Design of a composite bistable flexible wing and method of making same

Abstract

The application discloses a design scheme of a composite bistable flexible wing, which is composed of a wing vein, a reticular wing vein, a front edge sleeve and a wing root sleeve, and is different from the design scheme of a flexible wing used by a current micro flapping-wing aircraft in that the composite bistable flexible wing is designed through an included angle between the front edge sleeve and the wing root sleeve and the reticular wing vein, is a planar structure before being installed to the micro flapping-wing aircraft, and becomes a spatial curved surface structure with a bistable characteristic after being installed.The composite bistable flexible wing for the micro flapping-wing aircraft has the characteristics of low flapping noise, large lift, high aerodynamic efficiency, difficulty in fatigue failure and high reliability.A preparation method of the composite bistable flexible wing has five steps, and has the advantages of simple operation, good processing consistency and good engineering application value.

Description

Technical Field

[0001] This invention provides a design scheme and preparation method for a composite material bistable flexible wing, belonging to the field of aircraft design and manufacturing. Background Technology

[0002] Ornithoptering aircraft are aircraft that mimic the flight patterns of birds or insects in nature. Compared to traditional fixed-wing and rotary-wing aircraft, ornithoptering aircraft generate lift to overcome their own gravity, thrust to overcome aerodynamic drag, and control torque for flight control through the reciprocating flapping of their flexible wings. Existing research shows that at the scale of micro-aircraft, ornithoptering aircraft exhibit superior aerodynamic performance compared to traditional fixed-wing and rotary-wing aircraft. Micro-ornithoptering aircraft, mimicking the flight patterns of hummingbirds or insects, can perform hovering flight and a series of complex maneuvers, enabling them to fly in confined spaces with numerous obstacles. Furthermore, their biomimetic shape and flight mode give them strong stealth capabilities. Currently, micro-ornithoptering aircraft have become a research hotspot in the micro-aircraft field.

[0003] The flexible wings installed on existing micro flapping-wing aircraft are mainly composed of wing membranes and wing veins. The wing membranes are usually made of lightweight polymer films, kite fabric, or non-woven fabrics, while the wing veins are usually made of lightweight, high-strength composite material rods or composite material sheets. Together, they bear the aerodynamic and inertial loads that the flexible wing experiences during flapping.

[0004] The wing veins of the flexible wings used in existing micro flapping-wing aircraft mostly extend from the wing root or inner leading edge of the flexible wing to the trailing edge of the flexible wing. For example, the patent "A wing of a hovering flapping-wing aircraft with biomimetic wing rib form and shape" (publication number: CN 113998104 A) discloses a flexible wing in which five wing veins extend from the inner leading edge of the flexible wing to the trailing edge of the flexible wing. The patent "A design scheme and preparation method of a composite material wing for a micro flapping-wing aircraft" (publication number: CN 114872894 A) discloses a flexible wing in which three wing veins extend from the arc edge at the intersection of the leading edge and the wing root to the trailing edge of the flexible wing. The wing veins of the aforementioned flexible wing cannot effectively constrain the wing membrane. Due to the high flexibility of the wing membrane itself, coupled with the strong aerodynamic and inertial loads experienced by the flexible wing during flapping direction changes, the flexible wing exhibits severe high-frequency vibrations during this process. This results in noticeable wrinkling of the wing membrane and significant noise generation. This noise originates from both the structural noise generated by the flexible wing's own vibrations and the aerodynamic noise generated by the flexible wing causing vibrations in the surrounding air. The severe high-frequency vibrations and significant noise generated by the flexible wing during flapping direction changes have adverse effects on flexible wings and micro flapping-wing aircraft in several ways, including:

[0005] ① The noise generated by the flexible wings significantly reduces the stealth of the micro flapping-wing aircraft, making it easy for the micro flapping-wing aircraft to be detected when performing special missions such as battlefield reconnaissance and counter-terrorism rescue.

