Orthotropic chiral superstructures for morphing wings

Abstract

The orthotropic chiral superstructure comprises unit cells distributed in an array mode, a rib is a straight edge rib, two upper nodes are tangent to the upper rib, the distance between the circle centers of the two upper nodes is the node center distance a, a lower rib is a straight edge rib, two lower nodes are tangent to the lower rib, and the distance between the circle centers of the two upper nodes is the node center distance a. The left rib is a bent rib defined by a Bezier curve, the two ends of the left rib are connected and tangent to the upper node and the lower node on the left side respectively, the right rib is a bent rib defined by a Bezier curve, and the two ends of the right rib are connected and tangent to the upper node and the lower node on the right side respectively.

Description

Technical Field

[0001] The invention relates to the technical field of deformable wings, in particular to an orthogonal anisotropic chiral superstructure used for deformable wings. Background Art

[0002] Chiral superstructures are a new type of structure with unique physical properties. Through special microstructure design, they exhibit mechanical behaviors that traditional structures do not have. Among them, "chirality" refers to the asymmetry of the structure, similar to the human left and right hands. Although they are similar in appearance, they cannot be completely overlapped in the mirror image. Classical chiral superstructures are often composed of nodes and ribs, which have a tangent geometric relationship. Chiral superstructures can be classified according to the geometric relationship between nodes and ribs. Specifically: when the two adjacent nodes in a cell are located on both sides of the rib, the structure is called "handed"; if the two adjacent nodes in the cell are located on the same side of the rib, it is called "anti-handedness"; and when these two situations are mixed in a single cell, it is called "meta / super chirality". This asymmetry of the microscopic cell gives the chiral superstructure some unconventional mechanical responses, such as negative Poisson's ratio. Through this ingenious microscopic design, chiral superstructures can exhibit excellent mechanical properties at the macroscopic level, showing great application potential in the fields of variant structures, shock absorption and acoustic control.

[0003] Morphing wings allow aircraft to change their geometric shape in different environments to maintain optimal flight performance, and have better environmental adaptability and survivability than traditional aircraft. Currently, there are two main forms of application of chiral superstructures in morphing wings: one is to use the chiral superstructure as the main supporting structure of the wing by taking advantage of its light weight, compression resistance and shear resistance; the other is to use the chiral superstructure's small in-plane tensile stiffness and large out-of-plane bending stiffness to embed it in the wing skin as a deformable structure. Compared with mechanical deformation, embedding the chiral superstructure in the wing and using the elastic deformation of the flexible material itself can achieve changes in the span, chord length and other directions of the morphing wing. This method is not only lightweight, but also reduces the complexity of the structure, which helps to improve the overall performance of the morphing aircraft.

[0004] However, special deformation structures such as morphing wings often need to meet the deformation requirements of different deformation parts and different application occasions through the difference of in-plane and out-of-plane mechanical properties. Usually, for in-plane mechanical properties, it is easy to achieve large deformation to provide stronger deformation characteristics for the wing; while for out-of-plane mechanical properties, it is necessary to have high stiffness to provide good load-bearing characteristics for the wing. In recent years, researchers have conducted a lot of research in the field of deformation structures, but there is still the problem of difficulty in effectively adjusting in-plane and out-of-plane mechanical properties.

[0005] The information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the invention

[0006] In view of the shortcomings or defects of the prior art, an orthotropic chiral superstructure for a morphing wing is provided, which can make the in-plane and out-plane mechanical properties of the superstructure show stronger anisotropy in two mutually orthogonal directions under the condition of the same overall cell size. In addition, by changing the geometric shape of the curved ribs, the corresponding mechanical properties can be effectively adjusted.

[0007] The purpose of the present invention is achieved through the following technical solutions.

[0008] An orthotropic chiral superstructure for a morphing wing includes array-distributed unit cells, the unit cells comprising, The upper rib is a straight-edge rib. Two upper nodes, which are tangent to the upper ribs respectively, and the distance between the centers of the two upper nodes is the node center distance a, The lower rib is a straight-edge rib. Two lower nodes, which are tangent to the lower ribs respectively, and the distance between the centers of the two lower nodes is the node center distance a, The left rib is a curved rib defined by a Bezier curve. The two ends of the left rib are connected and tangent to the upper node and the lower node on the left side. The right rib is a curved rib defined by a Bezier curve, and two ends of the right rib are respectively connected and tangent to the upper node and the lower node on the right side.

