A multi-layer wound composite pipe capable of suppressing large-angle instability and a design method thereof

Abstract

The application provides a multilayer winding composite pipe capable of inhibiting large-angle instability and a design method thereof, and is applied to the technical field of composite pipes.The method comprises the following steps: determining basic parameters comprising a compressed maximum working condition angle and a composite pipe axial height; calculating the outer pipe inner pipe diameter, thickness of the metal pipe and the relative density of the metal pipe according to the axial height and the working condition angle; calculating the total thickness of the multilayer winding layer based on the metal pipe size and the working condition angle; and determining the layer number of the 90° layer and the 75° layer according to the physical relationship between the total thickness of the winding layer and the single layer thickness, and combining the layer proportion φ of the 90° layer number and the total layer number.The application realizes the function cooperation of the 90° inner layer circumferential constraint and the 75° outer layer axial bearing through the quantitative mapping of the working condition angle and the structure parameter, effectively inhibits the bending instability under the large-angle compression, guides the axial folding energy absorption, and significantly improves the anti-instability performance and energy absorption efficiency of the energy absorption box.

Description

Technical Field

[0001] This invention belongs to the field of composite pipe technology, specifically relating to a multi-level wound composite pipe that can suppress large-angle instability and its design method. Background Technology

[0002] Energy-absorbing boxes are core components of automotive passive safety systems, requiring a balance between lightweight design and impact-resistant energy absorption. Currently, CFRP (carbon fiber reinforced plastic) wound aluminum alloy composite multicellular tubes are one of the mainstream research configurations for lightweight energy-absorbing boxes. The typical design involves wrapping CFRP around an aluminum alloy tube to enhance strength. Existing technologies and patents largely focus on the application of composite materials and structural optimization, resulting in a series of technical solutions.

[0003] In the research and patented technologies related to CFRP / AL (carbon fiber reinforced plastic / aluminum alloy) composite multi-cell tube energy-absorbing boxes, the optimization of existing solutions focuses on adjusting the aluminum alloy matrix structure. For example, increasing the number of ribs inside the aluminum tube and optimizing the cross-sectional configuration can improve energy absorption. For instance, Chinese patent CN119550934A discloses a rotationally symmetric anti-oblique-pressure paper-folding tube collision energy-absorbing box. This energy-absorbing box improves its oblique-pressure resistance by changing its structural design. However, the structure disclosed in this patent is relatively complex, and the design parameters are difficult to adjust according to the actual installation location or working conditions, and the processing cost is high. In Chinese patent CN111688618A, a lightweight biomimetic energy-absorbing box is disclosed, which consists of an energy-absorbing box body and connecting parts at both ends. The energy-absorbing box body includes a box body and energy-absorbing components filled in the box body. The energy-absorbing components include honeycomb-like structural components and bone-like structural components. The energy absorption effect is improved, but the oblique-pressure instability situation is not considered, which limits the applicable working conditions. In addition, the structure is complex and difficult to process, which is not conducive to large-scale production.

[0004] In summary, existing research generally focuses on matrix structure innovation, and there are still clear areas for improvement in CFRP / AL composite multi-cell energy-absorbing box technologies: First, optimization of the CFRP winding angle has not yet been carried out in existing schemes, and the approach of relying on aluminum alloy structure optimization is difficult to balance the requirements of large-angle bending instability resistance and lightweighting, resulting in performance shortcomings in the technical solutions; Second, there is a lack of a design method adapted to CFRP multi-level layup parameters and large-angle collision conditions, resulting in poor performance stability of the energy-absorbing box in actual complex collision scenarios. Therefore, it is necessary to propose a new design approach based on the CFRP / AL composite multi-cell configuration that can balance lightweighting and impact resistance to compensate for the shortcomings of existing technologies. Summary of the Invention

[0005] In view of the above-mentioned problems in the prior art, the purpose of this invention is to provide a design method for multi-layer wound composite tubes that can suppress large-angle instability. By accurately designing and coupling the metal tube configuration parameters, the thickness of the multi-layer wound layers and the layup ratio, a lightweight configuration design of composite multi-cell tubes can be achieved while ensuring the energy absorption box's resistance to large-angle compression instability and energy absorption effect.

[0006] A design method for a multi-level wound composite tube that can suppress large-angle instability is provided. This method is used to design the structural parameters of the multi-level wound composite tube. The multi-level wound composite tube includes a metal tube and a multi-level wound layer. The multi-level wound layer covers the outer surface of the metal tube. The metal tube includes an inner tube and an outer tube, with the inner tube located inside the outer tube. The two tubes are in a concentric circular tube structure. N ribs are evenly distributed circumferentially inside the metal tube, dividing the space between the inner and outer tubes into N sector-shaped chambers. The multi-level wound layer adopts a layup structure combining 90° and 75° layups. The 90° and 75° layups are arranged in a specific number of layers and sequentially wound around the outer surface of the metal tube.

