Composite material top cover cross beam structure and preparation method

Abstract

The invention relates to the technical field of automobiles, in particular to a composite top cover beam structure and a preparation method. Comprising a top cover cross beam body which comprises a reinforced fiber fabric layer cured by a resin matrix; the top cover cross beam body comprises a cross beam section located in the middle and mounting parts located at the two ends of the cross beam section and used for being connected with a vehicle body side wall connecting plate; wherein the cross beam section is of a closed bearing structure with an internal space. According to the invention, the carbon fiber, glass fiber or aramid fiber reinforced composite material is combined with the HPRTM process, so that the weight of the top cover cross beam is greatly reduced on the premise of ensuring the same mechanical property as that of the traditional high-strength steel scheme.

Description

Technical Field

[0001] This invention relates to the field of automotive technology, and in particular to a composite material roof beam structure and its preparation method. Background Technology

[0002] The roof crossbeam is a critical safety component in the vehicle body structure. Its primary function is to protect the integrity of the passenger compartment structure by resisting roof crush and side impact deformation during rollovers or side collisions, thereby ensuring occupant safety. Currently, most mainstream roof crossbeams are made of hot-formed high-strength steel or other metal materials, and their structure typically consists of an upper plate, a lower plate, and multiple reinforcing components assembled through welding. While this metal solution offers mature mechanical support performance, its overall structure is relatively heavy, making it difficult to meet the urgent need for lightweight vehicle bodies in modern automobiles, especially new energy vehicles.

[0003] With rising global energy efficiency standards and range requirements, reducing vehicle energy consumption has become a core industry demand, making vehicle weight reduction an urgent priority. However, traditional metal roof beams often require large cross-sectional cavities to achieve high strength, which not only increases vehicle weight but also reduces interior space in the Z-direction, limiting the installation space for interior accessories and passenger headroom. Therefore, developing a composite material roof beam structure that can achieve significant weight reduction, optimize vehicle space, and possess high integration and excellent mechanical properties has become an important research direction in the current automotive manufacturing field. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned shortcomings in the prior art by proposing an intelligent composite material anti-collision beam structure and its preparation method.

[0005] To achieve the above objectives, the present invention provides a composite material top cover beam structure, comprising: The roof beam body includes a reinforcing fiber fabric layer cured from a resin matrix; the roof beam body includes a beam section located in the middle, and mounting portions located at both ends of the beam section for connecting the vehicle body side panel connecting plates; wherein the beam section is a closed load-bearing structure with an internal space.

[0006] By replacing traditional steel with resin-based reinforced fiber fabric and constructing a closed load-bearing structure with internal space, the weight of the top cover beam is reduced (the weight reduction ratio can reach 30% to 50%). At the same time, by utilizing the high moment of inertia characteristics of the closed section, the bending and torsional stiffness of the beam is guaranteed when it is subjected to force in the middle.

[0007] Preferably, the enclosed load-bearing structure includes: the crossbeam segment is composed of an upper composite material plate and a lower composite material plate that are joined and bonded together, and the internal space is a closed cavity enclosed by the upper plate and the lower plate.

[0008] The use of an upper and lower plate bonding configuration reduces the molding difficulty of complex cross-section composite material components. The upper and lower plates can be efficiently prepared separately through the HPRTM process. The closed cavity realizes a mechanical "box-shaped" structure, which provides the possibility for internal reinforcement or pipelines while ensuring structural strength.

[0009] Preferably, the enclosed load-bearing structure includes: the crossbeam segment is integrally cured by covering a foam core material with reinforced fiber fabric, and the internal space is filled with the foam core material.

[0010] Through the integrated design of fiber-coated foam core material, a high-performance sandwich structure is formed. The foam core material supports the fiber skin, which improves the specific stiffness of the structure and can effectively suppress the local instability of the fiber layer. Moreover, no secondary bonding is required, resulting in better structural integrity and load transfer continuity.

[0011] Preferably, the lower plate of the composite material is a laminated plate structure or a sandwich structure containing a foam core.

[0012] Based on the load requirements of different vehicle models, the lower plate is selected as a laminate or sandwich structure, realizing the "design on demand" of the structure; the use of a sandwich structure in the lower plate can improve its load-bearing capacity in the vertical direction without significantly increasing the crossbeam cross section height.

[0013] Preferably, the reinforcing fiber fabric layer includes a mixed carbon fiber fabric layer and a protective fabric layer; the protective fabric layer is located on the outermost surface of the top cover beam body, and the protective fabric layer is a glass fiber fabric layer or an aramid fabric layer.

[0014] By blending carbon fiber with glass / aramid fiber, the high strength of carbon fiber is utilized, while the outer protective fabric achieves electrical insulation (preventing electrochemical corrosion) or impact protection. This prevents carbon fiber debris from flying in the event of structural failure, thus improving the secondary safety of occupants.

