Method, system and apparatus for analyzing inherent properties of all-composite honeycomb core sandwich panels

Abstract

The application is a full composite honeycomb core sandwich plate inherent characteristic analysis method, system and device, relates to the material analysis technical field, and studies the inherent characteristic of the full composite honeycomb core sandwich plate in a way of combining theory with experiment. A theoretical model of the full composite honeycomb core sandwich plate is established based on the high-order shear deformation theory and Gibson equivalent theory, and the inherent characteristic is solved by using the orthogonal polynomial method and the energy method. The test piece of the full composite honeycomb core sandwich plate is prepared independently, and the modal knock experiment is carried out to verify the accuracy of the proposed theoretical calculation method.

Description

Technical Field

[0001] This invention relates to the field of material performance analysis technology, and in particular to methods, systems, and equipment for analyzing the inherent properties of fully composite honeycomb core sandwich panels. Background Technology

[0002] Fully composite honeycomb core sandwich panels have advantages such as high specific strength, high specific stiffness, and good impact resistance, and are therefore widely used in aerospace, automotive, sporting goods, and military equipment fields [1,2]. Currently, a large number of this type of sandwich structure exists in actual engineering projects. They typically operate under cantilever conditions, and these conditions are becoming increasingly demanding, making vibration problems particularly significant. In recent years, there have been numerous accidents caused by vibration problems, and fatigue failure and delamination damage caused by excessive vibration have received increasing attention.

[0003] Most current research focuses on composite plates made of single materials. Research on composite honeycomb sandwich panels is mostly conducted on metal structures, while research on the inherent properties of composite sandwich panels with honeycomb core layers based on higher-order shear deformation theory is rarely reported. Summary of the Invention

[0004] In order to overcome the shortcomings of the existing technology in terms of insufficient research on the inherent properties of composite sandwich panels based on high-order shear deformation theory, the main objective of this invention is to provide a method, system, and equipment for analyzing the inherent properties of fully composite honeycomb core sandwich panels.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for analyzing the inherent characteristics of a fully composite honeycomb core sandwich panel, comprising the following steps:

[0006] Under certain assumptions, a theoretical model of the fully composite honeycomb core sandwich panel is constructed based on the higher-order shear deformation theory.

[0007] Based on the geometric and material parameters of the fully composite honeycomb core sandwich panel, and combined with the theoretical model, the stress and strain relationship of the fiber layer, as well as the strain energy and kinetic energy, are obtained by utilizing the surface displacement of the fiber layer in the fully composite honeycomb core sandwich panel. The honeycomb layer in the fully composite honeycomb core sandwich panel is equivalent to an orthotropic monolayer plate. Based on the surface displacement of the orthotropic monolayer plate and using the material parameters of the orthotropic monolayer plate, combined with the stress and strain relationship of the equivalent honeycomb plate, the strain energy and kinetic energy of the equivalent honeycomb plate are obtained, and then the total strain energy and total kinetic energy of the fully composite honeycomb core sandwich panel are obtained.

[0008] The maximum strain energy and maximum kinetic energy are expressed using the orthogonal polynomial method. Based on the Ritz method, an energy function is introduced to obtain the characteristic equations of each natural frequency of the sandwich panel containing the fully composite honeycomb core. The characteristic equations are solved to obtain the natural frequencies and mode shapes of the sandwich panel containing the fully composite honeycomb core.

[0009] The geometric parameters of the fully composite honeycomb core sandwich panel include the length, width, and thickness of the fiberboard and the honeycomb panel, as well as the angle of the fiber layup in the fiberboard. The material parameters include the elastic modulus, shear modulus, and Poisson's ratio.

[0010] The method of obtaining the stress and strain relationship of the fiber layer, as well as the strain energy and kinetic energy, by utilizing the surface displacement of the fiber layer in the fully composite honeycomb core sandwich panel includes:

[0011] Based on the surface displacement of the fiber layer and the angle of fiber layer laying, the stress of each layer is expressed by the stress-rotation axis formula, and the strain and deflection of the plate are expressed by the displacement expression, thereby obtaining the stress-strain relationship. The stress-strain relationship is then substituted into the strain energy and kinetic energy formulas to obtain the strain energy and kinetic energy.

[0012] The assumptions are that the sandwich structure is symmetrical in the mid-plane, the normal stress in the thickness direction is ignored, and the quality of the adhesive is neglected.

[0013] A system for analyzing the inherent properties of a fully composite honeycomb core sandwich panel includes:

[0014] The modeling module constructs a theoretical model of the fully composite honeycomb core sandwich panel under certain assumptions and based on higher-order shear deformation theory.

