Bionic large-deformation C / PEEK composite material skin structure capable of being recovered for multiple times

Abstract

The invention discloses a bionic large-deformation C / PEEK composite material skin structure capable of being recovered for multiple times, and belongs to the field of wing skins. The novel jellyfish type honeycomb unit structure is provided by referring to the characteristics of efficient propulsion and a flexible structure when the jellyfish swims in water, and the extensibility of the structure is improved, the stress strain concentration is reduced and the aircraft instability phenomenon is reduced through uniform curvature and increase of the number of large-radian ligaments. The jellyfish type honeycomb structure unit is mainly composed of the center semicircular ring and the multiple ligaments, the structure is simple, and the structure can be conveniently optimized and improved; under the action of an external load, the semi-circular rings can rotate, at the moment, the multiple ligaments connected with the circular rings can deform, the circular rings and the ligaments in the structure increase additional design parameters for structural design, and the skin structure has enough rigidity under the aerodynamic load.

Description

Technical Field

[0001] The invention relates to a bionic large-deformation and multi-recovery C / PEEK composite material skin structure, belonging to the field of wing skins. Background Art

[0002] As an important means of transportation, airplanes have a wide range of uses. Aircraft are mainly used for commercial transportation of passengers and cargo, and are the core of the modern aviation industry. In addition, airplanes can be used to perform various military missions, or provide agricultural assistance such as sowing, environmental monitoring, spraying pesticides, and monitoring crop growth; airplanes can also be used for scientific surveys such as meteorological detection, geological exploration, land surveying, aerial photography, and marine research.

[0003] In order to ensure the safety and economy of the aircraft and enable it to undertake a variety of tasks, the structural design and material selection of the aircraft skin are particularly important. The aircraft skin is the structural part of the outer surface of the aircraft. It covers the aircraft's skeleton structure and forms the aircraft's appearance. The aircraft skin not only protects the aircraft's internal structure and components, but is also an important part of the aircraft's aerodynamic structure, affecting the aircraft's aerodynamic performance and overall structural strength. At the same time, the weight of the aircraft skin has a significant impact on the aircraft's overall weight. Lightweight skin helps reduce the aircraft's empty weight, improve load-bearing capacity, and reduce fuel consumption.

[0004] At present, there are many forms of structural design of aircraft skin. The sliced ​​skin is deformed by sliding or rotating between adjacent rigid skin segments, such as the "fish scale laminated" skin. This skin can meet the load-bearing and deformation requirements of the design, but may affect the smoothness and airtightness of the wing surface. The sandwich skin is composed of two upper and lower panels and an intermediate core material (such as honeycomb sandwich, foam plastic, corrugated board). This skin structure can provide good strength and rigidity for the aircraft and reduce weight. For example: Patent CN115009506A discloses a composite material flexible skin suitable for a variant aircraft and a manufacturing method. Specifically, it adopts a sandwich honeycomb structure, which can realize the unidirectional deformation condition of the skin, meet the requirements of in-plane coordinated deformation, and keep the wing surface closed and smooth in deformation. However, the manufacturing process of the sandwich skin structure is complicated and the cost is high, and it cannot meet the requirements of large deformation (>50%), high load-bearing, and recoverable deformation.

[0005] In the early days, the material of aircraft skin was mainly cloth or textile materials, but with the development of science and technology, the flight speed and altitude of aircraft continued to increase, and metal skin gradually replaced cloth skin. At present, the materials commonly used for skin include high-strength aluminum alloy, magnesium alloy, titanium alloy and composite materials, which are not only light, but also have higher strength and corrosion resistance. In particular, flexible skin has been very popular in the production of aircraft skin in recent years because of its integrated structure and function and the lack of complex driving equipment. For example, patent CN110920861B discloses a wing flexible skin structure, which includes multiple flanges and chiral units periodically arranged between the flanges; the wing flexible skin structure is made of shape memory alloy material, which can maintain the aerodynamic shape of the wing, meet the rigidity requirements of the aircraft skin, and have higher strength and corrosion resistance; but on the one hand, shape memory alloys are expensive, and their functions are strongly dependent on temperature, which means that at non-ideal temperatures, they will deform to a certain extent; on the other hand, shape memory alloy materials will suffer fatigue damage after multiple deformation and recovery cycles, resulting in material performance degradation or even fracture.

