Structural characteristic analysis method of bionic spiral arrangement fiber reinforced composite material

Abstract

The invention discloses a structural characteristic analysis method of a bionic spiral arrangement fiber reinforced composite material, which comprises the following steps: S1, establishing a continuous medium mechanical model of a single-layer composite material, and calculating an elastic modulus, a transverse elastic modulus and a shear modulus along a fiber direction; s2, establishing a fracture energy prediction model of the multilayer spiral laminated structure; s3, establishing an ultimate tensile strength prediction model under an off-axis tensile condition; s4, establishing an equivalent stiffness calculation model of the multilayer spiral laminated structure; s5, preparing composite material samples with different fiber orientation angles and laying layer numbers; s6, carrying out a mechanical property test; s7, model parameters are corrected; and S8, predicting mechanical properties under different structure parameters, and determining optimal structure parameters. According to the method, quantitative prediction and parameter optimization of the mechanical property of the spiral laminated structure are achieved by building the fracture energy superposition model, and the composite material with the excellent fracture property is designed based on the method.

Description

Technical Field

[0001] This invention belongs to the field of composite material performance analysis and structural design technology, specifically a method for analyzing the structural characteristics of biomimetic helical fiber reinforced composite materials. Background Technology

[0002] UV-curable resins (CG) have significant application value in additive manufacturing and precision molding due to their rapid photopolymerization characteristics, high forming accuracy, and good processing adaptability. However, their highly cross-linked molecular network structure results in limited fracture toughness and energy dissipation capacity, making them prone to brittle fracture under impact loads or crack-dominated failure conditions, which severely restricts their further expansion in structural and load-bearing applications.

[0003] To address the brittleness of UV-curable resins, existing toughening strategies include molecular structure modification, rubber phase toughening, and the introduction of nanofillers. While these methods improve the ductility and impact properties of the materials to some extent, they often fail to achieve a synergistic improvement in tensile strength and fracture toughness. Furthermore, high filler content or complex modification processes can easily introduce problems such as processing complexity and reduced curing efficiency. This indicates that relying solely on material composition control cannot fundamentally solve the fracture performance bottleneck of UV-curable resins.

[0004] Fiber reinforcement strategies based on structural design offer an engineering-feasible approach to improving the fracture properties of polymers. In nature, the scales on butterfly wings achieve stress dispersion and crack delay through a periodically arranged multi-layered lamellar structure, providing biomimetic inspiration for the design of high-toughness composite materials. Figures 1-3 As shown. However, how to quantitatively analyze the mechanical behavior of this biomimetic helical structure and establish an accurate predictive model remains a technical challenge in this field. Existing analytical methods mostly rely on experimental trial and error, lacking systematic theoretical modeling tools, making it difficult to achieve optimized design of structural parameters. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention aims to provide a method for analyzing the structural properties of biomimetic helical fiber-reinforced composite materials. By constructing a fracture energy superposition model, the mechanical properties of helical laminated structures can be quantitatively predicted and parameters optimized. Based on this method, composite materials with excellent fracture performance can be designed.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for analyzing the structural properties of biomimetic helical fiber-reinforced composites includes the following steps in sequence: Step S1: Establish a continuum mechanical model for a single-layer composite material and calculate the elastic modulus, transverse elastic modulus, and shear modulus along the fiber direction; Step S2: Based on the Griffith energy criterion, establish a fracture energy prediction model for multilayer helical laminates, decomposing the fracture energy into three parts: matrix cracking energy, interface dissipation energy, and fiber fracture energy, where the interface dissipation energy term characterizes the energy dissipation caused by interlaminar angle mismatch; Step S3: Based on the Tsai-Hill failure criterion, establish a prediction model for the ultimate tensile strength under off-axis tensile conditions; Step S4: Based on the classical layer... Step S5: Design and prepare a series of composite material samples with different fiber orientation angles and layup numbers, including single-layer reinforced structures and multi-layer helical laminated structures; Step S6: Conduct mechanical property tests on the prepared series of samples, obtain force-displacement response curves, and calculate the experimental values ​​of elastic modulus, ultimate tensile strength, and fracture energy; Step S7: Compare and verify the experimental values ​​with the theoretical prediction values ​​of steps S1-S4, and correct the model parameters; Step S8: Based on the verified theoretical model, predict the mechanical properties under different structural parameters, and determine the structural parameters that synergistically optimize fracture energy and ultimate tensile strength.

