Wood chip selection method and wood chip composite board

Abstract

The present invention provides a particle board selection method and a particle board composite board. The technical solution mainly includes the following steps: establishing a first RVE model of a two-dimensional representative volume unit with random distribution of particles; applying strain in the horizontal and vertical directions of the first RVE model to obtain stress cloud maps of horizontal loading and vertical loading; based on the stress cloud map, using a first mathematical model to calculate the volume average modulus to obtain the elastic modulus of particles of different sizes in the x-direction and y-direction; using a second mathematical model to select the particles of different sizes that meet the second mathematical model and form a first observation group; statistically analyzing the first observation group to obtain the selection range of the length and width of the rectangular particle board. A particle board composite board is also disclosed, including a surface board and the particle board obtained by the above selection method. The present solution can optimize the selection range of the particle board, so that the particle board has excellent mechanical properties.

Description

Technical Field

[0001] The invention relates to the field of particle board structures, in particular to a particle board selection method and a particle board composite board. Background Art

[0002] Multi-layer composite board is a common type of board with the advantages of affordable price, good material, easy processing and recyclability. The specific structure of the particle board can refer to the technical solution of patent application number 93243501.7, which discloses a bamboo large-piece particle board. Its main feature is that the original bamboo is sawed and radially sliced into bamboo large-piece shavings, which are then glued and randomly laid and hot-pressed to form a bamboo large-piece particle board.

[0003] Although the above scheme discloses the range of values for the length and thickness of the particle board, it does not disclose the range of values for the width, nor does it disclose what mechanical properties will be achieved by adopting the values within the above range. It is impossible to make the particle board have excellent mechanical properties by adjusting the size of the particle board.

[0004] Therefore, the problem of this solution is how to optimize the selection range of particle chips so that the particleboard has excellent mechanical properties. Summary of the Invention

[0005] The purpose of the present invention is to provide a particle board selection method and a particle board composite board, so as to optimize the selection range of the particle boards and make the particle board have excellent mechanical properties.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A wood shavings selection method comprises the following steps:

[0008] Establish the first RVE model of a two-dimensional representative volume unit with random particle distribution;

[0009] Apply strain in the horizontal and vertical directions of the first RVE model to obtain stress cloud diagrams of horizontal loading and vertical loading;

[0010] Based on the stress cloud map, a first mathematical model is used to calculate the volume average modulus to obtain the elastic modulus in the x-direction and the y-direction of particles of different sizes;

[0011] Using the second mathematical model, the particles of different sizes that meet the second mathematical model are selected and form a first observation group;

[0012] The statistical analysis of the first observation group resulted in the selected range of length and width of the rectangular wood shavings.

[0013] In the above-mentioned wood shavings selection method, the following steps are also included:

[0014] Establish a second RVE model consisting of a two-dimensional representative volume unit with random particle distribution and glue;

[0015] Applying stress to the second RVE model, the first and second curve groups of force-displacement for rectangular particles with different aspect ratios and sizes are obtained respectively;

[0016] The selected value ranges of the length and width of the rectangular shavings are combined with the first curve group and the second curve group to obtain a first composite selected value range of the length and width of the rectangular shavings.

[0017] In the above-mentioned shavings selection method, the elastic modulus of the rectangular shavings is set to 21.4 GPa, the tensile strength is 482 MPa, the density is 1.49 g / cm³, the Poisson's ratio is 0.23, and the fracture energy is 0.48 J / mm; the elastic modulus of the glue is 3200 GPa, the tensile strength is 7 MPa, the density is 1.19 g / cm³, the Poisson's ratio is 0.35, and the fracture energy is 0.08 J / mm.

[0018] In the above-mentioned wood shavings selection method, the following steps are also included:

[0019] A three-dimensional model of a pixel grid is established, and stress is applied to the three-dimensional model along three mutually perpendicular directions to obtain a second observation group with different aspect ratios and length-to-thickness ratios;

[0020] Statistical analysis was performed on the second observation group to obtain the value ranges of the aspect ratio and the aspect ratio of the rectangular wood chips;

[0021] The selected value ranges of the length and width of the rectangular shavings are combined with the selected value ranges of the aspect ratio and length-to-width ratio of the rectangular shavings to obtain the selected value ranges of the length, width and thickness of the rectangular shavings.

