to the composite material laminated structure during the assembly process is avoided. Description of the Drawings

[0056] 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 drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0057] Figure 1 It is a flowchart of the simulation method for assembly damage of composite material laminated structures considering errors and external loads provided by the present invention;

[0058] Figure 2 It is a flowchart of the analysis method for assembly damage of composite material connection structures considering geometric and force collaboration provided in the second embodiment of the present invention;

[0059] Figure 3 It is a schematic diagram of the damaged slice area around the hole of the composite material provided by the present invention;

[0060] Figure 4 It is a schematic diagram of the displacement boundary conditions required for the homogenization calculation of the material properties of the composite material microscopic RVE provided by the present invention; Figure 4 (a) Elastic modulus E provided by the present invention 11 , θ 12 , θ 13 Schematic diagram of the displacement boundary conditions required for Poisson's ratio; Figure 4 (b) Elastic modulus E provided by the present invention 22 , θ 21 , θ 22 Schematic diagram of the displacement boundary conditions required for Poisson's ratio; Figure 4(c) Elastic modulus E provided by the present invention 33 , θ 31 , θ 32 Schematic diagram of displacement boundary conditions required for Poisson's ratio Figure 4 (d) Shear modulus G provided by the present invention 12 Schematic diagram of displacement boundary conditions required Figure 4 (e) Shear modulus G provided by the present invention 13 Schematic diagram of displacement boundary conditions required Figure 4 (f) Shear modulus G provided by the present invention 23 Schematic diagram of displacement boundary conditions required

[0061] Figure 5 Schematic diagram of the dimensions of the interference pin structure provided by the present invention Figure 5 (a) Schematic diagram of the dimensions of the backing plate provided by the present invention Figure 5 (b) Schematic diagram of the dimensions of the bolt provided by the present invention Figure 5 (c) Schematic diagram of the dimensions of the composite laminate provided by the present invention

[0062] Figure 6 Schematic diagram of the simulation model of the composite pin connection with hole-making geometric deviation provided by the present invention

[0063] Figure 7 Compression force-displacement curve of the interference pinning process of the composite connection structure provided by the present invention

[0064] Figure 8 Schematic diagram of the tensile load model of the composite connection structure provided by the present invention

[0065] Figure 9 Tensile load-displacement curve of the composite connection structure provided by the present invention Detailed implementation manners

[0066] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0067] The object of the present invention is to provide a simulation method, system and device for assembly damage of a composite laminate structure considering errors and external loads, which improves the accuracy of prediction results and avoids the problem of damage to the composite laminate structure during the assembly process.

[0068] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0069] Example 1

[0070] Figure 1 The flowchart of the simulation method for assembly damage of a composite laminate structure considering errors and external loads provided by the present invention is as follows. Figure 1 As shown, a simulation method for assembly damage of a composite laminate structure considering errors and external loads includes:

[0071] Step 101: Calibrate the material properties of the composite laminate structure after hole-making, and quantitatively characterize the contact characteristics of the hole wall connection interface of the composite laminate structure after hole-making; the material properties include hole position deviation, hole diameter deviation, and hole perpendicularity deviation; the contact characteristics include damage state and tightening torque.

[0072] In practical applications, step 101 specifically includes: calibrating the damage range of the hole circumference area of the composite laminate structure after hole-making; slicing the composite laminate structure within the damage range at equal distances along the direction perpendicular to the fiber normal, and calibrating the fiber volume fraction and porosity coefficient of each sliced area; establishing a microscopic representative volume element with pores according to the fiber volume fraction and porosity coefficient; performing unidirectional loading in six degrees of freedom on the microscopic representative volume element with pores, homogenizing and calculating the equivalent material properties with hole-making damage, and establishing a constitutive model considering in-layer damage and inter-layer damage; determining the material properties of the composite laminate structure after hole-making according to the constitutive model; dividing the composite laminate structure after hole-making into 4 equal parts, and performing a friction coefficient calibration experiment on each divided composite laminate structure to quantitatively characterize the contact characteristics of the hole wall connection interface of the composite laminate structure after hole-making.

[0073] Furthermore, calibrate the material properties of the composite material after hole-making, and through a multi-scale characterization method, homogenize and calculate the material properties with hole-making damage, and establish a constitutive model considering in-layer damage and inter-layer damage. In addition, quantitatively characterize the contact characteristics of the connection interface after hole-making through a friction coefficient measurement experiment.

[0074] 1.1) Design the structural dimensions according to the requirements of the composite laminate hole-making experiment.

[0075] Use a drill bit to conduct a hole-making experiment. For the composite laminate after hole-making, use the composite material ultrasonic non-destructive testing technology to calibrate the damage range of the hole circumference area.

[0076] 1.2) Slice the composite laminate within the damaged area around the hole into N equal-distance regions perpendicular to the fiber normal direction, and use SEM electron microscopy scanning to detect and obtain the microscopic real images of each region. According to the microscopic images, calibrate the fiber volume fraction and porosity of each region. The calibration process uses a binary image processing program to perform pixel statistics on the fibers, matrix, and pores to obtain the fiber volume fraction and porosity.

[0077] 1.3) For each sliced region, perform microscale representative volume element (RVE) modeling with pores based on the fiber volume fraction and porosity. The periodicity and randomness of the element are realized by the random model algorithm.

[0078] Since the composite material shows transverse isotropy at the microscale, it can be regarded as two-dimensional for random modeling. Without loss of generality, assume that the center of one fiber is the coordinate origin, i.e., O 1 :(0, 0, 0), and the coordinates of the center of another fiber are O 2 :(x 2 , y 2 , z 2 ). The distance between O 1 , O 2 is l, and the polar angles are respectively denoted as θ. Therefore, O 2 :(x 2 , y 2 , z 2 ) can be expressed by l and θ:

[0079] x 2 = l·cosθ

[0080] y 2 = l·sinθ

[0081] To ensure the randomness of the fiber distribution, make l and θ randomly take values within their feasible regions, i.e., l = rand(l min , l max ), θ = rand(θ min , θ max ). Therefore, for the coordinates O:(x i , y i ) and O i+1 :(x i+1 , y i+1 ) of any two adjacent fiber centers, there is the following relationship:

[0082] x i+1 = x i + l·cosθ

[0083] y i+1 = y i + l·sinθ

[0084] Meanwhile, to ensure that there is no overlapping part between any two fibers, the following conditions also need to be met:

[0085] (x i -x k ) 2 +(y i -y k ) 2 ≤l min

[0086] where x k , y k are the horizontal and vertical coordinates of the existing fibers, respectively.

