Bionic large deformation and multiple recovery C / PEEK composite skin structure

Abstract

The application discloses a biomimetic large deformation and recoverable C / PEEK composite skin structure and belongs to the field of wing skin. The application draws lessons from the efficient propulsion and flexible structure characteristics of jellyfish when swimming in water, proposes a new jellyfish type honeycomb unit structure, and improves the extensibility of the structure, reduces stress and strain concentration, and reduces the instability of the airplane by means of uniform curvature and increasing the number of large-arc ligaments. The jellyfish type honeycomb structure unit is mainly composed of a center semicircular ring and a plurality of ligaments, the structure is simple, and the structure is convenient to optimize and improve; and under the action of external load, the semicircular ring rotates, at which time the plurality of ligaments connected with the circular ring are deformed, the circular ring and the ligaments in the structure add additional design parameters for the structural design, so that the skin structure of the application has sufficient rigidity under aerodynamic load.

Description

Technical Field

[0001] This invention relates to a biomimetic large deformation reversible C / PEEK composite material skin structure, belonging to the field of wing skin. Background Technology

[0002] Airplanes are an important means of transportation with a wide range of applications. Primarily used for commercial transport of passengers and cargo, they form the core of the modern aviation industry. Beyond this, airplanes can be used for various military missions, or to provide agricultural assistance such as seeding, environmental monitoring, pesticide spraying, and crop growth monitoring. They can also be used for scientific research activities such as meteorological observation, geological exploration, land surveying, aerial photography, and marine research.

[0003] To ensure aircraft safety and economy, and to enable them to perform a wide variety of missions, the structural design and material selection of aircraft skin are of paramount importance. Aircraft skin is the structural component of the aircraft's outer surface, covering the aircraft's skeletal structure and forming its shape. Aircraft skin not only protects the internal structures and components but is also a crucial part of the aircraft's aerodynamic structure, influencing its aerodynamic performance and overall structural strength. Furthermore, the weight of the aircraft skin significantly impacts the overall weight of the aircraft; lightweight skin helps reduce the aircraft's empty weight, increase payload capacity, and reduce fuel consumption.

[0004] Currently, there are various structural designs for aircraft skin. Segmented skins achieve deformation through sliding or rotation between adjacent rigid skin segments, such as "fish-scale" skins. This type of skin can meet design requirements for load-bearing and deformation, but may affect the smoothness and airtightness of the wing surface. Sandwich skins consist of upper and lower panels and an intermediate core material (such as honeycomb core, foam plastic, or corrugated board). This skin structure can provide aircraft with good strength and stiffness while reducing weight. For example, patent CN115009506A discloses a composite flexible skin suitable for variator aircraft and its manufacturing method. Specifically, it uses a sandwich honeycomb structure, which can achieve unidirectional deformation of the skin, meeting the requirements for in-plane coordinated deformation, and maintaining the wing surface closure and smooth shape during deformation. However, sandwich skin structures have complex manufacturing processes and high costs, and cannot meet the requirements for large deformation (>50%), high load-bearing capacity, and recoverable deformation.

[0005] Early aircraft skins were primarily made of fabric or textiles. However, with technological advancements and the increasing speed and altitude of aircraft, metal skins have gradually replaced fabric skins. Currently, commonly used skin materials include high-strength aluminum alloys, magnesium alloys, titanium alloys, and composite materials. These materials are not only lightweight but also possess higher strength and corrosion resistance. Flexible skins, in particular, have become increasingly popular in aircraft skin manufacturing in recent years due to their integrated structure and function, and the absence of complex drive systems. For example, patent CN110920861B discloses a flexible wing skin structure, which includes multiple wing edges and periodically arranged hand-shaped units between the wing edges. This flexible wing skin structure is made of shape memory alloy, which can maintain the aerodynamic shape of the wing, meet the rigidity requirements of aircraft skins, and possess higher strength and corrosion resistance. However, on the one hand, shape memory alloys are quite expensive, and their function is highly temperature-dependent, meaning they will deform to some extent under non-ideal temperatures. On the other hand, shape memory alloy materials suffer fatigue damage after multiple deformation and recovery cycles, leading to a decline in material performance or even fracture.

