A method for preparing an adaptive variable-diameter exhaust port buffer airbag

Abstract

The application discloses a preparation method of a self-adaptive variable-diameter exhaust port buffer air bag, and comprises the following steps: S1, selecting air bag fabric material and reinforcing belt material according to actual air drop buffer air bag falling speed V and load M; S2, designing the positional relationship between the combined air bag and the exhaust port; S3, designing the exhaust port of the multi-layer woven fabric; and S4, constructing an equivalent mechanical model based on the woven fabric material of the exhaust port, constructing the strength relationship between the air drop weight and each layer of woven fabric material of the exhaust port, and obtaining the exhaust port material with the structural characteristics of low hoop stiffness and high radial stiffness. The preparation method of the self-adaptive variable-diameter exhaust port buffer air bag can automatically change the size of the exhaust port according to the size of the air drop landing impact force of different weights, can automatically change according to the strength of the falling impact, improves the air drop success rate, and can realize the automatic expansion of the exhaust port without other mechanisms, and has the advantages of simple structure and easy realization.

Description

Technical Field

[0001] This invention relates to the field of airbag technology, and in particular to a method for preparing an adaptive variable-diameter exhaust port airbag. Background Technology

[0002] The spatiotemporal evolution of the geometric deformation of airbags and the interaction between aerodynamic structures and gas motion are highly complex. Currently, landing airbags are mainly classified into sealed, vented, combined, and intelligent types. Sealed airbags without vents are the earliest and simplest type. These airbags can land at relatively high speeds, have fewer requirements on landing attitude, and are more adaptable to relatively complex landing terrains. The landing cushioning system of the Mars Pathfinder lander developed by the Jet Laboratory (JPL) uses an omnidirectional airbag system without vents.

[0003] A vented airbag is an airbag that has the ability to vent during the cushioning process. Its vent area is a fixed value. Upon landing impact, the airbag is compressed, absorbing energy. When the pressure reaches the designed venting pressure, the vent opens, and the gas inside the airbag is released outwards to dissipate energy. The airbag's cushioning principle relies on the deformation of the airbag under compressive load to absorb energy. Therefore, its cushioning characteristics mainly depend on the airbag's deformation characteristics, i.e., its stiffness. Insufficient stiffness will result in an increased airbag height or insufficient remaining height. Excessive stiffness can lead to rebound and unacceptable secondary impacts on the landing equipment.

[0004] For vented airbags with a fixed vent area, selecting an appropriate opening size can limit the overload value within a reasonable range. Compared to sealed airbags, vented airbags have more advantages.

[0005] In existing technologies, only the influence of different exhaust port areas on the airbag cushioning effect has been studied. All domestic heavy-duty airdrop systems adopt a structure with a fixed exhaust port area. Once the exhaust port is opened, the exhaust port opening area remains unchanged until the cushioning ends. This results in a small counterweight range for the airbag, which cannot adapt well to airdrop systems of different weights.

[0006] Furthermore, the combined airbag combines the advantages of both venting and sealed airbags. Its basic structure consists of two layers: an outer airbag that releases energy through venting, and an inner sealed airbag that provides support and protection for the equipment, preventing damage from direct ground contact. However, the combined airbag structure is complex. Existing data on combined airbag cushioning lacks research on methods for applying combined airbags to buffer heavy equipment airdrops to avoid hard collisions between equipment and the ground. Clear conclusions regarding the cushioning effect of combined airbags are lacking, and detailed analytical and simulation methods for combined airbags are also absent.

[0007] Intelligent airbags are smart structures with active impact control. They can control the airbag's deflation status in real time based on pressure changes inside the airbag and external overload changes during the cushioning process, thus achieving active control of the cushioning process. However, the cushioning time of the airbag during an airdrop impact is extremely short, and achieving the ideal change pattern of the deflation port area places very high demands on the actuation mechanism. Therefore, this intelligent control method has significant shortcomings.

