CN108681650A - A kind of warp-knitted spacer fabric composite material stress analysis method - Google Patents

Abstract

The invention discloses a kind of warp-knitted spacer fabric composite material stress analysis method, this method establishes the structural model of warp-knitted spacer fabric enhancing polyurethane enhancing composite material including the use of finite element software；The parameters of finite element model are set, and the parameter includes paraphysis parameter, warp-knitted spacer fabric enhancing compound polyurethane material structural parameters between the band yarn mode for being spaced sley bar, each point and band yarn number correspondence, space fabric；According to carrying out mesh generation the characteristics of physical model.The stress compression rate curve obtained through finite element analysis by method provided by the present application is compared with compression test curve, although there are a small amount of deviations for the stress compression rate curve and trial curve of COMPOSITE FINITE ELEMENT simulation, but finite element modelling result provided by the present application still can reflect the variation tendency of sample compression performance well, and the theoretical foundation of structure design can be provided for the application in Practical Project.

Description

A stress analysis method for warp-knitted spacer fabric composites

technical field

The invention relates to the technical field of material performance analysis, in particular to a stress analysis method for warp-knitted spacer fabric composite materials.

Background technique

The warp-knitted spacer fabric has excellent compression resistance, impact resistance and high production efficiency. The composite material using it as a reinforcement has good mechanical properties in the thickness direction, and can significantly improve the interlayer shear strength. When subjected to external loads, especially dynamic loads, there will be no delamination. Good structural integrity, impact resistance, and low production cost make warp-knitted spacer fabric-reinforced polyurethane composites promising as a new type of cushioning material.

However, in the prior art, due to the lack of theoretical guidance on the change trend of the compressive properties of warp-knitted spacer fabric-reinforced polyurethane composite materials, it is necessary to use real materials for repeated tests in the structural design of spacer fabric-reinforced polyurethane composite materials during the production process. This makes the cost of the manufacturer greatly increased.

Contents of the invention

The invention provides a stress analysis method for warp-knitted spacer fabric composite materials.

The present invention provides following scheme:

A stress analysis method for a warp-knitted spacer fabric composite material, comprising:

Using finite element software, the structural model of warp-knitted spacer fabric-reinforced polyurethane-reinforced composites was established;

The parameters of the finite element model are set, and the parameters include the yarn laying mode of the interval bar, the corresponding relationship between each point and the laying yarn number, the spacer fabric spacer parameters, and the warp-knitted spacer fabric reinforced polyurethane composite material structure parameters;

Carry out grid division according to the characteristics of the solid model;

Apply load to the meshed solid model and enter the post-processing function to generate the stress-strain curve of the warp-knitted spacer fabric reinforced polyurethane composite material.

Preferable: establish the structural model of the warp-knitted spacer fabric reinforced polyurethane reinforced composite material, including:

Select a minimum complete cycle structure unit as the representative body unit, the representative body unit is the fabric structure unit formed by two spacer bars in a complete lapping cycle and the polyurethane foam matrix contained, and carry out the selected representative body unit The finite element analysis establishes the structural model.

Preferably: a single spacer wire model is established according to the motion track of the spacer bar; the single spacer body model is mirrored and arrayed in turn to form a three-dimensional geometric model of the overall arrangement of the spacer wires of the two spacer bars;

Build warp-knitted spacer fabrics to reinforce the upper and lower surfaces of polyurethane composites;

Bond and assemble the established three-dimensional geometric model of the upper and lower surfaces and the overall arrangement of the spacer wires to obtain a solid model of the spacer fabric;

Create a polyurethane foam solid model of the same volume as the spacer fabric;

The structure model is obtained by assembling the spacer fabric solid model and the polyurethane foam solid model.

Preferably: the method for establishing a single spacer wire model includes: first establishing point coordinates A, B, C, and D. Then in the two x-z planes, use straight lines to connect points A, B and points C, D respectively; and in the y-z plane, select an intermediate point O, and use a smooth curve to connect points B, O and C; take point A as Make a circle on the x-y plane with the center of the circle and a radius of 0.1mm, and drag the circle along the space curve ABCD to generate a single spacer wire solid model.

