A method for determining the strength of a flexible fabric membrane

Abstract

The invention discloses a method for determining the strength of a flexible fabric membrane, and relates to the field of flexible fabric membranes. The strength determination items include 7 items: a quadratic term of warp tensile stress ratio, a quadratic term of weft tensile stress ratio, a product term of warp and weft tensile stress ratio, a linear term of warp tensile stress ratio, a linear term of weft tensile stress ratio, a product term of warp tensile stress ratio and shear stress ratio, and a product term of weft tensile stress ratio and shear stress ratio. The sum of the values ​​of the 7 items is greater than or equal to 1, indicating that the flexible fabric membrane structure reaches strength damage. Only three basic strength parameters are needed: warp tensile strength, weft tensile strength, and shear strength. Not only can the secondary effect, tensile coupling, and tension-shear coupling effect of the fabric membrane material during biaxial stretching be accurately reflected, only three basic strength parameters are needed, the parameters are few, the use is simple, and the reliability and accuracy are high, which is conducive to the accurate strength design of the flexible fabric membrane structure under extreme load environment conditions.

Description

Technical Field

[0001] The invention relates to the field of flexible fabric membranes, and in particular to a method for determining the strength of a flexible fabric membrane. Background Art

[0002] Flexible fabric membrane is a widely used composite material, mainly used in civil engineering, aerospace and other industrial fields. Flexible fabric membrane consists of a fabric base fabric as a structural load-bearing layer and a polymer film or coating as a functional layer. The fabric base fabric is made of polymer fibers through spinning and weaving, and the functional layer is laminated or coated. It is significantly different from the widely used carbon fiber fabric reinforced epoxy resin rigid material. Flexible fabric membrane can only withstand tension, not pressure or bending moment. At the same time, it can only withstand a certain shear force under the condition of tension. Therefore, flexible fabric membrane is designed and applied to tension structures, such as typical inflatable tension and mechanical tension, to give full play to the tensile properties of flexible fabric membranes, and then adopt tensile strength design.

[0003] In the prior art, biaxial tensile tests are usually used for calibration. The damage determination of any flexible fabric tension structure is not only inaccurate in safety but also incorrect in position. Therefore, there is an urgent need for a determination method that can accurately reflect the tensile strength of flexible fabric membranes during biaxial stretching. Summary of the invention

[0004] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is how to accurately reflect the tensile strength of the flexible fabric membrane during biaxial stretching.

[0005] To achieve the above object, the present invention provides a method for determining the strength of a flexible fabric membrane, comprising 7 determination items: a quadratic term of warp tensile stress ratio, a quadratic term of weft tensile stress ratio, a warp and weft tensile stress ratio item, a linear term of warp tensile stress ratio, a linear term of weft tensile stress ratio, a product item of warp tensile stress ratio and shear stress ratio, and a product item of weft tensile stress ratio and shear stress ratio;

[0006] Determine whether the sum of the values ​​of the seven determination items is greater than 1;

[0007] If the sum of the values ​​of the seven judgment items is greater than 1, the flexible fabric membrane structure reaches strength failure.

[0008] Furthermore, the warp and weft tensile stress ratio term includes a warp and weft tensile stress ratio product term.

[0009] Furthermore, the warp and weft tensile stress ratio term includes a warp and weft tensile stress ratio coupling term.

[0010] Furthermore, the strength determination method includes three strength parameters: warp tensile strength, weft tensile strength, and shear strength.

[0011] Furthermore, the warp tensile strength is measured by a uniaxial tensile test of the flexible fabric membrane, with at least 5 valid tests, and a 5% dispersion coefficient statistical value X is taken.

[0012] Furthermore, the weft tensile strength is measured by a uniaxial tensile test of the flexible fabric membrane, with at least 5 valid tests, and a 5% dispersion coefficient statistical value Y is taken.

[0013] Further, the shear strength is measured by a biaxial tensile shear strength test of the flexible fabric membrane, with at least 5 valid tests and a 5% dispersion coefficient statistical value S.

