Light and thin flexible fabric protection equipment for large tank

Abstract

The invention discloses light and thin flexible fabric protection equipment for a large tank body. A key protection layer of the protection equipment is polypropylene plain woven fabric made of cross-shaped fibers. Through finite element simulation and impact experiments, the yarn section shape and the fabric organization structure of the fabric with the highest impact resistance are jointly analyzed and verified, and the yarn section shape and the fabric organization structure serve as preparation parameters of the fabric for manufacturing the protective equipment. Through the design of fabric preparation parameters, the prepared protective equipment can effectively absorb and dissipate impact energy when being impacted, and has the characteristics of lightness, thinness and compactness. The safety of the large tank body in the transportation process can be remarkably improved, deformation or damage caused by impact is reduced, and the transportation efficiency is improved.

Description

Technical Field

[0001] The present application relates to the field of mechanical engineering technology, and in particular to a thin and flexible fabric protective equipment for large tanks. Background Art

[0002] With the rapid development of the aerospace industry, the number of rocket launch missions has increased significantly, which has put forward higher requirements for the transportation safety of large tanks. During the transportation of rockets, especially when transported by rail, they may encounter natural hazards such as falling rocks, which pose a serious threat to the tanks and their internal precision instruments. Due to the limitation of the size of railway culverts, traditional metal protective equipment cannot meet the transportation needs of large-sized tanks due to its large thickness and high weight. Therefore, there is an urgent need for a new type of lightweight and compact protective equipment to ensure the safety of large tanks during transportation.

[0003] Fabric protective equipment has gradually attracted attention due to its unique performance. When impacted, the fabric can effectively reduce the damage caused by external impact energy based on the viscoelastic deformation of its flexible material, the internal friction between the microscopic molecular chains, and the external friction between the macroscopic yarns and fibers. At present, the flexible fabric protective equipment for large tanks is mainly non-woven fabrics, but non-woven fabrics themselves have a high density, poor energy absorption performance, large thickness, and are difficult to lay, which cannot meet the application requirements of protective equipment for large tanks. Summary of the invention

[0004] The embodiment of the present application provides a thin and flexible fabric protective equipment for large tanks, and improves its impact performance by designing the boundary conditions and organizational structure of the fabric, thereby meeting the transportation needs of large tanks.

[0005] In order to achieve the above object, the technical solution of the embodiment of the present invention is:

[0006] In a first aspect, an embodiment of the present invention provides a thin and flexible fabric protective equipment for a large tank, wherein the key protective layer of the protective equipment is a polypropylene plain woven fabric made of cross-shaped fibers; wherein the preparation parameters of the fabric are determined by the following steps:

[0007] Using polypropylene as raw material, through multi-parameter control of the spinneret hole type selection, pump supply and winding speed of the spinning machine, the prepared fiber is post-drawn and doubling by using the drafting equipment to prepare multifilament yarns with different mechanical properties and different cross-sectional shapes;

[0008] Using the prepared yarns with different cross-sectional shapes, fabrics with different organizational structures are obtained through plain, twill and satin weaving processes;

[0009] Using the preset finite element analysis software, the impact response characteristics of the prepared fabrics with different structures were simulated by finite element simulation, and the influence of the mechanical properties of the yarn, the surface friction coefficient and the fabric structure on the impact energy loss performance of the fabric were analyzed; the surface friction coefficient of the yarn was controlled by adjusting the twist and cross-sectional shape of the yarn; the mechanical properties and surface friction coefficient of the yarn were measured by a single yarn strength tester and a yarn friction coefficient tester;

[0010] According to the fabrics with different organizational structures, a falling ball impact experiment with the same parameters as the finite element simulation was designed to verify the accuracy of the finite element analysis results;

[0011] Based on the results of finite element simulation and falling ball impact test, the impact resistance of fabrics made of different yarn cross-sectional shapes and fabric structures was evaluated;

[0012] The yarn cross-sectional shape and fabric structure of the fabric with the highest impact resistance are used as preparation parameters for fabrics used to make protective equipment.

[0013] In some possible implementations, a finite element simulation is performed on the impact response characteristics of fabrics with different tissue structures using a preset finite element analysis software, including:

[0014] The yarn centerline equation is determined by the yarn cross-sectional shape and the yarn path, the yarn centerline is drawn according to the centerline equation, and then a single yarn model is obtained by scanning the yarn cross-sectional shape along the yarn centerline;

[0015] The yarns are arrayed according to a single yarn model to obtain a three-dimensional model of the fabric;

[0016] According to the anisotropy of the fiber material of the yarn, the elastic modulus, shear modulus and stiffness matrix of the yarn fiber in the axial and radial directions are determined, and the constitutive model of the fiber material is established; the constitutive model includes an elastic-plastic model and a failure model;

[0017] Finite element analysis pre-processing includes: importing the three-dimensional model of the fabric into the preset finite element analysis software; meshing the three-dimensional model of the fabric based on the constitutive model of the fiber material; setting the initial velocity, size and position of the impact object, as well as the boundary conditions of the fabric; defining the contact properties and setting the contact relationship between the impact object and the fabric;

[0018] Conduct finite element simulation, including: using the explicit dynamics solver of the finite element analysis software to simulate the response characteristics of the fabric when it is impacted; observe and record the displacement deformation, velocity change, energy absorption and loss parameters of the fabric during the impact process; analyze the influence of different tissue structures on the impact resistance of the fabric, including the degree of fabric deformation, stress wave propagation form, etc.

[0019] In some possible implementations, the cross-sectional shapes of the yarn include circular, trilobal, and cross-shaped; yarns with different cross-sectional shapes are prepared by adjusting the spinneret hole type of the spinning machine.

[0020] In some possible implementations, the preparation parameters also include the number of fabric layers; and a falling ball impact test is performed by adjusting the number of fabric layers to optimize the energy absorption performance and impact resistance of the fabric.

[0021] One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages:

[0022] In the embodiment of the present invention, the protective equipment uses a polypropylene plain woven fabric made of cross-shaped fibers. Through the design of fabric preparation parameters, the protective equipment made of such fibers exhibits better impact resistance than traditional round fiber plain woven fabrics when impacted, and is light, thin and compact. It can significantly improve the safety of large tanks during transportation, reduce deformation or damage caused by impact, and improve transportation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention, the accompanying drawings required for use in the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying any creative work.

