Composite frame variable cross-section profile and preparation method thereof

Abstract

According to the composite material frame variable cross-section profile and the preparation method thereof, a main beam profile structure is designed and manufactured in a segmented mode, a uniform cross-section section is manufactured by combining a pultrusion forming process and a vacuum infusion process through a two-step method, the bending strength of the profile is improved, and meanwhile the shearing strength of the profile is guaranteed; the variable cross-section section adopts a mixed structure of a metal inner layer and a composite material outer layer, so that the stress is dispersed, and meanwhile, the connection strength among the sections is improved; only one pultrusion die needs to be adopted for the two-step method manufacturing of the uniform-section sections, the die cost and the machining period are low, the pultrusion forming efficiency is high, and the profile manufacturing period is also shortened. And the metal structure of the variable cross-section section is directly used as a mold of the composite material layer, so that the mold cost and the manufacturing period are further reduced. The weight of the frame assembly is reduced, meanwhile, the bearing capacity is improved, the manufacturing period is shortened, meanwhile, the requirements for high performance and low cost are met, application and popularization of the composite frame are facilitated, and a certain technical support is provided for high-end equipment manufacturing.

Description

Technical Field

[0001] The invention belongs to the technical field of lightweight manufacturing of special automobiles, and in particular relates to a composite material vehicle frame variable-section profile and a preparation method thereof. Background Art

[0002] As the main load-bearing component of special vehicles, the frame has a large deadweight and carries the weight of the body, powertrain, cab, personnel and cargo. When driving on complex roads, it is subject to the synergistic effects of different bending moments, torques and shear forces, and the working conditions are relatively complex. Using composite materials to replace the original steel frame can greatly reduce the deadweight of the frame and improve the frame's carrying capacity. The frame longitudinal beams of certain models must be designed as variable-section profiles due to assembly requirements such as wheel hubs. The cross-section types are generally C-type, I-type, square, etc. At present, the use of vacuum infusion, OOA, autoclave and other processes to design and manufacture composite frames can achieve better performance, but high-precision molds must be prepared, which greatly increases the production cycle and cost, and is not conducive to mass promotion and application. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a composite frame variable cross-section profile and its preparation method in view of the deficiencies of the above-mentioned prior art, improve the main beam profile structure, design and manufacture in sections, and use a two-step method to manufacture the equal cross-section section in combination with the pultrusion molding process and the vacuum infusion process, which improves the bending strength of the profile while ensuring the shear strength of the profile; the variable cross-section section adopts a mixed structure of metal and composite materials, which disperses the stress and improves the connection strength between the sections. The two-step method of manufacturing the equal cross-section section only requires one pultrusion die, with low mold cost and processing cycle, high pultrusion efficiency, and reduced profile manufacturing cycle; the metal structure of the variable cross-section section is directly used as the mold of the composite layer, further reducing the mold cost and manufacturing cycle. Therefore, the present invention reduces the weight of the frame assembly while improving the bearing capacity and reducing the manufacturing cycle, while meeting the requirements of high performance and low cost, which is conducive to the promotion and application of composite frames and provides certain technical support for high-end equipment manufacturing.

[0004] The technical solution adopted by the present invention to solve the above-mentioned technical problems is:

[0005] A composite material frame variable cross-section profile, comprising a front section profile, a middle section profile and a rear section profile, wherein the front section profile and the rear section profile are of equal cross-section, the middle section profile is of variable cross-section, the front section profile has a different height from the rear section profile, the front end height of the middle section profile is the same as the front section profile, and the rear end height is the same as the rear section profile; the inner front end of the middle section profile extends forward to form a front end connecting section, and the inner rear end extends backward to form a rear end connecting section, and the rear end of the front section profile is provided with a front section groove adapted to the front end connecting section so that the front end connecting section is placed in the front section groove The inner and outer surfaces of the middle section profile are flush with the front section profile, and the front end of the rear section profile is provided with a rear section groove adapted to the rear end connecting section so that when the rear end connecting section is placed in the rear section groove, the inner and outer surfaces of the middle section profile are flush with the rear section profile; the front end connecting section and the front section groove are fixed by means of bonding and mechanical connection, and the rear end connecting section and the rear section groove are fixed by means of bonding and mechanical connection; the front section profile and the rear section profile are made of composite materials, and the inner layer of the middle section profile is made of metal material and the outer layer is made of composite materials.