[0015] The equivalent conversion module, based on the geometric and material parameters of the fully composite honeycomb core sandwich panel and combined with the theoretical model, uses the surface displacement of the fiber layers in the fully composite honeycomb core sandwich panel to obtain the stress and strain relationship of the fiber layers, as well as the strain energy and kinetic energy. It then converts the honeycomb layers in the fully composite honeycomb core sandwich panel into orthotropic monolayers. Based on the surface displacement of the orthotropic monolayers and using the material parameters of the orthotropic monolayers, combined with the stress and strain relationship of the equivalent honeycomb panel, it obtains the strain energy and kinetic energy of the equivalent honeycomb panel, and finally obtains the total strain energy and total kinetic energy of the fully composite honeycomb core sandwich panel.

[0016] The analysis module uses the orthogonal polynomial method to represent the maximum strain energy and maximum kinetic energy, and introduces an energy function according to the Ritz method to obtain the characteristic equations of each natural frequency of the sandwich panel containing the fully composite honeycomb core. Solving the characteristic equations yields the natural frequencies and mode shapes of the fully composite honeycomb core sandwich panel.

[0017] A computer device includes a memory and a processor, the memory storing a computer program that, when executed by the processor, causes the processor to perform the following steps:

[0018] Under certain assumptions, a theoretical model of the fully composite honeycomb core sandwich panel is constructed based on the higher-order shear deformation theory.

[0019] Based on the geometric and material parameters of the fully composite honeycomb core sandwich panel, and combined with the theoretical model, the stress and strain relationship of the fiber layer, as well as the strain energy and kinetic energy, are obtained by utilizing the surface displacement of the fiber layer in the fully composite honeycomb core sandwich panel. The honeycomb layer in the fully composite honeycomb core sandwich panel is equivalent to an orthotropic monolayer plate. Based on the surface displacement of the orthotropic monolayer plate and using the material parameters of the orthotropic monolayer plate, combined with the stress and strain relationship of the equivalent honeycomb plate, the strain energy and kinetic energy of the equivalent honeycomb plate are obtained, and then the total strain energy and total kinetic energy of the fully composite honeycomb core sandwich panel are obtained.

[0020] The maximum strain energy and maximum kinetic energy are expressed using the orthogonal polynomial method. Based on the Ritz method, an energy function is introduced to obtain the characteristic equations of each natural frequency of the sandwich panel containing the fully composite honeycomb core. The characteristic equations are solved to obtain the natural frequencies and mode shapes of the sandwich panel containing the fully composite honeycomb core.

[0021] A computer-readable storage medium storing a computer program, which, when executed by a processor, causes the processor to perform the following steps: under certain assumptions, constructing a theoretical model of the fully composite honeycomb core sandwich panel based on a higher-order shear deformation theorem;

[0022] Based on the geometric and material parameters of the fully composite honeycomb core sandwich panel, and combined with the theoretical model, the stress and strain relationship of the fiber layer, as well as the strain energy and kinetic energy, are obtained by utilizing the surface displacement of the fiber layer in the fully composite honeycomb core sandwich panel. The honeycomb layer in the fully composite honeycomb core sandwich panel is equivalent to an orthotropic monolayer plate. Based on the surface displacement of the orthotropic monolayer plate and using the material parameters of the orthotropic monolayer plate, combined with the stress and strain relationship of the equivalent honeycomb plate, the strain energy and kinetic energy of the equivalent honeycomb plate are obtained, and then the total strain energy and total kinetic energy of the fully composite honeycomb core sandwich panel are obtained.

[0023] The maximum strain energy and maximum kinetic energy are expressed using the orthogonal polynomial method. Based on the Ritz method, an energy function is introduced to obtain the characteristic equations of each natural frequency of the sandwich panel containing the fully composite honeycomb core. The characteristic equations are solved to obtain the natural frequencies and mode shapes of the sandwich panel containing the fully composite honeycomb core.

[0024] Compared with existing technologies, the advantages of this invention are as follows: Taking a sandwich panel with carbon nanotube / short fiber honeycomb as the core layer and fiber-reinforced composite board as the face layer as the research object, considering the anisotropy of the composite material face layer, the honeycomb core layer is treated based on Gibson's equivalent elastic modulus theory. A theoretical model is established using higher-order shear theory, and the inherent characteristics of the structure are solved using the energy method and orthogonal polynomial method. To verify the correctness of the proposed method, a sample was prepared using the fully composite honeycomb core sandwich panel as the research object, and a corresponding experimental system was built. The feasibility of the theory presented in this paper is demonstrated through experiments. The proposed calculation method has advantages such as accurate results, fast calculation speed, and wide applicability, and has guiding and reference value for engineering practice. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the geometric structure of the theoretical model of this invention;

[0026] Figure 2 This is a schematic diagram of the process of this invention;

[0027] Figure 3 This is a schematic diagram of the frequency-response pattern of the three-impact test of the fully composite honeycomb core sandwich panel of the present invention.

