A wing structure having a multi-layer sandwich skin

Abstract

The application relates to the technical field of aircraft structures, and discloses a wing structure with a multilayer sandwich skin, which comprises an upper wing skin and a lower wing skin, the upper wing skin and the lower wing skin each comprise, from outside to inside, an outer skin layer, a constraint layer, a soft package battery layer, an elastic support layer and an inner skin layer, and the outer skin layer, the constraint layer, the elastic support layer and the inner skin layer have deformation capacity; wherein the soft package battery layer generates thickness change in the charging and discharging process and serves as a variable height material; the thickness change is used for changing the height of the upper wing skin and / or the lower wing skin, so as to adjust the bending stiffness and / or the shear stiffness of the wing. The application places the soft package battery layer in the load bearing path of the wing skin and jointly forms a composite sandwich beam structure with the outer skin layer and the inner skin layer. The soft package battery layer participates in the stress of the sandwich beam structure while providing the energy storage function, so that the wing realizes the integration of energy storage and load bearing without increasing an independent energy storage cabin section.

Description

Technical Field

[0001] This invention relates to the field of aircraft structure technology, and in particular to a wing structure with multi-layered sandwich skin. Background Technology

[0002] With the development of new energy aircraft, hybrid-electric aircraft, and solar-powered drones, integrating energy storage devices into the wings has become a trend. Traditional wings mostly employ a spars-ribs-skin load-bearing system, with energy storage components typically placed additionally inside the wing box, leading to the following shortcomings:

[0003] In related technologies, energy storage components such as batteries are typically housed as independent parts within the wing box or in dedicated compartments, occupying additional structural space and increasing the complexity and weight of the wing's internal structure. Furthermore, wings have varying requirements for structural stiffness and shape under different flight conditions (such as takeoff, cruise, and maneuvering). However, existing wing structures typically rely on hydraulic mechanisms, pneumatic structures, or shape memory alloys for stiffness adjustment. These structures often require additional actuators or complex control systems, increasing both structural and system complexity and significantly constraining the wing's internal space and layout. Moreover, the rigid connection between energy storage components and the wing structure can easily have uncontrollable effects on the overall stiffness distribution and deformation characteristics of the wing, making it difficult to achieve stable and reliable stiffness adjustment under complex conditions, thus limiting the engineering application of related technologies. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a wing structure with a multi-layered sandwich skin, which enables the wing to integrate load-bearing, energy storage, and variable stiffness functions.

[0005] The present invention provides a wing structure with a multi-layer sandwich skin, including an upper wing skin and a lower wing skin. Both the upper wing skin and the lower wing skin include an outer skin layer, a constraint layer, a soft-pack battery layer, an elastic support layer and an inner skin layer arranged sequentially from the outside to the inside. The outer skin layer, the constraint layer, the elastic support layer and the inner skin layer have deformation capability. The pouch battery layer undergoes thickness changes during charging and discharging, serving as a variable height material. These thickness changes are used to alter the height of the upper and / or lower wing skin, thereby adjusting the wing's bending and / or shear stiffness.

[0006] Optionally, the constraint layer is made of a high-modulus thin-film material with a thickness of 0.1mm-0.3mm. The constraint layer is bonded to the outer skin layer and is used together with the outer skin layer to restrict the in-plane expansion of the pouch battery layer and guide the out-of-plane pressure generated by the outer skin layer to be transmitted to the pouch battery layer and the elastic support layer.

[0007] Optionally, the pouch cell layer can provide a thickness variation of 0.5mm–4mm, which guides the wing bending stiffness variation in the range of 10%–40%.

[0008] Optionally, a shear transfer zone is provided at the edge of the pouch cell layer. The pouch cell layer is connected to the constraint layer and the elastic support layer respectively by structural adhesive or flexible limiting structure, so that the shear load is effectively transferred between the constraint layer and the elastic support layer.

[0009] Optionally, the pouch battery layer is divided into multiple independent regions, each with its own independent battery management system. The battery management system is used to adjust the state of charge of each region to achieve stiffness control in different regions.

[0010] Optionally, the battery management system is connected to the controller, which dynamically adjusts the charging and discharging state of the pouch battery layer based on feedback information from strain sensors or acceleration sensors installed on the wing, in order to achieve real-time variable stiffness control of the wing.

[0011] Optionally, the outer skin layer, constraint layer, soft-pack battery layer, elastic support layer, and inner skin layer together form a composite sandwich beam, and the real-time height of the sandwich beam of the soft-pack battery layer is... Represented as: , in, h 0 Δ represents the initial height of the sandwich beam before the battery expands. t ( V Δ represents the thickness variation of the pouch cell layer. t ( V ) and voltage V Positive correlation; Bending stiffness of sandwich beams Real-time height of sandwich beam Satisfy the following formula: , in, E f The elastic modulus of the outer or inner skin layer. b The effective width of the outer or inner skin layer.

[0012] Optional, wing shear stiffness Real-time height of the sandwich beam Satisfy the following formula: , in, Gc ( V ) represents the equivalent shear modulus of the pouch cell layer as it varies with voltage.

[0013] Optionally, an elastic bracket is also provided around the soft-pack battery layer. The distance between the elastic bracket and the soft-pack battery layer is 4mm-6mm. The elastic bracket is connected to the constraint layer and the elastic support layer respectively.