[0008] In summary, while constructing a reasonable geometry for the airbag is crucial for accurately simulating and reproducing the multiphase flow dynamics of the airbag, current research mainly considers the geometry of the airbag with fixed exhaust port size or relying on the intelligent exhaust port absorption capacity of sensors. However, it neglects to design a novel adaptive variant exhaust port for the airbag based on bionics, which automatically adjusts the exhaust port size according to the impact magnitude to ensure that the pressure difference between the inside and outside of the airbag varies within the ideal range, thus maximizing the device's maximum overload and equipment stability. Summary of the Invention

[0009] The purpose of this invention is to provide a method for preparing an adaptive variable-diameter exhaust port buffer airbag. By changing the in-plane and thickness elastic modulus of the woven material in different regions outward from the central hole of the airbag, the deformation characteristics of the airbag in different regions outward from the central hole are controlled, thereby obtaining an airbag material with variable-diameter characteristics. This airbag can autonomously change according to the strength of the drop impact, thereby improving the success rate of airdrop.

[0010] To achieve the above objectives, the present invention provides a method for preparing an adaptive variable-diameter exhaust port buffer airbag, comprising the following steps:

[0011] S1. Select the airbag fabric material and reinforcing strip material based on the actual drop velocity V and load M of the air-dropped buffer airbag.

[0012] S2. Design the positional relationship between the combined airbag and the exhaust port;

[0013] S3. Design ventilation ports for multi-layered woven fabrics;

[0014] S4. Construct an equivalent mechanical model based on the woven material of the exhaust port, establish the relationship between the airdrop weight and the strength of each layer of woven material of the exhaust port, and obtain the exhaust port material with both low circumferential stiffness and high radial stiffness.

[0015] Preferably, in step S1, the airbag fabric material and the reinforcing belt material are both woven from warp and weft braided yarns, and the braided yarns are any one of nylon or polypropylene fibers.

[0016] Preferably, in step S1, the reinforcing strip material has a tensile strength of 3800–4200 N, a thickness of not less than 1.14 mm, and a density of 450–600 g / m³. 2 The elongation at break is not less than 25%.

[0017] Preferably, in step S2, the combined airbag includes an inner airbag and an outer airbag, the exhaust port and the outer airbag are integrally molded, and the outer airbag is also provided with an integrally molded reinforcing band.

[0018] The exhaust port is used to release energy through exhaust;

[0019] The reinforcing strip is used to enhance the strength of the airbag body;

[0020] The inner airbag is a sealed airbag used for the support and protection of the equipment, preventing damage caused by the equipment directly contacting the ground.

[0021] Preferably, the shape of the exhaust port is one or more of the following: circular, elongated slit, and rectangular.

[0022] The number of exhaust ports is one or more, specifically one of single-slit, double-slit, and triple-slit.

[0023] Preferably, in step S3, the exhaust port has a three-layer structure, including a first layer of woven fabric, a second layer of woven fabric, and a third layer of woven fabric arranged sequentially from the inside out with the exhaust gap as the center;

[0024] From a microscopic structural perspective, the gaps between the first layer of the woven fabric are larger than those between the second layer, and the gaps between the second layer are larger than those between the third layer.

[0025] The exhaust ports are all made of warp-woven yarn, weft-woven yarn, and resin.

[0026] Preferably, in step S4, the equivalent mechanical model construction of the woven material based on the vent includes the following steps:

[0027] S41. Define relevant parameters based on the microstructure of representative micro-elements;

[0028]

[0029] L w =a w t w +L wg

[0030] Where, r w α represents the radius of the weft-direction knitting yarn. w A represents the concave angle between weft yarns in a knitting pattern. wCross-sectional area of ​​weft-knitted yarn, a w and t w It refers to the cross-sectional shape factor and thickness of the weft-direction braided yarn; L wg and L w This indicates the gap and distance between adjacent weft yarns; in addition, changing the subscript "w" to "f" will indicate the parameters of the warp yarns.

