Structural slab for bamboo engineering and preparation method of structural slab

Abstract

The invention relates to the technical field of engineering wood products, and discloses a structural slab for bamboo engineering and a preparation method thereof.The structural slab comprises (n + 1) bamboo flaking layers and n reinforcing layers arranged between the adjacent bamboo flaking layers, the total number of the layers is 2n + 1, the included angle between the direction of the bamboo flaked fiber in the bamboo flaked layer and the direction of the bamboo flaked fiber in the adjacent bamboo flaked layer is 180 / n degrees, and n is not less than 3; the reinforcing layer comprises a plurality of heat transfer conducting bars arranged at intervals and a plurality of reinforcing areas separated by the heat transfer conducting bars, and the reinforcing areas are made of wood flakes; the structural slab is prepared by directionally paving the bamboo flaked layer and the reinforcing layer and carrying out hot press molding on the bamboo flaked layer and the reinforcing layer. According to the plate, the bamboo flakes are adopted as the main base material, the uniformity of the performance of the plate can be effectively enhanced through the design of the specific angle and the structure, and the rolling shear damage phenomenon of a conventional CLT plate is avoided to a certain degree.

Description

Technical Field

[0001] This invention relates to the technical field of engineered wood products, and in particular to a bamboo-based structural board for engineering applications and its preparation method. Background Technology

[0002] Cross-laminated timber (CLT) is an engineered wood product made of three or more layers of wood veneers glued together with adjacent layers having grain patterns at a certain angle. Compared with traditional wood products, CLT's unique veneer structure allows the performance advantages of wood to be fully utilized. It has better dimensional stability and superior in-plane and out-of-plane properties, and is often used as floor and wall panels in modern bamboo and wood structure buildings.

[0003] Patent CN114541644A discloses a pure solid wood orthogonal laminated timber (CLT), comprising orthogonally assembled and glued parallel layers and transverse layers located between adjacent parallel layers. The parallel layers are relatively hard solid wood layers, and each parallel layer has a substantially uniform density and thickness. The transverse layers are relatively soft solid wood layers, and each transverse layer also has a substantially uniform density and thickness. The thickness of each transverse layer is greater than 50% of the sum of the thicknesses of its two adjacent parallel layers. However, while CLT possesses excellent mechanical properties, its processing requires a large amount of solid wood sawn timber, and the sawn timber yield is only about 60%, resulting in relatively low resource utilization. Furthermore, wood is prone to rolling shear failure under radial and tangential stresses. Consequently, under out-of-plane loads, the transverse layers of CLT, which uses solid wood sawn timber as its base material, are also susceptible to rolling shear failure, leading to CLT performance not being fully realized and thus severely restricting its engineering applications. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a bamboo-based structural panel for engineering and its preparation method. It uses bamboo shavings as the main substrate, reducing costs and dependence on timber resources. Furthermore, by improving the preform structure of cross-laminated timber (CLT) and adding reinforcing materials to avoid the rolling shear failure mode of conventional CLT, this invention promotes the application of novel structural panels in modern bamboo engineering.

[0005] The objective of this invention is achieved through the following technical solution: In a first aspect, the present invention provides a bamboo-based structural panel for engineering, comprising n+1 layers of bamboo shavings and n reinforcing layers disposed between adjacent bamboo shavings, for a total of 2n+1 layers. The angle between the direction of the bamboo shaving fibers in the bamboo shavings layer and the direction of the bamboo shaving fibers in the adjacent bamboo shavings layer is 180 / n°, where n is not less than 3. The reinforcing layers include a plurality of heat-conducting strips disposed at intervals and a plurality of reinforcing regions separated by the heat-conducting strips. The reinforcing regions are made of wood shavings. The structural panel is obtained by oriented laying and hot pressing of the bamboo shavings layers and the reinforcing layers.