[0022] In the above-mentioned wood shavings selection method, the following steps are also included:

[0023] A tensile load is applied in a direction perpendicular to the particle board until the particle board is destroyed, and a third curve group and a fourth curve group of internal bonding strengths with different aspect ratios and length-to-thickness ratios are obtained respectively through a third mathematical model;

[0024] The dimension selection ranges of the length, width and thickness of the rectangular shavings are combined with the third curve group and the fourth curve group to obtain a second composite selection range of the length, width and thickness of the rectangular shavings.

[0025] In the above-mentioned wood shavings selection method, the following steps are also included:

[0026] The first RVE model is used to obtain the variation relationship of shear modulus with different aspect ratios and thicknesses;

[0027] The dimension selection ranges of the length, width and thickness of the rectangular shavings are compounded with the variation relationship of the shear modulus to obtain a third compound selection range of the length, width and thickness of the rectangular shavings.

[0028] In the above-mentioned wood chip selection method, the side length ratio of the rectangular particles in the first RVE model is greater than 24.

[0029] In the above-mentioned wood chip selection method, multiple RVE models are established, and the average coefficient of variation of the nearest neighbor distance of several RVE models is compared, and the RVE model with the smallest average coefficient of variation of the nearest neighbor distance is selected as the first RVE model.

[0030] In the above-mentioned wood chip value selection method, the step of applying strain in the horizontal direction and the vertical direction of the first RVE model to obtain stress cloud diagrams of horizontal loading and vertical loading includes:

[0031] Setting the elastic modulus of the wood chips =21.4GPa, Poisson's ratio =0.23; the adhesive is resin glue, and its elastic modulus =3200MPa, Poisson's ratio =0.35.

[0032] A particleboard composite board comprises two surface boards and particleboards obtained by the particleboard selection method as described above, wherein the particleboards are adhered to each other in a stacked manner to form a sandwich board, and the sandwich board is adhered between the two surface boards.

[0033] Compared with the prior art, the solution of the present invention has the following advantages:

[0034] This technical solution uses numerical simulation methods to analyze the effect of bamboo shavings morphology on the mechanical properties of bamboo fragrance board. Bamboo shavings are approximately rectangular in shape, and their dimensions include length, width and thickness. By selecting suitable aspect ratios and length-to-thickness ratios of shavings, it has a significant effect on the mechanical properties of bamboo boards, and the selection range of shavings is optimized, so that the particleboard has excellent mechanical properties.

[0035] Additional aspects and advantages of the present invention will be set forth in part in the following description, will become apparent from the following description, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0037] Figure 1 Flowchart of a method for selecting wood chips in one embodiment of the present invention;

[0038] Figure 2 This is a schematic diagram of the first RVE model structure in one embodiment of the present invention;

[0039] Figure 3 is a stress cloud diagram in one embodiment of the present invention;

[0040] Figure 4 is a graph showing a change in elastic modulus versus volume fraction of bamboo shavings in one embodiment of the present invention;

[0041] Figure 5 is a graph showing a change in elastic modulus versus aspect ratio of bamboo shavings in one embodiment of the present invention;

[0042] Figure 6 is a graph showing the change in elastic modulus with the size of square bamboo shavings in one embodiment of the present invention;

[0043] Figure 7 is a graph of aspect ratio-elastic modulus in one embodiment of the present invention;

[0044] Figure 8 is a graph of aspect ratio-elastic modulus in one embodiment of the present invention;

[0045] Figure 9 is a force-displacement curve diagram under different aspect ratios in one embodiment of the present invention;

[0046] Figure 10 The force-displacement curves of square particles of different sizes in one embodiment of the present invention;

[0047] Figure 11 A diagram of a three-dimensional random particle model in one embodiment of the present invention;

[0048] Figure 12 A three-dimensional damage cloud map in one embodiment of the present invention;

[0049] Figure 13 is a graph showing internal bonding strength at different aspect ratios in one embodiment of the present invention;

[0050] Figure 14 1 is a graph showing the internal bonding strength at different aspect ratios in an embodiment of the present invention. DETAILED DESCRIPTION

