An internal toughening micro-slit patch process for thick load-bearing wood panels

Abstract

The present application relates to a kind of internal toughening microslit insert process of thick layer load-bearing wood board.The process is formed by periodic arrangement microslit in the length direction in the interior of wood board, and microslit is alternately composed of throat and cavity.Throat is designed as narrow and short narrow channel, and internal gap is kept and water-repellent dry powder zone is arranged for crack capture and wet migration blocking;Cavity is wide and long containing area, and toughness primer and high modulus structural adhesive are applied, and insert piece is embedded in longitudinal grain direction and wood grain is offset angle, for crack deflection, bridging and energy consumption.Blind hole is arranged at both ends of microslit and wet-sensitive plug is installed, to realize humidity self-regulation and control.After the surface of wood board is closed, periodic crack energy dissipation unit is formed by pressing and curing.The present application can effectively inhibit crack straight-through, and significantly improve the toughness, durability and service safety of thick layer load-bearing wood board while maintaining bearing capacity.

Description

Technical Field

[0001] This invention belongs to the field of wood processing and composite material preparation, specifically a process for internal toughening micro-slit inlay of thick load-bearing wood panels. Background Technology

[0002] Wood, as a natural and renewable material, is lightweight, high-strength, easy to process, and has excellent decorative properties, making it widely used in construction, furniture, and structural engineering. With the increasing demands for load-bearing capacity and durability in modern construction and furniture industries, thick-layer load-bearing wood panels are gradually becoming key components. However, wood naturally possesses anisotropy and the tendency for cracks to propagate along the grain. When subjected to bending, impact, or changes in humidity, it is prone to splitting and brittle fracture, severely affecting its structural safety and service life.

[0003] To improve the mechanical properties of wood panels, existing technologies primarily employ the method of embedding reinforcing units inside or on the surface of the wood. For example, traditional continuous inlay processes typically involve machining continuous grooves along the length of the wood panel and embedding wood or composite material strips to enhance load-bearing capacity. However, this process has the following drawbacks:

[0004] The continuous inserts and adhesive layers form a through channel. When the wood board cracks, the crack will spread rapidly along the channel, leading to brittle fracture and making it difficult to achieve effective crack passivation and energy dissipation.

[0005] Continuous channels also become pathways for capillary water or moisture migration, which can easily cause interface deterioration and adhesive failure in humid and hot environments, leading to a decline in the long-term durability of the wood panels.

[0006] Due to the lack of a distributed energy dissipation structure, the energy consumption during crack propagation is limited, and toughness cannot be significantly improved.

[0007] Another existing technology is solid laminate board manufacturing, which improves the overall strength of wood through lamination and gluing. However, this process offers limited improvement in toughness, and once cracks form along the grain, there is a lack of effective containment and branching mechanisms, making rapid penetration easy. Furthermore, solid laminate boards lack internal humidity control structures, making them susceptible to interface damage due to humidity changes during long-term service.

[0008] In summary, existing wood reinforcement processes either lead to open crack channels and severe moisture migration, or are insufficient in toughening and durability, failing to meet the comprehensive requirements of high toughness, durability, and load-bearing stability for thick load-bearing wood panels under complex service environments. Therefore, a new internal toughening process is urgently needed, combining structural design and functional regulation to effectively control crack propagation paths, enhance energy dissipation capacity, and block moisture migration channels while maintaining the load-bearing capacity of the wood, thereby significantly improving the performance and lifespan of thick load-bearing wood panels. Summary of the Invention

[0009] The purpose of this invention is to provide an internal toughening micro-slot inlay process for thick load-bearing wooden boards. Through the synergistic effect of geometric design, interface control, material selection and humidity control measures, this invention forms a complete crack control and durability assurance system, achieving a comprehensive improvement in toughness, durability and load-bearing performance.