[0006] In the above scheme, the front section profile, the middle section profile and the rear section profile all include a web, an upper panel and a lower panel. The webs of the three sections are flush, the upper panel and the lower panel of the front section profile are parallel, the upper panel and the lower panel of the rear section profile are parallel, and the upper panel and the lower panel of the middle section profile are not parallel.

[0007] In the above solution, the lengths of the front connecting section and the rear connecting section are not less than 50 mm.

[0008] In the above scheme, the front section profile and the rear section profile are respectively manufactured in two steps of outer layer and inner layer, the outer layer is formed first and then the inner layer; the outer layer is formed by pultrusion process and the inner layer is formed by vacuum infusion process, and when the inner layer is formed, the front section groove area and the rear section groove area are not paved with reinforcing materials.

[0009] In the above scheme, the outer layers of the front section profile and the rear section profile are formed by pultrusion, and the pultruded reinforcement material adopts one or more of carbon fiber filaments, aramid fiber filaments, glass fiber filaments, quartz fiber filaments, basalt fiber filaments, and polyimide fiber filaments, and the resin adopts one of epoxy resin, vinyl resin, polyurethane resin, polyester resin, and phenolic resin; after the outer layer is cured and demolded, the inner surface is polished and trimmed, and the inner layer adopts vacuum infusion molding process, and the reinforcement material is laid on the inner surface of the outer layer in sequence and then vacuum infused, the vacuum infusion reinforcement material adopts one or more of carbon fiber fabric, aramid fabric, glass fiber fabric, quartz fiber fabric, basalt fiber fabric, and polyimide fiber fabric, and the resin adopts one of epoxy resin, vinyl resin, polyurethane resin, polyester resin, and phenolic resin.

[0010] In the above scheme, the metal inner layer of the middle section profile includes a front end connecting section, a rear end connecting section and a middle section therebetween, and the metal inner layer is formed as a whole by machining; the composite material outer layer of the middle section profile is vacuum infused after reinforcing materials are sequentially laid on the outer surface of the middle section of the metal inner layer, and the reinforcing materials for vacuum infusion are one or more of carbon fiber fabric, aramid fabric, glass fiber fabric, quartz fiber fabric, basalt fiber fabric, polyimide fiber fabric, and the resin is one of epoxy resin, vinyl resin, polyurethane resin, polyester resin, and phenolic resin; the front end connecting section and the rear end connecting section are not laid with reinforcing materials.

[0011] In the above solution, the thickness of the metal inner layer of the middle section profile is the same as the inner layer thickness of the front section profile and the rear section profile, and the thickness of the composite material outer layer of the middle section profile is the same as the outer layer thickness of the front section profile and the rear section profile.

[0012] In the above solution, the front end connecting section and the rear end connecting section are selected in the area where stress is not prominent.

[0013] Correspondingly, the present invention also proposes a method for preparing the above-mentioned composite material frame variable cross-section profile:

[0014] The front section profile and the rear section profile are both made in two steps. The first step is to use the pultrusion process to make the outer layer: the reinforcement material is fully impregnated with resin and then enters the mold through a guide device. The mold is a cavity mold with a hollow structure inside. The shape of the hollow structure is adapted to the front section profile or the rear section profile. After preliminary heating and curing in the mold, it is formed to the designed length through a traction device; after the outer layer is cured and demoulded, the inner surface is polished and trimmed; the second step is to use the vacuum infusion process to make the inner layer: after the trimming is completed, the reinforcement material is laid on the inner surface of the outer layer in sequence, and the reinforcement material is not laid in the front section groove and the rear section groove area. After the laying is completed, the guide net and breathable felt are laid on the innermost layer, and it is sealed with a vacuum bag and a sealing strip, and the inner layer is formed by the vacuum infusion process;