[0006] This invention uses bamboo shavings as the main substrate. Compared with wood, bamboo has stronger mechanical properties. Processing bamboo into shaving units improves its workability, increases board processing efficiency, and fully utilizes the mechanical strength of bamboo. Furthermore, wood is prone to shrinkage and swelling due to moisture, and defects such as knots in the plywood affect the performance stability of the final CLT (Continuous Laminate Threshold) board. The shaving morphology of bamboo effectively reduces the impact of shrinkage and swelling on the dimensional stability of the finished board. Moreover, bamboo, due to its material properties and shaving morphology, is less susceptible to rolling shear failure. In addition, controlling the fiber angle between adjacent shaving layers (<90°) effectively enhances the uniformity of board performance, ensuring similar mechanical properties in both in-plane directions. This also prevents the interlayer shear stress from being perpendicular to the bamboo shaving fiber direction under out-of-plane loads, effectively avoiding rolling shear failure and thus fully utilizing the strength of the upper and lower surface layers.

[0007] Furthermore, to improve the density and bonding performance between layers and enhance the load-bearing capacity of the board, a reinforcing layer is set between each layer. The reinforcing area in the reinforcing layer is made of wood. Therefore, the middle layers may experience rolling shear failure. By controlling the thickness of the layers and the fiber angle, this rolling shear failure can be avoided to some extent. Additionally, heat transfer strips with fixed spacing are set in the reinforcing layer to enhance the heat transfer rate of the board during hot pressing. This eliminates the need for pre-hot pressing each layer and then secondary cold pressing and gluing, allowing for direct hot pressing within the maximum preform thickness.

[0008] Preferably, the bamboo shavings have a thickness of 0.7~0.9mm, a width of 10~30mm, and a length of 100~150mm; the moisture content of the bamboo shavings is 8~12%.

[0009] Since the shape of bamboo shavings has a significant impact on the physical and mechanical properties of the finished board, larger bamboo shavings have good bending strength and plasticity, which is beneficial to improving the mechanical properties of the finished board. However, bamboo shavings that are too large are more likely to have gaps due to "bridging", resulting in lower density. Using bamboo shavings with the size specified in this invention can achieve higher mechanical properties of the board.

[0010] Preferably, the thickness of the bamboo shavings is 12-18 mm.

[0011] Preferably, the wood shavings have a thickness of 0.3~0.7mm, a width of 10~30mm, and a length of 100~150mm; the moisture content of the wood shavings is 6~8%.

[0012] Preferably, the thickness of the reinforcing layer is 2-5 mm.

[0013] Preferably, the width of the heat transfer strip is 20-50 mm, and the spacing between adjacent heat transfer strips is 300-1300 mm; more preferably, the heat transfer strip is disposed at the corresponding position of the joist, and the spacing between adjacent heat transfer strips is 305 mm, 406 mm, 610 mm or 1220 mm.

[0014] To reduce the impact of heat transfer strips on the performance of the structural panel in actual engineering, the heating strip area is positioned at the joist location, and the spacing between the two strips is taken from the joist spacing commonly used in wooden structures.

[0015] Preferably, the material used for the heat transfer strip is at least one of rubber material, silicone material and silicone grease material containing a thermally conductive medium; more preferably, the heat transfer strip is made of aluminum flexible plate, thermally conductive silicone sheet, rubber thermally conductive sheet or thermally conductive silicone grease sheet.

[0016] The heat transfer strips are made of materials that have thermal conductivity and do not affect the processing performance of the finished board.

[0017] Secondly, the present invention also provides a method for preparing a bamboo-based structural panel for engineering applications, comprising the following steps: (1) Applying glue: Apply glue to bamboo shavings and wood shavings separately; (2) Oriented installation: The bamboo shavings after applying glue are used as the bamboo shaving layer; the wood shavings after applying glue are used as the reinforcement area, and separated by heat transfer strips as the reinforcement layer; the bamboo shaving layer and the reinforcement layer are oriented to obtain the board blank; (3) Hot pressing: The slab is hot pressed once.

[0018] As a preferred method, the bamboo shavings are applied using atomized spraying, with the amount of adhesive applied being 10-15% of the oven-dry weight of the bamboo shavings.

[0019] Preferably, the wood shavings are glued, with the amount of glue being 5-10% of the oven-dry weight of the wood shavings.

[0020] Preferably, the adhesive used for applying the adhesive is a phenolic resin adhesive or an isocyanate adhesive (MDI).

[0021] Preferably, the hot pressing pressure is not less than 4 MPa, the temperature is 160~200℃, and the speed is 60~75 s / mm.

