A multi-material composite hoop layered bead structure and design method

Abstract

The present application relates to a multi-material composite annular layered bead structure and design method, and relates to the field of tire structure and manufacturing method thereof. The bead structure comprises a bead body, the bead body is composed of a plurality of composite layers which are concentrically stacked along the circumferential direction of a circular cross section; the plurality of composite layers at least include a first material layer and a second material layer, the first material layer has a first elastic modulus, and the second material layer has a second elastic modulus; the first material layer and the second material layer are arranged in a preset order in the radial direction of the circular cross section to form a gradient distribution of the elastic modulus, and the low elastic modulus material layer in the first material layer is arranged in a stress concentration area or a geometric shape mutation area of the circular cross section. The present application inhibits the initiation and propagation of fatigue cracks from the source, greatly improves the fatigue resistance and long-term service reliability of the bead, optimizes the weight and rolling energy consumption by introducing lightweight materials, and enhances the overall torsional stiffness and anti-deformation ability of the bead through the layered structure.

Description

Technical Field

[0001] This invention relates to the field of tire structure and manufacturing method, specifically to a multi-material composite circumferential layered bead structure and design method. Background Technology

[0002] The tire bead, located in the toe area on the inner side of the tire, provides positioning, load-bearing capacity, and airtightness through an interference fit with the rim. Currently, widely used bead structures typically consist of a single-grade copper-plated steel wire continuously wound to form a hexagonal, rectangular, or circular cross-section core ring, which shares stress with the tire carcass ply structure. In practical use, this type of steel wire ring exhibits a significant problem of localized stress concentration: due to abrupt changes in cross-sectional geometry and the characteristics of the spiral winding process, under inflation and rolling conditions, the stress level in specific areas is significantly higher than in the surrounding areas, forming obvious stress peaks and becoming a major cause of fatigue crack initiation and propagation. Simultaneously, the unidirectional winding structure exhibits strong anisotropy, making it relatively weak in resisting lateral and torsional loads. During long-term service, it is prone to fretting separation between the winding layers or loosening of the fit with the rim, thus affecting tire durability and driving safety.

[0003] In response to the aforementioned early failure problem caused by stress concentration, how to provide a multi-material composite circumferential layered bead structure and design method has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] To address at least one technical problem in the background art, the present invention provides a multi-material composite circumferential layered bead structure and design method. It employs heterogeneous material layers with gradient elastic modulus arranged concentrically along the circumferential direction. By actively placing the low-modulus buffer layer in the stress-sensitive area and configuring the high-modulus load-bearing layer on the main force transmission path, the stress concentration is effectively reduced from the structural design source, making the stress distribution of the cross section tend to be gentle, thereby significantly improving the fatigue resistance and long-term service reliability of the bead.

[0005] To achieve the above objectives, the present invention provides a multi-material composite circumferential layered bead structure, comprising: a bead body having a circular cross-section and being composed of multiple composite layers concentrically stacked along the circumference of the circular cross-section; the multiple composite layers comprising at least a first material layer and a second material layer, the first material layer having a first elastic modulus, the second material layer having a second elastic modulus, and the first elastic modulus being different from the second elastic modulus; wherein the first material layer and the second material layer are arranged in a predetermined order in the radial direction of the circular cross-section to form a gradient distribution of elastic modulus, and the low elastic modulus material layer in the first material layer is disposed in the stress concentration region or geometric abrupt region of the circular cross-section.

[0006] Furthermore, it also includes a bead core, disposed in the geometric center region of the circular cross-section of the bead body; the bead core is a solid filled structure with a third elastic modulus or a hollow structure; the third elastic modulus is lower than the elastic modulus of the first material layer and the second material layer.

[0007] Furthermore, the total number of layers in the multilayer composite layer is N, where N is an integer satisfying 3≤N≤5; the multilayer composite layer includes at least one steel wire bearing layer made of high-strength copper-plated steel wire, and at least one non-metallic fiber layer made of carbon fiber, aramid fiber, nylon fiber or their composite material woven tape.

