Bionic three-dimensional interlaminar self-locking spiral structure composite material and preparation method thereof

Abstract

The application discloses a kind of bionic three-dimensional interlaminar self-locking spiral structure composite material and preparation method thereof, and relates to the technical field of composite materials.The fiber resin prepreg is cut in a direction, and interlaminar interpenetration is carried out according to a preset spiral angle, so that a non-planar three-dimensional interlaminar self-locking structure and a spiral dislocation connection center are formed between the layers.Compared with the traditional planar laminated interface structure, the composite material provided by the application fundamentally suppresses delamination damage and improves interlaminar shear performance and post-peak bearing stability.The application can achieve customization of interlaminar mechanical properties by adjusting the spiral angle, and has high strength, high stiffness, excellent residual strength and long plateau failure characteristics, which breaks through the interlaminar delamination problem of traditional composite materials for a long time.The application can be widely used in aerospace, rail transportation, wind power blades and other high-end equipment fields.

Description

Technical Field

[0001] This invention relates to the field of composite material technology, and in particular to a method for preparing a biomimetic three-dimensional interlayer self-locking helical structure composite material. Background Technology

[0002] Fiber-reinforced resin matrix composites, due to their advantages such as lightweight, high specific strength, and high specific modulus, have been widely used in high-end equipment fields such as aerospace, rail transportation, wind power generation, and shipbuilding. Traditional composite laminates are formed by planar interface lamination, with the layers bonded only by resin. The interlayer bonding force is weak, making them prone to delamination damage under shear, impact, and fatigue loads. This leads to a sharp drop in structural stiffness and failure of load-bearing capacity, severely restricting the safety and durability of composite structures.

[0003] Natural load-bearing materials such as bivalve placentas, shells, and skeletons are essentially laminated composites composed of minerals and organic phases. Their interlayers employ a non-planar interlocking mechanism, which efficiently dissipates energy, inhibits crack propagation, and exhibits excellent anti-delamination and high toughness properties. Research shows that the nano-dislocation-like connection centers in the outer shell of bivalve placentas can tightly link adjacent mineral layers, forming an interconnected microcrack network upon damage, significantly improving energy dissipation efficiency. Theoretical analysis and experimental calculations both indicate that the interfacial fracture toughness is improved by nearly two orders of magnitude compared to classic laminated composites without connection centers. However, the current technical challenge lies in how to realize the three-dimensional helical self-locking design in composite materials.

[0004] Existing biomimetic composite materials mostly focus on improving two-dimensional planar structures, failing to achieve true three-dimensional interlayer self-locking and helical interconnection, thus making it difficult to fundamentally solve the problem of interlayer delamination. For example, Chinese patent CN117532964B provides a biomimetic gradient helical structure composite laminate containing several fiber helical units coaxially stacked along the thickness direction. Through the synergistic effect of fiber helical units with different rotation angles, the out-of-plane impact damage characteristics and damage distribution of the composite laminate are controlled, thereby improving the out-of-plane impact resistance of the composite laminate. Another example is the impact-resistant structure provided by Chinese patent CN114756912B, which is a laminate structure formed by stacking and bonding single-layer plates. It includes a matrix and fibers arranged in the same direction on the matrix. The fibers in the laminate are arranged in a helical shape from top to bottom, and adjacent single-layer plates are bonded together through an adhesive interface. For example, Chinese patent application CN121200461A provides a variable stiffness curved spiral impact-resistant composite material layup configuration, which starts from a 0° layup and increases the spiral angle θ with each layer, stacking the layers to form a symmetrical spiral variable stiffness laminate with good impact resistance and interlayer toughness. The composite panels prepared by the above-mentioned prior art improve the impact resistance by coaxially stacking fiber spiral units, single-layer spiral layup, and incremental spiral angle layup, but all of them have the defects of parallel fiber distribution, only resin bonding between layers, and no mechanical interlocking between layers. They fail to form interfacial interlocking between adjacent layers, and still have problems such as weak interlayer bonding, easy delamination, and rapid drop in peak load.