[0051] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0052] like Figure 1 As shown, the present invention provides a method for selecting wood chips, comprising the following steps:

[0053] Establish the first RVE model of a two-dimensional representative volume unit with random particle distribution;

[0054] Apply strain in the horizontal and vertical directions of the first RVE model to obtain stress cloud diagrams of horizontal loading and vertical loading;

[0055] Based on the stress cloud map, a first mathematical model is used to calculate the volume average modulus to obtain the elastic modulus in the x-direction and the y-direction of particles of different sizes;

[0056] Using the second mathematical model, the particles of different sizes that meet the second mathematical model are selected and form a first observation group;

[0057] The statistical analysis of the first observation group resulted in the selected range of length and width of the rectangular wood shavings.

[0058] Further improvements include the following steps:

[0059] Establish a second RVE model consisting of a two-dimensional representative volume unit with random particle distribution and glue;

[0060] Applying stress to the second RVE model, the first and second curve groups of force-displacement for rectangular particles with different aspect ratios and sizes are obtained respectively;

[0061] The selected value ranges of the length and width of the rectangular shavings are combined with the first curve group and the second curve group to obtain a first composite selected value range of the length and width of the rectangular shavings.

[0062] Preferably, the elastic modulus of the rectangular wood chips is set to 21.4 GPa, the tensile strength is 482 MPa, the density is 1.49 g / cm³, the Poisson's ratio is 0.23, and the fracture energy is 0.48 J / mm; the elastic modulus of the glue is set to 3200 GPa, the tensile strength is 7 MPa, the density is 1.19 g / cm³, the Poisson's ratio is 0.35, and the fracture energy is 0.08 J / mm.

[0063] Another improvement further includes the following steps:

[0064] A three-dimensional model of a pixel grid is established, and stress is applied to the three-dimensional model along three mutually perpendicular directions to obtain a second observation group with different aspect ratios and length-to-thickness ratios;

[0065] Statistical analysis was performed on the second observation group to obtain the value ranges of the aspect ratio and the aspect ratio of the rectangular wood chips;

[0066] The selected value ranges of the length and width of the rectangular shavings are combined with the selected value ranges of the aspect ratio and length-to-width ratio of the rectangular shavings to obtain the selected value ranges of the length, width and thickness of the rectangular shavings.

[0067] A further improvement of this embodiment further includes the following steps:

[0068] A tensile load is applied in a direction perpendicular to the particle board until the particle board is destroyed, and a third curve group and a fourth curve group of internal bonding strengths with different aspect ratios and length-to-thickness ratios are obtained respectively through a third mathematical model;

[0069] The dimension selection ranges of the length, width and thickness of the rectangular shavings are combined with the third curve group and the fourth curve group to obtain a second composite selection range of the length, width and thickness of the rectangular shavings.

[0070] As another improvement of this embodiment, the following steps are further included:

[0071] The first RVE model is used to obtain the variation relationship of shear modulus with different aspect ratios and thicknesses;

[0072] The dimension selection ranges of the length, width and thickness of the rectangular shavings are compounded with the variation relationship of the shear modulus to obtain a third compound selection range of the length, width and thickness of the rectangular shavings.

[0073] Preferably, the side length ratio of the rectangular particles in the first RVE model is greater than 24.

[0074] In actual operation, multiple RVE models are established, and the average coefficient of variation of the nearest neighbor distance of several RVE models is compared. The RVE model with the smallest average coefficient of variation of the nearest neighbor distance is selected as the first RVE model.

[0075] In the operation implementation, applying strain in the horizontal direction and the vertical direction of the first RVE model respectively to obtain stress cloud diagrams of horizontal loading and vertical loading includes:

[0076] Setting the elastic modulus of the wood chips =21.4GPa, Poisson's ratio =0.23; the adhesive is resin glue, and its elastic modulus =3200MPa, Poisson's ratio =0.35.

[0077] In addition, the second mathematical model includes the elastic modulus and volume component ratio of the wood chips and glue; the elastic modulus of the wood chips is set =21.4GPa, the volume component ratio of the wood chips =0.3, the elastic modulus of the glue =3200MPa, the volume component ratio of the glue =0.7.

