A concave folded shell-composite truss lattice core integrated energy-absorbing metamaterial structure
By setting an integrated structure of concave folded shell-composite truss lattice core inside the thin-walled shell, the instability problem of the combined structure of thin-walled shell and lattice core under axial load is solved, realizing the coordinated deformation and efficient energy absorption of shell and lattice core, and adapting to various working conditions.
Patent Information
- Application Number
- CN202611232706.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-14
- Publication Date
- 2026-11-06
AI Technical Summary
Existing thin-walled shell and lattice core combined structures suffer from unstable folding positions, concentrated local deformation, or lateral instability when subjected to axial loads. Furthermore, the lateral constraints of the outer peripheral members are limited, making it difficult to fully leverage the synergistic effect of the shell and lattice core.
Design an integrated energy-absorbing metamaterial structure of concave folded shell and composite truss lattice core. By setting a composite truss lattice core inside the outer thin-walled square shell, the axial repeating period length of the concave folded unit corresponds to the axial dimension of the composite truss lattice unit cell, and is integrally connected with the outer peripheral rods within the shell wall thickness range to form a multi-path force transmission network. The structure is integrally formed using metal additive manufacturing process.
It improves the stability and energy absorption capacity of the shell-core composite structure during compression deformation, avoids local instability caused by deformation incoordination, enhances the overall synergy of the structure and the energy absorption capacity per unit mass, and adapts to different buffering, protection and energy absorption working conditions.
Smart Images
Figure CN123044613A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the fields of metal additive manufacturing, lightweight structures and energy-absorbing protection technology, and in particular to an integrated energy-absorbing metamaterial structure of a concave folded shell-composite truss lattice core. Background Technology
[0002] Thin-walled shells, honeycomb structures, and lattice structures can be used for buffering, protection, and energy dissipation components. Thin-walled square shells are characterized by their regular shape, ease of arrangement, and high initial load-bearing capacity, but they may experience unstable folding positions, concentrated local deformation, or lateral instability under axial loads.
[0003] Lattice cores are lightweight and their structural response can be adjusted through unit cell topology and array configurations. When used alone, conventional lattice cores offer relatively limited lateral constraints on their peripheral members. When combined with an outer shell, if there is a lack of clear correspondence between the shell's folding period, the lattice unit cell height, and the shell-core interface, the synergy between the shell deformation and the lattice core deformation is insufficient, making it difficult to fully utilize the combined effect of shell constraints and the force transmission path of the lattice core.
[0004] Therefore, it is necessary to provide a metamaterial structure that can be synergistically constructed through concave folded units, composite truss lattice unit cells, and shell-core integrated connection to improve the load-bearing stability and energy absorption adaptability of the shell-core composite structure. Summary of the Invention
[0005] The purpose of this invention is to provide an integrated energy-absorbing metamaterial structure of concave folded shell-composite truss lattice core to solve the problems existing in the prior art.
[0006] To achieve the above objectives, the present invention provides an integrated energy-absorbing metamaterial structure of a concave folded shell and a composite truss lattice core, comprising an outer thin-walled square shell and a composite truss lattice core disposed inside the outer thin-walled square shell. The sidewalls of the outer thin-walled square shell are provided with concave folded units that are repeatedly distributed along the axial direction. The composite truss lattice core is formed by an array of multiple composite truss lattice unit cells in a three-dimensional direction. The axial repeating period length of the concave folded units corresponds to the axial dimension of the composite truss lattice unit cells. The members in the composite truss lattice core that intersect with the shell wall are integrally connected to the shell wall within the shell wall thickness range.
[0007] Preferably, the concave folded unit is composed of two folded surfaces that are inclined towards each other, and a concave valley line is formed in the axial middle of the unit cell of the composite truss lattice, which is located in the axial middle of the corresponding composite truss lattice unit cell.
[0008] Preferably, the composite truss lattice unit cell includes corner nodes located at the vertices of the cube, face-centered nodes located at the face centers of the cube, frame members connecting adjacent corner nodes, face-centered diagonal members connecting the face-centered nodes to the corner nodes of the corresponding faces, and inscribed octahedral members connecting adjacent face-centered nodes.
[0009] Preferably, the outer peripheral members of the composite truss lattice core are integrally connected to the shell wall of the outer thin-walled square shell in the intersecting connection area, the intersecting connection area is within the wall thickness range of the shell wall, and the outer peripheral members do not protrude beyond the outer surface of the outer thin-walled square shell.
[0010] Preferably, the angle formed by the two opposing inclined surfaces in the concave folded surface unit and the axial direction is α, the concave depth of the concave valley line relative to the adjacent convex ridge line is h, and the axial repeating period length of the concave folded surface unit is P, satisfying h=(P / 2)tanα.
