Composite thin-walled tube and manufacturing process

Abstract

This invention relates to a composite material thin-walled tube and its manufacturing process. The composite material thin-walled tube is made of a high-performance fiber-reinforced resin composite material, which includes a fiber reinforcement and a resin matrix. The fiber reinforcement is an etched high-performance fiber. The composite material thin-walled tube has a certain aspect ratio and a chamfer at the end. A thin-walled layer exists within the voids of the composite material thin-walled tube. The cross-section formed by the thin-walled layer and the outer wall layer of the composite material thin-walled tube is an irregular cross-section. Structurally, this irregular cross-section is divided into a load-bearing zone and a restraining zone. The load-bearing zone and the restraining zone respectively constitute the load-bearing layer and the restraining layer of the thin-walled tube along its length. This invention features lightweight and high energy absorption, with more efficient and stable energy absorption, solving the technical problem that composite material tubes are difficult to simultaneously achieve small deformation and high energy absorption.

Description

Technical Field

[0001] This invention relates to a thin-walled composite material tube and its manufacturing process, specifically to a fiber-reinforced resin composite thin-walled tube for absorbing energy in frontal collisions of automobiles and its manufacturing process, belonging to the field of composite material application technology. Background Technology

[0002] Fiber-reinforced resin composites have applications in various sectors of society, especially thin-walled pipes made of composite materials. These pipes are lightweight, high-strength, corrosion-resistant, and high-temperature resistant, and are widely used in pipeline transportation, civil engineering, aerospace, and rail transportation. However, they have very few engineering applications in the field of automotive collision energy absorption.

[0003] Thin-walled metal tubes, due to their high plasticity, good adaptability, relatively stable failure modes, and high strength, have been widely used in automotive front-end collision energy absorption. However, thin-walled metal tubes exhibit large deformation, low energy absorption, small peak load, and large load fluctuations during collisions, significantly reducing the survival probability of occupants. Furthermore, the heavier weight of thin-walled metal tubes increases vehicle energy consumption, and the lifespan of the metal is greatly reduced in hot and humid environments. Many vehicle manufacturers have not found suitable alternatives for energy absorption and still rely on thin-walled metal tubes, resulting in significant losses from traffic accidents each year.

[0004] Compared to metal thin-walled tubes, composite thin-walled tubes are lighter, can withstand higher loads, and exhibit less load fluctuation. In the frontal collision energy absorption zone of a vehicle, composite tubes are required to have low deformation while also possessing higher energy absorption characteristics to safely and stably reduce vehicle speed quickly. However, simple unidirectional composite thin-walled tubes are difficult to fix to a vehicle and lack high energy absorption. This problem limits the application of composite thin-walled tubes in the field of frontal collision energy absorption in automobiles. Summary of the Invention

[0005] To address the practical problems in existing technologies, this invention aims to provide a composite material thin-walled tube, solving the technical problem that existing composite material tubes are difficult to simultaneously achieve low deformation and high energy absorption. This invention adopts the following technical solution:

[0006] A composite material thin-walled tube is made of a high-performance fiber-reinforced resin composite material, which includes a fiber reinforcement and a resin matrix. The fiber reinforcement is an etched high-performance fiber. The head end of the composite material thin-walled tube is chamfered. The tube has a thin-walled layer in the voids. The cross-section formed by the thin-walled layer and the outer wall layer of the composite material thin-walled tube is an irregular cross-section. The irregular cross-section is structurally divided into a load-bearing zone and a restraining zone. The load-bearing zone and the restraining zone respectively constitute the load-bearing layer and the restraining layer of the composite material thin-walled tube in the axial direction of the thin-walled tube.

[0007] Preferably, the outermost layer of the planar geometry of the irregular cross-section is a regular hexagon, and the vertices of the regular hexagon are replaced by 6 first circles of the same size, the ratio of the diameter of the first circle to the side length of the regular hexagon is 1:4 to 1:8; inside the regular hexagon there are 6 second circles of the same size as the first circles, and the second circles and the first circles are regularly connected.

[0008] Preferably, the composite material thin-walled tube has a length of 5-15cm and an aspect ratio of 0.5:1-2:1; the load-bearing layer has a wall thickness of 0.2-4.7mm.

[0009] Preferably, the fiber orientation of the load-bearing layer is at an angle of 0~30° with the stress direction in space, and the fiber orientation of the binding layer is at an angle of 45~90° with the stress direction in space.

