A UHPC array-type protective structure, its fabrication method and application

Abstract

This invention relates to a UHPC gradient protection array structure, its fabrication method, and its application. The array includes multiple stacked protective layers, each composed of multiple protective units. Adjacent protective layers are chemically anchored. The center of a protective unit in the outer protective layer is aligned with the intersection of four adjacent protective units in the inner protective layer. Each protective unit comprises multiple stacked unit layers, each composed of multiple parallel protective wires extending along a predetermined cosine function. These wires are arranged along the predetermined cosine function to form a bidirectional cosine corrugated structure. Along the direction from the outer to the inner side of the UHPC gradient protection array structure, the angle between the extension direction of the protective wires in the unit layer and a predetermined reference direction varies at predetermined angular intervals to form a continuous Briggs-like spiral structure. The protective structure of this invention exhibits strong stability and penetration resistance.

Description

Technical Field

[0001] This invention relates to the field of ultra-high performance concrete protective materials, specifically to a UHPC array-type protective structure, its preparation method, and its application. Background Technology

[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.

[0003] Ultra-high performance concrete (UHPC), with its extremely low water-cement ratio, optimized particle size distribution, and steel fiber toughening properties, achieves compressive strength and excellent durability far exceeding that of ordinary concrete, making it an ideal material for defense projects and the protection of important buildings. In extreme dynamic load conditions such as high-speed penetration, the high strength of UHPC is considered the first line of defense against damage.

[0004] However, existing UHPC protective structures exhibit significant performance bottlenecks when dealing with high-velocity kinetic energy projectiles. Studies show that the highly dense matrix of UHPC leads to its inherent brittle behavior. Under strong impact loads, cracks tend to propagate rapidly along the straight path of least resistance, easily inducing projectile fragmentation, back-surface delamination, and overall brittle fracture. Existing reinforcement methods mostly employ randomly distributed short-cut steel fibers, which can provide some bridging stress, but due to the lack of spatial topological order guidance, it is difficult to forcibly change the crack propagation direction on a macroscopic scale.

[0005] Academics have attempted to replicate the Brigham and Women's structure in the UHPC using 3D printing technology, but face significant engineering challenges. On one hand, the size of existing 3D-printed components is limited, making direct application to large-scale military fortifications difficult. On the other hand, discrete modular assembly often results in continuous straight seams, causing stress gaps at the module interfaces of the biomimetic spiral structure, failing to provide global protective resistance. Furthermore, the inherent anisotropic weak interfaces between layers in 3D printing, without effective penetration filling and interface reinforcement, are highly susceptible to becoming early failure points during impact resistance. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a UHPC array-type protective structure, its fabrication method, and its application, thereby solving the engineering challenges encountered when replicating the Brigan structure in a UHPC using 3D printing technology.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution: In a first aspect, embodiments of the present invention provide a UHPC array-type protective structure, including multiple stacked protective layers, each protective layer consisting of multiple protective units, adjacent protective layers being fixed by chemical anchoring, wherein the center of the protective unit in the outer protective layer is aligned with the intersection of four adjacent protective units in the inner protective layer, the protective unit comprising multiple stacked unit layers, each unit layer consisting of multiple parallel protective wires, the protective wires extending along a predetermined cosine function, the multiple protective wires being arranged along a predetermined cosine function so that the unit layer forms a bidirectional cosine corrugated structure, along the direction from the outer to the inner side of the UHPC array-type protective structure, the angle between the extension direction of the protective wires of the unit layer and the predetermined reference direction varies at predetermined angle intervals to form a continuous Briggs spiral structure.

[0008] Optionally, in the protective unit, the outermost unit layer, as the impact-receiving surface layer, is made of UHPC without hollow glass microspheres, and its weight composition is: 900-1100 parts cement, 180-250 parts silica fume, 120-200 parts fly ash, 500-700 parts fine quartz sand, 25-45 parts amorphous alloy microwires, 5-12 parts nano clay, 35-55 parts high-efficiency water-reducing agent, and 180-240 parts water.

[0009] Optionally, in the protective unit, apart from the outermost unit layer, the remaining unit layers serve as the core energy-consuming layer, which is made of UHPC doped with hollow glass microspheres. Its weight composition is as follows: 900-1100 parts cement, 180-250 parts silica fume, 120-200 parts fly ash, 500-700 parts fine quartz sand, 25-45 parts amorphous alloy microwires, 5-12 parts nano clay, 35-55 parts high-efficiency water-reducing agent, 180-240 parts water, and 150-300 parts hollow glass microspheres.

[0010] Optionally, the fine gaps between adjacent unit layers and between adjacent protective wires in the unit layer are filled with a cured energy-absorbing repair fluid.

[0011] Optionally, the energy-absorbing repair fluid may be a shear-thickening fluid, a viscoelastic polymer slurry, or a nanoparticle-modified epoxy resin.

[0012] Optionally, the set angle interval is 25°-35°, preferably 30°.