[0011] Preferably, the composite truss lattice unit cell is a cubic unit cell, and the axial repeating period length P of the concave faceted element is related to the axial dimension a of the composite truss lattice unit cell. z Satisfying P=a z .
[0012] Preferably, the cross-sections of the frame members, face-centered diagonal members, and inscribed octahedral members of the composite truss lattice unit cell are all circular, and the member diameter d and the wall thickness t of the outer thin-walled square shell satisfy 0.5≤d / t≤1.
[0013] Preferably, the outer thin-walled square shell, the composite truss lattice core, and the intersecting connection areas are integrally formed in the same construction process using a metal additive manufacturing process.
[0014] Preferably, the angle α formed by the two opposing inclined folds and the axial direction ranges from 5° to 30°, the size of the composite truss lattice unit cell ranges from 10 mm to 30 mm, and the rod diameter d and the wall thickness t both range from 1 mm to 3 mm.
[0015] Preferably, the frame members, the face-centered diagonal members, and the inscribed octahedral members together constitute the multi-path force transmission network of the composite truss lattice unit cell. The outer thin-walled square shell provides boundary constraints for the composite truss lattice core, and the composite truss lattice core provides internal support for the concave folded surface unit.
[0016] Compared with the prior art, the present invention has the following advantages and technical effects: The present invention provides an integrated energy-absorbing metamaterial structure of a concave folded shell and a composite truss lattice core. The outer thin-walled square shell is provided with concave folded units that are repeatedly distributed along the axial direction, and the axial repeating period length of the concave folded units corresponds to the axial dimension of the composite truss lattice unit cell. Therefore, the outer thin-walled square shell has a predetermined local deformation region under axial compression, so that the folding deformation region of the outer shell corresponds to the axial position of the inner lattice core unit cell layer, which is beneficial to improving the stability of the shell-core composite structure during compression deformation.
[0017] The composite truss lattice unit cell of the present invention includes frame members, face-centered diagonal braces, and inscribed octahedral members, which can form a multi-path force transmission network jointly participated in by the outer frame bearing, in-plane diagonal braces, and internal diagonal members. This allows the internal lattice core to have more members participating in bearing and deformation energy dissipation during axial compression, which is beneficial to improving the energy absorption capacity per unit mass of the structure.
[0018] In this invention, the members intersecting the outer thin-walled square shell are integrally connected to the shell wall within the shell wall thickness range and do not protrude beyond the outer surface of the outer thin-walled square shell. This creates a continuous intersecting connection area and force transmission path between the outer thin-walled square shell and the composite truss lattice core. The outer thin-walled square shell provides boundary constraints for the composite truss lattice core, and the composite truss lattice core provides internal support for the concave folded surface units, thereby improving the load-bearing stability and overall synergy of the shell-core integrated structure during compression energy absorption.
[0019] This invention allows for adjustment of structural response by parameters such as concave angle, unit cell size, rod diameter, shell wall thickness, array quantity, and volume fraction, enabling the structure to adapt to different buffering, protection, and energy absorption requirements. Furthermore, this invention can be integrally formed during the same construction process using metal additive manufacturing, eliminating the need for independent mechanical fasteners, adhesive layers, or subsequent assembly connectors. This helps avoid discontinuities in connections caused by assembly interfaces and is suitable for the integrated manufacturing of complex concave folded shells and internal lattice topologies. Attached Figure Description
[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention.
[0021] Figure 1 This is a schematic diagram of the overall structure of the integrated energy-absorbing metamaterial structure of the concave folded shell-composite truss lattice core of the present invention.
[0022] Figure 2 This is a three-dimensional structural diagram of the composite truss lattice unit cell of the present invention.
[0023] Figure 3This is a schematic diagram showing the axial correspondence between the concave folded surface unit and the composite truss lattice unit cell layer of the present invention.
[0024] Figure 4 for Figure 3 A partially enlarged schematic diagram of the area where the outer peripheral member at point A intersects and is integrally connected with the outer thin-walled square shell.
[0025] Figure 5 This is a comparison diagram of the compressive stress-strain curves of the structure of the present invention, the straight-walled shell control structure, and the simplified core control structure under axial compression conditions.
[0026] Figure 6 This is a comparison diagram of the absorbed energy and specific absorbed energy of the structure of this invention, the straight-walled shell control structure, and the simplified core control structure.
[0027] In the figure: 1. Outer thin-walled square shell; 11. Concave folded element; 2. Composite truss lattice core; 21. Composite truss lattice unit cell; 211. Corner node; 212. Face-centered node; 213. Frame member; 214. Face-centered diagonal member; 215. Inscribed octahedral member; 3. Intersecting connection area. Detailed Implementation
[0028] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other. The described embodiments are merely some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. The invention will now be described in detail with reference to the accompanying drawings and embodiments.
