Calculation method for blanket curve of composite material

Abstract

The invention discloses a composite material blanket curve calculation method, and belongs to the field of composite material calculation programs.The method comprises the following steps that material attributes of different-angle laying layers are determined, and the material attributes comprise rigidity data and strength data; calculating equivalent modulus and strength values of the laminated plate under different layering proportions based on the rigidity data and the strength data; and drawing a blanket curve based on the equivalent modulus and the strength value. The modulus and strength blanket curves obtained through calculation are integrated in the same chart, and rapid and accurate query by designers is facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of composite material calculation programs, and in particular relates to a composite material blanket curve calculation method. Background Art

[0002] The blanket curve design method for composite laminates is a stiffness-based design method based on classical laminate theory. In general, the laminate design selects four plies of 0, 45, -45 and 90 degrees, and establishes the relationship curve between the in-plane modulus and strength of the [0 / ±45 / 90] series of laminates, namely the blanket curve, for preliminary design application.

[0003] The commonly used blanket curve uses one material for each ply angle, and the calculation results are relatively independent, the strength criterion is single, and the applicability is relatively weak. Therefore, a more applicable blanket curve design method is needed to make up for the shortcomings of the existing technology. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a composite material blanket curve calculation method to solve the above problems existing in the prior art.

[0005] To achieve the above object, the present invention provides a composite material blanket curve calculation method, comprising:

[0006] Determining material properties of plies laid at different angles, wherein the material properties include stiffness data and strength data;

[0007] Calculating the equivalent modulus and strength values ​​of the laminated plates at different ply ratios based on the stiffness data and strength data;

[0008] A blanket curve is plotted based on the equivalent modulus and strength values ​​of the laminate at different ply ratios.

[0009] Optionally, the stiffness data includes: axial elastic modulus, transverse elastic modulus, in-plane Poisson's ratio, in-plane shear modulus;

[0010] The strength data include: axial tensile strength, transverse tensile strength, axial compressive strength, transverse compressive strength, and shear strength.

[0011] Optionally, before calculating the equivalent modulus and strength values ​​of the laminated plate at different ply ratios, the method further includes determining the ply ratios of the plies at different angles and the ply order of the laminated plate;

[0012] Among them, the 0-degree ply ratio value is n: 0≤n≤1, n=0.01*p*o, o∈N, p is the interval of p%;

[0013] ±45 degree ply ratio value is m: 0≤m≤1-n, m=0.01*q*r, r∈N, q is the interval of q%;

[0014] The 90-degree ply ratio is l: l = 1-mn.

[0015] Optionally, the process of calculating the equivalent modulus includes:

[0016] Calculate the single-layer stiffness matrix based on the stiffness data of each layer of ply material;

[0017] The single-layer stiffness matrix corresponding to the plies at different angles is converted from the material coordinate system 1-2 to the global coordinate system xy using a coordinate transformation matrix;

[0018] All single-layer stiffness matrices in the global coordinate system are superimposed according to the ply order and thickness to construct the global stiffness matrix of the laminate;

[0019] The equivalent modulus is calculated based on the global stiffness matrix.

[0020] Alternatively, the expression for transforming from the material coordinate system 1-2 to the global coordinate system xy is:

[0021]

[0022] Where T is the coordinate transformation matrix, is the two-dimensional stiffness matrix in the global coordinate system, Q is the two-dimensional stiffness matrix in the material coordinate system, σ x represents the normal stress level in the x direction in the global coordinate system, σ y represents the normal stress level in the y direction in the global coordinate system, τ xy represents the shear stress level in the xy plane in the global coordinate system, ε x represents the normal strain level in the x direction in the global coordinate system, ε y represents the positive strain level in the y direction in the global coordinate system, γ xy Represents the shear strain level in the xy plane in the global coordinate system.