[0013] Optionally, the outer periphery of the protective unit is covered with a flexible polymer coating layer. The flexible polymer coating layer is made of a polymer with a set tensile elongation at break. Preferably, the flexible polymer coating layer is made of polyurea, polyurethane, elastic epoxy resin, or fiber-reinforced flexible composite material.

[0014] Optionally, adjacent protective units can be chemically anchored using a connecting coating with secondary hydration activity.

[0015] Secondly, embodiments of the present invention provide a method for fabricating the UHPC gradient protection array structure described in the first aspect, comprising the following steps: Multiple unit layers of the protective unit are printed sequentially using 3D printing to form the protective unit; At the construction site, multiple protective layers are laid sequentially on the surface of the object to be protected, from the inside out. When laying the current protective layer: First, the protective unit to be installed is positioned so that the center of the protective unit to be installed is aligned with the intersection of the four adjacent protective units in the completed protective layer. The extension direction of the protective wire of the innermost unit layer of the protective unit to be installed is at a set angle interval with the extension direction of the protective wire of the outermost unit layer of the completed inner protective layer. Then, the protective unit is chemically anchored to the laid protective layer.

[0016] Thirdly, embodiments of the present invention provide an application of the UHPC gradient protection array structure described in the first aspect in military fortifications, protective walls, individual blast shelters, and nuclear power plant shell reinforcement. The beneficial effects of this invention are as follows: 1. The UHPC gradient protection array structure of the present invention, along the direction from the outer to the inner side of the UHPC gradient protection array structure, the angle between the extension direction of the protective wire of the unit layer and the set reference direction varies at set angle intervals to form a continuous Briggs-like spiral structure, which forces the impact crack to undergo violent turning and bifurcation, significantly increasing the fracture energy and solving the technical problem of UHPC material being high-strength but brittle. At the same time, the protective layer of the protection array is composed of multiple protective units, which can be prefabricated in the factory and the protective layer can be assembled on site, greatly improving the rapid deployment capability and enabling 3D printing technology to be directly applied to large-scale military fortifications. Moreover, adjacent protective layers are fixed by chemical anchoring, wherein the center of the protective unit of the outer protective layer is aligned with the intersection of the four adjacent protective units in the inner protective layer. Combined with the self-locking effect of the bidirectional cosine corrugated structure of the unit layer, all through straight seams in the longitudinal and transverse directions of the protective structure are geometrically eliminated, forcing the impact energy to undergo multi-directional bifurcation and non-orthogonal reflection at the interface of the protective unit, greatly improving the overall stability and penetration resistance of the protective array structure.

[0017] 2. In the UHPC gradient protection array structure of the present invention, the outermost unit layer of the protection unit serves as the impact-receiving surface layer and is made of UHPC without hollow glass microspheres to form a high-strength UHPC matrix with good hardness. The remaining unit layers are made of UHPC doped with hollow glass microspheres to form a lightweight UHPC matrix with good toughness. The entire protection unit forms a gradient functional design. Combined with the filling of energy-absorbing repair fluid, it can induce shock wave attenuation by utilizing the wave impedance mismatch effect, thus achieving a balance between lightweight and ultra-high protection efficiency.

[0018] 3. In the UHPC gradient protection array structure of the present invention, adjacent protection units are chemically anchored and fixed by a connecting coating with secondary hydration activity, which transforms the physical contact of discrete modules into chemical bonding, ensuring the mechanical continuity of the array and the ability to prevent secondary damage under complex loads. Attached Figure Description

[0019] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0020] Figure 1 This is a schematic diagram of the overall structure of the protective structure of the present invention; Figure 2 This is a schematic diagram of the protective unit structure of the present invention; Figure 3 This is a schematic diagram of the outermost unit layer of the protective single layer of the present invention; Figure 4 This is a schematic diagram of the intermediate unit layer in the protection unit of the present invention; Figure 5 This is a schematic diagram of the innermost unit layer of the protective unit of the present invention; Detailed Implementation In one typical embodiment of this application, a UHPC array-type protection structure, such as Figure 1 As shown, it includes multiple protective layers, which are stacked along the thickness direction of the protective structure. Each protective layer is composed of multiple protective units, which have a square structure. The protective units of adjacent protective layers are staggered. In this embodiment, the center of the protective unit of the outer protective layer is aligned with the intersection of the four corresponding protective units of the inner protective layer. The protective units of each protective layer have the same structure. The protective unit is formed by stacking multiple unit layers along the thickness direction of the protective structure. The unit layer adopts a bidirectional cosine corrugated structure. The unit layer is composed of multiple protective wires arranged in parallel. The protective wires extend according to a set cosine function, and the multiple protective wires are arranged according to a set cosine function, so that the entire protective unit forms a bidirectional cosine corrugated structure.

[0021] For the entire array-type protection structure, along the direction from the outside to the inside of the UHPC array-type protection structure, the angle between the extension direction of the protective wire of the unit layer and the set reference direction varies at set angle intervals to form a continuous Briggan spiral structure.

