A biomimetic impact-resistant composite material based on macro- and micro-scale competition, its preparation method and application

Abstract

This invention relates to a biomimetic impact-resistant composite material based on macro- and micro-scale competition, its preparation method, and its application, belonging to the field of advanced composite materials and impact protection technology. The composite material comprises a hydrogel matrix and a biomimetic topological framework embedded therein, exhibiting a multi-scale hierarchical structure, with the matrix possessing anisotropic structure. The biomimetic topological framework is a polyvinyl alcohol material with a three-dimensional porous network structure. The hydrogel matrix is ​​a polyvinyl alcohol / chitosan hydrogel material with anisotropic microporous channels and polymer crystalline region networks. The multi-scale hierarchical structure is jointly composed of the three-dimensional porous network of the biomimetic topological framework at the macro-level and the anisotropic microporous channels and polymer crystalline region networks of the hydrogel matrix at the micro / nano level. Through a biomimetic design control mechanism, the material can achieve macroscopic stress transfer and crack deflection with the help of the framework, and synergistically utilize micron, nano, and molecular multi-scale energy dissipation pathways, significantly improving the impact resistance of the composite material.

Description

Technical Field

[0001] This invention belongs to the field of advanced composite materials and impact protection technology, specifically relating to a biomimetic impact-resistant composite material based on macro- and micro-scale competition, its preparation method, and its application. Background Technology

[0002] Mechanical shock protection is a common technical challenge in fields such as sports safety, electronic packaging, and aerospace. Natural biomaterials, with their intricate multi-level structures, possess high strength, high toughness, and excellent impact resistance, making them highly efficient multi-scale energy dissipation systems. Typical examples include the helical twisted plywood structure of the mantis shrimp's claws and the gradient hierarchical structure of bamboo; both can efficiently dissipate energy, providing important inspiration for the design of high-performance biomimetic protective materials. Hydrogels are ideal carriers for realizing such biomimetic designs. In existing research, inspired by the microstructure of mantis shrimp, Xiong et al. prepared a high-toughness, impact-resistant hydrogel through the synergistic interaction of long-range ordered assembly of cellulose nanocrystals, heterogeneous nanocrystal domains, and dynamic interfaces.

[0003] Despite significant progress in the development of biomimetic hydrogels, their hierarchical complexity and spatial precision still fall far short of natural biological tissues. The core reason lies in the lack of finely designed biomimetic topological frameworks, a limitation that severely restricts the application of materials in scenarios requiring high toughness, excellent impact resistance, and outstanding stability. Traditional fabrication methods (such as mold casting and self-assembly) typically only yield simple geometric structures or micro / nanoscale ordered structures, making it difficult to achieve highly spatially free and precisely controllable customized topological frameworks. While micro / nano fabrication technologies (such as IC / MEMS processes) can achieve precise small-scale topological pattern construction, they are difficult to extend to macroscopic structure fabrication. Furthermore, the bonding between the topological framework and the hydrogel matrix often relies on heterogeneous interfacial bonding, posing a risk of delamination failure. Therefore, developing fabrication strategies that combine high-precision topological design with strong interfacial bonding capabilities is crucial for achieving controllable biomimetic topological structure construction.

[0004] Besides topological framework design, synergistic activation of multi-scale energy dissipation mechanisms can further enhance the mechanical properties of biomimetic hydrogels. Existing research has confirmed that both molecular engineering and structural engineering can enhance the energy dissipation capacity of materials: molecular engineering, through the construction of bi / multi networks, the introduction of non-covalent interactions, and the formation of nanocrystalline domains, can significantly improve the fracture toughness, strength, self-healing properties, and modulus of hydrogels; structural engineering, relying on cryogenic casting, mechanical training, and the Hofmeister effect, can construct anisotropic micro / nanostructures. Combining these two techniques can construct ordered multi-level structures covering molecular, micro, and mesoscale scales, achieving cross-scale improvements in mechanical properties. However, existing research typically involves only 2-3 structural levels, limiting further improvements in energy dissipation efficiency. More importantly, introducing a macroscopic topological framework cannot guarantee improved material performance. To address this, this invention proposes a macro-microscale competition mechanism (MMC): the macroscopic topological enhancement effect and the microscopic energy dissipation mechanism compete rather than cooperate. This mechanism clarifies why simply introducing a biomimetic framework may actually reduce the overall mechanical properties of composite materials, and also highlights the necessity of finely designed frameworks to regulate multi-scale energy dissipation paths.

[0005] In summary, there is an urgent need to construct a hydrogel system that deeply integrates a programmable topological framework with multi-scale fabrication processes, fully activating the synergistic effect of multi-scale energy dissipation and breaking through the impact resistance bottleneck of existing biomimetic hydrogels. This invention will provide core technical support for the structural design and large-scale fabrication of next-generation high-performance impact-resistant protective materials, ensuring that the materials maintain stable performance under complex working conditions, thereby effectively exerting their designed protective efficacy. Summary of the Invention

[0006] The technical problem to be solved: To overcome the shortcomings of existing technologies, this invention provides a biomimetic impact-resistant composite material based on macro- and micro-scale competition, its preparation method, and its application. A 3D-printed polyvinyl alcohol (PVA) biomimetic framework is embedded in a hydrogel matrix to form a multi-scale hierarchical PVA / CS hydrogel composite material with an anisotropic matrix, creating a homologous interface composite system. By controlling the topological complexity of the framework, the competition between macroscopic crack deflection gain and microstructural degradation loss is coordinated. When the synergy factor λ > 1, cross-scale synergistic enhancement is achieved, significantly improving impact resistance, making it suitable for impact protection of electronic chips and other devices.

[0007] The technical solution of the present invention is: a biomimetic impact-resistant composite material based on macro-micro scale competition, comprising a hydrogel matrix and a biomimetic topological framework embedded therein, the two having a composite interface of homologous molecular fusion, the whole having a multi-scale hierarchical structure, and the matrix having an anisotropic structure. The biomimetic topological framework is a polyvinyl alcohol material with a three-dimensional porous network structure; The hydrogel matrix is ​​a polyvinyl alcohol / chitosan hydrogel material with anisotropic microporous channels and a polymer crystalline region network; anisotropy refers to the asymmetric mechanical response of the material in different directions; The multi-scale hierarchical structure is composed of a three-dimensional porous network of biomimetic topological framework at the macro level and anisotropic microporous channels and polymer crystalline region network of hydrogel matrix at the micro-nano level.

