A numerical simulation method for composite structures subjected to explosion impact

Abstract

The present invention provides a numerical simulation method for composite material structure under explosion impact, characterized in that it includes the following steps: constructing a finite element software Abaqus user material subroutine VUMAT according to a continuous medium mechanics model of damage in a composite material layer; establishing a composite material structure finite element model according to a cohesive force model of a tensile separation criterion, establishing a water area grid and explosion boundary conditions, solving according to an acoustic-solid coupling algorithm and an explicit time integration method, and obtaining simulation results based on the VUMAT user material subroutine. Compared with traditional explosion impact experiments, the numerical simulation method for composite material structure under explosion impact based on Abaqus proposed by the present invention is easy to repeat and has lower cost, and can accurately predict the mechanical properties and damage characteristics of composite material structure under explosion impact.

Description

Technical Field

[0001] The invention belongs to the technical field of impact dynamics, and in particular relates to a numerical simulation method for a composite material structure under explosion impact. Background Art

[0002] Fiber-reinforced composite materials have the advantages of low magnetism, high specific stiffness, and excellent corrosion resistance, while foam materials have the advantages of ultra-light weight and high energy absorption efficiency. The typical composite sandwich structure formed by the combination of the two is increasingly widely used in fields such as ship protection and minesweeping detection due to its superior performance. When composite ships perform combat missions, they will inevitably be threatened by attacks from mines, torpedoes, etc. The resulting explosion shock loads can cause structural damage, etc., causing the ship to lose its overall combat effectiveness. Therefore, studying the damage characteristics of composite structures under the action of explosion shock is of great significance to improving the explosion and shock resistance of composite ships.

[0003] Traditional explosion impact tests use explosive bags to simulate ammunition explosions in open waters. The experimental requirements are strict, the experimental costs are high, and the risks are great, making it difficult to use widely. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned deficiencies of the prior art and to provide a numerical simulation method for composite material structures under explosion impact.

[0005] The present invention is implemented in this way. The present invention provides a numerical simulation method for composite material structure under explosion impact, characterized in that it includes the following steps:

[0006] According to the continuous medium mechanics model of damage in the composite layer, the VUMAT user material subroutine is constructed, which mainly includes two parts: damage initiation judgment criterion and damage evolution. Specifically, the constitutive relationship of the composite single-layer plate is determined, the initial failure criterion of the composite laminate is established according to the constitutive relationship, and the material failure degradation model is established;

[0007] A finite element model of the composite structure is established according to the cohesive force model of the tensile separation criterion, a water area grid and explosion boundary conditions are established, and the solution is obtained according to the acoustic-solid coupling algorithm and the explicit time integration method. Simultaneously, the simulation results are obtained based on the VUMAT user material subroutine.

[0008] Furthermore, the initial failure criterion of the composite laminate adopts the Hashin failure criterion to determine the strength failure of the composite material; the expression of the Hashin failure criterion based on the strain form is as follows:

[0009] ε under fiber tensile failure mode 11 ≥0:

[0010]

[0011] in is the initial failure strain of fiber tension, X T is the longitudinal tensile strength, E1 is the fiber elastic modulus, is the fiber tensile failure judgment factor, is the tensile strain in the fiber direction;

[0012] ε under fiber compression failure mode 11 ≤0:

[0013]

[0014] in is the initial failure strain of fiber compression, X C is the longitudinal compressive strength, is the fiber compression failure judgment factor, is the compressive strain in the fiber direction;

[0015] ε under matrix tensile failure mode 22 ≥0:

[0016]

[0017] in Y T is the transverse tensile strength, E2 is the matrix elastic modulus, is the matrix tensile failure judgment factor, ε 22 is the strain in the matrix direction, ε 33 is the thickness direction strain, is the damage initiation strain of the element under tensile state in the matrix direction, is the initial shear failure strain, and is the out-of-plane shear strength, Z C Indicates the strength in the thickness direction, ε ij is the ij in-plane strain.