[0022] The protective unit has a square planar projection, is a square structure with a side length of L, and its outer surface is a bidirectional cosine corrugated surface with 90° rotational geometric symmetry.

[0023] In this embodiment, such as Figure 2 As shown, the protective unit consists of three stacked unit layers along the thickness direction of the protective structure. Each unit layer is composed of multiple protective wires arranged in parallel. The protective wires extend along a predetermined cosine function, and the multiple protective wires are distributed along the predetermined cosine function, thus forming a bidirectional cosine corrugated structure. Its morphology follows a double cosine function.

[0024] Where A is the ripple amplitude, λ is the ripple wavelength, x is the horizontal axis coordinate, and y is the vertical axis coordinate; In this embodiment, a set direction is selected as the reference direction, and the angle between the extension direction of the protective wire of the three-layer unit layer and the reference direction changes at set angle intervals along the direction from the outside to the inside.

[0025] The angle interval is set to 25°-35°, preferably 30°.

[0026] Therefore, in this embodiment, such as Figures 3-5 As shown, the angle between the extension direction of the protective wire of the outermost unit layer and the reference direction is 0°, the angle between the extension direction of the protective wire of the middle unit layer and the reference direction is 30°, and the angle between the extension direction of the protective wire of the innermost unit layer and the reference direction is 60°.

[0027] The protective unit adopts a functional gradient structure design, with the outermost unit layer being the impact-bearing surface layer on the impact side, and the remaining unit layers being the core energy dissipation layer.

[0028] In this embodiment, the outermost unit layer serves as the anti-missile surface layer and is made of UHPC without hollow glass microspheres. It comprises the following components by weight: 900-1100 parts cement, 180-250 parts silica fume, 120-200 parts fly ash, 500-700 parts fine quartz sand, 25-45 parts amorphous alloy microwires, 5-12 parts nano clay, 35-55 parts high-efficiency water-reducing agent, and 180-240 parts water.

[0029] The remaining unit layers are made of UHPC incorporating hollow glass microspheres, which includes the following components by weight: 900-1100 parts cement, 180-250 parts silica fume, 120-200 parts fly ash, 500-700 parts fine quartz sand, 25-45 parts amorphous alloy microwires, 5-12 parts nano clay, 35-55 parts high-efficiency water-reducing agent, 180-240 parts water, and 150-300 parts hollow glass microspheres.

[0030] In this embodiment, the unit layer is prepared by 3D printing.

[0031] The cement is silicate cement; Preferably, the silicate cement is grade 52.5 or grade 52.5R silicate cement.

[0032] The fly ash is either Grade I or Grade II fly ash.

[0033] The fine silica sand has a fineness of 100-200 mesh. As a fine aggregate, the fine silica sand ensures excellent extrudability and density of the slurry in the narrow flow channels of 3D printing.

[0034] The amorphous alloy microwires have a diameter of 0.1–0.3 mm, a length of 10–20 mm, and an aspect ratio controlled at 50–80. Preferably, the amorphous alloy microwire is an iron-based amorphous alloy microwire or a cobalt-based amorphous alloy microwire to provide optimal magnetic permeability and high strength and toughness.

[0035] The nano-clay is an inorganic rheology modifier used to establish a thixotropic network in the slurry, ensuring that the interlayer of the 3D printed material does not collapse and forms a natural bond. Preferably, the nano-clay is modified montmorillonite or attapulgite.

[0036] The high-efficiency water-reducing agent is a polycarboxylate-based water-reducing agent.

[0037] The protective unit is further surrounded by a flexible polymer coating layer to achieve the designed thickness. This flexible polymer coating layer is a readily available polymer with a defined tensile elongation at break.

[0038] Preferably, the polymer flexible coating layer is made of polyurea, polyurethane, elastic epoxy resin, or fiber-reinforced flexible composite material.

[0039] The protective structure in this embodiment is composed of three layers of protection stacked together, with multiple protective units of the innermost layer closely arranged on the surface of the structure to be protected.

[0040] The protective units of the second protective layer are laid on the surface of the innermost protective layer, and for each protective unit of the second protective layer, the center of the protective unit is aligned with the intersection of the four protective units of the innermost protective layer.

[0041] In this embodiment, the protective units of the second protective layer and the adjacent protective units of the first protective layer are chemically anchored and fixed by a connecting coating with secondary hydration activity.

[0042] The protective unit of the outermost third protective layer is laid on the surface of the second protective layer. For the protective unit of the third protective layer, the center of the protective unit is aligned with the intersection of the four protective units of the second protective layer.

[0043] In this embodiment, the protective unit of the third protective layer and the adjacent protective unit of the second protective layer are chemically anchored and fixed by a connecting coating with secondary hydration activity.

[0044] For bonding coatings with secondary hydration activity, existing coatings can be used, such as epoxy resin bonding coatings doped with nano-silica.