[0010] Preferably, the chamfer angle is 15~75°; the composite material thin-walled tube is installed by a slot connection or a socket connection.

[0011] Preferably, the high-performance fiber accounts for 50-65% of the volume of the composite material; the tensile strength of the high-performance fiber is 1900-4500 MPa.

[0012] Preferably, the high-performance fiber is a mixture of one or more of glass fiber, carbon fiber, Kevlar fiber, basalt fiber, and ultra-high molecular weight polyethylene fiber; the resin matrix is ​​a thermosetting resin or a thermoplastic resin; the resin matrix types used in the load-bearing layer and the binding layer are independent; and the fiber types used in the load-bearing layer and the binding layer are independent.

[0013] The present invention also provides a manufacturing process for the above-mentioned composite material thin-walled tube, comprising the following steps:

[0014] S1. Prepare the required high-performance fibers, resin matrix, and mold for later use;

[0015] S2. The etched high-performance fibers and resin matrix are used to form a continuous fiber-reinforced unidirectional prepreg tape;

[0016] S3. Using one or more of the resin matrix, the high-performance fiber, and the continuous fiber reinforced unidirectional prepreg tape as raw materials, the composite material thin-walled tube semi-finished product is prepared by overlay splicing method or pultrusion molding method.

[0017] S4. Grind the chamfer at the head end of the composite material thin-walled tube semi-finished product, cut and grind the tail end flat, and add the installation structure to obtain the composite material thin-walled tube.

[0018] Preferably, the specific steps of the covering and splicing method are as follows:

[0019] S31. Cut the continuous fiber reinforced unidirectional prepreg tape into strips of appropriate width and heat them appropriately to obtain softened prepreg tape;

[0020] S32. Wrap the prepreg tape around the mold in layers according to the preset thickness and fiber orientation, and then splice all the wrapped molds together.

[0021] S33. The outermost layer of the assembled mold is then covered with a predetermined number of layers to form the outer binding layer;

[0022] S34. Place the coated mold into a vacuum bag, vacuum it, and seal it to maintain a vacuum inside the bag;

[0023] S35. The vacuum bag is placed in a normal atmospheric pressure environment, cured, and demolded to obtain the composite material thin-walled tube semi-finished product.

[0024] Preferably, the pultrusion molding method comprises the following steps:

[0025] S31'. Add the resin matrix to a curing agent or plasticizer, mix and stir evenly to form a colloid;

[0026] S32'. After the etched continuous long fiber is impregnated through the impregnation tank containing the colloid, it is slowly passed through the restraint port of the pultrusion molding device, and then enters the heating and curing channel of the pultrusion molding device to form the thin-walled layer.

[0027] S34'. The continuous fiber-reinforced unidirectional prepreg tape is wrapped around the outermost layer of the thin-walled layer to form the outer binding layer, thereby obtaining the preform of the composite material thin-walled tube;

[0028] S34'. The preform can be heated and cured to obtain a composite material thin-walled tube semi-finished product.

[0029] The beneficial technical effects obtained by this invention are as follows:

[0030] (1) The present invention uses a high-performance fiber-reinforced resin composite material including fiber reinforcement and resin matrix, and the resulting composite thin-walled tube has the characteristics of light weight, high temperature resistance and corrosion resistance;

[0031] (2) The present invention rationally constructs an outer wall layer and an inner thin wall layer to form an irregular cross section with a special structure. The resulting composite material thin wall tube has the advantages of high strength and small deformation.

[0032] (3) The present invention has a chamfered design at the end of the composite thin-walled tube to trigger collision energy absorption, which can better stabilize the failure mode of the composite thin-walled tube, with higher load capacity and higher energy absorption. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of the composite material thin-walled tube of the present invention;

[0034] Figure 2 This is a partially enlarged schematic diagram of the chamfered corner of the composite material thin-walled tube of the present invention;

[0035] Figure 3a This is a schematic diagram of the composite material thin-walled tube insertion hole connection method of the present invention. Figure 3b This is a schematic diagram of the composite material thin-walled tube slot connection method of the present invention;

[0036] Figure 4 Schematic diagram of the composite material thin-walled tube irregular cross-section structure of the present invention;

[0037] Figure 5 This is a schematic diagram of the load-bearing zone and restraint zone structure of the composite material thin-walled tube with irregular cross-section according to the present invention;

[0038] Figure 6 This is a schematic diagram of the load-bearing layer and restraint layer structure of the composite material thin-walled tube after disassembly according to the present invention;

