Ballistic impact performance prediction and structural design method of fiber cloth / resin bullet-proof materials based on strain rate

Abstract

The present invention specifically relates to a method for predicting ballistic impact performance and structural design of fiber cloth / resin bullet-proof materials based on strain rate; the method comprises the following steps: (1) establishing a model of fiber cloth, resin and bullet; (2) determining the strain rate according to bulletproof requirements, and establishing the relationship between fiber cloth and resin material parameters and the strain rate; (3) determining cohesion parameters related to the strain rate; (4) determining a failure criterion related to the strain rate; (5) determining the bullet velocity and boundary conditions according to ballistic impact requirements and calculating and analyzing the model by calling a VUMAT subroutine to predict the damage behavior of the pre-designed fiber cloth / resin material during the ballistic impact process; (6) verifying the effectiveness of the model through experiments, and correcting the model by correcting the pre-designed structure and optimizing material parameters; (7) obtaining the structure of the fiber cloth / resin bullet-proof material with the required ballistic impact performance; the model of the present invention has the geometric shape of a real fiber cloth / resin bullet-proof material.

Description

Technical Field

[0001] The invention relates to the technical field of fiber-reinforced resin-based composite materials, and in particular to a strain rate-based ballistic impact performance prediction and structural design method for fiber cloth / resin bullet-proof materials. Background Art

[0002] Most current bulletproof material designs are based on energy dissipation, with a focus on protection against penetration and penetrating damage. However, the forces and damage in the initial impact stage, erosion stage, and fracture stage of the impact process are diverse, and the coupling effect of the shock wave spreading layer by layer is significant. Therefore, a single energy dissipation design is difficult to resist both penetrating and non-penetrating damage at the same time, and faces challenges such as insufficient protection against multiple impacts and a significant decrease in load-bearing capacity after impact.

[0003] Continuum finite element models are often used to simulate the ballistic penetration behavior of composite materials. Progressive damage material models use effective fabric properties to homogenize the composite structure into continuous layers, improving the realism of the results by merging experimental data in continuous layers. However, these models do not include delamination cracking between fiber cloth and fiber cloth, debonding between fiber cloth and resin matrix, fiber pull-out, etc. At the same time, the continuum model also ignores fiber cloth-fiber cloth delamination, friction sliding after fiber cloth-resin matrix debonding, and tensile straightening of fiber bundle undulations. The geometry of the tow and matrix can be modeled using a mesoscale approach, using a local-global model of the mesoscale structure at the impact location connected to the global continuum to solve these problems. In addition, the cohesive zone model method is often used to simulate fiber cloth-matrix debonding pull-out and matrix cracking.

[0004] Composite materials are subject to energy dissipation damage at many length scales. Mesoscale damage modes in composite materials consist of microscale damage mechanisms. Under impact loading, mesoscale woven composite structures will experience inter-tow transverse cracking and intra-tow delamination cracking, which meander through the matrix and around the fibers; the microscale damage mechanisms involved in mesoscale cracking include strain rate-dependent fiber damage, strain rate-dependent resin matrix failure, and rate-dependent fiber cloth-resin matrix interface failure. These mesoscale damage mechanisms can be implemented in finite element analysis. Summary of the invention

[0005] The present invention overcomes the shortcomings of the prior art and provides a strain rate-based fiber cloth / resin bullet-proof material ballistic impact performance prediction and structural design method, so as to reduce the error between finite element simulation results and experimental test results through parameters related to strain rate, thereby improving the accuracy and reliability of simulation results.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a strain rate-based ballistic impact performance prediction and structural design method of fiber cloth / resin bullet-proof materials, comprising the following steps:

[0007] S1. According to the structural parameters of the pre-designed fiber cloth / resin bullet-proof material, models of the fiber cloth, resin and bullet are established respectively;

[0008] S2. Testing the tensile mechanical properties of the fiber cloth and the resin, setting the loading rate related to the strain rate according to the ballistic performance requirements, obtaining the tensile properties of the fiber cloth and the resin under various loading rates, and establishing the relationship between the material parameters of the fiber cloth and the resin and the strain rate;

