Shear thickening fluid reinforced 3D printed porous thermoplastic polyurethane elastomer energy absorbing composite and method of making

Abstract

The present application relates to a kind of shear thickening fluid reinforced 3D printing thermoplastic polyurethane elastomer porous structure energy-absorbing composite material, the energy-absorbing composite material is filled with 3D printing porous thermoplastic polyurethane elastomer by shear thickening fluid and is prepared;The porous thermoplastic polyurethane elastomer is porous material with specific geometry and topology structure;The shear thickening fluid is the dispersion liquid of SiO2 and polyethylene glycol.The present application constructs thermoplastic polyurethane porous structure by 3D printing technology, then it is filled with shear thickening fluid and is modified, utilize the deformation of the porous structure of composite material under external load and convert into the shear strain of shear thickening material, to shear strain initiate the shear thickening behavior of shear thickening material, to realize the deformation energy-absorbing of 3D printing thermoplastic polyurethane elastomer porous structure and the synergistic high-efficiency energy-absorbing of the shear thickening energy-absorbing of shear thickening fluid.

Description

Technical Field

[0001] This invention relates to an energy-absorbing composite material with a porous structure of 3D-printed thermoplastic polyurethane elastomer reinforced by a shear-thickening liquid and its preparation method, belonging to the field of composite material technology. Background Technology

[0002] Energy-absorbing materials are widely used in aerospace, defense, transportation, and personal protective equipment. Achieving efficient energy absorption is a hot topic in modern engineering, and novel energy-absorbing materials and structural designs have become key to strategic research in advanced manufacturing and intelligent equipment. Traditional energy-absorbing materials (such as metal foams and rigid polymer foams) have good impact resistance but struggle to withstand cyclic impact loads and cannot meet the needs of flexible wearables. Polymer elastomers, with their high elastic deformation, exhibit excellent energy absorption and cushioning performance. In particular, porous elastomers (such as polyurethane foams and rubber sponges) demonstrate excellent energy absorption performance under quasi-static loads due to their high porosity and good elastic deformation characteristics. Porous elastomers possess the characteristics of cyclic energy absorption and flexible wearability, but their energy absorption efficiency is low due to limitations in material constitutive relations. Research on constructing efficient energy-absorbing systems solely based on material synthesis or structural design has reached a certain bottleneck. On the one hand, traditional polymer elastomer foaming processes struggle to precisely control the geometry and distribution of pores. Optimizing the pore structure through structural mechanics analysis and combining this with the precise customization capabilities of 3D printing provides a theoretical and technological foundation for designing and fabricating porous elastomer energy-absorbing metamaterials with specific geometries and topologies. On the other hand, shear-thickening fluids (STFs) are suspension systems composed of high-concentration micro / nanoparticle dispersions and organic small-molecule dispersion media, exhibiting efficient energy absorption and dissipation characteristics and excellent self-healing properties. Research on preparing protective composite materials using STFs to fill porous thermoplastic elastomers with lattice structures has improved energy absorption efficiency by more than 5 times, providing a reference for the synergistic construction of highly efficient energy-absorbing composite materials using porous elastomers and STFs with specific geometries and topologies. However, the lattice structure is a truss structure, making STF in composite materials easily lost. How to achieve the sealing design and synergistic energy absorption function of porous elastomers for STFs is a key theoretical and technical problem that urgently needs to be solved. Summary of the Invention

[0003] To address the practical problems in existing technologies, this invention aims to provide an energy-absorbing composite material with a porous structure of 3D-printed thermoplastic polyurethane elastomer reinforced by a shear-thickening fluid. This solves the technical problem that existing energy-absorbing materials, produced through single improvements to materials or structures, encounter obstacles in further enhancing their energy absorption efficiency. This invention constructs a porous thermoplastic polyurethane structure with specific geometry and topology using 3D printing technology, and then modifies it with a shear-thickening fluid (STF) to construct a composite system. The deformation of the porous structure of the composite material under external load is converted into shear strain in the shear-thickening fluid. This shear strain induces the shear-thickening behavior of the shear-thickening fluid, achieving synergistic and efficient energy absorption through the deformation energy absorption of the 3D-printed TPU porous structure and the shear-thickening energy absorption of the shear-thickening fluid.

[0004] The present invention adopts the following technical solution: an energy-absorbing composite material with a porous structure of 3D printed thermoplastic polyurethane elastomer reinforced by a shear thickening liquid (STF), wherein the energy-absorbing composite material is prepared by filling a porous thermoplastic polyurethane elastomer (3DP-TPU) with a shear thickening liquid (STF); the pores of the 3DP-TPU have a specific geometric and topological structure; the shear thickening liquid (STF) is a dispersion of SiO2 and polyethylene glycol (the relative molecular weight of polyethylene glycol is preferably 200-600, more preferably 200-400, for example polyethylene glycol 200 (PEG200) or polyethylene glycol 400 (PEG400)).

[0005] Preferably, the dispersion is prepared by grinding, diluting, heating and stirring monodisperse submicron SiO2 microspheres, wherein the particle size of the monodisperse submicron SiO2 microspheres is 100-500 nm; and the mass fraction of the dispersion is 70 wt%-76 wt%. The dispersion can be obtained by introducing SiO2 into a polyethylene glycol solution and mixing thoroughly. Other dispersed phases include nano-SiO2, nano-calcium carbonate, and other dispersion media such as polyethylene glycol and ethylene glycol.

[0006] Preferably, the geometry and topology of the 3DP-TPU pores include, but are not limited to, a three-period minimal surface structure, a square honeycomb structure, and a negative Poisson's ratio structure; the porosity of the porous structure is 40 to 80%.

[0007] Preferably, the thermoplastic polyurethane elastomer (TPU) used in the 3DP-TPU includes, but is not limited to, polyether-type or polyester-type thermoplastic polyurethane elastomers, with hardness including but not limited to 64D, 70A, 85A and 95A.

[0008] Preferably, the composite material has a regular shape or an irregular structure in appearance.

[0009] Furthermore, this invention also provides a method for preparing an energy-absorbing composite material with a porous structure of 3D-printed thermoplastic polyurethane elastomer reinforced by a shear-thickening liquid, comprising the following steps: S1. Preparation of shear thickening fluid (STF): Monodisperse submicron SiO2 microspheres are ground, diluted, heated and stirred to obtain shear thickening fluid (STF). S2. Design the geometry and topology of the pores in the porous structure, and use fused deposition modeling (FDM) to 3D print 3DP-TPU, wherein the pores have specific geometry and topology, and the pores of the 3DP-TPU are non-fully sealed pores; S3. Fix the 3DP-TPU and inject the shear thickening fluid (STF) into it under vacuum, so that the shear thickening fluid (STF) fully fills the porous structure of the 3D-TPU, to obtain the energy-absorbing composite material (3DP-TPU / STF) of the porous structure of the 3D printed thermoplastic polyurethane elastomer reinforced by the shear thickening fluid.