[0015] The middle section profile is made in two steps. The first step is to form the metal inner layer by machining. After the metal inner layer is machined, its outer surface is polished and cleaned. The second step is to use the vacuum infusion process to make the composite material outer layer: the outer surface of the middle section of the metal inner layer is paved with reinforcement materials in sequence, and the front connecting section and the rear connecting section are not paved with reinforcement materials. After the paving is completed, the outermost layer is paved with a guide net and a breathable felt, which is sealed with a vacuum bag and a sealing strip, and the outer layer is formed by the vacuum infusion process.

[0016] After the front section profile, the rear section profile and the middle section profile are manufactured, they are assembled, and the front connecting section and the rear connecting section of the middle section profile are placed in the front section groove of the front section profile and the rear section groove of the rear section profile respectively, and the overlapping area is bonded with structural adhesive;

[0017] After the structural adhesive is cured, at least two through holes are respectively opened in the bonding areas of the face plate and the web along the length direction, and fastening parts are used for fastening connection.

[0018] In the above method, the panel width is widened when the front section profile, the rear section profile and the middle section profile are manufactured, and then cut to the designed width after the manufacturing is completed.

[0019] The beneficial effects of the present invention are:

[0020] The present invention designs and manufactures the main beam profile structure in sections, wherein the equal-section section is manufactured by a two-step method in combination with a pultrusion process and a vacuum infusion process, which improves the bending strength of the profile while ensuring the shear strength of the profile. Specifically, the outer layer adopts a pultrusion process, and the fiber reinforcement direction of the profile manufactured by the pultrusion process is 0 degrees, and the resin content is low, which can effectively improve the bending strength of the profile while ensuring the shear strength; the inner layer adopts a vacuum infusion process, and the vacuum infusion process uses fabric as a reinforcing material. The fabric is laid at different angles to increase the fiber reinforcement in the 90° and ±45° directions, which can ensure the shear strength of the profile. The two-step method only requires one pultrusion die, the mold cost is low, and the processing cycle is short, thereby reducing the profile manufacturing cycle. In addition, the pultrusion molding efficiency is high. The equal-section sections can all use large-tow fibers, and the raw material cost can be reduced by more than 30% compared with the same-level small-tow fibers. The pultrusion process is used for manufacturing, and the mold cost is lower than that of vacuum infusion, OOA, autoclave, molding and other processes, and the molding efficiency is improved by more than 10%. Comprehensive assessment shows that the overall cost can be reduced by more than 30%.

[0021] The variable cross-section section adopts a hybrid structure of metal and composite materials, which disperses stress and improves the connection strength between each section. Specifically, the variable cross-section section is prone to stress concentration due to the sudden change in shape, and as a structure connecting the front section and the rear section, the force is relatively complex. If a pure composite structure is used for connection, the shear resistance of the composite material is weak and it is easy to fail due to shearing. The hybrid structure of metal and composite materials can effectively disperse stress, improve the shear resistance of the overall structure, and improve the connection strength. The metal inner layer of the variable cross-section section is directly used as the mold for the outer layer of the composite material, further reducing the mold cost and production cycle.

[0022] In summary, the present invention reduces the weight of the frame assembly while improving the bearing capacity and reducing the production cost and cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0024] Figure 1 is an overall structural diagram of a composite material frame with a variable cross-section according to an embodiment of the present invention;

[0025] Figure 2yes Figure 1 An enlarged view of the local structure of the variable-section area of ​​the composite frame variable-section profile shown;

[0026] Figure 3 yes Figure 1 An enlarged view of the partial structure of the front section of the composite vehicle frame variable cross-section profile shown;

[0027] Figure 4 yes Figure 1 An enlarged view of the local structure of the rear section of the composite vehicle frame variable cross-section profile shown;

[0028] Figure 5 yes Figure 1 An enlarged view of the local structure of the middle section of the composite vehicle frame variable cross-section profile shown;

[0029] Figure 6 yes Figure 1 Schematic diagram of bonding overlapping areas of variable-section profiles of a composite vehicle frame.