[0009] In the orthogonal anisotropic chiral superstructure for deformable wings, the shape of the left rib or the right rib is determined by the coordinates of the five control points of the Bezier curve, wherein the starting and ending points P0 are fixed to the outer edge of the upper node, the starting and ending points P4 are fixed to the outer edge of the lower node, the constrained adjustable point P1 and the adjacent starting and ending points P0 are maintained on the same vertical line, the constrained adjustable point P3 and the adjacent starting and ending points P4 are maintained on the same vertical line, and the adjustable point P2 is located between the constrained adjustable point P1 and the constrained adjustable point P3. The shape of the left rib or the right rib is adjusted by changing the coordinates of the constrained adjustable point P1, the adjustable point P2, and the constrained adjustable point P3.

[0010] In the orthotropic chiral superstructure for deformable wings, the starting and ending points P0 and the starting and ending points P4 are fixed points.

[0011] In the orthotropic chiral superstructure for deformable wings, the left rib and the right rib are symmetrical.

[0012] In the orthogonal anisotropic chiral superstructure for deformable wings, the distance between the center of the circle of the lower node on the left and the upper node is the node center distance a, and the distance between the center of the circle of the lower node on the right and the upper node is the node center distance a.

[0013] In the orthotropic chiral superstructure for deformable wings, the node center distance a is 10 mm.

[0014] In the orthotropic chiral superstructure for deformable wings, the wall thickness t of the ribs and nodes is 1 mm, and the node diameter d is 4 mm.

[0015] In the orthotropic chiral superstructure for deformable wings, the Bezier curve is a fourth-order Bezier curve.

[0016] In the orthotropic chiral superstructure for deformable wings, both the upper ribs and the lower ribs are horizontal ribs.

[0017] In the orthotropic chiral superstructure for deformable wings, the unit cell is a symmetrical structure.

[0018] In the orthotropic chiral superstructure for deformable wings, the material used is nylon material with an elastic modulus of 1700 MPa and a Poisson's ratio of 0.42.

[0019] Compared with the prior art, the present invention has the following beneficial effects: The present invention is a chiral superstructure with curved ribs designed based on Bezier curves. Under the condition of the same overall cell size, the in-plane and out-plane mechanical properties of the superstructure can show stronger anisotropy in two mutually orthogonal directions. Moreover, by changing the geometric shape of the curved ribs, the corresponding mechanical properties can be effectively adjusted.

[0020] The above description is only an overview of the technical solution of the present invention. In order to make the technical means of the present invention clearer and to achieve the extent that those skilled in the art can implement it according to the contents of the specification, and in order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are exemplified below. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] By reading the detailed description of the preferred specific embodiments below, various other advantages and benefits of the present invention will become clear to those of ordinary skill in the art. The drawings in the specification are only for the purpose of illustrating the preferred embodiments and are not considered to be limitations of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative work. Moreover, the same reference numerals are used to represent the same components throughout the drawings.

[0022] In the attached picture: Figure 1 A schematic diagram of the unit cell design of the chiral superstructure disclosed in the present invention; Figure 2 is an overall schematic diagram of the chiral superstructure disclosed in the present invention; Figure 3 It is a schematic diagram of the compression deformation of the chiral superstructure disclosed in the present invention in the x-axis direction; Figure 4 It is a schematic diagram of the compression deformation of the chiral superstructure disclosed in the present invention in the y-axis direction; Figure 5 It is a schematic diagram of the bending deformation of the chiral superstructure disclosed in the present invention along the x-axis direction; Figure 6 It is a schematic diagram of the bending deformation of the chiral superstructure disclosed in the present invention along the y-axis direction; Figure 7 It is a schematic diagram of adjusting the equivalent elastic modulus in the orthogonal direction by changing the control points of the Bezier curve disclosed in the present invention; Figure 8 It is a schematic diagram of adjusting the equivalent Poisson's ratio in the orthogonal direction by changing the control points of the Bezier curve disclosed in the present invention; Fig. 9 It is a schematic diagram of adjusting the equivalent bending stiffness in the orthogonal direction by changing the control points of the Bezier curve disclosed in the present invention; Fig.10 Schematic diagram of application of the chiral superstructure disclosed in the present invention on a deformable wing.

[0023] The present invention is further explained below in conjunction with the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0024] The specific embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the specific embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to enable the scope of the present invention to be fully communicated to those skilled in the art.

[0025] It should be noted that certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. This specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in the functions of the components as the criterion for distinction. As mentioned throughout the specification and claims, "including" or "comprising" is an open term, so it should be interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment of the present invention, but the description is based on the general principles of the specification and is not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the attached claims.

[0026] To facilitate understanding of the embodiments of the present invention, several specific embodiments will be further explained below with reference to the accompanying drawings, and each of the accompanying drawings does not constitute a limitation on the embodiments of the present invention.

