Anti-deformation environment-friendly gluing process based on wood microstructure regulation and control

Abstract

The invention provides an anti-deformation environment-friendly gluing process based on wood microstructure regulation and control. The anti-deformation environment-friendly gluing process sequentially comprises the steps of pattern pretreatment, breathing groove structure treatment, ecological solidification intermediate layer arrangement and gluing press fit and maintenance. Wherein a non-penetrating disturbance line path is arranged in a junction area of the morning timber and the evening timber, and a wave band type tension point is introduced, so that stress release is induced, and crack propagation is blocked; a micro breathing groove and suction stress pattern structure is etched on a gluing interface, and a deformable microcavity buffer layer is constructed; and a natural fiber intermediate layer with moisture absorption expansion and dry shrinkage tightening behaviors is clamped between the adhesive layers, so that a dynamic locking mechanism is formed. According to the process system, a'guiding-buffering-locking 'multi-stage synergistic structure is constructed, the warping resistance, crack resistance and size stability of the glued wooden product in a complex humid and hot environment are effectively improved, and the process system is suitable for the fields of floors, furniture, high-end wood veneers and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of wood processing and gluing materials, and in particular relates to an anti-deformation and environmentally friendly gluing process based on wood microstructure regulation. Background Art

[0002] Wood, due to its natural beauty, ease of processing, and high strength-to-weight ratio, is widely used in a variety of fields, including architectural decoration, furniture manufacturing, and flooring. Especially with the growing emphasis on environmental protection, glued laminated timber products, due to their high resource utilization, diverse shapes, and superior environmental performance, have become an important alternative to solid wood products. However, because wood is an anisotropic, naturally porous material, it is significantly affected by changes in ambient temperature and humidity. It is prone to shrinkage and expansion during use, which can lead to structural instability issues such as warping, cracking, and delamination of the glue layer, severely limiting its reliability and durability in engineering applications.

[0003] The commonly used anti-deformation treatment technologies currently include the following categories:

[0004] Physical constraint structure method: For example, external constraint force is applied to the plywood by adding metal ribs, constraint frames or back pressure structures. However, this method relies on external components, which increases product weight and manufacturing costs, and may fail due to loosening of the rib structure during long-term use.

[0005] Chemical stabilization treatment: Chemical modification of wood using polymer resin impregnation, heat-pressing stabilizers or cross-linking agents can improve dimensional stability to a certain extent, but it is often accompanied by the use of highly toxic synthetic chemicals, making it difficult to meet green environmental protection standards.

[0006] Process improvement method: such as adjusting drying parameters, gluing ratio, hot pressing time and other process conditions. Although it can partially alleviate stress concentration, it does not essentially solve the problem of constructing stress release and absorption mechanisms from the perspective of wood structure. The anti-deformation effect is limited and is easily affected by fluctuations in raw materials.

[0007] Furthermore, existing gluing processes often treat wood as a passive bonding target, lacking the ability to actively control its internal microstructure. During long-term cyclic swelling and shrinkage, shear fatigue accumulates at the interface between the adhesive layer and the wood, easily leading to structural cracking or debonding. This problem is particularly acute when used in underfloor heating or in high-humidity environments.

[0008] Therefore, a new environmentally friendly gluing process based on wood microstructure regulation is urgently needed. This process can systematically construct stress release, buffering, and locking mechanisms at three levels: the wood's bulk structure, the gluing interface, and the intermediary coupling structure. This allows for the production of deformation-resistant, fatigue-resistant, and highly stable glulam products. This technology should not only comply with green environmental standards and avoid the use of highly toxic chemical additives, but also possess good industrial feasibility and compatibility with a wide variety of wood species to meet the increasingly stringent requirements of modern wood products for environmental protection, safety, and dimensional stability. Summary of the Invention

[0009] The purpose of the present invention is to disclose an anti-deformation and environmentally friendly gluing process based on the regulation of wood microstructure. The present invention realizes the transformation of the wood gluing structure from "passive fixation" to "active coordination", embeds an elastic buffer mechanism, a humidity response mechanism and a path induction mechanism in the material body, and constructs a three-dimensional multi-level stress management system.

[0010] The technical solution adopted by the present invention is as follows: an anti-deformation and environmentally friendly gluing process based on wood microstructure regulation, comprising the following steps:

[0011] S1. Disturbance pretreatment: The wood sheets to be glued are subjected to a disturbance path induction treatment along their thickness. Shallow disturbance grains are driven along a set curve at the junction of the early and late wood to form stress-oriented fracture bands, which are used to induce stress release along a specified path during the drying process.

[0012] S2. Breathing groove structure treatment: Etch a non-through micro-breathing groove grid on the contact surface of the glued wood. The breathing groove depth is 20 to 80 microns. It is used to form stress-compensating micro-cavities during the glue pressing and drying process, and slowly release the concentrated interfacial stress caused by wood shrinkage or swelling;

[0013] S3. Setting up an ecological shrinkage intermediary layer: A follicle-shaped intermediary layer made of natural plant fiber material is sandwiched between the glued layers. The intermediary layer expands when it absorbs moisture in the early stage and shrinks and tightens when it dries in the later stage, so as to form a self-locking clamping force that dynamically responds to the breathing rhythm of the wood during the gluing process;

[0014] S4. Gluing, pressing and curing: After the wood is treated, adhesive is applied, and directional pressing and segmented temperature-controlled curing are carried out to ultimately form environmentally friendly glued wood products with high dimensional stability and anti-warping capabilities.