[0006] ② The violent vibration and noise generated by the flexible wing consume some of the energy that should have been used to generate continuous lift or thrust, reducing the aerodynamic efficiency of the flexible wing and the endurance of the micro flapping-wing aircraft.

[0007] ③ The severe vibration of the flexible wing makes the wing membrane and wing veins more susceptible to fatigue failure, significantly reducing the service life of the flexible wing and the reliability of the micro flapping-wing aircraft.

[0008] Therefore, this invention provides a design scheme and preparation method for a composite material bistable flexible wing. This composite material bistable flexible wing avoids severe vibration during the flapping direction change by its own bistable characteristics, significantly reduces the noise generated by the flapping of the flexible wing, and improves the aerodynamic efficiency and service life of the flexible wing. The preparation method of the composite material bistable flexible wing is simple and feasible, and has good processing consistency. Summary of the Invention

[0009] The purpose of this invention is to provide a design scheme and preparation method for a composite material bistable flexible wing, in order to solve the problems of severe vibration, significant noise, and easy fatigue failure of the flexible wing in current micro flapping-wing aircraft during the flapping direction conversion.

[0010] This invention discloses a design scheme for a composite material bistable flexible wing. In the design scheme, the composite material bistable flexible wing is composed of a wing membrane, a mesh wing vein, a leading edge sleeve, and a wing root sleeve. The difference from the flexible wing design scheme used in current micro flapping-wing aircraft is that, through the angle design between the leading edge sleeve and the wing root sleeve and the mesh wing vein design, the composite material bistable flexible wing is a planar structure when installed in front of the micro flapping-wing aircraft, and a spatial curved surface structure when installed in rear of the micro flapping-wing aircraft. Moreover, this structure has bistable characteristics.

[0011] The bistable characteristic refers to the fact that the composite bistable flexible airfoil has two mirror-symmetric structural stability states, each of which is a spatial curved surface structure close to a conical surface. In one structural stability state, if subjected to a strong load acting from the convex direction to the concave direction, the composite bistable flexible airfoil will rapidly transition to the other structural stability state; if subjected to a load acting from the concave direction to the convex direction, the composite bistable flexible airfoil will maintain its current structural stability state.

[0012] The angle design between the leading-edge sleeve and the wing root sleeve: Before being installed on the micro flapping-wing aircraft, the composite bistable flexible wing is a planar structure. At this time, the angle between the leading-edge sleeve and the wing root sleeve on the plane is greater than 90 degrees. The micro flapping-wing aircraft has two support rods for mounting the composite bistable flexible wing. One support rod is inserted into the leading-edge sleeve to drive the composite bistable flexible wing to flap back and forth, and the other support rod is inserted into the wing root sleeve to fix the wing root position of the composite bistable flexible wing. Normally, the angle between the two support rods is 90 degrees. Therefore, after the composite bistable flexible wing is installed on the micro flapping-wing aircraft, the composite bistable flexible wing will naturally form a spatial curved surface structure.

[0013] Mesh Vein Design: The mesh vein design of the composite bistable flexible wing consists of two parts: lateral veins and supporting veins. These two types of veins differ in shape, location, and function. The lateral veins are multiple radial veins originating from the arcuate edge at the intersection of the leading edge and the wing root, mimicking the longitudinal veins in insect wings. Two of these lateral veins are located on the leading edge and the wing root of the composite bistable flexible wing, respectively. The remaining lateral veins extend from the arcuate edge at the intersection of the leading edge and the wing root to the outer trailing edge. The main function of the lateral veins is to bear the aerodynamic and inertial loads on the composite bistable flexible wing and maintain its biomimetic shape. There must be at least one lateral vein, and it must include the lateral vein that originates from the arcuate edge at the intersection of the leading edge and the wing root and extends to the outer trailing edge. The supporting wing veins consist of multiple parallel veins, mimicking the transverse veins in insect wings. One supporting wing vein extends from the outermost leading edge (wingtip) of the composite bistable flexible wing to the lowest point of the wing root. The other supporting wing veins extend from the leading edge to the wing root, or from the outer trailing edge to the inner trailing edge. The main function of the supporting wing veins is to reduce the angle between the leading edge sleeve and the wing root sleeve from greater than 90° to 90° after the composite bistable flexible wing is installed on the micro flapping-wing aircraft. As the distance decreases, the supporting veins bend and deform. Since the supporting veins can bend and deform in either normal direction to the left or right of the wing membrane, and can quickly change the direction of bending deformation after being subjected to a load opposite to the direction of deformation, the bending supporting veins give the composite bistable flexible wing bistable characteristics. The number of supporting veins is not less than one, and it must include a supporting vein extending from the outermost leading edge of the composite bistable flexible wing (i.e., the wingtip) to the lowest position of the wing root. This supporting vein plays a dominant role in the bistable characteristics.