[0006] It is evident that the existing aircraft skin manufacturing process is complex and costly, and cannot meet the requirements of large deformation (>50%), high load-bearing capacity, and recoverable deformation. Furthermore, the skin may suffer fatigue damage after multiple deformation and recovery cycles and cannot adapt to temperature changes. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a biomimetic, large-deformation, reversibly recoverable C / PEEK composite material skin structure. Specifically, this invention draws inspiration from the efficient propulsion and flexible structure of jellyfish swimming in water, proposing a novel jellyfish-shaped honeycomb unit structure. By achieving uniform curvature and increasing the number of large-arc ligaments, the structure's extensibility is improved, stress and strain concentration is reduced, and aircraft instability is minimized. The jellyfish-shaped honeycomb structure unit of this invention mainly consists of a central semicircular ring and multiple ligaments. The structure is simple and easy to optimize. Under external loads, the semicircular ring rotates, causing the multiple ligaments connected to it to deform. The ring and ligaments in the structure add additional design parameters, ensuring sufficient stiffness of the skin structure under aerodynamic loads. Furthermore, the jellyfish-shaped honeycomb structure unit also exhibits high fatigue resistance, meeting the requirements for large deformation (>50%), high load-bearing capacity, and recoverable deformation.

[0008] In this invention, the skin structure utilizes C / PEEK composite material, which refers to carbon fiber reinforced polyetheretherketone (PEEK) composite material. This material combines the high strength of carbon fiber with the excellent properties of PEEK, possessing advantages such as high strength, high rigidity, high temperature resistance, corrosion resistance, excellent wear resistance, and lightweight. The flexible deformable skin structure of this invention, combining the jellyfish-shaped honeycomb unit structure with C / PEEK composite material, exhibits good ductility. This not only meets the aerodynamic integrity requirements of the wing structure during deformation but also effectively improves aircraft reliability, allowing the wing skin to adapt to temperature changes, reducing the aircraft's empty weight, increasing payload capacity, reducing fuel consumption, and lowering skin maintenance costs.

[0009] The first objective of this invention is to provide a biomimetic C / PEEK composite material skin structure capable of multiple deformations and recovery, wherein the skin structure is composed of multiple flanges and jellyfish-shaped honeycomb structure units periodically arranged between the flanges;

[0010] Each jellyfish-shaped honeycomb structural unit is symmetrical about the horizontal centerline and the vertical centerline, including the flanges on both sides, four structural sub-units on the inner side of the flanges, and the curved beam ligament 6 on the vertical centerline;

[0011] The four structural sub-units on the inner side of the flange are symmetrical to each other along the horizontal centerline and along the vertical centerline. Each structural sub-unit includes: a first semi-circular ring 2, a second semi-circular ring 3, a first arc-shaped ligament 4, and a second arc-shaped ligament 5.

[0012] Among them, the flange 1, the second arc-shaped ligament 5, the second semi-circular ring 3, the first semi-circular ring 2, the first arc-shaped ligament 4, and the curved beam ligament 6 are connected in sequence;

[0013] The second arc-shaped ligament 5 is connected to the second semicircular ring 3 in the same direction, the second semicircular ring 3 is connected to the first semicircular ring 2 in the opposite direction, and the first semicircular ring 2 is connected to the first arc-shaped ligament 4 in the same direction.

[0014] The central axes of the first semicircular ring 2 and the second semicircular ring 3 are located on the same horizontal plane as the central axis of the second arc-shaped ligament 5, and are set at equal distances.

[0015] The end of the first arc-shaped ligament 4 that connects to the curved beam ligament 6 is connected to the first arc-shaped ligament of the adjacent structural subunit, forming a semi-circular ring.

[0016] In one embodiment of the present invention, the flange 1 is connected to one end of the second arcuate ligament 5, the other end of the second arcuate ligament 5 is connected to one end of the second semicircular ring 3, the other end of the second semicircular ring 3 is connected to one end of the first semicircular ring 2, the other end of the first semicircular ring 2 is connected to the first arcuate ligament 4, and the other end of the first arcuate ligament 4 is connected to the curved beam ligament 6.

[0017] In one embodiment of the present invention, multiple flanges are arranged in parallel and at equal intervals.

[0018] In one embodiment of the present invention, the central axis of the first arc-shaped ligament 4 is located on the vertical symmetry plane of the jellyfish-shaped honeycomb structure unit, and the central axis of the second arc-shaped ligament 5 is located on the outer side of the flange 1.

[0019] In one embodiment of the present invention, the first semicircular ring 2 and the second semicircular ring 3 have the same radius.

[0020] In one embodiment of the present invention, the jellyfish-shaped honeycomb structure unit satisfies the following dimensional relationship:

[0021] H = 2*(r1+r2) + h

[0022] r1 = r2 + r3

[0023] Where r1 is the radius of the first arc-shaped ligament 4, r2 is the radius of the second arc-shaped ligament 5, r3 is the radius of the first semicircular ring 2 and the second semicircular ring 3, H is the length of the jellyfish-shaped honeycomb structure unit, and h is the spacing between the upper and lower adjacent structural sub-units, which is 2mm.