[0027] For a better understanding, Figures 1 to 10 As shown, an orthotropic chiral superstructure for a morphing wing includes array-distributed unit cells, wherein the unit cells include: The upper rib is a straight-edge rib. Two upper nodes, which are tangent to the upper ribs respectively, and the distance between the centers of the two upper nodes is the node center distance a, The lower rib is a straight-edge rib. Two lower nodes, which are tangent to the lower ribs respectively, and the distance between the centers of the two lower nodes is the node center distance a, The left rib is a curved rib defined by a Bezier curve. The two ends of the left rib are connected and tangent to the upper node and the lower node on the left side. The right rib is a curved rib defined by a Bezier curve, and two ends of the right rib are respectively connected and tangent to the upper node and the lower node on the right side.

[0028] In a preferred embodiment of the orthotropic chiral superstructure for deformable wings, the shape of the left rib or the right rib is determined by the coordinates of the five control points of the Bezier curve, wherein the starting and ending points P0 are fixed to the outer edge of the upper node, the starting and ending points P4 are fixed to the outer edge of the lower node, the constrained adjustable point P1 and the adjacent starting and ending points P0 are maintained on the same vertical line, the constrained adjustable point P3 and the adjacent starting and ending points P4 are maintained on the same vertical line, and the adjustable point P2 is located between the constrained adjustable point P1 and the constrained adjustable point P3. The shape of the left rib or the right rib is adjusted by changing the coordinates of the constrained adjustable point P1, the adjustable point P2, and the constrained adjustable point P3.

[0029] In a preferred embodiment of the orthotropic chiral superstructure for a deformable wing, the starting and ending points P0 and the starting and ending points P4 are fixed points.

[0030] In a preferred embodiment of the orthotropic chiral superstructure for a deformable wing, the left rib and the right rib are symmetrical.

[0031] In the preferred embodiment of the orthotropic chiral superstructure for deformable wings, the distance between the center of the lower node on the left and the center of the upper node is the node center distance a, and the distance between the center of the lower node on the right and the center of the upper node is the node center distance a.

[0032] In a preferred embodiment of the orthotropic chiral superstructure for deformable wings, the node center distance a is 10 mm.

[0033] In the preferred embodiment of the orthotropic chiral superstructure for a deformable wing, the wall thickness t of the ribs and nodes is 1 mm, and the node diameter d is 4 mm.

[0034] In a preferred embodiment of the orthotropic chiral superstructure for a deformable wing, the Bezier curve is a fourth-order Bezier curve.

[0035] In a preferred embodiment of the orthotropic chiral superstructure for a deformable wing, the unit cell is a symmetrical structure.

[0036] In the preferred embodiment of the orthotropic chiral superstructure for deformable wings, the material used is nylon material with an elastic modulus of 1700 MPa and a Poisson's ratio of 0.42.

[0037] In one embodiment, both the upper ribs and the lower ribs are horizontal ribs.

[0038] In one embodiment, a Bezier curve is a smooth curve constructed based on mathematical principles. Its shape is defined by a series of control points. These points can be adjusted to finely control the curvature and direction of the curve, achieving a high degree of customization and flexibility. The smoothness of the Bezier curve comes from its continuous first-order and second-order derivatives, which is very suitable for occasions that require continuous transitions. At the same time, by changing the coordinates of the control points, a curve configuration of any shape and curvature can be achieved, which has a huge design space.

[0039] In summary, the Bezier curve greatly improves the flexibility and efficiency of the design and manufacturing process with its advantages of high smoothness and good controllability. Therefore, this design introduces the Bezier curve into the design of the curved ribs of chiral metamaterials, and realizes the design of curved ribs with specific curve shapes by defining the position coordinates of the control points. Using the fourth-order Bezier curve with five control points as the design tool, an anti-quadruple-chirality metastructure is designed.

[0040] The geometric parameters of the anti-quadruciality superstructure mainly include the node center distance a (10mm), the rib and node wall thickness t (1mm), and the node diameter d (4mm). In the design, the upper and lower ribs are straight-edge ribs, which are tangent to the outer edges of the adjacent nodes respectively. The left and right ribs are symmetrical to each other and are defined by a fourth-order Bezier curve. Their shapes are determined by the coordinates of the five control points of the Bezier curve. Among them, the starting and ending points P0 and P4 are fixed to the outer edge of the node and are fixed points. P1 and P3 are constrained adjustable points, which are respectively kept on the same vertical line with the adjacent fixed points to ensure that the ribs are in a tangent relationship with the outer edge of the node; P2 is an adjustable point. By changing the coordinates of the adjustable point / constrained adjustable point, the shape of the left and right ribs can be customized. When studying the influence of the rib geometry on the deformation mode of the superstructure, the coordinates of the adjustable point can be restricted. In order to ensure that the thickness of the curved rib is the same as that of the rest of the cell, another Bezier curve, namely P5~P9, needs to be defined. Among them, P5~P9 correspond to P0~P4 one by one, and have the same ordinates, but differ in abscissa by t (rib thickness). The coordinates of the curved ribs of the superstructure are as follows: P0 (3,0); P1 (3,5); P2 (10,10); P3 (3,15); P4 (3,20); P5 (2,0); P6 (2,5); P7 (9,10); P8 (2,15); P9 (2,20).