[0028] Figure 4 This is a schematic diagram illustrating the change in fiberboard thickness caused by the increase in the number of fiber layers in this invention;

[0029] Figure 5 This is a schematic diagram illustrating the effect of increasing the honeycomb wall thickness on the honeycomb layer according to the present invention;

[0030] Figure 6 This is a schematic diagram illustrating the effect of increasing the honeycomb wall length on the honeycomb layer according to the present invention;

[0031] Figure 7 This is a schematic diagram of the natural frequencies and mode shapes calculated by experiments and theories in this invention;

[0032] Figure 8 This is a schematic diagram of the calculation process for the natural frequency of the fully composite honeycomb core sandwich panel of the present invention;

[0033] Reference numerals: 1 represents fiber direction, 2 represents fiber transverse direction, 3 represents direction perpendicular to plane 1-2. Detailed Implementation

[0034] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0035] Example:

[0036] Combination Figure 1-8 The method for analyzing the inherent properties of a fully composite honeycomb core sandwich panel includes the following steps:

[0037] Under certain assumptions, a theoretical model of the fully composite honeycomb core sandwich panel is constructed based on the higher-order shear deformation theory.

[0038] Based on the geometric and material parameters of the fully composite honeycomb core sandwich panel, and combined with the theoretical model, the stress and strain relationship of the fiber layer, as well as the strain energy and kinetic energy, are obtained by utilizing the surface displacement of the fiber layer in the fully composite honeycomb core sandwich panel. The honeycomb layer in the fully composite honeycomb core sandwich panel is equivalent to an orthotropic monolayer plate. Based on the surface displacement of the orthotropic monolayer plate and using the material parameters of the orthotropic monolayer plate, combined with the stress and strain relationship of the equivalent honeycomb plate, the strain energy and kinetic energy of the equivalent honeycomb plate are obtained, and then the total strain energy and total kinetic energy of the fully composite honeycomb core sandwich panel are obtained.

[0039] The maximum strain energy and maximum kinetic energy are expressed using the orthogonal polynomial method. Based on the Ritz method, an energy function is introduced to obtain the characteristic equations of each natural frequency of the sandwich panel containing the fully composite honeycomb core. The characteristic equations are solved to obtain the natural frequencies and mode shapes of the sandwich panel containing the fully composite honeycomb core.

[0040] The geometric parameters of the fully composite honeycomb core sandwich panel include the length, width, and thickness of the fiberboard and the honeycomb panel, as well as the angle of the fiber layup in the fiberboard. The material parameters include the elastic modulus, shear modulus, and Poisson's ratio.

[0041] The specific assumptions include:

[0042] 1. The sandwich structure is symmetrical in the middle plane;

[0043] 2. The normal stress in the thickness direction can be ignored;

[0044] 3. The layers are perfectly bonded together, and the quality of the adhesive is negligible.

[0045] The method of obtaining the stress-strain relationship, strain energy, and kinetic energy of the fiber layer by utilizing the surface displacement of the fiber layer in the fully composite honeycomb core sandwich panel includes the following steps:

[0046] Establish the xoy coordinate system by using the middle surface of the fully composite honeycomb core sandwich panel as the reference plane;

[0047] Based on the surface displacement of the fiber layers and the angle of fiber layer laying, the stress of each layer is expressed using the stress-rotation formula, and the strain and deflection of the plate are expressed using displacement expressions, thus obtaining the stress-strain relationship. Specifically, considering the influence of the mid-surface layer displacement, the fiber layer displacement field is expressed as:

[0048]

[0049] Introducing ψ x and ψ y Simplify the above displacement field formula:

[0050]

[0051] The stress-strain relationship of the fully composite honeycomb core sandwich panel is expressed as follows:

[0052]

[0053] In the formula, ε1, ε2, ε3, ε4, ε5, and ε6 represent the linear strain and shear strain in the x, y, and z directions, respectively, where ε 0 ,ε s ,κ 0 ,κ 2 , The results are as follows:

[0054]

[0055] The stress-strain relationship of ACHCSP can be deduced from the above formula as follows:

[0056]

[0057] In the formula, σ1 and σ2 are the stresses in the x and y directions, respectively, σ4, σ5, and σ6 are the stresses in the yz, xz, and xy directions, respectively, and ε i These correspond to strain in different directions;

[0058] For the upper and lower fiber layers, the elements in formula (5) are represented as follows:

[0059]

[0060] In the formula, E f1 E f2 These are the elastic values ​​of the fiber layer along the fiber direction and perpendicular to the fiber direction, respectively, G. f12 G f13 and G f23 These are the shear moduli in various directions within the plane; v f12 ,v f21 This is the Poisson's ratio in directions 1 and 2;

[0061] The fiber material and the principal axis of the plate are at a certain angle. Based on the stress-strain rotation formula, the stress-strain relationship of the k-th layer is derived as follows:

[0062]

[0063] in, The off-axis stiffness coefficient is expressed as follows:

[0064]

[0065] Substituting the stress-strain relationship into the strain energy and kinetic energy formulas, we obtain the strain energy and kinetic energy; the strain energy and kinetic energy of the fiber layer are shown below:

[0066]

[0067]

[0068] In the formula σ Fi ,ε Fi ρ represents the stress and strain of the fiber layer, respectively. F A represents the density of the fiber laminate, and A represents the area of ​​the laminate.

