Frp-wood composite i-beam

Abstract

The application belongs to the technical field of structural engineering, and discloses a FRP-wood composite I-shaped member, which comprises, from top to bottom, an upper flange plate, an intermediate web plate and a lower flange plate, and has an overall I-shaped cross-section structure; wherein the upper flange plate and the lower flange plate are both FRP-wood base structure composite plates, which are sequentially stacked and glued by FRP, wood base structure plates and FRP; the intermediate web plate is formed by tightly and closely connecting two FRP-wood C-shaped laminated plates in a flat and straight face-to-face manner through structural adhesive; and the FRP-wood C-shaped laminated plate is formed by sequentially stacking and gluing FRP, multiple layers of wood rotary-cut veneers and FRP. The application fully utilizes the synergistic advantages of FRP and wood by material combination and I-shaped cross-section structure design, realizes light weight, high strength, high rigidity, high durability, and can efficiently utilize fast-growing wood, small-diameter wood and other low-quality wood resources. The FRP-wood composite I-shaped member obtained by the application can replace structural members for bending and compression in engineering structures.

Description

Technical Field

[0001] This invention belongs to the technical field of structural engineering, and more specifically, relates to an FRP-wood composite I-beam component. Background Technology

[0002] Wood, as a natural and renewable building material, possesses advantages such as low density, high specific strength, beautiful texture, and ease of processing. It also has ecological functions of carbon sequestration and oxygen release during its growth, resulting in significant environmental benefits. However, the mechanical properties of natural wood are affected by inherent defects such as knots, grain variations, and decay, as well as factors like moisture content changes and regional differences, leading to problems such as large performance dispersion, susceptibility to cracking, and insufficient durability. Furthermore, the scarcity of high-quality, large-diameter timber resources and the long-term reliance on imports for raw materials required for timber structure engineering result in high costs and hinder the sustainable development of modern timber structure construction. Therefore, developing composite structural technologies that can efficiently utilize low-quality timber such as fast-growing and small-diameter timber while significantly improving their mechanical properties and durability has become an important research direction in the field of timber structure engineering.

[0003] Fiber-reinforced polymer (FRP) is a highly engineered material composed of fibers and resins, and has advantages such as corrosion resistance, lightweight, high strength, and convenient construction.

[0004] Existing FRP-wood composite structures reported in the technology mostly use rectangular solid cross-sections or simple cladding construction forms. Although these can improve load-bearing capacity, stiffness, and ductility to some extent, their cross-sectional material distribution is not entirely reasonable, resulting in a less than ideal ratio of strength to apparent density (specific strength). This makes it difficult to fully meet the dual requirements of modern wood structures for lightweight components and high load-bearing efficiency. Furthermore, if rotary-cut veneers are attempted to be made into cross-sections with curved corners, large-curvature curling along the grain of the veneer is necessary. However, cross-grain curling of wood is prone to fiber splitting, breakage, and other damage, making it difficult to guarantee the quality of the finished product. Regarding the connection between the flanges and the web, traditional wooden I-beam joists typically use a glued connection where the web ends are inserted into pre-grooved flange slots. The glued area is limited by the groove depth and web thickness, resulting in limited contact surface. Moreover, stress concentration occurs at the root of the groove due to abrupt changes in cross-section. When the flange wood is subjected to stress in the cross-grain direction, splitting cracks easily form along the perimeter of the groove, leading to insufficient connection reliability. Summary of the Invention

[0005] To address the aforementioned deficiencies or improvement needs of existing technologies, the present invention aims to provide an FRP-wood composite I-beam component. Through material combination and I-beam cross-section structural design, it fully leverages the synergistic advantages of FRP and wood, achieving lightweight, high strength, high rigidity, and high durability, while efficiently utilizing low-quality timber resources such as fast-growing and small-diameter timber. The FRP-wood composite I-beam component obtained by this invention can replace structural components subjected to bending and compression in engineering structures.

[0006] To achieve the above objectives, according to one aspect of the present invention, an FRP-wood composite I-beam is provided, comprising, from top to bottom, an upper flange, a middle web, and a lower flange, which are tightly connected by a structural adhesive; the FRP-wood composite I-beam has an overall I-shaped cross-sectional structure; wherein, the upper flange and the lower flange are both made of FRP-wood-based structural composite panels; the middle web is formed by two FRP-wood C-shaped laminates tightly joined together by a structural adhesive in a flat, face-to-face manner, such that the cross-sectional profile of the middle web is two mirror-symmetrical, oppositely facing C-shapes, with the opening of each C-shape facing laterally outward from the I-shaped cross-sectional structure; Each of the aforementioned FRP-wood-based structural composite panels is composed of FRP, wood-based structural panels, and FRP stacked sequentially and glued together with structural adhesives; the wood-based structural panels are oriented strand board or structural plywood. Any of the aforementioned FRP-wood C-type laminates is made by sequentially stacking FRP, multi-layer rotary-cut wood veneers, and FRP and gluing them together with structural adhesives. Its cross-section has two arc-shaped bends, thus forming a C-shaped cross-section.