Preferable: Carry out grid division according to the characteristics of the solid model; including:

Use the free mesh division in the finite element software for grid division; set the surface grid thickness, quality, and entity grid type parameters of the solid model, and use the grid generation tool to perform grid division on the solid model.

Preferable: apply loads to the meshed solid model, including:

Constrain one end of the solid model, and apply a compressive load to the other end; when compressing in the z direction on the upper surface of the solid model, set constraints on the degrees of freedom of all nodes on the lower surface of the solid model, that is, set each node The translational degrees of freedom in the x, y, and z directions are all zero, and the rotational degrees of freedom around the x, y, and z axes are all set to zero.

Preferable: apply a uniform load to the upper surface of the solid model; select the appropriate applied node force, uniform load and specified displacement.

Preferably: the load is applied in multiple load steps, and the compressive displacement load is applied in 12 load steps on the upper surface of the structural model, each step compressing 0.38mm.

According to the specific embodiments provided by the invention, the invention discloses the following technical effects:

Through the present invention, a method for stress analysis of warp-knitted spacer fabric composite materials can be realized. In one implementation, the method can include using finite element software to establish a structural model of warp-knitted spacer fabric-reinforced polyurethane-reinforced composite materials; the settings are limited The parameters of the meta-model, the parameters include the laying method of the spacer bar, the corresponding relationship between each point and the laying number, the spacer yarn parameters of the spacer fabric, and the structural parameters of the polyurethane composite material reinforced by the warp-knitted spacer fabric; according to the characteristics of the solid model Carrying out grid division; applying a load to the grid-divided solid model and entering the post-processing function to generate the stress-strain curve of the warp-knitted spacer fabric-reinforced polyurethane composite material. Comparing the stress-compression rate curve obtained by finite element analysis with the compression test curve through the method provided by this application, the compression stress-compression rate curve of the composite material simulated by the finite element method and the compression deformation curve obtained by the test are generally in good agreement. Although there is a small amount of deviation between the stress-compression rate curve and the test curve of the finite element simulation of composite materials, the finite element simulation results provided by this application can still reflect the change trend of the compressive properties of the sample well, which can be used for practical engineering applications. Provide the theoretical basis for structural design.

Of course, any product implementing the present invention does not necessarily need to achieve all the above-mentioned advantages at the same time.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the embodiments. Obviously, the accompanying drawings in the following description are only some of the present invention. Embodiments, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

Fig. 1 is the flow chart of the warp knitted spacer fabric composite material stress analysis method provided by the embodiment of the present invention;

Figure 2 is the number of traverse stitches -2;

Figure 3 is the number of traverse stitches -3;

Figure 4 is the number of traversing stitches -4;

Figure 5 shows the global arrangement of spacer filaments in WSF1;

Figure 6 shows the global arrangement of spacer filaments in WSF2;

Figure 7 is the global arrangement of WSF3 spacer filaments;

Fig. 8 is the trajectory of spacer bar GB3;

Fig. 9 is a solid model of a single spacer wire;

Fig. 10 is the solid model of spacer fabric;

Figure 11 is a solid model of polyurethane foam;

Fig. 12 is a composite material representative volume unit;

Figure 13 is the grid division of the composite material representative volume;

Fig. 14 is a comparison chart of the compression test curve and the finite element simulation curve.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention belong to the protection scope of the present invention.

Example

Referring to Fig. 1, a kind of stress analysis method of warp-knitted spacer fabric composite material provided for the embodiment of the present invention, as shown in Fig. 1, this method comprises utilizing finite element software, establishes the structural model of warp-knitted spacer fabric reinforced polyurethane reinforced composite material Concretely, select a minimum complete cycle structure unit as representative body unit, described representative body unit is the fabric structure unit formed by two spacer bars in a complete lap yarn cycle and the polyurethane foam matrix that comprises, to the selected The structural model is established by finite element analysis on behalf of the body element.