[0030] In the figure: 10, front section profile; 11, front section groove;

[0031] 20. Middle section profile; 21. Front end connecting section; 22. Rear end connecting section; 23. Middle section;

[0032] 30. rear section profile; 31. rear section groove;

[0033] 41. Belly plate; 42. Upper panel; 43. Lower panel. DETAILED DESCRIPTION

[0034] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0035] like Figure 1-6As shown in the figure, a composite material frame variable cross-section profile provided by an embodiment of the present invention is divided into three sections, including a front section profile 10, a middle section profile 20 and a rear section profile 30. The front section profile 10 and the rear section profile 30 are of equal cross-section, the middle section profile 20 is of variable cross-section, the front section profile 10 is different in height from the rear section profile 30, the front end height of the middle section profile 20 is the same as the front section profile 10, and the rear end height is the same as the rear section profile 30; the inner front end of the middle section profile 20 extends forward to form a front end connection The connecting section 21 and the rear end of the inner layer extend backward to form a rear end connecting section 22. The rear end of the front section profile 10 is provided with a front section groove 11 adapted to the front section connecting section 21, so that when the front section connecting section 21 is placed in the front section groove 11, the inner and outer surfaces of the middle section profile 20 are flush with the front section profile 10. The front end of the rear section profile 30 is provided with a rear section groove 31 adapted to the rear section connecting section 22, so that when the rear section connecting section 22 is placed in the rear section groove 31, the inner and outer surfaces of the middle section profile 20 are flush with the rear section profile 30. The front section connecting section 21 is fixed to the front section groove 11 by means of bonding and mechanical connection, and the rear section connecting section 22 is fixed to the rear section groove 31 by means of bonding and mechanical connection. The front section profile 10 and the rear section profile 30 are made of composite materials, and the inner layer of the middle section profile 20 is made of metal material and the outer layer is made of composite materials.

[0036] Further optimization, the front section profile 10, the middle section profile 20 and the rear section profile 30 all include a web 41, an upper panel 42 and a lower panel 43, the webs of the three sections are flush, the upper panel and the lower panel of the front section profile 10 are parallel, the upper panel and the lower panel of the rear section profile 30 are parallel, and the upper panel and the lower panel of the middle section profile 20 are not parallel.

[0037] Further optimization is performed by selecting the stress-free region for the front connecting section 21 and the rear connecting section 22. The length of the front connecting section 21 and the rear connecting section 22 is not less than 50 mm.

[0038] Further optimization is performed, the front section profile 10 and the rear section profile 30 are respectively manufactured in two steps of outer layer and inner layer, the outer layer is formed first and then the inner layer; the outer layer is formed by pultrusion process and the inner layer is formed by vacuum infusion process, when the inner layer is formed, no reinforcing material is laid in the front section groove 11 and the rear section groove 31 areas.

[0039] Further optimization, the outer layers of the front section profile 10 and the rear section profile 30 are made by pultrusion process, and the pultruded reinforcement material adopts one or more of carbon fiber filaments, aramid fiber filaments, glass fiber filaments, quartz fiber filaments, basalt fiber filaments, and polyimide fiber filaments. In this embodiment, large-tow carbon fiber filaments are used, which have higher strength and lower material cost. The resin adopts one of epoxy resin, vinyl resin, polyurethane resin, polyester resin, and phenolic resin. In this example, epoxy resin is used, which has good strength, toughness and processability; after the outer layer is cured and demolded, the inner surface is polished and trimmed. The inner layer is formed by a vacuum infusion process, and the reinforcing materials are laid in sequence on the inner surface of the outer layer before vacuum infusion. The laying angle is designed according to the stress conditions, and the number of layers is determined according to the thickness of the fabric. The reinforcing material for vacuum infusion is one or more of carbon fiber fabric, aramid fabric, glass fiber fabric, quartz fiber fabric, basalt fiber fabric, and polyimide fiber fabric. In this embodiment, large-tow carbon fiber fabric is used, which has higher strength and lower material cost. The resin is one of epoxy resin, vinyl resin, polyurethane resin, polyester resin, and phenolic resin. In this example, epoxy resin is used, which has good strength, toughness and processability.