[0024] In one embodiment of the present invention, the shape of the curved beam ligament 6 satisfies the cosine curve y = 0.6sin0.4x.

[0025] In one embodiment of the present invention, the thickness of the skin structure is 3-5 mm.

[0026] In one embodiment of the present invention, the wall thickness of each jellyfish-shaped honeycomb structure unit is 0.6-1.0 mm; that is, the wall thickness w of the flange 1, the first semicircular ring 2, the second semicircular ring 3, the first arc-shaped ligament 4, and the second arc-shaped ligament 5 is equal, and satisfies:

[0027] w = 0.6-1.0 mm.

[0028] In one embodiment of the present invention, the radius r1 of the first arc-shaped ligament 4 is 13-19 mm, the radius r2 of the second arc-shaped ligament 5 is 11-15 mm, the inner diameter r3 of the first semicircular ring 2 and the second semicircular ring 3 is 2-4 mm, the distance L between the outer sides of the two flanges is 29-39 mm, and the height H of the jellyfish-shaped honeycomb structure unit is 50-70 mm.

[0029] Preferably, the radius r1 of the first arc-shaped ligament 4 is 16mm, the radius r2 of the second arc-shaped ligament 5 is 13mm, the radius r3 of the first semicircular ring 2 and the second semicircular ring 3 is 3mm, the distance L between the outer sides of the two flanges is 34mm, and the height H of the jellyfish-shaped honeycomb structure unit is 60mm.

[0030] In one embodiment of the invention, the skin structure is made of C / PEEK composite material.

[0031] The second objective of this invention is to provide a method for preparing a biomimetic C / PEEK composite skin structure capable of multiple deformations and recovery, comprising the following steps:

[0032] By 3D printing C / PEEK composite materials, a biomimetic large deformation and repeatedly recoverable C / PEEK composite skin structure can be obtained.

[0033] In one embodiment of the present invention, the C / PEEK composite material can be obtained commercially or prepared by oneself.

[0034] In one embodiment of the present invention, the preparation method of C / PEEK composite material is as follows:

[0035] Surface-modified carbon fibers are obtained by modifying the surface of carbon fibers.

[0036] Surface-modified carbon fibers and PEEK resin are mixed, extruded, cooled, cured, and cut into blocks to obtain C / PEEK composite materials.

[0037] The specifications for the carbon fiber are: diameter 80-100μm, length 3mm, and purity ≥99%.

[0038] The modification treatment involves loading carbon fibers into a Soxhlet extractor and treating them with acetone in a water bath at 75-85°C for 45-60 hours.

[0039] PEEK resin needs to be dried at 110-120℃ for 4-6 hours before use;

[0040] The mass ratio of carbon fiber to PEEK resin is 2:8-10;

[0041] The mixing conditions are as follows: place the mixture in a high-speed mixer and mix for 8-20 minutes at 230-250℃ and 3000-5000 rpm.

[0042] The extrusion molding conditions are 360-380℃ and 20-30g / min.

[0043] Cooling is rapid cooling;

[0044] Curing is carried out at 200-220℃ for 2-4 hours;

[0045] Cutting into pieces means cutting them into pieces the size of the masterbatch.

[0046] In one embodiment of the present invention, the parameters for 3D printing are set as follows:

[0047] The temperatures of the printing nozzle, platform, and cavity were set to 415-420℃, 125-135℃, and 85-95℃, respectively; the filling density, printing speed, and printing layer thickness of the C / PEEK composite material were set to 100%, 9-11 mm / s, and 3-5 mm, respectively.

[0048] In one embodiment of the present invention, the surface of the C / PEEK composite material skin structure is smooth and flat, without obvious defects or damage, and the dimensional parameters meet the design parameters.

[0049] The third objective of this invention is the application of the biomimetic, large-deformation, reversible C / PEEK composite skin structure described herein in the aerospace field.

[0050] A fourth objective of this invention is to provide an aircraft skin that employs the C / PEEK composite material skin structure described herein.

[0051] Beneficial effects

[0052] (1) The skin structure of the present invention draws on the efficient propulsion and flexible structure characteristics of jellyfish swimming in water, and proposes a basic configuration with jellyfish-shaped honeycomb structure unit, which ensures the integrity of the aerodynamic shape of the skin structure during deformation and can have sufficient stiffness under aerodynamic load.

[0053] (2) This invention improves the extensibility of the structure and reduces stress and strain concentration by using uniform curvature and increasing the number of large-arc ligaments.

[0054] (3) The jellyfish-shaped honeycomb structure unit of the present invention uses a curved beam ligament structure, which further disperses stress, reduces aircraft instability, and meets the requirements of large deformation.