[0009] S3, conduct type I and II fracture toughness tests on the fiber cloth / resin bulletproof material, establish type I and II load-displacement curves respectively and determine the cohesion parameters related to the strain rate;

[0010] S4, based on the failure criterion of two-dimensional Hashin composite materials, determine the failure criterion of three-dimensional Hashin composite materials related to strain rate and incorporate it into the VUMAT subroutine;

[0011] S5. Performing ballistic impact finite element simulation on the pre-designed fiber cloth / resin bullet-proof material to obtain the corresponding ballistic penetration behavior of the fiber cloth / resin bullet-proof material;

[0012] S6, experimentally verify the finite element model, prepare the fiber cloth / resin bulletproof material and conduct a ballistic impact test to obtain the measured result of the limit velocity of the ballistic impact; when the difference between the measured value of the ballistic limit velocity of the pre-designed fiber cloth / resin bulletproof material and the finite element simulation value exceeds 10%, re-enter step S1 to modify the model by changing the pre-designed structure and optimizing the material parameters; until the difference between the measured value of the ballistic limit velocity of the fiber cloth / resin bulletproof material and the finite element simulation value does not exceed 10%, determine that the model is valid;

[0013] S7. Obtain a fiber cloth / resin bulletproof material structure with desired ballistic impact performance.

[0014] As a further improvement of the technical solution of the present invention, a 1 / 2 model is established in step S1 for ballistic impact finite element simulation, wherein the ballistic impact area is a mesoscale model and the rest is a uniform continuous model to improve the efficiency of simulation calculations.

[0015] As a further improvement of the technical solution of the present invention, the fiber cloth is a combination of one or more organic synthetic fiber cloths, with a single layer thickness of 0.1 to 2.0 mm and a surface density of 100 to 1000 g / m 2 ; The resin is a mixture of one or more of epoxy resin, unsaturated polyester resin and phenolic resin.

[0016] As a further improvement of the technical solution of the present invention, the organic synthetic fiber cloth is ultra-high molecular weight polyethylene fiber cloth, glass fiber cloth, carbon fiber cloth, basalt fiber cloth, aramid fiber cloth, poly(p-phenylene benzobisoxazole) fiber or nylon fiber cloth.

[0017] As a further improvement of the technical solution of the present invention, the loading rate associated with ballistic impact set in step S2 is a loading rate corresponding to a high strain rate, and the high strain rate is 1 to 5000s -1 .

[0018] As a further improvement of the technical solution of the present invention, the energy release rate in step S3 is calculated by energy domain integration, and the formula used is:

[0019]

[0020] Where: J is the energy release rate; is the strain energy density; x 1 is the crack extension direction; n 1 For x 1 The component of the unit vector perpendicular to the counterclockwise path around the crack tip; T i is the component of the traction vector; u i are the components of the displacement vector; dΓ is the length increment along the contour line.

[0021] As a further improvement of the technical solution of the present invention, the calculation formula of the damage evolution in the three-dimensional Hashin composite material failure criterion related to the strain rate in step S4 is:

[0022]

[0023] Where: d I is the damage variable; is the elastic strain in the corresponding direction; is the initial elastic strain in the corresponding direction; is the final failure when the corresponding damage variable reaches 1, ft, fc, mt and mc represent fiber tension, fiber compression, matrix tension and matrix compression respectively; α is the direction correction coefficient;

[0024] The elasticity-stiffness calculation formula is:

[0025]

[0026] The strength calculation formula is:

[0027]

[0028] Cohesive unit damage evolution:

[0029]

[0030]

[0031] As a further improvement of the technical solution of the present invention, the finite element simulation process in step S5 is:

[0032] (1) According to the structural parameters of the pre-designed fiber cloth / resin bulletproof material, the geometric models of the fiber cloth, resin and bullet are established respectively; (2) The material parameters related to the strain rate are determined and assigned to the geometric model;

[0033] (3) Assemble and mesh the fiber cloth, resin, and bullets;

[0034] (4) Adding a strain rate-dependent cohesive force model between the fiber cloth and the resin;

[0035] (5) Determine bullet velocity and boundary conditions based on ballistic impact requirements;

[0036] (6) The model is calculated and analyzed by calling the VUMAT subroutine, the velocity-time curve and the energy-time curve of each part are extracted, and the damage behavior of the pre-designed fiber cloth / resin bullet-proof material during the ballistic impact process is predicted.