[0069] The step of obtaining the strain energy and kinetic energy of the equivalent honeycomb panel based on the surface displacement of the orthotropic single-layer plate and utilizing the material parameters of the orthotropic single-layer plate, combined with the stress-strain relationship of the equivalent honeycomb panel, includes the following steps:

[0070] Based on higher-order shear deformation theory, and considering the shear strain problem of thick plates, the displacement field of the honeycomb layer is determined as follows:

[0071]

[0072] Where H is the coefficient of the higher-order term H = z - 4z 3 / 3h 2 ,φ x φ y This is the axial deflection distance;

[0073] The honeycomb cells in the honeycomb layer are regular hexagons. By using the Gibson equivalence method, the honeycomb layer is equivalent to a single-layer plate. After the equivalence, its related parameters also change.

[0074]

[0075] Where, ρ c For the equivalent density, ρ s The density of the material before the equivalent;

[0076]

[0077] Among them, t c Let λ be the thickness of the cell wall of the hexagonal honeycomb unit, and temporarily take 1, then η = 2l² / l¹. These are Young's moduli in directions 1, 2, and 3, respectively.

[0078]

[0079] in, The shear modulus in the 12-axis direction. The shear modulus in the 13th direction. The Young's modulus in the 23 direction;

[0080]

[0081] in, This represents the Poisson's ratio in the equivalent 12 directions;

[0082] The strain energy and kinetic energy of the equivalent honeycomb panel can be determined by using the stress-strain relationship using the equivalent parameters.

[0083]

[0084]

[0085] According to the theory of higher-order shear deformation, the strain energy and kinetic energy of the honeycomb layer are as follows:

[0086] The total strain energy and kinetic energy of the honeycomb layer are as follows:

[0087] U = U F +U V (16a)

[0088] T = T F +T V (16b).

[0089] The method involves using orthogonal polynomials to represent the maximum strain energy and maximum kinetic energy, and introducing an energy function based on the Ritz method to obtain the characteristic equations for the natural frequencies of the sandwich panel containing the fully composite honeycomb core. Solving these characteristic equations yields the natural frequencies and mode shapes of the sandwich panel. The steps include:

[0090] Assume the vibration displacement of the surface layer in the laminate is expressed as:

[0091] w0(x,y,t)=e iωt W(ξ,η) (17)

[0092] According to the Ritz method, the mid-surface displacement can be expressed as:

[0093]

[0094] Where M and N are the cutoff coefficients for solving the problem using the Ritz method, and a mn ,b mn ,c mn ,d mn ,emn These are undetermined parameters, where ω is the natural frequency of the plate, and P is the P value. m (ξ) and P n (η) is the orthogonal characteristic polynomial; its specific expression is as follows:

[0095]

[0096]

[0097] Among them B k and P k For coefficient parameters, Let be the characteristic polynomial of orthogonality, and its expression is as follows:

[0098]

[0099] Where W(ξ) is the coefficient of the weight function, which is usually taken as 1 in the orthogonalization process; p, q, r, s are related to the boundary conditions of the fiber reinforced plate. If the boundary condition of the fiber reinforced plate is cantilever, then p = 2, q = r = s = 0.

[0100] Substituting equation (20) into (16), and setting sin(ωt) = 1 and cos(ωt) = 1, we can obtain the maximum potential energy U containing the undetermined Ritz parameters. max and maximum kinetic energy E max :

[0101]

[0102] Define the energy function:

[0103] L=T max -U max (twenty two)

[0104] Differentiating the energy function of the fiber-reinforced plate by the undetermined coefficients yields:

[0105]

[0106] Solving the energy equation for the minimum undetermined parameters yields the generalized eigenvalue problem, which in turn leads to...

[0107] (K-ω 2 M)q=F (24)

[0108] When the matrix coefficients of q are 0, the natural frequencies of the fully composite honeycomb core sandwich panel are obtained, and the mode shapes are plotted based on the natural frequencies.

[0109] Example 2

[0110] Based on Example 1, in this example, the inherent characteristic analysis system for the fully composite honeycomb core sandwich panel includes:

[0111] The modeling module constructs a theoretical model of the fully composite honeycomb core sandwich panel under certain assumptions and based on higher-order shear deformation theory.