[0022] Compared with the prior art, the present invention has the following beneficial effects: (1) The board uses bamboo shavings as the main substrate, which has a more flexible assembly processing method and can realize assembly design at a specific angle; through the design of specific angles and structures, the uniformity of the board performance can be effectively enhanced, and to a certain extent, the rolling shear failure phenomenon of conventional CLT boards can be avoided. (2) The reinforcing layer set between adjacent bamboo shaving layers can effectively improve the overall uniformity of the board and the connection performance of adjacent bamboo shaving layers; (3) The heat-conducting strips set in the reinforcing layer can enhance the heat transfer efficiency of the plate in hot pressing and realize the one-time hot pressing of the thick plate. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure plate in this invention.

[0024] Figure 2 This is a schematic diagram of the angle design between adjacent bamboo shaving layers in Example 1.

[0025] The attached figures are labeled as follows: 1. Bamboo shaving layer; 101. Surface bamboo shaving; 102. Secondary bamboo shaving; 103. Third bamboo shaving; 2. Reinforcing layer; 201. Reinforcing area; 202. Heat transfer strip. Detailed Implementation

[0026] The technical solution of the present invention will be illustrated below with specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0027] The preparation method of the bamboo-based structural panel for engineering in this invention includes the following steps: (1) Preparation of bamboo shavings and wood shavings: Bamboo shavings with a moisture content of 8~12% are obtained through processes such as sawing raw bamboo, shaving bamboo tubes, and drying shavings. The dimensions are: thickness 0.7~0.9mm, width 10~30mm, and length 100~150mm. Wood shavings with a moisture content of 6~8% are obtained through processes such as peeling wood and planing wood shavings. The dimensions are: thickness 0.3~0.7mm, width 10~30mm, and length 100~150mm. (2) Applying glue: Apply glue to bamboo shavings and wood shavings separately; apply glue to bamboo shavings by atomizing the glue, with the amount of glue being 10-15% of the oven-dry weight of the bamboo shavings; apply glue to wood shavings by atomizing the glue, with the amount of glue being 5-10% of the oven-dry weight of the wood shavings; (3) Oriented installation: The shavings after applying glue are used as the bamboo shaving layer; the wood shavings after applying glue are used as the reinforcement area, and are separated by heat transfer strips as the reinforcement layer. The heat transfer strips are set at intervals, with a spacing of 300~1300mm between adjacent heat transfer strips and a width of 20~50mm. The bamboo shaving layer and the reinforcement layer are oriented to obtain a board blank. The board blank includes n+1 layers of bamboo shavings and n layers of reinforcement layers set between adjacent bamboo shaving layers. The total number of layers is 2n+1. The thickness of the bamboo shaving layer is 12~18mm, the thickness of the reinforcement layer is 2~5mm, and the angle between the direction of the bamboo shaving fibers in the bamboo shaving layer and the direction of the bamboo shaving fibers in the adjacent bamboo shaving layer is 180 / n°, where n is not less than 3. (4) Hot pressing: The board blank is hot pressed once using a large-format press (8 feet * 64 feet) at a pressure of not less than 4 MPa, a temperature of 160~200℃, and a time of 60~75 s / mm to obtain a bamboo structural board for engineering, with a design density of 850 kg / m³. 3 .

[0028] In a specific embodiment of the present invention, the heat transfer strip is made of aluminum flexible plate, thermally conductive silicone sheet, rubber thermally conductive sheet or thermally conductive silicone grease sheet.

[0029] In a specific embodiment of the present invention, the heat transfer strip is made of thermally conductive silicone sheet, the heat transfer medium is aluminum oxide (Al2O3), the heat resistance temperature is -40~200℃, and the thermal conductivity is 5W / m∙k.

[0030] In a specific embodiment of the present invention, the adhesive used for applying the adhesive is a phenolic resin adhesive or an isocyanate adhesive (MDI).

