Flexible anti-cutting and anti-stabbing fabric and preparation method thereof

Abstract

The invention relates to a flexible anti-cutting and anti-stabbing fabric and a preparation method thereof, and belongs to the technical field of protective materials. The fabric comprises an outer layer and an inner layer, the outer layer is of a four-order density gradually-changing knitted structure, the surface density is gradually reduced from outside to inside, and the outer layer is sequentially composed of weft insertion weave, tuck weave, tuck-plain weave composite weave and tuck weave; the inner layer is of a three-dimensional spaced structure and comprises a top layer, a bottom layer and a connecting system, and the connecting system is connected with the top layer and the bottom layer through double-spiral elastic connecting yarn in an alternate tucking mode. And the outer layer and the inner layer are integrally compounded and molded through coil stringing. The preparation method adopts a double-needle-bed computerized flat knitting machine or a warp knitting machine, and is realized through the steps of outer layer knitting, inner layer knitting and compounding, circulation and after-treatment. Puncture energy is dispersed through the gradient density outer layer, impact is absorbed through the three-dimensional interval inner layer, the 24 J protection requirement of the GA68-2024 standard of the Ministry of Public Security can be met only through one to two layers, and meanwhile, flexibility, breathability and comfort are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of anti-cutting and anti-piercing fabric, in particular to a flexible anti-cutting and anti-piercing fabric and a preparation method thereof. BACKGROUND

[0002] High-performance flexible anti-cutting and anti-piercing fabric is an important research direction in the field of personal protective equipment, and has a wide range of applications in law enforcement, security, military and outdoor sports scenarios. Traditional anti-cutting and anti-piercing fabric usually adopts the design idea of "stacking multiple layers of uniform density materials", relying on simply increasing the thickness to achieve protection, resulting in a heavy and stiff overall fabric, poor air and moisture permeability, and seriously affecting the wearing comfort, thereby limiting its further application.

[0003] There are multi-layer anti-cutting and anti-piercing structures in the prior art that are integrally knitted using a full-fashioned knitting process, which to some extent improves the interlayer bonding force and integrity of the fabric, and attempts to enhance the protective performance by introducing functional treated yarns. However, such structures still have several deficiencies in design: first, there is a lack of systematic energy dissipation gradient design between the functional layers, and the protective mechanism mainly relies on the stacking of homogeneous materials and a single friction energy dissipation method, with a single energy dissipation path. Second, due to the lack of an outer layer structure with high density and high stiffness to preferentially bear and deflect the load, the inner layer cushioning structure is prone to bear too concentrated stress. Third, some of the functional treated materials used may have durability problems, with performance declining after multiple uses or washes, and at the same time, the original flexibility of the fabric may be sacrificed.

[0004] Therefore, there is still a need to develop an integrated fabric structure that achieves a good balance between anti-cutting and anti-piercing performance, durability, flexibility and wearing comfort. SUMMARY

[0005] The purpose of the present application is to overcome the deficiencies in the prior art and provide a flexible anti-cutting and anti-piercing fabric and a preparation method thereof.

[0006] To achieve the above object, the technical scheme adopted by the present application is: the first aspect is to provide a flexible anti-cutting fabric, which comprises an outer layer and an inner layer, the outer layer is a four-step density gradient knitted structure, which comprises a first step, a second step, a third step and a fourth step from outside to inside, the face density of the four-step density gradient knitted structure decreases step by step from outside to inside, and the transition zone between adjacent two steps is seamlessly connected by knitting; the face density of the second step is reduced by 5%-30% compared with the first step, the face density of the third step is reduced by 5%-30% compared with the second step, and the face density of the fourth step is reduced by 5%-30% compared with the third step; if the decreasing rate is too low (<5%), the gradient is not obvious, and the stress dispersion effect is limited; if the decreasing rate is too high (>30%), it may cause sudden change of structural stiffness, causing uneven stress concentration and diffusion, which is not conducive to smooth transition of energy; wherein the first step is a weft insertion stitch, the second step is a tuck stitch, the third step is a tuck-and-plain composite stitch, and the fourth step is a tuck stitch; the outer layer is knitted by a first yarn, the yarn count of the first yarn is 100-1000D, and the yarn strength is ≥20 cn / dtex; the inner layer is a three-dimensional spacing structure, which comprises a top layer, a bottom layer and a connecting system, the top layer is knitted by a second yarn, the second yarn is twisted with the first yarn, the bottom layer is woven by a third yarn, the connecting system is composed of two yarns with different elasticity by spiral twisting, and is connected between the top layer and the bottom layer in a way that the front and back needle beds alternately tuck, forming a three-dimensional spacing layer that buffers impact; the third yarn is selected from one or more of cotton, modal, lyocell and bamboo fiber; the fourth step of the outer layer and the top layer of the inner layer are integrally formed by knitting in a way that the loops are intertwined with each other.

