Negative Poisson's ratio shear thickening interlayer composite material based on 3D printing-pouring integrated process and preparation method of negative Poisson's ratio shear thickening interlayer composite material

Abstract

The invention discloses a negative-Poisson-ratio shear thickening interlayer composite material based on a 3D printing-pouring integrated process and a preparation method thereof, relates to the field of composite materials, and aims to solve the problem that existing shear thickening glue serving as an impact-resistant material is poor in impact resistance and shape stability. The anti-impact composite material comprises shear thickening glue, a negative Poisson's ratio structural frame and carbon fiber plates, the shear thickening glue is filled into the negative Poisson's ratio structural frame, and the carbon fiber plates are arranged on the upper surface and the lower surface of the negative Poisson's ratio structural frame. The method comprises the following steps: placing the shear thickening glue on the negative Poisson's ratio structural frame, standing, filling gaps of the negative Poisson's ratio structural frame with the shear thickening glue, and adhering a layer of carbon fiber plate to each of the upper surface and the lower surface of the negative Poisson's ratio structural frame to obtain the sandwich type negative Poisson's ratio impact-resistant composite material. The composite material disclosed by the invention has relatively high impact resistance and a stable geometrical shape. The method is used for preparing the impact-resistant composite material.

Description

Technical Field

[0001] This invention relates to the field of composite materials, and more particularly to a negative Poisson's ratio shear thickening sandwich composite material based on a 3D printing-infusion integrated process and its preparation method. Background Technology

[0002] Shear-thickened adhesives (STGs) are a class of "clay-like" materials exhibiting characteristics of amorphous linear polymers. At low strain rates, STGs display fluid properties; upon impact, they rapidly harden, exhibiting solid properties, and then return to their initial state after the impact. Compared to the widely studied shear-thickening fluids (STFs), STGs have higher viscosity, making them easier to encapsulate and carry. Because STGs can absorb a large amount of energy during liquid-solid phase transitions, they have significant application potential in protection and impact resistance.

[0003] However, STG has a limited energy absorption capacity, and it may be "broken down" by a single, ultra-high energy impact, indicating insufficient impact resistance. Additionally, STG has a certain degree of fluidity, resulting in poor shape stability. Summary of the Invention

[0004] The present invention aims to address the problem that existing shear-thickened adhesives have poor impact resistance and shape stability as impact-resistant materials, and provides a negative Poisson's ratio shear-thickened sandwich composite material based on a 3D printing-infusion integrated process and its preparation method.

[0005] This invention relates to a negative Poisson's ratio shear-thickening sandwich composite material based on a 3D printing-infusion integrated process, comprising a shear-thickening adhesive, a negative Poisson's ratio structural frame, and carbon fiber plates. The shear-thickening adhesive is filled into the negative Poisson's ratio structural frame, and the carbon fiber plates are disposed on the upper and lower surfaces of the negative Poisson's ratio structural frame.

[0006] The negative Poisson's ratio structural frame is a multi-layered structure with at least three layers.

[0007] This invention relates to a method for preparing a negative Poisson's ratio shear thickening sandwich composite material based on a 3D printing-infusion integrated process, comprising the following steps:

[0008] 1. Boric acid and dimethyl silicone oil are mixed and reacted at 220~240 ℃ for 6 h; after cooling, a shear thickening adhesive is obtained.

[0009] 2. Based on the designed three-dimensional model, a negative Poisson's ratio structural frame was fabricated using 3D printing.

[0010] 3. Place the shear thickening adhesive on the negative Poisson's ratio structural frame and let it stand for 24~48 hours to allow the shear thickening adhesive to penetrate and fill the gaps in the negative Poisson's ratio structural frame. Then, attach a layer of carbon fiber plate to the upper and lower surfaces of the negative Poisson's ratio structural frame to obtain the composite material.

[0011] Furthermore, in step one, the mass ratio of boric acid to dimethyl silicone oil is (10~20):100.