[0010] The technical solution adopted in this invention is as follows:

[0011] An internal toughening micro-slot inlay process for thick load-bearing wooden boards includes the following steps:

[0012] S1. Micro-slits are formed along the length of the interior of a thick wooden board, the micro-slits including throats and cavities that are periodically and continuously arranged and connected in sequence, wherein the width of the throat is smaller than the width of the cavity;

[0013] S2. A water-repellent dry powder band is provided at the throat, and an underfill gap is maintained so that the throat becomes a crack-catching zone, which is used to block capillary water migration and guide cracks to initiate, stop or deflect here.

[0014] S3. Apply tough base adhesive and high modulus structural adhesive sequentially in the cavity, and embed a wooden inlay. The longitudinal grain direction of the inlay is offset at a certain angle from the main grain direction of the wood board, so as to form a bridging and pull-out energy dissipation effect when the crack enters the cavity.

[0015] S4. Blind holes are machined at both ends of the micro-slit, and moisture-sensitive plugs are pressed in. The moisture-sensitive plugs expand radially to close the channel when wet and retract to maintain ventilation when dry.

[0016] S5. After pressing and curing, the micro-slits are made into periodic crack energy-dissipating units.

[0017] The larynx is 0.20–0.45 mm wide, the cavity is 1.2–1.8 mm wide, the cavity is 4–10 mm long, and the periodic pitch is 40–60 mm.

[0018] The underfill gap in the throat has a thickness of 0.1–0.2 mm, which is used to absorb the stress of wet expansion and dry shrinkage and delay crack propagation.

[0019] The wooden inlay has an island structure, a thickness of 0.8–1.5 mm, a length that is basically the same as the cavity, and an offset angle of 10°–15° from the main grain direction of the wood.

[0020] The ends of the wooden inlays are machined into R2-3mm round noses to reduce stress concentration and increase the probability of crack deflection.

[0021] The coating rate of the toughening base coat is 25–40 g / m². 2 It is used to provide an energy-dissipating interface during crack propagation; the high-modulus structural adhesive has a filling rate of 60–70% in the cavity and is used to form a load-bearing and bridging interface.

[0022] The water-repellent dry powder tape is formed from wax-based or fluorine / silicone modified micropowder, with a thickness of 2–5 μm, and forms a high contact angle interface near the throat to enhance capillary breaking function.

[0023] The moisture-sensitive embolism is molded from cork powder, cellulose fiber, and a moisture-absorbing and swelling modifier, with a dry density of 0.35–0.45 g / cm³. 3 With a wet volume expansion rate of 2% to 6%, it is used to maintain the self-closing function of the throat port for a long time.

[0024] Among them, a 10% to 20% blind section is left at the end of the micro-slit to prevent the end crack from extending to the edge of the wood.

[0025] This also includes creating shallow grooves or covering the surface of the wood board with a thin wood veneer to achieve an apparent seal. The shallow grooves or veneer are isolated from the throat and do not fill the gaps, so as to balance the appearance integrity and the internal toughening function.

[0026] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0027] In traditional continuous inlay processes, once a crack propagates along the adhesive line or continuous channel of the inlay, it is prone to rapid penetration, leading to brittle failure. This invention, by forming a periodic "throat-cavity" structure within the wood panel, causes the crack to be repeatedly captured, deflected, and branched during propagation, thereby lengthening the propagation path, increasing the energy required for propagation, and significantly improving the crack resistance and toughness of the wood panel.

[0028] In traditional processes, continuous adhesive layers or fiber channels become pathways for moisture and water migration, leading to interface degradation and decreased durability. This invention incorporates a sub-fill gap at the throat, supplemented by a water-repellent dry powder tape, and moisture-sensitive plugs at both ends of the micro-slit. This actively blocks capillary water channels and self-adjusts the sealing state according to ambient humidity, effectively suppressing interface failure caused by moisture migration.

[0029] Ordinary solid laminates lack internal energy-dissipating structures, and once a crack appears, it propagates linearly along the grain direction, with energy unable to be effectively dissipated. This invention incorporates inserts and a flexible-hard gradient adhesive layer within the cavity. When a crack enters the cavity, it is not only forced to deflect by the anisotropic inserts, but also continuously dissipates energy during insert removal and adhesive layer shearing, thus achieving a stable energy dissipation mechanism and preventing sudden damage.