[0010] Preferably, in step S1, S11. Weigh a certain amount of the monodisperse submicron SiO2 and grind it thoroughly in a mortar until it is powdery. The particle size range of the monodisperse submicron SiO2 microspheres is 100-500 nm. S12. Pour powdered SiO2 into a container, add 80-100 wt% anhydrous ethanol, and place it in an ultrasonic grinder for ultrasonic dispersion for 0.5-1 h to fully and evenly disperse the SiO2 powder in the anhydrous ethanol to obtain an ethanol dispersion of SiO2. S13. Add 30-43 wt% of polyethylene glycol to the ethanol dispersion of SiO2. Optionally, the polyethylene glycol is polyethylene glycol 200 or polyethylene glycol 400. Place it in an ultrasonic pulverizer and ultrasonically disperse for 6-10 hours to ensure thorough and uniform mixing, thereby obtaining a dispersion of SiO2 with ethanol and polyethylene glycol 200 or a dispersion of SiO2 with ethanol and polyethylene glycol 400. S14. Place the container containing the dispersion obtained in step S13 into an electric thermostatic oil bath, set the temperature to 60~80℃, and heat and stir until the anhydrous ethanol is completely removed. S15. After cooling the dispersion obtained in step S14, a shear thickener (STF) is obtained.

[0011] Preferably, in step S2, The non-fully sealed channels are sealed by sealing the multi-faceted channels of 3D-TPU, leaving one side or part unsealed to ensure that the channels are open. The 3DP-TPU uses thermoplastic polyurethane elastomer (TPU) with hardness including but not limited to 64D, 70A, 85A and 95A; The porosity of the 3D-TPU constructed by the 3D printing process ranges from 40% to 80%. The 3D-TPU has a regular or irregular geometric shape. The geometry and topology of the 3D-TPU include, but are not limited to, a three-period minimal surface structure, a square honeycomb structure, and a negative Poisson's ratio structure.

[0012] Preferably, in step S3, S31. Place the 3D printed 3DP-TPU sample into the container and fix the sample to the bottom of the container to prevent the sample from floating. S32. Pour the prepared shear-thickening fluid (STF) into a container, ensuring the liquid level covers the sample; S33. Place the beaker in a vacuum drying oven, set the vacuum degree to 0.05 ~ 0.1 MPa, and leave it for a sufficient time until the shear thickening liquid (STF) completely fills the 3DP-TPU before taking it out; S34. By bonding and sealing the unsealed side or local area of ​​a 3D-printed thermoplastic polyurethane elastomer (3DP-TPU) filled with shear thickening fluid (STF) using thermoplastic polyurethane elastomer (TPU) sheets of the same grade, an energy-absorbing composite material (3DP-TPU / STF) with a porous structure of shear thickening fluid reinforced with 3D-printed thermoplastic polyurethane elastomer is prepared.

[0013] Preferably, the thermoplastic polyurethane elastomer (TPU) sheet used is 0.1-2.0 mm thick, and the bonding is hot melt bonding.

[0014] The beneficial technical effects obtained by this invention are as follows:

[0015] (1) The present invention adopts a technical solution of filling the porous structure of 3D printed thermoplastic polyurethane elastomer (3DP-TPU) with shear thickening liquid (STF). The resulting 3DP-TPU / STF composite material has significantly improved constant strain compressive stress, specific volume energy absorption (SEAv), energy dissipation coefficient (∆U / U), etc. Moreover, with the increase of compression rate, the buffer energy absorption efficiency of 3DP-TPU / STF is significantly improved, and it has good cycle stability and energy dissipation capacity. Dynamic impact test shows that the shear thickening material of the obtained 3DP-TPU / STF composite material significantly improves the buffer performance of the composite system and significantly enhances the buffer energy absorption performance, especially under low hardness, high porosity and TPMS structure.

[0016] (2) The present invention adopts a technical solution of filling the porous structure of 3D printed thermoplastic polyurethane elastomer (3DP-TPU) with shear thickening fluid (STF). The extremely small curved surface structure has high porosity, three-dimensional interconnected channel network and excellent additive manufacturing adaptability. It can effectively constrain the internally encapsulated shear thickening fluid (STF), promote particle agglomeration and blockage under shear action, induce liquid-solid transformation (shear thickening), and thus realize the synergistic effect of elastic deformation of 3D printed TPU and enhanced energy consumption of STF.

[0017] (3) The shear thickening fluid (STF) of the present invention uses a silica / polyethylene glycol (SiO2 / PEG) system as raw material, which has excellent durability, high load-bearing capacity and good interfacial compatibility with other materials. The high viscosity and self-healing ability of the shear thickening fluid (STF) can significantly improve the overall performance of the structure. The shear thickening fluid (STF) of a certain concentration has both a significant shear thickening effect and good fluidity: the former can achieve efficient energy dissipation under impact load and ensure the dynamic stability of the composite material; the latter ensures the operability of the processing, takes into account both performance improvement and process adaptability, and further expands the application scenarios of the material. Attached Figure Description

[0018] Figure 1 This is a flowchart of the STF preparation process for a shear-thickening liquid-reinforced 3D-printed thermoplastic polyurethane elastomer porous structure energy-absorbing composite material according to the present invention.

[0019] Figure 2 This is a flowchart illustrating the preparation process of an energy-absorbing composite material with a porous structure of thermoplastic polyurethane elastomer reinforced by a shear-thickening liquid, according to the present invention.

[0020] Figure 3 This is a schematic diagram of the TPMS structure of an energy-absorbing composite material with a porous structure of 3D printed thermoplastic polyurethane elastomer reinforced by a shear thickening liquid, according to the present invention.

[0021] Figure 4 This is a detailed schematic diagram of the TPMS structural model of an energy-absorbing composite material with a porous structure of 3D-printed thermoplastic polyurethane elastomer reinforced by a shear-thickening liquid, according to the present invention, wherein: Figure 4 -a is a unit cell diagram of the TPMS structural model; Figure 4 -b represents the front view of the TPMS structure model; Figure 4 -c represents a side view of the TPMS structural model; Figure 4 -d represents the top view of the TPMS structural model.

[0022] Figure 5 This is a schematic diagram of the SHC structure of an energy-absorbing composite material with a porous structure of 3D printed thermoplastic polyurethane elastomer reinforced by a shear thickening liquid, according to the present invention.

[0023] Figure 6 This is a detailed schematic diagram of the SHC structural model of an energy-absorbing composite material with a porous structure of 3D-printed thermoplastic polyurethane elastomer reinforced by a shear thickening liquid, according to the present invention, wherein: Figure 6 -a is the unit cell diagram of the SHC structural model; Figure 6 -b represents the front view of the SHC structural model; Figure 6 -c represents the side view of the SHC structural model; Figure 6 -d represents the top view of the SHC structural model.

[0024] Figure 7 This is a schematic diagram of the NPR structure of an energy-absorbing composite material with a porous structure of 3D printed thermoplastic polyurethane elastomer reinforced by a shear thickening liquid, according to the present invention.

