Multi-angle continuous fiber reinforced composite fatigue life estimation method and system

Abstract

The present application relates to a multi-angle continuous fiber reinforced composite material fatigue life estimation method and system, the method comprises: obtaining the analysis result of stress analysis of the structure, determining the stress distribution of each layer in the material principal coordinate system; according to the stress distribution of each layer, judge whether each layer occurs fiber or matrix failure mode, and update the material parameters of the failure layer; the structure is analyzed again after updating the material parameters, and the material parameters are updated, it is assumed that when half or more of the total number of layers appears fiber or matrix failure mode, the structure loses the carrying capacity, at this time, the total number of cycles is taken as the fatigue life of the fiber reinforced composite structure. The present application estimates the fatigue life of the structure by stress analysis of each layer of the structure, and simulates the material degradation of the structure with the increase of the use time by changing the material parameters, so as to estimate the fatigue life of the structure, and realizes the fatigue life estimation of the structure.

Description

Technical Field

[0001] This invention relates to the field of materials testing technology, and in particular to a method and system for estimating the fatigue life of multi-angle continuous fiber reinforced composite materials. Background Technology

[0002] like Figure 1 As shown, multilayer continuous fiber-reinforced materials are bonded together using a hot-melt bonding method. Adjacent composite layers are cross-laid, with fibers at a specific layup angle. Compared to traditional materials, continuous fiber-reinforced composites offer advantages such as light weight, corrosion resistance, designability, and recyclability, demonstrating broad application prospects and high demand in marine engineering, aerospace, rail transportation, and civil engineering, attracting increasing attention from researchers and engineers. Furthermore, they hold promise for further expansion into clean energy sectors such as wind power, photovoltaics, and hydrogen storage. All of these applications place high demands on the fatigue life of the structure.

[0003] However, due to the complex material composition and fiber reinforcement characteristics, obtaining the fatigue life of structural components made from these materials is extremely difficult. Even with the same material composition, standard composite components with different fiber layup angles exhibit significant differences in fatigue life. Furthermore, due to anisotropy, the fatigue life of the same standard component differs along its long and short sides. Therefore, obtaining the fatigue life of fiber-reinforced composite standard components with a specific layup design has become a major challenge restricting the preliminary design of corresponding engineering structures. Summary of the Invention

[0004] To overcome the problem that existing technologies cannot predict the fatigue life of structural components made of multi-angle continuous fiber reinforced composite materials, this invention provides a method and system for estimating the fatigue life of multi-angle continuous fiber reinforced composite materials.

[0005] In a first aspect, to address the aforementioned technical problems, this invention provides a method for estimating the fatigue life of multi-angle continuous fiber reinforced composite materials, comprising:

[0006] S1. Obtain the analysis results of stress analysis on structural components with multi-angle continuous fiber reinforced composite materials, and determine the stress distribution of each layup in the material principal coordinate system;

[0007] S2. Based on the stress distribution of each ply in the principal coordinate system of the material, determine whether each ply has a fiber or matrix failure mode. If any ply has a fiber or matrix failure mode, the material parameters of the ply are updated using the sudden degradation criterion. If any ply does not have a fiber or matrix failure mode, the material parameters of the ply are updated using the preset progressive degradation criterion.

[0008] S3. Repeat S1-S3 for the structural components with updated material parameters until fiber or matrix failure modes occur at half or more of the total number of layers, and the structural components lose their load-bearing capacity.

[0009] S4. The total number of cycles corresponding to when the structural component loses its load-bearing capacity is taken as the fatigue life of the fiber-reinforced composite structural component.

[0010] Secondly, the present invention provides a fatigue life estimation system for multi-angle continuous fiber reinforced composite materials, comprising:

[0011] The stress distribution determination module is used to obtain the analysis results of stress analysis on structural components with multi-angle continuous fiber reinforced composite materials, and to determine the stress distribution of each ply in the material principal coordinate system.

[0012] The material parameter modification module is used to determine whether each ply has a fiber or matrix failure mode based on the stress distribution of each ply in the material principal coordinate system. If any ply has a fiber or matrix failure mode, the material parameters of the ply are updated using the sudden degradation criterion. If any ply does not have a fiber or matrix failure mode, the material parameters of the ply are updated using the preset progressive degradation criterion.

[0013] The loop module is used to repeatedly execute the functions corresponding to the stress distribution determination module, material parameter modification module and loop module on the structural component after the material parameters are updated, until the fiber or matrix failure mode occurs when half or more of the total number of layers, and the structural component loses its load-bearing capacity.

[0014] The fatigue life estimation module is used to determine the fatigue life of fiber-reinforced composite material structures by the total number of cycles at which a structural component loses its load-bearing capacity.