[0018] ε under matrix compression failure mode 22 ≤0

[0019]

[0020] Furthermore, the damage state variables of fiber tensile damage, fiber compression damage, matrix tensile damage, and matrix compression damage defined by the material failure degradation model are respectively:

[0021]

[0022] Where: is the damage state variable, i = 1, 2, where 1 represents fiber, 2 represents matrix, T represents tensile damage, and C represents compressive damage; is the damage initiation strain of the unit in tension or compression in the i direction, i = 1, 2, where 1 represents the fiber direction and 2 represents the matrix direction; is the failure strain of the element in tension or compression in the i direction, ε ii is the strain in the i direction;

[0023]

[0024] Where X T(C) Indicates the tensile or compressive strength in the fiber direction, Y T(C) Indicates the tensile or compressive strength in the matrix direction; l represents the characteristic length of the unit. For a three-dimensional solid unit, l is the cube root of the unit volume; by inputting the tensile strain energy of the fiber Fiber compression strain energy Matrix tensile strain energy Matrix compressive strain energy Assuming a linear softening model during the damage evolution process, the fiber tensile damage, fiber compressive damage, matrix tensile damage, and matrix compressive damage in the above equations can be evaluated.

[0025] Furthermore, the cohesive force model of the stretch separation criterion adopts element-based viscous behavior.

[0026] Beneficial effects:

[0027] The numerical simulation method for composite material structures under explosion impact proposed in the present invention is easy to repeat and has lower cost compared with traditional explosion impact experiments, and can accurately predict the mechanical properties and damage characteristics of composite material structures under explosion impact. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solution of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 It is a flow chart of the numerical simulation method of explosion impact effect on composite material structure of the present invention.

[0030] Figure 2 Numerical simulation analysis process of progressive damage within composite materials layers.

[0031] Figure 3 Laminate material coordinate system.

[0032] Figure 4 It is a material damage model under uniaxial loading.

[0033] Figure 5 It is a three-dimensional schematic diagram of the cohesive unit.

[0034] FIG6( a ) is a composite sandwich structure used in the composite sandwich structure underwater explosion impact geometric model of the present invention; FIG6( b ) is a box model and a water area model of the present invention.

[0035] Figure 7(a) is a schematic diagram of the fiber direction damage of the explosion-proof plate.

[0036] Figure 7(b) is a schematic diagram of tensile damage in the explosion-facing plate in the matrix direction.

[0037] Figure 7(c) is a schematic diagram of the compression damage in the direction of the base of the explosion-facing plate.

[0038] Figure 7(d) is a schematic diagram of the fiber direction damage of the back explosion plate.

[0039] Figure 7(e) is a schematic diagram of tensile damage in the back explosion panel matrix direction.

[0040] Figure 7(f) is a schematic diagram of compression damage in the back blast panel matrix direction.

[0041] Figure 7(g) is a schematic diagram of delamination damage.

[0042] Figure 7(h) is the energy absorption time history curve of each part. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0044] A numerical simulation method for a composite material structure under explosion impact provided by an embodiment of the present invention mainly comprises the following steps:

[0045] S1. Construct VUMAT user material subroutine based on the continuous medium mechanics model of damage in composite material layer, which mainly includes two parts: damage initiation criterion and damage evolution. Because when Abaqus software performs explicit dynamic calculations, the composite material mechanics model provided by the software is only applicable to two-dimensional shell elements, ignoring the influence of in-plane transverse shear and thickness direction, and cannot completely control the damage of composite materials. If you want to completely control the progressive damage of composite materials in various modes, you need to refer to Figure 2 Write a VUMAT subroutine for user-defined material behavior. The subroutine is written in Fortran language and mainly includes two parts: damage initiation criterion and damage evolution.

[0046] Further, S1, constructing a VUMAT user material subroutine based on a continuous medium mechanics model of damage within a composite material layer, specifically including:

[0047] S11. Determine the constitutive relationship of the composite single-layer plate.

[0048] In the classic laminate theory, composite laminates need to be laid out and belong to the layer structure. For single-layer plates, the longitudinal direction is usually specified, refer to Figure 3 That is, the laying direction of the fiber is direction 1; the transverse direction of laying is direction 2, and the thickness direction perpendicular to directions 1 and 2 is direction 3.

[0049] In determining the constitutive relationship of a composite single-layer plate, the composite single-layer plate is different from isotropic materials such as metals. The material of the composite single-layer plate exhibits orthotropic anisotropy. Under the three-dimensional stress state and the material principal axis coordinate system, the stress-strain relationship of the composite single-layer plate in the lossless state is: represents the effective stress tensor, C is the elastic tensor of the material when it is not damaged, ε represents the strain, and the constitutive relation of the composite single-layer plate can be specifically described as follows:

[0050]

[0051] Among them, the values ​​of each element in the stiffness matrix can be obtained according to the elastic modulus and:

[0052]

[0053] In formula (2), E1 is the longitudinal (along the fiber direction) elastic modulus, E2 is the transverse (perpendicular to the fiber direction) elastic modulus, G 12 , G 13 , G 23 are the shear moduli in three directions, ν 12 ,ν 13 ,ν 21 ,ν 23 ,ν 31 ,ν 32 is the Poisson's ratio in each direction.

