CN112537438A - Flexible skin based on unit structure - Google Patents
Flexible skin based on unit structure Download PDFInfo
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- CN112537438A CN112537438A CN202011498870.8A CN202011498870A CN112537438A CN 112537438 A CN112537438 A CN 112537438A CN 202011498870 A CN202011498870 A CN 202011498870A CN 112537438 A CN112537438 A CN 112537438A
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- flexible
- unit
- flexible skin
- layer
- skin based
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64C—AEROPLANES; HELICOPTERS
- B64C3/00—Wings
- B64C3/26—Construction, shape, or attachment of separate skins, e.g. panels
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T50/00—Aeronautics or air transport
- Y02T50/10—Drag reduction
Abstract
The invention belongs to the field of airplane structure design, and particularly relates to a flexible skin based on a unit structure. The invention provides a flexible skin technology based on the use requirements of moving parts such as advanced aircraft variant structures, flexible structures and the like, and meets the comprehensive performance requirements of the aircraft on pneumatic loading, large deformation, surface quality and the like in the flying process.
Description
Technical Field
The invention belongs to the field of airplane structure design, and particularly relates to a flexible skin based on a unit structure.
Background
The next generation of aircraft platform gradually develops from a conventional and fixed structure to an unconventional, non-directional and variable flight mode, and develops from a direction of pursuing single aerodynamic performance to a pneumatic-structure-stealth-control integration direction. At present, the most advanced fighter aircraft adopt unconventional layout such as folding wings, variable sweepback wings, non-vertical tails or variable folding tail wings, self-adaptive front and rear edges, wing body fusion and the like. In order to shorten the take-off and landing distance and consider high-speed attack and low-speed cruise standby, the optimal performance of a plurality of design points is achieved, and the layout form of a variable configuration becomes a potential scheme.
Years of research in the field of domestic and foreign variant technologies show that the gains in pneumatic efficiency are greatly reduced by the cost of the increase in weight, complexity and volume of a mechanically-driven rigid variant mechanism, so that further intensive research and application are limited. Researchers in this variation technology are not limited to changing the angle or position of a rigid wing member, but include the concepts of flexibility, no gaps, smoothness, continuity, and improved aerodynamic efficiency of an aircraft through shape changes.
In the research of variant airplanes, the flexible skin design technology is the bottleneck of implementation of variant schemes. When the flexible skin bears the aerodynamic load of the airplane, the large deformation can be realized in the skin surface, so that the design requirement of the morphing airplane is met. At present, the research of the domestic and foreign variant technology mainly focuses on the design of intelligent materials and wing structures, and the research on the design of flexible skins is very little.
The wing skin of the early airplane is made of fiber materials, but as the flying speed increases, the aerodynamic load also increases, and materials with better rigidity and stability are needed. The main materials used for aircraft skins are now rigid metal panels (e.g. aluminium alloys), and the use of high-strength high-modulus glass fibre or carbon fibre/epoxy reinforced composites is increasing. The panels are typically reinforced with stiffeners and the skin is supported by chordwise ribs and spanwise beams. From the perspective of load transmission, the difficulty of replacing the existing rigid skin with the flexible skin, which has good rigidity and high strength, is conceivable.
Disclosure of Invention
The purpose of the invention is as follows: the flexible skin technology based on the use requirements of the advanced aircraft variant structure, the flexible structure and other moving parts is provided, and the comprehensive performance requirements of the aircraft on pneumatic loading, large deformation, surface quality and the like in the flying process are met.
The technical scheme is as follows: providing a flexible skin based on a unit structure, wherein the flexible skin comprises an upper-layer microcell structure 1, a lower-layer microcell structure 2, a plurality of foldable flexible units 3 and L-shaped interface units 4 which are sequentially connected;
the flexible unit 3 is positioned between the upper-layer microcell structure 1 and the lower-layer microcell structure 2; the upper-layer microcell structure 1 and the lower-layer microcell structure 2 are plate-shaped structures;
when the flexible skin is in a stretching state, the front end surface and the rear end surface of the flexible unit 3 are square, the flexible unit 3 is in a hexahedral structure, and the hexahedron is a cuboid or a cube; when the flexible skin is in an initial state, the flexible unit 3 is in a folded state, the front end face and the rear end face are folded towards the inner part close to the hexahedron along the oblique cross crease of the end faces, and the upper end face and the lower end face are folded towards the central line close to the hexahedron along the vertical symmetry line of the hexahedron;
the two ends of a plurality of foldable flexible units 3 connected in sequence are connected with an L-shaped interface unit 4.
Optionally, the upper-layer microcell structure 1 and the lower-layer microcell structure 2 are corrugated plate structures.
Optionally, the upper-layer microcell structure 1 and the lower-layer microcell structure 2 are zigzag structures.
Optionally, the heights of the upper layer microcell structure 1 and the lower layer microcell structure 2 are less than 1 mm.