[0045] In two adjacent protective layers, the protective unit of one layer is offset from the protective unit of the other layer by a distance D in both horizontal directions, where D = L / 2. This design ensures precise interlocking of the crests and troughs of the adjacent protective units. This stacking logic, combined with the corrugated interlocking relationship of the protective units, achieves significant gains in impact resistance: First, it completely eliminates the inherent longitudinal and lateral through-straight seams (weak channels) of the modular protective layers from a geometric topology perspective, fundamentally preventing the slippage and penetration of high-speed kinetic energy projectiles or metal jets along the seams. Second, bidirectional translation ensures that the geometric center of the upper-layer protective unit is precisely located at the intersection of the four lower-layer protective units. When the impact surface is subjected to a concentrated, strong impact load, this configuration forces the stress flow to be uniformly distributed laterally (45° direction). Finally, the staggered, overlapping interfaces, combined with the cosine corrugated surface, force the transmitted shock wave to undergo non-orthogonal reflection and multiple path bifurcations when passing through the protective unit interfaces, greatly improving the overall structural stability and resistance to multiple strikes of the discrete assembly array.

[0046] Along the direction from the outside to the inside of the UHPC array-type protective structure, the angle between the extension direction of the protective wires of the unit layer and the set reference direction varies at set angle intervals to form a continuous Briggan spiral structure.

[0047] In this embodiment, along the direction from the outside to the inside, the angles between the extension directions of the protective wires of the three unit layers of the outermost protective layer and the set reference direction are 0°, 30°, and 60°, respectively.

[0048] Correspondingly, along the direction from the outside to the inside, the angles between the extension directions of the protective wires of the three unit layers of the middle protective layer and the set reference direction are 90°, 120°, and 150°, respectively. That is, when the protective unit of the second protective layer is placed, it is equivalent to rotating the protective unit of the first protective layer by 90°.

[0049] The angles between the extension directions of the protective wires in the three unit layers of the outermost protective layer and the set reference direction are 180°, 210°, and 240°, respectively. That is, when the protective unit of the third protective layer is placed, it is equivalent to rotating the protective unit of the second protective layer by 90°.

[0050] In this way, the entire protective structure is constructed in the form of a Brigan spiral structure that mimics the limbs of a peacock mantis shrimp. The directional arrangement of the unit layers inside the protective unit focuses on the initial deflection and spiral twisting of the crack at the microscale. The protective units of adjacent protective layers are rotated 90° and stacked together to play a global relay role across the protective layers. This geometric configuration simulates the impact resistance mechanism of the limbs of a peacock mantis shrimp, forcing the crack to undergo extreme spatial deflection. By torturing the path, the fracture energy consumption is greatly increased, and the impact kinetic energy of the projectile is fully converted into localized non-catastrophic failure.

[0051] The protective unit in this embodiment also employs a gradient material configuration. The outermost unit layer uses a high-strength UHPC matrix without hollow glass microspheres to form a high-strength hard shell, which can effectively passivate and break the impact projectile, reducing the penetration damage of the projectile core into the deeper layers of the material. The middle and inner unit layers use a lightweight UHPC matrix containing hollow glass microspheres, which can absorb a large amount of residual kinetic energy through the phase transition collapse of the micro-airbags, forming a lightweight tough core. Multiple unit layers are stacked in the thickness direction, macroscopically forming a multilayer impedance mismatch system of alternating "high-strength hard shell - lightweight tough core". Although this system can cause strong reflection and dissipation of stress waves at the heterogeneous interface, traditional structures are prone to tensile delamination and macroscopic shear slip under this condition. This embodiment utilizes the geometric self-locking effect of the bidirectional cosine corrugated structure of the unit layer to forcibly transform lateral shear loads into vertical compressive loads on the corrugated slope. Combined with the cross-interface chemical bonding constructed by the connecting coating with secondary hydration activity between the protective units of the adjacent two protective layers, and the elastic buffering effect of the polymer flexible coating layer, it effectively resists the tearing effect of interfacial tensile waves and completely overcomes the mechanical defects of traditional multi-layer soft-hard alternating armor that are prone to interfacial disintegration and delamination.

[0052] In this embodiment, the gradient material of the unit layer and the overall Brigan helix structure of the protective structure work synergistically to achieve ultra-high protective energy efficiency and lightweight materials (density <1800kg / m³). 3 Optimization of ).

[0053] Furthermore, for a single protective unit, the micro-gaps between adjacent unit layers and between adjacent protective wires in a unit layer are filled with a cured energy-absorbing repair fluid. The energy-absorbing repair fluid is a fluid medium with shear thickening or high damping properties, and existing materials can be used.

[0054] Preferably, the energy-absorbing repair fluid is a shear-thickening fluid (STF), a viscoelastic polymer slurry, or a nanoparticle-modified epoxy resin.

[0055] The fabrication method of the UHPC array-type protective structure in this embodiment includes the following steps: Step (1): Prepare high-strength UHPC material without hollow glass microspheres and lightweight UHPC material with hollow glass microspheres respectively. Put each component into a high-shear mixer and mix evenly to obtain the corresponding slurry.

