Load-bearing compliant morphing folding structure for folding a wing flutter model

Abstract

The present application belongs to the technical field of aircraft flutter model design and wind tunnel test, and particularly relates to a loadable flexible deformation folding structure for a folding wing flutter model, comprising: an inner wing, an outer wing, a driving connection mechanism and a flexible loadable honeycomb skin; the driving connection mechanism comprises: a driving motor, a slot-shaped connecting piece and a motor clamp; a root rib of the inner wing is connected with an aircraft body or a basic support structure, and three motor clamps are fixed on an end surface of an end rib of the inner wing; the driving motor is fixedly connected through the three motor clamps; a main joint is fixed on a root rib of the outer wing; the main joint is connected with an output shaft of the driving motor through the slot-shaped connecting piece, and the driving motor drives the outer wing to rotate through the slot-shaped connecting piece and the main joint; and the flexible loadable honeycomb skin is arranged between the end rib of the inner wing and the root rib of the outer wing.

Description

Technical Field

[0001] This invention belongs to the field of aircraft flutter model design and wind tunnel testing technology, specifically relating to a load-bearing, compliant deformation folding structure for a folding wing flutter model. Background Technology

[0002] Future combat aircraft will need to possess comprehensive capabilities including high speed, high maneuverability, long endurance, and all-aspect stealth. They will adopt innovative aerodynamic layouts with intelligent variability features, achieving efficient control of aerodynamic forces through active deformation. Folding wings are a currently popular variability layout; their typical characteristics are described below. Figure 1 Wings deployed status Figure 2 The outer wings fold upwards to indicate the opinion Figure 3 .

[0003] However, variant aircraft have variable wing shapes, low structural stiffness, and complex material composition. Their fluid-structure interaction mechanism is extremely complex. If their flutter and other aeroelastic problems cannot be effectively solved, it will not only affect the performance of advanced technical indicators of the fighter jet, but may even lead to catastrophic accidents.

[0004] The most significant difference in flutter characteristics between folding wings and conventional wings is that the folding angle of the outer wing changes during flight, causing alterations in both structural dynamics and aerodynamics, resulting in substantial variations in flutter characteristics with the folding angle. Therefore, studying the variation of flutter characteristics with folding angle has become an important research area in folding wing flutter design. Furthermore, the influence of compliant load-bearing structures on flutter characteristics during folding wings' variant processes is also unclear and requires further investigation.

[0005] Current methods for studying the flutter characteristics of folding wings include frequency domain simulation based on discrete folding angles and wind tunnel testing based on discrete angles. There is an urgent need for a design scheme for a load-bearing, compliant deformation folding structure / mechanism that can be used for flutter models of folding wings. This would allow for flutter wind tunnel testing to study the flutter characteristics of folding wings with compliant load-bearing structures during the dynamic folding process, providing crucial technical support for flutter characteristic research of folding-wing aircraft and the design of wing folding schemes. Summary of the Invention

[0006] The purpose of this invention is to propose a load-bearing, compliant deformation folding structure / mechanism design for a flutter model of a folding wing. A closed-loop controllable drive device with a reduction gear is designed to achieve variable-rate dynamic deflection of the folding wing. By designing a grooved cross-section connector and matching it with the front and rear connecting springs, the bending support stiffness of the outer wing can be adjusted by the drive motor and the grooved cross-section connector. The torsional support stiffness of the outer wing can be adjusted by the grooved cross-section connector and the front and rear springs. A zero Poisson's ratio honeycomb structure with a flexible skin achieves the shape-binding of the transition section between the inner and outer wings. This allows for continuous aerodynamic deformation between the inner and outer wings during dynamic folding and provides a certain aerodynamic load-bearing capacity.

[0007] The technical solution of the present invention:

[0008] A load-bearing compliant deformable folding structure for a flutter model of a folding wing includes: an inner wing, an outer wing, a drive connection mechanism, and a flexible load-bearing honeycomb skin;

[0009] The drive connection mechanism includes: a drive motor, a slotted connector, and a motor clamp;

[0010] The root rib of the inner wing is connected to the fuselage or basic support structure, and three motor clamps are fixed on the end face of the inner wing end rib; the drive motor is fixedly connected through the three motor clamps.