[0024] Figure 1 A schematic diagram of a flexible fabric for a thin and flexible fabric protective equipment for a large tank provided for the implementation of the present invention;

[0025] Figure 2a is a schematic diagram of the yarn cross section of a circular fiber;

[0026] Figure 2b is a schematic diagram of the yarn cross section of a trilobal fiber;

[0027] Figure 2c Schematic diagram of the cross-sectional view of the yarn of the cross-shaped fiber;

[0028] Figure 3a It is a schematic diagram of the structure of plain fabric;

[0029] Figure 3b It is a schematic diagram of the twill fabric structure;

[0030] Figure 3c is a schematic diagram of the structure of satin fabric;

[0031] Figure 4a It is a schematic diagram of the basic unit of yarn and weft yarn in plain weave fabric;

[0032] Figure 4b The figure is a schematic diagram of the plain fabric yarn interlacing form and the equation for determining the yarn centerline path;

[0033] Figure 5 The figure is a schematic diagram of the interlacing form of twill fabric yarns and the equation for determining the path of the yarn centerline;

[0034] Figure 6 The diagram is a schematic diagram of the yarn interlacing form of satin fabric and the equation for determining the path of the yarn centerline;

[0035] Figure 7 Schematic diagram of the boundary of the maximum stress criterion and the maximum strain criterion in the stress space in an embodiment of the present invention;

[0036] Figure 8 Schematic diagram of stress propagation after a plain fabric is impacted in an embodiment of the present invention;

[0037] Fig. 9 Schematic diagram of displacement-time curve of fabric in impact direction under different friction coefficients of yarn;

[0038] Fig.10 It is a schematic diagram of the speed-time curve of the fabric under different friction coefficients of the yarn;

[0039] Fig.11a It is a schematic diagram of the fabric displacement deformation-time curve;

[0040] Fig.11b It is a schematic diagram of the impactor velocity-time curve;

[0041] Fig.12 It is a schematic diagram of the energy absorption curve of various factors of fabrics with different organizational structures over time;

[0042] Fig.13 is a schematic diagram of a fabric fixing platform;

[0043] Fig.14 Schematic diagram of displacement-time curves of yarn woven fabrics with different friction coefficients when impacted in an embodiment of the present invention;

[0044] Fig.15a This is the impact test image of twill fabric;

[0045] Fig.15b This is the impact test image of the satin fabric;

[0046] Fig.16 Schematic diagram of the displacement curve of three double-layer fabrics with different organizational structures when subjected to impact. DETAILED DESCRIPTION

[0047] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0048] In the relevant description of this embodiment, the terms "including, containing, having" and the like are open terms and are generally understood to include but not be limited to; the term "at least one" is generally understood to mean one or more, where "plurality" refers to two or more; the term "at least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items, for example, "at least one of a, b or c", or "at least one of a, b and c", can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively; the symbol "A / B" is used to describe the selection relationship of associated objects, generally indicating an "or" relationship before and after.

[0049] In the following description of the present embodiment, the terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0050] Those skilled in the art should understand that in the following description of the embodiments of the present application, the order of serial numbers does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0051] Those skilled in the art will appreciate that the numerical ranges in the embodiments of the present application are to be construed as also specifically disclosing each intermediate value between the upper and lower limits of the scope. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the range is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded in the scope.

[0052] Unless otherwise specified, the technical / scientific terms used herein have the same meanings as those generally understood by those skilled in the art to which this application belongs. Although this application only describes preferred methods and materials, any methods and materials similar or equivalent to these may also be used in the implementation or testing of this application. All documents mentioned in this specification are incorporated by reference to disclose and describe methods and / or materials related to the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0053] In order to illustrate the technical solution of the present invention, specific embodiments are provided below for illustration.

[0054] With the rapid development of the aerospace industry, the number of rocket launch missions has increased significantly, which has put forward higher requirements for the transportation safety of large tanks. During the transportation of rockets, especially when transported by rail, they may encounter natural hazards such as falling rocks, which pose a serious threat to the tanks and their internal precision instruments. Due to the limitation of the size of railway culverts, traditional metal protective equipment cannot meet the transportation needs of large-sized tanks due to its large thickness and high weight. Therefore, there is an urgent need for a new type of lightweight and compact protective equipment to ensure the safety of large tanks during transportation.

[0055] Fabric protective equipment has gradually attracted attention due to its unique performance. When impacted, the fabric can effectively reduce the longitudinal penetration of impact energy based on its viscoelastic deformation, internal friction between microscopic molecular chains, and external friction between macroscopic yarns and fibers. Currently, non-woven fabrics are the main type of flexible fabric protective equipment for large tanks. However, non-woven fabrics themselves have a high density, poor energy absorption performance, large thickness, and are difficult to lay, which cannot meet the application requirements of protective equipment for large tanks.

[0056] Based on this, an embodiment of the present invention provides a thin and flexible fabric protective equipment for large tanks. By designing the boundary conditions and organizational structure of the fabric, its effect on impact performance is improved, which can meet the transportation needs of large tanks. Figure 1 A schematic diagram of a flexible fabric for a thin and flexible fabric protective equipment for a large tank provided for the implementation of the present invention, wherein the key protective layer of the thin and flexible fabric protective equipment for a large tank is as follows Figure 1 The cross-shaped fibers shown are made from a polypropylene plain woven fabric. Figure 1 In the figure, a is a front view of the fabric under a microscope. b is a cross-sectional view of the fibers of the fabric under a microscope.

[0057] In some embodiments, the preparation parameters of the fabric are determined by the following steps:

[0058] S11, using polypropylene as raw material, through multi-parameter control of spinneret hole type selection, pump supply and winding speed of the melt spinning machine, post-drafting and doubling the prepared fibers by using a drafting device, to prepare multifilament yarns with different mechanical properties and different cross-sectional shapes;

[0059] It is understandable that the mechanical properties of multifilament yarn, as the basic unit in the fabric system, greatly affect the overall impact resistance of the fabric. When the fabric is impacted, the main failure form is the tensile breakage of the yarn. Most of the kinetic energy of the impactor is converted into strain energy dissipated by the elongation of the yarn, including the elastic strain and plastic strain of the yarn. The energy absorbed during the elongation of the yarn can be expressed by the following formula:

[0060]

[0061] Among them, E tensi l e is the total energy absorbed by the yarn tensile deformation, ε max is the ultimate strain of the yarn, and σ(ε) is the stress-strain relationship of the yarn during the stretching process.

[0062] The amount of energy absorbed during yarn stretching is affected by many factors, including the ultimate strain rate of the yarn itself and the tensile strength at different strain rates. Polypropylene material slices pass through the spinneret holes in a high-temperature molten state and are cooled to form primary fibers. The fiber polymer chains are in a disordered and low-orientation state. At this time, the primary fiber has a high elongation and a low tensile strength, and has no use value. After stretching, the molecular chain is oriented in the axial direction, and the fiber will have better mechanical properties. The fiber will obtain different mechanical properties after being stretched at different ratios. With the increase of the stretching ratio, the orientation of the fiber's macromolecular chain increases, the elastic modulus of the fiber in its axial direction also increases, and the elongation at break decreases. This method can obtain yarns with the same linear density, the same cross-sectional size, but different elastic-plastic modulus and elongation at break. Primary fibers of different linear densities can be obtained by different process parameters. Its process parameters can be expressed by the following formula:

[0063]

[0064] Among them, N t is the linear density of the monofilament, c is the extrusion volume per unit number of turns of the metering pump, v pump is the metering pump speed, ρ is the melt density of the fiber material, v win d is the final winding speed, and f is the number of spinneret holes.