[0014] Furthermore, the method for biaxial tensile shear strength test of the flexible fabric membrane comprises:

[0015] S1. Use a standard biaxial tensile cross-shaped specimen and use a biaxial tensile testing machine to perform biaxial tensioning to a set stress value;

[0016] S2. Using a standard drawing frame to clamp the four arms of the cross-shaped specimen, testing and recording the strain value of the core area of ​​the biaxial tension cross-shaped specimen;

[0017] S3, unloading the biaxial tensile testing machine, disassembling the frame and the biaxial tensile cross-shaped specimen as a whole, testing and recording the strain value of the core area of ​​the biaxial tensile cross-shaped specimen;

[0018] S4. Install the drawing frame and the clamped cross-shaped specimen as a whole into the uniaxial tensile testing machine, remove the diagonal supporting connecting rod, apply tensile loading to the drawing frame, and cause shear deformation of the cross-shaped specimen until the specimen is destroyed, and record the tension and deformation;

[0019] S5. Calculate shear stress and shear strain based on the force and deformation relationship of the cross-shaped specimen;

[0020] Repeat steps S1-S5 for at least 5 valid tests and take the 5% dispersion coefficient statistical value.

[0021] Furthermore, a standard biaxial tensile cross-shaped specimen is used, and biaxial tensioning is performed using a biaxial tensile testing machine to achieve a set stress value.

[0022] Furthermore, the biaxial tensile cross-shaped specimen that has achieved a set tension state is subjected to shear loading using a frame method, and the cross-shaped specimen undergoes tensile shear deformation and tensile shear failure.

[0023] Compared with the prior art, the implementation of the present invention achieves the following technical effects:

[0024] 1. The method for determining the strength of flexible fabric membranes provided by the present invention can accurately reflect the secondary effect, tensile coupling, and tension-shear coupling effect of fabric membrane materials during biaxial stretching, effectively measure and characterize the composite stress strength of flexible fabric membrane materials, and can provide technical support for the strength design and analysis of major practical projects.

[0025] 2. The flexible fabric membrane strength determination method provided by the present invention combines the material mechanics theory with actual experiments. It is simple to use, has only three basic strength parameters, few parameters, high reliability and accuracy, which is beneficial to the accurate strength design of flexible fabric structures under extreme load environment conditions, and is beneficial to the use and promotion of flexible fabric membrane materials.

[0026] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A biaxial tensile cross-shaped specimen for a biaxial tensile shear strength test according to a preferred embodiment of the present invention;

[0028] Figure 2 A preferred embodiment of the present invention is a frame clamping a cross-shaped test piece;

[0029] Figure 3 It is a drawing frame tensile loading test of a preferred embodiment of the present invention;

[0030] Figure 4 It is a frame plan view of a preferred embodiment of the present invention;

[0031] Figure 5 It is a structural schematic diagram of a base plate of a preferred embodiment of the present invention;

[0032] Figure 6 It is a structural schematic diagram of a pressing plate of a preferred embodiment of the present invention;

[0033] Figure 7 It is a loading joint diagram of a preferred embodiment of the present invention.

[0034] In the picture

[0035] 1-biaxial tension cross-shaped specimen; 2-frame; 3-loading joint; 201-base plate; 202-pressure plate; 203-support connecting rod. DETAILED DESCRIPTION

[0036] The following describes several preferred embodiments of the present invention with reference to the drawings in the specification, so that the technical content is clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the protection scope of the present invention is not limited to the embodiments mentioned in the text.

[0037] In the drawings, components with the same structure are indicated by the same numerical reference numerals, and components with similar structures or functions are indicated by similar numerical reference numerals. The size and thickness of each component shown in the drawings are arbitrarily shown, and the present invention does not limit the size and thickness of each component. In order to make the illustration clearer, the thickness of the components is appropriately exaggerated in some places in the drawings.