[0011] A main connector is fixed to the root rib of the outer wing; the main connector is connected to the output shaft of the drive motor through a slotted connector, and the drive motor drives the outer wing to rotate through the slotted connector and the main connector;

[0012] Flexible load-bearing honeycomb skin is arranged between the end ribs of the inner wing and the root ribs of the outer wing.

[0013] Furthermore, the motor has a built-in reduction gearbox to amplify the motor's rotational torque and provide support stiffness in the bending direction of the outer wing.

[0014] Furthermore, the drive connection mechanism also includes: front and rear spring plate supports and front and rear spring plates;

[0015] The inner wing root rib is fixed with front and rear spring plate supports, which are located on both sides of the three motor clamps along the flight direction;

[0016] Two auxiliary connectors are provided on the outer wing end rib, and the positions of the two auxiliary connectors correspond to the front and rear spring plate supports;

[0017] One end of the front and rear spring plates is hinged to the front and rear spring plate supports respectively, and the other end is fixedly connected to two auxiliary joints respectively;

[0018] The front and rear spring plates are used to provide and adjust the supporting torsional stiffness of the outer wing.

[0019] Furthermore, the flexible load-bearing honeycomb skin is composed of a zero Poisson's ratio honeycomb and a silicone rubber skin.

[0020] Furthermore, the flexible load-bearing honeycomb skin is prepared by the following method:

[0021] Step 1: Prepare a zero Poisson's ratio honeycomb. The shape of the zero Poisson's ratio honeycomb is the same as the aerodynamic shape between the inner wing end rib and the outer wing root rib, with a negative tolerance of 0.5mm reserved. At the same time, a cavity with the same shape as the drive connection mechanism is machined in the zero Poisson's ratio honeycomb.

[0022] Step 2: Prepare the mold, which is a complete female mold composed of upper and lower halves. The shape of the female mold is the same as the aerodynamic shape between the inner wing end rib and the outer wing root rib.

[0023] Step 3: Mix components A and B of the foamed silicone rubber in a 1:1 ratio and stir well in a container;

[0024] Step 4: Spread the mixed foamed silicone rubber onto PTFE cloth to form a silicone rubber film with a thickness of 1.5mm ± 0.5mm;

[0025] Step 5: Apply the silicone rubber film to the inner surface of the lower half of the mold;

[0026] Step 6: Place the zero Poisson's ratio honeycomb in the lower half mold covered with a silicone rubber film, apply pressure to the upper surface of the zero Poisson's ratio honeycomb with a heavy object, place it in an oven for foaming and vulcanization, and make a silicone rubber lower skin that is bonded to the honeycomb on the lower surface of the zero Poisson's ratio honeycomb.

[0027] Step 7: Using the upper mold, repeat steps 3 to 6 to create a silicone rubber upper skin that adheres to the honeycomb on the upper surface of the zero Poisson's ratio honeycomb, thereby obtaining a compliant load-bearing honeycomb skin that includes the zero Poisson's ratio honeycomb and the silicone rubber skins on the upper and lower surfaces.

[0028] Furthermore, the foaming and vulcanization process parameters are as follows: heating to 70℃ and holding for 20 minutes; heating to 150℃ and holding for 30 minutes; cooling ≤60℃; heating and cooling rate 3~5℃ per minute.

[0029] Furthermore, the cell shape of a zero Poisson's ratio honeycomb is hexagonal, with two sides parallel to each other and parallel to the heading, and the other four sides forming two parallel ">" shapes in the same direction.

[0030] Furthermore, the flexible load-bearing honeycomb skin is bonded to the end ribs of the inner wing, the root ribs of the outer wing, and the outer surface of the drive connection mechanism.

[0031] The beneficial effects of this invention are:

[0032] This invention can be directly applied to experimental research on the flutter characteristics of compliant folding wings of future aircraft with intelligent variant features, providing important technical support for the flutter design of such aircraft.

[0033] The invented load-bearing compliant deformation folding structure / mechanism was applied to the flutter model design of a folding wing. This allows the outer wing to fold upwards or downwards at different angular rates. The compliant load-bearing honeycomb and skin structure achieves a compliant shape in the folding transition section and possesses a certain aerodynamic load-bearing capacity, without tearing or bulging, thus meeting design requirements. The outer wing can fold upwards or downwards at ±40 degrees. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the variant aircraft with its outer wing folded at 0°.