[0015] Preferably, the closed cavity is further provided with a metal reinforcing component; the metal reinforcing component includes a W-shaped steel connecting bracket, which is disposed at the middle mounting point of the mounting part and / or the crossbeam segment; the W-shaped steel connecting bracket is fixed between the upper plate and the lower plate of the composite material by a structural adhesive layer and fasteners.

[0016] The pre-installed W-shaped steel connecting bracket provides internal rigid support for the composite material shell, effectively solving the problem of local crushing that is prone to occur in composite materials under bolt tightening load. Through the hybrid connection mode of "adhesive bonding + screw bonding", the advantages of metal and composite materials complement each other, enhancing the load diffusion capacity and collision reliability at the installation point.

[0017] Preferably, the thickness of the reinforcing fiber fabric layer at the mounting portion and at the locally preset reinforcement points is greater than its thickness at other locations on the crossbeam segment.

[0018] By implementing localized thickening designs in key areas such as the installation section, precise material distribution is achieved. This ensures sufficient shear and compressive strength in the connection area while keeping the non-critical areas of the beam thin and light, thus optimizing structural efficiency and reducing weight.

[0019] Preferably, the height dimension of the top cover beam body in the vehicle height direction is smaller than the height dimension of a metal beam with equivalent mechanical properties.

[0020] Thanks to the excellent specific strength of composite materials, this structure can achieve the same cross-sectional force as a metal beam with a smaller cross-sectional height Z, thereby freeing up physical space in the roof of the vehicle, improving the headroom comfort of passengers, and providing greater flexibility for the arrangement of interior accessories.

[0021] Preferably, the mounting part is attached to the vehicle side panel connecting plate from top to bottom, and a structural adhesive layer is provided between the mounting part and the vehicle side panel connecting plate.

[0022] The top-down bonding assembly method utilizes gravity-assisted positioning to optimize the assembly process in the final assembly workshop; combined with the structural adhesive layer, it not only enhances the connection strength but also serves to seal, reduce vibration, and isolate dissimilar materials.

[0023] This application also discloses a method for preparing a composite material top cover beam, including: Step 1: Based on the construction of the closed load-bearing structure, prepare a prefabricated body made of reinforcing fiber fabric, or prepare a prefabricated body made of reinforcing fiber fabric covering foam core material. Increase the number of reinforcing fiber fabric layers at the installation location to achieve local thickening, and ensure that the protective fabric layer is on the outermost side of the layup. Step 2: Place the preform into a mold, inject resin using a high-pressure resin transfer molding process, and cure to obtain a composite material molded part; Step 3: According to the design requirements, the multiple composite material molding parts are bonded together and closed, or the integrally molded top cover beam body is obtained directly in step 2.

[0024] The HPR™ high-pressure resin transfer molding process enables rapid curing of composite parts. Through local thickening and protective layer design in the preform stage, the molded products have high dimensional accuracy, fiber content and surface quality, making them suitable for large-scale automated production.

[0025] Compared with the prior art, the composite material roof beam structure and its preparation method disclosed in this invention have the following significant advantages: This invention achieves significant weight reduction in the roof beam by employing carbon fiber, glass fiber, or aramid fiber reinforced composite materials combined with the HPRTM process, while ensuring equivalent mechanical properties to traditional high-strength steel solutions. To meet the needs of different vehicle models, this invention provides various solutions, ranging from simplified laminated closed cavities to highly integrated sandwich structures, flexibly balancing cost and strength requirements. Specifically, by pre-installing foam core materials or W-shaped steel connecting brackets in key stress areas, the bending resistance, local stiffness, and overall stability of the structure are significantly improved, effectively meeting the dual requirements of new energy vehicles for reduced energy consumption and enhanced safety.

[0026] The design fully leverages the functional designability of composite materials, achieving structural and functional integration through multi-layered material blending. The inner layer utilizes carbon fiber to provide extremely high specific strength and specific stiffness, while the outer surface is covered with glass fiber or aramid material. This not only achieves excellent insulation and corrosion resistance, avoiding the risk of electrochemical corrosion, but more importantly, in the event of ultimate structural failure, the outer fabric can effectively prevent debris from flying, enhancing secondary protection and safety for occupants.

