Pyrolysis dynamics simulation analysis method for lightning stroke damage of carbon fiber composite material

Abstract

The invention relates to the technical field of composite material lightning protection, in particular to a pyrolytic dynamics simulation analysis method for lightning stroke damage of a carbon fiber composite material. According to the technical scheme, the method comprises the following steps that a new model is established in ABAQUS / CAE, a carbon fiber composite material is established, a laminated plate laying layer is defined, a multi-physical field analysis step is set, load current density is applied to a lightning stroke action area, the pyrolysis behavior of the carbon fiber composite material under lightning stroke high Joule heat is simulated based on a pyrolysis kinetic model, and operation is established in a Job module. And parallel computing parameters are selected and submitted for solution, temperature field distribution is checked, and the current density diffusion trend is verified. Through the electric-thermal-structure coupling model, the conductivity gradient design and the lightning arc model, refined prediction of CFRP lightning stroke damage is achieved, the damage area is reduced, the lightning stroke process is accurately simulated, and the adaptation and protection effects on the lightning stroke environment are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lightning protection for composite materials, and particularly to a pyrolysis kinetics simulation analysis method for lightning strike damage of carbon fiber composite materials. Background Art

[0002] In recent years, carbon fiber reinforced composite materials (CFRP) have been widely used in the field of civil airliners due to their many advantages such as light weight, excellent corrosion resistance, outstanding fatigue resistance, and low coefficient of thermal expansion. However, compared with metal materials, the matrix resin in CFRP is an insulator with poor overall conductivity. When struck by lightning, the direct effects of lightning arc attachment, high-pressure shock waves, and magnetic forces will cause resin pyrolysis and fiber damage in the composite material, thus affecting the integrity and reliability of the composite material structure on the aircraft.

[0003] At present, most lightning strike damage analyses adopt a single temperature field or a simplified electro-thermal coupling model, ignoring the dynamic evolution of the degree of pyrolysis and the superposition effect of fiber directions between layers, resulting in insufficient accuracy of damage prediction. In addition, existing protection designs rely on highly conductive coatings or metal meshes, lacking a systematic solution based on material parameter optimization. Therefore, this application proposes a pyrolysis kinetics simulation analysis method for lightning strike damage of carbon fiber composite materials. Summary of the Invention

[0004] The object of the present invention is to address the problem of insufficient accuracy in existing research on lightning strike damage of composite materials in the background art, and to propose a pyrolysis kinetics simulation analysis method for lightning strike damage of carbon fiber composite materials.

[0005] The technical solution of the present invention: A pyrolysis kinetics simulation analysis method for lightning strike damage of carbon fiber composite materials, comprising the following steps:

[0006] Create a new model in ABAQUS / CAE, select the Static static analysis step and the Transient coupled transient analysis step and set the time step size, create the geometry of a laminated plate with 3D shell elements or solid elements, and define the size of the laminated plate to match the lightning action area;

[0007] Create carbon fiber composite material (CFRP), define the orthotropic elastic modulus, Poisson's ratio, shear modulus, input the anisotropic thermal conductivity, define the anisotropic conductivity, and set the anisotropic coefficient of thermal expansion;

[0008] Define the ply layup of the laminated plate, and specify the material properties and fiber directions layer by layer to reflect the anisotropic behavior of the composite material;

[0009] Set up multi-physics analysis steps, create a Coupled Thermal-Electric analysis step, set the time increment scheme, and check the key output variables in Field Output Requests;

[0010] Apply a current density to the lightning strike area and set zero electric potential at the edge of the laminate;

[0011] Simulate the pyrolysis behavior of carbon fiber composites under high Joule heat of lightning strikes based on the pyrolysis kinetics model;

[0012] Create a job in the Job module, select parallel computing parameters and submit for solution, check the temperature field distribution, verify the current density diffusion trend, and compare the consistency of the damage area with the experimental data.

[0013] Optionally, the laminate model size is 150mm×100mm×4.8mm, composed of 32 layers of 0.15mm unidirectional sheets stacked in [45° / 0° / −45° / 90°] 4S, and divided into 74592 elements using 8-node linear coupled thermoelectric elements, with the element size increasing gradually from the center to the four sides.

[0014] Optionally, read the electric field and temperature field through a subroutine to solve the degree of pyrolysis, update the material parameters based on the degree of pyrolysis, and perform electro-thermal field coupling calculations, with the state variables updated with the calculation step size.

[0015] Optionally, the electro-thermal-structural coupling analysis model satisfies the formula:

[0016]

[0017] where: V is the material volume, S is the surface area, ρ is the material density, U is the internal energy, is the derivative of the internal energy with respect to time, is the variation of temperature, is the temperature, is the spatial coordinate, k is the thermal conductivity, q is the heat flux per unit area of the object, and r is the heat density.

