Carbon fiber panel sandwich structure with quasi-zero stiffness characteristic

Abstract

The invention discloses a carbon fiber panel sandwich structure with a quasi-zero stiffness characteristic, which belongs to the field of metamaterials and comprises an upper carbon fiber laminated plate, a lower carbon fiber laminated plate and a unit cell array core layer structure. The unit cell array core layer structure is composed of a plurality of unit cell arrays; each unit cell is of an integrally-formed structure, is composed of a pair of orthogonal Euler buckling beams and a semi-arc supporting base, has the advantages of being high in static rigidity and low in dynamic rigidity and has the good vibration isolation characteristic. And the unit cell structures are arrayed transversely or longitudinally, so that different performance characteristics can be obtained, and the method has very flexible designability. And through combination with the carbon fiber panel, multiple functions of light weight, high bearing capacity, high strength, excellent vibration reduction performance and the like can be realized.

Description

Technical Field

[0001] The invention relates to the technical field of metamaterial structure vibration isolation, and in particular to a carbon fiber panel sandwich structure with quasi-zero stiffness characteristics. Background Art

[0002] Metamaterial refers to a man-made material with unique properties that do not exist in nature. These materials exhibit special properties in many fields such as mechanics, optics and acoustics, which are impossible to achieve with traditional materials. The uniqueness of metamaterials does not come from the properties of the materials they are made of, but is the result of precise size and shape design of their structures. Quasi-zero stiffness is a relatively common metamaterial property. Quasi-zero stiffness structures have the characteristics of high static stiffness and low dynamic stiffness. High static stiffness ensures the load-bearing capacity of the structure, while low dynamic stiffness reduces the natural frequency of the structure, broadens the vibration reduction frequency band, and overcomes the contradiction between load-bearing and vibration reduction in linear systems.

[0003] Traditional quasi-zero stiffness vibration isolation structures are often complicated to design, involving complex spring systems, and have disadvantages such as heavy weight and large space occupation, which limits their further development in aerospace, precision instruments and other fields. Summary of the invention

[0004] Aiming at the problems existing in the prior art, the present invention discloses a carbon fiber panel sandwich structure with quasi-zero stiffness characteristics.

[0005] The present invention is achieved in that:

[0006] A carbon fiber panel sandwich structure with quasi-zero stiffness characteristics, characterized in that the structure comprises: two upper and lower carbon fiber laminates, and a single cell array core structure between the upper and lower carbon fiber laminates; the carbon fiber laminates have the ability to bear and resist deformation, the single cell array core structure in the middle provides quasi-zero stiffness characteristics, the sandwich structure has bearing capacity, and its deformation is reversible. The panel is a carbon fiber composite laminate, which is light and high-strength.

[0007] The core layer structure providing quasi-zero stiffness characteristics is composed of multiple unit cell arrays; the unit cell includes: a contact platform, an orthogonal Euler beam under the contact platform, and a semicircular arc support; the orthogonal Euler beam and the semicircular arc support are coupled on a fixed support. The quasi-zero stiffness unit cell structure is composed of an orthogonal Euler beam and a semicircular arc support segment. In the quasi-zero stiffness unit cell structure, the orthogonal Euler beam provides negative stiffness, and the semicircular arc support segment provides positive stiffness. For quasi-zero stiffness structures under different unit cell arrangements, the bearing capacity of the structure can be improved by increasing the number of unit cells in a single layer, and the range of the quasi-zero stiffness segment can be expanded by increasing the number of layers of the sandwich structure.

[0008] Furthermore, in the unit cell structure: a thin cube contact platform, an orthogonal Euler beam with two ends fixed and a semicircular arc support are coupled on a fixed support, the orthogonal buckling Euler beam provides negative stiffness characteristics, and the semicircular arc segment structure provides positive stiffness characteristics, and the positive and negative stiffness coupling realizes quasi-zero stiffness characteristics. The unit cell structure improves the stability of the structure by orthogonally designing the Euler beam. The unit cell structure is designed with a cube contact surface to increase the contact area with the panel, which is conducive to secondary solidification molding.

[0009] Furthermore, in the core layer unit cell, the orthogonal buckling Euler beam adopts TPU flexible material, whose high elasticity and high toughness can easily complete the specified deformation such as buckling.

[0010] Furthermore, the structure is formed by secondary curing of two upper and lower carbon fiber laminates and a unit cell array core layer structure; the carbon fiber laminates are all made of carbon fiber plain fabric prepreg materials, and the carbon fiber laminates are prepared by vacuum high temperature and pressure curing; the unit cell array core layer has load-bearing capacity, and its deformation is reversible.

[0011] Furthermore, the unit cell array core layer is stacked in a horizontal or vertical array to achieve changes in bearing capacity or vibration reduction amplitude.