[0023] Optionally, the global stiffness matrix of the laminate is inverted to obtain the flexibility relationship between the internal forces and internal moments representing the strain and curvature,

[0024] Wherein, the flexibility relation is:

[0025]

[0026] Where ABD represents the overall stiffness matrix of the laminate, K is the bending-torsion curvature vector of the mid-plane of the plate, and ε 0is the plate mid-surface strain vector, N is the internal force vector per unit width on the laminate cross section, and M is the internal moment vector per unit width on the laminate cross section.

[0027] Optionally, the process of calculating the intensity value includes:

[0028] Determine the stress level value and strain level value in the main direction of each single layer based on the flexibility relationship;

[0029] Selecting a strength judgment criterion based on the stress level value and the strain level value to evaluate the strength performance of the laminate;

[0030] The intensity value is determined based on the selected intensity criterion.

[0031] Optionally, the strength judgment criteria include but are not limited to: maximum stress criterion, Tsai-Hill failure criterion, Tsai-Wu failure criterion.

[0032] The present invention also provides a computer terminal device, comprising:

[0033] one or more processors;

[0034] A memory, coupled to the processor, for storing one or more programs;

[0035] When the one or more programs are executed by the one or more processors, the one or more processors implement a composite material blanket curve calculation method.

[0036] The present invention also provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, a composite material blanket curve calculation method is implemented.

[0037] Compared with the prior art, the present invention has the following advantages and technical effects:

[0038] The present invention determines the material properties of plies at different angles, calculates the equivalent modulus and strength values ​​of the laminate at different ply ratios based on stiffness data and strength data; and draws a blanket curve based on the equivalent modulus and strength values.

[0039] In the present invention, different materials can be selected for the 0-degree, ±45-degree and 90-degree ply materials to participate in the calculation, the material system has a higher degree of freedom, and a variety of failure criteria can be selected for determination in the calculation of strength values, which has a stronger selectivity. The modulus and strength blanket curves calculated by the present invention are integrated in the same chart, which is convenient for designers to quickly and accurately query. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0041] Figure 1 is a calculation flow chart of an embodiment of the present invention;

[0042] Figure 2 A blanket graph of the output of an embodiment of the present invention. DETAILED DESCRIPTION

[0043] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0044] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0045] Embodiment 1

[0046] A composite material blanket curve calculation method is provided. By giving the materials of 0-degree, ±45-degree and 90-degree plies, the equivalent modulus and strength values ​​of the material system under different ply ratios are calculated and summarized into charts for reference and use by composite material designers.

[0047] like Figure 1 As shown, a method for calculating a blanket curve of a composite material is provided in this embodiment, comprising the following steps: determining material properties of plies at different angles, wherein the material properties include stiffness data and strength data; calculating the equivalent modulus and strength values ​​of the laminate at different ply ratios based on the stiffness data and strength data; and drawing a blanket curve based on the equivalent modulus and strength values.

[0048] This embodiment consists of three parts: information input, calculation and information output.

[0049] The information input module requires designers to determine the material properties of three types of angle plies: 0 degrees, ±45 degrees, and 90 degrees, including stiffness data: axial elastic modulus E1, transverse elastic modulus E2, in-plane Poisson's ratio μ 12 , in-plane shear modulus G 12 , and strength data: axial tensile strength X t , Transverse tensile strength Y t , axial compressive strength X c , Transverse compressive strength Y c , shear strength S.

[0050] As a specific implementation of this embodiment, the three angle ply materials in this embodiment are all T300 grade carbon fiber unidirectional composite materials.

[0051] The calculation principle of the operation module is:

[0052] 1. Take p% (p = 100 / d, d∈N + The 0-degree ply ratio is determined as n (0≤n≤1, n=0.01*p*o, o∈N) at an interval of d>1), and the ±45-degree ply ratio is determined as m (0≤m≤1-n, m=0.01*q*r, r∈N) at an interval of q% (q≤p), then the 90-degree ply ratio is l=1-mn.