[0015] The beneficial effects of this invention are as follows: Stress analysis is performed on structural components with multi-angle continuous fiber-reinforced composite materials, and the analysis results determine whether fiber or matrix failure modes occur in each ply. Regardless of whether fiber or matrix failure modes occur, material parameters degrade over time. Therefore, different modes are used to update the material parameters of each ply exhibiting fiber or matrix failure modes. Stress analysis is then performed on the structure with updated material parameters. This process is repeated until fiber or matrix failure modes occur in half or more of the total number of plies, indicating that the structure has lost its load-bearing capacity, thus allowing for the estimation of the structure's fatigue life. This application estimates the fatigue life of structural components by performing stress analysis on each ply of the structure and simulating material degradation over time by changing material parameters. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0017] Figure 1 This is a schematic diagram of the continuous fiber reinforced material plate of the present invention;

[0018] Figure 2 This is a flowchart illustrating the fatigue life estimation method for multi-angle continuous fiber reinforced composite materials according to an embodiment of the present invention.

[0019] Figure 3 A flowchart for constructing the progressive degradation criterion;

[0020] Figure 4 This is a flowchart of the stress analysis;

[0021] Figure 5 This is a schematic cross-sectional view of the continuous fiber reinforced material plate of the present invention.

[0022] Figure 6 This is a schematic diagram of the fatigue life estimation system for multi-angle continuous fiber reinforced composite materials according to an embodiment of the present invention. Detailed Implementation

[0023] The following embodiments are further explanations and supplements to the present invention and do not constitute any limitation on the present invention.

[0024] The fatigue life estimation method and system for multi-angle continuous fiber reinforced composite materials according to embodiments of the present invention are described below with reference to the accompanying drawings.

[0025] like Figure 2 As shown, this invention provides a method for estimating the fatigue life of multi-angle continuous fiber reinforced composite materials, including:

[0026] S1. Obtain the analysis results of stress analysis on structural components with multi-angle continuous fiber reinforced composite materials, and determine the stress distribution of each layup in the material principal coordinate system.

[0027] S2. Based on the stress distribution of each ply in the principal coordinate system of the material, determine whether each ply has a fiber or matrix failure mode. If any ply has a fiber or matrix failure mode, the material parameters of the ply are updated using the sudden degradation criterion. If any ply does not have a fiber or matrix failure mode, the material parameters of the ply are updated using the preset progressive degradation criterion.

[0028] S3. Repeat S1-S3 for the structural components with updated material parameters until fiber or matrix failure modes occur in half or more of the total number of layers, at which point the structural components lose their load-bearing capacity.

[0029] S4. The total number of cycles corresponding to when the structural component loses its load-bearing capacity is taken as the fatigue life of the fiber-reinforced composite structural component.

[0030] For example, if a structural component loses its load-bearing capacity after a total of 100 cycles, then the fatigue life is the stress cycle that the material can withstand for 100 cycles.

[0031] This embodiment performs stress analysis on a structure with multi-angle continuous fiber-reinforced composite materials. Based on the analysis results, it determines whether each ply has experienced fiber or matrix failure modes. Regardless of whether fiber or matrix failure modes occur, material parameters will degrade over time. Therefore, different modes are used to update the material parameters of each ply experiencing fiber or matrix failure modes. Stress analysis is then performed on the structure with updated material parameters. This process is repeated until fiber or matrix failure modes occur in half or more of the total number of plies, indicating that the structure has lost its load-bearing capacity, thus allowing for the estimation of the structure's fatigue life. This application estimates the fatigue life of a structure by performing stress analysis on each ply and simulating material degradation over time by changing material parameters.

[0032] Optionally, such as Figure 3 As shown, the process of obtaining the preset progressive degradation criterion includes:

[0033] S11. Obtain multiple specimens with three laying angles of 0°, 90° and ±45°, and divide each specimen into test specimens and measurement specimens.

[0034] The specimens must meet the test specimen preparation standards of ASTM D3039. Therefore, specimens with three laying angles of 0°, 90° and ±45° were selected.

[0035] S12. Perform tensile fatigue tests on the test specimens using different stress level cycles to determine the total number of cyclic loading cycles for the test specimens.

[0036] The stress level is set according to the actual situation. In this embodiment, four stress levels of 80%, 70%, 60% and 50% of the total stress level of the equipment can be used to conduct cyclic tensile fatigue tests on the test specimen in sequence.

[0037] S13. Determine multiple preset loading counts based on the total number of loop loading counts.

[0038] The preset loading count is selected based on experience, choosing representative counts such as the count corresponding to the moment when the material degradation rate is the highest, or the count corresponding to the moment when the material first undergoes deformation.

[0039] S14. Perform tensile fatigue tests on the test specimens using different stress level cycles, and stop the test at each preset loading number, remove the test specimens, and perform static tensile tests to determine the residual stiffness and residual strength of the test specimens.

[0040] In this embodiment, the degree of fatigue life attenuation of the material is represented by residual stiffness and residual strength, as follows:

[0041]

[0042] Where E represents the residual stiffness, E s The static stiffness is represented by n, the preset number of loading cycles, σ, the stress level, κ, and N. f ε represents the fatigue life under stress level. f R represents the average strain at failure, and R represents the residual strength. s The static strength is represented by β and α, λ and γ, which are unknown parameters set based on tensile fatigue tests.

