3D printing-based three-dimensional concave negative poisson's ratio assembly type composite protective structure and preparation method

Abstract

The application discloses a three-dimensional inner recessed negative Poisson's ratio assembly type composite protective structure based on 3D printing, which is characterized by comprising a three-dimensional double-branch inner recessed hexagonal cell body, a steel screw rod and light foamed material, the three-dimensional double-branch inner recessed hexagonal cell body is formed by linearly rotating two double-branch inner recessed hexagonal cells by 90 degrees along a long axis direction to form an orthogonal three-dimensional cell body, a hole is left in the middle of a vertical side branch inclined rib, a high-strength screw rod is arranged to pass through and fix adjacent cell bodies, and the light foamed material is uniformly dispersed in the negative Poisson's ratio structure. Furthermore, the application provides a preparation method of the three-dimensional inner recessed negative Poisson's ratio assembly type composite protective structure based on 3D printing. The application greatly improves the rigidity of the outer inclined rib of the structure, greatly improves the rigidity in the vertical direction, avoids the overall structure from being locally damaged too early, and thus better impact resistance and deformation resistance of the structure are achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of building engineering, and particularly relates to a three-dimensional concave negative Poisson's ratio fabricated composite protective structure based on 3D printing and a preparation method. BACKGROUND

[0002] Modern engineering continuously puts forward new requirements and challenges to structures and materials, negative Poisson's ratio structures have many characteristics and advantages that other traditional structures do not have, for example, strong shear resistance, strong fracture resistance and large energy absorption capacity. It is just because of the unique advantages of these negative Poisson's ratio structures that they have unique functions of explosion and penetration resistance, impact resistance, shock absorption, deformation and improvement of basic mechanical properties, which have wide application in the fields of ships, aerospace and explosion protection. At present, the application scene of the negative Poisson's ratio structure in the building industry is the optimization of structures taking steel as the raw material, and few designs of negative Poisson's ratio structures are carried out for concrete materials. When the traditional concave structure is bearing, stress concentration occurs at the corner points between the unit cell walls, and the rest is less stressed. SUMMARY

[0003] In order to overcome the shortcomings of the prior art, the application provides a three-dimensional concave negative Poisson's ratio fabricated composite protective structure based on 3D printing and a preparation method, which greatly improves the stiffness of the outer diagonal rib of the structure and greatly improves the vertical stiffness, avoids premature local damage of the overall structure, and thus realizes better impact resistance and deformation capacity of the structure.

[0004] The technical scheme adopted by the application to solve the technical problems is:

[0005] A three-dimensional concave negative Poisson's ratio fabricated composite protective structure based on 3D printing, comprising a three-dimensional double-branch concave hexagonal unit cell body, a steel screw rod and a lightweight foamed material, the three-dimensional double-branch concave hexagonal unit cell body is a right-angle three-dimensional unit cell body formed by linearly rotating two double-branch concave hexagonal units by 90 degrees along the long axis direction, the basic geometric parameters include a horizontal side length h, a unit outer cell wall length l1, a unit inner cell wall length l2, an angle θ1 between the outer diagonal wall of the unit cell body and the vertical line, an angle θ2 between the inner diagonal wall of the unit cell body and the vertical line and a unit cell body wall thickness t, the height y and the length x of the unit cell body are calculated by the following formulas:

[0006] x = 2 (h - l2 - sin θ2)

[0007] y = 2l1 - cos θ1

[0008] Holes are left in the middle of the vertical side branch diagonal rib for the high-strength screw rod to pass through and fix the adjacent unit cell bodies, and the lightweight foamed material is uniformly filled in the negative Poisson's ratio structure.

[0009] Further, in the three-dimensional double-branch inner recessed hexagonal cell unit, the angle θ1 between the outer side inclined wall of the cell body and the vertical line is 16 degrees, the angle θ2 between the inner side inclined wall of the cell body and the vertical line is 30 degrees, the wall thickness t of the cell body is 10 to 30 mm, and the horizontal length h is 100 to 200 mm.

[0010] In the three-dimensional double-branch inner recessed hexagonal cell body, a hole with a diameter of 5 to 10 mm is left in the middle of the vertical eight side branches, which is used for passing and fixing the adjacent cell body by a high-strength screw rod.