[0065] In some embodiments, the cross-sectional shapes of the yarn include circular, trilobal and cross-shaped; yarns with different cross-sectional shapes are prepared by adjusting the spinneret hole type of the spinning machine.

[0066] In the embodiment of the present invention, yarns with different cross-sectional shapes and mechanical properties can be prepared using polypropylene as the raw material by regulating multiple parameters such as the spinneret hole type selection, pump supply, winding speed, and draft ratio of the spinning machine.

[0067] By using spinnerets with different hole shapes, yarns with different cross-sectional shapes can be produced. For example, Figure 2a to Figure 2c Fibers with different cross-sectional shapes. Figure 2a is a schematic diagram of the yarn cross section of a circular fiber. Figure 2b is a schematic diagram of the yarn cross section of a trilobal fiber. Figure 2c Schematic diagram of the cross-section of the yarn of cross-shaped fibers.

[0068] S12, using the prepared yarns with different cross-sectional shapes and mechanical properties to obtain fabrics corresponding to different tissue structures through plain, twill and satin weaving processes;

[0069] It is understandable that fabrics with different structures have different response characteristics when receiving impact, and the contact area of ​​the yarns in the fabrics is also different. Therefore, when determining the fabric preparation parameters, the embodiment of the present invention prepares fabrics with different structures and analyzes the impact resistance of the fabrics, thereby determining the fabric structure suitable for the thin and flexible fabric protective equipment for large tanks.

[0070] For example, Figure 3a to Figure 3c They are schematic diagrams of the microscopic surface of fabrics with different organizational structures. Figure 3a Schematic diagram of plain weave fabric. Figure 3b Schematic diagram of twill fabric. Figure 3c Schematic diagram of satin fabric.

[0071] S13, using a preset finite element analysis software, finite element simulation is performed on the impact response characteristics of the prepared fabrics with different tissue structures, and the influence of the yarn microscopic properties, the surface friction coefficient of the yarn, and the fabric structure on the fabric impact energy loss performance is analyzed; wherein the surface friction coefficient of the yarn is controlled by adjusting the twist and cross-sectional shape of the yarn; the mechanical properties and surface friction coefficient of the yarn are measured by a single yarn strength tester and a yarn friction coefficient tester;

[0072] S14, verifying the accuracy of the finite element analysis results by simulating a falling ball impact experiment with the same parameters according to the fabric design of the prepared fabrics with different organizational structures and finite element simulation;

[0073] S15, evaluating the impact resistance of fabrics made of different yarn cross-sectional shapes and fabric structures based on the results of finite element simulation and falling ball impact test;

[0074] Specifically, in the above step S13, the finite element simulation process specifically includes:

[0075] S131, determining a yarn centerline equation according to the yarn cross-sectional shape and the yarn path, drawing the yarn centerline according to the centerline equation, and then obtaining a single yarn model by scanning the yarn cross-sectional shape along the yarn centerline;

[0076] S132, arraying the yarns according to the single yarn model to obtain a three-dimensional model of the fabric;

[0077] S133, according to the anisotropy of the fiber material of the yarn, determining the elastic modulus, shear modulus and stiffness matrix of the yarn fiber in the axial and radial directions, and establishing a constitutive model of the fiber material; the constitutive model includes an elastic-plastic model and a failure model;

[0078] S134, finite element analysis pre-processing, including: importing the three-dimensional model of the fabric into the preset finite element analysis software; meshing the three-dimensional model of the fabric based on the constitutive model of the fiber material; setting the initial velocity, size and position of the impact object and boundary conditions; defining contact properties and setting the contact relationship between the impact object and the fabric;

[0079] S135, performing finite element simulation, including: using the explicit dynamics solver of the finite element analysis software to simulate the response characteristics of the fabric when it is impacted; observing and recording the displacement deformation, velocity change, energy absorption and loss parameters of the fabric during the impact process; analyzing the influence of different mechanical properties and organizational structures on the impact resistance of the fabric, including the size of the fabric deformation and the form of stress wave propagation.

[0080] Specifically, when conducting a finite element model of the impact resistance of a fabric, a three-dimensional model of the fabric needs to be established first. The above-mentioned preset finite element software can be any existing three-dimensional simulation software, such as SolidWorks, Rhino, etc.

[0081] First, in order to facilitate the establishment of the model and the finite element analysis, appropriate idealized assumptions can be made for the yarn and fabric structure. These include: assuming that the cross-sectional shape of a single yarn in the fabric is the same everywhere, ignoring the changes in the cross-sectional shape of the yarn caused by extrusion and tension at specific nodes; the yarns in the fabric are usually in close contact, but in the process of model establishment, contact and interference problems will cause the warp and weft yarns to combine at the intersection to form a cross-shaped fixed node, while ignoring the friction movement between the yarns, resulting in simulation distortion, so tiny gaps are retained between the warp and weft yarns during the modeling process; in the process of finite element analysis mesh division, the smallest size component should also meet the requirement of at least four layers of mesh in different directions. Limited by computer calculation efficiency, the minimum scale of the fabric model is established at the yarn level, ignoring the gaps left in the fiber bundles inside the yarn and the friction movement between the fibers.

[0082] As an orthotropic, compressible, viscoelastic material, yarn is composed of multiple fiber bundles twisted or held together. Due to the tension and extrusion inside the fabric, the cross-section of the yarn is often not an ideal circle. Yarn cross-sectional parameters including cross-sectional shape and cross-sectional diameter are indispensable parameters for fabric model establishment. The cross-sectional shape of the yarn is affected by many factors, including twist, tension and spinning method.

[0083] When the yarn twist is high, the ratio of the major axis to the minor axis of the yarn will also be reduced accordingly. And the cross-sectional shape of the yarn after the yarn is woven into a sample cloth on a loom is usually an irregular ellipse. In the embodiment of the present invention, the cross-sectional shape of the yarn can be simplified during the process of establishing the fabric model, for example, it can be idealized into an ellipse with a major axis to minor axis ratio of 2:1.

[0084] After determining the cross-sectional shape of the yarn, it is further necessary to determine the yarn path. Methods for determining the yarn path include the usual broken line method and the segmented fitting method. The broken line method regards the yarn path as the splicing of multiple straight lines, and the discontinuity of its first-order derivative does not conform to the actual path of the yarn in the fabric. The warp and weft curve equations are established on the basis of the Peirce symbol (Peirce) theoretical model, the path of the yarn centerline in the coordinate system and the curvature change of the yarn are determined, and the yarn centerline equation is determined by curve fitting. At the same time, the yarn path curve is appropriately adjusted to minimize the finite element analysis distortion caused by the interference problem between the warp and weft yarns.