[0014] The outer wing veins and supporting wing veins intersect to form a mesh-like wing vein pattern similar to that of an insect's wing. This divides the wing membrane of the composite bistable flexible wing into multiple smaller local areas, making the load distribution of the entire wing membrane more uniform and thus improving the service life of the composite bistable flexible wing. When the wing membrane is damaged locally due to initial damage, fatigue, collision with a sharp object, or excessive load, the mesh-like wing veins will limit the damage to the local area, preventing the entire composite bistable flexible wing from being completely destroyed. This allows the composite bistable flexible wing to continue flapping and generating a certain aerodynamic force.

[0015] During the change of flapping direction, the composite bistable flexible airfoil experiences a strong inertial load due to the large angular acceleration. This inertial load acts from the convex to the concave direction, causing the airfoil to rapidly transition from its current structurally stable state to another. Because the transition to a stable state is very short, and with the support of the supporting fins, the composite bistable flexible airfoil no longer experiences severe high-frequency vibrations, and wrinkles no longer appear on the fin membrane. The mechanical and aerodynamic noise generated by the composite bistable flexible airfoil is very low, and it is less prone to fatigue failure. Furthermore, the composite bistable flexible airfoil does not consume a large amount of energy during high-frequency vibrations, thus improving its aerodynamic efficiency. From the moment the composite bistable flexible airfoil changes its flapping direction until the next change, it is subjected to a strong aerodynamic load from the concave to the convex direction. This allows the composite bistable flexible airfoil to maintain its current structural stability. The convex direction of the spatial curved surface structure of the composite bistable flexible airfoil is opposite to the flapping direction. During this process, the geometric angle of attack of the composite bistable flexible airfoil does not change significantly, which helps the composite bistable flexible airfoil generate higher lift.

[0016] The advantages of the composite material bistable flexible airfoil design scheme of the present invention are:

[0017] ① The present invention provides a design scheme for a composite material bistable flexible wing. By designing the included angle between the leading edge sleeve and the wing root sleeve and the mesh wing vein design, the composite material bistable flexible wing has bistable characteristics, which reduces the noise generated by the flapping of the composite material bistable flexible wing, extends the time from the start of use to fatigue failure of the composite material bistable flexible wing, and improves the aerodynamic efficiency and lift generated by the flapping of the composite material bistable flexible wing.

[0018] ②The present invention provides a design scheme for a composite material bistable flexible wing. Through the mesh wing vein design, the load-bearing capacity of the composite material bistable flexible wing is improved, thereby enhancing the reliability of the micro flapping-wing aircraft.

[0019] This invention discloses a method for preparing a composite material bistable flexible airfoil, the preparation steps of which are as follows:

[0020] Step 1: Cut a polymer film with an area equal to that of multiple composite bistable flexible wings to prepare the wing membrane.