[0040] Further optimization, the metal inner layer of the middle section profile 20 includes a front end connecting section 21, a rear end connecting section 22 and an intermediate section 23 therebetween. The metal inner layer is formed as a whole by machining. The thickness of the metal inner layer is the same as the thickness of the inner layer of the front section profile 10 and the rear section profile 30. The metal can be one of steel, aluminum alloy, and titanium alloy. The outer layer of the composite material of the middle section profile 20 is vacuum infused after reinforcing materials are sequentially laid on the outer surface of the metal inner layer middle section 23. The thickness of the outer layer of the composite material is the same as the thickness of the outer layer of the front section profile 10 and the rear section profile 30. The reinforcing material for vacuum infusion is one or more of carbon fiber fabric, aramid fabric, glass fiber fabric, quartz fiber fabric, basalt fiber fabric, and polyimide fiber fabric. In this embodiment, large-tow carbon fiber fabric is used, which has higher strength and lower material cost. The resin is one of epoxy resin, vinyl resin, polyurethane resin, polyester resin, and phenolic resin. In this example, epoxy resin is used, which has good strength, toughness and processability. The front connecting section 21 and the rear connecting section 22 are not laid with reinforcing materials.

[0041] After further optimization, the front, middle and rear sections of the profile 30 are formed, and then they can be assembled. After assembly, all areas of the frame are of equal thickness and consistent with the initial appearance. The specific assembly method is: first, the overlapping areas are bonded with structural adhesive. After the adhesive is cured, holes are opened in the bonding areas of the profile panels and webs, and fasteners (such as bolts, etc.) are used for connection.

[0042] In the embodiment provided by the present invention, the thickness of all surfaces of the frame is the same, which is 20 mm. The front section and the rear section are C-profiles of equal cross-section, and the middle section is a C-profile of variable cross-section. The front section C-profile is 150 mm high and 2000 mm long, and the rear section C-profile is 250 mm high and 4000 mm long. The front end of the middle section is 150 mm high, and the rear end of the middle section is 250 mm high and 800 mm long.

[0043] The upper and lower panels of the front and rear sections are parallel and perpendicular to the web, with a panel width of 80mm. The upper and lower panels of the middle section are not parallel, but are perpendicular to the web, with a panel width of 80mm. The upper panels of the front, middle and rear sections are continuous, and the lower panels form a three-section structure, sloping downward from front to back.

[0044] The composite frame is designed in three sections. The front, middle and rear connection areas are selected as areas where stress does not change suddenly. Therefore, the middle section extends 100mm towards the front and rear sections. The length of the front section is reduced to 1900mm, the height is 150mm, the thickness is 20mm, and the thickness of the area near the middle section 100mm is 14mm; the length of the rear section is reduced to 3900mm, the height is 250mm, the thickness is 20mm, and the thickness of the area near the middle section 100mm is 14mm.

[0045] The middle section is a variable-section C-shaped material with a thickness of 20mm. It extends 100mm to the front and rear sections respectively, and has a length of 1000mm. In order to connect with the front and rear sections and improve the connection strength, it extends 100mm to both ends to form an overlapping area with the front and rear sections. The thickness of the overlapping area of ​​the middle section is 6mm, and the total thickness is 20mm after superimposing the 14mm overlapping area of ​​the front and rear sections. The total length of the middle section is 1200mm.