[0078] A particleboard composite board comprises two surface boards and particleboards obtained by the particleboard selection method as described above, wherein the particleboards are adhered to each other in a stacked manner to form a sandwich board, and the sandwich board is adhered between the two surface boards.

[0079] The specific implementation process is to treat bamboo shavings as rectangular particles in a two-dimensional state. Use professional graphics software Digimat to generate a two-dimensional representative volume unit RVE (i.e., the first RVE model) with random particle distribution, as shown in the following figure: Figure 2 shown.

[0080] To obtain a valid RVE, the ratio of the particle characteristic dimension (the long side of the rectangle) to the RVE side length was ensured to be greater than 24. The generated RVEs were statistically analyzed, and the average coefficient of variation of the nearest neighbor distance was used to assess the randomness and uniformity of the model. Among the multiple RVEs generated, the model with the smallest average coefficient of variation of the nearest neighbor distance was selected as the RVE for the numerical simulation.

[0081] The equivalent elastic modulus of the bamboo shavings was analyzed. The finite element simulation method was used to apply stress or strain to the RVE model. Then, the mean field homogenization method was used to solve the effective performance of the composite material. It was assumed that the model was always in a linear elastic and plane strain state during the deformation process, and the bamboo shavings particles and the binder were ideally bonded. A four-node linear plane strain element (CPE4) was used. The elastic modulus of the bamboo shavings was obtained by experimental testing. =21.4GPa, Poisson's ratio =0.23; the adhesive is resin glue, and its elastic modulus =3200MPa, Poisson's ratio =0.35.

[0082] To obtain the elastic modulus in the x-direction and y-direction, a 0.5% strain in the horizontal direction and a 0.5% strain in the vertical direction can be applied to the left side of the RVE, respectively. or Distribution Figure 3 shown.

[0083] Depend on Figure 3 From the stress cloud diagram, we can see that the stress distribution under the two loading methods is obviously different. Particles with a smaller angle with the loading direction will bear greater stress.

[0084] For 2D models, the volume average modulus can be expressed as the volume average stress and the corresponding volume average strain, so the equivalent elastic modulus can be calculated using the following formula:

[0085] (3-1)

[0086] in, N Indicates the number of divided units, and Respectively represent i Normal stress and normal strain of each element, Indicates the i The area of a unit.

[0087] Formula 3-1 is the first mathematical model.

[0088] The elastic modulus results of RVE at different particle sizes are shown in Table 3-1 and Figures 4 to 6 shown.

[0089] Table 3-1 Elastic modulus corresponding to different particle sizes

[0090]

[0091] Note: 1 represents the elastic modulus of RVE along the x direction; 2 represents the elastic modulus of RVE along the y direction; particle size is length × width

[0092] from Figure 4 It can be seen that the elastic modulus values measured in the x-direction and the y-direction are very close, indicating that the particle distribution uniformity of the RVE model is good.

[0093] From Table 3-1 and Figure 4 It can be seen that the elastic modulus increases nonlinearly with the increase in the volume fraction of bamboo shavings. When the volume fraction of bamboo shavings increases from 5% to 37%, the elastic modulus increases from 3064MPa to 6038MPa, nearly doubling. This shows that the volume fraction of bamboo shavings has a significant impact on the overall elastic modulus.

[0094] According to the micromechanics of composite materials, the Voigt hypothesis and the Reuss hypothesis can be used to determine the upper and lower limits of the equivalent elastic modulus of composite materials, respectively.

[0095] According to the Voigt hypothesis, the equivalent elastic modulus of the bamboo fragrance board can be calculated as follows:

[0096] (3-2)

[0097] According to the Reuss hypothesis, the equivalent elastic modulus of the bamboo fragrance board can be calculated as follows:

[0098] (3-3)

[0099] Among them, E represents the equivalent elastic modulus of the bamboo fragrance board, 、 are the elastic moduli of bamboo shavings and glue, 、 are the volume component ratios of bamboo shavings and glue, respectively.

[0100] Pick =21.4GPa, =0.3, =3200MPa, =0.7, according to formula (3-2) and (3-3), the equivalent elastic modulus is 4296MPa< E <8660MPa, which is the second mathematical model. As can be seen from Table 3-1, when the bamboo shavings component ratio is 30%, the equivalent elastic modulus is within this range, which is the first observation group.