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

[0007] In order to solve the above technical problems, the present invention provides a bionic large deformation and multiple recovery C / PEEK composite material skin structure. Specifically, the present invention draws on the characteristics of efficient propulsion and flexible structure of jellyfish when swimming in water, proposes a new jellyfish-type honeycomb unit structure, and improves the ductility of the structure by uniform curvature and increasing the number of large-arc ligaments, reduces stress and strain concentration, and reduces aircraft instability. The jellyfish-type honeycomb structure unit of the present invention is mainly composed of a central semicircular ring and a plurality of ligaments, and has a simple structure, which is convenient for optimizing and improving the structure; and under the action of external loads, the semicircular ring will rotate, and at this time, the plurality of ligaments connected to the ring will deform, and the rings and ligaments in the structure add additional design parameters to the structural design, so that the skin structure of the present invention has sufficient rigidity under aerodynamic loads. In addition, the jellyfish-type honeycomb structure unit also has high fatigue resistance, and can meet the requirements of large deformation (>50%), high load-bearing capacity, and recoverable deformation.

[0008] The skin structure of the present invention uses a C / PEEK composite material, which refers to a carbon fiber reinforced polyetheretherketone (Carbon Fiber Reinforced Polyetheretherketone) composite material. This material combines the high strength of carbon fiber and the excellent performance of PEEK, and has the advantages of high strength, high rigidity, high temperature resistance, corrosion resistance, excellent wear resistance and light weight. The flexible deformable skin structure combining the jellyfish-shaped honeycomb unit structure of the present invention with the C / PEEK composite material has good ductility, which not only meets the aerodynamic shape integrity requirements of the wing structure during the deformation process, but also can effectively improve the reliability of the aircraft, make the wing skin adapt to temperature changes, reduce the empty weight of the aircraft, improve the load-bearing capacity, reduce fuel consumption, and reduce the cost of skin maintenance and repair.

[0009] The first object of the present invention is to provide a bionic large deformation and multiple recovery C / PEEK composite material skin structure, the skin structure is composed of a plurality of flanges and jellyfish-shaped honeycomb structural units periodically arranged between the flanges;

[0010] Each jellyfish-shaped honeycomb structural unit is symmetrical about the horizontal center line and the vertical center line, and includes flanges on both sides, four structural subunits inside the flanges, and a curved beam ligament 6 on the vertical center line;

[0011] The four structural subunits on the inner side of the flange are symmetrical to each other along the horizontal center line and along the vertical center line, and each structural subunit includes: a first semicircular ring 2, a second semicircular 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 semicircular ring 3, the first semicircular 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 and the central axis of the second arc-shaped ligament 5 are located on the same horizontal plane and are arranged at equal distances;

[0015] The end of the first arc-shaped ligament 4 connected to the curved beam ligament 6 is connected to the first arc-shaped ligament of the adjacent structural subunit to form a semicircular ring.

[0016] In one embodiment of the present invention, the flange 1 is connected to one end of the second arc-shaped ligament 5, the other end of the second arc-shaped 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 arc-shaped ligament 4, and the other end of the first arc-shaped ligament 4 is connected to the curved beam ligament 6.

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

[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 outside of the flange 1 .

[0019] In one embodiment of the present invention, the radii of the first semicircular ring 2 and the second semicircular ring 3 are equal.

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

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

[0022] r1=r2+r3

[0023] Wherein 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 distance between the upper and lower adjacent structural subunits, which is 2 mm.

[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 the 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 meet the following conditions:

[0027] w=0.6-1.0mm.

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

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

[0031] The second object of the present invention is to provide a method for preparing a bionic large deformation and multiple recovery C / PEEK composite material skin structure, comprising the following steps:

[0032] The C / PEEK composite material was 3D printed to obtain a bionic large deformation and multiple recovery C / PEEK composite material skin structure.

[0033] In one embodiment of the present invention, the C / PEEK composite material can be purchased from the market or prepared by itself.

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

[0035] Performing modification treatment on the surface of carbon fiber to obtain surface-modified carbon fiber;

[0036] The surface-modified carbon fiber and PEEK resin are mixed, extruded, cooled, cured, and cut into pieces to obtain a C / PEEK composite material;

[0037] Among them, the specifications of carbon fiber are: diameter 80-100μm, length 3mm, purity ≥99%;

[0038] The modification treatment is to put the carbon fiber into a Soxhlet extractor and treat it with acetone in a water bath at 75-85°C for 45-60h;

[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: placing the mixture in a high-speed mixer at 230-250°C and 3000-5000 rpm for 8-20 minutes;

[0042] The extrusion molding conditions are extrusion at 360-380°C and 20-30g / min;

[0043] Cooling is rapid cooling;

[0044] Curing is done at 200-220°C for 2-4h;

[0045] Cutting is to cut into master batch size.

