CN213808600U - Fiber layering mode conversion metamaterial structure - Google Patents
Fiber layering mode conversion metamaterial structure Download PDFInfo
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- CN213808600U CN213808600U CN202021194908.8U CN202021194908U CN213808600U CN 213808600 U CN213808600 U CN 213808600U CN 202021194908 U CN202021194908 U CN 202021194908U CN 213808600 U CN213808600 U CN 213808600U
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Abstract
The utility model discloses a fiber layering mode conversion metamaterial structure, which comprises more than three layers of symmetrically stacked fiber layering single-layer plates; the thickness of each fiber-laminated single-layer board is uniform, and each fiber-laminated single-layer board comprises a fiber material and a medium matrix. The utility model discloses a fibrous mode of laying designs metamaterial in adjustment fibre shop sheet monolayer board, can also guarantee that material structural strength and mechanical properties are not destroyed when realizing efficient mode conversion, realize the integrated design of this mode conversion metamaterial structure and function. The utility model discloses preparation is simple, and cost of maintenance is low, and structural strength is high, and density is low, possess wide market prospect in the mode conversion field.
Description
Technical Field
The utility model relates to a mode conversion metamaterial field, concretely relates to fibre shop layer mode conversion metamaterial structure.
Background
The mode conversion is one of the basic physical phenomena in the fluctuation field, and with the rapid advance of scientific technology, the research in the mode conversion field is more and more deep, and the method has important application value in various fields such as industry, military and the like. For example, in structural nondestructive testing, since longitudinal waves are easy to excite but are not sensitive to crack defects, the longitudinal waves are often converted into transverse waves which are beneficial to crack detection but difficult to excite by using a mode conversion phenomenon; in medical ultrasonic imaging and medical diagnosis, the propagation speed and the energy dissipation degree of transverse waves in different tissues of a human body are obviously different, and similarly, mode conversion is needed to convert easily excited longitudinal waves into transverse waves which are difficult to excite; in the military field, modal conversion is a key working mechanism of various vibration isolation and noise reduction structures, and if a submarine structure meets the bearing requirement, longitudinal waves can be converted into shear waves because shear waves are easily and fully absorbed, so that the risk of discovery is remarkably reduced; in high speed train, aircraft design, it can be used to reduce internal noise, etc. Therefore, the improvement of the conversion efficiency of the modal converter and the improvement of the mechanical property of the modal converter are always problems to be solved in the field of modal conversion.
At present, with the introduction of metamaterials into the field of modal conversion, the anisotropic design of metamaterials plays a very critical role in research and exploration for improving modal conversion efficiency. With the intensive research on the mode conversion phenomenon of the metamaterial, a plurality of theories such as an ideal TFPR theory, a mode conversion impedance matching theory and the like are established by scholars, and based on the high-quality theories, the full-mode conversion metamaterial is successfully designed.
However, the anisotropic design of the metamaterial is realized by digging holes on a base material, and the method can achieve the purpose of regulating and controlling the anisotropic property of the material, but destroys the structural strength of the original material. However, the modal converter is often applied to military, industrial and other fields with more requirements on structural mechanical properties, and thus, the application of the high-efficiency modal converter is limited to a great extent by the anisotropic design manner.
Aiming at the current situation that the structural strength and the mechanical property are insufficient in the design of the high-efficiency modal converter at present, a natural anisotropic material is introduced, a new structural design idea of the anisotropic metamaterial with integrated structure and function is explored, the modal conversion is realized at high efficiency while the mechanical property is considered, and the problem of being worthy of exploration is solved.
Disclosure of Invention
In order to solve the problems existing in the prior art, the utility model aims to provide a design idea and a method of a fiber layer modal conversion metamaterial structure; the concept of fiber layering mode conversion metamaterial structure which can realize high-efficiency mode conversion and has the characteristics of excellent mechanical property and the like is provided by taking anisotropy as a bridge and combining a fiber reinforced composite material with the characteristics of natural anisotropy, excellent mechanical property, low cost, strong corrosion resistance and the like with a metamaterial capable of realizing high-efficiency mode conversion.