[0085] In the actual structure of a fabric, the yarns are divided into warp and weft, which have slight differences in cross-sectional size and thickness. However, considering the balance of efficiency and slight differences in performance, it can be assumed in the fabric model that all warp and weft yarns have exactly the same structural dimensions and material properties.

[0086] First, construct the curve equation of the yarn path in plain weave fabric. The yarn path in plain weave fabric has regularity. Taking a basic unit of weft yarn, it can be as follows Figure 4a As shown, Figure 4a Schematic diagram of the basic unit of yarn and weft yarn in the plain weave fabric in the embodiment of the present invention. Figure 4a As shown in the figure, the major axis and minor axis of the yarn are determined to be a 1 , b 1 The buckling wave height of the yarn is h j , the length between adjacent yarns is S j .

[0087] The establishment of the warp yarn path curve equation in the plain weave woven fabric includes: on the rectangular coordinate system, drawing the relative position relationship between the warp yarn and the weft yarn in the plain weave fabric, such as Figure 4b As shown. Among them, x represents the warp axis, y represents the weft axis, and z represents the normal direction perpendicular to the fabric.

[0088] Assume that the path curve equation of the warp yarn is expressed as Z = f(x), x∈(-S j , S j ), observe that the path equation f(x) is an even function symmetric about the center line Z axis, that is, it only needs to satisfy the following conditions: find the equation Z = f(x) at x∈(0, S j ) area. The warp yarn passes through points A, B, and C, and there are horizontal tangents at points B and C with a slope of 0. At point B, it is tangent to the minor semi-axis of the yarn cross section, and the radius of curvature of the yarn centerline at this point is a 1 .

[0089] The polynomial curve fitting method is adopted for the yarn path. If the degree is too high, the calculation cost will be increased, and if the degree is too low, it is difficult to ensure its accuracy. In the embodiment of the present invention, a fifth-order polynomial can be selected, and the center line trajectory of the yarn is assumed to be:

[0090] f(x)=α 5 x 5 +α 4 x 4 +α 3 x 3 +α 2 x 2 +α 1 x+α 0

[0091] a 1 to a 5 They can represent the long axes of five consecutive yarns respectively. The warp path curve equation can be expressed as:

[0092]

[0093] The weft yarn and the warp yarn have the same path curve equation. Based on similar ideas, the path curve equation of the weft yarn is expressed as:

[0094]

[0095] The main difference between the yarn path of twill and satin fabrics and that of plain fabrics is the float length in the yarn. Due to the existence of tension in the yarn, the float length BC segment and CD segment in the yarn can be regarded as straight lines.

[0096] For example, Figure 5 Schematic diagram of the yarn path of twill fabric. Figure 6 Schematic diagram of the yarn path of satin fabric.

[0097] The equation of the warp centerline of twill fabric is expressed as:

[0098]

[0099] The equation of the warp centerline of satin fabric is expressed as:

[0100]

[0101] Among them, a 0 、a 1… a 5 The coefficients are the same as those of the yarn centerline equation for plain fabrics.

[0102] After obtaining the yarn centerline equation, the yarn centerline can be drawn through a curve driven by the equation, and then a single yarn model can be obtained by scanning the yarn cross section along the yarn centerline. After obtaining the single yarn model in the warp and weft directions of the fabric, the yarns are arrayed and checked for interference positions, and the centerline curvature of the yarns at the interference positions is adjusted to construct fabric models corresponding to different tissue structures.

[0103] In some embodiments, in order to save computer computing power, only a 1 / 4 fabric model may be established, and the constructed 1 / 4 model can achieve the same simulation result as the full-size model through mirror symmetry.

[0104] In some embodiments, in the above step S133, the axial elastic modulus reflects the stress-strain relationship of the fiber when it is stretched or compressed in the axial direction. Through a standard tensile test, the ratio of the stress increase to the length change of the fiber in the axial direction can be measured to calculate the axial elastic modulus. The shear modulus represents the ability of the fiber to resist deformation when subjected to shear force. For anisotropic materials, it may be necessary to consider shear moduli in different directions, such as axial-radial shear modulus and radial-radial shear modulus.

[0105] The stiffness matrix is ​​a mathematical representation of the relationship between stress and strain in all directions of a material. For anisotropic materials, the stiffness matrix will contain multiple independent elastic constants that reflect the response of the material in different loading directions. Through experimental measurements and theoretical derivations, a stiffness matrix that reflects the anisotropic properties of yarn fibers can be constructed.

[0106] Considering the elastic deformation and plastic deformation stages that fiber materials may experience during stress, the elastoplastic model combines the elastic theory and plastic theory to describe the behavior of materials under different stress states. Due to the orientation of the macromolecular chains in textile fibers, the mechanical properties of the fibers in the axial and radial directions are completely different, but the material properties in the radial plane are isotropic. Therefore, by determining the elastic modulus, shear modulus, and stiffness matrix of the fiber in the axial and radial directions, a more realistic material model can be obtained.

[0107] In some embodiments, the elastic-plastic model of the fiber material can be expressed as:

[0108]

[0109] Where E is the elastic modulus in the axial direction, c is the strength of the yarn when it reaches 1% of the total deformation, l is the clamping length of the single yarn tensile strength tester, N t is the linear density of the yarn, ρ is the density of the fiber material, s is the elongation of the yarn when the total deformation reaches 1%, σ is the tensile stress, and ε is the tensile strain.

[0110] In some embodiments, the failure model for the fiber material includes a maximum stress failure criterion and a maximum strain failure criterion.

[0111] Among them, the maximum stress failure criterion is expressed as:

[0112]

[0113] τ 12 |<s LT

[0114] in, They represent the ultimate compressive stress and ultimate tensile stress of the material in its longitudinal direction, They represent the ultimate compressive stress and ultimate tensile stress of the material in its transverse direction, respectively, |τ 12 | represents the limiting shear stress in the material plane.

[0115] The maximum strain failure criterion is expressed as:

[0116]

[0117] γ 12 |<eLT

[0118] in, They represent the ultimate compressive strain and ultimate tensile strain of the material in its longitudinal direction, They represent the ultimate compressive strain and ultimate tensile strain of the material in its transverse direction, γ 12 | represents the limiting shear strain in the material plane.