[0005] Currently, there are no composite material structures that combine biological interlocking centers with helical structures, either domestically or internationally. There is an urgent need to develop a biomimetic three-dimensional self-locking composite material that can be industrially prepared, has significantly improved interlayer performance, and provides stable post-peak load-bearing capacity. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a biomimetic three-dimensional interlayer self-locking helical composite material and its preparation method. Unlike existing classic 2D laminates with planar interfaces, the biomimetic three-dimensional interlayer self-locking helical composite material provided by this invention features interlocking interfaces between adjacent layers and incorporates a helical hybrid design, achieving a 3D helical self-locking design. This overcomes the defects of weak interlayer structure, easy delamination, and rapid load drop after peak load. Through the bridging mechanism of helical interlocking and connecting centers, interlayer reinforcement, toughening, and load stabilization are integrated. This invention is specifically achieved through the following technologies.

[0007] This invention provides a method for preparing a biomimetic three-dimensional interlayer self-locking helical structure composite material, comprising the following steps:

[0008] Prepare several resin prepregs composed of unidirectional fibers and cut to the design dimensions, and determine the helical angle and the total number of lay-up layers;

[0009] A slit is formed in the middle of each resin prepreg by cutting along the fiber direction.

[0010] All the resin prepregs are laid layer by layer, and adjacent resin prepregs are interlaced with each other through the slit at the spiral angle.

[0011] The product is thermosetting, cooled and demolded to obtain the finished biomimetic three-dimensional interlayer self-locking spiral structure composite material; the upper and lower adjacent resin prepregs of the finished product form a spiral interlocking center that penetrates the layer thickness, and the spirally formed resin prepregs interweave to form a three-dimensional self-locking spiral configuration.

[0012] In the above preparation method, the resin prepreg is cut into slits and then inter-layered from the slits. After curing, a spiral interlayer interlocking center that penetrates the thickness of the layer is formed, which acts as a crack bridging site and can resist interlayer slippage, deflection crack propagation, and inhibit delamination.

[0013] Alternatively, when laying all the resin prepregs layer by layer according to the helical angle, a commercially available rotating device can be used to precisely control the layup angle. This rotating device generally consists of a worm gear, a worm wheel, a rotating shaft, and a working platform, and the helical angle of each layer can be precisely controlled by adjusting the handle.

[0014] Furthermore, the length of the slit is slightly greater than half the width of the resin prepreg along the fiber direction.

[0015] In this invention, "slightly greater than" specifically means that the length of the slit is slightly greater than 1 / 2 of the width of the resin prepreg along the fiber direction, in order to facilitate the insertion of the resin prepreg next time and to prevent wrinkles from forming here.

[0016] Furthermore, the width of the slit does not exceed the thickness of the resin prepreg.

[0017] Furthermore, the helix angle is 22.5°-90°.

[0018] Furthermore, the helix angle is 22.5°-60°.

[0019] When the set helix angle is ≤60°, the mechanical properties of composite materials with three-dimensional interlocking structures are superior to those of planar interface structures. When the helix angle is 90°, the effect of interlayer three-dimensional interlocking weakens, and the interlayer resistance decreases, but the structural stiffness still has a considerable improvement effect.

[0020] Specifically, compared to traditional planar laminated spiral structures, composite materials prepared with a preset spiral angle of 22.5° show a 24.17% increase in interlaminar shear strength, a 41.56% increase in stiffness, a 37.96% increase in residual strength, and an 823.80% increase in post-peak plateau length. Composite materials prepared with a preset spiral angle of 45° show an 11.40% increase in interlaminar shear strength, a 22.89% increase in stiffness, a 61.83% increase in residual strength, and a 314.37% increase in post-peak plateau length. Composite materials prepared with a preset spiral angle of 60° show a 10.50% increase in interlaminar shear strength, a 10.59% increase in stiffness, a 12.54% increase in residual strength, and a 13.39% increase in post-peak plateau length. Although the interlocking effect of the 90° interlaminar interlocking spiral structure decreases and the performance slightly declines, the structural stiffness is still increased by 16.52%, which is still a considerable improvement.