[0031] S42. Calculate the crimp angle θ of the weft knitting yarn. fc Similarly, the curl angle θ of the warp yarn can be obtained. wc θ fc The calculation process is as follows:

[0032]

[0033] S43. Calculate the length L of the straight section of the weft knitting yarn. fs The fiber volume fraction κ of the weft braided yarn was obtained. w Fiber volume fraction κ of warp-knitted yarn f and fiber volume fraction κ per unit volume of braided yarn u Then calculate the fiber volume fraction V of the braided yarn. f As shown in the following formula:

[0034]

[0035] κ w =4A w [(2r f +t w )θ wc +L ws ]

[0036] κ f =4A f [(2r w +t f )θ fc +L fs ]

[0037] κ u =4(t) w +t f )L w L f

[0038]

[0039] Wherein, κ is the fiber filling fraction, with a value of 0.6 to 0.8;

[0040] S44. Calculate the flexibility matrix at the corners of warp and weft braided yarns:

[0041]

[0042] in, It is achieved by adjusting the warp curl angle θ of infinitesimal yarn segments. wc and latitude curl angle θ fc The compliance matrix is ​​obtained by averaging; S w To convert the warp yarn into a flexibility matrix in a global coordinate system, S f Convert the weft-direction knitting yarn into a flexibility matrix in a global coordinate system;

[0043] Softness matrix of warp-knitted yarn The softness matrix of weft knitting yarn The following formulas are given respectively:

[0044]

[0045] Where, λ wc and λ fc These represent the proportions of the length of the crimped portion of the warp and weft yarns to the total length, respectively.

[0046] S45, Stiffness matrix of average warp yarn Stiffness matrix of average weft braided yarn and resin stiffness matrix C m Calculate the overall stiffness matrix C of the woven fabric material. e The specific steps are as follows:

[0047]

[0048] in, and C is obtained by inverting its flexibility matrix. m Obtained from the following formula:

[0049]

[0050] Among them, v m This indicates the Poisson's ratio of the resin;

[0051] S46. Calculate the stiffness parameters of the first, second, and third layers of woven fabric in the warp (xx), weft (yy), and thickness (zz) directions using the following formula:

[0052]

[0053] Among them, E xx E yy E zz These represent the tensile modulus in the warp, weft, and thickness directions, respectively; G xy Gyz G zx These represent the shear modulus in each direction; v xy v yz v zx These represent the Poisson's ratio in each direction;

[0054] S47. When the entire airdrop system falls and impacts the ground, the radial force, weft force, and thickness force on the exhaust port fabric are respectively expressed as F x F y F z Let represent it, and its relation is as follows:

[0055]

[0056] Wherein, σ1, σ2, and σ3 represent the proportionality factors of the radial force, weft force, and thickness force on the exhaust port woven fabric to the airdrop weight, which are obtained through experiments and simulations; M0 represents the weight of the airdrop platform when unloaded.

[0057] Preferably, in step S44, S w With S f The following formulas are given respectively:

[0058] S w =[T w ] T [S wc [T] w ]

[0059] S f =[T f ]T[S fc [T] f ]

[0060] Matrix [S] wc ] and [S fc Calculated by the following formula:

[0061]

[0062] Where E, G, and v represent the stiffness parameters of the braided yarn in different directions within the fiber plane, with E representing tensile modulus, G representing shear modulus, and v representing Poisson's ratio;

[0063] [T w [T] represents the established yarn crimp transformation matrix. w ] T Its inverse matrix is ​​represented by the following formula:

[0064]

[0065] Where m = cosθ, n = sinθ, and θ represents the direction of the warp fiber. wc θ represents the weft fiber. fc .

[0066] Preferably, in step S47, the strength of the vent braid should satisfy the following relationship:

[0067]

[0068] Where F represents the force exerted on the vent fabric in different directions, by F x F y F z Let N represent the forces in each layer of fabric in three different directions. Since the airbag exhaust port has a three-layer structure, N1 represents the forces in the first layer of fabric in three different directions, N2 represents the forces in the second layer of fabric in three different directions, and N3 represents the forces in the third layer of fabric in three different directions. l represents the lateral length of each layer of fabric. Since the exhaust port has a three-layer structure, l1 represents the lateral length of the first layer of fabric, l2 represents the lateral length of the second layer of fabric, and l3 represents the lateral length of the third layer of fabric. These represent the proportion of impact resistance contributed by each layer of the woven fabric, determined by its length.