[0039] Figure 7 This is a schematic diagram of the irregular cross-section of the thin-walled tube in Embodiment 1 of the present invention;

[0040] Figure 8a This is a schematic diagram of the thin-walled tube trapezoidal mold in Embodiment 1 of the present invention. Figure 8b This is a schematic diagram of the thin-walled tube circular mold in Embodiment 1 of the present invention. Figure 8c This is a schematic diagram of the thin-walled tube hexagonal mold in Embodiment 1 of the present invention;

[0041] Figure 9 This is a schematic diagram of the irregular cross-section of the thin-walled tube in Embodiment 2 of the present invention;

[0042] Figure 10a This is a schematic diagram of the thin-walled tube triangular mold in Embodiment 2 of the present invention. Figure 10b This is a schematic diagram of the thin-walled tube circular mold in Embodiment 2 of the present invention. Figure 10c This is a schematic diagram of the thin-walled tube hexagonal mold in Embodiment 2 of the present invention;

[0043] Figure 11 These are schematic diagrams of the irregular cross-sections of the thin-walled tubes in Embodiments 3 and 4 of the present invention;

[0044] Figure 12a This is a schematic diagram of the thin-walled tube triangular mold in Embodiment 3 of the present invention. Figure 12b This is a schematic diagram of the thin-walled tube circular mold in Embodiment 3 of the present invention.

[0045] 1-Composite thin-walled tube, 2-Outer wall layer, 3-Thin wall layer, 4-Irregular cross-section, 41-Bearing area, 42-Binding area, 421-Outer binding area, 422-Inner binding area, 43-First circle, 44-Second circle, 5-Chamfer, 6-Mounting part, 81-Outer binding layer, 82-Inner binding layer. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some preferred embodiments of this application, but not all embodiments. In addition, for clarity and brevity, descriptions of known functions and structures are omitted in the embodiments.

[0047] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, B exists alone, and A and B exist simultaneously. In this article, the term " / and" describes another type of relationship between related objects, indicating that two relationships can exist. For example, A / and B can mean: A exists alone, and A and B exist alone.

[0048] (I) Composite material thin-walled tube

[0049] The composite thin-walled tube of the present invention is made of a high-performance fiber-reinforced resin composite material, wherein the high-performance fiber-reinforced resin composite material includes a fiber reinforcement and a resin matrix. For example... Figure 1As shown, the composite thin-walled tube 1 has a certain length-to-diameter ratio. Its outer periphery forms the outer wall layer 2 of the composite thin-walled tube, and thin-walled layers 3 exist in the gaps within the composite thin-walled tube 1. The cross-section formed by the thin walls in the gaps, i.e., the cross-section formed by the outer wall layer 2 and the thin-walled layer 3, is an irregular cross-section 4. In the composite thin-walled tube 1, high-performance fibers account for 50-65% of the volume of the composite material. The length of the composite thin-walled tube 1 is usually 5-15 cm, with a length-to-diameter ratio of 0.5:1-2:1. The composite thin-walled tube 1 has a chamfer 5 at the head end and an installation part 6 at the tail end. The chamfer 5 is set in the outer wall layer 2, specifically by cutting the edges of the outer wall layer 2 into a certain bevel, with an inner higher and outer lower design, such as... Figure 2 As shown, the chamfer 5 angle is 15~75°. A larger angle results in a higher initial peak load on the thin-walled tube, leading to unstable breakage and reduced breakage efficiency. A smaller angle slightly decreases the initial peak load, providing more stable guidance for breakage and improving breakage efficiency. The mounting part 6 is located at the tail end of the composite material thin-walled tube 1. The mounting method can be either a plug connection or a slot connection, as shown below. Figure 3a and Figure 3b As shown.

[0050] (ii) Fiber reinforcement

[0051] The fiber reinforcement is made of high-performance fibers that have undergone etching treatment. High-performance fibers are characterized by high strength and high modulus, and also possess certain high-temperature resistance and corrosion resistance. The tensile breaking strength of this fiber reinforcement is 1900~4500MPa, preferably 3000~4000MPa. The tensile breaking strength of the fiber mainly affects the load-bearing capacity and energy absorption of the composite thin-walled tube. If the tensile breaking strength of the fiber is too low, the maximum load-bearing capacity of the fiber will be exceeded even when the axial load on the thin-walled tube is not large, and buckling will easily occur in the middle of the thin-walled tube, resulting in low peak load and small total energy absorption. If the tensile breaking strength of the fiber is too high, the thin-walled tube will only begin to break under very large axial loads, resulting in particularly high peak loads and large accelerations. This can lead to rapid deceleration of the vehicle and potential injury to passengers.