[0029] like Figures 1 to 4 As shown, this invention provides an integrated energy-absorbing metamaterial structure of a concave folded shell and a composite truss lattice core, comprising an outer thin-walled square shell 1 and a composite truss lattice core 2 disposed inside the outer thin-walled square shell 1. With the height direction of the structure as the axial z-direction, the four sidewalls of the outer thin-walled square shell 1 are each composed of multiple concave folded units 11 arranged repeatedly along the z-direction. Each concave folded unit 11 consists of two opposing inclined folds, forming a concave valley line towards the composite truss lattice core 2 at the axial center. The composite truss lattice core 2 is formed by an array of multiple composite truss lattice unit cells 21 arranged along the x, y, and z orthogonal directions. The axial repeating period length P of the concave folded unit 11 is related to the axial dimension a of the composite truss lattice unit cell 21. zCorrespondingly, the concave valley line is located at the axial center of the corresponding composite truss lattice unit cell layer. The outer peripheral members of the composite truss lattice core 2 near the outer thin-walled square shell 1 geometrically intersect with the outer thin-walled square shell 1 and are integrally connected with the shell wall within the intersection connection area 3. The intersection connection area 3 is located within the wall thickness t of the shell wall. The outer peripheral members do not protrude beyond the outer surface of the outer thin-walled square shell 1, and the outer surface of the final structure is defined by the outer surface of the outer thin-walled square shell 1.
[0030] By setting concave folded surface units 11 that are repeatedly distributed along the axial direction on the outer thin-walled square shell 1, and setting the axial repeating period length of the concave folded surface units 11 to correspond to the axial dimension of the composite truss lattice unit cell 21, the outer thin-walled square shell 1 can have a preset local deformation area when subjected to axial compression. This makes the folding deformation area of the outer shell and the inner lattice core unit cell layer form a one-to-one correspondence in axial position, which is beneficial to improving the overall stability of the shell-core composite structure during compression deformation and avoiding local instability and sudden drop in load-bearing capacity caused by deformation incoordination. Meanwhile, by integrally connecting the outer peripheral members of the composite truss lattice core 2 that intersect with the shell wall within the shell wall thickness range, and without penetrating the outer surface of the outer thin-walled square shell 1, a continuous solid force transmission path can be formed between the outer thin-walled square shell 1 and the composite truss lattice core 2. The outer thin-walled square shell 1 can provide effective boundary constraints for the composite truss lattice core 2, and the composite truss lattice core 2 can provide internal support for the concave folded surface unit 11, thereby improving the load-bearing stability and overall synergy of the shell-core integrated structure during the compression energy absorption process.
[0031] Further optimizing the technical solution, the composite truss lattice unit cell 21 includes eight corner nodes 211 located at the eight vertices of the cube, six face-centered nodes 212 located at the centers of the six faces of the cube, twelve frame members 213 connecting adjacent corner nodes 211, twenty-four face-centered diagonal members 214 formed by connecting each face-centered node 212 with the four corner nodes 211 of its respective face, and twelve inscribed octahedral members 215 connecting adjacent face-centered nodes 212. The frame members 213, face-centered diagonal members 214, and inscribed octahedral members 215 together constitute the multi-path truss lattice unit cell 21.
[0032] By simultaneously incorporating frame members 213, face-centered diagonal braces 214, and inscribed octahedral members 215 into the composite truss lattice unit cell 21, a multi-path force transmission network can be formed, involving the outer frame bearing, in-plane diagonal bracing, and internal diagonal members. This allows the internal lattice core to have more members participating in bearing and deformation energy dissipation during axial compression, thereby improving the structure's energy absorption capacity per unit mass. Frame members 213 constitute the external frame of the unit cell, bearing the main axial compressive load and providing structural stability; face-centered diagonal braces 214 provide in-plane diagonal support, distributing the axial load to the frame members 213; and inscribed octahedral members 215 form an octahedral configuration within the unit cell, undergoing bending and buckling deformation during compression, thus absorbing more energy.
[0033] To further optimize the technical solution, the angle formed by the two opposing inclined surfaces in the concave folded unit 11 and the axial direction is α. The concave depth of the concave valley line relative to the adjacent convex edge line is h. The axial repeating period length of the concave folded unit 11 is P, satisfying h = (P / 2)tanα. Through the above geometric relationship, each concave folded unit 11 and a layer of composite truss lattice unit cell 21 form a precise correspondence in axial position, ensuring that the concave valley line is exactly located at the axial center of the corresponding composite truss lattice unit cell layer.