[0069] Therefore, the present invention employs the above-mentioned method for preparing an adaptive variable-diameter exhaust port buffer airbag, which has the following beneficial effects:

[0070] (1) The adaptive variable diameter exhaust hole buffer airbag proposed in this invention can adjust the strength of the material in different regions and the deformation characteristics of the airbag in different regions along the central hole by changing the properties (in-plane and thickness elastic modulus) of the woven material in different regions along the central hole. It can automatically change the size of the exhaust hole according to the magnitude of the impact force of airdrop landing of different weights. It can autonomously change according to the strength of the drop impact, improve the success rate of airdrop, and achieve autonomous expansion of the exhaust hole without the need for other mechanisms. The structure is simple and easy to implement.

[0071] (2) This invention adjusts the strength of the first to third layers of materials to adapt to the impact force of airdrops under different weights and working conditions. By controlling the width of each woven material and the gaps in the radial and weft directions, the variation law of the circumferential stiffness, radial and thickness stiffness of the material is studied to obtain the structural characteristics of the exhaust hole material with both low circumferential stiffness and high radial stiffness. The opening of the exhaust hole gap increases with the increase of the impact stress of the airbag falling, ensuring that the gas discharge speed inside the airbag is uniform and not too fast or too slow, thereby reducing the occurrence of overturning and rollover.

[0072] (3) The present invention uses a variable diameter exhaust hole buffer airbag without adding any other additional structures and devices, and without increasing the weight of the airbag. It is lightweight and does not increase the complexity of use. Attached Figure Description

[0073] Figure 1 This is a flowchart of an embodiment of the preparation method of an adaptive variable-diameter exhaust port buffer airbag according to the present invention;

[0074] Figure 2 This is a schematic diagram of the exhaust port position in an embodiment of the preparation method of an adaptive variable diameter exhaust port buffer airbag of the present invention, wherein (a) is a single slit, (b) is a double slit, and (c) is a triple slit;

[0075] Figure 3 This is a schematic diagram of the exhaust port structure of an embodiment of the preparation method of an adaptive variable diameter exhaust port buffer airbag of the present invention, wherein (a) is a schematic diagram of a single slit, (b) is an enlarged view of the exhaust port, and (c) is a schematic diagram of the microstructure of the exhaust port.

[0076] Figure 4 This is a schematic diagram of the relevant parameters of the exhaust port in an embodiment of the preparation method of an adaptive variable diameter exhaust port buffer airbag of the present invention;

[0077] Figure 5 This is a schematic diagram of the exhaust port microstructure of an embodiment of the preparation method of an adaptive variable diameter exhaust port buffer airbag of the present invention, wherein (a) is a schematic diagram of a representative micro-element and (b) is a schematic diagram of the relevant parameters of the micro-element. Detailed Implementation

[0078] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0079] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0080] Example 1

[0081] like Figure 1 As shown, a method for preparing an adaptive variable-diameter exhaust port buffer airbag includes the following steps:

[0082] S1. Select the airbag fabric material and reinforcing strip material based on the actual drop velocity V and load M of the air-dropped buffer airbag.

[0083] Both the airbag fabric and the reinforcing belt are made of warp and weft braided yarns, and the braided yarns can be either nylon or polypropylene fiber.

[0084] The reinforcing strip material must meet the following airbag strength standards: tensile strength of the reinforcing strip material is 3800–4200 N, thickness is not less than 1.14 mm, and density is 450–600 g / m³. 2 The elongation at break is not less than 25%.

[0085] S2. Design the positional relationship between the combined airbag and the exhaust port.