[0041] Figures 7 to 9 The methods of adjusting the in-plane and out-plane mechanical properties of the chiral superstructure by changing the coordinates of the control points of the Bezier curve are respectively demonstrated. Among them, the equivalent elastic modulus and the equivalent Poisson's ratio are important indicators of the in-plane deformation characteristics of the superstructure, which are used to measure the degree to which the superstructure is easy to deform. The equivalent bending stiffness is an important indicator of the out-of-plane mechanical properties of the superstructure, which is used to measure the ability of the structure to resist out-of-plane loads. It can be seen that under different adjustable point coordinates, the in-plane and out-plane mechanical properties of the superstructure have obvious differences in the mutually orthogonal x and y directions. In addition, important in-plane and out-plane mechanical performance parameters such as the equivalent elastic modulus, the equivalent Poisson's ratio and the equivalent bending stiffness all show a high sensitivity to the change of the control point coordinates. This shows that without changing the overall size of the superstructure cell, by changing the control point coordinates, not only can the difference in the in-plane and out-plane mechanical properties be enhanced, but also a method of accurately adjusting the in-plane and out-plane mechanical properties of the superstructure is provided. At the same time, it should be pointed out that the change in the coordinates of the control point P2 shown in the figure is only one of the adjustment methods. However, it is still not difficult to see that this method can effectively adjust the in-plane and out-plane mechanical properties of the superstructure without changing the overall size of the superstructure cell.

[0042] Fig.10The schematic diagram of the application of the chiral superstructure involved in the present invention on the morphing wing is shown. It should be pointed out that the superstructure filling method shown in the figure is only a schematic diagram. In practice, according to the shape of the morphing wing and the needs of the deformation occasion, the filling method can be flexibly adjusted, such as filling in the wing frame or filling in the skin, etc.

[0043] The basic principles of the present application are described above in conjunction with specific embodiments. However, it should be noted that the advantages, strengths, effects, etc. mentioned in the present application are only examples and not limitations, and it cannot be considered that these advantages, strengths, effects, etc. are required by each embodiment of the present application. In addition, the specific details disclosed above are only for the purpose of illustration and ease of understanding, not for limitation, and the above details do not limit the present application to being implemented by adopting the above specific details.

[0044] The above description has been given for the purpose of illustration and description. In addition, this description is not intended to limit the embodiments of the present application to the forms disclosed herein. Although multiple example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, changes, additions and sub-combinations thereof.

Claims

1. An orthotropic chiral superstructure for a morphing wing, characterized in that: It includes array-distributed unit cells, the unit cells including, The upper rib is a straight-edge rib. Two upper nodes, which are tangent to the upper ribs respectively, and the distance between the centers of the two upper nodes is the node center distance a, The lower rib is a straight-edge rib. Two lower nodes, which are tangent to the lower ribs respectively, and the distance between the centers of the two lower nodes is the node center distance a, The left rib is a curved rib defined by a Bezier curve. The two ends of the left rib are connected and tangent to the upper node and the lower node on the left side. The right rib is a curved rib defined by a Bezier curve, and two ends of the right rib are respectively connected and tangent to the upper node and the lower node on the right side.

2. The orthotropic chiral superstructure for a morphing wing according to claim 1, characterized in that: Preferably, the left ribs and the right ribs are symmetrical.

3. The orthotropic chiral superstructure for a morphing wing according to claim 1, characterized in that: The distance between the center of the circle of the lower node and the upper node on the left is the node center distance a, and the distance between the center of the circle of the lower node and the upper node on the right is the node center distance a.

4. The orthotropic chiral superstructure for a morphing wing according to claim 3, characterized in that: The node center distance a is 10 mm.

5. The orthotropic chiral superstructure for a morphing wing according to claim 4, characterized in that: The wall thickness t of the ribs and nodes is 1 mm, and the node diameter d is 4 mm.

6. The orthotropic chiral superstructure for a morphing wing according to claim 1, characterized in that: The Bezier curve is a fourth-order Bezier curve.

7. The orthotropic chiral superstructure for a morphing wing according to claim 1, characterized in that: The material used is nylon.

8. The orthotropic chiral superstructure for a morphing wing according to claim 7, characterized in that: The elastic modulus of nylon material is 1700 MPa and the Poisson's ratio is 0.42.

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