[0119] The maximum strain failure criterion measures whether a material fails based on its strain size, but in common practical structural analysis, it is also converted into the failure boundary of the material in the stress space. The relationship between material stress and strain can be expressed as:

[0120]

[0121] There is also a stress-strain relationship in the transverse direction of the material, which can be obtained by further simplification:

[0122]

[0123] According to the above formula, the minimum boundary of the maximum stress failure criterion and the maximum strain failure criterion in the stress space can be obtained by Figure 7 express. Figure 7 Schematic diagram of the boundary of the maximum stress criterion and the maximum strain criterion in the stress space in the embodiment of the present invention. Figure 7 It can be found from the maximum stress failure criterion and the maximum strain failure criterion that when both ends of the material are subjected to positive loads, that is, tensile stress (shown as the position of the first quadrant in the figure), the maximum strain failure criterion is more relaxed than the maximum stress failure criterion, and the material can withstand greater tensile stress between the two axial directions. However, in reality, the material has already been damaged when it exceeds the solid line boundary of the first quadrant. On the contrary, Figure 7 In the fourth quadrant, that is, when the longitudinal stress is tensile and the transverse stress is compressive, the maximum strain failure criterion is more stringent than the maximum stress failure criterion.

[0124] In some embodiments, the forces on the yarn in the fabric can be idealized as being subjected to tensile forces in the transverse direction and compressive forces in the longitudinal direction. The stress space is the same as the stress form in the fourth quadrant. In this quadrant, the maximum strain failure criterion is more stringent than the maximum stress failure criterion. Therefore, the fabric material model in the embodiment of the present invention can adopt the maximum strain failure criterion.

[0125] The present invention can use ABAQUS finite element software to analyze the impact energy dissipation performance of fabrics. ABAQUS / Explicit, as an explicit analysis solver of ABAQUS finite element software, is a finite element product suitable for simulating transient dynamics. It can better solve complex contact problems, highly nonlinear problems, and material failure degradation problems in high-speed dynamic events.

[0126] In some embodiments, in the above step S134, the fabric model constructed above is imported into the finite element analysis software, and key parameters such as density, elastic modulus, Poisson's ratio, and yield strength of the material are input. These parameters will directly affect the accuracy of the simulation results. Considering the fiber direction and weaving method of the fabric, the orthogonality or anisotropy of the material is defined.

[0127] Specifically, in the ABAQUS-Part module, the finite element fabric model can use the 1 / 4 fabric model drawn above. In the simulation of the falling ball impact test, the fabric can be fixed in a square frame of, for example, 240mm*240mm, and a three-dimensional fabric model of size 120mm*120mm can be established. The impact object of the model can be a steel sphere with a radius of 20mm.

[0128] In the ABAQUS-Property module, considering the orthotropic properties of fiber materials, it is necessary to determine the elastic modulus, shear modulus and Poisson's ratio in three directions of the yarn. When assigning materials to the yarn, it is necessary to determine the main direction of the material. Select Part-Orientation to determine the main direction of the yarn parts and add material properties.

[0129] In the finite element simulation, the impactor can be a spherical impactor made of structural steel. Since the modulus of the structural steel itself is much higher than the modulus of the fiber material in three directions, the deformation during the impact process can be ignored. Therefore, it is reasonable to regard the impactor as a rigid object and specify the center of mass of the impactor as the reference point. Its own mesh unit will not participate in the finite element solution calculation process. The fabric finite element model adopts the maximum strain failure criterion.

[0130] In the ABAQUS-Interaction module, the contact behavior is set to general contact. The yarn friction coefficient measured by the fiber friction coefficient tester is set in the tangent direction, the friction formula adopts penalty, hard contact is adopted in the normal direction, and separation after contact is allowed.

[0131] In the ABAQUS-Load module, the initial velocity perpendicular to the fabric plane is first applied to the spherical impactor, and its displacement in the plane direction is constrained to 0. Then the fabric boundary is constrained.

[0132] In the ABAQUS-Mesh module, the impact object and the yarn are meshed separately. The linear reduced integration hexahedral solid element (C3D8R) is used for both the impact object and the yarn components. Its advantages are fast calculation, less shear self-locking phenomenon under bending load, and more accurate displacement solution. However, the element type (C3D8R) has only one integration point at the center of the element, and hourglass control is required. The three edges of the impact object are meshed separately, and its global size is controlled to 2.8mm. Similarly, the yarn is meshed to ensure that the number of mesh layers on the major axis and minor axis of the yarn is not less than four, and the global size can be controlled to 0.7mm.

[0133] In the ABAQUS-Visualization module, the propagation law of stress in the fabric, the displacement of the fabric in the impact direction, and the proportion of energy absorption of each factor in the fabric absorbing the kinetic energy of the impact object are analyzed, and an analysis process is proposed to determine how different variables affect the impact energy dissipation performance of the fabric. The energy analysis method of the fabric that absorbs the kinetic energy of the impact object is studied. Except for the kinetic energy generated by the velocity given to the spherical impact object in the initial step, there is no external energy input during the entire impact process, that is, the entire system maintains energy conservation, and the kinetic energy during the impact process is converted into multiple parts absorbed by the fabric, which can be expressed by the following formula:

[0134] E I +E v +E FD +E KE -E W =E Total = constant

[0135] Among them, E I is the internal energy, E v is the system damping viscous dissipated energy, E FD is the friction dissipation energy, E KE is kinetic energy, E W is the energy applied by the external load. The sum of these energies is the difference in the kinetic energy change of the spherical impactor, which can be expressed by the following formula:

[0136]

[0137] Among them, v initial is the initial velocity of the impactor, v end is the residual velocity of the impactor at the end of the impact process. In the numerical model, E Total Must be constant, but generally has an error of less than 1%.

[0138] The energy conversion during the entire impact process is output through ODB-History Output, where E lRepresented by ALLIE, it can be further converted to:

[0139] ALLIE=ALLSE+ALLPD+ALLCD+ALLAE

[0140] Among them, ALLSE represents the strain energy stored in the system, ALLPD represents the energy absorbed by the plastic strain of the system, ALLCD represents the viscoelastic dissipated energy, and ALLAE represents the pseudo strain energy.

[0141] Since C3D8R units are used for fabric meshing, the single integration point of the C3D8R unit will cause deformation that exists mathematically but will not be physically realized during the impact process, and the pseudo strain energy must be kept less than 10% of the total energy of the system. In the embodiment of the present invention, the fiber material model is defined as an elastic-plastic material and due to the high flexibility of the entire fabric, the vibration and thermal energy phenomena caused by the system and material damping during the impact process are not considered. By studying the energy conversion during the impact process, it is possible to analyze how the fabric converts and absorbs the kinetic energy of the impact object during the impact process. In subsequent experiments, the energy conversion process is observed by changing the parameter indicators of the yarn and fabric, and then the optimization law of the fabric's impact resistance is obtained.

[0142] In the above step S135, firstly, a finite element simulation is performed on the impact resistance of fabrics woven from yarns with different mechanical properties.

[0143] The fabric model and impact finite element model constructed above are used to simulate the impact response characteristics of the fabric under different impact velocities.