Establish a single spacer wire model according to the movement track of the spacer bar; perform mirroring and array operations on the single spacer wire entity model in turn to form a three-dimensional geometric model of the overall arrangement of the spacer wires of the two spacer bars;

Build warp-knitted spacer fabrics to reinforce the upper and lower surfaces of polyurethane composites;

Bond and assemble the established three-dimensional geometric model of the upper and lower surfaces and the overall arrangement of the spacer wires to obtain a solid model of the spacer fabric;

Create a polyurethane foam solid model of the same volume as the spacer fabric;

The structure model is obtained by assembling the spacer fabric solid model and the polyurethane foam solid model.

The method for establishing a single spacer wire model includes: first establishing point coordinates A, B, C, and D. Then in the two x-z planes, use straight lines to connect points A, B and points C, D respectively; and in the y-z plane, select an intermediate point O, and use a smooth curve to connect points B, O and C; take point A as Make a circle on the x-y plane with the center of the circle and a radius of 0.1mm, and drag the circle along the space curve ABCD to generate a single spacer wire solid model.

The parameters of the finite element model are set, and the parameters include the yarn laying mode of the interval bar, the corresponding relationship between each point and the laying yarn number, the spacer fabric spacer parameters, and the warp-knitted spacer fabric reinforced polyurethane composite material structure parameters;

Carry out mesh division according to the characteristics of the solid model; use the free mesh division in the finite element software to divide the mesh; set the surface mesh thickness, quality, and solid mesh type parameters of the solid model, and use the grid generation tool to generate the solid model Perform mesh division. Constrain one end of the solid model, and apply a compressive load to the other end; when compressing in the z direction on the upper surface of the solid model, set constraints on the degrees of freedom of all nodes on the lower surface of the solid model, that is, set each node The translational degrees of freedom in the x, y, and z directions are all zero, and the rotational degrees of freedom around the x, y, and z axes are all set to zero. Apply a uniform load to the upper surface of the solid model; select the appropriate applied nodal force, uniform load, and specified displacement. When the load is applied, it is applied in multiple load steps, and the compressive displacement load is applied in 12 load steps on the upper surface of the structural model, and each step is compressed by 0.38 mm.

Apply load to the meshed solid model and enter the post-processing function to generate the stress-strain curve of the warp-knitted spacer fabric reinforced polyurethane composite material.

In order to further illustrate the scheme provided by the present application, the following is illustrated by specific examples:

The analysis and calculation process of ANSYS finite element analysis software can be roughly divided into three steps: pre-processing, load loading and post-solution processing. The pre-processing process includes establishing the solid model of the analysis object, setting various parameters of the finite element model (including calculation type, unit type and material property parameters, etc.), and then performing grid division according to the characteristics of the solid model. For the solid model that has been meshed, you can apply loads to it and enter the post-processing function to read the calculation results.

This application establishes solid models for composite materials and applies pressure loads to solve them. For composite material samples, the basic geometric parameters required in the modeling process are as follows:

The laying methods of spacer bars of fabrics WSF1, WSF2 and WSF3 are: GB3: 1-0, 2-1/2-1, 1-0//, GB4: 2-1, 1-0/1-0, 2-1 //; GB3: 1-0, 3-2/3-2, 1-0 //, GB4: 3-2, 1-0/1-0, 3-2 //; GB3: 1- 0, 4-3/4-3, 1-0//, GB4: 4-3, 1-0/1-0, 4-3//, the corresponding lap yarn movement diagram is shown in Figure 2 and Figure 3 , Figure 4, Figure 5, Figure 6, Figure 7 shown.