[0101] When the particle volume fraction is the same, the elastic modulus values corresponding to different aspect ratios are as follows: Figure 4 and Figure 5 As shown in Table 3-1 and Figure 5 It can be seen that when the volume fraction of bamboo shavings remains unchanged, the elastic modulus increases significantly with the increase of aspect ratio. Figure 6 It can be seen that for square wood chips, the equivalent elastic modulus increases slightly with the increase of the side length of the wood chips.

[0102] Conclusion: Numerical simulation results of the 2D model show that the elastic modulus increases significantly with increasing aspect ratio. However, for square shavings with equal length and width, the elastic modulus remains essentially unchanged after the side length exceeds 10 mm. Therefore, it is advisable to use a bamboo shaving width similar to the bamboo wall thickness (5 mm to 10 mm).

[0103] Taking advantage of the cuboid feature of the particles, they are divided into pixel grids and loaded along three mutually perpendicular directions to obtain the elastic moduli in different directions.

[0104] Keeping the width of bamboo shavings particles constant, the effects of different aspect ratios on the equivalent elastic modulus of bamboo particleboard were analyzed. The results are shown in Table 3-2 and Figure 7 shown.

[0105] Table 3-2 Elastic modulus simulation results under different aspect ratios

[0106]

[0107] The results show that the larger the aspect ratio, the higher the elastic modulus in all three directions. However, when the aspect ratio exceeds 24, the increase in the elastic modulus caused by the increase in the aspect ratio gradually slows down.

[0108] Table 3-3 and Figure 8 The effects of different aspect ratios on the elastic modulus are given.

[0109] Table 3-3 Elastic modulus test results at different aspect ratios

[0110]

[0111] Tables 3-2 and 3-3 are for the second observation group.

[0112] The results show that when the aspect ratio of the particles increases, the equivalent elastic modulus of the material will increase accordingly, but when the aspect ratio exceeds 2.4, the increase in the equivalent elastic modulus caused by the increase in the aspect ratio gradually slows down.

[0113] The static flexural strength of bamboo particleboard was analyzed. Bamboo particleboard is a brittle material, and its static flexural strength is primarily determined by its tensile fracture properties. Therefore, by simulating and analyzing the tensile fracture values of bamboo particleboard, we indirectly analyzed the influence of bamboo particle morphology on its static flexural strength. A two-dimensional model (i.e., the second RVE model) consisting of bamboo particles and glue was established. The bamboo particles were treated as an elastic-brittle material, and their damage was determined using the maximum principal stress criterion. The glue was treated as a viscoelastic material, and the cohesive constitutive model was used as the damage model, with the quadratic stress criterion used as the damage criterion. The performance parameters of the two materials are shown in Tables 3-4 and 3-5.

[0114] Table 3-4 Performance parameters of bamboo particles

[0115]

[0116] Table 3-5 Mechanical properties of adhesives[7]

[0117]

[0118] Figure 9 The force-displacement curves of the 2D RVE at different aspect ratios (i.e., the first curve group) are shown. As can be seen from the figure, as the aspect ratio increases, both the tensile fracture strength and fracture toughness decrease.

[0119] Figure 10 The force-displacement curves for different square particle sizes (i.e., the second set of curves) are presented. As can be seen, the ultimate strengths for the three types of particles are similar. For particles with the same aspect ratio, larger particle sizes result in smaller displacements at fracture. This is because larger particles, with the same volumetric composition ratio, have smaller spacing between bamboo shavings, leading to more pronounced stress concentration. This results in higher localized stresses, making crack initiation and fracture more likely.

[0120] Combine Figure 9 and Figure 10 It can be seen that the length and width of bamboo shavings should be close, and the length and width should not be too large, which is conducive to improving the fracture strength and fracture toughness of RVE.

[0121] The internal bonding strength of the wood chip is analyzed. The bonding strength refers to the bonding strength or bonding quality between the wood chips or fibers on the surface layer of the board and the underlying material (undecorated board) or between the facing material and the base material (decorated board). It is calculated by the ratio of the maximum destructive tensile force of the surface layer perpendicular to the board surface to the bonding area of the specimen. The calculation formula is as follows:

[0122] (3-2)

[0123] in, Indicates the internal bonding strength of the specimen, It represents the maximum load that the specimen can withstand before failure. A Indicates the area of the glue-applied surface.