[0014] Optionally, the elastic support and the elastic support layer are integrated, with the elastic support layer having a thickness of 1mm–5mm. The elastic support and the elastic support layer are made of silicone rubber, thermoplastic polyurethane, or lightweight foam to allow out-of-plane expansion of the pouch cell layer and provide a shear load transfer channel.

[0015] The technical solution provided by the embodiments of the present invention has the following advantages compared with the prior art: This invention provides a wing structure with a multi-layered sandwich skin. Inside the upper and lower wing skins, from the outside in, an outer skin layer, a constraint layer, a pouch battery layer, an elastic support layer, and an inner skin layer are sequentially arranged. The pouch battery layer is positioned within the load-bearing path of the wing skin and, together with the outer and inner skin layers, forms a composite sandwich beam structure. Through this structural arrangement, the pouch battery layer provides energy storage while participating in the stress distribution of the sandwich beam structure, enabling the wing to integrate energy storage and load-bearing without adding a separate energy storage compartment, thus improving the utilization efficiency of the wing structure space. This invention utilizes the thickness change of the pouch battery layer during charging and discharging to directly change the height between the outer and inner skin layers, thereby adjusting the bending and shear stiffness of the wing sandwich beam structure. This stiffness adjustment method can be achieved by controlling the battery's state of charge, eliminating the need for additional mechanical actuators, hydraulic systems, or shape memory materials, reducing the structural complexity and added weight inside the wing. This invention features a constraint layer connected to the outer skin layer on the side of the pouch battery layer and an elastic support layer on the side closer to the inner skin layer. This restricts and controls the direction of thickness variation in the pouch battery layer. The constraint layer limits the in-plane expansion of the pouch battery layer and guides its deformation in the thickness direction. The elastic support layer transmits shear loads to the inner skin layer while allowing thickness variations, thus ensuring the deformation stability and load transmission continuity of the pouch battery layer during charging and discharging. Through the aforementioned sandwich beam structure and battery thickness variation mechanism, the wing can simultaneously change its bending stiffness and shear stiffness while maintaining its original load-bearing capacity. This allows the wing's bending and torsional characteristics to change controllably with operating conditions, thereby improving the wing's adaptability to vibration, flutter, and large deformation conditions without significantly increasing structural weight. Attached Figure Description

[0016] Figure 1 A schematic diagram of the overall structure of a wing structure with multi-layer sandwich skin provided for an embodiment of the present invention; Figure 2 This is a schematic diagram of the wing surface cross-sectional structure provided in an embodiment of the present invention; Figure 3This is a schematic diagram illustrating the changes in the charging and discharging thickness of the wing skin and the pouch battery layer provided in an embodiment of the present invention. Figure 4 This is a schematic diagram of the partitioned variable stiffness control arrangement provided in an embodiment of the present invention; Figure 5 The voltage change and battery thickness change curves during the charging and discharging process of the soft-pack battery layer are provided in the embodiments of the present invention.

[0017] Explanation of reference numerals in the attached figures: 1. Pouch battery; 2. Wing skin; 3. Wing spars; 4. Wing ribs; 5. Flaps; 6. Battery management system; 201. Upper wing skin; 202. Lower wing skin; 203. Outer skin layer; 204. Constraint layer; 205. Elastic support; 206. Elastic support layer; 207. Inner skin layer; 208. Pouch battery layer. Detailed Implementation

[0018] The following detailed description of a specific embodiment of the present invention is provided in conjunction with the accompanying drawings. However, it should be understood that the scope of protection of the present invention is not limited to the specific embodiment.

[0019] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the technical solution of this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0020] The present invention will be described below through several specific embodiments. To keep the following description of the embodiments clear and concise, detailed descriptions of known functions and components may be omitted. When any component of an embodiment of the present invention appears in more than one drawing, the component may be represented by the same reference numerals in each drawing.

[0021] like Figure 1 , Figure 2 and Figure 3As shown, this embodiment of the invention provides a wing structure with a multi-layer sandwich skin. The wing includes a pouch battery 1, a wing skin 2, a spars 3, wing ribs 4, flaps 5, and a battery management system 6. The wing skin 2 includes an upper wing skin 201 and a lower wing skin 202. Both the upper wing skin 201 and the lower wing skin 202 include, from the outside to the inside, an outer skin layer 203, a constraint layer 204, a pouch battery layer 208, an elastic support layer 206, and an inner skin layer 207. The outer skin layer 203, constraint layer 204, elastic support layer 206, and inner skin layer 207 have deformation capabilities. The pouch battery layer 208 undergoes thickness changes during charging and discharging, serving as a variable height material. The thickness change is used to alter the height of the upper wing skin 201 and / or the lower wing skin 202, thereby adjusting the wing's bending stiffness and / or shear stiffness.