[0007] As a further preferred embodiment of the present invention, the FRP-wood C-laminate is formed by sequentially stacking and gluing FRP, multi-layer rotary-cut wood veneer and FRP, and then pressing and curing it in a C-mold. Preferably, in the FRP-wood C-laminate: the grain direction of any one layer of rotary-cut veneer is parallel to the axis of the component, and the normal direction of the C-section is parallel to the axis of the component; the FRP is unidirectional fiber FRP or bidirectional fiber FRP, wherein, when the FRP is unidirectional fiber FRP, the fiber direction is perpendicular to the axis of the component; when the FRP is bidirectional fiber FRP, at least one fiber direction is perpendicular to the axis of the component.

[0008] As a further preferred embodiment of the present invention, each of the FRP-wood C-type laminates comprises 4 to 8 layers of rotary-cut wood veneer, wherein the thickness of each rotary-cut wood veneer layer is 0.5 mm to 3 mm; The two FRP-wood C-type laminates in the intermediate web have the same number of layers and thickness of rotary-cut veneer.

[0009] As a further preferred embodiment of the present invention, for any FRP-wood-based structural composite board, when the wood-based structural board is oriented strand board (OSB), the FRP is either unidirectional fiber FRP or bidirectional fiber FRP. Specifically, when the FRP is unidirectional fiber FRP, the fiber direction is parallel to the main direction of the OSB and is also parallel to the axis of the component; when the FRP is bidirectional fiber FRP, at least one fiber direction is parallel to the main direction of the OSB. When the wood-based structural board is structural plywood, the FRP is unidirectional fiber FRP or bidirectional fiber FRP. When the FRP is unidirectional fiber FRP, the fiber direction is parallel to the grain direction of the surface veneer of the structural plywood and is also parallel to the axis of the component. When the FRP is bidirectional fiber FRP, at least one fiber direction is parallel to the grain direction of the surface veneer of the structural plywood.

[0010] As a further preferred embodiment of the present invention, for any one of the FRP-wood-based structural composite boards, the thickness of the wood-based structural board is 9mm to 25mm.

[0011] As a further preferred embodiment of the present invention, the C-shaped cross-section of each FRP-wood C-type laminate is formed from top to bottom by a first horizontal section, a first arc-shaped bend, a vertical section, a second arc-shaped bend, and a second horizontal section connected in sequence, wherein the first horizontal section is parallel to the second horizontal section and is perpendicular to the vertical section. The two FRP-wood C-type laminates are bonded together in a vertical segment-to-vertical manner, such that: the first horizontal segments of the two pieces are joined together to form the top flat surface of the intermediate web, and this joined flat surface is fully bonded to the bottom surface of the upper flange plate by structural adhesive; the second horizontal segments of the two pieces are joined together to form the bottom flat surface of the intermediate web, and this joined flat surface is fully bonded to the top surface of the lower flange plate by structural adhesive. The upper flange plate is parallel to the lower flange plate and has the same size; Preferably, the radii of the first arc-shaped bend and the second arc-shaped bend are... R With the thickness of each layer of rotary-cut veneer t ratio R / t The range is 10 to 40; Each of the aforementioned FRP-wood C-type laminates is symmetrical from top to bottom, and the dimensional relationship satisfies the following: the ratio of (outer contour radius of the first arc-shaped bend + length of the vertical section + outer contour radius of the second arc-shaped bend) to (length of the first horizontal section + outer contour radius of the first arc-shaped bend) is 2 to 4.

[0012] As a further preferred embodiment of the present invention, the fiber reinforcement of the FRP is one or more of glass fiber, carbon fiber, basalt fiber, jute fiber, and flax fiber; and the matrix of the FRP is one or more of epoxy resin, phenolic resin, polyurethane, urea-formaldehyde resin, or emulsion polymer isocyanate.

[0013] As a further preferred embodiment of the present invention, the structural adhesives used at the connection between the upper flange and the middle web, the connection between the middle web and the lower flange, and the connection between the two FRP-wood C-type laminates in the middle web may be the same or different, and they are independently selected from one or more of epoxy resin, phenolic resin, polyurethane, urea-formaldehyde resin or emulsion polymer isocyanate.