[0030] While continuous insert technology can improve static load-bearing capacity to some extent, it is difficult to avoid problems such as wet migration and brittle propagation. This invention achieves a balance between flexible energy dissipation and strong load-bearing capacity through periodic structural units, maintaining overall load-bearing capacity and dimensional stability while improving toughness, thus avoiding performance limitations.

[0031] Existing products are prone to interfacial peeling, splitting, and deformation under damp heat cycling or long-term load. This invention, through multi-layered toughening and moisture control design, slows down the crack propagation rate, keeps the interface stable, and significantly improves the splitting resistance, thereby extending the service life and service safety of the wood board.

[0032] Compared with existing technologies, this invention is not a single improvement, but rather a complete crack control and durability assurance system formed through the synergistic effect of geometric design, interface control, material selection and humidity control measures, achieving a comprehensive improvement in toughness, durability and load-bearing performance. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the process of the present invention;

[0034] Figure 2 This is a schematic diagram of a wooden board after the insert of the present invention has been embedded;

[0035] Figure 3 This is a cross-sectional schematic diagram of the wooden board of the present invention.

[0036] In the diagram, 1. Thick wooden board; 2. Micro-slit; 21. Throat; 22. Cavity; 23. Underfilled gap; 3. Patch; 4. Water-repellent dry powder tape; 51. Tough base adhesive; 52. High modulus structural adhesive; 6. Blind hole; 7. Moisture-sensitive plug. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the 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 merely illustrative and not intended to limit the invention.

[0038] See Figures 1 to 3 This invention relates to

[0039] This invention relates to a process for internal toughening micro-slit inlay in thick load-bearing wood panels. The process involves forming a periodically arranged micro-slit structure 2 along the length of the wood panel 1. Each micro-slit 2 consists of alternating throats 21 and cavities 22. The throats 21 are narrow and short channels, while the cavities 22 are wide and long receiving areas. An underfill gap 23 is maintained in the throat 21 region and a water-repellent dry powder strip 4 is provided. A toughening primer 51 and a high-modulus structural adhesive 52 are applied to the cavity 22 region, and a wood inlay 3 is embedded. Blind holes 6 are provided at both ends of the micro-slits 2, and moisture-sensitive plugs 7 are installed. The surface is then sealed. After pressing and curing, the micro-slits 2 form periodic crack energy-dissipating units within the wood panel 1, thereby significantly improving the toughness, durability, and load-bearing stability of the wood panel 1. The following detailed description is provided with reference to specific embodiments.

[0040] In this embodiment, 30mm thick larch laminated solid wood was selected as the thick layer board 1, with an average wood density of approximately 0.55g / cm³. 3 The moisture content is between 10% and 12%, ensuring dimensional stability during processing and consistent performance of the final product. The thickness of the thick-layer wood board 1 is generally between 25 and 50 mm, which can be selected according to different load-bearing requirements. The micro-slit 2 structure of the present invention extends along the thickness direction of the wood board 1, therefore the wood board 1 itself must have sufficient thickness to accommodate the complete micro-slit 2 unit.

[0041] Microslits 2 are formed inside the thick wood panel 1 using CNC step milling. The geometry of the microslits 2 consists of periodically arranged throats 21 and cavities 22. The throats 21 are designed with a width between 0.20 and 0.45 mm, a length of 2 to 3 mm, and a depth of 60 to 90% of the thickness of the wood panel 1, avoiding complete penetration through the wood panel 1 to maintain the continuity and load-bearing capacity of the matrix. The main function of the throats 21 is to form a crack-catching zone, blocking the continuous migration of capillary water, and guiding crack initiation, cessation, or deflection during crack propagation. The cavities 22 are designed with a width between 1.2 and 1.8 mm and a length of 4 to 10 mm, serving as energy-dissipating zones to accommodate the adhesive layer and wood veneer 3. The cavities 22 and throats 21 are arranged alternately to form a complete periodic structure, with the pitch of each cycle controlled within the range of 40 to 60 mm. This design ensures that when a crack extends along the wooden board 1, it will encounter the throat 21 and cavity 22 multiple times, thus being continuously blocked and having its energy dissipated, significantly improving the overall toughness.