[0031] Example 1 The preparation method of bamboo-based structural panels for engineering includes the following steps: (1) Preparation of bamboo shavings and wood shavings: Bamboo shavings with a moisture content of 8~12% are obtained through processes such as sawing raw bamboo, shaving bamboo tubes, and drying shavings. The dimensions are: thickness 0.7~0.9mm, width 10~30mm, and length 120mm. Wood shavings with a moisture content of 6~8% are obtained through processes such as peeling wood and planing wood shavings. The dimensions are: thickness 0.3~0.7mm, width 10~30mm, and length 120mm. (2) Glue application: Apply glue (isocyanate adhesive) to bamboo shavings by atomized spraying, with the amount of glue applied being 12% of the oven-dry weight of the bamboo shavings; apply glue (isocyanate adhesive) to wood shavings by atomized spraying, with the amount of glue applied being 8% of the oven-dry weight of the wood shavings; (3) Oriented installation: The bamboo shavings after applying glue are used as the bamboo shaving layer; the wood shavings after applying glue are used as the reinforcement area, and are separated by heat transfer strips (heat transfer silicone sheets) as the reinforcement layer. The heat transfer strips are set at intervals, with a spacing of 406mm between adjacent heat transfer strips and a width of 25mm. The bamboo shaving layer and the reinforcement layer are oriented to obtain a board blank. The board blank has 7 layers, the bamboo shaving layer has 4 layers, and the reinforcement layer has 3 layers. The thickness of the bamboo shaving layer is 15±0.2mm, and the thickness of the reinforcement layer is 2±0.2mm. (4) Hot pressing: The board blank is hot pressed in one step using a large-format press (8 feet * 64 feet) at a pressure of 4 MPa, a temperature of 180℃, and a speed of 75 s / mm to obtain a bamboo structural board for engineering, with a design density of 850 kg / m³. 3 .

[0032] like Figure 1 The diagram shows a structural panel for bamboo engineering applications. Bamboo shavings layer 1 and reinforcing layer 2 are alternately arranged, and the surface layer of the structural panel is entirely bamboo shavings layer 1. The angle between the direction of the bamboo shaving fibers in one bamboo shaving layer and the direction of the bamboo shaving fibers in the adjacent bamboo shaving layers is 60°. Figure 2 As shown, the angle between the fiber direction indicated by the arrow in the surface bamboo shavings 101 and the fiber direction indicated by the arrow in the second-layer bamboo shavings 102 is 60°, and the angle between the fiber direction indicated by the arrow in the second-layer bamboo shavings 102 and the fiber direction indicated by the arrow in the third-layer bamboo shavings 103 is 60°. Additionally, the reinforcing layer 2 includes spaced-apart reinforcing regions 201 and heat-conducting strips 202.

[0033] Example 2 The difference from Example 1 is that n takes the value of 4.

[0034] The preparation method of bamboo-based structural panels for engineering includes the following steps: (1) Preparation of bamboo shavings and wood shavings: Bamboo shavings with a moisture content of 8~12% are obtained through processes such as sawing raw bamboo, shaving bamboo tubes, and drying shavings. The dimensions are: thickness 0.7~0.9mm, width 10~30mm, and length 120mm. Wood shavings with a moisture content of 6~8% are obtained through processes such as peeling wood and planing wood shavings. The dimensions are: thickness 0.3~0.7mm, width 10~30mm, and length 120mm. (2) Glue application: Apply glue (isocyanate adhesive) to bamboo shavings by atomized spraying, with the amount of glue applied being 12% of the oven-dry weight of the bamboo shavings; apply glue (isocyanate adhesive) to wood shavings by atomized spraying, with the amount of glue applied being 8% of the oven-dry weight of the wood shavings; (3) Oriented installation: The bamboo shavings after applying glue are used as the bamboo shaving layer; the wood shavings after applying glue are used as the reinforcement area, and are separated by heat transfer strips (heat transfer silicone sheets) as the reinforcement layer. The heat transfer strips are set at intervals, the spacing between adjacent heat transfer strips is 406mm, and the width of the heat transfer strips is 25mm; the bamboo shaving layer and the reinforcement layer are oriented to obtain a board blank. The board blank has 9 layers, the bamboo shaving layer has 5 layers, and the reinforcement layer has 4 layers. The thickness of the bamboo shaving layer is 15±0.2mm, the thickness of the reinforcement layer is 2±0.2mm, and the angle between the direction of the bamboo shaving fibers in the bamboo shaving layer and the direction of the bamboo shaving fibers in the adjacent bamboo shaving layer is 45°. (4) Hot pressing: The board blank is hot pressed once by a large-format press (8 feet * 64 feet) at a pressure of 4 MPa, a temperature of 180℃ and a speed of 75 s / mm to obtain a bamboo engineering structural board.