[0025] Figure 8 This is a detailed schematic diagram of the NPR structure model of an energy-absorbing composite material with a porous structure of 3D-printed thermoplastic polyurethane elastomer reinforced by a shear-thickening liquid, according to the present invention, wherein: Figure 8 -a is a unit cell diagram of the NPR structural model; Figure 8 -b represents the front view of the NPR structural model; Figure 8 -c represents a side view of the NPR structural model; Figure 8 -d represents the top view of the NPR structural model.

[0026] Figure 9 The stress-strain curves of 3DP-TPU and 3DP-TPU / STF samples with different hardnesses under different compression rates are shown for the energy-absorbing composite material of 3D printed thermoplastic polyurethane elastomer porous structure reinforced by shear thickening liquid of the present invention.

[0027] Figure 10 This diagram shows the energy absorption performance of 3DP-TPU and 3DP-TPU / STF samples with different hardnesses at different compression rates for an energy-absorbing composite material of a porous 3D-printed thermoplastic polyurethane elastomer reinforced with a shear thickening liquid according to the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some preferred embodiments of this application, but not all embodiments. In addition, for clarity and brevity, descriptions of known functions and structures are omitted in the embodiments.

[0029] In this document, STF refers to shear thickening fluid; 3DP-TPU refers to 3D-printed thermoplastic polyurethane elastomer without shear thickening fluid filling and with specific geometry and topology of internal channels; 3DP-TPU / STF refers to the energy-absorbing composite material of the porous structure of 3D-printed thermoplastic polyurethane elastomer reinforced by the shear thickening fluid of this invention.

[0030] (I) Energy-absorbing composite material with porous structure of 3D printed thermoplastic polyurethane elastomer reinforced by shear thickening fluid

[0031] Shear thickening fluid (STF) is a dispersion made from monodisperse submicron SiO2 microspheres through grinding, dilution, heating, and stirring. The particle size of the SiO2 microspheres ranges from 100 to 500 nm. The concentration of the shear thickening fluid (STF) is defined by the mass fraction of SiO2, ranging from 70 wt% to 76 wt%. The actual concentration is adjusted according to the particle size of the SiO2 microspheres; for smaller SiO2 microspheres, a lower concentration of STF is used, while for larger SiO2 microspheres, a higher concentration of STF is used.

[0032] Thermoplastic polyurethane elastomers (TPUs) include, but are not limited to, polyether-based or polyester-based thermoplastic polyurethane elastomers. Optionally, the thermoplastic polyurethane elastomers (TPUs) may be sourced from BASF's Elastollan 1195A, Elastollan 1185A, and Elastollan 1170A. TPU hardness includes, but is not limited to, 64D, 70A, 85A, and 95A. Based on the designed pore geometry and topology, thermoplastic polyurethane elastomer (TPU) was 3D printed using fused deposition modeling (FDM). The resulting 3DP-TPUs included three-period minimal surface structures (TPMS) with Schwarz Diamond, Gyroid, and Neovius unit cells; square and hexagonal honeycomb structures (SHC); and negative Poisson's ratio structures (NPR). The 3DP-TPUs with different topologies were defined as follows: the TPU with the three-period minimal surface structure was 3DP-TPMS-TPU; the TPU with the honeycomb structure was 3DP-SHC-TPU; and the TPU with the negative Poisson's ratio structure was 3DP-NPR-TPU. Figures 3-8 The diagram shown is a schematic representation of the structure and details of the three types of 3D-TPU.

[0033] The porosity of the 3DP-TPU in this invention ranges from 40% to 80%. By adjusting the porosity, the STF content filled in the 3DP-TPU can be controlled, thereby regulating the energy absorption behavior of the 3DP-TPU / STF. Specifically, the porosity is directly proportional to the mass of the filled STF and the increase in energy absorption of the 3DP-TPU / STF. The appearance and geometry of the 3DP-TPU do not affect the achievement of the technical effect of this invention and can be customized according to requirements. It can be a regular polyhedron or an irregular structure. Regular polyhedra include, but are not limited to, cubes or cuboids; irregular structures include, but are not limited to, prisms or spheres.

[0034] By filling 3D-printed thermoplastic polyurethane elastomer (3DP-TPU) with shear-thickening fluid (STF), the energy-absorbing composite material of the porous structure of 3D-printed thermoplastic polyurethane elastomer reinforced by shear-thickening fluid (STF) of the present invention can be obtained, namely 3DP-TPU / STF. Accordingly, the energy-absorbing composite materials of the aforementioned three-period minimal surface structure (TPMS), square and hexagonal honeycomb structure (SHC), and negative Poisson's ratio structure (NPR) of the present invention are defined as: 3DP-TPMS-TPU / STF, 3DP-SHC-TPU / STF, and 3DP-NPR-TPU / STF, respectively.

[0035] (II) Preparation method of energy-absorbing composite material with porous structure of thermoplastic polyurethane elastomer reinforced by shear thickening liquid for 3D printing

[0036] The present invention discloses a method for preparing a shear-thickening liquid-reinforced 3D-printed thermoplastic polyurethane elastomer porous structure energy-absorbing composite material (3DP-TPU / STF), comprising the following steps:

[0037] Step S1, Preparation of Shear Thickening Fluid (STF): Monodisperse submicron SiO2 microspheres are ground, diluted, heated, and stirred to obtain a shear thickening fluid (STF). Specifically, this includes:

[0038] S11. Weigh a certain amount of the monodisperse submicron SiO2 and grind it thoroughly in a mortar until it is powdery. The particle size range of the monodisperse submicron SiO2 microspheres is 100-500 nm.

[0039] S12. Pour powdered SiO2 into a container, add 80-100 wt% anhydrous ethanol (EtOH) to the powdered SiO2, so that the SiO2 is completely submerged, and then put it into an ultrasonic pulverizer for ultrasonic dispersion for 0.5-1 h, so that the SiO2 powder is fully and evenly dispersed in anhydrous ethanol (EtOH) to obtain an ethanol dispersion of SiO2.

[0040] S13. Add 30-43 wt% polyethylene glycol to the ethanol dispersion of SiO2, and then put it into an ultrasonic pulverizer for ultrasonic dispersion for 6-10 hours to make it fully and evenly mixed, so as to obtain a dispersion of SiO2 with ethanol and polyethylene glycol.

[0041] The relative molecular weight of polyethylene glycol is preferably 200-600, more preferably 200-400, for example polyethylene glycol 200 (PEG200) or polyethylene glycol 400 (PEG400), and the result is a dispersion of SiO2 with ethanol and polyethylene glycol 200, or a dispersion of SiO2 with ethanol and polyethylene glycol 400.

[0042] S14. Place the container containing the dispersion obtained in step S13 into an electric thermostatic oil bath, set the temperature to 60-80℃, and heat and stir until anhydrous ethanol (EtOH) is completely removed.

[0043] S15. After cooling the dispersion obtained in step S14, a shear thickener (STF) is obtained.

[0044] Step S2: Design the geometry and topology of the porous structure, and use fused deposition modeling (FDM) process to 3D print the porous structure of thermoplastic polyurethane elastomer (TPU) to obtain a 3D printed thermoplastic polyurethane elastomer with a specific geometry and structure. The pores of the 3D printed thermoplastic polyurethane elastomer are non-fully sealed pores.

