Coplanar origami honeycomb structure

Abstract

The invention discloses a coplanar origami honeycomb structure which is formed by in-plane and / or out-of-plane mirror images of basic origami units, and each basic origami unit is formed by splicing four folding subunits; each folding subunit comprises an upper plane, a lower plane, two middle planes and five inclined planes; the five inclined planes are two first inclined planes for connecting the upper plane and the two middle planes, two second inclined planes for connecting the lower plane and the two middle planes, and a third inclined plane for connecting the two first inclined planes and the two second inclined planes; the four folding subunits are spliced at the upper plane position to form an upper platform, and the four folding subunits are spliced at the middle plane position to form four middle platforms. An upper coplanar platform area and a lower coplanar platform area which are formed after a paper folding structure is folded are fully utilized, face-to-face connection between all layers of structures is achieved, the assembling complexity is reduced, the connection strength is improved, meanwhile, geometric parameters can be flexibly set and optimized according to specific application requirements in the initial design stage, and the design efficiency is improved. And the method has good engineering adaptability and application flexibility.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of honeycomb structure, in particular to a foldable honeycomb structure. BACKGROUND

[0002] In recent years, honeycomb structure has been fully developed and widely used in aerospace, transportation and building structure protection, etc. It has many functions such as energy consumption, collision protection, sound absorption and noise reduction. With the continuous evolution of structural design, foldable structure shows flexible geometric variability and good anti-collision energy absorption performance because it can realize controllable folding and unfolding along the fold line. The introduction of foldable structure into honeycomb structure brings new design ideas and functional expansion. In the existing design, the foldable honeycomb structure is usually assembled by fold line to fold line between the layers of foldable structure. This method has defects such as small contact area, high connection difficulty, low connection strength, etc., which is easy to become a weak link of the whole structure, and then affects its mechanical properties and service life. In addition, the traditional foldable honeycomb structure does not have a platform area after folding, and the single layer structure usually forms a relatively sharp vertex at the intersection of the fold lines. This kind of geometric feature increases the process difficulty in the manufacturing process. Therefore, in actual manufacturing, the traditional foldable honeycomb structure often needs to use three-dimensional printing and other integrated forming methods, which has high manufacturing process cost, low efficiency and complex process, and is not conducive to its popularization and application in engineering practice. SUMMARY

[0003] In view of the above technical problems, the present application provides a coplanar foldable honeycomb structure which significantly improves the connection strength between layers and the stability of the whole structure, and helps to fully exert the mechanical properties of foldable honeycomb structure.

[0004] The technical scheme adopted by the present application to solve its technical problems is: A coplanar foldable honeycomb structure is composed of basic foldable units in-plane and / or out-of-plane mirror image, wherein the basic foldable unit is composed of four foldable sub-units; the foldable sub-unit is composed of one upper plane, one lower plane, two middle planes and five inclined planes, the five inclined planes are two first inclined planes connecting the upper plane and the two middle planes, two second inclined planes connecting the lower plane and the two middle planes, and a third inclined plane connecting the two first inclined planes and the two second inclined planes; the four foldable sub-units are spliced at the upper plane position to form an upper platform, and spliced at the middle plane position to form four middle platforms.

[0005] The outer contour of the folded subunit in the fully unfolded state is rectangular, and the rectangle contains four vertices; each of the vertices is composed of three first creases and one second crease, wherein the folding directions of the first creases and the second crease are opposite, and adjacent two vertices have one common crease; the four vertices divide the rectangle into nine panels, and the panel interior angles of the four panels adjacent to each vertex are 90°, 90°, and (180°- ), respectively, 30°-75°; the included angle between the normal vectors of the two panels with panel interior angles of 90° pointing to the same side is the folding angle , 1°-Min{ , 119°}.

[0006] The nine panels of the folded subunit in the fully unfolded state are a first rectangular panel, a second rectangular panel, a third rectangular panel, a fourth rectangular panel, a fifth rectangular panel, a sixth rectangular panel, a first trapezoidal panel, a second trapezoidal panel, and a parallelogram panel, the parallelogram panel is a middle panel composed of four vertices, the first rectangular panel and the second rectangular panel are located at two opposite corners of the rectangle and have the same size, the third rectangular panel and the fourth rectangular panel are located at the other two opposite corners of the rectangle and have the same size, the fifth rectangular panel is located between the first rectangular panel and the third rectangular panel, the sixth rectangular panel is located between the second rectangular panel and the fourth rectangular panel, the first trapezoidal panel is located between the first rectangular panel and the fourth rectangular panel, and the second trapezoidal panel is located between the second rectangular panel and the third rectangular panel.