[0007] Further, the first yarn is prepared by mixing one or more of polyethylene, aramid, PBO filament, nylon, polyester and metal wire.

[0008] Further, the mass ratio of the splicing of the spandex and the first yarn is 3:97-15:85, and the twist is 400 twists / m-800 twists / m; if the proportion of spandex is too low (less than 3%), the yarn elasticity is insufficient, and the inner layer buffering effect is poor; if the proportion of spandex is too high (more than 15%), the yarn strength decreases, affecting the interlayer bonding force and overall protection performance; the splicing twist of the second yarn is controlled between 400-800 twists / m, to ensure the stability of the splicing structure and the good flexibility of the yarn.

[0009] Further, the two different elastic yarns are both elastic yarns, including a high-elasticity yarn and a medium-elasticity yarn; the breaking elongation of the high-elasticity yarn is ≥ 50%, and the breaking elongation of the medium-elasticity yarn is 20%~40%. By constructing such a "pure elasticity" system, under impact load, the high-elasticity yarn first undergoes large deformation to absorb most of the energy, and the medium-elasticity yarn provides initial stiffness and recovery force to control the deformation process and prevent the high-elasticity yarn from being plastically damaged or broken due to excessive stretching. The two are coordinated to achieve the unity of fast response, high energy absorption efficiency, controllable rebound and excellent durability.

[0010] Further, the flexible anti-puncture fabric has a grammage of 280g / m²~1000g / m².

[0011] The second aspect is to provide a preparation method of the above-mentioned flexible anti-puncture fabric, which is integrally knitted by using a double-needle bed multi-axial warp knitting machine, wherein the warp knitting machine is equipped with a multi-axial laying-in device and a plurality of guide bars, the guide bars include a first group of guide bars for knitting an outer layer, a second group of guide bars for knitting an inner layer, and a spacing guide bar for forming a connection system; the preparation method comprises the following steps: S1. Yarn configuration and system preparation: configure yarns to corresponding guide bars and set knitting program; that is, configure the first yarn for knitting the outer layer structure to the first group of guide bars; configure the second yarn for knitting the top layer of the inner layer to a front needle bed guide bar in the second group of guide bars; configure the third yarn for knitting the bottom layer of the inner layer to a rear needle bed guide bar in the second group of guide bars; and configure the double helix elastic connection yarn to the spacing guide bar; S2. Integrally knitting the outer layer and the inner layer structure: start the warp knitting machine, and under program control, the multi-axial laying-in device and each guide bar work cooperatively to synchronously perform the following knitting actions: (a) Knitting the four-step density gradient structure of the outer layer Lay the first yarn through the multi-axial laying-in device, and at the same time, form loops on the front needle bed by the first group of guide bars to form a knitted structure with gradually decreasing surface density from the outside to the inside; set a transition area between each step, and before the completion of the previous step, the guide bar of the next step intervenes in work in advance, so that the yarns of adjacent two steps naturally interlace and intertwine with each other during knitting to form an integrated connection structure; the four-step density gradient structure includes, in sequence, a first-step super-dense laid-in stitch formed by simultaneously feeding two first yarns in parallel without twist in the same course; a second-step high-density tuck stitch formed on the inner side of the first step by adjusting the density of the laid-in yarn and the tuck structure; a third-step medium-density tuck-and-flat composite stitch formed by further adjusting the arrangement density of the yarn and the stitch structure; and a fourth-step low-density tuck stitch formed by increasing the spacing between the weft yarns; the decreasing rate of the surface density of each step is 5% to 30%; (b) weaving the inner layer three-dimensional spacing structure and realizing interlaminar compounding: while weaving the outer layer fourth-order structure, feeding the second yarn through the front needle bed guide bar, continuing to weave on the front needle bed to form the top layer of the inner layer; synchronously feeding the third yarn through the back needle bed guide bar, weaving the bottom layer of the inner layer on the back needle bed; feeding the double helix elastic connecting yarn through the spacing guide bar, the double helix elastic connecting yarn is alternatively tuck knitted on the front needle bed and the back needle bed in a 'V' shape or 'W' shape path, connecting the top layer and the bottom layer to form the connecting system and the three-dimensional spacing structure; wherein the fourth order of the outer layer and the top layer of the inner layer are integrally compounded by the knitted weaving mode of loop interpenetration. S3. Circulation: the whole machine needle bed system synchronously and coordinately operates, and the weaving process of step S2 is repeated until the fabric base fabric of the required length is woven. S4. Post-treatment: the fabric base fabric obtained in step S3 is introduced into a heat setting machine at a tension of 5-10 N / m, and is subjected to heat treatment at a temperature of 60-105 DEG C, and then is cooled and set to obtain a flexible anti-cutting fabric with smooth surface and stable size.