[0008] Furthermore, one of the non-metallic fiber layers is a low-modulus buffer layer, whose elastic modulus is lower than that of the steel wire bearing layer, and is arranged in the geometric corner area with the smallest radius of curvature in the circular cross section or in contact with the edge of the tire carcass.

[0009] Furthermore, the low-modulus buffer layer is composed of monofilaments of nylon or aramid fibers arranged in an oriented manner, woven tape, or multidirectional fabric.

[0010] Furthermore, the steel wire bearing layer is formed by multiple strands of high-strength copper-plated steel wire through spiral winding, parallel winding, or braiding processes.

[0011] Furthermore, the fiber arrangement direction of at least one layer of the multilayer composite layer forms an angle of 0° to ±30° with the circumferential tangent direction of the circular cross-section, which is used to optimize the load-bearing capacity in a certain direction.

[0012] A design method for a multi-material composite circumferentially layered bead structure, used to design the multi-material composite circumferentially layered bead structure described in any of the above-mentioned embodiments, includes the following steps: Step S1: Construct a finite element simulation model that includes the initial bead structure and its surrounding tire components and rim, and input the preset inflation, loading and rolling loads. Step S2: Perform nonlinear finite element analysis to obtain stress field distribution cloud maps of the initial tire bead structure under different working conditions, and identify stress peak regions, stress gradient abrupt change regions, and main force transmission paths. Step S3: Based on the analysis results of S2, define design variables, including: the total number of material layers N, the candidate material types for each material layer, the thickness of each material layer, and the radial arrangement order of each material layer; Step S4: With the optimization objective of minimizing the maximum von Mises stress or the maximum first principal stress of the bead cross section, or maximizing the safety factor of each layer of material, and with the preset manufacturing process constraints and cost constraints as boundary conditions, establish a multi-objective optimization model. Step S5: Solve the multi-objective optimization model using a genetic algorithm, simulated annealing algorithm, or particle swarm optimization algorithm to obtain the Pareto optimal solution set; Step S6: Select a solution from the Pareto optimal solution set. This solution defines the optimal material selection, thickness ratio, and spatial stacking sequence for each material layer. Based on this, generate the final design of the tire bead by actively placing the low-modulus material layer in the stress concentration region and placing the high-modulus material layer in the main load-bearing region.

[0013] Furthermore, the candidate materials in step S3 include at least: high-strength copper-plated steel wire, carbon fiber / epoxy resin composite material, aramid fiber / epoxy resin composite material, nylon fiber / epoxy resin composite material, and woven tape prepreg made of the above fibers.

[0014] Furthermore, after generating the final design in step S6, the process also includes generating CNC code for automated fiber / tape laying equipment or automated winding equipment based on the fiber arrangement angle and stacking process of each selected material layer, so as to achieve automated manufacturing.

[0015] The beneficial effects of this invention are as follows: This invention employs a circumferentially concentric layered structure with a gradient distribution of elastic modulus. Low-modulus materials are actively placed in areas of geometric abrupt changes and stress sensitivity, effectively mitigating localized stress concentration in the bead cross-section. This significantly reduces the risk of fatigue crack initiation and improves the bead's fatigue resistance and long-term durability under complex operating conditions. By introducing low-density non-metallic materials such as carbon fiber and aramid fiber, combined with a hollow or lightweight core filling design, the bead's weight is significantly reduced while maintaining structural load-bearing strength, thus contributing to lower tire weight and rolling energy consumption. The circumferential composite structure of the multilayer composite material enhances the overall torsional stiffness and deformation resistance of the bead, effectively preventing loosening and interlayer separation during use. Furthermore, the cross-sectional layup can be customized based on simulation data, balancing high reliability and flexible adaptability. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the present invention applied to a tire; Figure 2 This is a schematic diagram of the circular tire bead, the main structure of the present invention. Figure 3 Force analysis of the main structure of the invention: the circular tire bead Figure 1 ; Figure 4 Force analysis of the main structure of the invention: the circular tire bead Figure 2 ; Figure 5 Force analysis of the main structure of the invention: the circular tire bead Figure 3 .