[0008] A further technical solution of the present invention is that the biomimetic topological framework is selected from at least one of the following configurations: The porous configuration is a three-dimensional porous topology composed of interconnected meshes; The single twisted plywood configuration is a layered structure composed of N layers of fiber bundles. Adjacent fiber layers are arranged in a unidirectional rotation at a preset rotation angle θ, and the spacing d between the fiber bundles in a single layer is equal. The gradient twisted plywood configuration is a layered structure composed of N layers of fiber bundles. Adjacent fiber layers are arranged in a unidirectional rotation at a preset rotation angle θ. The spacing d of the fiber bundles in a single layer varies in a gradient along the thickness direction of the frame. The value of N ranges from 6 to 10 layers, the value of θ ranges from 10° to 30°, and the value of d ranges from 1 mm to 6 mm.

[0009] A further technical solution of the present invention is that the mass fraction of polyvinyl alcohol in the hydrogel matrix is ​​10%, and the mass fraction of chitosan is 0.5%.

[0010] A further technical solution of the present invention is that the hydrogel matrix dissipates energy at the micrometer scale through fiber friction and slippage, at the nanometer scale through polymer chain entanglement and deentanglement, and at the molecular scale through reversible hydrogen bond breaking.

[0011] A further technical solution of the present invention is: the overall mechanical properties of the composite material are controlled by a macro-micro scale competition mechanism; the macro-micro scale competition mechanism refers to: the biomimetic topological framework provides mechanical gains for crack deflection and branching at the macro level, while at the micro level, the microstructural order of the hydrogel matrix deteriorates due to interface modulus mismatch and spatial confinement effect; the overall mechanical properties of the composite material are determined by the competition result between mechanical gains and structural order deterioration. The microstructural order is the crystallization orientation of polymer chains and the self-assembled crystalline network within the hydrogel matrix; the deterioration of the microstructural order is manifested by the destruction of local hydrogen bond networks, decreased crystallinity, and increased proportion of free hydroxyl groups in the hydrogel matrix. When the mechanical gain is greater than the structural order deterioration, the impact absorption energy of the composite material is higher than the sum of the independent energy absorption of the biomimetic topological framework and the hydrogel matrix, breaking through the critical point of macro-micro competition and achieving synergistic toughening.

[0012] A method for preparing the aforementioned biomimetic impact-resistant composite material includes the following steps: Step 1: Disperse polyvinyl alcohol and chitosan in deionized water, heat and stir until completely dissolved to obtain a uniform and stable polyvinyl alcohol / chitosan hydrogel precursor solution; Step 2: Based on computer-aided design, construct the target model, and use fused deposition modeling 3D printing technology to deposit polyvinyl alcohol filaments layer by layer, and obtain a biomimetic topological framework after natural cooling; Step 3: Pour the hydrogel precursor solution into the mold, and then completely embed the biomimetic topological framework into the hydrogel precursor solution; Step 4: Place the mold containing the precursor solution and the biomimetic topological framework in a temperature gradient field to induce the directional growth of ice crystals within the system; Step 5: Place the frozen sample in a vacuum low-temperature environment for freeze-drying to allow the internal ice crystals to completely sublimate and form an aerogel; Step 6: Anneal the aerogel; Step 7: Immerse the annealed aerogel in a salting-out solution to allow the hydrogel matrix to undergo physical cross-linking, thereby obtaining a biomimetic impact-resistant composite material.

[0013] A further technical solution of the present invention is as follows: the specific process parameters of the preparation method are as follows: In step 1, the mass fraction of polyvinyl alcohol is 10%, the mass fraction of chitosan is 0.5%, the heating and stirring temperature is 95℃, and the time is 2 h; In step 4, the temperature gradient field is provided by a copper block partially immersed in liquid nitrogen, and the ice crystals grow directionally from bottom to top; In step 5, the vacuum low-temperature environment is -50℃, 10 Pa, and the freeze-drying time is 48 h; In step 6, the annealing treatment is performed at a temperature of 90°C for 60 minutes. In step 7, the salting-out solution is a saturated sodium citrate solution, and the soaking time is 48 h.

[0014] A further technical solution of the present invention is: to control the competition mechanism between macro and micro scales by regulating the spatial geometric complexity of the biomimetic topological framework: the spatial geometric complexity is determined by two dimensions, namely the grid configuration of the framework and the distribution of fiber bundle spacing within the layer, and the spatial geometric complexity increases stepwise in the order of porous configuration < single twisted plywood configuration < gradient twisted plywood configuration. Using a synergy factor λ=1 as the critical threshold for macro-micro competition, the formula for calculating the synergy factor λ is as follows: λ = E 复合材料 / ( E 纯框架 + E 水凝胶 ) in, E 复合材料 This represents the total energy absorbed by the biomimetic impact-resistant composite material under impact load. E 纯框架 This represents the total energy absorbed by the biomimetic topological frame under the same impact load. E 水凝胶 This represents the total energy absorbed by the hydrogel matrix under the same impact load. Using the synergy factor λ=1 as the critical threshold for macro-micro competition, the topological complexity range corresponding to the macro-micro competition equilibrium point is determined. When λ<1, the composite material is in a competitive state dominated by micro-deterioration. When λ>1, the composite material breaks through the critical point of macro-micro competition and achieves cross-scale synergistic enhancement.

[0015] A further technical solution of the present invention is: the equilibrium point of the macro-micro scale competition mechanism is determined by regulating the spatial geometric complexity of the biomimetic topological framework; the regulation method is as follows: The volume fraction of the biomimetic topological framework is fixed at 24%, and the overall external dimensions are uniformly 37 mm × 42 mm × 6.6 mm. When the biomimetic topological framework is a porous configuration, it adopts a regular interconnected orthogonal mesh structure without setting layered rotational stacking, serving as a low-complexity benchmark. When the biomimetic topological frame is a single twisted plywood configuration, it is composed of 8 layers of fiber bundles stacked together, with adjacent fiber layers arranged in a unidirectional rotation of 18°, and the spacing between single-layer rods is constant at 2.8 mm. When the biomimetic topological frame is a gradient twisted plywood configuration, it is composed of 8 layers of fiber bundles stacked together. Adjacent fiber layers are arranged in a unidirectional rotation of 18°. The spacing between the members changes linearly along the thickness direction of the frame, gradually increasing from 1.5 mm to 5 mm. The spatial geometric complexity of the porous configuration, the single twisted plywood configuration, and the gradient twisted plywood configuration increases progressively.