[0054] S12. Establish the initial failure criterion of composite laminates based on the constitutive relationship.

[0055] Construct the material constitutive model and introduce the failure criterion in the VUMAT subroutine. The strength of the material is an important indicator to measure the bearing capacity of the material. When the stress reaches the material strength limit, different degrees of damage will occur. The strength indicators of composite materials mainly include fiber tensile strength, fiber compression strength, matrix tensile strength, matrix compression strength, and in-plane shear strength. The initial failure criterion of the composite laminate adopts the Hashin failure criterion to judge the strength failure of the composite material; the expression of the Hashin failure criterion based on the strain form is as follows:

[0056] ε under fiber tensile failure mode 11 ≥0:

[0057]

[0058] in is the initial failure strain of fiber tension, X T is the longitudinal tensile strength, E1 is the fiber elastic modulus, is the fiber tensile failure judgment factor, is the tensile strain in the fiber direction.

[0059] ε under fiber compression failure mode 11 ≤0:

[0060]

[0061] in is the initial failure strain of fiber compression, X C is the longitudinal compressive strength, is the fiber compression failure judgment factor, is the compressive strain in the fiber direction;

[0062] ε under matrix tensile failure mode 22 ≥0:

[0063]

[0064] in Y T is the transverse tensile strength, E2 is the matrix elastic modulus, is the matrix tensile failure judgment factor, ε 22 is the strain in the matrix direction, ε 33 is the thickness direction strain, is the damage initiation strain of the element under tensile state in the matrix direction, is the initial shear failure strain, and is the out-of-plane shear strength, Z C Indicates the strength in the thickness direction, ε ijThe present invention adopts the basic tensile failure mode to not only consider the strain in the matrix direction, but also more fully consider the thickness direction and shear failure.

[0065] ε under matrix compression failure mode 22 ≤0:

[0066]

[0067] in, is the damage initiation strain of the element under compression in the matrix direction

[0068] The use of this matrix compression failure makes the simulation structure more accurate.

[0069] S13. Establish a material failure degradation model and complete the construction of the continuous medium mechanics model of damage in the composite material layer described in the VUMAT user material subroutine.

[0070] After a composite material is damaged, its mechanical properties will decrease. The most obvious phenomenon is the decrease in the macroscopic elastic modulus, which is called material degradation. In this embodiment, the material failure degradation adopts a degradation method based on fracture toughness. This degradation method not only ensures the calculation accuracy, but also has physical significance. The method of using formulas to express the damage state variables can also ensure continuity. When using this degradation method, the defined damage state variables of fiber tensile damage, fiber compression damage, matrix tensile damage, and matrix compression damage are:

[0071]

[0072] Where: is the damage state variable, i = 1, 2, where 1 represents fiber and 2 represents matrix; T represents tensile damage, C represents compressive damage, ε ii is the strain in the i direction, is the damage initiation strain of the unit in tension or compression in the i direction, i = 1, 2, where 1 represents the fiber direction and 2 represents the matrix direction. is the failure strain of the unit in tension or compression in the i direction;

[0073]

[0074]

[0075] Where X T(C) Indicates the tensile or compressive strength in the fiber direction, Y T(C) Indicates the tensile or compressive strength in the matrix direction; l represents the characteristic length of the unit. For a three-dimensional solid unit, l is the cube root of the unit volume. By inputting the tensile strain energy of the fiber Fiber compression strain energy Matrix tensile strain energy Matrix compressive strain energy Assuming a linear softening model during the damage evolution, the five damage values ​​in the above equations can be evaluated.

[0076] From the above discussion, we know that the damage evolution process of composite materials is related to the release of strain energy. The more serious the material damage, the more strain energy is released. When the released strain energy increases to the fracture energy of the material, it means that the material has completely failed. In the energy release process, the unit characteristic length l (the characteristic length of the three-dimensional unit in the finite element software Abaqus is the cube root of the unit volume) is introduced to reduce the dependence of the material damage evolution process on the mesh size.

