Energy-absorbing shock-reducing wood with gradient porosity structure and method for producing same

Abstract

The present application belongs to energy-absorbing shock-absorbing wood with gradient pore structure and its preparation method, and the energy-absorbing shock-absorbing wood comprises at least two layers of wood layers with different pore structures, wherein the porosity of the surface layer wood is 40-50%, the porosity of the intermediate layer wood is 50-70%, and the porosity of the core layer wood is 70-90%; the intermediate layer wood is one layer or several superimposed layers, the core layer wood is one layer or several superimposed layers, and the intermediate layer wood and the core layer wood can be alternately superimposed; the surface layer wood, the intermediate layer wood and the core layer wood can be alternately superimposed. The present application builds the pore gradient from the surface layer to the core by wood modification and gradient design of wood pores, realizes progressive collapse, and optimizes the strength and energy absorption; through the synergistic effect of gradient pore structure and chemical modification, the wood is endowed with high energy absorption, functionalization and controllable shock absorption performance.

Description

Technical Field

[0001] This invention relates to energy-absorbing and shock-absorbing wood with a gradient pore structure and its preparation method, which is suitable for energy-absorbing and shock-absorbing cushioning packaging, especially in fields with high safety requirements such as shock absorbers for nuclear fuel transport containers. Background Technology

[0002] Traditional energy-absorbing and vibration-damping materials suffer from problems such as high cost, non-degradability, high energy consumption, and poor temperature resistance. For example, metal honeycomb is heavy and prone to plastic deformation; polymer foam has poor radiation resistance and is prone to high-temperature failure. Gradient porous materials manufactured by chemical foaming or template methods are costly and have complex processes (such as requiring high-temperature sintering). Wood, on the other hand, is a graded porous solid honeycomb material composed of natural biomass polymers. It has environmental compatibility, including being renewable, carbon-fixing, having low processing energy consumption, low environmental pollution, and being biodegradable and recyclable. It also has high specific stiffness and specific strength, and can absorb a large amount of compressive energy through large plastic deformation under relatively low stress. It is lightweight and has good energy absorption, vibration damping, heat insulation, and sound absorption properties.

[0003] Currently, the filling material used in shock absorbers for spent nuclear fuel transport containers is mainly wood. Balsa wood has a higher energy absorption ratio along the grain than polyurethane foam and metal honeycomb materials, and its energy dissipation capacity is comparable to that of fiber-reinforced composite materials.

[0004] The number, size, shape, and distribution of pores in wood-based energy-absorbing and vibration-damping materials significantly influence their mechanical, deformation, and energy absorption properties. Energy absorption capacity increases with increasing porosity and pore size; however, excessively high porosity reduces overall strength and stiffness, requiring a trade-off. Different tree species and densities exhibit varying pore structures and energy absorption characteristics. Natural wood exhibits significant anisotropy, resulting in unstable energy absorption; randomly distributed pores make graded energy absorption difficult (e.g., differentiated responses to low-velocity and high-velocity impacts). A well-designed gradient porous structure can effectively improve the compression ratio and energy absorption efficiency of wood. Utilizing physical and / or chemical methods to regulate the composition and porous structure of wood can enhance its mechanical and energy absorption properties, while also endowing it with corrosion resistance, flame retardancy, fire resistance, and radiation resistance, enabling it to meet the demands of high-performance applications such as shock absorbers for large spent fuel transport containers.

[0005] However, there has been a lack of technology on how to construct an increasing pore gradient from the surface to the core within the wood to achieve gradual collapse and optimize strength and energy absorption in synergy. Through the synergistic effect of gradient pore structure and chemical modification, wood can be endowed with high energy absorption (high energy absorption value), functionalization (such as flame retardancy, corrosion resistance, and neutron absorption), and controllable shock absorption properties, thereby producing energy-absorbing and shock-absorbing wood that meets the multifunctional needs of multiple fields such as transportation, packaging, sports equipment, and aerospace. Summary of the Invention

[0006] The purpose of this invention is to design an energy-absorbing and shock-absorbing wood with a gradient pore structure and its preparation method. By modifying the wood and designing the gradient of the wood pores, a pore gradient that increases from the surface to the core is constructed inside the wood to achieve gradual collapse, thereby optimizing strength and energy absorption. Through the synergistic effect of the gradient pore structure and chemical modification, the wood is endowed with high energy absorption, functionalization and controllable shock absorption performance.

[0007] Therefore, the present invention provides an energy-absorbing and shock-absorbing wood with a gradient pore structure. 1. An energy-absorbing and shock-absorbing wood with a gradient pore structure, composed of wood, characterized in that: the shock-absorbing wood comprises at least two layers of wood with different pore structures, wherein the surface layer has a porosity of 40-50%, the intermediate layer has a porosity of 50-70%, and the core layer has a porosity of 70-90%; the intermediate layer is one layer or several layers stacked together, and the core layer is one layer or several layers stacked together; the intermediate layer and the core layer can be alternately stacked, and the surface layer, intermediate layer, and core layer can be alternately stacked together.

[0008] Shock-absorbing wood is composed of several layers of surface wood, intermediate wood, and core wood stacked one on top of the other, or staggered and alternating, assembled into a blank, impregnated with resin, and pressed and cured; or it is composed of several layers of surface wood, intermediate wood, and core wood stacked one on top of the other, or staggered and alternating, assembled into a blank, impregnated with liquid for modification, impregnated with resin, and pressed and cured.

[0009] The shock-absorbing wood contains ≥1wt% boron and ≥0.5wt% phosphorus.

[0010] As a further description of the above technical solution: the number of shock-absorbing wood layers is even or odd, with at least 2 layers for even-numbered layers and at least 1 layer for odd-numbered layers. The upper or lower surface, or both upper and lower surfaces, of the shock-absorbing wood are surface material, intermediate material, or core material, and the thickness of the same layer is the same.

[0011] As a further description of the above technical solution: the wood grain axes of the superimposed or alternately superimposed layers are set at 0° to 90° between the upper and lower adjacent layers, and the wood splicing joints of the upper and lower adjacent layers are set at 20° to 90° between the length and width.

[0012] A method for preparing energy-absorbing and shock-absorbing wood with a gradient pore structure, characterized by comprising the following steps:

[0013] (1) Obtaining wood with different porosities, including:

[0014] (a) By selecting woods with different densities, woods with different porosities can be obtained;

[0015] The porosity is 40-50% and the density of the surface material is above 0.65g / cm³. It includes oak, beech, walnut, ironwood, green sandalwood, four-oak wood, birch, ironwood, green bark, ebony, and teak.