[0112] The equivalent conversion module, based on the geometric and material parameters of the fully composite honeycomb core sandwich panel and combined with the theoretical model, uses the surface displacement of the fiber layers in the fully composite honeycomb core sandwich panel to obtain the stress and strain relationship of the fiber layers, as well as the strain energy and kinetic energy. It then converts the honeycomb layers in the fully composite honeycomb core sandwich panel into orthotropic monolayers. Based on the surface displacement of the orthotropic monolayers and using the material parameters of the orthotropic monolayers, combined with the stress and strain relationship of the equivalent honeycomb panel, it obtains the strain energy and kinetic energy of the equivalent honeycomb panel, and finally obtains the total strain energy and total kinetic energy of the fully composite honeycomb core sandwich panel.

[0113] The analysis module uses the orthogonal polynomial method to represent the maximum strain energy and maximum kinetic energy, and introduces an energy function according to the Ritz method to obtain the characteristic equations of each natural frequency of the sandwich panel containing the fully composite honeycomb core. Solving the characteristic equations yields the natural frequencies and mode shapes of the fully composite honeycomb core sandwich panel.

[0114] The system can be run using existing MATLAB software. The specific steps are as follows:

[0115] (1) Input the geometric and material parameters of the composite sandwich panel.

[0116] First, the length, width, and thickness of the fiberboard and the honeycomb panel need to be given separately. For the fiberboard, the angle of the fiber layup for each layer needs to be given. Second, the corresponding elastic modulus, shear modulus, Poisson's ratio, and material density of the fiber layer and the equivalent honeycomb layer need to be given.

[0117] (2) Equivalent calculation of honeycomb panels

[0118] Because the complex structure of honeycomb panels makes it difficult to calculate their inherent properties, the honeycomb panels are simplified into single-layer panels. The original material parameters of the honeycomb panels, such as elastic modulus, shear modulus, and Poisson's ratio, are converted into equivalent material parameters through an equivalent method.

[0119] (3) Calculation of maximum strain energy of fiber and honeycomb layer using orthogonal polynomial method

[0120] Since the fiber laminate has an angled layup, we use the stress-rotation axis formula to represent the stress of each layer, the displacement expression to represent the strain and deflection of the plate, and the orthogonal polynomial method to express the stress and strain. Substituting these into the strain energy formula, we can express the maximum strain energy using undetermined parameters.

[0121] (4) Calculate the maximum strain energy of the fiber layer and the honeycomb layer using the orthogonal polynomial method.

[0122] Substituting the displacement expression into the kinetic energy expression, we can obtain a kinetic energy expression using mode shape functions, and express the maximum kinetic energy using the orthogonal polynomial method.

[0123] (5) Solve for natural frequencies using the Ritz method

[0124] The maximum kinetic energy T in the above steps max and maximum strain energy U max The energy function is expressed using the orthogonal polynomial method, and then the characteristic equation of the honeycomb composite sandwich panel is obtained by taking the partial derivative of the energy function with respect to all the undetermined eigenvectors using the Ritz method. Solving the characteristic equation yields the natural frequencies of the honeycomb composite sandwich panel.

[0125] (6) Solve for the mode shape diagram

[0126] The mode shape function is solved using orthogonal polynomials, and the mode shape diagram of the plate is plotted using MATLAB. The specific solution process is as follows: Figure 8 As shown.

[0127] A computer device includes a memory and a processor, the memory storing a computer program that, when executed by the processor, causes the processor to perform the following steps:

[0128] Under certain assumptions, a theoretical model of the fully composite honeycomb core sandwich panel is constructed based on the higher-order shear deformation theory.

[0129] Based on the geometric and material parameters of the fully composite honeycomb core sandwich panel, and combined with the theoretical model, the stress and strain relationship of the fiber layer, as well as the strain energy and kinetic energy, are obtained by utilizing the surface displacement of the fiber layer in the fully composite honeycomb core sandwich panel. The honeycomb layer in the fully composite honeycomb core sandwich panel is equivalent to an orthotropic monolayer plate. Based on the surface displacement of the orthotropic monolayer plate and using the material parameters of the orthotropic monolayer plate, combined with the stress and strain relationship of the equivalent honeycomb plate, the strain energy and kinetic energy of the equivalent honeycomb plate are obtained, and then the total strain energy and total kinetic energy of the fully composite honeycomb core sandwich panel are obtained.

[0130] The maximum strain energy and maximum kinetic energy are expressed using the orthogonal polynomial method. Based on the Ritz method, an energy function is introduced to obtain the characteristic equations of each natural frequency of the sandwich panel containing the fully composite honeycomb core. The characteristic equations are solved to obtain the natural frequencies and mode shapes of the sandwich panel containing the fully composite honeycomb core.