[0021] Step 2: Take a piece of prepreg fabric and cut out multiple complete prepreg mesh wing veins. The reinforcing fibers of the prepreg fabric are arranged along the length of the supporting wing veins, so that the supporting wing veins have bidirectional bending ability. Apply a small amount of epoxy resin to the prepreg mesh wing veins, and then attach them to both sides of the polymer film obtained in Step 1. It is required that the mesh wing veins attached to both sides are mirror-symmetrical with respect to the polymer film, and a certain interval should be maintained between the prepreg mesh wing veins attached to the same side of the polymer film, so as to leave part of the polymer film to make the leading edge sleeve and the wing root sleeve when cutting the wing film later.

[0022] Step 3: According to the planar shape of the composite bistable flexible airfoil, cut the polymer film with prepreg mesh veins pasted on both sides obtained in Step 2 to obtain the semi-finished product of the composite bistable flexible airfoil.

[0023] Step 4: Roll up the polymer film left at the leading edge and wing root of the semi-finished composite bistable flexible wing and attach it in reverse to the outer wing veins located at the leading edge and wing root to form the leading edge sleeve and wing root sleeve.

[0024] Step 5: Cover both sides of the semi-finished composite bistable flexible wing with the leading edge sleeve and wing root sleeve attached in Step 4 with a layer of release cloth. Then place the semi-finished product covered with release cloth into a vacuum bag and place the vacuum bag in an oven. Set the heating temperature and heating time of the oven and turn on the power to heat. After heating, the prepreg mesh wing veins are completely cured into mesh wing veins. The polymer film constituting the leading edge sleeve and wing root sleeve is also firmly attached to the outer wing veins of the leading edge and wing root. After waiting for the temperature inside the oven to cool naturally to the room temperature, take out the composite bistable flexible wing from the vacuum bag. The preparation is complete.

[0025] The “polymer film” mentioned in step one is a polyimide film, polyester fiber film, polytetrafluoroethylene film, polyetheretherketone film, polyphenylene sulfide film, or polybenzimidazole film.

[0026] In step two, the "prepreg fabric" refers to a composite material whose matrix is ​​epoxy resin, styrene, styrene-butadiene, trans-polyisoprene, cyanate ester, polyurethane, polynorbornene, polyimide, bismaleimide, polyamide, polyphenylene sulfide, polyaryletherketone, or polyvinyl alcohol; and whose reinforcing fiber is carbon fiber, glass fiber, Kevlar fiber, boron fiber, plant fiber, or chopped fibers of the above fibers.

[0027] The "release cloth" mentioned in step four is a fabric woven from glass fiber and coated with polytetrafluoroethylene.

[0028] The advantages of the method for preparing a composite bistable flexible wing of the present invention are: the method for preparing a composite bistable flexible wing of the present invention directly obtains a complete mesh wing structure by cutting and cutting prepreg fabric, which simplifies the previous process of laying prepreg wing veins one by one, and improves the preparation efficiency and processing consistency of the composite bistable flexible wing. Attached Figure Description

[0029] Figure 1 A planar schematic diagram of a composite material bistable flexible airfoil

[0030] Figure 2 An isometric schematic diagram of a composite material bistable flexible airfoil.

[0031] Figure 3 This is a schematic diagram of two mirror-symmetric structural stability states of a composite bistable flexible airfoil.

[0032] Figure 4 A schematic diagram of a composite material bistable flexible wing installed on a micro flapping-wing aircraft to form a spatial curved surface structure.

[0033] Figure 5 This is a schematic diagram of the mesh-like fins of a composite bistable flexible airfoil.

[0034] Figure 6 This is a schematic diagram illustrating the process by which a composite material bistable flexible airfoil transitions from one structurally stable state to another when changing its flapping direction.

[0035] Figure 7 This is a schematic diagram of a composite material bistable flexible wing that maintains structural stability from one change in flapping direction to the next change in flapping direction.

[0036] Figure 8 An exploded view of step two in a method for fabricating a composite bistable flexible wing.

[0037] Figure 9 This is a schematic diagram of step three in a method for fabricating a composite bistable flexible airfoil.