[0012] Furthermore, the raw materials used for 3D printing in step two are 7100Pro nylon, HP 7500 nylon, or HP7600 nylon.

[0013] Furthermore, the 3D printing method in step two is selective laser sintering.

[0014] Furthermore, the three-dimensional model described in step two is a multi-layered structure composed of three-dimensional cell structures; each layer is formed by 19 three-dimensional cell structures arranged in a hexagonal close-packed pattern: one three-dimensional cell structure is arranged at the center, six three-dimensional cell structures are arranged in the first ring around the center, and twelve three-dimensional cell structures are arranged in the second ring. Adjacent three-dimensional cell structures are seamlessly connected to form a single-layer structure; multiple single-layer structures are stacked at equal intervals along the vertical direction, with a minimum of three layers.

[0015] Furthermore, the three-dimensional cell structure is a spatially symmetrical three-dimensional structure formed by the intersection of three unit cell structures at the central axis, wherein the included angle between adjacent unit cell structures is 60°.

[0016] Furthermore, the unit cell structure is a concave hexagon.

[0017] The beneficial effects of this invention are:

[0018] The negative Poisson's ratio (NPR) structural framework employed in this invention exhibits unique tensile and compressive effects, meaning it generates an inward contraction and aggregation effect under compression, rather than the outward expansion characteristic of traditional structures. This special mechanical response can significantly improve the material's impact resistance and energy absorption capacity.

[0019] This invention utilizes the flow characteristics of shear-thickened adhesive (STG) at low strain rates, allowing it to fully penetrate the voids of a negative Poisson's ratio structure. After filling, the STG is mechanically confined by the geometric constraints of the frame and the interfacial viscosity, thereby significantly improving the interfacial bonding and shape stability of the composite system. The spatial confinement and mechanical constraint of the STG by the negative Poisson's ratio structural frame effectively enhances its impact resistance. Carbon fiber plates are bonded to the upper and lower surfaces of the composite structure, serving as high-modulus confinement layers and playing a crucial role in structural support and energy transfer within the system.

[0020] The negative Poisson's ratio structural framework employed in this invention is a multi-layered structure, including a hexagonal close-packed three-dimensional cell structure. When subjected to vertical compression, the cell structure contracts inward, transforming lateral expansion into "inward binding," causing the injected shear-thickening gel (STG) to be instantly subjected to volume compression, resulting in a 2-3 order of magnitude increase in apparent viscosity, forming a "self-locking damping pad." This further improves impact resistance.

[0021] Furthermore, due to the spatial confinement effect of the negative Poisson's ratio structural frame, the cold flow characteristics of STG are significantly suppressed, and the composite material can still maintain good geometric stability after standing for 24 hours. Attached Figure Description

[0022] Figure 1 This is the concave hexagonal unit cell structure in the negative Poisson's ratio structural framework of Example 1;

[0023] Figure 2 This is the three-dimensional cell structure in the negative Poisson's ratio structural framework of Example 1;

[0024] Figure 3 This is a design drawing of the negative Poisson's ratio structural frame for Example 1;

[0025] Figure 4 This is a physical image of the negative Poisson's ratio structural frame of Example 1;

[0026] Figure 5 A physical image of the negative Poisson's ratio structure after filling with shear-thickened adhesive;

[0027] Figure 6 Here is a photograph of the sandwich-type negative Poisson's ratio impact-resistant composite material prepared in Example 1;

[0028] Figure 7 Comparison of impact load suppression effects of the sandwich-type negative Poisson's ratio impact-resistant composite material prepared in Example 1;

[0029] Figure 8 For ball impact testing;

[0030] Figure 9 This is a diagram showing the state of the glass slide after it has been impacted.