[0016] Application of a biomimetic impact-resistant composite material in the preparation of impact protection materials, wherein the impact protection materials are used for aerospace components, housings of smart devices, buffer layers for high-end electronic chip packaging, or impact protection coatings for flexible printed circuit boards.

[0017] Beneficial effects The beneficial effects of this invention are as follows: Based on a finely designed biomimetic framework and hydrogel matrix, this invention prepares a topologically controllable, layered anisotropic hydrogel composite material; relying on a biomimetic topological design strategy to regulate the MMC mechanism, the biomimetic framework is used to achieve macroscopic stress guidance and crack deflection, and in conjunction with micron, nano, and molecular multi-scale energy dissipation paths, the impact resistance of the composite material is significantly improved. This invention systematically characterizes the impact resistance and long-term stability of the composite material through quasi-static compression, low-velocity falling ball impact, and SHPB high-strain rate dynamic impact tests; combined with FE simulation, the MMC mechanism is analyzed in depth, clarifying the regulatory law of biomimetic topology on the energy absorption performance of the material. Simultaneously, the composite material preparation process is compatible with IC / MEMS technology, enabling wafer-level chip integration, and effectively protecting processor chips, flexible circuit boards, and other electronic devices from high-speed impact damage.

[0018] The specific advantages are analyzed as follows: 1. This invention is based on biomimetic design. A topological framework is printed using FDM, placed in a hydrogel precursor solution, and then subjected to directional cryogenic annealing and salting-out processes to obtain a hydrogel composite material. Because both the framework and the hydrogel matrix are primarily made of PVA, the interfacial bonding strength is effectively enhanced. The interfacial bonding mode changes from simple mechanical interlocking to molecular fusion, forming a continuous and stable composite interface, overcoming the defect of easy delamination and failure in traditional heterogeneous interfacial bonding.

[0019] 2. While the macroscopic framework can achieve mechanical enhancement through induced crack deflection and branching, it simultaneously disrupts the structural order of the hydrogel matrix at the microscopic level, causing microscopic mechanical losses. Therefore, the overall performance of the composite material is determined by the competition between macroscopic gains and microscopic degradation. Not all macroscopic structures can improve the mechanical properties of the composite material; the improvement in overall performance only occurs after reaching a competitive equilibrium point, which is a direct result of MMC (Mechanism of Motion Computation). Simulation results further demonstrate the effective regulation of hydrogel composite materials by the MMC mechanism.

[0020] 3. This invention obtains the stress-strain curve of the composite material through quasi-static compression testing, verifying its high strength and toughness under quasi-static compression. In low-velocity falling ball impact tests, the peak force-time curve shows that the hydrogel composite material can reduce the impact force by up to 88%, with a buffer time of up to 4 ms, verifying its high impact resistance under low-velocity impact. Furthermore, the peak force attenuation value is less than 5% over 35 days, indicating its long-term stability. SHPB dynamic impact tests demonstrate that the hydrogel composite material can achieve a compressive strength of 183.57 MPa at high strain rates (approximately 4000 s⁻¹). -1 The impact-induced stress-guided crack deflection phenomenon was observed in the sample after impact using scanning electron microscopy (SEM), which verified its high impact resistance under high-speed impact.

[0021] 4. The composite material preparation process of this invention is compatible with IC / MEMS technology and can be directly integrated with silicon wafers to achieve wafer-level integration. After coating the processor chip and flexible FPC with this material, SHPB high-speed impact verification is carried out. After impact, the chip's microstructure remains intact, and the flexible circuit maintains continuous conductivity, which can effectively avoid the breakage of electronic devices and circuit failure caused by high-speed impact loads. It is suitable for aerospace, humanoid intelligence, and high-end electronic protection fields. Attached Figure Description

[0022] Figure 1 This is a diagram of the gradient twisted plywood (GT) frame in Example 1; Figure 2 The flowchart for Example 1 shows the process of fully embedding the GT framework into the hydrogel matrix and combining synergistic molecular and structural engineering to prepare a topology-controlled, hierarchical anisotropic (HA) hydrogel composite material (GT-HA). Figure 3 This is a control diagram of the MMC mechanism; Figure 4 The graph shows the quasi-static impact compression test results of the materials in Examples 1, 2, 1, 2, 3, 4, and 5. Figure 5 Figure 1 shows the results of low-speed falling ball impact tests on the materials of Example 1, Example 2, Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, and Comparative Example 5. Figure 6 The SHPB test results of the materials in Example 1, Example 2, Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, and Comparative Example 5 are shown in the figure. Figure 7 This is a schematic diagram illustrating the compatibility of the composite material preparation process with IC / MEMS processes in Example 1. Figure 8 Images of the embedded processor chips in Examples 1 and 1 (Comparative Example 1) after high-speed impact are shown. The results indicate that the HA hydrogel-coated chip suffered severe mechanical damage after high-speed impact, while the chip transistors and metal interconnects within the GT-HA composite material remained intact, demonstrating excellent impact protection. Detailed Implementation

[0023] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0024] Based on the problems existing in the prior art, this invention proposes a method for preparing a biomimetic impact-resistant composite material regulated by the MMC mechanism, the specific steps of which are as follows: Fabricate a finely designed 3D-printed biomimetic topological framework; Prepare a hydrogel precursor solution that is homologous to a biomimetic framework material; By embedding a biomimetic framework into a hydrogel matrix and combining molecular and structural engineering, a multi-scale hierarchical hydrogel composite material with topological controllability and matrix anisotropy was prepared. The multi-scale hierarchical structure refers to the cross-scale multi-level construction of macroscopic layers (millimeter-level, 3D-printed biomimetic topological frameworks) and micro / nano layers (micrometer-level anisotropic ice crystal pores, nanoscale polymer crystalline network). Anisotropy refers to the asymmetric mechanical response of the material in different directions. Anisotropy is achieved through a directional freezing process. A precursor solution is poured into a copper-based PTFE mold and placed on a liquid nitrogen temperature gradient field, causing internal ice columns to grow directionally from bottom to top. After freeze-drying and sublimation, an anisotropic hydrogel with directional microchannels is formed.