[0037] As a further improvement of the technical solution of the present invention, in the experimental verification in step S6, the preparation process of the fiber cloth / resin bullet-proof material used for testing is as follows:

[0038] ①Prepare resin glue

[0039] Add resin and curing agent in proportion, mix well and set aside;

[0040] ②Preparation of prepreg by resin transfer molding process

[0041] The resin transfer molding system includes a mold, a vacuum bag arranged on the upper surface of the mold, and a first pipe fitting and a second pipe fitting, wherein one end of the first pipe fitting and the second pipe fitting are respectively connected to the inside of the vacuum bag, and the other end is respectively connected to a glue storage tank or a buffer tank; the buffer tank is also connected to a vacuum pump through a third pipe fitting, and the vacuum pump is connected to the inside of the buffer tank through the third pipe fitting; a solenoid wrapped with a glue suction felt is provided at the liquid outlet of the first pipe fitting in the vacuum bag, and the solenoid is laid along the edge of the fiber cloth preform, and the tail of the solenoid does not contact the liquid inlet of the second pipe fitting; when the vacuum pump is turned on, the vacuum bag starts to shrink and quickly wraps the fiber cloth preform, and the resin in the glue storage tank is injected into the vacuum bag under vacuum negative pressure, and then the fiber cloth preform is impregnated through the solenoid wrapped with the glue suction felt, and the injection rate and injection time are regulated by the injection temperature according to the viscosity-temperature relationship of the resin, so that the resin fully impregnates the fiber cloth preform; the preparation of the prepreg is completed;

[0042] ③Preparation of fiber cloth / resin bulletproof materials by molding process:

[0043] The prepreg prepared in step ② is placed in a mold and compression molded to complete the preparation of the fiber cloth / resin bulletproof material.

[0044] As a further improvement of the technical solution of the present invention, the structure with the required ballistic impact performance obtained in step S7 includes the types of fiber cloth and resin, the number of fiber cloth layers, the thickness of the fiber cloth / resin bulletproof material, and the volume fraction of the fiber cloth in the fiber cloth / resin bulletproof material.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] (1) The model of the present invention has the geometric shape of a real fiber cloth / resin bulletproof material, and the ballistic limit velocity can be predicted more accurately through the strain rate-dependent material constitutive relationship.

[0047] (2) The strain rate-based model of the present invention has a more accurate deformation mechanism at a lower scale and can be used to study the deformation mechanism during ballistic impact. In the material structure design framework, the mesoscale model can introduce different resins, fiber cloths with different morphologies, and different fiber cloth volume fractions, and realize the quantification of energy dissipation. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 A flow chart of the strain rate-based ballistic impact performance prediction and structural design method of a fiber cloth / resin bulletproof material of the present invention.

[0049] Figure 2 Schematic diagram of the model of the fiber cloth / resin bullet-proof material in Example 1 of the present invention.

[0050] Figure 3A diagram showing the process of simulating ballistic impact in Example 1 of the present invention.

[0051] Figure 4 Example 1 of the present invention is a resin transfer molding system for preparing a measured fiber cloth / resin bullet-proof material.

[0052] Figure 5 A schematic cross-sectional view of the measured and simulated results of ballistic impact in Example 1 of the present invention.

[0053] Figure 6 Schematic diagram of back injuries from the measured and simulated ballistic impact results in Example 1 of the present invention.

[0054] The following are marked in the figure:

[0055] 1-mold, 2-vacuum bag, 3-first pipe fitting, 4-second pipe fitting, 5-glue storage tank, 6-buffer tank, 7-third pipe fitting, 8-vacuum pump, 9-fiber cloth preform. DETAILED DESCRIPTION

[0056] The present invention is further described below in conjunction with specific embodiments.