[0011] The three-dimensional double-branch inner recessed hexagonal cell unit is prepared by 3D printing of high-strength and high-toughness fiber concrete material, and the compressive strength reaches more than 100 MPa, and the ultimate tensile strain reaches more than 5%.

[0012] The raw materials of the light foaming material are fast-hardening silicate cement, 40-200 mesh quartz powder, 30% pure hydrogen peroxide, 7.0% calcium content calcium stearate, polycarboxylic acid water reducer and water, and the weight ratio of each component is as follows: cement: 150-200 parts, quartz powder: 100-130 parts, hydrogen peroxide: 10-13 parts, calcium stearate: 5-7 parts, polycarboxylic acid water reducer: 1.0-1.3 parts, water: 125-165 parts.

[0013] The compressive strength of the light foaming material reaches more than 5 MPa, and the density is 200-400 kg / m 3 , and the setting time is 10-15 minutes.

[0014] A preparation method of a three-dimensional inner recessed negative Poisson's ratio assembly type composite protective structure based on 3D printing, comprising the following steps:

[0015] S1: splice any two pre-printed three-dimensional negative Poisson's ratio structure basic units, align the pre-reserved holes in the middle of the side branch inclined ribs, and then pass the fastening screw rod through the holes and fasten with nuts;

[0016] S2: according to the size needs of the actual structure, sequentially arrange the three-dimensional negative Poisson's ratio structure basic units through space expansion to further form a three-dimensional negative Poisson's ratio protective structure body;

[0017] S3: pour the stirred cement-based light foaming slurry into the interior of the assembled three-dimensional structure body outside the supporting template, and after the foaming material is hardened, remove the mold and maintain it to the specified age.

[0018] The technical concept of the present application is that the present application improves the traditional inner recess structure by adopting the method of adding support arms, and is named as double inner recess honeycomb (DRH), as shown in the figure, six basic geometric parameters h, l1, l2, θ1, θ2 and t2 determine the special size of the basic DRH unit cell, wherein h is the horizontal side length, l1 is the length of the outer cell wall, l2 is the length of the inner cell wall, θ1 is the included angle of the outer side inclined wall of the unit cell with the vertical line, θ2 is the included angle of the inner side inclined wall of the unit cell with the vertical line, t is the cell wall thickness, and the other two indexes are the cell height y and the length x, and the cell height y and the length x can be derived from the other several parameters.

[0019] x = 2 (h - l2 - sinθ2)

[0020] y = 2l1 - cosθ1

[0021] The novel three-dimensional double inner recess structure in the present application is different from the traditional structure, and the stiffness of the outer side inclined rib is increased according to the stress characteristics of the high-strength and high-toughness cement-based material through theoretical and experimental calculation, on the one hand, the elastic modulus of the unit cell body is increased by more than 3 times compared with the traditional inner recess structure, which greatly improves the stiffness of the structure in the vertical direction; on the other hand, the local reinforcement of the lateral inclined rib changes the stress distribution state of the cell body when stressed, so that the overall structure will not be damaged locally too early. The absolute value of the negative Poisson's ratio of the three-dimensional novel double inner recess structure of the present application is also much higher than that of the traditional inner recess structure

[0022] The beneficial effects of the present application mainly include:

[0023] 1. The stiffness of the structure on the outer side inclined rib is greatly improved, the vertical stiffness is greatly improved, the overall structure is prevented from being damaged locally too early, and the impact resistance and deformation resistance of the structure are improved.

[0024] 2. The form and angle of the novel double inner recess structure unit are designed by the 3D printing method, the fiber structure unit in the light foaming material and the stacking array distribution thereof are designed, and a prefabricated concrete structure template with a special form is obtained by combination; the assembled composite protective structure with a negative Poisson's ratio effect is prepared by using high-strength bolts

[0025] 3. The present application adopts a 3D printing method to make a double inner recess structure. The novel three-dimensional double inner recess structure adopts a 3D printing method to improve the efficiency of making the structure, greatly saving the time for making the protective structure. The processing is simple and easy to realize.

[0026] 4. The double concave structure achieves closure in the middle, which greatly improves the vertical stiffness of the structure and avoids local damage to the overall structure, especially at the corners of the three-dimensional model, where damage is prone to occur. This structure can effectively improve the ability to resist impact and deformation.