[0055] (4) The skin knot of the present invention can be scaled proportionally to meet the requirements of different scenarios.

[0056] (5) The skin structure of the present invention adopts C / PEEK composite material, which combines the high strength of carbon fiber and the excellent performance of PEEK. It has the advantages of high strength and high rigidity, high temperature resistance, corrosion resistance, excellent wear resistance and light weight. This makes the flexible deformable skin that combines the jellyfish honeycomb structure unit with C / PEEK composite material have good ductility. It not only meets the aerodynamic integrity requirements of the wing structure during deformation, but also effectively improves the reliability of the aircraft, makes the skin adapt to temperature changes, reduces the empty weight of the aircraft, increases the load capacity, reduces fuel consumption, and reduces the maintenance and repair cost of the skin.

[0057] (6) The skin structure of the present invention has sufficient elasticity and deformability in the plane and can withstand sufficiently large aerodynamic loads out of the plane, providing support for the configuration changes of the variant aircraft such as variable chord length, variable span or variable sweep angle in various mission modes.

[0058] (7) The skin structure of the present invention can be obtained by arranging jellyfish-type honeycomb structure units in a periodic manner. The structure is simple and convenient for optimization and improvement. Attached Figure Description

[0059] Figure 1 This is a three-dimensional structural diagram of the C / PEEK composite skin structure in Example 1.

[0060] Figure 2 This is a planar schematic diagram of the jellyfish-shaped honeycomb structure unit of the C / PEEK composite skin structure in Example 1; wherein, 1 is the flange, 2 is the first semicircular ring, 3 is the second semicircular ring, 4 is the first arc-shaped ligament, 5 is the second arc-shaped ligament, and 6 is the curved beam ligament.

[0061] Figure 3 This is a schematic diagram of the jellyfish-shaped honeycomb structure unit of the C / PEEK composite material skin structure in Example 1; where r1 and r2 are the radii of the first and second arc-shaped ligaments, respectively, r3 is the inner diameter of the semicircular ring, H is the length of the jellyfish-shaped honeycomb structure unit, h is the spacing between the upper and lower adjacent structural sub-units, w is the wall thickness, and L is the distance between the outer sides of the two flanges.

[0062] Figure 4 The image shows a tensile test diagram of the C / PEEK composite skin structure in Example 2; where Mises is used to describe the equivalent stress of the material under complex three-dimensional stress state.

[0063] Figure 5 This is a planar schematic diagram of a jellyfish-shaped honeycomb structure unit in Comparative Example 1 that does not use the intermediate curved beam ligament, where 1 is the flange, 2 is the first semicircular ring, 3 is the second semicircular ring, 4 is the first arc-shaped ligament, and 5 is the second arc-shaped ligament.

[0064] Figure 6 This is a schematic diagram of the jellyfish-shaped honeycomb structure unit in Comparative Example 1 before and after stretching.

[0065] Figure 7 This is a planar schematic diagram showing the transformation of the semi-circular ring structure in the jellyfish-shaped honeycomb structure unit of Comparative Example 2 into a curved structure.

[0066] Figure 8 This is a planar schematic diagram showing the result of changing the semi-circular ring structure in the jellyfish-shaped honeycomb structure unit of Comparative Example 3 to a straight line structure.

[0067] Figure 9 This is a schematic diagram of the structural unit in Comparative Example 4. Detailed Implementation

[0068] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0069] Test method:

[0070] 1. Tensile testing of skin structure

[0071] In-plane tensile tests were conducted on the zero Poisson's ratio C / PEEK composite skin structure at room temperature using a universal testing machine (INSTRON 5967). The test standard was ISO 572-2, and the loading speed of the universal testing machine was 5 mm / min.

[0072] 2. High-speed tensile-compression cyclic load test of skin structure

[0073] The ability of the wing skin to rapidly achieve 50% in-plane deformation within 10 seconds was simulated using a universal testing machine (INSTRON5967) at room temperature. The loading speed was set to 234 mm / min, and the interval between each loading was 0 seconds to simulate the rapid and continuous deformation of the wing skin.

[0074] 3. Stress concentration test of skin structure:

[0075] A solid model of the C / PEEK composite skin structure was constructed in Solidworks software and saved as a STEP file. Based on the constructed macroscopic model of the zero Poisson's ratio C / PEEK composite skin structure, the mechanical property parameters of C / PEEK material were introduced, and the simulation calculation of the zero Poisson's ratio C / PEEK composite skin structure was carried out using ABAQUS software (3DS, Dassault Systèmes, France). After the simulation calculation was completed, the stress-strain cloud map of the honeycomb reinforcement was obtained, and the stress concentration phenomenon of the material could be observed.