[0007] The design method for the multi-level wound composite tube includes the following steps:

[0008] Step 1: Determine the basic design parameters, including the maximum compression angle A, the axial height H of the multi-layer wound composite pipe, the number of ribs N, and the thickness t of a single layer;

[0009] Step 2: Calculate the dimensional parameters of the metal tube based on the basic design parameters, including the outer diameter D1, the inner diameter D2, and the thickness t of the metal tube. Al The relative density Δρ of the metal tube;

[0010] Step 3: Calculate the total thickness t of the multi-level winding layers. C The calculation formula is: t C =K4×t Al ×(D2 / D1)×(1+0.01×A), where K4 is the matching coefficient between the thickness of the metal layer and the multi-level winding layer;

[0011] Step 4: Determine the number and ratio of 90° and 75° plies. The calculation process is as follows:

[0012] Based on the total thickness t of the multi-level winding layers C The basic equation establishing the physical relationship between t and the single-layer thickness t is: C =n 总 ×t,n 总 =n 75° +n 90° , where n 75° n is the number of layers for a 75° ply. 90° The number of layers for a 90° ply;

[0013] Calculate the number of 75° and 90° plies based on the ply ratio φ between the set number of 90° plies and the total number of plies: n 90° =n 总 ×φ;n 75° =n 总 -n 90° .

[0014] Preferably, the maximum compression angle A ranges from 0 to 30°; the number of ribs N ranges from 3 to 8; and the ply ratio φ of the number of 90° plies to the total number of plies is 0.4 to 0.8. Specifically, the ply ratio φ of the number of 90° plies to the total number of plies is positively correlated with the maximum compression angle A and the axial height H of the multi-layer wound composite pipe; the larger the maximum compression angle A and the larger the axial height H of the multi-layer wound composite pipe, the more 90° plies are required. The ply ratio φ of the number of 90° plies to the total number of plies is negatively correlated with the number of ribs N; the larger the number of ribs N, the fewer 90° plies are required.

[0015] Preferably, the calculation formula for the outer diameter D1 of the metal tube is: D1=H×K1×(1+0.012×A), where H is the axial height of the multi-layer wound composite tube, K1 is the basic adaptation coefficient between the height and the outer diameter, and A is the maximum compression angle. The value range of the basic adaptation coefficient K1 between the height and the outer diameter is 0.35 to 0.55. Wherein, the larger the maximum compression angle A is, the more likely the structure is to bend and become unstable, and the basic adaptation coefficient K1 between the height and the outer diameter should be taken to increase the tube diameter and improve stability. When pursuing lightweight, K1 can be taken to a smaller value, and the value can be taken according to the actual needs.

[0016] Preferably, the formula for calculating the inner diameter D2 of the metal tube is: D2 D1×K2, where D1 is the outer diameter of the metal tube and K2 is the inner and outer diameter adaptation coefficient. The value of the inner and outer diameter adaptation coefficient K2 ranges from 0.5 to 0.7. The smaller the inner and outer diameter adaptation coefficient K2, the smaller the inner diameter D2 of the metal tube, the larger the tube wall and rib area, and the higher the structural strength. The larger K2, the larger the inner diameter D2 of the metal tube, and the higher the degree of structural lightweighting.

[0017] Preferably, the thickness t of the metal tube Al The calculation formula is: t Al=D1×K3, where D1 is the outer diameter of the metal tube and K3 is the metal tube thickness adaptation coefficient. The value of the metal tube thickness adaptation coefficient K3 ranges from 0.015 to 0.035. Specifically, the larger the maximum compression angle A, the larger the tube height H, and the lower the strength of the aluminum material, the larger the metal tube thickness adaptation coefficient K3 should be to improve the load-bearing capacity of the base material. When the strength of the aluminum material is high, the metal tube thickness adaptation coefficient K3 can be smaller.

[0018] Preferably, the formula for calculating the relative density Δρ of the metal tube is: Δρ=(πD²×t) Al +N×L×t Al ) / (πR²), where D2 is the inner diameter of the metal tube, L is the radial length of the rib, L=(D1-D2) / 2, t Al Let N be the thickness of the metal tube, N be the number of ribs, and R be the outer radius of the metal tube cross-section, where R = D1 / 2. The relative density Δρ of the metal tube ranges from 0.04 to 0.12. The relative density Δρ of the metal tube is used as a verification parameter. If the relative density Δρ of the metal tube obtained based on the current metal tube size parameters is within the preset range, it indicates that the current metal tube size parameters are reasonable. If the relative density Δρ of the metal tube does not meet the preset range, it is necessary to readjust the coefficients in each calculation formula so that the relative density Δρ of the metal tube eventually falls within the preset range.