[0015] The disturbance grain path is an S-shaped, fish-scale or umbrella-shaped bifurcated curve, the disturbance grain depth is 5% to 15% of the wood thickness, and the angle between the disturbance grain direction and the wood grain direction is 10° to 30°.

[0016] The disturbance pattern is formed by a mechanical acupuncture device or an ultrasonic vibration device, and the ultrasonic vibration device is used to stimulate the micro-lysis structure of the intercellular layer along the boundary area between the earlywood and latewood.

[0017] The breathing grooves are arranged in a cross or oblique grid pattern, with a groove width of 50 to 150 microns and a groove spacing of 300 to 800 microns.

[0018] The breathing groove is partially filled with glue during the gluing process to form a closed microcavity, and the microcavity is used to absorb the shear stress and expansion stress of the glue layer during the subsequent drying and shrinkage.

[0019] The follicle-shaped intermediate layer is selected from hemp fiber, rush, reed silk or cottonseed shell fiber, and its cross-sectional shape is an elliptical cluster or a flat ribbon, with a thickness of 0.5 to 1.5 mm.

[0020] The intermediate layer is softened by natural steam before lamination, and its surface is sprayed with natural beeswax powder to delay the onset of moisture absorption and expansion.

[0021] The ecological shrinkage intermediary layer shrinks synchronously with the changes in the internal humidity of the wood during the curing process, forming a dynamically distributed "wood reinforcement" structure to resist warping and interlayer cracking.

[0022] Among them, the bonding maintenance adopts a segmented moisture control strategy, including a high-humidity slow-release stage and a low-temperature setting stage, which is used to coordinate the release of disturbance wrinkle stress and the locking reaction of the intermediate layer.

[0023] The wood is natural solid wood board, LVL laminated lumber or finger-jointed board, which is suitable for scenes with high requirements on dimensional stability such as flooring, furniture, and building finishes.

[0024] The beneficial effects of the present invention include:

[0025] The present invention discloses an anti-deformation and environmentally friendly gluing process based on the regulation of wood microstructure. By introducing a disturbance grain induction path, a breathing groove buffer structure and an ecological shrinkage intermediary layer, a multi-level stress coordination system is constructed from the wood core layer to the gluing interface and then to the intermediary structure, thereby achieving systematic suppression of structural deformations such as warping, cracking and delamination in glued products.

[0026] First, a disturbance path is set at the junction of the earlywood and latewood of the wood sheet. The release direction of internal stress during drying is guided by S-shaped, fish-scale, or umbrella-shaped curves. Tension points, such as elliptical dimples or fisheye buffers, are introduced at the inflection points or endpoints of the disturbance, forming an active control network for crack induction and termination. This structure not only induces stress diversion but also prevents crack propagation, playing a dual role of stress guidance and passivation, and providing a geometric foundation for subsequent interlayer anchoring.

[0027] Secondly, a grid of non-through breathing grooves is constructed on the gluing interface. The grooves are 20 to 80 microns deep and 50 to 150 microns wide, arranged in diagonal, cross, or honeycomb patterns. Stress-absorbing microstructures, such as stepped, spiral, or capillary grooves, are further introduced within the grooves to enhance their compressibility and viscoelastic buffering capacity. After gluing, the breathing grooves form a composite structure of enclosed microcavities and grained walls. During use, they effectively absorb the shear and tensile stresses in the glue layer caused by shrinkage and expansion of the wood, forming elastic "micro-shock absorbers."

[0028] To achieve dynamic clamping and locking as the wood changes in size, an ecological shrinkage interlayer made of follicle-like natural plant fibers, such as hemp, rush, or reed, is introduced between the glued layers. This interlayer expands upon absorbing moisture and then shrinks upon drying. During the curing period, it responds to the wood's "breathing rhythm" and creates an inherent locking force. The tension points also serve as anchoring areas for the interlayer during its contraction, enhancing its positional stability and long-term binding force.

[0029] During the bonding process, directional pressing and segmented curing control enable the synergistic effects of stress induction, adhesive layer buffering, and interlayer locking. The segmented moisture control strategy, which includes high-humidity slow-release and low-humidity setting stages, ensures that the disturbance pattern, breathing grooves, and interlayer each complete their stress coordination tasks at different stages, forming a staggered, coordinated, closed-loop control chain.

[0030] The technical benefits achieved by this process structure have been validated by multiple test data sets, including dimensional stability testing, interlaminar shear fatigue testing, adhesive layer crack rate statistics, and long-term cyclic swelling experiments. These results demonstrate superior performance compared to control samples that did not utilize this process. In particular, under alternating high humidity / dry heat conditions, specimen deformation was significantly reduced, crack propagation was effectively controlled, and adhesive layer debonding rates decreased by over 60%.