[0045] Specifically, the geometry and topology of the holes are designed, such as a three-period minimal surface structure (TPMS), a honeycomb structure (SHC), or a negative Poisson's ratio structure (NPR), etc., and then the aforementioned 3D printing process is used to print thermoplastic polyurethane elastomer (3DP-TPU) with specific geometry and structure. In this process, by controlling the 3D printing process, the multi-faceted channels of the 3D-TPU are sealed, leaving one side or part unsealed to ensure that the channels are open.

[0046] Furthermore, the TPU used has hardnesses including 64D, 70A, 85A, and 95A. The porosity of the porous TPU constructed by 3D printing ranges from approximately 40% to 80%, and the appearance geometry can be customized according to requirements, including but not limited to regular polyhedra (cubes, cuboids) or irregular structures (cylinders, spheres).

[0047] Step S3: Fix the thermoplastic polyurethane elastomer (3DP-TPU) and inject shear thickening fluid into it under vacuum, ensuring the shear thickening fluid fully fills the porous structure of the 3DP-TPU, resulting in an energy-absorbing composite material of shear thickening fluid-reinforced 3D-printed thermoplastic polyurethane elastomer porous structure, namely 3DP-TPU / STF. The specific operating steps in a laboratory environment are as follows:

[0048] S31. Place the 3DP-TPU sample into the container and fix the sample to the bottom to prevent it from floating.

[0049] S32. Pour the prepared STF into the container, ensuring the liquid level covers the 3DP-TPU sample.

[0050] S33. Place the container in a vacuum drying oven, set the vacuum level to 0.05 ~ 0.1 MPa, and leave it for a sufficient time until the shear thickening liquid completely fills the 3DP-TPU before removing it.

[0051] S34. By bonding and sealing the unsealed side or local area of ​​3DP-TPU filled with shear thickening liquid using TPU sheets of the same brand, a 3DP-TPU / STF energy-absorbing composite material is prepared.

[0052] The TPU (thermoplastic polyurethane elastomer) sheet used is the same grade as the TPU used in 3DP-TPU, with a thickness of 0.5-2.0 mm, and hot melt adhesive is used for bonding.

[0053] The present invention will be further illustrated by the following examples.

[0054] Example 1

[0055] A 3DP-NPR-TPU / STF energy-absorbing composite material with a TPU hardness of 70A, a porosity of 60%, and a negative Poisson's ratio structure, and its preparation method.

[0056] Step S1. Preparation of shear-thickening fluid:

[0057] 152g of monodisperse submicron SiO2 microspheres (500 nm particle size) were weighed and poured into a container. 121.6g of anhydrous ethanol (EtOH) (80 wt% of SiO2) was added until the powdered SiO2 was completely submerged. The container was then placed in an ultrasonic cleaner and stirred while sonicating for 0.5h to ensure the SiO2 was fully and uniformly dispersed in the anhydrous ethanol (EtOH). Next, 48g of polyethylene glycol 200 (PEG 200) (32 wt% of SiO2) was added, and the mixture was again placed in an ultrasonic pulverizer and sonicated for 6h to ensure thorough and uniform mixing. The container was then placed in an electrically heated constant-temperature oil bath at 60℃ and heated while stirring for 8h. Once the viscosity increased to the point where the rotor could no longer rotate, the stirring was stopped. The mixture was then manually stirred every 15 minutes, repeated 8 times, to remove the anhydrous ethanol (EtOH). Finally, after cooling, a shear-thickened fluid (STF) with a mass fraction of 76% was obtained.

[0058] Step S2. Structural Design and 3D Printing

[0059] The geometry and topology of the holes are designed to have a negative Poisson's ratio, using 3D printing filament with a hardness of 70A and a porosity of 60%. A 3D printer is then used to print a cubic thermoplastic polyurethane elastomer (3DP-NPR-TPU) with dimensions of 20*20*20mm and a negative Poisson's ratio structure. By adjusting the 3D printing process, the multi-faceted holes of the 3DP-NPR-TPU are sealed, leaving one side of the cube unsealed to ensure the holes remain open.

[0060] S3. Preparation of 3DP-NPR-TPU / STF energy-absorbing composite material

[0061] S31. Place the 3DP-NPR-TPU sample into the beaker and fix the sample to the bottom to prevent it from floating.

[0062] S32. Pour the STF prepared in step S1 into a beaker, making sure the liquid level is 5-10 mm above the 3DP-TPU sample.

[0063] S33. Place the beaker in a vacuum drying oven, set the vacuum level to 0.05 MPa, and leave it for 1 hour until the shear thickening liquid completely fills the 3DP-NPR-TPU before removing it.

[0064] S34. By bonding and sealing the unsealed side of 3DP-NPR-TPU filled with shear thickening liquid using TPU sheets of the same brand, a 3DP-NPR-TPU / STF energy-absorbing composite material is prepared.

[0065] The TPU (thermoplastic polyurethane elastomer) sheet used is the same grade as the TPU used in 3DP-NPR-TPU, with a thickness of 1.0mm, and is bonded using hot melt adhesive.

[0066] Example 2

[0067] TPU with a hardness of 85A and a porosity of 60%, a square honeycomb structure 3DP-SHC-TPU / STF energy-absorbing composite material and its preparation method.

[0068] Step S1. Preparation of shear-thickening fluid:

[0069] 152g of monodisperse submicron SiO2 microspheres (100 nm in diameter) were weighed and poured into a container. 152g of anhydrous ethanol (EtOH) (100 wt% SiO2) was added until the powdered SiO2 was completely submerged. The container was then placed in an ultrasonic cleaner and ultrasonically stirred for 0.5 hours to ensure the SiO2 was fully and uniformly dispersed in the anhydrous ethanol (EtOH). Next, 48g of polyethylene glycol 200 (PEG 200) (32 wt% SiO2) was added, and the mixture was again ultrasonically dispersed in an ultrasonic pulverizer for 6 hours to ensure thorough and uniform mixing. The container was then placed in an electrically heated constant-temperature oil bath at 75°C and heated while stirring for 6 hours. Once the viscosity increased to the point where the rotor could no longer rotate, the stirring was stopped. Manual stirring was performed every 15 minutes, repeating this process 8 times to remove the anhydrous ethanol (EtOH). Finally, after cooling, a shear-thickened fluid (STF) with a mass fraction of 76% was obtained.

[0070] Step S2. Structural Design and 3D Printing

[0071] The geometry and topology of the holes are designed as a square honeycomb structure, using 3D printing filament with a hardness of 85A and a porosity of 60%. The aforementioned 3D printer is then used to print a cube-shaped thermoplastic polyurethane elastomer 3DP-SHC-TPU with dimensions of 20*20*20mm and a square honeycomb structure. By adjusting the 3D printing process, the multi-faceted channels of the 3DP-SHC-TPU are sealed, leaving one side of the cube unsealed to ensure the channels remain open.

[0072] S3. Preparation of 3DP-SHC-TPU / STF energy-absorbing composite material

[0073] S31. Place the 3DP-SHC-TPU sample into the beaker and fix the sample to the bottom to prevent it from floating.