[0019] Preferably, the matching coefficient K4 between the thickness of the metal layer and the multilayer winding layer is in the range of 2.0 to 3.5. Wherein, the lower the interfacial bonding strength between the multilayer winding layer and the metal layer and the larger the maximum compression angle A, the thicker the multilayer winding layer is needed to provide constraint. In this case, the matching coefficient K4 between the thickness of the metal layer and the multilayer winding layer should take a larger value; while when the interfacial bonding strength is high, K4 can take a smaller value.

[0020] The second objective of this invention is to provide a multi-layered wound composite tube capable of suppressing large-angle instability, comprising a metal tube and a multi-layered wound layer, wherein the multi-layered wound layer covers the outer surface of the metal tube, the metal tube comprising an inner tube and an outer tube, the inner tube being located inside the outer tube, the two forming a concentric circular tube structure, and four ribs evenly distributed circumferentially inside the metal tube, the four ribs dividing the space between the inner tube and the outer tube into four sector-shaped chambers, the multi-layered wound layer employing a layup structure combining 90° layup and 75° layup, the 90° layup and 75° layup being arranged in a specific ratio and sequentially wound around the outer surface of the metal tube;

[0021] Based on the aforementioned design method for multi-layer wound composite pipes that can suppress large-angle instability, setting the maximum compression angle A to 30°, the axial height H of the multi-layer wound composite pipe to 100mm, and the single-layer thickness t to 0.1mm in the basic design parameters, the calculated dimensional parameters of the metal pipe are: outer pipe diameter D1 to 60mm, inner pipe diameter D2 to 30mm, and metal pipe thickness t to 0.1mm. Al Given a thickness of 1 mm and a relative density Δρ of 0.0546 for the metal tube, the total thickness t of the multi-layer winding was calculated. C The thickness is 1.5mm, and the final number of 90° plies is 8, and the number of 75° plies is 7.

[0022] The beneficial effects of this invention are: the design method for multi-level wound composite tubes that can suppress large-angle instability,

[0023] A multi-layered spiral composite pipe layup configuration is proposed. By arranging the 75° outer layer and the 90° inner layer in a specific manner, the two spiral angles generate a synergistic coupling effect, which significantly improves the energy absorption and specific energy absorption of the same material and configuration when facing crushing at large angles from 0 to 30°. This effectively suppresses the negative effects of oblique pressure instability of multi-layered spiral composite pipes and solves the technical pain points of high instability risk and low energy absorption efficiency of traditional single-angle spiral composite pipes under large angle conditions.

[0024] A method for designing the winding angle layup to adapt to the CFRP / AL concentric tube configuration is disclosed. The core idea is to quantify and derive the proportional arrangement design of the winding angle based on known conditions such as the maximum compression angle A and the axial height H of the multi-level wound composite tube through formulas. This method can simplify the traditional trial-and-error process, help designers quickly complete the initial layup adjustment, adapt to different large-angle working conditions, and avoid the instability of components under large-angle compression and bending, thereby maximizing the energy absorption effect.

[0025] This design method can directly determine the number and proportion of layers through formula derivation without complex iterative calculations; the CFRP winding and aluminum alloy multi-cell tube forming processes used are mature and easy to scale up; the composite structure interface is compatible with conventional industrial testing standards, with low risk of interlayer delamination and high reliability, and has good prospects for engineering application. Attached Figure Description

[0026] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0027] Figure 1 This is a schematic diagram of the CFRP multilayer wound aluminum alloy composite multicell tube configuration in Embodiment 1 of the present invention;

[0028] Figure 2 This is a comparison diagram of the deformation of the five configurations in Embodiment 2 of the present invention at the same moment under 30° oblique compression;

[0029] Figure 3 This is a comparison chart of the reaction force-compression curves for the five configurations in Embodiment 2 of the present invention;

[0030] Figure 4 This is a bar chart showing the energy absorption of the five configurations in Embodiment 2 of the present invention.

[0031] The markings in the diagram are: 1. Aluminum alloy multi-cell inner tube; 2. CFRP multi-level winding layer;

[0032] Figure 2 Figure (a) in Example 2 shows the deformation of the configuration under 30° oblique compression.

[0033] Figure 2 Figure (b) in Example 2 shows the deformation of control group 1 under 30° oblique compression.

[0034] Figure 2 Figure (c) in Example 2 shows the deformation of control group 2 under 30° oblique compression.

[0035] Figure 2 Figure (d) in Example 2 shows the deformation of control group 3 under 30° oblique compression.

[0036] Figure 2 Figure (e) in Example 2 shows the deformation of control group 4 under 30° oblique compression. Detailed Implementation

[0037] Example 1

[0038] like Figure 1 As shown, a multi-layer wound composite tube that can suppress large-angle instability includes an aluminum alloy multi-cell inner tube 1 and a CFRP multi-layer wound layer 2.

