Methods and equipment for predicting the compressive strength of composite laminates under humid and hot conditions

Abstract

This invention relates to the field of composite material structural strength analysis and life prediction, specifically a method and device for predicting the compressive strength of composite laminates under humid and hot conditions. The method includes: discretizing each layer of the laminate to be predicted using three-dimensional solid elements; constructing a micromechanical model of stiffness degradation of a single-layer plate under humid and hot conditions, and calculating the elastic constants of the single-layer plate; calculating off-axis humid and hot strain parameters based on the elastic constants of the single-layer plate, and applying the off-axis humid and hot strain parameters to each layer of the discretized laminate to obtain a strained laminate; applying axial compressive displacement at the boundary of the strained laminate through displacement loading to obtain a displaced laminate; solving for the progressive damage parameters of the laminate based on the displaced laminate, and predicting the compressive strength of the laminate to be predicted based on the progressive damage parameters of the laminate. This method can reveal the influence of humid and hot environments on compressive strength, providing technical support for the strength design and environmental adaptability assessment of composite material structures.

Description

Technical Field

[0001] This invention generally relates to the field of composite material structural strength analysis and life prediction, and more specifically, to a method and equipment for predicting the compressive strength of composite laminates under humid and hot conditions. Background Technology

[0002] Composite laminates, due to their superior properties such as high specific strength and high specific modulus, have become key structural materials in aerospace and other fields. However, during long-term service, the coupled effect of temperature and humidity significantly degrades their compressive strength. On the one hand, high-temperature environments lead to a decrease in the modulus of the resin matrix and interfacial strength, weakening the stress transfer efficiency between the fiber and matrix. On the other hand, moisture diffuses into the matrix and interfacial regions, reducing matrix stiffness and glass transition temperature through plasticization, while also damaging interfacial bonding strength. More importantly, there is a significant coupling effect between temperature and humidity: high temperatures accelerate moisture diffusion, and the decrease in glass transition temperature after moisture absorption further exacerbates thermal degradation. The combined effect of these two factors on compressive strength far exceeds the sum of the effects of any single factor.

[0003] For the analysis of compressive strength of laminates, classical laminate theory is the most widely used. Existing research methods either rely on a large number of experiments to establish empirical relationships or calculate hydrothermal stress by applying temperature and humidity fields using the finite element method.

[0004] However, existing research methods still suffer from problems such as a lack of systematic characterization of micromechanical mechanisms, a lack of a unified theoretical framework for the coupling of hygrothermal and mechanical strain, and a lack of standardized procedures for numerical implementation. Furthermore, they have significant shortcomings when dealing with hygrothermal environments: on the one hand, they have failed to establish the joint action mechanism of hygrothermal strain and mechanical strain, making it impossible to accurately describe the redistribution characteristics of internal forces; on the other hand, they assume that material properties are constant, neglecting the stiffness degradation process caused by hygrothermal environments. Summary of the Invention

[0005] According to the present invention, a scheme for predicting the compressive strength of composite laminates under humid and hot conditions is provided. This scheme reveals the influence of humid and hot environments on compressive strength, providing technical support for the strength design and environmental adaptability assessment of composite material structures.

[0006] In a first aspect of the invention, a method for predicting the compressive strength of composite laminates under humid and hot conditions is provided. The method includes: The layers of the laminate to be predicted are discretized using three-dimensional solid elements to obtain a discrete laminate. A micromechanical model of stiffness degradation of a single-layer plate under humid and hot conditions was constructed, and the elastic constants of the single-layer plate were calculated. The off-axis hydrothermal strain parameters are calculated based on the elastic constant of the single-layer plate, and the off-axis hydrothermal strain parameters are applied to each layer of the discrete laminate to obtain the strained laminate. A displacement laminate is obtained by applying axial compressive displacement to the boundary of the strain laminate through displacement loading. The progressive damage parameters of the laminate are obtained by solving the displacement laminate, and the compressive strength of the laminate to be predicted is predicted based on the progressive damage parameters of the laminate.

[0007] Further, the calculation of the off-axis hydrothermal strain parameters based on the elastic constants of the single-layer plate includes: The coefficient of hygrothermal expansion was calculated based on the elastic constant of a single-layer plate using micromechanical analysis. A hydrothermal strain equation is constructed based on the aforementioned hydrothermal expansion coefficient, and the hydrothermal linear strain and shear strain are calculated according to the aforementioned hydrothermal strain equation. The hygrothermal linear strain and shear strain are respectively converted into eccentric hygrothermal strain; the converted hygrothermal linear strain and shear strain are used as eccentric hygrothermal strain parameters.

[0008] Furthermore, the characteristic feature is that the formula for calculating the coefficient of hygrothermal expansion is: in, The coefficient of thermal expansion is the coefficient in the first direction; The coefficient of fiber expansion; It is the fiber's elastic modulus; This represents the fiber volume fraction. The coefficient of thermal expansion of the matrix; The elastic modulus of the matrix; This represents the volume fraction of the matrix. The coefficient of thermal expansion is the coefficient in the second direction; The fiber's Poisson's ratio; Poisson's ratio of the matrix; The coefficient of hygroscopic expansion is the coefficient of thermal expansion in the first direction. The coefficient of moisture expansion of the fiber; It is the ratio of fiber moisture content to matrix moisture content; The coefficient of moisture expansion of the matrix; The matrix density; Fiber density; It is a single-layer density; This is the coefficient of hygroscopic expansion in the second direction.

[0009] Furthermore, the method of applying axial compressive displacement to the boundary of the strain-laminated plate by displacement loading includes: Pre-set fixed constraints and degrees of freedom constraints; The bottom edge of the strain-insulated laminate is constrained using fixed supports. Using degree-of-freedom constraints, the Z-direction degrees of freedom of the left and right sides of the strained laminate are constrained respectively.

[0010] Furthermore, the step of solving the progressive damage parameters of the laminate based on the displacement laminate includes: Extract the total load of the laminate from the displacement laminate; and divide the total load of the laminate into several load increment steps; Pre-defined failure and convergence criteria; Traverse all load increment steps, and based on the preset failure criterion, use the Newton-Raphson iterative method to solve each load increment step iteratively until the convergence criterion is met; then calculate the asymptotic damage parameters corresponding to each load increment step based on the results of the iterative solution. The progressive damage parameters of all load increment steps are used as the progressive damage parameters of the laminate.