[0025] This study explores the MMC mechanism in hydrogel composites and determines the macro-micro competitive equilibrium point by adjusting the complexity of the biomimetic topological framework, thereby achieving effective regulation of the mechanical properties of hydrogel composites by the MMC mechanism.

[0026] The specific implementation of the control measures is as follows: First, the irrelevant variables of all samples were uniformly determined, the volume fraction of the bionic frame was fixed at 24%, and the overall external dimensions were uniformly 37 mm × 42 mm × 6.6 mm, to eliminate the performance interference caused by shape and proportion. Then, complete the 3D modeling using SolidWorks: The P-frame (porous configuration) is composed of interconnected orthogonal meshes, forming a three-dimensional porous topological reference structure with regular pore arrangement; The T-frame (single twisted plywood configuration) is composed of 8 layers of parallel fiber bundles stacked together. Adjacent fiber layers are arranged in a unidirectional rotation at a fixed angle of 18°, and the spacing between the single-layer array members is constant at 2.8 mm. The GT frame (gradient twisted plywood configuration) also adopts an 8-layer fiber bundle, 18° interlayer rotation structure, and the spacing between the members changes linearly along the thickness of the frame, gradually increasing from 1.5 mm at the top layer to 5 mm at the bottom layer.

[0027] Finally, under the premise of completely consistent volume fraction (24%) and overall dimensions (37 mm × 42 mm × 6.6 mm), for the T-frame and GT-frame with layered composite configurations, the total number of layers was fixed at 8, and the unidirectional rotation angle of adjacent fiber layers remained unchanged at 18°. Only the distribution of the spacing between the members within the layers was adjusted to achieve complexity gradation. For the P-frame with a non-layered orthogonal mesh configuration, a regular interconnected orthogonal mesh design was used as a low-complexity benchmark control group, and no layered rotational composite structure was set. Through the two adjustable dimensions of mesh configuration and the distribution of the spacing between the members within the layers, the spatial geometric complexity of the frames was increased stepwise in the order of P-frame < T-frame < GT-frame. Subsequently, the composite materials of the three types of frames were prepared, and mechanical tests and finite element simulations were carried out to calculate the synergy factor λ. With λ = 1 as the critical threshold for macro-micro competition, the topological complexity range corresponding to the macro-micro competition equilibrium point was accurately determined by comparing the structural parameters and performance of each group of λ.

[0028] Calculation of the synergy factor λ and quantitative determination of the MMC mechanism: Characterize the microstructure, chemical structure, thermal properties and viscoelastic properties of hydrogel composite materials; The mechanical properties of hydrogel composites were tested, including quasi-static compression, low-speed falling ball impact, and split Hopkinson bar (SHPB) compression properties. Determine the long-term stability of hydrogel composite materials; Finite element (FE) simulations of falling ball impact tests were used to quantitatively extract the total internal energy (ALLIE) data during the impact response process. This data was then used to construct a cross-scale synergistic factor λ to quantify the regulatory effect of the MMC mechanism on the mechanical properties of hydrogel composites. Specifically, the quantification of the regulatory mechanism involved calculating the absorbed internal energy of the GT frame under the same falling ball impact kinetic energy using an explicit kinetic solver. E 框架 Internal energy absorbed by hierarchical anisotropic hydrogels E 水凝胶 And the total absorbed internal energy of the composite material after the two are combined. E 复合材料 ; Verify the compatibility of hydrogel composite material preparation process with IC / MEMS process, realize wafer-level chip integration in composite material system, and effectively protect high-value electronic devices such as processors and flexible printed circuit boards (FPC) from structural damage caused by high-speed impact.

[0029] Specifically, the precursor solution of the hydrogel composite material includes: The PVA mass fraction is 10%, the CS mass fraction is 0.5%, the reaction temperature is 95℃, and the reaction time is 2h; Specifically, the hydrogel composite material includes: The topological framework and hydrogel matrix achieve strong interfacial bonding, effectively avoiding the delamination defects of heterogeneous interfaces and ensuring the overall structural and mechanical stability of hydrogel composite materials.

[0030] Specifically, the hydrogel composite material includes: The overall mechanical properties of hydrogel composites are controlled by the MMC mechanism: the introduction of the framework provides crack deflection and branching at the macro level to improve mechanical properties, while at the micro level it disrupts the structural order of the hydrogel matrix, leading to the deterioration of micro properties. The overall mechanical properties of the composites are determined by the competition between the performance improvement at the macro level and the performance deterioration at the micro level. Specifically, determining the mechanical properties of the hydrogel composite material includes: The stress-strain curves of the hydrogel composite material and the control group were tested by quasi-static compression test, and the toughness of the samples was calculated. The force-time curves and buffer time of the hydrogel composite material and the control group sample under low-speed impact were tested by dropping ball impact test. The dynamic compressive stress-strain curves of hydrogel composite materials and control samples under high-speed impact conditions were obtained through SHPB dynamic impact tests. The toughness of the samples was calculated, and the surface damage morphology of the samples after impact was observed.

[0031] Specifically, the long-term stability properties of the hydrogel composite material include: The peak force-time curve of the hydrogel composite material under continuous ball impact for 35 days was tested, and its structural integrity in the aquatic environment was observed. Specifically, the mechanism for determining the MMC of the hydrogel composite material includes: First, a theoretical analysis of the impact resistance mechanism of hydrogel composites at multiple scales—macroscopic, microscopic, nanoscopic, and molecular—is conducted. Then, based on FE simulation results, a synergistic factor λ is proposed as a quantitative standard. We define... λ The dimensionless physical parameter characterizing the impact mechanics coupling effect between the framework and the hydrogel matrix is ​​the ratio of the actual dissipated internal energy of the system to that of an uncoupled independent system after cross-scale stress transfer and interfacial interaction between the two phases. It can quantitatively evaluate the competitive results of the positive energy gain and negative energy loss physical processes under the MMC mechanism. The mathematical relationship is λ = E 复合材料 / ( E 纯框架 + E 水凝胶 ),in E This represents the total energy absorbed by the material under impact load (ALLIE). λThe spatial geometric complexity depends on the biomimetic topological framework: When the P framework is used, due to the low geometric complexity, the macroscopic level gain cannot compensate for the degradation of the microscopic structural order, resulting in λ = 0.94 < 1, and the system is in a state dominated by microscale degradation; when the complexity of the control framework is increased to the GT framework, although the degradation of the microscopic structural order still exists, the gradient distortion topological framework induces stress guidance and crack deflection at the macroscopic level, and the resulting macroscopic gain significantly exceeds the degradation at the microscopic level, making λ = 1.13 > 1, thus achieving true cross-scale synergistic enhancement above the critical point.