[0031] Figure 10 The graph shows the state change over time of the sandwich-type negative Poisson's ratio impact-resistant composite material prepared in Example 1. Detailed Implementation

[0032] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

[0033] Specific Implementation Method 1: This implementation method is based on a negative Poisson's ratio shear-thickening sandwich composite material using a 3D printing-infusion integrated process, comprising a shear-thickening adhesive, a negative Poisson's ratio structural frame, and carbon fiber plates. The shear-thickening adhesive is filled into the negative Poisson's ratio structural frame, and the carbon fiber plates are disposed on the upper and lower surfaces of the negative Poisson's ratio structural frame.

[0034] This invention fills a negative Poisson's ratio (NPR) structural framework with a solid-state gas oxidizer (STG). The energy absorption mechanism of the STG is mainly manifested in the rapid hardening of the material under dynamic impact, generating a large number of reversible microcracks, and the stress is released through instantaneous crack propagation. The inward cohesion effect of the negative Poisson's ratio structure during compression accelerates the loading of the STG, thereby stimulating its faster hardening reaction and increasing its energy storage modulus. Simultaneously, the tensile expansion effect of the negative Poisson's ratio structure helps to induce and propagate the microcracks within the STG, further enhancing the energy dissipation effect. Finally, through the plastic deformation of the negative Poisson's ratio structure, the phase transformation hardening of the STG, and interfacial frictional slip, a three-level energy dissipation system is constructed, significantly improving the energy dissipation capacity of the composite material.

[0035] Carbon fiber plates are bonded to the upper and lower surfaces of the composite structure. These plates, acting as high-modulus confinement layers, play a crucial role in structural support and energy transfer within the system. On one hand, the carbon fiber plates provide external confinement to the internal STG layer, further suppressing its flow and deformation under static loads or impacts. On the other hand, during impacts, the carbon fiber plates disperse external impact loads along the in-plane direction and, through coordinated deformation with the negative Poisson's ratio structure and the STG layer, achieve multi-path stress transmission and dissipation. This forms a multi-layered energy absorption system of "rigid confinement of carbon fiber plates—energy absorption by NPR structural deformation—STG phase transformation hardening," further enhancing the overall impact resistance of the composite material.

[0036] Specific Implementation Method Two: The negative Poisson's ratio structural frame described in this implementation method is a multi-layered structure with at least three layers. Other steps and parameters are the same as in Specific Implementation Method One.

[0037] Specific Implementation Method 3: This implementation method is based on a 3D printing-infusion integrated process for preparing negative Poisson's ratio shear thickening sandwich composite materials, including the following steps:

[0038] 1. Boric acid and dimethyl silicone oil are mixed and reacted at 220~240 ℃ for 6 h; after cooling, a shear thickening adhesive is obtained.

[0039] 2. Based on the designed 3D model, a negative Poisson's ratio structural frame is fabricated using 3D printing.

[0040] 3. Place the shear thickening adhesive on the negative Poisson's ratio structural frame and let it stand for 24~48 hours to allow the shear thickening adhesive to penetrate and fill the gaps in the negative Poisson's ratio structural frame. Then, attach a layer of carbon fiber plate to the upper and lower surfaces of the negative Poisson's ratio structural frame to obtain a sandwich-type negative Poisson's ratio impact-resistant composite material.

[0041] Specific Implementation Method Four: In step one of this implementation method, the mass ratio of boric acid to dimethyl silicone oil is (10~20):100. Other steps and parameters are the same as in Specific Implementation Method Three.

[0042] Specific Implementation Method Five: In step one of this implementation method, the mass ratio of boric acid to dimethyl silicone oil is 15:100. Other steps and parameters are the same as in Specific Implementation Method Three or Four.

[0043] Specific Implementation Method Six: In step two of this implementation method, the raw material used for 3D printing is 7100Pro nylon, HP7500 nylon, or HP 7600 nylon. Other steps and parameters are the same as in Specific Implementation Methods Three to Five.

[0044] Specific Implementation Method Seven: In step two of this implementation method, the 3D printing method is selective laser sintering. Other steps and parameters are the same as in Specific Implementation Methods Three through Six.