[0035] Example 3 The difference from Example 1 is that the spacing and width of the heat transfer strips, as well as the thickness of the bamboo shavings layer and the reinforcing layer, are different.

[0036] The preparation method of bamboo-based structural panels for engineering includes the following steps: (1) Preparation of bamboo shavings and wood shavings: Bamboo shavings with a moisture content of 8~12% are obtained through processes such as sawing raw bamboo, shaving bamboo tubes, and drying shavings. The dimensions are: thickness 0.7~0.9mm, width 10~30mm, and length 120mm. Wood shavings with a moisture content of 6~8% are obtained through processes such as peeling wood and planing wood shavings. The dimensions are: thickness 0.3~0.7mm, width 10~30mm, and length 120mm. (2) Glue application: Apply glue (isocyanate adhesive) to bamboo shavings by atomized spraying, with the amount of glue applied being 12% of the oven-dry weight of the bamboo shavings; apply glue (isocyanate adhesive) to wood shavings by atomized spraying, with the amount of glue applied being 8% of the oven-dry weight of the wood shavings; (3) Oriented installation: The bamboo shavings after applying glue are used as the bamboo shaving layer; the wood shavings after applying glue are used as the reinforcement area, and are separated by heat transfer strips (heat transfer silicone sheets) as the reinforcement layer. The heat transfer strips are set at intervals, the spacing between adjacent heat transfer strips is 610mm, and the width of the heat transfer strips is 35mm; the bamboo shaving layer and the reinforcement layer are oriented to obtain a board blank. The board blank has 7 layers, the bamboo shaving layer has 4 layers, and the reinforcement layer has 3 layers. The thickness of the bamboo shaving layer is 17±0.2mm, the thickness of the reinforcement layer is 4±0.2mm, and the angle between the direction of the bamboo shaving fibers in the bamboo shaving layer and the direction of the bamboo shaving fibers in the adjacent bamboo shaving layer is 60°. (4) Hot pressing: The board blank is hot pressed once by a large-format press (8 feet * 64 feet) at a pressure of 4 MPa, a temperature of 180℃ and a speed of 75 s / mm to obtain a bamboo engineering structural board.

[0037] Comparative Example 1 The difference from Example 1 is that n takes the value of 2.

[0038] The preparation method of bamboo-based structural panels for engineering includes the following steps: (1) Preparation of bamboo shavings and wood shavings: Bamboo shavings with a moisture content of 8~12% are obtained through processes such as sawing raw bamboo, shaving bamboo tubes, and drying shavings. The dimensions are: thickness 0.7~0.9mm, width 10~30mm, and length 120mm. Wood shavings with a moisture content of 6~8% are obtained through processes such as peeling wood and planing wood shavings. The dimensions are: thickness 0.3~0.7mm, width 10~30mm, and length 120mm. (2) Glue application: Apply glue (isocyanate adhesive) to bamboo shavings by atomized spraying, with the amount of glue applied being 12% of the oven-dry weight of the bamboo shavings; apply glue (isocyanate adhesive) to wood shavings by atomized spraying, with the amount of glue applied being 8% of the oven-dry weight of the wood shavings; (3) Oriented installation: The bamboo shavings after applying glue are used as the bamboo shaving layer; the wood shavings after applying glue are used as the reinforcement area, and are separated by heat transfer strips (heat transfer silicone sheets) as the reinforcement layer. The heat transfer strips are set at intervals, the spacing between adjacent heat transfer strips is 406mm, and the width of the heat transfer strips is 35mm; the bamboo shaving layer and the reinforcement layer are oriented to obtain a board blank. The board blank has 5 layers, the bamboo shaving layer has 3 layers, and the reinforcement layer has 2 layers. The thickness of the bamboo shaving layer is 15±0.2mm, the thickness of the reinforcement layer is 2±0.2mm, and the angle between the direction of the bamboo shaving fibers in the bamboo shaving layer and the direction of the bamboo shaving fibers in the adjacent bamboo shaving layer is 90°. (4) Hot pressing: The board blank is hot pressed once by a large-format press (8 feet * 64 feet) at a pressure of 4 MPa, a temperature of 180℃ and a speed of 75 s / mm to obtain a bamboo engineering structural board.