Table 1 Corresponding relationship between each point and lap yarn number

fabric number A A' B B' C C' D. D' WSF1 1-0 2-1 2-1 1-0 2-1 1-0 1-0 2-1 WSF2 1-0 3-2 3-2 1-0 3-2 1-0 1-0 3-2 WSF3 1-0 4-3 4-3 1-0 4-3 1-0 1-0 4-3

Table 2 Spacer Fabric Spacer Parameters

Table 3 Structural parameters of warp-knitted spacer fabric reinforced polyurethane composites

According to the geometric parameters, select a minimum complete cycle structure unit as the representative body unit, that is, the fabric structure unit formed by the spacer bar GB3 and GB4 in a complete lapping cycle and the polyurethane foam matrix contained in it, and carry out the selected representative body unit Finite element analysis.

Firstly, a spacer wire model with a diameter of 0.2 mm is established according to the movement trajectory of the spacer bar GB3 of the sample as shown in Figure 8, as shown in Figure 9.

The process of establishing a single spacer wire model: first establish point coordinates A(0,0,7.76), B(2.82,0,0), C(2.82,-1,7.76), D(0,-1,0). Then in the two x-z planes, use straight lines to connect points A, B and points C, D respectively; and in the y-z plane, select an intermediate point O (2.82, -0.3, 3.88), and use a smooth curve to connect points B and O Connect with C to simulate the actual spatial bending shape of spacer filaments. Make a circle on the x-y plane with point A as the center and 0.1mm as the radius, and drag the circle along the space curve ABCD to generate a spacer wire solid model.

Perform operations such as "mirror image" and "array" on the solid model of a single spacer wire in sequence to form a three-dimensional geometric model of the overall arrangement of the spacer wires of the two spacer bars GB3 and GB4. The next step is to create the upper and lower surfaces of the spacer fabric. According to the existing literature research, the compression characteristics of the spacer fabric are mainly determined by the elastic core material, and the minimal deformation of the surface layer during the compression process has little influence on the final result. Therefore, in order to simplify the calculation difficulty and ensure the convergence of the model, in the process of establishing the solid model of the spacer fabric in this application, the upper and lower surfaces of the fabric are simplified as solid panels. According to the actual measurement of the spacer fabric, the thickness of the upper and lower panels of the fabric is 0.7mm. Establish a block with two points (0,0,7.06) and (2.82,-1,7.76), which is the upper surface of the fabric. Here, the volume overlapping with the spacer wire in the upper surface block needs to be subtracted to simulate the threading of the spacer wire in the upper surface coil. Using the same method, build the lower surface of the fabric. The established upper and lower surfaces and spacer wire models are bonded and assembled to obtain a spacer fabric solid model, as shown in Figure 10.

Next, a polyurethane foam model with the same volume as the spacer fabric is established. In order to ensure the calculation accuracy, the polyurethane foam model needs to subtract the volume of spacer filaments distributed in its volume, as shown in Figure 11.

Finally, the solid model of the spacer fabric was assembled with the solid model of the polyurethane foam from which the spacer filaments were removed to obtain a composite material representative body unit model, as shown in Figure 12.

Define element and material properties

According to the characteristics of the composite material model in this application, combined with the principle of finite element analysis, the SOLID 10 node 92 analysis element type is used for the model in the mechanical analysis.

In terms of the definition of material properties, the polyurethane foam matrix, panel and spacer wire in the composite material representative body unit are respectively defined. The polyurethane matrix material whose constitutive relation is nonlinear is defined as isotropic elastomer, but its constitutive relation is nonlinear. For composite panels, it is actually a spacer fabric panel impregnated with polyurethane foam, which can be regarded as a unidirectional composite material, which is theoretically transversely isotropic, so the panel can be defined as an orthotropic body. Spacer filaments are similar to polyurethane foams and are also defined as nonlinear orthotropic materials.

Definition of polyurethane foam and spacer wire material properties

The parameters required for the definition of nonlinear isotropic materials include: tensile elastic modulus, Poisson's ratio, tensile stress-strain relationship, and bulk density. The first three can be obtained through the tensile test of the material, and the bulk density of the material can also be calculated by the drainage method. The parameters of polyurethane foam and spacer wire are shown in Table 4, where E is the elastic modulus of the material, μ is the Poisson’s ratio of the material, and ρ is the bulk density of the material.