[0038] In the prior art, flexible fabric membrane material is a widely used composite material, mainly used in civil engineering, aerospace and other industrial fields. Flexible fabric membrane material consists of a fabric base fabric as a structural load-bearing layer and a polymer film or coating as a functional layer. The fabric base fabric is made of polymer fibers through spinning and weaving, and the functional layer is laminated or coated. It is significantly different from the widely used carbon fiber fabric reinforced epoxy resin rigid material. The flexible fabric membrane can only withstand tension, not pressure or bending moment. At the same time, it can only withstand a certain shear force under the condition of tension. Therefore, flexible fabric membrane materials are designed and applied to tension structures, such as typical pneumatic tensioning and mechanical tensioning, to give full play to the tensile properties of flexible fabric membrane materials, and then adopt tensile strength design.

[0039] At present, in the field of tensioned flexible fabric membrane structures, such as the "Technical Code for Membrane Structures" (CECS158-2015) in the field of architectural membrane structures and the FAA Airship Design Criteria-1995, the most basic strength criterion is the maximum tensile stress criterion.

[0040]

[0041] Where: f,w , σ f,f - Maximum stress values ​​in the longitudinal and latitudinal directions under various load combinations;

[0042] f r,w 、f r,f - Design value of tensile strength in warp and weft directions of membrane material;

[0043] f k,w 、f k,f - Standard values ​​of tensile strength in the warp and weft directions of membrane materials;

[0044] ζ-strength reduction factor;

[0045] γ R -Partial coefficient of membrane material resistance;

[0046] The strength criterion based on maximum stress is very simple, that is, the maximum stress of the structure meets the warp or weft design strength of the flexible fabric membrane material, the structural strength meets the requirements, and the structure is safe. However, in a large number of engineering practices, it is found that even if the maximum stress of the structure is small, the maximum stress design criterion has a large safety factor, and the structure is damaged. Due to the morphology, manufacturing, and load of the flexible fabric membrane structure, bidirectional tensile stress and shear stress often exist in the structure. Therefore, the engineering field and some researchers apply the composite stress criterion widely used in rigid composite materials to the strength design of flexible fabric membrane structures.

[0047] The main classical strength criteria for rigid composite materials are:

[0048] Tsai-Hill Criterion

[0049] Yeh-Stratton Criteria

[0050] Norris Criteria

[0051] In the formula, X, Y are the tensile strength in the warp direction and the tensile strength in the weft direction of the flexible fabric membrane, S is the shear strength of the flexible fabric membrane, δ x , δ y , τ xy It is the longitudinal stress, latitudinal stress and shear stress of any point under the internal load of the flexible fabric membrane structure.

[0052] The composite stress strength criterion based on rigid composite materials takes into account the coupling effect of biaxial tension and the contribution of shear force to strength, which can improve some of the shortcomings of the maximum stress strength criterion in formula (1). According to engineering application practice, these criteria are still different from actual engineering. In order to meet the extreme needs of engineering, academia and engineering are still committed to establishing more accurate strength design criteria. "Biaxial strength determination of woven fabric composite for airship structural envelope based on novel specimens" (Compositestructures, 2017, 10 (184): 1126-1136) by Shi Taibai et al. introduced a new specimen and experimental analysis that can be used for biaxial tensile strength test of airship skin materials. "A method for determining the biaxial tensile strength of fabric membrane materials" (ZL201810982452.2) by Chen Wujun et al. invented a biaxial tensile strength criterion based on the biaxial tensile determination action coefficient, as follows

[0053]

[0054] Where: x is the longitudinal stress of the fabric membrane under biaxial tension, δ y is the latitudinal stress of the fabric membrane under biaxial tension, X is the warp uniaxial tensile strength of the fabric membrane, Y is the weft uniaxial tensile strength of the fabric membrane, α is the first correlation coefficient, β is the second correlation coefficient, γ is the third correlation coefficient, φ is the fourth correlation coefficient, and ω is the fifth correlation coefficient.

[0055] For the case of only biaxial tension in engineering, formula (5) can provide a more reasonable strength design. However, as a basic criterion, formula (5) requires the warp and weft uniaxial tensile strength X / Y of the flexible fabric membrane material, as well as five action coefficients, which need to be calibrated through a biaxial tensile test. The core problem is that this criterion does not consider the contribution of shear force to the strength of the structure. Therefore, the damage judgment of any flexible fabric tension structure is not only inaccurate in safety, but also incorrect in position. The judgment criteria (1)-(4) have similar problems.