[0027] 5. Lightweight foamed materials can effectively enhance the cement-based composite materials described in this invention. Through the design of crystal microstructure, the Poisson's ratio is greatly reduced, resulting in a negative Poisson's ratio effect, thereby significantly improving the energy absorption modulus, energy dissipation modulus, and energy storage modulus. Attached Figure Description

[0028] Figure 1 It is a two-dimensional diagram of a double-invaginated cell body. Detailed Implementation

[0029] The present invention will now be further described with reference to the accompanying drawings.

[0030] Reference Figure 1 A 3D-printed, three-dimensional concave negative Poisson's ratio assembled composite protective structure includes a three-dimensional double-branched concave hexagonal unit cell, a steel screw, and lightweight foam material. The three-dimensional double-branched concave hexagonal unit cell is formed by rotating two double-branched concave hexagonal units 90 degrees along their major axis to create an orthogonal three-dimensional unit cell. Basic geometric parameters include the horizontal side length h, the length of the outer cell wall l1, the length of the inner cell wall l2, the angle θ1 between the outer inclined wall and the vertical line, the angle θ2 between the inner single cell inclined wall and the vertical line, and the unit cell wall thickness t. The height y and length x of the unit cell are calculated using the following formula:

[0031] x = 2(h - l² - sinθ²)

[0032] y = 2l1 - cosθ1;

[0033] The vertical side support ribs have holes in the middle for high-strength screws to pass through and fix adjacent unit cells. The lightweight foam material is uniformly dispersed in the negative Poisson's ratio structure.

[0034] Furthermore, in the three-dimensional double-branched concave hexagonal unit cell, the angle θ1 between the outer oblique wall of the unit cell and the vertical line is 16 degrees, the angle θ2 between the inner oblique wall of the unit cell and the vertical line is 30 degrees, the unit cell wall thickness t is 10 to 30 mm, and the horizontal side length h is 100 to 200 mm.

[0035] In the three-dimensional double-branched concave hexagonal unit cell, there are holes with a diameter of 5 to 10 mm in the middle of the eight vertical side oblique ribs, which are used for high-strength screws to pass through and fix adjacent unit cells.

[0036] The three-dimensional bi-branched concave hexagonal unit cell is 3D printed from high-strength and high-toughness fiber concrete material, with a compressive strength of over 100 MPa and an ultimate tensile strain of over 5%.

[0037] The raw materials for the lightweight foamed material are rapid-hardening silicate cement, 40-200 mesh quartz powder, 30% purity hydrogen peroxide, 7.0% calcium stearate, polycarboxylate superplasticizer, and water. The weight ratios of each component are as follows: cement: 150-200 parts, quartz powder: 100-130 parts, hydrogen peroxide: 10-13 parts, calcium stearate: 5-7 parts, polycarboxylate superplasticizer: 1.0-1.3 parts, and water: 125-165 parts.

[0038] The lightweight foamed material has a compressive strength of over 5 MPa and a density of 200-400 kg / m³. 3 The setting time is 10-15 minutes.

[0039] A method for fabricating a three-dimensional concave negative Poisson's ratio assembled composite protective structure based on 3D printing includes the following steps:

[0040] S1: Connect any two pre-printed three-dimensional negative Poisson ratio structural basic units to each other, align the pre-reserved holes in the middle of the side support diagonal ribs, and then pass the fastening screws through the holes and tighten them with nuts.

[0041] S2: Based on the actual structural size requirements, the basic units of the three-dimensional negative Poisson's ratio structure are sequentially arranged and repeated through spatial expansion to form a three-dimensional negative Poisson's ratio protective structure.

[0042] S3: After the assembled three-dimensional structure is supported by a formwork, the mixed cement-based lightweight foamed slurry is poured into the interior of the protective structure. After the foamed material has solidified and hardened, the formwork is removed and the structure is cured to the specified age.

[0043] Example 1

[0044] A 3D-printed structural unit exhibiting the Poisson's ratio effect, wherein the structural unit is a double-branched concave hexagonal unit cell, and the three-dimensional double-concave negative Poisson's ratio structure is a three-layered structure formed by rotating two double-branched concave hexagonal units 90 degrees along their long axis to form an orthogonal three-dimensional unit cell arranged in an orderly manner.

[0045] The lightweight concrete exhibiting the Poisson's ratio effect is composed of multiple 3D-printed units, each incorporating a lightweight foamed material. Eight vertical side ribs have 5-10 mm diameter holes in their center for high-strength screws to pass through and secure adjacent unit cells. The three-dimensional, double-concave, negative Poisson's ratio structure is arranged in a directional, ordered, and dense array.