[0039] Among them, the aluminum alloy multi-cell inner tube 1 includes an inner tube and an outer tube. The inner tube is located inside the outer tube, and the two form a concentric circular tube structure. Furthermore, four ribs are evenly distributed along the circumference inside the aluminum alloy multi-cell inner tube 1. The four ribs divide the concentric circular tube into four symmetrical fan-shaped chambers. The ribs and the inner and outer tubes are integrally formed.

[0040] The CFRP multi-layer winding layer 2 is wrapped around the outer surface of the aluminum alloy multi-cell inner tube 1, and adopts a "90° inner layer combined with 75° outer layer" layup structure, with the 90° layup and 75° layup arranged in a specific number of layers.

[0041] Example 2

[0042] A design method for a multi-level wound composite tube capable of suppressing large-angle instability, used to achieve the multi-level wound composite tube structure as described in Example 1, includes the following specific steps:

[0043] Step 1: Define the basic design parameters.

[0044] The maximum compression angle is set to A=30°, the axial height of the multi-layer wound composite pipe is H=100mm (determined according to the vehicle installation boundary conditions), the number of ribs is N=4 (preferred value of 3≤N≤8), and the thickness of the CFRP single layer is t=0.1mm.

[0045] Step 2: Calculate the core dimension parameters of aluminum alloy multi-cell inner tube 1.

[0046] 2.1 Calculate the diameter D1 of the outer tube in the aluminum alloy multi-cell inner tube 1:

[0047] The calculation formula (1) is: D1 = H × K1 × (1 + 0.012 × A)

[0048] According to step one, the maximum compression angle A is 30°, the axial height H of the multi-layer wound composite pipe is 100mm, and the basic adaptation coefficient K1 between the height and the outer diameter is 0.45 in the range of 0.35~0.55 (taking into account both anti-instability performance and lightweight).

[0049] Substituting A=30° and H=100mm into formula (1), we get:

[0050] D1=100mm×0.45×(1+0.012×30)=100×0.45×1.36=61.2mm

[0051] Based on the engineering machining accuracy, the value is rounded to D1=60mm (the error is controlled within a reasonable range to meet the machining feasibility).

[0052] 2.2 Calculate the diameter D2 of the inner tube in aluminum alloy multi-cell inner tube 1:

[0053] The calculation formula (2) is: D2 D1×K2, where K2 is the inner and outer diameter matching coefficient, and is 0.5 within the range of 0.5 to 0.7.

[0054] Substituting D1=60mm into formula (2), we get: D2=60mm×0.5=30mm; this value can balance the structural strength and lightweight requirements of the aluminum alloy inner tube.

[0055] It is important to note that the diameters D1 of the outer tube and D2 of the inner tube both correspond to the diameters of the center plane (neutral plane) of the tube wall. For example, when the wall thickness is 1mm, the corresponding actual inner diameter is 29.5mm, the outer diameter is 30.5mm, and the wall thickness is 1mm.

[0056] 2.3 Setting the thickness t of the aluminum alloy tube Al :

[0057] The calculation formula (3) is: t Al =D1×K3, where K3 is the aluminum tube thickness adaptation coefficient, which is 0.017 in the range of 0.015~0.035 (adjusted in combination with the strength characteristics of 6061-T6 aluminum alloy material).

[0058] Substituting D1=60mm into formula (3) yields: t Al =60mm×0.017≈1mm, which meets the bearing capacity requirements of aluminum tube foundation.

[0059] 2.4 Calculation of the relative density Δρ of aluminum alloy multi-cell tube 1:

[0060] The calculation formula (4) is: Δρ=(πD2×t) Al +N×L×t Al ) / (πR²)

[0061] Substituting R=D1 / 2=30mm, L=(D1-D2) / 2=(60-30) / 2=15mm, and N=4 into formula (4), we obtain:

[0062] Δρ=(π×30×1+4×15×1) / (π×30²)=(30π+60) / (900π)

[0063] ≈(94.25+60) / 2827.43≈154.25 / 2827.43≈0.0546

[0064] Δρ=0.0546 is within a reasonable range of 0.04 to 0.12, which quantitatively verifies that the lightweight design meets the standards.

[0065] Step 3: Calculate the total CFRP winding thickness t C :

[0066] The calculation formula (5) is: t C =K4×t Al ×(D2 / D1)×(1+0.01×A)

[0067] Among them, the aluminum-CFRP thickness matching coefficient K4 is taken as 2.5 within the range of 2.0~3.5 (corresponding to a tensile shear strength of 35~45MPa at the CFRP-aluminum alloy interface, determined according to GB / T1447-2005 test), and the aluminum alloy tube thickness t Al =1mm, D2 / D1=30 / 60=0.5, A=30°.

[0068] Substituting the above parameters into formula (5) yields: t C=2.5×1×0.5×(1+0.01×30)=2.5×0.5×1.3=1.625mm. Considering the ease of ply fabrication and lightweight requirements, the result is slightly adjusted to t. C =1.5mm (deviation ≤5%, meets design requirements).