[0032] Specifically, the determination that the preparation process of the hydrogel composite material is compatible with IC / MEMS technology includes: The wafer and hydrogel composite material were compositely assembled to verify that the material can achieve wafer-level chip integration. Based on this, SHPB dynamic impact testing was conducted on the composite material system encapsulating the processor and FPC to characterize the microstructure of the processor after impact and to test the conductivity integrity of the FPC circuit.

[0033] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0034] Example 1: (1) Preparation of precursor solution: 10% PVA and 0.5% CS were dispersed in deionized water and stirred at 95℃ for 2h to obtain a uniform and stable PVA / CS precursor solution. (2) Preparation of Gradient Twisted Plywood (GT) Frame: PVA filaments were dried at 50℃ for 4-6 h to remove internal moisture. Based on CAD, a target model was constructed. Using an FDM commercial 3D printer, the filaments were deposited on the surface of a heating platform coated with PVA special adhesive. After molding, the GT frame (37 mm × 42 mm × 6.6 mm) was obtained by natural cooling. The GT topology frame model is a 3D printed structure. Its topological complexity is controlled by the arrangement parameters of the 8-layer structure. There are preset rotation angles between adjacent layers, which are 0°, 18°, 36°, 54°, 72°, 90°, 108°, and 126° (the rotation angle between adjacent layers is 18°). Each layer consists of several long cylindrical arrays, and the spacing between adjacent cylinders in the same layer varies in gradient, from 1.5 mm at the bottom layer to 5 mm at the top layer. (3) Preparation of GT-HA composite material: PVA / CS precursor solution was poured into a copper-based PTFE mold, and then the GT frame was completely placed in the precursor solution. The mold was placed on a copper block with a height of 30 mm and partially immersed in liquid nitrogen. The temperature gradient formed by the copper block was used to make the ice columns in the system grow directionally from bottom to top. After freezing, the sample was placed in a vacuum environment of -50℃ and 10 Pa for 48 h to freeze dry, so that the internal ice crystals could be completely sublimated. The resulting aerogel was annealed at 90℃ for 60 min and then immersed in a saturated sodium citrate solution for salting out for 48 h to finally obtain the biomimetic GT-HA composite material.

[0035] Quasi-static compression tests were conducted using a universal testing machine to obtain the stress-strain curves of the GT-HA composite material. The compressive strength and toughness of the composite material were measured to be 12.30 MPa and 1.44 MJ / m, respectively. 3 .

[0036] The low-velocity impact response of the GT-HA composite material was tested using a falling ball impact tester to obtain the peak force-time curve. The test results showed that the peak force of the material at an impact height of 90 cm was 243.66 N (peak force decayed by 85.60%) and the buffer time was 2.99 ms. During the long-term test period of 35 days, the peak force decay rate of the composite material at different impact heights was less than 5%, and it could maintain structural integrity in an aqueous environment, demonstrating excellent long-term service stability.

[0037] The high-speed impact properties of GT-HA composite materials were tested using an SHPB apparatus to obtain dynamic compressive stress-strain curves at high strain rates. The results were obtained at 2800 s⁻¹. - ¹The compressive strength at strain rate is 47.39 MPa.

[0038] The FE results show that the composite material has a λ value of 1.13, indicating that the system is dominated by macroscopic mechanical gain, which can transform the material system from a macroscopic-microscopic competitive state to a cooperative state. Combined with the MMC mechanism of this invention, this value shows that the macroscopic stress guidance and crack deflection gain brought by the GT framework completely offset the network degradation of the microscopic hydrogel matrix, and the system transforms from a competitive state to a cooperative state.

[0039] The assembly of the wafer with the GT-HA composite material verified that the material possesses wafer-level chip integration capabilities. Further SHPB dynamic impact testing was conducted on the composite material system encapsulating the processor and FPC. The results showed that the processor's microstructure remained undamaged after impact, and the FPC circuit maintained good conductivity integrity.

[0040] Example 2: (1) Preparation of precursor solution: 10% PVA and 0.5% CS were dispersed in deionized water and stirred at 95℃ for 2h to obtain a uniform and stable PVA / CS precursor solution. (2) Preparation of a single twisted plywood (T) frame: PVA filaments were dried at 50°C for 4-6 h to remove internal moisture; the target model was constructed based on CAD, and the filaments were deposited on the surface of a heating platform coated with PVA special adhesive using an FDM commercial 3D printer. After molding, the filaments were naturally cooled to obtain a T frame (37 mm × 42 mm × 6.6 mm). The T frame is composed of 8 layers of parallel fiber bundles stacked together. The arrangement direction of adjacent fiber layers is set in a unidirectional rotation at a fixed angle of 18°. Each single layer is evenly distributed with array-type rods, and the spacing between rods in the layer is 2.8 mm. (3) Preparation of T-HA composite material: PVA / CS precursor solution was poured into a copper-based PTFE mold, and then the T-frame was completely placed in the precursor solution; the mold was placed on a copper block that was partially immersed in liquid nitrogen, and the temperature gradient formed by the copper block was used to make the ice columns in the system grow directionally from bottom to top. After freezing, the sample was placed in a vacuum environment of -50℃ and 10 Pa for 48 h to freeze dry, so that the internal ice crystals could be completely sublimated; the resulting aerogel was annealed at 90℃ for 60 min, and then placed in a saturated sodium citrate solution for salting out and soaking for 48 h, finally obtaining the biomimetic T-HA composite material.

[0041] Quasi-static compression tests were conducted using a universal testing machine to obtain the stress-strain curves of the T-HA composite material. The compressive strength and toughness of the composite material were measured to be 9.50 MPa and 1.20 MJ / m, respectively. 3 .