[0046] The method for preparing the above-mentioned composite material frame variable cross-section profile is as follows:

[0047] The front section is made in two steps, the first step is to make the outer layer, and the second step is to make the inner layer. The outer layer is 1900mm long and 14mm thick, and is made by pultrusion. When the outer layer is made, the panel width is widened to 110mm. When the outer layer is made, the panel is widened by 30mm to reserve the bagging area and process edge for the second step of vacuum infusion molding. The fiber used is a large-tow carbon fiber tow, and the resin used is epoxy resin. After the carbon fiber tow is fully infiltrated with resin, it enters the mold through a guide device. The mold is a cavity mold with an internal shape of a C-shaped hollow structure. After preliminary heating and curing in the mold, it is formed to 1900mm through a traction device. After the outer layer is cured and demolded, the inner surface is polished and trimmed. After finishing, the inner surface is paved with large-tow carbon fiber biaxial fabric in sequence, with paving angles of 0° / 45° / 90° / -45°. The number of layers is determined by the thickness of the fabric. When the inner layer is made, the width needs to be increased to 90mm, and the reserved process edge is cut together with the outer layer later, so that the width size of the profile is more accurate. The single-layer thickness of the fabric in this embodiment is 0.4mm, the number of layers is 15, and there is no need to lay fabric near the 100mm length area in the middle section. After paving is completed, the innermost layer is paved with a guide net and a breathable felt, which is sealed with a vacuum bag and a sealing strip. The inner layer is formed by a vacuum infusion process with a 6mm thickness, and the molding length is 1800mm. After the front section is formed, the width of the outer panel is 110mm, and the width of the inner panel is 90mm. The profile is cut to a uniform panel width of 80mm to complete the production of the front section.

[0048] The production method of the rear section is the same as that of the front section, which is divided into two steps. The outer layer of the rear section is 3900mm long and 14mm thick. It is made by pultrusion. When the outer layer is made, the panel width is widened to 110mm. The fiber used is large-tow carbon fiber tow, and the resin used is epoxy resin. After the outer layer is cured and demoulded, the inner surface is polished and trimmed. After the trimming is completed, the inner surface is paved with large-tow carbon fiber biaxial fabric in sequence. The paving angle is 0° / 45° / 90° / -45°. The single-layer thickness of the fabric is 0.4mm, and the number of layers is 15. When the inner layer is made, the width needs to be increased to 90mm. There is no need to lay fabric near the 100mm length area of ​​the middle section. The inner layer is 6mm and the molding length is 3800mm. After the rear section is formed, the width of the outer panel is 110mm and the width of the inner panel is 90mm. The profile is cut to a uniform panel width of 80mm to complete the production of the rear section.

[0049] The middle section is designed and manufactured with a metal-composite hybrid structure. The inner layer is metal and the outer layer is composite material. The inner metal structure is 1200mm long and 6mm thick, and is machined with Q460 steel. The width of the C-profile panel is widened to 110mm during machining. After the inner layer is machined, the outer surface is polished with fine sandpaper and cleaned with acetone. After cleaning, the outer surface is paved with large-tow carbon fiber biaxial fabric in sequence. The paving angles are 0° / 45° / 90° / -45°. The number of layers is determined by the thickness of the fabric. The single-layer thickness of the fabric in this embodiment is 0.4mm, and the number of layers is 35. There is no need to lay fabric in the 100mm length area near both ends. After paving is completed, the outermost layer is paved with a guide net and breathable felt, sealed with a vacuum bag and sealing strips, and the outer layer of 14mm is formed by a vacuum infusion process, and the forming length is 1000mm. After the middle section is formed, the panel width is 110mm. The profile is cut to a panel width of 80mm to complete the production of the middle section.

[0050] The front section, middle section and rear section are assembled after processing. The 100mm overlapping area between the front section and the middle section is bonded with epoxy structural adhesive, and the 100mm overlapping area between the middle section and the rear section is bonded with structural adhesive.

[0051] After the structural adhesive is cured, at least two through holes are opened along the length direction in the bonding area of ​​the face plate and the web, and fastened with M16 bolts.