[0074] S32. Pour the STF prepared in step S1 into a beaker, making sure the liquid level is 5-10 mm above the 3DP-TPU sample.

[0075] S33. Place the beaker in a vacuum drying oven, set the vacuum level to 0.07 MPa, and leave it for 1 hour until the shear thickening liquid completely fills the 3DP-SHC-TPU before removing it.

[0076] S34. By bonding and sealing the unsealed side of 3DP-SHC-TPU filled with shear thickening liquid using TPU sheets of the same brand, a 3DP-SHC-TPU / STF energy-absorbing composite material is prepared.

[0077] The TPU (thermoplastic polyurethane elastomer) sheet used is the same grade as the TPU used in 3DP-SHC-TPU, with a thickness of 1.0mm, and is bonded using hot melt adhesive.

[0078] Example 3

[0079] A 3DP-TPMS-TPU / STF energy-absorbing composite material with a TPU hardness of 95A and a porosity of 60%, featuring a three-period minimal curved surface structure and its preparation method.

[0080] Step S1. Preparation of shear-thickening fluid:

[0081] Weigh 140g of monodisperse submicron SiO2 microspheres (500 nm particle size) and pour them into a container. Add 140g of anhydrous ethanol (100wt% of SiO2) until the powdered SiO2 is completely submerged. Place the container in an ultrasonic cleaner and stir while sonicating for 1 hour to ensure the SiO2 is fully and uniformly dispersed in the anhydrous ethanol (EtOH). Then add 60g of polyethylene glycol 200 (PEG200) (43wt% of SiO2) and place the container in an ultrasonic pulverizer for another 6 hours to ensure thorough and uniform mixing. Place the container in an electrically heated constant-temperature oil bath at 80℃ and heat while stirring for 6 hours. Once the viscosity increases to the point where the rotor cannot rotate, turn off the stirring. Stir manually every 15 minutes, repeating this process 8 times to remove the anhydrous ethanol (EtOH). Finally, after cooling, a shear-thickened fluid (STF) with a mass fraction of 70% is obtained.

[0082] Step S2. Structural Design and 3D Printing

[0083] The geometry and topology of the holes are designed as a three-period minimal surface structure, using 3D printing filament with a hardness of 95A and a porosity of 60%. The aforementioned 3D printer is then used to print a cubic thermoplastic polyurethane elastomer (3DP-TPMS-TPU) with a size of 20*20*20mm and a gyroid-based three-period minimal surface structure. By controlling the 3D printing process, the multi-faceted channels of the 3DP-TPMS-TPU are sealed, leaving one side of the cube unsealed to ensure the channels remain open.

[0084] S3. Preparation of 3DP-TPMS-TPU / STF energy-absorbing composite material

[0085] S31. Place the 3DP-TPMS-TPU sample into the beaker and fix the sample to the bottom to prevent it from floating.

[0086] S32. Pour the STF prepared in step S1 into a beaker, making sure the liquid level is 5-10 mm above the 3DP-TPU sample.

[0087] S33. Place the beaker in a vacuum drying oven, set the vacuum level to 0.1 MPa, and leave it for 1 hour until the shear thickening liquid completely fills the 3DP-TPMS-TPU before removing it.

[0088] S34. By bonding and sealing the unsealed side of 3DP-TPMS-TPU filled with shear thickening liquid using TPU sheets of the same grade, a 3DP-TPMS-TPU / STF energy-absorbing composite material is prepared.

[0089] The TPU (thermoplastic polyurethane elastomer) sheet used is the same grade as the TPU used in 3DP-TPMS-TPU, with a thickness of 1.0mm, and is bonded using hot melt adhesive.

[0090] Example 4

[0091] A 3DP-TPMS-TPU / STF energy-absorbing composite material with a TPU hardness of 70A and a porosity of 40%, comprising a three-period minimal curved surface structure, and its preparation method.

[0092] Step S1. Preparation of shear-thickening fluid:

[0093] 146g of monodisperse submicron SiO2 microspheres (500 nm particle size) were weighed and poured into a container. 146g of anhydrous ethanol (EtOH) (100 wt% SiO2) was added until the powdered SiO2 was completely submerged. The container was then placed in an ultrasonic cleaner and stirred while sonicating for 0.5 hours to ensure the SiO2 was fully and uniformly dispersed in the anhydrous ethanol (EtOH). Next, 54g of polyethylene glycol 400 (PEG 400) (39 wt% SiO2) was added, and the mixture was again placed in an ultrasonic pulverizer and sonicated for 8 hours to ensure thorough and uniform mixing. The container was then placed in an electrically heated constant-temperature oil bath at 80℃ and heated while stirring for 6 hours. Once the viscosity increased to the point where the rotor could no longer rotate, the stirring was stopped. Manual stirring was performed every 15 minutes, repeating this process 8 times to remove the anhydrous ethanol (EtOH). Finally, after cooling, a shear-thickened fluid (STF) with a mass fraction of 73% was obtained.

[0094] Step S2. Structural Design and 3D Printing

[0095] The geometry and topology of the holes are designed as a three-period minimal surface structure, using 3D printing filament with a hardness of 70A and a porosity of 40%. Then, the aforementioned 3D printer is used to print a 20*20*20mm cube-shaped thermoplastic polyurethane elastomer (3DP-TPMS-TPU) with a gyroid-like cellular structure and a three-period minimal surface structure. By controlling the 3D printing process, the multi-faceted channels of the 3DP-TPMS-TPU are sealed, leaving one side of the cube unsealed to ensure the channels remain open.

[0096] S3. Preparation of 3DP-TPMS-TPU / STF energy-absorbing composite material

[0097] S31. Place the 3DP-TPMS-TPU sample into the beaker and fix the sample to the bottom to prevent it from floating.

[0098] S32. Pour the STF prepared in step S1 into a beaker, making sure the liquid level is 5-10 mm above the 3DP-TPU sample.

[0099] S33. Place the beaker in a vacuum drying oven, set the vacuum level to 0.05 MPa, and leave it for 1 hour until the shear thickening liquid completely fills the 3DP-TPMS-TPU before removing it.

[0100] S34. By bonding and sealing the unsealed side of 3DP-TPMS-TPU filled with shear thickening liquid using TPU sheets of the same grade, a 3DP-TPMS-TPU / STF energy-absorbing composite material is prepared.

[0101] The TPU (thermoplastic polyurethane elastomer) sheet used is the same grade as the TPU used in 3DP-TPMS-TPU, with a thickness of 0.5mm, and is bonded using hot melt adhesive.

[0102] Example 5

[0103] A 3DP-TPMS-TPU / STF energy-absorbing composite material with a TPU hardness of 70A and a porosity of 80%, featuring a three-period minimal curved surface structure and its preparation method.