[0018] Optionally, when simulating the pyrolysis behavior based on the pyrolysis kinetics model, the pyrolysis kinetics equation of a single-step reaction expresses the reaction rate as an equation of temperature and conversion rate, and the pyrolysis kinetics constant k is defined as a function of temperature T by the Arrhenius-type equation, and the numerical calculation expression of the degree of pyrolysis is derived.

[0019] Optionally, the pyrolysis kinetics model derives the degree of pyrolysis based on the Arrhenius equation, and the pyrolysis kinetics constant:

[0020] ,

[0021] Among them, A is the pre-exponential factor, E is the activation energy, R is the gas constant (R = 8.314 J / mol / K), and T is the pyrolysis time.

[0022] Optionally, when defining the laminate layup, the material properties include elastic modulus, thermal conductivity, and electrical conductivity, and the fiber directions include 0°, 90°, and ±45°.

[0023] Optionally, in the applied load and boundary conditions, the lightning strike action area is the surface center point or area.

[0024] Optionally, it further includes designing an electrical conductivity gradient optimization strategy along the thickness direction, and reducing the lightning strike damage area through the synergistic effect of the surface high-conductivity layer and the internal exponentially decaying conductivity layer.

[0025] Optionally, the electrical conductivity of the surface high-conductivity layer ≥ 1×10 4 S / m.

[0026] Compared with the prior art, the present application includes at least one of the following beneficial technical effects:

[0027] By constructing an electro-thermal-structural coupling model and introducing a non-uniform temperature rise pyrolysis degree parameter. The pyrolysis degree model dynamically correlates with the degradation of material properties such as elastic modulus and electrical conductivity, and combines the interlayer fiber direction superposition effect to accurately simulate the entire process of delamination damage from the surface resin ablation to the internal fiber fracture of CFRP, realizing refined prediction of lightning strike damage.

[0028] Propose an electrical conductivity gradient design along the thickness direction. The surface high-conductivity layer (≥ 1×10 4 S / m) quickly disperses the lightning current and reduces the local Joule heat accumulation; the electrical conductivity of the intermediate layer decays gradually, avoiding the concentration of current at the interlayer interface. By optimizing the conductive distribution, the lightning strike damage area is significantly reduced.

[0029] By establishing a spatio-temporal variable lightning arc model and a Gaussian distribution current density formula, combining the IEC standard waveform and the dynamic expansion equation of the arc channel radius, accurately simulate the diffusion of lightning strike transient current and heat distribution, and truly restore the thermo-electrical coupling effect under the actual lightning strike environment, improving the authenticity of the lightning strike process simulation.

[0030] The present invention realizes refined prediction of CFRP lightning strike damage, reduces the damage area, and accurately simulates the lightning strike process through an electro-thermal-structural coupling model, an electrical conductivity gradient design, and a lightning arc model, improving the adaptation and protection effect for the lightning strike environment. Description of the Drawings

[0031] Figure 1It is a flow chart of a pyrolysis kinetics simulation analysis method for lightning strike damage of carbon fiber composites.

[0032] Figure 2 It is the programming idea for the subroutine USDFLD.

[0033] Figure 3 It is a schematic diagram of the geometric model and boundary conditions for finite element analysis.

[0034] Figure 4 It is a contour map of the pyrolysis degree of carbon fiber composites under lightning strike damage based on ABAQUS simulation. Specific implementation manners

[0035] The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0036] Embodiment

[0037] As Figure 1 shown, a pyrolysis kinetics simulation analysis method for lightning strike damage of carbon fiber composites proposed by the present invention is applied to electromagnetic shielding materials, with carbon fiber composites as the object. The measured target material is modeled and corresponding parameters are set through ABAQUS simulation software. The measurement inversion method uses an electro-thermal-structural coupling model and introduces a non-uniform temperature rise pyrolysis degree parameter, realizing a refined prediction of CFRP lightning strike damage. The following will explain each step in detail.

[0038] Step 1: As Figure 3 , a three-dimensional model of a CFRP laminate is established in ABAQUS / CAE. The geometric finite element model size of the electro-thermal-pyrolysis degree coupling of CFRP lightning strike damage is 150 mm × 100 mm × 4.8 mm, which is stacked by 32 layers of unidirectional prepreg (single layer thickness 0.15 mm), and the layup sequence is 45° / 0° / −45° / 90° 45° / 0° / −45° / 90° for 4 times of layup.