[0017] Wherein, 1-first composite layer; 2-second composite layer; 3-third composite layer; 4-fourth composite layer; 5-bead core. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0020] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0021] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0022] Furthermore, the terms "installation," "setup," "equipped with," "connection," "linking," and "socketing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0023] To achieve the above objectives, such as Figure 1 and Figure 2 As shown, the present invention provides a multi-material composite circumferential layered bead structure, comprising: a bead body having a circular cross-section and being composed of multiple composite layers concentrically stacked along the circumference of the circular cross-section; the multiple composite layers comprising at least a first material layer and a second material layer, the first material layer having a first elastic modulus, the second material layer having a second elastic modulus, and the first elastic modulus being different from the second elastic modulus; wherein the first material layer and the second material layer are arranged in a predetermined order in the radial direction of the circular cross-section to form a gradient distribution of elastic modulus, and the low elastic modulus material layer in the first material layer is disposed in the stress concentration region or geometric abrupt region of the circular cross-section.

[0024] The gradient distribution is not a simple increase or decrease layer by layer, but rather an active design based on the stress simulation analysis results of the bead structure under target working conditions. Its core strategy is to actively and selectively place layers of material with relatively low elastic modulus in stress concentration areas or regions of geometric abrupt changes revealed by the simulation analysis; while placing layers of material with relatively high elastic modulus along the main force transmission path. Through this layered configuration, the stress and tension distribution of the entire bead cross-section is actively controlled.

[0025] Its working principle is as follows: When the tire bead is under load, the high-elastic-modulus load-bearing layer acts as a skeleton, bearing the main structural load and maintaining its shape. Meanwhile, the low-elastic-modulus buffer layer, located in the stress concentration area, generates less stress under the same strain, or through its larger elastic deformation, redistributes the stress originally concentrated at sharp corners or interfaces to a larger area. This effectively smooths out stress peaks and valleys, making the stress distribution across the entire cross-section more uniform and significantly reducing excessively high local stress peaks. This fundamentally inhibits the initiation of fatigue cracks, greatly improving the tire bead's fatigue resistance under complex working conditions and its long-term reliability.

[0026] The invention also includes a bead core disposed at the geometric center of the circular cross-section of the bead body; the bead core is a solid filled structure with a third elastic modulus or a hollow structure; the third elastic modulus is lower than the elastic modulus of the first material layer and the second material layer. The bead core can be a hollow structure, with its internal cavity forming a weight-reducing cavity; or it can be a solid structure filled with a low-density, low-elastic-modulus material (such as lightweight foamed metal, high-performance polymer foam, or elastomer). This design further reduces the weight of the bead without significantly affecting the overall structural stiffness, and the radial compressive stiffness of the bead can be fine-tuned by adjusting the modulus of the filling material, optimizing the contact pressure distribution between the bead and the rim, and improving airtightness.

[0027] The total number of layers in the multi-layer composite layer is N, where N is an integer satisfying 3≤N≤5; the multi-layer composite layer includes at least one steel wire bearing layer made of high-strength copper-plated steel wire, and at least one non-metallic fiber layer made of carbon fiber, aramid fiber, nylon fiber or their composite material woven tape.

[0028] One of the non-metallic fiber layers is a low-modulus buffer layer, whose elastic modulus is lower than that of the steel wire bearing layer, and it is arranged in the geometric corner area with the smallest radius of curvature in the circular cross section or in contact with the edge of the tire carcass.

[0029] The low-modulus buffer layer is composed of monofilaments of nylon or aramid fibers arranged in an oriented manner, woven tape, or multidirectional fabric.