[0012] Further, in step S1, when weaving the first-order super-dense weft insertion structure, a "double-fiber parallel weft insertion" mode is adopted, that is, two first yarns are simultaneously fed in parallel without twisting through the weft insertion device in the same weaving course.

[0013] Further, in step S4, the heat setting is immediately followed by rapid cooling and setting in a cooling zone, and the cooling rate is not less than 10-20 DEG C / min to below 40 DEG C.

[0014] Compared with the prior art, the above technical scheme has the following technical effects: The present application breaks through the traditional thinking mode of homogenous layering of protective materials, and constructs an integrated composite structure combining a four-order gradient density protective outer layer of "outer dense inner sparse" and a three-dimensional spacing buffer inner layer of "stretching-compression" dual-mode energy absorption. The penetration of a sharp object (such as a knife) is a dynamic energy concentration process, and the four-order gradient density structure of the outer layer converts the concentrated penetration energy into dispersed stress through physical design of the structure gradient, and dissipates it step by step. Compared with conventional plain woven fabric and knitted plain weave, the fiber aggregation degree at the knife tip is improved, and the resistance of the knife is stronger. Therefore, compared with the conventional aramid or polyethylene fabric which needs 50-60 layers to meet the 24J energy penetration resistance requirement in the GA68-2024 standard of the Ministry of Public Security, the flexible anti-cutting fabric provided by the present application only needs 1-2 layers to meet the protection requirements of the Ministry of Public Security.

[0015] The fabric of the present application has good inherent flexibility and ductility due to the overall structure formed based on the knitting process. The continuous air channels formed by the three-dimensional spacer layer help to improve the air and moisture permeability. The inner layer is made of soft and skin-friendly material, which not only ensures the protection performance, but also significantly improves the wearing comfort, and is suitable for long-term dressing requirements.

[0016] The integrated weaving of the outer layer and the inner layer is realized by knitting programming, and the layers are connected through loop stringing, which enhances the interface bonding strength and avoids the problems of rigidity, easy delamination and air permeability reduction caused by traditional lamination or coating process, and is also conducive to improving production efficiency and product consistency. DETAILED DESCRIPTION

[0017] The present application will be further described below in conjunction with specific embodiments, but not as a limitation of the present application. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0018] Example 1 This embodiment provides a flexible anti-cut and anti-puncture fabric with a face density of 720 g / m², which realizes excellent anti-cut and anti-puncture performance, flexibility and comfort through the integration of gradient density structure and three-dimensional spacer layer. The fabric structure includes an outer layer and an inner layer, wherein the outer layer adopts a four-order density gradient structure to resist cutting and puncture, and the inner layer adopts a three-dimensional spacer structure to absorb impact energy and provide air permeability. The design parameters, preparation process and performance of the fabric are described in detail below.

[0019] 1. Fabric structure design (1) Outer layer The outer layer is composed of 800D high-strength and high-modulus polyethylene filaments (first yarn) (strength 32 cN / dtex), which adopts a four-order density gradient structure, and the density decreases step by step from outside to inside, forming a gradient impedance effect to disperse and dissipate impact energy. The specific parameters of the four-order structure are as follows: 1) First order (super-dense weft insertion structure): Process: "double-filament parallel weft insertion" process is adopted, and two 800D high-strength and high-modulus polyethylene filaments (first yarn) are guided by the first group of guide bars to be fed into the same structure layer of the fabric in parallel without twist at the same time through the weft insertion device.

[0020] Advantages: A single weft insertion operation can introduce twice the number of cut-resistant yarns, greatly improving weaving efficiency and the speed of building a high-density protective layer. At the same time, the two yarns are parallel and untwisted, which can share and disperse stress when impacted by sharp objects, effectively avoiding the risk of premature breakage of a single yarn due to stress concentration. The parallel yarns can form a wider and denser protective surface, reducing the gaps between the yarns and making the first-stage structure more uniform and without weak points, thereby significantly improving the cut and puncture resistance of the outermost layer of the fabric.

[0021] Parameters: 8 warp rows; warp feed 1.8mm / warp row; areal density controlled at 170-180g / m². The areal density of the four outer layers refers to the local weight of that layer, not the areal density of the entire fabric.