[0008] As a further improvement to the above technical solution:

[0009] Four samples of the single-layer reinforced structure were obtained, with fiber orientation angles of 0°, 15°, 30°, and 45°, respectively. Four samples of the multi-layer helical laminated structure were also obtained, each containing five layers, with interlayer rotation angles of [missing information]. The angles are fixed at 0°, 15°, 30°, and 45° respectively, and the interlayer rotation angle is... The sample has a first layer fiber orientation angle of 0° and a second layer fiber orientation angle of 0°. The third layer is 2 The 4th layer is 3 The 5th floor is 4 .

[0010] The mechanical property test was conducted using uniaxial tensile loading at a loading rate of 1 mm / min. The specimen dimensions were 60 mm × 30 mm × 2 mm, with a pre-fabricated notch in the middle with a depth and width of 5 mm.

[0011] The calculation formulas for the elastic modulus along the fiber direction, the transverse elastic modulus, and the shear modulus mentioned in step S1 are as follows:

[0012]

[0013]

[0014]

[0015] In the formula: Elastic modulus along the fiber direction, in GPa; This refers to the fiber's elastic modulus, expressed in GPa. The elastic modulus of UV resin is expressed in GPa. The fiber volume fraction is dimensionless. Fiber orientation angle, in degrees; This is the transverse elastic modulus, in GPa. Shear modulus, in GPa; Fiber shear modulus, in GPa; This represents the shear modulus of UV resin, expressed in GPa.

[0016] The fracture energy prediction model mentioned in step S2 is as follows:

[0017]

[0018] In the formula: The fracture energy of the five-layer helical laminate structure is expressed in kJ / m². The matrix cracking energy is expressed in kJ / m². Fiber tensile strength, in MPa; The thickness is for a single layer, in mm. is the interfacial shear stress of the i-th layer, in MPa; Let be the shear modulus of the i-th layer, in GPa.

[0019] A biomimetic helical fiber-reinforced composite material includes multiple reinforcing layers and a UV-curable resin matrix layer, wherein the reinforcing layers are UV-curable resin layers containing mesh glass fibers, and the matrix layer is a UV-curable resin layer without glass fibers; adjacent reinforcing layers are laid in a fixed angle along the same direction to form a helical laminate structure with periodic orientation changes.

[0020] The fixed angle is 15°, 30° or 45°, and the number of layers is 1 to 10; the glass fiber is an in-plane continuous mesh structure.

[0021] A method for preparing the composite material includes the following steps: Step P1: Modeling the sample using 3D modeling software and exporting an STL format file; Step P2: Slicing the sample using slicing software to generate printing control code; Step P3: Using a photopolymerization 3D printing device, printing layer by layer with UV-curable resin as the matrix, with a uniform layer thickness of 50 µm; Step P4: After printing six consecutive layers of UV-curable resin, laying a layer of mesh glass fiber, with the fiber's main direction rotating layer by layer according to a preset spiral structure; Step P5: Layer-by-layer curing is achieved by UV irradiation, with a single layer curing time of 10 s. After laying the fiber layer, the fiber layer and the resin layer below it need to be additionally cured to ensure that the fiber and resin are fully bonded. The curing time for the bottom layer (i.e., the first reinforcing layer) is 30 s, and the curing time for each subsequent reinforcing layer is 15 s; Step P6: Repeating steps P4-P5 until the designed number of layers (e.g., 5 reinforcing layers) and the preset rotation angle are reached to form a spiral laminated structure.

[0022] The photopolymer 3D printing equipment has a wavelength of 405 nm and a pixel resolution of 22 µm.

[0023] The beneficial effects of this invention are:

[0024] (1) A fracture energy superposition model was established for biomimetic helical laminated structures. The fracture energy of the multilayer structure was decomposed into three parts: matrix cracking energy, interface dissipation energy, and fiber fracture energy. An interface slip energy dissipation term caused by interlayer angle mismatch was also introduced. This model is a mathematical description of the mechanical properties of helical structures. It can quantitatively predict the fracture energy increase under different interlayer rotation angles and has significant predictive and design guidance functions.