[0030] The steel wire support layer is formed by multiple strands of high-strength copper-plated steel wires through spiral winding, parallel winding, or braiding processes.

[0031] By blending high-strength, high-modulus but high-density steel wires with various fibers that have lower density, excellent specific strength and specific modulus but different elongation at break, an optimal balance can be achieved between load-bearing capacity, fatigue toughness, lightweighting, and cost.

[0032] Due to its high modulus, low density, and good fatigue resistance, the carbon fiber layer is placed in the inner region near the geometric center of the bead, or, based on simulation results, in a specific stress-sensitive area, to provide stiffness and reduce weight. Meanwhile, the high-strength copper-plated steel wire layer is placed in the main load-bearing area near the outer edge of the bead, bearing the main tensile and shear loads due to its excellent toughness and adhesion to rubber.

[0033] Given the common phenomenon that abrupt changes in cross-sectional geometry, such as the tire toe or heel, are areas of greatest stress concentration, low-modulus nylon or aramid fiber filling layers are specifically incorporated into these areas. Aramid or nylon fibers have a lower elastic modulus than steel wire and carbon fiber, but possess excellent toughness and elongation at break. Precisely filling these areas with these fibers acts like adding flexible hinges to a rigid framework, effectively absorbing strain energy, mitigating localized stress concentration, and preventing crack initiation.

[0034] In the multilayer composite layer, the fiber arrangement direction of at least one layer of material forms an angle of 0° to ±30° with the circumferential tangent direction of the circular cross-section, which is used to optimize the load-bearing capacity in a certain direction.

[0035] This invention also provides a design method for a multi-material composite circumferential layered bead structure, comprising the following steps: Step S1: Construct a finite element simulation model that includes the initial bead structure and its surrounding tire components and rim, and input the preset inflation, loading and rolling loads. Step S2: Perform nonlinear finite element analysis to obtain stress field distribution cloud maps of the initial tire bead structure under different working conditions, and identify stress peak regions, stress gradient abrupt change regions, and main force transmission paths. Step S3: Based on the analysis results of S2, define design variables, including: the total number of material layers N, the candidate material types for each material layer, the thickness of each material layer, and the radial arrangement order of each material layer; the candidate material types include at least: high-strength copper-plated steel wire, carbon fiber / epoxy resin composite material, aramid fiber / epoxy resin composite material, nylon fiber / epoxy resin composite material, and woven tape prepreg made of the above fibers.

[0036] Step S4: With the optimization objective of minimizing the maximum von Mises stress or the maximum first principal stress of the bead cross section, or maximizing the safety factor of each layer of material, and with the preset manufacturing process constraints and cost constraints as boundary conditions, establish a multi-objective optimization model. Step S5: Solve the multi-objective optimization model using a genetic algorithm, simulated annealing algorithm, or particle swarm optimization algorithm to obtain the Pareto optimal solution set; Step S6: Select a solution from the Pareto optimal solution set. This solution defines the optimal material selection, thickness ratio, and spatial stacking sequence for each material layer. Based on this, the final design of the tire bead is generated by actively placing the low-modulus material layer in the stress concentration region and placing the high-modulus material layer in the main load-bearing region. After generating the final design in Step S6, the process also includes generating CNC code for automated fiber / tape laying equipment or automated winding equipment based on the fiber arrangement angle and stacking process of each selected material layer, to achieve automated manufacturing.