[0022] Function: As the outermost line of defense, it generates local impedance through high modulus and close arrangement to resist blade penetration and convert point impact into area impact, consuming initial energy.

[0023] 2) Second-order (high-density clustered structure): Parameters: Uses 800D high-strength, high-modulus polyethylene filament; warp feed 2.0mm / row; as the warp feed increases, the weft spacing increases, resulting in a decrease in the areal density of this level; 6 rows are woven; every 3 stitches form 1 loop; areal density is controlled at 140-150g / m².

[0024] Function: It receives the stress transmitted in the first stage. The suspended arc structure formed by the clustered tissue has a certain degree of elasticity. It can diffuse the concentrated stress from the first stage to a wider area around the impact point through slight deformation, avoiding the rapid penetration of stress in the vertical direction and delaying the puncture process.

[0025] 3) Third stage (medium-density tucked-plain composite structure): Parameters: Uses 800D high-strength, high-modulus polyethylene filament; warp feed 2.3mm / row; alternating knitting of tuck stitches (1 tuck stitch every 4 needles) and plain knitting structure, knitting 5 rows; areal density transitions to 120-130g / m².

[0026] Function: The third stage is the transition zone of gradient change. The reduction of surface density and the composite design of the structure make its stiffness gradually decrease while its flexibility increases. It also continues to weaken and disperse the stress wave intensity transmitted from the second stage, realizing a smooth transition from "rigid resistance" to "flexible absorption". It is an important link in energy dissipation.

[0027] 4) Fourth stage (low-density clustered structure): Parameters: Uses 800D high-strength, high-modulus polyethylene filament; warp feed 2.6mm / row; 1 tuck every 5 needles, 4 rows of weaving; areal density reduced to 100-110g / m².

[0028] Function: As the final ring of the outer layer and the preparatory layer for connecting the inner layer, its main function is to provide a final buffer for the residual stress after the first three stages of dissipation, and to transfer the greatly reduced stress to the inner layer in a gentler manner. At the same time, its loose structure provides good compatibility with the coil in series integration of the outer top layer, ensuring the firmness of the interlayer bond.

[0029] When faced with an impact, a single-density structure will experience stress concentration due to abrupt changes in impedance, making it susceptible to instantaneous penetration. However, the continuous four-level gradient design creates a smooth transition zone from extremely high impedance to medium impedance, avoiding stress wave reflection and superposition caused by drastic changes in material properties. This allows impact energy to be attenuated more smoothly and efficiently layer by layer.

[0030] (2) Inner layer (buffered skin-friendly inner layer) The inner layer consists of a top layer and a bottom layer, which are connected by double-helix elastic yarns to form a three-dimensional spacer structure, providing cushioning and breathability.

[0031] 1) Top floor: Yarn: The second yarn is made of spandex and 800D high-strength, high-modulus polyethylene filament twisted together. The mass ratio of spandex to polyethylene filament is 10:90, and the twist is 600 twists / meter. This parameter design allows the second yarn to maintain high strength while possessing excellent elasticity, providing ideal mechanical properties for the inner and outer layers.

[0032] Structure: Plain weave, combining high strength and elasticity.

[0033] 2) Bottom layer (skin-friendly layer): Yarn: Combed cotton and modal blended yarn (third yarn) are used, with a blending ratio of 7:3 and a yarn count of 32S.

[0034] Fabric: 1+1 rib knit for enhanced skin-friendliness and breathability.

[0035] 3) Connecting the system: It uses a double-helix elastic connecting yarn, which is composed of a 70D spandex yarn (550% breaking elongation) and a 75D polypropylene terephthalate (PTT) yarn (30% breaking elongation) twisted together.

[0036] Knitting method: By alternating loop knitting on the front and back needle beds, the top layer and bottom layer are connected to form a three-dimensional spacer layer, ensuring cushioning performance and structural stability.

[0037] (3) Composite of outer and inner layers The outer fourth layer and the inner top layer are integrally formed through a knitted composite process using interlocking coils. This structural interconnection achieves a synergistic protection that combines rigidity and flexibility: the outer layer resists and disperses cutting stress, while the inner layer absorbs and buffers residual energy. The outer layer primarily serves a defensive function, utilizing its high modulus and density to resist and disperse the puncture and cutting stress of sharp objects, decomposing the powerful impact energy into multiple smaller energy packets. The inner layer mainly functions to absorb, using the compressibility of its three-dimensional spacer structure and the stretchability of its elastic connecting yarns to absorb and buffer the remaining energy transmitted after being dissipated by the outer layer. This "hard resistance first, soft absorption later" design forms a continuous, multi-mode energy dissipation channel. The outer layer solves the problem of traditional soft cushioning structures being easily punctured due to a lack of surface rigidity; the inner layer solves the problem of traditional rigid protective materials causing blunt force trauma to the human body after stress breakthrough due to a lack of buffer. Together, they elevate the material's puncture and cut resistance to a new level.