[0011] Furthermore, the step of iteratively solving each load increment step using the Newton-Raphson iterative method based on the preset failure criterion includes: Construct equilibrium equations based on load increment steps; Extract the stiffness matrix from the displacement laminate; Based on the equilibrium equation and stiffness matrix, an incremental equilibrium equation is constructed; the incremental equilibrium equation is solved to obtain the displacement increment; and the strain of the load increment step is calculated based on the displacement increment of the load increment step. If the strain of the load increment step satisfies the failure criterion, the stiffness of the displacement laminate is reduced.

[0012] Furthermore, the failure criterion is: in, The coefficients of the quadratic term in the failure criterion equation; The coefficients of the first-order term in the failure criterion equation; For the constant term of the failure discrimination equation; The intensity coefficient is the 11-component Tsai-Wu. The 12-component Tsai-Wu strength coefficient; The mechanical strain components of the first layer plate; The mechanical strain components of the second layer plate; The 22-component Tsai-Wu strength coefficient; The 66-component Tsai-Wu strength coefficient; The mechanical strain components of the sixth layer plate; The intensity coefficient is the 1-component Tsai-Wu. The strength coefficient is a two-component Tsai-Wu. The first layer of plate is the wet-heat strain component. This represents the hydrothermal strain component of the second layer plate; The sixth layer plate is the wet heat strain component; This is the failure detection function; The strain ratio is for a single-layer plate.

[0013] Furthermore, the calculation of the progressive damage parameters corresponding to each load increment step based on the results of the iterative solution includes: The stress of the load increment step is calculated based on the strain and off-axis hydrothermal strain parameters of the load increment step. The nodal displacements are calculated based on the displacement increment step of the load. The nodal displacement, strain, stress, and stiffness matrices of the load increment step are used as the corresponding asymptotic damage parameters for the load increment step.

[0014] Furthermore, the compressive strength of the laminate to be predicted is predicted based on the progressive damage parameters of the laminate, including: Load-displacement curves are plotted based on the progressive damage parameters of the laminate; the peak load of the load-displacement curve is the ultimate load. The ratio of the ultimate load to the area of ​​the laminate to be predicted is taken as the compressive strength of the laminate to be predicted.

[0015] In a second aspect of the invention, an electronic device is provided. The electronic device includes at least one processor; and a memory communicatively connected to the at least one processor; the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the method of the first aspect of the invention.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects: This invention breaks through the limitations of traditional methods that rely on extensive experiments to establish empirical relationships or simply apply temperature and humidity fields. Through an integrated process of fine discretization of three-dimensional solid units, micromechanical modeling of damp-heat stiffness degradation, precise application of off-axis damp-heat strain, and analysis of the entire progressive damage process, it solves the problems of existing technologies such as lack of micromechanical mechanism characterization, inconsistent damp-heat-mechanical strain coupling framework, and neglect of dynamic degradation of material properties. The compressive strength prediction accuracy can reach over 94%, improving the reliability and engineering applicability of the prediction results and providing standardized technical support for the strength design and extreme environment adaptability assessment of composite material structures.

[0017] It should be understood that the description in the Summary of the Invention is not intended to limit the key or essential features of the embodiments of the present invention, nor is it intended to restrict the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0018] The above and other features, advantages, and aspects of the various embodiments of the present invention will become more apparent from the accompanying drawings and the following detailed description. In the drawings, the same or similar reference numerals denote the same or similar elements, wherein: Figure 1 A flowchart illustrating a method for predicting the compressive strength of composite laminates under humid and hot conditions according to an embodiment of the present invention is shown. Figure 2 A flowchart for calculating off-axis hydrothermal strain parameters according to an embodiment of the present invention is shown; Figure 3 A flowchart illustrating the application of axial compressive displacement according to an embodiment of the present invention is shown; Figure 4 A flowchart illustrating the solution of progressive damage parameters for a laminate according to an embodiment of the present invention is shown; Figure 5 A flowchart illustrating the iterative solution for each load increment step according to an embodiment of the present invention is shown; Figure 6 A flowchart illustrating the calculation of progressive damage parameters for each load increment step according to an embodiment of the present invention is shown; Figure 7 A flowchart illustrating the prediction of compressive strength according to an embodiment of the present invention is shown; Figure 8 A comparison diagram of predicted and experimental load-displacement curves under the ET1W environment according to an embodiment of the present invention is shown; Figure 9 A comparison diagram of predicted and experimental load-displacement curves under the ET2W environment according to an embodiment of the present invention is shown; Figure 10 A block diagram of an exemplary electronic device capable of implementing embodiments of the present invention is shown; Among them, 1000 is an electronic device, 1001 is a computing unit, 1002 is a ROM, 1003 is a RAM, 1004 is a bus, 1005 is an I / O interface, 1006 is an input unit, 1007 is an output unit, 1008 is a storage unit, and 1009 is a communication unit. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Furthermore, the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0021] In this invention, by establishing a finite element analysis model, the compressive limit load of laminates under different temperature and humidity conditions can be accurately predicted, revealing the influence of humid and hot environment on compressive strength, and providing technical support for the structural strength design and environmental adaptability assessment of composite materials.

[0022] Example 1

[0023] Figure 1 A flowchart illustrating the method for predicting the compressive strength of composite laminates under humid and hot conditions according to an embodiment of the present invention is shown.

[0024] The method includes S101~S105: S101. Use three-dimensional solid elements (HEX8 elements, 8 nodes, 6 degrees of freedom) to discretize each layer of the laminate to be predicted, and obtain the discrete laminate.

[0025] Specifically, discretization refers to: discretizing the width and length directions into several elements according to geometric dimensions to ensure element quality and calculation accuracy; wherein, the force transmission between boundary elements and nodes is continuous and there are no singular nodes.

[0026] S102. Construct a micromechanical model of stiffness degradation of a single-layer plate under humid and hot conditions, and calculate the elastic constants of the single-layer plate.

[0027] Specifically, the micromechanical model of stiffness degradation in a single-layer plate under humid and hot conditions refers to: based on classical laminated plate theory, assuming that the laminated plate satisfies the straight normal assumption, and establishing the constitutive equations for the humid and hot internal forces NTH and MTH by integrating along the thickness direction: in, The constitutive equation for the hygrothermal internal forces NTH is given. This is an index for the number of laminate layers; This represents the total number of layers in the laminate. For the first The reduced stiffness matrix of the layer in the off-axis direction (i.e., the off-axis stiffness matrix). This is the component of the damp-heat strain; For the first The hygrothermal strain components of the laminate; For the first Thickness coordinates of the upper surface of the shelf; For the first Thickness coordinates of the lower surface of the shelf; The constitutive equation for the hygrothermal internal torque MTH is given. This is the coordinate transformation matrix; This represents the material's principal direction stiffness matrix.