[0027] Thanks to the excellent molding properties of composite materials, the structure of this invention can achieve higher cross-sectional forces with smaller cross-sectional dimensions, thereby effectively reducing the space occupied by the crossbeam in the Z-direction of the vehicle body. Compared to the large cavity structure commonly found in metal solutions, this invention significantly frees up Z-direction space in the vehicle's roof, providing a more ample installation environment for interior accessories and improving passenger headroom comfort. Furthermore, the use of a "glue + screw" assembly method from top to bottom greatly optimizes the convenience and reliability of the final assembly process. Attached Figure Description

[0028] Figure 1 This is a perspective view of a specific embodiment of the present invention; Figure 2 This is a left view of a specific embodiment of the present invention; Figure 3 This is a front view of a specific embodiment of the present invention; Figure 4 This is a perspective view of yet another specific embodiment of the present invention; Figure 5 This is a perspective view of yet another specific embodiment of the present invention; Figure 6 This is a perspective view of another specific embodiment of the present invention. Detailed Implementation

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Example 1

[0030] See attached document Figure 1-3 This embodiment discloses a basic structure. The top cover beam body is formed by bonding an upper composite material plate and a lower composite material plate together with an epoxy structural adhesive to form a closed cavity.

[0031] Both the upper and lower panels utilize carbon fiber fabric as the primary load-bearing layer, with layup angles including combinations of 0°, 90°, and ±45°. To prevent electrochemical corrosion from contact between the carbon fiber and the metal body, a layer of plain-weave fiberglass fabric is laid on the outermost surface of both the upper and lower panels as a protective layer. This protective layer not only provides insulation but also makes the surface of the crossbeam smoother, facilitating subsequent adhesive sealing with the body side panels.

[0032] This embodiment reduces weight by more than 40% compared to steel beams of equivalent performance while maintaining strength. The hybrid design of carbon fiber core and glass fiber surface layer achieves a weight reduction of more than 40% compared to steel beams of equal strength. Simultaneously, the insulating properties of the outer glass fiber effectively block the electrochemical corrosion path between the internal conductive carbon fiber and the metal body, fundamentally solving the corrosion failure problem of dissimilar material connections and significantly extending the service life of structural components. Example 2

[0033] See attached document Figure 4 This embodiment, based on Example 1, provides additional reinforcement to the mounting portions at both ends. Within the internal cavity formed by the upper and lower composite material plates, corresponding to the mounting areas at both ends of the vehicle body, a W-shaped high-strength steel connecting bracket is arranged.

[0034] The W-shaped steel connecting bracket is pre-fixed to the inside of the lower plate using structural adhesive. During installation, high-strength bolts pass through the upper plate, the central slot of the bracket, and the lower plate, locking the entire crossbeam assembly to the vehicle side panel. The W-shaped structure design provides the bracket with high compressive support in the Z direction, effectively preventing crushing deformation of the composite material sheet during bolt tightening. Simultaneously, this combination of "composite shell + metal frame" significantly improves the roof's energy absorption performance in rollover collisions.

[0035] By pre-installing a W-shaped high-strength steel connecting bracket inside the composite material cavity, the excellent compressive strength of the metal bracket bears the axial clamping force when the bolts are tightened, effectively preventing micro-cracks or crushing of the composite laminate due to local pressure. This combination structure of "composite shell + metal skeleton" not only improves the reliability of the connection point, but also enhances the energy absorption characteristics and deformation resistance of the vehicle in rollover accidents. Example 3

[0036] See attached document Figure 5This embodiment discloses an asymmetrical split structure. The upper composite material plate is a pure carbon fiber laminate, while the lower composite material plate is constructed as a sandwich structure with a partial foam core.

[0037] Specifically, in the central stress-bearing core area of ​​the lower plate, a rigid polyurethane foam core material with a thickness of 3mm to 5mm is embedded between two layers of carbon fiber fabric. This design significantly increases the section modulus of the lower plate without significantly increasing the overall thickness of the crossbeam, thereby enhancing the crossbeam's resistance to instability under central compression. Because the upper plate remains a thin laminate, the projected height of the entire assembly in the Z direction is strictly controlled, leaving more space for the arrangement of interior headliner components.

[0038] The asymmetrical structure with partial core sandwich in the lower plate improves the moment of inertia and instability resistance of the middle section of the component by introducing foam core material only in the core area of ​​the lower plate. Meanwhile, the upper plate maintains a thin laminated structure, which effectively controls the overall projection height of the crossbeam in the Z direction. This improves the structural strength while reserving valuable installation space for the arrangement of interior accessories on the roof. Example 4

[0039] See attached document Figure 6 This embodiment discloses a highly integrated one-piece sandwich beam. The interior of the top cover beam body is a single-piece molded PMI polymethacrylamide foam core, and the exterior is fully enclosed by a continuous carbon fiber fabric layer.

[0040] This structure contains no secondary bonding surfaces, and its reinforcing fibers remain continuous at the corners of the beam, eliminating the risk of stress concentration during bonding. Due to the high specific stiffness of the PMI foam, the beam can uniformly transmit force across its entire cross-section when subjected to lateral impact loads. Furthermore, this embodiment utilizes the HPRTM process to achieve simultaneous impregnation and curing of the resin onto the fiber and foam surfaces, resulting in exceptional structural integrity. This integrated structure occupies 15mm less space in the Z-direction compared to traditional metal beams, significantly improving occupant headroom.