[0016] The porosity is 50-70%, and the density of the intermediate layer is 0.3-0.65 g / cm³. It includes poplar, pine, fir, cedar, larch, spruce, cork pine, Douglas fir, kapok, and African ragweed.

[0017] The porosity is 70-90%, and the density of the core layer is below 0.3 g / cm³. It includes metasequoia, cedar, soft pine, balsa wood, and paulownia.

[0018] Timber is sorted and stacked according to density or porosity to form clearly marked piles of surface wood, intermediate wood, and core wood.

[0019] (b) Or, by mechanically drilling, a regular or irregular array of holes is constructed in the wood. By adjusting the parameters of the array, the hole shape, and the arrangement density, the pore diameter is 0.5 to 10 mm, the porosity range is 50% to 90%, and the hole shape is precisely controlled to obtain wood with different porosities.

[0020] When wood of the same density is used as energy-absorbing and shock-absorbing wood, the wood with a porosity of 50-70% formed by drilling is the middle layer, the wood with a porosity of 70-90% formed by drilling is the core layer, and the un-drilled wood is used as the surface layer.

[0021] Wood with different porosities formed by drilling holes of the same density is sorted and stacked to form labeled piles of surface wood, intermediate wood, and core wood.

[0022] When using wood of different densities as energy-absorbing and shock-absorbing wood, wood with a porosity of 40-50% in natural or drilled wood is used as the surface layer, wood with a porosity of 50-70% in natural or drilled wood is used as the middle layer, and wood with a porosity of 70-90% in natural or drilled wood is used as the core layer.

[0023] (c) Or obtained by alternating assembly of blanks; when wood of the same density is used as energy-absorbing and shock-absorbing wood, the wood in the same layer is composed of several strips of wood arranged side by side, and the blocks in the same layer are arranged at intervals of different widths to form the surface layer, intermediate layer or core layer.

[0024] (d) Alternatively, by controlling the temperature, pressure, and time parameters during the hot-pressing process, segmented hot-pressing can be performed to prepare a compressible layer with a gradient pore structure. When using wood of the same density as energy-absorbing and shock-absorbing wood, the wood layer is subjected to two stages of high-temperature compression. In the first stage, a high temperature of 150~220℃, a high pressure of 5~15 MPa, and a short time of 1~5 seconds are used for rapid compression of the wood surface. In the second stage, the pressure is reduced by 3~8 MPa or the temperature is reduced to 110~150℃ and the time is reduced to 6~10 seconds for compression of the core layer, forming a transition zone. The temperature difference between the upper and lower pressure plates is 10~20℃, so that the degree of compression varies in different parts of the wood. Alternatively, by controlling the pressure curve through a program, linearly decreasing or stepwise decreasing, a continuous density gradient can be achieved to obtain a controlled hot-pressed layer.

[0025] (2) Based on the requirements of energy-absorbing and shock-absorbing wood products, perform functional chemical treatment on each layer of the wood;

[0026] (3) According to the needs of energy-absorbing and shock-absorbing wood products, the units with regular dimensions of each layer are processed with fixed length, fixed width and fixed thickness. The thickness of the same layer is the same. Each layer is dried and the moisture content after drying is controlled at 5-12% to obtain dried layers.

[0027] (4) Applying adhesive to each layer of dried wood that constitutes energy-absorbing and shock-absorbing wood: Apply water-based two-component isocyanate adhesive to the surface of each layer of dried wood that constitutes energy-absorbing and shock-absorbing wood, with an adhesive application amount of 280-360 g / m², and the mass ratio of the main agent to the curing agent in the two-component isocyanate adhesive is 8-15.

[0028] (5) Assembly of energy-absorbing and shock-absorbing wood products: divided into assembly of dried layers of wood with different densities, assembly of dried layers of wood with artificial pore array, assembly of alternating layers, and assembly of mixed layers;

[0029] (a) Assembly of dried wood layers with different densities: Wood layers with a density of less than 0.3 g / cm³ are selected as core layers, wood layers with a density of 0.3 to 0.65 g / cm³ are selected as intermediate or surface layers, and wood layers with a density of more than 0.65 g / cm³ are selected as surface layers; the intermediate layer is a single layer or several layers stacked together; the core layer is a single layer or several layers stacked together; the intermediate layer and the core layer can be stacked alternately in one or more layers; the surface layer, intermediate layer and core layer can be stacked alternately in one or more layers; the thickness of adjacent layers may be the same or different; the wood grain of adjacent layers may be the same or different; the wood species of adjacent layers may be the same or different.

[0030] (b) Drying each layer of wood in artificial hole array: Wood with a porosity of 50-60% formed by drilling is used as surface layer, wood with a porosity of 60-70% formed by drilling is used as middle layer, wood with a porosity of 70-90% formed by drilling is used as core layer. The drilling surfaces of adjacent layers are arranged downwards, upwards, or staggered. The hole type, hole diameter, and hole array arrangement of the drilling surfaces of adjacent layers are different. The outer end face of the surface layer is the non-porous plane of the half-hole formed layer.

[0031] (c) Alternating assembly: When using timber of the same density as energy-absorbing and shock-absorbing timber, the timber in the same layer is composed of several strips or blocks of the same or different widths arranged side by side. The gaps form a surface layer with a porosity of 40-50%, the gaps form an intermediate layer with a porosity of 50-70%, and the gaps form a core layer with a porosity of 70-90%. The blocks in the same layer are arranged at intervals of different widths. The width of the blocks in the same layer is the same, while the width of the blocks in adjacent layers is different. The gaps between adjacent layers are staggered, and the length directions of the blocks in the upper and lower adjacent layers are staggered at 20° to 90°.

[0032] (d) Mixed assembly: According to the user's requirements for energy-absorbing and shock-absorbing wood products, the energy-absorbing and shock-absorbing wood products are one or more of the following: dried layers, artificially perforated dried layers, alternating assembled layers, and controlled hot-pressed layers, or alternating layers.

[0033] (6) Apply glue to the intersecting surfaces of the layers that make up the energy-absorbing and shock-absorbing wood, and then compact it mechanically, saw it, and cut the shock-absorbing wood into the required length, width, and height dimensions.

[0034] (7) Pressurize the cut energy-absorbing and shock-absorbing wood into the press, press and solidify it, and then reduce the pressure.

[0035] (8) Processing: trim the edges of the energy-absorbing and shock-absorbing wood to obtain energy-absorbing and shock-absorbing wood products. The thickness of the products is 10 to 1000 mm, the length range is 1 to 20 m, and the width is 0.5 to 3 m.