[0045] Specific Implementation Method Eight: The three-dimensional model described in step two of this implementation method is a multi-layered structure composed of three-dimensional cell structures; each layer is formed by 19 three-dimensional cell structures arranged in a hexagonal close-packed pattern: one three-dimensional cell structure is arranged at the center, six three-dimensional cell structures are arranged in the first ring around the center, and twelve three-dimensional cell structures are arranged in the second ring. Adjacent three-dimensional cell structures are seamlessly connected to form a single-layer structure; multiple single-layer structures are stacked at equal intervals along the vertical direction, with at least three layers. Other steps and parameters are the same as in Specific Implementation Methods Three to Seven.

[0046] Specific Implementation Method Nine: The three-dimensional cell structure described in this implementation method consists of three unit cell structures intersecting at the central axis to form a spatially symmetrical three-dimensional structure, wherein the included angle between adjacent unit cell structures is 60°. Other steps and parameters are the same as in Specific Implementation Method Eight.

[0047] Specific Implementation Method Ten: The unit cell structure described in this implementation method is a concave hexagon. Other steps and parameters are the same as in Specific Implementation Method Nine.

[0048] The embodiments of the present invention will be described in detail below. The following embodiments are implemented based on the technical solution of the present invention, and detailed implementation schemes and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0049] Example 1:

[0050] This embodiment presents a negative Poisson's ratio shear-thickened sandwich composite material based on a 3D printing-infusion integrated process, prepared according to the following method:

[0051] I. Design of a negative Poisson's ratio structural frame

[0052] like Figure 1 As shown, this is a concave hexagonal unit cell structure. Its horizontal bars 101 and vertical bars 103 are parallel, and an angle 104 of 60° is formed between horizontal bars 101 and diagonal bars 102. The unit cell structure rotates twice along its central vertical axis, forming a spatially symmetrical three-dimensional cellular structure from the intersection of three unit cell structures. The angle between adjacent unit cell structures is 60°. Figure 2 As shown.

[0053] The negative Poisson's ratio structural framework described in this embodiment is a three-layer structure composed of three-dimensional cell structures. Each layer consists of 19 three-dimensional cell structures arranged in a hexagonal close-packed pattern: one three-dimensional cell structure is arranged at the center, six three-dimensional cell structures are arranged in the first ring around the center, and twelve three-dimensional cell structures are arranged in the second ring. Adjacent three-dimensional cell structures are seamlessly connected by shared spacer 103 to form a single-layer structure. Three single-layer structures are stacked at equal intervals along the vertical direction to obtain the negative Poisson's ratio structural framework, as shown below. Figure 3 As shown.

[0054] II. Preparation of Shear Thickening Gel (STG)

[0055] Boric acid and dimethyl silicone oil were mixed at a mass ratio of 15:100 and reacted at 240 °C for 6 h. After cooling, a shear thickening adhesive was obtained.

[0056] III. Preparation of Negative Poisson's Ratio Structural Frameworks

[0057] Following the design in step one, 7100Pro nylon was selected as the raw material, and a negative Poisson's ratio structural framework was prepared using selective laser sintering (SLS); the physical image is shown below. Figure 4 As shown;

[0058] IV. Preparation of Impact-Resistant Composite Materials

[0059] The shear-thickening adhesive was placed on a negative Poisson's ratio structural frame and left to stand for 48 hours. Its cold-flow properties allowed it to penetrate and fill the voids in the frame. A sample image is shown below. Figure 5 As shown; then, a layer of carbon fiber plate is glued to the upper and lower surfaces of the negative Poisson's ratio structural frame to obtain a sandwich-type negative Poisson's ratio impact-resistant composite material, as shown. Figure 6 As shown.