[0022] In this embodiment of the invention, the outer skin layer 203 is made of carbon fiber reinforced composite material or metal skin to bear the main in-plane tensile and compressive stresses. The outer skin layer 203 can adopt conventional wing skin materials and structural forms, and an appropriate structural matching design is carried out according to the characteristics of the soft-pack battery layer 208 participating in load-bearing and thickness variation. By reasonably selecting the outer skin material type, the layup method of [0-45 45 0]s or [0 90 90 0]s, or the thickness configuration, it can meet the basic load-bearing and aerodynamic requirements of the wing, while cooperating with the constraint layer and battery layer to bear the load. According to the stiffness and strength requirements, the layup range is 5-10 layers, so that it can maintain stable in-plane load-bearing capacity and good deformation coordination during battery expansion or contraction. This design is conducive to ensuring the continuity of load transfer and structural stability, thereby adapting to the variable stiffness adjustment process of the wing. The inner skin layer 207 or the upper wall panel of the wing box serves as the main load-bearing structure, forming a sandwich beam with the outer skin layer 203. The inner skin layer 207 or the upper wall panel of the wing box can adopt conventional forms found in existing wing structures, and can be adapted to the characteristics of the pouch battery layer 208 in terms of load-bearing and thickness variation. By rationally matching its material type or thickness configuration, it forms a stable sandwich load-bearing structure with the outer skin and intermediate layer, thereby ensuring the continuity of load transfer and the reliability of the overall structure. For example, carbon fiber reinforced composite materials, glass fiber reinforced composite materials, or lightweight metal materials can be used, with the thickness preferably set in the range of approximately 1mm–2mm. This thickness range, while meeting the overall load-bearing and stiffness requirements of the wing, can form a stable sandwich load-bearing structure with the outer skin layer 203, constraint layer 204, pouch battery layer 208, and elastic support layer 206, and exhibits good structural adaptability to changes in the thickness of the pouch battery layer 208. By matching the materials and thickness as described above, the continuous transmission of bending and shear loads in the sandwich beam can be ensured, avoiding local stress concentration caused by changes in battery thickness, thereby improving the overall structural reliability.

[0023] This invention provides a wing structure with a multi-layered sandwich skin. Inside the upper and lower wing skins, from the outside in, an outer skin layer, a constraint layer, a pouch battery layer, an elastic support layer, and an inner skin layer are sequentially arranged. The pouch battery layer is positioned within the load-bearing path of the wing skin and, together with the outer and inner skin layers, forms a composite sandwich beam structure. Through this structural arrangement, the pouch battery layer provides energy storage while participating in the stress distribution of the sandwich beam structure, enabling the wing to integrate energy storage and load-bearing without adding a separate energy storage compartment, thus improving the utilization efficiency of the wing structure space. This invention utilizes the thickness change of the pouch battery layer during charging and discharging to directly change the height between the outer and inner skin layers, thereby adjusting the bending and shear stiffness of the wing sandwich beam structure. This stiffness adjustment method can be achieved by controlling the battery's state of charge, eliminating the need for additional mechanical actuators, hydraulic systems, or shape memory materials, reducing the structural complexity and added weight inside the wing. This invention features a constraint layer connected to the outer skin layer on the side of the pouch battery layer and an elastic support layer on the side closer to the inner skin layer. This restricts and controls the direction of thickness variation in the pouch battery layer. The constraint layer limits the in-plane expansion of the pouch battery layer and guides its deformation in the thickness direction. The elastic support layer transmits shear loads to the inner skin layer while allowing thickness variations, thus ensuring the deformation stability and load transmission continuity of the pouch battery layer during charging and discharging. Through the aforementioned sandwich beam structure and battery thickness variation mechanism, the wing can simultaneously change its bending stiffness and shear stiffness while maintaining its original load-bearing capacity. This allows the wing's bending and torsional characteristics to change controllably with operating conditions, thereby improving the wing's adaptability to vibration, flutter, and large deformation conditions without significantly increasing structural weight.

[0024] Optionally, the constraint layer 204 is made of a high-modulus thin-film material with a thickness of 0.1mm-0.3mm. The constraint layer 204 is bonded to the outer skin layer 203 and is used together with the outer skin layer 203 to restrict the in-plane expansion of the soft-pack battery layer 208 and guide the out-of-plane pressure generated by the outer skin layer 203 to be transmitted to the soft-pack battery layer 208 and the elastic support layer 206.

[0025] The constraint layer 204 is a high-stiffness thin layer, such as CFRP / metal foil or fiber-reinforced metal laminate, with a thickness of 0.1–0.3 mm. Located inside the outer skin layer 203, it is bonded to the outer skin layer 203 to form a planar cooperative deformation structure. Its functions include: restricting the free expansion direction of the pouch cell layer, thus uniformizing thickness variation; transferring out-of-plane pressure to the cell; and preventing local bulging or unstable deformation. The constraint layer 204 is a functional layer specifically designed for the thickness variation characteristics of the pouch cell layer 208. Its material, thickness, and arrangement are all designed around the out-of-plane expansion and load transfer requirements of the pouch cell layer 208. This constraint layer 204 uses a high-modulus thin-layer material and works in conjunction with the outer skin layer 203 to restrict the in-plane free deformation of the cell and uniformly guide its out-of-plane expansion. This design avoids local bulging and unstable deformation, while improving the efficiency of out-of-plane load and shear load transfer, thereby ensuring the structural stability and controllability of the variable stiffness adjustment process.

[0026] Optionally, the pouch cell layer 208 can provide a thickness variation of 0.5 mm to 4 mm, which guides the wing bending stiffness variation in the range of 10% to 40%.