[0036] As a further description of the above technical solution: as needed, timber with a gradient porosity structure can be spliced ​​to be longer or wider. When splicing the length of each layer of timber, the splicing joints of adjacent timbers in the same layer are staggered. The thickness of the timber layers spliced ​​to be longer or wider is the same, and the joints of adjacent upper and lower layers are staggered or staggered at 20° to 90°.

[0037] As a further description of the above technical solution: the functional chemical treatment is:

[0038] (a) Preparation of composite modified solution;

[0039] (b) Place each layer into the reaction vessel and immerse it in the composite modification solution contained therein. Evacuate the vessel to a vacuum degree of -0.08 to -0.10 MPa and maintain it for 30 to 60 minutes. Depressurize the vessel and apply pressure of 0.6 to 1.2 MPa. Maintain the pressure for 1 to 4 hours. Repeat the above process 1 to 5 times to obtain the treated layer.

[0040] (c) The treated layer is air-dried to a moisture content of 40-50%, and the modifier is fully cured by gradient heating and then dried to a moisture content of 5-15% or an average moisture content of ≤12% to obtain a functionalized modified layer.

[0041] As a further description of the above technical solution: the composite modified solution is prepared by thoroughly stirring a polymeric main agent with a solid content of 5-25%, a functional auxiliary agent of 0.1-15 wt%, and an additive of 0.1-5 wt% until uniformly dispersed.

[0042] As a further description of the above technical solution: the polymeric main agent is one or more of polyurethane, epoxy resin, polyvinyl alcohol, polyethylene, polypropylene, polyamide, silicone rubber, and butyl rubber, mixed to form a solution or emulsion.

[0043] As a further description of the above technical solution: the functional additive is one or more of boric acid, borax, glutaraldehyde, nano-calcium borate, boron carbide, nano-cellulose, ammonium polyphosphate, and ammonium dihydrogen phosphate.

[0044] As a further description of the above technical solution: the additive is one or more of polyethylene glycol, citric acid, silane coupling agent or glycerin.

[0045] The present invention has the following beneficial effects:

[0046] 1. This invention constructs an increasing pore gradient from the surface to the core of the wood through wood modification and gradient pore design, achieving gradual collapse and optimizing strength and energy absorption in synergy; through the synergistic effect of gradient pore structure and chemical modification, the wood is endowed with high energy absorption, functionalization and controllable shock absorption performance.

[0047] The product of this invention has high energy absorption capacity: Referring to standards such as GB / T 1927.11-2022 "Test Methods for Physical and Mechanical Properties of Defect-Free Small Samples of Wood - Part 11: Determination of Compressive Strength Along the Grain" and GB / T 1927.12-2021 "Test Methods for Physical and Mechanical Properties of Defect-Free Small Samples of Wood - Part 12: Determination of Compressive Strength Across the Grain," the test material is processed into samples with length, width, and height of 30-50 mm, 30-50 mm, and 30 mm respectively. These samples are placed inside a rigid stainless steel hoop with a wall thickness ≥10 mm and subjected to universal testing using a 20 mm diameter circular steel indenter at a loading speed of 2-20 mm / min.-1 With a compression stroke ≥70%, stress-strain curves are obtained, and compressive strength and compression ratio energy absorption are calculated. The gradient structure of this invention allows wood to withstand lower densities (<0.300 g·cm³). -3 Under certain conditions, the energy absorption in parallel with the grain reaches over 70 kJ / kg.

[0048] The product of this invention has multiple functions: referring to standards such as GB / T 2406-2008 "Determination of Combustion Behavior by Oxygen Index Method for Plastics" and GB / T13942.1-2009 "Laboratory Test Method for Natural Deterioration Resistance of Wood", it can test the flame retardant and anti-corrosion properties of wood. The gradient structure and function optimize the flame retardant properties (LOI≥40%) and anti-corrosion properties (Level 1) of wood are excellent, and it also has functions such as neutron shielding.

[0049] 2. This invention achieves synergistic innovation in structure and function by combining gradient pore structure with chemical modification. Through boron treatment and fire-retardant synergistic modification, it endows the material with functions such as neutron absorption, fire retardancy, and corrosion resistance. By combining high-density surface layer impact resistance with porous core layer energy absorption, it balances the material's lightweight, energy absorption efficiency, and mechanical strength, resolving the contradiction between strength and energy absorption. It has many advantages such as abundant resources, renewability, environmentally friendly production, low cost, no formaldehyde release, simple process, good energy absorption, flame retardancy, and corrosion resistance. It can be widely used in shock-absorbing and cushioning materials for transportation, sports equipment, aerospace, and other fields with stringent impact energy absorption requirements, especially in high-safety fields such as shock absorbers for nuclear fuel transport containers. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the structure of each wood block according to the present invention, which controls porosity through pore shape;

[0051] Figure 2 This is a schematic diagram of the two-layer gradient pore structure wood structure of the present invention;

[0052] Figure 3 This is a schematic diagram of the three-layer gradient pore structure wood structure of the present invention;

[0053] Figure 4 This is a schematic diagram of the five-layer gradient pore structure wood structure of the present invention;

[0054] Figure 5 This is a schematic diagram of the timber structure of the spliced-length-and-width gradient pore structure of the present invention;

[0055] Figure 6 This is a schematic diagram of the structure of the blank product with an array of holes according to the present invention;

[0056] Figure 7 This is a structural schematic diagram of the alternating assembly of the blank product according to the present invention;

[0057] Figure 8 This is a schematic diagram of the structure of the hybrid preform product of the present invention;

[0058] Figure 9 This is the compressive stress-strain curve of the gradient structure wood of the present invention.

[0059] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. To facilitate understanding of the technical means, creative features, and achieved objectives and effects of the present invention, the present invention will be further elaborated below with reference to specific embodiments. However, the following embodiments are merely preferred embodiments of the present invention and not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments without creative effort are all within the protection scope of the present invention. Unless otherwise specified, the construction methods in the following embodiments are conventional methods. Unless otherwise specified, the materials, devices, equipment, etc., used in the following embodiments can be obtained commercially.

[0060] Example 1: Gradient pore structure wood prepared by gluing wood with different porosities: Wood with different densities was taken, wherein wood with a porosity of 40-50% was used as surface material 1, wood with a porosity of 51-70% was used as intermediate material 2, and wood with a porosity of 71-90% was used as core material 3.