[0069] Step 4: Determine the number of 90° and 75° plies.

[0070] 4.1 Establish the basic equation: t C =n 总 ×t, where n 总 =n 75° +n 90° Substitute the total CFRP winding thickness t C =1.5mm, CFRP single-layer thickness t=0.1mm, therefore n 总 =n 75° +n 90° =15 floors.

[0071] 4.2 Determine the ply ratio φ between the number of 90° plies and the total number of plies.

[0072] Based on structural requirements and the load-bearing capacity of the inner layer, the ply ratio φ of 90° plies to the total number of plies is set to be in the range of 0.4~0.8.

[0073] Considering that the layup ratio φ of 90° layups to total layups is positively correlated with the maximum compression angle A and the axial height H of the multi-layer wound composite pipe, the larger the maximum compression angle A and the larger the axial height H of the multi-layer wound composite pipe, the more 90° layups are required. Conversely, the layup ratio φ of 90° layups to total layups is negatively correlated with the number of ribs N; the larger the number of ribs N, the fewer 90° layups are required. In this embodiment, the maximum compression angle A is limited to 30°, the axial height H of the multi-layer wound composite pipe is selected as 100mm, and the number of ribs N is selected as 4. Therefore, the layup ratio φ of 90° layups to total layups can be selected as 0.5.

[0074] 4.3 Calculate the number of 90° ply and 75° ply based on the set ply ratio φ.

[0075] n 90° =n 总 ×φ=15×0.5=7.5. Since the number of layers is an integer, it is rounded according to the conventional engineering rules, and n is finally determined. 90° =8 floors; then n 75° =n 总 -n 90° =15-8=7 floors.

[0076] In summary, the core parameters of this embodiment are finally determined as follows: the diameter D1 of the outer tube in the aluminum alloy multi-cell inner tube 1 is 60mm, the diameter D2 of the inner tube in the aluminum alloy multi-cell inner tube 1 is 30mm, and the thickness t of the aluminum tube and rib plate is... Al =1mm, total CFRP winding thickness t C =1.5mm, 90° layup number n 90° =8 layers, 75° ply number n 75° =7 floors.

[0077] In this embodiment, the aluminum alloy multi-cell inner tube 1 is made of 6061-T6 aluminum alloy and is integrally formed by extrusion molding. After molding, it undergoes aging heat treatment at 175℃ for 8 hours to ensure the strength of the matrix. The CFRP multi-level winding layer 2 is made of T700 type carbon fiber reinforced epoxy resin prepreg with a fiber volume content of 60%. In addition, the outer surface of the aluminum alloy multi-cell inner tube 1 is sandblasted and then coated with KH-550 silane coupling agent to improve the interfacial bonding strength with the CFRP winding layer.

[0078] The preparation process of this embodiment is as follows: First, an aluminum alloy multi-cell inner tube 1 is prepared by extrusion molding. After heat treatment and surface pretreatment, it is fixed to the chuck of a CNC winding machine. The winding tension is set to 0.6 MPa and the winding speed is 4 r / min (suitable for small-sized tubes). First, 8 layers of CFRP prepreg are wound at a winding angle of 90° to form the inner layer. Then, the winding angle is switched to 75° to wind 7 layers of CFRP prepreg to form the outer layer. After winding, the composite blank is put into a vacuum bag and cured using a vacuum-assisted resin transfer molding process. The curing parameters are 120°C, 0.1 MPa, and 2 h. After curing, both ends are cut to obtain the final product.

[0079] The composite multicell tube prepared in this embodiment exhibits no bending instability during the 30° large-angle compression test. The deformation mode is uniform axial compression deformation, and the load transfer is stable, achieving synergistic optimization of anti-instability and energy absorption performance.

[0080] To further verify the innovation and superiority of the multi-layered layup configuration and design method of "combining a 90° inner layer with a 75° outer layer" in this embodiment, four control groups were set up for comparative experiments. All control groups were proposed based on conventional design ideas in the field and were highly representative, comprehensively covering design schemes easily conceived by those skilled in the art. The total CFRP thickness (1.5 mm), aluminum alloy substrate dimensions, preparation process, and test conditions of all control groups were consistent with those in this embodiment to ensure the fairness and accuracy of the experimental comparison. The basis for setting up each control group is as follows:

[0081] Control group 1: CFRP / aluminum alloy composite pipe with only 90° single-layer layup (15 layers, t=0.1mm, n) 90°=15), this group is the most basic and conventional single-angle layup scheme in the field of CFRP winding. It is the simplified scheme that those skilled in the art will first consider when designing. Its core advantage is that it is easy to process and does not require complicated layup angle switching. It has a certain effect of suppressing bending instability when compressed at large angles.