[0039] Step 2: Define the following boundary conditions for the geometric finite element model of the CFRP lightning strike damage material in the Abaqus material module: Electrical conductivity: along the fiber direction , transverse . Thermal conductivity: along the fiber direction , transverse . Heat capacity and density: Initial density ρ = 1.52 × 10³ kg / m³, specific heat capacity C_p = 1.065 × 10³ J / (kg·K). Among them, the use of custom code USFLD can dynamically modify or define material properties, state variables or field variables, and can simulate complex material behaviors or physical processes. As Figure 2 shown, the pyrolysis degree (α) is dynamically associated with the material properties by calling the subroutine USDFLD.

[0040] Step 3: Select an 8-node linear coupled thermoelectric element for electro-thermal analysis, which supports the coupled calculation of current density (IVOL) and temperature (TEMP) and is used to calculate thermal stress and damage. The formula for the electro-thermal-structural coupling analysis model is as follows:

[0041]

[0042] In the formula: V is the volume of the material, S is the surface area, ρ is the material density, U is the internal energy, is the derivative of the internal energy with respect to time, is the variation of temperature, is the temperature, is the spatial coordinate, k is the thermal conductivity, q is the heat flux per unit area of the object, and r is the heat density.

[0043] Step 4: As shown in Figure 3 , adopt a high-density mesh (element side length ≤ 0.5 mm) in the lightning strike area (surface center), and gradually coarsen other areas (element side length 2 mm). Each layer is divided into at least 3 layers of elements to capture the temperature gradient and the interlayer stress distribution. There are approximately 74,592 elements in total to ensure the balance between calculation efficiency and accuracy.

[0044] Step 5: Multi-physics coupling analysis step settings: Select Coupled Thermal-Electric to simulate the lightning strike transient process. The total duration is 1 ms, the initial time step is 1e-8 s, the maximum time step is 1e-6 s, enable automatic time increment control, and record the current density (IVOL), temperature (TEMP), heat flux (HFL), and degree of pyrolysis (SDV1).

[0045] Step 6: Select Coupled Temp-Displacement to calculate thermal stress and damage evolution, and import the temperature field and degree of pyrolysis field of the electro-thermal analysis step as the initial conditions. Define the interlayer Cohesive element, and the delamination failure is triggered when the interface stress > 20 MPa or the degree of pyrolysis α > 0.6. In order to clarify the pyrolysis behavior of carbon fiber composites under high Joule heat caused by lightning strikes, it is necessary to derive the expression of the degree of pyrolysis under a complex temperature program. The pyrolysis kinetic equation of a single-step reaction can express the reaction rate as an equation of temperature and conversion rate:

[0046]

[0047] In the formula: α is the degree of pyrolysis, is the pyrolysis time, k is the pyrolysis kinetic constant, is the reaction function related to the degree of pyrolysis.

[0048] The pyrolysis kinetic constant k is a function of temperature T and is defined by the Arrhenius-type equation:

[0049]

[0050] where: A is the pre-exponential factor, E is the activation energy, and R is the gas constant (R = 8.314 J / mol / K).

[0051] Substituting Equation (2) into Equation (1) gives:

[0052]

[0053] Integrating the above equation gives:

[0054]

[0055] where: is a function related to the degree of pyrolysis , C is a constant. Drawing on the idea of the dynamic explicit algorithm, let and take the difference to derive the recurrence formula, resulting in Equation (5):

[0056]

[0057] where is the time variable, , respectively represent the moments corresponding to the th step and the th step, is the temperature function varying with time .

[0058] Based on the trapezoidal integration formula, Equation (5) is approximated to obtain Equation (6):

[0059]

[0060] where: is the time step, Select the nth-order (n≠1) reaction model, , are the temperatures corresponding to the moments , respectively; Select the nth-order (n≠1) reaction model, and Equation (6) is rewritten as:

[0061]

[0062] Among them, , correspond to the pyrolysis degrees at times , respectively. is the order of the reaction model, and then the numerical calculation expression of the pyrolysis degree is deduced as:

[0063]

[0064] Step 7: Read the temperature (TEMP) and current density (IVOL) of each integration point through the USDFLD subroutine, dynamically adjust the material properties (such as conductivity, elastic modulus) according to the pyrolysis degree value, and transfer them to the next increment step. Set the maximum number of iterations to 50 and the residual tolerance to 1e-6 to ensure the convergence of the nonlinear problem. Output the full-field data (temperature, stress, damage variable) every 0.1 ms.