[0077] When composite materials fail, the linear degradation model in the progressive degradation model is used. The damage model is referenced Figure 4 The material fracture energy measured by experiment is S OPR When the material begins to be damaged at point P, strain energy begins to be released. As the strain increases, the degree of damage to the material increases, and the strain energy release increases. The strain energy released at a certain point (Q) during the damage process is the area S enclosed by points O, P, and Q. OPQ , at this time the stiffness becomes (1-dii) times the original, when the strain energy (S OPQ ) is equal to the critical fracture energy of the material point (S OPR ), it means that this material point has completely failed.

[0078] In the embodiment of the present invention, before determining the constitutive relation of the composite single-layer plate in S11, it also includes updating the unit strain according to the applied load to obtain the current strain value ε t+Δt =ε t +Δε t+Δt , where ε t is the dependent variable of the previous step, Δε t+Δt is the current strain increment.

[0079] In the embodiment of the present invention, when the current strain value is obtained, it is determined whether the material is damaged at this time. After the material is damaged, the stiffness matrix and unit stress update are completed using the continuous medium mechanics model of damage in the composite material layer. When the material is not damaged, the stiffness matrix and unit stress update are completed directly. When the process is not completed, the load is applied again to complete the automatic iteration.

[0080] S2. Establish a finite element model of the composite material structure according to the cohesive force model of the tensile separation criterion, establish a water area grid and explosion boundary conditions, and obtain simulation results based on the acoustic-solid coupling algorithm and the explicit time integration method and the VUMAT user material subroutine. Specifically:

[0081] S21. Establish a 3D deformable composite sandwich panel explosion impact damage geometry model.

[0082] S22. The cohesive force model of the tensile separation criterion is used to describe the delamination damage of a typical composite material plate structure. The cohesive force model of the tensile separation criterion adopts unit-based viscous behavior, that is, inserting interface units.

[0083] When a typical composite plate structure is subjected to a strong impact load, not only in-plane damage but also delamination damage will occur. The present invention adopts a cohesive force model to describe the delamination damage of a typical composite plate structure, and adopts a unit-based viscous behavior. The interface unit can simulate the bonding very carefully, directly control the contact grid, and simulate a zero-thickness or finite-thickness adhesive layer. A macroscopic cohesive criterion can be used to divide the traction across the contact surface into individual components. Reference Figure 5 For a three-dimensional cohesive unit, it can be understood that there is an intermediate surface that divides the cohesive unit into two surfaces, upper and lower.

[0084] The cohesive element contains three stress components, namely, the normal stress σ along the thickness direction n and two shear stresses σ perpendicular to the thickness direction s and σ t , corresponding to three delamination damage modes, and their corresponding displacements are δ n , δ s and δ t When the normal stress and shear stress are independent of each other, the decoupled form of the stress-displacement relationship can be expressed as:

[0085]

[0086] Where: K nn , K ss , K tt is an invariant. In Abaqus software, you need to enter E nn 、E ss 、E tt and effective thickness to express K nn , K ss , K tt .

[0087] The damage process of the cohesive unit used to simulate delamination is divided into two stages: damage initiation and damage evolution. In the finite element software Abaqus, four criteria are provided to determine whether delamination damage has begun: maximum nominal stress failure criterion, maximum nominal strain failure criterion, quadratic nominal stress failure criterion and quadratic nominal strain initial criterion. The present invention uses the quadratic nominal stress failure criterion to determine material delamination damage:

[0088]

[0089] Where: <σ n >、<σ s >、<σ t > respectively represent the normal stress in the thickness direction and the two shear stresses perpendicular to the thickness. N max , S max 、T max They represent the interface strength in the thickness direction and in the two shear directions perpendicular to the thickness, and S max =T max .

[0090] In the finite element software Abaqus, the damage evolution of the cohesive unit adopts an energy-based linear attenuation model, which is similar to the linear degradation model of composite material failure. During the delamination process, the interlaminar stress increases with the increase of relative displacement. When the stress reaches the interlaminar stress intensity, the bilinear response process reaches the softening stage; the relative displacement continues to increase, and the stress will gradually decrease along the linear segment until the relative displacement reaches the complete separation displacement and the stress drops to 0. If the load is unloaded and then loaded again in the middle, the material stiffness will not continue to degrade from the initial stiffness. When the interlaminar separation displacement reaches the damage starting displacement δ0, the material strength is reduced, as shown in formulas (12) to (14). Among them, σ n is the normal stress along the thickness direction, σ s and σ t are two shear stresses perpendicular to the thickness direction, and d is the damage state variable. When d = 0, it means that the material is not damaged; when d = 1, it means that the material is completely damaged. In the numerical calculation process, as the material strength components are reduced, the strength in the three directions is continuously updated.