[0104] Step S1. Preparation of shear-thickening fluid:

[0105] Weigh 152g of monodisperse submicron SiO2 microspheres (500 nm particle size) and pour them into a container. Add 152g of anhydrous ethanol (EtOH) at 100wt% of SiO2 until the powdered SiO2 is completely submerged. Place the container in an ultrasonic cleaner and stir while sonicating for 0.5h to ensure the SiO2 is fully and uniformly dispersed in the anhydrous ethanol (EtOH). Then add 48g of polyethylene glycol 400 (PEG 400) at 32wt% of SiO2 and sonicate again in an ultrasonic pulverizer for 8h to ensure thorough and uniform mixing. Place the container in an electrically heated constant-temperature oil bath at 80℃ and heat while stirring for 6h. Once the viscosity increases to the point where the rotor cannot rotate, turn off the stirring and manually stir every 15min, repeating this process 8 times to remove the anhydrous ethanol (EtOH). Finally, after cooling, a shear-thickened fluid (STF) with a mass fraction of 76% is obtained.

[0106] Step S2. Structural Design and 3D Printing

[0107] The geometry and topology of the holes are designed as a three-period minimal surface structure, using 3D printing filament with a hardness of 70A and a porosity of 80%. Then, the aforementioned 3D printer is used to print a 20*20*20mm cube-shaped thermoplastic polyurethane elastomer (3DP-TPMS-TPU) with a gyroid-like cellular structure and a three-period minimal surface structure. By controlling the 3D printing process, the multi-faceted channels of the 3DP-TPMS-TPU are sealed, leaving one side of the cube unsealed to ensure the channels remain open.

[0108] S3. Preparation of 3DP-TPMS-TPU / STF energy-absorbing composite material

[0109] S31. Place the 3DP-TPMS-TPU sample into the beaker and fix the sample to the bottom to prevent it from floating.

[0110] S32. Pour the STF prepared in step S1 into a beaker, making sure the liquid level is 5-10 mm above the 3DP-TPU sample.

[0111] S33. Place the beaker in a vacuum drying oven, set the vacuum level to 0.05 MPa, and leave it for 1 hour until the shear thickening liquid completely fills the 3DP-TPMS-TPU before removing it.

[0112] S34. By bonding and sealing the unsealed side of 3DP-TPMS-TPU filled with shear thickening liquid using TPU sheets of the same grade, a 3DP-TPMS-TPU / STF energy-absorbing composite material is prepared.

[0113] The TPU (thermoplastic polyurethane elastomer) sheet used is the same grade as the TPU used in 3DP-TPMS-TPU, with a thickness of 2.0mm, and is bonded using hot melt adhesive.

[0114] Comparative Example 1

[0115] Preparation method of 3DP-TPMS-TPU energy-absorbing material with TPU hardness of 70A, cubic geometry, and gyroid three-period minimal surface structure (without shear thickening fluid).

[0116] Step S1. Structural Design and 3D Printing

[0117] The geometry and topology of the holes are designed as a three-period minimal surface structure, using 3D printing filament with a hardness of 70A. The aforementioned 3D printer is then used to print a 20*20*20mm thermoplastic polyurethane elastomer (3DP-TPMS-TPU) with a gyroid-based three-period minimal surface structure and a porosity of 60%. By controlling the 3D printing process, the multi-faceted pores of the 3DP-TPMS-TPU are sealed, leaving one side of the cube unsealed to ensure the pores remain open.

[0118] S2. Preparation of 3DP-TPMS-TPU energy-absorbing material

[0119] 3DP-TPMS-TPU energy-absorbing material was prepared by bonding the unsealed side of 3DP-TPMS-TPU without shear thickening liquid to TPU sheets of the same brand.

[0120] The TPU (thermoplastic polyurethane elastomer) sheet used is the same grade as the TPU used in 3DP-TPMS-TPU, with a thickness of 1.0mm, and is bonded using hot melt adhesive.

[0121] Comparative Example 2

[0122] A 3DP-TPMS-TPU / STF energy-absorbing composite material with a 60% STF mass fraction and a three-period minimal curved surface structure, and its preparation method.

[0123] Step S1. Preparation of shear-thickening fluid:

[0124] Weigh 120g of monodisperse submicron SiO2 microspheres (500 nm particle size) and pour them into a container. Add 120g of anhydrous ethanol (EtOH) until the powdered SiO2 is completely submerged. Place the container in an ultrasonic cleaner and stir while sonicating for 0.5h to ensure the SiO2 is fully and uniformly dispersed in the anhydrous ethanol (EtOH). Then add 80g of polyethylene glycol 200 (PEG 200) and sonicate again in an ultrasonic pulverizer for 6h to ensure thorough and uniform mixing. Place the container in an electrically heated constant-temperature oil bath at 80℃ and heat while stirring for 6h. Once the viscosity increases to the point where the rotor cannot rotate, turn off the stirring. Stir manually every 15 minutes, repeating this process 8 times to remove the anhydrous ethanol (EtOH). Finally, after cooling, a shear-thickened fluid (STF) with a mass fraction of 60% is obtained.

[0125] Step S2. Structural Design and 3D Printing

[0126] The geometry and topology of the holes are designed as a three-period minimal surface structure, using 3D printing filament with a hardness of 70A and a porosity of 60%. The aforementioned 3D printer is then used to print a cubic thermoplastic polyurethane elastomer (3DP-TPMS-TPU) with a size of 20*20*20mm and a gyroid-based three-period minimal surface structure. By controlling the 3D printing process, the multi-faceted channels of the 3DP-TPMS-TPU are sealed, leaving one side of the cube unsealed to ensure the channels remain open.

[0127] S3. Preparation of 3DP-TPMS-TPU / STF energy-absorbing composite material

[0128] S31. Place the 3DP-TPMS-TPU sample into the beaker and fix the sample to the bottom to prevent it from floating.

[0129] S32. Pour the STF prepared in step S1 into a beaker, making sure the liquid level is 5-10 mm above the 3DP-TPU sample.

[0130] S33. Place the beaker in a vacuum drying oven, set the vacuum level to 0.05 MPa, and leave it for 1 hour until the shear thickening liquid completely fills the 3DP-TPMS-TPU before removing it.

[0131] S34. By bonding and sealing the unsealed side of 3DP-TPMS-TPU filled with shear thickening liquid using TPU sheets of the same grade, a 3DP-TPMS-TPU / STF energy-absorbing composite material is prepared.

[0132] The TPU (thermoplastic polyurethane elastomer) sheet used is the same grade as the TPU used in 3DP-TPMS-TPU, with a thickness of 1.0mm, and is bonded using hot melt adhesive.

[0133] Comparative Example 3

[0134] A 3DP-TPMS-TPU / STF energy-absorbing composite material with a porosity of 20% and a three-period minimal curved surface structure and its preparation method.

[0135] Step S1. Preparation of shear-thickening fluid:

[0136] 152g of monodisperse submicron SiO2 microspheres (500 nm particle size) were weighed and poured into a container. A certain amount of anhydrous ethanol (EtOH) was added until the powdered SiO2 was completely submerged. The container was then placed in an ultrasonic cleaner and ultrasonically stirred for 0.5 hours to ensure the SiO2 was fully and uniformly dispersed in the anhydrous ethanol (EtOH). Next, 48g of polyethylene glycol 200 (PEG 200) was added, and the mixture was again ultrasonically dispersed in an ultrasonic pulverizer for 6 hours to ensure thorough and uniform mixing. The container was then placed in an electrically heated constant-temperature oil bath at 80℃ and heated while stirring for 6 hours. Once the viscosity increased to the point where the rotor could no longer rotate, the stirring was stopped. Manual stirring was performed every 15 minutes, repeating this process 8 times to remove the anhydrous ethanol (EtOH). Finally, after cooling, a shear-thickened fluid (STF) with a mass fraction of 76% was obtained.