[0056] In order to solve the technical problems in the above-mentioned prior art, on the one hand, the present invention provides a method for determining the strength of a flexible fabric membrane, comprising 7 determination items: a quadratic term of warp tensile stress ratio, a quadratic term of weft tensile stress ratio, a warp and weft tensile stress ratio item, a linear term of warp tensile stress ratio, a linear term of weft tensile stress ratio, a product item of warp tensile stress ratio and shear stress ratio, and a product item of weft tensile stress ratio and shear stress ratio;

[0057] Determine whether the sum of the values ​​of the seven determination items is greater than 1;

[0058] If the sum of the values ​​of the seven judgment items is greater than 1, the flexible fabric membrane structure reaches strength failure.

[0059] Furthermore, the warp and weft tensile stress ratio term includes a warp and weft tensile stress ratio product term.

[0060] Furthermore, the warp and weft tensile stress ratio term includes a warp and weft tensile stress ratio coupling term.

[0061] Furthermore, the strength determination method includes three strength parameters: warp tensile strength, weft tensile strength, and shear strength.

[0062] Furthermore, the warp tensile strength is measured by a uniaxial tensile test of the flexible fabric membrane, with at least 5 valid tests, and a 5% dispersion coefficient statistical value X is taken.

[0063] Furthermore, the weft tensile strength is measured by a uniaxial tensile test of the flexible fabric membrane, with at least 5 valid tests, and a 5% dispersion coefficient statistical value Y is taken.

[0064] Further, the shear strength is measured by a biaxial tensile shear strength test of the flexible fabric membrane, with at least 5 valid tests and a 5% dispersion coefficient statistical value S.

[0065] Furthermore, the method for biaxial tensile shear strength test of the flexible fabric membrane comprises:

[0066] S1. Use a standard biaxial tensile cross-shaped specimen and use a biaxial tensile testing machine to perform biaxial tensioning to a set stress value;

[0067] S2. Using a standard drawing frame to clamp the four arms of the cross-shaped specimen, testing and recording the strain value of the core area of ​​the biaxial tension cross-shaped specimen;

[0068] S3, unloading the biaxial tensile testing machine, disassembling the frame and the biaxial tensile cross-shaped specimen as a whole, testing and recording the strain value of the core area of ​​the biaxial tensile cross-shaped specimen;

[0069] S4. Install the drawing frame and the clamped cross-shaped specimen as a whole into the uniaxial tensile testing machine, remove the diagonal supporting connecting rod, apply tensile loading to the drawing frame, and cause shear deformation of the cross-shaped specimen until the specimen is destroyed, and record the tension and deformation;

[0070] S5. Calculate shear stress and shear strain based on the force and deformation relationship of the cross-shaped specimen;

[0071] Repeat steps S1-S5 for at least 5 valid tests and take the 5% dispersion coefficient statistical value.

[0072] Furthermore, a standard biaxial tensile cross-shaped specimen is used, and biaxial tensioning is performed using a biaxial tensile testing machine to achieve a set stress value.

[0073] Furthermore, the biaxial tensile cross-shaped specimen that has achieved a set tension state is subjected to shear loading using a frame method, and the cross-shaped specimen undergoes tensile shear deformation and tensile shear failure.

[0074] On the other hand, the present invention provides a tensile-shear coupled composite stress strength criterion for flexible fabric membranes, the specific expression of which is as follows:

[0075]

[0076] Where: x is the tensile stress of the membrane material in the flexible fabric tension structure, δ y is the latitudinal tensile stress of the membrane material of the flexible fabric tension structure, τ xy is the shear stress of the flexible fabric tension structure, X is the uniaxial tensile strength of the flexible fabric membrane in the warp direction, Y is the uniaxial tensile strength of the flexible fabric membrane in the weft direction, and S is the shear strength of the flexible fabric membrane.