[0012] The present invention provides a carbon fiber panel sandwich structure with quasi-zero stiffness characteristics, characterized in that the orthogonal Euler beams provide the negative stiffness parts required in the quasi-zero stiffness structure, and take the first-order buckling mode as the initial state of the beam without prestress. The middle short column bears the vertical load. In the process of the Euler beam bending downward, the bending energy increases monotonically, and the compression energy increases to a maximum value near the center line and decreases after exceeding the center line. After the Euler beam passes through the center line, the decrease rate of the compression energy of the Euler beam is faster than the increase rate of the bending energy, resulting in a negative force area, that is, a negative stiffness area.

[0013] In the present invention, the two orthogonal Euler beams are orthogonally arranged to suppress the occurrence of the second-order buckling mode. When an Euler beam is subjected to a vertical load and is about to enter the second-order buckling mode and deflect, the orthogonal Euler beam orthogonal to it will suppress its deflection, thereby suppressing the occurrence of the second buckling mode.

[0014] The beneficial effects of the present invention compared with the prior art are:

[0015] The unit cell of the present invention is an integrally formed structure, which is composed of a pair of orthogonal Euler buckling beams and a semicircular arc support base, and has the characteristics of high static stiffness and low dynamic stiffness, and has good vibration isolation characteristics. Different performance characteristics can be obtained by arranging the unit cell structure horizontally or vertically, and it has very flexible designability. By combining with carbon fiber panels, multiple functions such as light weight, high load-bearing capacity, high strength and excellent vibration reduction performance can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic diagram of a quasi-zero stiffness unit cell structure in the present invention;

[0017] Figure 2 is a schematic diagram of a quasi-zero stiffness sandwich structure in the present invention;

[0018] Figure 3 is the load-displacement curve of the quasi-zero stiffness structure in the present invention;

[0019] Figure 4 is the elastic wave transmissibility curve of the quasi-zero stiffness sandwich structure in the present invention;

[0020] Among them, 1-contact table, 2-orthogonal Euler beam, 3-semicircular arc support, 4-fixed support. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail by enumerating examples below. It should be noted that the specific implementation described here is only used to explain the present invention and is not used to limit the present invention.

[0022] Figure 1 It is a schematic diagram of a quasi-zero stiffness unit cell structure, which consists of a thin cube contact platform 1, an orthogonal Euler beam 2 with two ends fixed, and a semicircular arc support 3 coupled to a fixed support 4.

[0023] The present invention provides the negative stiffness part required in the quasi-zero stiffness structure by introducing the Euler beam, takes the first-order buckling mode as the initial state of the beam without prestress, and the middle short column bears the vertical load. In the process of the Euler beam bending downward, the bending energy increases monotonically, and the compression energy increases to the maximum value near the center line and decreases after exceeding the center line. After the Euler beam passes through the center line, the decreasing speed of the compression energy is faster than the increasing speed of the bending energy, which will produce a negative force area, that is, a negative stiffness area.

[0024] In the present invention, the orthogonal arrangement of the two Euler beams can suppress the occurrence of the second-order buckling mode. When an Euler beam is subjected to a vertical load and is about to enter the second-order buckling mode and deflect, the Euler beam orthogonal to it will suppress its deflection, thereby suppressing the occurrence of the second buckling mode.

[0025] The quasi-zero stiffness of the present invention does not adopt the traditional spring structure, avoiding the shortcomings of large space occupation and large mass, but uses a unit cell structure formed in an integrated manner by 3D printing.

[0026] Figure 2 It is a schematic diagram of a quasi-zero stiffness sandwich structure, which consists of two carbon fiber epoxy resin laminates and a core layer structure of a unit cell 2×2 array.

[0027] The formed carbon fiber laminate and core layer are combined into a sandwich structure through secondary curing. The load displacement curve of the above quasi-zero stiffness structure is obtained through quasi-static compression test and ABAQUS numerical simulation. Figure 3 As shown. Figure 3 It can be seen that when the load does not reach the effective load of quasi-zero stiffness, the structure approximately exhibits linear elasticity and the stiffness is positive. When the load reaches the effective load of quasi-zero stiffness, the stiffness of the structure is approximately zero, and the Euler beam buckles and presents negative stiffness, which offsets the positive stiffness of the semicircular arc support segment. When the load increases further, the stiffness of the structure presents a positive value again.

[0028] For quasi-zero stiffness structures under different unit cell arrangements, the bearing capacity of the structure can be improved by increasing the number of unit cells in a single layer, while the range of the quasi-zero stiffness segment can be expanded by increasing the number of layers of the sandwich structure.