[0043] S15. Based on each residual stiffness and each residual strength, a progressive degradation criterion is constructed through data fitting.

[0044] Since all parameters except β and α, λ and γ can be measured in each static tensile test, after multiple static tensile tests, the measured values ​​can be substituted into the above formula for data fitting to obtain the values ​​of β and α, λ and γ, thus obtaining the complete progressive degradation criterion.

[0045] Optionally, the preset number of loads includes the median of the total number of loop loads, 1 / 3 of the total number of loop loads, and 2 / 3 of the total number of loop loads.

[0046] The above values ​​are the most representative values, but other representative values ​​may also be used.

[0047] Optionally, such as Figure 4 As shown, the analysis results of stress analysis on a structural component with multi-angle continuous fiber reinforced composite material are obtained, and the stress distribution of each layup in the material principal coordinate system is determined, including:

[0048] S21. Determine the compliance matrix of each ply in the principal material coordinate system based on the material parameters of each ply.

[0049] The material parameters include the elastic modulus, Poisson's ratio, and shear modulus of the fiber-reinforced composite material along the three principal directions. The three elastic moduli are E1, E2, and E3, and the three Poisson's ratios are v1, v2, v3, v4, v5, v6, v7 23 v 13 and v 12 The three elastic moduli are G 23 G 13 and G 12 .

[0050] The compliance matrix of each ply in the principal material coordinate system is:

[0051]

[0052] Among them, c (i) c represents the compliance matrix in the principal coordinate system. ij The elements in the compliance matrix are determined in the following way:

[0053]

[0054] S22. Change the compliance matrix of each ply from the material principal coordinate system to the Cartesian coordinate system to determine the compliance matrix in the Cartesian coordinate system.

[0055] Based on the laying pattern of each layer of material, a coordinate transformation matrix is ​​constructed as follows:

[0056]

[0057] Among them, T (i) Represents the coordinate transformation matrix. Let i be the layup angle of the i-th ply;

[0058] The compliance matrix of each ply is transformed from the material principal coordinate system to the Cartesian coordinate system using a coordinate transformation matrix, as follows:

[0059]

[0060] Among them, C (i) This represents the compliance matrix in the Cartesian coordinate system.

[0061] S23. Obtain the thickness ratio matrix and area ratio matrix of each ply in the entire ply cross section.

[0062] The thickness ratio matrix is ​​used with [t] (1) t (2) …t (i) … t (n) The specific meaning is as follows:

[0063]

[0064] like Figure 5 As shown, t i This represents the thickness of the i-th ply, where i is the total thickness of all plies.

[0065] The area ratio matrix is ​​represented by [A] (1) A (2) …A (i) … A (n) The specific meaning is as follows:

[0066]

[0067] like Figure 5 As shown, A i Let A be the thickness of the i-th ply, and let A be the total thickness of all plies.

[0068] S24. For each ply, determine different homogenization stress calculation coefficients based on the compliance matrix, thickness ratio matrix, and area ratio matrix in the Cartesian coordinate system.

[0069] Different homogenization stress calculation coefficients are expressed by the following formulas:

[0070]

[0071] Among them, C 23 C 33 The coefficients represent different homogenization stress calculation factors, where n represents the layer number of the i-th ply, and i represents the i-th ply. and Based on the compliance matrix C in the Cartesian coordinate system (i) The following formula is used to calculate:

[0072]

[0073] S25. For each layup, determine the stress distribution in the Cartesian coordinate system based on different homogenization stress calculation coefficients.

[0074] The formula for stress distribution in Cartesian coordinates is as follows:

[0075]

[0076] in, These represent the stresses in the three directions experienced by the i-th ply in the Cartesian coordinate system, respectively. Let represent the shear stresses in the three directions of the i-th ply in the Cartesian coordinate system, and σ represent the stress level.

[0077] S26. Transform the actual stress distribution of each ply from the Cartesian coordinate system to the material principal coordinate system to determine the stress distribution in the material principal coordinate system.

[0078] The formula for stress distribution in the principal coordinate system of the material is as follows:

[0079]

[0080] in, These represent the stresses in the three directions experienced by the i-th ply in the principal coordinate system of the material, respectively. Let T represent the shear stresses in the three directions of the i-th ply in the principal coordinate system of the material, respectively. (i) This represents the coordinate transformation matrix.