[0021] Furthermore, the cutting method can be selected from common methods such as paper cutting machine cutting or laser cutting.

[0022] Furthermore, the width of the slit is 20-180 μm.

[0023] Furthermore, the fiber areal density of the resin prepreg is 20-180 g / m³. 2 .

[0024] Furthermore, the resin prepreg is a structure formed by impregnating fibers with thermosetting resin and / or thermoplastic resin. For example, thermosetting epoxy resin.

[0025] Furthermore, the fibers in the resin prepreg are one or more materials selected from carbon fiber, glass fiber, and aramid fiber.

[0026] The present invention also provides a biomimetic three-dimensional interlayer self-locking helical structure composite material prepared by the above preparation method. The working principle of the significantly enhanced interlayer mechanical properties is as follows: (1) a helical interlocking center that penetrates the thickness of the material is formed inside the material. The fibers of adjacent layers intertwine with each other, generating a mechanical locking effect, thereby restricting interlayer slip and increasing the interfacial shear resistance; (2) the helical interlocking center acts as a crack bridging point, deflecting the crack propagation path and inhibiting delamination; (3) the three-dimensional helical microstructure makes the stress uniformly distributed along the thickness direction, reducing local stress concentration; (4) the failure mode (i.e. the damage form when the dominant structure fails) changes from the traditional "rapid interlayer delamination" to "multi-scale progressive damage", prolonging the post-peak plateau period.

[0027] The aforementioned composite materials are particularly suitable for main load-bearing structural components of high-end equipment in fields such as aerospace, rail transportation, and wind power.

[0028] Compared with the prior art, the advantages of the present invention are:

[0029] 1. Significantly improved interlaminar performance: By comparing the short beam shear performance of the three-dimensional interlocking spiral structure and the traditional planar laminated spiral structure, it was found that the biomimetic three-dimensional interlocking spiral composite material provided by this invention solves the interlaminar delamination problem from the structural root, exhibiting stronger interlaminar shear strength, stiffness, higher residual strength and better plateau period.

[0030] 2. Significantly enhanced post-peak load-bearing capacity: The biomimetic three-dimensional interlayer self-locking helical structure composite material provided by this invention has a significantly extended post-peak plateau period, making the structure safer and exhibiting excellent impact and fatigue resistance.

[0031] 3. Customizable performance: By adjusting the helix angle, the mechanical properties between layers can be precisely controlled to match the requirements of different working conditions.

[0032] 4. Strong process compatibility and wide range of applications: It is consistent with the hot-pressing curing process of traditional laminates, which is easy to scale up for industrial production; it is suitable for high-end fields such as aerospace main shear structure, wind turbine blade main beam, rail transit vehicle body, and high-performance pressure vessel. Attached Figure Description

[0033] Figure 1 The diagram shows the fabrication process of a biomimetic three-dimensional interlayer self-locking helical composite material. (a)-(c) detail the fabrication steps of the helical composite material with an interlayer self-locking structure, and (d) shows the internal morphology of the cured three-dimensional interlayer self-locking helical structure with a helical angle of 22.5° obtained from CT scanning.

[0034] Figure 2 Here is a diagram of a spiral structure with a pure resin interface. (i) is a schematic diagram of the structure; (ii) is a SEM image of the cross-section of the spiral laminate composite material, showing that the fibers are distributed in parallel and the fibers between the layers are not connected to each other.

[0035] Figure 3 The structure is a biomimetic three-dimensional interlayer self-locking helical structure. (i) is a schematic diagram of the structure; (ii) is a cross-sectional view, showing that fibers from different layers interweave to form an interlocking center.