[0028] In this embodiment, the calculation process for the elastic constant of the single-layer plate is as follows: (1) Calculate the glass transition temperature: in, It is the glass transition temperature; To effectively balance the moisture absorption rate (%); This is the glass transition temperature in the dry state at room temperature.

[0029] (2) Constructing dimensionless temperature parameters: in, This is a dimensionless temperature parameter; Operating temperature; This refers to the reference temperature or room temperature.

[0030] (3) Through and Empirical fitting of the power exponent was used to determine the elastic modulus, shear modulus, and Poisson's ratio of the single-layer plate under the influence of temperature and humidity: in, The elastic modulus of a single-layer plate in the 1st direction under humid and hot conditions; The elastic modulus in the 1 direction of a single-layer plate under dry conditions at room temperature; This represents the current fiber volume fraction. This refers to the dry fiber volume fraction. This is a dimensionless temperature parameter; The elastic modulus in the 2-direction of a single-layer plate under humid and hot conditions; The elastic modulus in the 2-direction of a single-layer plate under dry conditions at room temperature; It is the glass transition temperature; Operating temperature; Reference temperature or room temperature; The shear modulus of a single-layer plate in the (1,2) plane under humid and hot conditions; The shear modulus of a single-layer plate in the (1,2) plane under dry conditions at room temperature; Poisson's ratio along the axial direction of a single-layer plate; Poisson's ratio for the fibers in a single-layer board; This represents the resin volume fraction. is the Poisson's ratio of the single-layer slab matrix.

[0031] Specifically, the elastic modulus in direction 1 of the single-layer plate under humid and hot conditions, the elastic modulus in direction 2 of the single-layer plate under humid and hot conditions, the shear modulus in the plane (1,2) of the single-layer plate under dry conditions at room temperature, and the Poisson's ratio of the single-layer plate are all elastic constants of the single-layer plate.

[0032] S103. Calculate the off-axis hydrothermal strain parameters based on the elastic constant of the single-layer plate, and apply the off-axis hydrothermal strain parameters to each layer of the discrete laminate to obtain the strained laminate.

[0033] In this embodiment, as Figure 2 As shown, the calculation of the off-axis hydrothermal strain parameters based on the elastic constant of the single-layer plate includes S201~S203: S201. The coefficient of hygrothermal expansion is calculated based on the elastic constant of a single-layer plate using micromechanical analysis.

[0034] In this embodiment, the formula for calculating the coefficient of hygrothermal expansion is: in, The coefficient of thermal expansion is the coefficient in the first direction; The coefficient of fiber expansion; It is the fiber's elastic modulus; This represents the fiber volume fraction. The coefficient of thermal expansion of the matrix; The elastic modulus of the matrix; This represents the volume fraction of the matrix. The coefficient of thermal expansion is the coefficient in the second direction; The fiber's Poisson's ratio; Poisson's ratio of the matrix; The coefficient of hygroscopic expansion is the coefficient of thermal expansion in the first direction. The coefficient of moisture expansion of the fiber; It is the ratio of fiber moisture content to matrix moisture content; The coefficient of moisture expansion of the matrix; The matrix density; Fiber density; It is a single-layer density; This is the coefficient of hygroscopic expansion in the second direction.

[0035] This embodiment uses a stiffness-weighted hybrid rule to replace the traditional volume-weighted model, which improves the scientific nature of the calculation. At the same time, it introduces the fiber-matrix moisture distribution coefficient and density correction term, breaking through the assumption of uniform moisture distribution. It can be derived with only the basic physical parameters of the fiber and matrix, without the need for a large number of special experiments, thus ensuring the accuracy of subsequent predictions of off-axis hydrothermal strain and overall compressive strength.

[0036] S202. Construct a hygrothermal strain equation based on the hygrothermal expansion coefficient, and calculate the hygrothermal linear strain and shear strain according to the hygrothermal strain equation.

[0037] In this embodiment, constructing a hydrothermal strain equation based on the aforementioned hydrothermal expansion coefficient refers to considering the anisotropy of the fiber and matrix in terms of thermal expansion and hydrothermal expansion properties, and establishing a hydrothermal strain equation for the main direction (direction 1-2) of the single-layer plate.

[0038] Specifically, the equations for hydrothermal strain and shear strain are as follows: in, The first layer of plate is the wet-heat strain component. The coefficient of thermal expansion is the coefficient in the first direction; This refers to the change in temperature. The coefficient of hygroscopic expansion is the coefficient of thermal expansion in the first direction. To effectively balance the changes in moisture absorption; This represents the hydrothermal strain component of the second layer plate; The coefficient of thermal expansion is the coefficient in the second direction; The coefficient of hygroscopic expansion in the second direction; The shear strain components in the plane (1,2) are the components of the shear strain.

[0039] S203. Perform off-axis hydrothermal strain conversion on the hydrothermal linear strain and shear strain respectively; use the converted hydrothermal linear strain and shear strain as off-axis hydrothermal strain parameters.

[0040] In this embodiment, the off-axis hydrothermal strain conversion of the hydrothermal linear strain and shear strain refers to: for any layup angle in the laminate... For a single-layer plate, the hydrothermal strain in the principal direction is transformed to the xy coordinate system in the off-axis direction through coordinate transformation: in, For the first Off-axis hydrothermal strain components of the laminate; The first layer of plate is the wet-heat strain component. This represents the hydrothermal strain component of the second layer plate; For the first Off-axis hydrothermal strain components of the laminate; The off-axis shear strain components are in the plane (1,2); This refers to the ply angle.

[0041] This embodiment overcomes the limitations of simply applying the overall temperature and humidity field or calculating the strain in the main direction by calculating the off-axis wet and hot strain. It quantifies the linear strain and shear strain at any ply angle, accurately characterizes the interlayer deformation constraint and stress concentration, and effectively reduces the deviation in strength prediction.

[0042] S104. By applying axial compressive displacement to the boundary of the strained laminate, a displacement laminate is obtained.

[0043] In this embodiment, as Figure 3 As shown, the method of applying axial compressive displacement to the boundary of the strain-insulated laminate by displacement loading to prevent out-of-plane displacement includes steps S301 to S303: S301. Preset fixed constraints and degree-of-freedom constraints. The fixed constraints are as follows: The degrees of freedom are constrained as follows: .