[0081] Optionally, the fiber or matrix failure modes include fiber tensile failure mode, fiber compressive failure mode, matrix tensile failure mode, matrix compressive failure mode, fiber-matrix shear failure mode, and delamination failure mode, and the material parameters include the material's residual stiffness and residual strength; wherein, the residual stiffness includes parameters E1, E2, E3, and v. 23 v 13 v 23 v 32 v 31 v 21 G 23 G 13 and G 12 Where E1, E2, and E3 represent the elastic moduli of the residual stiffness in directions 1, 2, and 3 in the principal coordinate system of the material, respectively, v 23 v 13 v 12 v 32 v 31 v 21 G represents the Poisson's ratio of the residual stiffness in the principal coordinate system of the material in planes 2-3, 1-3, 1-2, 3-2, 3-1, and 2-1. 23 G 13 and G 12 Represents the shear modulus of residual stiffness in the 2-3, 1-3, and 1-2 planes in the principal coordinate system. Residual strength includes the parameter Y. t Y c S 12 Z t and Z c , where Y t and Y c S represents the remaining strength in the fiber tangential direction, specifically the tensile strength and compressive strength, respectively. 12 Z represents the residual strength in the 1-2 plane of the material's principal coordinate system, where Z represents the shear strength. t and Z cThese represent the remaining strength in the three directions of tensile and compressive strength in the material's principal coordinate system, respectively. Additionally, a plane refers to the plane formed by two directions in the principal coordinate system, such as G. 23 This represents the plane formed by the residual stiffness in directions 2 and 3 in the principal coordinate system.

[0082] In addition, the formula for the fiber tensile failure mode is as follows:

[0083]

[0084] in, The tensile failure coefficients of the fiber are represented by σ1 and τ. 12 τ 13 X is obtained from the stress distribution in the principal coordinate system of the material. t (n, σ, κ), X 12 (n, σ, κ) and X 13 (n, σ, κ) represent the residual intensity at the corresponding X. t X 12 X 13 The components in the direction, n, σ, and κ, represent the number of cycles, stress level, and stress ratio, respectively.

[0085] The formula for fiber compression failure mode is as follows:

[0086]

[0087] in, The fiber compression failure coefficient, σ1, is obtained from the stress distribution in the material's principal coordinate system. c (n, σ, κ) represents the component of residual strength in the corresponding fiber direction, where n, σ, and κ represent the number of cycles, stress level, and stress ratio, respectively.

[0088] The formula for the matrix tensile failure mode is as follows:

[0089]

[0090] The tensile failure factors of the matrix are represented by σ2, σ3, and τ. 12 τ 13 τ 23 Y is obtained from the stress distribution in the principal coordinate system of the material. t (n, σ, κ) X 12 (n, σ, κ), X 13 (n, σ, κ) represent the residual intensity in the corresponding Y. t , X 12 X 13The components in the direction, n, σ, and κ, represent the number of cycles, stress level, and stress ratio, respectively.

[0091] The formula for matrix compression failure mode is as follows:

[0092]

[0093]

[0094] in, The matrix compressibility failure coefficients, σ2, σ3, and τ, represent the matrix compressibility failure coefficients. 12 τ 23 Y is obtained from the stress distribution in the principal coordinate system of the material. c (n, σ, κ), X 23 (n, σ, κ), X 12 (n, σ, κ), X 13 (n, σ, κ) represent the residual intensity in the corresponding Y. c X 23 X 12 X 13 The components in the direction, n, σ, and κ, represent the number of cycles, stress level, and stress ratio, respectively.

[0095] The formula for the fiber-matrix shear failure mode is as follows:

[0096]

[0097] in, The fiber-matrix shear failure coefficients, σ1 and τ, represent the fiber-matrix shear failure coefficients 12 τ 23 X is obtained from the stress distribution in the principal coordinate system of the material. c (n, σ, κ), X 12 (n, σ, κ), X 13 (n, σ, κ) represent the residual intensity at the corresponding X. c X 12 X 13 The components in the direction, n, σ, and κ, represent the number of cycles, stress level, and stress ratio, respectively.

[0098] The formula for the delamination failure mode is as follows:

[0099]

[0100] in, Delamination failure coefficients, σ3, τ 13 τ 23 Z is obtained from the stress distribution in the principal coordinate system of the material. t (n, σ, k), X 13 (n, σ, k), X23 (n, σ, k) represent the residual intensity at the corresponding Z. t X 13 X 23 The components in the direction, n, σ, and κ, represent the number of cycles, stress level, and stress ratio, respectively.

[0101] It should be noted that if any failure coefficient is greater than 1, it is judged as the corresponding failure mode. For example, if the fiber tensile failure coefficient is greater than 1, it indicates that the fiber tensile failure mode has occurred.

[0102] If any ply experiences a fiber or matrix failure mode, the material parameters of that ply are modified using a sudden degradation criterion, including:

[0103] If any ply experiences fiber tensile failure mode or fiber compressive failure mode, the residual stiffness and residual strength of the material corresponding to that ply will suddenly drop to zero.

[0104] If any ply experiences matrix tensile failure, the residual stiffness of that ply will suddenly drop to zero in the elastic modulus of directions 2 and 3 in the principal coordinate system, the Poisson's ratio in the 3-1 plane in the principal coordinate system will suddenly drop to zero, and the residual strength will suddenly drop to zero in the tensile strength in the fiber tangential direction.

[0105] The parameters of residual stiffness degenerate as follows:

[0106]

[0107] The material parameter for residual strength is the tensile strength Y in the fiber tangential direction. t It suddenly dropped to zero.