[0039] Comparative Example 2 The difference from Example 1 is that it still has 7 layers, but the angle is 90°. The preparation method of bamboo-based structural panels for engineering includes the following steps: (1) Preparation of bamboo shavings and wood shavings: Bamboo shavings with a moisture content of 8~12% are obtained through processes such as sawing raw bamboo, shaving bamboo tubes, and drying shavings. The dimensions are: thickness 0.7~0.9mm, width 10~30mm, and length 120mm. Wood shavings with a moisture content of 6~8% are obtained through processes such as peeling wood and planing wood shavings. The dimensions are: thickness 0.3~0.7mm, width 10~30mm, and length 120mm. (2) Glue application: Apply glue (isocyanate adhesive) to bamboo shavings by atomized spraying, with the amount of glue applied being 12% of the oven-dry weight of the bamboo shavings; apply glue (isocyanate adhesive) to wood shavings by atomized spraying, with the amount of glue applied being 8% of the oven-dry weight of the wood shavings; (3) Oriented installation: The bamboo shavings after applying glue are used as the bamboo shaving layer; the wood shavings after applying glue are used as the reinforcement area, and are separated by heat transfer strips (heat transfer silicone sheets) as the reinforcement layer. The heat transfer strips are set at intervals, the spacing between adjacent heat transfer strips is 406mm, and the width of the heat transfer strips is 35mm; the bamboo shaving layer and the reinforcement layer are oriented to obtain a board blank. The board blank has 7 layers, the bamboo shaving layer has 4 layers, and the reinforcement layer has 3 layers. The thickness of the bamboo shaving layer is 15±0.2mm, the thickness of the reinforcement layer is 2±0.2mm, and the angle between the direction of the bamboo shaving fibers in the bamboo shaving layer and the direction of the bamboo shaving fibers in the adjacent bamboo shaving layer is 90°. (4) Hot pressing: The board blank is hot pressed once by a large-format press (8 feet * 64 feet) at a pressure of 4 MPa, a temperature of 180℃ and a speed of 75 s / mm to obtain a bamboo engineering structural board.

[0040] Comparative Example 3 The difference from Example 1 is that no heat transfer strips are provided in the reinforcement layer.

[0041] The preparation method of bamboo-based structural panels for engineering includes the following steps: (1) Preparation of bamboo shavings and wood shavings: Bamboo shavings with a moisture content of 8~12% are obtained through processes such as sawing raw bamboo, shaving bamboo tubes, and drying shavings. The dimensions are: thickness 0.7~0.9mm, width 10~30mm, and length 120mm. Wood shavings with a moisture content of 6~8% are obtained through processes such as peeling wood and planing wood shavings. The dimensions are: thickness 0.3~0.7mm, width 10~30mm, and length 120mm. (2) Glue application: Apply glue (isocyanate adhesive) to bamboo shavings by atomized spraying, with the amount of glue applied being 12% of the oven-dry weight of the bamboo shavings; apply glue (isocyanate adhesive) to wood shavings by atomized spraying, with the amount of glue applied being 8% of the oven-dry weight of the wood shavings; (3) Oriented installation: The shavings after applying glue are used as the bamboo shaving layer; the wood shavings after applying glue are used as the reinforcement layer; the bamboo shaving layer and the reinforcement layer are oriented to obtain a board blank. The board blank has 7 layers, the bamboo shaving layer has 4 layers, and the reinforcement layer has 3 layers. The thickness of the bamboo shaving layer is 15±0.2mm, the thickness of the reinforcement layer is 2±0.2mm, and the angle between the direction of the bamboo shaving fibers in the bamboo shaving layer and the direction of the bamboo shaving fibers in the adjacent bamboo shaving layer is 60°. (4) Hot pressing: The board blank is hot pressed once by a large-format press (8 feet * 64 feet) at a pressure of 4 MPa, a temperature of 180℃ and a speed of 200 s / mm to obtain a bamboo engineering structural board.