[0044] S302. Use fixed support constraints to constrain the bottom edge of the strain laminate.

[0045] S303. Using degree-of-freedom constraints, constrain the Z-direction degrees of freedom of the left and right sides of the strained laminate, respectively.

[0046] This embodiment, through boundary constraints and displacement loading, compared with traditional force loading and fully constrained boundaries, avoids the iterative non-convergence problem caused by stiffness degradation during progressive damage, can fully capture the peak and descent segments of the load-displacement curve, and accurately simulates the compression condition through bottom edge fixed support and side Z-direction constraint, effectively suppressing out-of-plane buckling interference without introducing additional in-plane constraint stress, ensuring that the failure mode is consistent with the test, and improving the accuracy of ultimate load prediction.

[0047] S105. Solve for the progressive damage parameters of the laminate based on the displacement laminate, and predict the compressive strength of the laminate to be predicted based on the progressive damage parameters of the laminate.

[0048] In this embodiment, as Figure 4As shown, the stepwise damage parameter calculation of the laminate based on the displacement laminate includes steps S401~S404: S401. Extract the total load of the laminate from the displacement laminate; and divide the total load of the laminate into several load increment steps. The total load of the laminate refers to the sum of all external forces borne by the laminate.

[0049] Specifically, the total load of the laminate is divided into several load increment steps, including: setting the increment step size, dividing the total load of the laminate into several load increment steps according to the increment step size, and the step size of each load increment step is equal to the preset increment step size.

[0050] S402, Preset failure criteria and convergence criteria.

[0051] Specifically, the failure criterion is: in, The coefficients of the quadratic term in the failure criterion equation; The coefficients of the first-order term in the failure criterion equation; For the constant term of the failure discrimination equation; The intensity coefficient is the 11-component Tsai-Wu. The 12-component Tsai-Wu strength coefficient; The mechanical strain components of the first layer plate; The mechanical strain components of the second layer plate; The 22-component Tsai-Wu strength coefficient; The 66-component Tsai-Wu strength coefficient; The mechanical strain components of the sixth layer plate; The intensity coefficient is the 1-component Tsai-Wu. The strength coefficient is a two-component Tsai-Wu. The first layer of plate is the wet-heat strain component. This represents the hydrothermal strain component of the second layer plate; The sixth layer plate is the wet heat strain component; This is the failure detection function; For a single-layer plate strain ratio; For total dependent variable; For the first Mechanical strain components of the laminate; For the first Hygrothermal strain components of the laminate; This is the layer index of the laminate; The ultimate tensile strain in one direction of a single-layer plate; The compressive limit strain in direction 1 of a single-layer plate; This represents the in-plane shear limit strain. The ultimate tensile strain in two directions for a single-layer plate; The value represents the compressive limit strain in the two directions of a single-layer plate.

[0052] In this embodiment, the convergence criterion is as follows: the energy convergence criterion is used as the convergence criterion for the iterative equation; after iterating one increment step, the internal energy increment is compared with the initial energy increment; when the ratio of the internal energy increment to the initial energy is not greater than the convergence coefficient ɛ, the solution of that increment step is considered an exact solution, the iteration stops, and the calculation proceeds to the next increment step; when the ratio of the internal energy increment to the initial energy is greater than the convergence coefficient ɛ, the iteration continues until an exact solution is obtained. Specifically, the ratio of the internal energy increment to the initial energy not being greater than the factor ɛ can be expressed as: in, Let be the structural node displacement vector in the j-th iteration during the i-th load increment step; This is the load / displacement scaling factor; Unit load vector; For a single-layer plate strain ratio; For the ith load increment step, the nodal displacement increment vector in the 1st iteration; Let be the initial nodal displacement vector for the i-th load increment step; ɛ is the convergence coefficient, typically taken as 10. -2 Up to 10 -5 .

[0053] The failure criterion constructed using the above formula breaks through the limitations of traditional criteria that only consider mechanical strain or the superposition of damp heat stress alone. Based on the coupling mechanism of "total strain = mechanical strain + damp heat strain", it introduces the strain ratio R to establish a unified discrimination equation, quantitatively characterizes the nonlinear coupling effect between the two, accurately predicts the critical failure state under different damp heat environments, avoids the problem of strength overestimation under high damp heat conditions, and is highly compatible with the progressive damage algorithm of displacement loading, with good computational convergence.

[0054] S403. Traverse all load increment steps, and based on the preset failure criterion, use the Newton-Raphson iterative method to solve each load increment step iteratively until the convergence criterion is met; then calculate the asymptotic damage parameters corresponding to each load increment step based on the results of the iterative solution.

[0055] In this embodiment, as Figure 5 As shown, based on the preset failure criterion, the Newton-Raphson iterative method is used to solve each load increment step iteratively, including S501~S504: S501. Construct the equilibrium equations based on the load increment steps. The equilibrium equations are as follows: in, The equilibrium equations; This is the external load vector; This is the internal force vector of the structure; For secant stiffness matrix; This represents the displacement vector of the structural nodes.

[0056] S502. Extract the stiffness matrix from the displacement laminate. The stiffness matrix can be expressed as: in, , the stiffness matrix of the k-th layer in the off-axis direction in the laminate; Let be the longitudinal positive stiffness component in the off-axis direction of the k-th layer; Let be the lateral positive stiffness component in the off-axis direction of the k-th layer; Let be the Poisson's ratio coupling stiffness component in the off-axis direction of the k-th layer; Let be the in-plane shear stiffness component along the off-axis direction of the k-th layer; Let be the tensile-shear coupling stiffness component in the off-axis direction of the k-th layer; Let be the compression-shear coupling stiffness component in the off-axis direction of the k-th layer; Let cosine be the angle between the structural coordinate system and the material principal axis coordinate system. , The angle between the fiber direction and the x-axis of the structure; Let be the sine of the angle between the structural coordinate system and the material principal axis coordinate system. ; The longitudinal positive axis stiffness under the principal axis of the material; The transverse positive axis stiffness under the principal axis of the material; The Poisson's ratio coupling stiffness under the principal axes of the material; The shear stiffness of the material along its principal axes; The elastic modulus in the 1 direction of a single-layer plate under dry conditions at room temperature; The elastic modulus in the 2-direction of a single-layer plate under dry conditions at room temperature; Poisson's ratio along the axial direction of a single-layer plate; Poisson's ratio along two axes for a single-layer plate; is the shear modulus of the prepreg in the (1,2) plane under dry conditions at room temperature.