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

[0047] The temperatures of the printing nozzle, platform and chamber were set to 415-420°C, 125-135°C and 85-95°C, respectively; the filling density, printing preparation 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 the present invention is to apply the bionic large deformation and multiple recovery C / PEEK composite material skin structure described in the present invention in the aerospace field.

[0050] A fourth object of the present invention is to provide an aircraft skin, which adopts the C / PEEK composite material skin structure described in the present invention.

[0051] Beneficial Effects

[0052] (1) The skin structure of the present invention draws on the efficient propulsion and flexible structural characteristics of jellyfish when swimming in water, and proposes a jellyfish-shaped honeycomb structure unit as the basic configuration, which ensures that the aerodynamic shape of the skin structure is intact during the deformation process and has sufficient rigidity under aerodynamic loads.

[0053] (2) The present invention improves the ductility of the structure and reduces stress and strain concentration by making the curvature uniform and increasing the number of large-arc ligaments.

[0054] (3) The jellyfish-shaped honeycomb structural unit of the present invention uses a curved beam ligament structure, which further disperses the stress, reduces the instability of the aircraft, 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, and 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 combining jellyfish-shaped honeycomb structure units and C / PEEK composite material have good ductility, which not only meets the aerodynamic shape integrity requirements of the wing structure during the deformation process, but also effectively improves the reliability of the aircraft, enables the skin to adapt to temperature changes, reduces the empty weight of the aircraft, improves the load-bearing capacity, reduces fuel consumption, and reduces the maintenance and overhaul costs of the skin.

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

[0058] (7) The skin structure of the present invention can be obtained by periodically arranging the jellyfish-shaped honeycomb structural units, which has a simple structure and is convenient for optimizing and improving the structure. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0061] Figure 3 Schematic diagram of the size of the jellyfish-type honeycomb structure unit of the C / PEEK composite skin structure in Example 1; wherein r1 and r2 are the radii of the first arc-shaped ligament and the second arc-shaped ligament respectively, r3 is the inner diameter of the semicircular ring, H is the length of the jellyfish-type honeycomb structure unit, h is the spacing between the upper and lower adjacent structural subunits, w is the wall thickness, and L is the spacing between the outer sides of the two flanges.

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

[0063] Figure 5 It is a plan view of the jellyfish-shaped honeycomb structure unit in comparative example 1 without using the middle curved beam ligament, wherein 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 Schematic diagram of the jellyfish-shaped honeycomb structure unit in Comparative Example 1 before and after stretching.

[0065] Figure 7 It is a plan view schematically showing that the semicircular ring structure in the jellyfish-shaped honeycomb structure unit in Comparative Example 2 is changed into a curved structure.

[0066] Figure 8 It is a plan view schematically showing that the semicircular ring structure in the jellyfish-shaped honeycomb structure unit in Comparative Example 3 is changed into a straight line structure.

[0067] Fig. 9 Schematic diagram of the structural unit in Comparative Example 4. DETAILED DESCRIPTION

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

[0069] Test method:

[0070] 1. Tensile test of skin structure

[0071] The in-plane tensile test of the zero Poisson's ratio C / PEEK composite skin structure was carried out 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 tension-compression cyclic load test of skin structure

[0073] To simulate the skin's ability to quickly achieve a 50% large deformation in the plane within 10 s, a universal testing machine (INSTRON5967) was used for testing at room temperature. The loading speed was set to 234 mm / min, and the interval between each loading was 0 s to simulate the rapid and uninterrupted deformation of the wing skin.

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

[0075] A solid model of the C / PEEK composite skin structure was constructed in Solidworks software and saved in STEP file format. Based on the constructed macroscopic model of the zero Poisson's ratio C / PEEK composite skin structure, the mechanical properties parameters of the 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 diagram 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% (mass percentage), carbon fiber length is 80-100 μm; purchased from INTAMSYS manufacturer;

[0078] 3D printer: FDM printer (D260HT, WIIBOOX, China); semi-industrial equipment specially used for preparing PEEK materials, purchased from INTAMSYS manufacturer;

[0079] Carbon fiber: purity ≥99%, tensile modulus 290Gpa, linear density 0.45g / cm 3 , purchased from Zhongfu Shenying Carbon Fiber Co., Ltd.;

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

[0081] In order 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 in conjunction with the accompanying drawings in the embodiments of the present invention.