[0131] A computer-readable storage medium storing a computer program, which, when executed by a processor, causes the processor to perform the following steps: under certain assumptions, constructing a theoretical model of the fully composite honeycomb core sandwich panel based on a higher-order shear deformation theorem;

[0132] Based on the geometric and material parameters of the fully composite honeycomb core sandwich panel, and combined with the theoretical model, the stress and strain relationship of the fiber layer, as well as the strain energy and kinetic energy, are obtained by utilizing the surface displacement of the fiber layer in the fully composite honeycomb core sandwich panel. The honeycomb layer in the fully composite honeycomb core sandwich panel is equivalent to an orthotropic monolayer plate. Based on the surface displacement of the orthotropic monolayer plate and using the material parameters of the orthotropic monolayer plate, combined with the stress and strain relationship of the equivalent honeycomb plate, the strain energy and kinetic energy of the equivalent honeycomb plate are obtained, and then the total strain energy and total kinetic energy of the fully composite honeycomb core sandwich panel are obtained.

[0133] The maximum strain energy and maximum kinetic energy are expressed using the orthogonal polynomial method. Based on the Ritz method, an energy function is introduced to obtain the characteristic equations of each natural frequency of the sandwich panel containing the fully composite honeycomb core. The characteristic equations are solved to obtain the natural frequencies and mode shapes of the sandwich panel containing the fully composite honeycomb core.

[0134] Example 2:

[0135] Based on Example 1, this example verifies the feasibility of the analysis process of this application through experiments. The main contents include three parts: preparation of experimental samples, construction and testing of the experimental testing platform, and comparison and verification of results. This verifies the correctness of the proposed solution model for the inherent properties of the fully composite honeycomb core sandwich panel based on higher-order shear deformation theory.

[0136] The fully composite honeycomb core sandwich panel includes upper and lower panels and a honeycomb core layer. The upper and lower fiberboard layers are prepared by laying orthogonal fiber layers with resin as the matrix, and the fiber layup pattern is [0° / 90°]21. The honeycomb core layer is formed by thoroughly mixing a CR17 glass fiber / carbon nanotube reinforced resin-based solution and then casting it through a hexagonal honeycomb mold. The specific steps are as follows:

[0137] First, add an appropriate amount of IN2 flow-conducting resin and 10% TX-10 emulsifier by mass into a beaker and mix well. Place the beaker in a 40°C water bath and stir at 500 rad / min for 30 minutes until all air bubbles in the resin are removed.

[0138] Then, using an electronic balance, 0.5% carbon nanotubes and CR17 glass fibers were measured from the resin solution. The two reinforcements were added to the solution being stirred and stirred at 500 rad / min for 30 min until the reinforcements and resin matrix were mixed evenly.

[0139] Next, using a balance, 30% by mass of AT30 slow curing agent was added to the well-mixed glass fiber / carbon nanotube reinforced resin base solution. The mixture was then stirred for 5 minutes under a 40°C water bath to ensure that the curing agent and the resin base solution were fully mixed.

[0140] Finally, the thoroughly mixed glass fiber / carbon nanotube reinforced resin solution was placed in a preheated vacuum drying oven for vacuum degassing treatment. The oven temperature was 80℃ and the vacuum degree was 10-4 Pa.

[0141] After the above steps, the defoamed mixed solution is slowly poured into a hexagonal honeycomb silicone mold for molding, and then demolded after standing for 15-24 hours.

[0142] The prepared honeycomb core is bonded to the upper and lower fiberboard layers using an adhesive film. Before bonding, ensure the surface is free of condensation and cut the core to the size of the honeycomb layers before bonding. After bonding, place the core in a hot oven at 150°C for 30 minutes to cure, and you will obtain a fully composite honeycomb core sandwich panel.

[0143] The geometric and material parameters of the obtained fully composite honeycomb core sandwich panel are shown in Table 3.1.

[0144] Table 1 Geometric and material parameters of the fully composite honeycomb core sandwich panel

[0145]

[0146] A testing system for the inherent characteristics of a fully composite honeycomb sandwich panel was constructed. The test panel was constrained by a cantilever. The testing system mainly consisted of a portable LMSSCADAS data acquisition instrument, a PCB353B15 accelerometer, a PCB086C01 modal force hammer, and an LMSTest.lab mobile workstation. Before testing, the clamping length was determined to be 40mm. The test panel was then divided into 10 equal parts along its length and 5 equal parts along its width, and each measuring point was labeled. Next, the PCB accelerometer was attached to measuring points 17 and 50 on the test piece, respectively. The placement of points 17 and 50 is shown in the figure. Figure 2 .

[0147] When testing the natural frequency of the structure, a multi-point excitation and multi-point response method was adopted, and modal force hammers were used to excite each point on the full composite honeycomb core sandwich plate. (I) The test bandwidth was set to 0-3000Hz. (II) The resolution was 0.5Hz. (III) The window function was Hanning window.

[0148] To ensure data accuracy, each point needs to be effectively stimulated three times during the testing process. Figure 3 The frequency response functions obtained from hammering at three different measuring points are given.

[0149] To verify the correctness of the proposed model, the natural frequencies and mode shapes of the fully composite honeycomb core sandwich panel were obtained and compared with the calculation results. Figure 7 Table 2 in the table shows the theoretically calculated frequency A, the experimental frequency B, and the errors and mode shapes of both.