[0077] The criteria of the present invention require three parameters: the warp uniaxial tensile strength X of the flexible fabric membrane material, the weft uniaxial tensile strength Y of the flexible fabric membrane material, and the shear strength S of the flexible fabric membrane material.

[0078] Further, the warp uniaxial tensile strength X of the flexible fabric membrane material is determined by a standard uniaxial tensile strength test, with at least 5 valid tests, and a 5% dispersion coefficient statistical value X is taken;

[0079] Furthermore, the uniaxial tensile strength Y of the flexible fabric membrane material in the weft direction is determined by a standard uniaxial tensile strength test, with at least 5 valid tests and a 5% coefficient of dispersion statistical value Y;

[0080] Further, the shear strength S of the flexible fabric membrane material is determined by a biaxial tensile shear strength test, with at least 5 valid tests, and a 5% dispersion coefficient statistical value S is taken;

[0081] Further, the steps of the biaxial tensile shear strength test are:

[0082] 1. Use a standard biaxial tensile cross-shaped specimen 1 (such as Figure 1 ), biaxial tension is performed using a biaxial tensile testing machine to set stress values ​​Nx1 and Ny1 (such as Figure 2 );

[0083] 2. Use standard frame 2 (such as Figure 4 ) Tightly clamp the four arms of the biaxial tensile cross-shaped specimen 1, add a diagonal support link 203, test and record the specimen strain value ε x1 , ε y1 ; Unload the biaxial tensile testing machine, remove the biaxial tensile cross-shaped specimen 1 from the biaxial tensile testing machine, and cut off the four-arm extension part;

[0084] 3. Remove the supporting link 203, frame 2 bears the load, and the biaxial tensile cross-shaped specimen 1 rebounds to stress Nx2 and Ny2, and the specimen strain value ε is tested and recorded. x2 , ε y2 ;

[0085] 4. Install the frame 2 and the clamped biaxial tensile cross-shaped specimen 1 into the uniaxial tensile testing machine. Connect the loading joint 3 diagonally to the frame 2. Apply tensile loading to the loading joint 3. The biaxial tensile cross-shaped specimen 1 undergoes shear deformation until the specimen is destroyed. Record the tensile force F and deformation ε. xt , ε yt ;

[0086] 5. According to the relationship between the force and deformation of the cross-shaped specimen 1, the shear stress Si and the shear strain γ of the cross-shaped specimen 1 are calculated;

[0087] 6. Repeat steps 1-5 for at least 5 valid tests and take the 5% coefficient of dispersion statistics;

[0088] Example 1

[0089] like Figure 1 As shown, a biaxial tension cross-shaped specimen 1 for a biaxial tension shear strength test of a flexible fabric membrane material according to a tensile-shear coupling composite stress strength criterion is shown in a preferred embodiment of the present invention.

[0090] Figure 1 It is a top view of the manufactured biaxial tension cross-shaped specimen 1, which includes a central core area and four outriggers, the ends of the outriggers are clamping sections, and the warp and weft lines of the flexible fabric membrane are parallel to the outriggers.

[0091] At the same time, at least two slits parallel to the arms are respectively arranged on the four arms of the biaxial tension cross-shaped specimen 1. In this embodiment, two slits parallel to the arms are respectively arranged on the four arms, and the corners between the arms are chamfered at right angles.

[0092] Figure 1 In the figure, the total length of the flexible fabric membrane biaxial tension cross-shaped specimen 1 is Ls, the arm length is La, the clamping section length is a, the core area is a square with a side length of w, the parallel slit ends are d away from the core edge, and the radius of the chamfered corners between the arms is R. The above parameters can be designed according to the characteristics of the flexible fabric membrane and the test needs.

[0093] Example 2

[0094] On the basis of Example 1, Figure 2 As shown, a frame 2 clamps a biaxial tension cross-shaped specimen 1 of a flexible fabric membrane material tension-shear coupling composite stress strength criterion according to a preferred embodiment of the present invention.