[0042] In the throat region 21, an underfill gap 23 is maintained, with a thickness between 0.10 and 0.20 mm. The underfill gap 23 is a tiny, unfilled void that provides an energy dissipation and stopping point for cracks, preventing them from directly penetrating the throat region 21 and instead forcing them to stop, become passive, or change direction. Simultaneously, a water-repellent dry powder tape 4 is sprayed onto the throat 21 surface. This dry powder tape 4 can be a mixture of wax-based powder and fluorosilicone-modified micropowder, with the wax-based powder comprising 50-80% and the fluorosilicone-modified micropowder comprising 20-50%. The average particle size of the dry powder is 3-8 μm, and the coating thickness is 2-5 μm, which significantly increases the contact angle of the throat 21 surface to over 95°, thereby blocking the continuous upward path of capillary water. This design ensures that the throat 21 not only serves as a crack control zone but also prevents wet migration during long-term use, improving durability.

[0043] In cavity 22, a two-layer adhesive system is applied. First, a toughening primer 51 is applied. This primer is a modified polyurethane with a cured modulus between 200 and 400 MPa and an elongation at break of not less than 50%. The toughening primer 51 is applied by dot or line coating, with a coverage rate of 25–40 g / m². 2 The primary function is to provide a flexible energy-dissipating interface, allowing energy to dissipate through the deformation of the base adhesive 51 when a crack enters the cavity 22. Subsequently, a high-modulus structural adhesive 52 is applied, using a two-component epoxy resin with a cured modulus of 1.5–2.0 GPa and a shear strength ≥8 MPa. This adhesive is applied intermittently with a filler ratio of 60–70%, providing load-bearing capacity and forming a high-strength interface with the insert 3. This flexible-hardness gradient adhesive system forms inside the cavity 22, enabling energy dissipation while maintaining load-bearing strength during crack propagation.

[0044] A wooden inlay 3 is embedded in the cavity 22. The inlay 3 is made of birch or maple and has a density of 0.55–0.70 g / cm³. 3 The insert 3 is constructed as an island structure, with a thickness of 0.8–1.5 mm. Its length is approximately the same as that of the cavity 22, while its width is 0.1–0.2 mm smaller than that of the cavity 22 for ease of installation. The longitudinal grain direction of the insert 3 is offset by 10–15° relative to the main grain direction of the wood panel 1. This design aims to force the crack to deflect when it encounters the oppositely oriented insert 3 as it propagates to the cavity 22, thereby increasing the crack path length and propagation energy. The ends of the insert 3 are machined into rounded noses with a radius of 2–3 mm to avoid stress concentration caused by sharp corners. During installation, the insert 3 is pressed in after the adhesive is applied to the cavity 22, allowing it to bond with the tough base adhesive 51 and the high-modulus structural adhesive 52 to form a stable bridging energy-dissipating unit. During crack propagation, the insert 3 will experience pull-out and slippage. This process, accompanied by the stretching and shearing of the adhesive layer, can continuously dissipate energy and improve overall toughness.

[0045] Blind holes 6, 4–6 mm in diameter and 6–12 mm in depth, are machined at both ends of the micro-slit 2 for installing moisture-sensitive plugs 7. The moisture-sensitive plugs 7 are made from a mixture of cork powder, cellulose fibers, and a moisture-absorbing and expanding agent in a ratio of 50–70%:15–25%:15–25%. The dry density of the plugs 7 is 0.35–0.45 g / cm³. 3 Between these values, the wet volume expansion rate is 2–6%. When the ambient humidity increases, the plug 7 absorbs moisture and expands, radially sealing the blind hole 6 channel and blocking moisture migration; when the environment is dry, the plug 7 contracts, maintaining ventilation and preventing internal water accumulation. The plug 7 is removable and replaceable, ensuring long-term moisture control. This design gives the micro-slit 2 self-sealing properties at both ends, further improving the durability of the wooden board 1.