[0061] like Figure 2 As shown, wood with a gradient porosity structure can be a two-layer structure: a superposition of core and intermediate layers, a superposition of core and surface layers, a superposition of two core layers with different porosities, a superposition of intermediate and surface layers, a superposition of two intermediate layers with different porosities, and a superposition of two surface layers with different porosities. When two layers of wood are superimposed, the difference in porosity between different types of wood is at least 10%. Figure 2 The core layer 3 is made of soft pine with a porosity of 71-90%, and the middle layer 2 is made of larch with a porosity of 50-70%. The wood is processed into blocks of the same thickness of 20mm, length of 15cm and width of 5cm. Water-based two-component isocyanate adhesive is applied to the upper and lower surfaces of the blocks at a rate of 280-360g / m². The mass ratio of the main agent to the curing agent is 8-15. The two layers are stacked with the same axial grain and cold-pressed at room temperature to obtain wood with a discrete gradient pore structure.

[0062] like Figure 3As shown, wood with a gradient porosity structure can be a three-layer structure: a combination of core wood, top layer wood, and intermediate layer wood; a combination of two core layers and one intermediate layer wood; a combination of two core layers and one top layer wood; a combination of one core layer and two intermediate layer wood; a combination of one core layer and two top layer wood; a combination of three core layers with different porosities; a combination of three intermediate layers with different porosities; and a combination of three top layer woods with different porosities. When three layers of wood are stacked, the difference in porosity between different types of wood is at least 10%. Figure 3 The core layer 3 is made of paulownia with a porosity of 71-90%, the middle layer 2 is made of larch with a porosity of 51-70%, and the surface layer 1 is made of beech with a porosity of 40-50%. The wood is processed into blocks of the same thickness of 20mm and length and width of 10cm. The upper and lower surfaces of the blocks are coated with a water-based two-component isocyanate adhesive with a coating amount of 280-360g / m². The mass ratio of the main agent to the curing agent is 8-15. The three layers are stacked with the same longitudinal grain and cold-pressed at room temperature to obtain wood with a discrete gradient pore structure.

[0063] like Figure 4 As shown, wood with a gradient porosity structure can be a multi-layered structure: a superposition of several core layers, several surface layers and several intermediate layers; a superposition of several core layers and several intermediate layers; a superposition of several core layers and several surface layers; a superposition of several core layers with different porosities; a superposition of several intermediate layers with different porosities; a superposition of several surface layers with different porosities; and when several woods are superimposed, the difference in porosity between different types of wood is at least 10%.

[0064] Figure 4The core layer 3 is made of fir wood with a porosity of 71-90%, the intermediate layer 2 is made of larch wood with a porosity of 51-70%, and the surface layer 1 is made of walnut wood with a porosity of 40-50%. The wood is processed into blocks of the same thickness of 20mm, length of 15cm, and width of 5cm. 5-15 parts by weight of nano-calcium borate and nano-cellulose, 1-10 parts by weight of B4C nano-slurry, 1-5 parts by weight of KH-550 silane coupling agent, 0.1-0.5 parts by weight of nano-cellulose dispersant, and 50-80 parts by weight of water are mixed thoroughly with citric acid to adjust the pH to 4-6. 5-25 parts by weight of polyurethane and 2.5 parts by weight of active polymerization inhibitors and other additives are added. The mixture is stirred under heating to 80-100℃ to ensure thorough mixing, thus preparing a multi-functional composite modifier. The wood blocks are immersed in the above-mentioned composite modification solution in a reaction vessel and subjected to vacuum-pressurization treatment at a vacuum degree of -0.08 to -0.10 MPa for 30 to 60 minutes; then, a pressure of 0.6 to 1.2 MPa is applied and the pressure is maintained for 1 to 4 hours. This process is repeated 1 to 5 times. The wood blocks are then removed and air-dried to approximately 50% moisture content. The modifier is fully cured by gradually increasing the temperature at intervals of 10 to 30°C, and then dried to 5 to 15% moisture content (average moisture content ≤ 12%). A water-based two-component isocyanate adhesive is then applied to the upper and lower surfaces of the blocks at a rate of 280 to 360 g / m².

[0065] The mass ratio of the main agent to the curing agent is 8–15, and the wood blocks of adjacent layers are staggered along the grain direction at an angle of 20°–90°. Five layers are stacked, with the surface layer 1 located at one end, the inner end of the surface layer 1 being the intermediate layer 2, and the core layer located between the two intermediate layers 2. The five layers are placed in a press and subjected to a pressure of 1–10 MPa at room temperature for 20–90 minutes to obtain wood with a multi-effect composite modification of discrete gradient pore structure.

[0066] like Figure 5 As shown, timber with a gradient porosity structure can be spliced ​​to different lengths and widths as needed. When splicing timber of different layers, the splicing joints of adjacent timbers in the same layer are staggered. When splicing timber of the same layer to different lengths or widths, the thickness of the timber layers is the same, and the joints of adjacent upper and lower layers are staggered or staggered at 20° to 90°. The wood with a gradient porosity structure consists of surface layer 11 located on the upper and lower end faces, intermediate layer 21 located at the inner ends of the upper and lower end faces, and core layer 31 located in the middle. The joints 4 of adjacent wood in the same layer are staggered. The joints of adjacent upper and lower layers are staggered at 90°. The intersecting surfaces of adjacent wood in the same layer are coated with a water-based two-component isocyanate adhesive with an adhesive amount of 280-360 g / m² and a mass ratio of main agent to hardener of 8-15. When it is loaded into the press, the pressing method, pressing direction, pressure of 6 MPa, curing temperature of 5-140°C, and time of 20-90 min can be selected according to the type of adhesive and the thickness of the board to obtain the wood with a gradient porosity structure.

[0067] Of course, the wood strips or boards before splicing and widening can be treated with functional properties first. This involves adding 5-15 parts by weight of one or more of the following: ammonium polyphosphate, ammonium dihydrogen phosphate, glutaraldehyde, boric acid, borax, nano calcium borate, and nanocellulose; 1-10 parts by weight of B4C nano-slurry; 1-5 parts by weight of KH-550 silane coupling agent; 0.1-0.5 parts by weight of nanocellulose dispersant; and 50-80 parts by weight of water. The pH is adjusted to 4-6 with citric acid and thoroughly mixed. Then, 5-25 parts by weight of one or more prepolymer solutions of polyurethane, epoxy resin, polyvinyl alcohol, polyethylene, polypropylene, polyamide, silicone rubber, and butyl rubber, as well as 2.5 parts by weight of active polymerization inhibitors and other additives, are added and stirred under heating conditions to ensure thorough mixing, thus producing a multi-functional composite modifier. Wood is immersed in the above-mentioned composite modification solution and subjected to vacuum-pressurization treatment (vacuum degree -0.08 to -0.10 MPa, pressure held for 30 to 60 minutes; then pressure applied at 0.6 to 1.2 MPa, pressure held for 1 to 4 hours; the above process is repeated 1 to 5 times) to air-dry the treated wood to a moisture content of approximately 50%. The modifier is then fully cured by a gradient temperature increase at intervals of 10 to 30°C, and dried to a moisture content of 5 to 15% (average moisture content ≤ 12%) to obtain functionally modified wood blocks. These blocks exhibit flame retardancy (LOI ≥ 40%) reaching the flame-retardant A-level; corrosion resistance reaching the strong corrosion-resistant level 1; and through the synergistic effect of the water-soluble hydrogen-containing resin and boron salt compound, they also possess neutron shielding functions.