[0037] This invention overturns the traditional model of passively bearing stress in homogeneous tire beads. Through a design concept of elastic modulus gradient distribution and precise placement according to the stress field, a low-modulus buffer layer is used as an active stress regulator, positioned within the inherent stress concentration area. This results in a reduction of the maximum stress peak of the tire bead cross-section by more than 20% compared to traditional structures under the same load, with a more gradual stress distribution. This fundamentally delays or even prevents the initiation and propagation of fatigue cracks. Experimental data shows that its cyclic fatigue life can be increased several times or even an order of magnitude, greatly enhancing the long-term reliability and safety of the tire under complex and harsh operating conditions. By introducing low-density, high-performance non-metallic materials such as carbon fiber and aramid fiber, combined with a hollow or lightweight foam core design, significant weight reduction is achieved while maintaining or even improving the structural load-bearing capacity. For example, replacing part of the steel wire layer with a carbon fiber layer can reduce weight by 30%-40% without reducing strength. The reduction in bead weight directly reduces the overall weight and rotational inertia of the tire, helping to reduce rolling resistance, improve vehicle fuel economy, or extend the driving range of electric vehicles, resulting in significant economic and social benefits. The circumferential composite structure of multilayer composite materials, especially when woven composite layers or non-zero winding angles are introduced, alters the strong anisotropy of a single helical winding structure. This structure not only provides excellent circumferential tensile stiffness but also significantly improves the radial shear stiffness, lateral bending stiffness, and overall torsional stiffness of the bead. This monolithic integrity effectively suppresses interlayer fretting wear and the risk of loosening from the rim, ensuring the long-term stability of the bead's structural integrity throughout its lifespan. Based on simulation analysis and multi-objective optimization design methods, every design variable, from material selection and ply thickness to stacking sequence, can be precisely optimized, achieving a perfect combination of high performance, high reliability, and high adaptability. This provides unprecedented freedom for the design of high-performance tires.

[0038] Example 1

[0039] This embodiment provides a multi-material composite circular bead structure suitable for high-performance passenger car radial tires. (Refer to...) Figure 1 and Figure 2 The bead structure is an overall ring-shaped body with a circular cross-section, with four composite layers arranged concentrically from the inside out and a bead core 5 located in the center.

[0040] according to Figures 3 to 5 The simplified mechanical analysis and more detailed finite element simulation results shown identify the area near the toe corner (i.e. Figure 1 The lower left corner of the cross-section shown and the end point of the tire carcass ply flange are high stress concentration areas. Based on this, the specific configuration of each layer from the center outward in this embodiment is as follows: The bead core 5 is solidly filled with closed-cell polyurethane foam. Its density is only 0.4 g / cm³, and its elastic modulus is approximately 50 MPa. This design aims to provide central support while minimizing weight and acting as a buffer against radial crushing.

[0041] First composite layer 1: Located at the innermost layer, it is an aramid fiber buffer layer. It is formed by impregnating Kevlar 29 fibers with a denier of 1500D with epoxy resin, and then winding them circumferentially in parallel. The fiber volume content is approximately 60%. This layer has a Young's modulus of 80 GPa and a thickness of 0.8 mm. Its low modulus and excellent toughness allow it to directly face the interfacial stress caused by the flanging of the tire carcass, acting as the first-level buffer.

[0042] The second composite layer 2 is a carbon fiber reinforced load-bearing / transition layer. It utilizes prepreg tape made of T700 grade carbon fiber and epoxy resin, woven and stacked at a cross-weave angle of ±15°. This layer has a Young's modulus of 140 GPa and a thickness of 1.2 mm. This layer provides high stiffness, while its woven structure enhances resistance to complex stresses.

[0043] The third composite layer 3 constitutes the high-strength copper-plated steel wire main load-bearing layer. It is composed of multiple high-strength copper-plated steel wires with a diameter of 1.2mm (Young's modulus of approximately 200GPa) tightly arranged through a spiral winding process, with a thickness of approximately 2.5mm. This is the core skeleton that bears the tension of the tire carcass ply caused by air pressure. The main load-bearing layer ensures sufficient safety margin.

[0044] The fourth composite layer 4, located on the outermost layer, is a nylon fiber restraint / protection layer. It is formed by winding nylon fiber braided tape, with a Young's modulus of approximately 20 GPa and a thickness of 1.0 mm. This layer has two main functions: firstly, it acts as an outer protective layer to prevent mechanical damage to the inner steel wires during manufacturing and assembly; secondly, its high elongation at break allows it to effectively match the deformation of the outer bead compound and interlayer rubber, preventing interface debonding.