[0087] 1.4) The properties of the fiber and the matrix material are obtained according to the standards of the composite material supplier.

[0088] Unidirectional loading in six degrees of freedom is applied to the microscopic representative volume element respectively, and the equivalent material properties with hole-making damage are obtained through homogenization calculation, and a constitutive model considering in-layer damage (material damage degradation) and inter-layer damage (delamination) is established. The elastic moduli in three directions are obtained by unidirectional loading in three directions respectively, and the shear moduli in three directions are obtained by combined shear loading.

[0089] To meet the periodic boundary conditions, for the elastic modulus E 11 :

[0090] X Front -X Back =X Assigned

[0091] X Top,Left -X Bottom,Right =0

[0092] Y Top,Front,Left -Y Bottom,Back,Right =0

[0093] Z Front,Top,Left -Y Back,Bottom,Right =0

[0094] For the shear modulus G 12 :

[0095] X Front,Left -X Back,Right =0

[0096] Y Front -Y Back =X Assigned

[0097] X Top -X Bottom =X Assigned

[0098] Y Top,Left -Y Bottom,Right = 0

[0099] Z Front,Top,Left -Y Back,Bottom,Right = 0

[0100] Among them, X, Y, and Z are the displacement components along the X, Y, and Z directions respectively. X Assigned is the specified displacement value, and the remaining elastic moduli E 22 , E 33 and the shear moduli G 13 , G 23 are solved and loaded in a similar process as above.

[0101] 1.5) According to the relevant literature on composite material hole making, it can be seen that along one circle of the hole circumference, the surface roughness of the hole wall changes significantly and the pattern is distinct.

[0102] Along the hole circumference of 0° - 90° and 180° - 270°, the hole wall is smooth and the surface roughness is small; along the hole circumference of 90° - 180° and 270° - 360°, the hole wall is rough and the surface roughness is large; the composite material laminate after hole making is cut along the 0° - 180° and 90° to 270° directions into four pieces; the friction coefficient calibration experiments are respectively carried out on the four 1 / 4 composite material hole walls to quantitatively characterize the contact characteristics (surface roughness) of the connection interface after hole making.

[0103] Step 102: Establish a geometric and force collaborative pin connection simulation model of the composite material laminated structure according to the material properties and the contact characteristics.

[0104] In practical applications, step 102 specifically includes: establishing a three-dimensional geometric model of the bolt, and establishing a three-dimensional geometric model of the composite laminate structure according to the material properties; during the assembly process, the laminates of the composite laminate structure are in surface contact with each other, the hole wall area is divided into four parts, a friction relationship is established between the bolt and each part of the composite material hole wall area, and the friction relationship is added to the contact characteristics; restricting the degrees of freedom of the three translational directions and the three rotational directions of the composite laminate structure and the base, restricting the five degrees of freedom of the bolt moving in the horizontal and vertical directions, setting the axial displacement of the bolt along the hole, establishing an interference pin load constraint, and under the above restrictions, establishing a composite material stress-strain constitutive relationship according to the equivalent material properties with hole-making damage; determining the contact stress between the bolt and the composite material hole wall area according to the composite material stress-strain constitutive relationship and the contact characteristics with the added friction relationship; based on the three-dimensional geometric model of the bolt and the three-dimensional geometric model of the composite laminate structure, according to the contact stress, performing damage analysis on the composite laminate structure by using the maximum stress criterion and the three-dimensional Hashin failure criterion, and establishing a geometric and force collaborative pin connection simulation model.

[0105] Furthermore, comprehensively considering the geometric factors (including hole position deviation, hole diameter deviation, hole perpendicularity deviation) and force factors (damage state of the composite material hole wall connection interface, tightening torque) in the assembly connection process, a geometric and force collaborative pin connection simulation model of the composite material structure is established. In the present invention, the composite material is a carbon fiber composite material.

[0106] 2.1) According to the requirements in ASTM D-5961, use ABAQUS software to establish a three-dimensional geometric model of the carbon fiber composite material and the bolt. Since the length of the bolt shank is greater than the laminate thickness of the connection structure, the threaded part is ignored, and the bolt is simplified into a "T"-shaped solid model, and the identification names of each three-dimensional geometric model are set. When modeling the composite laminate, the geometric errors caused by the actual hole-making process need to be considered, including hole position deviation, hole diameter deviation, and hole perpendicularity deviation.

[0107] 2.2) The carbon fiber composite material adopts a reduced integration hexahedral element C3D8R, and enhanced hourglass control is set to reduce mesh distortion. The metal bolt is set as a rigid body to facilitate the subsequent calculation of the interference amount.

[0108] 2.3) Divide the hole wall area into a cross shape, dividing it into four regions. In the assembly, surface-to-surface contact is used between the upper and lower composite laminates, and a friction relationship is established between the bolt and each carbon fiber composite hole wall area. Define the master surface and the slave surface, and add the friction coefficient and "hard" contact in the contact properties. The friction coefficient of each region adopts the value characterized by the calibration in step 1.5, and the setting of the contact characteristics of the connection interface after considering the hole-making is completed.

[0109] 2.4) According to the actual test conditions, restrict the degrees of freedom of the three translation directions and the three rotation directions of the carbon fiber composite laminate and the base, and restrict the five degrees of freedom of the bolt except for the movement in the z direction; set the axial displacement of the bolt along the hole, and establish an interference pin load constraint.