[0057] S503. Based on the equilibrium equation and stiffness matrix, construct the incremental equilibrium equation; solve the incremental equilibrium equation to obtain the displacement increment; then calculate the strain of the load increment step according to the displacement increment of the load increment step.

[0058] In this embodiment, the incremental balance equation is: in, For tangent stiffness matrix; This represents the current displacement increment of the structure; This represents the current load increment on the structure.

[0059] Specifically, assuming the current load increment step is the th The step involves calculating the strain of the load increment step based on the displacement increment of the load increment step, including: in, For the first The total strain field of the step, i.e. the strain of the load increment step; This represents the total strain field at the end of the previous increment step; The strain increment resulting from the displacement increment in this incremental step is... Calculated.

[0060] The total strain field (i.e., the strain of the load increment step) will be used as the strain of the load increment step to determine whether each single layer has failed.

[0061] S504. If the strain of the load increment step meets the failure criterion, the stiffness of the displacement laminate is reduced. If the strain of the load increment step does not meet the failure criterion, it indicates that no new damage has occurred in the material within the current increment step, and the material stiffness matrix remains unchanged.

[0062] In this embodiment, reducing the stiffness of the displacement laminate includes: (1) Under compressive load, the matrix stiffness degrades in the following way: (2) The stiffness degradation mode of the matrix under tensile load is expressed as follows: (3) The stiffness degradation mode of the fiber under compressive load is expressed as follows: (4) The stiffness degradation mode of the fiber under tensile load is expressed as follows: (5) Layered damage is represented by a full stiffness degradation mode as follows: in, Let be the elastic modulus of the material in the principal direction under humid and hot conditions after the i-th damage iteration; Let be the elastic modulus of the material in the principal direction under humid and hot conditions before the i-th damage iteration; This represents the shear modulus of the material in the 1-2 plane under humid and hot conditions after the i-th damage iteration. Let be the shear modulus in the 1-2 plane of the material under humid and hot conditions before the i-th damage iteration; Let be the shear modulus of the material in plane 2-3 (the transverse plane perpendicular to the fiber direction) under humid and hot conditions after the i-th damage iteration; Let be the shear modulus of the material in the 2-3 plane under humid and hot conditions before the i-th damage iteration; is the Poisson's ratio along the 1-axis of a single-layer plate.

[0063] Specifically, after iteratively solving each load increment step using the Newton-Raphson iterative method, the convergence criterion is checked: if converged, the next load increment step is entered; if not converged, the displacement increment is updated, the strain field is recalculated, and failure judgment is performed again, until the current increment step reaches convergence and all material integration points have completed failure judgment, before the next increment step can be entered.

[0064] This embodiment solves the problem of non-convergence of iteration caused by abrupt stiffness changes during progressive damage in traditional methods by using incremental Newton-Raphson iterative solutions. Each incremental step judges failure in real time and reduces stiffness according to mode differences, fully capturing the entire process from damage initiation to expansion to final failure. It is highly compatible with the damp-heat-mechanical coupling failure criterion and significantly improves the prediction accuracy of ultimate load and failure mode.

[0065] In this embodiment, as Figure 6As shown, the step of calculating the progressive damage parameters corresponding to each load increment step based on the results of the iterative solution includes S601~S603: S601. Calculate the stress of the load increment step based on the strain and off-axis hydrothermal strain parameters of the load increment step. The specific formula is as follows: in, The stress is the stress at each load increment step. Strain for each load increment step; These are the off-axis hydrothermal strain parameters.

[0066] S602. Calculate the nodal displacements of the load increment step based on the displacement increment. The nodal displacements are the nodal displacement fields of each node at the end of the current increment step, directly output by the finite element software, including U... X U Y U Z and rotational degrees of freedom (U) R ).

[0067] Specifically, for the finite element discretization of the first... For each element, the strain components at any Gaussian integral point within it are obtained from the nodal displacements of that element using geometric equations: in, The element node displacement vector; It is a geometric matrix, consisting of the partial derivatives of the element shape functions with respect to the coordinates; The displacements are the nodal displacements of the element.

[0068] S603. Use the nodal displacement, strain, stress, and stiffness matrix of the load increment step as the asymptotic damage parameters corresponding to that load increment step.

[0069] This embodiment calculates progressive damage parameters for each load increment step, accurately separates damp heat and mechanical strain to obtain the real stress field, synchronously records dynamic changes in displacement and stiffness, and fully tracks the damage evolution.

[0070] S404. Use the progressive damage parameters of all load increment steps as the progressive damage parameters of the laminate.

[0071] This embodiment achieves the tracking of the damage process from initiation to failure by solving the asymptotic damage parameters of the laminate. Combined with failure and convergence criteria, it ensures the reliability of the calculation and provides a complete dynamic data foundation for compressive strength prediction.

[0072] In this embodiment, as Figure 7 As shown, the compressive strength of the laminate to be predicted is predicted based on the progressive damage parameters of the laminate, including S701~S702: S701. Plot a load-displacement curve based on the progressive damage parameters of the laminate; the peak load of the load-displacement curve is the ultimate load.

[0073] Specifically, the nodal displacements in the progressive damage parameters are used as the x-axis, and the stresses in the progressive damage parameters are used as the y-axis to plot the load-displacement curve.

[0074] S702. The ratio of the ultimate load to the area of ​​the laminate to be predicted is taken as the compressive strength of the laminate to be predicted.

[0075] This embodiment extracts the peak ultimate load and calculates the compressive strength based on the full-process load-displacement curve, which has clear physical meaning and strong engineering applicability.

[0076] Example 2

[0077] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment uses T300 / 985LV carbon fiber / epoxy resin prepreg laminate as an example, but the scope of protection of this invention is not limited thereto.

[0078] (1) Test specimen materials and parameters The test specimen consisted of 8 layers of T300 / 985LV carbon fiber / epoxy resin prepreg, with a single prepreg thickness of 0.381 mm. The layup sequence was [+45° / 90° / -45° / 90° / 90° / -45° / 90° / +45°], for a total of 8 layers and a total thickness of 3.05 mm. The dimensions were 150 mm × 100 mm. The basic properties of the material in the room temperature dry state are shown in Table 1.

[0079] Table 1 The effective equilibrium moisture absorption capacity Mm = 0.82 wt% and the moisture diffusion constant Dz = 1.91 × 10⁻⁷ mm were obtained through moisture absorption conditioning tests (70°C / 85% RH). 2 / s.