[0065] Step 8: Enter the Visualization module, click Result → Field Output in the menu bar, select the state variable SDV1 under User Defined Field in the variable list, and click the Plot Contours button to generate a contour plot. As Figure 4 Figure (a) and Figure (b) in

[0066] The above specific embodiments are only several alternative embodiments of the present invention. Based on the technical solution of the present invention and the relevant inspirations of the above embodiments, those skilled in the art can make various alternative improvements and combinations to the above specific embodiments.

Claims

1. A pyrolysis kinetics simulation analysis method for lightning strike damage of carbon fiber composites, characterized in that, It includes the following steps: Create a new model in ABAQUS / CAE, select the Static static analysis step and the Transient coupled transient analysis step and set the time step size, create the laminate geometry of 3D shell elements or solid elements, and define the laminate size to match the lightning strike area; Create carbon fiber composite materials, define the orthotropic elastic modulus, Poisson's ratio, shear modulus, input the anisotropic thermal conductivity, define the anisotropic electrical conductivity, and set the anisotropic thermal expansion coefficient; Define the laminate layup and specify the material properties and fiber directions layer by layer; Set the multi-physics analysis step, create the Coupled Thermal-Electric analysis step, set the time increment scheme, and check the key output variables in Field Output Requests; Apply the load current density in the lightning strike area and set zero electric potential at the laminate edge; Simulate the pyrolysis behavior of carbon fiber composite materials under high Joule heat of lightning strike based on the pyrolysis kinetics model; Create a job in the Job module, select the parallel computing parameters and submit the solution, check the temperature field distribution, verify the current density diffusion trend, and compare the consistency between the damaged area and the test data.

2. The pyrolysis kinetics simulation analysis method for lightning strike damage of a carbon fiber composite material according to claim 1, wherein The size of the laminate model is 150mm×100mm×4.8mm, which is stacked by 32 layers of 0.15mm unidirectional sheets in the [45° / 0° / −45° / 90°] 4S stack, and 74592 elements are divided by 8-node linear coupled thermoelectric elements, and the element size increases gradually from the center to the four sides.

3. The pyrolysis kinetics simulation analysis method for lightning strike damage of carbon fiber composite materials according to claim 1, characterized in that Read the electric field and temperature field through a subroutine to solve the degree of pyrolysis, update the material parameters based on the degree of pyrolysis and then perform the electro-thermal field coupling calculation, and the state variables are updated with the calculation step size.

4. The pyrolysis kinetics simulation analysis method for lightning strike damage of carbon fiber composites according to claim 3, characterized in that, The electro-thermal-structural coupling analysis model satisfies the formula: Where: V is the volume of the material, S is the surface area, ρ is the material density, U is the internal energy, is the derivative of the internal energy with respect to time, is the variation of the temperature, is the temperature, is the spatial coordinate, k is the thermal conductivity, q is the heat flux per unit area of the object, and r is the heat density.

5. A pyrolysis kinetics simulation analysis method for lightning strike damage of carbon fiber composites according to claim 1, characterized in that, When simulating the pyrolysis behavior based on the pyrolysis kinetics model, the pyrolysis kinetics equation of a single-step reaction expresses the reaction rate as an equation of temperature and conversion rate, and the pyrolysis kinetics constant k is defined as a function of temperature T by the Arrhenius type equation, and the numerical calculation expression of the degree of pyrolysis is derived.

6. The pyrolysis kinetics simulation analysis method for lightning strike damage of a carbon fiber composite material according to claim 5, wherein The pyrolysis kinetics model derives the degree of pyrolysis based on the Arrhenius equation, and the pyrolysis kinetics constant: , where A is the pre-exponential factor, E is the activation energy, R is the gas constant, and T is the pyrolysis time.

7. A pyrolysis kinetics simulation analysis method for lightning strike damage of carbon fiber composites according to claim 1, characterized in that, When defining the laminate layup, the material properties include elastic modulus, thermal conductivity, and electrical conductivity, and the fiber directions include 0°, 90°, and ±45°.

8. A pyrolysis kinetics simulation analysis method for lightning strike damage of carbon fiber composites according to claim 1, characterized in that, In the application of load and boundary conditions, the lightning strike area is the surface center point or area.

9. The pyrolysis kinetics simulation analysis method for lightning strike damage of a carbon fiber composite material according to claim 1, characterized in that It also includes designing an electrical conductivity gradient optimization strategy along the thickness direction to reduce the lightning strike damage area through the synergistic effect of the high-conductivity layer on the surface and the exponentially decaying conductive layer inside.

10. The pyrolysis kinetics simulation analysis method for lightning strike damage of carbon fiber composites according to claim 9, wherein, The conductivity of the surface high-conductivity layer ≥ 1×10 4 S / m.

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