[0052] The specific surface area of ​​fibers primarily affects the strength of the fiber-resin interface, which in turn influences the energy absorption of the composite thin-walled tube. Increasing the fiber specific surface area leads to increased fiber-resin interface strength, more complete fiber breakage within the resin, and higher energy absorption in the thin-walled tube. This invention employs plasma or chemical reagents to etch the fiber surface, thereby increasing the fiber specific surface area.

[0053] (III) Resin Matrix

[0054] The resin matrix can be composed of thermosetting resin or thermoplastic resin. Thermosetting resins include at least one of epoxy resin, phenolic resin, unsaturated resin, furan resin, melamine, formaldehyde resin, polybutadiene resin, and silicone resin. Thermoplastic resins include at least one of polyethylene, polyvinyl chloride, polystyrene, polyamide, and polyoxymethylene. The type of resin matrix affects the energy absorption of the thin-walled tube. Thin-walled tubes with thermosetting resin matrices mainly exhibit a brittle progressive fracture mode with high energy absorption; thin-walled tubes with thermoplastic resin matrices mainly exhibit a ductile failure mode with lower energy absorption. The thermosetting or thermoplastic resins used in this invention will differ in molding methods; thermoplastic resin products are relatively complex to mold and have better impact resistance.

[0055] (iv) Continuous fiber reinforced unidirectional prepreg tape

[0056] Continuous fiber-reinforced unidirectional prepreg tape is made of etched high-performance fibers and a resin matrix. It is formed by mixing and stirring the resin matrix and curing agent to create a colloid, then impregnating the unidirectional fibers to form a composite preform, often appearing as a "tape". In the preparation of the composite thin-walled tube of this invention, continuous fiber-reinforced unidirectional prepreg tape can be self-made, or mass-produced finished fiber prepreg tape can be used. Finished fiber prepreg tape is a material that can be cured and formed by heating or other activation methods.

[0057] (v) Cross-section of thin-walled tube made of composite materials

[0058] The cross-section of the composite material thin-walled tube of the present invention, namely the irregular cross-section 4, in some embodiments, has the shape of the irregular cross-section 4 as follows: Figure 4 As shown, the outermost layer of the irregular cross-section 4 is a regular hexagon, the vertices of which are replaced by six identical first circles 43. Inside the irregular cross-section 4, six identical second circles 44 are added, and the second circles 44 and the first circles 43 are regularly connected to form the irregular cross-section 4. At this point, the aspect ratio of the composite thin-walled tube is the ratio of the length of the composite thin-walled tube 1 to the length of the diagonal of the regular hexagon. Structurally, the irregular cross-section 4 is divided into a load-bearing zone 41 and a restraint zone 42, as shown... Figure 5 As shown, the areas containing the irregular cross-sections of the outer wall layer 2 and the thin-walled layer 3 are both load-bearing areas 41; the bolded lines indicate the binding area 42. The binding area 42 can consist only of the outer binding area 421, located on the periphery of a regular hexagon, formed by a predetermined number of layers of continuous fiber-reinforced unidirectional prepreg tape covering the outermost side of the thin-walled tube; the binding area 42 can also include both the outer binding area 421 and the inner binding area 422, with the inner binding area 422 located inside the shape formed by the regular connection of the second circle 44. The load-bearing area 41 and the binding area 42 respectively constitute the load-bearing layer and the binding layer 8 of the thin-walled tube 1 along the axial direction of the thin-walled tube. Correspondingly, the binding layer 8 can consist only of the outer binding layer 81, or it can include both the outer binding layer 81 and the inner binding layer 82, as shown in the example. Figure 6 As shown. The wall thickness of the load-bearing layer is typically related to the side length of the regular hexagon, with a wall thickness to side length ratio of 1:64 to 1:32, and a value of 0.2 to 4.7 mm. The wall thickness of the outer and inner binding layers is typically 0.5 to 2 times the wall thickness of the load-bearing layer. The diameter of the first circle 43 is in the ratio of the hexagon's side length to 1:4 to 1:8, and the second circle 44 is the same size as the first circle 43.