[0068] like Figure 1 As shown, when the types of wood are limited, regular or irregularly arranged pore arrays can be constructed in the wood by mechanical drilling 5. By adjusting the pore array parameters, pore shape, and arrangement density, the pore diameter can be precisely controlled from 0.5 to 10 mm, the porosity range can be from 50% to 90%, and the pore shape can be precisely controlled to obtain wood with different porosities. Figure 1 (a) A block of wood with equal-sized holes, the hole diameter being 0.5–2 mm. Figure 1 (b) A block of wood with a central hole of uniform diameter, the hole diameter being 2.05–7 mm. Figure 1 (c) A block of wood with large, uniform pores, the pore diameter being 7.05–10 mm. Figure 1 (d) refers to wood blocks with gradually changing holes, i.e., the same wood block includes wood blocks with small, medium and large holes of equal diameter. Hole types include semi-through holes 51 that only pass through one board surface, through holes 52 that pass through two board surfaces, vertical holes and oblique holes.

[0069] like Figure 6 As shown, when arranging the perforated array into blanks, when using wood of the same density as energy-absorbing and shock-absorbing wood, the wood with a porosity of 50-70% formed by perforation is the intermediate layer, the wood with a porosity of 70-90% formed by perforation is the core layer, and the unperforated wood is the surface layer.

[0070] Figure 6 In this process, poplar wood is processed into five identical blocks, each 20mm thick, 15cm long, and 5cm wide. Two of these blocks have identical semi-through holes 51, 10mm deep, made on one side, resulting in a middle layer 2 with a porosity of 65%. Another block has identical through holes 52, 20mm long, made on both sides, resulting in a core layer 3 with a porosity of 85%. Adhesive is applied to the intersecting surfaces of each layer. The five layers are stacked, with the upper and lower surface layers 1 being un-drilled blocks. The inner ends of the two surface layers 1 are middle layer 2 blocks with semi-through holes 51 facing outwards. The core layer is a block with through holes 52, located between the non-porous surfaces of the two middle layers 2. The five layers are placed in a press at room temperature under a pressure of 0.3–3 MPa for 20–90 minutes to obtain wood with a discrete gradient pore structure.

[0071] When using wood of different densities as energy-absorbing and shock-absorbing wood, wood with a porosity of 40-50% in natural or drilled wood is used as the surface layer, wood with a porosity of 50-70% in natural or drilled wood is used as the middle layer, and wood with a porosity of 70-90% in natural or drilled wood is used as the core layer.

[0072] like Figure 7 As shown, when assembling blanks alternately, when wood of the same density is used as energy-absorbing and shock-absorbing wood, the wood in the same layer is composed of several strips of wood arranged side by side, and the strips of wood in the same layer are arranged at intervals of different widths to form the surface layer, intermediate layer or core layer.

[0073] Figure 7 In this process, poplar wood is processed into two blocks of wood with a thickness of 20mm, a length of 14cm, and a width of 7cm, which are the surface layer material 1; five short strips 6 with a thickness of 20mm, a length of 14cm, and a width of 1cm, which are the middle layer material 2; and four long strips 7 with a thickness of 20mm, a length of 14cm, and a width of 3cm, which are the core layer material 3.

[0074] Five short strips 6 are placed side-by-side with a 0.5mm spacing on the end face of a 20mm thick, 14cm long, and 7cm wide wooden block. The long sides of the two short strips 6 at both ends are aligned with the long sides of the end face of the wooden block. There is a 0.5mm gap 8 between adjacent short strips 6, forming a core layer 3 with a porosity of 90%. Four long strips 7 are placed side-by-side on the upper end face of the core layer 3, with their long sides offset from the long sides of the short strips 6 at 90°. The long and wide sides of the two short strips 6 at both ends are aligned with the long and wide sides of the end face of the wooden block. There is a 0.5mm gap 7 between adjacent long strips 7, forming an intermediate layer 2 with a porosity of 60%. Then, a surface layer 1 of a wooden block is placed on top of the intermediate layer 2. Glue is applied to the intersecting surfaces of each layer, and the four layers are stacked. The four layers are placed in a press at room temperature under a pressure of 0.3–3MPa for 20–90 minutes to obtain wood with a discrete gradient pore structure.

[0075] like Figure 8 As shown, during the mixed assembly process, according to the user's requirements for energy-absorbing and shock-absorbing wood products, the energy-absorbing and shock-absorbing wood products are one or more of the following: dried layers, artificially perforated array dried layers, alternating assembled layers, and controlled hot-pressed layers, in combination or in alternating layers.

[0076] Figure 8 In this process, poplar wood is processed into two blocks, each 20mm thick, 14cm long, and 7cm wide, to form the surface layer 1; five short strips, each 20mm thick, 14cm long, and 1cm wide, form the core layer 3; and a piece of wood, 20mm thick, 14cm long, and 7cm wide, has the same number and size of through holes 52 made on both sides, with a through hole length of 20mm, resulting in a core layer 3 with a porosity of 85%.

[0077] Five short strips 6 are placed side by side with a spacing of 0.5 mm on the end face of a 20 mm long, 14 cm long and 7 cm wide wooden block. The long sides of the short strips 6 at both ends are aligned with the long sides of the end face of the wooden block. There is a 0.5 mm spacing space 8 between adjacent short strips 6, forming a core layer material 3 with a porosity of 90%. The core layer material 3 with through holes 52 is placed on the upper end face of the core layer material 3 of the short strips. On the upper end face of the core layer material 3 with through holes 52, another layer of short strip core layer material 3 and a wooden block are placed in sequence as the surface material 1. The intersecting surfaces of each layer are glued. The five layers are stacked and placed in a press at room temperature with a pressure of 0.3-3 MPa for 20-90 minutes to obtain wood with a discrete gradient pore structure.

[0078] The above Figure 2 As for Figure 8 All the wood panels shown can be treated with functional properties, so they will not be described in detail here.