[0046] After the adhesive is applied and the insert 3 is installed, the entire assembly is pressed at a pressure of 0.6–1.0 MPa and a temperature of 60–80°C for 20–40 minutes to ensure complete curing of the adhesive layer and stable bonding of the insert 3. During the pressing process, the pressure and temperature should be controlled to be uniform to avoid the adhesive from accidentally filling the throat 21, thus maintaining the integrity of the underfill gap 23. After curing, a sealing treatment is performed on the surface of the wood board 1. Two methods can be selected: First, a shallow groove of 1.5–3 mm depth is milled on the surface of the wood board 1, with the bottom of the groove at least 3 mm away from the throat 21. A thin strip of the same material is embedded in the groove, glued and fixed, and sanded flush; Second, a 0.5–0.8 mm thick veneer wood or melamine veneer is applied to the entire surface to cover it. Regardless of the method, it is necessary to prevent the adhesive from seeping into the throat 21 area to ensure the function of the underfill gap 23.

[0047] The finished wood panel 1, after performance testing, exhibited excellent toughening effects. In the three-point bending test, the crack was captured and deflected in the throat region 21, preventing the formation of a through crack. Within the cavity 22, the insert 3 and the adhesive layers 51 and 52 formed a bridge. When the crack propagated, the insert 3 was pulled out and slipped, and the adhesive layers 51 and 52 underwent shear deformation, resulting in significant energy dissipation. Compared to the control panel without this process, the average energy dissipation was increased by 2–3 times. In the damp heat cycling test, the sample was placed in a 30–90% relative humidity cycling environment for 5 cycles. The test results showed that the interfacial shear strength retention rate reached over 85%, significantly better than the 70% of the traditional continuous insert process. In the splitting resistance test, the splitting load along the grain direction increased by 30–40%, demonstrating good crack resistance stability. In the capillary climb test at the port, the sample end was exposed to water for 30 minutes. The water line along the front edge of the seam was less than or equal to 15 mm, while the control plate exceeded 40 mm, proving that the 21-segment capillary design at the throat effectively blocked wet migration.

[0048] This invention achieves the following through the combined effects of geometric structural design, functional gaps and coatings, a multi-layer adhesive system (51, 52), energy bridging elements, and a moisture control unit: cracks are captured and deflected at the throat 21; cracks encounter the insert 3 at the cavity 22 for bridging and energy dissipation during pull-out; adhesive layers 51, 52 provide crack resistance and load-bearing functions with a soft-hard gradient; dry powder tape 4 and moisture-sensitive plug 7 block moisture migration; and a periodic structure ensures that cracks are repeatedly blocked and energy is accumulated. As a result, the toughness, durability, and load-bearing capacity of the thick-layer wood panel 1 are significantly improved.

[0049] Specifically, when microcracks develop in the wood panel 1 under load, the cracks propagate rapidly along the main grain direction of the wood. Due to the presence of periodic throats 21 inside, the cracks are forced to concentrate in this area when they propagate to the throats 21. The throats 21 have small geometric dimensions and contain underfilled gaps 23, which causes the cracks to become blunted due to energy concentration after entering the throats 21, significantly reducing their propagation rate. Inside the cavity 22, there are inserts 3 offset from the main grain of the wood at a 10–15° angle. When the cracks encounter the inserts 3, they are forced to turn or branch, thereby lengthening the crack path and significantly increasing the energy required for propagation.

[0050] After the adhesive layers 51 and 52 have cured, the wooden insert 3 in cavity 22 is firmly bonded to the substrate. When a crack enters cavity 22 and attempts to penetrate, the insert 3 acts as a "bridge," connecting the upper and lower interfaces of the crack. Under continuous external force, the insert 3 will be gradually pulled out or slid out. During this process, the tough base adhesive 51 undergoes large deformation and absorbs energy, while the high-modulus structural adhesive 52 provides pull-out resistance and shear energy dissipation. The entire process of insert 3 being pulled out is equivalent to a gradual energy dissipation mechanism, which not only consumes a lot of energy but also significantly slows down the crack propagation rate.