[0108] If any ply experiences matrix compression failure, the residual stiffness of that ply will suddenly drop to zero in the elastic modulus of directions 2 and 3 in the principal coordinate system, the Poisson's ratio in the 3-1 plane in the principal coordinate system will suddenly drop to zero, and the residual strength will suddenly drop to zero in the compressive strength in the fiber tangential direction.

[0109] The parameters of residual stiffness degenerate as follows:

[0110]

[0111] The material parameter for residual strength is the compressive strength Y in the fiber tangential direction. c It suddenly dropped to zero.

[0112] If any ply experiences fiber-matrix shear failure, the Poisson's ratio of the residual stiffness of that ply in planes 1-2 and 2-1 of the material principal coordinate system will suddenly drop to zero, the shear modulus in plane 1-2 of the material principal coordinate system will suddenly drop to zero, and the shear strength of the residual strength in plane 1-2 of the material principal coordinate system will suddenly drop to zero.

[0113] The parameters of residual stiffness degenerate as follows:

[0114]

[0115] The material parameters for residual strength are the shear strength S in the 1-2 plane of the material principal coordinate system. 12 It suddenly dropped to zero.

[0116] If any ply experiences delamination failure, the residual stiffness of that ply will suddenly drop to zero in the 3-direction elastic modulus in the principal coordinate system, the Poisson's ratio in the 3-2 and 3-1 planes in the principal coordinate system will suddenly drop to zero, and the residual strength will suddenly drop to zero in the 3-direction tensile and compressive strengths in the principal coordinate system.

[0117] The parameters of residual stiffness degenerate as follows:

[0118]

[0119] Material parameters for residual strength: tensile strength Z in three directions in the principal coordinate system of the material. t and compressive strength Z c It suddenly dropped to zero.

[0120] Furthermore, if no fiber or matrix failure mode occurs in any ply, the material parameters of that ply are modified using a preset progressive degradation criterion. Specifically, the residual stiffness and residual strength are directly calculated using the following formula:

[0121]

[0122] Optionally, based on publicly available experimental data from research papers, a laying angle of [45 / 0 / -45 / 90] can be used. S Taking glass fiber reinforced high-density polyethylene composite material as an example, the theoretical estimation process of its fatigue life is briefly explained. The ultimate strength of the material obtained from static strength tests is shown in Table 1.

[0123] Table 1

[0124]

[0125] Meanwhile, based on fatigue test and residual fatigue test data, the residual stiffness degradation parameters λ and γ in the three directions of 0°, 90° and ±45° of the material were obtained, and these parameters are listed in Table 2.

[0126] Table 2

[0127]

[0128] Meanwhile, due to the lack of residual strength data, it is assumed that the residual strength degradation law is consistent with the residual stiffness, that is, the residual strength degradation parameters β and α are equal to the residual strength degradation parameters λ and γ, respectively. These parameters are substituted into the progressive degradation criterion. Simultaneously, a fatigue life estimation method for multi-angle continuous fiber-reinforced composite materials is implemented based on static material test data. Fiber or matrix failure modes are also introduced, and the fatigue life of the specimen is obtained through iterative calculations.

[0129] Table 3 presents the theoretical and experimental results of fatigue life estimation for glass fiber reinforced high-density polyethylene composites with a layup angle of [45 / 0 / -45 / 90]S under two fatigue load conditions with stress ratios of 0.8 and 0.65.

[0130] Table 3

[0131]

[0132] A comparison of the experimental data and estimation results in Table 3 shows that the fatigue life estimation method for standard continuous fiber reinforced composite materials with arbitrary laying angles established in this paper can provide a relatively accurate fatigue life prediction.

[0133] like Figure 6 As shown, the present invention provides a fatigue life estimation system for multi-angle continuous fiber reinforced composite materials, comprising:

[0134] The stress distribution determination module is used to obtain the analysis results of stress analysis on structural components with multi-angle continuous fiber reinforced composite materials, and to determine the stress distribution of each ply in the material principal coordinate system.

[0135] The material parameter modification module is used to determine whether each ply has a fiber or matrix failure mode based on the stress distribution of each ply in the material principal coordinate system. If any ply has a fiber or matrix failure mode, the material parameters of the ply are updated using the sudden degradation criterion. If any ply does not have a fiber or matrix failure mode, the material parameters of the ply are updated using the preset progressive degradation criterion.

[0136] The loop module is used to repeatedly execute the functions corresponding to the stress distribution determination module, material parameter modification module and loop module on the structural component after the material parameters are updated, until the fiber or matrix failure mode occurs when half or more of the total number of layers, and the structural component loses its load-bearing capacity.

[0137] The fatigue life estimation module is used to determine the fatigue life of fiber-reinforced composite material structures by the total number of cycles at which a structural component loses its load-bearing capacity.

