High-performance wood-plastic composite frame structure for building doors and windows

Abstract

This invention discloses a high-performance wood-plastic composite frame structure for building doors and windows, belonging to the field of building materials technology. The frame structure includes a wood-plastic outer wall and an internal cavity. A continuous support mesh structure composed of an array of topological units is integrally formed within the cavity. The topological units are configured with a tensile geometry exhibiting a negative Poisson's ratio effect, including multiple load-bearing members and connecting nodes. When the wood-plastic outer wall experiences axial expansion tensile strain due to heat, the topological units compensate for this displacement through node rotation and member bending, thereby significantly reducing interfacial shear stress and suppressing the arching deformation of the frame. When external fasteners are subjected to axial pull-out force, the topological units undergo centripetal contraction deformation, enhancing the frictional gripping force on the fasteners. This invention resolves thermal stress through microscopic geometric reconstruction, effectively addressing the shortcomings of poor thermal stability and insufficient nail-holding power in wood-plastic profiles.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a high-performance wood-plastic composite frame structure for building doors and windows. Background Technology

[0002] Wood-plastic composites are composite materials made from wood fibers or plant fibers, thermoplastic plastics, and processing aids through extrusion. They are widely used in building doors and windows, outdoor paving, and other fields due to their combination of the natural texture of wood and the corrosion resistance and low maintenance costs of plastics. However, the complex microstructure of wood-plastic composite profiles and the limitations of porous extrusion processes still present significant technical challenges in their practical applications.

[0003] First, the thermophysical properties of wood-plastic composites (WPC) differ significantly from those of traditional aluminum alloys or steel. WPC typically has a higher coefficient of linear expansion than metal reinforcements. In extreme outdoor climates, the profiles are exposed to strong, one-sided sunlight, resulting in a large temperature gradient between the sun-exposed and shaded sides. Because WPC profiles often employ a hollow structure with low thermal conductivity, this temperature difference is difficult to eliminate quickly through heat conduction, leading to severe, non-uniform axial thermal expansion. This thermal strain imbalance directly causes significant bow-shaped bending deformation in the profiles, severely impacting the opening and closing flexibility, airtightness, and long-term structural stability of door and window systems.

[0004] Secondly, the microstructure of wood-plastic composites (WPC) determines their mechanical behavior, exhibiting significant anisotropy and low local toughness. During the screwing-in process of hardware fasteners, micro-cracks are easily generated in the substrate. When the fastener is subjected to pull-out forces generated by strong winds or negative pressure, the straight reinforcing ribs inside traditional profiles lack a dynamic load distribution mechanism, leading to extreme stress concentration in the thread engagement area. Due to the limited shear strength of the WPC substrate, fasteners are highly susceptible to stripping, loosening, and even pulverizing tearing of the substrate.

[0005] Current conventional solutions typically involve lining the profile cavity with continuous rigid metal reinforcing steel, or installing straight or triangular rigid reinforcing ribs on the inner wall. However, introducing steel reinforcement increases the difficulty of the assembly process and creates a significant thermal bridging effect, reducing the thermal performance of the profile. Straight reinforcing ribs, on the other hand, are static rigid constraints, which generate huge internal interface shear stresses when resisting the expansion of the outer wall. They cannot achieve strain self-regulation at the geometric level and cannot provide adaptive locking protection for fasteners. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a high-performance wood-plastic composite frame structure for building doors and windows, so as to solve the technical problems of existing wood-plastic profiles being prone to thermal deformation and insufficient nail holding power.

[0007] The above-mentioned technical objective of the present invention is achieved through the following technical solution: a high-performance wood-plastic composite frame structure for building doors and windows, comprising a wood-plastic outer wall and an internal cavity enclosed by the wood-plastic outer wall;

[0008] The internal cavity is integrally formed with a continuous support mesh structure, which is composed of multiple topological unit cells arranged in a periodic or quasi-periodic array. The topological unit cell includes multiple load-bearing members and connecting nodes that connect adjacent load-bearing members. The topological unit cell is configured as an extruded geometry with a negative Poisson's ratio effect.