[0079] Segmented hot pressing can be achieved by controlling the temperature, pressure, and time parameters during the hot pressing process to prepare compressible laminates with gradient pore structures. When using wood of the same density as energy-absorbing and shock-absorbing wood, the wood laminate is subjected to two stages of high-temperature compression. The first stage uses a high temperature of 150~220℃, a high pressure of 5~15 MPa, and a short pressing time of 1~5 seconds to rapidly compress the surface layer of the wood. The second stage reduces the pressure by 3~8 MPa or lowers the temperature to 110~150℃ and presses for 6~10 seconds to compress the core layer, forming a transition zone. The temperature difference between the upper and lower pressing plates is 10~20℃, resulting in different degrees of compression in different parts of the wood. Alternatively, a continuous density gradient can be achieved by controlling the pressure curve through program control, linear decrease, or stepwise decrease, thus controlling the hot-pressed laminate. For example, a poplar block with a thickness of 8cm and a length and width of 14cm is selected. The pressure direction is perpendicular to the grain direction, and the poplar block undergoes two stages of high-temperature compression. The first stage uses a high temperature of 200℃, a high pressure of 12 MPa, and a short pressing time of 2 seconds to rapidly compress the surface layer of the wood. The second stage uses a pressure of 5 MPa and a temperature of 200℃ for 4 seconds to compress the core layer, forming a transition zone with a temperature difference of 10~20℃ between the upper and lower pressure plates. The porosity of the wood within 1cm of the upper and lower end faces is measured to be 45%, the porosity within 1cm to 2cm of the upper and lower end faces is 60%, and the porosity of the middle layer within 2cm is 72%. This achieves a continuous density gradient, allowing for control of the hot-pressed layer material.

[0080] Example 2: Take wood A with a porosity of 69% and wood B with a porosity of 93%. Process the wood into blocks of the same thickness of 30mm and length and width of 10cm. Coat the upper and lower surfaces of the blocks with a water-based two-component isocyanate adhesive at a coating amount of 280-360g / m². The mass ratio of the main agent to the curing agent is 8-15. Stack the wood A-wood B-wood A in three layers along the same axial grain and cold press them at room temperature to obtain wood ABA with a discrete gradient pore structure.

[0081] To obtain ABA in the wood, referring to GB / T 1927.11-2022 "Test Methods for Physical and Mechanical Properties of Wood in Defect-Free Small Samples - Part 11: Determination of Compressive Strength Along the Grain", the test material was processed into samples with a length, width, and height of 30 mm, 30 mm, and 30 mm respectively. These samples were placed inside a stainless steel hoop and subjected to universal testing using a 20 mm diameter circular steel indenter with a loading speed of 10 mm·min. -1 With a compression stroke ≥70%, the stress-strain curve is obtained, and its strength and specific energy absorption are calculated.

[0082] The measured data are shown in Table 1 below:

[0083]

[0084] like Figure 9 As shown, the compressive stress-strain curve of ABA wood with gradient structure optimization demonstrates that the ABA gradient structure effectively reduces the initial peak stress and plateau stress of the compression curve, and prolongs the time to enter the densification process through gradual collapse. Compared with wood A, the density of ABA gradient wood is reduced by about 27%, but the energy absorption per unit mass is increased by about 3%. It can be seen that gradient structure optimization can effectively control the energy absorption and shock absorption performance of wood and achieve lightweighting.

[0085] Example 2: Preparation of surface compressed cedar wood with a gradient pore structure by segmented hot pressing under hydrothermal control conditions:

[0086] 1) Moisture content distribution control: Soak tangential cedar wood with dimensions of 550mm (length) × 80mm (width) × 35~60mm (height) in water at room temperature for 1~4 hours, then remove it and place it in a sealed bag for 12~36 hours.

[0087] 2) Preheating treatment: Preheating treatment is carried out under the clamping of the hot press plate. The preheating temperature is 140-180 ℃ and the preheating time is 1-60 min. By adjusting the preheating time, surface compressed fir wood with one or two low porosity high density layers can be obtained.

[0088] 3) Intermittent compression: After preheating, intermittent compression is performed directly on the hot press. The compression time is 1-15 s and the interval time is 15-40 s. The compression load is 4-12 MPa. The target thickness is 30 mm and the compression rate is 30-50%, controlled by a thickness gauge.

[0089] 4) Pressure holding stage: After the compression process is completed, maintain a load of 3-7 MPa for 15-45 minutes, and remove it after cooling to room temperature.

[0090] 5) Density test: The density distribution along the thickness of the wood was tested using an X-ray cross-sectional density meter. The density of the compressed wood was calculated based on the test results. The results showed that the density value within 2-3 mm of the upper and lower surfaces exceeded 0.800 g·cm³. −3 The average density of the compressed layer reaches 0.683 g·cm³. −3 Compared with the control material, it is 86% higher, with the maximum porosity in the compressed wood being about 78% and the minimum porosity being about 46%.

[0091] 6) Performance Testing: Referring to GB / T 1927.12—2021 "Test Methods for Physical and Mechanical Properties of Unblemished Small Specimens of Wood Part 12: Determination of Cross-Grain Compressive Strength", the specimens were processed into length, width, and height samples of 30 mm, 30 mm, and 30 mm respectively. These samples were placed within a self-made steel hoop and subjected to universal testing using a 20 mm diameter circular steel indenter with a loading speed of 5 mm / min. -1 With a compression stroke ≥70%, the stress-strain curve is obtained, and its strength and specific energy absorption are calculated.

[0092] The control material was untreated raw material, and the measured data are shown in Table 2 below:

[0093]

[0094] Example 3

[0095] Wood with a gradient porosity structure is obtained by mechanical drilling, and then modified by impregnation with a multi-effect composite modifier to prepare functional modified wood with a gradient porosity structure:

[0096] (1) Construction of the graded pore structure of wood:

[0097] a. The air-dried test material is processed into a sample with a length, width and height of 30 mm, 30 mm and 30 mm respectively. Holes are drilled along the grain of the wood fibers on the cross section. The hole diameter increases uniformly from the outside to the inside along the radial direction of the test material. The outer hole diameter is small (0-4 mm), the middle hole diameter is medium (3-7 mm), and the inner hole diameter is large (5-10 mm). The spacing between holes is ≥2r.

[0098] b. Use high-precision clamps to firmly hold the wood sample on the worktable to ensure flatness and accurate positioning;

[0099] c. Pre-set the drilling program (position, depth, automatic or manual tool change) on the CNC drilling machine. Use a higher speed (8000-12000 rpm) for small diameter holes and a lower speed (4000-6000 rpm) for large diameter holes.

