A tensile and compressive performance simulation method for composite material structure

Abstract

The application discloses a tensile and compressive performance simulation method for a composite material structure, and comprises the following steps: establishing a finite element model of the composite material structure; substituting the compressive modulus to perform initial simulation solving, and obtaining initial stress and strain distribution; judging the tensile and compressive state of an element according to the stress of the main direction of the fiber; respectively assigning the tensile modulus and the compressive modulus to the tensile element and the compressive element; performing updated simulation solving; verifying the correspondence between the element state and the parameters, and repeating the state judgment until convergence is achieved, the simulation precision of the application can be improved by about 5%, the weak points of the structure can be accurately identified, the invalid design redundancy can be reduced to realize weight reduction and cost reduction, and the damage analysis can be respectively performed based on the tensile strength and the compressive strength, and the application is suitable for the mechanical performance checking of the composite material structure in the fields of aviation and spaceflight.

Description

Technical Field

[0001] This invention belongs to the field of composite material structure design technology, specifically relating to a simulation method for the tensile and compressive properties of composite material structures. Background Technology

[0002] Fiber-reinforced composite materials possess excellent properties such as high strength, fatigue resistance, low density, and corrosion resistance, and are widely used in various fields such as aviation, aerospace, wind power, transportation, and sports equipment. Due to the significant anisotropy of fiber-reinforced composite materials, reasonable structural design optimization and performance verification are key to fully leveraging their mechanical property advantages.

[0003] In the design phase of composite material products, it is usually necessary to use finite element software to simulate and verify the mechanical behavior of the product in order to avoid damage caused by overload during actual use. In the existing technology, since the tensile properties of composite materials are generally better than their compressive properties, designers generally use the relatively weak compressive properties of composite materials as the material parameters of the overall structure for simulation and verification. In this way, a certain design redundancy is retained to prevent structural damage due to overload.

[0004] However, existing technologies have obvious drawbacks:

[0005] 1. The difference in mechanical properties between the tension and compression parts of the structure was ignored, and the simulation results deviated from the actual situation, failing to truly reflect the stress distribution of the product;

[0006] 2. For products operating under complex conditions, simulation results may mask the actual weak points of the structure, which is not conducive to the identification of risk points and targeted reinforcement.

[0007] 3. This results in excessive performance redundancy in the load-bearing components, which is detrimental to the weight reduction design of the product and increases production costs;

[0008] 4. It is impossible to determine whether failure has occurred based on the tensile or compressive state of the structure, which reduces the accuracy of simulation verification;

[0009] Therefore, we propose a simulation method for the tensile and compressive properties of composite material structures. Summary of the Invention

[0010] The purpose of this invention is to provide a simulation method for the tensile and compressive properties of composite material structures to solve the problems mentioned in the background art.

[0011] To achieve the above objectives, the present invention provides the following technical solution: a simulation method for the tensile and compressive properties of composite material structures, comprising the following steps:

[0012] S1. Establish the finite element model of the composite material structure;

[0013] S2. Initial simulation solution: Substitute the compressive modulus parameters and obtain the initial stress and strain distribution of the model through finite element solution;

[0014] S3. Unit tension / compression state determination: Based on the initial stress-strain distribution, determine the tension or compression state of each unit;

[0015] S4. Assigning material parameters: Assign tensile modulus parameters to tension elements and compressive modulus parameters to compression elements;

[0016] S5. Updated simulation solution: Based on the assigned material parameters, perform finite element calculations to obtain the updated stress and strain distribution;

[0017] S6. Convergence judgment: Verify whether the updated unit tension / compression state corresponds to the assigned modulus parameters. If they correspond, output the result; otherwise, return to S3 and re-execute.

[0018] Preferably, in S1, establishing a finite element model of the composite material structure specifically includes: using 3D modeling software to establish a geometric model of the composite material structure, importing the geometric model of the composite material structure into finite element software, and performing mesh generation to form a computable finite element model, wherein the finite element model includes the geometric parameters, load conditions, and constraint conditions of the structure.

[0019] Preferably, in S2, the initial simulation solution is executed based on the user material subroutine of the finite element calculation software. The user material subroutine has built-in tensile and compressive performance parameters of the composite material. During the initial simulation solution, the compressive modulus in the compressive performance parameters is called and substituted into the model for finite element solution.

[0020] Preferably, in S3, the determination of the tension / compression state of the element is based on the principal fiber stress corresponding to the element:

[0021] When the principal stress of the fiber is positive, the element is determined to be a tension element;

[0022] When the principal stress of the fiber is negative, the element is determined to be a compression element.