[0091]

[0092] σ s =(1-d)σ s (13)

[0093] σ t =(1-d)σ t (14)

[0094] S23, establishing a water area grid and explosion boundary conditions, solving according to the acoustic-solid coupling algorithm and the explicit time integration method, and calling the VUMAT user material subroutine to obtain simulation results.

[0095] Based on the acoustic fluid balance condition, the acoustic-solid coupling method discretizes the fluid domain into a fluid-solid coupling equation that can be solved using the explicit time integration method. When the loss of fluid flow momentum is considered and the fluid is assumed to be adiabatic and compressible, the small-amplitude motion equation of the fluid can be obtained as follows:

[0096]

[0097] Where p is the pressure function in the flow field, ρ f is the density function, x is the spatial coordinate of the particle, and are the spatial motion speed and acceleration respectively. γ is the fluid viscous damping coefficient, θ i are parameter variables related to watershed density and velocity, and each quantity is independent of each other.

[0098] To simplify the calculation, the viscosity of the fluid is generally ignored. Assuming that the fluid is compressible, the formula can be simplified to:

[0099]

[0100] In the formula, u f is the fluid velocity, K f is the bulk modulus of the fluid.

[0101] The simulation method described above is described below with examples.

[0102] In this embodiment, the geometric model of explosion impact damage of a 3D deformable composite sandwich panel is shown in Figure 6. The geometric model consists of three parts, namely, the water area, the box structure and the specimen. Specifically, the plane size of the composite sandwich structure is 1m×1m. Considering the connection method between different materials, a 1mm thick adhesive layer is set between the panel and the core layer; the upper panel is used as the explosion-proof panel with a thickness of 9mm; the core layer uses hard PVC foam with a thickness of 100mm; the lower panel is used as a double explosion panel with a thickness of 12mm. Considering the influence of the height of the box structure on the structure, a box structure with the same length and width as the specimen is established, with dimensions of 1.01×1.01×1m 3 , take the thickness as 5mm, and set the box structure as a rigid body, ignoring the influence of the deformation of the box structure on the typical composite sandwich structure. Since the air behind the ship structure can flow in and out freely in the actual environment, this method assumes that the air inside the box structure is a vacuum. Set the water area size to about 6 times the structure size, that is, the water area size is 6×6×6m 3, the Y direction is specified as the water depth direction. In this embodiment, there is a free surface on the water surface, and it is necessary to apply a 0 pressure boundary condition on the free surface to simulate the free surface of the water area. Since the structure is always in a back-to-air environment, and the influence of the deformation of the box-type structure on the calculation is ignored, the box-type structure is set as a rigid body to fix all degrees of freedom. In order to prevent the sound waves from reflecting at the flow field boundary and affecting the calculation accuracy, this example sets a non-reflection boundary condition at the flow field boundary, indicating that the shock wave can pass through the surface without reflection. The five end faces of the water area of ​​the calculation model in this example are set as plane non-reflection boundary conditions.