[0110] 2.5) Establish the stress-strain constitutive relationship of the carbon fiber composite, considering the influence of hole-making damage on the degradation of material properties. The stress-strain constitutive relationship of the carbon fiber composite can be expressed according to the equivalent material properties with hole-making damage calculated by homogenization in step 1.4 as:

[0111]

[0112] In the formula, σ n , σ t are the normal stress component and the shear stress component respectively; ε n , ε t are the normal strain component and the shear strain component respectively; C n , C t are the stiffnesses in the normal and shear directions.

[0113] 2.6) Combine the three-dimensional finite element model. According to the contact stress between the bolt and the composite hole wall, perform stress analysis on the carbon fiber composite elements using the maximum stress criterion and the three-dimensional Hashin failure criterion. Use the material failure criterion to perform damage analysis on each carbon fiber composite element to judge whether the element is damaged. If damaged, use the corresponding stiffness reduction model to reduce the current material stiffness and update the stress; if not damaged, the element stiffness remains unchanged; establish a composite damage model.

[0114] The maximum stress criterion and the three-dimensional Hashin failure criterion:

[0115] (1) Fiber tensile failure (σ 11 ≥0):

[0116]

[0117] (2) Fiber compressive failure (σ 11 <0):

[0118]

[0119] (3) In-plane matrix tensile failure (σ 22 +σ 33 ≥0):

[0120]

[0121] (4) In-plane matrix compressive failure (σ 22 +σ 33 <0):

[0122]

[0123] (5) Out-of-plane matrix tensile failure (σ 33 ≥0):

[0124]

[0125] (5) Out-of-plane matrix compressive failure ((σ 33 <0):

[0126]

[0127] In the formula, σ 11 , σ 22 , σ 33 are the principal stresses in the x, y, and z directions respectively; σ 12 , σ 13 , σ 23 are the in-plane shear stresses in the corresponding directions; X c , X t , Y c , Y t , Z c , Z t are the tensile and compressive ultimate strengths in the x, y, and z directions respectively, with the subscript t indicating tension and c indicating compression; S 12 , S 13 , S 23 are the shear ultimate strengths in the corresponding directions; when F ft , F fc , F mt , F mc , F nt , F nc ≥1, the carbon fiber composite unit is damaged; otherwise, the unit is not damaged.

[0128] When the carbon fiber composite unit is damaged, the material damage stiffness matrix will be activated, and a damage variable is introduced to characterize the damage process. When the material is not damaged, the damage variable is 0; when damaged, 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 is expressed as follows:

[0129]

[0130] Wherein:

[0131] b 1 = 1 - d f (21)

[0132] b 2 = 1 - d m (22)

[0133] b 3 = 1 - d s (23)

[0134] Three independent damage variables are considered: d f 、d m 、d s ; d f represents the degradation in the fiber direction; d m represents the degradation along the direction perpendicular to the fiber; d s represents the degradation of the shear performance parallel to the fiber direction. The relationships are as follows:

[0135] d f = 1 - (1 - d FT )(1 - d FC ) (24)

[0136] d m = 1 - (1 - d MT )(1 - d MC ) (25)

[0137] d s = 1 - (1 - d f )(1 - smt × d MT )(1 - smc × d MC ) (26)

[0138] In the formula, d FT 、d FC are the damage variables in the fiber tension and compression directions; d MT 、d MC are the damage variables in the matrix tension and compression directions; smt, smc are the coefficients of the shear modulus loss caused by the matrix tension and compression failures.

[0139] Step 103: Establish a geometric and force collaborative tensile load simulation model of the composite laminate structure according to the geometric and force collaborative pin connection simulation model.

[0140] In practical applications, after the three-dimensional finite element model of the interference pin of the composite material connection structure is analyzed, the press-fit force-displacement curve is compared to verify the accuracy of the geometric and force collaborative pin connection simulation model; the stress state and damage distribution of the elements are calculated and obtained in step 102, and the restart data is saved.

[0141] In practical applications, the failure criterion and stiffness reduction model are damage models, which together with the pin connection geometric model form a geometric and force collaborative pin connection simulation model. In the geometric and force collaborative pin connection simulation model, it is necessary to set the output of restart data so as to obtain the result file of the pin connection simulation model that can be read, and read the output residual stress field and damage field.

[0142] In practical applications, step 103 specifically includes: reading the pin connection simulation result file and outputting the residual stress field and damage field during the pinning process; the pin connection simulation result file is the result file obtained by the geometric and force collaborative pin connection simulation model; according to the pin connection simulation result file, establish a moving coupling reference point for the upper and lower laminates in the composite material laminate structure, restrict the degrees of freedom of the upper and lower laminates, add a static tensile position to the upper laminate, and apply a bolt pre-tightening force, set a predefined field for the upper and lower laminates in the composite material laminate structure, and complete the setting operation; based on the setting operation, select the result of the last analysis step in the geometric and force collaborative pin connection simulation model, import the stress state and damage distribution brought during the pinning process, establish a tensile three-dimensional model inheriting the pinning force field, and complete the dynamic transfer and evolution process of the force field; perform stress analysis on the tensile three-dimensional model according to the failure criterion and stiffness reduction model, and establish the geometric and force collaborative tensile load simulation model.

[0143] Furthermore, according to the restart data of the geometric and force collaborative pin connection simulation model, import the composite material laminate lap joint structure model with geometric deformation field and physical damage field in ABAQUS. On this basis, establish a geometric and force collaborative tensile load simulation model for the composite material connection structure, and perform dynamic transfer and evolution of the geometric field and force field across stages.

[0144] 4.1) Use ABAQUS software to establish a three-dimensional geometric model of carbon fiber composite material and bolts. Among them, the composite material laminate is imported from the pin connection simulation result file, and a three-dimensional model inheriting the geometric deformation field of the pinning is established to complete the dynamic transfer and evolution process of the geometric field. Since the elastoplastic damage of the bolt is not considered, an "I"-shaped bolt model is established to replace the "T"-shaped bolt model.

[0145] 4.2) The material properties of the metal bolt and the composite material are the same as those of the composite material structure geometric and force collaborative pin connection simulation model established in step 102.