[0031] The present invention realizes the transformation of wood gluing structure from "passive fixation" to "active coordination", embeds elastic buffer mechanism, humidity response mechanism and path induction mechanism in the material body, and constructs a three-dimensional multi-level stress management system. Its structural solution is green and environmentally friendly, highly compatible, and can be industrially processed. It is particularly suitable for scenes with high requirements for dimensional stability and environmental performance, such as solid wood flooring, floor heating panels, high-end furniture and decorative panels. This invention not only achieves significant innovation at the structural level, but also proposes a subversive "self-regulating coordination" mechanism in the gluing concept, which has significant technological progress and industrial promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the overall process of the present invention;

[0033] Figure 2 Detailed flow diagram of the process of the present invention;

[0034] Figure 3 This is a schematic flow chart of the S4 gluing, pressing and curing process of the present invention. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0036] Embodiment one:

[0037] See also Figures 1 to 3 , an anti-deformation and environmentally friendly gluing process based on wood microstructure regulation, comprising the following steps:

[0038] S1. Disturbance pretreatment:

[0039] In the process of the present invention, the wood sheets to be glued are first subjected to a grain path induction pretreatment, which aims to reconstruct the stress release path of the wood during the drying process through artificially designed microstructural intervention, so as to suppress typical deformation problems such as warping, cracking of edges and corners, and damage to the glue layer.

[0040] Specifically, this step selects the junction of the earlywood and latewood of the lumber sheet as the location for the disturbance grain placement. Due to the significant density difference between the earlywood and latewood, this area experiences the most dramatic stress changes during shrinkage. Therefore, artificially guiding the stress release along a pre-set path in this area plays a key role in the dimensional stability of the overall structure.

[0041] The disturbance grain is preferably a shallow groove-like structure that does not extend through the thickness of the wood sheet, carved along a predetermined nonlinear path. Such disturbance grain paths include, but are not limited to, S-shaped, fish-scale, and umbrella-shaped bifurcations. These curvilinear forms offer excellent stress dispersion and flow-conducting capabilities, effectively disrupting the tendency of shrinkage stress to concentrate in a single principal direction. The disturbance grain, with its orientation forming an angle of 10° to 30° with the main grain direction, induces a staggered stress release, thereby eliminating the natural defects of traditional plywood: longitudinal cracking and transverse warping.

[0042] The depth of the disturbance grain is controlled to be 5% to 15% of the wood thickness, sufficient to disrupt cell arrangement and stress paths without significantly weakening the wood's overall strength. The spacing between the disturbance grains can be set based on the wood species and board size, generally within the range of 10 to 40 mm. The grains can be arranged in parallel, staggered, or in a regional grid pattern, creating a stress-guiding network that achieves "localized pressure relief and regional diffusion."

[0043] Disturbance patterns can be created in two ways: mechanical needling, which uses a CNC needle roller or puncture device equipped with a microneedle array to create a directional disturbance on the wood surface along a set trajectory. Ultrasonic vibration, which uses a low-power, flexible ultrasonic vibrator to slide across the surface of the earlywood-latewood interface at a frequency of 20-40 kHz, inducing micro-lysis reactions in the intercellular layers. The latter is particularly suitable for woods with clear growth rings and a soft cell structure, such as poplar and fir. Ultrasonic excitation can effectively establish the starting points of microscopic stress channels without destroying the fiber skeleton.

[0044] After the grain disturbance treatment is completed, it is recommended to preliminarily dry the wood sheets at a low temperature of 40-60°C and control the relative humidity to decrease in stages so that the stress in the grain disturbance area can be released first in the early stage of drying to avoid stress concentration in the entire sheet.

[0045] Through the above-mentioned grain pretreatment steps, not only a "guiding network" of the shrinkage path is established, but also a stress coordination basis is provided for the subsequent breathing trough structure and ecological shrinkage intermediary layer, realizing the overall anti-deformation strategy of plywood from "source stress control" to "multi-layer stress buffering".

[0046] S2. Breathing groove structure processing:

[0047] In the present invention, in order to further alleviate the problems of cracking, delamination, warping and so on caused by uneven force on the bonding interface during the shrinkage or swelling of wood, a non-through micro-breathing groove structure is preset between the contact surfaces of the mutually glued wood sheets to serve as a stress-balancing buffer cavity.

[0048] Specifically, the breathing grooves are shallowly etched microchannels with a depth of 20 to 80 microns and a width of 50 to 150 microns. The grooves do not penetrate the main structure of the wood, but are embedded only in the outermost surface of the glued surface. The spacing of the breathing grooves is controlled to be 300 to 800 microns, and the density and layout can be adjusted according to the size of the glued material, the density of the wood species, and the application scenario.

[0049] Breathing grooves can be arranged in regular patterns, such as a cross, diagonal grid, or honeycomb, creating a microstructured grid on the bonded surface that exhibits multi-directional ductility and continuous deformation buffering. A cross-shaped grid facilitates balanced deformation stress in different directions, while a diagonal arrangement better aligns with the wood grain, mitigating expansion transfer in the main grain direction. A honeycomb pattern provides multi-point support and stress distribution.

[0050] During the actual gluing process, since the breathing groove structure is located in a concave position on the wood surface, some glue can flow into the groove during the pressing stage. However, due to the shallow depth and narrow groove mouth, the glue will not completely fill the groove cavity. Instead, a part of the compressed gas or local glue layer thinning cavity will be retained inside it, thereby forming a "closed microcavity" structure during the subsequent drying process.