[0027] Since the outer skin layer 203, constraint layer 204, pouch battery layer 208, elastic support layer 206, and inner skin layer 207 form a sandwich beam structure, changes in the height of the sandwich beam directly affect the bending moment of inertia of the structure. In this invention, a thickness variation of 0.5mm–4mm in the pouch battery layer 208 can cause a significant change in the height of the sandwich beam, allowing for an adjustment range of approximately 10%–40% in the wing's bending stiffness. This achieves a substantial stiffness change under relatively small structural deformation conditions. The selection of a thickness variation range of 0.5mm–4mm for the pouch battery layer 208 is a usable deformation range determined under the premise of ensuring battery safety, cycle stability, and structural reliability. Thickness variations within this range can significantly affect the wing sandwich height without causing battery structural instability or performance degradation, thereby achieving a considerable stiffness adjustment effect while maintaining good controllability and reversibility.

[0028] The thickness of the pouch battery layer 208 can controllably change from 0.5mm to 4mm during charging and discharging. This invention uses it as a variable-height sandwich layer to adjust the local sandwich height, thereby changing the bending moment of inertia, regional bending stiffness, and shear stiffness, while the battery itself provides energy storage. The pouch battery layer 208 can adopt existing pouch battery structures without changing its basic electrochemical composition; it is simply an adaptive improvement to meet the requirements of load-bearing and thickness variation utilization in the wing structure. The improvements are mainly reflected in the strength of the battery's outer packaging structure, the deformability in the thickness direction, and the interface matching design with the surrounding structure, to ensure stable thickness variation and load transfer without affecting battery safety and performance. For example, structural reinforcement and adaptation based on the existing pouch battery layer packaging form, the outer packaging still adopts a flexible encapsulation film covering the cell stack structure. However, by improving the mechanical strength of the encapsulation film, setting a local reinforcing layer on the outside of the encapsulation film, or strengthening the edge area, the battery can withstand out-of-plane compressive loads from the wing structure while maintaining its original sealing and electrochemical performance. It can also achieve stable and repeatable thickness-direction deformation during charging and discharging without instability, bulging, or localized damage. The interface matching design of the surrounding structure refers to the use of surface contact or flexible transition connection methods between the pouch battery layer and the constraint layer and elastic support layer. Through structural adhesives, flexible bonding layers, or limiting structures, the force connection between the battery and adjacent structures is achieved, so that when the battery expands in the thickness direction, its deformation can be gradually constrained by the adjacent structures and participate in load bearing. This interface matching method avoids stress concentration caused by rigid constraints and ensures the continuous transmission of out-of-plane loads and shear loads in the sandwich beam.

[0029] Optionally, the edge of the pouch battery layer 208 is provided with a shear transfer zone, which establishes a stable and continuous shear load transfer path between the pouch battery layer and the constraint layer and the elastic support layer as the thickness of the pouch battery layer changes. The pouch battery layer 208 is connected to the constraint layer 204 and the elastic support layer 206 respectively through structural adhesive or flexible limiting structure, so that the shear load is effectively transferred between the constraint layer 204 and the elastic support layer 206.

[0030] The elastic support layer 206 is made of silicone rubber, TPU, or lightweight foam material, forming a surface contact with the bottom of the battery. This allows for out-of-plane expansion of the battery while providing a channel for shear load transfer. The elastic support layer can be configured as an elastic material layer with a certain thickness range, preferably approximately 1mm–5mm. This thickness range provides the necessary deformation space for the out-of-plane expansion of the pouch battery layer during charging and discharging, while ensuring the effective transfer of shear loads between structural layers, thus balancing variable stiffness adjustment capability and structural stability.

[0031] Optionally, the pouch battery layer 208 is divided into multiple independent regions, each with its own independent battery management system 6. The battery management system 6 is used to adjust the state of charge (SOC) of each region to achieve stiffness control in different regions. An independent region refers to a battery functional zone divided along the wing spanwise direction. Each zone is independent at the control level and is configured with its own independent battery management system 6 to adjust its SOC individually. Each independent region may contain one or more pouch battery cells, which can be connected in series, parallel, or series-parallel configurations. Electrically, each independent region is connected to the wing's internal power bus via a controlled circuit, thus enabling external power supply while maintaining independent stiffness adjustment within each zone. The relevant electrical connections are achieved through circuit channels located inside the wing, without affecting the wing's structural load-bearing capacity.

[0032] This invention divides the pouch battery layer 208 into multiple independent control regions, controlling its state of charge through independent BMS, thereby achieving differentiated control of the sandwich height and stiffness in different regions of the wing. Through this structural arrangement, the wing can form different stiffness distributions according to its spanwise position, avoiding the insufficient adaptability problems caused by the fixed overall stiffness or only overall adjustment of traditional wings. This invention can achieve the following effects: maintaining high stiffness in the wing root region to improve bending resistance; adjusting the stiffness of the mid-section as needed to optimize aeroelasticity; reducing stiffness in the wingtip region for flutter suppression; and achieving a multi-regional, distributed, and real-time adjustable wing stiffness distribution. In the embodiments of this invention, such as... Figure 4 As shown, the wing root region maintains a high charge state, the wing middle region adjusts the charge state according to the flight conditions, and the wingtip region maintains a low charge state, thereby achieving zoned stiffness distribution optimization and improving the wing's aeroelastic performance and flutter suppression capability.