Alternatively, the contact end face of the adjacent flexible units 3 is a common one.
Optionally, the L-shaped interface unit, the upper micro-unit structure 1, the lower micro-unit structure 2, and the plurality of foldable flexible units 3 connected in sequence are an integrally formed structure.
Optionally, the folds of the flexible unit 3 are flexible links.
Optionally, the flexible connecting member is a flexible gel.
Optionally, the L-shaped interface unit, the upper micro-unit structure 1, the lower micro-unit structure 2, and the plurality of foldable flexible units 3 connected in sequence are made of a super-elastic titanium alloy material.
Has the advantages that: the flexible skin based on the unit structure has large deformation in the in-plane stress direction, does not deform in the vertical stress direction, and has normal pneumatic load capable of being borne by the bending rigidity of the hexahedral unit structure, so that the flexible skin integrally realizes the performances of large deformation, high bearing capacity and zero Poisson ratio; the folding principle of flexible skins based on cell structures theoretically has a large amount of deformation.
Drawings
FIG. 1 is a schematic view of a flexible skin structure based on a cell structure;
FIG. 2 is a schematic diagram of a folding process of the foldable unit structure;
FIG. 3 is a schematic diagram of an application position of a flexible skin based on a unit structure;
FIG. 4 is a schematic view of a flexible skin surface treatment based on a cell structure;
fig. 5 is an enlarged structure view of a region A of the flexible skin surface layer based on the unit structure.
Detailed Description
A flexible skin based on a unit structure is used for moving parts such as a variant structure and a flexible structure of an advanced aircraft, and meets the requirements of the bearing capacity of the aircraft in a flight environment and the smoothness and continuity of the body appearance in the variant process through the elasticity and the rigidity of the flexible skin, so that the optimal comprehensive performance of the aircraft at a plurality of design points in the motion process is realized. By means of the unit structure capable of generating large deformation and the combination of unit structures with different sizes, various performance requirements such as large deformation in a plane, high normal bearing capacity, good surface quality and the like are met. By comprehensive design optimization of unit structure parameters, unit combination forms, unit forming and material distribution, the flexible skin scheme with different deformation and normal stiffness requirements can be realized, and the application requirements of the aircraft on parts such as a variant structure, a self-adaptive control surface and the like are met.
In the embodiment, a flexible skin based on a unit structure is provided, which is used for pneumatic sealing of the positions of control surfaces such as flaps and ailerons of an advanced aircraft, and meets the requirement of smooth and continuous appearance of the control surfaces of the aircraft during deflection and state maintenance, as shown in fig. 1; in fig. 1, the left side is the initial state of the flexible skin, and the right side is the stretching state.
Fig. 3 is a schematic view of an application part of a flexible skin based on a cell structure, and in combination with fig. 3, a flexible skin based on a cell structure is provided, where the flexible skin includes an L-shaped interface unit 4, an upper micro-cell structure 1, a lower micro-cell structure 2, and a plurality of foldable flexible units 3 connected in sequence. The flexible unit 3 is positioned between the upper-layer microcell structure 1 and the lower-layer microcell structure 2; the upper-layer microcell structure 1 and the lower-layer microcell structure 2 are plate-shaped structures. The two ends of a plurality of foldable flexible units 3 which are connected in sequence are connected with the L-shaped interface unit.
With reference to fig. 1 and 2, when the flexible skin is in a stretched state, front and rear end surfaces of the flexible unit 3 are square, the flexible unit 3 is in a hexahedral structure, and the hexahedron is a cuboid or a cube; when flexible skin is in initial condition, flexible unit 3 is fold condition, two terminal surfaces are folded to the inside that is close to the hexahedron along the oblique cross crease of terminal surface around, and two terminal surfaces are folded to the central line that is close to the hexahedron along the vertical symmetry line of hexahedron from top to bottom. The contact end face of the adjacent flexible unit 3 is a common one.
The folding effect is realized by controlling the distance between the left side surface and the right side surface. The distance between the front side and the rear side of the hexahedron can be reasonably arranged according to the requirement of bearing rigidity.
In this embodiment, as shown in fig. 3, the flexible skin based on the unit structure is connected to the main wing surface and the control surface through an L-shaped interface unit, where the L-shaped interface unit is of a metal structure and has a thickness of generally 3-5 mm. And flexible unit arrays of flexible skins are arranged between the interfaces, and flexible units which are sequentially connected are arranged. The thickness of the flexible skin is generally designed not to exceed 20mm, depending on the internal spatial conditions of the aircraft structure.
In this embodiment, the flexible skin based on the unit structure takes the folded position as an initial state, and when an in-plane tensile load is applied, the unit structure array of the flexible skin generates corresponding deformation and is gradually unfolded into a hexahedron, and the flexible skin is in a maximum deformation state when the flexible skin is completely unfolded into the hexahedron. When the tensile load is removed, the unit structure is restored to the original state by the elasticity of the unit structure itself.