[0038] Furthermore, the inner three-dimensional spacer structure not only provides cushioning but also creates continuous air channels, ensuring excellent breathability and moisture permeability. The skin-friendly bottom layer directly contacts the skin, providing a comfortable wearing experience. This makes the protective gear suitable for extended wear while providing safety, solving the problems of traditional stab-proof vests being heavy, stuffy, and stiff.

[0039] 2. Preparation process The integrated knitting process is performed using a warp knitting machine equipped with a double needle bed and a multi-axial weft insertion device. The specific steps are as follows: S1. Yarn Configuration and System Preparation: The 800D high-strength, high-modulus polyethylene filament (first yarn) used for weaving the outer layer structure is configured in the first group of guide bars; the yarn (second yarn) made by twisting spandex and 800D high-strength, high-modulus polyethylene filament together for weaving the inner top layer is configured in a front needle bed guide bar in the second group of guide bars; the combed cotton and modal blended yarn (third yarn) used for weaving the inner bottom layer is configured in a rear needle bed guide bar in the second group of guide bars; the double-helix elastic connecting yarn is configured in the spacer guide bar.

[0040] S2. Integrated knitting of outer and inner layers: Start the warp knitting machine and execute the following actions synchronously under program control: (a) Weaving outer layer fourth-order density gradient structure The first yarn is laid out using a multi-axial weft insertion device, and simultaneously fixed in loops on the front needle bed using the first set of guide bars, forming a gradient structure from the first to the fourth level in sequence; the levels are seamlessly connected by the continuous weaving of the guide bars.

[0041] (b) Weave the inner layer and combine it with the outer layer. While starting to knit the fourth stage of the outer layer, the front needle bed comb is activated, the second yarn is fed in, and knitting continues on the front needle bed to form the top layer of the inner layer. At this time, the loops of the fourth stage of the outer layer and the starting row of loops of the top layer of the inner layer are integrated and connected through loop interlocking.

[0042] At the same time, the third yarn, cotton / modal blended yarn, is fed into the back needle bed comb and knitted on the back needle bed as the inner bottom layer (1+1 rib structure).

[0043] The double-helix elastic connecting yarn is fed through the spacer comb and knitted alternately in a 'V' shaped path on the front and back needle beds, connecting the top and bottom layers to form a three-dimensional spacer layer.

[0044] S3, Loop: Repeat step S2 until the desired length of fabric greige is woven.

[0045] S4. Post-processing: Heat setting: The fabric is fed into a heat setting machine under a tension of 5 N / m and heat-treated at 100°C to relax the internal stress of the fibers.

[0046] Rapid cooling: Cooling to below 40°C at a rate of 15°C / min inhibits the formation of large-size crystals in UHMWPE, promotes microcrystalline structure, and enhances toughness and flexibility.

[0047] Finally, the fabric is rolled up to obtain a smooth surface and dimensionally stable fabric.

[0048] 3. Performance Testing After weaving, the fabric has a thickness of 1.4 mm and a areal density of 720 g / m². According to the GA 68-2024 standard "Police Stab-Proof Vest," it was tested using a Class A stab-proof vest standard knife (D1), and the fabric was not penetrated under 24J of impact energy. Furthermore, the fabric achieves a balance between protection, flexibility, and comfort; the outer gradient structure effectively resists cuts, the inner spacer structure provides impact cushioning and breathability, and the bottom layer is skin-friendly and comfortable.

[0049] Through the integrated design of four-level density gradient and three-dimensional spacer layer, a balance between "protection and flexibility" is achieved. It can achieve the stab-proof standard without the need for multiple layers, and the weight is reduced by more than 40% compared with the traditional structure, making it suitable for long-term wear.

[0050] Example 2 This embodiment provides a flexible cut-resistant fabric with an areal density of 480 g / m². Its overall structural principle is the same as that of Embodiment 1, including an integrated composite design of an outer four-level density gradient structure and an inner three-dimensional spacer layer. However, by adjusting material parameters and structural details, a lighter and thinner design is achieved. The differences from Embodiment 1 are described in detail below.

[0051] 1. Fabric structure design (1) Outer layer First stage: The "double-filament parallel weft insertion" process is adopted, and two 400D aramid yarns (Kevlar29, first yarn) (strength 25cN / dtex) are inserted simultaneously without twisting. The warp feed is 2.2mm / row, 7 rows are woven, and the areal density is 115-120g / m².