In order to achieve the above purpose, the utility model adopts the following technical scheme:
the utility model provides a fibre is spread layer mode conversion metamaterial structure, this fibre is spread layer mode conversion metamaterial structure: a fiber layering mode conversion metamaterial structure comprises a metamaterial and base materials bonded at two ends of the metamaterial, wherein the thickness of the base materials is equal to the total thickness of the metamaterial, and the base materials, the metamaterial and the base materials are arranged in sequence along the wave propagation direction; the metamaterial is formed by stacking more than three layers of single-layer plates in one or more types and in multiple directions.
The one or more types of single-layer plates forming the metamaterial are all composed of base media and fiber materials, and the types of the single-layer plates are determined by the types of the base media and the fiber materials and the thicknesses of the single-layer plates; wherein the matrix medium includes any one of epoxy resin and rubber; wherein the fiber material comprises one or more of carbon fiber, glass fiber and metal wire; the number of single-layer boards of at most one type is odd.
The single-layer plates are stacked and bonded according to a preset angle and sequence, the stacking and bonding structure of the whole metamaterial is required to be symmetrical about the middle plane of the metamaterial, the angle is an included angle between the wave propagation direction and the main shaft direction of the single-layer plates, and the included angle is-90 degrees to-90 degrees.
If the plurality of single-layer plates forming the metamaterial are the same matrix medium and the same fiber material, the plurality of single-layer plates are required to exist, wherein the included angle between the main shaft direction of each single-layer plate and the wave propagation direction is the same and ranges from-90 degrees to 90 degrees, and the total thickness of the single-layer plates is larger than the thickness of the single-layer plates at other angles in the ratio of the thickness of the metamaterial.
In the metamaterial, the maximum modal conversion efficiency is achieved by designing the included angle (-90 degrees) between the main shaft direction of each single-layer plate and the wave propagation direction. Wherein, the maximum modal conversion efficiency is required to be more than 80%. Wherein the maximum modal conversion efficiency TTThe value of (d) corresponds to the following formula:
in the formula, v0Representing the poisson's ratio of the matrix material.
The metamaterial comprises one or more fiber laying structures which are arranged periodically in the direction of wave transmission, and the total length d of the metamaterial in the direction conforms to the following equation (called as material condition)
In the formula: c11、C66、C16-effective material parameters of the metamaterial structure; ρ — the density of the metamaterial structure; f. ofBQW-the minimum frequency at which the maximum conversion efficiency occurs; d-metamaterial length in wave propagation direction; n isFS，nSS-a natural number, nFS<nSSAnd n isSS-nFSIs an odd number.
Effective material parameter C of the metamaterial structure11、C66、C16Can be calculated by
Wherein N is the number of single-layer board layers etakIs the thickness of the single-layer board k,
is the off-axis modulus component (theta) of the single-layer board kkThe laying angle of the single-layer board k), different off-axis modulus components exist at different angles, and the off-axis modulus component can be calculated by the following formula
In the formula, the in-plane stress state conversion modulus of the single-layer sheet is calculated from the following formula
In the formula, E1-longitudinal tensile compression modulus of elasticity; e2-transverse tensile compression modulus of elasticity; g12-a shear modulus of elasticity; v. of12-the primary poisson's ratio; v. of21-the secondary poisson's ratio.
Compared with the prior art, the utility model has the advantages of it is following:
the utility model provides a fibre is spread layer mode conversion metamaterial structure compares in current high efficiency mode conversion metamaterial structure of punching, does not destroy the structural strength of original material, has solved the problem that current mode conversion material structural strength, mechanical properties are short of. The material structure has excellent specific strength and specific modulus, and also has the advantages of simple production and forming process, low maintenance and manufacturing cost, corrosion resistance, fatigue resistance and the like; the most important is to ensure high-efficiency modal conversion, so that the requirement of the modal converter on the environment is reduced, the cost is reduced, the structural function is integrated, and simultaneously, a plurality of applicable fields are increased. Finally, the utility model discloses an idea can provide valuable reference for the design of novel structure function integration material.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a schematic diagram of the structure of the fiber layer anisotropic mode conversion metamaterial of the present invention.
Fig. 2 is a design case of the anisotropic mode conversion metamaterial structure of a fiber layer (aluminum is a base material) according to the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art all belong to the protection scope of the present invention.