[0042] Comparative Example 4 The difference from Example 1 is that no reinforcement layer is provided.

[0043] The preparation method of bamboo-based structural panels for engineering includes the following steps: (1) Preparation of bamboo shavings: Through the process of sawing raw bamboo, shaving bamboo tubes, and drying shavings, bamboo shavings with a moisture content of 8~12% are obtained, with the following dimensions: thickness 0.7~0.9mm, width 10~30mm, and length 120mm; (2) Applying adhesive: Apply adhesive (isocyanate adhesive) to the bamboo shavings by atomizing spraying. The amount of adhesive applied is 12% of the oven-dry weight of the bamboo shavings. (3) Oriented laying: The shavings after gluing are laid in an oriented manner to obtain a board blank. The board blank consists of 7 layers, and the thickness of each layer of bamboo shavings is 15±0.2mm. The angle between the direction of the bamboo shavings fiber in the bamboo shavings layer and the direction of the bamboo shavings fiber in the adjacent bamboo shavings layer is 60°. (4) Hot pressing: The board blank is hot pressed once by a large-format press (8 feet * 64 feet) at a pressure of 4 MPa, a temperature of 180℃ and a speed of 200 s / mm to obtain a bamboo engineering structural board.

[0044] Comparative Example 5 The difference from Example 1 is that the size of the bamboo shavings is too large.

[0045] The preparation method of bamboo-based structural panels for engineering includes the following steps: (1) Preparation of bamboo shavings and wood shavings: Bamboo shavings with a moisture content of 8~12% are obtained through processes such as sawing raw bamboo, shaving bamboo tubes, and drying shavings. The dimensions are: thickness 1.1~1.3mm, width 40~50mm, and length 150mm. Wood shavings with a moisture content of 6~8% are obtained through processes such as peeling wood and planing wood shavings. The dimensions are: thickness 0.3~0.7mm, width 10~30mm, and length 120mm. (2) Glue application: Apply glue (isocyanate adhesive) to bamboo shavings by atomized spraying, with the amount of glue applied being 12% of the oven-dry weight of the bamboo shavings; apply glue (isocyanate adhesive) to wood shavings by atomized spraying, with the amount of glue applied being 8% of the oven-dry weight of the wood shavings; (3) Oriented installation: The bamboo shavings after applying glue are used as the bamboo shaving layer; the wood shavings after applying glue are used as the reinforcement area, and are separated by heat transfer strips (heat transfer silicone sheets) as the reinforcement layer. The heat transfer strips are set at intervals, the spacing between adjacent heat transfer strips is 406mm, and the width of the heat transfer strips is 25mm; the bamboo shaving layer and the reinforcement layer are oriented to obtain a board blank. The board blank has 7 layers, the bamboo shaving layer has 4 layers, and the reinforcement layer has 3 layers. The thickness of the bamboo shaving layer is 15±0.2mm, the thickness of the reinforcement layer is 2±0.2mm, and the angle between the direction of the bamboo shaving fibers in the bamboo shaving layer and the direction of the bamboo shaving fibers in the adjacent bamboo shaving layer is 60°. (4) Hot pressing: The board blank is hot pressed once by a large-format press (8 feet * 64 feet) at a pressure of 4 MPa, a temperature of 180℃ and a speed of 75 s / mm to obtain a bamboo engineering structural board.

[0046] Table 1 As shown in Table 1, the structural plate of the present invention can better avoid rolling shear failure under out-of-plane loads. Thus, Examples 1-3 can obtain higher static bending strength parallel to the grain compared to Comparative Examples 1-5, while ensuring high elastic modulus parallel to the grain and internal bond strength. The overall mechanical properties of the plate are good.

[0047] In Comparative Example 1, n is 2, resulting in a 5-layer board with 3 bamboo shaving layers and 2 reinforcing layers. The angle between the direction of the bamboo shaving fibers in the bamboo shaving layers and the direction of the bamboo shaving fibers in adjacent bamboo shaving layers is 90°. In Comparative Example 2, n is 3, resulting in a 7-layer board with 4 bamboo shaving layers and 3 reinforcing layers. However, the angle between the direction of the bamboo shaving fibers in the bamboo shaving layers and the direction of the bamboo shaving fibers in adjacent bamboo shaving layers is still 90°. The static bending strength, modulus of elasticity, and internal bond strength of the structural boards obtained in Comparative Examples 1-2 are all much lower than those in Example 1. This is mainly because the angle between the shaving fibers in adjacent bamboo shaving layers is large, affecting the uniformity of the board's properties and making the board prone to rolling shear failure, thus leading to poor mechanical properties of the structural board.