[0080] (2) Implementation steps This embodiment uses two humid and hot environments as examples: ET1W (85°C / 0.82 wt% moisture absorption) and ET2W (128°C / 0.82 wt% moisture absorption).

[0081] Step 1: Calculate the coefficient of hygrothermal expansion in the principal direction of a single-layer plate.

[0082] Based on the micromechanical formulas, substituting the elastic modulus and coefficient of thermal expansion of T300 fiber and epoxy matrix, we obtain: Take the coefficient of moisture expansion as For ET1W environments (85°C), °C, (wt%), calculated as follows: Similarly, the ET2W environment (128°C) was calculated. Based on this, the off-axis hydrothermal strain can be calculated for layup angles of +45°, -45°, 0°, and 90°. This step outputs the hydrothermal strain of each single layer in the off-axis direction, which serves as the input for step 2.

[0083] Step 2: Construct constitutive equations for additional internal forces and moments in laminated plates under humid and hot conditions.

[0084] Based on classical laminate theory, it is assumed that the laminate satisfies the straight normal assumption and that the deformation of each layer is coordinated. The additional internal forces and moments generated in the laminate under humid and hot conditions are caused by the humid and hot strain of each layer being constrained by the overall deformation of the laminate. Regarding temperature changes... and effectively balance moisture absorption The thermal strain of the k-th layer in the off-axis direction of the laminate C. This has been determined in step 1. The reduced stiffness matrix of this layer in the off-axis direction is: It reflects the off-axis stiffness characteristics of the material after coordinate transformation of the principal direction stiffness.

[0085] By multiplying the hydrothermal strain of each individual layer by the stiffness matrix and integrating along the thickness direction of the laminate, the hydrothermal internal force per unit width of the laminate can be obtained. and humid internal torque : in, Let be the reduced stiffness matrix of the k-th layer in the off-axis direction; Let k be the hydrothermal strain vector of the k-th layer; , represents the thickness coordinates of the upper and lower surfaces of the k-th layer; n is the total number of layers (n=8 in this embodiment).

[0086] The off-axis stiffness matrix is ​​calculated as follows: Where [Q] is the material principal direction stiffness matrix, and [T] is the coordinate transformation matrix.

[0087] In this embodiment, the layup sequence is symmetrical, and the calculated hygrothermal internal force value is small and can be ignored; the hygrothermal internal force is used as the equivalent input of the initial stress field in the subsequent finite element analysis. The output of the hygrothermal internal force of the laminate in this step is used for the equivalent application of the hygrothermal load in step 5.

[0088] Step 3: Establish a micromechanical model of stiffness degradation of a single-layer plate under humid and hot conditions. This step strictly follows the formula in step 3 of this invention to calculate the engineering elastic constant of single-layer slabs under humid and hot conditions, as shown in Table 2: Table 2 This step outputs the elastic constants of a single-layer plate after degradation under humid and hot conditions, which are used for defining material properties in the finite element model in step 5.

[0089] Step 4: Construct a failure criterion for the strength of the damp-heat-mechanical coupling. Assume that the strain at a point in a single-layer plate under humid and hot conditions is equal to the sum of the mechanical strain and the humid and hot strain: Based on the Tsai-Wu strength theory, the strain ratio is introduced. Establish a failure criterion applicable to the combined effects of hydrothermal strain and mechanical strain: The coefficients a, b, and c are determined by the ultimate strain, the hydrothermal strain, and the Tsai-Wu strength coefficient. The single layer is then determined to be faulty.

[0090] Taking a +45° layer in an ET2W environment as an example, assuming a certain incremental step of mechanical strain =0.002, from step 1, we obtain the hydrothermal strain. =0.001, then the total strain =0.003. Substitute the material's ultimate strain value into the failure equation to determine if failure has occurred. This step outputs the failure criterion, which is used for failure determination in each incremental step in step 5.

[0091] Step 5: Finite Element Modeling and Solution a. Geometric and Mesh Modeling The laminate was discretized using 3D solid elements (HEX8 elements, 8 nodes, 6 degrees of freedom). A geometric model of 150 mm × 100 mm × 3.05 mm was built in Patran, with one element per layer along the thickness direction, for a total of 8 layers. Non-critical areas of the in-plane mesh used a 5 mm coarse mesh, while the central region (approximately 50 mm × 50 mm) was refined to 1 mm, resulting in a total of approximately 12,000 elements. Force transmission between boundary elements and nodes was continuous, with no singular nodes.

[0092] b. Material property definition and application of damp heat load The elastic constants from the ET1W or ET2W environments in Table 2 are assigned to the corresponding single layers in the finite element model. Simultaneously, the off-axis hydrothermal strain calculated in step 1 is applied as the initial strain to each single layer to simulate the free expansion effect caused by temperature changes and moisture absorption. Alternatively, the hydrothermal strain can be automatically calculated by the solver by directly applying the temperature and humidity fields; both methods are equivalent.

[0093] c. Application of compressive load and boundary conditions A displacement loading method was used, applying x-axis compressive displacement to the upper boundary of the model in 100 incremental steps, with the displacement gradually increasing from 0 to 1.0 mm. The bottom edge was fixed; the z-axis degrees of freedom of the element nodes on both sides were constrained to prevent out-of-plane displacement.

[0094] d. Progressive damage solution algorithm The nonlinear equilibrium equations are solved using a hybrid incremental / Newton-Raphson iterative method. The total load is divided into several load increment steps, and the Newton-Raphson iterative method is used within each increment step. The equilibrium equations are as follows: The corresponding incremental balance equation is: In the formula, For the tangent stiffness matrix, This represents the current displacement increment of the structure. This represents the current load increment on the structure.

[0095] In each incremental step, the current strain field is first calculated, and then the failure criteria in step 4 are used to determine whether each layer has failed. If the failure condition is met, the material stiffness is reduced according to the failure mode.

[0096] Specifically, reducing material stiffness includes: (1) Under compressive load, the matrix stiffness degrades in the following way: (2) The stiffness degradation mode of the matrix under tensile load is expressed as follows: (3) The stiffness degradation mode of the fiber under compressive load is expressed as follows: (4) The stiffness degradation mode of the fiber under tensile load is expressed as follows: (5) Layered damage is represented by a full stiffness degradation mode as follows: The degraded stiffness is used for the next iteration until the energy convergence criterion is met (convergence coefficient is 10⁻⁴). This step outputs the displacement, strain, stress, and stiffness state at the end of each incremental step.