[0095] The biaxial tensile cross-shaped specimen 1 has a longitudinal tensile force Nx1 and a latitudinal tensile force Ny1. At this time, the strain in the core area is ε x1 , ε y1 .

[0096] The frame 2 tightly clamps the four extension arms of the biaxial tensile cross-shaped specimen 1, and adds supporting connecting rods 203 at the diagonals. Then, the biaxial tensile testing machine is unloaded, and the biaxial tensile cross-shaped specimen 1 is disassembled from the biaxial tensile testing machine, and the extension parts of the four arms are cut off;

[0097] Example 3

[0098] In Example 2, Figure 4 As shown in FIG. 2 , a flexible fabric membrane material tensile shear coupling composite stress strength criterion of a preferred embodiment of the present invention is shown. The four bottom plates 201 are connected end to end as a four-bar linkage, and the hinge is a ball groove bearing. Figure 5 and Figure 6As shown, the bottom plate 201 has a single ear at one end, two ears at the other end, and concave holes evenly distributed in the middle section, ensuring that the frame 2 is coplanar as a whole, and the hinge axis is eccentric to ensure that it can be completely folded. The pressure plate 202 is a long strip pressure plate with evenly distributed sunken circular holes, and a single-sided roller wire increases the friction coefficient. It matches the concave section in the middle section of the bottom plate 201 and is consistent with the arm width w of the biaxial tensile cross-shaped specimen 1. One pair of corners of the frame 2 is a supporting connecting rod 203, and the other pair of corners are connected to the loading joint 3. Figure 6 One end of the loading joint 3 is a U-shaped fork, connected to the hinge shaft of the frame 2, and the threaded cylindrical section is connected to the uniaxial tensile testing machine, equipped with a pre-tightening nut, a pin shaft and a pin hole.

[0099] The material of the frame 2 and the loading joint 3 can be high-strength alloy steel, stainless steel, light alloy, etc. The specific dimensions (length, width, thickness), bolts, hinges, etc. can be designed and selected according to the size of the biaxial tensile cross-shaped specimen 1 and the strength of the flexible fabric membrane material.

[0100] Example 4

[0101] On the basis of Example 2, combined with Frame 2 of Example 3, as shown in FIG. Figure 3 As shown, it is a frame tensile loading test of a flexible fabric membrane material tensile-shear coupling composite stress strength criterion according to a preferred embodiment of the present invention.

[0102] The supporting connecting rod 203 of the frame 2 is removed, the frame 2 is self-balanced, the biaxial tensile cross-shaped specimen 1 rebounds, and the specimen strain value ε is tested and recorded. x2 , ε y2 According to the stress-strain curve Nx-ε of the low-cycle biaxial tensile test of the same flexible fabric membrane material x 、Ny-ε y , calibrate and calculate the stress Nx2 and Ny2 after springback;

[0103] Install the frame 2 and the tightly clamped biaxial tensile cross-shaped specimen 1 into the uniaxial tensile testing machine. Connect the loading joint 3 diagonally to the frame 2. Apply tensile loading to the loading joint 3. Shear deformation occurs in the biaxial tensile cross-shaped specimen 1. When the biaxial tensile cross-shaped specimen 1 is tensile shear failure, record the tensile force F and deformation ε. xt , ε yt ;

[0104] According to the mechanical relationship between force and deformation of the biaxial tensile cross-shaped specimen 1, the shear stress Si and shear strain γ are calculated;

[0105]

[0106] Where α is the initial angle of the biaxial tensile cross specimen 1 (usually 90°), and w is the arm width of the biaxial tensile cross specimen (e.g. Figure 1 ), γ is the shear angle, ε xtand ε yt is the elongation deformation in the loading direction and the diagonal contraction deformation of the biaxial tensile cross specimen 1 (e.g. Figure 3 ).