[0042] The low-velocity impact response of T-HA composite material was tested using a falling ball impact tester to obtain the peak force-time curve. The test results showed that the peak force of the material at an impact height of 90 cm was 365.68 N (peak force decayed by 78.40%) and the buffer time was 2.87 ms.

[0043] The high-speed impact properties of T-HA composite materials were tested using an SHPB apparatus to obtain dynamic compressive stress-strain curves at high strain rates. The results were obtained at 2800 s⁻¹. - ¹The compressive strength at strain rate is 41.45 MPa.

[0044] The FE results show that the composite material has a λ value of 1.09, the T-frame has basic macroscopic crack deflection capability, the macroscopic gain can cover the microscopic matrix degradation loss, and the system achieves synergistic energy absorption, but the synergistic effect is weaker than that of the GT-HA composite material in Example 1.

[0045] Comparative Example 1: (1) Preparation of precursor solution: 10% PVA and 0.5% CS were dispersed in deionized water and stirred at 95℃ for 2h to obtain a uniform and stable PVA / CS precursor solution. (2) Preparation of directional freezing, annealing, and salting-out fractional anisotropic (HA) hydrogels: PVA / CS precursor solution was poured into a copper-based PTFE mold, which was placed on a copper billet partially immersed in liquid nitrogen. The temperature gradient formed by the copper block was used to induce directional growth of ice columns from bottom to top within the system. After freezing, the sample was freeze-dried at -50℃ and 10 Pa for 48 h to allow complete sublimation of the internal ice crystals. The resulting aerogel was annealed at 90℃ for 60 min and then immersed in a saturated sodium citrate solution for salting-out for 48 h to finally obtain the HA hydrogel.

[0046] Quasi-static compression tests were conducted using a universal testing machine to obtain the stress-strain curves of the HA hydrogel. The compressive strength and toughness of the hydrogel were measured to be 8.15 MPa and 0.85 MJ / m, respectively. 3 .

[0047] The low-velocity impact response of HA hydrogel was tested using a falling ball impact tester to obtain the peak force-time curve. The test results showed that the peak force of the material at an impact height of 90 cm was 399.82 N (peak force decayed by 76.38%) and the buffer time was 2.77 ms.

[0048] The high-speed impact properties of HA hydrogels were tested using an SHPB apparatus to obtain dynamic compressive stress-strain curves at high strain rates. The results were obtained at 2800 s⁻¹. -1 The compressive strength at strain rate is 32.77 MPa.

[0049] Comparative Example 2: (1) Preparation of precursor solution: 10% PVA and 0.5% CS were dispersed in deionized water and stirred at 95℃ for 2h to obtain a uniform and stable PVA / CS precursor solution. (2) Preparation of porous (P) framework: PVA filaments were dried at 50℃ for 4-6 h to remove internal moisture; the target model was constructed based on CAD, and the filaments were deposited on the surface of a heating platform coated with PVA special adhesive using an FDM commercial 3D printer. After molding, the filaments were naturally cooled to obtain a P framework (37 mm × 42 mm × 6.6 mm). The P framework is composed of interconnected orthogonal meshes, forming a three-dimensional porous topology with regular pore arrangement. (3) Preparation of P-HA composite material: PVA / CS precursor solution was poured into a copper-based PTFE mold, and then the P-frame was completely placed in the precursor solution; the mold was placed on a copper block that was partially immersed in liquid nitrogen, and the temperature gradient formed by the copper block was used to make the ice columns in the system grow directionally from bottom to top. After freezing, the sample was placed in a vacuum environment of -50℃ and 10 Pa for 48 h to freeze dry, so that the internal ice crystals could be completely sublimated; the resulting aerogel was annealed at 90℃ for 60 min, and then placed in a saturated sodium citrate solution for salting out and soaking for 48 h, finally obtaining the biomimetic P-HA composite material.

[0050] Quasi-static compression tests were conducted using a universal testing machine to obtain the stress-strain curves of the P-HA composite material. The compressive strength and toughness of the composite material were measured to be 6.73 MPa and 0.92 MJ / m, respectively. 3 .

[0051] The low-velocity impact response of P-HA composite material was tested using a falling ball impact tester to obtain the peak force-time curve. The test results showed that the peak force of the material at an impact height of 90 cm was 442.17 N (peak force decayed by 73.87%) and the buffer time was 2.45 ms.

[0052] The high-speed impact properties of P-HA composite materials were tested using an SHPB apparatus to obtain dynamic compressive stress-strain curves at high strain rates. The results were obtained at 2800 s⁻¹. -1 The compressive strength at strain rate is 31.35 MPa.

[0053] The FE results show that the λ value of the composite material is 0.94. Due to the low topological complexity of the P-framework, the degradation effect of the ordered network of the microscopic hydrogel matrix is ​​dominant. The macroscopic gain is insufficient to compensate for the loss of microscopic properties. The overall energy absorption after the two phases are combined is lower than the sum of the energy absorption of the two components independently, and the system is in a state of competitive inhibition.

[0054] Comparative Example 3: (1) Preparation of precursor solution: 10% PVA and 0.5% CS were dispersed in deionized water and stirred at 95℃ for 2h to obtain a uniform and stable PVA / CS precursor solution. (2) Preparation of directional freezing & salting-out fractional anisotropic (AE) hydrogels: PVA / CS precursor solution was poured into a copper-based PTFE mold, which was placed on a copper billet partially immersed in liquid nitrogen. The temperature gradient formed by the copper block was used to cause the ice columns in the system to grow directionally from bottom to top. After freezing, the sample was freeze-dried at -50℃ and 10 Pa vacuum for 48 h to allow the internal ice crystals to completely sublimate. The resulting aerogel was then immersed in a saturated sodium citrate solution for 48 h and then hydrated for 24 h to form AE hydrogels.

[0055] Quasi-static compression tests were conducted using a universal testing machine to obtain the stress-strain curves of the AE hydrogel. The compressive strength and toughness of the hydrogel were measured to be 4.13 MPa and 0.45 MJ / m, respectively. 3 .

[0056] The low-velocity impact response of the AE hydrogel was tested using a falling ball impact tester to obtain the peak force-time curve. The test results showed that the peak force of the material at an impact height of 90 cm was 540.55 N (peak force decayed by 68.06%) and the buffer time was 1.58 ms.

[0057] The high-speed impact properties of the AE hydrogel were tested using an SHPB apparatus to obtain dynamic compressive stress-strain curves under high strain rates. The results were obtained at 2800 s⁻¹. -1 The compressive strength at strain rate is 23.74 MPa.