[0033] Optionally, the battery management system is connected to the controller. The controller dynamically adjusts the charging and discharging state of the pouch battery layer 208 based on feedback information from strain sensors or accelerometers mounted on the wing, thereby achieving real-time variable stiffness control of the wing. The strain sensors or accelerometers are located on structural positions such as the wing skin 2, wing spars 3, or wing box that reflect the wing's bending or vibration state, and are used to collect wing structural response information. The controller sends control commands to the corresponding area of ​​the battery management system based on the sensor signals, adjusting the charging and discharging state of the pouch battery layer 208, thus achieving real-time adjustment of the wing stiffness through changes in battery thickness.

[0034] Optionally, the outer skin layer 203, the constraint layer 204, the soft-pack battery layer 208, the elastic support layer 206, and the inner skin layer 207 together form a composite material sandwich beam, and the real-time height of the sandwich beam of the soft-pack battery layer 208 is... Represented as: , in,h 0 Δ represents the initial height of the sandwich beam before the battery expands. t ( V ) represents the thickness variation of the pouch cell layer 208, Δ t ( V ) and voltage V Positive correlation; Bending stiffness of sandwich beams Real-time height of sandwich beam Satisfy the following formula: , in, E f The elastic modulus of the outer skin layer 203 or the inner skin layer 207. b The effective width of the outer skin layer 203 or the inner skin layer 207.

[0035] The specific mechanism of variable stiffness is as follows: The thickness change of the soft-pack battery layer 208 during charging and discharging is as follows: Figure 5 As shown, its thickness t With voltage V It has a significant positive correlation, but there is no specific formula; thickness t The relationship between battery thickness and voltage or state of charge is usually monotonically positively correlated, but due to the influence of battery material system, structural form, and operating conditions, there is no unified analytical function expression. In engineering practice in this field, battery thickness variation is usually obtained through experimental testing, and its relationship with voltage or state of charge is generally characterized in the form of experimental curves. Let the standard thickness of the 208 pouch battery layer be... t 0, thickness change is Δ t ( V If the real-time thickness of the soft-pack battery layer 208 is then expressed as:

[0036] , Where, Δ t ( V The volume expansion caused by lithium intercalation during charging is determined by the volume expansion, typically ranging from 0.5mm to 4mm.

[0037] The outer skin layer 203, constraint layer 204, soft-pack battery layer 208, elastic support layer 206, and inner skin layer 207 form a structure similar to a sandwich beam, with an equivalent sandwich height. h It can be written as: , in, h 0The initial core height is the height of the battery pack before it expands. This initial core height refers to the initial structural spacing between the outer skin layer 203 and the inner skin layer 207 when the thickness of the pouch battery layer 208 remains unchanged under the reference voltage. Its value is determined during the wing structure design phase. This height can be calculated by geometrically superimposing the thicknesses of the outer skin layer 203, the constraint layer 204, the initial thickness of the pouch battery layer 208, the elastic support layer 206, the inner skin layer 207, and necessary structural gaps.

[0038] Bending stiffness of sandwich beams Approximately: , in, E f The elastic modulus of the outer skin layer 203 or the inner skin layer 207. b This represents the effective width of the outer skin layer 203 or the inner skin layer 207. Substitute... h ( V )have to:

[0039] , Therefore, the relative change in bending stiffness is: , in, EI 0 This represents the initial bending stiffness of the wing sandwich beam when the thickness of the pouch battery layer has not changed (at the reference voltage).

[0040] Therefore, it can be seen that increasing the battery thickness by only 3%–5% can result in a 10%–40% increase in bending stiffness. This is because the moment of inertia is quadratically related to the core height, which is the core of the variable stiffness mechanism of this invention.

[0041] Optional, wing shear stiffness Real-time height of the sandwich beam Satisfy the following formula: , in, Gc ( V ) represents the equivalent shear modulus of the 208 pouch cell layer as a function of voltage.

[0042] Specifically, wing shear stiffness Approximately expressed as: , in, Gc ( V () represents the equivalent shear modulus of the battery layer as a function of voltage. h ( VThe thickness of the variable-height sandwich core is shown in the figure. As the voltage increases, the internal tensile stress of the battery increases, and its equivalent out-of-plane compressive modulus is significantly improved, which can be written as:

[0043] , in, G 0 This represents the equivalent shear modulus of the pouch cell layer under a reference voltage condition. ∆G(V) This is the increase in shear modulus due to changes in the state of charge (SOC) of the battery.

[0044] therefore: , High voltage state G c The rate of increase is faster than the rate of increase in the denominator caused by thickness expansion, therefore the overall performance is as follows: K s ( V ) V It increases as it grows.