[0023] Preferably, in S4, the parameter assignment operation is performed through the user material subroutine, and the built-in tensile modulus parameter is called for the unit determined to be under tension, while the compressive modulus parameter used in S2 is retained for the unit determined to be under compression.

[0024] Preferably, in S5, the finite element calculation is automatically completed by the finite element software, and the overall stress and strain distribution of the calculated structure is updated based on the assigned material parameters of each element.

[0025] Preferably, the convergence criterion in S6 is: the tension and compression states of all elements correspond one-to-one with the elastic modulus parameters assigned to them, that is, all tension elements are matched with tensile modulus and all compression elements are matched with compressive modulus; if this criterion is not met, return to S3 to re-judge the tension and compression states of the elements, and repeat S4-S6 until the convergence condition is met.

[0026] Preferably, the composite material is a fiber-reinforced composite material, wherein the tensile properties of the fiber-reinforced composite material are better than its compressive properties. The tensile property parameter also includes tensile strength, and the compressive property parameter also includes compressive strength. The failure analysis of the unit is performed based on the tensile strength and compressive strength respectively.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] 1. Improve simulation accuracy and realistically reflect stress state: This invention solves the deviation problem of single-parameter simulation in the prior art by distinguishing the tensile and compressive states of structural units and assigning corresponding modulus parameters to them respectively. As verified by the embodiments, the stress and strain calculation results are corrected by about 5%, which can more realistically reflect the actual stress level of the structure.

[0029] 2. Accurately identify weak points and improve structural safety: Simulation results can accurately expose the tensile and compressive weak areas of the structure, avoiding the defects of existing technology that cover up risk points. Designers can strengthen weak parts in a targeted manner without uniformly strengthening the entire structure, which greatly improves the structural safety of the product.

[0030] 3. Reduce unnecessary redundancy and achieve weight reduction and cost reduction: This invention can effectively reduce unreasonable excessive design redundancy in the load-bearing part, provide data support for the reasonable distribution of design redundancy, and the structural optimization design based on this can achieve product weight reduction while ensuring safety, thereby reducing raw material and manufacturing costs.

[0031] 4. Supports independent tensile and compressive failure analysis, expanding application scenarios: Based on the independent failure determination of tensile strength and compressive strength, it solves the problem that existing technologies cannot distinguish between tensile and compressive states to determine failure, and can meet the needs of high-end fields such as aviation and aerospace for refined verification of composite material structures. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the method flow of the present invention;

[0033] Figure 2 This is a schematic diagram of a pull rod according to a specific embodiment of the present invention;

[0034] Figure 3 This is a schematic diagram of a one-dimensional rod finite element model according to a specific embodiment of the present invention. Detailed Implementation

[0035] 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.

[0036] The present invention provides a simulation method for the tensile and compressive properties of composite material structures, comprising the following steps:

[0037] S1. Establishing a finite element model of the composite material structure: Use 3D modeling software to establish a geometric model of the composite material structure, import the geometric model into the finite element software, and perform mesh generation to form a computable finite element model. The finite element model includes the geometric parameters, load conditions, and constraint conditions of the structure.

[0038] S2. Initial Simulation Solution: The user material subroutine of the finite element calculation software performs the initial simulation solution. The user material subroutine has built-in tensile and compressive property parameters of the composite material. During the initial simulation solution, only the compressive modulus in the compressive property parameter is called and substituted into the model for finite element solution to obtain the initial stress and strain distribution of the model.

[0039] S3. Determination of tension and compression state of unit: Based on the initial stress and strain distribution, the stress in the principal direction of the fiber corresponding to the unit is used as the criterion. When the stress in the principal direction of the fiber is positive, the unit is determined to be a tension unit; when the stress in the principal direction of the fiber is negative, the unit is determined to be a compression unit.

[0040] S4. Material Parameter Assignment: The parameter assignment operation is performed through the user material subroutine. For the unit determined to be under tension, the built-in tensile modulus parameter is called, and for the unit determined to be under compression, the compressive modulus parameter used in S2 is retained.

[0041] S5. Updated simulation solution: Based on the assigned material parameters of each element, the finite element software automatically completes the finite element calculation to obtain the updated overall stress and strain distribution of the structure.

[0042] S6. Convergence Judgment: Verify whether the updated element tension / compression state corresponds completely one-to-one with the assigned modulus parameters, i.e., all tension elements are matched with tensile modulus and all compression elements are matched with compressive modulus. If they correspond, output the result. If the standard is not met, return to S3 to re-judge the element tension / compression state and repeat S4-S6 until the convergence condition is met.