[0051] This type of microcavity can act as a "flexible buffer chamber" or "glue layer shock absorber" during the dynamic dry-wet changes of wood during use, with the following mechanism of action:

[0052] Stress sharing: When glued timber shrinks or expands due to changes in ambient humidity, the microcavities in the breathing grooves can absorb some of the shear stress and expansion stress through gas compression or local deformation, preventing the stress from directly acting on the glue line itself.

[0053] Deformation delay: Since the compression and recovery of the microcavity structure have a certain hysteresis, it can provide a buffer time window at the initial stage of external deformation trend, delay the response of the adhesive layer structure, and effectively suppress warping, blistering and adhesive layer brittle cracking;

[0054] Interface softening: The adhesive layer in the breathing groove area is no longer in a rigid solidified state, but has a certain degree of "structural variability" embedded in it, thereby improving the elastic matching ability and fatigue resistance of the bonding interface as a whole.

[0055] The breathing groove can be formed in various ways, for example:

[0056] Laser micro-etching equipment is used for high-speed scanning to form patterned micro-grooves, which is suitable for high-precision customized plates;

[0057] Or use CNC micro-tooth hot pressing die head to roll groove mesh synchronously during hot pressing pre-pressing stage, which is suitable for large-scale continuous production;

[0058] Alternatively, flexible cold die rollers can be used for embossing in a semi-dry state, which is suitable for cost-sensitive manual panel processing scenarios.

[0059] This breathing groove structure forms a synergistic relationship with the disturbance path described in S1: the former relieves the shear stress at the bonding interface, while the latter establishes a stress pilot channel inside the wood. The two together construct a full-link stress harmonization system "from the wood core to the interface".

[0060] Through the above design, the breathing groove not only provides a physical buffering function, but also structurally integrates the "bonding stress adjustment" function into the glue line for the first time, breaking through the traditional perception that the glue layer only plays a fixing role, and realizing an innovative model in which the material itself actively participates in stress management.

[0061] S3. Ecological shrinkage intermediary layer settings:

[0062] To further enhance the dimensional stability and interfacial toughness of glued timber during long-term use, this invention innovatively introduces an eco-shrinkage interlayer between adjacent wood plies. Made from natural plant fibers, this interlayer exhibits biological hygroscopic expansion and drying-shrinkage behavior. Through its natural moisture-responsive properties, it provides synchronous clamping and self-locking structural restraint during the wood's "breathing" process, significantly enhancing the glued structure's resistance to warping, cracking, and delamination.

[0063] Specifically, the intermediary layer is selected from natural plant materials such as hemp fiber, rush, reed silk, and cottonseed hull fiber. These materials generally have a porous structure, a high cellulose content, and good humidity responsiveness. After pre-treatment, they are formed into a follicle-like structure, which has a certain elastic expansion space and a loose arrangement, but can be overall contracted when contracted.

[0064] The typical cross-sectional shape of the intermediary layer is an elliptical cluster or a flat ribbon, and the thickness is controlled between 0.5 and 1.5 mm to ensure that it does not constitute a structural obstacle in the adhesive layer while fully exerting its deformation capacity. The intermediary layer can be arranged in the following two ways:

[0065] Strip layout: The intermediary layers are arranged equidistantly along the long side of the gluing surface, which is suitable for large-sized panels;

[0066] Point array layout: multiple clustered intermediary blocks are evenly arranged, suitable for gluing structures of small and medium-sized furniture.

[0067] In order to optimize its expansion-contraction response rhythm, the intermediary layer is subjected to natural steam softening treatment before pressing to enhance its flexibility and open the micropore structure; then a layer of beeswax powder or natural vegetable oil can be sprayed on the surface to have a slight hydrophobic effect, which is used to delay the initial moisture absorption and prevent it from expanding prematurely during the pressing process, affecting the bonding uniformity.

[0068] After gluing, during the pressing process and initial curing stage, the intermediary layer first absorbs trace moisture from the glue or the environment, slowly expanding to fill the micro gaps or uneven contact surfaces in the glue layer; then, during the drying and curing process, as the ambient humidity drops, the moisture in its internal structure evaporates, the fibers shrink and tighten, forming a stable clamping state.

[0069] It is worth noting that the clamping force comes from the overall shrinkage and contraction behavior of the natural fiber network, without the need for any external tensioning device or synthetic prestressed material. It is an "adaptive locking mechanism" naturally constructed by the structural body.

[0070] This dynamic clamping behavior of the interlayer is synchronized with the wood's own shrinkage rhythm, providing continuous micro-scale constraint compensation during the wood's dimensional changes. Its effects are manifested in the following ways:

[0071] Compensatory clamping: When the wood is slightly deformed due to drying or environmental changes, the interlayer can provide "internal reinforcement" in the opposite direction to offset the interfacial tension;

[0072] Flexible coupling: The intermediary layer is not completely solidified into a rigid block, but it still has a certain buffering capacity inside and is able to absorb micro-fluctuations in the stress of the adhesive layer;

[0073] "Reinforcement in wood" mechanism: Multiple intermediary layers form a dynamic shrinkage network inside the board, which is equivalent to a kind of embedded reinforcement, enhancing the stability of the overall structure.

[0074] This invention proposes for the first time the use of natural intermediary structures with biological swelling and shrinkage behavior for internal stress management of wood glued structures, breaking the previous limitation that deformation resistance could only be improved through rigidity enhancement or external reinforcement, and achieving a new stabilization mechanism for dynamic stress coupling among the glue layer, wood body and intermediary layer.