[0048] In Comparative Example 3, no heat transfer strips were included in the reinforcing layer, and in Comparative Example 4, no reinforcing layer was included. Therefore, both Comparative Examples 3 and 4 suffer from poor heat transfer efficiency during the hot-pressing process due to the lack of heat transfer strips, requiring longer hot-pressing times. Although extending the time ensures the board is formed in one hot-pressing step, the excessively low heat conduction rate causes the surface adhesive layer to cure first, followed by the core adhesive layer. This significant difference in curing rates between the core and surface layers leads to a decrease in the material's mechanical properties. Furthermore, in Comparative Example 4, the lack of alternating layers of wood as a reinforcing layer and bamboo shavings significantly affects the density and bonding performance between the bamboo shaving layers, further reducing the board's mechanical properties.

[0049] In Comparative Example 5, because larger bamboo shavings were used, gaps were more likely to form between the larger bamboo shavings due to "bridging," resulting in lower density and consequently a decrease in the mechanical properties of the resulting board.

[0050] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made using the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A bamboo-based structural panel for engineering applications, characterized in that, It includes n+1 layers of bamboo shavings and n reinforcing layers between adjacent bamboo shavings, for a total of 2n+1 layers. The angle between the direction of the bamboo shaving fibers in the bamboo shavings layer and the direction of the bamboo shaving fibers in the adjacent bamboo shavings layer is 180 / n°, and n is not less than 3. The reinforcing layer includes several heat-conducting strips spaced apart and several reinforcing regions separated by the heat-conducting strips. The reinforcing regions are made of wood shavings. The structural board is made by oriented laying and hot pressing of the bamboo shavings layer and the reinforcing layer.

2. The bamboo-based structural panel for engineering applications according to claim 1, characterized in that, The bamboo shavings have a thickness of 0.7~0.9mm, a width of 10~30mm, and a length of 100~150mm.

3. The bamboo-based structural panel for engineering applications according to claim 1 or 2, characterized in that, The thickness of the bamboo shavings is 12~18mm.

4. The bamboo-based structural panel for engineering applications according to claim 1, characterized in that, The wood shavings are 0.3-0.7 mm thick, 10-30 mm wide, and 100-150 mm long.

5. The bamboo-based structural panel for engineering applications according to claim 1 or 4, characterized in that, The thickness of the reinforcing layer is 2~5mm.

6. The bamboo-based structural panel for engineering applications according to claim 1, characterized in that, The width of the heat transfer strip is 20~50mm, and the spacing between adjacent heat transfer strips is 300~1300mm.

7. The bamboo-based structural panel for engineering applications according to claim 1 or 6, characterized in that, The heat transfer strip is made of at least one of the following materials: rubber, silicone, and silicone grease containing a heat-conducting medium.

8. A method for preparing a bamboo-based structural panel for engineering applications as described in any one of claims 1-7, characterized in that, Includes the following steps: (1) Applying glue: Apply glue to bamboo shavings and wood shavings separately; (2) Oriented installation: The bamboo shavings after applying glue are used as the bamboo shaving layer; the wood shavings after applying glue are used as the reinforcement area, and separated by heat transfer strips as the reinforcement layer; the bamboo shaving layer and the reinforcement layer are oriented to obtain the board blank; (3) Hot pressing: The slab is hot pressed once.

9. The method for preparing bamboo-based structural panels for engineering applications according to claim 8, characterized in that, Apply glue to bamboo shavings at a rate of 10-15% of their oven-dry weight; apply glue to wood shavings at a rate of 5-10% of their oven-dry weight.

10. The method for preparing bamboo-based structural panels for engineering applications according to claim 8 or 9, characterized in that, The hot pressing pressure is not less than 4 MPa, and the temperature is 160~200℃.

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