[0107] The preferred specific embodiments of the present invention are described in detail above. It should be understood that ordinary technicians in the field can make many modifications and changes based on the concept of the present invention without creative work. Therefore, all technical solutions that can be obtained by technicians in the technical field based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for determining the strength of a flexible fabric membrane, characterized in that: It includes 7 judgment items: The quadratic term of the tensile stress ratio in the longitudinal direction The quadratic term of latitudinal tensile stress ratio Longitudinal and latitudinal tensile stress ratio The linear term of the tensile stress in the longitudinal direction The linear term of latitudinal tensile stress ratio The product of the ratio of longitudinal tensile stress and the ratio of shear stress The product of the latitudinal tensile stress ratio and the shear stress ratio Among them, δ x is the tensile stress of the membrane material in the flexible fabric tension structure, δ y is the latitudinal tensile stress of the membrane material of the flexible fabric tension structure, τ xy is the shear stress of the flexible fabric tension structure, X is the uniaxial tensile strength of the flexible fabric membrane material in the warp direction, Y is the uniaxial tensile strength of the flexible fabric membrane material in the weft direction, and S is the shear strength of the flexible fabric membrane material; Determine whether the sum of the values ​​of the seven determination items is greater than 1; If the sum of the values ​​of the seven judgment items is greater than 1, the flexible fabric membrane structure reaches strength failure.

2. The method for determining the strength of a flexible fabric membrane according to claim 1, wherein: The longitudinal and latitudinal tensile stress ratio term includes the longitudinal and latitudinal tensile stress ratio product term.

3. The method for determining the strength of a flexible fabric membrane according to claim 1, characterized in that: The longitudinal and latitudinal tensile stress ratio term includes a longitudinal and latitudinal tensile stress ratio coupling term.

4. The method for determining the strength of a flexible fabric membrane according to claim 1, wherein: The strength determination method includes three strength parameters: warp tensile strength, weft tensile strength, and shear strength.

5. The method for determining the strength of a flexible fabric membrane according to claim 4, characterized in that: The warp tensile strength is measured by a uniaxial tensile test of the flexible fabric membrane, with at least 5 valid tests and a 5% dispersion coefficient statistical value X.

6. The method for determining the strength of a flexible fabric membrane according to claim 4, characterized in that: The weft tensile strength is measured by a uniaxial tensile test of the flexible fabric membrane, with at least 5 valid tests and a 5% dispersion coefficient statistical value Y.

7. The method for determining the strength of a flexible fabric membrane according to claim 4, wherein: The shear strength is measured by a biaxial tensile shear strength test of the flexible fabric membrane, with at least 5 valid tests and a 5% dispersion coefficient statistical value S.

8. The method for determining the strength of a flexible fabric membrane according to claim 7, characterized in that: The method for the biaxial tensile shear strength test of the flexible fabric membrane comprises: S1. Use a standard biaxial tensile cross-shaped specimen and use a biaxial tensile testing machine to perform biaxial tensioning to a set stress value; S2. Using a standard drawing frame to clamp the four arms of the cross-shaped specimen, testing and recording the strain value of the core area of ​​the biaxial tension cross-shaped specimen; S3, unloading the biaxial tensile testing machine, disassembling the frame and the biaxial tensile cross-shaped specimen as a whole, testing and recording the strain value of the core area of ​​the biaxial tensile cross-shaped specimen; S4. Install the drawing frame and the clamped cross-shaped specimen as a whole into the uniaxial tensile testing machine, remove the diagonal supporting connecting rod, apply tensile loading to the drawing frame, and cause shear deformation of the cross-shaped specimen until the specimen is destroyed, and record the tension and deformation; S5. Calculate shear stress and shear strain based on the force and deformation relationship of the cross-shaped specimen; Repeat steps S1-S5 for at least 5 valid tests and take the 5% dispersion coefficient statistical value.

9. The method for determining the strength of a flexible fabric membrane according to claim 8, wherein: A standard biaxial tensile cross-shaped specimen is used, and biaxial tension is performed using a biaxial tensile testing machine to achieve the set stress value.

10. The method for determining the strength of a flexible fabric membrane according to claim 8, wherein: The biaxial tensile cross-shaped specimen that has achieved a set tension state is subjected to shear loading using a frame method, and the cross-shaped specimen undergoes tensile shear deformation and tensile shear failure.

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