[0057] Example 1

[0058] A strain rate-based method for predicting ballistic impact performance and structural design of ultra-high molecular weight polyethylene fiber cloth / epoxy bullet-proof materials comprises the following steps:

[0059] S1. The model structure is determined according to the pre-designed structure of ultra-high molecular weight polyethylene fiber cloth / epoxy bullet-proof material, in which the fiber bundle thickness is 0.4 mm and the width is 0.8 mm. The fibers and matrix constituting the filament bundle are represented as a continuum with a fiber cloth volume fraction of about 60%. A 1 / 2 model is established for ballistic impact finite element simulation, in which the ballistic impact area is a mesoscale model and the rest is a uniform continuous model.

[0060] S2. Use a universal testing machine to test the tensile mechanical properties of ultra-high molecular weight polyethylene fiber cloth and epoxy resin, set the strain rate corresponding to the ballistic performance requirements, and establish the relationship between the tensile properties and strain rate of ultra-high molecular weight polyethylene fiber cloth and epoxy resin.

[0061] S3. Use a universal testing machine to test the type I and II fracture toughness of the ultra-high molecular weight polyethylene fiber cloth / epoxy bulletproof material, set different strain rates corresponding to different ballistic impact properties, establish type I and II load-displacement curves, and determine the cohesive stiffness related to the strain rate as 10 6 MPa, Type I fracture energy is 310J / mm 2 , Type II fracture energy is 630J / mm 2 .

[0062] S4. Determine the strain rate-dependent failure criterion of three-dimensional Hashin composite materials and incorporate it into the Abaqus subroutine.

[0063] The calculation formula for damage evolution in the failure criterion of three-dimensional Hashin composite materials is:

[0064]

[0065] Where: d I is the damage variable; is the elastic strain in the corresponding direction; is the initial elastic strain in the corresponding direction; is the final failure when the corresponding damage variable reaches 1, ft, fc, mt and mc represent fiber tension, fiber compression, matrix tension and matrix compression respectively; α is the direction correction coefficient;

[0066] The elasticity-stiffness calculation formula is:

[0067]

[0068] The strength calculation formula is:

[0069]

[0070] Cohesive unit damage evolution:

[0071]

[0072]

[0073] S5. Perform finite element simulation on the pre-designed ultra-high molecular weight polyethylene fiber cloth / epoxy bullet-proof material to obtain its ballistic penetration behavior.

[0074] In this embodiment, the thermosetting resin system comprises bisphenol A epoxy resin TS481 and amine curing agent TS487; the ultra-high molecular weight polyethylene fiber cloth is a unidirectional cloth with a thickness of 0.5 mm, a width of 1 mm, and a surface density of 900 g / m 2 . Use Figure 5 The resin transfer molding system shown is prepared.

[0075] A hard single-sided mold 1 is used, and eight layers of demoulding cloth and ultra-high molecular weight polyethylene fiber unidirectional cloth are laid thereon and fixed to obtain a fiber cloth preform 9, a demoulding cloth, a breathable felt, a glue-absorbing felt, and a vacuum bag 2; the vacuum pump 8 is turned on, the vacuum bag 2 begins to shrink and quickly wraps the fiber cloth preform 9, and the epoxy resin mixture system in the glue storage tank 5 is injected into the vacuum bag 2 under vacuum negative pressure, and then the fiber cloth preform 9 is impregnated through the solenoid wrapped with the glue-absorbing felt, and according to the viscosity-temperature relationship of the resin system, the injection temperature is used to control the injection rate and injection time, and the injection temperature is determined to be 40°C, the injection rate is 200mL / s, and the injection time is 10min; the preparation of ultra-high molecular weight polyethylene fiber cloth / epoxy prepreg is completed.

[0076] The obtained ultra-high molecular weight polyethylene fiber cloth / epoxy prepreg was transferred to a molding machine for compression molding at a molding temperature of 60°C. After gelling for 1 hour, the pressure was increased to 6 MPa and cured for 5 hours to complete the preparation of the ultra-high molecular weight polyethylene fiber cloth / epoxy bullet-proof material.