[0086] The combined airbag consists of an inner airbag and an outer airbag. The exhaust port and the outer airbag are integrally molded. The outer airbag is also equipped with an integrally molded reinforcing band, which consists of several cross-shaped strips on the outer airbag. The reinforcing band is used to enhance the strength of the airbag body, which can effectively reduce the risk of airbag rupture and improve the stability and safety of the airbag.

[0087] The inner airbag is a sealed airbag used to support and protect the equipment, preventing damage from direct contact with the ground. The vent is used to release energy. Upon landing impact, the outer airbag is compressed, absorbing energy. When the pressure reaches the designed venting pressure, the vent opens, releasing the energy by venting the gas inside. The vent shape can be circular, elongated slit-shaped, or rectangular, or one or more of these shapes. The number of vents can be one or more, specifically a single slit, double slit, or triple slit, and their positions are as follows... Figure 2 As shown.

[0088] S3. Design exhaust ports for multi-layered woven fabrics.

[0089] like Figure 3 As shown, the exhaust port has a three-layer structure, consisting of a first layer of woven fabric, a second layer of woven fabric, and a third layer of woven fabric arranged sequentially from the inside out, centered on the exhaust gap. From a microscopic perspective, the gaps between the first layer of woven fabric are larger than those between the second layer, and the gaps between the second layer of woven fabric are larger than those between the third layer. (As shown...) Figure 5 As shown in (a), the exhaust ports are all made of warp braided yarn, weft braided yarn and resin.

[0090] S4. Construct an equivalent mechanical model based on the woven material of the exhaust port, establish the relationship between the airdrop weight and the strength of each layer of woven material in the exhaust port, and obtain an exhaust port material with both low circumferential stiffness and high radial stiffness by adjusting the strength of the first to third layers of material.

[0091] The specific calculation process is as follows:

[0092] like Figure 4 As shown, l represents the lateral length of each layer of woven fabric. Since the vent has a three-layer structure, l1 represents the lateral length of the first layer of woven fabric, l2 represents the lateral length of the second layer of woven fabric, and l1 represents the lateral length of the third layer of woven fabric.

[0093] like Figure 5 As shown in (b), the parameters related to the microstructure of the representative infinitesimal element can be determined by the following formula:

[0094]

[0095] L w =a w t w +L wg

[0096] Where, r w α represents the radius of the weft-direction knitting yarn. w A represents the concave angle between weft yarns in a knitting pattern. w Cross-sectional area of ​​weft-knitted yarn, a w and t w It refers to the cross-sectional shape factor and thickness of the weft-direction braided yarn; L wg and L w This indicates the gap and distance between adjacent weft yarns. Additionally, changing the subscript "w" to "f" will display the parameters for the warp yarns.

[0097] S42, the curl angle of the weft knitting yarn (θ) fc The calculation is as follows:

[0098]

[0099] Similarly, the curl angle (θ) of the warp yarn can be obtained. wc ).

[0100] S43, Length of straight section of weft knitting yarn (L) fs The calculation is as follows:

[0101]

[0102] The fiber volume fraction κ of the weft braided yarn was obtained. w Fiber volume fraction κ of warp-knitted yarn f and fiber volume fraction κ per unit volume of braided yarn u Then calculate the fiber volume fraction V of the braided yarn. f As shown in the following formula:

[0103] κ w =4A w [(2r f +t w )θ wc +L ws ]

[0104] κ f =4Af [(2r w +t f )θ fc +L fs ]

[0105] κ u =4(t) w +t f )L w L f

[0106]

[0107] The fiber filling fraction κ ranges from 0.6 to 0.8, depending on the force applied to the preform during the fiber / matrix system processing.