[0046] A method for fabricating a three-dimensional concave negative Poisson's ratio prefabricated protective structure based on 3D printing, wherein the fabrication method is a prefabricated skeleton method, including the following steps:

[0047] (1) Preparation: Based on the requirements of the negative Poisson's ratio structural unit, its structure is printed using a 3D printer. The structure has holes with a diameter of 5 to 10 mm in the middle of its 8 vertical side support diagonal ribs, which are used for high-strength screws to pass through and fix adjacent unit cells. The 3D printed cell structure is then polished.

[0048] (2) Applying release agent: Applying a release agent to the surface of the precast steel reinforcement formwork to increase interfacial adhesion and deformation synergy; the primer is an epoxy resin primer.

[0049] (3) Casting: Lightweight concrete is mixed according to the concrete mix design and poured into the 3D printed three-dimensional concave negative Poisson's ratio structure template. After static curing, a 3D printed three-dimensional concave negative Poisson's ratio prefabricated protective structure unit with negative Poisson's ratio properties is obtained.

[0050] Comparative experiment: A standard 3D-printed structure (square) was used, with all other conditions the same as the 3D-printed three-dimensional concave negative Poisson's ratio structure.

[0051] In order to obtain the Poisson's ratio of the 3D-printed three-dimensional concave negative Poisson's ratio structure prepared according to the above method, the present application used the following method to test the test block.

[0052] (I) Testing Methods

[0053] Specimen preparation: Ordinary structural cubic lightweight concrete specimens with dimensions of 400mm×400mm×400mm and 400mm×400mm×400mm were prepared using the methods described in Examples 1-5. Simultaneously, control group specimens of the same dimensions were prepared, which were ordinary cubic cast concrete structures. The 400mm×400mm×400mm specimens were used for modulus and strength testing, while the 400mm×400mm×400mm specimens were used for Poisson's ratio testing.

[0054] The specific method for strength testing is as follows: Prepare test blocks with dimensions of 400mm×400mm×400mm. According to the national standard "Standard for Test Methods of Mechanical Properties of Ordinary Concrete" GB / T50081-2016, use a mechanical testing machine to measure its compressive strength and flexural strength. Each group of test blocks is measured three times and the average value is taken to obtain the final strength result.

[0055] The specific method for Poisson's ratio testing is as follows: Prepare a specimen with dimensions of 400mm × 400mm × 400mm, and load it using a mechanical testing machine. Stop loading when it reaches 60% of its maximum strength. Measure the transverse strain (εx) and longitudinal strain (εy) of the paste specimen at this point, and calculate the Poisson's ratio using the formula ν = -εx / εy. Given that the Poisson's ratio of ordinary cement-based materials (i.e., the cement specimen in the control group of this application) is 0.25, and the Poisson's ratio of the concave hexagonal negative Poisson's ratio structure is -0.5, the volume ratio of the negative Poisson's ratio structure in the paste specimen can be calculated.

[0056] The specific method for testing the energy absorption modulus is as follows: Prepare a specimen with dimensions of 400mm×400mm×1600mm, and perform a compression test on it along the axial direction using a mechanical testing machine to obtain the stress-strain (σ-ε) curve of the specimen. The maximum stress σ is known. m Then according to the formula The energy absorption modulus of the material is obtained.

[0057] Example 2

[0058] In order to obtain the Poisson's ratio of the 3D-printed three-dimensional concave negative Poisson's ratio structure prepared according to the above method, the present application used the following method to test the test block.

[0059] (I) Testing Methods

[0060] Specimen preparation: Ordinary structural cubic lightweight concrete specimens with dimensions of 400mm×400mm×400mm and 400mm×400mm×400mm were prepared using the methods described in Examples 1-5. Simultaneously, control group specimens of the same dimensions were prepared, which were ordinary cubic cast concrete structures. The 400mm×400mm×400mm specimens were used for modulus and strength testing, while the 400mm×400mm×400mm specimens were used for Poisson's ratio testing.

[0061] The specific method for strength testing is as follows: Prepare test blocks with dimensions of 400mm×400mm×400mm. According to the national standard "Standard for Test Methods of Mechanical Properties of Ordinary Concrete" GB / T50081-2016, use a mechanical testing machine to measure its compressive strength and flexural strength. Each group of test blocks is measured three times and the average value is taken to obtain the final strength result.