[0034] By setting a quantitative relationship between the angle α formed by the two opposing inclined folds in the concave folded unit 11 and the axial direction, the concave depth h, and the axial repeating period length P, the geometric configuration of the concave folded unit 11 can be precisely controlled. This ensures that the position of the concave valley line corresponds precisely to the axial center of the composite truss lattice unit cell 21, thereby ensuring that the folding deformation position of the outer thin-walled square shell 1 and the unit cell deformation position of the composite truss lattice core 2 are spatially coordinated. This avoids deformation incoordination and reduced load-bearing capacity caused by the mismatch between the shell folding period and the lattice unit cell height, thus improving the overall coordinated deformation capacity and energy absorption efficiency of the structure.
[0035] The technical solution was further optimized. The composite truss lattice unit cell 21 is a cubic unit cell. The axial repeating period length P of the concave folded element 11 is related to the axial dimension a of the composite truss lattice unit cell 21. z Satisfying P=a z By setting the composite truss lattice unit cell 21 as a cubic unit cell and making the axial repeating period length P of the concave faceted element 11 equal to the axial dimension a of the composite truss lattice unit cell 21. zThis allows each concave folded unit 11 to correspond exactly to a complete layer of composite truss lattice unit cell 21, ensuring that each concave folded unit 11 of the shell is fully aligned with a layer of unit cell of the internal lattice core in the axial position. This maximizes the synergistic effect of shell folding deformation and lattice core crushing deformation, which is beneficial to improving the overall load-bearing capacity and energy absorption efficiency of the structure during compression.
[0036] Further optimizing the technical solution, the cross-sections of the frame members 213, face-centered diagonal members 214, and inscribed octahedral members 215 of the composite truss lattice unit cell 21 are all circular, and the member diameter d and the wall thickness t of the outer thin-walled square shell 1 satisfy 0.5 ≤ d / t ≤ 1. By setting the ratio of the member diameter d to the wall thickness t of the outer thin-walled square shell 1 within the range of 0.5 to 1, a good geometric matching relationship can be achieved between the members of the lattice core and the shell wall thickness. When d / t is less than 0.5, the member diameter is too small, resulting in insufficient load-bearing capacity and stability of the lattice core; when d / t is greater than 1, the member diameter is too large, which will increase the structural mass and worsen the geometric integration effect between the members and the shell wall in the intersection connection area 3, hindering the formation of a continuous force transmission path. Controlling d / t between 0.5 and 1 ensures both structural lightweighting and good geometric integration and mechanical transmission between the members and the shell wall in the intersection connection area 3, thereby improving the overall load-bearing efficiency and energy absorption performance of the structure.
[0037] Further optimizing the technical solution, the outer thin-walled square shell 1, the composite truss lattice core 2, and the intersecting connection area 3 are integrally formed in the same construction process using metal additive manufacturing. By adopting metal additive manufacturing to integrally form the outer thin-walled square shell 1, the composite truss lattice core 2, and the intersecting connection area 3 in the same construction process, it is possible to eliminate the need for independent mechanical fasteners, adhesive layers, or subsequent assembly connectors between the shell and the lattice core. This avoids material discontinuities and abrupt changes in mechanical properties caused by the assembly interface, ensuring a metallurgically bonded integrated structure at the shell-core interface. Simultaneously, integral forming allows for precise control of the complex geometric configuration of the concave folded unit 11 and the internal topology of the lattice core, ensuring a precise correspondence between the shell folding period and the lattice unit cell height. This is suitable for the integrated manufacturing of complex concave folded shells and internal lattice topologies, thereby improving the overall performance and manufacturing precision of the structure.
[0038] Further optimizing the technical solution, the included angle α formed by the two opposing inclined folded surfaces and the axial direction ranges from 5° to 30°, the size of the composite truss lattice unit 21 ranges from 10mm to 30mm, and the rod diameter d and wall thickness t both range from 1mm to 3mm. By setting the inclination angle α of the concave folded surface unit 11 within the range of 5° to 30°, the concave depth and deformation mode of the concave folded surface unit 11 can be adjusted under different energy absorption requirements. When the α angle is smaller, the concave depth is shallower, and the shell folding deformation is more gradual; when the α angle is larger, the concave depth is larger, the shell folding deformation is more severe, and the energy absorption capacity is enhanced. Setting the size of the composite truss lattice unit 21 within the range of 10mm to 30mm can adapt to the design requirements of components of different scales. The smaller the unit cell size, the higher the degree of discretization of the lattice core and the higher the adjustment accuracy of the structural response; the larger the unit cell size, the better the macroscopic uniformity of the lattice core and the higher the manufacturing efficiency. Setting both the rod diameter d and wall thickness t within the range of 1mm to 3mm ensures the manufacturability of the structure in metal additive manufacturing processes, while also providing sufficient mechanical properties. By adjusting these parameters, the structure can be adapted to different buffering, protection, and energy absorption requirements, thereby improving the flexibility and adaptability of structural design.