[0041] The HPRTM process enables the integrated molding of PMI foam core material and continuous fiber skin, completely eliminating the secondary adhesive interface present in traditional split structures and avoiding the risk of adhesive aging or peeling. With the extremely high specific stiffness of the core material, this structure can achieve the design strength with a more compact cross-sectional size, maximizing the headroom for occupants. Example 5

[0042] This embodiment provides a method for preparing the high-performance composite material top cover beam structure of Examples 1-4. Step 1: Based on the construction of the closed load-bearing structure, prepare a prefabricated body made of reinforcing fiber fabric, or prepare a prefabricated body made of reinforcing fiber fabric covering foam core material. Increase the number of reinforcing fiber fabric layers at the installation location to achieve local thickening, and ensure that the protective fabric layer is on the outermost side of the layup. Step 2: Place the preform into the mold, inject resin using a high-pressure resin transfer molding process and cure it to obtain the composite material molded part; Step 3: According to the design requirements, multiple composite material molded parts are bonded together to close them, or the one-piece molded top cover beam body is obtained directly in step 2.

[0043] By introducing a W-shaped high-strength steel connecting bracket inside the composite material cavity, this embodiment utilizes its unique geometric configuration to provide extremely high vertical support stiffness, effectively offsetting the axial clamping force generated by the high-strength bolts during tightening. This fundamentally solves the problem of insufficient compressive strength in the Z-direction of the composite laminate, which is prone to local crushing or micro-cracks. This design not only ensures the long-term stability of the preload at the connection point, preventing loosening of the connection during long-term vehicle operation, but also achieves high-rigidity locking between the crossbeam and the vehicle body side panel.

[0044] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A composite material roof beam structure, characterized in that, include: The top cover beam body includes a layer of reinforcing fiber fabric cured from a resin matrix; The top cover crossbeam body includes a crossbeam section located in the middle, and mounting parts located at both ends of the crossbeam section for connecting the vehicle side panel connecting plate; The crossbeam segment is a closed load-bearing structure with internal space.

2. The composite material top cover beam structure according to claim 1, characterized in that, The enclosed load-bearing structure includes: The crossbeam segment is composed of an upper composite material plate and a lower composite material plate that are bonded together and joined to each other, and the internal space is a closed cavity enclosed by the upper plate and the lower plate.

3. The composite material top cover beam structure according to claim 1, characterized in that, The enclosed load-bearing structure includes: The crossbeam segment is integrally cured by covering a foam core material with reinforced fiber fabric, and the internal space is filled with the foam core material.

4. The composite material top cover beam structure according to claim 2, characterized in that, The lower plate of the composite material is a laminated plate structure or a sandwich structure containing a foam core.

5. The composite material top cover beam structure according to claim 1, characterized in that, The reinforcing fiber fabric layer includes a mixed carbon fiber fabric layer and a protective fabric layer; The protective fabric layer is located on the outermost surface of the top cover beam body, and the protective fabric layer is a glass fiber fabric layer or an aramid fabric layer.

6. The composite material top cover beam structure according to claim 2, characterized in that, The closed cavity is also equipped with a metal reinforcement component; The metal reinforcement component includes a W-shaped steel connecting bracket, which is disposed at the middle mounting point of the mounting part and / or the crossbeam segment; The W-shaped steel connecting bracket is fixed between the upper and lower composite material plates by structural adhesive and fasteners.

7. The composite material top cover beam structure according to claim 1, characterized in that, The thickness of the reinforcing fiber fabric layer at the mounting section and at the locally preset reinforcement points is greater than its thickness at other locations on the crossbeam section.

8. The composite material top cover beam structure according to claim 1, characterized in that, The height dimension of the top cover crossbeam body in the vehicle height direction is smaller than the height dimension of a metal crossbeam with equivalent mechanical properties.

9. The composite material top cover beam structure according to claim 1, characterized in that, The mounting part is attached to the vehicle side panel connecting plate from top to bottom, and a structural adhesive layer is provided between the mounting part and the vehicle side panel connecting plate.

10. The method for preparing the composite material top cover beam structure according to any one of claims 1 to 9, characterized in that, Includes the following steps: Step 1: Based on the construction of the closed load-bearing structure, prepare a prefabricated body made of reinforcing fiber fabric, or prepare a prefabricated body made of reinforcing fiber fabric covering foam core material. Increase the number of reinforcing fiber fabric layers at the installation location to achieve local thickening, and ensure that the protective fabric layer is on the outermost side of the layup. Step 2: Place the preform into a mold, inject resin using a high-pressure resin transfer molding process, and cure to obtain a composite material molded part; Step 3: According to the design requirements, the multiple composite material molding parts are bonded together and closed, or the integrally molded top cover beam body is obtained directly in step 2.

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