[0137] Step S2. Structural Design and 3D Printing

[0138] The geometry and topology of the holes are designed as a three-period minimal surface structure, using 3D printing filament with a hardness of 70A and a porosity of 20%. Then, the aforementioned 3D printer is used to print a 20*20*20mm cube-shaped thermoplastic polyurethane elastomer (3DP-TPMS-TPU) with a gyroid-like cellular structure and a three-period minimal surface structure. By controlling the 3D printing process, the multi-faceted channels of the 3DP-TPMS-TPU are sealed, leaving one side of the cube unsealed to ensure the channels remain open.

[0139] S3. Preparation of 3DP-TPMS-TPU / STF energy-absorbing composite material

[0140] S31. Place the 3DP-TPMS-TPU sample into the beaker and fix the sample to the bottom to prevent it from floating.

[0141] S32. Pour the STF prepared in step S1 into a beaker, making sure the liquid level is 5-10 mm above the 3DP-TPU sample.

[0142] S33. Place the beaker in a vacuum drying oven, set the vacuum level to 0.05 MPa, and leave it for 1 hour until the shear thickening liquid completely fills the 3DP-TPMS-TPU before removing it.

[0143] S34. By bonding and sealing the unsealed side of 3DP-TPMS-TPU filled with shear thickening liquid using TPU sheets of the same grade, a 3DP-TPMS-TPU / STF energy-absorbing composite material is prepared.

[0144] The TPU (thermoplastic polyurethane elastomer) sheet used is the same grade as the TPU used in 3DP-TPMS-TPU, with a thickness of 1.0mm, and is bonded using hot melt adhesive.

[0145] Comparative Example 4

[0146] A 3DP-TPMS-TPU / STF energy-absorbing composite material with a three-period minimal curved surface structure and its preparation method (based on Example 5, with some parameters and processes changed).

[0147] Step S1. Preparation of shear-thickening fluid:

[0148] Weigh 152g of monodisperse submicron SiO2 microspheres (500 nm particle size) and pour them into a container. Add 152g of anhydrous ethanol (EtOH) until the powdered SiO2 is completely submerged. Place the container in an ultrasonic cleaner and stir while sonicating for 0.5h to ensure the SiO2 is fully and uniformly dispersed in the anhydrous ethanol (EtOH). Then add 48g of polyethylene glycol 200 (PEG 200) and place the container in an ultrasonic pulverizer for another 2h to ensure thorough and uniform mixing. Place the container in an electrically heated constant-temperature oil bath at 50℃ and heat while stirring for 2h. Once the viscosity increases to the point where the rotor cannot rotate, turn off the stirring. Stir manually every 15 minutes, repeating twice to remove the anhydrous ethanol (EtOH). After cooling, a shear-thickened fluid (STF) with a mass fraction of 76% is obtained.

[0149] Step S2. Structural Design and 3D Printing

[0150] The geometry and topology of the holes are designed as a three-period minimal surface structure, using 3D printing filament with a hardness of 70A and a porosity of 60%. The aforementioned 3D printer is then used to print a cubic thermoplastic polyurethane elastomer (3DP-TPMS-TPU) with a size of 20*20*20mm and a gyroid-based three-period minimal surface structure. By controlling the 3D printing process, the multi-faceted channels of the 3DP-TPMS-TPU are sealed, leaving one side of the cube unsealed to ensure the channels remain open.

[0151] S3. Preparation of 3DP-TPMS-TPU / STF energy-absorbing composite material

[0152] S31. Place the 3DP-TPMS-TPU sample into the beaker and fix the sample to the bottom to prevent it from floating.

[0153] S32. Pour the STF prepared in step S1 into a beaker, making sure the liquid level is 5-10 mm above the 3DP-TPU sample.

[0154] S33. Place the beaker in a vacuum drying oven, set the vacuum level to 1 MPa, and leave it for 10 minutes until the shear thickening liquid completely fills the 3DP-TPMS-TPU before removing it.

[0155] S34. By bonding and sealing the unsealed side of 3DP-TPMS-TPU filled with shear thickening liquid using TPU sheets of the same grade, a 3DP-TPMS-TPU / STF energy-absorbing composite material is prepared.

[0156] The TPU (thermoplastic polyurethane elastomer) sheet used is the same grade as the TPU used in 3DP-TPMS-TPU, with a thickness of 1.0mm, and is bonded using hot melt adhesive.

[0157] Table 1 Performance test results of embodiments and comparative examples of the present invention

[0158] Figure 9 The stress-strain curves of 3DP-TPU and 3DP-TPU / STF samples with compression rates of (a) 5 mm / min, (b) 50 mm / min, (c) 200 mm / min, and (d) 500 mm / min and different hardness are shown for this invention. Figure 10 The diagram shows the energy absorption performance of 3DP-TPU and 3DP-TPU / STF samples with different hardnesses at different compression rates according to the present invention, where (a) represents the specific energy absorption (SEAv) and (b) represents the increase in energy absorption. Figure 9 , Figure 10 As shown in Table 1, under the aforementioned preparation conditions, the 3DP-TPU / STF energy-absorbing composite material exhibits excellent performance in key indicators such as 60% compressive strain, energy absorption efficiency, energy dissipation coefficient, and impact force attenuation rate. Compared with the unfilled STF control group (Comparative Example 1), the composite material with STF filling shows significantly improved performance. However, when the STF concentration is too low (Comparative Example 2), the material performance deteriorates significantly, failing to fully utilize the core function of shear thickening effect. When the porosity is too low (Comparative Example 3), although the TPMS-TPU / STF composite material possesses a certain structural strength, its energy dissipation capacity is insufficient, and the elastic matrix releases the stored elastic potential energy, making it difficult to achieve effective energy dissipation. Conversely, excessively high porosity weakens the constraint effect of the pore structure on the STF, resulting in insufficient shear-induced effect during deformation, also failing to achieve ideal performance. In addition, other process factors (Comparative Example 4), such as uneven STF dispersion and residual anhydrous ethanol, can also lead to performance degradation.

[0159] As can be seen, the technical solution of filling the porous structure of 3D printed thermoplastic polyurethane elastomer (3DP-TPU) with shear thickening fluid (STF) in this invention significantly improves the compressive stress at constant strain, energy absorption per unit volume (SEAv), and energy dissipation coefficient (ΔU / U) of the resulting 3DP-TPU / STF composite material. Moreover, with the increase of compression rate, the buffer energy absorption efficiency of 3DP-TPU / STF is significantly improved, exhibiting good cycle stability and energy dissipation capability. Especially when using a minimal curved surface structure, it combines high porosity, a three-dimensional interconnected channel network, and excellent additive manufacturing adaptability, which can effectively constrain the internally encapsulated shear thickening fluid (STF), promoting particle agglomeration and blockage under shear action, inducing liquid-solid transition (shear thickening), and thus achieving a synergistic effect of elastic deformation of 3D printed TPU and enhanced energy dissipation of STF.