[0062] The specific method for Poisson's ratio testing is as follows: Prepare a specimen with dimensions of 400mm × 400mm × 400mm, and load it using a mechanical testing machine. Stop loading when it reaches 60% of its maximum strength. Measure the transverse strain (εx) and longitudinal strain (εy) of the paste specimen at this point, and calculate the Poisson's ratio using the formula ν = -εx / εy. Given that the Poisson's ratio of ordinary cement-based materials (i.e., the cement specimen in the control group of this application) is 0.25, and the Poisson's ratio of the concave hexagonal negative Poisson's ratio structure is -0.5, the volume ratio of the negative Poisson's ratio structure in the paste specimen can be calculated.

[0063] The specific method for testing the energy absorption modulus is as follows: Prepare a specimen with dimensions of 400mm×400mm×1600mm, and perform a compression test on it along the axial direction using a mechanical testing machine to obtain the stress-strain (σ-ε) curve of the specimen. The maximum stress σ is known. m Then according to the formula The energy absorption modulus of the material is obtained.

[0064] Example 3

[0065] The 3D-printed three-dimensional concave negative Poisson's ratio prefabricated protective structure includes a negative Poisson's ratio structure uniformly dispersed within it. The negative Poisson's ratio structure is a layered structure formed by the orderly arrangement of concave hexagonal unit cells. Each concave hexagonal unit cell includes two opposing angles, which are concave inwards towards the inside of the hexagon, with two parallel long sides on either side of the angles. Specifically, the orderly arrangement involves multiple concave hexagonal unit cells connected end-to-end, with their long sides overlapping in pairs, forming rows. Adjacent rows of concave hexagonal unit cells are staggered and connected by the overlapping sides of the angles, thus creating the layered structure. The volume ratio of the negative Poisson's ratio structure in the 3D-printed three-dimensional concave negative Poisson's ratio prefabricated protective structure is 40%.

[0066] A method for fabricating a three-dimensional concave negative Poisson's ratio prefabricated protective structure based on 3D printing, wherein the fabrication method is a prefabricated skeleton method, including the following steps:

[0067] (1) Preparation: Based on the requirements of the negative Poisson's ratio structural unit, its structure is printed using a 3D printer. The structure has holes with a diameter of 5 to 10 mm in the middle of its 8 vertical side support diagonal ribs, which are used for high-strength screws to pass through and fix adjacent unit cells. The 3D printed cell structure is then polished.

[0068] (2) Applying release agent: Applying a release agent to the surface of the precast steel reinforcement formwork to increase interfacial adhesion and deformation synergy; the primer is an epoxy resin primer.

[0069] (3) Casting: Lightweight concrete is mixed according to the concrete mix design and poured into the 3D printed three-dimensional concave negative Poisson's ratio structure template. After static curing, a 3D printed three-dimensional concave negative Poisson's ratio prefabricated protective structure unit with negative Poisson's ratio properties is obtained.

[0070] Comparative experiment: A standard 3D-printed structure (square) was used, with all other conditions the same as the 3D-printed three-dimensional concave negative Poisson's ratio structure.

[0071] The lightweight composite material is composed of rapid-hardening silicate cement, fine quartz powder, 30% pure hydrogen peroxide, 7.0% calcium stearate, polycarboxylate superplasticizer, and water. The weight proportions of each component are as follows: cement: 190 parts, quartz powder: 125 parts, hydrogen peroxide: 13 parts, calcium stearate: 7 parts, polycarboxylate superplasticizer: 1.3 parts, and water: 155 parts.

[0072] The preparation method of the lightweight composite material includes the following steps: (1) Pour the rapid-hardening silicate cement into the mixing device and stir at low speed for about 1 minute to make the mixture uniform; then slowly add an appropriate amount of water and continue stirring at low speed for 30 seconds to make the cement uniformly dispersed in the water; (2) Add polycarboxylate superplasticizer to the mixing device and stir at low speed for 30 seconds; (3) Continue stirring at high speed for 35 seconds, and add calcium stearate with a calcium content of 7.0% and quartz powder while stirring, switch to low speed stirring, continue stirring for 10 seconds, and then quickly pour it into a 3D printed three-dimensional concave negative Poisson ratio assembled protective structure mold. Then, move the test block to a cool and dry place for curing for a period of time (usually 24 hours). After the test block has a certain strength, remove the mold and send it to the curing room for curing until the test age to obtain concrete. Among them, the speed of low-speed stirring is 50 r / min, and the speed of high-speed stirring is 300 r / min.