[0150] As can be seen from Table 2, the errors between the first 5 frequencies obtained in the experiment and the theoretically calculated frequencies are all between 1.03% and 8.73%, which is within the allowable error range. Furthermore, the trend of the calculated mode shapes is basically consistent with that of the experimentally tested mode shapes. Therefore, the correctness of the theoretical model proposed in the application can be verified.

[0151] Since fiberboard is composed of multiple orthogonally laid anisotropic fiber layers, in order to avoid changing the structure of the fiber layers, this section discusses the influence of fiberboards with 21, 31, and 41 fiber layers on the natural frequency of the fully composite honeycomb core sandwich panel by varying the fiberboard thickness. The calculated natural frequencies of the fully composite honeycomb core sandwich panel under different fiberboard thicknesses are shown in Table 3.

[0152] Table 3 Natural frequencies of fully composite honeycomb core sandwich panels with different unit wall lengths

[0153]

[0154] The data in Table 3 show that the natural frequency of the fully composite honeycomb core sandwich panel increases with the increase of the cell wall length. This is mainly because, with the increase of the cell wall length, the quality of the middle cell layer of the fully composite honeycomb core sandwich panel will significantly decrease when the overall geometric dimensions remain unchanged. Figure 4 As shown, mass plays a dominant role over stiffness at this point, thus increasing the natural frequency of the fully composite honeycomb core sandwich panel.

[0155] The basic working principle of this invention is as follows: Based on higher-order shear deformation theory, this application establishes a theoretical model of a fully composite honeycomb core sandwich panel and uses the orthogonal polynomial method to solve for the natural frequencies of the fully composite honeycomb core sandwich panel. Experimental verification of the accuracy of the proposed theoretical model through the preparation of test samples shows that the error between the experimental and theoretically calculated natural frequencies is between 1.03% and 8.73%, and the calculated mode shapes are basically consistent with the experimental mode shapes, proving that the theoretical model proposed in this paper can be used to predict the natural frequencies and mode shapes of fully composite honeycomb core sandwich panel structures.

[0156] (1) As the thickness of the upper and lower fiberboards increases, the natural frequency of the fully composite honeycomb core sandwich panel decreases to varying degrees, but has little effect on its mode shape. This indicates that the increase in fiberboard thickness leads to a significant increase in its stiffness matrix, thereby increasing its natural frequency.

[0157] (2) As the thickness of the cell wall increases, the natural frequency of the full composite cell sandwich panel gradually decreases. Taking the first natural frequency as an example, when the cell wall thickness increases from 2mm to 5mm, its natural frequency decreases from 243.4Hz to 186.7Hz. This is because the mass matrix increases with the increase of the cell wall thickness. At this time, the mass matrix plays a dominant role, so the natural frequency of the full composite cell sandwich panel decreases.

[0158] (3) As the wall length of the cell unit increases, the natural frequency of the full composite cell core sandwich panel shows an increasing trend. This is because as the wall length of the cell unit increases, the mass of the cell layer decreases significantly without changing the overall size, resulting in a decrease in the mass matrix and thus an increase in the natural frequency.

[0159] It should be noted that, in this invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0160] The above embodiments are merely illustrative examples of the present invention and do not constitute a limitation on the scope of protection of the present invention. Any designs that are the same as or similar to the present invention are within the scope of protection of the present invention.

Claims

1. A method for analyzing the inherent properties of a fully composite honeycomb core sandwich panel, characterized in that, Includes the following steps: Under certain assumptions, a theoretical model of the fully composite honeycomb core sandwich panel is constructed based on the theory of higher-order shear deformation. The specific assumptions include: the sandwich structure is symmetrical in the middle plane; the normal stress in the thickness direction and the mass of the adhesive are ignored; Based on the geometric and material parameters of the fully composite honeycomb core sandwich panel, and combined with the theoretical model, the stress and strain relationship of the fiber layer, as well as the strain energy and kinetic energy, are obtained by utilizing the surface displacement of the fiber layer in the fully composite honeycomb core sandwich panel. The honeycomb layer in the fully composite honeycomb core sandwich panel is equivalent to an orthotropic monolayer plate. Based on the surface displacement of the orthotropic monolayer plate and using the material parameters of the orthotropic monolayer plate, combined with the stress and strain relationship of the equivalent honeycomb plate, the strain energy and kinetic energy of the equivalent honeycomb plate are obtained, and then the total strain energy and total kinetic energy of the fully composite honeycomb core sandwich panel are obtained. The maximum strain energy and maximum kinetic energy are expressed using the orthogonal polynomial method. Based on the Ritz method, an energy function is introduced to obtain the characteristic equations of each natural frequency of the sandwich panel containing the fully composite honeycomb core. The characteristic equations are solved to obtain the natural frequencies and mode shapes of the sandwich panel containing the fully composite honeycomb core.