[0007] The first rectangular panel and the second rectangular panel are square panels with the same length and width, and the lengths of the fifth rectangular panel and the sixth rectangular panel are twice the widths.

[0008] The panel interior angle is 60°; and the folding angle is 60° or 70.4°.

[0009] The basic origami unit is mirror imaged in the XY plane to obtain a basic origami layer; and the basic origami unit is mirror imaged in the XY plane and then rotated by 90° around the Z axis to obtain a layer-assembled origami unit.

[0010] The basic origami layers of the layer-assembled origami unit are obtained by mirror imaging the previous basic origami layer through the XY plane or by mirror imaging the previous basic origami layer through the XY plane and then rotating by 90° around the Z axis.

[0011] A skin is arranged between adjacent basic origami layers of the layer-assembled origami unit.

[0012] The skin is a cross-shaped skin.

[0013] The cross skin is formed by intersecting a plurality of narrow rectangular strips or a plurality of wide rectangular strips; adjacent basic origami layers are connected through the narrow rectangular strips or the wide rectangular strips of the cross skin.

[0014] By the above technical solution, compared with the prior art, the application has the following beneficial technical effects: 1、The co-planar origami honeycomb structure provided by the application makes full use of the co-planar platform area formed after folding of the origami structure, realizes the face-to-face connection mode between layers, significantly improves the connection strength between layers and the stability of the overall structure compared with the traditional crease-to-crease connection mode, and helps to better exert the mechanical properties of the origami honeycomb structure.

[0015] 2、Thanks to the existence of the co-planar platform area and the face-to-face connection mode, the structure can be obtained by metal stamping and other methods, and the co-planar platform area is connected by adhesive bonding, which reduces the assembly complexity, thereby effectively reducing the manufacturing cost and improving the preparation efficiency and engineering feasibility.

[0016] 3、The co-planar origami honeycomb structure provided by the application has anisotropic characteristics, but through a series of assembly modes such as symmetry, rotation or cross skin pulling, the origami honeycomb structure can realize anisotropy and approximate isotropy, and in the compression process, the folding plastic deformation guided by the crease, the pulling connection of the cross skin and the collision buckling between the panels can effectively dissipate external energy, and exhibit excellent buffering performance and energy absorption capacity.

[0017] 4、The co-planar origami honeycomb structure provided by the application has good structural parameter adjustability, and the geometric parameters can be flexibly set and optimized according to specific application requirements in the initial design stage, which not only realizes directional regulation and control of the mechanical properties of the overall structure, but also adapts to different directions of buffering and energy absorption requirements, and thus has good engineering adaptability and application flexibility. BRIEF DESCRIPTION OF DRAWINGS

[0018] The application will be further described below in combination with the drawings and examples.

[0019] Figure 1 is a three-dimensional schematic view of example 1 provided by the application; Figure 2 is a structure schematic view of a folded subunit provided by the application; Figure 3 is a structure schematic view of a basic origami unit composed of four folded subunits; Figure 4is a perspective view of the basic origami structure provided by the present invention Figure 5 is a perspective view of the assembly of example 1 provided by the present invention Figure 6 is an X-plane view of the assembly of example 1 provided by the present invention Figure 7 is a Y-plane view of the assembly of example 1 provided by the present invention Figure 8 is a perspective view of example 2 provided by the present invention Figure 9 is a structural plane view of the large cross skin provided by the present invention Figure 10 is a structural plane view of the small cross skin provided by the present invention Figure 11 is a perspective view of the assembly of example 2 provided by the present invention Figure 12 is an X-plane view of the assembly of example 2 provided by the present invention Figure 13 is a Y-plane view of the assembly of example 2 provided by the present invention Figure 14 is a perspective view of example 3 provided by the present invention Figure 15 is a perspective view of the assembly of example 3 provided by the present invention Figure 16 is an X-plane view of the assembly of example 3 provided by the present invention Figure 17 is a Y-plane view of the assembly of example 3 provided by the present invention Figure 18 is an average stress-strain curve for example 1 provided by the present invention Figure 19 is an average stress-strain curve for example 2 provided by the present invention Figure 20 is an average stress-strain curve for example 3 provided by the present invention 1 is the basic origami unit, 11 is the folding sub-unit, 103 is the third rectangular piece, 104 is the fourth rectangular piece, 105 is the fifth rectangular piece, 106 is the sixth rectangular piece, 107 is the first trapezoidal piece, 108 is the second trapezoidal piece, 109 is the parallelogram piece, 2 is the basic origami structure, 21 is the first layer of origami structure, 22 is the second layer of origami structure, 23 is the third layer of origami structure, and 24 is the fourth layer of origami structure. 25 is the fifth layer of origami structure, 26 is the sixth layer of origami structure, 31 is a complete upper coplanar platform, 32 is a 1 / 2 upper coplanar platform, 33 is a 1 / 4 upper coplanar platform, 41 is a complete lower coplanar platform, 42 is a 1 / 2 lower coplanar platform, 43 is a 1 / 4 lower coplanar platform, 5 is a large cross skin, 6 is a small cross skin, 7 is a narrow rectangular strip, 8 is a wide rectangular strip, 91 is a 1 / 2 first middle platform, and 92 is a 1 / 2 second middle platform. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to the accompanying drawings. It should be understood that all dimensions and dimensional relationships, in-plane angles and folding angles, the number of basic origami units, the number of layers in the basic origami structure, and the number of cross-shaped skins used in this embodiment are merely illustrative examples and do not limit the scope of protection of the present invention.