[0036] Figure 4The following is a comparison of the load-displacement curves and plateau periods of an interlaminar self-locking spiral structure with a helix angle of 22.5° and a traditional planar laminated structure. Specifically, (a) shows the load-displacement curve of the traditional planar laminated structure; (b) shows the load-displacement curve of the biomimetic three-dimensional interlaminar self-locking spiral structure; (c) shows a phase diagram comparing the interlaminar shear strength and stiffness of the three-dimensional interlaminar self-locking spiral structure and the traditional planar laminated spiral structure; and (d) shows a phase diagram comparing the residual strength, residual strength ratio, and plateau period length of the three-dimensional interlaminar self-locking spiral structure and the traditional planar laminated spiral structure.

[0037] Figure 5 Radar graphs comparing the mechanical properties of interlaminar self-locking helical structures with different helix angles (22.5°, 45°, 60°, and 90°) with those of traditional planar laminated helical structures. (a): I22.5; (b): I45; (c): I60; (d): I90.

[0038] Figure 6 This is a schematic diagram of the operation in Example 1, in which all resin prepregs are laid layer by layer and adjacent resin prepregs are interlaced with each other through slits at a spiral angle. Detailed Implementation

[0039] The technical solution 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.

[0040] In some embodiments of the present invention, a composite material with a biomimetic three-dimensional interlayer self-locking helical structure is provided. The composite material is an integral composite laminate structure integrating 3D helical and self-locking features, rather than a simple planar laminate. All single layers are connected together. Helical dislocation-shaped connection centers are formed between the layers to achieve mechanical interlocking between the layers. Adjacent layers are arranged at a predetermined helical angle. The helical dislocation-shaped connection centers can resist slippage, bridge cracks, disperse stress, and suppress delamination.

[0041] The method for preparing the above-mentioned composite material provided by the present invention is as follows:

[0042] S1. Prepare several resin prepregs composed of unidirectional fibers and cut to the design dimensions, and determine the helical angle and the total number of lay-up layers;

[0043] S2. Cut a slit in the resin prepreg along the fiber direction at the middle of each resin prepreg.

[0044] S3, such as Figure 1 (a)-(c) and Figure 6As shown, all the resin prepregs are laid layer by layer, and adjacent resin prepregs are interlaced with each other through the slit at the spiral angle.

[0045] S4. Thermosetting molding, cooling and demolding, and processing to obtain the finished product of the biomimetic three-dimensional interlayer self-locking spiral structure composite material.

[0046] The two adjacent resin prepregs in the finished product form a spiral interlocking center that extends through the layer thickness, and the spirally formed resin prepregs interweave to form a three-dimensional self-locking spiral configuration.

[0047] Optionally, in order to fully utilize the performance of the helical interlocking center and the three-dimensional self-locking helical configuration, facilitate the insertion of the next resin prepreg, and avoid problems such as wrinkles, the length of the slit can be designed to be slightly greater than half the width of the resin prepreg along the fiber direction, and the width of the slit can be designed not to exceed the thickness of the resin prepreg.

[0048] Optionally, the predetermined helix angle is 22.5°-90°. For example, 22.5°, 45°, 60°, and 90° can be selected.

[0049] Optionally, the thickness of the resin prepreg is 20-180 μm.

[0050] Optionally, the fiber areal density of the resin prepreg is 20-180 g / m². 2 .

[0051] Optionally, the resin prepreg is a structure formed by impregnating fibers with thermosetting resin and / or thermoplastic resin.

[0052] Optionally, the fibers of the resin prepreg are one or more materials selected from carbon fiber, glass fiber, and aramid fiber.

[0053] In the following specific implementation examples, for ease of comparison, the resin prepreg is made by impregnating carbon fibers in thermosetting epoxy resin to form a thickness of 120 μm and a fiber areal density of 120 g / m². 2 A layered material structure.