[0039] Further optimizing the technical solution, the frame members 213, face-centered diagonal members 214, and inscribed octahedral members 215 together constitute a multi-path force transmission network of the composite truss lattice unit cell 21. The outer thin-walled square shell 1 provides boundary constraints for the composite truss lattice core 2, and the composite truss lattice core 2 provides internal support for the concave folded surface unit 11. Through the multi-path force transmission network formed by the frame members 213, face-centered diagonal members 214, and inscribed octahedral members 215, during axial compression, the axial load can be transmitted and dissipated through multiple paths simultaneously via the direct bearing of the frame members 213, the oblique component force transmission of the face-centered diagonal members 214, and the bending deformation of the inscribed octahedral members 215, thus avoiding a sudden drop in the overall load-bearing capacity due to local failure of a single force transmission path. Meanwhile, the boundary constraints provided by the outer thin-walled square shell 1 to the composite truss lattice core 2 effectively limit the free buckling of the outer peripheral members of the lattice core, improving the overall stability of the lattice core. The internal support provided by the composite truss lattice core 2 to the concave folded element 11 effectively suppresses excessive inward collapse of the shell during compression, ensuring a stable deformation mode during folding. The bidirectional interaction and constraint relationship between the outer thin-walled square shell 1 and the composite truss lattice core 2 is beneficial to improving the overall load-bearing stability and energy absorption efficiency of the structure during compression energy absorption.
[0040] The technical solution was further optimized, and the number of arrays of the composite truss lattice core 2 along the three orthogonal directions were n respectively. x n y and n z , where n x and ny For 3 to 5, n z The initial volume fraction φ of the metamaterial structure is 15%≤φ≤35%, where φ=Vs / (Lx×Ly×H), Vs is the solid volume of the metamaterial structure, and Lx, Ly and H are the circumscribed length, width and height of the metamaterial structure, respectively.
[0041] By limiting the range of the number of arrays of the composite truss lattice core 2 in three orthogonal directions and the range of the initial volume fraction of the overall structure, the structure can have a sufficient number of unit cells in the x and y directions to form an in-plane constraint effect, and a sufficient number of unit cell layers in the z direction to provide sufficient energy dissipation path. At the same time, by controlling the volume fraction between 15% and 35%, it is possible to avoid the structure being too sparse, resulting in insufficient load-bearing capacity, or too dense, resulting in excessive mass. This is beneficial for adjusting the relative density and mechanical response of the structure according to specific buffering and energy absorption requirements.
[0042] The integrated energy-absorbing metamaterial structure of concave folded shell and composite truss lattice core provided by this invention is implemented as follows under axial compression: When an axial compressive load is applied to the upper surface of the structure, the outer thin-walled square shell 1 first bears the compressive load. Since the four sidewalls of the outer thin-walled square shell 1 are all provided with axially repeating concave folded units 11, and the axial repeating period length P of the concave folded unit 11 is consistent with the axial dimension a of the composite truss lattice unit 21... z Correspondingly, the concave valley line is located at the axial center of the corresponding composite truss lattice unit cell. Therefore, during axial compression, the folding deformation of the outer thin-walled square shell 1 is first triggered at the concave valley line position and gradually unfolds along the predetermined geometric configuration of the concave folded surface unit 11. At the same time, the compressive load is transferred from the outer thin-walled square shell 1 to the composite truss lattice core 2 through the intersecting connection region 3. In the composite truss lattice core 2, the frame members 213 of the composite truss lattice unit cell 21 serve as the main axial load-bearing members, bearing the compressive load. The face-centered diagonal members 214 distribute the load to the frame members 213 through diagonal support. The inscribed octahedral members 215 undergo bending and buckling deformation during compression, thereby absorbing a large amount of energy. Because the outer peripheral members of the composite truss lattice core 2 are integrally connected to the shell wall of the outer thin-walled square shell 1 within the intersecting connection area 3 and do not protrude beyond the outer surface of the shell, the outer thin-walled square shell 1 provides effective lateral boundary constraints on the composite truss lattice core 2, limiting the free buckling of the outer peripheral members of the lattice core; at the same time, the composite truss lattice core 2 provides internal support to the concave folded surface unit 11, suppressing excessive collapse of the shell during compression. As the compression displacement continues to increase, the multiple concave folded surface units 11 of the outer thin-walled square shell 1 undergo folding deformation in sequence, and the multiple composite truss lattice unit cells 21 layers of the composite truss lattice core 2 undergo crushing deformation in sequence. The shell folding deformation and the lattice core crushing deformation correspond and cooperate layer by layer in the axial position until the structure is completely compacted.