[0053] As a specific implementation of this embodiment, the 0-degree ply ratio value is n (0≤n≤1, n=0.05o, o∈N) determined at intervals of 5%, and the ±45-degree ply ratio value is m (0≤m≤1-n, m=0.01r, r∈N) determined at intervals of 1%, then the 90-degree ply ratio value is l=1-mn.

[0054] 2. The ply laying sequence of the laminate is [90 / 45 / 0 / -45] s Symmetrical ply, total number of plies is 8, total ply thickness is t, then [90 / 45 / 0 / -45] s The thickness distribution of each layer of the laminate is [0.5*(1-mn)t / 0.25*mt / 0.5*nt / 0.25*mt / 0.25*mt / 0.5*nt / 0.25*mt / 0.5*(1-mn)t].

[0055] As a specific implementation of this embodiment, the ply laying sequence of the laminate is [90 / 45 / 0 / -45] s Symmetrical ply, total number of plies is 8, total ply thickness is 1, then [90 / 45 / 0 / -45] s The thickness distribution of each layer of the ply is [0.5(1-mn) / 0.25m / 0.5n / 0.25m / 0.25m / 0.5n / 0.25m / 0.5(1-mn)].

[0056] The process of calculating the equivalent modulus includes: calculating the single-layer stiffness matrix based on the stiffness data of each layer of the laminate material; using the coordinate transformation matrix to transform the single-layer stiffness matrix corresponding to the laminates at different angles from the material coordinate system to the global coordinate system; superimposing all the single-layer stiffness matrices in the global coordinate system according to the lamination sequence and thickness to construct the global stiffness matrix of the laminate; and calculating the equivalent modulus based on the global stiffness matrix.

[0057] 3.Through the stiffness data of each layer (E1, E2, μ 12 , G12 ) calculates the stiffness matrix of each ply, and combines the ply angle, ply sequence and thickness data to obtain the overall stiffness matrix ABD of the laminate. The steps are as follows:

[0058]

[0059] in,

[0060]

[0061] Formula (1) can be written as a relationship in which strain is used to express stress:

[0062]

[0063] Among them, Q is the two-dimensional stiffness matrix, which is inverted by the two-dimensional flexibility matrix S.

[0064] When the ply angle is θ, the stress-strain relationship of the single layer in the global coordinate xy is as follows:

[0065]

[0066] Where T is the coordinate transformation matrix.

[0067]

[0068] Considering that the laminate is composed of multiple single-layer plates, the stress-strain relationship of the kth single layer is:

[0069]

[0070] For laminated panels

[0071]

[0072] In the formula, K x K is the bending deflection rate in the x direction of the plate midplane, y K is the bending deflection of the plate in the y direction, xy is the xy plane distortion rate of the plate midplane, ε 0 x is the normal strain in the x direction of the plate midplane, ε 0 y is the normal strain in the y direction of the plate mid-plane, γ 0 xy is the shear strain in the xy plane of the plate mid-plane.

[0073] Let N x is the tensile and compressive internal force per unit width in the x direction on the cross section of the laminate, N y is the tensile and compressive internal force per unit width in the y direction on the cross section of the laminate, N xy is the shear internal force per unit width in the xy plane of the laminate cross section, Mx is the internal moment of the cross section of the laminate in the x direction per unit width, M y is the internal moment of the laminate in the y direction per unit width on the cross section, M xy is the torsional internal moment per unit width in the xy plane on the cross section of the laminate, and its stress with the laminate should satisfy formula (8):

[0074]

[0075] Therefore, the relationship between the internal force, internal moment and strain of the laminate can be transformed into

[0076]

[0077] Abbreviated as

[0078]

[0079] The laminate stiffness matrix ABD is obtained.

[0080] The ABD matrix of the laminate is equivalent to the stiffness matrix Q of the single-layer plate. According to formulas (1) to (3), the longitudinal modulus E1, transverse modulus E2, and shear modulus G of the laminate under simple tension and compression can be obtained. 12 .