[0009] Furthermore, the topological unit cell is a concave hexagonal unit cell or a double V-shaped bowtie unit cell; The connecting node includes a concave vertex that is recessed into the topological unit cell, and the angle between adjacent force-bearing members at the concave vertex is 60° to 120°.

[0010] Furthermore, the topological unit cell is configured such that when it is subjected to tensile strain caused by the thermal expansion of the wood-plastic outer wall in the first direction, it drives the connecting node to rotate and causes the topological unit cell to generate a lateral expansion displacement in a second direction perpendicular to the first direction, so as to reduce the interfacial thermal shear stress between the supporting mesh structure and the wood-plastic outer wall and suppress the overall bow-shaped deformation of the frame structure.

[0011] Furthermore, the topological unit cell is configured such that when the external fastener is screwed into the support mesh structure and subjected to an outward axial pull-out force, the topological unit cell is driven to generate a contraction deformation that converges toward the radial center of the fastener, thereby increasing the interfacial contact pressure and frictional clamping force between the fastener and the support mesh structure.

[0012] Furthermore, at the center of the connecting nodes in the supporting mesh structure, flexible composite cables are inserted along the extrusion direction of the frame structure. The flexible composite cable is located at the concave apex.

[0013] Furthermore, the lateral bending stiffness of the flexible composite cable is lower than the deformation stiffness of the topological unit cell when it undergoes lateral expansion or centripetal contraction. The flexible composite cable has axial tensile strength to provide axial tensile support when the deformation of the connection node reaches a set threshold due to the ultimate load on the frame structure.

[0014] Furthermore, let the wall thickness of the stressed member be... The wall thickness of the wood-plastic outer wall is Both conditions are met: This is to ensure that the stressed member has the ability to bend and deform and does not buckle under compression.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention achieves strain absorption through geometric reconstruction under heated conditions by configuring the supporting mesh structure with a tensile geometry exhibiting a negative Poisson's ratio effect. When the wood-plastic outer wall undergoes axial thermal expansion and exerts axial tension on the internal supporting mesh structure, the connecting nodes of the concave structure rotate, and the stressed members drive the topological unit cells to generate lateral expansion displacement through geometric deformation. This lateral expansion displacement provides displacement compensation for the expansion of the outer wall, thereby reducing the interfacial thermal shear stress between the supporting mesh structure and the outer wall, and thus suppressing the overall bow-shaped bending of the frame structure.

[0016] 2. This invention achieves an adaptive enhancement of nail-holding force through the negative Poisson's ratio characteristic of the supporting mesh structure. When the fastener is screwed into the supporting mesh structure and subjected to an outward axial pull-out force, the local tensile stress drives the surrounding topological unit cells to undergo shrinkage deformation, converging towards the radial center of the fastener. This radial shrinkage deformation increases the interfacial contact pressure between the fastener and the supporting mesh structure, thereby improving the pull-out strength and stability of the fastener in the wood-plastic composite substrate.

[0017] 3. This invention achieves an increase in ultimate strength without hindering the lateral deformation of the structure by co-extruding and inserting flexible composite cables at the concave apex. Because the flexible composite cables have low lateral bending stiffness, they do not impede the lateral expansion or centripetal contraction of the topological unit cell; while under extreme loads, the axial tensile support provided by the flexible composite cables prevents destructive tearing of the support mesh structure.

[0018] 4. This invention achieves a balance between structural stiffness and deformation capacity by setting the thickness ratio of the load-bearing members to the outer wall between 0.4 and 0.8. This thickness range ensures that the load-bearing members possess the necessary geometric reconstruction deformation capacity while simultaneously enhancing the resistance to buckling instability of the supporting mesh structure under compression. Attached Figure Description

[0019] Figure 1 A macroscopic cross-sectional schematic diagram of a high-performance wood-plastic composite frame structure for building doors and windows provided in an embodiment of the present invention; Figure 2 for Figure 1 A magnified view of a portion of point A in the middle; Figure 3 This is a diagram illustrating the dynamic geometric reconstruction force principle of a topological unit cell under axial thermal expansion tensile strain, provided in an embodiment of the present invention. Figure 4 This is a schematic diagram illustrating the radial contraction force of a topological unit cell under the pull-out force of an external fastener, as provided in an embodiment of the present invention.