[0025] (2) Achieving parameter optimization under theoretical guidance: Based on the verified theoretical model, this invention determines the range of structural parameters (interlaminar rotation angle) that optimizes the synergy between strength and toughness. =30°-45°, ply number ≥5), avoiding the high cost and low efficiency of the traditional "trial and error method", and demonstrating the substantial contribution of theoretical models to structural design.

[0026] (3) Eight samples with different structural parameters were prepared by the system and mechanical tests were conducted. The comparison between the experimental values ​​and the theoretical predictions showed that the increase in equivalent stiffness was consistent and the increase in fracture energy was highly consistent with the model prediction (error <10%), which verified the correctness and reliability of the theoretical model.

[0027] (4) The control effect of orientation angle was revealed: By comparing the mechanical response of single-layer reinforced structure, it was found that as the orientation angle increases, the load-bearing stability of the sample after the peak load is significantly enhanced, and the downward segment of the force-displacement curve gradually becomes flat, indicating that fiber orientation rotation can effectively change the stress distribution state during crack propagation.

[0028] (5) The enhancement effect of the number of layers was discovered: By comparing single-layer and five-layer helical structures, the fracture energy and fracture work of the five-layer structure were significantly higher than those of the single-layer structure under the 15°-45° off-axis orientation. In particular, under the 30° and 45° orientation, the fracture energy of the five-layer structure was increased by more than three times, and the ultimate tensile strength was increased by about 60%-90%, which confirmed the significant advantage of multilayer helical structures in improving the toughness of composite materials.

[0029] (6) This method relies only on fiber-matrix elastic parameters and interlayer rotation angle, and is applicable to various material systems such as epoxy resin, thermosetting acrylic resin, and photocurable polymer, as well as composite material structures on the micron to meter scale. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the scale structure of a butterfly wing.

[0031] Figure 2 This is a schematic diagram of a biomimetic spiral laminated composite material structure.

[0032] Figure 3 This is another schematic diagram of a biomimetic spiral laminated composite material structure.

[0033] Figure 4 This is a schematic diagram of the glass fiber layup of a sample structure prepared according to an embodiment of the present invention (orientation angle is 30°).

[0034] Figure 5 This is a schematic diagram of a sample prepared according to an embodiment of the present invention being fractured after being stretched.

[0035] Figure 6 This is a photograph of a sample prepared according to an embodiment of the present invention after being stretched and then fractured.

[0036] Figure 7 This is a force-displacement response curve of a pure UV-curable resin according to an embodiment of the present invention.

[0037] Figure 8 This is a force-displacement response curve of a single-layer glass fiber reinforced sample with a fiber orientation angle of 0°, according to an embodiment of the present invention.

[0038] Figure 9 This is a force-displacement response curve of a single-layer glass fiber reinforced sample with a fiber orientation angle of 15°, according to an embodiment of the present invention.

[0039] Figure 10 This is a force-displacement response curve of a single-layer glass fiber reinforced sample with a fiber orientation angle of 30°, according to an embodiment of the present invention.

[0040] Figure 11This is a force-displacement response curve of a single-layer glass fiber reinforced sample with a fiber orientation angle of 45°, according to an embodiment of the present invention.

[0041] Figure 12 This is a force-displacement response curve of a five-layer glass fiber reinforced sample with a fiber orientation angle of 0°, according to an embodiment of the present invention.

[0042] Figure 13 This is a comparison diagram of the fracture energy of a pure UV-curable resin and a single-layer glass fiber reinforced sample under different fiber orientation angles, according to an embodiment of the present invention.

[0043] Figure 14 This is a comparison diagram of the fracture energy of a pure UV-curable resin and a five-layer glass fiber reinforced sample under different fiber orientation angles, according to an embodiment of the present invention.

[0044] Figure 15 This is a comparison diagram of the ultimate tensile strength of a pure UV-curable resin and a single-layer glass fiber reinforced sample under different fiber orientation angles, according to an embodiment of the present invention.

[0045] Figure 16 This is a comparison diagram of the ultimate tensile strength of a pure UV-curable resin and a five-layer glass fiber reinforced sample under different fiber orientation angles, according to an embodiment of the present invention. Detailed Implementation

[0046] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0047] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0048] A method for analyzing the structural properties of biomimetic helical fiber-reinforced composite materials is presented, including theoretical model construction, sample design and preparation, mechanical property testing, model verification, and parameter optimization. These are described in detail below.