[0144] For example, if the rockfall height is 20m and 80m respectively, that is, the impactor speed is 20m / s and 40m / s respectively, and the impactor is a steel ball with a radius of 20mm, the initial kinetic energy of the corresponding spherical impactor, that is, the input energy of the entire system, is 12.9J and 51.6J. When the fabric is impacted, the propagation law of stress in the fabric can be seen in Figure 8 As shown, Figure 8 Schematic diagram of stress propagation after a plain fabric is impacted in an embodiment of the present invention. Figure 8 Parts a to d are schematic diagrams of stress cloud diagrams at different times.

[0145] According to the stress propagation form when the fabric is impacted, the yarn in direct contact with the impact object bears the greatest stress and deformation. The maximum stress occurs at the moment when the speed of the impact object decreases to 0m / s, the maximum stress on the yarn is 87.7Mpa, and the maximum deformation reaches 0.453 after the impact. The maximum deformation of the model during the impact process is 0.453, which does not exceed the strain limit of the material itself of 0.79.

[0146] When the fabric is impacted, the maximum stress value occurs in the center area where the fabric is in direct contact with the impactor, and the maximum strain value also appears in the same position, mainly plastic deformation. Even when the spherical impactor leaves the fabric at a reverse speed after the speed drops to 0m / s, the deformation of the fabric does not recover. Both the maximum stress value and the maximum strain value occur in the center area where the fabric is in direct contact with the impactor, indicating that this position is the most likely location for the fabric to fail.

[0147] It can be understood that the displacement distance of the fabric in the impact direction is also an important representation of its impact resistance. The smaller the displacement distance in the impact direction means that the impact resistance of the flexible fabric protective equipment is better, which reduces the force transmission from the fabric to the protected tank body, thereby avoiding deformation of the protected tank body.

[0148] Afterwards, the effect of yarn friction coefficient on the impact resistance of fabrics was analyzed.

[0149] Specifically, using the same finite element model and fiber material, different surface friction coefficients are set for the yarn and the results of the finite element simulation are comprehensively analyzed. For example, the yarn friction coefficients are set to 0.12, 0.25, 0.40, 0.55, and 0.70 respectively. The contact mode in the simulation can refer to the general contact defined in the above-mentioned ABAQUS-Interaction module. The impact speed can be set to, for example, 20m / s, and the analysis step, i.e., the impact time history, is also set to 8ms for finite element simulation.

[0150] Through finite element simulation, it can be found that the impact response characteristics of the fabric change due to the change in friction coefficient. And the displacement-time curve of the fabric in the impact direction and the impact object velocity change curve with time can be obtained respectively. Fig. 9 and Fig.10 As shown. Among them, Fig. 9 Schematic diagram of the displacement-time curve of the fabric in the impact direction under different friction coefficients of the yarn. Fig.10 Schematic diagram of the speed-time curve of fabric under different friction coefficients of yarn. Fig. 9 It can be seen that the friction coefficient of the yarn has a direct effect on the displacement deformation of the fabric in the impact direction. As the friction coefficient between the yarns increases, the displacement deformation of the fabric in the impact direction gradually decreases, and the displacement deformation is more relevant when the friction coefficient is between 0.12 and 0.40. However, when the friction coefficient u exceeds 0.40, the effect of the increase in the friction coefficient on the displacement deformation of the fabric gradually decreases.

[0151] See also Fig.10As shown in the figure, compared with the displacement deformation of the fabric in the impact direction, different yarn friction coefficients have no effect on the residual reverse velocity of the impactor. However, when the impactor contacts the fabric with a larger surface friction coefficient, the velocity decreases more obviously, and the velocity drops to 0 m / s faster. However, after the elastic deformation of the fabric recovers, the reverse velocity obtained by the impactor is the same, which is 7.2 m / s, and does not change due to the change in the yarn friction coefficient.

[0152] It is understandable that the friction energy absorption of fabrics caused by different friction coefficients has the same trend as the displacement deformation of fabrics in the impact direction. They are all more sensitive when the friction coefficient is between 0.12 and 0.40. The reason for the increase in friction energy absorption is that the tangential movement of the yarn during the impact process requires a greater force due to the increase in the friction coefficient. As the friction coefficient increases, the increase in friction energy absorption gradually becomes gentle.

[0153] Afterwards, in the above step S135, the impact resistance of fabrics with different structures can be further simulated by finite element method. Fabrics with different structures have different response characteristics when subjected to impact, and the contact area of ​​yarns in the fabrics is also inconsistent. The boundary condition definition of the fabric also has a great influence on the impact response of the fabric, and the propagation form of stress waves in fabrics with different boundary conditions is also different.

[0154] The present invention adopts three kinds of weave structures, namely plain weave, twill weave and satin weave, to analyze and verify the response characteristics of fabrics with different weave structures when subjected to impact.

[0155] Different from plain fabrics, twill and satin fabrics do not have mirror symmetry, so 1 / 4 models cannot be used for finite element analysis. Therefore, full-scale models are established for satin and twill fabrics. The three fabric models of plain, twill and satin adopt the same yarn section coefficient, buckling wave height and distance between adjacent yarns.

[0156] For example, the displacement of the fabric in the impact direction and the velocity of the impact object over time are shown as follows: Fig.11a and 11b As shown. Among them, Fig.11a is a schematic diagram of the fabric displacement deformation-time curve. Fig.11b Schematic diagram of the impactor velocity-time curve.

[0157] See also Fig.11a and Fig.11b As shown in the figure, when fabrics with different organizational structures are impacted, the displacement deformation of plain fabric is the largest, which is 47.5mm. The displacement deformation of twill fabric and satin fabric in the impact direction are 42.9mm and 41.4mm respectively. Fig.11aIt can be found that the plain fabric has the largest rebound distance in the z direction after reaching the maximum displacement deformation, the rebound distance of the twill fabric is in the middle, and the rebound distance of the satin fabric in the impact direction is the smallest. The same phenomenon exists in the impact object speed, that is, the impact object has a higher rebound speed when impacting the plain fabric, reaching 7.1m / s, and the rebound speed when impacting the twill and satin fabrics is 5.6m / s and 3.1m / s respectively. The fabric rebound distance and the reverse speed of the impact object depend on the elastic strain energy absorption of the fabric during the impact process.