[0043] This embodiment is a specific implementation method of the present invention, such as... Figure 2 and Figure 3As shown, a fiber-reinforced composite rod fixed at both ends is used as the simulation object. The rod is made of M40J composite unidirectional tape with a tensile modulus Et of 210 GPa and a compressive modulus Ec of 190 GPa. The rod has a length l = 200 mm and a cross-sectional area A = 100 mm². A concentrated force F = 100 N is applied to the right at the midpoint of the rod. The specific steps are as follows:

[0044] S1: Establishing the finite element model:

[0045] The geometric model of the rod was created using 3D modeling software. The geometric model was then imported into finite element software, and the rod was meshed to form a one-dimensional finite element model. The model has 3 nodes and 2 elements. Nodes 1 and 3 are fixed constraint ends, and node 2 is the midpoint loading end. The model includes geometric parameters such as the length and cross-sectional area of ​​the rod, as well as boundary conditions such as concentrated force loads and fixed constraints.

[0046] S2: Initial simulation solution:

[0047] The initial simulation solution is performed based on the user material subroutine of the finite element calculation software. The user material subroutine has built-in performance parameters such as tensile modulus of 210GPa and compressive modulus of 190GPa of M40J composite material. During the initial simulation solution, only the compressive modulus Ec=190GPa is called and substituted into two elements to perform finite element solution to obtain the initial stress and strain distribution of the model.

[0048] The initial displacements of each node were obtained by finite element software calculation, where the displacement of node 1 u1=0 and the displacement of node 3 u3=0.

[0049] Based on the displacement calculation of the element strain, the strain of element 1 is: ;

[0050] The strain of element 2 is: ;

[0051] Based on the strain calculation of the initial stress of the element, the stress of element 1 is: ;

[0052] The stress in element 2 is: ;

[0053] S3: Unit tension / compression state judgment:

[0054] Based on the initial stress-strain distribution results, the fiber principal direction stress of the element is used as the criterion: if the fiber principal direction stress of element 1 is positive, element 1 is determined to be a tension element, and the elastic modulus E1=Et is assigned; if the fiber principal direction stress of element 2 is negative, element 2 is determined to be a compression element, and the elastic modulus E2=Ec is assigned.

[0055] S4: Assigning material parameters:

[0056] The parameter assignment operation is performed by the user material subroutine. The built-in tensile modulus Et=210GPa is called for element 1, which is determined to be a tension element; and the compressive modulus Ec=190Gpa is retained for element 2, which is determined to be a compression element.

[0057] S5: Simulation solution after update:

[0058] Substitute the assigned material parameters into the finite element model, and the finite element software will automatically complete the updated simulation calculations to obtain the updated stress-strain distribution:

[0059] The strain of element 1 is: The stress is: ;

[0060] The strain of element 2 is: The stress is: .

[0061] Step S6: Convergence Judgment

[0062] Verify the correspondence between the updated element tension / compression state and the assigned modulus parameters: Element 1 is a tension element, matched with tensile modulus; Element 2 is a compression element, matched with compressive modulus. The states and parameters of all elements correspond completely one-to-one, satisfying the convergence condition, and output the final stress-strain simulation results.

[0063] Based on the final simulation results, the tensile strength and compressive strength parameters of the M40J composite material can be combined to perform failure analysis on element 1 and element 2 respectively, and determine whether the rod will fail under the load.

[0064] When using only the compressive modulus as a material parameter, the stress in element 1 in the above example is: The strain is: ; Element 2 stress ,strain .

[0065] In this embodiment, the composite material is a fiber-reinforced composite material. The tensile properties of the fiber-reinforced composite material are better than its compressive properties. The tensile property parameters also include tensile strength, and the compressive property parameters also include compressive strength. The failure analysis of the unit is performed based on the tensile strength and compressive strength respectively.

[0066] Table 1 below shows a comparison of simulation results between the prior art (using only the compressive modulus Ec) and the present invention (using both tensile and compressive modulus Et / Ec):

[0067] Element 1 strain ε1 2.63με 2.5με -5% Element 1 stress σ1 0.5MPa 0.525MPa +5% Element 2 strain ε2 −2.63με −2.5με -5% Element 2 stress σ2 -0.5MPa -0.475MPa -5%

[0068] As shown in Table 1, the existing technology uses a single compressive modulus for simulation, which underestimates the stress in tensile element 1 and overestimates the stress in compressive element 2, failing to reflect the true stress state. This invention corrects the stress-strain results by assigning differentiated parameters, making the simulation data more realistic. The stress in tensile element 1 increases by 5%, and the stress in compressive element 2 decreases by 5%, accurately reflecting the difference in mechanical response caused by the difference in tensile and compressive properties of composite materials. Based on the simulation results of this invention, designers can specifically strengthen the tensile element 1 region without over-strengthening the element 2 region, thus achieving optimized design.