[0076] Raw materials and equipment involved in the embodiments:

[0077] C / PEEK composite material: carbon fiber content is 10% (by mass), carbon fiber length is 80-100μm; purchased from INTAMSYS.

[0078] 3D printer: FDM printer (D260HT, Wiiboox, China); a quasi-industrial-grade device specifically designed for the preparation of PEEK materials, purchased from INTAMSYS.

[0079] Carbon fiber: purity ≥99%, tensile modulus 290 GPa, linear density 0.45 g / cm³ 3 Purchased from Sinoma Shenying Carbon Fiber Co., Ltd.

[0080] PEEK resin: tensile modulus 170 GPa, linear density 4.1 g / cm³ 3 Purchased from Jilin Zhongyan Polymer Materials Co., Ltd.

[0081] To better illustrate the purpose and advantages of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0082] Example 1

[0083] A biomimetic, large-deformation, repeatedly recoverable C / PEEK composite material skin structure, the three-dimensional structure diagram is as follows. Figure 1 ;

[0084] The skin structure is composed of multiple flanges and jellyfish-shaped honeycomb structural units arranged periodically between the flanges;

[0085] A schematic diagram of a jellyfish-shaped honeycomb structure unit is shown below. Figure 2 ;

[0086] Each jellyfish-shaped honeycomb structural unit is symmetrical about the horizontal centerline and the vertical centerline, including the flanges on both sides, four structural sub-units on the inner side of the flanges, and the curved beam ligament 6 on the vertical centerline;

[0087] The four structural sub-units on the inner side of the flange are symmetrical to each other along the horizontal centerline and along the vertical centerline. Each structural sub-unit includes: a first semi-circular ring 2, a second semi-circular ring 3, a first arc-shaped ligament 4, and a second arc-shaped ligament 5.

[0088] Among them, the flange 1, the second arc-shaped ligament 5, the second semi-circular ring 3, the first semi-circular ring 2, the first arc-shaped ligament 4, and the curved beam ligament 6 are connected in sequence;

[0089] The second arc-shaped ligament 5 is connected to the second semicircular ring 3 in the same direction, the second semicircular ring 3 is connected to the first semicircular ring 2 in the opposite direction, and the first semicircular ring 2 is connected to the first arc-shaped ligament 4 in the same direction.

[0090] The central axes of the first semicircular ring 2 and the second semicircular ring 3 are located on the same horizontal plane as the central axis of the second arc-shaped ligament 5, and are set at equal distances.

[0091] The end of the first arc-shaped ligament 4 that connects to the curved beam ligament 6 is connected to the first arc-shaped ligament of the adjacent structural subunit, forming a semicircle;

[0092] The shape of the curved beam ligament 6 satisfies the cosine curve y = 0.6sin0.4x.

[0093] Furthermore, the flange 1 is connected to one end of the second arcuate ligament 5, the other end of the second arcuate ligament 5 is connected to one end of the second semicircular ring 3, the other end of the second semicircular ring 3 is connected to one end of the first semicircular ring 2, the other end of the first semicircular ring 2 is connected to the first arcuate ligament 4, and the other end of the first arcuate ligament 4 is connected to the curved beam ligament 6.

[0094] Furthermore, multiple wing edges are arranged parallel and at equal intervals;

[0095] Furthermore, the central axis of the first arc-shaped ligament 4 is located on the vertical symmetry plane of the jellyfish-shaped honeycomb structural unit, and the central axis of the second arc-shaped ligament 5 is located on the outer side of the flange 1.

[0096] Furthermore, the radii of the first semicircular ring 2 and the second semicircular ring 3 are equal;

[0097] Furthermore, the jellyfish-shaped honeycomb structural unit satisfies the following dimensional relationships:

[0098] H = 2*(r1+r2) + h

[0099] r1 = r2 + r3

[0100] Where r1 is the radius of the first arc-shaped ligament 4, r2 is the radius of the second arc-shaped ligament 5, r3 is the radius of the first semicircular ring 2 and the second semicircular ring 3, H is the length of the jellyfish-shaped honeycomb structure unit, and h is the spacing between the upper and lower adjacent structural sub-units, which is 2mm.

[0101] Furthermore, the thickness of the skin structure is 3-5mm.

[0102] Furthermore, the wall thickness of the jellyfish-shaped honeycomb structure units is 0.6-1.0 mm;

[0103] That is: the wall thickness w of flange 1, first semicircular ring 2, second semicircular ring 3, first arcuate ligament 4, and second arcuate ligament 5 are equal, and satisfy:

[0104] w = 0.6-1.0 mm.