[0108] S44. The flexibility matrix at the corners of warp and weft braided yarns is given by the following formula:

[0109]

[0110] in, It is achieved by adjusting the warp and weft curl angles (θ) of infinitesimal yarn segments. wc θ fc S is obtained by averaging the flexibility matrix of ). w With S f For warp and weft braided yarns (equal to the flexibility matrix of unidirectional braided yarns, S) wc and S fc The flexibility matrix, converted to a reference global coordinate system, is given by the following formula:

[0111] S w =[T w ]T[S wc [T] w ]

[0112] S f =[T f ] T [S fc [T] f ]

[0113] Matrix [S] wc ] and [S fc Calculated by the following formula:

[0114]

[0115] Where E, G, and v represent the stiffness parameters of the braided yarn in different directions within the fiber plane. The braided yarn can be any of nylon or polyvinyl chloride fibers; in this embodiment, T300 fiber is used uniformly, and the specific parameters are shown in the table below:

[0116] Table 1. Isotropic parameters of fiber materials for braided yarns

[0117]

[0118] [T w [T] represents the established yarn crimp transformation matrix. w ] T Let represent its inverse matrix. It is calculated using the following formula:

[0119]

[0120] Where m = cosθ, n = sinθ, and θ represents the direction of the warp fiber. wc θ represents the weft fiber. fc .

[0121] The flexibility matrix of the warp-knitted yarn The softness matrix of weft knitting yarn It is given by the following formula:

[0122]

[0123] Where, λ wc and λ fc These represent the proportion of the length of the crimped portion of the warp and weft yarns to the total length, respectively.

[0124] S45, Stiffness matrix of average warp yarn Stiffness matrix of average weft braided yarn and resin stiffness matrix C m Calculate the overall stiffness matrix C of the woven fabric material. e The specific steps are as follows:

[0125]

[0126] in, and It can be obtained by inverting its flexibility matrix, C m Obtained from the following formula:

[0127]

[0128] Among them, v m This indicates the Poisson's ratio of the resin.

[0129] S46. Calculate the stiffness parameters of the vented woven fabric in the warp (xx), weft (yy), and thickness (zz) directions using the following formulas, including tensile modulus (E), shear modulus (G), and Poisson's ratio (v):

[0130]

[0131] Among them, E xx E yy E zz G represents the tensile modulus (E) in the warp (xx), weft (yy), and thickness (zz) directions, respectively; xy G yz G zx These represent the shear modulus (G) in each direction; v xy v yz v zx These represent the Poisson's ratio (v) in each direction.

[0132] S47. Assuming the velocity of the airdropped component upon impact with the ground is constant, the radial force, weft force, and thickness force on the exhaust port fabric of the entire airdrop system upon impact with the ground are respectively expressed as F. x F y F z Let represent it, and its relation is as follows:

[0133]

[0134] Wherein, σ1, σ2, and σ3 represent the proportionality factors of the radial force, weft force, and thickness force on the exhaust port woven fabric to the airdrop weight, which are obtained through experiments and simulations; M0 represents the weight of the airdrop platform when unloaded.

[0135] To ensure a uniform and stable exhaust velocity during the exhaust process and prevent the exhaust port from tearing, the strength of the woven fabric at the exhaust port should satisfy the following relationship:

[0136]

[0137] Where F represents the force exerted on the vent fabric in different directions, by F x F y F z N represents the three different forces in each layer of the fabric. Since the airbag exhaust port has a three-layer structure, N1 represents the three different forces in the first layer of fabric, N2 represents the three different forces in the second layer of fabric, and N3 represents the three different forces in the third layer of fabric. These represent the contribution ratio of each layer of the woven fabric to the impact resistance, determined by its length. Based on practical experience, the outermost layer of woven fabric around the seam has a higher density, resulting in greater impact resistance. Based on experimental and simulation optimization, a value of 5 can be adopted. <l1<15mm;15<l2<25mm;25<l3<35mm。