[0138] Optionally, the system also includes a progressive degradation criterion acquisition module, which is specifically used for:

[0139] Multiple specimens with three laying angles of 0°, 90° and ±45° were obtained, and each specimen was divided into test specimens and measurement specimens;

[0140] Tensile fatigue tests were conducted on the test specimens using different stress level cycles to determine the total number of cyclic loading cycles for the test specimens;

[0141] Based on the total number of loop loads, determine multiple preset load counts;

[0142] Tensile fatigue tests were conducted on the test specimens using different stress level cycles. At each preset loading cycle, the test was stopped, the test specimens were removed, and static tensile tests were performed to determine the residual stiffness and residual strength of the test specimens.

[0143] Based on the remaining stiffness and remaining strength, a progressive degradation criterion is constructed through data fitting.

[0144] Optionally, the preset number of loads includes the median of the total number of loop loads, 1 / 3 of the total number of loop loads, and 2 / 3 of the total number of loop loads;

[0145] The gradual degradation criterion acquisition module is specifically used for:

[0146] Based on the total number of loop loads, the median of the total number of loop loads, 1 / 3 of the total number of loop loads, and 2 / 3 of the total number of loop loads are used as the preset number of loads.

[0147] Optionally, the stress distribution determination module is specifically used for:

[0148] Based on the material parameters of each ply, determine the compliance matrix of each ply in the principal material coordinate system;

[0149] The compliance matrix of each ply is transformed from the material principal coordinate system to the Cartesian coordinate system to determine the compliance matrix in the Cartesian coordinate system.

[0150] Obtain the thickness ratio matrix and area ratio matrix of each ply in the entire ply cross section;

[0151] For each ply, different homogenization stress calculation coefficients are determined based on the compliance matrix, thickness ratio matrix, and area ratio matrix in the Cartesian coordinate system.

[0152] For each ply, the stress distribution in the Cartesian coordinate system is determined based on different homogenization stress calculation coefficients;

[0153] The stress distribution of each ply is transformed from the Cartesian coordinate system to the material principal coordinate system to determine the stress distribution in the material principal coordinate system.

[0154] Optionally, the fiber or matrix failure modes include fiber tensile failure mode, fiber compression failure mode, matrix tensile failure mode, matrix compression failure mode, fiber-matrix shear failure mode, and delamination failure mode, and the material parameters include residual stiffness and residual strength.

[0155] The loop module is specifically used for:

[0156] If any ply experiences a fiber or matrix failure mode, the material parameters of that ply are modified using the sudden degradation criterion, including:

[0157] If any ply experiences fiber tensile failure mode or fiber compressive failure mode, the residual stiffness and residual strength of the material corresponding to that ply will suddenly drop to zero.

[0158] If any ply experiences matrix tensile failure mode, the residual stiffness of that ply will suddenly drop to zero in the elastic modulus of directions 2 and 3 in the principal coordinate system of the material, the Poisson's ratio in the 3-1 plane in the principal coordinate system of the material will suddenly drop to zero, and the residual strength will suddenly drop to zero in the tensile strength in the fiber tangential direction.

[0159] If any ply experiences matrix compression failure, the residual stiffness of that ply will suddenly drop to zero in the elastic modulus of directions 2 and 3 in the principal coordinate system of the material, the Poisson's ratio in the 3-1 plane in the principal coordinate system of the material will suddenly drop to zero, and the residual strength will suddenly drop to zero in the compressive strength in the fiber tangential direction.

[0160] If any ply experiences fiber-matrix shear failure, the Poisson's ratio of the residual stiffness of that ply in planes 1-2 and 2-1 of the material principal coordinate system will suddenly drop to zero, the shear modulus in plane 1-2 of the material principal coordinate system will suddenly drop to zero, and the shear strength of the residual strength in plane 1-2 of the material principal coordinate system will suddenly drop to zero.

[0161] If any ply experiences delamination failure, the residual stiffness of that ply will suddenly drop to zero in the 3-direction elastic modulus in the principal coordinate system, the Poisson's ratio in the 3-2 and 3-1 planes in the principal coordinate system will suddenly drop to zero, and the residual strength will suddenly drop to zero in the 3-direction tensile and compressive strengths in the principal coordinate system.

[0162] Those skilled in the art will recognize that this invention can be implemented as a system, method, or computer program product. Therefore, this disclosure can be embodied in the following forms: it can be entirely hardware, entirely software (including firmware, resident software, microcode, etc.), or a combination of hardware and software, generally referred to herein as a "circuit," "module," or "system." Furthermore, in some embodiments, the invention can also be implemented as a computer program product contained in one or more computer-readable media, which contains computer-readable program code. Computer-readable storage media can be, for example, but not limited to—electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatuses, or devices, or any combination thereof.