[0105] Furthermore, the radius r1 of the first arc-shaped ligament 4 is 13-19 mm;

[0106] The radius r2 of the second arc-shaped ligament 5 is 11-15 mm;

[0107] The inner diameter r3 of the first semicircular ring 2 and the second semicircular ring 3 is 2-4mm;

[0108] The distance L between the outer edges of the two flanges is 29-39 mm;

[0109] The height H of the jellyfish-shaped honeycomb structure unit is 50-70mm.

[0110] Example 2: Parameter optimization of jellyfish-type honeycomb structure unit size

[0111] Based on the skin structure of Example 1, extensive experiments have shown that the skin structure performs well when the jellyfish-shaped honeycomb structural units in Example 1 satisfy the following dimensional relationships:

[0112] H = 2*(r1+r2) + h

[0113] r1 = r2 + r3

[0114] Where r1 is the radius of the first arc-shaped ligament 4;

[0115] r2 is the radius of the second arc-shaped ligament 5;

[0116] r3 is the radius of the first semicircular ring 2 and the second semicircular ring 3;

[0117] H is the length of the jellyfish-shaped honeycomb structure unit;

[0118] h is the spacing between adjacent upper and lower structural sub-units, with a value of 2mm.

[0119] A schematic diagram of the jellyfish-shaped honeycomb structure unit dimensions is shown below. Figure 3 .

[0120] The following example illustrates this:

[0121] The specific parameters used for r1, r2, r3, H, and c1 are shown in Table 1 below:

[0122] Table 1. Skin structure schemes satisfying the dimensional relationship H=2*(r1+r2)+h, r1=r2+r3

[0123]

[0124] The performance of the skin structure is shown in Table 2.

[0125] Table 2 shows the performance of skin structures that satisfy the dimensional relationships H = 2*(r1 + r2) + h, r1 = r2 + r3.

[0126]

[0127] As can be seen from Table 2, when the jellyfish-shaped honeycomb structure unit satisfies the above-mentioned dimensional relationship, the skin structure has better performance; when the tensile deformation degree of scheme No. 4 is 50%, it has the ability to withstand large deformation, has good ductility, and the stress concentration phenomenon is reduced; after the scheme No. 2 is subjected to 50% in-plane deformation, its maximum material strain is 4.847E+01, and the deformation is uniform.

[0128] Example 3

[0129] A method for preparing a biomimetic C / PEEK composite skin structure capable of multiple deformations and recovery includes the following steps:

[0130] (1) Construct a solid model of the C / PEEK composite material skin structure of Example 1 in Solidworks software (the radius r1 of the first arc-shaped ligament 4 is 16mm, the radius r2 of the second arc-shaped ligament 5 is 13mm, the radius r3 of the first semicircular ring 2 and the second semicircular ring 3 is 3mm, the distance L between the outer sides of the two flanges is 34mm, the height H of the jellyfish-shaped honeycomb structure unit is 60mm, and the wall thickness w is 0.6mm), and save the model as an STL file;

[0131] (2) Import the STL file into the slicing software CURA and set the printing process parameters:

[0132] The temperatures of the printing nozzle, platform, and chamber were set to 420℃, 130℃, and 90℃, respectively. The filling density, printing speed, and printing layer thickness of the commercially available C / PEEK composite material were set to 100%, 10mm / s, and 0.1mm, respectively.

[0133] (3) After the process parameters are set, the G-code file generated by the slicing software CURA is imported into the 3D printer. The 3D printer is used to print the C / PEEK composite material skin structure by stacking the material from bottom to top, and the C / PEEK composite material skin structure (the thickness of the skin structure is 4mm) is obtained.

[0134] The obtained skin structure was subjected to performance testing, and the test results are as follows:

[0135] The surface of the C / PEEK composite skin structure is smooth and flat, without obvious defects or damage, and the dimensional parameters all conform to the dimensional relationship of Example 2.

[0136] Its skin structure performance is shown in Table 3 below;

[0137] Table 3 Performance test results of the skin structure

[0138]

[0139] Example 4

[0140] The preparation method of the commercially available C / PEEK composite material in Example 3 is adjusted as follows:

[0141] Carbon fibers with a length of 80-100 μm were loaded into a Soxhlet extractor and treated with acetone in a water bath at 80 °C for 48 h to obtain surface-modified carbon fibers.

[0142] The PEEK resin was dried at 120°C for 5 hours to remove moisture and volatiles.

[0143] Surface-modified carbon fiber and PEEK resin were mixed at a mass ratio of 2:7 at 240°C and 3500 rpm for 10 min, and then extruded at 370°C at a speed of 25 g / min.

[0144] The C / PEEK composite material was obtained by rapidly cooling with water, curing in a vacuum oven at 210°C for 3 hours, and cutting into masterbatch size.