[0014] According to another aspect of the present invention, the present invention provides a method for manufacturing the above-mentioned FRP-wood composite I-beam component, comprising the following steps: The manufacturing steps of FRP-wood C-laminate are as follows: FRP, multi-layer rotary-cut wood veneer, and FRP are stacked in sequence and bonded together with structural adhesive. Then, they are placed in a C-shaped mold and pressed and cured to form FRP-wood C-laminate. The manufacturing steps of the flange panel are as follows: FRP, wood-based structural board and FRP are stacked in sequence and bonded with structural adhesive, and then pressure is applied for curing to form FRP-wood-based structural composite panel; Assembly steps for I-beam components: Take two FRP-wood composite structural panels as the upper flange and lower flange respectively, and join the two FRP-wood C-type laminate back to back with structural adhesive to form the middle web; then, tightly connect the upper flange, middle web, and lower flange from top to bottom with structural adhesive to form an integral I-beam structure. After curing, the FRP-wood composite I-beam component is obtained.

[0015] Compared with the prior art, the above-described technical solutions conceived in this invention can achieve the following beneficial effects: (1) This invention utilizes corrosion-resistant FRP combined with wood to form an FRP-wood composite I-beam with high specific strength and low carbon content. The FRP layers on both sides of the web effectively constrain the internal wood plywood, further enhancing the shear capacity and structural stability of the web; the flanges use FRP-wood-based structural composite panels, utilizing the high tensile strength and elastic modulus of the surface FRP to improve the bending capacity and local stability of the flanges. The entire component uses lightweight fiber-reinforced composite materials and wood, achieving lightweight construction and greatly facilitating the transportation, hoisting, and on-site installation of the component, making it particularly suitable for wood-structured buildings in areas with inconvenient transportation.

[0016] (2) In this invention, the rotary-cut wood veneer is preferably rolled and pressed into a C-shaped cross-section web with an arc angle. Since the grain direction of the rotary-cut wood veneer is perpendicular to the grain direction, and the grain direction of the rotary-cut wood veneer is preferably parallel to the axis direction of the component, the normal direction of the C-shaped cross-section is parallel to the axis direction of the component (the axis direction of the component is the length direction of the component). The rolling forming process conforms to the natural texture of the wood and reduces damage to the wood fibers. By symmetrically assembling FRP and rotary-cut wood veneer (i.e., stacking FRP, multi-layer rotary-cut wood veneer and FRP in sequence, so as to be symmetrical from top to bottom) and pressing them together, the transverse constraint effect of FRP on the wood fibers is utilized to effectively suppress the generation of damage such as fiber splitting and breaking during the rolling process, so that the rotary-cut wood veneer of fast-growing timber can be successfully formed into a C-shaped cross-section with an arc angle.

[0017] (3) Compared with the traditional wooden I-beam joists, the web end is inserted into the pre-grooved flange and glued together. In this invention, the top and bottom flat surfaces of the C-shaped web are fully bonded to the flange, which significantly increases the bonding area and avoids the damage to the integrity of the flange caused by the grooving. It has good connection reliability and overall collaborative working ability of the components.

[0018] (4) The FRP-wood laminate structure in this invention has a significant synergistic effect. Taking compression as an example, FRP sheets alone are prone to fiber buckling under compression, failing to fully utilize their high strength characteristics; wood also has low strength when compressed alone in the transverse direction. In this invention, after bonding FRP with rotary-cut wood veneer to form an integral laminate structure, the wood provides continuous out-of-plane support for FRP, inhibiting its buckling under compression; FRP also exerts a restraining effect on the wood, limiting its deformation. As shown in the comparative tests of Example 3 and Comparative Example 1 below, the compressive strength of the FRP-wood laminate along the transverse direction of the rotary-cut wood veneer is much higher than the performance of FRP and wood under compression alone.

[0019] (5) Compared with the rectangular solid cross section of FRP-wood composite components, the I-shaped cross section of the present invention concentrates the material in the upper and lower flanges, and the use of C-shaped web increases the moment of inertia of the cross section without increasing the amount of material used, thereby obtaining a higher specific strength (i.e., the ratio of strength to apparent density), achieving the dual goals of lightweight components and high load-bearing efficiency.

[0020] For a component with a rectangular solid cross-section, let the width of the rectangular cross-section be... b The height is h ,area A 1 is b × h Section modulus W 1 is:

[0021] The I-shaped cross-section of this invention can have the same outer dimensions, assuming the height is... h Width is b Assuming the width of the upper and lower flanges is... b The thickness is 0.1. h The web thickness is 0.1. h ,area A 2 is 0.28 b × h Section modulus W 2 is:

[0022] Assuming the material strength is f The calculated specific strength of the two sections reveals the following:

[0023] in, M 1 represents the flexural capacity of the rectangular solid member's cross-section. M 2 represents the flexural bearing capacity of the I-shaped member's cross-section; it can be seen that the specific strength of the I-shaped cross-section is higher than that of the rectangular cross-section.

[0024] (6) The FRP-wood composite I-beams obtained by this invention are mainly made of rotary-cut veneers and oriented strand board (or structural plywood) processed from fast-growing and small-diameter timber, which reduces the dependence on large-diameter logs and conforms to the concept of sustainable development. At the same time, the carbon emissions of FRP-wood composite structures are much lower than those of steel and concrete components, which has significant ecological benefits. The FRP-wood-based structural composite board is bonded and fixed to FRP-wood C-type laminates, and FRP-wood C-type laminates are bonded and fixed to each other with structural adhesives, ensuring the collaborative working ability of each component during service.