[0052] In the present invention, the front section and the rear section are formed, and the outer layer adopts the pultrusion process. The fiber reinforcement direction of the profile produced by the pultrusion process is 0 degrees, and the resin content is low, which can effectively improve the bending strength of the profile while ensuring the shear strength; the inner layer adopts the vacuum infusion process, and the vacuum infusion process uses fabric as a reinforcing material. The fabric is laid at different angles to increase the fiber reinforcement in the 90° and ±45° directions, which can ensure the shear strength of the profile. The two-step method only requires one pultrusion mold, the mold cost is low, and the processing cycle is short, thereby reducing the profile production cycle. In addition, the pultrusion molding efficiency is high. Since the front section and the rear section use large-tow carbon fiber, the raw material cost can be reduced by more than 30% compared with the same level of small-tow carbon fiber. The pultrusion process is used for production, and the mold cost is lower than vacuum infusion, OOA, autoclave, molding and other processes, and the molding efficiency is increased by more than 10%. Comprehensive evaluation shows that the overall cost can be reduced by more than 30%.

[0053] The middle section is a variable cross-section. Due to the sudden change in shape, stress is easily concentrated. Moreover, as a structure connecting the front section and the back section, the force is relatively complex. If a pure composite structure is used for connection, the shear resistance of the composite material is weak and it is easy to fail due to shearing. However, the hybrid structure of metal and composite materials can effectively disperse stress, improve the shear resistance of the overall structure, and increase the connection strength. The metal layer in this hybrid structure can be directly used as a mold for the composite layer, further reducing the mold cost and cycle.

[0054] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0055] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation modes, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. A composite material frame with variable cross-section, characterized in that: The invention comprises a front section profile, a middle section profile and a rear section profile, wherein the front section profile and the rear section profile are of equal cross-section, the middle section profile is of variable cross-section, the height of the front section profile is different from that of the rear section profile, the front end height of the middle section profile is the same as that of the front section profile, and the rear end height is the same as that of the rear section profile; the front end of the inner layer of the middle section profile extends forward to form a front end connecting section, and the rear end of the inner layer extends backward to form a rear end connecting section, and the rear end of the front section profile is provided with a front section groove adapted to the front end connecting section so that when the front end connecting section is placed in the front section groove, the middle section profile is connected to the front section profile. The inner and outer surfaces of the middle section profile are flush, and the front end of the rear section profile is provided with a rear section groove adapted to the rear end connecting section so that when the rear end connecting section is placed in the rear section groove, the inner and outer surfaces of the middle section profile and the rear section profile are flush; the front end connecting section and the front section groove are fixed by means of bonding and mechanical connection, and the rear end connecting section and the rear section groove are fixed by means of bonding and mechanical connection; the front section profile and the rear section profile are made of composite materials, and the inner layer of the middle section profile is made of metal material and the outer layer is made of composite materials.

2. The composite material frame variable cross-section profile according to claim 1, characterized in that: The front section profile, the middle section profile and the rear section profile all include a web, an upper panel and a lower panel. The webs of the three sections are flush, the upper panel and the lower panel of the front section profile are parallel, the upper panel and the lower panel of the rear section profile are parallel, and the upper panel and the lower panel of the middle section profile are not parallel.

3. The composite material frame variable cross-section profile according to claim 1, characterized in that: The lengths of the front connecting section and the rear connecting section are not less than 50 mm.

4. The composite material frame variable cross-section profile according to claim 1, characterized in that: The front section profile and the rear section profile are respectively manufactured in two steps, the outer layer and the inner layer. The outer layer is formed first and then the inner layer. The outer layer is formed by pultrusion and the inner layer is formed by vacuum infusion. When the inner layer is formed, no reinforcing material is laid in the front section groove area and the rear section groove area.