[0158] For example, Fig.12 It is a schematic diagram of the energy absorption curve of various factors of fabrics with different organizational structures over time; Fig.12 In the figure, a is the elastic strain energy absorption-time curve, b is the plastic strain energy absorption-time curve, c is the fabric kinetic energy-time curve, and d is the friction energy absorption-time curve. Fig.12 As shown in the figure, the velocity of the impactor can be found to have a significantly different velocity attenuation trend when impacting fabrics of different structures. The velocity attenuation is faster when impacting satin fabric, followed by twill fabric and plain fabric. From the perspective of energy conversion, it can also be found that during the impact process, the elastic strain energy absorption, plastic strain energy absorption and fabric kinetic energy of satin fabric all reach the peak value first among the three fabrics with different structures. This mainly depends on the degree of curling of the yarn in the fabric. The yarns in fabrics with different structures have different degrees of curling. The curling degree of the yarn in plain fabric is the highest, while the curling degree of the yarn in satin fabric is the lowest. Fabrics of different structures have the same thickness in the z direction, that is, the buckling wave height of the yarn is the same. It can be seen that among fabrics of the same length, the distance between the center lines of the yarns of plain fabric is the longest, while the distance between the center lines of the yarns of twill fabric and satin fabric is smaller than that of plain fabric.

[0159] When the fabric is impacted, the yarn from the impact center to the edge area will present a V-shape to transfer stress. In plain fabric, since the main yarn is longer and has a higher degree of curling, the main yarn needs to undergo a greater deformation when presenting a V-shape, and in the process of deformation, it drives more yarn movement. Therefore, during the impact process, the time when the conversion and absorption of various types of energy of plain fabric reaches the peak is significantly later than that of twill fabric and satin fabric, but the elastic strain energy absorption is higher than the latter two. The main yarn of satin fabric has the shortest yarn centerline length, presents a V-shape earlier during the impact process, deforms earlier, reaches the yield strength of the fiber material earlier, and undergoes plastic deformation. And due to the low degree of curling, the driving effect on the adjacent yarn is weak, so its main energy absorption mode is plastic strain energy absorption. During the impact process, the main yarn in the plain fabric undergoes more tangential movement before deforming into a V-shape and drives more yarns to participate in the entire impact response, so more energy is taken away by friction in the plain fabric, while the friction energy absorption of twill fabric and satin fabric is lower than that of plain fabric. From the analysis of the impact process, the performance of satin fabric is the best during low-speed impact. The displacement of the fabric in the impact direction and the rebound speed of the impact object are both the lowest values, which shows that when facing low-speed impact, the energy absorption performance is better when the yarn in the fabric is relatively straight.

[0160] In addition, under the condition of higher speed impact, satin fabric still has a faster response speed, and breaks first in the impact process. The elastic strain energy absorption and plastic strain energy absorption of satin fabric also reach the peak earlier, which is consistent with the performance when the impact speed is 20m / s. Since the curling degree of yarn in twill and satin fabrics is lower, their overall elastic strain energy absorption and plastic strain energy absorption are also lower than those of plain fabrics. The main reason is that for fabrics of the same size, the yarn centerline distance in plain fabrics is longer, and a single yarn absorbs more energy than the yarn in twill and satin fabrics.

[0161] On the other hand, the analysis of the impact resistance of fabrics under different boundary conditions can also be determined by the above finite element analysis method. Through finite element simulation of different boundary conditions, it can be determined that the fabric with four fixed sides has less displacement deformation when resisting impact, and the impact resistance of the fabric with four fixed sides is completely better than that of the fabrics with the other two fixed boundary conditions. The energy absorption performance is better under different speed impacts when the four fixed sides are fixed.

[0162] In the embodiment of the present invention, the drop ball impact test platform is mainly composed of a drop ball impact tester, a fabric fixing platform and a high-speed camera. The fabric fixing platform can be a self-designed and processed steel fixing platform, the end face size of the fixed frame is 320mmX320mm, and the fixed fabric size boundary is 240mmX240mm, which is consistent with the fabric size in the finite element analysis. Four equidistant bolts are used on one side to ensure the tightness of the upper and lower end faces, so that the fabric can be completely fixed and the drop ball impact position is ensured to be in the center of the fixed fabric. The fabric fixing platform can be as follows Fig.13 shown.

[0163] Firstly, impact tests were carried out on fabrics with yarns of different friction coefficients.

[0164] The control of yarn friction coefficient is mainly through the following methods to twist the yarn to make the yarn surface smoother, thereby reducing the friction coefficient of the yarn surface. For yarns with different fiber cross-sectional shapes, their friction coefficient can be changed by twisting. For example, the friction coefficient can be expressed as:

[0165]

[0166] Among them, f 0 、f 1 is the tension on both ends of the fiber, μ is the friction coefficient between the fiber and the friction roller surface, θ is the contact angle between the fiber and the friction roller, in radians, e is a natural constant, and f 1 is the tension f 0 and hook load difference.

[0167] For example, Fig.14 Schematic diagram of displacement-time curves of yarn woven fabrics with different friction coefficients in embodiments of the present invention when subjected to impact. Fig.14 It can be seen that through the falling ball impact test, it can be concluded that the different friction coefficients of the yarns in the fabric have an effect on the displacement of the fabric in the impact direction, and the trend is the same as the finite element simulation results: the greater the friction coefficient of the yarn itself, the smaller the displacement deformation of the fabric in the impact direction. However, unlike the finite element simulation, the different friction coefficients of the yarns in the impact test have a more obvious effect on the displacement results of the fabric, and the displacement deformation of the untwisted yarn fabric is also reduced relative to the twisted yarn fabric. The main reason is that the finite element model is based on the modeling of the yarn scale, ignoring the effect of the friction between the fiber bundles inside the yarn on the impact displacement. The increase in the friction coefficient of the yarn is conducive to enhancing the impact resistance of the fabric, and the performance of the fabric woven with untwisted yarn is also better than that of the fabric woven with twisted yarn.

[0168] Afterwards, a drop ball impact test is performed on fabrics of different structures, and a drop ball impact test can be performed on single-layer fabrics and multi-layer (eg, double-layer) fabrics.

[0169] For example, Fig.15a This is the impact test image of twill fabric. Fig.15b These are images of impact tests on satin fabric. Fig.16 Schematic diagram of the displacement-time curve of fabrics with different organizational structures when subjected to impact.

[0170] From the results of the impact test, it can be seen that when facing a low-speed impact in which the fabric is not penetrated, the maximum displacement of twill and satin fabrics is smaller than that of plain fabric, which is consistent with the trend of the results of the finite element analysis. In addition, the recovery amount of plain and twill fabrics after the maximum displacement deformation is also greater than that of satin fabric. From the finite element analysis, it is known that this phenomenon occurs because the main yarn of the satin fabric undergoes plastic strain earlier after the impact, resulting in a smaller rebound distance.

[0171] It is understandable that when a fabric is impacted, the number of fabric layers and the displacement distance in the impact direction are nonlinear, and when single-layer fabrics with different organizational structures cooperate with each other, the overall impact resistance of the fabric will also be different. Impact tests of three double-layer fabrics, plain-plain, plain-twill, and plain-satin, were designed, and the experimental results were analyzed to obtain the influence of the cooperation of single-layer fabrics with different organizational structures on the overall impact resistance. The speed and mass of the impact object applied in the impact test did not change, which was consistent with the loading conditions of the impact test of single-layer fabrics with different organizational structures. The double-layer fabrics are not cured and connected, and the natural bonding treatment method may cause the double-layer fabrics to slip at the fixed boundary. It is necessary to use double-sided tape on the upper end surface of the fabric fixing platform, and fully tighten the upper and lower end bolts to avoid deviations in the experimental results due to slippage. After the impact test on the double-layer fabric, there was no obvious wrinkle or colloid overflow at the fixed boundary of the fabric, indicating that the fabric boundary did not slip during the impact.