[0043] This invention uses an outer thin-walled square shell 1 with axially repeating concave folded surface units 11, the axial repeating period length of which corresponds to the axial dimension of the composite truss lattice unit cell 21. This allows the outer thin-walled square shell 1 to have a predetermined local deformation area under axial compression, solving the problems of unstable folding positions, concentrated local deformation, or lateral instability in existing thin-walled shell structures, and improving the stability of the shell-core composite structure during compression deformation. The composite truss lattice unit cell 21 simultaneously includes frame members 213, face-centered diagonal braces 214, and inscribed octahedral members 215, forming a multi-path force transmission network involving the outer frame, in-plane diagonal braces, and internal diagonal members. This solves the problem of a single force transmission path in conventional lattice cores and improves the energy absorption capacity per unit mass of the structure. By integrating the members intersecting the shell wall in the composite truss lattice core 2 with the shell wall within the shell wall thickness range without protruding beyond the outer surface of the outer thin-walled square shell 1, a continuous intersecting connection area 3 and force transmission path are formed between the outer thin-walled square shell 1 and the composite truss lattice core 2. This solves the problems of material discontinuity and abrupt changes in mechanical properties at the connection interface in existing shell-core composite structures, and improves the load-bearing stability and overall synergy of the integrated shell-core structure during compression energy absorption. In addition, by adjusting parameters such as concave angle, unit cell size, member diameter, shell wall thickness, array number, and volume fraction, the structure can adapt to different buffering, protection, and energy absorption requirements. By integrally forming the structure during the same construction process using metal additive manufacturing, there is no need for independent mechanical fasteners, adhesive layers, or subsequent assembly connectors, avoiding connection discontinuities caused by assembly interfaces.
[0044] Example: Please see Figures 1 to 4 This embodiment provides an integrated energy-absorbing metamaterial structure consisting of a concave folded shell and a composite truss lattice core. The structure includes an outer thin-walled square shell 1 and a composite truss lattice core 2 disposed inside the outer thin-walled square shell 1. With the height direction of the structure as the axial z-direction, each of the four sidewalls of the outer thin-walled square shell 1 is composed of multiple concave folded units 11 arranged repeatedly along the z-direction. Each concave folded unit 11 consists of two opposing inclined folds, forming a concave valley line towards the composite truss lattice core 2 at its axial center.
[0045] like Figure 2As shown, the composite truss lattice core 2 is formed by an array of multiple composite truss lattice unit cells 21 arranged along three orthogonal directions: x, y, and z. Each composite truss lattice unit cell 21 includes: eight corner nodes 211 located at the eight vertices of the cube; six face-centered nodes 212 located at the centers of the six faces of the cube; twelve frame members 213 connecting adjacent corner nodes 211; twenty-four face-centered diagonal members 214 formed by connecting each face-centered node 212 with the four corner nodes 211 of its respective face; and twelve inscribed octahedral members 215 connecting adjacent face-centered nodes 212. The frame members 213, face-centered diagonal members 214, and inscribed octahedral members 215 together constitute the multipath truss lattice unit cell 21.
[0046] like Figure 3 As shown, the axial repeating period length P of the concave folded element 11 is related to the axial dimension a of the composite truss lattice unit cell 21. z In this embodiment, the corresponding setting satisfies P=a. z The concave valley line is located at the axial midpoint of the corresponding composite truss lattice unit cell layer. The angle between the two opposing inclined surfaces in the concave folded element 11 and the axial direction is α. The concave depth of the concave valley line relative to the adjacent convex edge is h, and the two satisfy h = (P / 2)tanα. Through the above geometric relationship, each concave folded element 11 corresponds axially to one layer of composite truss lattice unit cell 21.
[0047] like Figure 3 and Figure 4 As shown, the peripheral members of the composite truss lattice core 2 near the outer thin-walled square shell 1 geometrically intersect with the outer thin-walled square shell 1 and are integrally connected to the shell wall within the intersection connection area 3. The intersection connection area 3 is located within the wall thickness t of the shell wall, and the peripheral members do not protrude beyond the outer surface of the outer thin-walled square shell 1; therefore, the outer surface of the final structure is defined by the outer surface of the outer thin-walled square shell 1. It should be noted that the peripheral members refer to the original members in the composite truss lattice core located at the shell-core junction and intersecting with the shell wall of the outer thin-walled square shell; the peripheral members are not independent members additionally provided along the inner wall of the shell.
[0048] In the 3D modeling implementation, an outer thin-walled square shell 1 and a composite truss lattice core 2 can be established first, so that the lattice core and the shell wall form an intersecting area; then, the lattice entities within the outer contour of the shell are retained, and the retained lattice entities are combined with the shell to form a continuous integral entity. This modeling process is only used to obtain the above-mentioned product structure, and its final structural feature is that the peripheral rods are integrally connected with the shell wall within the intersecting connection area 3, and do not protrude beyond the outer surface of the shell.