[0075] This structure is particularly suitable for the following scenarios:

[0076] Solid wood furniture and floor cores that are exposed to humidity fluctuations for a long time;

[0077] Pursuing "zero formaldehyde" and "all plant-based" environmentally friendly adhesive materials;

[0078] Panel products with wide bonding interface and high dimensional accuracy requirements.

[0079] By introducing the ecological shrinkage intermediary layer, the present invention constructs an endogenous, green, self-regulating stress control system, which significantly improves the long-term reliability and environmental applicability of the wood material glued structure.

[0080] S4. Gluing, pressing and curing:

[0081] See also Figure 3 After completing the disturbance pattern path induction process, etching the breathing groove structure, and laying the ecological shrinkage interlayer, the present invention enters the key steps of the gluing process: gluing, pressing, and segmented curing and shaping. This step not only achieves the initial setting of the glue and bonding, but also ensures the coordinated function of disturbance pattern release, microgroove cushioning, and interlayer locking.

[0082] 1) Gluing and assembly

[0083] Use environmentally friendly water-based adhesive (such as soybean-based glue, formaldehyde-free polyvinyl alcohol glue or natural modified starch glue) and apply glue evenly on the wood contact surface with breathing groove structure. The glue amount should be controlled at 80-150g / m 2 , adjust appropriately according to the adsorption capacity of wood and the density of the trough.

[0084] After gluing, the panels are assembled immediately, ensuring that the disturbance path and breathing groove grid are aligned. Simultaneously, an eco-shrinkage interlayer is placed in a pre-set position between the adhesive layers. To prevent the interlayer from expanding and disturbing the adhesive layer due to premature moisture absorption during the lamination process, a "beeswax coating delayed expansion" technique or a high initial lamination pressure can be used for rapid prototyping.

[0085] 2) Directional pressing process

[0086] The pressing process adopts a multi-stage pressure / temperature zone control strategy:

[0087] The first stage: initial pressing and low temperature shaping (40-60℃)

[0088] The pressure is moderate (0.4-0.6MPa) and lasts for 4-6 minutes, so that the glue is evenly distributed and penetrates into the breathing groove; the interlayer begins to adapt to the temperature and humidity and slightly expands to fill the gap, but the overall structure is still in a "stress relief" state;

[0089] The second stage: heating and hot pressing curing (90-120℃)

[0090] Increase the pressure to 0.8-1.0 MPa and maintain for 6-12 minutes (depending on the thickness of the board and the type of adhesive). The adhesive layer completes the polymerization reaction, the interlayer begins to slowly absorb moisture and expand, and the disturbance path is further released, forming a preliminary structural synergy state.

[0091] The third stage: cooling and slow-release pressure (50-60℃)

[0092] The pressure is slightly reduced and maintained for 2 to 5 minutes to release some of the compressive stress, avoid bulging of the edge of the adhesive layer, and provide a transitional stable structure for subsequent maintenance.

[0093] 3) Sectional moisture control maintenance

[0094] After pressing and forming, the plywood is moved into a curing environment for a 24-48 hour period of moisture-controlled curing. The process is as follows:

[0095] Phase 1: High humidity slow release (relative humidity 60% to 70%, temperature 25 to 30°C)

[0096] This stage promotes the natural release of stress in the disturbance path, preventing it from suddenly erupting during the later deformation. At the same time, the interlayer continues to slowly absorb moisture and expand, forming an initial clamping force that is closely attached to the adhesive layer.

[0097] The second stage: dehumidification and shaping (relative humidity drops to 30% to 40%, temperature 20 to 25°C)

[0098] Control the humidity to drop slowly to avoid sudden changes in external stress; at this time, the moisture in the intermediary layer begins to evaporate and shrink, eventually forming a stable biological self-locking contraction belt, and the "wood rib" structure is fully in place.

[0099] Segmented humidity control not only provides a softer drying and shrinkage environment for wood, but also enables the aforementioned grain disturbance paths, breathing groove microcavities and ecological shrinkage layers to complete stress induction, shear expansion buffering and structural locking functions in staggered times, avoiding interference between their functions and forming a staggered and coordinated anti-deformation closed loop.

[0100] 4) Applicable materials and application scenarios

[0101] This process is suitable for processing many types of glued wood products, including but not limited to:

[0102] Natural solid wood panels: used for high-end furniture door panels, tabletops, floor surfaces, etc.

[0103] LVL (Laminated Veneer Lumber) structural panels: used for load-bearing components that require high resistance to internal tensile stress or interface warping;

[0104] Finger-jointed panels: Add a stabilizing layer to the traditional panels, suitable for large-area decorative panels, countertops, etc.

[0105] It is particularly suitable for application scenarios where the humidity and heat environment changes repeatedly, the splicing interface is wide, and strict dimensional accuracy is required, such as floor heating floors, kitchen and bathroom furniture, and building decorative wall panels.

[0106] Example 2:

[0107] In order to further prevent cracks from extending across zones between disturbance strips, the present invention introduces a band-type tension point structure into the disturbance strip path to construct a crack termination mechanism and a disturbance strip stabilization mechanism. The tension point is a local geometric expansion structure arranged at the end of the disturbance strip path, at the inflection point, or at the intersection with the annual ring. The preferred form is an elliptical concave pit, a fisheye end, or a pot-mouth-shaped buffer zone. Its size is slightly larger than the main groove of the disturbance strip, the depth is increased by 5 to 10 microns, and the width is 1.5 to 2 times the width of the disturbance strip groove. The spacing of the tension points can be set to 100 to 200 mm according to the size of the plate, using single-end point arrangement or two-way staggered arrangement.