[0038] Figure 10 A partial schematic diagram of the leading edge sleeve of a composite material bistable flexible airfoil.

[0039] Figure 11 A flowchart of a method for fabricating a composite bistable flexible airfoil.

[0040] In the picture:

[0041] 1: Wing membrane 2: Reticulated wing veins 3: Leading edge sleeve 4: Wing root sleeve

[0042] 5: Polymer film; 6: Prepreg mesh fins; 7: Support rod; 8: Support rod

[0043] 201: External Wing Vein 202: External Wing Vein 203: External Wing Vein 204: External Wing Vein

[0044] 205: External wing vein; 206: Supporting wing vein; 207: Supporting wing vein; 208: Supporting wing vein Detailed Implementation

[0045] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0046] This invention discloses a composite material bistable flexible wing, comprising a wing membrane 1, a mesh wing vein 2, a leading edge sleeve 3, and a wing root sleeve 4, as shown below. Figure 1 and Figure 2 As shown, the difference between this design and the flexible wing design used in current micro flapping-wing aircraft is that, through the angle design between the leading edge sleeve 3 and the wing root sleeve 4 and the mesh wing vein design, the composite material bistable flexible wing is a planar structure when installed in front of the micro flapping-wing aircraft and a spatial curved surface structure when installed behind the micro flapping-wing aircraft, and this structure has bistable characteristics.

[0047] The aforementioned bistable characteristic refers to the fact that the composite material bistable flexible airfoil has two mirror-symmetric structural stable states, such as... Figure 3 As shown, each structural stability state is a spatial curved surface structure that approximates a conical surface. In one structural stability state, if the composite bistable flexible airfoil is subjected to a strong load acting from the convex direction to the concave direction, it will rapidly transition to another structural stability state; if subjected to a load acting from the concave direction to the convex direction, it will maintain its current structural stability state.

[0048] Design of the angle between the leading edge sleeve 3 and the wing root sleeve 4: Before being installed on the micro flapping-wing aircraft, the composite bistable flexible wing has a planar structure. At this time, the angle between the leading edge sleeve 3 and the wing root sleeve 4 of the composite bistable flexible wing on the plane is greater than 90 degrees. Figure 1 and Figure 2As shown. The micro flapping-wing aircraft has support rods 7 and 8 for mounting a composite bistable flexible wing. Support rod 7 is inserted into the leading-edge sleeve 3 to drive the composite bistable flexible wing to flap reciprocate. Support rod 8 is inserted into the wing root sleeve 4 to fix the wing root position of the composite bistable flexible wing. Typically, the angle between the two support rods is 90 degrees. Therefore, after the composite bistable flexible wing is installed on the micro flapping-wing aircraft, it will naturally form a spatial curved surface structure, such as... Figure 4 As shown.

[0049] Mesh Wing Vein 2 Design: The mesh wing vein 2 of the composite bistable flexible wing consists of two parts: the external wing veins and the supporting wing veins. The two types of wing veins differ in shape, position, and function, such as... Figure 5 As shown. The wing veins are multiple radial veins originating from the arc edge at the intersection of the leading edge and the wing root, mimicking the longitudinal veins in insect wings. Wing vein 201 is located on the leading edge of the composite bistable flexible wing, wing vein 205 is located on the wing root, and the remaining wing veins (including wing veins 202, 203, and 204) extend from the arc edge at the intersection of the leading edge and the wing root to the outer trailing edge. The main function of the wing veins is to bear the aerodynamic and inertial loads on the composite bistable flexible wing and maintain the biomimetic shape of the composite flexible wing. There must be at least one wing vein, and it must include a wing vein that extends from the arc edge at the intersection of the leading edge and the wing root to the outer trailing edge. The supporting wing veins (including supporting wing veins 206, 207, and 208) are multiple parallel wing veins, mimicking the transverse veins in insect wings. Supporting wing vein 207 extends from the outermost leading edge (wingtip) of the composite bistable flexible wing to the lowest point of the wing root. Supporting wing vein 206 extends from the leading edge to the wing root. Supporting wing vein 208 extends from the outer trailing edge to the inner trailing edge. The main function of the supporting wing veins is to ensure that after the composite bistable flexible wing is installed on the micro flapping-wing aircraft, the angle between the leading edge sleeve 3 and the wing root sleeve 4 is adjusted from the original angle. When the angle is reduced from 90° to 90°, the distance between the two ends of the supporting wing vein decreases, thus causing the supporting wing vein to bend and deform. Since the supporting wing vein can bend and deform in any normal direction on either side of the wing membrane 1, and after being subjected to a load opposite to the direction of deformation, the supporting wing vein can quickly change the direction of bending deformation, the bent supporting wing vein gives the composite material bistable flexible wing bistable characteristics. The number of supporting wing veins is not less than one, and it must include a supporting wing vein 207 that extends from the outermost leading edge of the composite material bistable flexible wing (i.e., the wingtip) to the lowest position of the wing root. The supporting wing vein 207 plays a dominant role in the bistable characteristics.