[0025] (7) In addition, FRP material has good corrosion resistance, moisture resistance and biological erosion resistance. When wrapped on the outside of wood, it can effectively protect the internal wood material, extend the service life of the component, and is suitable for harsh environments such as dampness and corrosion.

[0026] (8) The present invention can preferably use the radius of the arc angle of the C-shaped section. R With the thickness of single-layer rotary-cut veneer t ratio R / t Setting it to 10-40 provides strong operational flexibility in the process and can avoid... R / t Too small a diameter can easily lead to fiber splitting or breakage (if the curling curvature of rotary-cut wood veneer is too large in the transverse direction, the tensile strain at the outer edge of the bent section of the wood fiber will exceed the wood's transverse tensile strain limit, causing the fiber to easily split or break), and to avoid R / t If the size is too large, the bonding area between the intermediate web and the flange is too small.

[0027] (9) The FRP-wood C-type laminate used in this invention is preferably a symmetrical structure. The height-to-width ratio of the web of the C-shaped section (i.e., the ratio of (the outer contour radius of the first arc-shaped bend + the length of the vertical section + the outer contour radius of the second arc-shaped bend) to (the length of the first horizontal section + the outer contour radius of the first arc-shaped bend) is preferably 2 to 4. This ensures the overall stability of the component and avoids that if the height-to-width ratio is too large, the web is prone to local buckling when subjected to shear, which will not fully utilize the load-bearing potential of the material. Also, if the height-to-width ratio is too small, the material will be too concentrated near the neutral axis, and the moment of inertia advantage of the I-shaped section will be weakened. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the formation of the FRP-wood C-type laminated web of the present invention.

[0029] Figure 2 This is a schematic diagram of the formation of the FRP-oriented particleboard flange of the present invention.

[0030] Figure 3 This is a schematic diagram illustrating the formation of the FRP-wood composite I-beam component of the present invention.

[0031] Figure 4 This is a structural schematic diagram of the FRP-wood composite I-beam component of the present invention.

[0032] Figure 5 This is a schematic cross-sectional view of the FRP-wood C-type laminate of the present invention.

[0033] Figure 6 The figures show the physical sample and test results of the FRP-wood composite I-beams prepared in Example 1, illustrating their flexural bearing capacity. Figure 6 (a) in the diagram corresponds to the actual experimental setup. Figure 6 (b) in the figure corresponds to the experimental results.

[0034] Figure 7 The images show physical specimens of GFRP-laminated wood composite panels prepared in Example 3, and a comparison of the physical specimens and test results of wood composite panels prepared in Comparative Example 1. Figure 7 Image (a) shows a physical specimen of a GFRP-wood laminate. Figure 7 (b) in the image corresponds to the physical specimen of the wood-laminated board. Figure 7 (c) and (d) in the figure are comparison charts of the corresponding experimental results.

[0035] The meanings of the labels in the figures are as follows: 1 is rotary-cut wood veneer; 2 is FRP; 3 is a C-type mold; 4 is FRP-wood C-type laminate (i.e., FRP-wood C-type laminate web); 5 is oriented strand board (OSB); 6 is FRP-OSB composite board (i.e., FRP-OSB flange); 7 is FRP-wood composite I-beam; 8 is GFRP-wood laminate compression specimen; 9 is GFRP-wood laminate tensile specimen; 10 is GFRP-wood laminate shear specimen; 11 is wood laminate compression specimen; 12 is wood laminate tensile specimen; 13 is wood laminate shear specimen. Detailed Implementation

[0036] 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. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0037] Example 1: The FRP-wood composite I-beam component in this embodiment, such as Figure 4 As shown, from top to bottom, it includes an upper flange, a middle web, and a lower flange, which are tightly connected by structural adhesive. The upper flange and the lower flange are both made of FRP-wood-based structural composite panels. The middle web is made of two FRP-wood C-shaped laminates that are tightly joined back to back by structural adhesive. The FRP-wood composite I-beam has an overall I-shaped cross-section structure (that is, the middle web is made of two FRP-wood C-shaped laminates that are tightly joined together by structural adhesive in a flat facing manner, so that the cross-sectional profile of the middle web is two mirror-symmetrical back-to-back C-shapes, and the opening of each C-shape faces the lateral outer side of the I-shaped cross-section structure).