[0051] The cavity 22 employs a gradient design of "flexible and tough base adhesive 51 + rigid high-modulus structural adhesive 52". When a crack initiates, it first acts on the tough base adhesive 51, whose low modulus and high ductility blunt the crack tip, preventing instantaneous penetration. Subsequently, the crack propagates to the high-modulus structural adhesive 52, which provides greater resistance and shear strength, requiring more energy for the crack to continue propagating. This synergistic effect of the flexible and rigid adhesive layers ensures energy dissipation without compromising load-bearing capacity.

[0052] The underfilled gap 23 within the throat 21, together with the water-repellent dry powder tape 4, cuts off the continuous channels of capillary water within the wood. After the water-repellent dry powder tape 4 is applied, the contact angle of the throat 21 surface is ≥95°, preventing water molecules from forming a stable capillary ascent path. Moisture-sensitive plugs 7 are installed in the blind holes 6 at both ends of the micro-slit. When humidity is high, the plugs 7 absorb moisture, expand, and seal the channels, preventing water vapor from entering; under dry conditions, the plugs 7 shrink, maintaining gas exchange and preventing moisture retention. This system ensures that although the micro-slit 2 exists, it does not become a weak point for moisture migration, but rather actively controls humidity.

[0053] The throat 21 and cavity 22 of the micro-slit 2 are arranged periodically, with a pitch controlled at 40–60 mm. As the crack propagates within the wooden board 1, it encounters multiple "capture-deflection-energy dissipation" units. Each unit consumes some energy, and the crack propagation direction and speed are altered multiple times, ultimately achieving a significant deceleration and energy dissipation effect. This periodic blocking mechanism is similar to the "reinforced concrete bridging crack" principle, ensuring that the crack cannot penetrate rapidly in a straight line.

[0054] The throat 21 can be opened on one side or staggered vertically; the depth of the single-sided opening is 30-50% of the thickness t of the wood board 1, preferably located in the ±10%t region of the neutral axis in the thickness direction; in the double shallow throat structure with staggered vertical opening, the throat depth on each side is 0.2-0.35t, and the upper and lower throat segments are staggered in the length direction, with no through cut at any cross section. The bridging effect between the insert 3 and the adhesive layers 51 and 52 enables the wood board 1 to exhibit higher toughness and ductility under bending or tensile conditions, avoiding brittle fracture. The presence of the moisture-sensitive plug 7 ensures durability during long-term use and prevents moisture cycling from causing adhesive layer failure or wood decay.

[0055] As can be seen from the above embodiments, the internal toughening micro-slit inlay process of the thick load-bearing wooden board 1 of the present invention not only solves the problems of wet migration channels and brittle failure in the traditional continuous inlay process, but also achieves a comprehensive effect of crack capture, crack deflection, bridging energy consumption, and durability improvement through periodic crack energy dissipation units. Although the throat 21 is a narrow area that may become a crack initiation point, under the action of the underfill gap 23 and the water-repellent dry powder band 4, the crack is restricted and regulated here, and instead enters the energy dissipation area of ​​the cavity 22. Under the synergistic effect of the inlay 3 and the adhesive layers 51 and 52, the energy is gradually consumed, and sudden penetration will not occur. The periodic structure makes the crack continuously blocked and energy dissipated on the propagation path, thereby significantly improving the bending fatigue life and long-term service safety of the thick wooden board 1.

[0056] To further verify the effectiveness of the internal toughening micro-slot inlay process for thick-layer load-bearing wood panels of this invention, the applicant prepared multiple sets of samples with different parameter combinations and conducted comparative experiments with existing mainstream wood panel products. The purpose of this experiment is:

[0057] Verification of toughening effect: The effects of the throat 21, cavity 22, insert 3 and adhesive layer system 51 and 52 in microcrack 2 on inhibiting crack propagation and achieving bridging energy dissipation were investigated by three-point bending fatigue test and splitting load test.