[0056] Step (2): Using the slurry prepared in step (1), the protective unit is prepared using a 3D printing device. According to the bidirectional cosine wave surface planning path, the nozzle outlet diameter is set to 20-25mm (preferably 25mm). The nozzle height is adjusted so that the single-layer printing height is strictly controlled at 0.6-0.8 times the nozzle outlet diameter (preferably 16mm). Utilizing the high shear induction effect, the outermost single-layer impact-resistant surface layer is first printed using high-strength UHPC slurry. Then, the process is continuously switched to lightweight UHPC slurry to print the middle and inner core energy consumption areas. The combination printing of three unit layers with the protective filament and the reference direction angles of 0° / 30° / 60° is completed in sequence to obtain a standard unit matrix with a total thickness of approximately 48mm. Step (3) Gap filling and surface coating treatment: After the protective unit has been hardened or semi-hardened, the energy-absorbing repair liquid is introduced into the micro gaps between the protective filaments and between adjacent unit layers by vacuum pressure infiltration, ultrasonic induced impregnation, or in-situ follow-up spraying process, using capillary action. After stabilization, a flexible polymer coating layer with a thickness of about 1 mm is wrapped on each of the two sides of the protective unit, so that the final standard thickness of the unit reaches 50 mm. Step (4): On-site assembly and chemical anchoring: At the construction site, multiple protective layers are laid sequentially on the surface of the object to be protected, from the inside out. When laying the current protective layer: First, the protective unit to be installed is positioned so that the center of the protective unit to be installed is aligned with the intersection of the four adjacent protective units in the completed protective layer. That is, the outer protective unit and the corresponding inner protective unit are equivalent to a translation distance D. The translation distance D and the wavelength λ of the bidirectional cosine corrugated surface satisfy the functional relationship D=n·λ / 2 (where n is a positive integer). There is a 30° angular gap between the extension direction of the protective wire of the innermost unit layer of the protective unit to be installed and the extension direction of the protective wire of the outermost unit layer of the inner protective layer that has been laid. That is, after the outer protective unit and the inner protective unit keep their postures consistent, they are rotated 90° for laying.

[0057] Then, a bonding coating with secondary hydration activity is applied to the surface of the protective unit that is to be connected to the laid protective layer, thereby chemically anchoring and fixing the protective unit to the laid protective layer.

[0058] In step (2), by setting the nozzle diameter and using a lamination pressure flattening coefficient of 0.6-0.8, the resulting extrusion stretching force, combined with the high shear induction of the flow field, forces amorphous alloy microfilaments with a length of 10-20 mm to achieve a height orientation greater than 90% along the printing path, avoiding nozzle clogging and maximizing the bridging and toughening effect of the fibers. At the same time, a perfect physical and geometric closed loop is achieved between the micro-rheological extrusion parameters, the functional gradient boundary line, and the macro-module standard size of 50 mm.

[0059] This embodiment also provides the application of the UHPC array-type protective structure in military fortifications, protective walls, individual blast shelters, and nuclear power plant shell reinforcement. The above-mentioned protective structure is provided on the impact-facing surface of military fortifications and individual blast shelters, on the stress-bearing surface of protective walls, and on the surface of nuclear power plant shells.

[0060] To enable those skilled in the art to more clearly understand the technical solution of this application, the technical solution of this application will be described in detail below with reference to specific embodiments and comparative examples. The raw materials and equipment used in this embodiment are all known products. This embodiment does not have special restrictions on the source of raw materials used in the following embodiments; commercially available products well-known to those skilled in the art can be used.

[0061] Example 1 A UHPC array-type protective structure includes 3D-printed protective units made of gradient materials and the protective structure composed of them. The total thickness of the protective structure is 150mm, and it is composed of 3 layers of protective units (side length L=250mm, total thickness of a single layer 50mm) arranged and stacked in a staggered manner according to a 1-4-9 step number.

[0062] Detailed configuration of the protective unit's geometry and structure: The amplitude A of the bidirectional cosine corrugated surface on the outer surface is 5mm, and the wavelength λ is 125mm. x is the horizontal axis coordinate, and y is the vertical axis coordinate. The protective unit contains three layers of printing paths, employing a Briggs spiral layup strategy. The angles between the oriented protective wires and the reference direction are 0°, 30°, and 60° from bottom to top, respectively. To simulate the hardness gradient of the mantis shrimp's impact zone, the protective unit uses a functionally graded (FGM) material: the impact-receiving layer (16mm thick, corresponding to the bottom 0° printing path) uses a high-strength UHPC matrix without hollow glass microspheres; the core energy dissipation zone (32mm thick, corresponding to the middle and upper 30° / 60° printing paths) uses a lightweight UHPC substrate with a high content of hollow glass microspheres. A 1mm thick polyurea coating is sprayed onto each of the two sides of the protective unit, forming a standard thickness of 50mm.