Table 4 Parameters of polyurethane foam and spacer wire

Table 5 Stress-strain relationship of polyurethane foam materials

strain(%) Stress (MPa) strain(%) Stress (MPa) 0 0 100 0.148 20 0.041 120 0.158 40 0.079 140 0.164 60 0.106 145 0.166 80 0.131 153 0.169

Table 6 Stress-strain relationship of spacer wire

strain(%) Stress (GPa) strain(%) Stress (GPa) 0 0 9.41556 1.577 1.04426 0.323 11.60292 1.933 3.06833 0.66 13.62699 2.306 4.76579 0.811 15.65105 2.737 7.44736 1.165 17.46025 3.112

Composite Panel Material Property Definitions

Since the reinforcement spacer fabric and polyurethane foam matrix used in this application are not defined in the material library of the software, they need to be defined by the user. As mentioned above, the composite panel can be regarded as a spacer fabric panel impregnated with polyurethane foam, which is theoretically equivalent to a unidirectional composite material, so its engineering elastic constant can be obtained by the unidirectional composite elastic parameter estimation formula.

Before solving the engineering elastic parameters of the composite panel, the engineering elastic parameters of the spacer fabric panel must be obtained. For this reason, the applicant splits the upper and lower surfaces of the warp-knitted spacer fabric sample WSF2 along the spacer layer, and removes the spacer filaments bonded to the upper and lower surfaces. The obtained single-layer fabric is subjected to a tensile test to solve its elastic parameters. The calculation results of the elastic parameters of the single-layer fabric are shown in Table 6-4, where E is the material elastic modulus (MPa), and G is the material shear modulus (MPa), μ is the Poisson's ratio of the material, the subscript 1 indicates the wale direction of the spacer fabric, 2 indicates the course direction of the spacer fabric, and 3 indicates the direction perpendicular to the 1 and 2 planes.

Elastic parameters of table 7 single-layer fabric

Material E1 E2 E3 G12 G23 G13 12 twenty three 13 single layer fabric panel 11.77* 5.83* 5.83 3.96* 2.25 3.96 0.35* 0.3* 0.35

*Determined by experiment.

At present, there are many theoretical formulas for estimating the elastic parameters of unidirectional composite materials. This application selects the following formula according to the characteristics of the warp-knitted spacer fabric reinforcement and the polyurethane matrix material:

E _x ＝(1-V _f )E ₁ +V _f E _f

E _y ＝E _z ＝E _f E ₂ /((1-V _f )E ₂ +V _f E _f )

G _xy ＝G _xz ＝G _f G ₁₂ /((1-V _f )G _f +V _f G ₁₂ )

v _xy ＝v _xz ＝(1-V _f )μ ₁₂ +V _f v _f

v _yx =v _xy E _y /E _x

v _yz =(1-V _f )μ ₂₃ +V _f (2v _f -μ ₂₃ )

Among them, Ex, Ey, Ez, Gxy, Gxz, Gyz, vxy, vyx and vyz are the elastic parameters of the composite material panel, E1 is the elastic modulus of the single-layer fabric along the warp direction, and E2 is the elastic modulus of the single-layer fabric along the weft direction G12 and G23 are the shear modulus of the single-layer fabric, Ef is the elastic modulus of the matrix, Gf is the shear modulus of the matrix, μ12 and 23 are the Poisson’s ratio of the single-layer fabric, νf is the Poisson’s ratio of the matrix, and Vf is the matrix volume content.

The volume content of the polyurethane foam matrix can be determined by subtracting the volume content of polyester filaments (spacer fabric) from the total volume of the composite. The method of determining the volume content of the spacer fabric in the composite material is as follows: Calculate the polyester thickness of the spacer fabric after melting (that is, without gaps), and then divide the obtained polyester thickness by the thickness of the composite material to obtain the volume of polyester filaments in the composite material content. The formula for calculating the volume content of polyester filaments is:

In the formula, Vs-y is the volume content of polyester filaments, ρS is the surface density of the spacer fabric (g/m2), ρP is the volume density of polyester filaments (g/m3), and hS is the thickness of the single-layer spacer fabric (mm).