[0054] Example: Preparation of biomimetic three-dimensional interlayer self-locking helical composite materials with different helical angles

[0055] like Figure 1 As shown, the preparation method of the biomimetic three-dimensional interlayer self-locking helical structure composite material provided in this embodiment is as follows:

[0056] S1. Select a resin prepreg composed of unidirectional carbon fibers (thickness 120 μm, fiber areal density 120 g / m²). 2Cut to the design size, set the spiral angle to 22.5°, 45°, 60°, and 90°, and lay a total of 16 layers.

[0057] S2. Using a laser cutting machine, the resin is cut along the fiber direction in the middle of the prepreg width to form a slit; the slit length is half the width of the resin prepreg + 2 mm, and the width is 80 μm.

[0058] S3, such as Figure 1 (a)-(c) and Figure 6 As shown, a rotating device is used to lay the resin prepreg layer by layer at a preset spiral angle. Each layer of resin prepreg rotates at a set spiral angle (22.5°, 45°, 60°, 90°), so that the resin prepreg of the upper layer passes through the slit of the resin prepreg of the lower layer.

[0059] S4. Place the stacked preform into the mold, heat-press and solidify it (180℃, 0.6 MPa), cool and demold it, and process it into a standard sample (18 mm long, 6 mm wide, and 1.92 mm thick).

[0060] The final biomimetic three-dimensional interlaminar self-locking helical laminate with a helical angle of 22.5° is shown in the cross-section. Figure 3 As shown in (ii) above. Observe the fifth layer structure along the thickness direction, which differs from the traditional planar laminated spiral structure (such as...). Figure 2 In (ii) of the biomimetic three-dimensional interlayer self-locking spiral laminate, the fibers are parallelly distributed and do not connect with each other. The fibers span different layers and interweave with fibers from other layers to form interlocking centers.

[0061] Comparative Example: Preparation of Traditional Planar Laminated Helical Composite Materials with Different Helix Angles

[0062] The preparation method of the traditional planar laminated helical composite material provided in this comparative example is as follows:

[0063] S1. Cut the prepreg composed of fibers in one direction according to the design dimensions, and determine the helix angles as 22.5°, 45°, 60°, and 90°, with a total of 16 layers.

[0064] S2. Place the laminated preform into a mold, cure it using a hot pressing process, cool and demold it to prepare a traditional planar laminated spiral structure composite material.

[0065] Experimental Example: Performance Testing of Composite Materials

[0066] This experiment uses composite materials prepared in the examples and comparative examples to test the interlaminar shear strength, stiffness, residual strength, plateau length and strength properties of composite materials with different helix angles.

[0067] Short beam shear tests were conducted according to ASTM D 2344. The specimen dimensions were: 18 mm long, 6 mm wide, and 1.92 mm thick, with a fiber content of approximately 53.6%. The tests were performed using an MTS universal testing machine with a span of 12 mm. The test was conducted at a crosshead displacement rate of 1.0 mm / min, with a loading head diameter of 6 mm and a support diameter of 3 mm.

[0068] The performance test results are analyzed below.

[0069] like Figure 4 As shown in Figure (a), the planar interface laminate exhibits a continuous decrease in force immediately after reaching the peak load, with a short plateau period. Figure (b) shows that the three-dimensional helical self-locking structure exhibits a stable plateau, with the force remaining at a higher peak value. Figure (c) shows that the three-dimensional helical self-locking structure has a 24% increase in shear strength and a 41% increase in stiffness compared to the traditional helical structure. Figure (d) shows that the three-dimensional helical self-locking structure has a 38% increase in residual strength and an over 800% extension in plateau period displacement compared to the traditional helical structure.