[0021] As preferred embodiments of the invention, three different embodiments of symmetrical, rotated, or cross-shaped skinned rafting assembly are provided, namely Embodiment 1, Embodiment 2, and Embodiment 3.

[0022] Example 1: like Figures 1-4 As shown, this embodiment provides a coplanar origami honeycomb structure symmetrically assembled in the Z direction. The Z direction is defined as out-of-plane relative to the XY plane, and the XY plane is defined as in-plane. This structure is a 6-layer origami honeycomb structure obtained by symmetrically assembling the basic origami structure 2 as the first layer through the XY plane. The basic origami structure 2 is composed of 3×3 basic origami units 1 arranged symmetrically and interlocked through the XZ and YZ planes. The basic origami unit 1 is composed of four folded sub-units 11 spliced ​​together. The folded sub-unit 11 is composed of 9 quadrilateral pieces. There are creases at the connection between adjacent pieces. There are four vertices inside. Each vertex is composed of three mountain creases and one valley crease (or three valley creases and one mountain crease), as detailed in the figure. Figure 2 The thick solid lines represent mountain folds, and the dashed lines represent valley folds. In its fully unfolded state, the folded subunit 11 has a rectangular outer contour with geometric parameters a, b, c, and d. The interior angles of the four adjacent faces at each vertex are 90°, 90°, 90°, and 90° respectively. and (180°- The angle between the normal vectors pointing to the same side of two adjacent facets with an interior angle of 90° is used as the folding angle. , For 1°~Min{ The folded subunit 11 is folded along creases to form four rectangular panels parallel to the XY plane. The first and second rectangular panels, with the largest and smallest Z values ​​respectively, serve as the upper coplanar platform 33 and the lower coplanar platform 43. The remaining two diagonally positioned rectangular panels are the third rectangular panel 103 and the fourth parallel rectangular panel 104. The upper coplanar platform 33 is connected to the third rectangular panel 103 via the fifth rectangular panel 105, and the lower coplanar platform 43 is connected to the fourth rectangular panel 104 via the sixth rectangular panel 106. The fifth rectangular panel 105 and the sixth rectangular panel 106 are the same size and parallel to each other, both inclined relative to the XY plane and perpendicular to the XZ plane. The upper coplanar platform 33 (1 / 4 section) is connected to the fourth rectangular plate 104 via the first trapezoidal plate 107. The lower coplanar platform 43 (1 / 4 section) is connected to the third rectangular plate 103 via the second trapezoidal plate 108. The first trapezoidal plate 107 and the second trapezoidal plate 108 are of the same size and parallel to each other, and both are inclined relative to the XY plane and perpendicular to the YZ plane. The sixth rectangular plate 106, the fifth rectangular plate 105, the second trapezoidal plate 108, and the first trapezoidal plate 107 are connected by a parallelogram plate 109. Figure 3 A basic origami unit 1 is shown, comprising a complete upper coplanar platform 31, four quarter lower coplanar platforms 43, two half-first middle platforms 91, and two half-second middle platforms 92. A complete upper coplanar platform 31 is composed of the quarter-upper coplanar platforms 33 of four adjacent folding sub-units 1. A half-first middle platform 91 is composed of two third rectangular panels 103, and a half-second middle platform 92 is composed of two fourth rectangular panels 104. The upper and lower coplanar platforms provide a connecting interface for the assembly of the basic origami structure 2 in the Z-direction. By combining the quarter-upper coplanar platforms 33 or the quarter-lower coplanar platforms 43 of two or four folding sub-units 11, half-upper coplanar platforms 32 or half-lower coplanar platforms 42, or complete upper coplanar platforms 31 or complete lower coplanar platforms 41 can be formed, respectively. A complete upper coplanar platform 31 or a complete lower coplanar platform 41 is located inside each layer of the origami structure. A half-upper coplanar platform 32 or a half-lower coplanar platform 42 is located at the edge of each layer of the origami structure. A quarter-upper coplanar platform 33 or a quarter-lower coplanar platform 43 is located diagonally across each layer of the origami structure. It should be noted that, for ease of description, all upper coplanar platforms and all lower coplanar platforms of each layer of the origami structure are collectively referred to as the upper coplanar platform group and the lower coplanar platform group of that layer of the origami structure, respectively. In this embodiment, the following conditions are met: =60°, = 60°, b = 2d = 2a = 10 mm, c = 10.8 mm, and the face sheet thickness is 0.1 mm. The same mold was used to process each layer of the origami structure by metal stamping. Six layers of the origami structure were prepared.