[0049] In this embodiment, the composite truss lattice unit cell 21 is a cubic unit cell with a unit cell size a of 20 mm, i.e., a x =a y =az =20mm; the axial repeating period length P of the concave folded surface unit 11 is 20mm, the angle α formed by the two opposing inclined folded surfaces in the concave folded surface unit 11 and the axial direction is 10°, and the concave depth h can be obtained from h=(P / 2)tanα as approximately 1.76mm. The outer thin-walled square shell 1 has an outer length Lx of 60mm, an outer width Ly of 60mm, and an outer height H of 100mm; the number of arrays of the composite truss lattice core 2 in the x, y, and z directions are n respectively. x =3、n y =3 and n z =5.
[0050] The cross-sections of frame member 213, face-centered diagonal member 214, and inscribed octahedral member 215 are all circular, with a member diameter d of 2 mm. The wall thickness t of the outer thin-walled square shell 1 is 2 mm, satisfying 0.5 ≤ d / t ≤ 1. The initial volume fraction φ of the structure in this embodiment is calculated according to φ = Vs / (Lx × Ly × H), which is approximately 22.77%. In other embodiments, the included angle α formed by the two opposing inclined surfaces in the concave folded unit 11 and the axial direction can be adjusted within the range of 5° to 30°, the unit cell size a can be selected within the range of 10 mm to 30 mm, the member diameter d and the wall thickness t can be selected within the range of 1 mm to 3 mm respectively, and the array number can be set according to the component size and the target load direction.
[0051] This embodiment can be prepared using metal additive manufacturing processes, specifically laser powder bed melting. The outer thin-walled square shell 1, the composite truss lattice core 2, and the intersecting connection area 3 are integrally formed in the same construction process; no independent mechanical fasteners, adhesive layers, or subsequent assembly connectors are provided between the shell and the lattice core. The material can be a metal suitable for laser powder bed melting, such as AlSi10Mg.
[0052] Under axial compression, the concave folded surface unit 11 of the outer thin-walled square shell 1 can provide a local deformation area. The composite truss lattice core 2 forms a multi-path force transmission through frame members 213, face-centered diagonal members 214 and inscribed octahedral members 215. The intersecting integral connection between the outer peripheral members and the shell wall forms a continuous solid force transmission path between the shell and the lattice core, which is conducive to the coordinated occurrence of shell folding deformation and local crushing deformation of the lattice core, and improves the structure's continuous energy dissipation capacity during compression.
[0053] To verify the compressive energy absorption performance of the structure of this invention, three structural models were established using the finite element method for comparative analysis: the structure of this invention, the straight-walled shell comparison structure, and the simplified core comparison structure. The structure of this invention adopts the aforementioned integrated structure of concave folded shell and composite truss lattice core. The straight-walled shell comparison structure replaces the outer thin-walled square shell with a straight-walled square shell, while maintaining the same connection method between the composite truss lattice core and the shell core. The simplified core comparison structure removes the inscribed octahedral members from the structure of this invention, retaining the frame members and face-centered diagonal members. All three structures use the same materials, have the same external dimensions, the same compression conditions, and the same boundary conditions, and their masses are similar. The masses of the structure of this invention, the straight-walled shell comparison structure, and the simplified core comparison structure are 218.86g, 216.39g, and 219.18g, respectively.
[0054] like Figure 5 The figure shows the compressive stress-strain curves of three structures under axial compression conditions. Figure 5 It is evident that all three structures exhibited high load-bearing capacity in the initial compression stage, with a decrease in load-bearing capacity occurring within approximately 15%-20% of the compressive strain range, subsequently entering a fluctuating load-bearing stage. Specifically, the peak compressive stress of the structure of this invention was approximately 65.42 MPa, lower than the 68.40 MPa of the straight-walled shell control structure and the 72.33 MPa of the simplified core control structure; the structure of this invention maintained a high load-bearing recovery level in the later stages of compression. Calculating the crushing efficiency based on the ratio of average compressive stress to peak compressive stress, the crushing efficiencies of the structure of this invention, the straight-walled shell control structure, and the simplified core control structure were approximately 0.576, 0.532, and 0.475, respectively, indicating that the structure of this invention possesses good sustained load-bearing capacity while reducing peak compressive stress.
[0055] like Figure 6 The figure shows a comparison of the absorbed energy and specific energy absorption of the three structures. At 60% strain, the absorbed energies of the structure of this invention, the straight-walled shell control structure, and the simplified core control structure are 8133.06 J, 7857.12 J, and 7418.02 J, respectively, corresponding to specific energy absorptions of 37.16 J / g, 36.31 J / g, and 33.85 J / g. The specific energy absorption of the structure of this invention is approximately 2.34% higher than that of the straight-walled shell control structure and approximately 9.80% higher than that of the simplified core control structure. These results indicate that the structure of this invention has a high energy absorption capacity per unit mass under approximately equal mass conditions.