[0138] Example 2

[0139] The actual drop velocity (V) of the air-dropped buffer airbag is approximately 8 m / s, and the load capacity (M) is 500 kg. The outer airbag fabric is made of nylon canvas, with a warp stiffness of 3000 N / cm, a weft stiffness of 2160 N / cm, and a density of 240 g / m³. 2 The inner airbag fabric is made of brocade, with a warp and weft stiffness of 350 N / 5 cm and a density of 49 g / m³. 2 The reinforcing strip material has a tensile strength of 3920 N, a thickness of not less than 1.14 mm, and a density of 450 g / m³. 2 The elongation at break is not less than 25%. The vent has a total of three layers, each with warp and weft yarns of the same thickness t. w =0.3mm, the gap between adjacent braided yarns in the first layer is 5mm, and the cross-sectional shape factor is 3; the gap in the second layer is 3mm, and the cross-sectional shape factor is 5; the gap in the third layer is 1mm, and the cross-sectional shape factor is 8. The warp and weft braided yarns use the same material—T300 fiber, and its specific parameters are shown in Table 1. Based on the formula in Example 1, the geometric parameters and stiffness parameters of the three-layer braided yarn are shown in Tables 2 and 3 below.

[0140] Table 2 Geometric parameters of braided yarns

[0141]

[0142]

[0143] Table 3 Stiffness parameters of braided yarns

[0144] Mechanical parameters First layer (MPa) Second layer (MPa) Third layer (MPa) <![CDATA[E xx ]]> 1.02e+04 1.93e+04 3.66e+04 <![CDATA[E yy ]]> 1.02e+04 1.93e+04 3.62e+04 <![CDATA[E zz ]]> 5.43e+03 8.52e+03 1.75e+04 <![CDATA[G xy ]]> 3.46e+03 4.98e+03 7.94e+03 <![CDATA[G yz ]]> 3.24e+03 4.47e+03 6.89e+03 <![CDATA[G zx ]]> 3.24e+03 4.47e+03 6.91e+03 <![CDATA[v xy ]]> 0.134 0.097 0.0782 <![CDATA[v yz ]]> 0.324 0.309 0.288 <![CDATA[v zx ]]> 0.173 0.137 0.139

[0145] Therefore, the present invention adopts the above-mentioned method for preparing an adaptive variable-diameter exhaust port buffer airbag, which automatically changes the size of the exhaust port according to the magnitude of the impact force of airdrop landing of different weights. It can autonomously change according to the strength of the drop impact, improve the success rate of airdrop, and can achieve autonomous expansion of the exhaust port without the need for other mechanisms. The structure is simple and easy to implement.