[0097] Step 6: Intensity Prediction and Result Output After solving all load increment steps, extract the following results: a. Extract the load-displacement curve to obtain the ultimate load Pmax. For the ET1W environment, the predicted ultimate load is 56.48 kN; for the ET2W environment, the predicted ultimate load is 53.16 kN.

[0098] b. The failure load and compressive strength under different humid and hot environments are compared with the experimental values ​​in Table 3.

[0099] Table 3 As shown in Table 3, the predicted compressive limit load values ​​of the method of the present invention agree well with the experimental values ​​under the two humid and hot environments of ET1W and ET2W, with relative errors of 5.5% and 5.1%, respectively, both less than 6%. This result indicates that the method for predicting the compressive strength of composite laminates considering humid and hot environments proposed in this invention has high calculation accuracy and can meet the requirements of engineering applications.

[0100] Appendix Figure 8 and attached Figure 9 The load-displacement curves of the predicted (Experiment) and experimental (Simulation) results under ET1W and ET2W environments are compared. It can be seen that the predicted curve and the experimental curve almost completely overlap in the elastic stage and also show good consistency in the nonlinear rising stage. The deviation of the peak load is controlled within 5.5%, proving the effectiveness of the hydrothermal strain constitutive model, the stiffness degradation micromechanical model, and the hydrothermal-mechanical coupling failure criterion in this invention. The differences in the curves after the peak load mainly stem from the fact that the finite element model did not consider the minor initial defects existing in the manufacturing process of the test specimen, but the overall trend is consistent, and the failure modes match well.

[0101] According to embodiments of the present invention, a complete framework for compressive strength analysis in humid and hot environments is established, achieving a unified characterization of temperature, humidity, material degradation, and strain coupling, with a prediction accuracy exceeding 94%. This approach enables quantitative differentiation of the influence of temperature, humidity, and coupling effects, revealing nonlinear superposition characteristics. Furthermore, the model is based on component physical parameters, independent of specific material systems, and possesses strong versatility; the complete process from humid and hot strain calculation to finite element solution is clearly defined, facilitating integration into mainstream software and demonstrating good engineering applicability. In addition, it can directly output compressive failure strain under different humid and hot environments, providing design allowable values ​​for structural strength verification.

[0102] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, because according to the present invention, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are all optional embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0103] According to embodiments of the present invention, an electronic device is also provided.

[0104] Figure 10 A schematic block diagram of an electronic device 1000 that can be used to implement embodiments of the present invention is shown. The electronic device is intended to represent various forms of digital computers, such as laptop computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The electronic device may also represent various forms of mobile devices, such as personal digital processors, cellular phones, smartphones, wearable devices, and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely illustrative and are not intended to limit the implementation of the invention described and / or claimed herein.

[0105] Electronic device 1000 includes a computing unit 1001, which can perform various appropriate actions and processes according to a computer program stored in read-only memory (ROM) 1002 or a computer program loaded into random access memory (RAM) 1003 from storage unit 1008. The RAM 1003 may also store various programs and data required for the operation of electronic device 1000. The computing unit 1001, ROM 1002, and RAM 1003 are interconnected via bus 1004. An input / output (I / O) interface 1005 is also connected to bus 1004.

[0106] Multiple components in electronic device 1000 are connected to I / O interface 1005, including: input unit 1006, such as keyboard, mouse, etc.; output unit 1007, such as various types of displays, speakers, etc.; storage unit 1008, such as disk, optical disk, etc.; and communication unit 1009, such as network card, modem, wireless transceiver, etc. Communication unit 1009 allows electronic device 1000 to exchange information / data with other devices through computer networks such as the Internet and / or various telecommunications networks.

[0107] The computing unit 1001 can be various general-purpose and / or special-purpose processing components with processing and computing capabilities. Some examples of the computing unit 1001 include, but are not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various special-purpose artificial intelligence (AI) computing chips, various computing units running machine learning model algorithms, a digital signal processor (DSP), and any suitable processor, controller, microcontroller, etc. The computing unit 1001 performs the various methods and processes described above, such as methods S101-S105. For example, in some embodiments, methods S101-S105 may be implemented as computer software programs tangibly contained in a machine-readable medium, such as storage unit 1008. In some embodiments, part or all of the computer program may be loaded and / or installed on the electronic device 1000 via ROM 1002 and / or communication unit 1009. When the computer program is loaded into RAM 1003 and executed by the computing unit 1001, one or more steps of methods S101-S105 described above may be performed. Alternatively, in other embodiments, the computing unit 1001 may be configured to execute methods S101 to S105 by any other suitable means (e.g., by means of firmware).

[0108] Various embodiments of the systems and techniques described above herein can be implemented in digital electronic circuit systems, integrated circuit systems, field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), application-specific standard products (ASSPs), systems-on-a-chip (SoCs), payload-programmable logic devices (CPLDs), computer hardware, firmware, software, and / or combinations thereof. These various embodiments may include implementations in one or more computer programs that can be executed and / or interpreted on a programmable system including at least one programmable processor, which may be a dedicated or general-purpose programmable processor, capable of receiving data and instructions from a storage system, at least one input device, and at least one output device, and transmitting data and instructions to the storage system, the at least one input device, and the at least one output device.

[0109] The program code used to implement the methods of the present invention can be written in any combination of one or more programming languages. This program code can be provided to a processor or controller of a general-purpose computer, special-purpose computer, or other programmable data processing device, such that when executed by the processor or controller, the program code causes the functions / operations specified in the flowcharts and / or block diagrams to be implemented. The program code can be executed entirely on the machine, partially on the machine, as a standalone software package partially on the machine and partially on a remote machine, or entirely on a remote machine or server.

[0110] In the context of this invention, a machine-readable medium can be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, apparatus, or device. A machine-readable medium can be a machine-readable signal medium or a machine-readable storage medium. Machine-readable media can include, but are not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination of the foregoing. More specific examples of machine-readable storage media include electrical connections based on one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM), optical fibers, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the foregoing.

[0111] To provide interaction with a user, the systems and techniques described herein can be implemented on a computer having: a display device for displaying information to the user (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor); and a keyboard and pointing device (e.g., a mouse or trackball) through which the user provides input to the computer. Other types of devices can also be used to provide interaction with the user; for example, feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form (including sound input, voice input, or tactile input).