[0059] In some embodiments, the irregular cross-section 4 is composed of two nested regular hexagons of different sizes. A first circle 43 and a second circle 44 replace the vertices of the outer large regular hexagon and the inner small regular hexagon, respectively. The sides of the two regular hexagons can be parallel, such as... Figure 7 As shown; the sides of two regular hexagons can also form a certain angle, such as Figure 9 As shown. In some other embodiments, the first circles 43 of the outer hexagon are diagonally connected to each other, and the second circle 44 is located at the midpoint between each diagonal first circle 43 and the center point of the outer hexagon, as shown. Figure 11 As shown.

[0060] The shape of the irregular cross section 4 affects the energy absorption of the thin-walled tube. A complex cross section increases the load-bearing area, which will increase both the peak load and the average load. However, an overly dense cross section will lead to a decrease in crushing efficiency and a decrease in specific energy absorption.

[0061] It should be noted that the outer wall layer 2 and the thin-walled layer 3 are distinguished by their external structural shape, while the load-bearing layer and the binding layer 8 are distinguished by their mechanical properties. The outer wall layer 2 is typically composed of the load-bearing layer located on the periphery of the large regular hexagon and the outer binding layer 81, with its wall thickness being the sum of the load-bearing layer wall thickness and the outer binding layer 81 wall thickness. The inner binding layer 82 and the load-bearing layer together constitute the thin-walled layer 3, which is located on the inner side of the shape formed by the connection of the six second circles 44, with its wall thickness being the sum of the load-bearing layer wall thickness and the inner binding layer 82 wall thickness. The remaining part of the thin-walled layer 3 is structurally overlapped with the load-bearing layer, and its wall thickness is twice that of the load-bearing layer wall thickness.

[0062] (vi) Fiber orientation

[0063] The fiber orientation of the composite thin-walled tube 1 of the present invention differs between the load-bearing layer and the binding layer 8. The fiber orientation of the load-bearing layer fibers is 0~30°, preferably 0°; the fiber orientation of the binding layer 8 fibers is 45~90°, preferably 90°. Fiber orientation affects the energy absorption of the thin-walled tube. The composite thin-walled tube 1 has the strongest axial load-bearing capacity when the fiber orientation of the load-bearing layer fibers is 0°; the composite thin-walled tube 1 has the best binding performance when the fiber orientation of the binding layer 8 fibers is 90°. Fiber orientation affects the energy absorption of the composite thin-walled tube 1. If the fiber orientation is all close to 0°, the peak load of the thin-walled tube is particularly high, but the load decrease rate is also particularly fast, resulting in low energy absorption; if the fiber orientation is all close to 90°, the peak load of the thin-walled tube is not high, resulting in low energy absorption.

[0064] (vii) Key performance parameters of composite thin-walled tubes

[0065] 1) Density: The ratio of mass to volume, which can indirectly measure whether a thin-walled tube is lightweight.

[0066] 2) Total energy absorption: The total energy absorbed during the structural breakage process, mainly used to evaluate the energy absorber's ability to dissipate energy through plastic deformation or breakage;

[0067] 3) Specific energy absorption: The ratio of total absorbed energy to the mass of broken material, used to compare the energy absorption of different materials and structures;

[0068] 4) Initial peak crushing force: The peak crushing force in the early stage of the structural crushing process, which can be used to compare the maximum load-bearing capacity of the structure;

[0069] 5) Average load: The distance of the broken structure is obtained by dividing the total absorbed energy by the force-displacement curve, which can be used to compare the overall impact resistance;

[0070] 6) Crushing load efficiency: The ratio of average crushing force to peak crushing force, used to assess the stability of the crushing process.

[0071] (viii) Manufacturing process of composite material thin-walled tubes

[0072] 1) Preparation of continuous fiber reinforced unidirectional prepreg tape:

[0073] I) Prepare the required high-performance fibers and resin matrix, add the resin matrix to the curing agent or plasticizer, mix and stir evenly to make a colloid for later use.

[0074] Optionally, the curing agent may be a dicyandiamide-based curing agent, an imidazole-based curing agent, a Lewis acid-based curing agent, a D-230 polyetheramine curing agent, a 593 curing agent, an NX-2040 curing agent, an IPD curing agent, or an 810 curing agent. The plasticizer may be a DOP plasticizer, a DBP plasticizer, a DOS plasticizer, a DOA plasticizer, or a trimethyl phosphate. The curing agent or plasticizer constitutes 2-20 wt% of the resin matrix, preferably 5-15 wt%, for example, 6 wt%, 8 wt%, 10 wt%, 12 wt%, or 15 wt%.