[0146] 4.3) In the contact setting, the friction coefficient of each area of the hole wall still adopts the value characterized by the calibration in step 1.5, and the friction property between the bolt and the composite material hole wall unit inheriting the equivalent stress and damage is established; the composite material hole wall unit is the contact unit between the model hole wall corresponding to the above-mentioned hole wall area and the bolt in the simulation model.

[0147] 4.4) In the load boundary setting, the motion coupling reference points of the upper and lower laminates are established, and the degrees of freedom of the upper and lower laminates are restricted. A static tensile displacement is added to the upper laminate, and the bolt pre-tightening force is applied; in order to avoid conflicts in the bolt cross-section properties, the bolt cross-section properties are set to the default in the mesh setting.

[0148] 4.5) Read the simulation result file of the pin connection, set the predefined field for the upper and lower laminates, select the result of the last analysis step of the pin simulation model, import the stress state and damage distribution brought by the pinning process, and establish a three-dimensional tensile model inheriting the pinning force field to complete the dynamic transfer and evolution process of the force field.

[0149] 4.6) Combine the failure criterion and stiffness reduction model in the geometric and force collaborative pin connection simulation model, perform stress analysis on the above-mentioned composite material interference connection structure tensile model, judge whether each composite material unit is damaged or its stiffness is reduced, and establish a damage model.

[0150] Step 104: Perform stress analysis on the tensile process of the composite material laminated structure according to the geometric and force collaborative tensile load simulation model, and predict the damage state and tensile strength during the assembly process.

[0151] In practical applications, after the geometric and force collaborative tensile load simulation model of the composite material connection structure is completed, compare the load-displacement curves, analyze the assembly damage state, and verify the accuracy of the geometric and force collaborative tensile load simulation model.

[0152] The present invention reduces the material cost and preparation cycle of the test method, provides a basis for optimizing the process design, and promotes the development of advanced composite material connection technologies.

[0153] Example Two

[0154] This example takes the T300 / TED-85 carbon fiber composite material (lay-up sequence: [0 / 45 / -45 / 90]3s) and Ti6Al4V bolt material as examples. Figure 2 The flowchart of the assembly damage analysis method for the composite material connection structure considering geometric and force collaboration provided by the second embodiment of the present invention is as follows. Figure 2 As shown, it includes the following steps:

[0155] Step 1: Calibrate the material properties of the composite material after hole making. Through the method of multi-scale characterization, homogenize and calculate the material properties of the material with hole-making damage, and establish a constitutive model considering intra-layer damage (material damage degradation) and inter-layer damage (delamination). In addition, through the friction coefficient measurement experiment, quantitatively characterize the contact characteristics (surface roughness) of the connection interface after hole making.

[0156] 1.1) According to the requirements of the composite laminate hole-making experiment, design specimens with a length of 135 mm and a width of 36 mm to be stacked into a laminated structure, and the overlapping part is a square area with a side length of 36 mm. Use a twist drill to conduct the hole-making experiment to obtain a T700 composite laminate structure with a 5.93 mm hole.

[0157] 1.2) According to the requirements of HB 7825-2007, use an RSflite composite material ultrasonic non-destructive detector to detect the area around the hole after hole making, and determine that the damage area is approximately 3 mm around the hole.

[0158] 1.3) Divide the composite laminate within the damaged area around the hole into three equal parts, each part with a span of 1 mm, and cut along the center of the area perpendicular to the fiber normal, as Figure 3 shown. Use SEM electron microscopy scanning detection to obtain the microscopic real images of each area. Then, according to the microscopic images, calibrate the fiber volume fraction θ f and the porosity fraction θ p for each area. The calibration process uses a MATLAB binary image processing program to perform pixel statistics on fibers, matrices, and pores to obtain the fiber volume fraction and the porosity fraction. Table 1 shows the fiber volume fraction and porosity fraction tables for different area positions, and the calibration results for different positions are shown in Table 1.

[0159] Table 1

[0160]

[0161] 1.4) For each area, according to the fiber volume fraction θ f and the porosity fraction θ p , use the random modeling algorithm in content step 1.3) to establish a geometric model of a microscopic representative volume element (RVE) with pores, where the periodicity and randomness of the element are realized by the random model algorithm.

[0162] 1.5) The fiber and matrix properties of the T700 composite material used in this example are shown in Table 2. Assign material properties to the microscopic RVE model. According to content step 1.4, apply periodic boundary conditions to the element in six directions respectively, as Figure 4 shown, where, E 11 , E 22 , E 33are the elastic moduli in three directions; G 12 , G 13 , G 23 are the shear moduli; θ 12 is the Poisson's effect value generated in the 2 - direction under the load in the 1 - direction, θ 13 is the Poisson's effect value generated in the 3 - direction under the load in the 1 - direction, θ 21 is the Poisson's effect value generated in the 1 - direction under the load in the 2 - direction, θ 22 is the Poisson's effect value generated in the 2 - direction under the load in the 2 - direction; θ 31 is the Poisson's effect value generated in the 1 - direction under the load in the 3 - direction, θ 32 is the Poisson's effect value generated in the 2 - direction under the load in the 3 - direction, and all of them belong to material properties. Figure 4 In Figure 4 , the corresponding quantities can be obtained by applying unidirectional loading through periodic boundary conditions. By performing 6 - time loading, all material properties can be obtained. The displacement applied on the surface of the RVE is resisted inside, and boundary nodal forces are generated on the boundary surface of the displacement. The default setting of ABAQUS does not output the reaction force data. Therefore, it is necessary to output the displacement on a specific surface for a specified reference point. The reaction force value at the reference point is the sum of the relevant - direction main boundary nodal forces generated at the affected boundary nodes. Table 2 is the material property table of T700 composite material fibers and matrix materials, as shown in Table 2.

[0163] Table 2

[0164]

[0165] 1.6) After completing the ABAQUS finite - element periodic loading calculation, write a Python script to read the displacement and nodal force of the reference point in the odb result file, export the displacement deformation and reaction force after periodic loading, and according to the homogenized material property calculation formula:

[0166]

[0167]

[0168]

[0169] Perform homogenized calculation of equivalent material properties on the results, and establish an equivalent constitutive model considering hole - making damage and material damage degradation. Table 3 is the homogenized equivalent material parameter table for three regions around the hole, and the equivalent material parameters for each region are shown in Table 3.