[0052] Second stage: Use 400D aramid yarn (Kevlar 29), with a warp feed of 2.4mm / row, forming a tuck loop every 4 stitches, knitting 6 rows, with a surface density of 105-110g / m².

[0053] Third stage: Select 400D aramid yarn (Kevlar 29), with a warp feed of 2.6mm / row, knit tuck (1 tuck every 5 stitches) and plain knit structure, knit 5 rows, with a surface density of 95-100g / m².

[0054] Fourth stage: Use 400D aramid yarn (Kevlar 29), with a warp feed of 2.8mm / row, 1 tuck every 6 stitches, knit 3 rows, and reduce the areal density to 80-90g / m².

[0055] (2) Inner layer The inner structure is the same as in Example 1, including a top layer, a bottom layer, and a connecting system, but the material parameters are different: Top layer: The second yarn is a twisted yarn of spandex and 400D aramid, with a spandex to aramid mass ratio of 5:95 and a twist of 500 twists / meter. The weave is a plain weave.

[0056] Bottom layer: 32-count yarn (third yarn) blended with lyocell and cotton fibers in a 50 / 50 ratio, woven in a 1+1 rib structure.

[0057] Connection system: Same as in Example 1, using double helix elastic connecting yarn (composed of 70D spandex and 75D PTT), the top layer and bottom layer are connected by alternating loop knitting on the front and back needle beds.

[0058] The outer fourth layer and the inner top layer are integrally formed by coil stringing, as in Example 1.

[0059] 2. Preparation process The preparation process is the same as in Example 1, using a warp knitting machine equipped with a double needle bed and a multi-axial weft insertion device, but the finishing parameters are different: Heat setting: The fabric is fed into the heat setting machine under a tension of 5 N / m and heat-treated at 60°C. The lower tension and temperature treatment is used to lock in the fabric shape and protect its soft hand feel.

[0060] Cooling: Rapid cooling and shaping at a cooling rate of 10°C / min.

[0061] Other steps (such as the order of weaving the outer and inner layers) are the same as in Example 1.

[0062] 3. Performance Testing After weaving, the fabric thickness is 1.2mm and the areal density is 480g / m². According to the GA 68-2024 "Police Stab-Proof Vest" standard, using a Class A stab-proof vest standard knife D1 test, two layers are required to achieve an impact energy of 24J without being penetrated.

[0063] Example 3 This embodiment provides a flexible cut-resistant fabric with an areal density of 970 g / m². Its overall structural principle is the same as in Embodiment 1, including an integrated composite design of an outer layer with a four-level density gradient structure and an inner three-dimensional spacer layer. However, by using higher-performance materials and tighter structural parameters, stronger protective performance is achieved. The differences from Embodiment 1 are described in detail below.

[0064] 1. Fabric structure design (1) Outer layer First stage: The "double-filament parallel weft insertion" process is adopted, with two 1000D PBO filaments (strength 30cN / dtex) inserted simultaneously without twisting, with a warp feed of 1.8mm / column, 10 rows of weaving, and a surface density of 240-250g / m².

[0065] Second stage: Use 1000D PBO filament, with a warp feed of 2.0mm / row, forming a tuck loop every 3 stitches, knitting 8 rows, with a surface density of 220-230g / m².

[0066] Third stage: 1000D PBO filament is used, with a warp feed of 2.2mm / row, knitted in a tucked loop (1 loop every 4 stitches) and plain knit structure, knitted in 6 rows, with an areal density of 160-170g / m². The decrease rate of the third stage compared to the second stage is approximately 26.1%, which is adapted to the high stiffness characteristics of PBO fiber to ensure that stress is quickly dispersed and not concentrated.

[0067] Fourth stage: Use 1000D PBO filament, with a warp feed of 2.4mm / row, 1 tuck every 5 stitches, knit 5 rows, and reduce the areal density to 140-150g / m².

[0068] (2) Inner layer The inner structure is the same as in Example 1, including a top layer, a bottom layer, and a connecting system, but the material parameters are different: Top layer: The second yarn is a twisted yarn composed of spandex and PBO filaments, with a spandex to PBO mass ratio of 15:85 and a twist of 600 twists / meter. It is woven in a plain weave.

[0069] Bottom layer: Made of 60S pure cotton yarn with a ribbed weave to enhance skin-friendliness and breathability.

[0070] Connection system: Same as in Example 1, using double helix elastic connecting yarn (composed of 70D spandex and 75D PTT), the top layer and bottom layer are connected by alternating loop knitting on the front and back needle beds.