[0049] The theoretical model construction corresponds to steps S1 to S4, including stiffness modeling of single-layer composite materials (step S1), construction of fracture energy superposition model (step S2), construction of ultimate tensile strength prediction model (step S3), and equivalent stiffness model of multi-layer helical laminated structure (step S4).

[0050] Stiffness modeling of single-layer composite materials involves establishing a continuum mechanical model of the single-layer composite material. It is assumed that the material consists of glass fiber and a UV resin matrix, with a fiber volume fraction of... The matrix volume fraction is , Elastic modulus of glass fiber Take 70 GPa, UV resin elastic modulus Take 2.5 GPa, glass fiber shear modulus Take 30 GPa, UV resin shear modulus The Pa value is 0.9 GPa. In this embodiment, Take 0.3, the matrix volume fraction is Take 0.7.

[0051] Elastic modulus along the fiber direction The calculation formula is:

[0052]

[0053] In the formula: Elastic modulus along the fiber direction, in GPa; The elastic modulus of glass fiber is expressed in GPa. The elastic modulus of UV resin is expressed in GPa. The fiber volume fraction is dimensionless. The fiber orientation angle is expressed in degrees (°).

[0054] transverse elastic modulus and shear modulus The calculation formula is:

[0055]

[0056]

[0057] In the formula: The transverse elastic modulus, in GPa, represents the elastic modulus of the composite material when the load direction is perpendicular to the fiber. The in-plane shear modulus of a unidirectional composite material (referring to a composite material layer in which all glass fibers are arranged in parallel along the same direction) under off-axis tension, in GPa, represents the material’s resistance to shear deformation. The shear modulus of glass fiber, expressed in GPa, is an inherent property of the fiber components. This is the shear modulus of UV resin, expressed in GPa, and is an inherent property of the matrix components.

[0058] In this embodiment, the following is taken Calculate 0°, 15°, 30°, and 45° respectively.

[0059] The fracture energy superposition model, based on the Griffith energy criterion, establishes a fracture energy prediction model for multi-layered helical laminated structures. The total fracture energy is then calculated. Decomposed into matrix cracking energy Interface dissipation energy and fiber breaking energy Three parts:

[0060]

[0061] In the formula: Total fracture energy, in kJ / m²; The matrix cracking energy is expressed in kJ / m². Let be the energy dissipated at the i-th interface, in kJ / m². is the fracture energy of the i-th fiber layer, in kJ / m²; N is the number of layers.

[0062] For single-layer structures, the main contributions come from fiber bridging and matrix cracking:

[0063]

[0064] In the formula: The fracture energy of a single-layer structure is expressed in kJ / m². The tensile strength of glass fiber is expressed in MPa and can be obtained through monofilament tensile testing or by consulting a material handbook. The thickness is for a single layer, in mm.

[0065] For a multi-layered helical structure, each layer introduces angular mismatch and interface slip, leading to crack path extension. The energy consumption term for interface slip is... Therefore, the fracture energy prediction model for a five-layer structure is as follows:

[0066]

[0067] In the formula: The fracture energy of the five-layer helical laminate structure is expressed in kJ / m². Let be the interfacial shear stress of the i-th layer, in MPa. Its value can be determined by short beam shear test (ASTM D2344) or estimated by micromechanical model. Let be the shear modulus of the i-th layer of the composite material, in GPa, derived from the shear modulus formula in step S1. The calculated shear modulus of the non-component material. or In this embodiment =50 µm.

[0068] The ultimate tensile strength prediction model uses the Tsai-Hill failure criterion to estimate the ultimate tensile strength (UTS) under off-axis tension. It is assumed that the principal crack propagates along the maximum shear plane when the monolayer composite is stretched off-axis, and the strength criterion is as follows:

[0069]

[0070] In the formula: ,for Directional normal stress components, in MPa; The y-direction normal stress component is expressed in MPa. X represents the shear stress component, in MPa; X represents the tensile strength along the fiber direction, in MPa, the value of which is determined experimentally (e.g., ASTM D3039, ASTM D3518); S represents the shear strength, in MPa, the value of which is determined experimentally (e.g., ASTM D3039, ASTM D3518).

[0071] Among them, shear stress component The calculation formula is:

[0072]

[0073] In the formula: The applied tensile stress is expressed in MPa.