[0145] Everything else remains the same as in Example 3, with the skin structure obtained through 3D printing.

[0146] The obtained skin structure was subjected to performance testing, and the test results are as follows:

[0147] Table 4 Performance test results of the skin structure

[0148]

[0149] Comparative Example 1

[0150] The curved beam ligament 6 in Example 1 is omitted; otherwise, it remains the same as in Example 3, with the structure as follows: Figure 5 .

[0151] The obtained skin structure was subjected to performance testing, and the test results are as follows:

[0152] Table 5 Test Results

[0153]

[0154] Note: One-dimensional deformation capability refers to deformation in one direction.

[0155] The deformed state is as follows Figure 6 As shown, from Figure 6It can be seen that the skin structure prepared in Comparative Example 1 has poor one-dimensional deformation ability and suffers from structural instability; while the structure of the embodiment has good one-dimensional deformation ability.

[0156] Comparative Example 2

[0157] In Example 1, the first semicircular ring 2 and the second semicircular ring 3 are adjusted to be composed of three semicircles with a radius of 1 mm connected together. All other aspects remain the same as in Example 3, with the structure as follows: Figure 7 .

[0158] The obtained skin structure was subjected to performance testing, and the test results are as follows:

[0159] Table 6 Test Results

[0160]

[0161] As can be seen from Table 6, after changing the semicircular ring to a curve (connected by three semicircles with a radius of 1 mm), the structure cannot undergo large deformation. When the deformation reaches about 30%, the structure is damaged. This is because changing the semicircular ring to a curve (connected by three semicircles with a radius of 1 mm) increases the number of stress concentration points, and the force cannot be well transmitted, eventually leading to structural failure at multiple stress concentration points.

[0162] Comparative Example 3

[0163] In Example 1, the first semicircular ring 2 and the second semicircular ring 3 are adjusted to be straight lines 2 and 3, respectively, while the rest remains the same as in Example 3. The structure is as follows: Figure 8 .

[0164] The obtained skin structure was subjected to performance testing, and the test results are as follows:

[0165] Table 7 Test Results

[0166] 8％ yes 2.578E+02 Structural damage 13％ yes 2.390E+02 Structural damage 15％ yes 2.289E+02 Structural damage

[0167] As can be seen from Table 7, after changing the semi-circular ring structure to a straight line structure, the tensile deformation of the structure decreased significantly, and the structure was prone to breakage at the connection point, which could not meet the usage requirements.

[0168] Comparative Example 4

[0169] The structure of Example 3 is adjusted to adopt... Figure 9 The structure has the following parameters:

[0170] The radii R1 and R2 are both 10 mm, the radius R3 is 2.5 mm, h1 is 2 mm, the distance L1 between the outer sides of the two flanges is 30 mm, the height H1 of the honeycomb structure unit is 42 mm, and the wall thickness of the structure unit is 0.6 mm.

[0171] Everything else remains the same as in Example 3, resulting in a skin structure.

[0172] The obtained skin structure was subjected to performance testing, and the test results are as follows:

[0173] Table 8 Test Results

[0174]

[0175] As can be seen from Table 8, stress concentration occurs in the structures of Comparative Example 4 under the same degree of deformation. The maximum stress of the tensile material is greater than that of Example 1, the material's deformation capacity is also poor, and it is prone to fracture at the stress concentration point. The material's recovery capacity after deformation is also poor.

[0176] Comparative Example 5

[0177] In Example 3, the C / PEEK composite material was changed to aluminum alloy material (purchased from Beijing Yanbang New Material Technology Co., Ltd.). An ISLM280 3D printer was used, with AlSi10Mg aluminum alloy powder as the material. The process parameters were: laser power 200W, scanning speed 2.0m / s, and layer thickness 4mm.

[0178] Everything else remains the same as in Example 3, resulting in a skin structure.

[0179] The obtained skin structure was subjected to performance testing, and the test results are as follows:

[0180] Table 9 Test Results

[0181]

[0182] As can be seen from Table 9, under the same degree of tensile deformation, the stress concentration phenomenon of this material is more serious, and it is easy to break at the joint, which affects its tensile properties. Moreover, because the aluminum alloy has greater stiffness, the maximum stress when stretching the material is greater than that in Example 1, and it is not easy to deform.

[0183] Comparative Example 6

[0184] The preparation method of the C / PEEK composite material in Example 4 is adjusted as follows:

[0185] Carbon fibers with a length of 80-100 μm were loaded into a Soxhlet extractor and treated with acetone in a water bath at 80 °C for 48 h to obtain surface-modified carbon fibers.