[0035] Figure 2 A schematic diagram of the variant aircraft with its outer wing folded upwards at an angle of 40°.

[0036] Figure 3 A schematic diagram of the outer surface of a load-bearing, compliantly deformable folding structure used in a flutter model of a folding wing;

[0037] Figure 4 This is a schematic diagram of the internal structure of a load-bearing, compliantly deformable folding structure used in a flutter model of a folding wing.

[0038] Figure 5 This is a schematic diagram of a spring sheet;

[0039] Figure 6 Top view of a flexible, load-bearing honeycomb structure;

[0040] Figure 7 Schematic diagram of flexible load-bearing honeycomb skin;

[0041] In the figure, 1-inner wing, 2-outer wing, 3-inner wing end rib, 4-outer wing root rib, 5-drive motor, 6-reduction gearbox, 7-slotted connector, 8-motor clamp, 9-front spring plate support, 10-rear spring plate support, 11-front spring plate, 12-rear spring plate, 13-flexible load-bearing honeycomb skin. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0043] A load-bearing, compliantly deformable folding structure for a folding wing flutter model is characterized by comprising an inner wing 1, an outer wing 2, an inner wing end rib 3, an outer wing root rib 4, a drive motor 5, a reduction gearbox 6, a grooved connector 7, a motor clamp 8, a front spring plate support 9, a rear spring plate support 10, a front spring plate 11, a rear spring plate 12, and a flexible load-bearing honeycomb skin 13. A schematic diagram of the overall structure is shown below. Figure 4 The present invention will now be described step by step.

[0044] 1)Reference Figure 3 The inner wing 1 is made of an aluminum alloy frame and a composite material skin, and the geometric parameters of the frame and skin are determined based on simulation design results. PMI foam can be used to fill the gaps between the skins.

[0045] 2) The root rib of the inner wing 1 is connected to the fuselage or foundation support structure via three lugs. The end rib 3 of the inner wing 1 is equipped with three motor clamps 8, a front spring plate support 9, and a rear spring plate support 10, as shown below. Figure 4 As shown.

[0046] 3) The outer wing 2 is used to simulate the dynamic characteristics of the outer wing of the variant aircraft, and its structural design is the same as that of the inner wing 1. The root rib 4 of the outer wing is provided with one main joint and two auxiliary joints, wherein the main joint is connected to the output shaft of the drive motor 5 through a slotted connector 7;

[0047] 4) The drive motor 5 contains a reduction gearbox 6, which can reduce the speed of the motor and amplify its rotational torque. The output shaft of the drive motor 5 is the input of the reduction gearbox 6. The drive motor 5 and the reduction gearbox 6 are coaxially mounted in the motor clamp 8 and tightened with bolts. The front end face of the reduction gearbox 6 is tightened to the flange of the motor clamp 8 with screws to ensure that the motor does not rotate within the clamp 8. The drive motor 5 is equipped with an angle sensor, and by designing a closed-loop control drive device, variable-rate dynamic deflection of the folding wing can be achieved.

[0048] 5) The cross-section of the grooved connector 7 is grooved, and the cross-sectional parameters are determined through simulation analysis to simulate the required bending and torsional stiffness. The grooved connector 7 is locked to the output shaft of the reduction gearbox 6 by a keyway to ensure that there is no gap between the reduction gear output shaft and the grooved connector. The outer end of the grooved connector 7 is bolted to the main joint of the outer wing root rib to drive the outer wing, thereby realizing the up-and-down folding motion of the outer wing relative to the inner wing around the axis of the reduction gear.

[0049] 6) The front spring plate support 9 and the rear spring plate support 10 are used to install the front spring plate 11 and the rear spring plate 12;

[0050] 7) Both the front spring plate 11 and the rear spring plate 12 are long strip steel plates with a rectangular cross-section in the middle effective section. The inner end of the spring plate is a cylindrical connector. The cylindrical connector at the inner end of the front spring plate 11 is hinged to the front spring plate support 9 by a bearing, and the cylindrical connector at the inner end of the rear spring plate 12 is hinged to the rear spring plate support 10 by a bearing. They do not provide rotational stiffness around the flight direction. The other end of the spring plate is a square boss connector with bolt holes, which is bolted to the two auxiliary connectors of the inner wing support rib. The front and rear spring plate combination provides torsional support stiffness of the outer wing relative to the inner wing. (Spring plate illustration) Figure 5 .