[0075] II) High-performance fibers are etched using chemical agents or oxygen plasma, and the etched high-performance fibers are unidirectionally immersed in the above-mentioned colloid to form a continuous fiber-reinforced unidirectional prepreg tape.

[0076] In some embodiments, prepreg tapes may be used directly.

[0077] 2) Composite material thin-walled tube semi-finished product

[0078] I) Prepare the mold according to the designed irregular cross-sectional shape, determine the thickness and fiber orientation of the load-bearing layer and the binding layer, and calculate the number of layers that the continuous fiber unidirectional prepreg tape corresponding to the preset thickness needs to cover.

[0079] II) Composite thin-walled tube semi-finished products are made from one or more of resin matrix, high-performance fiber, colloid, continuous fiber reinforced unidirectional prepreg tape or finished prepreg tape as raw materials, and can be made by overlay splicing method or pultrusion molding method.

[0080] Among them, the coating and splicing method uses one or more of resin matrix, high-performance fiber, colloid, continuous fiber reinforced unidirectional prepreg tape or finished prepreg tape as raw materials to produce composite material thin-walled tube semi-finished products. The specific steps are as follows:

[0081] S31. Cut the continuous fiber reinforced unidirectional prepreg tape into strips of appropriate width and heat it appropriately to obtain a softened prepreg tape;

[0082] S32. The continuous fiber unidirectional prepreg tape is wrapped around the mold in layers according to the preset thickness and fiber orientation;

[0083] S33. Assemble all the covered molds together, and then cover the outermost part of the assembled mold with the preset number of layers;

[0084] S34. Place the coated mold into a vacuum bag, vacuum it, and seal it to maintain a vacuum inside the bag;

[0085] S35. The vacuum bag is placed in a normal atmospheric pressure environment, cured, and demolded to obtain the composite material thin-walled tube semi-finished product.

[0086] The pultrusion molding method uses a resin matrix, high-performance fibers, and the aforementioned continuous fiber-reinforced unidirectional prepreg tape, along with a pultrusion molding apparatus, to prepare composite thin-walled tube semi-finished products. The specific steps are as follows:

[0087] S31'. After the etched continuous long fiber is impregnated through the impregnation tank containing the colloid, it is slowly passed through the restraint port of the pultrusion molding device, and then enters the heating and curing channel of the pultrusion molding device to form the thin-walled layer.

[0088] S32'. The continuous fiber-reinforced unidirectional prepreg tape is wrapped around the outermost layer of the thin-walled layer to form the outer binding layer, thereby obtaining the preform of the composite material thin-walled tube;

[0089] S33'. The preform can be heated and cured to obtain a composite material thin-walled tube semi-finished product.

[0090] The two different molding methods each have their own applicability. From the perspective of raw material composition, if the entire load-bearing layer is made of prepreg tape, the overmolding method is usually used. From the perspective of thin-walled tube cross-section, the overmolding method has a wider range of applications than the pultrusion method. If the cross-section contains an inner binding layer, the overmolding method is usually used. From the perspective of load-bearing layer fiber orientation, if the load-bearing layer fiber is not at 0°, the overmolding method is usually used. From the perspective of the technical indicators of the resulting product, the fiber volume ratio of the pultrusion method is lower than that of the overmolding method. From the perspective of manufacturing efficiency, the manufacturing efficiency and raw material utilization rate of the pultrusion method are higher than those of the overmolding method.

[0091] 3) Composite material thin-walled tubes

[0092] The composite material thin-walled tube semi-finished product is obtained by grinding a chamfer at the beginning of the tube wall and cutting or grinding the end where the installation part is located. Example 1

[0093] Raw materials: 7901 epoxy resin, TC35 carbon fiber, Lewis acid curing agent.

[0094] The thin-walled tube is 6 ± 0.2 cm long with a length-to-diameter ratio of approximately 1:1. Its irregular cross-section 4 consists of two parallel nested regular hexagons of different sizes, connected at their nodes by circles. Specifically, the outer hexagon has six first circles 43 at its vertices, and the inner hexagon has six second circles 44 at its vertices. Figure 7 As shown. The side length of the outer regular hexagon is 32mm, and the ratio of the side length of the regular hexagon to the diameter of the circle is 4:1, that is, the diameters of the first circle 43 and the second circle 44 are 8mm.