[0186] Dry the PEEK resin at 120°C for 5 hours;

[0187] Surface-modified carbon fiber and PEEK resin were mixed at a mass ratio of 2:7, mixed at 180℃ and 2000rpm for 10min, extruded at 370℃ and 25g / min, rapidly cooled by water cooling, cured in a vacuum oven at 210℃ for 3h, and cut into masterbatch size to obtain C / PEEK composite material.

[0188] Everything else remains the same as in Example 4, resulting in a skin structure.

[0189] The obtained skin structure was subjected to performance testing, and the test results are as follows:

[0190] Table 10 Test Results

[0191]

[0192] As can be seen from Table 10, under the same degree of tensile deformation, this material exhibits stress concentration, which affects its tensile properties. Furthermore, changes in parameter settings reduce the uniformity of material mixing, making it prone to printing defects and increasing printing difficulties.

[0193] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A biomimetic C / PEEK composite skin structure capable of multiple deformations and recovery, characterized in that, The skin structure is composed of multiple flanges and jellyfish-shaped honeycomb structural units arranged periodically between the flanges; Each jellyfish-shaped honeycomb structural unit is symmetrical about the horizontal centerline and the vertical centerline, including four structural sub-units located on the inner side of the flange and a curved beam ligament located on the vertical centerline (6). The four structural sub-units on the inner side of the flange are symmetrical to each other along the horizontal centerline and along the vertical centerline. Each structural sub-unit includes: a first semi-circular ring (2), a second semi-circular ring (3), a first arc-shaped ligament (4), and a second arc-shaped ligament (5). The flange (1), the second arcuate ligament (5), the second semicircular ring (3), the first semicircular ring (2), the first arcuate ligament (4), and the curved beam ligament (6) are connected in sequence; The second arc-shaped ligament (5) is connected to the second semicircular ring (3) in the same direction, the second semicircular ring (3) is connected to the first semicircular ring (2) in the opposite direction, and the first semicircular ring (2) is connected to the first arc-shaped ligament (4) in the same direction. The central axes of the first semicircular ring (2) and the second semicircular ring (3) are on the same horizontal plane as the central axis of the second arc-shaped ligament (5), and are set at equal distances. The end of the first arc-shaped ligament (4) that connects to the curved beam ligament (6) is connected to the first arc-shaped ligament of the adjacent structural subunit, forming a semi-circular ring; The jellyfish-shaped honeycomb structural unit satisfies the following dimensional relationships: H = 2 * (r1 + r2) + h r1=r2+r3 Where r1 is the radius of the first arc-shaped ligament (4), r2 is the radius of the second arc-shaped ligament (5), r3 is the radius of the first semicircular ring (2) and the second semicircular ring (3), H is the length of the jellyfish-shaped honeycomb structure unit, and h is the spacing between the upper and lower adjacent structural sub-units.

2. The biomimetic large deformation reversible C / PEEK composite skin structure according to claim 1, characterized in that, The central axis of the first arc-shaped ligament (4) is located on the vertical symmetry plane of the jellyfish-shaped honeycomb structure unit, and the central axis of the second arc-shaped ligament (5) is located on the outside of the flange (1).

3. The biomimetic large deformation reversible C / PEEK composite skin structure according to claim 1, characterized in that, The radii of the first semicircular ring (2) and the second semicircular ring (3) are equal.

4. The biomimetic large deformation reversible C / PEEK composite skin structure according to claim 1, characterized in that, The shape of the curved beam ligament (6) satisfies the curve y=0.6sin0.4x.

5. The biomimetic large deformation reversible C / PEEK composite material skin structure according to claim 1, characterized in that, The wall thickness of each jellyfish-shaped honeycomb structure unit is 0.6-1.0 mm; that is, the wall thickness w of the flange (1), the first semicircular ring (2), the second semicircular ring (3), the first arc-shaped ligament (4), and the second arc-shaped ligament (5) are equal and satisfy: w=0.6-1.0mm.

6. The biomimetic large deformation reversible C / PEEK composite skin structure according to claim 1, characterized in that, The skin structure is made of C / PEEK composite material; the thickness of the skin structure is 3-5mm.

7. A method for preparing the biomimetic large deformation reversible C / PEEK composite skin structure according to any one of claims 1-6, characterized in that, Includes the following steps: By 3D printing C / PEEK composite materials, a biomimetic large deformation and repeatedly recoverable C / PEEK composite skin structure can be obtained.

8. The application of the biomimetic large deformation reversible C / PEEK composite skin structure according to any one of claims 1-6 in the aerospace field.

9. An aircraft skin, characterized in that, It employs the biomimetic large deformation reversible C / PEEK composite skin structure as described in any one of claims 1-6.

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