[0045] Optionally, an elastic support 205 is also provided around the periphery of the pouch battery layer 208. The distance between the elastic support 205 and the pouch battery layer 208 is 4mm-6mm. The elastic support 205 is connected to the constraint layer 204 and the elastic support layer 206 respectively. In practical applications, the elastic support 205 can be designed as a strip, block, grid, quadrilateral deformable structure, honeycomb, or continuous elastic layer, etc., depending on the wing structure arrangement and stress requirements, as long as it can provide elastic support for the pouch battery layer 208 and allow its thickness direction deformation. The elastic support 205 is set at the circumferential or edge position of the pouch battery layer 208 to limit and support the battery layer. This arrangement is an illustrative embodiment. In practical applications, the elastic support 205 can be set at part of the edge or the entire circumferential position of each independent area according to the size and stress requirements of the independent area, and it is not required to be continuously set around all independent areas.

[0046] The elastic support 205 ensures the stability of the position of the soft-pack battery layer 208 while allowing the soft-pack battery layer 208 to undergo necessary elastic deformation in the thickness direction. It also plays a role in transmitting shear loads and buffering stress concentration, thereby improving the stability and reliability of the overall structure. The distance between the elastic support 205 and the soft-pack battery layer 208 can be set to about 4mm-6mm. This distance matches the maximum expected thickness change of the soft-pack battery layer 208, ensuring that the soft-pack battery layer 208 is not rigidly constrained in the initial expansion stage. After reaching the working expansion state, the elastic support participates in support and load transmission, thereby ensuring the safety and controllability of the variable stiffness adjustment process.

[0047] Optionally, the elastic bracket 205 and the elastic support layer 206 are integrated. The thickness of the elastic support layer 206 is 1mm–5mm. The elastic bracket 205 and the elastic support layer 206 are made of silicone rubber, thermoplastic polyurethane or lightweight foam to allow out-of-plane expansion of the pouch battery layer 208 and provide a shear load transfer channel.

[0048] The elastic bracket 205 is disposed at the circumferential or edge position of the soft-pack battery layer and is integrally formed with the elastic support layer 206. It is used to limit and support the soft-pack battery layer 208, ensuring the stability of the position of the soft-pack battery layer 208 while allowing it to undergo controllable deformation along the thickness direction, and participate in the transmission of shear load after the battery expands.

[0049] like Figure 5 As shown, the voltage of the pouch battery layer 208 changes with the state of charge (SOC) during charging and discharging, and the battery thickness also undergoes a reversible change. Specifically, when the battery is gradually charged from a low SOC to a high SOC, as the voltage rises from approximately 3.2V to about 4.2V, the graphite layer and lithium-intercalation structure material inside the pouch battery layer undergo volume expansion, resulting in a typical increase in battery thickness of 3%–8%. The thickness variation range of the pouch battery layer selected in this invention is 0.5mm–4mm. Figure 5 As shown, its thickness change has a significant positive correlation with the voltage rise, and it has good controllability and reversibility.

[0050] In the wing structure provided by this invention, this thickness variation is directly used to adjust the equivalent height of the wing sandwich spar. h The soft-pack battery layer 208 serves as a variable-height layer for the sandwich beam, with its thickness varying by Δ. t This will result in the height of the sandwich beam. h An equal change Δ h ≈Δ t The core height can be determined based on the approximate relationship of the bending moment of inertia of the sandwich beam. h For bending stiffness EI ( V The effect of the battery is quadratic, so even if the battery causes a 3%–5% change in altitude, it can cause a 10%–40% change in the local bending stiffness of the wing.

[0051] Meanwhile, battery charging and discharging not only change the battery thickness but also its equivalent out-of-plane compressive modulus. Under high voltage, the battery experiences greater internal stress, leading to an increased equivalent compressive modulus, which enhances the ability of the pouch structure to transmit shear loads. Therefore, the wing's shear stiffness also increases with battery voltage. When the wing needs improved local torsional stiffness or enhanced flutter resistance, increasing the state of charge of the battery in that area can increase the shear capacity of the support layer and battery stack, thus achieving a synergistic improvement in shear stiffness.

[0052] In summary, through Figure 5 Based on the battery thickness-voltage relationship shown, this invention establishes the following clear stiffness adjustment logic chain: (1) Battery voltage ↑ → Battery thickness ↑ (2) Battery thickness ↑ → Core height h ↑(3) Sandwich height↑→ Bending moment of inertia I ↑→ Significantly improved bending stiffness (4) Battery high voltage state → Equivalent compressive modulus ↑→ Improved shear stiffness (5) Changes in bending / shear stiffness → Active adjustment of overall wing stiffness This chain-like mechanism, where thickness is controlled by voltage and stiffness by thickness, enables real-time variable stiffness control of the wing without the need for additional hydraulic mechanisms or smart material actuators, and is the core of this invention.

[0053] To enable the pouch battery layer 208 to withstand bending and shear loads, this embodiment of the invention employs: a constraint layer 204 and structural adhesive forming a load transfer interface; an elastic support layer 206 to achieve shear transfer of the pouch battery layer 208; shear transfer zones at the edges of the pouch battery layer 208; and a zoned sandwich stability design. This allows the pouch battery layer 208 to withstand localized out-of-plane pressure, shear loads, and partial bending, thus extending its function beyond energy storage to become an integral part of the wing structure.

[0054] The control system includes: a zoned battery management system (BMS), a battery voltage controller, wing strain / acceleration sensors, and a controller, which can automatically adjust the wing stiffness according to the flight status.