[0023] As shown in Figures 5-7 , the specific assembly method of this embodiment is described in detail. The six-layer origami structure is assembled in the Z direction. The basic origami structure 2 is used as the first layer origami structure 21, the second layer origami structure 22 is symmetrical to the first layer origami structure 21 about the XY plane, the third layer origami structure 23 is symmetrical to the second layer origami structure 22 about the XY plane, the fourth layer origami structure 24 is symmetrical to the third layer origami structure 23 about the XY plane, the fifth layer origami structure 25 is symmetrical to the fourth layer origami structure 24 about the XY plane, and the sixth layer origami structure 26 is symmetrical to the fifth layer origami structure 25 about the XY plane. The adjacent layers of the origami structure are directly connected by the upper coplanar platform group of the lower layer origami structure and the lower coplanar platform group of the upper layer origami structure, effectively enhancing the interlayer connection strength.

[0024] Example 2: As shown in Figures 8-10 , this embodiment provides a coplanar origami honeycomb structure that is symmetrical in the Z direction and assembled by cross-skin pull faces. This embodiment introduces a large cross-skin 5 and a small cross-skin 6 based on Example 1. The large cross-skin 5 is composed of a plurality of narrow rectangular strips 7 and a plurality of wide rectangular strips 8 that are perpendicular to each other, and the small cross-skin 6 is composed of a plurality of wide rectangular strips 8. The adjacent layers of the origami structure are indirectly connected by the large cross-skin 5 or the small cross-skin 6.

[0025] The specific assembly method of this embodiment is shown in Figures 11-13 . For convenience of description, all the intersection areas between the large cross-skin rectangular strips are grouped as large rectangular area groups, and all the intersection areas between the small cross-skin rectangular strips are grouped as small rectangular area groups, and the side length of each rectangular area is 1 times or 2 times the length a. The first layer origami structure 21 and the second layer origami structure 22, the third layer origami structure 23 and the fourth layer origami structure 24, the fifth layer origami structure 25 and the sixth layer origami structure 26 are connected by the upper coplanar platform group of the corresponding lower layer origami structure and the lower coplanar platform group of the upper layer origami structure and the small rectangular area group of the small cross-skin 6. The second layer origami structure 22 and the third layer origami structure 23, the fourth layer origami structure 24 and the fifth layer origami structure 25 are connected by the upper coplanar platform group of the corresponding lower layer origami structure and the lower coplanar platform group of the upper layer origami structure and the large rectangular area group of the large cross-skin 5.

[0026] Example 3: As shown in Figure 14As shown, the embodiment provides a co-planar origami honeycomb structure which is symmetrical in Z direction, rotated and assembled by cross skin pull surface, and the difference from the embodiment 2 is that the folding angle of the embodiment is =70.4°, and the fourth layer origami structure 24 is obtained by symmetrical rotation of the third layer origami structure 23 in XY plane and rotation of 90° around Z axis. As a further illustration, the folding angle =70.4° selected in the embodiment can make the lower co-planar platform group of the fourth layer origami structure 24 after symmetrical rotation exactly align with the upper co-planar platform group of the third layer origami structure 23.

[0027] Referring to the specific assembly method described in the embodiment 2, the specific assembly method of the embodiment is as shown in Figures 15-17 .