[0020] In the diagram: 1. Wood-plastic composite outer wall; 2. Internal cavity; 3. Supporting mesh structure; 4. Topological unit cell; 5. Load-bearing member; 6. Connection node; 7. Flexible composite cable. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Wherein, Figure 1 The cross-sectional structure of the frame structure of the present invention at any location is shown, illustrating the structure of the wood-plastic outer wall 1 and its internal cavity 2, as well as the overall layout relationship of the support mesh structure 3 integrally formed in the internal cavity 2. Figure 2 The specific geometric configuration of the topological unit cell 4 in the supporting mesh structure 3 is shown, including the concave topological unit structure composed of force-bearing rods 5 and connecting nodes 6, which is used to illustrate the basis of its geometric reconstruction. Figure 3 This demonstrates that when the wood-plastic outer wall 1 experiences axial expansion due to temperature changes, the topological unit cell 4, through the rotation of the connecting node 6 and the bending deformation of the stressed member 5, generates a lateral expansion in the direction perpendicular to the axial direction to compensate for the thermal strain at the interface, thereby reducing the shear stress at the interface and suppressing the bow-shaped deformation of the frame structure. Figure 4 This demonstrates that when the fastener is subjected to axial pull-out force during use, the topological unit cell 4 undergoes contraction deformation along the radial direction of the fastener under the action of bending of the stressed member 5 and node movement, thereby enhancing the interfacial contact pressure between the fastener and the supporting mesh structure 3 and achieving an adaptive clamping effect.

[0022] This embodiment provides a high-performance wood-plastic composite frame structure for building doors and windows, the macroscopic cross-sectional structure of which is shown in... Figure 1The profile is integrally formed through a co-extrusion process. Its outer shell is composed of a wood-plastic composite outer wall 1, and the interior is a hollow structure forming an internal cavity 2. Within the internal cavity 2, a supporting mesh structure 3 is integrally co-extruded along the profile's extension direction. The supporting mesh structure 3 does not employ traditional straight reinforcing ribs; instead, it consists of multiple topological units 4 arranged in an array to fill the internal cavity 2. This array arrangement allows the supporting mesh structure 3 to exhibit overall coordinated deformation characteristics determined by the geometry of the topological units on a macroscopic scale. Both the wood-plastic composite outer wall 1 and the supporting mesh structure 3 are made from a wood-plastic composite material modified from wood fiber and high-density polyethylene (HDPE) to ensure the continuity of the material interface and the consistency of thermal shrinkage. Compared to traditional profiles using straight reinforcing ribs or honeycomb filling structures, the supporting mesh structure 3 in this embodiment achieves active adjustment of the load response path through the geometric reconstruction of the topological units 4, rather than simply relying on material stiffness to improve load-bearing capacity.

[0023] Figure 2 The microstructure details of the topological unit cell 4 in the supporting mesh structure 3 are shown in detail. In this embodiment, each topological unit cell 4 is a concave hourglass-shaped or bowtie-shaped geometric unit. This specific tensile geometry is the structural basis for achieving the negative Poisson's ratio effect. The unit consists of multiple interconnected force-bearing members 5 and connecting nodes 6 located at the intersection of the force-bearing members 5. Specifically, each topological unit cell 4 includes two parallel lateral vertical force-bearing members 5 on the left and right, and a top V-shaped diagonal bar and a bottom V-shaped diagonal bar located between these two lateral vertical bars and concave towards the geometric center of the unit cell, respectively. The vertices of the top and bottom V-shaped diagonal braces are arranged opposite each other, and the vertices of the top and bottom V-shaped diagonal braces do not contact each other to form the concave structure at the center of the unit cell. A vertical force-bearing member 5 extends upward from the vertices of the top V-shaped diagonal braces, and a vertical force-bearing member 5 extends downward from the vertices of the bottom V-shaped diagonal braces, for mechanical connection with the topological unit cells 4 of adjacent levels, respectively. The connection nodes 6 are located at the geometric inflection points or intersections of the vertical and diagonal members.