[0058] Verification of moisture control durability: The effects of the throat underfill gap 23, water-repellent dry powder strip 4, blind hole 6 and moisture-sensitive plug 7 on blocking moisture migration and maintaining interface strength were evaluated through capillary climb test and damp heat cycle shear test.

[0059] Compared with existing processes: two commonly used products in the market were selected as controls: one is a continuous laminated board C1, and the other is a regular solid laminated board C2. Neither of them contains the periodic micro-slits and humidity control unit described in this invention. The test results are used to demonstrate the performance advantages of this invention.

[0060] Determining the process window: By designing six different combinations within the parameter range disclosed in this invention, the effects of different throat depths, cavity sizes, underfill thicknesses, and insert materials on overall performance are explored, and the optimal parameter range is screened to provide a basis for industrial applications.

[0061] All tests were conducted under the same wood substrate, dimensions, and environmental conditions to ensure the comparability and scientific validity of the results. The test data cover four aspects: wet migration, durability, toughening properties, and acoustic properties, comprehensively reflecting the differences between this invention and existing technologies.

[0062] Specifically, the sample material was larch laminated solid wood, 30mm thick, with a density of approximately 0.55g / cm³. 3 Moisture content 10–12%.

[0063] Sample size: 300mm×50mm×30mm.

[0064] Processing method: The sample of this invention is formed by CNC stepped milling to create a micro-slit 2, including a throat 21, a cavity 22, an underfill gap 23, a dry powder tape 4, adhesive layers 51 and 52, a insert 3, a blind hole 6, and a moisture-sensitive plug 7, and then surface sealing treatment is performed. The control sample uses a mainstream conventional continuous insert laminate or a common solid laminate.

[0065] Test items and conditions:

[0066] Capillary climb test: The tip is in contact with water for 30 minutes, and the height of the waterline front is recorded (mm).

[0067] Shear strength retention rate during wet heat cycling: The cycle was repeated 5 times, with each stage lasting 12 hours, and the interfacial shear strength retention rate (%) was measured.

[0068] Three-point bending fatigue residual strength: The residual strength retention rate (%) was measured after a span of 240 mm, a maximum load of 60% of the static bending limit, and 1 × 10^5 cycles.

[0069] Splitting load: Measure the increase (%) in splitting limit load relative to the blank plate when stretched in the parallel grain direction.

[0070] Acoustic performance: 50–500Hz sweep frequency excitation, measure the increase in peak sound pressure level relative to the blank plate (dB).

[0071] The experimental results are summarized in the table below:

[0072]

[0073] Results analysis:

[0074] ① The capillary climb rate of E1–E6 in this invention is ≤14mm, which is significantly better than C1 (41mm) and C2 (28mm). This indicates that the wet control system consisting of throat 21 + underfill gap 23 + dry powder belt 4 + plug 7 is effective.

[0075] ② The shear retention rate of E1–E6 is 85–90%, which is higher than that of C1 (72%) and C2 (76%). This demonstrates that the adhesive layer gradient and humidity control structure ensure interfacial stability in humid and hot environments.

[0076] ③ Bending fatigue residual strength: E1–E6 87–90%, while C1 70% and C2 62%. Splitting load increase: E1–E6 increased by 36–41%, C1 22%, and C2 0%. The periodic “throat-cavity-throat” unit of this invention effectively inhibits direct crack penetration.

[0077] ④ The acoustic increment of this invention is only +0.9 to 1.5 dB; C1 +4.8 dB, C2 +2.9 dB. This indicates that the underfill gap and discontinuous cavity reduce resonance and squeaking.

[0078] ⑤ E3 (bamboo fiber) and E2 (maple) have the best balance; although E6 (carbon fiber) has a slightly higher acoustic increment (+1.5dB), its strength and durability are still better than the control.

[0079] In summary, the embodiments of the present invention (E1–E6) are significantly superior to mainstream continuous laminates (C1) and ordinary solid laminates (C2) in terms of moisture migration control, durability, toughening performance and acoustic stability.

[0080] 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 within the protection scope of the present invention.