5. The composite material frame variable cross-section profile according to claim 4, characterized in that: The outer layers of the front section profile and the rear section profile are formed by a pultrusion process, and the pultruded reinforcement material is one or more of carbon fiber yarn, aramid fiber yarn, glass fiber yarn, quartz fiber yarn, basalt fiber yarn, and polyimide fiber yarn, and the resin is one of epoxy resin, vinyl resin, polyurethane resin, polyester resin, and phenolic resin; after the outer layer is cured and demoulded, the inner surface is polished and trimmed, and the inner layer is formed by a vacuum infusion process, and the reinforcement material is laid on the inner surface of the outer layer in sequence and then vacuum infused, and the vacuum infusion reinforcement material is one or more of carbon fiber fabric, aramid fabric, glass fiber fabric, quartz fiber fabric, basalt fiber fabric, and polyimide fiber fabric, and the resin is one of epoxy resin, vinyl resin, polyurethane resin, polyester resin, and phenolic resin.

6. The composite material frame variable cross-section profile according to claim 4, characterized in that: The metal inner layer of the middle section profile includes a front end connecting section, a rear end connecting section and a middle section therebetween, and the metal inner layer is formed as a whole by machining; the composite material outer layer of the middle section profile is vacuum infused after reinforcing materials are sequentially laid on the outer surface of the middle section of the metal inner layer, and the reinforcing materials for vacuum infusion are one or more of carbon fiber fabrics, aramid fabrics, glass fiber fabrics, quartz fiber fabrics, basalt fiber fabrics, and polyimide fiber fabrics, and the resin is one of epoxy resin, vinyl resin, polyurethane resin, polyester resin, and phenolic resin; the front end connecting section and the rear end connecting section are not laid with reinforcing materials.

7. The composite material frame variable cross-section profile according to claim 6, characterized in that: The thickness of the metal inner layer of the middle section profile is the same as the inner layer thickness of the front section profile and the rear section profile, and the thickness of the composite material outer layer of the middle section profile is the same as the outer layer thickness of the front section profile and the rear section profile.

8. The composite material frame variable cross-section profile according to claim 1, characterized in that: The front end connecting section and the rear end connecting section are selected in areas where stress is not prominent.

9. The method for preparing a composite material frame variable cross-section profile according to any one of claims 1 to 8, characterized in that: The front section profile and the rear section profile are both made in two steps. The first step is to use the pultrusion process to make the outer layer: the reinforcement material is fully impregnated with resin and then enters the mold through a guide device. The mold is a cavity mold with a hollow structure inside. The shape of the hollow structure is adapted to the front section profile or the rear section profile. After preliminary heating and curing in the mold, it is formed to the designed length through a traction device; after the outer layer is cured and demoulded, the inner surface is polished and trimmed; the second step is to use the vacuum infusion process to make the inner layer: after the trimming is completed, the reinforcement material is laid on the inner surface of the outer layer in sequence, and the reinforcement material is not laid in the front section groove and the rear section groove area. After the laying is completed, the guide net and breathable felt are laid on the innermost layer, and it is sealed with a vacuum bag and a sealing strip, and the inner layer is formed by the vacuum infusion process; The middle section profile is made in two steps. The first step is to form the metal inner layer by machining. After the metal inner layer is machined, its outer surface is polished and cleaned. The second step is to use the vacuum infusion process to make the composite material outer layer: the outer surface of the middle section of the metal inner layer is paved with reinforcement materials in sequence, and the front connecting section and the rear connecting section are not paved with reinforcement materials. After the paving is completed, the outermost layer is paved with a guide net and a breathable felt, which is sealed with a vacuum bag and a sealing strip, and the outer layer is formed by the vacuum infusion process. After the front section profile, the rear section profile and the middle section profile are manufactured, they are assembled, and the front connecting section and the rear connecting section of the middle section profile are placed in the front section groove of the front section profile and the rear section groove of the rear section profile respectively, and the overlapping area is bonded with structural adhesive; After the structural adhesive is cured, at least two through holes are respectively opened in the bonding areas of the face plate and the web along the length direction, and fastening parts are used for fastening connection.

10. The method for preparing a composite material vehicle frame variable cross-section profile according to claim 9, characterized in that: The panel width is widened when the front section profile, the rear section profile and the middle section profile are manufactured, and then cut to the designed width after the manufacturing is completed.

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