[0050] The outer wing veins and supporting wing veins intersect to form a mesh-like wing vein 2 similar to the wing veins of an insect. This divides the wing membrane 1 of the composite bistable flexible wing into multiple smaller local areas, making the load distribution of the entire wing membrane 1 more uniform and thus improving the service life of the composite bistable flexible wing. When a local area of ​​the wing membrane 1 is damaged due to initial damage, fatigue, collision with a sharp object, or excessive load, the mesh-like wing vein 2 will limit the damage to the local area, preventing the entire composite bistable flexible wing from being completely destroyed. This allows the composite bistable flexible wing to continue flapping and generating a certain aerodynamic force.

[0051] During the change of flapping direction, the composite bistable flexible airfoil experiences a strong inertial load due to the large angular acceleration. This inertial load acts precisely from the convex surface of the composite bistable flexible airfoil towards the concave surface, causing the airfoil to rapidly transition from its current structurally stable state to another. Figure 6 As shown. Because the process of transitioning to a stable structural state requires a very short time, and under the support of the supporting wing veins, the composite bistable flexible wing no longer experiences severe high-frequency vibrations, and wrinkles no longer appear on the wing membrane 1. The mechanical and aerodynamic noise generated by the composite bistable flexible wing is very weak, and it is less prone to fatigue failure. Furthermore, the composite bistable flexible wing does not consume a large amount of energy during high-frequency vibrations, thus improving aerodynamic efficiency. From one change in flapping direction to the next, due to the strong aerodynamic load from the concave to the convex direction, the composite bistable flexible wing can maintain its current structural stability. The convex direction of the spatial curved surface structure of the composite bistable flexible wing is opposite to the flapping direction, as shown in the example. Figure 7 As shown, the geometric angle of attack of the composite bistable flexible airfoil does not change significantly during this process, which helps the composite bistable flexible airfoil generate higher lift.

[0052] This invention discloses a method for preparing a composite material bistable flexible airfoil, the preparation steps of which are as follows:

[0053] Step 1: Cut a polymer film 5 with an area equal to that of multiple composite bistable flexible wings to prepare the wing membrane 1.

[0054] Step Two: Take a piece of prepreg fabric and cut out multiple complete prepreg mesh wing veins 6. The reinforcing fibers of the prepreg fabric are arranged along the length of the supporting wing veins (including supporting wing veins 206, 207, and 208) to give the supporting wing veins bidirectional bending capability. Apply a small amount of epoxy resin to the prepreg mesh wing veins 6, and then attach them to both sides of the polymer film 5 obtained in Step One, as shown below. Figure 8 As shown; the prepreg mesh wing veins 6 pasted on both sides are required to be mirror-symmetrical with respect to the polymer film 5, and a certain interval needs to be maintained between the prepreg mesh wing veins 6 pasted on the same side of the polymer film 5, so that a portion of the polymer film can be left to make the leading edge sleeve 3 and the wing root sleeve 4 when cutting the wing film 1 later.