[0060] Using the sandwich-type negative Poisson's ratio impact-resistant composite material prepared in Example 1 as a specimen (sandwich-type STG-NPR specimen), and a layer of carbon fiber plate was respectively glued to the upper and lower surfaces of the shear thickener to prepare a sandwich-type STG specimen as a control, the following experiments were conducted:

[0061] (1) The specimens were impacted using a drop hammer tester with energies of 3J, 5J, 7J, and 10J respectively. A comparison of the impact load suppression effects of sandwich-type negative Poisson's ratio impact-resistant composite materials and sandwich-type STG specimens is shown in the figure below. Figure 7 As shown, by Figure 7 It can be seen that, under the same impact energy, the maximum load of the sandwich STG-NPR specimen is reduced by 18.59% (3J), 43.94% (5J), 36.15% (7J) and 33.66% (10J) respectively compared with the sandwich STG specimen, indicating that the negative Poisson's ratio structural frame significantly suppresses the peak impact load through stress dispersion.

[0062] (2) A falling ball impact test was conducted on the sample prepared in Example 1. A stainless steel ball with a mass of 0.5 kg was dropped freely from a height of 1 m to impact the sample placed on a rigid base. Ten glass slides with a thickness of 1 mm were placed below the sample to evaluate the transmission and attenuation of impact energy. The impact process was as follows: Figure 8 As shown. Under these experimental conditions, a steel ball falls freely from a height of h1 = 1 m and, after impacting the material surface, rebounds to a maximum height of h2 = 0.33 m. The energy absorption rate ƞ exhibited by the material in this impact can be calculated using the following formula:

[0063]

[0064] Calculation results show that about 67% of the impact energy is absorbed by the material, mainly used for plastic deformation, internal friction and heat conversion.

[0065] After the impact test, all glass slides underwent a macroscopic inspection. The condition of the glass slides after the impact was as follows: Figure 9 As shown in the figure. The results indicate that none of the glass plates showed any breakage or visible cracks, demonstrating that under the impact conditions, the samples effectively absorbed the impact energy and avoided damage to the base glass.

[0066] In this embodiment, 19 three-dimensional cell structures are arranged in a hexagonal close packing (HCP), which is the densest in the plane and has no straight through gaps, so that the local point load can be instantly distributed to 6+12 "cell chains". The first ring of 6 three-dimensional cell structures is equivalent to the "first buffer ring", and the second ring of 12 three-dimensional cell structures is equivalent to the "second energy dissipation ring", realizing gradient stiffness. The three single-layer structures are stacked at equal intervals to realize the "three-stage crushing" out of the plane. (1) There is no misalignment between layers, and the vertical direction forms continuous longitudinal ribs, which improves the early bending stiffness. (2) When the drop hammer continues to press down, the three layers crush in sequence: the upper layer first compacts → the middle layer shrinks with negative Poisson's ratio to hold the ribs tightly → the lower layer begins to crush, giving a three-stage load platform, which significantly extends the effective stroke. When compressed vertically, the cells contract inward, turning the lateral expansion into an "inward binding" that causes the injected shear thickener (STG) to be instantly subjected to volume compression, resulting in a jump in apparent viscosity of 2 to 3 orders of magnitude, forming a "self-locking damping pad" that further improves impact resistance.

[0067] The state change over time of the sandwich-type negative Poisson's ratio impact-resistant composite material prepared in Example 1 is shown in the figure below. Figure 10 As shown. Figure 10 The evolution of STG at different time points after filling the frame was shown. The results show that the frame effectively delayed the cooling flow and deformation process of STG, enabling the composite system to maintain good geometric stability after long-term placement.

[0068] This invention employs a three-dimensional negative Poisson's ratio structure as a support frame, utilizing its spatial network structure to constrain and fix polyborosiloxane alkyl shear thickener (STG). Due to the significant cold flow characteristics of STG, it is difficult to maintain shape stability over a long period under normal conditions. However, through the structural design proposed in this invention, STG can slowly penetrate and fill the gaps in the frame in the initial stage due to its own fluidity, thereby achieving a high degree of integration with the three-dimensional frame.