[0071] The outer fourth layer and the inner top layer are integrally formed by coil stringing, as in Example 1.

[0072] 2. Preparation process The preparation process is the same as in Example 1, using a warp knitting machine equipped with a double needle bed and a multi-axial weft insertion device, but the finishing parameters are different: Heat setting: The fabric is fed into a heat setting machine under a tension of 8 N / m and heat-treated at 90°C to relax the internal stress of the fibers.

[0073] Cooling: Rapid cooling and shaping at a cooling rate of 15°C / min.

[0074] Other steps (such as the order of weaving the outer and inner layers) are the same as in Example 1.

[0075] 3. Performance Testing After weaving, the fabric thickness is 2.3mm and the areal density is 970g / m². According to the GA 68-2024 "Police Stab-Proof Vest" standard, using a Class A stab-proof vest standard knife D1 test, a single layer can achieve an impact energy of 24J without being penetrated, providing an option for practitioners with higher requirements for protective performance.

[0076] Comparative Example 1 In comparison, this comparative example provides a cut-resistant fabric with an inner layer structure identical to that of Example 1, differing only in the outer layer structure: the outer layer employs a single tuck weave with a weight of approximately 540 g / m², without a density gradient design. Specific parameters are as follows: Outer layer: Yarn: The same 800D high-strength, high-modulus polyethylene filament (strength 32cN / dtex) as in Example 1 is used.

[0077] Tuck structure: single tuck stitch, with 4 stitches forming 1 tuck stitch, and the warp feed is uniformly set at 2.2mm / row, continuously knitted for 23 rows, with no density gradient change.

[0078] Preparation process: Except for the outer layer weaving parameters, the remaining steps (including the inner layer structure, composite method and finishing process) are consistent with those in Example 1.

[0079] Performance testing: After weaving, the fabric thickness is 1.3mm and the total areal density is 715g / m². According to the GA 68-2024 standard "Police Stab-Proof Vest", a Class A stab-proof vest standard knife (D1) was used for testing. The results showed that a single layer of fabric could not withstand 24J of impact energy and was penetrated by the knife tip during the test.

[0080] With the yarn material being exactly the same as in Example 1, Comparative Example 1, lacking a gradient density design in its outer layer structure, experienced a significant decrease in its cut and puncture resistance. When impacted by sharp objects such as knives, energy was concentrated at the point of contact with the blade tip. The single-structure fabric could not effectively achieve stress dispersion and energy dissipation at multiple levels, causing the concentrated stress to penetrate the fabric rapidly.

[0081] The results show that relying solely on high-strength yarns or surface treatments, without a gradient density structure of "dense on the outside and sparse on the inside," is insufficient to meet the requirements for high-strength cut and puncture resistance. This further confirms the crucial role of the fourth-order density gradient design in achieving continuous energy decay and improving cut and puncture resistance in this invention.

[0082] The above description is merely a preferred embodiment of the present invention and does not limit the implementation and protection scope of the present invention. Those skilled in the art should realize that any equivalent substitutions and obvious changes made based on the content of the present invention specification should be included within the protection scope of the present invention.

Claims

1. A flexible cut-resistant fabric, comprising an outer layer and an inner layer, characterized in that, The outer layer is a four-level density gradient knitted structure, consisting of four levels from the outside to the inside: the first level, the second level, the third level, and the fourth level. The areal density of the four-level density gradient knitted structure decreases gradually from the outside to the inside, and adjacent levels are seamlessly connected through transition zones formed by knitting. The areal density of the first level is 110-250 g / m²; the areal density of the second level is 5%-30% lower than that of the first level; the areal density of the third level is 5%-30% lower than that of the second level; and the areal density of the fourth level is 5%-30% lower than that of the third level. Specifically, the first level is an ultra-dense weft-inserted structure, the second level is a high-density tucked structure, the third level is a medium-density tucked-plain weave composite structure, and the fourth level is a low-density tucked structure. The outer layer is woven from the first yarn. The first yarn has a count of 100-1000D and a yarn strength ≥20cn / dtex. The inner layer has a three-dimensional spacer structure, including a top layer, a bottom layer, and a connecting system. The top layer is woven from a second yarn, which is made by twisting spandex with the first yarn. The bottom layer is woven from a third yarn. The connecting system consists of two yarns with different elasticities twisted in a spiral manner and connected between the top and bottom layers by alternating loops on the front and back needle beds, forming a three-dimensional spacer layer to buffer impact. The third yarn is selected from one or more blends of cotton, modal, lyocell, and bamboo fiber. The fourth layer of the outer layer and the top layer of the inner layer are integrally formed by a knitting method in which loops are interlocked.