[0038] In this embodiment, the FRP-wood-based structural composite board is specifically an FRP-oriented strand board composite board 6; correspondingly, the manufacturing process of the FRP-wood composite I-beam component includes the following steps (the FRP used in each step is selected as unidirectional glass fiber reinforced composite material GFRP, and the structural adhesive is selected as epoxy resin; both are commercially available): S1: Fabrication of FRP-wood C-type laminate: such as Figure 1As shown, this embodiment uses commercially available 1.5 mm thick rotary-cut wood veneer, which is stacked in a symmetrical assembly sequence of "FRP / multi-layer rotary-cut wood veneer / FRP". In this embodiment, four layers of rotary-cut wood veneer are used between the two FRP layers. In this embodiment, the fiber direction of FRP 2 is perpendicular to the grain direction of rotary-cut wood veneer 1 to enhance the mechanical properties of the rotary-cut wood veneer in the cross-grain direction. Structural adhesive is applied between each layer, and after stacking, the whole assembly is placed in a C-shaped mold 3 and cured under a pressure of 0.1 MPa to form an FRP-wood C-shaped laminate 4 with rounded corners.

[0039] Each FRP-wood C-shaped plywood has a C-shaped cross-section formed by sequentially connecting a first horizontal section, a first curved bend, a vertical section, a second curved bend, and a second horizontal section (e.g., Figure 5 As shown in the figure, the first horizontal segment is parallel to the second horizontal segment and both are perpendicular to the vertical segment. The C-shaped cross-section of each FRP-wood C-type laminate is a symmetrical structure (the connecting surface of the two FRP-wood C-type laminates on the left and right sides, tightly joined together by structural adhesive, i.e., the straight surface corresponding to the vertical segment extending along the length direction in the outer contour line). In this embodiment, each FRP-wood C-type laminate obtained after sawing has a length of 2400mm, a height of 200mm (i.e., the outer contour radius of the first arc-shaped bend + the length of the vertical segment + the outer contour radius of the second arc-shaped bend), a flange width of 80mm (i.e., the length of the first horizontal segment and the second horizontal segment), and an arc radius (the outer contour radius of the first arc-shaped bend and the second arc-shaped bend) of 20mm.

[0040] S2: Fabrication of FRP-Oriented Strand Board Composite Panels: (e.g., ...) Figure 2 As shown, the components are assembled according to a symmetrical structure of "FRP / Oriented Strand Board / FRP". The Oriented Strand Board is commercially available, cut to a thickness of 12mm, a width of 200mm, and a length of 2400mm. Based on the structural requirements of the component, the fiber direction of FRP 2 is set parallel to the main direction within the Oriented Strand Board 5 (according to standard GB / T41715-2022, the main direction is the length direction of the board) to enhance longitudinal tensile / compressive strength. Structural adhesive is applied between each layer and cured under a pressure of 0.1 MPa to form the FRP-Oriented Strand Board composite panel 6, which serves as the upper and lower flanges of the I-beam component.

[0041] S3: Assembly of FRP-wood composite I-beam components: such as Figure 3As shown, FRP-wood C-laminate 4 is used as the web, and two FRP-wood C-laminate 4 are placed between two FRP-oriented strand board (OSB) composite panels 6 to form an I-shaped cross-section. Structural adhesive is uniformly applied to the contact surfaces of the web and flanges, and the contact surfaces of the two FRP-wood C-laminate 4. A pressure of 0.1 MPa is applied to ensure tight bonding of all components, forming an integral structure and fully ensuring the collaborative working ability between the components. After the structural adhesive has completely cured, a complete FRP-wood composite I-beam component 7 is finally obtained.

[0042] like Figure 6 As shown in (a), a four-point bending test was conducted on the FRP-wood composite I-beam (7) prepared in this embodiment to test its bending performance. The calculated span of the component was 2200 mm, and the spacing between the loading points was 800 mm. The test results showed that the ultimate bending bearing capacity of the FRP-wood composite I-beam could reach 13.3 kN·m, and it could be used as a bending member, such as... Figure 6 As shown in (b) of the diagram.

[0043] Example 2: The FRP-wood composite I-beam in this embodiment includes, from top to bottom, an upper flange, a middle web, and a lower flange, which are tightly connected by structural adhesive. The upper flange and the lower flange are both made of FRP-wood-based structural composite panels. The middle web is formed by two FRP-wood C-shaped laminates that are tightly joined back-to-back by structural adhesive. The FRP-wood composite I-beam has an overall I-shaped cross-sectional structure.

[0044] In this embodiment, the FRP-wood-based structural composite board is specifically an FRP-structural plywood composite board; correspondingly, the manufacturing process of the FRP-wood composite I-beam includes the following steps (the FRP used in each step is unidirectional glass fiber reinforced composite material GFRP, and the structural adhesive is epoxy resin; both are commercially available): S1: Fabrication of FRP-Wood C-Laminated Board: In this embodiment, commercially available 1.5 mm thick rotary-cut wood veneer is selected and stacked in a symmetrical assembly sequence of "FRP / multi-layer rotary-cut wood veneer / FRP". In this embodiment, four layers of rotary-cut wood veneer are used between two layers of FRP. In this embodiment, the fiber direction of the FRP is perpendicular to the grain direction of the rotary-cut wood veneer to enhance the mechanical properties of the rotary-cut wood veneer in the cross-grain direction. Structural adhesive is applied between each layer, and after stacking, the whole assembly is placed in a C-shaped mold and cured under a pressure of 0.1 MPa to form an FRP-wood C-laminated board with rounded corners.