[0100] d. Start the program, and the machine tool will automatically drill according to the preset coordinates, drill bit commands, and depth;

[0101] e. The radial pore size of the test material gradually increases, with the minimum external porosity being about 68% and the maximum internal porosity being about 84%, thus obtaining wood with a gradually increasing pore structure.

[0102] (2) Preparation of multi-effect composite modifier:

[0103] a. First, mix 5-15 parts by weight of one or more of the following: ammonium polyphosphate, ammonium dihydrogen phosphate, glutaraldehyde, boric acid, borax, nano calcium borate, and nanocellulose (the mass ratio of ammonium phosphate, ammonium dihydrogen phosphate, and boron is 1:1.5-2.5), 1-10 parts by weight of B4C nano-slurry, 1-5 parts by weight of KH-550 silane coupling agent, 0.1-0.5 parts by weight of nanocellulose dispersant, and 50-80 parts by weight of water. Adjust the pH to 4-6 with citric acid and stir thoroughly.

[0104] b. Add 5 to 25 parts by weight of one or more prepolymer solutions of polyurethane, polyvinyl alcohol, epoxy resin, and polyamide, and 2.5 parts by weight of active polymerization inhibitor, and stir under heating conditions to make them fully mixed to prepare a multifunctional composite modifier with multiple effects.

[0105] (3) Vacuum pressure impregnation treatment of wood:

[0106] The wood with a gradient pore structure prepared above was placed in a treatment tank; a vacuum was applied to -0.08 to -0.10 MPa and maintained for 30 minutes; a composite modifier solution was drawn in; the pressure was increased to 0.6 to 1.0 MPa and maintained for 1 to 4 hours; the process was repeated 1 to 2 times; the material was discharged; it was air-dried until the moisture content was below 50%, and then transferred to a drying oven for artificial drying using a softer standard (60 to 103°C) with progressively increasing temperatures until the moisture content of the board was ≤12%, thus obtaining modified wood with a gradient pore structure.

[0107] 4) Performance Testing: The control material was untreated raw material. Referring to GB / T 1927.12—2021 "Test Methods for Physical and Mechanical Properties of Untreated Small Specimens of Wood - Part 12: Determination of Cross-Stretch Compressive Strength", a self-made steel hoop large deformation compressive strength testing device was used to test the strength and specific energy absorption of the untreated wood and the wood after functional structure optimization. Referring to GB / T 2406-2008 "Determination of Combustion Behavior by Oxygen Index Method for Plastics" and GB / T 13942.1-2009 "Laboratory Test Method for Natural Deterioration Resistance of Wood", the flame retardant and anti-corrosion properties of the test materials were determined. The results are as follows:

[0108]

[0109] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An energy-absorbing and shock-damping wood with a gradient pore structure, made of wood, characterized in that: The shock-absorbing wood comprises at least two layers of wood with different pore structures, wherein the porosity of the surface layer is 40-50%, the porosity of the intermediate layer is 50-70%, and the porosity of the core layer is 70-90%; the intermediate layer is one layer or several layers stacked together, and the core layer is one layer or several layers stacked together; the intermediate layer and the core layer can be stacked alternately, and the surface layer, intermediate layer, and core layer can be stacked alternately with each other; Shock-absorbing wood is composed of several layers of surface wood, intermediate wood, and core wood stacked one on top of the other, or staggered and alternating, assembled into a blank, impregnated with resin, and pressed and cured; or it is composed of several layers of surface wood, intermediate wood, and core wood stacked one on top of the other, or staggered and alternating, assembled into a blank, impregnated with liquid for modification, impregnated with resin, and pressed and cured. The shock-absorbing wood contains ≥1wt% boron and ≥0.5wt% phosphorus.

2. The energy-absorbing and shock-absorbing wood with a gradient pore structure according to claim 1, characterized in that: The number of shock-absorbing wood layers is either even or odd. Even-numbered layers are at least 2 layers, and odd-numbered layers are at least 1 layer. The upper or lower surface, or both upper and lower surface, of the shock-absorbing wood is a surface layer, an intermediate layer, or a core layer, and the thickness of the same layer is the same.

3. The energy-absorbing and shock-absorbing wood with a gradient pore structure according to claim 1, characterized in that: Several layers are stacked or alternately stacked, with the wood grain axes of the upper and lower adjacent layers staggered at 0° to 90°, and the joints of the upper and lower adjacent layers staggered at 20° to 90°.