[0051] 8) The main function of the flexible load-bearing honeycomb skin 13 is to shape the transition section connecting the inner and outer wings, enabling continuous deformation of the aerodynamic shape between the inner and outer wings during dynamic folding, and possessing a certain aerodynamic load-bearing capacity. The flexible load-bearing honeycomb skin 13 is composed of a specially designed zero Poisson's ratio honeycomb and silicone rubber skin. The specific preparation steps are as follows:

[0052] a) Prepare a zero Poisson's ratio honeycomb. The cell shape of the zero Poisson's ratio honeycomb is hexagonal, with two sides of 1 mm thickness that are parallel to each other and parallel to the heading, and the other four sides of 0.2 mm thickness that form two parallel ">" shapes in the same direction. See Figure 6 While bearing aerodynamic forces, it can achieve stretching and compression along the span and exhibits zero Poisson's ratio characteristics, that is, when the honeycomb is subjected to external stretching or compression, the width of the honeycomb itself does not change;

[0053] b) Based on the wing shape, the zero Poisson's ratio honeycomb prepared in step a is CNC machined to make the honeycomb shape consistent with the wing shape between the inner and outer wings, with a negative tolerance of 0.5mm reserved, and the width consistent with the width between the inner and outer wings.

[0054] c) A cavity with the same shape as the drive connection mechanism is machined in the zero Poisson's ratio honeycomb to ensure that the zero Poisson's ratio honeycomb can wrap the drive connection mechanism while closely fitting the shape of the drive connection mechanism, so as to realize the supporting effect of the upper and lower surfaces of the drive connection mechanism on the honeycomb.

[0055] d) Prepare a mold based on the aerodynamic shape of the wing test piece. The mold is a female mold composed of upper and lower halves, and the shape of the female mold is consistent with the aerodynamic shape between the inner wing end rib and the outer wing root rib.

[0056] e) Mix components A and B of the foamed silicone rubber in a 1:1 ratio and stir evenly in a container;

[0057] f) The stirred foamed silicone rubber is made into a silicone rubber film with a thickness of about 1.5 mm ± 0.5 mm on PTFE cloth. The thickness is determined by simulation calculation. While ensuring that it can withstand aerodynamic forces, it can be stretched or compressed under the action of the drive motor.

[0058] g) Cover the lower female mold surface with a silicone rubber film;

[0059] h) Place the CNC-machined honeycomb from step c onto the silicone rubber film laid in the mold, ensuring that the outline of the honeycomb matches the outline on the mold. Apply weights to the surface of the zero Poisson's ratio honeycomb and place it in an oven for foaming and vulcanization.

[0060] i) The foaming and vulcanization of silicone rubber are completed by heating in an oven: The process parameters are: heating to 70°C and holding for 20 minutes; heating to 150°C and holding for 30 minutes; cooling ≤60°C; heating and cooling rate 3~5°C per minute;

[0061] j) Remove the wing honeycomb, clean off the excess silicone rubber around it, and a silicone rubber lower skin that fits the honeycomb can be made on the lower surface of the zero Poisson's ratio honeycomb.

[0062] k) Place the zero Poisson's ratio honeycomb with the lower skin prepared in step j) into the upper mold with the silicone film laid on it, and repeat steps h), i), and j) to form a silicone rubber upper skin that is attached to the honeycomb on the upper surface of the zero Poisson's ratio honeycomb.

[0063] l) The flexible load-bearing honeycomb skin 13 can be manufactured through the above steps, see Figure 7 .

[0064] 9) Bond the inner end face of the flexible load-bearing honeycomb skin 13 to the inner wing end rib 3, and then bond the outer end face of the flexible load-bearing honeycomb skin 13 to the outer wing root rib 4.

[0065] The above steps can complete a load-bearing, compliant deformation folding structure for a folding wing flutter model.