[0103] Set the explosion source and analysis step. The explosion source in this example uses TNT explosives with an explosive equivalent of 8kg, an explosion distance of 2.8m, an impact factor of 1.01, and the explosives are detonated 2m below the free liquid surface. Set the Dynamic / Explicit dynamic explicit analysis step to analyze the explosion impact response simulation of a typical composite sandwich structure, and the duration is set to 18ms. In order to obtain the deformation of the composite sandwich structure, a node set is established at the midpoint of the composite sandwich structure, and the node displacement history curve is output. In order to obtain the energy absorption of each part of the composite sandwich structure, the energy absorption history curve of each part is output and submitted to the solver for solution. 16-core parallel computing is used, and the final calculation time is about 4h, which is much shorter than the traditional experimental method. The damage and energy absorption of the composite sandwich panel are obtained by calculation, as shown in Figure 7. The deflection at the center of the structure can intuitively reflect the deformation of the structure. Figure 7(a)-Figure 7(g) The time history curves of the midpoint deflection of the front explosion plate and the back explosion plate of the composite sandwich panel are shown. It can be seen from Figure 7(b) that the change of the midpoint deflection of the front explosion plate of the structure is very similar to that of the midpoint of the back explosion plate. The displacement peaks of the two points are 72.02mm and 64.17mm respectively, and the deflections of the two points show a relatively obvious oscillation phenomenon afterwards. In addition, it can be seen from Figure 7(a) that the deformation speed of the front explosion plate is much higher than that of the back explosion plate. Therefore, it can be found that the load transmission capacity of the rigid PVC foam core layer is crucial to improving the explosion resistance of the structure. In the process of load transmission through the core layer, the back explosion plate has undergone significant deformation. The higher the deformation degree of the back explosion plate, the lower the explosion-proof performance of the composite material. For the composite sandwich panel, the displacement time of the back explosion plate is delayed by about 0.12ms relative to the front explosion plate, and the displacement of the back explosion plate is reduced by about 10mm relative to the front explosion plate. In order to more intuitively observe the energy absorption of each component, the energy absorption of each part of the structure is output, as shown in Figure 7(h). As can be seen from the figure, the energy absorbed by each part increases with time and eventually tends to a certain stability. The core layer absorbs most of the energy through plastic deformation during the entire explosion impact process. The energy absorbed by the front explosion surface of the structure is greater than that absorbed by the back explosion surface, and the viscous layer absorbs less energy. This shows that the core layer plays a good role in energy dissipation in the explosion and impact protection of the structure.

[0104] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A numerical simulation method for composite material structure under explosion impact, characterized in that: The following steps are involved: According to the continuous medium mechanics model of damage in the composite layer, the VUMAT user material subroutine is constructed, including two parts: damage initiation criterion and damage evolution. Specifically, the constitutive relationship of the composite single-layer plate is determined, the initial failure criterion of the composite laminate is established according to the constitutive relationship, and the material failure degradation model is established; A finite element model of a composite material structure is established according to the cohesive force model of the tensile separation criterion, a water area grid and explosion boundary conditions are established, and the solution is obtained according to the acoustic-solid coupling algorithm and the explicit time integration method. Simultaneously, simulation results are obtained based on the VUMAT user material subroutine. The initial failure criterion of the composite laminate adopts the Hashin failure criterion to determine the strength failure of the composite material. The expression of the Hashin failure criterion based on strain form is as follows: ε under fiber tensile failure mode 11 ≥0: in is the initial failure strain of fiber tension, X T is the longitudinal tensile strength, E1 is the fiber elastic modulus, is the fiber tensile failure judgment factor, is the tensile strain in the fiber direction; ε under fiber compression failure mode 11 ≤0: in is the initial failure strain of fiber compression, X C is the longitudinal compressive strength, is the fiber compression failure judgment factor, is the compressive strain in the fiber direction; ε under matrix tensile failure mode 22 ≥0: in Y T is the transverse tensile strength, E2 is the matrix elastic modulus, is the matrix tensile failure judgment factor, ε 22 is the strain in the matrix direction, ε 33 is the thickness direction strain, is the damage initiation strain of the element under tensile state in the matrix direction, is the initial shear failure strain, and is the out-of-plane shear strength, Z C Indicates the strength in the thickness direction, ε ij is the in-plane strain, G 13 , G 23 is the shear modulus; ε under matrix compression failure mode 22 ≤0 in, is the damage initiation strain of the element under compression in the matrix direction; The damage state variables of fiber tensile damage, fiber compression damage, matrix tensile damage, and matrix compression damage defined in the material failure degradation model are: Where: is the damage state variable, i = 1, 2, where 1 represents fiber, 2 represents matrix, T represents tensile damage, and C represents compressive damage. is the damage initiation strain of the unit in tension or compression in the i direction, i = 1, 2, where 1 represents the fiber direction and 2 represents the matrix direction; is the failure strain of the element in tension or compression in the i direction, ε ii is the strain in the i direction; Where X T(C) Indicates the tensile or compressive strength in the fiber direction, Y T(C) Indicates the tensile or compressive strength in the matrix direction; l represents the characteristic length of the unit. For a three-dimensional solid unit, l is the cube root of the unit volume; by inputting the tensile strain energy of the fiber Fiber compression strain energy Matrix tensile strain energy Matrix compressive strain energy Assuming a linear softening model during the damage evolution process, the fiber tensile damage, fiber compressive damage, matrix tensile damage, and matrix compressive damage in the above equations can be evaluated.

2. The numerical simulation method for composite material structure under explosion impact according to claim 1, characterized in that: The cohesive force model of the stretch-separation criterion adopts element-based viscous behavior.

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