[0082] Control group 2: CFRP / aluminum alloy composite pipe with only 75° single layup (15 layers, t=0.1mm, n) 75° =15), similar to control group 1, both belong to the conventional approach of single-angle plying. 75° is an angle with high energy absorption in existing studies and is often used to improve axial bearing capacity. Selecting this group can verify whether single optimized plying angle can solve the problem of large-angle compression instability, covering the conventional design logic of "single-angle optimization".

[0083] Control group 3: A multi-layered CFRP / aluminum alloy composite pipe (15 layers, t=0.1mm, n) formed by laying up equal numbers of layers from the inside out at 90°, 75°, 60°, 45°, and 30° angles. 90° =3,n 75° =3,n 60° =3,n 45° =3,n 30° =3), this group is designed based on the conventional extension of the idea of ​​"multi-level winding" - if those skilled in the art think of using multi-angle composite winding, they are prone to fall into the inertia of thinking that "the more angles the better", and will combine all the mainstream layup angles (30°, 45°, 60°, 75°, 90°) that have appeared in existing research, in an attempt to improve performance through comprehensive coverage of angles. This group can verify the limitations of the conventional idea of ​​"full-angle composite", highlighting the innovation of the invention of "precisely selecting dual angles".

[0084] Control group 4: A multi-layer ply configuration combining a 90° inner layer and a 75° outer layer was used, and the ply was applied according to n... 90° :n 75° =4:11 ratio CFRP / aluminum alloy composite pipe (15 layers, t=0.1mm, n) 90° =4,n 75° =11), this group is based on the double-angle ply concept of the present invention, but the ply ratio φ of the number of 90° ply to the total number of ply is about 0.267, which is not within the range of 0.4 to 0.8 of the ply ratio φ set in the present invention. It belongs to the conventional attempt of "imitating the double-angle configuration but not mastering the core design logic" - even if those skilled in the art think of using a combination of 90° and 75° double angles, they will randomly set the ply ratio and cannot achieve precise coupling between angle and ratio. This group can verify the rationality and necessity of the ply ratio calculation formula of the present invention and prove that non-standard ratios cannot achieve the expected performance.

[0085] Furthermore, experimental analysis was conducted using HyperMesh finite element simulation software. Figure 1 , Figure 2 All images are screenshots of the effects of the co-simulation of HyperMesh and LS-Dyna.

[0086] The experimental results show that the deformation mode, reaction force-compression curve, and energy absorption of this embodiment are significantly different from those of the four control groups. The specific analysis is as follows:

[0087] (1) Deformation mode analysis: combined with Figure 2 It can be seen that the composite pipe in this embodiment ( Figure 2 In Figure (a), during the 30° large-angle compression process, the whole body exhibits uniform axial folding deformation, with no obvious bending, bulging, or interlayer peeling. The symmetrical fan-shaped cells of the aluminum alloy inner tube collapse synchronously along the axial direction. The CFRP winding layer and the aluminum matrix deform together, and the deformation mode is regular and controllable, with no local instability.

[0088] Control group 1 (90° single layup, Figure 2 Figure (b) shows that the overall bending instability and end interlayer tearing are present. The tube body is bent significantly along the compression eccentricity direction. Due to insufficient axial bending resistance, the CFRP winding layer shows obvious interlayer cracking at the end. The deformation mode is mainly bending, and the axial collapse is extremely insufficient.

[0089] Control group 2 (75° single layup, Figure 2 Figure (c) shows local bulging instability and uneven axial shrinkage. Significant bulging occurs in the middle of the tube due to the lack of circumferential constraints. Axial folding only occurs in local areas. The CFRP layer wrinkles along with the bulging, and the overall deformation coordination is poor.

[0090] Control group 3 (all-angle composite layup, Figure 2 Figure (d) shows that the overall twisting and bending, slippage between multiple layers, and multi-angle plying leads to disordered stress path, asymmetrical twisting and bending of the tube body, obvious slippage between ply layers due to shear stress concentration, and no stable axial folding shape.

[0091] Control group 4 (non-standard ratio double-angle layup, Figure 2 Figure (e) shows local bending and peeling of the surface CFRP. Insufficient 90° layup leads to weak circumferential constraint and local bending deformation of the tube body. Excessive 75° layup causes overload on the outer layer, peeling of the surface CFRP from the aluminum substrate, and local failure during deformation.

[0092] (2) Analysis of reaction force-compression curve: combined with Figure 3As shown in the reaction force-compression curve, the curve in this embodiment shows a step-like and steady upward trend. The reaction force gradually increases with the increase of compression. Although there are small oscillations (corresponding to axial folding energy absorption), there is no obvious drop segment, and the oscillation amplitude is stable, indicating that the load transfer is continuous during the compression process and the structure has excellent anti-instability ability. This characteristic comes from the precise ratio matching of "90° inner layer and 75° outer layer". The 90° inner layer provides stable circumferential constraints, and the 75° outer layer bears the axial load. The two work together to guide the structure to produce orderly axial folding. Each fold releases energy through small oscillations while maintaining the overall load-bearing capacity.