[0045] The FRP-wood C-type laminate prepared in this embodiment has a sawed length of 2400mm, a height of 200mm, a flange width of 80mm, and a radius of curvature of 20mm.

[0046] S2: Fabrication of FRP-Structural Plywood Composite Panels: The panels are assembled according to a symmetrical structure of "FRP / Structural Plywood / FRP". Commercially available structural plywood is cut to a thickness of 12mm, a width of 200mm, and a length of 2400mm. Based on the structural requirements, the fiber direction of the FRP is set parallel to the grain direction of the inner surface of the structural plywood to enhance longitudinal tensile / compressive strength. Structural adhesive is applied between each layer and cured under 0.1 MPa pressure to form the FRP-structural plywood composite panel, which serves as the upper and lower flanges of the I-beam structure.

[0047] S3: Assembly of FRP-wood composite I-beams: Using FRP-wood C-laminates as the web, two FRP-wood C-laminates are placed between two FRP-structural plywood composite panels to form an I-beam cross-section. Structural adhesive is evenly applied to the contact surfaces of the web and flanges, and the contact surfaces of the two FRP-wood C-laminates. A pressure of 0.1 MPa is applied to ensure tight bonding of all components, forming an integral structure and fully ensuring the collaborative working ability between the components. After the structural adhesive has fully cured, a complete FRP-wood composite I-beam is obtained.

[0048] Example 3: Following a symmetrical assembly sequence of "FRP / multi-layer rotary-cut veneer / FRP", compressive property specimen 8, tensile property specimen 9, and shear property specimen 10 of unidirectional GFRP-wood laminate were prepared. Figure 7 As shown in (a) of the specimen. The material property test specimens consist of two layers of unidirectional GFRP bonded together by four layers of rotary-cut wood veneer (using epoxy resin as a structural adhesive). The fiber direction of the unidirectional GFRP is perpendicular to the grain direction of the rotary-cut wood veneer. The tensile specimen has a cross-sectional dimension of 13 mm × 7 mm, the compression specimen has a cross-sectional dimension of 13 mm × 7 mm, and the shear specimen has a shear surface dimension of 31 mm × 7 mm.

[0049] The tests were conducted according to the operating specifications of ASTM D638-22, ASTM D6641 / D6641M-23, and ASTM D7078 / D7078M-20, respectively. The test results showed that when loaded along the grain direction of the wood, the tensile strength was 73.9 MPa, the compressive strength was 30.4 MPa, and when sheared parallel to the grain direction of the wood, the shear strength was 14.0 MPa.

[0050] Example 4: This embodiment is largely the same as Embodiment 1, except that in step S1, the radius of curvature of the C-shaped mold is adjusted to 15 mm, the number of wood veneer layers remains 4 (each veneer layer is still 1.5 mm thick), and the FRP layers remain one on the top and one on the bottom. The remaining steps and process parameters (pressure 0.1 MPa, type of structural adhesive, etc.) remain unchanged.

[0051] Example 5: This embodiment is largely the same as Embodiment 1, except that in step S1, the radius of the C-shaped mold is adjusted to 40 mm, the number of wood veneer layers remains 4 (each veneer is 1 mm thick), and the FRP layers remain one on the top and one on the bottom. The remaining steps and process parameters (pressure 0.1 MPa, type of structural adhesive, etc.) remain unchanged.

[0052] Example 6: This embodiment is largely the same as Embodiment 1, except that in step S1, the bottom flat surface of the C-shaped mold is adjusted to 200 mm (corresponding to a vertical section of 200 mm for the FRP-wood laminate), the number of wood veneer layers remains 4 (veneer thickness remains 1.5 mm), and the FRP layers remain one on the top and one on the bottom. After cutting, the lengths of the first and second horizontal sections of the FRP-wood C-shaped laminate are both 40 mm. In step S2, the width of the oriented strand board after cutting is 120 mm, and the remaining steps and process parameters (pressure 0.1 MPa, type of structural adhesive, etc.) remain unchanged.

[0053] Example 7: This embodiment is basically the same as Embodiment 1, except that in step S1, the bottom flat surface of the C-shaped mold is adjusted to 80 mm (corresponding to an 80 mm vertical section of the FRP-wood laminate), the number of wood veneer layers remains 4 (veneer thickness remains 1.5 mm), and the FRP layers remain one on the top and one on the bottom. After cutting, the length of the first and second horizontal sections of the FRP-wood C-shaped laminate is 40 mm. In step S2, the width of the oriented strand board after cutting is 120 mm, and the remaining steps and process parameters (pressure 0.1 MPa, type of structural adhesive, etc.) remain unchanged.