[0074] In this embodiment, X = 500 MPa and S = 30 MPa were determined experimentally. Under uniaxial tension and Under the condition that = 0, the solution can be obtained. This is the theoretical prediction value of UTS.

[0075] For the equivalent stiffness model of multilayer helical laminated structures, such as for an N-layer helical laminated structure, the fiber direction of each layer... (i=1~N), thickness is The overall stiffness matrix was calculated using classical laminated theory [A]:

[0076]

[0077] In the formula: This represents the overall stiffness matrix of the laminated structure, in N / mm. is the simplified stiffness matrix of the i-th layer after coordinate transformation, in MPa; The thickness of the i-th layer is in mm.

[0078] in The calculation formula is:

[0079]

[0080] In the formula: This is a coordinate rotation matrix, dimensionless; This is the stiffness matrix in local coordinates, in MPa. and The standard formula from classical layering theory can be used.

[0081]

[0082]

[0083] In the formula, It is the longitudinal elastic modulus (along the fiber direction), taken from step S1. ; It is the transverse elastic modulus (perpendicular to the fiber direction), taken from step S1. , It is the in-plane shear modulus, taken from step S1. ; It is the principal Poisson's ratio, which is taken as 0.25 in this paper and is dimensionless; It is a secondary Poisson ratio, satisfying , dimensionless. Let be the fiber orientation angle, in degrees. For the i-th layer, its fiber orientation angle is . Then the coordinate rotation matrix of this layer is ,Right now exist = The value at that location.

[0084] Equivalent elastic modulus of laminated structure The calculation formula is:

[0085]

[0086] In the formula: The equivalent elastic modulus of the laminated structure is expressed in GPa. for The element in the first row and first column of the matrix, in MPa.

[0087] In this embodiment, the interlayer rotation angle was calculated. The equivalent stiffness of the five-story structure at 0°, 15°, 30°, and 45° is compared with that of a single-story structure.

[0088] The sample design and preparation corresponds to step S5, which involves first designing the structural parameters and then designing the preparation process.

[0089] To systematically study the effects of fiber orientation angle and layup number on the mechanical properties of composite materials, two types of samples were designed: a single-layer reinforced structure and a multi-layer helical laminate structure.

[0090] For the single-layer reinforced structure: there are 4 samples in total, each containing one layer of mesh glass fiber reinforcement (i.e., a UV-curable resin layer containing glass fibers). The fiber orientation angles of the 4 samples are 0°, 15°, 30° and 45°, respectively, and are denoted as G-0-1, G-15-1, G-30-1 and G-45-1.

[0091] For the multilayer helical laminated structure: there are 4 samples in total, each containing 5 layers of mesh glass fiber reinforcement, with adjacent reinforcement layers at a fixed angle along the same direction. Rotational laying. Interlayer rotation angles of the four samples. The angles are fixed at 0°, 15°, 30° and 45° respectively, and are denoted as G-0-5, G-15-5, G-30-5 and G-45-5 respectively.

[0092] For the interlayer rotation angle is The fiber orientation angles of each layer of the sample are as follows: Layer 1: 0° (reference layer);

[0093] Level 2: ; Level 3: 2 ; 4th floor: 3 ; Level 5: 4 .

[0094] in, The sample with a fiber angle of 0° (G-0-5) served as the control group. All five fiber layers had a fiber angle of 0° and no helical features. Samples with helical angles of 15°, 30°, and 45° were used as the experimental group, representing laminated structures with different degrees of helicity.

[0095] Figure 4 This is a schematic diagram of the glass fiber layup of the sample structure with an orientation angle of 30° prepared in this embodiment.

[0096] The specific parameters of the above 8 samples are summarized in Table 1.

[0097] Table 1. Samples with different glass fiber orientations

[0098]

[0099] For the preparation process, the composite material samples were prepared by a combination of lamination and layer-by-layer UV curing.

[0100] First, 3D modeling and slicing were performed: SolidWorks 2020 software was used for 3D modeling. The sample geometry was 60 mm × 30 mm × 2 mm (length × width × thickness), with a pre-made notch in the center, the depth and width of which were both 5 mm. The model file was exported in STL format and sliced ​​using CHITUBOX (Basic) software, with the layer thickness uniformly set to 50 µm, generating G-code. It was then imported into the printing equipment for manufacturing.