[0055] Step 3: According to the planar shape of the composite bistable flexible wing, the polymer film 5 with prepreg mesh veins 6 attached to both sides obtained in Step 2 is cut to obtain a semi-finished product of the composite bistable flexible wing, such as... Figure 9 As shown.

[0056] Step 4: The polymer film remaining at the leading edge of the semi-finished composite bistable flexible wing is rolled up and pasted in reverse onto the wing vein 201 located at the leading edge, forming the leading edge sleeve 3, as shown below. Figure 10 As shown, the polymer film left at the root of the semi-finished composite bistable flexible wing is rolled up and pasted in reverse onto the outer wing vein 205 located at the wing root to form the wing root sleeve 4.

[0057] Step 5: Cover both sides of the semi-finished composite bistable flexible wing with the leading edge sleeve 3 and wing root sleeve 4 attached in Step 4 with a layer of release cloth. Then place the semi-finished product covered with release cloth into a vacuum bag and place the vacuum bag in an oven. Set the heating temperature and heating time of the oven and turn on the power to heat. After heating, the prepreg mesh wing vein 6 is completely cured into mesh wing vein 2. The polymer film constituting the leading edge sleeve 3 and wing root sleeve 4 is also firmly attached to the outer wing vein 201 and outer wing vein 205 of the leading edge and wing root. After waiting for the temperature inside the oven to cool naturally to the room temperature, take out the composite bistable flexible wing from the vacuum bag. The preparation is complete.

[0058] The “polymer film” mentioned in step one is a polyimide film, polyester fiber film, polytetrafluoroethylene film, polyetheretherketone film, polyphenylene sulfide film, or polybenzimidazole film.

[0059] In step two, the "prepreg fabric" refers to a composite material whose matrix is ​​epoxy resin, styrene, styrene-butadiene, trans-polyisoprene, cyanate ester, polyurethane, polynorbornene, polyimide, bismaleimide, polyamide, polyphenylene sulfide, polyaryletherketone, or polyvinyl alcohol; and whose reinforcing fiber is carbon fiber, glass fiber, Kevlar fiber, boron fiber, plant fiber, or chopped fibers of the above fibers.

[0060] The "release cloth" mentioned in step four is a fabric woven from glass fiber and coated with polytetrafluoroethylene.

Claims

1. A composite bimorph flexible wing, characterized in that: the flexible wing is composed of a wing membrane, a netted wing vein, a leading edge sleeve and a wing root sleeve, and is used for a micro flapping-wing aircraft; the composite bimorph flexible wing is flat before being installed on the micro flapping-wing aircraft, and forms a spatial curved surface structure after being installed on the micro flapping-wing aircraft, and the structure has a bimorph characteristic; the netted wing vein is a netted structure composed of a plurality of contour wing veins and a plurality of support wing veins; the contour wing veins include two wing veins at the intersection of the leading edge and the wing root of the composite bimorph flexible wing, and a plurality of wing veins extending from the inner leading edge to the outer trailing edge of the composite bimorph flexible wing, the number of the contour wing veins is not less than three, and must include the wing vein extending from the circular arc edge at the intersection of the leading edge and the wing root of the composite bimorph flexible wing to the outer trailing edge; the support wing veins include the wing vein extending from the wing tip to the lowermost position of the wing root of the composite bimorph flexible wing, the wing vein extending from the leading edge to the wing root of the composite bimorph flexible wing, and the wing vein extending from the outer trailing edge to the inner trailing edge of the composite bimorph flexible wing, the number of the support wing veins is not less than one, and must include the wing vein extending from the wing tip to the lowermost position of the wing root of the composite bimorph flexible wing; the leading edge sleeve and the wing root sleeve are thin film sleeve structures, and are respectively located at the leading edge and the wing root of the composite bimorph flexible wing; the flexible wing is flat before being installed on the micro flapping-wing aircraft, and the included angle between the leading edge sleeve and the wing root sleeve on the plane is greater than 90 degrees; after the flexible wing is installed on the micro flapping-wing aircraft, the included angle between the leading edge sleeve and the wing root sleeve is 90 degrees, forming a spatial curved surface structure.