[0170] Table 3

[0171]

[0172] 1.7) According to the relevant literature on hole making in composite materials, it can be seen that along the circumference of the hole, the surface roughness of the hole wall changes significantly and regularly. Along the hole circumference of 0°-90° and 180°-270°, the hole wall is smooth and the surface roughness is small; along the hole circumference of 90°-180° and 270°-360°, the hole wall is rough and the surface roughness is large. The composite laminate after hole making is cut along the directions of 0°-180° and 90°-270° into four pieces. The friction coefficient calibration experiments are respectively carried out on the four 1 / 4 composite material hole walls to quantitatively characterize the contact characteristics (surface roughness) of the connection interface after hole making. Table 4 shows the friction coefficient table of the hole wall measured in the experiment, and the friction coefficient of the hole wall area is shown in Table 4.

[0173] Table 4

[0174]

[0175] Step 2: Considering comprehensively the geometric factors (including hole position deviation, hole diameter deviation, hole perpendicularity deviation) and force factors (damage state of the connection interface of the composite material hole wall, tightening torque) in the assembly connection process, establish a simulation model for the geometric and force collaborative pin connection of the composite material structure.

[0176] 2.1) The structure and dimensions required in ASTM D-5961 are as Figure 5 shown, where Figure 5 the size of the base plate (BASEPLATE) shown in (a) is: both the length and width are 36, and the inner hole diameter Φ is 8; Figure 5 the size of the bolt (BOLT) shown in (b) is: the length in the horizontal direction is 10, the width is 4, and the diameter Φ in the vertical direction is 6; Figure 5 the size of the composite laminate shown in (c) is: the length is 135, the width is 36, the length from the inner hole center to the wide side of the composite laminate is 18, the length from the inner hole center to the long side of the composite laminate is 18, the inner hole diameter Φ is 5.93. The composite laminates are respectively named PLATE1&PLATE2, the metal bolt is BOLT, and the base plate is BASEPLATE. Use the ABAQUS software to establish a three-dimensional geometric model of the carbon fiber composite laminate and the bolt. Since the length of the bolt shank is greater than the stacking thickness of the connection structure, the thread part is ignored and the bolt is simplified into a "T" shape model, and its material parameters are shown in Table 5. When modeling the composite laminate, the geometric errors brought by the actual hole-making process need to be considered, including hole position deviation, hole diameter deviation, hole perpendicularity deviation, as Figure 6 shown. In order to verify the representativeness of the model, in this example model, the upper composite material plate has standard-sized holes, and the lower composite material plate considers a hole position deviation of 0.1 mm, a hole diameter deviation of 0.1 mm, and a hole perpendicular deviation of 0.5°. Table 5 is the material parameter table of the Ti6Al4V bolt, as shown in Table 5.

[0177] Table 5

[0178]

[0179] Among them, E is the elastic modulus of the bolt, and V is the Poisson's ratio.

[0180] 2.2) The carbon fiber composite material adopts a reduced integration hexahedron element C3D8R, and enhanced hourglass control is set to reduce mesh distortion. The metal bolt is set as a rigid body to facilitate the subsequent calculation of interference amounts.

[0181] 2.3) The hole wall area is divided into four regions by cross-blocking. In the assembly, surface-to-surface contact is used between the upper and lower composite laminates. A friction relationship is established between the bolt and the hole wall area of each carbon fiber composite material. The master surface and the slave surface are defined, and the friction coefficient and "hard" contact are added in the contact properties. The friction coefficient of each region adopts the value characterized by the calibration in Table 4, and the setting of the contact characteristics of the connection interface after considering hole making is completed.

[0182] 2.4) According to the actual test conditions, the degrees of freedom in the three translational directions and the three rotational directions of the carbon fiber composite material and the base are restricted, and the five degrees of freedom of the bolt except for the movement in the z direction are restricted. An interference pin displacement of 8.5 mm is established in the load module.

[0183] 2.5) According to the homogenization calculation results in step 1.6, the hole circumference area is divided into three regions at intervals of 1 mm. The material parameters in Table 3 are assigned to each region correspondingly. The constitutive equation of each region can be expressed as:

[0184]

[0185] In the formula, σ n , σ t are the normal stress component and the shear stress component respectively; ε n , ε t are the normal strain component and the shear strain component respectively; C n , C t are the stiffness in the normal and shear directions.

[0186] Thus, the simulation geometric model of the collaborative pin connection of the composite material structure geometry and force is completed, as Figure 6 shown.

[0187] 2.6) Combining with the three-dimensional finite element model, according to the contact stress between the bolt and the composite material hole wall, the corresponding material failure criterion is used to conduct damage analysis on each adhesive layer and carbon fiber composite material unit, judge whether the unit is damaged, and establish a composite material damage model.

[0188] In addition to homogenizing the calculated material properties, Table 6 shows the strength parameters of the T700 composite material, and the strength parameters of the T700 carbon fiber composite material are shown in Table 6.

[0189] Table 6

[0190]

[0191] Among them, XT is the fiber tensile strength, XC is the fiber compressive strength, YT is the in-plane matrix tensile strength, YC is the in-plane matrix compressive strength, ZT is the out-of-plane matrix tensile strength, ZC is the out-of-plane matrix compressive strength, and S12, S13, and S23 are the shear strengths, with the unit of MPa.

[0192] The material damage criterion adopts the maximum stress criterion and the three-dimensional Hashin failure criterion in Content Step 2.7, and the degradation criterion is the progressive damage criterion.

[0193] Step 3: After the three-dimensional finite element model of the interference pin in the composite material connection structure stops analyzing, compare the press-fit force-displacement curves. As Figure 7 shown, verify the accuracy of the model; the stress state and damage distribution of the composite laminate element are calculated and obtained in Step 2, perform the restart setting, and save the restart data.