[0108] The Zhang Ying point structure has the following three functions:

[0109] Crack termination mechanism: During the drying process, if fine cracks extend along the disturbance zone, when encountering the tension point area, its flaring geometry can significantly reduce the stress concentration in front of the crack tip, inducing the crack to blunt, terminate or change its path at this point, thereby effectively blocking the risk of tearing of the board surface;

[0110] Buffering mechanism between disturbance grain segments: The tension points act as "flexible nodes" in the disturbance grain path, absorbing micro-stress fluctuations between adjacent disturbance grain segments. This provides buffering during wood shrinkage or thermal expansion, preventing the disturbance grain band from failing due to its own brittle fracture.

[0111] Intermediary layer locking anchoring mechanism: The tension point area can also serve as the anchoring area of ​​the subsequent ecological shrinkage intermediary layer, forming a "glue layer pressure convergence point" during the bonding process, enhancing the attachment positioning of the intermediary layer when it shrinks, and forming a synergistic structure of "path-intermediary-stress".

[0112] The formation of disturbance grains and tension points can be achieved through integrated CNC machining: flaring parameters can be preset in the CNC trajectory planning; or, in manual operation, a round-headed punch can be used to manually apply pressure to form micro-dimples. After processing, it is recommended that the wood sheets be initially dried at a low temperature of 40-60°C, with a controlled decrease in relative humidity. This allows stress to be released in the disturbance grain areas and tension points during the initial drying phase, preventing stress concentration in large areas.

[0113] Through the above-mentioned disturbance pattern + tension point composite structure, not only the "active guidance network" of the shrinkage path is established, but also the crack "termination node" and the intermediate collaborative interface are formed, which greatly improves the toughness, durability and structural adaptability of the bonded structure in complex humid and hot environments, and provides a basic stable framework for the subsequent breathing groove buffer system and the intermediate layer locking system.

[0114] Example 3:

[0115] During the actual gluing process, because the breathing groove structure is located in a recessed position on the wood surface, some glue will flow into the groove during the pressing stage. However, the present invention has found that if the traditional groove body is completely filled with glue, it is easy to form "rigid ridges", which will cause stress concentration in local areas and weaken the flexible cushioning effect. To this end, the present invention further introduces "stress absorption lines" microstructures in the breathing groove wall to construct a groove body adjustment mechanism with compressibility and viscoelastic hysteresis.

[0116] The "absorption pattern" microstructure refers to a stepped, spiral or capillary stripe-like concave structure micro-engraved along the longitudinal or lateral direction of the inner wall of the respiratory groove. The depth of the concave pattern is 5 to 15 microns and the width is 20 to 40 microns. The morphology includes:

[0117] Longitudinal stepped groove: carved along the axial direction of the groove body to enhance the ability to absorb axial flexible deformation;

[0118] Spiral gentle slope groove: arranged in a spiral shape around the groove wall, with viscous buffering capacity in the shear direction;

[0119] Capillary grooves: simulate the structure of plant ducts, which not only have micro cavities but also facilitate the retention of some gas to form "micro air bags".

[0120] After the glue flows into the breathing groove during the pressing process, it will not completely fill the groove due to the shrinkage of the groove and the existence of suction lines. A small amount of elastic space is retained between the groove wall and the glue. After the glue solidifies, a "closed microcavity + wall buffer" composite structure is formed.

[0121] The microstructure has the following three functional effects:

[0122] Partially flexible trough: The stress absorption pattern makes the originally hard trough have the ability to collapse elastically, avoiding the shear concentration around the trough caused by the "hardening" of the structure after gluing;

[0123] Enhanced shear wave buffering capacity: When wood expands / contracts at a microscale due to moisture absorption or drying shrinkage, the cavities between the stress lines compress / relax, providing a micro-"deformation buffer" effect;

[0124] Improved fatigue resistance: Since the stress absorption line structure can partially accommodate long-term deformation, it can effectively delay the failure mode of the adhesive layer such as peeling and bursting due to "shear fatigue".

[0125] This structure is particularly suitable for bonding parts of multi-layer wood boards, composite floor substrates and decorative layers that are sensitive to humidity fluctuations and are prone to "bulging".

[0126] The absorption pattern structure can be generated by the following processes:

[0127] During the laser micro-etching stage, the main groove and the groove wall texture are engraved simultaneously at one time;

[0128] Using a special CNC rolling die, the surface contains micro-convex stripes, which naturally form grooves when pressed together;

[0129] Alternatively, a continuous groove micro-concave structure can be formed by pre-treating the bonding surface (such as directional abrasive belt drawing).

[0130] Through the introduction of this microstructure, the function of the breathing groove is upgraded from a single "residual cavity type buffer" to a composite mechanism of "active groove wall deformation + adaptive compression absorption + multi-cycle anti-fatigue", realizing the anti-deformation evolution function at the material level, which is a significant breakthrough in the functionality of the existing groove structure.