[0056] Combination Figure 5 and Figure 6It can be seen that the structure of the present invention does not rely on increasing the initial peak compressive stress to obtain energy absorption. Instead, it still obtains the highest energy absorption, specific energy absorption, and crushing force efficiency among the three structures when the peak compressive stress is relatively low. This indicates that the combination of the concave folded shell, the composite truss lattice core, and the shell-core intersecting integral connection is beneficial to improving the overall buffering and energy absorption performance of the structure.
[0057] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.
Claims
1. A concave folded shell-composite truss lattice core integrated energy-absorbing metamaterial structure, characterized in that, It includes an outer thin-walled square shell (1) and a composite truss lattice core (2) disposed inside the outer thin-walled square shell (1). The sidewall of the outer thin-walled square shell (1) is provided with concave folded surface units (11) that are repeatedly distributed along the axial direction. The composite truss lattice core (2) is formed by an array of multiple composite truss lattice unit cells (21) in a three-dimensional direction. The axial repeating period length of the concave folded surface unit (11) is set to correspond to the axial dimension of the composite truss lattice unit cell (21). The rods in the composite truss lattice core (2) that intersect with the shell wall are integrally connected to the shell wall within the shell wall thickness range.
2. The integrated energy-absorbing metamaterial structure of concave folded shell-composite truss lattice core according to claim 1, characterized in that, The concave folded unit (11) is composed of two folded surfaces that are inclined towards each other, and a concave valley line is formed in the middle of the axial direction towards the composite truss lattice core (2). The concave valley line is located in the middle of the axial direction of the corresponding composite truss lattice unit cell.
3. The integrated energy-absorbing metamaterial structure of concave folded shell-composite truss lattice core according to claim 1, characterized in that, The composite truss lattice unit cell (21) includes a corner node (211) at the vertex of the cube, a face center node (212) at the face center of the cube, a frame member (213) connecting the adjacent corner nodes (211), a face center diagonal member (214) connecting the face center node (212) to the corner node (211) on the corresponding face, and an inscribed octahedral member (215) connecting the adjacent face center nodes (212).
4. The integrated energy-absorbing metamaterial structure of concave folded shell-composite truss lattice core according to claim 1, characterized in that, The outer peripheral members of the composite truss lattice core (2) and the shell wall of the outer thin-walled square shell (1) are integrally connected in the intersecting connection area (3). The intersecting connection area (3) is located within the wall thickness range of the shell wall, and the outer peripheral members do not protrude out of the outer surface of the outer thin-walled square shell (1).
5. The integrated energy-absorbing metamaterial structure of concave folded shell-composite truss lattice core according to claim 2, characterized in that, The angle between the two opposing inclined surfaces in the concave folded surface unit (11) and the axial direction is α. The concave depth of the concave valley line relative to the adjacent convex ridge line is h. The axial repeating period length of the concave folded surface unit (11) is P, which satisfies h=(P / 2)tanα.
6. The integrated energy-absorbing metamaterial structure of concave folded shell-composite truss lattice core according to claim 1, characterized in that, The composite truss lattice unit cell (21) is a cubic unit cell, the axial repeating period length P of the inner concave fold surface unit (11) is equal to the axial size a of the composite truss lattice unit cell (21) z Satisfies P=a z .
7. The integrated energy-absorbing metamaterial structure of concave folded shell-composite truss lattice core according to claim 5, characterized in that, The cross-sections of the frame members (213), face-centered diagonal members (214), and inscribed octahedral members (215) of the composite truss lattice unit cell (21) are all circular, and the diameter d of the member and the wall thickness t of the outer thin-walled square shell (1) satisfy 0.5≤d / t≤1.
8. The integrated energy-absorbing metamaterial structure of concave folded shell-composite truss lattice core according to claim 1, characterized in that, The outer thin-walled square shell (1), the composite truss lattice core (2), and the intersecting connection area (3) are integrally formed in the same construction process through metal additive manufacturing.
9. The integrated energy-absorbing metamaterial structure of concave folded shell-composite truss lattice core according to claim 7, characterized in that, The angle α formed by the two opposing inclined folds and the axial direction ranges from 5° to 30°, the size of the composite truss lattice unit cell (21) ranges from 10 mm to 30 mm, and the rod diameter d and the wall thickness t both range from 1 mm to 3 mm.
10. The integrated energy-absorbing metamaterial structure of concave folded shell-composite truss lattice core according to claim 3, characterized in that, The frame members (213), the face-centered diagonal members (214), and the inscribed octahedral members (215) together constitute the multi-path force transmission network of the composite truss lattice unit cell (21). The outer thin-walled square shell (1) provides boundary constraints to the composite truss lattice core (2), and the composite truss lattice core (2) provides internal support to the concave folded surface unit (11).