[0163] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0164] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for estimating the fatigue life of multi-angle continuous fiber reinforced composite materials, characterized in that, include: S1. Obtain the analysis results of stress analysis on structural components with multi-angle continuous fiber reinforced composite materials, and determine the stress distribution of each layup in the material principal coordinate system, wherein the stress distribution includes stress and shear stress in three directions in the material principal coordinate system; S2. Based on the stress distribution of each ply in the principal coordinate system and the material parameters of each ply, determine whether a fiber or matrix failure mode has occurred in each ply. If any ply has a fiber or matrix failure mode, the material parameters of the ply are updated using the sudden degradation criterion. If any ply does not have a fiber or matrix failure mode, the material parameters of the ply are updated using the preset progressive degradation criterion. The material parameters include at least residual stiffness and residual strength. S3. Repeat S1-S3 for the structure after updating the material parameters until fiber or matrix failure mode occurs at half or more of the total number of layers, and the structure loses its load-bearing capacity. S4. The total number of cycles at which the structural component loses its load-bearing capacity is taken as the fatigue life of the fiber-reinforced composite structural component.

2. The method according to claim 1, characterized in that, The process of obtaining the preset progressive degradation criterion includes: Multiple specimens with three laying angles of 0°, 90° and ±45° were obtained, and each specimen was divided into test specimens and measurement specimens; Tensile fatigue tests were conducted on the test specimens using different stress level cycles to determine the total number of cyclic loading cycles for the test specimens; Based on the total number of loop loads, multiple preset load counts are determined; Tensile fatigue tests were performed on the test specimens using different stress level cycles. At each preset loading cycle, the test was stopped, the test specimens were removed, and static tensile tests were performed to determine the residual stiffness and residual strength of the test specimens. Based on each residual stiffness and each residual strength, a progressive degradation criterion is constructed through data fitting.

3. The method according to claim 2, characterized in that, The preset number of load counts includes the median of the total number of loop loads, 1 / 3 of the total number of loop loads, and 2 / 3 of the total number of loop loads.

4. The method according to claim 1, characterized in that, Obtain the analysis results of stress analysis on structural components with multi-angle continuous fiber reinforced composites, and determine the stress distribution of each layup in the material principal coordinate system, including: Based on the material parameters of each ply, determine the compliance matrix of each ply in the principal material coordinate system; The compliance matrix of each ply is transformed from the material principal coordinate system to the Cartesian coordinate system to determine the compliance matrix in the Cartesian coordinate system; Obtain the thickness ratio matrix and area ratio matrix of each ply in the entire ply cross section; For each ply, different homogenization stress calculation coefficients are determined based on the compliance matrix, thickness ratio matrix, and area ratio matrix in the Cartesian coordinate system. For each ply, the stress distribution in the Cartesian coordinate system is determined based on the different homogenization stress calculation coefficients. The stress distribution of each ply is transformed from the Cartesian coordinate system to the material principal coordinate system to determine the stress distribution in the material principal coordinate system.

5. The method according to claim 1, characterized in that, The fiber or matrix failure modes include fiber tensile failure mode, fiber compression failure mode, matrix tensile failure mode, matrix compression failure mode, fiber-matrix shear failure mode, and delamination failure mode. The material parameters include residual stiffness and residual strength. If any ply experiences a fiber or matrix failure mode, the material parameters of that ply are modified using a sudden degradation criterion, including: If any ply experiences fiber tensile failure mode or fiber compressive failure mode, the residual stiffness and residual strength of the material corresponding to that ply will suddenly drop to zero. If any ply experiences matrix tensile failure mode, the residual stiffness of that ply will suddenly drop to zero in the elastic modulus of directions 2 and 3 in the principal coordinate system of the material, the Poisson's ratio in the 3-1 plane in the principal coordinate system of the material will suddenly drop to zero, and the residual strength will suddenly drop to zero in the tensile strength in the fiber tangential direction. If any ply experiences matrix compression failure, the residual stiffness of that ply will suddenly drop to zero in the elastic modulus of directions 2 and 3 in the principal coordinate system of the material, the Poisson's ratio in the 3-1 plane in the principal coordinate system of the material will suddenly drop to zero, and the residual strength will suddenly drop to zero in the compressive strength in the fiber tangential direction. If any ply experiences fiber-matrix shear failure, the Poisson's ratio of the residual stiffness of that ply in planes 1-2 and 2-1 of the material principal coordinate system will suddenly drop to zero, the shear modulus in plane 1-2 of the material principal coordinate system will suddenly drop to zero, and the shear strength of the residual strength in plane 1-2 of the material principal coordinate system will suddenly drop to zero. If any ply experiences delamination failure, the residual stiffness of that ply will suddenly drop to zero in the 3-direction elastic modulus in the principal coordinate system, the Poisson's ratio in the 3-2 and 3-1 planes in the principal coordinate system will suddenly drop to zero, and the residual strength will suddenly drop to zero in the 3-direction tensile and compressive strengths in the principal coordinate system.