[0112] The systems and technologies described herein can be implemented in computing systems that include backend components (e.g., as a data server), or computing systems that include middleware components (e.g., an application server), or computing systems that include frontend components (e.g., a user computer with a graphical user interface or web browser through which a user can interact with implementations of the systems and technologies described herein), or any combination of such backend, middleware, or frontend components. The components of the system can be interconnected via digital data communication of any form or medium (e.g., a communication network). Examples of communication networks include local area networks (LANs), wide area networks (WANs), and the Internet.

[0113] Computer systems can include clients and servers. Clients and servers are generally located far apart and typically interact via communication networks. Client-server relationships are created by computer programs running on the respective computers and having a client-server relationship with each other. Servers can be cloud servers, servers in distributed systems, or servers incorporating blockchain technology.

[0114] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0115] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for predicting the compressive strength of composite laminates under humid and hot conditions, characterized in that, include: The layers of the laminate to be predicted are discretized using three-dimensional solid elements to obtain a discrete laminate. A micromechanical model of stiffness degradation of a single-layer plate under humid and hot conditions was constructed, and the elastic constants of the single-layer plate were calculated. The off-axis hydrothermal strain parameters are calculated based on the elastic constant of the single-layer plate, and the off-axis hydrothermal strain parameters are applied to each layer of the discrete laminate to obtain the strained laminate. A displacement laminate is obtained by applying axial compressive displacement to the boundary of the strain laminate through displacement loading. The progressive damage parameters of the laminate are obtained by solving the displacement laminate, and the compressive strength of the laminate to be predicted is predicted based on the progressive damage parameters of the laminate.

2. The method according to claim 1, characterized in that, The calculation of the off-axis hydrothermal strain parameters based on the elastic constants of the single-layer plate includes: The coefficient of hygrothermal expansion was calculated based on the elastic constant of a single-layer plate using micromechanical analysis. A hydrothermal strain equation is constructed based on the aforementioned hydrothermal expansion coefficient, and the hydrothermal linear strain and shear strain are calculated according to the aforementioned hydrothermal strain equation. The hygrothermal linear strain and shear strain are respectively converted into eccentric hygrothermal strain; the converted hygrothermal linear strain and shear strain are used as eccentric hygrothermal strain parameters.

3. The method according to claim 2, characterized in that, The formula for calculating the coefficient of hygrothermal expansion is: in, The coefficient of thermal expansion is the coefficient in the first direction; The coefficient of fiber expansion; It is the fiber's elastic modulus; This represents the fiber volume fraction. The coefficient of thermal expansion of the matrix; The elastic modulus of the matrix; This represents the volume fraction of the matrix. The coefficient of thermal expansion is the coefficient in the second direction; The fiber's Poisson's ratio; Poisson's ratio of the matrix; The coefficient of hygroscopic expansion is the coefficient of thermal expansion in the first direction. The coefficient of moisture expansion of the fiber; It is the ratio of fiber moisture content to matrix moisture content; The coefficient of wet expansion of the matrix; The matrix density; Fiber density; It is a single-layer density; This is the coefficient of hygroscopic expansion in the second direction.

4. The method according to claim 1, characterized in that, The method of applying axial compressive displacement to the boundary of the strain-laminated plate by displacement loading includes: Pre-set fixed constraints and degrees of freedom constraints; The bottom edge of the strain-insulated laminate is constrained using fixed supports. Using degree-of-freedom constraints, the Z-direction degrees of freedom of the left and right sides of the strained laminate are constrained respectively.

5. The method according to claim 1, characterized in that, The method of solving the progressive damage parameters of the laminate based on the displacement laminate includes: Extract the total load of the laminate from the displacement laminate; and divide the total load of the laminate into several load increment steps; Pre-defined failure and convergence criteria; Traverse all load increment steps, and based on the preset failure criterion, use the Newton-Raphson iterative method to solve each load increment step iteratively until the convergence criterion is met; then calculate the asymptotic damage parameters corresponding to each load increment step based on the results of the iterative solution. The progressive damage parameters of all load increment steps are used as the progressive damage parameters of the laminate.

6. The method according to claim 5, characterized in that, The step of iteratively solving for each load increment step using the Newton-Raphson iterative method based on the preset failure criterion includes: Construct equilibrium equations based on load increment steps; Extract the stiffness matrix from the displacement laminate; Based on the equilibrium equation and stiffness matrix, an incremental equilibrium equation is constructed; the incremental equilibrium equation is solved to obtain the displacement increment; and the strain of the load increment step is calculated based on the displacement increment of the load increment step. If the strain of the load increment step satisfies the failure criterion, the stiffness of the displacement laminate is reduced.

7. The method according to claim 5 or 6, characterized in that, The failure criterion is as follows: in, The coefficients of the quadratic term in the failure criterion equation; The coefficients of the first-order term in the failure criterion equation; For the constant term of the failure discrimination equation; The intensity coefficient is the 11-component Tsai-Wu. The intensity coefficient is the 12-component Tsai-Wu. The mechanical strain components of the first layer plate; The mechanical strain components of the second layer plate; The 22-component Tsai-Wu strength coefficient; The 66-component Tsai-Wu strength coefficient; The mechanical strain components of the sixth layer plate; The intensity coefficient is the 1-component Tsai-Wu. The strength coefficient is a two-component Tsai-Wu. The first layer of plate is the wet-heat strain component. This represents the hydrothermal strain component of the second layer plate; The sixth layer plate is the wet-heat strain component; This is the failure detection function; The strain ratio is for a single-layer plate.

8. The method according to claim 6, characterized in that, The calculation of the progressive damage parameters corresponding to each load increment step based on the results of the iterative solution includes: The stress of the load increment step is calculated based on the strain and off-axis hydrothermal strain parameters of the load increment step. The nodal displacements are calculated based on the displacement increment step of the load. The nodal displacement, strain, stress, and stiffness matrices of the load increment step are used as the corresponding asymptotic damage parameters for the load increment step.

9. The method according to claim 1, characterized in that, Predicting the compressive strength of a laminate based on its progressive damage parameters includes: Load-displacement curves are plotted based on the progressive damage parameters of the laminate; the peak load of the load-displacement curve is the ultimate load. The ratio of the ultimate load to the area of ​​the laminate to be predicted is taken as the compressive strength of the laminate to be predicted.

10. An electronic device, comprising at least one processor; and a memory communicatively connected to said at least one processor; characterized in that, The memory stores instructions that can be executed by the at least one processor to enable the at least one processor to perform the method of any one of claims 1-9.

Images