[0077] S6. Experimentally verify the results of finite element simulation; use 9mm live bullets to conduct ballistic tests on the ultra-high molecular weight polyethylene fiber cloth / epoxy bulletproof material obtained in S5, and the bullet speed is 200-400m / s. It is finally determined that the ballistic limit velocity of the ultra-high molecular weight polyethylene fiber cloth / epoxy bulletproof material is 221m / s, and the finite element simulation result is 213m / s. The difference between the measured value and the finite element simulation value of the ballistic limit velocity of the ultra-high molecular weight polyethylene fiber cloth / epoxy bulletproof material is 3%. It is determined that the model is valid, and the structure of the ultra-high molecular weight polyethylene fiber cloth / epoxy resin bulletproof material is obtained, wherein the number of layers of the ultra-high molecular weight polyethylene fiber cloth is 8, the thickness of the fiber cloth / resin bulletproof material is 4mm, and the volume fraction of the fiber cloth is 62%.

[0078] Adaptive changes made according to actual needs are within the scope of protection of the present invention. The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A strain rate-based method for predicting ballistic impact performance and structural design of fiber cloth / resin bulletproof materials, characterized in that: The following steps are involved: S1. According to the structural parameters of the pre-designed fiber cloth / resin bulletproof material, models of the fiber cloth, resin and bullet are established respectively; a 1 / 2 model is established for ballistic impact finite element simulation, wherein the ballistic impact area is a mesoscale model and the rest is a uniform continuous model; the fiber cloth is a combination of one or more organic synthetic fiber cloths, with a single layer thickness of 0.1 to 2.0 mm and a surface density of 100 to 1000 g / m 2 ; The resin is a mixture of one or more of epoxy resin, unsaturated polyester resin and phenolic resin; S2. Testing the tensile mechanical properties of the fiber cloth and the resin, setting the loading rate related to the strain rate according to the ballistic performance requirements, obtaining the tensile properties of the fiber cloth and the resin under various loading rates, setting the strain rate corresponding to the ballistic performance requirements, and establishing the relationship between the tensile properties of the fiber cloth and the resin and the strain rate; S3. Conduct type I and type II fracture toughness tests on the fiber cloth / resin bulletproof material, set different strain rates corresponding to different ballistic impact performance, establish type I and type II load-displacement curves, and determine the cohesive stiffness, type I fracture energy, and type II fracture energy related to the strain rate; S4. Based on the two-dimensional Hashin composite failure criterion, the three-dimensional Hashin composite failure criterion related to strain rate is determined and incorporated into the VUMAT subroutine; the calculation formula for damage evolution in the three-dimensional Hashin composite failure criterion related to strain rate is: Where: d I is the damage variable; is the elastic strain in the corresponding direction; is the initial elastic strain in the corresponding direction; is the final failure when the corresponding damage variable reaches 1, ft, fc, mt and mc represent fiber tension, fiber compression, matrix tension and matrix compression respectively; α is the direction correction coefficient; S5. Performing ballistic impact finite element simulation on the pre-designed fiber cloth / resin bullet-proof material to obtain the corresponding ballistic penetration behavior of the fiber cloth / resin bullet-proof material; S6, experimentally verify the finite element model, prepare the fiber cloth / resin bulletproof material and conduct a ballistic impact test to obtain the measured result of the limit velocity of the ballistic impact; when the difference between the measured value of the ballistic limit velocity of the pre-designed fiber cloth / resin bulletproof material and the finite element simulation value exceeds 10%, re-enter step S1 to modify the model by changing the pre-designed structure and optimizing the material parameters; until the difference between the measured value of the ballistic limit velocity of the fiber cloth / resin bulletproof material and the finite element simulation value does not exceed 10%, determine that the model is valid; S7. Obtain a fiber cloth / resin bulletproof material structure with desired ballistic impact performance.

2. The method for predicting ballistic impact performance and structural design of fiber cloth / resin bulletproof materials based on strain rate according to claim 1, characterized in that: The organic synthetic fiber cloth is ultra-high molecular weight polyethylene fiber cloth, glass fiber cloth, carbon fiber cloth, basalt fiber cloth, aramid fiber cloth, poly(p-phenylene benzobisoxazole) fiber or nylon fiber cloth.