[0054] Comparative Example 1: This comparative example does not use FRP. Accurate compression property test specimen 11, tensile property test specimen 12, and shear property test specimen 13 for wood-plywood are prepared separately. Figure 7 As shown in (b) of the figure. The wood-laminated plywood specimens were made of four layers of rotary-cut veneer (adjacent layers of rotary-cut veneer were bonded together with epoxy resin as a structural adhesive). The tensile specimens had a cross-sectional dimension of 13 mm × 6 mm, the compression specimens had a cross-sectional dimension of 13 mm × 6 mm, and the shear specimens had a shear surface dimension of 31 mm × 6 mm.

[0055] The tests were conducted according to the operating specifications of ASTM D638-22, ASTM D6641 / D6641M-23, and ASTM D7078 / D7078M-20, respectively. The test results showed that when loaded along the grain direction of the wood, the tensile strength was 5.6 MPa, the compressive strength was 15.5 MPa, and when sheared parallel to the grain direction of the wood, the shear strength was 8.4 MPa.

[0056] Comparison of test results between sample 1 and sample 3: Figure 7 As shown in (c) and (d) above. Because the GFRP thickness is approximately 0.5 mm, it is prone to buckling under pressure and cannot withstand stress (when FRP sheets are subjected to pressure alone, they are highly susceptible to fiber micro-buckling due to the lack of out-of-plane support). The compressive strength of the GFRP-wood laminate in Example 3 is higher than that of the wood laminate specimen in Comparative Example 1, demonstrating the synergistic effect between GFRP and wood laminate. This invention uses structural adhesives to bond FRP to wood (wood-based structural boards or multi-layer rotary-cut veneers). The wood provides continuous support for the FRP, inhibiting FRP fiber buckling, while the FRP, in turn, constrains the lateral expansion deformation of the wood, significantly improving its transverse compressive strength, demonstrating a clear synergistic effect.

[0057] The above embodiments are merely examples. Besides GFRP, other FRPs such as carbon fiber, basalt fiber, jute fiber, and flax fiber can also be used (of course, glass fiber reinforced composites and epoxy resins are widely used and considered relatively economical raw materials due to their excellent performance and low cost). Furthermore, in addition to unidirectional fiber FRPs, bidirectional fiber FRPs can also be used (in which case, at least one fiber direction in the bidirectional fiber FRP must be consistent with the fiber direction of the unidirectional fiber FRP). For example, in addition to epoxy resins, structural adhesives can also be other structural adhesives such as phenolic resins, polyurethanes, urea-formaldehyde resins, or emulsion polymer isocyanates. Furthermore, the thickness of each layer of rotary-cut wood veneer and the thickness of the wood-based structural board can be flexibly adjusted according to actual conditions (the thickness of common rotary-cut wood veneer is 0.5mm~3mm, and the thickness of common oriented strand board (OSB) and structural plywood is 9mm~25mm).

[0058] Those skilled in the art will readily understand that the above description is merely 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 scope of protection of the present invention.

Claims

1. An FRP-wood composite I-beam component, characterized in that, The structure consists of an upper flange, a middle web, and a lower flange, which are tightly connected by structural adhesive. The FRP-wood composite I-beam has an overall I-shaped cross-section structure. The upper flange and the lower flange are both made of FRP-wood-based structural composite panels. The middle web is formed by two FRP-wood C-shaped laminates (4) that are tightly connected by structural adhesive in a flat, face-to-face manner, so that the cross-sectional profile of the middle web is two mirror-symmetrical back-to-back C-shapes, and the opening of each C-shape faces the lateral outer side of the I-shaped cross-section structure. In this case, any one of the FRP-wood-based structural composite boards is made by sequentially stacking FRP (2), wood-based structural board and FRP (2) and gluing them together with structural adhesive; the wood-based structural board is oriented strand board or structural plywood; Any of the FRP-wood C-type laminates (4) is made by sequentially stacking FRP (2), multi-layer wood rotary-cut veneer (1) and FRP (2) and gluing them together with structural adhesive. Its cross-section has two arc-shaped bends, thus forming a C-shaped cross-section.

2. The FRP-wood composite I-beam component as described in claim 1, characterized in that, The FRP-wood C-type laminate (4) is made by sequentially stacking and gluing FRP (2), multi-layer wood rotary-cut veneer (1) and FRP (2), and then pressing and curing it in a C-type mold (3); Preferably, in the FRP-wood C-type laminate (4): the grain direction of any layer of rotary-cut wood veneer (1) is parallel to the axis of the component, and the normal direction of the C-shaped section is parallel to the axis of the component; the FRP (2) is unidirectional fiber FRP or bidirectional fiber FRP, wherein when the FRP (2) is unidirectional fiber FRP, the fiber direction is perpendicular to the axis of the component; when the FRP (2) is bidirectional fiber FRP, at least one fiber direction is perpendicular to the axis of the component.