[0081] 4. According to the calculated laminate ABD matrix inversion, the flexibility relationship between internal forces and internal moments expressing strain and curvature can be obtained as follows:

[0082]

[0083] By setting the values ​​of N and M, the deformation response of the laminate under different working conditions can be obtained, and the stress level σ and strain level ε in the main direction of each single layer can be inversely deduced by formulas (3) to (7). Where N1 = [1, 0, 0] ′ and M1 = [0, 0, 0] ′ represent the axial tensile load of unit size, N2 = [-1, 0, 0] ′ and M2 = [0, 0, 0] ′ represent the axial compression load of unit size, and N3 = [0, 0, 1] ′ and M3 = [0, 0, 0] ′ represent the in-plane shear load of unit size.

[0084] The process of calculating the strength value includes: determining the stress level value and the strain level value in the main direction of each single layer based on the flexibility relationship; selecting a strength judgment criterion based on the stress level value and the strain level value to evaluate the strength performance of the laminate; and determining the strength value based on the selected strength judgment criterion.

[0085] 5. According to the calculated stress level data of each single layer in the main direction σ1 (normal stress in material coordinate system 1), σ2 (normal stress in material coordinate system 2), τ 12(shear stress in the 12th direction of the material coordinate system), ε1 (normal strain in the 1st direction of the material coordinate system), ε2 (normal strain in the 2nd direction of the material coordinate system), γ 12 (Shear strain in the 12-direction of the material coordinate system), you can choose to use one of the following strength judgment criteria to check the strength of the composite laminate:

[0086] a Maximum stress criterion:

[0087]

[0088] Where, X t , Y t is the axial and transverse tensile strength of each single layer, X c , Y c is the axial and transverse compressive strength of each single layer, and S is the shear strength of each single layer.

[0089] b Tsai-Hill failure criterion:

[0090]

[0091] Where X and Y correspond to the axial and transverse strengths of each single layer, respectively (the judgment of tension and compression depends on whether the stress is tension or compression), and S is the shear strength of each single layer.

[0092] c Tsai-Wu failure criterion:

[0093]

[0094] In the formula

[0095] F 12 Pick

[0096] dOther failure criteria.

[0097] As a preferred solution of this embodiment, the Tsai-Wu failure criterion is selected to perform strength verification of the composite laminate.

[0098] By using the algebraic relationship of the corresponding strength criterion, the maximum value of the ratio of stress (or strain) to ultimate strength under the basic load can be obtained. Since the load and stress-strain satisfy a linear correlation, the minimum failure load coefficient of the composite laminate can be directly obtained through the maximum value. The product of this coefficient and the basic load is the ultimate strength of the composite laminate.

[0099] The axial tensile load N1 can be used to calculate the axial tensile strength X of the laminate. xtThe axial compressive load N2 can be used to calculate the axial compressive strength X of the laminate. xc The in-plane shear load N3 can be used to calculate the longitudinal and transverse shear strength S of the laminate. xy .

[0100] 6. A range of modulus and strength values ​​can be obtained by selecting different p and q values.

[0101] like Figure 2 As shown, the information output module needs to output the blanket curve of the composite material modulus or strength. The horizontal coordinate of the curve corresponds to the ±45 degree ply ratio, and the vertical coordinate corresponds to the modulus value or strength value. The horizontal and vertical coordinates of any point in the curve can be queried through the program query function.

[0102] Embodiment 2

[0103] This embodiment also provides a computer terminal device, including:

[0104] one or more processors;

[0105] A memory, coupled to the processor, for storing one or more programs;

[0106] When the one or more programs are executed by the one or more processors, the one or more processors implement a composite material blanket curve calculation method.

[0107] Embodiment 3

[0108] This embodiment further provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, a method for calculating a blanket curve of a composite material is implemented.