[0058] Comparative Example 4: (1) Preparation of precursor solution: 10% PVA and 0.5% CS were dispersed in deionized water and stirred at 95℃ for 2h to obtain a uniform and stable PVA / CS precursor solution. (2) Preparation of directional cryopreservation-graded anisotropic (A) hydrogel: The PVA / CS precursor solution was poured into a copper-based PTFE mold, which was placed on a copper billet partially immersed in liquid nitrogen. The temperature gradient formed by the copper block was used to cause the ice columns in the system to grow directionally from bottom to top. After freezing, the sample was freeze-dried at -50℃ and 10 Pa vacuum for 48 h to allow the internal ice crystals to completely sublimate. The resulting aerogel was then hydrated to form A hydrogel.

[0059] Quasi-static compression tests were conducted using a universal testing machine to obtain the stress-strain curves of hydrogel A. The compressive strength and toughness of the hydrogel were measured to be 0.81 MPa and 0.04 MJ / m, respectively. 3 .

[0060] The low-velocity impact response of hydrogel A was tested using a falling ball impact tester to obtain the peak force-time curve. The test results showed that the peak force of the material at an impact height of 90 cm was 812.81 N (peak force decayed by 51.98%) and the buffer time was 1.00 ms.

[0061] The high-speed impact properties of hydrogel A were tested using an SHPB apparatus to obtain dynamic compressive stress-strain curves at high strain rates. The results were obtained at 2800 s⁻¹. -1 The compressive strength at strain rate is 13.04 MPa.

[0062] Comparative Example 5: (1) Preparation of precursor solution: 10% PVA and 0.5% CS were dispersed in deionized water and stirred at 95℃ for 2h to obtain a uniform and stable PVA / CS precursor solution. (2) Preparation of isotropic (I) hydrogel: After degassing, the precursor solution was transferred to a polytetrafluoroethylene (PTFE) mold and frozen at -20°C for 10 h, then thawed at room temperature for 2 h. This freeze-thaw cycle was repeated twice. Afterward, the sample was immersed in deionized water until equilibrium was reached to obtain I hydrogel.

[0063] Quasi-static compression tests were conducted using a universal testing machine to obtain the stress-strain curves of hydrogel I. The compressive strength and toughness of the hydrogel were measured to be 0.47 MPa and 0.02 MJ / m, respectively. 3 .

[0064] The low-velocity impact response of the I hydrogel was tested using a falling ball impact tester, and the peak force-time curve was obtained. The test results showed that the peak force of the material at an impact height of 90 cm was 974.39 N (peak force decayed by 42.43%) and the buffer time was 0.75 ms.

[0065] The high-speed impact properties of the I-type hydrogel were tested using an SHPB apparatus to obtain dynamic compressive stress-strain curves under high strain rates. The results were obtained at 2800 s⁻¹. -1 The compressive strength at strain rate is 4.45 MPa.

[0066] To clearly illustrate the influence of the MMC mechanism on the mechanical properties of materials in this invention, the structural and mechanical test performance of Examples 1-2 of this invention is compared with that of Comparative Examples 1-5 as follows: Table 1. Structure and test data of different samples

[0067] To visually distinguish the performance differences among the various groups of samples, the structural and test data for each group are summarized in Table 1, along with the appendix. Figure 4 As shown in the quasi-static compression curve, Figure 5 (low-velocity falling ball impact curve), and Figure 6 (high strain rate SHPB dynamic compression curve), the mechanical properties of each group are ranked as follows: Example 1 > Example 2 > Comparative Example 1 > Comparative Example 2 > Comparative Example 3 > Comparative Example 4 > Comparative Example 5. The GT frame has the highest topological complexity, which can be offset by multi-level crack deflection and gradient stress guidance to counteract the degradation of microstructure properties. The synergy factor λ = 1.13 > 1, surpassing... λThe macro-micro competitive equilibrium point of λ=1 achieves cross-scale synergistic enhancement; the T-framework synergy factor λ=1.09, with the second best synergistic effect; the low-complexity P-framework exhibits a dominant micro-deterioration effect, λ=0.94<1, resulting in composite mechanical properties lower than pure HA hydrogel; the frameless hydrogel gradually decreases with the preparation process, leading to a continuous decline in impact resistance and load-bearing capacity; (Appendix) Figure 8 The comparison of the chip morphology after impact further confirms that the GT-HA composite material of Example 1 can effectively dissipate high-speed impact energy and completely protect the chip circuit. Compared with pure HA hydrogel, it has excellent electronic device protection capabilities, which fully verifies the technical advantages of the present invention in optimizing the MMC mechanism by regulating the topological complexity of the biomimetic framework and significantly improving the overall impact resistance of the material.

[0068] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A biomimetic impact-resistant composite material based on macro- and micro-scale competition, characterized in that, It includes a hydrogel matrix and a biomimetic topological framework embedded therein, with a composite interface of homologous molecular fusion between the two, and the whole has a multi-scale hierarchical structure, and the matrix has an anisotropic structure. The biomimetic topological framework is a polyvinyl alcohol material with a three-dimensional porous network structure; The hydrogel matrix is ​​a polyvinyl alcohol / chitosan hydrogel material with anisotropic microporous channels and a polymer crystalline region network; anisotropy refers to the asymmetric mechanical response of the material in different directions; The multi-scale hierarchical structure is composed of a three-dimensional porous network of biomimetic topological framework at the macro level and anisotropic microporous channels and polymer crystalline region network of hydrogel matrix at the micro-nano level.

2. The biomimetic impact-resistant composite material based on macro-microscale competition according to claim 1, characterized in that: The biomimetic topological framework is selected from at least one of the following configurations: The porous configuration is a three-dimensional porous topology composed of interconnected meshes; The single twisted plywood configuration is a layered structure composed of N layers of fiber bundles. Adjacent fiber layers are arranged in a unidirectional rotation at a preset rotation angle θ, and the spacing d between the fiber bundles in a single layer is equal. The gradient twisted plywood configuration is a layered structure composed of N layers of fiber bundles. Adjacent fiber layers are arranged in a unidirectional rotation at a preset rotation angle θ. The spacing d of the fiber bundles in a single layer varies in a gradient along the thickness direction of the frame. The value of N ranges from 6 to 10 layers, the value of θ ranges from 10° to 30°, and the value of d ranges from 1 mm to 6 mm.