[0024] Furthermore, a flexible composite cable 7 is provided at specific connection nodes 6 in the supporting mesh structure 3, particularly at the center of the concave apex (i.e., the apex of the aforementioned V-shaped diagonal bar). This flexible composite cable 7 is directly inserted and positioned within the central aperture of the connection node 6 during the extrusion process and is tightly physically wrapped by the wood-plastic composite substrate to form a composite structure. In this embodiment, the flexible composite cable 7 is made of high-strength aramid fiber bundles or ultra-high molecular weight polyethylene fiber bundles. Its physical characteristics are: extremely low bending stiffness in the transverse direction, allowing it to flex synchronously with the rotation of the connection node 6, thus not hindering the tensile deformation of the topological unit cell 4; and extremely high tensile modulus and breaking strength in the longitudinal direction (profile axial direction). This design allows the flexible composite cable 7 to act as a stress defense line. When the frame structure is subjected to extreme external pull-out forces or severe thermal strain causing the load-bearing members 5 of the wood-plastic composite substrate to reach their strain limits, the flexible composite cable 7 can intervene to bear the main axial tensile force, preventing the supporting mesh structure 3 from shattering or failing.

[0025] The dynamic process of thermal stress relief in the profile in this embodiment is referenced. Figure 3 When the frame structure is installed outdoors, the wood-plastic composite outer wall 1 experiences axial thermal expansion due to strong sunlight. Because the ends of the profiles are restricted by door / window corners or walls, this thermal expansion is converted into axial thermal expansion tensile strain along the profile's extension direction. Since the supporting mesh structure 3 and the wood-plastic composite outer wall 1 are integrally formed, this tensile strain acts synchronously on the topological unit cell 4. At this time, the connecting node 6, acting as the geometric hinge center, rotates under tension, causing the stressed members 5 to bend or displace. Specifically, the originally inwardly concave V-shaped diagonal bars are forced to unfold into a straight state due to vertical tension. During this geometric reconstruction process, the flattening of the V-shaped diagonal bars generates a lateral expansion force perpendicular to the axial direction, thereby pushing the stressed members 5 on both sides to expand in the profile wall thickness direction. This lateral expansion displacement helps to compensate for the interface thermal strain, thus helping to reduce or alleviate the thermal shear stress at the interface between the supporting mesh structure 3 and the wood-plastic composite outer wall 1. This allows the thermal strain to be released or redistributed through the shape change of the topological configuration, thereby suppressing or reducing the significant bow-shaped bending of the frame structure.

[0026] The dynamic process of profile-enhanced nail-holding force in this embodiment is referenced. Figure 4When external fasteners, such as self-tapping screws, are screwed into the supporting mesh structure 3, their threads physically engage with the stressed members 5 because the diameter of the fastener is usually larger than the gap of the topological unit cell 4. When the fastener is subjected to an axial pull-out force perpendicular to the plane of the paper during use, the supporting mesh structure 3 at the stress point is locally subjected to an outward pulling force. For the negative Poisson's ratio topological unit cell 4 of this invention, this axial tension will drive the unit cell to produce radial contraction. Specifically, the stressed members 5 around the stress point will converge towards the radial center of the fastener under the action of node movement. This inward contraction displacement helps to increase the positive pressure between the fastener threads and the supporting mesh structure 3, thereby helping to improve the pull-out strength and stability of the fastener in the wood-plastic composite substrate. This clamping effect, which increases with the pull-out force, helps to compensate for the technical defects of the wood-plastic composite substrate itself, such as low shear strength and easy loosening.