3. The FRP-wood composite I-beam component as described in claim 1, characterized in that, Each of the aforementioned FRP-wood C-type laminates (4) comprises 4 to 8 layers of rotary-cut wood veneer (1), wherein the thickness of each layer of rotary-cut wood veneer (1) is 0.5 mm to 3 mm; The two FRP-wood C-type laminates (4) in the intermediate web have the same number of layers and thickness of wood rotary-cut veneer.

4. The FRP-wood composite I-beam as described in claim 1, characterized in that, For any of the FRP-wood-based structural composite boards, when the wood-based structural board is oriented strand board (OSB), the FRP (2) is either unidirectional fiber FRP or bidirectional fiber FRP. When the FRP (2) is unidirectional fiber FRP, the fiber direction is parallel to the main direction of the OSB and is also parallel to the axis of the component. When the FRP (2) is bidirectional fiber FRP, at least one fiber direction is parallel to the main direction of the OSB. When the wood-based structural board is structural plywood, the FRP (2) is unidirectional fiber FRP or bidirectional fiber FRP. When the FRP (2) is unidirectional fiber FRP, the fiber direction is parallel to the grain direction of the surface of the structural plywood and is also parallel to the axis of the component. When the FRP (2) is bidirectional fiber FRP, at least one fiber direction is parallel to the grain direction of the surface of the structural plywood.

5. The FRP-wood composite I-beam as described in claim 1, characterized in that, For any one of the aforementioned FRP-wood-based structural composite panels, the thickness of the wood-based structural panel is 9mm~25mm.

6. The FRP-wood composite I-beam as described in claim 1, characterized in that, Each of the FRP-wood C-type laminates (4) has a C-shaped cross section formed from top to bottom by a first horizontal section, a first arc-shaped bend, a vertical section, a second arc-shaped bend, and a second horizontal section connected in sequence. The first horizontal section is parallel to the second horizontal section and is perpendicular to the vertical section. The two FRP-wood C-type laminates (4) are bonded together in a vertical segment-to-vertical manner, such that: the first horizontal segments of the two are joined together to form the top flat surface of the intermediate web, and the joined flat surface is fully bonded to the bottom surface of the upper flange plate by structural adhesive; the second horizontal segments of the two are joined together to form the bottom flat surface of the intermediate web, and the joined flat surface is fully bonded to the top surface of the lower flange plate by structural adhesive. The upper flange plate is parallel to the lower flange plate and has the same size; Preferably, the radii of the first arc-shaped bend and the second arc-shaped bend are... R With the thickness of each layer of rotary-cut veneer t ratio R / t The range is 10 to 40; Each of the aforementioned FRP-wood C-type laminates (4) is symmetrical from top to bottom, and the dimensional relationship satisfies the following: the ratio of (outer contour radius of the first arc-shaped bend + length of the vertical section + outer contour radius of the second arc-shaped bend) to (length of the first horizontal section + outer contour radius of the first arc-shaped bend) is 2 to 4.

7. The FRP-wood composite I-beam as described in claim 1, characterized in that, The fiber reinforcement of the FRP (2) is one or more of glass fiber, carbon fiber, basalt fiber, jute fiber, and flax fiber; the matrix of the FRP (2) is one or more of epoxy resin, phenolic resin, polyurethane, urea-formaldehyde resin, or emulsion polymer isocyanate.

8. The FRP-wood composite I-beam as described in claim 1, characterized in that, The structural adhesives used at the connection between the upper flange and the middle web, the connection between the middle web and the lower flange, and the connection between the two FRP-wood C-type laminates (4) in the middle web are the same or different, and they are independently selected from one or more of epoxy resin, phenolic resin, polyurethane, urea-formaldehyde resin or emulsion polymer isocyanate.

9. The method for manufacturing the FRP-wood composite I-beam as described in any one of claims 1-8, characterized in that, Includes the following steps: The manufacturing steps of FRP-wood C-laminate are as follows: FRP, multi-layer rotary-cut wood veneer, and FRP are stacked in sequence and bonded together with structural adhesive. Then, they are placed in a C-shaped mold and pressed and cured to form FRP-wood C-laminate. The manufacturing steps of the flange panel are as follows: FRP, wood-based structural board and FRP are stacked in sequence and bonded with structural adhesive, and then pressure is applied for curing to form FRP-wood-based structural composite panel; Assembly steps for I-beam components: Take two FRP-wood composite structural panels as the upper flange and lower flange respectively, and join the two FRP-wood C-type laminate back to back with structural adhesive to form the middle web; then, tightly connect the upper flange, middle web, and lower flange from top to bottom with structural adhesive to form an integral I-beam structure. After curing, the FRP-wood composite I-beam component is obtained.

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