[0146] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing an adaptive caliber exhaust port bumper airbag, characterized in that, The method comprises the following steps: S1, selecting airbag fabric material and reinforcing belt material according to actual air-drop buffer airbag falling speed V and load M; S2, designing the positional relationship between the combined airbag and the air outlet; S3, designing the air outlet of the multi-layer woven fabric; S4, constructing an equivalent mechanical model based on the woven fabric material of the air outlet, constructing the relationship between the air-drop weight and the strength of each layer of woven fabric material of the air outlet, and obtaining the structural characteristics of the air outlet material with low hoop stiffness and high radial stiffness; In step S1, the airbag fabric material and the reinforcing belt material are woven from warp knitting yarn and weft knitting yarn, and the knitting yarn is any one of nylon and polyamide fiber; In step S1, the reinforcing belt material has a breaking strength of 3800-4200 N, a thickness of not less than 1.14 mm, a density of 450-600 g / m 2 , and an elongation at break of not less than 25%. In step S2, the combined airbag includes an inner airbag and an outer airbag, the air outlet is designed in one piece with the outer airbag, and the outer airbag is further provided with a reinforcing belt formed in one piece; The air outlet is used for energy release through air exhaust; The reinforcing belt is used to enhance the strength of the airbag body; The inner airbag is a closed airbag used for supporting and protecting the equipment to avoid damage caused by direct contact with the ground; In step S3, the air outlet is a three-layer structure including a first layer of woven fabric, a second layer of woven fabric and a third layer of woven fabric arranged in order from the inside to the outside with the air exhaust gap as the center; From the microstructure, the gap of the first layer of woven fabric is larger than that of the second layer of woven fabric, and the gap of the second layer of woven fabric is larger than that of the third layer of woven fabric; The air outlet is woven from warp knitting yarn, weft knitting yarn and resin; The outer airbag fabric material is silk sailcloth, the warp stiffness is 3000N / cm, and the weft stiffness is 2160N / cm. The inner airbag fabric material is silk, and the warp stiffness and weft stiffness are both 350N / 5cm; In step S4, the equivalent mechanical model is constructed based on the woven fabric material of the air outlet, comprising the following steps: S41, defining related parameters through the microstructure of a representative micro-element; ； ； ； ； wherein, R represents the radius of the weft knitted yarn, Θ represents the concave angle between the weft knitted yarns, A represents the cross-sectional area of the weft knitted yarn, and is the cross-sectional shape factor and thickness of the weft knitted yarn; and represents the gap and distance between the adjacent weft knitted yarns; in addition, the subscript ” is changed to ”, the above then represents each parameter of the warp knitted yarn; S42, calculating the crimp angle of the weft knitted yarn , and the crimp angle of the warp knitted yarn is obtained in the same way ; S43, calculating the length of the straight portion of the weft knitted yarn , obtaining the fiber volume fraction of the weft knitted yarn , the fiber volume fraction of the warp knitted yarn , the fiber volume fraction of the knitted yarn per unit volume , recalculating the fiber volume fraction of the knitted yarn ; S44, calculating the flexibility matrix at the corner of the warp knitting yarn and the weft knitting yarn: ； ； wherein, is obtained by averaging the flexibility matrices of the warp curl angle and the weft curl angle of an infinitesimal yarn segment; is the flexibility matrix of the warp knitted yarn converted with reference to the global coordinate system, is the flexibility matrix of the weft knitted yarn converted with reference to the global coordinate system; Flexibility matrix of warp knitted yarns Flexibility matrix of weft knitted yarns are given by the following equations, respectively: ； ； wherein, and L and L represent the proportion of the length of the warp and weft knitted yarn crimped portion, respectively, to the total length; S45, calculating an overall stiffness matrix of the braid material by averaging the stiffness matrix of the warp direction braided yarns , averaging the stiffness matrix of the weft direction braided yarns , and the resin stiffness matrix ;​ S46, calculate the stiffness parameters of the warp direction of the first layer of braid, the second layer of braid and the third layer of braid by the following formula: , the weft direction , the thickness direction of the first layer of braid, the second layer of braid and the third layer of braid ； wherein, Ei, E2, E3 respectively represent tensile modulus in the longitudinal, latitudinal, and thickness directions; Gi, G2, G3 respectively represent shear modulus in each direction; Pi, P2, P3 respectively represent Poisson's ratio in each direction; S47, the radial force, the weft force and the thickness direction force of the exhaust port braid when the whole air drop system falls on the ground are respectively represented by F x , F y , F z , and the relationship is as follows: ； wherein, M0 represents the weight of the air delivery platform when empty; and wherein the ratio of the radial force, the weft force and the thickness force to the air delivery weight is a factor measured by tests and simulations. In step S47, the strength of the air outlet woven fabric should satisfy the following relationship: ； Where F represents the forces in different directions on the fabric of the exhaust port, and is represented by F x , F y , F z ; N represents the forces in three different directions on each layer of the woven fabric, since the air bag exhaust port has a three-layer structure, so N 1 represents the forces in three different directions on the first layer of the woven fabric, N 2 represents the forces in three different directions on the second layer of the woven fabric, N 3 represents the forces in three different directions on the third layer of the woven fabric; represents the length of the transverse direction of each layer of the woven fabric, since the exhaust port has a three-layer structure, so represents the length of the transverse direction of the first layer of the woven fabric, represents the length of the transverse direction of the second layer of the woven fabric, represents the length of the transverse direction of the third layer of the woven fabric; respectively represent the contribution proportion of each layer of the woven fabric parameter to the impact resistance, which is determined by the length, 5 <15mm; 15 <25mm; 25 <35mm.

2. The method for preparing an adaptive variable-diameter exhaust port buffer airbag according to claim 1, characterized in that, The shape of the air outlet is one or more of a circle, a long slit and a rectangle; The number of air outlets is one or more, specifically one of single slit, double slit and three slits.

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