The surface density and thickness of the single-layer fabric are measured through experiments: 390.84g/m2 and 0.7mm respectively, and the volume density of the polyester filament is 1.38g/m3. The volume content of the single-layer fabric is calculated according to formula (6-2) is 40.4%, then the matrix volume content in the composite panel is 59.6%. According to the formula (6-1), the elastic parameters of the composite panel are:

Ex＝4.78MPa Ey＝Ez＝0.31MPa

Gyz＝0.058MPa Gxy＝Gxz＝0.076MPa

vxy=0.32 vyx=0.2 vyz=0.3

Representative Volume Element Meshing

The core of the finite element calculation method is to discretize the continuous whole into sub-regions, that is, the aforementioned units. Therefore, the quality of grid division has a significant impact on the finite element calculation results. At the same time, the degree of grid division density also indirectly determines the calculation time and required memory size. In general, the smaller the mesh size, the more elements there are in the model and the longer the calculation time required.

In this paper, the free meshing in the software is used for meshing. After setting the parameters of model surface mesh thickness, quality, solid mesh type, etc., using the mesh generation tool, the model after meshing the composite material representative volume unit is shown in Figure 13. The composite material model is partitioned by tetrahedral elements. The meshed sample of the model contains 14597 elements.

Apply boundary conditions and loads

The compression analysis of the composite material representative volume element model is the compression test of the simulated sample, which is realized by constraining one end of the model and applying a compressive load to the other end. When the composite material is compressed in the z direction, set constraints on the degrees of freedom of all nodes on the lower surface of the model, that is, set the translational degrees of freedom of each node in the x, y, and z directions to be zero, and at the same time , y, and z-axis rotational degrees of freedom are all set to zero.

Apply a uniform load to the upper surface of the model. There are options to apply nodal forces, uniform loads, and specified displacements. This application chooses to apply a specified displacement to the upper surface of the model. From the results of the compression test, it can be seen that the compression curve of the sample changes nonlinearly, so when applying the load, it needs to be applied in multiple load steps to obtain an accurate solution. Therefore, the compressive displacement load is applied in 12 load steps on the upper surface of the finite element model, and each step is compressed by 0.38 mm.

The stress-compressibility curve obtained through finite element analysis by the method provided in this application is compared with the compression test curve, and the results are shown in FIG. 14 . It can be seen from Fig. 14 that the compressive stress-compression rate curve of the composite material simulated by finite element is in good agreement with the compressive deformation curve obtained from the test, but there is a small amount of deviation, which is mainly because: in the process of finite element analysis, the composite The material is assumed to be an ideal elastic body, and its deformation completely obeys Hooke's law, and the friction between the polyurethane foam and the spacer wire is ignored. In the actual compression process, the compression deformation of the composite material does not completely obey Hooke's law. Law, and the friction between polyurethane foam and spacer wire also exists objectively. Although there is a small amount of deviation between the stress-compression rate curve and the test curve of the finite element simulation of composite materials, the finite element simulation results provided by the application can still reflect the change trend of the compressive properties of the sample well, which can provide a basis for practical engineering applications. Theoretical basis for structural design.

The structural parameters of the warp-knitted spacer fabric have a significant impact on the energy absorption performance of the composite material. The composite material with a large number of needle back traverses, a thinner spacer yarn, and a larger thickness has a higher energy absorption performance under the condition of a small stress value. On the contrary, the composite material with smaller spacer needle back traverse number, thicker spacer, and smaller thickness is more suitable for use as an energy absorption material under high stress conditions. Therefore, in practical engineering applications, Polyurethane-based composites with different energy absorption properties can be obtained by adjusting the structural parameters of the fabric to meet different application requirements

It should be noted that in this application, relative terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that these entities or operations Any such actual relationship or order exists between. Furthermore, the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article or apparatus comprising a set of elements includes not only those elements, but also includes elements not expressly listed. other elements of or also include elements inherent in such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article or apparatus comprising said element.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present invention are included in the protection scope of the present invention.