[0194] Step 4: According to the restart data of the interference pin model, import the composite laminate lap joint structure model with geometric deformation fields and physical damage fields in ABAQUS. On this basis, establish a geometric and force collaborative tensile load simulation model for the composite material connection structure, and perform the dynamic transfer and evolution of the cross-stage geometric field and force field.

[0195] 4.1) Use the ABAQUS software to establish a three-dimensional geometric model of the carbon fiber composite material and the bolt. Among them, the deformation model of the composite laminate is imported from the simulation result file of the pin connection, establish a three-dimensional model that inherits the geometric deformation field of the pin, and complete the dynamic transfer and evolution process of the geometric field. Since the elastoplastic damage of the bolt is not considered, establish an "I"-shaped bolt model to replace the "T"-shaped bolt model, and construct a tensile load model for the composite material connection structure, as Figure 8 shown.

[0196] 4.2) The material properties of the metal bolt and the composite material are the same as those of the composite material structure geometric and force collaborative pin connection simulation model established in Step 2.

[0197] 4.3) In the contact module, the friction coefficient of each area of the hole wall still adopts the value calibrated and characterized in Step 1.7, and establish the friction property between the bolt and the composite material hole wall element that inherits the equivalent stress and damage.

[0198] 4.4) In the load and boundary module, establish the kinematic coupling reference points for the upper and lower composite laminates, restrict the degrees of freedom of the upper and lower composite laminates, add a static tensile displacement of 5 mm to the upper composite laminate, and apply the bolt pre-tightening force. To avoid conflicts in the bolt cross-section properties, set the bolt cross-section properties to the default in the mesh module.

[0199] 4.5) Read the simulation result file of the pin connection, set the predefined fields for the upper and lower composite laminates, select the result of the last analysis step of the pin simulation model, import the stress state and damage distribution brought by the pinning process, and establish a three-dimensional tensile model that inherits the pinning force field to complete the dynamic transfer and evolution process of the force field.

[0200] 4.6) Combine the failure criterion and stiffness reduction model in step three to perform stress analysis on the above tensile model of the composite interference connection structure, judge whether each composite material unit is damaged or perform stiffness reduction, and establish a damage model.

[0201] Step Five: After the model stops analyzing, the tensile load at this time is the tensile strength of the composite interference connection structure, and output the tensile load-displacement curve, as Figure 9 shown. Table 7 is a comparison table of the tensile test and prediction results. The prediction effect is shown in Table 7, and the strength prediction of the composite connection structure considering the coordination of geometry and force is completed.

[0202] Table 7

[0203]

[0204] Example Three

[0205] In order to execute the method corresponding to the above Example One to achieve the corresponding functions and technical effects, the following provides a simulation system for the assembly damage of a composite laminated structure considering errors and external loads.

[0206] A simulation system for the assembly damage of a composite laminated structure considering errors and external loads includes:

[0207] A material property and contact characteristic determination module for calibrating the material properties of the composite laminated structure after hole-making and quantitatively characterizing the contact characteristics of the hole wall connection interface of the composite laminated structure after hole-making; the material properties include hole position deviation, hole diameter deviation, and hole perpendicularity deviation; the contact characteristics include damage state and tightening torque.

[0208] In practical applications, the material property and contact characteristic determination module specifically includes: a damage range calibration unit for calibrating the damage range of the hole-periphery region of the composite laminate structure after hole-making; a fiber volume coefficient and porosity coefficient calibration unit for slicing the composite laminate structure within the damage range at equal distances along a direction perpendicular to the fiber normal and calibrating the fiber volume coefficient and porosity coefficient of each sliced region; a microscopic representative volume element with pores establishment unit for establishing a microscopic representative volume element with pores according to the fiber volume coefficient and porosity coefficient; a constitutive model establishment unit considering in-layer damage and inter-layer damage for performing unidirectional loading with six degrees of freedom on the microscopic representative volume element with pores, homogenizing and calculating the equivalent material properties with hole-making damage, and establishing a constitutive model considering in-layer damage and inter-layer damage; a material property determination unit for determining the material properties of the composite laminate structure after hole-making according to the constitutive model; and a contact characteristic determination unit for equally dividing the composite laminate structure after hole-making into 4 pieces, performing a friction coefficient calibration experiment on each equally divided composite laminate structure, and quantitatively characterizing the contact characteristics of the hole-wall connection interface of the composite laminate structure after hole-making.

[0209] A geometric and force collaborative pin connection simulation model establishment module for establishing a geometric and force collaborative pin connection simulation model of the composite laminate structure according to the material properties and the contact characteristics.

[0210] In practical applications, the geometric and force collaborative pin connection simulation model establishment module specifically includes: a three-dimensional geometric model establishment unit for establishing a three-dimensional geometric model of the bolt and a three-dimensional geometric model of the composite laminate structure according to the material properties; a friction relationship establishment unit for performing surface-to-surface contact between the laminates of the composite laminate structure during the assembly process, dividing the hole wall area into cross blocks, establishing a friction relationship between the bolt and each composite hole wall area block, and adding the friction relationship to the contact characteristics; a composite material stress-strain constitutive relationship establishment unit for restricting the degrees of freedom of the three translational directions and the three rotational directions of the composite laminate structure and the base, restricting the five degrees of freedom of the bolt's horizontal and vertical movements, setting the axial displacement of the bolt along the hole, establishing an interference pin load constraint, and under the above restrictions, establishing a composite material stress-strain constitutive relationship according to the equivalent material properties with hole-making damage; a contact stress determination unit for determining the contact stress between the bolt and the composite hole wall area according to the composite material stress-strain constitutive relationship and the contact characteristics with the added friction relationship; a geometric and force collaborative pin connection simulation model establishment unit for performing damage analysis on the composite laminate structure based on the three-dimensional geometric model of the bolt and the three-dimensional geometric model of the composite laminate structure according to the contact stress, and establishing the geometric and force collaborative pin connection simulation model by using the maximum stress criterion and the three-dimensional Hashin failure criterion.

[0211] The geometric and force collaborative tensile load simulation model establishment module is used to establish the geometric and force collaborative tensile load simulation model of the composite laminate structure according to the geometric and force collaborative pin connection simulation model.