[0093] In the control groups 1 and 2, after the initial reaction force rapidly climbed to its peak, the reaction force dropped sharply to a low level and continued to fluctuate due to bending instability. This indicates that after the structure became unstable, it lost its effective load-bearing capacity and could only absorb a small amount of energy through local residual deformation.

[0094] The control group's curve 3 showed a low peak value and an early drop, with a reaction force peak value significantly lower than that of this embodiment. Moreover, the drop occurred even with a small amount of compression, and the subsequent reaction force remained in the low range. Due to the uncoordinated force distribution of the multi-angle plying, the structure lacked stiffness and was prone to premature overall instability, making it impossible to form a stable folding energy absorption process.

[0095] The control group 4 curve was stable in the early stage and gradually decreased in the middle stage. The initial reaction force trend was similar to that of this embodiment. However, in the middle stage, the load-bearing capacity gradually decreased due to interlayer peeling, and the reaction force slowly decreased. Although it was better than the single-angle layup control group, the oscillation amplitude gradually decreased and the energy absorption efficiency continued to decline, which was far inferior to the stable oscillation energy absorption characteristics of this embodiment.

[0096] (3) Energy absorption analysis: combined with Figure 4 As shown in the energy absorption bar chart, the energy absorption of this embodiment is significantly higher than that of the four control groups, and the height of the bar chart is the highest among all groups. The core reason is the orderly axial folding deformation mode: the structure continuously generates stable axial folding during compression. Each fold absorbs energy through the coordinated energy absorption of CFRP fiber breakage, resin shearing and aluminum alloy cell plastic deformation. The integral area (energy absorption) under the reaction force curve is maximized, which fully utilizes the energy absorption potential of the composite structure.

[0097] The energy absorbed by control group 1 was lower than that in this embodiment. Due to early bending and local tearing instability, the axial orderly folding energy absorption process was terminated prematurely, and energy could only be dissipated through local failure, resulting in insufficient energy absorption.

[0098] The control group 2 had lower energy absorption because early bulging and edge failure instability interrupted the axial folding energy absorption process. It could only absorb energy through a small amount of wrinkle deformation, and the small integral area under the reaction force curve showed that its energy absorption effect was insufficient.

[0099] The energy absorption of the control group 3 was lower than that of this embodiment. This was because the multi-angle layup caused stress disorder, interlayer slippage consumed some energy, and overall instability resulted in insufficient energy absorption during folding, thus significantly reducing the energy absorption efficiency.

[0100] Although the energy absorption of control group 4 was higher than that of the single-angle layup control group, it was still lower than that of this embodiment. This was because the load-bearing capacity was reduced due to interlayer peeling, the continuity of folded energy absorption was disrupted, the energy absorption process was interrupted in advance, and efficient energy absorption of the entire compression stroke could not be achieved.

[0101] In summary, this invention selects 75° and 90° as the core layup angles for multi-level CFRP winding. This selection was determined through systematic analysis and optimization, considering the stress characteristics under large-angle compression conditions, the material synergy mechanism, and the results of comparative experiments. A 75° layup effectively enhances the axial load-bearing capacity and bending resistance of the structure, while a 90° layup strengthens circumferential restraint and suppresses bulging and overall instability. Matching these two angles according to the proportions determined by the design method of this invention achieves synergistic optimization of axial load-bearing capacity and circumferential restraint, enabling the composite tube to maintain a stable deformation mode during large-angle compression and improving the structure's resistance to instability and energy absorption efficiency. Through reasonable matching and precise design of the layup angles and proportions, the CFRP winding layer and the aluminum alloy multi-cell tube can fully exert their synergistic effect, achieving superior mechanical properties and energy absorption characteristics, thereby meeting the requirements for use under large-angle compression conditions.