[0070] like Figure 5 As shown in Figure (a), the orange area represents our designed 22.5° helical self-locking structure, while the black area represents the traditional 22.5° helical structure. The 22.5° self-locking structure exhibits a 24.17% increase in interlaminar shear strength, a 41.56% increase in stiffness, a 37.96% increase in residual strength, and an 823.80% extension of the post-peak plateau period. Figure (b) shows that the orange area represents our designed 45° helical self-locking structure, while the black area represents the traditional 45° helical structure. The 45° self-locking structure exhibits an 11.40% increase in interlaminar shear strength, a 22.89% increase in stiffness, a 61.83% increase in residual strength, and a 314.37% extension of the post-peak plateau period. Figure (c) shows that the orange area represents our designed 60° helical self-locking structure, while the black area represents the traditional 60° helical structure. The 60° self-locking structure exhibits a 10.50% increase in interlaminar shear strength, a 10.59% increase in stiffness, a 12.54% increase in residual strength, and a 13.39% extension of the post-peak plateau period. As shown in Figure (d), the orange area represents our designed three-dimensional helical self-locking 90° structure, while the black area represents the traditional helical 90° structure. The 90° self-locking structure exhibits a weakened interlocking effect and a 16.52% increase in stiffness, while other properties slightly decline. Compared to planar interface helical structures, the biomimetic three-dimensional helical self-locking microstructures with helical angles of 22.5°, 45°, and 60° all demonstrate enhanced shear strength, stiffness, higher residual strength, and a better plateau period. The 90° structure still retains its advantage in stiffness improvement.

[0071] The above detailed embodiments describe the implementation of the present invention; however, the present invention is not limited to the specific details described in the above embodiments. Within the scope of the claims and technical concept of the present invention, various simple modifications and changes can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

Claims

1. A method for preparing a biomimetic three-dimensional interlayer self-locking helical structure composite material, characterized in that, Includes the following steps: Prepare several resin prepregs composed of unidirectional fibers and cut to the design dimensions, and determine the helical angle and the total number of lay-up layers; A slit is formed in the middle of each resin prepreg by cutting along the fiber direction. All the resin prepregs are laid layer by layer, and adjacent resin prepregs are interlaced with each other through the slit at the spiral angle. The product is thermosetting, cooled and demolded to obtain the finished biomimetic three-dimensional interlayer self-locking spiral structure composite material; the upper and lower adjacent resin prepregs of the finished product form a spiral interlocking center that penetrates the layer thickness, and the spirally formed resin prepregs interweave to form a three-dimensional self-locking spiral configuration.

2. The method for preparing the biomimetic three-dimensional interlayer self-locking helical structure composite material according to claim 1, characterized in that, The length of the slit is slightly greater than half the width of the resin prepreg along the fiber direction.

3. The method for preparing the biomimetic three-dimensional interlayer self-locking helical structure composite material according to claim 1, characterized in that, The width of the slit does not exceed the thickness of the resin prepreg.

4. The method for preparing the biomimetic three-dimensional interlayer self-locking helical structure composite material according to claim 1, characterized in that, The helix angle is 22.5°-90°; Furthermore, the helix angle is 22.5°-60°.

5. The method for preparing the biomimetic three-dimensional interlayer self-locking helical structure composite material according to claim 1, characterized in that, The thickness of the resin prepreg is 20-180 μm.

6. The method for preparing the biomimetic three-dimensional interlayer self-locking helical structure composite material according to claim 1, characterized in that, The fiber areal density of the resin prepreg is 20-180 g / m³. 2 .

7. The method for preparing the biomimetic three-dimensional interlayer self-locking helical structure composite material according to claim 1, characterized in that, The resin prepreg is a structure formed by impregnating fibers with thermosetting resin and / or thermoplastic resin.

8. The method for preparing the biomimetic three-dimensional interlayer self-locking helical structure composite material according to claim 1, characterized in that, The fibers in the resin prepreg are one or more of the following materials: carbon fiber, glass fiber, and aramid fiber.

9. A biomimetic three-dimensional interlayer self-locking helical structure composite material prepared by the preparation method according to any one of claims 1-8.

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