[0101] Printing equipment and materials: A photopolymer 3D printer (Sonic Mini 8K, Phrozen, Shenzhen, China) was used, with a UV light source wavelength of 405 nm and a pixel resolution of 22 µm in the X and Y directions. The matrix material was a commercially available standard UV-curable resin (Anycubic, Shenzhen, China), and the reinforcing phase was a mesh glass fiber.

[0102] Then, layer-by-layer printing and layup: The G-code is imported into the printing equipment, and printing begins with UV-curable resin as the matrix. After printing six consecutive layers of UV-curable resin (total thickness 300 µm), printing is paused, and a layer of mesh glass fiber is manually laid, with the fiber's main direction rotating layer by layer according to the preset spiral structure. UV curing is then performed, with a curing time of 10 seconds for each layer and 30 seconds for the bottom layer. The above steps are repeated until the designed number of layers and rotation angle are reached, forming a spiral laminated structure. Therefore, the physical thickness of each reinforcing layer consists of six resin layers (300 µm) and one fiber layer (thickness ignored or included in the fiber layer thickness), with a total thickness of approximately 300 µm. However, to maintain consistency with the single-layer thickness t (i.e., the equivalent thickness of each reinforcing layer) in the theoretical model, the equivalent thickness t = 300 µm for each reinforcing layer is defined in this invention, and other parameters in the model (such as fiber volume fraction) are also calculated based on this equivalent thickness.

[0103] To ensure the reliability and repeatability of the experimental results, three sets of samples were prepared under each structural parameter condition. Figures 7-12 The three curves of different colors represent the results corresponding to the three groups of samples.

[0104] The mechanical property testing corresponds to step S6, which uses an electronic universal testing machine (Huaheng) for uniaxial tensile testing. All tests are conducted at room temperature using a displacement-controlled loading method with a loading rate set at 1 mm / min. Force signals are acquired in real-time by a high-precision sensor, and the specimen is continuously stretched until complete fracture. Figure 5 , 6 As shown, the force-displacement response curves are recorded.

[0105] Calculate the following mechanical parameters based on experimental data: stress ,strain Elastic modulus E, ultimate tensile strength UTS, fracture energy .

[0106] stress : The ratio of applied force to the initial cross-sectional area of ​​the specimen; strain : The ratio of the axial displacement of the specimen to the initial gauge length; Elastic modulus E: The initial linear stage of the stress-strain curve ( The slope within the range of 0-0.025; Ultimate tensile strength (UTS): the maximum stress value in the stress-strain curve; Fracture energy. The stress-strain curve is integrated, and the area between the loading start point and the complete fracture point is calculated using the trapezoidal integral method to characterize the energy absorption capacity of the material per unit volume.

[0107] After the test results are obtained, they are analyzed from the following three aspects: the influence of fiber orientation angle on mechanical response, the influence of the number of layups on mechanical properties, and the energy dissipation and ultimate tensile strength characteristics.

[0108] The effect of fiber orientation angle on mechanical response Figures 8-11 Typical force-displacement curves of single-layer glass fiber reinforced structures under different orientation conditions are shown. Figure 12 The force-displacement response curves of a five-layer glass fiber reinforced specimen with a fiber orientation angle of 0° are shown. It can be seen that the force-displacement response of the composite material exhibits significant differences as the glass fiber orientation angle increases.

[0109] Specimens with low orientation angles (0°-15°) exhibited a rapid decrease in load-bearing capacity after reaching peak load, and the fracture process was sudden. When the orientation angle increased to 30°-45°, the load-bearing stability of the specimens after peak load significantly improved, the descent of the force-displacement curve gradually flattened, and the failure process became more gradual. This indicates that fiber orientation rotation effectively altered the stress distribution during crack propagation, inducing various energy-dissipating behaviors such as fiber-resin interface slippage, local debonding, and mesh structure rearrangement.

[0110] Regarding the effect of the number of layers on mechanical properties, under the same orientation angle, the mechanical properties of single-layer and five-layer reinforced structures are compared, and the key parameters are summarized in Table 2.

[0111] Table 2 Mechanical property parameters for different ply numbers and orientation angles

[0112]

[0113] At 0° orientation, the mechanical properties of single-layer and five-layer samples are almost identical, and increasing the number of plies has no significant reinforcing effect, indicating that the load-bearing capacity is dominated by the axial tension of the fibers. At off-axis orientation, the effect of the number of plies is significantly enhanced: at 15°, the fracture energy of the five-layer structure is significantly higher than that of the single-layer structure; at 30° and 45°, the fracture energy of the five-layer structure increases by more than three times, and the ultimate tensile strength increases by about 60%-90%.