6. A fatigue life estimation system for multi-angle continuous fiber reinforced composite materials, characterized in that, include: The stress distribution determination module is used to obtain the analysis results of stress analysis on structural components with multi-angle continuous fiber reinforced composite materials, and to determine the stress distribution of each ply in the material principal coordinate system, wherein the stress distribution includes stress and shear stress in three directions in the material principal coordinate system; The material parameter modification module is used to determine whether each ply has experienced fiber or matrix failure modes based on the stress distribution of each ply in the principal material coordinate system and the material parameters of each ply. If any ply experiences fiber or matrix failure modes, the material parameters of the ply are updated using a sudden degradation criterion. If any ply does not experience fiber or matrix failure modes, the material parameters of the ply are updated using a preset progressive degradation criterion. The material parameters include at least residual stiffness and residual strength. The loop module is used to repeatedly execute the functions corresponding to the stress distribution determination module, material parameter modification module and loop module on the structure after the material parameters are updated, until the fiber or matrix failure mode occurs when half or more of the total number of layers, and the structure loses its load-bearing capacity. The fatigue life estimation module is used to determine the fatigue life of fiber-reinforced composite material structures by the total number of cycles at which a structural component loses its load-bearing capacity.

7. The system according to claim 6, characterized in that, The system also includes a progressive degradation criterion acquisition module, which is specifically used for: Multiple specimens with three laying angles of 0°, 90° and ±45° were obtained, and each specimen was divided into test specimens and measurement specimens; Tensile fatigue tests were conducted on the test specimens using different stress level cycles to determine the total number of cyclic loading cycles for the test specimens; Based on the total number of loop loads, multiple preset load counts are determined; Tensile fatigue tests were performed on the test specimens using different stress level cycles. At each preset loading number, the test was stopped, the test specimens were removed, and static tensile tests were performed to determine the remaining stiffness and remaining strength of the test specimens. Based on the remaining stiffness and remaining strength, a progressive degradation criterion is constructed through data fitting.

8. The system according to claim 7, characterized in that, The preset number of load counts includes the median of the total number of loop load counts, 1 / 3 of the total number of loop load counts, and 2 / 3 of the total number of loop load counts; The gradual degradation criterion acquisition module is specifically used for: Based on the total number of loop loading cycles, the median of the total number of loop loading cycles, 1 / 3 of the total number of loop loading cycles, and 2 / 3 of the total number of loop loading cycles are used as the preset number of loading cycles.

9. The system according to claim 6, characterized in that, The stress distribution determination module is specifically used for: Based on the material parameters of each ply, determine the compliance matrix of each ply in the principal material coordinate system; The compliance matrix of each ply is transformed from the material principal coordinate system to the Cartesian coordinate system to determine the compliance matrix in the Cartesian coordinate system; Obtain the thickness ratio matrix and area ratio matrix of each ply in the entire ply cross section; For each ply, different homogenization stress calculation coefficients are determined based on the compliance matrix, thickness ratio matrix, and area ratio matrix in the Cartesian coordinate system. For each ply, the stress distribution in the Cartesian coordinate system is determined based on the different homogenization stress calculation coefficients. The stress distribution of each ply is transformed from the Cartesian coordinate system to the material principal coordinate system to determine the stress distribution in the material principal coordinate system.

10. The system according to claim 6, characterized in that, The fiber or matrix failure modes include fiber tensile failure mode, fiber compression failure mode, matrix tensile failure mode, matrix compression failure mode, fiber-matrix shear failure mode, and delamination failure mode. The material parameters include residual stiffness and residual strength. The loop module is specifically used for: If any ply experiences a fiber or matrix failure mode, the material parameters of that ply are modified using a sudden degradation criterion, including: If any ply experiences fiber tensile failure mode or fiber compressive failure mode, the residual stiffness and residual strength of the material corresponding to that ply will suddenly drop to zero. If any ply experiences matrix tensile failure mode, the residual stiffness of that ply will suddenly drop to zero in the elastic modulus of directions 2 and 3 in the principal coordinate system of the material, the Poisson's ratio in the 3-1 plane in the principal coordinate system of the material will suddenly drop to zero, and the residual strength will suddenly drop to zero in the tensile strength in the fiber tangential direction. If any ply experiences matrix compression failure, the residual stiffness of that ply will suddenly drop to zero in the elastic modulus of directions 2 and 3 in the principal coordinate system of the material, the Poisson's ratio in the 3-1 plane in the principal coordinate system of the material will suddenly drop to zero, and the residual strength will suddenly drop to zero in the compressive strength in the fiber tangential direction. If any ply experiences fiber-matrix shear failure, the Poisson's ratio of the residual stiffness of that ply in planes 1-2 and 2-1 of the material principal coordinate system will suddenly drop to zero, the shear modulus in plane 1-2 of the material principal coordinate system will suddenly drop to zero, and the shear strength of the residual strength in plane 1-2 of the material principal coordinate system will suddenly drop to zero. If any ply experiences delamination failure, the residual stiffness of that ply will suddenly drop to zero in the 3-direction elastic modulus in the principal coordinate system, the Poisson's ratio in the 3-2 and 3-1 planes in the principal coordinate system will suddenly drop to zero, and the residual strength will suddenly drop to zero in the 3-direction tensile and compressive strengths in the principal coordinate system.

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