[0055] like Figures 1 to 4 As shown, this embodiment of the invention provides a wing structure with a multi-layered sandwich skin, which includes, from the outside to the inside: The outer skin layer 203 uses T700 / M21 carbon fiber prepreg with a layup pattern of [45 / 0 / −45 / 90]s. The outer skin layer 203 mainly bears the in-plane tension and compression under the bending load of the wing, and also serves as the aerodynamic shape of the wing.

[0056] The constraint layer 204 is a high-modulus CFRP thin layer with a thickness of approximately 0.2 mm laid on the inner surface of the outer skin layer 203 and uniformly bonded by structural adhesive. The structural adhesive can be a high-strength adhesive commonly used in aerospace structures, such as epoxy structural adhesives, modified epoxy adhesives, or polyurethane structural adhesives, which possess good shear strength, fatigue resistance, and compatibility with composite materials. The functions of the constraint layer 204 include: limiting the expansion of the pouch battery layer 208 along the wing surface; ensuring a more uniform distribution of the thickness increment of the pouch battery layer 208 along the wing surface; and improving the out-of-plane load transfer capability.

[0057] The pouch battery layer 208 uses a 3.8mm thick pouch lithium battery. The pouch battery layer 208 is fixed between the constraint layer 204 and the elastic support layer 206 using structural adhesive and localized point bonding. This fixing method ensures battery position stability and load transfer continuity while allowing necessary controllable deformation of the pouch battery layer 208 in the thickness direction, thus not affecting the variable stiffness adjustment effect caused by thickness changes. The initial thickness of approximately 3.8mm for the pouch battery layer 208 was determined while considering the wing structure layout space, battery energy density, and available thickness variation range. This thickness allows for significant and controllable out-of-plane thickness changes within a safe operating range, effectively participating in the sandwich height adjustment. After full charging, the thickness increases to 5.1mm. The battery's equivalent compression modulus is approximately 15MPa–25MPa, providing both energy storage and serving as an adjustable height sandwich material. In this embodiment, the battery is divided into four independent regions. This division is based on the requirements of wing spanwise load distribution and variable stiffness control accuracy, which helps to achieve differentiated adjustment of stiffness in different wing regions while ensuring controllable control complexity. Each region is equipped with an independent BMS module (Battery Management System), which can adjust the state of charge of each segment to change the local stiffness.

[0058] The elastic support layer 206 is made of closed-cell foam material with a density of 120 kg / m³–150 kg / m³ and a thickness of 3 mm. This layer allows the battery to expand inward and provides the necessary shear stiffness so that the load can be transferred from the outer skin through the battery to the inner skin layer.

[0059] The inner skin layer 207 / wing box upper wall panel is made of a 1.2 mm thick composite material plate, forming a sandwich beam-like structure with the outer skin layer 203. This structure bears the main part of the wing bending moment.

[0060] This embodiment describes a variable stiffness adjustment process centered on the change in the thickness of the pouch battery layer 208. It is assumed that the battery thickness change in the mid-region of the outer wing section is Δ. t =1.3mm, then the corresponding change in the height of the sandwich beam is Δ h ≈Δ t .

[0061] The relationship between bending stiffness and core height can be approximated as: Therefore, when battery charging leads to a 3%–5% increase in height, the local bending stiffness can be increased to 10%–30%.

[0062] During flight missions, stiffness can be increased by increasing the battery voltage in the wingtip area based on feedback from the wingtip vibration sensor, thereby improving flutter resistance; during cruise, the voltage in this area is reduced to make the wing more compliant and reduce lift pulsation.

[0063] The shear load path is as follows: outer skin layer → constraint layer → soft-pack battery layer → elastic support layer → inner skin layer / wing box structure.

[0064] In this embodiment, when the battery is at 4V, its out-of-plane equivalent compressive modulus increases by approximately 20–25%, resulting in a corresponding increase in the wing's shear stiffness. This effect can be used to improve the wing's local torsional stiffness, enabling it to maintain a stable aerodynamic shape during high angle-of-attack maneuvers.

[0065] The embodiment employs a three-level segmentation system—wing root, mid-section, and wingtip—to achieve more refined intelligent adjustment: Flange root region (high stiffness region): Maintain high voltage (4V-4.2V) to improve overall bending strength.

[0066] Central region (adaptation zone): Dynamically control battery voltage (3.6V-4V) according to flight phase to optimize aeroelasticity.

[0067] Wingtip region (flutter reduction region): Maintain a low voltage (3.2V-3.6V) to reduce local stiffness and achieve "passive flutter suppression".

[0068] The above design enables real-time adjustable wing stiffness distribution without the need for additional variable stiffness actuators.

[0069] Structural integration and manufacturing processes: (1) Composite material layup: The outer skin and the constraint layer adopt a co-curing process to ensure interface quality.

[0070] (2) Battery fixing method: a combination of local structural adhesive and spot bonding with flexible limiting piece is used to ensure shear transmission and avoid excessive battery constraint.

[0071] (3) Installation of elastic support layer: The elastic material is integrally hot-pressed to fully fit the bottom surface of the battery and improve the shear transmission stability.

[0072] (4) Electrical system integration: Each battery zone is equipped with an independent voltage and temperature acquisition unit and connected to the main control BMS; the BMS communicates with the intelligent structure control unit through the CAN bus to realize closed-loop regulation.