[0114] Analysis of energy dissipation and ultimate tensile strength characteristics Figure 13 and 14 The study demonstrates the variation of fracture energy under different structures. The fracture energy of all glass fiber reinforced structures is significantly higher than that of pure resin. The fracture energy of the five-layer helical structure is most prominent in the range of 15°-45°, indicating that the multi-layer orientation rotational layup increases the tortuosity of the crack propagation path and effectively delays crack penetration by introducing complex stress redistribution and interlayer interaction through interlayer orientation mismatch.

[0115] Figure 15 and 16 The ultimate tensile strength was compared. In multilayer helical structures, with the increase of the number of layers and the introduction of orientation rotation, the strength becomes less sensitive to the orientation angle, reflecting a more balanced anisotropic load-bearing capacity.

[0116] in, Figures 13-16 The black lines on each bar represent error bars.

[0117] Model verification and parameter optimization correspond to steps S7~S8. Model verification corresponds to step S7, which compares the calculated values ​​of the theoretical model in step 1 with the experimental values ​​in Table 2 from three perspectives: equivalent stiffness, ultimate tensile strength and fracture energy.

[0118] Equivalent stiffness: theoretically calculated Consistent with the increasing trend of the experimental peak load, in When the angle is between 30° and 45°, the increase in single-layer structure is about 60%-90% compared to five-layer structure, which is consistent with the experimental value.

[0119] Ultimate tensile strength: The trend of UTS predicted by the Tsai-Hill criterion is consistent with the experimental value, and the average relative error between the theoretical and experimental values ​​in the range of 15°-45° is less than 10%.

[0120] Fracture energy: The fracture energy predicted by the fracture energy superposition model for the five-layer structure is more than 2 times higher, which is in good agreement with the experimental value (more than 3 times higher), verifying the correctness of the model. The introduction of the interface slip energy dissipation term reasonably explains the energy dissipation mechanism of the multilayer helical structure.

[0121] Parameter optimization corresponds to step S8, which predicts the interlayer rotation angle based on the validated theoretical model. The fracture energy and ultimate tensile strength under the ply number N. Model predictions show that: When the angle is <15°, the energy contribution from interface slip is small, and the increase in fracture energy is limited; when When the angle is 30°-45°, the energy dissipation of interface slip is significantly enhanced, and the fracture energy reaches the optimal level; when the number of layers N≥5, the superposition effect of energy dissipation by multiple mechanisms tends to be stable.

[0122] Based on experimental data and theoretical predictions, the optimal structural parameter was determined to be: interlayer rotation angle. =30°-45°, ply number ≥5. Within this parameter range, the composite material can achieve optimal synergy between fracture energy (≥11 kJ / m²) and ultimate tensile strength (≥17MPa).

[0123] As shown above, this embodiment fully demonstrates the specific process of studying biomimetic spirally arranged glass fiber reinforced UV-curable resin composite materials using the analytical method of the present invention (steps S1~S8).

[0124] It should be noted that the analytical method of this invention relies solely on the fiber-matrix elastic parameters and interlaminar rotation angle, and is not limited to a specific material system. This method can also be applied for analysis and optimization by changing the matrix material (such as epoxy resin, thermosetting acrylic resin, etc.) or adjusting the structural dimensions, thus demonstrating its wide applicability.