[0066] The above description is merely a specific embodiment of the present invention, providing a detailed description of the invention. Parts not covered herein are conventional techniques. However, the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. The scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A load-bearing, compliantly deformable folding structure for a flutter model of a folding wing, characterized in that: The structure includes: an inner wing, an outer wing, a drive connection mechanism, and a flexible load-bearing honeycomb skin; The drive connection mechanism includes: a drive motor, a slotted connector, and a motor clamp; The root rib of the inner wing is connected to the fuselage or basic support structure, and three motor clamps are fixed on the end face of the inner wing end rib; the drive motor is fixedly connected through the three motor clamps. A main connector is fixed to the root rib of the outer wing; the main connector is connected to the output shaft of the drive motor through a slotted connector, and the drive motor drives the outer wing to rotate through the slotted connector and the main connector; A flexible load-bearing honeycomb skin is arranged between the end ribs of the inner wing and the root ribs of the outer wing. The drive connection mechanism further includes: front and rear spring plate supports and front and rear spring plates; the front and rear spring plate supports are fixed on the inner wing root rib, respectively located on both sides of the three motor clamps along the flight direction; the outer wing end rib is provided with two auxiliary joints, the positions of the two auxiliary joints corresponding to the front and rear spring plate supports; the spring plates are all long strip steel plates with a rectangular cross-section in the middle effective section, the inner end of the spring plate is a cylindrical joint, and the other end of the spring plate is a square boss joint with bolt holes; one end of the front and rear spring plates is respectively hinged to the front and rear spring plate supports by bearings, and the other end is respectively fixedly connected to the two auxiliary joints by bolts; the front and rear spring plates are used to provide and adjust the supporting torsional stiffness of the outer wing; The flexible load-bearing honeycomb skin is composed of zero Poisson's ratio honeycomb and silicone rubber skin. The unit shape of the zero Poisson's ratio honeycomb is hexagonal, with two sides being 1 mm thick, parallel to each other and parallel to the flight direction, and the other four sides being 0.2 mm thick, forming two parallel "">" shapes in the same direction.

2. The structure according to claim 1, characterized in that: The motor has a built-in reduction gearbox, which amplifies the motor's rotational torque and provides support stiffness in the bending direction of the outer wing.

3. The structure according to claim 2, characterized in that: The flexible load-bearing honeycomb skin is prepared by the following method: Step 1: Prepare the mold, which is a complete female mold composed of upper and lower halves. The shape of the female mold is the same as the aerodynamic shape between the inner wing end rib and the outer wing root rib. Step 1: Prepare a zero Poisson's ratio honeycomb. The shape of the zero Poisson's ratio honeycomb is the same as the aerodynamic shape between the inner wing end rib and the outer wing root rib, with a negative tolerance of 0.5mm reserved. At the same time, a cavity with the same shape as the drive connection mechanism is machined in the zero Poisson's ratio honeycomb. Step 2: Prepare the mold, which is a complete female mold composed of upper and lower halves. The shape of the female mold is the same as the aerodynamic shape between the inner wing end rib and the outer wing root rib. Step 3: Mix components A and B of the foamed silicone rubber in a 1:1 ratio and stir well in a container; Step 4: Spread the mixed foamed silicone rubber onto PTFE cloth to form a silicone rubber film with a thickness of 1.5mm ± 0.5mm; Step 5: Apply the silicone rubber film to the inner surface of the lower half of the mold; Step 6: Place the zero Poisson's ratio honeycomb in the lower half mold covered with a silicone rubber film, apply pressure to the upper surface of the zero Poisson's ratio honeycomb with a heavy object, place it in an oven for foaming and vulcanization, and make a silicone rubber lower skin that is bonded to the honeycomb on the lower surface of the zero Poisson's ratio honeycomb. Step 7: Using the upper mold, repeat steps 3 to 6 to create a silicone rubber upper skin that adheres to the honeycomb on the upper surface of the zero Poisson's ratio honeycomb, thereby obtaining a compliant load-bearing honeycomb skin that includes the zero Poisson's ratio honeycomb and the silicone rubber skins on the upper and lower surfaces.

4. The structure according to claim 3, characterized in that: The foaming and vulcanization process parameters are as follows: heat up to 70℃ and hold for 20 minutes; heat up to 150℃ and hold for 30 minutes; cool down to ≤60℃; heating and cooling rate is 3~5℃ per minute.

5. The structure according to claim 4, characterized in that: The cell shape of a zero Poisson's ratio honeycomb is hexagonal, with two sides parallel to each other and parallel to the heading, and the other four sides forming two parallel "">" shapes in the same direction.

6. The structure according to claim 5, characterized in that: The flexible load-bearing honeycomb skin is bonded to the end ribs of the inner wing, the root ribs of the outer wing, and the outer surface of the drive connection mechanism.

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