4. A method for preparing energy-absorbing and shock-absorbing wood with a gradient pore structure as described in claim 1, characterized in that: Includes the following steps: (1) Obtaining wood with different porosities, including: (a) By selecting woods with different densities, woods with different porosities can be obtained; The porosity is 40-50% and the density of the surface material is above 0.65g / cm³. It includes oak, beech, walnut, ironwood, green sandalwood, four-oak wood, birch, ironwood, green bark, ebony, and teak. The porosity is 50-70%, and the density of the intermediate layer is 0.3-0.65 g / cm³. It includes poplar, pine, fir, cedar, larch, spruce, cork pine, Douglas fir, kapok, and African ragweed. The porosity is 70-90%, and the density of the core layer is below 0.3 g / cm³. It includes metasequoia, cedar, soft pine, balsa wood, and paulownia. Timber is sorted and stacked according to density or porosity to form clearly marked piles of surface wood, intermediate wood, and core wood. (b) Or, by mechanically drilling, a regular or irregular array of holes is constructed in the wood. By adjusting the parameters of the array, the hole shape, and the arrangement density, the pore diameter is 0.5 to 10 mm, the porosity range is 50% to 90%, and the hole shape is precisely controlled to obtain wood with different porosities. When wood of the same density is used as energy-absorbing and shock-absorbing wood, the wood with a porosity of 50-70% formed by drilling is the middle layer, the wood with a porosity of 70-90% formed by drilling is the core layer, and the un-drilled wood is used as the surface layer. Wood with different porosities formed by drilling holes of the same density is sorted and stacked to form labeled piles of surface wood, intermediate wood, and core wood. When using wood of different densities as energy-absorbing and shock-absorbing wood, wood with a porosity of 40-50% in natural or drilled wood is used as the surface layer, wood with a porosity of 50-70% in natural or drilled wood is used as the middle layer, and wood with a porosity of 70-90% in natural or drilled wood is used as the core layer. (c) Or obtained by alternating assembly of blanks; when wood of the same density is used as energy-absorbing and shock-absorbing wood, the wood in the same layer is composed of several strips of wood arranged side by side, and the blocks in the same layer are arranged at intervals of different widths to form the surface layer, intermediate layer or core layer. (d) Alternatively, by controlling the temperature, pressure, and time parameters during the hot-pressing process, segmented hot-pressing can be performed to prepare a compressible layer with a gradient pore structure. When using wood of the same density as energy-absorbing and shock-absorbing wood, the wood layer is subjected to two stages of high-temperature compression. In the first stage, a high temperature of 150~220℃, a high pressure of 5~15 MPa, and a short time of 1~5 seconds are used for rapid compression of the wood surface. In the second stage, the pressure is reduced by 3~8 MPa or the temperature is reduced to 110~150℃ and the time is reduced to 6~10 seconds for compression of the core layer, forming a transition zone. The temperature difference between the upper and lower pressure plates is 10~20℃, so that the degree of compression varies in different parts of the wood. Alternatively, by controlling the pressure curve through a program, linearly decreasing or stepwise decreasing, a continuous density gradient can be achieved to obtain a controlled hot-pressed layer. (2) Based on the requirements of energy-absorbing and shock-absorbing wood products, perform functional chemical treatment on each layer of the wood; (3) According to the needs of energy-absorbing and shock-absorbing wood products, the units with regular dimensions of each layer are processed with fixed length, fixed width and fixed thickness. The thickness of the same layer is the same. Each layer is dried and the moisture content after drying is controlled at 5-12% to obtain dried layers. (4) Applying adhesive to each layer of dried wood that constitutes energy-absorbing and shock-absorbing wood: Apply water-based two-component isocyanate adhesive to the surface of each layer of dried wood that constitutes energy-absorbing and shock-absorbing wood, with an adhesive application amount of 280-360 g / m², and the mass ratio of the main agent to the curing agent in the two-component isocyanate adhesive is 8-15. (5) Assembly of energy-absorbing and shock-absorbing wood products: divided into assembly of dried layers of wood with different densities, assembly of dried layers of wood with artificial pore array, assembly of alternating layers, and assembly of mixed layers; (a) Assembly of dried wood layers with different densities: Wood layers with a density of less than 0.3 g / cm³ are selected as core layers, wood layers with a density of 0.3 to 0.65 g / cm³ are selected as intermediate or surface layers, and wood layers with a density of more than 0.65 g / cm³ are selected as surface layers; the intermediate layer is a single layer or several layers stacked together; the core layer is a single layer or several layers stacked together; the intermediate layer and the core layer can be stacked alternately in one or more layers; the surface layer, intermediate layer and core layer can be stacked alternately in one or more layers; the thickness of adjacent layers may be the same or different; the wood grain of adjacent layers may be the same or different; the wood species of adjacent layers may be the same or different. (b) Drying each layer of wood in artificial hole array: Wood with a porosity of 50-60% formed by drilling is used as surface layer, wood with a porosity of 60-70% formed by drilling is used as middle layer, wood with a porosity of 70-90% formed by drilling is used as core layer. The drilling surfaces of adjacent layers are arranged downwards, upwards, or staggered. The hole type, hole diameter, and hole array arrangement of the drilling surfaces of adjacent layers are different. The outer end face of the surface layer is the non-porous plane of the half-hole formed layer. (c) Alternating assembly: When using timber of the same density as energy-absorbing and shock-absorbing timber, the timber in the same layer is composed of several strips or blocks of the same or different widths arranged side by side. The gaps form a surface layer with a porosity of 40-50%, the gaps form an intermediate layer with a porosity of 50-70%, and the gaps form a core layer with a porosity of 70-90%. The blocks in the same layer are arranged at intervals of different widths. The width of the blocks in the same layer is the same, while the width of the blocks in adjacent layers is different. The gaps between adjacent layers are staggered, and the length directions of the blocks in the upper and lower adjacent layers are staggered at 20° to 90°. (d) Mixed assembly: According to the user's requirements for energy-absorbing and shock-absorbing wood products, the energy-absorbing and shock-absorbing wood products are one or more of the following: dried layers, artificially perforated dried layers, alternating assembled layers, and controlled hot-pressed layers, or alternating layers. (6) Apply glue to the intersecting surfaces of the layers that make up the energy-absorbing and shock-absorbing wood, and then compact it mechanically, saw it, and cut the shock-absorbing wood into the required length, width, and height dimensions. (7) Pressurize the cut energy-absorbing and shock-absorbing wood into the press, press and solidify it, and then reduce the pressure. (8) Processing: trim the edges of the energy-absorbing and shock-absorbing wood to obtain energy-absorbing and shock-absorbing wood products. The thickness of the products is 10 to 1000 mm, the length range is 1 to 20 m, and the width is 0.5 to 3 m.

5. The method according to claim 4, characterized in that: As needed, timber with a gradient porosity structure can be spliced ​​to be longer or wider. When splicing timber of different layers, the splicing joints of adjacent timbers in the same layer are staggered. Timber layers that are spliced ​​to be longer or wider have the same thickness, and the joints of adjacent upper and lower layers are staggered or staggered at 20° to 90°.

6. The method according to claim 4, characterized in that: The aforementioned functional chemical treatment is: (a) Preparation of composite modified solution; (b) Place each layer into the reaction vessel and immerse it in the composite modification solution contained therein. Evacuate the vessel to a vacuum degree of -0.08 to -0.10 MPa and maintain it for 30 to 60 minutes. Depressurize the vessel and apply pressure of 0.6 to 1.2 MPa. Maintain the pressure for 1 to 4 hours. Repeat the above process 1 to 5 times to obtain the treated layer. (c) The treated layer is air-dried to a moisture content of 40-50%, and the modifier is fully cured by gradient heating and then dried to a moisture content of 5-15% or an average moisture content of ≤12% to obtain a functionalized modified layer.

7. The method according to claim 6, characterized in that: The composite modified solution is prepared by thoroughly stirring a polymeric main agent with a solid content of 5-25%, a functional auxiliary agent of 0.1-15 wt%, and an additive of 0.1-5 wt% until it is uniformly dispersed.

8. The method according to claim 7, characterized in that: The polymeric main agent is one or more of polyurethane, epoxy resin, polyvinyl alcohol, polyethylene, polypropylene, polyamide, silicone rubber, and butyl rubber, mixed to form a solution or emulsion.

9. The method according to claim 7, characterized in that: The functional additives mentioned are one or more of the following: boric acid, borax, glutaraldehyde, nano-calcium borate, boron carbide, nano-cellulose, ammonium polyphosphate, and ammonium dihydrogen phosphate.

10. The method according to claim 7, characterized in that: The additive is one or more of polyethylene glycol, citric acid, silane coupling agent or glycerin.

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