[0045] The intensity of the distributed force on the wire coil in the radial direction is expressed in N / mm, and its magnitude is... This refers to the elastic force generated in the tire body due to air pressure. This is the angle between the fiber arrangement direction and the tangent direction of the circular cross-section. For uniform units, it can be considered as the angle between the fiber arrangement direction and the tangent direction of the circular cross-section. The elastic force generated by the steel wires of the tire carcass within the range of radius. and This represents the force exerted by the rim on the steel coil. To maintain a consistent unit, it can be considered as a force per unit circumferential length. The constraint force provided for the interval of radius.

[0046] Assuming torque equilibrium, for Figure 4 As shown, there are It represents torque.

[0047] for Figure 5 As shown, there are Inflation pressure, It is the vertical distance from the vertex of the sub-mouth to the wheel axle.

[0048] According to the basic theories of mechanics of materials,

[0049] in, This represents the tensile stiffness of the wire coil. The elastic modulus of the steel wire coil. Let be the cross-sectional area of ​​the wire coil. . This represents the elongation of the wire coil. Assume the design diameter of the wire coil is... The diameter after deformation is Then there is

[0050] Taking the tire carcass from the horizontal axis to the reverse end point C as the research object, the axial equilibrium equation is established as follows:

[0051] in, The perpendicular distance from the reverse end point C to the wheel axle; It can be obtained.

[0052] therefore,

[0053] So,

[0054] For a toroidal layered structure, each layer of material has a different elastic modulus. and cross-sectional area ( i =1,2,…,n), where, Under axial tension, assuming no relative slippage between layers, the overall equivalent tensile stiffness is... The sum of the tensile stiffness of each layer:

[0055] Therefore, the tensile stiffness of the composite wire ring with a layered annular structure... for:

[0056] Analysis of ultimate stress (based on the maximum normal stress criterion)

[0057] For a circular layered wire ring, the first i radial displacement of the layer for

[0058] Radial stress With circumferential stress for

[0059] in, The inner radius of the ring layer, The outer radius of the ring layer, For elastic modulus, Poisson's ratio, , These are coefficients to be determined.

[0060] For a layered structure with a circular cross-section, the maximum normal stress criterion is stated as follows:

[0061] Therefore, for multi-material composite round bead tires, it is necessary to judge each layer individually, and the criteria are as follows:

[0062] Then the safety factor for each layer Defined as:

[0063] In this structure, the elastic modulus exhibits a radial gradient distribution of low (polyurethane) - medium-low (aramid) - medium-high (carbon fiber) - high (steel wire) - low (nylon), which is not a monotonous change but a customized configuration based on stress field characteristics and functional requirements. Finite element simulation verification shows that, compared to a traditional six-layer pure steel wire bead with equivalent load-bearing capacity, the maximum von Mises stress at the toe corner of this embodiment is reduced by approximately 28%, the total weight is reduced by approximately 32%, and the first torsional and lateral bending modal frequencies are increased by 15% and 22%, respectively, demonstrating superior resistance to deformation.

[0064] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A multi-material composite circumferential layered bead structure, characterized in that, include: The bead body has a circular cross-section and is composed of multiple composite layers concentrically stacked along the circumference of the circular cross-section. The multiple composite layers include at least a first material layer and a second material layer. The first material layer has a first elastic modulus, and the second material layer has a second elastic modulus. The first elastic modulus and the second elastic modulus are different. The first material layer and the second material layer are arranged in a predetermined order in the radial direction of the circular cross-section to form a gradient distribution of elastic modulus. The low elastic modulus material layer in the first material layer is disposed in the stress concentration region or the geometric abrupt change region of the circular cross-section.