[0069] Negative Poisson's ratio structural frames act as a "skeleton" in composite materials: 1. Anti-cold flow effect: The frame forms a spatial confinement for the STG, significantly reducing its free flow and enabling the material to maintain the stability of its overall shape over a longer time scale; 2. Enhanced mechanical properties: Under external forces, the frame and STG jointly bear the load, exhibiting a synergistic effect similar to reinforced concrete, which can effectively improve the stiffness and impact resistance of composite materials.

Claims

1. A negative Poisson's ratio shear thickening sandwich composite material based on a 3D printing-infusion integrated process, characterized in that, The composite material includes a shear thickening adhesive, a negative Poisson's ratio structural frame, and a carbon fiber plate. The shear thickening adhesive is filled into the negative Poisson's ratio structural frame, and the carbon fiber plate is disposed on the upper and lower surfaces of the negative Poisson's ratio structural frame.

2. The negative Poisson's ratio shear thickening sandwich composite material based on 3D printing-infusion integrated process according to claim 1, characterized in that, The negative Poisson's ratio structural frame is a multi-layered structure with at least three layers.

3. The method for preparing the negative Poisson's ratio shear thickening sandwich composite material based on the 3D printing-infusion integrated process as described in claim 1, characterized in that, The method includes the following steps:

1. Boric acid and dimethyl silicone oil are mixed and reacted at 220~240 ℃ for 6 h; after cooling, a shear thickening adhesive is obtained.

2. Based on the designed three-dimensional model, a negative Poisson's ratio structural frame was fabricated using 3D printing.

3. Place the shear thickening adhesive on the negative Poisson's ratio structural frame and let it stand for 24~48 hours to allow the shear thickening adhesive to penetrate and fill the gaps in the negative Poisson's ratio structural frame. Then, attach a layer of carbon fiber plate to the upper and lower surfaces of the negative Poisson's ratio structural frame to obtain the composite material.

4. The method for preparing a negative Poisson's ratio shear-thickened sandwich composite material based on a 3D printing-infusion integrated process according to claim 3, characterized in that, In step one, the mass ratio of boric acid to dimethyl silicone oil is (10~20):

100.

5. The method for preparing a negative Poisson's ratio shear-thickened sandwich composite material based on a 3D printing-infusion integrated process according to claim 3, characterized in that, In step one, the mass ratio of boric acid to dimethyl silicone oil is 15:

100.

6. The method for preparing a negative Poisson's ratio shear-thickened sandwich composite material based on a 3D printing-infusion integrated process according to claim 3 or 4, characterized in that, In step two, the 3D printing uses 7100Pro nylon, HP 7500 nylon, or HP 7600 nylon as the raw materials.

7. The method for preparing a negative Poisson's ratio shear-thickened sandwich composite material based on a 3D printing-infusion integrated process according to claim 6, characterized in that, In step two, the 3D printing method is selective laser sintering.

8. The method for preparing a negative Poisson's ratio shear-thickened sandwich composite material based on a 3D printing-infusion integrated process according to claim 7, characterized in that, The three-dimensional model described in step two is a multi-layered structure composed of three-dimensional cell structures; each layer is formed by 19 three-dimensional cell structures arranged in a hexagonal close-packed pattern: one three-dimensional cell structure is arranged in the center, six three-dimensional cell structures are arranged in the first ring around the center, and twelve three-dimensional cell structures are arranged in the second ring. Adjacent three-dimensional cell structures are seamlessly connected to form a single-layer structure. Multiple single-layer structures are stacked at equal intervals along the vertical direction, with a minimum of three layers.

9. The method for preparing a negative Poisson's ratio shear-thickened sandwich composite material based on a 3D printing-infusion integrated process according to claim 8, characterized in that, The three-dimensional cell structure is a spatially symmetrical three-dimensional structure formed by the intersection of three single-cell structures at the central axis, wherein the included angle between adjacent single-cell structures is 60°.

10. The method for preparing a negative Poisson's ratio shear-thickened sandwich composite material based on a 3D printing-infusion integrated process according to claim 9, characterized in that, The unit cell structure is a concave hexagon.

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