[0073] The embodiments described in this specification are merely examples of implementations of the inventive concept and are for illustrative purposes only. The scope of protection of this invention should not be considered limited to the specific forms described in these embodiments; rather, it extends to equivalent technical means conceived by those skilled in the art based on the inventive concept.

Claims

1. A three-dimensional concave negative Poisson's ratio assembled composite protective structure based on 3D printing, characterized in that, It includes a three-dimensional double-branched concave hexagonal unit cell, a steel screw, and a lightweight foam material. The three-dimensional double-branched concave hexagonal unit cell is formed by rotating two double-branched concave hexagonal units 90 degrees along their major axis to create an orthogonal three-dimensional unit cell. The basic geometric parameters include the horizontal side length. h unit cell wall length l 1 Cell wall length within a unit l 2 The angle between the outer oblique wall of the unit cell and the vertical line θ 1 The angle between the oblique wall of the inner side of the unit cell and the vertical line θ 2 and cell wall thickness t Height of unit cell y and length x Then it is calculated by the following formula: ； The vertical side support diagonal ribs have holes in the middle for steel screws to pass through and fix adjacent unit cells. The lightweight foamed material is uniformly filled in the negative Poisson's ratio structure.

2. The 3D-printed, three-dimensional concave negative Poisson's ratio assembled composite protective structure as described in claim 1, characterized in that, In the three-dimensional double-branched concave hexagonal unit cell, the angle between the outer oblique wall of the unit cell and the vertical line is... θ 1 The angle is 16 degrees, the angle between the oblique wall of the inner side of the unit cell and the vertical line. θ 2 The temperature is 30 degrees Celsius, and the cell wall thickness is [missing information]. t The length is 10 to 30 mm, and the horizontal side length is... h It is 100 to 200 mm.

3. The 3D-printed three-dimensional concave negative Poisson's ratio assembled composite protective structure as described in claim 1 or 2, characterized in that, In the three-dimensional double-branched concave hexagonal unit cell, there are holes with a diameter of 5 to 10 mm in the middle of the eight vertical side oblique ribs, which are used for steel screws to pass through and fix adjacent unit cells.

4. The 3D-printed three-dimensional concave negative Poisson's ratio assembled composite protective structure as described in claim 1 or 2, characterized in that, The three-dimensional double-supported concave hexagonal unit cell is prepared by 3D printing of fiber-reinforced concrete material, with a compressive strength of over 100 MPa and an ultimate tensile strain of over 5%.

5. The 3D-printed three-dimensional concave negative Poisson's ratio assembled composite protective structure as described in claim 1 or 2, characterized in that, The raw materials for the lightweight foamed material are rapid-hardening silicate cement, 40-200 mesh quartz powder, 30% purity hydrogen peroxide, 7.0% calcium stearate, polycarboxylate superplasticizer, and water. The weight ratios of each component are as follows: cement: 150-200 parts, quartz powder: 100-130 parts, hydrogen peroxide: 10-13 parts, calcium stearate: 5-7 parts, polycarboxylate superplasticizer: 1.0-1.3 parts, and water: 125-165 parts.

6. The 3D-printed three-dimensional concave negative Poisson's ratio assembled composite protective structure as described in claim 5, characterized in that, The lightweight foamed material has a compressive strength of over 5 MPa and a density of 200-400 kg / m³. 3 The setting time is 10-15 minutes.

7. A method for fabricating a three-dimensional concave negative Poisson's ratio assembled composite protective structure based on 3D printing as described in claim 1, characterized in that, The method includes the following steps: S1: Connect any two pre-printed three-dimensional negative Poisson ratio structural basic units to each other, align the pre-reserved holes in the middle of the side support diagonal ribs, and then pass the fastening screws through the holes and tighten them with nuts. S2: Based on the actual structural size requirements, the basic units of the three-dimensional negative Poisson's ratio structure are sequentially arranged and repeated through spatial expansion to form a three-dimensional negative Poisson's ratio protective structure. S3: After the assembled three-dimensional structure is supported by a formwork, the mixed cement-based lightweight foamed slurry is poured into the interior of the protective structure. After the foamed material has solidified and hardened, the formwork is removed and the structure is cured to the specified age.

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