2. The method for analyzing the inherent characteristics of the fully composite honeycomb core sandwich panel according to claim 1, characterized in that, The geometric parameters of the fully composite honeycomb core sandwich panel include the length, width, and thickness of the fiberboard and the honeycomb panel, as well as the angle of the fiber layup in the fiberboard. The material parameters include the elastic modulus, shear modulus, and Poisson's ratio.

3. A system for analyzing the inherent characteristics of a fully composite honeycomb core sandwich panel, characterized in that: include: The modeling module constructs a theoretical model of the fully composite honeycomb core sandwich panel under certain assumptions and based on higher-order shear deformation theory. The specific assumptions include: the sandwich structure is symmetrical in the middle plane; the normal stress in the thickness direction and the mass of the adhesive are ignored; The equivalent conversion module, based on the geometric and material parameters of the fully composite honeycomb core sandwich panel and combined with the theoretical model, uses the surface displacement of the fiber layers in the fully composite honeycomb core sandwich panel to obtain the stress and strain relationship of the fiber layers, as well as the strain energy and kinetic energy. It then converts the honeycomb layers in the fully composite honeycomb core sandwich panel into orthotropic monolayers. Based on the surface displacement of the orthotropic monolayers and using the material parameters of the orthotropic monolayers, combined with the stress and strain relationship of the equivalent honeycomb panel, it obtains the strain energy and kinetic energy of the equivalent honeycomb panel, and finally obtains the total strain energy and total kinetic energy of the fully composite honeycomb core sandwich panel. The analysis module uses the orthogonal polynomial method to represent the maximum strain energy and maximum kinetic energy, and introduces an energy function according to the Ritz method to obtain the characteristic equations of each natural frequency of the sandwich panel containing the fully composite honeycomb core. Solving the characteristic equations yields the natural frequencies and mode shapes of the fully composite honeycomb core sandwich panel.

4. A computer device, characterized in that, The computer device includes a memory and a processor. The memory stores a computer program, which, when executed by the processor, causes the processor to perform the following steps: Under certain assumptions, a theoretical model of the fully composite honeycomb core sandwich panel is constructed based on higher-order shear deformation theory. The specific assumptions include: the core structure is symmetrical in the middle plane; the normal stress in the thickness direction and the mass of the adhesive are ignored. Based on the geometric and material parameters of the fully composite honeycomb core sandwich panel, and combined with the theoretical model, the stress and strain relationship of the fiber layer, as well as the strain energy and kinetic energy, are obtained by utilizing the surface displacement of the fiber layer in the fully composite honeycomb core sandwich panel. The honeycomb layer in the fully composite honeycomb core sandwich panel is equivalent to an orthotropic monolayer plate. Based on the surface displacement of the orthotropic monolayer plate and using the material parameters of the orthotropic monolayer plate, combined with the stress and strain relationship of the equivalent honeycomb plate, the strain energy and kinetic energy of the equivalent honeycomb plate are obtained, and then the total strain energy and total kinetic energy of the fully composite honeycomb core sandwich panel are obtained. The maximum strain energy and maximum kinetic energy are expressed using the orthogonal polynomial method. Based on the Ritz method, an energy function is introduced to obtain the characteristic equations of each natural frequency of the sandwich panel containing the fully composite honeycomb core. The characteristic equations are solved to obtain the natural frequencies and mode shapes of the sandwich panel containing the fully composite honeycomb core.

5. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, causes the processor to perform the following steps: Under certain assumptions, based on higher-order shear deformation theory, construct a theoretical model of the fully composite honeycomb core sandwich panel; the specific assumptions include: the core structure is symmetrical in the middle plane; and the normal stress in the thickness direction and the mass of the adhesive are ignored. Based on the geometric and material parameters of the fully composite honeycomb core sandwich panel, and combined with the theoretical model, the stress and strain relationship of the fiber layer, as well as the strain energy and kinetic energy, are obtained by utilizing the surface displacement of the fiber layer in the fully composite honeycomb core sandwich panel. The honeycomb layer in the fully composite honeycomb core sandwich panel is equivalent to an orthotropic monolayer plate. Based on the surface displacement of the orthotropic monolayer plate and using the material parameters of the orthotropic monolayer plate, combined with the stress and strain relationship of the equivalent honeycomb plate, the strain energy and kinetic energy of the equivalent honeycomb plate are obtained, and then the total strain energy and total kinetic energy of the fully composite honeycomb core sandwich panel are obtained. The maximum strain energy and maximum kinetic energy are expressed using the orthogonal polynomial method. Based on the Ritz method, an energy function is introduced to obtain the characteristic equations of each natural frequency of the sandwich panel containing the fully composite honeycomb core. The characteristic equations are solved to obtain the natural frequencies and mode shapes of the sandwich panel containing the fully composite honeycomb core.

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