2. A composite bistable flexible wing as in claim 1, wherein: The micro flapping-wing aircraft has two support rods for installing the composite bimorph flexible wing, one of the support rods is inserted into the leading edge sleeve to drive the composite bimorph flexible wing to flap reciprocally, and the other support rod is inserted into the wing root sleeve to fix the wing root position of the composite bimorph flexible wing.

3. The composite bistable flexible wing of claim 1, wherein: The wing membrane of the flexible wing is composed of a polymer film, the netted wing vein is obtained by curing a prepreg fabric in a high temperature environment, and the leading edge sleeve and the wing root sleeve are composed of a polymer film.

4. The method of claim 1-3, wherein: The preparation steps of the composite bimorph flexible wing are as follows: Step 1: cutting a polymer film with an area equal to a plurality of composite bimorph flexible wings to prepare a wing membrane; Step 2: taking a prepreg fabric, cutting a plurality of complete prepreg netted wing veins from the prepreg fabric, applying a small amount of epoxy resin to the prepreg netted wing veins, and then pasting them on both sides of the polymer film obtained in Step 1; the netted wing veins pasted on both sides are required to be mirror-symmetric with the polymer film, and a certain interval is required to be maintained between the prepreg netted wing veins pasted on the same side of the polymer film, so as to leave part of the polymer film to make the leading edge sleeve and the wing root sleeve when the wing membrane is cut subsequently; Step 3: cutting the polymer film with the prepreg netted wing veins pasted on both sides obtained in Step 2 according to the plane contour of the composite bimorph flexible wing, to obtain a semi-finished product of the composite bimorph flexible wing. Step four: the polymer film left at the leading edge and the wing root of the semi-finished product of the composite bi-stable flexible wing is rolled and reversely pasted on the pre-preg netted wing veins at the leading edge and the wing root, forming a leading edge sleeve and a wing root sleeve; Step five: each side of the semi-finished product of the composite bi-stable flexible wing with the leading edge sleeve and the wing root sleeve pasted in step four is covered with a layer of release cloth, then the semi-finished product covered with the release cloth is placed in a vacuum bag, and the vacuum bag is placed in an oven, and the heating temperature and heating time of the oven are set, and then the oven is powered on for heating; After heating, the pre-preg netted wing veins are completely cured into netted wing veins, and the polymer film constituting the leading edge sleeve and the wing root sleeve is firmly pasted on the outer shape wing veins of the leading edge and the wing root, and after the temperature in the oven is naturally cooled to room temperature, the composite bi-stable flexible wing is taken out from the vacuum bag, and the preparation is completed.

5. The method for preparing a composite material bistable flexible wing as described in claim 4, characterized in that: The polymer film can be a polyimide film, a polyester fiber film, a polytetrafluoroethylene film, a polyether ether ketone film, a polyphenylene sulfide film, or a polybenzimidazole film.

6. The method for preparing a composite material bistable flexible wing as described in claim 4, characterized in that: The netted wing vein pre-preg fabric has a matrix of epoxy resin, styrene, styrene-butadiene, trans-polyisoprene, cyanate ester, polyurethane, polynorbornene, polyimide, bismaleimide, polyamide, polyphenylene sulfide, polyaryletherketone, and polyvinyl alcohol, and reinforcing fibers of carbon fiber, glass fiber, Kevlar fiber, boron fiber, plant fiber, or fabric of the above fibers or chopped fibers of the above fibers.

7. The method for preparing a composite material bistable flexible airfoil as described in claim 4, characterized in that: The "release cloth" in step five is a fabric woven from glass fiber and coated with polytetrafluoroethylene on the surface.

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