Claims

1. A process for internal toughening micro-slot inlay of thick load-bearing wooden boards, characterized in that, Includes the following steps: S1. A micro-slit (2) is formed along the length direction inside the thick wooden board (1). The micro-slit (2) includes a throat (21) and a cavity (22) that are periodically and continuously arranged and connected in sequence, wherein the width of the throat (21) is smaller than the width of the cavity (22). S2. A water-repellent dry powder band (4) is provided in the throat (21), and an underfill gap (23) is retained, so that the throat (21) becomes a crack-catching area, which is used to block capillary water migration and guide cracks to initiate, stop or deflect here; S3. Apply tough base adhesive (51) and high modulus structural adhesive (52) in sequence in the cavity (22), and embed a wooden inlay (3). The longitudinal grain direction of the inlay (3) is offset at a certain angle from the main grain direction of the wood board (1), so as to form a bridging and pull-out energy dissipation effect when the crack enters the cavity (22). S4. Blind holes (6) are machined at both ends of the micro-slit (2), and moisture-sensitive plugs (7) are pressed in. The moisture-sensitive plugs (7) expand radially to close the channel when wet and retract to maintain ventilation when dry. S5. After pressing and curing, the micro-slits (2) are formed into periodic crack energy-consuming units.

2. The internal toughening micro-slot inlay process for thick load-bearing wooden boards according to claim 1, characterized in that... The larynx (21) has a width of 0.20–0.45 mm, the cavity (22) has a width of 1.2–1.8 mm, the cavity (22) has a length of 4–10 mm, and the periodic pitch is 40–60 mm.

3. The internal toughening micro-slot inlay process for thick load-bearing wooden boards according to claim 1, characterized in that... The underfill gap (23) of the throat (21) has a thickness of 0.1–0.2 mm and is used to absorb the stress of wet expansion and dry shrinkage and delay crack propagation.

4. The internal toughening micro-slot inlay process for a thick load-bearing wooden board according to any one of claims 1 to 3, characterized in that... The wood inlay (3) has an island structure with a thickness of 0.8–1.5 mm. Its length is basically the same as that of the cavity (22), and its offset angle from the main grain direction of the wood board (1) is 10°–15°.

5. The internal toughening micro-slot inlay process for a thick load-bearing wooden board according to claim 4, characterized in that... The ends of the wooden inlay (3) are processed into R2-3mm round noses to reduce stress concentration and increase the probability of crack deflection.

6. The internal toughening micro-slot inlay process for a thick load-bearing wooden board according to claim 1, characterized in that... The coating rate of the tough base coat (51) is 25–40 g / m². 2 The high modulus structural adhesive (52) is used to provide an energy-dissipating interface during crack propagation; the high modulus structural adhesive (52) has a filling rate of 60–70% in the cavity (22) to form a load-bearing and bridging interface.

7. The internal toughening micro-slot inlay process for thick load-bearing wooden boards according to claim 1, characterized in that... The water-repellent dry powder tape (4) is formed from wax-based or fluorine / silicone modified micropowder with a thickness of 2–5 μm, forming a high contact angle interface near the throat (21) to enhance capillary breaking function.

8. The internal toughening micro-slot inlay process for thick load-bearing wooden boards according to claim 1, characterized in that... Moisture-sensitive embolism (7) is molded from cork powder, cellulose fiber and moisture-absorbing swelling modifier, with a dry density of 0.35–0.45 g / cm³. 3 With a wet volume expansion rate of 2% to 6%, it is used to maintain the self-closing function of the throat port for a long time.

9. The internal toughening micro-slot inlay process for thick load-bearing wooden boards according to claim 1, characterized in that... : The end of the micro-slit (2) retains a 10% to 20% blind section to avoid the end crack extending to the edge of the wooden board (1).

10. The internal toughening micro-slot inlay process for a thick load-bearing wooden board according to claim 1, characterized in that... It also includes setting shallow grooves or covering thin wood veneer on the surface of the wood board (1) to achieve apparent closure, wherein the shallow grooves or veneer are isolated from the throat (21) and do not fill the underfill gap (23) in order to balance appearance integrity and internal toughening function.

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