In the embodiment, when the flexible skin based on the unit structure applies normal pneumatic load, the skin is small in area and small in overall load. In the process of gradually unfolding from the folded state, the area of the skin is increased, and the whole load borne by the skin is also increased. The unit structure is transited from a folded state to a hexahedral state, and the integral stress form of the flexible skin is adaptive to the increase of the pneumatic load.
Further, as shown in fig. 4 and 5, the upper-layer microcell structure 1 and the lower-layer microcell structure 2 are corrugated plate structures. Or, the upper layer microcell structure 1 and the lower layer microcell structure 2 are zigzag structures. In this embodiment, the heights of the upper layer microcell structure 1 and the lower layer microcell structure 2 are less than 1 mm; the corrugated structure or the sawtooth structure of the upper layer microcell structure 1 and the lower layer microcell structure 2 is as small as possible under the condition of the forming process operation, and is generally controlled within 1mm, as shown in fig. 5; so as to meet the requirements of smooth and continuous surface quality and not to influence the aerodynamic performance of the aircraft.
Furthermore, the L-shaped interface unit, the upper micro-unit structure 1, the lower micro-unit structure 2 and the plurality of foldable flexible units 3 which are connected in sequence are of an integrally formed structure.
In this embodiment, the flexible skin based on the cell structure is formed by advanced additive manufacturing technology 4D printing technology. The hexahedral unit structure main body and the microcellular structure are made of metal materials, the foldable crease positions are made of high-toughness flexible materials, the combination principle of the hexahedral unit structure main body and the microcellular structure is similar to that of muscles and bones, and the high-deformation, high-strength and high-fatigue performance can be realized through an advanced additive manufacturing technology. In particular, the foldable fold locations are comprised of flexible gel.
In addition, the L-shaped interface unit, the upper-layer micro-unit structure 1, the lower-layer micro-unit structure 2 and the plurality of foldable flexible units 3 which are connected in sequence are made of a super-elastic titanium alloy material.
Claims (9)
1. The flexible skin based on the unit structure is characterized by comprising an L-shaped interface unit, an upper-layer microcell structure (1), a lower-layer microcell structure (2) and a plurality of foldable flexible units (3) which are sequentially connected;
the flexible unit (3) is positioned between the upper-layer microcell structure (1) and the lower-layer microcell structure (2); the upper-layer micro-unit structure (1) and the lower-layer micro-unit structure (2) are plate-shaped structures;
when the flexible skin is in a stretching state, the front end surface and the rear end surface of the flexible unit (3) are square, the flexible unit (3) is in a hexahedral structure, and the hexahedron is a cuboid or a cube; when the flexible skin is in an initial state, the flexible unit (3) is in a folded state, the front end face and the rear end face are folded towards the inner part close to the hexahedron along the inclined cross crease of the end faces, and the upper end face and the lower end face are folded towards the middle line close to the hexahedron along the vertical symmetry line of the hexahedron;
the two ends of a plurality of foldable flexible units (3) which are connected in sequence are connected with the L-shaped interface unit.
2. The flexible skin based on a cellular structure according to claim 1, characterized in that the upper layer microcellular structure (1) and the lower layer microcellular structure (2) are corrugated plate structures.
3. The flexible skin based on a cell structure, according to claim 1, characterized in that the upper layer microcell structure (1) and the lower layer microcell structure (2) are zigzag structures.
4. The flexible skin based on a cell structure according to claim 2 or 3, characterized in that the upper layer microcell structure (1) and the lower layer microcell structure (2) have a height of less than 1 mm.
5. The flexible skin based on a cell structure according to claim 1, characterized in that the contacting end face of adjacent flexible cells (3) is a common one.
6. The flexible skin based on a cell structure according to claim 1, characterized in that the L-shaped interface unit, the upper micro-cell structure (1), the lower micro-cell structure (2) and the plurality of foldable flexible cells (3) connected in sequence are an integrally formed structure.
7. The flexible skin based on a cell structure according to claim 1, characterized in that the folds of the flexible cells (3) are flexible links.
8. The flexible skin based on a unit structure of claim 7, wherein the flexible connectors are flexible colloids.
9. The flexible skin based on a cell structure of claim 1, wherein the L-shaped interface unit, the upper micro-cell structure (1), the lower micro-cell structure (2) and the plurality of foldable flexible units (3) connected in sequence are made of a super-elastic titanium alloy material.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202011498870.8A CN112537438B (en) | 2020-12-17 | 2020-12-17 | Flexible skin based on unit structure |
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| CN202011498870.8A CN112537438B (en) | 2020-12-17 | 2020-12-17 | Flexible skin based on unit structure |
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| CN112537438B CN112537438B (en) | 2022-07-12 |
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