[0160] The embodiments described above are merely illustrative of several implementations of the present invention, designed to facilitate a detailed understanding of the technical solutions of the present invention, but should not be construed as limiting the scope of protection of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided by the present invention through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this invention patent should be determined by the content of the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A shear-thickening fluid-reinforced 3D-printed thermoplastic polyurethane elastomer porous structure energy-absorbing composite material, characterized in that: The energy-absorbing composite material is prepared by filling a 3D-printed porous thermoplastic polyurethane elastomer (3DP-TPU) with a shear thickening fluid (STF); the pores of the 3DP-TPU have a specific geometry and topology; the shear thickening fluid (STF) is a dispersion of SiO2 and polyethylene glycol.

2. The energy-absorbing composite material with a porous structure of 3D-printed thermoplastic polyurethane elastomer reinforced by a shear-thickening liquid according to claim 1, characterized in that: The dispersion is prepared by grinding, diluting, heating and stirring monodisperse submicron SiO2 microspheres, the particle size of which is 100-500 nm; the polyethylene glycol is polyethylene glycol 200 (PEG200) or polyethylene glycol 400 (PEG400); the mass fraction of the dispersion is 70 wt%-76 wt%.

3. The energy-absorbing composite material with a porous structure of 3D-printed thermoplastic polyurethane elastomer reinforced by a shear-thickening liquid according to claim 2, characterized in that: The geometry and topology of the 3DP-TPU pores include, but are not limited to, a three-period minimal surface structure, a square honeycomb structure, and a negative Poisson's ratio structure; the porosity of the porous structure is 40-80%.

4. The energy-absorbing composite material with a porous structure of 3D-printed thermoplastic polyurethane elastomer reinforced by a shear-thickening liquid according to claim 3, characterized in that: The thermoplastic polyurethane elastomer (TPU) used in the 3DP-TPU includes, but is not limited to, polyether-type or polyester-type thermoplastic polyurethane elastomers, with hardness including but not limited to 64D, 70A, 85A and 95A.

5. The energy-absorbing composite material with a porous structure of 3D-printed thermoplastic polyurethane elastomer reinforced by a shear-thickening liquid according to claim 4, characterized in that: The composite material has a regular or irregular geometric shape.

6. A method for preparing an energy-absorbing composite material with a porous structure of thermoplastic polyurethane elastomer reinforced by a shear-thickening liquid according to any one of claims 1 to 5, characterized in that: Includes the following steps: S1. Preparation of shear thickening fluid (STF): Monodisperse submicron SiO2 microspheres are ground, diluted, heated and stirred to obtain shear thickening fluid (STF). S2. Design the geometry and topology of the pores in the porous structure, and use fused deposition modeling (FDM) to 3D print 3DP-TPU, wherein the pores have specific geometry and topology, and the pores of the 3DP-TPU are non-fully sealed pores; S3. Fix the 3DP-TPU and inject the shear thickening fluid (STF) into it under vacuum, so that the shear thickening fluid (STF) fully fills the porous structure of the 3D-TPU, to obtain the energy-absorbing composite material (3DP-TPU / STF) of the porous structure of the 3D printed thermoplastic polyurethane elastomer reinforced by the shear thickening fluid.

7. The method for preparing an energy-absorbing composite material with a porous structure of thermoplastic polyurethane elastomer reinforced by a shear-thickening liquid according to claim 6, characterized in that: In step S1, S11. Weigh a certain amount of the monodisperse submicron SiO2 and grind it thoroughly in a mortar until it is powdery. The particle size range of the monodisperse submicron SiO2 microspheres is 100-500 nm. S12. Pour powdered SiO2 into a container, add 80-100 wt% anhydrous ethanol, and place it in an ultrasonic grinder for ultrasonic dispersion for 0.5-1 h to fully and evenly disperse the SiO2 powder in the anhydrous ethanol to obtain an ethanol dispersion of SiO2. S13. Add 30-43 wt% of polyethylene glycol to the ethanol dispersion of SiO2, wherein the polyethylene glycol is polyethylene glycol 200 or polyethylene glycol 400, and then place it in an ultrasonic pulverizer for ultrasonic dispersion for 6-10 hours to ensure thorough and uniform mixing, thereby obtaining a dispersion of SiO2 with ethanol and polyethylene glycol 200, or a dispersion of SiO2 with ethanol and polyethylene glycol 400. S14. Place the container containing the dispersion obtained in step S13 into an electric thermostatic oil bath, set the temperature to 60-80℃, and heat and stir until the anhydrous ethanol is completely removed. S15. After cooling the dispersion obtained in step S14, a shear thickener (STF) is obtained.

8. The method for preparing an energy-absorbing composite material with a porous structure of thermoplastic polyurethane elastomer reinforced by a shear-thickening liquid according to claim 6, characterized in that: In step S2, The non-fully sealed channels are sealed by sealing the multi-faceted channels of 3D-TPU, leaving one side or part unsealed to ensure that the channels are open. The 3DP-TPU uses thermoplastic polyurethane elastomer (TPU) with hardness including but not limited to 70A, 85A, and 95A; The porosity of the 3D-TPU constructed by the 3D printing process ranges from 40% to 80%. The 3D-TPU has a regular or irregular geometric shape. The geometry and topology of the 3D-TPU include, but are not limited to, a three-period minimal surface structure, a honeycomb structure, and a negative Poisson's ratio structure.

9. The method for preparing an energy-absorbing composite material with a porous structure of thermoplastic polyurethane elastomer reinforced by a shear-thickening liquid according to claim 8, characterized in that: In step S3, S31. Place the 3D printed 3DP-TPU sample into the container and fix the sample to the bottom of the container to prevent the sample from floating. S32. Pour the prepared shear thickening fluid (STF) into a container, ensuring the liquid level is 5-10 mm above the sample; S33. Place the beaker in a vacuum drying oven, set the vacuum degree to 0.05~0.1Mpa, and leave it for 1 hour until the shear thickening liquid (STF) completely fills the 3DP-TPU before taking it out; S34. By bonding and sealing the unsealed side or local area of ​​a 3D-printed thermoplastic polyurethane elastomer (3DP-TPU) filled with shear thickening fluid (STF) using thermoplastic polyurethane elastomer (TPU) sheets of the same grade, an energy-absorbing composite material (3DP-TPU / STF) with a porous structure of shear thickening fluid reinforced with 3D-printed thermoplastic polyurethane elastomer is prepared.

10. The method for preparing an energy-absorbing composite material with a porous structure of thermoplastic polyurethane elastomer reinforced by a shear-thickening liquid according to claim 9, characterized in that: The thermoplastic polyurethane elastomer (TPU) sheet used is 0.5-2.0 mm thick, and the bonding is hot melt bonding.

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