2. The flexible cut-resistant fabric according to claim 1, characterized in that, The first yarn is prepared by blending one or more of polyethylene, aramid, PBO filament, nylon, polyester, and metal wire.

3. The flexible cut-resistant fabric according to claim 1, characterized in that, The mass ratio of the spandex to the first yarn in the twist is 3:97 to 15:85, and the twist is 400 twists / meter to 800 twists / meter.

4. The flexible cut-resistant fabric according to claim 1, characterized in that, Both yarns with different elasticities are elastic yarns, including one high-elasticity yarn and one medium-elasticity yarn; the breaking elongation of the high-elasticity yarn is ≥50%, and the breaking elongation of the medium-elasticity yarn is 20%~40%.

5. The flexible cut-resistant fabric according to claim 1, characterized in that, The weight of the flexible cut-resistant fabric is 280g / m² to 1000g / m².

6. A method for preparing a flexible cut-resistant fabric as described in any one of claims 1-5, characterized in that, Integrated knitting is performed using a multi-axial warp knitting machine equipped with a double needle bed. The warp knitting machine is equipped with a multi-axial weft insertion device and multiple guide bars. The guide bars include a first set of guide bars for knitting the outer layer, a second set of guide bars for knitting the inner layer, and spacer guide bars for forming a connecting system. The process includes the following steps: S1. Yarn Configuration and System Preparation: Configure the yarn to the corresponding guide bars and set the knitting program; that is, configure the first yarn for knitting the outer layer structure to the first group of guide bars; configure the second yarn for knitting the inner top layer to a front needle bed guide bar in the second group of guide bars; configure the third yarn for knitting the inner bottom layer to a back needle bed guide bar in the second group of guide bars; configure the double helix elastic connecting yarn to the spacer guide bars; S2. Integrated knitted outer and inner layer structure: Upon starting the warp knitting machine, under program control, the multi-axial weft insertion device works in conjunction with each guide bar to synchronously execute the following knitting actions: (a) Weaving outer layer fourth-order density gradient structure The first yarn is laid using a multi-axial weft insertion device, and simultaneously fixed in loops by the first set of guide bars on the front needle bed, forming a knitted structure with a gradually decreasing surface density from the outside to the inside. A transition zone is set between each step, allowing the guide bars of the next step to intervene before the previous step is completed, so that the yarns of adjacent steps naturally interweave and interlock during the knitting process, forming an integrated connection structure. The four-step density gradient structure sequentially includes: a first-step ultra-dense weft insertion structure formed by simultaneously feeding two first yarns in parallel without twist in the same row; a second-step high-density tucked structure formed inside the first step by adjusting the weft yarn density and tucked structure; a third-step medium-density tucked-plain weave composite structure formed by further adjusting the yarn arrangement density and structure; and a fourth-step low-density tucked structure formed by increasing the weft yarn spacing. The decrease rate of surface density for each step is 5% to 30%. (b) Weaving the inner three-dimensional spaced structure and achieving interlayer composite: While weaving the outer fourth-order structure, the second yarn is fed in through the front needle bed comb and weaving continues on the front needle bed to form the top layer of the inner layer; simultaneously, the third yarn is fed in through the back needle bed comb and the bottom layer of the inner layer is woven on the back needle bed; double helical elastic connecting yarn is fed in through the spaced comb, and the double helical elastic connecting yarn is alternately looped and woven on the front and back needle beds in a 'V' or 'W' shape to connect the top layer and the bottom layer, forming the connecting system and the three-dimensional spaced structure; wherein, the fourth order of the outer layer and the top layer of the inner layer are integrally composited by a knitting method in which loops are interlocked; S3. Cycle: All combing systems of the machine operate synchronously and in coordination, repeating step S2 until the required length of fabric greige is woven; S4. Finishing: The fabric greige obtained in step S3 is introduced into a heat setting machine with a tension of 5~10N / m, and heat-treated at a temperature of 60~105℃. Then it is cooled and set to obtain a smooth surface and dimensionally stable flexible cut-resistant fabric.

7. The preparation method according to claim 6, characterized in that, In step S1, when weaving the first-order ultra-dense weft-insertion structure, the "double-filament parallel weft-insertion" method is adopted, that is, the two first yarns are fed in parallel and without twist in the same weaving row through the weft-insertion device.

8. The preparation method according to claim 6, characterized in that, In step S4, immediately after heat setting, the product enters the cooling zone for rapid cooling and setting, cooling to below 40°C at a cooling rate of not less than 10-20°C / minute.