[0102] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A design method for a multi-level wound composite tube capable of suppressing large-angle instability, used to design the structural parameters of the multi-level wound composite tube, the multi-level wound composite tube comprising a metal tube and multi-level wound layers, the multi-level wound layers covering the outer surface of the metal tube, characterized in that, The metal tube includes an inner tube and an outer tube, with the inner tube located inside the outer tube. The two form a concentric circular tube structure. N ribs are evenly distributed along the circumference inside the metal tube. The N ribs divide the space between the inner tube and the outer tube into N sector-shaped chambers. The multi-level winding layer adopts a 90° ply and a 75° ply structure. The 90° ply and the 75° ply are arranged in a specific number of layers and are wound sequentially on the outer surface of the metal tube. The design method for the multi-level wound composite tube includes the following steps: Step 1: Determine the basic design parameters, including the maximum compression angle A, the axial height H of the multi-layer wound composite pipe, the number of ribs N, and the thickness t of a single layer; Step 2: Calculate the dimensional parameters of the metal tube based on the basic design parameters, including the outer diameter D1, the inner diameter D2, and the thickness t of the metal tube. Al The relative density Δρ of the metal tube; Step 3: Calculate the total thickness t of the multi-level winding layers. C The calculation formula is: t C =K4×t Al ×(D2 / D1)×(1+0.01×A), where K4 is the matching coefficient between the thickness of the metal layer and the multi-level winding layer; Step 4: Determine the number of 90° and 75° plies. The calculation process is as follows: Based on the total thickness t of the multi-level winding layers C The basic equation establishing the physical relationship between t and the single-layer thickness t is: C =n 总 ×t,n 总 =n 75° +n 90° , where n 75° n is the number of layers for a 75° ply. 90° The number of layers for a 90° ply; Calculate the number of 75° and 90° plies based on the ply ratio φ between the set number of 90° plies and the total number of plies: n 90° =n 总 ×φ;n 75° =n 总 -n 90° Among them, the ply ratio φ of the number of 90° plies to the total number of plies is positively correlated with the maximum compression angle A and the axial height H of the multi-level wound composite pipe, while the ply ratio φ of the number of 90° plies to the total number of plies is negatively correlated with the number of ribs N.

2. The design method for a multi-level wound composite tube capable of suppressing large-angle instability according to claim 1, characterized in that, The maximum compression angle A ranges from 0 to 30°; the number of ribs N ranges from 3 to 8; and the ply ratio φ of the 90° ply number to the total ply number is 0.4 to 0.

8.

3. The design method for a multi-level wound composite tube capable of suppressing large-angle instability according to claim 2, characterized in that, The formula for calculating the outer diameter D1 of the metal tube is: D1=H×K1×(1+0.012×A), where H is the axial height of the multi-layer wound composite tube, K1 is the basic adaptation coefficient between the height and the outer diameter, and A is the maximum compression angle. The value range of the basic adaptation coefficient K1 between the height and the outer diameter is 0.35 to 0.

55.

4. The design method for a multi-level wound composite tube capable of suppressing large-angle instability according to claim 3, characterized in that, The formula for calculating the inner diameter D2 of the metal tube is: D2 = D1 × K2, where D1 is the outer diameter of the metal tube and K2 is the inner and outer diameter matching coefficient. The value range of the inner and outer diameter matching coefficient K2 is 0.5 to 0.

7.

5. The design method for a multi-level wound composite tube capable of suppressing large-angle instability according to claim 4, characterized in that, The thickness t of the metal tube Al The formula for calculating t is: Al =D1×K3, where D1 is the outer diameter of the metal tube and K3 is the metal tube thickness adaptation coefficient, and the value range of the metal tube thickness adaptation coefficient K3 is 0.015 to 0.

035.

6. The design method for a multi-level wound composite tube capable of suppressing large-angle instability according to claim 5, characterized in that, The formula for calculating the relative density Δρ of the metal tube is: Δρ = (πD² × t) Al +N×L×t Al ) / (πR²), where D2 is the inner diameter of the metal tube, L is the radial length of the rib, L=(D1-D2) / 2, t Al Where N is the thickness of the metal tube, N is the number of ribs, and R is the outer radius of the cross-section of the metal tube, R=D1 / 2; the relative density Δρ of the metal tube ranges from 0.04 to 0.

12.

7. The design method for a multi-level wound composite tube capable of suppressing large-angle instability according to claim 1, characterized in that, The matching coefficient K4 between the thickness of the metal layer and the multi-layer winding layer ranges from 2.0 to 3.

5.

8. A multi-level wound composite pipe capable of suppressing large-angle instability, characterized in that, The device includes a metal tube and a multi-level winding layer. The multi-level winding layer covers the outer surface of the metal tube. The metal tube includes an inner tube and an outer tube, with the inner tube located inside the outer tube. The two tubes have a concentric circular tube structure. Four ribs are evenly distributed circumferentially inside the metal tube. The four ribs divide the space between the inner tube and the outer tube into four sector-shaped chambers. The multi-level winding layer adopts a layup structure that combines 90° layup and 75° layup. The 90° layup and 75° layup are arranged in a specific ratio and wound sequentially on the outer surface of the metal tube. According to any one of claims 1 to 7, the design method for a multi-layer wound composite pipe capable of suppressing large-angle instability, setting the maximum compression angle A as 30°, the axial height H of the multi-layer wound composite pipe as 100mm, and the single-layer thickness t as 0.1mm in the basic design parameters, then the calculated dimensional parameters of the metal pipe are: outer pipe diameter D1 as 60mm, inner pipe diameter D2 as 30mm, and metal pipe thickness t as... Al Given a thickness of 1 mm and a relative density Δρ of 0.0546 for the metal tube, the total thickness t of the multi-layer winding was calculated. C The thickness is 1.5mm, and the final number of 90° plies is 8, and the number of 75° plies is 7.

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