[0063] UHPC matrix composition: (1) High-strength UHPC matrix (bomb-resistant surface layer): 1000 parts of 52.5 grade silicate cement, 200 parts of silica fume, 150 parts of grade I fly ash, 600 parts of 200-mesh fine quartz sand, 35 parts of iron-based amorphous alloy microwires (0.2 mm in diameter and 15 mm in length), 8 parts of modified montmorillonite, 45 parts of polycarboxylate superplasticizer, and 200 parts of water. (2) Lightweight UHPC matrix (core energy consumption area): Based on the above high-strength UHPC matrix composition, an additional 200 parts of hollow glass microspheres (HGMs) are added.

[0064] Its preparation method is as follows: (1) The dry powder components of the high-strength slurry and the lightweight slurry were stirred and mixed separately. Some water and water-reducing agent were added and stirred evenly. Then, amorphous alloy microwires and modified montmorillonite were added and stirred evenly to obtain two mixtures with thixotropic properties.

[0065] (2) A 3D printing device with a nozzle outlet diameter of 25mm was used, and the nozzle height was adjusted to set the single-layer printing height to 16mm. According to the double cosine surface planning path with wavelength λ=125mm, the high-strength UHPC slurry was first used to print the impact surface layer, and then the lightweight UHPC slurry was continuously switched to complete the core energy consumption area. The three-layer unit layer combination printing with the protective wire and the reference direction angle of 0° / 30° / 60° was completed in sequence. After curing at room temperature for 24h, it was subjected to high-temperature steam curing at 85℃ for 48h to obtain the protective unit.

[0066] (3) Shear thickening fluid (STF) is introduced into the gap between the filaments formed by 3D printing through vacuum pressure infiltration process, and then a 1 mm thick polyurea coating layer is sprayed on each of the two sides of the protective unit.

[0067] (4) At the assembly site, epoxy resin bonding coating doped with nano-silica is first applied to the lateral corrugated connection surfaces of each unit. Then, the protective units are arranged sequentially from the outer side (projectile-facing surface) to the inner side (projectile-rearing surface) in arrays of 1, 4, and 9 units. In adjacent layers of protective units, the outer layer of protective units is translated by 125mm in both the x and y axes relative to the inner layer of protective units (satisfying D=n·λ / 2, where n=2) and rotated by 90° to achieve bidirectional staggered stacking. The physical interlocking force of the stacked pressing down is used to fully squeeze and wet the bonding coating in the micro-interface, completing the chemical anchoring.

[0068] Example 2 The only difference between this embodiment and Embodiment 1 is that the wavelength of the bidirectional cosine corrugated surface is adjusted to λ = 250 mm. During assembly, the misalignment translation of each layer in the x and y directions remains at 125 mm, satisfying the misalignment matching formula D = n·λ / 2 (where n = 1). Based on the geometric characteristics of the bidirectional cosine surface, which overlaps in phase after simultaneous bidirectional translation by half a wavelength and rotation by 90°, the modules of each layer can still achieve precise physical interlocking under these parameters. The remaining structural parameters, material ratios, and fabrication processes are exactly the same as in Embodiment 1.

[0069] Comparative Example 1: Equal Mass Polyurea-Coated Integral Cast UHPC Target Plate The difference between this comparative example and Example 1 is that it does not employ modular assembly, nor does it include an internally printed spiral path or a bidirectional corrugated surface. It directly uses the "high-strength UHPC matrix" formulation from Example 1. To maintain a similar overall structural size to Example 1, this comparative example uses a solid, homogeneous target plate with dimensions of 540mm × 540mm × 150mm, formed by integral casting. Both the projectile-facing and projectile-repellent surfaces of this target plate are coated with a 1mm thick polyurea coating layer, identical to that in Example 1, but without the internal STF penetration filling and chemical anchoring interface.

[0070] Comparative Example 2: Array without macroscopic spiral (translation but no rotation) The difference between this comparative example and Example 1 is that after the pre-coating of the connecting paint on-site, the protective units are still stacked with a staggered logic, shifted 125mm in both the x and y axes, but the 90° physical rotation between adjacent layers is eliminated. Although this array achieves corrugated geometric interlocking and staggered joints, it loses the global Brigand spiral relay mechanism in the thickness direction (the internal path of each protective unit only repeats in the 0°-60° range).

[0071] Comparative Example 3: Array without microscopic spirals (with rotation but no internal spirals) The difference between this comparative example and Example 1 is that the 30° spiral stepping strategy of the protective filaments inside the 3D printed protective unit is eliminated. The three printing paths within the protective unit are all set to be parallel with an angle of 0° relative to the reference direction. During assembly, the array is still stacked according to Example 1, with a translation of 125mm and a rotation of 90°. Macroscopically, this array degenerates into a simple 0° / 90° orthogonal laminated structure, which is prone to abrupt changes in stiffness, rather than a biomimetic continuous spiral network.

[0072] Comparative Example 4: Non-gradient material (all lightweight) array The difference between this comparative example and Example 1 is that the functional gradient (FGM) design of the 16mm hard shell and 32mm tough core of the single protective unit is cancelled, and all three layers of the substrate are printed using a "lightweight UHPC substrate" doped with 200 parts of hollow glass microspheres.