[0069] Compared with the prior art, the present invention has the following beneficial effects:

[0070] 1. Improve simulation accuracy and realistically reflect stress state: This invention solves the deviation problem of single-parameter simulation in the prior art by distinguishing the tensile and compressive states of structural units and assigning corresponding modulus parameters to them respectively. As verified by the embodiments, the stress and strain calculation results are corrected by about 5%, which can more realistically reflect the actual stress level of the structure.

[0071] 2. Accurately identify weak points and improve structural safety: Simulation results can accurately expose the tensile and compressive weak areas of the structure, avoiding the defects of existing technology that cover up risk points. Designers can strengthen weak parts in a targeted manner without uniformly strengthening the entire structure, which greatly improves the structural safety of the product.

[0072] 3. Reduce unnecessary redundancy and achieve weight reduction and cost reduction: This invention can effectively reduce unreasonable excessive design redundancy in the load-bearing part, provide data support for the reasonable distribution of design redundancy, and the structural optimization design based on this can achieve product weight reduction while ensuring safety, thereby reducing raw material and manufacturing costs.

[0073] 4. Supports independent tensile and compressive failure analysis, expanding application scenarios: Based on the independent failure determination of tensile strength and compressive strength, it solves the problem that existing technologies cannot distinguish between tensile and compressive states to determine failure, and can meet the needs of high-end fields such as aviation and aerospace for refined verification of composite material structures.

[0074] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A simulation method for the tensile and compressive properties of composite material structures, characterized in that, Includes the following steps: S1. Establish the finite element model of the composite material structure; S2. Initial simulation solution: Substitute the compressive modulus parameters and obtain the initial stress and strain distribution of the model through finite element solution; S3. Unit tension / compression state determination: Based on the initial stress-strain distribution, determine the tension or compression state of each unit; S4. Assigning material parameters: Assign tensile modulus parameters to tension elements and compressive modulus parameters to compression elements; S5. Updated simulation solution: Based on the assigned material parameters, perform finite element calculations to obtain the updated stress and strain distribution; S6. Convergence judgment: Verify whether the updated unit tension / compression state corresponds to the assigned modulus parameters. If they correspond, output the result; otherwise, return to S3 and re-execute.

2. The simulation method for tensile and compressive properties of composite material structures according to claim 1, characterized in that: In S1, establishing a finite element model of a composite material structure specifically includes: using 3D modeling software to establish a geometric model of the composite material structure, importing the geometric model of the composite material structure into the finite element software, and performing mesh generation to form a computable finite element model, wherein the finite element model includes the geometric parameters, load conditions, and constraint conditions of the structure.

3. The simulation method for tensile and compressive properties of composite material structures according to claim 1, characterized in that: In S2, the initial simulation solution is executed based on the user material subroutine of the finite element calculation software. The user material subroutine has built-in tensile and compressive property parameters of the composite material. During the initial simulation solution, the compressive modulus in the compressive property parameters is called and substituted into the model for finite element solution.

4. The simulation method for tensile and compressive properties of composite material structures according to claim 1, characterized in that: In S3, the determination of the tension / compression state of an element is based on the principal stress of the fiber corresponding to the element: When the principal stress of the fiber is positive, the element is determined to be a tension element; When the principal stress of the fiber is negative, the element is determined to be a compression element.

5. The simulation method for tensile and compressive properties of composite material structures according to claim 3, characterized in that: In S4, the parameter assignment operation is performed through the user material subroutine. For units determined to be under tension, the built-in tensile modulus parameter is called, and for units determined to be under compression, the compressive modulus parameter used in S2 is retained.

6. The simulation method for tensile and compressive properties of composite material structures according to claim 1, characterized in that: In S5, the finite element calculation is automatically completed by the finite element software, and the overall stress and strain distribution of the calculated structure is updated based on the assigned material parameters of each element.

7. The simulation method for tensile and compressive properties of composite material structures according to claim 1, characterized in that: The convergence criterion in S6 is that the tension and compression states of all elements correspond one-to-one with the elastic modulus parameters assigned to them, that is, all tension elements are matched with tensile modulus and all compression elements are matched with compressive modulus. If this criterion is not met, return to S3 to re-judge the tension and compression states of the elements, and repeat S4-S6 until the convergence condition is met.

8. A simulation method for tensile and compressive properties of composite material structures according to any one of claims 1-7, characterized in that: The composite material is a fiber-reinforced composite material, and the tensile properties of the fiber-reinforced composite material are better than its compressive properties. The tensile property parameter also includes tensile strength, and the compressive property parameter also includes compressive strength. The failure analysis of the unit is performed based on the tensile strength and compressive strength respectively.

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