[0095] The ratio of the load-bearing layer wall thickness to the side length of the regular hexagon is 1:40, and the wall thickness is 0.8 mm. The wall thickness of the binding layer is the same as that of the load-bearing layer. The fiber orientation of the load-bearing layer is 0±5°, and the thickness after curing is 0.8±0.1 mm (4 layers of carbon fiber prepreg tape). The fiber orientation of the inner and outer binding layers is 90±5°, and the thickness after curing is 0.8±0.1 mm (4 layers of carbon fiber prepreg tape). The TC35 carbon fiber has a tensile strength of 4000 MPa, a thin-walled tube fiber volume ratio of 65±5%, and is prepared by a coating splicing method with a chamfer of 45°.

[0096] The preparation steps are as follows:

[0097] S1. Mix epoxy resin 7901 and Lewis acid curing agent in a ratio of 100:5 and stir evenly to prepare a colloid for later use.

[0098] S2. T35 carbon fiber is etched using 65% concentrated nitric acid. The etched carbon fiber is then unidirectionally immersed in the above colloid to form a continuous fiber-reinforced unidirectional prepreg tape.

[0099] S3. Cut the continuous fiber reinforced epoxy resin unidirectional prepreg tape obtained in step S2 into strips with a width of 6cm according to the 0° and 90° fiber orientations, and then place them in an environment of 60° for 10~15min to obtain softened prepreg tape.

[0100] S4. Wrap the softened carbon fiber reinforced unidirectional prepreg tape from step S3 with four layers of prepreg tape. Figure 7 On the mold corresponding to the irregular cross-section thin-walled tube shown, wherein, Figure 8a The trapezoidal mold shown and Figure 8b The prepreg tape covered by the circular mold shown has a fiber orientation of 0°, forming a thin-walled tube load-bearing layer; Figure 8c The fiber orientation of the prepreg tape covered by the hexagonal mold shown is 90°, forming a thin-walled tube inner binding layer;

[0101] S5. Join all the covered molds together, and then wrap the outermost part of the assembled mold with 4 layers of prepreg tape as an outer binding layer.

[0102] S6. Place the mold with the outermost binding layer into a vacuum bag and evacuate it. The vacuum pressure should reach 1MPa. Then seal the vacuum interface and maintain the vacuum state inside the bag.

[0103] S7. Place the sealed vacuum bag from step S6 into a normal atmospheric pressure environment with a heating rate of 1~2℃, heat it to 120℃ and hold it for 1.5 hours, then demold it at a cooling rate of 1~2℃ to 60℃ to obtain a composite material thin-walled tube semi-finished product.

[0104] S8. Grind the wall of the end of the composite thin-walled tube semi-finished product obtained in step S7 to form a 45° chamfer, and cut or grind the end flat to obtain the composite thin-walled tube. Example 2

[0105] Raw materials: 7901 epoxy resin, TC35 carbon fiber, Lewis acid curing agent.

[0106] The thin-walled tube is 6 ± 0.2 cm long with a length-to-diameter ratio of approximately 1:1. The irregular cross-section 4 consists of two nested regular hexagons of different sizes, connected by circles at their nodes. Specifically, the outer hexagon has six first circles 43 at its vertices, and the inner hexagon has six second circles 44 at its vertices. Figure 9 As shown. The side length of the outer hexagon is 32mm, and the ratio of the side length of the regular hexagon to the diameter of the circle is 4:1, that is, the diameters of the first circle 43 and the second circle 44 are 8mm.

[0107] The ratio of the load-bearing layer wall thickness to the side length of the regular hexagon is 1:40, and the wall thickness is 0.8 mm. The wall thickness of the binding layer is the same as that of the load-bearing layer. The fiber orientation of the load-bearing layer is 0±5°, and the thickness after curing is 0.8±0.1 mm (4 layers of carbon fiber prepreg tape). The fiber orientation of both the inner and outer binding layers is 90±5°, and the thickness after curing is 0.8±0.1 mm (4 layers of carbon fiber prepreg tape). The TC35 carbon fiber has a tensile strength of 4000 MPa, a thin-walled tube fiber volume ratio of 65±5%, and is prepared using a coating splicing method with a chamfer of 45°.

[0108] The preparation steps are as follows:

[0109] S1. Mix epoxy resin 7901 and Lewis acid curing agent in a ratio of 100:5 and stir evenly to prepare a colloid for later use.