[0124] By applying a tensile load in the direction perpendicular to the particle board, it causes tensile failure and thus obtains its internal bonding strength.

[0125] The random algorithm in Digimat is used to generate a three-dimensional bamboo shavings model diagram, such as Figure 11 To ensure continuity of stress transfer between the matrix and the bamboo shavings, the mesh was created with shared nodes between the bamboo shavings and the binder. Steel plates were applied to the upper and lower surfaces, using quadratic tetrahedral elements (C3D10) with a 1mm element size. Cohesive elements were globally inserted to simulate fracture failure, using a four-node three-dimensional bonded element (COH3D6).

[0126] Figure 12 The damage cloud diagram of the 3D model shows that under the tensile load along the thickness direction, damage mainly occurs in the matrix, and cracks propagate along the particle boundaries and in the matrix, causing damage to the boundaries and the matrix.

[0127] Figure 13 The vertical force-displacement curves for different aspect ratios (i.e., the third curve group) are shown. As can be seen, the ultimate load changes significantly with changes in aspect ratio, with larger aspect ratios exhibiting greater ultimate bearing capacity. When the aspect ratio increases from 8.33 to 25, the internal bond strength increases by 5.06%.

[0128] Figure 14 The vertical force-displacement curves for different aspect ratios (i.e., the fourth curve group) are given. As can be seen from the figure, the ultimate load remains essentially unchanged under different aspect ratios. When the aspect ratio increases from 1 to 5, the internal bond strength only increases by 1.41%.

[0129] Therefore, the comparison Figure 13 and Figure 14 It is found that the effect of aspect ratio on internal bonding strength is greater than that of length-to-width ratio.

[0130] The nail holding force of wood chips was analyzed, and a numerical simulation method similar to the analysis of equivalent elastic modulus was used to obtain the shear modulus at different aspect ratios and thicknesses, as shown in Tables 3-6 and 3-7. Among them, G12 represents the shear modulus within the plane, which is related to the nail holding force of the board edge; G13 and G13 represent the shear modulus in the plane parallel to the thickness direction, which is related to the nail holding force of the board surface.

[0131] Table 3-6 Shear modulus of different aspect ratios

[0132]

[0133] Table 3-7 Shear modulus of different thicknesses

[0134]

[0135] It can be seen from the data in Table 3-6 that G12 increases with the decrease of aspect ratio, while the out-of-plane shear moduli G13 and G23 decrease with the decrease of aspect ratio, but the change of G12 with aspect ratio is greater than that of the out-of-plane shear modulus; it can be seen from the data in Table 3-7 that G12 decreases with the increase of flake thickness, while the out-of-plane shear moduli G13 and G23 remain basically unchanged with the change of flake thickness.

[0136] It can be seen that the nail holding force of the board surface is not significantly affected by the morphology of bamboo shavings, but bamboo shavings with equal length and width and thinness are beneficial to improving the nail holding force of the board edge.

[0137] In summary, (1) both the aspect ratio and the length-to-thickness ratio have a significant effect on the elastic modulus. The larger the aspect ratio or the length-to-width ratio, the higher the elastic modulus in all three directions. When the aspect ratio exceeds 24, the increase in the elastic modulus caused by the increase in the aspect ratio gradually slows down; when the aspect ratio exceeds 2.4, the increase in the equivalent elastic modulus caused by the increase in the aspect ratio gradually slows down.

[0138] (2) The length and width have a significant impact on tensile strength. To improve static bending strength, the length-to-width ratio should be as equal as possible.

[0139] (3) The aspect ratio has little effect on the internal bonding strength, while the thickness has a more significant effect on the internal bonding strength. The thinner the wood shavings, the higher the internal bonding strength.

[0140] (4) The length-to-thickness ratio and the length-to-width ratio mainly affect the nail holding strength of the board edge, and have little effect on the nail holding strength of the board surface. Thin bamboo shavings with equal length and width are conducive to improving the nail holding strength of the board edge.