[0212] In practical applications, the geometric and force collaborative tensile load simulation model establishment module specifically includes: a rivet connection simulation result file reading unit for reading the rivet connection simulation result file; the rivet connection simulation result file is the result file obtained by the geometric and force collaborative rivet connection simulation model; a setting operation completion unit for establishing a motion coupling reference point for the upper and lower laminates in the composite laminate structure according to the rivet connection simulation result file, restricting the degrees of freedom of the upper and lower laminates, adding a static tensile position to the upper laminate, applying a bolt pre-tightening force, and setting a predefined field for the upper and lower laminates in the composite laminate structure to complete the setting operation; a tensile three-dimensional model establishment unit inheriting the rivet force field for selecting the result of the last analysis step in the geometric and force collaborative rivet connection simulation model based on the setting operation, importing the stress state and damage distribution brought during the rivet insertion process, and establishing a tensile three-dimensional model inheriting the rivet force field to complete the dynamic transfer and evolution process of the force field; a geometric and force collaborative tensile load simulation model establishment unit for performing stress analysis on the tensile three-dimensional model according to the failure criterion and stiffness reduction model to establish the geometric and force collaborative tensile load simulation model.

[0213] A damage state and tensile strength determination module for performing stress analysis on the tensile process of the composite laminate structure according to the geometric and force collaborative tensile load simulation model to predict the damage state and tensile strength during the assembly process.

[0214] Embodiment 4

[0215] An electronic device includes a memory and a processor. The memory is used to store a computer program, and the processor runs the computer program to enable the electronic device to execute the composite laminate structure assembly damage simulation method considering errors and external loads described in Embodiment 1.

[0216] A computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, it implements the composite laminate structure assembly damage simulation method considering errors and external loads described in Embodiment 1.

[0217] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the description of the method part.

[0218] In this article, specific examples are used to elaborate on the principles and implementation modes 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; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation modes and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A simulation method for assembly damage of composite laminate structures considering errors and external loads, characterized in that, it includes: Calibrate the material properties of the composite laminate structure after standard hole-making, and quantitatively characterize the contact characteristics of the hole wall connection interface of the composite laminate structure after hole-making; the material properties include hole position deviation, hole diameter deviation, and hole perpendicularity deviation; the contact characteristics include damage state and tightening torque; Establish a geometric and force collaborative pin connection simulation model of the composite laminate structure according to the material properties and the contact characteristics; Establish a geometric and force collaborative tensile load simulation model of the composite laminate structure according to the geometric and force collaborative pin connection simulation model; Conduct stress analysis on the tensile process of the composite laminate structure according to the geometric and force collaborative tensile load simulation model, and predict the damage state and tensile strength during the assembly process.

2. The simulation method for assembly damage of composite laminate structures considering errors and external loads according to claim 1, characterized in that, The calibration of the material properties of the composite laminate structure after hole-making and the quantitative characterization of the contact characteristics of the hole wall connection interface of the composite laminate structure after hole-making specifically include: Calibrate the damage range of the hole circumference area of the composite laminate structure after hole-making; Slice the composite laminate structure within the damage range at equal distances along the direction perpendicular to the fiber normal, and calibrate the fiber volume fraction and porosity coefficient of each sliced area; Establish a microscopic representative volume element with pores according to the fiber volume fraction and porosity coefficient; Perform one-way loading in six degrees of freedom on the microscopic representative volume element with pores, homogenize and calculate the equivalent material properties with hole-making damage, and establish a constitutive model considering intra-layer damage and inter-layer damage; Determine the material properties of the composite laminate structure after hole-making according to the constitutive model; Divide the composite laminate structure after hole-making into 4 equal parts, conduct friction coefficient calibration experiments on each equal-parted composite laminate structure, and quantitatively characterize the contact characteristics of the hole wall connection interface of the composite laminate structure after hole-making.

3. The simulation method for assembly damage of composite laminate structures considering errors and external loads according to claim 2, characterized in that, The establishment of the geometric and force collaborative pin connection simulation model of the composite laminate structure according to the material properties and the contact characteristics specifically includes: Establish a three-dimensional geometric model of the bolt, and establish a three-dimensional geometric model of the composite laminate structure according to the material properties; During the assembly process, the laminates of the composite laminate structure are in surface-to-surface contact, the hole wall area is divided into four parts, a friction relationship is established between the bolt and each part of the composite hole wall area, and the friction relationship is added to the contact characteristics; Restrict the degrees of freedom of the composite laminate structure and the base in three translational directions and three rotational directions, restrict the five degrees of freedom of the bolt in the horizontal and vertical directions, set the axial displacement of the bolt along the hole, establish an interference pin load constraint, and under the above restrictions, establish the composite material stress-strain constitutive relationship according to the equivalent material properties of the drilled hole damage; Determine the contact stress between the bolt and the composite material hole wall region according to the composite material stress-strain constitutive relationship and the contact characteristics with added friction relationship; Based on the three-dimensional geometric model of the bolt and the three-dimensional geometric model of the composite laminate structure, according to the contact stress, use the maximum stress criterion and the three-dimensional Hashin failure criterion to perform damage analysis on the composite laminate structure, and establish the geometric and force collaborative pin connection simulation model.

4. The composite laminate structure assembly damage simulation method considering errors and external loads according to claim 3, characterized in that, The establishment of the geometric and force collaborative tensile load simulation model of the composite laminate structure according to the geometric and force collaborative pin connection simulation model specifically includes: Read the pin connection simulation result file and output the residual stress field and damage field during the pin connection process; the pin connection simulation result file is the result file obtained by the geometric and force collaborative pin connection simulation model; According to the pin connection simulation result file, establish the motion coupling reference points of the upper and lower laminates in the composite laminate structure, restrict the degrees of freedom of the upper and lower laminates, add a static tensile position to the upper laminate, apply the bolt pre-tightening force, and set the pre-defined field for the upper and lower laminates in the composite laminate structure to complete the setting operation; Based on the setting operation, select the result of the last analysis step in the geometric and force collaborative pin connection simulation model, import the stress state and damage distribution brought during the pinning process, and establish a tensile three-dimensional model inheriting the pinning force field to complete the dynamic transfer and evolution process of the force field; Perform stress analysis on the tensile three-dimensional model according to the failure criterion and stiffness reduction model, and establish the geometric and force collaborative tensile load simulation model.