3. The method for predicting ballistic impact performance and structural design of fiber cloth / resin bulletproof materials based on strain rate according to claim 1, characterized in that: The loading rate associated with ballistic impact set in step S2 is the loading rate corresponding to the high strain rate, and the high strain rate is 1 to 5000s -1 .

4. The method for predicting ballistic impact performance and structural design of fiber cloth / resin bulletproof materials based on strain rate according to claim 1, characterized in that: In step S3, the energy release rate is calculated by integrating the energy domain, and the formula used is: Where: J is the energy release rate; is the strain energy density; x1 is the crack extension direction; n1 is the component of the unit vector x1 perpendicular to the counterclockwise path around the crack tip; T i is the component of the traction vector; u i are the components of the displacement vector; dΓ is the length increment along the contour line.

5. The method for predicting ballistic impact performance and structural design of fiber cloth / resin bulletproof materials based on strain rate according to claim 1, characterized in that: The finite element simulation process in step S5 is: (1) According to the structural parameters of the pre-designed fiber cloth / resin bullet-proof material, the geometric models of the fiber cloth, resin and bullet are established respectively; (2) Determine the material parameters related to the strain rate and assign them to the geometric model; (3) Assemble and mesh the fiber cloth, resin, and bullets; (4) Adding a strain rate-dependent cohesive force model between the fiber cloth and the resin; (5) Determine bullet velocity and boundary conditions based on ballistic impact requirements; (6) The model is calculated and analyzed by calling the VUMAT subroutine, the velocity-time curve and the energy-time curve of each part are extracted, and the damage behavior of the pre-designed fiber cloth / resin bullet-proof material during the ballistic impact process is predicted.

6. The method for predicting ballistic impact performance and structural design of fiber cloth / resin bulletproof materials based on strain rate according to claim 1, characterized in that: In the experimental verification in step S6, the preparation process of the fiber cloth / resin bullet-proof material used for the test is as follows: ①Prepare resin glue Add resin and curing agent in proportion, mix well and set aside; ②Preparation of prepreg by resin transfer molding process The resin transfer molding system comprises a mold (1), a vacuum bag (2) arranged on the upper surface of the mold (1), and a first pipe fitting (3) and a second pipe fitting (4); one end of the first pipe fitting (3) and the second pipe fitting (4) are respectively connected to the inside of the vacuum bag (2), and the other end is respectively connected to a glue storage tank (5) or a buffer tank (6); the buffer tank (6) is also connected to a vacuum pump (8) through a third pipe fitting (7), and the vacuum pump (8) is connected to the inside of the buffer tank (6) through the third pipe fitting (7); the liquid outlet of the first pipe fitting (3) in the vacuum bag (2) is provided with a screw wrapped with a glue suction felt. The solenoid is laid along the edge of the fiber cloth preform (9), and the tail of the solenoid does not contact the liquid inlet of the second pipe (4); when the vacuum pump (8) is turned on, the vacuum bag (2) begins to shrink and quickly wraps the fiber cloth preform (9), and the resin in the glue storage tank (5) is injected into the vacuum bag (2) under vacuum negative pressure, and then the fiber cloth preform (9) is impregnated through the solenoid wrapped by the glue suction felt, and the injection rate and injection time are regulated by the injection temperature according to the viscosity-temperature relationship of the resin, so that the resin fully impregnates the fiber cloth preform (9); and the preparation of the prepreg is completed; ③Preparation of fiber cloth / resin bulletproof materials by molding process: The prepreg prepared in step ② is placed in a mold and compression molded to complete the preparation of the fiber cloth / resin bulletproof material.

7. The method for predicting ballistic impact performance and structural design of fiber cloth / resin bulletproof materials based on strain rate according to claim 1, characterized in that: The structure with the required ballistic impact performance obtained in step S7 includes the types of fiber cloth and resin, the number of fiber cloth layers, the thickness of the fiber cloth / resin bulletproof material, and the volume fraction of the fiber cloth in the fiber cloth / resin bulletproof material.

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