[0028] The finite element models of the embodiment 1, the embodiment 2 and the embodiment 3 as shown in Figure 1 , Figure 8 and Figure 14 are respectively established in the application, all the materials are defined as aluminum materials, and the finite element numerical calculation of compression performance in X, Y and Z directions is completed, and the average stress-strain curves after non-dimensional treatment are obtained, as shown in Figures 18-20 . Figure 18 It is shown that the embodiment 1 has excellent energy absorption capacity in X and Y directions, and the structure has anisotropic characteristics. Figure 19 It is shown that compared with the embodiment 1, the energy absorption capacity of the embodiment 2 in Z direction is significantly improved, and the structure has anisotropic characteristics. Figure 20 It is shown that the average stress-strain curves of the embodiment 3 in X and Y directions are completely consistent, and the average stress-strain curve in Z direction presents a certain fluctuation, but basically fluctuates around the average stress-strain curves in X and Y directions, and the structure has approximately isotropic characteristics, and has good energy absorption capacity in three directions.

[0029] The number of layers of the basic origami structure 2, the number and the small cross skin 6 of the large cross skin 5, the number of the basic origami unit 1 and the folding subunit 11 and the related geometric dimensions can be flexibly adjusted according to the specific application requirements. At the same time, the short side dimension of the narrow rectangular strip 7 and the wide rectangular strip 8, the in-plane angle of the folding subunit 1 and the corresponding folding angle are also adjustable parameters, which can be optimized and set according to different engineering scenarios, and adapt to diversified application requirements.

Claims

1. A coplanar origami honeycomb structure, composed of basic origami units mirrored in-plane and / or out-of-plane, characterized in that, The basic origami unit is composed of four folding sub-units; each folding sub-unit consists of an upper plane, a lower plane, two middle planes, and five inclined planes. The five inclined planes are two first inclined planes connecting the upper plane and the two middle planes, two second inclined planes connecting the lower plane and the two middle planes, and a third inclined plane connecting the two first inclined planes and the two second inclined planes. The four folding sub-units are joined together at the upper plane position to form an upper platform, and joined together at the middle plane position to form four middle platforms.

2. The coplanar origami honeycomb structure according to claim 1, characterized in that, The folded subunit has a rectangular outer contour in its fully unfolded state, containing four vertices. Each vertex consists of three first creases and one second crease, with the first and second creases folding in opposite directions. Adjacent vertices share a common crease. The four vertices divide the rectangle into nine facets, with the interior angles of the four facets adjacent to each vertex being 90°, 90°, 90°, and 90° respectively. and (180°- ), The angle is 30° to 75°; the angle between the normal vectors pointing to the same side of two adjacent facets with an interior angle of 90° is used as the folding angle. , For 1°~Min{ ,119°}.

3. The coplanar origami honeycomb structure according to claim 2, characterized in that, The folded subunit, in its fully unfolded state, comprises nine panels: a first rectangular panel, a second rectangular panel, a third rectangular panel, a fourth rectangular panel, a fifth rectangular panel, a sixth rectangular panel, a first trapezoidal panel, a second trapezoidal panel, and a parallelogram panel. The parallelogram panel is the middle panel formed by the four vertices. The first and second rectangular panels are located at two opposite corners of the rectangle and have the same size. The third and fourth rectangular panels are located at the other two opposite corners of the rectangle and have the same size. The fifth rectangular panel is located between the first and third rectangular panels. The sixth rectangular panel is located between the second and fourth rectangular panels. The first trapezoidal panel is located between the first and fourth rectangular panels. The second trapezoidal panel is located between the second and third rectangular panels.

4. The coplanar origami honeycomb structure according to claim 3, characterized in that, The first and second rectangular patches are square patches with the same length and width, while the fifth and sixth rectangular patches have a length that is twice their width.

5. The coplanar origami honeycomb structure according to claim 2, characterized in that, internal angle The folding angle is 60°. The value can be either 60° or 70.4°.

6. The coplanar origami honeycomb structure according to any one of claims 1-5, characterized in that, The basic origami unit is mirrored in-plane to form a basic origami layer; the basic origami unit is mirrored out-of-plane to form a layered origami unit.

7. The honeycomb structure according to claim 6, characterized in that, The basic origami layer of the layered origami unit is obtained by mirroring the previous basic origami layer in the XY plane or by rotating it 90° around the Z-axis after symmetry in the XY plane.

8. The coplanar origami honeycomb structure according to claim 6, characterized in that, A skin is provided between adjacent basic origami layers of the layered origami unit.

9. The coplanar origami honeycomb structure according to claim 8, characterized in that, The skin is a cross-shaped skin.

10. The coplanar origami honeycomb structure according to claim 8, characterized in that, The cross-shaped skin is formed by the intersection of several narrow rectangular strips or several wide rectangular strips; adjacent basic origami layers are connected by the narrow or wide rectangular strips of the cross-shaped skin.

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