[0082] Example 1

[0083] A bionic large deformation and multiple recovery C / PEEK composite skin structure, the three-dimensional structure is shown in the figure Figure 1 ;

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

[0085] The schematic diagram of the jellyfish-shaped honeycomb structure unit is as follows: Figure 2 ;

[0086] Each jellyfish-shaped honeycomb structural unit is symmetrical about the horizontal center line and the vertical center line, and includes flanges on both sides, four structural subunits inside the flanges, and a curved beam ligament 6 on the vertical center line;

[0087] The four structural subunits on the inner side of the flange are symmetrical to each other along the horizontal center line and along the vertical center line, and each structural subunit includes: a first semicircular ring 2, a second semicircular 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 semicircular ring 3, the first semicircular 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 and the central axis of the second arc-shaped ligament 5 are located on the same horizontal plane and are arranged at equal distances;

[0091] The end of the first arc-shaped ligament 4 connected to the curved beam ligament 6 is connected to the first arc-shaped ligament of the adjacent structural subunit to form 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 arc-shaped ligament 5, the other end of the second arc-shaped 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 arc-shaped ligament 4, and the other end of the first arc-shaped ligament 4 is connected to the curved beam ligament 6.

[0094] Further, the plurality of flanges are arranged in parallel and at equal distances;

[0095] Furthermore, 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;

[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 size relationship:

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

[0099] r1=r2+r3

[0100] Wherein 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 distance between the upper and lower adjacent structural subunits, which is 2 mm.

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

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

[0103] 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:

[0104] w=0.6-1.0mm.

[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 2-4 mm;

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

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

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

[0111] Based on the skin structure of Example 1, after a large number of experiments, it was found that when the jellyfish-shaped honeycomb structure unit in Example 1 meets the following size relationship, the skin structure has better performance:

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

[0113] r1=r2+r3

[0114] Wherein, 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 distance between the upper and lower adjacent structural subunits, and its value is 2 mm.

[0119] Schematic diagram of the unit size of the jellyfish-type honeycomb structure Figure 3 .

[0120] Here are some examples:

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

[0122] Table 1 Skin structure scheme satisfying the size relationship of H = 2*(r1+r2)+h, r1 = r2+r3

[0123]

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

[0125] Table 2 Performance table of skin structure satisfying the size relationship of H = 2*(r1+r2)+h, r1 = r2+r3

[0126]

[0127] It can be seen from Table 2 that when the jellyfish-shaped honeycomb structural unit meets the above-mentioned size relationship, the skin structure has better performance; when the tensile deformation degree of the scheme No. 4 is 50%, it has the ability to withstand large deformation, good ductility, and the stress concentration phenomenon is weakened; after the scheme No. 2 withstands 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 bionic large-deformation and multi-recoverable C / PEEK composite material skin structure comprises the following steps:

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

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

[0132] The printing nozzle, platform and chamber temperatures were set to 420 °C, 130 °C and 90 °C, respectively, and the filling density, printing preparation speed and printing layer thickness of the commercially available C / PEEK composite were set to 100%, 10 mm / s and 0.1 mm, 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, and the C / PEEK composite material skin structure is printed by stacking the material from bottom to top using the 3D printer to obtain the C / PEEK composite material skin structure (the thickness of the skin structure is 4 mm).

[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 are consistent with the dimensional relationship of Example 2.

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

[0137] Table 3 Performance test results of skin structure

[0138]

[0139] Example 4

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

[0141] The carbon fibers with a length of 80-100 μm were placed in 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] The 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 extruded at 370°C at a speed of 25 g / min.

[0144] The mixture was rapidly cooled by water cooling, cured in a vacuum oven at 210°C for 3 h, and cut into masterbatch size to obtain a C / PEEK composite material;

[0145] The rest is consistent with Example 3, and the skin structure is obtained by 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 skin structure

[0148]

[0149] Comparative Example 1

[0150] The curved beam ligament 6 in the embodiment 1 is omitted, and the rest is consistent with the embodiment 3. The structure is 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 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 the problem of structural instability, while the structure of the embodiment has very good one-dimensional deformation ability.

[0156] Comparative Example 2

[0157] The first semicircle ring 2 and the second semicircle ring 3 in Example 1 are adjusted to be connected by three semicircles with a radius of 1 mm, and the rest are consistent with Example 3, and the structure is 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] It can be seen from Table 6 that after the semicircular ring is changed into a curve (connected by 3 semicircles with a radius of 1 mm), the structure cannot undergo a large deformation. When the deformation reaches about 30%, the structure is damaged. This is because after the semicircular ring is changed into a curve (connected by 3 semicircles with a radius of 1 mm), the stress concentration points will increase, the force cannot be transmitted well, and eventually the structure fails at multiple stress concentration points.