[0141] The above descriptions are only partial embodiments of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for selecting wood chips, characterized in that: The following steps are involved: Establish the first RVE model of a two-dimensional representative volume unit with random particle distribution; Apply strain in the horizontal and vertical directions of the first RVE model to obtain stress cloud diagrams of horizontal loading and vertical loading; Based on the stress cloud map, a first mathematical model is used to calculate the volume average modulus to obtain the elastic modulus in the x-direction and the y-direction of particles of different sizes; Using the second mathematical model, the particles of different sizes that meet the second mathematical model are selected and form a first observation group; The statistical analysis of the first observation group resulted in the selected range of length and width of the rectangular wood shavings.

2. The wood chip selection method according to claim 1, wherein: The following steps are also included: Establish a second RVE model consisting of a two-dimensional representative volume unit with random particle distribution and glue; Applying stress to the second RVE model, the first and second curve groups of force-displacement for rectangular particles with different aspect ratios and sizes are obtained respectively; The selected value ranges of the length and width of the rectangular shavings are combined with the first curve group and the second curve group to obtain a first composite selected value range of the length and width of the rectangular shavings.

3. The wood chip selection method according to claim 2, wherein: The elastic modulus of the rectangular wood chips is set to 21.4 GPa, the tensile strength is 482 MPa, the density is 1.49 g / cm³, the Poisson's ratio is 0.23, and the fracture energy is 0.48 J / mm; the elastic modulus of the glue is set to 3200 GPa, the tensile strength is 7 MPa, the density is 1.19 g / cm³, the Poisson's ratio is 0.35, and the fracture energy is 0.08 J / mm.

4. The wood chip selection method according to claim 1, wherein: The following steps are also included: A three-dimensional model of a pixel grid is established, and stress is applied to the three-dimensional model along three mutually perpendicular directions to obtain a second observation group with different aspect ratios and length-to-thickness ratios; Statistical analysis was performed on the second observation group to obtain the value ranges of the aspect ratio and the aspect ratio of the rectangular wood chips; The selected value ranges of the length and width of the rectangular shavings are combined with the selected value ranges of the aspect ratio and length-to-width ratio of the rectangular shavings to obtain the selected value ranges of the length, width and thickness of the rectangular shavings.

5. The wood chip selection method according to claim 4, wherein: The following steps are also included: A tensile load is applied in a direction perpendicular to the particle board until the particle board is destroyed, and a third curve group and a fourth curve group of internal bonding strengths with different aspect ratios and length-to-thickness ratios are obtained respectively through a third mathematical model; The dimension selection ranges of the length, width and thickness of the rectangular shavings are combined with the third curve group and the fourth curve group to obtain a second composite selection range of the length, width and thickness of the rectangular shavings.

6. The wood chip selection method according to claim 4, characterized in that: The following steps are also included: The first RVE model is used to obtain the variation relationship of shear modulus with different aspect ratios and thicknesses; The dimension selection ranges of the length, width and thickness of the rectangular wood chip are compounded with the variation relationship of the shear modulus to obtain a third compound selection range of the length, width and thickness of the rectangular wood chip.

7. The wood chip selection method according to claim 1, wherein: The side length ratio of the rectangular particles in the first RVE model is greater than 24.

8. The wood chip selection method according to claim 1, wherein: Multiple RVE models were established, and the average coefficient of variation of the nearest neighbor distances of several RVE models was compared. The RVE model with the smallest coefficient of variation of the average nearest neighbor distances was selected as the first RVE model.

9. The wood chip selection method according to claim 1, wherein: The step of applying strain in the horizontal direction and the vertical direction of the first RVE model to obtain stress cloud diagrams of horizontal loading and vertical loading includes: Setting the elastic modulus of the wood chips =21.4GPa, Poisson's ratio =0.23; the adhesive is resin glue, and its elastic modulus =3200MPa, Poisson's ratio =0.

35.

10. A particleboard composite board comprising two surface boards, characterized in that: It also includes shavings obtained by the shavings selection method according to any one of claims 1 to 9, wherein the shavings are adhered to each other in a stacked manner to form a sandwich panel, and the sandwich panel is adhered between two surface panels.

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