[0131] The breathing groove and its stress absorption pattern structure, the S1 disturbance pattern induction system and the S3 ecological intermediary layer form a synergistic system, realizing a complete closed loop from wood core stress guidance, dynamic buffering of the glue layer to interface adaptive locking, further improving the overall stability and long-term adaptability of the glued structure of the present invention.

[0132] This specification designed and implemented a systematic comparative test to quantitatively analyze the performance of each key innovative step in this process (perturbation path induction, breathing groove microstructure, and ecological shrinkage intermediary layer) in actual bonding applications, with particular attention paid to the following three key technical issues:

[0133] The problem of wood cracking extension being difficult to effectively curb: conventional drying treatment cannot actively guide the stress release path, and uncontrolled cracks are likely to form at the edges and corners of the board or at the junction of early and late wood, eventually leading to cracking and deformation of the finished product.

[0134] Glue peeling and fatigue cracking problems: Due to the asynchronous swelling and shrinkage of wood and stress concentration, the gluing interface is prone to local debonding or "shear fatigue" during multi-cycle environmental changes, causing interlayer damage and reduced structural life.

[0135] Insufficient anti-warping ability: The existing panel structure has poor dimensional stability in a humid and hot environment, and is prone to overall warping or curling, which limits its applicability in scenarios such as underfloor heating floors and high-end furniture.

[0136] In this experiment, four groups of plywood samples were constructed, corresponding to no innovative treatment (control group) and different implementation plans of the present invention (including the basic disturbance grain-breathing groove-intermediate layer solution, the tension point mechanism in Example 2, and the absorption grain structure in Example 3), and quantitative comparison was carried out under the same wood material, gluing conditions and dry-wet cycle environment.

[0137] The tests employed image processing, ultrasonic scanning, and standardized mechanical stripping methods to measure crack rate, adhesive fatigue failure, and interface deformation, ensuring objectivity and repeatability. The test results were used to systematically evaluate the effectiveness of the proposed three-in-one gluing strategy: "source stress induction - interface buffering - intermediate layer locking." This validated the practical value and innovation of this process in improving the structural stability and environmental adaptability of glulam products.

[0138] 1. Test Prerequisites and Sample Design

[0139]

[0140] 2. Sample Grouping

[0141]

[0142]

[0143] 3. Test parameters and methods

[0144]

[0145] 4. Test results comparison table

[0146] Group Corner crack rate Adhesive layer peeling rate Number of fatigue cracks Warpage Group A (Traditional Crafts) 7.60％ 12.30％ 9 articles 5.2mm / m Group B (Basic Plan) 2.40％ 5.80％ 4 2.1mm / m Group C (+Zhang Yingdian) 1.10％ 5.20％ 3 1.8mm / m Group D (+absorption lines) 2.20％ 2.90％ 1 1.5mm / m

[0147] 5. Results Analysis and Conclusion

[0148] The basic scheme (Group B) has significantly improved the cracking and peeling problems of plywood under dry-wet cycles, with warpage reduced by about 59.6% and interface cracks reduced by more than 50%, proving the basic effectiveness of the S1-S3 synergistic mechanism in source stress guidance and interface stress buffering.

[0149] After the "tension point" is introduced in Example 2 (Group C), the corner crack rate drops to 1.1%, which is the best. This shows that it has a significant effect on the crack termination mechanism, effectively preventing cracks from extending across the boundaries between the disturbance paths and enhancing the stability of the disturbance paths.

[0150] In Example 3 (Group D), a viscoelastic buffering mechanism was introduced by the “stress absorption line” microstructure of the breathing groove wall, which further reduced the adhesive layer peeling rate to 2.9% and the number of fatigue cracks to 1, indicating that the structure can continuously absorb microstrains during multi-cycle stress disturbances and delay interface degradation.

[0151] Comprehensive evaluation: The present invention significantly improves the overall anti-deformation ability, achieving a complete closed loop from "stress guidance → buffering → locking"; innovatively introduces natural structural induction and biological response mechanisms, and gets rid of dependence on synthetic reinforcement materials; all core performance indicators are superior to existing traditional solutions.

[0152] The core implementation principle of the present invention is to establish a multi-level, multi-scale, multi-stage coordinated stress regulation system during the wood gluing process through means such as disturbance grain induction, breathing groove buffering, ecological intermediary clamping, and segmented pressing and moisture control maintenance, thereby significantly improving the dimensional stability and reliability of the wooden structure.

[0153] First, the wood is pre-treated with disturbance grain before gluing, that is, a non-through shallow disturbance grain path is carved at the junction of early and late wood. This area is where stress mutations are easily concentrated. The internal stress of the wood during shrinkage is guided by the disturbance grain to be released along the set path, destroying its concentration trend in the main grain direction. In order to prevent the cracks from continuing to expand between the disturbance grain bands, a band-type tension point structure is further set at the end or inflection point of the disturbance grain path, such as an elliptical concave or a fisheye-shaped expansion area. These geometric nodes have multiple functions such as terminating cracks, alleviating stress fluctuations between disturbance grain segments, and serving as anchor points for the intermediate layer, thereby constructing a composite path network of "stress induction + stress termination + anchoring synergy".