[0172] For example, taking double-layer fabric as an example, Fig.16The figure is a schematic diagram of the displacement curve of three double-layer fabrics with different organizational structures when they are impacted. By conducting a falling ball impact test on fabrics with different organizational structures, it can be determined that the displacement deformation of the double-layer fabric when it is impacted has decreased, but the decrease distance is not large. The displacement deformation of plain, twill and satin fabrics has decreased after the impact test with a layer of plain fabric. The time when the double-layer fabric reaches the maximum displacement has been advanced compared with the single-layer fabric. An obvious point of the double-layer fabric compared with the single-layer fabric is that its rebound distance is higher than that of the single-layer fabric. The rebound distance has a positive correlation with the elastic strain energy absorption of the fabric. It can be known that the proportion of elastic strain energy absorption to the total kinetic energy of the impact object of the double-layer fabric is higher than that of the single-layer fabric. Therefore, the displacement of the double-layer fabric in the impact direction when facing the impact has decreased compared with the single-layer fabric, and the response speed is faster, reaching the maximum displacement deformation earlier, and the elastic strain energy absorption ratio of the double-layer fabric is higher than that of the single-layer fabric.

[0173] S16, using the yarn cross-sectional shape and fabric structure of the fabric with the highest impact resistance as the preparation parameters of the fabric for making protective equipment.

[0174] In the embodiment of the present invention, according to the above finite element simulation and the corresponding drop ball impact test verification, the impact response characteristics of different fabrics can be analyzed respectively, and the microscopic yarn performance, yarn friction coefficient and woven fabric structure and other factors can be systematically studied to study the impact energy loss performance of the fabric, so that the yarn cross-sectional shape and fabric structure of the fabric with the highest impact resistance can be determined as the preparation parameters of the fabric for making the protective equipment. It is determined that the cross-shaped fiber plain weave fabric has better impact resistance than the circular fiber plain weave fabric, and the circular fiber satin fabric has better impact resistance than the circular fiber plain weave and circular fiber twill fabrics. It can be obtained from the analysis and test results that when the fabric is fixed on the four sides, the impact resistance of the fabric can be best exerted. In this way, the cross-shaped plain weave fabric prepared by using the preparation parameters can be used as one of the alternatives for large tank protective equipment. It can effectively absorb and dissipate impact energy when it is impacted, and it has the characteristics of being light, thin and compact, which can significantly improve the safety of large tanks during transportation, reduce deformation or damage caused by impact, and improve transportation efficiency.

[0175] In some embodiments, the above-mentioned preparation parameters may also include the number of fabric layers; by adjusting the number of fabric layers to perform finite element simulation and corresponding parameter drop ball impact tests, the energy absorption performance and impact resistance of the fabric may be further optimized.

[0176] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other. Each embodiment focuses on the differences from other embodiments.

[0177] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit the present application. Although the present application has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present application.

Claims

1. A thin and flexible fabric protective equipment for large tanks, characterized in that: The key protective layer of the protective equipment is made of a polypropylene plain woven fabric made of cross-shaped fibers; wherein the preparation parameters of the fabric are determined by the following steps: Using polypropylene as raw material, through multi-parameter control of the spinneret hole type selection, pump supply and winding speed of the melt spinning machine, the prepared fiber is post-drawn and doubling by using a drafting device to prepare multifilament yarns with different mechanical properties and different cross-sectional shapes; Using the prepared yarns with different cross-sectional shapes, fabrics with different organizational structures are obtained through plain, twill and satin weaving processes; Using the preset finite element analysis software, the impact response characteristics of the prepared fabrics with different structures were simulated by finite element simulation, and the surface friction coefficient of the shaped fiber yarn and the influence of the fabric structure on the fabric impact energy loss performance were analyzed; the surface friction coefficient of the yarn was controlled by adjusting the twist and cross-sectional shape of the yarn; the mechanical properties and surface friction coefficient of the yarn were measured by a single yarn strength tester and a yarn friction coefficient tester; According to the prepared fabrics with different organizational structures, a falling ball impact experiment with the same parameters as the finite element simulation is designed to verify the accuracy of the finite element analysis results; According to the results of the finite element simulation and the falling ball impact test, the impact resistance of fabrics prepared by fiber yarns with different cross-sectional shapes and fabric structures is evaluated; The yarn cross-sectional shape and fabric structure of the fabric with the highest impact resistance are used as preparation parameters for the fabric used to make the protective equipment.

2. The thin and flexible fabric protective equipment for large tanks according to claim 1 is characterized in that: The finite element analysis software is used to simulate the impact response characteristics of the fabrics with different tissue structures, including: Determine the yarn centerline equation by the yarn cross-sectional shape and the yarn path, draw the yarn centerline according to the centerline equation, and then obtain a single yarn model by scanning the yarn cross-sectional shape along the yarn centerline; The yarns are arrayed according to a single yarn model to obtain a three-dimensional model of the fabric; According to the anisotropy of the fiber material of the yarn, the elastic modulus, shear modulus and stiffness matrix of the yarn fiber in the axial and radial directions are determined, and a constitutive model of the fiber material is established; the constitutive model includes an elastic-plastic model and a failure model; Finite element analysis pre-processing includes: importing the three-dimensional model of the fabric into the preset finite element analysis software; meshing the three-dimensional model of the fabric based on the constitutive model of the fiber material; setting the initial velocity, size and position of the impact object, as well as the boundary conditions of the fabric; defining the contact properties and setting the contact relationship between the impact object and the fabric; Conduct finite element simulation, including: using the explicit dynamics solver of the finite element analysis software to simulate the response characteristics of the fabric when it is impacted; observe and record the displacement deformation, velocity change, energy absorption and loss parameters of the fabric during the impact process; analyze the influence of different tissue structures on the impact resistance of the fabric.

3. The thin and flexible fabric protective equipment for large tanks according to claim 2 is characterized in that: The cross-sectional shapes of the yarn include circular, trilobal and cross-shaped; yarns with different cross-sectional shapes are prepared by adjusting the spinneret hole type of the spinning machine.

4. The thin and flexible fabric protective equipment for large tanks according to claim 3 is characterized in that: The preparation parameters also include the number of fabric layers; by adjusting the number of fabric layers, finite element simulation and corresponding parameter drop ball impact test are performed to optimize the energy absorption performance and impact resistance of the fabric.

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