[0162] Comparative Example 3

[0163] The first semicircular ring 2 and the second semicircular ring 3 in Example 1 are adjusted to straight lines 2 and 3, and the rest are consistent with 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] Degree of tensile deformation Stress concentration phenomenon Maximum tensile test material stress (Mpa) Deformation results 8％ yes 2.578E+02 Structural damage 13％ yes 2.390E+02 Structural damage 15％ yes 2.289E+02 Structural damage

[0167] It can be seen from Table 7 that after the semicircular ring structure is changed to a straight line structure, the tensile deformation degree of the structure is greatly reduced, and the structure is prone to break at the connection, which cannot meet the use requirements.

[0168] Comparative Example 4

[0169] Adjust the structure of Example 3 to adopt Fig. 9 The structure of 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] The rest is consistent with Example 3 to obtain 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] It can be seen from Table 8 that under the same degree of deformation, the structure of Example 4 shows stress concentration phenomenon, and the maximum stress of the tensile material is greater than that of Example 1. The deformation capacity of the material is also poor, and the material is prone to fracture at the stress concentration point. The material's recovery ability after deformation is also poor.

[0176] Comparative Example 5

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

[0178] The rest is consistent with Example 3 to obtain 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] It can be seen from Table 9 that 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 connection, affecting its tensile properties. Moreover, because the rigidity of aluminum alloy is relatively large, the maximum stress during the stretching of the material is greater than that of 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] The carbon fibers with a length of 80-100 μm were placed in a Soxhlet extractor and treated with acetone in a water bath at 80° C. for 48 h to obtain surface-modified carbon fibers;

[0186] The PEEK resin was dried at 120°C for 5 hours;

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

[0188] The rest is consistent with Example 4 to obtain 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] It can be seen from Table 10 that under the same tensile deformation degree, this material has stress concentration phenomenon, which affects its tensile properties, and the change of parameter setting reduces the mixing uniformity of the material, which is easy to cause printing defects and increase printing difficulties.

[0193] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A bionic large deformation and multiple recovery C / PEEK composite skin structure, characterized in that: The skin structure is composed of multiple flanges and jellyfish-shaped honeycomb structural units periodically arranged between the flanges; Each jellyfish-shaped honeycomb structural unit is symmetrical about a horizontal center line and a vertical center line, and includes flanges located on both sides, four structural subunits inside the flanges, and a curved beam ligament (6) located on the vertical center line; The four structural subunits on the inner side of the flange are symmetrical to each other along the horizontal center line and along the vertical center line, and each structural subunit comprises: a first semicircular ring (2), a second semicircular ring (3), a first arc-shaped ligament (4) and a second arc-shaped ligament (5); The flange (1), the second arc-shaped ligament (5), the second semicircular ring (3), the first semicircular ring (2), the first arc-shaped 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) and the central axis of the second arc-shaped ligament (5) are located on the same horizontal plane and are arranged at equal distances; The end of the first arc-shaped ligament (4) connected to the curved beam ligament (6) is connected to the first arc-shaped ligament of the adjacent structural subunit to form a semicircular ring.

2. The bionic large deformation and multiple recovery C / PEEK composite material skin structure according to claim 1 is 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 bionic large deformation and multiple recovery C / PEEK composite material skin structure according to claim 1 is characterized in that: The radii of the first semicircular ring (2) and the second semicircular ring (3) are equal.

4. The bionic large deformation and multiple recovery C / PEEK composite material skin structure according to claim 1 is characterized in that: The jellyfish-shaped honeycomb structural unit satisfies the following size relationship: H=2*(r1+r2)+h r1＝r2+r3 Wherein 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 structural unit, and h is the spacing distance between the upper and lower adjacent structural subunits.

5. The bionic large deformation and multiple recovery C / PEEK composite material skin structure according to claim 1 is characterized in that: The shape of the curved beam ligament (6) satisfies the cosine curve y=0.6sin0.4x.

6. The bionic large deformation and multiple recovery C / PEEK composite material skin structure according to claim 1 is characterized in that: The wall thickness of the jellyfish-shaped honeycomb structure unit is 0.6-1.0mm; 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.

7. The bionic large deformation and multiple recovery C / PEEK composite material skin structure according to claim 1 is characterized in that: The skin structure is made of C / PEEK composite material; the thickness of the skin structure is 3-5 mm.

8. A method for preparing the bionic large deformation and multiple recovery C / PEEK composite material skin structure according to any one of claims 1 to 7, characterized in that: The steps include: The C / PEEK composite material was 3D printed to obtain a bionic large deformation and multiple recovery C / PEEK composite material skin structure.

9. Application of the bionic large deformation and multiple recovery C / PEEK composite skin structure described in any one of claims 1 to 7 in the aerospace field.

10. An aircraft skin, characterized in that: It adopts the bionic large deformation and multiple recovery C / PEEK composite material skin structure described in any one of claims 1 to 7.

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