[0154] Secondly, non-through micro-breathing grooves are etched into the contact interface of the wood, forming a stress-buffering network within the glue layer. These breathing grooves are arranged in a crisscross or diagonal grid pattern. During the glue-pressing process, some of the grooves are filled with glue, but the microcavity structure remains within, forming a "flexible shock-absorbing zone." Simultaneously, "stress-absorbing grain" microstructures are introduced into the groove walls, further constructing a groove system that is elastically collapsible, provides shear buffering, and has a delayed response, significantly improving the dynamic compatibility and fatigue resistance of the interface.

[0155] Next, a follicle-shaped ecological shrinkage intermediary layer made of natural plant fibers is sandwiched between the glued layers. This intermediary layer absorbs moisture and fills the gaps in the early stage of gluing, and shrinks and tightens due to water loss during the later drying process, forming an "endogenous muscle force" synchronized with the shrinkage process of the wood, that is, a natural dynamic clamping mechanism of "slow release of swelling during moisture-self-locking of shrinkage during moisture", providing a stable and lasting internal restraint force for the glued structure.

[0156] During the entire process, through gluing, sheet assembly and segmented pressing control (including initial pressure shaping, hot pressing curing, slow release and cooling) and combined with subsequent segmented moisture control curing (high humidity slow release → low humidity shaping), the disturbance stress release, groove microcavity buffering and intermediary layer locking functions are coordinated and played in time, forming a set of anti-deformation closed-loop mechanism with clear rhythm and staggered action.

[0157] Ultimately, this process is applicable to a variety of glulam structural products, including solid wood panels, LVL (Laminated Laminated Lumber), and finger-jointed panels. It demonstrates exceptional stability and durability, particularly in applications requiring high dimensional accuracy and subject to dramatic fluctuations in humidity and heat, such as floor heating floors, kitchen and bathroom furniture, and architectural veneer panels. The entire process, encompassing structural design, interface buffering, and material self-regulation, transforms glulam structures from passive deformation resistance to active stress guidance, dynamic reinforcement locking, and flexible buffering, representing a significant breakthrough in traditional gluing technology.

[0158] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An anti-deformation environmentally friendly gluing process based on wood microstructure regulation, characterized in that: The steps include: S1. Disturbance pretreatment: The wood sheets to be glued are subjected to a disturbance path induction treatment along their thickness. Shallow disturbance grains are driven along a set curve at the junction of the early and late wood to form stress-oriented fracture bands, which are used to induce stress release along a specified path during the drying process. S2. Breathing groove structure treatment: Etch a non-through micro-breathing groove grid on the contact surface of the glued wood. The breathing groove depth is 20 to 80 microns. It is used to form stress-compensating micro-cavities during the glue pressing and drying process, and slowly release the concentrated interfacial stress caused by wood shrinkage or swelling; S3. Setting up an ecological shrinkage intermediary layer: A follicle-shaped intermediary layer made of natural plant fiber material is sandwiched between the glued layers. The intermediary layer expands when it absorbs moisture in the early stage and shrinks and tightens when it dries in the later stage, so as to form a self-locking clamping force that dynamically responds to the breathing rhythm of the wood during the gluing process; S4. Gluing, pressing and curing: After the wood is treated, adhesive is applied, and directional pressing and segmented temperature-controlled curing are carried out to ultimately form environmentally friendly glued wood products with high dimensional stability and anti-warping capabilities.

2. The process according to claim 1, characterized in that: The disturbance grain path is an S-shaped, fish-scale or umbrella-shaped bifurcated curve, the disturbance grain depth is 5% to 15% of the wood thickness, and the angle between the disturbance grain direction and the wood grain direction is 10° to 30°.

3. The process according to claim 1, characterized in that: The disturbance pattern is formed by a mechanical needling device or an ultrasonic vibration device, and the ultrasonic vibration device is used to stimulate the micro-lysis structure of the intercellular layer along the boundary area between the earlywood and latewood.

4. The process according to claim 1, wherein: The breathing grooves are arranged in a cross or oblique grid shape, with a groove width of 50 to 150 microns and a groove spacing of 300 to 800 microns.

5. The process according to claim 1, characterized in that: The breathing groove is partially filled with glue during the gluing process to form a closed microcavity. The microcavity is used to absorb the shear stress and expansion stress of the glue layer during the subsequent drying and shrinking.

6. The process according to claim 1, characterized in that: The follicle-shaped intermediate layer is selected from hemp fiber, rush, reed silk or cottonseed shell fiber, and its cross-section shape is elliptical cluster or flat belt, and its thickness is 0.5-1.5 mm.

7. The process according to claim 6, characterized in that: The intermediate layer is softened by natural steam before lamination, and its surface is sprayed with natural beeswax powder to delay the onset of moisture absorption and expansion.

8. The process according to claim 1, characterized in that: The ecological shrinkage intermediary layer shrinks synchronously with the changes in the internal humidity of the wood during the curing process, forming a dynamically distributed "wood reinforcement" structure to resist warping and interlayer cracking.

9. The process according to claim 1, characterized in that: The bonding curing adopts a segmented moisture control strategy, including a high-humidity slow-release stage and a low-temperature setting stage, which is used to coordinate the release of disturbance wrinkle stress and the locking reaction of the intermediate layer.

10. The process according to claim 1, characterized in that: The wood is natural solid wood board, LVL laminated lumber or finger-jointed board, which is suitable for scenes with high requirements for dimensional stability, such as flooring, furniture, and building finishes.

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