Claims (8)

1. a warp-knitted spacer fabric composite material stress analysis method, is characterized in that, described method comprises: utilize finite element software, set up the structural model that warp-knitted spacer fabric strengthens polyurethane reinforced composite material; Every parameter of finite element model is set , the parameters include the yarn laying mode of the interval bar, the corresponding relationship between each point and the laying yarn number, the spacer fabric spacer parameters, the warp-knitted spacer fabric reinforced polyurethane composite material structural parameters; grid division is carried out according to the characteristics of the solid model; Loads are applied to the meshed solid model and entered into the post-processing function to generate the stress-strain curve of the warp-knitted spacer fabric-reinforced polyurethane composite material. 2. warp-knitted spacer fabric composite material stress analysis method according to claim 1 is characterized in that, setting up the structural model of warp-knitted spacer fabric reinforced polyurethane reinforced composite material comprises: choosing a minimum complete circulation structural unit as representative body The representative unit is a fabric structural unit formed by two spacer bars in a complete lapping cycle and the polyurethane foam matrix contained therein. A finite element analysis is carried out on the selected representative unit to establish a structural model. 3. warp-knitted spacer fabric composite stress analysis method according to claim 2, is characterized in that, set up a single spacer wire model according to the motion locus of spacer bar; Carry out mirror image, array operation to single spacer body model successively , forming a three-dimensional geometric model of the overall arrangement of the spacer wires of the two spacer bars; establishing the upper and lower surfaces of the warp-knitted spacer fabric reinforced polyurethane composite material; the established three-dimensional geometric model of the upper and lower surfaces and the overall arrangement of the spacer wires Bonding and assembling to obtain the solid model of the spacer fabric; establishing a solid model of polyurethane foam with the same volume as the spacer fabric; assembling the solid model of the spacer fabric with the solid model of the polyurethane foam to obtain the structural model. 4. warp-knitted spacer fabric composite material stress analysis method according to claim 3, is characterized in that, described single spacer wire model building method comprises: at first set up point coordinates A, B, C, D; Then in two In the x-z plane, use a straight line to connect points A, B and points C, D respectively; while in the y-z plane, select an intermediate point O, and connect points B, O and C with a smooth curve; take point A as the center of the circle, 0.1 mm Make a circle on the x-y plane for the radius, and drag the circle along the space curve ABCD to generate a single spacer wire solid model. 5. warp-knitted spacer fabric composite material stress analysis method according to claim 1, is characterized in that, carries out grid division according to the characteristics of solid model; Comprise: use free grid division in finite element software to carry out grid division; Set Fine-tune the surface mesh thickness, quality, and solid mesh type parameters of the solid model, and use the grid generation tool to mesh the solid model. 6. The warp-knitted spacer fabric composite material stress analysis method according to claim 1, is characterized in that, applying a load to the solid model divided into grids comprises: one end of the solid model is constrained, and the other end applies a compressive load To achieve this; when the upper surface of the solid model is compressed in the z direction, the degrees of freedom of all nodes on the lower surface of the solid model are constrained, that is, the translational degrees of freedom in the x, y, and z directions of each node are set to be equal to At the same time, the rotational degrees of freedom around the x, y, and z axes are all set to zero. 7. warp knitted spacer fabric composite material stress analysis method according to claim 6, is characterized in that, applies uniform load to solid model upper surface; Selects appropriate to apply nodal force, uniform load and specified displacement. 8. warp knitted spacer fabric composite material stress analysis method according to claim 7, is characterized in that, when applying load, be divided into a plurality of load steps and apply, divide 12 load steps and apply compressive displacement load on the upper surface of described structure model , each step compresses 0.38 mm.