[0109] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A composite material blanket curve calculation method, characterized in that: The following steps are involved: Determining material properties of plies laid at different angles, wherein the material properties include stiffness data and strength data; Calculating the equivalent modulus and strength values ​​of the laminated plates at different ply ratios based on the stiffness data and strength data; Blanket curves are plotted based on the equivalent modulus and strength values ​​of the laminates at different ply ratios.

2. The composite material blanket curve calculation method according to claim 1, characterized in that: The stiffness data include: axial elastic modulus, transverse elastic modulus, in-plane Poisson's ratio, and in-plane shear modulus; The strength data include: axial tensile strength, transverse tensile strength, axial compressive strength, transverse compressive strength, and shear strength.

3. The composite material blanket curve calculation method according to claim 2, characterized in that: Before calculating the equivalent modulus and strength values ​​of the laminates at different ply ratios, it also includes determining the ply ratios of the plies at different angles and the ply sequence of the laminates; Among them, the 0-degree ply ratio value is n: 0≤n≤1, n=0.01*p*o, o∈N, p is the interval of p%; ±45 degree ply ratio value is m: 0≤m≤1-n, m=0.01*q*r, r∈N, q is the interval of q%; The 90-degree ply ratio is l: l = 1-mn.

4. The composite material blanket curve calculation method according to claim 3, characterized in that: The process of calculating the equivalent modulus includes: Calculate the single-layer stiffness matrix based on the stiffness data of each layer of ply material; The single-layer stiffness matrix corresponding to the plies at different angles is converted from the material coordinate system 1-2 to the global coordinate system xy using a coordinate transformation matrix; All single-layer stiffness matrices in the global coordinate system are superimposed according to the ply order and thickness to construct the global stiffness matrix of the laminate; The equivalent modulus is calculated based on the global stiffness matrix.

5. The composite material blanket curve calculation method according to claim 4, characterized in that: The expression for converting from the material coordinate system 1-2 to the global coordinate system xy is: Where T is the coordinate transformation matrix, is the two-dimensional stiffness matrix in the global coordinate system, Q is the two-dimensional stiffness matrix in the material coordinate system, σ x represents the normal stress level in the x direction in the global coordinate system, σ y represents the normal stress level in the y direction in the global coordinate system, τ xy represents the shear stress level in the xy plane in the global coordinate system, ε x represents the normal strain level in the x direction in the global coordinate system, ε y represents the positive strain level in the y direction in the global coordinate system, γ xy Represents the shear strain level in the xy plane in the global coordinate system.

6. The composite material blanket curve calculation method according to claim 4, characterized in that: The global stiffness matrix of the laminate is inverted to obtain the flexibility relationship between the internal force and internal moment representing the strain and curvature, Wherein, the flexibility relation is: Where ABD represents the overall stiffness matrix of the laminate, K is the bending-torsion curvature vector of the mid-plane of the plate, and ε 0 is the plate mid-surface strain vector, N is the internal force vector per unit width on the laminate cross section, and M is the internal moment vector per unit width on the laminate cross section.

7. The composite material blanket curve calculation method according to claim 6, characterized in that: The process of calculating the intensity value includes: Determine the stress level value and strain level value in the main direction of each single layer based on the flexibility relationship; Selecting a strength judgment criterion based on the stress level value and the strain level value to evaluate the strength performance of the laminate; The intensity value is determined based on the selected intensity criterion.

8. The composite material blanket curve calculation method according to claim 7, characterized in that: The strength judgment criteria include but are not limited to: maximum stress criterion, Tsai-Hill failure criterion, and Tsai-Wu failure criterion.

9. A computer terminal device, characterized in that: include: one or more processors; A memory, coupled to the processor, for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the composite material blanket curve calculation method according to any one of claims 1 to 8.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the composite material blanket curve calculation method according to any one of claims 1 to 8 is implemented.

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