[0073] The control system consists of sensors, a BMS, a battery module, and a controller, and its workflow is as follows: (1) Acceleration sensors and strain gauges are installed on the wing surface to monitor vibration and bending conditions in real time.

[0074] (2) The controller determines whether it is close to the flutter point based on the vibration frequency.

[0075] (3) If it approaches the critical point, the controller increases the battery voltage in the wingtip area → increases the local stiffness.

[0076] (4) After the aircraft stabilizes, the battery voltage is automatically reduced to restore its flexibility.

[0077] (5) The entire process is automated, without the need for traditional hydraulic or mechanical variable stiffness mechanisms on the air.

[0078] This new mechanism, which enhances rigidity upon charging, is achieved by the battery itself, eliminating the need for other actuators, significantly reducing weight, and improving maintainability.

[0079] The above inventions are merely a few specific embodiments of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A wing structure with a multi-layered sandwich skin, characterized in that, The aircraft includes an upper wing skin (201) and a lower wing skin (202). Both the upper wing skin (201) and the lower wing skin (202) include an outer skin layer (203), a constraint layer (204), a soft-pack battery layer (208), an elastic support layer (206), and an inner skin layer (207) arranged sequentially from the outside to the inside. The outer skin layer (203), the constraint layer (204), the elastic support layer (206), and the inner skin layer (207) have deformation capabilities. The soft-pack battery layer (208) undergoes a thickness change during charging and discharging, serving as a variable height material; the thickness change is used to alter the height of the upper wing skin (201) and / or the lower wing skin (202), thereby adjusting the wing's bending stiffness and / or shear stiffness.

2. The wing structure with multi-layer sandwich skin as described in claim 1, characterized in that, The constraint layer (204) is made of a high-modulus thin-film material with a thickness of 0.1mm-0.3mm. The constraint layer (204) is bonded to the outer skin layer (203) and is used together with the outer skin layer (203) to restrict the in-plane expansion of the soft-pack battery layer (208) and guide the out-of-plane pressure generated by the outer skin layer (203) to be transmitted to the soft-pack battery layer (208) and the elastic support layer (206).

3. The wing structure with multi-layered sandwich skin as described in claim 1, characterized in that, The pouch battery layer (208) can provide a thickness variation of 0.5 mm to 4 mm, which guides the wing bending stiffness variation range of 10% to 40%.

4. The wing structure with multi-layer sandwich skin as described in claim 1, characterized in that, The edge of the soft-pack battery layer (208) is provided with a shear transfer zone. The soft-pack battery layer (208) is connected to the constraint layer (204) and the elastic support layer (206) respectively by structural adhesive or flexible limiting structure, so that the shear load is effectively transferred between the constraint layer (204) and the elastic support layer (206).

5. The wing structure with multi-layered sandwich skin as described in claim 1, characterized in that, The pouch battery layer (208) is divided into multiple independent regions, each region is equipped with an independent battery management system (6), the battery management system (6) is used to adjust the state of charge of each region to achieve stiffness control of different regions.

6. The wing structure with multi-layer sandwich skin as described in claim 5, characterized in that, The battery management system is connected to the controller, which dynamically adjusts the charging and discharging state of the pouch battery layer (208) based on feedback information from strain sensors or acceleration sensors installed on the wing, so as to realize real-time variable stiffness control of the wing.

7. The wing structure with multi-layer sandwich skin as described in claim 6, characterized in that, The outer skin layer (203), constraint layer (204), soft-pack battery layer (208), elastic support layer (206), and inner skin layer (207) together form a composite material sandwich beam. The real-time height of the sandwich beam of the soft-pack battery layer (208) is... Represented as: ， in, h 0 Δ represents the initial height of the sandwich beam before the battery expands. t ( V ) represents the thickness variation of the pouch cell layer (208), where Δ t ( V ) and voltage V Positive correlation; The bending stiffness of the sandwich beam Real-time height of sandwich beam Satisfy the following formula: ， in, E f The elastic modulus of the outer skin layer (203) or the inner skin layer (207) is given. b The effective width of the outer skin layer (203) or the inner skin layer (207).

8. The wing structure with multi-layer sandwich skin as described in claim 7, characterized in that, The shear stiffness of the wing Real-time height of the sandwich beam Satisfy the following formula: ， in, Gc ( V ) represents the equivalent shear modulus of the pouch cell layer (208) as it varies with voltage.

9. The wing structure with multi-layered sandwich skin as described in claim 1, characterized in that, An elastic bracket (205) is also provided on the periphery of the soft-pack battery layer (208). The distance between the elastic bracket (205) and the soft-pack battery layer (208) is 4mm-6mm. The elastic bracket (205) is connected to the constraint layer (204) and the elastic support layer (206) respectively.

10. The wing structure with multi-layer sandwich skin as described in claim 9, characterized in that, The elastic bracket (205) and the elastic support layer (206) are integrated. The thickness of the elastic support layer (206) is 1mm–5mm. The materials of the elastic bracket (205) and the elastic support layer (206) are silicone rubber, thermoplastic polyurethane or lightweight foam, so as to allow the out-of-plane expansion of the soft-pack battery layer (208) and provide a shear load transfer channel.

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