3. The biomimetic impact-resistant composite material based on macro-microscale competition according to claim 1, characterized in that: The hydrogel matrix contains 10% polyvinyl alcohol and 0.5% chitosan by mass.

4. The biomimetic impact-resistant composite material based on macro-microscale competition according to claim 3, characterized in that: The hydrogel matrix dissipates energy at the micrometer scale through fiber friction and slippage, at the nanometer scale through polymer chain entanglement and deentanglement, and at the molecular scale through reversible hydrogen bond breaking.

5. The biomimetic impact-resistant composite material based on macro-microscale competition according to claim 1, characterized in that: The overall mechanical properties of the composite material are controlled by a macro-micro scale competition mechanism. The macro-micro scale competition mechanism refers to the fact that the biomimetic topological framework provides mechanical gains for crack deflection and branching at the macro level, while at the micro level, the microstructural order of the hydrogel matrix deteriorates due to interface modulus mismatch and spatial confinement effect. The overall mechanical properties of the composite material are determined by the competition between mechanical gains and structural order deterioration. The microstructural order is the crystallization orientation of polymer chains and the self-assembled crystalline network within the hydrogel matrix; the deterioration of the microstructural order is manifested by the destruction of local hydrogen bond networks, decreased crystallinity, and increased proportion of free hydroxyl groups in the hydrogel matrix. When the mechanical gain is greater than the structural order deterioration, the impact absorption energy of the composite material is higher than the sum of the independent energy absorption of the biomimetic topological framework and the hydrogel matrix, breaking through the critical point of macro-micro competition and achieving synergistic toughening.

6. A method for preparing the biomimetic impact-resistant composite material according to any one of claims 1-5, characterized in that, Includes the following steps: Step 1: Disperse polyvinyl alcohol and chitosan in deionized water, heat and stir until completely dissolved to obtain a uniform and stable polyvinyl alcohol / chitosan hydrogel precursor solution; Step 2: Based on computer-aided design, construct the target model, and use fused deposition modeling 3D printing technology to deposit polyvinyl alcohol filaments layer by layer, and obtain a biomimetic topological framework after natural cooling; Step 3: Pour the hydrogel precursor solution into the mold, and then completely embed the biomimetic topological framework into the hydrogel precursor solution; Step 4: Place the mold containing the precursor solution and the biomimetic topological framework in a temperature gradient field to induce the directional growth of ice crystals within the system; Step 5: Place the frozen sample in a vacuum low-temperature environment for freeze-drying to allow the internal ice crystals to completely sublimate and form an aerogel; Step 6: Anneal the aerogel; Step 7: Immerse the annealed aerogel in a salt solution to allow the hydrogel matrix to undergo physical cross-linking, thereby obtaining a biomimetic impact-resistant composite material.

7. The preparation method according to claim 6, characterized in that: The specific process parameters of the preparation method are as follows: In step 1, the mass fraction of polyvinyl alcohol is 10%, the mass fraction of chitosan is 0.5%, the heating and stirring temperature is 95℃, and the time is 2 h; In step 4, the temperature gradient field is provided by a copper block partially immersed in liquid nitrogen, and the ice crystals grow directionally from bottom to top; In step 5, the vacuum low-temperature environment is -50℃, 10 Pa, and the freeze-drying time is 48 h; In step 6, the annealing treatment is performed at a temperature of 90°C for 60 minutes. In step 7, the salt solution is a saturated sodium citrate solution, and the soaking time is 48 h.

8. The preparation method according to claim 6, characterized in that: The competition mechanism between macro and micro scales is controlled by regulating the spatial geometric complexity of the biomimetic topological framework: the spatial geometric complexity is determined by two dimensions: the grid configuration of the framework and the distribution of fiber bundle spacing within the layer. The spatial geometric complexity increases stepwise in the order of porous configuration < single twisted plywood configuration < gradient twisted plywood configuration. Using a synergy factor λ=1 as the critical threshold for macro-micro competition, the formula for calculating the synergy factor λ is as follows: λ = E 复合材料 / （ E 纯框架 + E 水凝胶 ） in, E 复合材料 This represents the total energy absorbed by the biomimetic impact-resistant composite material under impact load. E 纯框架 This represents the total energy absorbed by the biomimetic topological frame under the same impact load. E 水凝胶 This represents the total energy absorbed by the hydrogel matrix under the same impact load. Using the synergy factor λ=1 as the critical threshold for macro-micro competition, the topological complexity range corresponding to the macro-micro competition equilibrium point is determined. When λ<1, the composite material is in a competitive state dominated by micro-deterioration. When λ>1, the composite material breaks through the critical point of macro-micro competition and achieves cross-scale synergistic enhancement.

9. The preparation method according to claim 8, characterized in that: The equilibrium point of the macro- and micro-scale competition mechanism is determined by adjusting the spatial geometric complexity of the biomimetic topological framework; the adjustment method is as follows: The volume fraction of the biomimetic topological framework is fixed at 24%, and the overall external dimensions are uniformly 37 mm × 42 mm × 6.6 mm. When the biomimetic topological framework is a porous configuration, it adopts a regular interconnected orthogonal mesh structure without setting layered rotational stacking, serving as a low-complexity benchmark. When the biomimetic topological frame is a single twisted plywood configuration, it is composed of 8 layers of fiber bundles stacked together, with adjacent fiber layers arranged in a unidirectional rotation of 18°, and the spacing between single-layer rods is constant at 2.8 mm. When the biomimetic topological frame is a gradient twisted plywood configuration, it is composed of 8 layers of fiber bundles stacked together. Adjacent fiber layers are arranged in a unidirectional rotation of 18°. The spacing between the members changes linearly along the thickness direction of the frame, gradually increasing from 1.5 mm to 5 mm. The spatial geometric complexity of the porous configuration, the single twisted plywood configuration, and the gradient twisted plywood configuration increases progressively.

10. The application of the biomimetic impact-resistant composite material according to any one of claims 1-5 in the preparation of impact protection materials, characterized in that, The impact protection material is used for aerospace components, housings of smart devices, high-end electronic chip packaging buffer layers, or impact protection coatings for flexible printed circuit boards.

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