[0027] Furthermore, the dimensional parameters of the supporting mesh structure 3 have been optimized in this embodiment. The wall thickness of the load-bearing member 5... Wall thickness of wood-plastic outer wall 1 The ratio is set between 0.4 and 0.8. This range helps to balance structural stiffness and deformation capacity: if... If the value is too small (below 0.4), the overall stiffness of the supporting mesh structure 3 may be insufficient, making it prone to creep failure during long-term service, and the stressed members 5 are prone to buckling instability under lateral pressure; if If the ratio is too large (exceeding 0.8), the topological unit cell 4 will have a strong structural rigidity, which will lead to an increase in the rotational resistance of the connecting node 6, thereby potentially limiting the negative Poisson's ratio effect and reducing the ability to compensate for thermal expansion.

[0028] In summary, this embodiment alters the material's response to external loads and environmental strain by incorporating a specific negative Poisson's ratio topological mesh within the wood-plastic composite profile. The expansion of concave vertices facilitates expansion compensation to prevent bending, while localized radial contraction helps achieve pull-out resistance through clamping. This structural design helps systematically reduce the risk of thermal deformation in wood-plastic composite profiles and improve the reliability of mechanical connections without introducing heterogeneous components such as steel reinforcement.

[0029] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-performance wood-plastic composite frame structure for building doors and windows, comprising a wood-plastic outer wall (1) and an internal cavity (2) enclosed by the wood-plastic outer wall (1), characterized in that: The internal cavity (2) is integrally formed with a continuous support mesh structure (3), which is composed of multiple topological unit cells (4) arranged in a periodic or quasi-periodic array. The topological unit cell (4) includes multiple force-bearing members (5) and connecting nodes (6) connecting adjacent force-bearing members (5). The topological unit cell (4) is configured as an irrigated geometry with a negative Poisson's ratio effect.

2. The high-performance wood-plastic composite frame structure for building doors and windows according to claim 1, characterized in that: The topological unit cell (4) is a concave hexagonal unit cell or a double V-shaped bow unit cell; The connecting node (6) includes a concave vertex that is recessed into the topological unit cell (4), and the angle between adjacent force-bearing members (5) at the concave vertex is 60° to 120°.

3. A high-performance wood-plastic composite frame structure for building doors and windows according to claim 1 or 2, characterized in that: The topological unit cell (4) is configured such that when it is subjected to tensile strain caused by the thermal expansion of the wood-plastic outer wall (1) in the first direction, it drives the connecting node (6) to rotate and causes the topological unit cell (4) to generate a lateral expansion displacement in the second direction perpendicular to the first direction, so as to reduce the interfacial thermal shear stress between the supporting mesh structure (3) and the wood-plastic outer wall (1) and suppress the bow-shaped deformation of the frame structure as a whole.

4. A high-performance wood-plastic composite frame structure for building doors and windows according to claim 1 or 2, characterized in that: The topological unit cell (4) is configured such that when the external fastener is screwed into the support mesh structure (3) and subjected to an outward axial pull-out force, the topological unit cell (4) is driven to generate a contraction deformation that converges toward the radial center of the fastener, thereby increasing the interface contact pressure and frictional clamping force between the fastener and the support mesh structure (3).

5. A high-performance wood-plastic composite frame structure for building doors and windows according to claim 2, characterized in that: At the center of the connecting node (6) of the supporting mesh structure (3), a flexible composite cable (7) is inserted along the extrusion direction of the frame structure. The flexible composite cable (7) is located at the concave apex.

6. A high-performance wood-plastic composite frame structure for building doors and windows according to claim 5, characterized in that: The lateral bending stiffness of the flexible composite cable (7) is lower than the deformation stiffness of the topological unit cell (4) when it undergoes lateral expansion or centripetal contraction. The flexible composite cable (7) has axial tensile strength to provide axial tensile support when the deformation of the connecting node (6) reaches a set threshold due to the ultimate load on the frame structure.

7. The high-performance wood-plastic composite frame structure for building doors and windows according to claim 1, characterized in that: Let the wall thickness of the stressed member (5) be... The wall thickness of the wood-plastic outer wall (1) is Both conditions are met: So that the stressed member (5) has the ability to bend and deform and does not buckle under pressure.

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