[0125] Finally, it is necessary to state that the above embodiments are only used to further illustrate the technical solution of the present invention in detail, and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A method for analyzing the structural properties of biomimetic helical fiber-reinforced composite materials, characterized in that, The following steps are performed in sequence: Step S1: Establish a continuous medium mechanical model of a single-layer composite material and calculate the elastic modulus, transverse elastic modulus, and shear modulus along the fiber direction; Step S2: Based on the Griffith energy criterion, a fracture energy prediction model for multilayer helical laminated structures is established, and the fracture energy is decomposed into three parts: matrix cracking energy, interface dissipation energy and fiber fracture energy. Among them, the interface dissipation energy term characterizes the energy dissipation caused by interlayer angle mismatch. Step S3: Establish a prediction model for ultimate tensile strength under off-axis tensile conditions based on the Tsai-Hill failure criterion; Step S4: Establish an equivalent stiffness calculation model for multi-layered helical laminated structures based on classical laminated theory; Step S5: Design and prepare a series of composite material samples with different fiber orientation angles and layup numbers, including single-layer reinforced structures and multi-layer helical laminated structures; Step S6: Perform mechanical property tests on the prepared series of samples, obtain force-displacement response curves, and calculate the experimental values ​​of elastic modulus, ultimate tensile strength, and fracture energy. Step S7: Compare and verify the experimental values ​​with the theoretical prediction values ​​from steps S1-S4, and correct the model parameters accordingly; Step S8: Based on the verified theoretical model, predict the mechanical properties under different structural parameters, and determine the structural parameters that optimize the fracture energy and ultimate tensile strength.

2. The analytical method according to claim 1, characterized in that: Four samples of the single-layer reinforced structure were obtained, with fiber orientation angles of 0°, 15°, 30°, and 45°, respectively. Four samples of the multi-layer helical laminated structure were also obtained, each containing five layers, with interlayer rotation angles of [missing information]. The angles are fixed at 0°, 15°, 30°, and 45° respectively, and the interlayer rotation angle is... The sample has a first layer fiber orientation angle of 0° and a second layer fiber orientation angle of 0°. The third layer is 2 The 4th layer is 3 The 5th floor is 4 .

3. The analytical method according to claim 1, characterized in that: The mechanical property test was conducted using uniaxial tensile loading at a loading rate of 1 mm / min. The specimen dimensions were 60 mm × 30 mm × 2 mm, with a pre-fabricated notch in the middle with a depth and width of 5 mm.

4. The analytical method according to claim 1, characterized in that: The calculation formulas for the elastic modulus along the fiber direction, the transverse elastic modulus, and the shear modulus mentioned in step S1 are as follows: ； ； ； In the formula: Elastic modulus along the fiber direction, in GPa; This refers to the fiber's elastic modulus, expressed in GPa. The elastic modulus of UV resin is expressed in GPa. The fiber volume fraction is dimensionless. Fiber orientation angle, in degrees; This is the transverse elastic modulus, in GPa. Shear modulus, in GPa; Fiber shear modulus, in GPa; This represents the shear modulus of UV resin, expressed in GPa.

5. The analytical method according to claim 4, characterized in that: The fracture energy prediction model mentioned in step S2 is as follows: ； In the formula: The fracture energy of the five-layer helical laminate structure is expressed in kJ / m². The matrix cracking energy is expressed in kJ / m². Fiber tensile strength, in MPa; The thickness is for a single layer, in mm. is the interfacial shear stress of the i-th layer, in MPa; Let be the shear modulus of the i-th layer, in GPa.

6. A biomimetic spirally arranged fiber-reinforced composite material, characterized in that: It includes multiple reinforcing layers and a UV-curable resin matrix layer, wherein the reinforcing layers are UV-curable resin layers containing mesh glass fibers, and the matrix layer is a UV-curable resin layer without glass fibers; adjacent reinforcing layers are laid in a fixed angle along the same direction to form a spiral laminated structure with periodic orientation changes.

7. The composite material according to claim 6, characterized in that: The fixed angle is 15°, 30° or 45°, and the number of layers is 1 to 10; the glass fiber is an in-plane continuous mesh structure.

8. A method for preparing the composite material of claim 6, characterized in that, Includes the following steps: Step P1: Use 3D modeling software to create a sample model and export it as an STL file; Step P2: Use slicing software to perform slicing and generate print control code; Step P3: Using a photopolymer 3D printing device, print layer by layer with UV-curable resin as the matrix, and set the layer thickness to 50 µm. Step P4: After printing six layers of UV-curable resin consecutively, lay a layer of mesh glass fiber, with the main direction of the fiber rotating layer by layer according to the preset spiral structure. Step P5: UV irradiation is used to achieve layer-by-layer curing. The curing time for a single layer is 10 s, and the curing time for the bottom layer is 30 s. Step P6: Repeat steps P4-P5 until the designed number of layers and rotation angle are reached to form a spiral laminated structure.

9. The method according to claim 8, characterized in that: The photopolymer 3D printing equipment has a wavelength of 405 nm and a pixel resolution of 22 µm.

Images