According to the utility model discloses an embodiment provides a fibre and spreads layer mode conversion metamaterial structure.
As shown in fig. 1, the fiber layer mode conversion metamaterial structure according to the embodiment of the present invention includes:
the fibre of the utility model example is spread layer mode conversion metamaterial 2, place it in base material 1 that the symmetry more than three piles up the setting, one or more type single layer board bonding has constituteed the utility model discloses the example. In the example, a fiber lay mode conversion metamaterial structure 2 is formed by 3 symmetrically stacked carbon fiber-epoxy resin orthotropic single-layer plates (11 and 12 respectively represent single-layer plates with two laying angles), and is placed in a base material aluminum 1; as can be seen from fig. 1, the total thickness of the single-layer plate 11 is greatest in the total thickness of the metamaterial structure.
In this example, the matrix material is consistent with the total thickness of the metamaterial, preferably 0.01 m; the thickness of the three layers of single-layer plates forming the metamaterial structure is one third of the total thickness; the fiber lay mode conversion metamaterial structure comprises a plurality of fiber lay structures which are periodically arranged in two directions which are parallel and vertical to the wave propagation direction, wherein the total length d (parallel to the wave propagation direction) of the fiber lay mode conversion metamaterial structure is preferably 0.5m, and the total width (vertical to the wave propagation direction) is not greatly influenced by the mode conversion efficiency and the frequency result, so that the total width is determined according to the specific application requirement.
At the position ofIn the measurement process, a basic model is modeled in COMSOL software, parameters of materials of all parts are set, and mode conversion efficiency T at different angles can be obtained by adjusting the laying angle of a single-layer plate, adding periodic displacement and carrying out frequency scanningT(ratio of transmitted T wave to incident L wave energy) with increasing frequency. Before adjusting the angle, to avoid a blind attempt, first, the design target (theoretical maximum conversion efficiency) is estimated using the following formula
In the formula, v0Representing the poisson's ratio of the matrix material. Reuse of C11＝C66Under the condition, the paving angle is estimated, the adjustment range is further expanded, and the paving mode with the maximum conversion efficiency is designed and analyzed.
In the present example, the poisson's ratio of the base material aluminum 1 is 0.37, and the target for conversion efficiency can be estimated to be 92.10%; reuse of C11＝C66Under the condition, the laying mode can be obtained as that the single-layer board 11 is laid at 49 degrees and the single-layer board 12 is laid at-49 degrees; subsequently, the angle setting range is slightly enlarged for design analysis. In the analysis of the present example, adjusting the ply directions of the single- ply boards 11 and 12, finally, the maximum conversion efficiency 92.44% can be obtained at the preferred angle of laying the single-ply board 11 at 49 ° and the single-ply board 12 at-50 °, which substantially achieves full mode conversion. As shown in fig. 2, the conversion efficiency varies periodically with frequency, and may be m (m is 1, 3, 5 …) times fBQW(in this example fBQW16.1kHz) for maximum conversion efficiency.
In the design process of the fiber layer mode conversion metamaterial structure, after a design analysis result is obtained, the result needs to be further verified, namely effective material parameters are calculated and verified. In the verification process, the plane stress state reduced modulus is firstly obtained through known parameters of the single-layer plate, and the following formula is shown:
in the formula, E1-longitudinal tensile compression modulus of elasticity; e2-transverse tensile compression modulus of elasticity; g12-a shear modulus of elasticity; v. of12-the primary poisson's ratio; v. of21-the secondary poisson's ratio. Further, the following formula is used to obtain the design laying angle thetakOff-axis modulus component of each lower monolayer sheet
Then, the effective material parameter can be obtained by the effective material parameter calculation formula:
1. wherein N is the number of single-layer board layers etakIs the thickness of a single layer of board k. Finally, whether the verification result meets the material condition is verified:
in the formula: c11、C66、C16-effective material parameters of the metamaterial structure; ρ — the density of the metamaterial structure; f. ofBQW-the minimum frequency at which the maximum conversion efficiency occurs;d-metamaterial length in wave propagation direction; n isFS，nSS-a natural number, nFS<nSSAnd n isSS-nFSIs an odd number. If the fiber layer mode conversion metamaterial structure meets the requirements, the design result is reasonable, and the related fiber layer mode conversion metamaterial structure can realize high-efficiency mode conversion.