[0029] Figure 4 To obtain the elastic wave transmissibility curve of the quasi-zero stiffness sandwich structure, a dynamic vibration test was conducted on the sandwich structure. The elastic wave transmissivity T is calculated as follows:

[0030]

[0031] In the frequency range of 0-100Hz, elastic wave transmittance of preloaded sandwich panels below target load, equal to target load, and above target load was measured. According to the quasi-static compression test and simulation results of quasi-zero stiffness sandwich structures, two groups of load conditions below target load were selected, which were 3.6kg and 4.3kg, respectively, the load condition equal to target load was selected as 5.2kg, and the load condition above target load was selected as 6.5kg. Figure 4It can be seen that the vibration transmissibility of the preload below and above the target preload is higher than that of the target preload, that is, only under the effective load of the quasi-zero stiffness platform section can the vibration reduction effect of the structure be optimal. The transmissibility curve gradually decreases to below zero after experiencing a resonance peak in the low-frequency band. In the low-frequency range of 0-50Hz, the average elastic wave transmissibility under 3.6kg, 4.3kg, 5.2kg, and 6.5kg preloads is 1.92, -2.31, -11.52, and -3.05dB, respectively. Under a preload of 5.2kg, the stiffness of the structure is close to zero, so the natural frequency of the structure is close to zero, and the resonance peak occurs at 11Hz. The transmissibility is less than zero above a frequency of 15Hz, showing better vibration reduction characteristics in the low-frequency range. When the preload deviates from the target load, whether it is high or low, the vibration reduction effect is relatively poor. In addition, as the preload increases to the target preload, the frequency of the resonance peak of the curve gradually decreases, which is consistent with the decrease in natural frequency caused by the gradual decrease in structural stiffness. When the preload is higher than the target load, the corresponding frequency when the resonance peak occurs increases again. This is because the stiffness of the structure increases, resulting in an increase in the natural frequency.

[0032] The above description is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements without departing from the principle of the present invention, and these improvements should also be regarded as within the protection scope of the present invention.

Claims

1. A carbon fiber panel sandwich structure with quasi-zero stiffness characteristics, characterized in that: The structure includes: two upper and lower carbon fiber laminates, and a unit cell array core structure between the upper and lower carbon fiber laminates; the carbon fiber laminates have the ability to bear and resist deformation, and the unit cell array core structure in the middle provides quasi-zero stiffness characteristics; The unit cell array core layer structure is composed of a plurality of unit cell arrays; the unit cell comprises: a contact platform (1), an orthogonal Euler beam (2) below the contact platform (1), and a semicircular arc support (3); the orthogonal Euler beam (2) and the semicircular arc support (3) are coupled to a fixed support (4).

2. The carbon fiber panel sandwich structure with quasi-zero stiffness characteristics according to claim 1, characterized in that: In the unit cell structure, a thin cubic contact platform (1), an orthogonal Euler beam (2) with fixed supports at both ends, and a semicircular arc support (3) are coupled on a fixed support (4); the orthogonal buckled Euler beam provides negative stiffness characteristics, and the semicircular arc segment structure provides positive stiffness characteristics, and the positive and negative stiffness coupling realizes quasi-zero stiffness characteristics; the quasi-zero stiffness structure under different unit cell arrangements improves the bearing capacity of the structure by increasing the number of unit cells in a single layer; and the range of the quasi-zero stiffness segment is expanded by increasing the number of layers of the sandwich structure.

3. The carbon fiber panel sandwich structure with quasi-zero stiffness characteristics according to claim 1, characterized in that: The orthogonal Euler beam (2) is made of TPU flexible material.

4. The carbon fiber panel sandwich structure with quasi-zero stiffness characteristics according to claim 1, characterized in that: The structure is formed by secondary curing of two upper and lower carbon fiber laminates and a unit cell array core layer structure; the carbon fiber laminates are all made of carbon fiber plain fabric prepreg materials, and the carbon fiber laminates are prepared by vacuum high temperature and pressure curing; the unit cell array core layer has load-bearing capacity, and its deformation is reversible.

5. The carbon fiber panel sandwich structure with quasi-zero stiffness characteristics according to claim 1, characterized in that: The unit cell array core layer is stacked in a horizontal or vertical array to achieve changes in the bearing capacity or vibration reduction amplitude.

6. A carbon fiber panel sandwich structure with quasi-zero stiffness characteristics according to any one of claims 1 to 5, characterized in that: The orthogonal Euler beam (2) provides the negative stiffness portion required in the quasi-zero stiffness structure, and takes the first-order buckling mode as the initial state of the beam without prestress. The middle short column bears the vertical load. During the downward deflection of the Euler beam, the bending energy increases monotonically, and the compression energy increases to a maximum value near the center line and decreases after exceeding the center line. After the Euler beam passes through the center line, the decreasing speed of the compression energy is faster than the increasing speed of the bending energy, resulting in a negative force area, that is, a negative stiffness area.

7. The carbon fiber panel sandwich structure with quasi-zero stiffness characteristics according to claim 6, characterized in that: The two orthogonal Euler beams (2) are orthogonally arranged to suppress the occurrence of the second-order buckling mode. When an Euler beam is subjected to a vertical load and is about to enter the second-order buckling mode and deflect, the orthogonal Euler beam (2) orthogonal to it will suppress its deflection, thereby suppressing the occurrence of the second buckling mode.

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