[0073] Comparative Example 5: Energy-absorbing filler and chemical anchoring array The difference between this comparative example and Example 1 is that the vacuum pressure permeation STF treatment in step (3) is cancelled; and during assembly in step (4), no connecting coating with secondary hydration activity is applied, and the modules are stacked together by dry physical staggered joints only by bidirectional cosine corrugated surfaces.

[0074] Experimental Example The protective structures of Examples 1, 2 and Comparative Examples 1-5 were tested for their resistance to high-speed projectile penetration. The test method included the following steps: Step 1: The test object is prepared as the 1-4-9 stepped array target described in this embodiment. The base dimensions are 750×750mm², the top dimensions of the projectile-facing surface are 250×250mm², and the total thickness in the ballistic direction is 150mm. To simulate actual armor boundary conditions, a lightweight aluminum alloy frame is used to constrain the array. A pointed oval projectile with a diameter of 28mm is used, and the projectile material is 30CrMnSi2A high-strength alloy steel (yield strength 1466MPa, ultimate strength 1770MPa, Rockwell hardness 55HRC).

[0075] Step 2: Launch the projectile using a first-stage light air cannon (or gun barrel) to strike the geometric center of the target's frontal surface (first layer of protection unit) vertically. The target impact velocity is set to be controlled at 400±10m / s. During the process, a high-speed camera installed on the side of the trajectory is used to capture the projectile's penetration process and the dynamic sliding response of the target's side to obtain relevant kinematic parameters.

[0076] Step 3: By measuring the residual velocity of the projectile on the target, the crater area on the back surface, the target mass loss rate, and the array structure integrity level, the penetration resistance and cooperative stress state of the target material are comprehensively evaluated. In the table, the target mass loss rate is calculated as the percentage of all debris collected and weighed after firing, representing the initial total mass of the target. The lower this value, the stronger the resistance to collapse and cracking. Array structure integrity is graded into four levels based on the corrugated self-locking state and slippage between modules: Level I (Excellent): The array is intact, with no macroscopic slippage between layers, no module detachment, and only local damage in the impact area. Level II (Good): The structure remains stable, with slight lateral slippage between modules (slippage displacement <5mm), and the corrugated self-locking remains effective. Level III (Medium): Significant lateral slippage and debonding occur between layers (slippage displacement 5~15mm), boundary modules become loose, but overall disintegration does not occur. Level IV (Poor): The ripple self-locking mechanism completely fails, and the module is severely misaligned, scattered, or the array disintegrates.

[0077] Table 1. Test results of resistance to high-speed projectile penetration.

[0078] As shown in Table 1, Example 1 demonstrates the excellent anti-projectile penetration performance of the array-type protective structure. With a target thickness of 150 mm, the residual velocity of the projectile in Example 1 is only 142.5 m / s, significantly lower than the other examples. This indicates that the array, through the synergistic effect of the "1-4-9" stepped configuration, the Bouligand spiral printing path, and the bidirectional cosine wave geometric self-locking, exhibits superior impact energy absorption capabilities, effectively reducing the projectile's penetration kinetic energy. Furthermore, Example 1 shows an extremely low target mass loss rate (only 1.5%), with the crater damage area on the back surface controlled at 19800 mm². Although the target sustained some damage upon impact, compared to the other examples, the damage area on the back surface was significantly localized. This fully demonstrates the structure's extremely high impact toughness and ability to suppress fragmentation (collapse) under the combined effect of polyurea coating and STF (shear-thickening liquid) filling, verifying the array's excellent damage localization and synergistic self-locking characteristics.

[0079] Example 2 increased the wavelength of the bidirectional cosine wave (λ=250mm), resulting in a residual velocity of 148.6m / s, slightly higher than Example 1. Although its target mass loss rate (1.8%) remained low and the damage area on the back surface was similar to that of Example 1, the increased wavelength led to a decrease in the density of engagement nodes between wave crests and troughs per unit area, weakening the energy dissipation efficiency of the mechanical engagement between structural layers. Therefore, its overall penetration resistance, while slightly inferior to Example 1, was still significantly better than Comparative Examples 1-5.

[0080] Comparative Example 1 did not employ a modular stepped configuration and a biomimetic corrugated self-locking interface; it only used a monolithically cast homogeneous solid plate of equal mass. Test results showed that, under the same thickness and polyurea coating conditions, its residual velocity reached as high as 188.4 m / s, the mass loss rate increased to 3.5%, and the damage area on the projectile's back surface expanded to 31200 mm². This indicates that traditional solid homogeneous plates have significant shortcomings in stress wave dispersion, reducing the kinetic energy of high-speed projectiles, and resisting fragmentation.