In this example, some known parameters are as follows: e1＝139.00GPa，E1＝9.00GPa，v12＝0.3200， G12＝5.50GPa，v210.0207; specific values of the reduced modulus in the plane stress state can be obtained: q11＝139.93GPa，Q12＝2.90GPa，Q22＝9.06GPa，Q665.50 GPa; then, respectively obtain θ1＝49°、θ2Off-axis modulus component of the single-layer board under two laying angles of-50 degrees:
further, the values of the effective material parameters can be found:
finally, the result f can be obtainedBQWWhen 16.1kHz, nFS＝3.0020<nSSWhen 4.0006, n is foundFSAnd nSSApproximated by an integer and the difference is odd. From this, it can be concluded that: the designed fiber layering mode conversion metamaterial structure can realize high-efficiency mode conversion.
It is worth mentioning that the total thickness of the single-layer board at a certain laying angle is required to be the largest in the ratio of the total thickness of the metamaterial structure in the design, which is supported by experiments. Taking this example as an example, the thickness between the single-layer board 11 and the single-layer board 12 is adjusted, and the design of angle adjustment is performed; we have found that when the total thickness of the single-layer boards at each laying angle is consistent in the proportion of the total thickness of the metamaterial structure, high-efficiency mode conversion cannot be realized.
In the practical application process, the types of the single-layer boards, the materials of the single-layer boards, the stacking quantity, the stacking mode, the length of the fiber laying-up metamaterial and other influencing factors can be adjusted according to the frequency band required in the application. Accordingly, the scope of the present invention is not limited to a certain size, a certain mode, or a certain type of material. In addition, the above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (6)
1. A fiber layering mode conversion metamaterial structure is characterized in that: the wave propagation structure comprises a metamaterial (2) and base materials (1) bonded at two ends of the metamaterial (2), wherein the thickness of the base materials (1) is equal to the total thickness of the metamaterial (2), and the base materials (1), the metamaterial (2) and the base materials (1) are arranged in sequence along the wave propagation direction; the metamaterial (2) is formed by stacking more than three layers of single-layer plates in one or more types and in multiple directions.
2. A fiber lay mode converting metamaterial structure as claimed in claim 1, wherein: the one or more types of single-layer plates forming the metamaterial (2) are all composed of matrix media and fiber materials, and the types of the single-layer plates are determined by the types of the matrix media and the fiber materials and the thicknesses of the single-layer plates; wherein the matrix medium includes any one of epoxy resin and rubber; the number of single-layer boards of at most one type is odd.
3. A fiber lay mode converting metamaterial structure as claimed in claim 1, wherein: the whole metamaterial stacking and bonding structure is symmetrical to the middle plane of the metamaterial (2), the angle of the single-layer plate is an included angle between the wave propagation direction and the main shaft direction of the single-layer plate, and the included angle is-90 degrees.
4. A fiber lay mode converting metamaterial structure as claimed in claim 1, wherein: if a plurality of single-layer plates forming the metamaterial (2) are made of the same matrix medium and the same fiber material, a plurality of single-layer plates are required, wherein the included angle between the main shaft direction of each single-layer plate and the wave propagation direction is the same and ranges from-90 degrees to 90 degrees, and the total thickness of the single-layer plates is larger than the thickness of the single-layer plates at other angles in the ratio of the thickness of the metamaterial.
5. A fiber lay mode converting metamaterial structure as claimed in claim 1, wherein: in the metamaterial (2), the maximum modal conversion efficiency is achieved by designing an included angle of-90 degrees between the main axis direction of each single-layer plate and the wave propagation direction, wherein the maximum modal conversion efficiency is more than 80%.
6. A fiber lay mode converting metamaterial structure as claimed in claim 1, wherein: the metamaterial (2) comprises one or more fiber layering structures arranged periodically in the wave transmission direction, and the total length d of the metamaterial (2) in the wave transmission direction is smaller than 100 m.
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