2. The multi-material composite circumferential layered bead structure as described in claim 1, characterized in that, It also includes a bead core, which is disposed in the geometric center region of the circular cross-section of the bead body; the bead core is a solid filled structure with a third elastic modulus or a hollow structure; the third elastic modulus is lower than the elastic modulus of the first material layer and the second material layer.

3. The multi-material composite circumferential layered bead structure as described in claim 2, characterized in that, The total number of layers in the multi-layer composite layer is N, where N is an integer satisfying 3≤N≤5; the multi-layer composite layer includes at least one steel wire bearing layer made of high-strength copper-plated steel wire, and at least one non-metallic fiber layer made of carbon fiber, aramid fiber, nylon fiber or their composite material woven tape.

4. The multi-material composite circumferential layered bead structure as described in claim 3, characterized in that, One of the non-metallic fiber layers is a low-modulus buffer layer, whose elastic modulus is lower than that of the steel wire bearing layer, and it is arranged in the geometric corner area with the smallest radius of curvature in the circular cross section or in contact with the edge of the tire carcass.

5. The multi-material composite circumferential layered bead structure as described in claim 4, characterized in that, The low-modulus buffer layer is composed of monofilaments of nylon or aramid fibers arranged in an oriented manner, woven tape, or multidirectional fabric.

6. A multi-material composite circumferential layered bead structure as described in claim 3 or 5, characterized in that, The steel wire support layer is formed by multiple strands of high-strength copper-plated steel wires through spiral winding, parallel winding, or braiding processes.

7. The multi-material composite circumferential layered bead structure as described in claim 3, characterized in that, In the multilayer composite layer, the fiber arrangement direction of at least one layer of material forms an angle of 0° to ±30° with the circumferential tangent direction of the circular cross-section, which is used to optimize the load-bearing capacity in a certain direction.

8. A design method for a multi-material composite circumferential layered bead structure, characterized in that, The design of the multi-material composite circumferential layered bead structure according to any one of claims 1-7 includes the following steps: Step S1: Construct a finite element simulation model that includes the initial bead structure and its surrounding tire components and rim, and input the preset inflation, loading and rolling loads. Step S2: Perform nonlinear finite element analysis to obtain stress field distribution cloud maps of the initial tire bead structure under different working conditions, and identify stress peak regions, stress gradient abrupt change regions, and main force transmission paths. Step S3: Based on the analysis results of S2, define design variables, including: the total number of material layers N, the candidate material types for each material layer, the thickness of each material layer, and the radial arrangement order of each material layer; Step S4: With the optimization objective of minimizing the maximum von Mises stress or the maximum first principal stress of the bead cross section, or maximizing the safety factor of each layer of material, and with the preset manufacturing process constraints and cost constraints as boundary conditions, establish a multi-objective optimization model. Step S5: Solve the multi-objective optimization model using a genetic algorithm, simulated annealing algorithm, or particle swarm optimization algorithm to obtain the Pareto optimal solution set; Step S6: Select a solution from the Pareto optimal solution set. This solution defines the optimal material selection, thickness ratio, and spatial stacking sequence for each material layer. Based on this, generate the final design of the tire bead by actively placing the low-modulus material layer in the stress concentration region and placing the high-modulus material layer in the main load-bearing region.

9. The design method of a multi-material composite circumferential layered bead structure as described in claim 8, characterized in that, The candidate materials in step S3 include at least: high-strength copper-plated steel wire, carbon fiber / epoxy resin composite material, aramid fiber / epoxy resin composite material, nylon fiber / epoxy resin composite material, and woven tape prepreg made of the above fibers.

10. The design method of a multi-material composite circumferential layered bead structure as described in claim 8, characterized in that, After generating the final design in step S6, the process further includes generating CNC code for automated fiber / tape laying equipment or automated winding equipment based on the fiber arrangement angle and stacking process of each selected material layer, so as to achieve automated manufacturing.

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