5. A composite laminate structure assembly damage simulation system considering errors and external loads, characterized in that, including: A material property and contact characteristic determination module for calibrating the material properties of the composite laminate structure after drilling and quantitatively characterizing the contact characteristics of the hole wall connection interface of the composite laminate structure after drilling; the material properties include hole position deviation, hole diameter deviation, and hole perpendicularity deviation; the contact characteristics include damage state and tightening torque; A geometric and force collaborative pin connection simulation model establishment module for establishing the geometric and force collaborative pin connection simulation model of the composite laminate structure according to the material properties and the contact characteristics; A geometric and force collaborative tensile load simulation model establishment module for establishing the geometric and force collaborative tensile load simulation model of the composite laminate structure according to the geometric and force collaborative pin connection simulation model; Damage state and tensile strength determination module, which is used to perform stress analysis on the tensile process of the composite laminate structure according to the geometric and force collaborative tensile load simulation model, and predict the damage state and tensile strength during the assembly process.

6. The composite laminate structure assembly damage simulation system considering errors and external loads according to claim 5, wherein, The material property and contact characteristic determination module specifically includes: Damage range calibration unit, which is used to calibrate the damage range of the hole perimeter area of the composite laminate structure after drilling; Fiber volume coefficient and porosity coefficient calibration unit, which is used to slice the composite laminate structure within the damage range at equal distances along the direction perpendicular to the fiber normal, and calibrate the fiber volume coefficient and porosity coefficient of each sliced area; Microscopic representative volume element with pores establishment unit, which is used to establish a microscopic representative volume element with pores according to the fiber volume coefficient and porosity coefficient; Constitutive model establishment unit considering in-layer damage and inter-layer damage, which is used to perform unidirectional loading with six degrees of freedom on the microscopic representative volume element with pores, homogenize and calculate the equivalent material properties with drilling damage, and establish a constitutive model considering in-layer damage and inter-layer damage; Material property determination unit, which is used to determine the material properties of the composite laminate structure after drilling according to the constitutive model; Contact characteristic determination unit, which is used to divide the composite laminate structure after drilling into 4 equal parts, perform friction coefficient calibration experiments on each equal-parted composite laminate structure, and quantitatively characterize the contact characteristics of the hole wall connection interface of the composite laminate structure after drilling.

7. The composite laminate structure assembly damage simulation system considering errors and external loads according to claim 6, wherein, The geometric and force collaborative stud connection simulation model establishment module specifically includes: Three-dimensional geometric model establishment unit, which is used to establish a three-dimensional geometric model of the bolt, and establish a three-dimensional geometric model of the composite laminate structure according to the material properties; Friction relationship establishment unit, which is used to perform surface-to-surface contact between the laminates of the composite laminate structure during the assembly process, divide the hole wall area into four parts in a cross shape, establish a friction relationship between the bolt and each part of the composite hole wall area, and add the friction relationship to the contact characteristics; Composite material stress-strain constitutive relationship establishment unit, which is used to restrict the degrees of freedom of the three moving directions and the three rotating directions of the composite laminate structure and the base, restrict the five degrees of freedom of the bolt moving in the horizontal and vertical directions, set the bolt displacement along the hole axis, establish an interference stud load constraint, and under the above restrictions, establish a composite material stress-strain constitutive relationship according to the equivalent material properties with drilling damage; Contact stress determination unit, which is used to determine the contact stress between the bolt and the composite hole wall area according to the composite material stress-strain constitutive relationship and the contact characteristics with the added friction relationship. Geometric and Force Coordinated Riveting Connection Simulation Model Establishment Unit, which is used to perform damage analysis on the composite material laminated structure based on the three-dimensional geometric model of the bolt and the three-dimensional geometric model of the composite material laminated structure, and establish the geometric and force coordinated riveting connection simulation model according to the contact stress by using the maximum stress criterion and the three-dimensional Hashin failure criterion.

8. The composite material laminated structure assembly damage simulation system considering errors and external loads according to claim 7, wherein, the geometric and force coordinated tensile load simulation model establishment module specifically includes: Riveting Connection Simulation Result File Reading Unit, which is used to read the riveting connection simulation result file and output the residual stress field and damage field during the riveting connection process; the riveting connection simulation result file is the result file obtained by the geometric and force coordinated riveting connection simulation model; Setting Operation Completion Unit, which is used to establish the motion coupling reference points of the upper and lower laminates in the composite material laminated structure according to the riveting connection simulation result file, restrict the degrees of freedom of the upper and lower laminates, add a static tensile position to the upper laminate, apply bolt pre-tightening force, and set the pre-defined field for the upper and lower laminates in the composite material laminated structure to complete the setting operation; Tensile Three-Dimensional Model Establishment Unit Inheriting the Riveting Force Field, which is used to select the result of the last analysis step in the geometric and force coordinated riveting connection simulation model based on the setting operation, import the stress state and damage distribution brought during the riveting process, establish a tensile three-dimensional model inheriting the riveting force field, and complete the dynamic transfer and evolution process of the force field; Geometric and Force Coordinated Tensile Load Simulation Model Establishment Unit, which is used to perform stress analysis on the tensile three-dimensional model according to the failure criterion and stiffness reduction model, and establish the geometric and force coordinated tensile load simulation model.

9. An electronic device, wherein, it includes a memory and a processor, the memory is used to store a computer program, and the processor runs the computer program so that the electronic device executes the composite material laminated structure assembly damage simulation method considering errors and external loads according to any one of claims 1-4.

10. A computer-readable storage medium, wherein, it stores a computer program, and when the computer program is executed by a processor, it implements the composite material laminated structure assembly damage simulation method considering errors and external loads according to any one of claims 1-4.

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