[0081] Comparative Examples 2 and 3 eliminated the 90° rotation between macroscopic layers and the spiral printing path at the microscopic level, respectively. Although both still possessed some corrugated self-locking or macroscopic deflection effects, their residual velocities were 172.3 m / s and 162.1 m / s, respectively. While these figures were better than those of the homogeneous solid plate, they were still significantly higher than those of Example 1. This indicates that without the coordination of "global spiral relay" or "internal wire torsion," simple corrugated translation or macroscopic rotation has very limited effect on improving ballistic performance. The corresponding increase in target mass loss rate and the damage area of ​​the back surface further highlights the significant gap between them and Example 1 in terms of interlayer shear resistance and microscopic crack resistance.

[0082] Comparative Example 4, a completely lightweight structure without material gradients, resulted in a residual velocity surge to 248.5 m / s; Comparative Example 5, a corrugated dry-jointed structure without polyurea coating and STF filling, had a residual velocity of 215.2 m / s. The extreme tests of these two single-variable sets show that the lack of "hardness gradation" significantly weakens the projectile passivation effect, while the absence of polyurea and STF results in the loss of "dynamic confining pressure constraint," with both exhibiting kinetic energy dissipation efficiencies far lower than in Example 1. Comparative Example 5, in particular, showed significant structural loosening and back collapse under intense impact loads, with its mass loss rate soaring to 12.6%.

[0083] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A UHPC gradient protection array structure, characterized in that, The system includes multiple stacked protective layers, each consisting of multiple protective units. Adjacent protective layers are fixed by chemical anchoring. The center of the protective unit in the outer protective layer is aligned with the intersection of four adjacent protective units in the inner protective layer. The protective unit includes multiple stacked unit layers, each consisting of multiple parallel protective wires. The protective wires extend along a set cosine function, and the multiple protective wires are arranged along the set cosine function to form a bidirectional cosine corrugated structure in the unit layer. Along the direction from the outside to the inside of the UHPC gradient protective array structure, the angle between the extension direction of the protective wires in the unit layer and the set reference direction varies at set angle intervals to form a continuous Briggs spiral structure.

2. The UHPC gradient protection array structure as described in claim 1, characterized in that, In the protective unit, the outermost unit layer serves as the bomb-receiving surface layer. It is made of UHPC without hollow glass microspheres, and its weight composition is as follows: 900-1100 parts cement, 180-250 parts silica fume, 120-200 parts fly ash, 500-700 parts fine quartz sand, 25-45 parts amorphous alloy microwires, 5-12 parts nano clay, 35-55 parts high-efficiency water-reducing agent, and 180-240 parts water.

3. The UHPC gradient protection array structure as described in claim 1, characterized in that, In the protective unit, except for the outermost unit layer, the remaining unit layers serve as the core energy-consuming layer. They are made of UHPC with hollow glass microspheres incorporated into them. The weight composition is as follows: 900-1100 parts cement, 180-250 parts silica fume, 120-200 parts fly ash, 500-700 parts fine quartz sand, 25-45 parts amorphous alloy microwires, 5-12 parts nano clay, 35-55 parts high-efficiency water-reducing agent, 180-240 parts water, and 150-300 parts hollow glass microspheres.

4. The UHPC gradient protection array structure as described in claim 1, characterized in that, In the protective unit, the fine gaps between adjacent unit layers and between adjacent protective wires in the unit layer are filled with solidified energy-absorbing repair fluid.

5. The UHPC gradient protection array structure as described in claim 2, characterized in that, The energy-absorbing repair fluid uses shear-thickening fluid, viscoelastic polymer slurry, or nanoparticle-modified epoxy resin.

6. The UHPC gradient protection array structure as described in claim 1, characterized in that, The set angle interval is 25°-35°, preferably 30°.

7. The UHPC gradient protection array structure as described in claim 1, characterized in that, The outer periphery of the protective unit is covered with a flexible polymer coating layer. The flexible polymer coating layer is made of a polymer with a set tensile elongation at break. Preferably, the flexible polymer coating layer is made of polyurea, polyurethane, elastic epoxy resin, or fiber-reinforced flexible composite material.

8. The UHPC gradient protection array structure as described in claim 1, characterized in that, Adjacent protective units are chemically anchored and fixed using a connecting coating with secondary hydration activity.

9. A method for fabricating a UHPC gradient protection array structure according to any one of claims 1-8, characterized in that, Includes the following steps: Multiple unit layers of the protective unit are printed sequentially using 3D printing to form the protective unit; At the construction site, multiple protective layers are laid sequentially on the surface of the object to be protected, from the inside out. When laying the current protective layer: First, the protective unit to be installed is positioned so that the center of the protective unit to be installed is aligned with the intersection of the four adjacent protective units in the completed protective layer. The extension direction of the protective wire of the innermost unit layer of the protective unit to be installed is at a set angle interval with the extension direction of the protective wire of the outermost unit layer of the completed inner protective layer. Then, the protective unit is chemically anchored to the laid protective layer.

10. The application of the UHPC gradient protection array structure according to any one of claims 1-8 in military fortifications, protective walls, individual blast shelters, and nuclear power plant shell reinforcement.

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