[0110] S2. T35 carbon fiber is etched using argon plasma, and the etched carbon fiber is unidirectionally immersed in the above colloid to form a continuous fiber-reinforced unidirectional prepreg tape.

[0111] S3. Cut the continuous fiber reinforced epoxy resin unidirectional prepreg tape into 6cm strips according to the 0° and 90° fiber orientations respectively, and then place them in a 60° environment for 10~15min to obtain softened prepreg tape;

[0112] S4. Wrap the softened carbon fiber reinforced unidirectional prepreg tape from S3 with four layers of prepreg tape. Figure 9 On the mold corresponding to the irregular cross-section thin-walled tube shown, where, Figure 10a The triangular mold shown and Figure 10b The fiber orientation of the prepreg tape wrapped on the circular mold shown is 0±5°, forming a thin-walled tube load-bearing layer; Figure 10cThe fiber orientation of the prepreg tape on the hexagonal mold shown is 90±5°, forming a thin-walled tube inner binding layer;

[0113] S5. Assemble all the completed molds together, and then wrap the outermost part of the assembled mold with 4 layers of prepreg tape as an outer binding area;

[0114] S6. Place the mold completed in S5 into a vacuum bag and evacuate it. The vacuum pressure should reach 1MPa. Then seal the vacuum interface and maintain the vacuum state inside the bag.

[0115] S7. Place the sealed vacuum bag from S6 into a normal atmospheric pressure environment with a heating rate of 1~2℃, heat it to 120℃ and hold it for 1.5 hours, then demold it at a cooling rate of 1~2℃ to 60℃ to obtain a composite material thin-walled tube semi-finished product.

[0116] S8. Grind the wall of the first end of the composite thin-walled tube semi-finished product obtained in S7 to form a 45° chamfer, and cut or grind the second end flat to obtain the composite thin-walled tube. Example 3

[0117] Raw materials: Finished fiber-reinforced epoxy resin unidirectional prepreg tape made from 7901 epoxy resin and TC35 carbon fiber.

[0118] The thin-walled tube is 6 ± 0.2 cm long, with a length-to-diameter ratio of approximately 1:1. The irregular cross-section 4 consists of diagonally connected regular hexagons, with a circle added at each diagonal and the midpoint connecting it to the center point. Specifically, the outer hexagonal vertices are composed of six first circles 43, and the inner hexagonal vertices are composed of six second circles 44. Figure 11 As shown. The side length of the outer hexagon is 32mm, and the ratio of the side length of the regular hexagon to the diameter of the circle is 4:1, that is, the diameters of the first circle 43 and the second circle 44 are 8mm.

[0119] The ratio of the load-bearing layer wall thickness to the side length of the regular hexagon is 1:40, and the wall thickness is 0.8 mm. The wall thickness of the binding layer is the same as that of the load-bearing layer. The fiber orientation of the load-bearing layer is 0±5°, and the thickness after curing is 0.8±0.1 mm (4 layers of carbon fiber prepreg tape). The fiber orientation of the outer binding layer is 90±5°, and the thickness after curing is 0.8±0.1 mm (4 layers of carbon fiber prepreg tape). The TC35 carbon fiber has a tensile strength of 4000 MPa, a thin-walled tube fiber volume ratio of 65±5%, and is prepared using a coating splicing method with a chamfer of 45°.

[0120] The preparation steps are as follows:

[0121] S1. Cut the continuous fiber reinforced epoxy resin unidirectional prepreg tape into strips of appropriate width according to the 0° and 90° fiber orientations, and then place it in a 60° environment for 10~15 minutes to obtain a softened prepreg tape.

[0122] S2. The softened carbon fiber reinforced unidirectional prepreg tape from S1 is wrapped with four layers of prepreg tape. Figure 11 On the mold corresponding to the irregular cross-section thin-walled tube shown, where, Figure 12a The triangular mold shown and Figure 12b The prepreg tape wrapped around the circular mold shown has a fiber orientation of 0±5°, forming a thin-walled tube load-bearing layer;

[0123] S3. Join all the covered molds together, and then wrap 4 layers of prepreg tape on the outermost side of the assembled mold, with the fiber orientation being 90±5°, to form a thin-walled tube outer binding layer.

[0124] S4. Place the mold with the outermost binding layer into a vacuum bag and evacuate it. The vacuum pressure should reach 1MPa. Then seal the vacuum interface and maintain the vacuum state inside the bag.

[0125] S5. Place the sealed vacuum bag from S4 into a normal atmospheric pressure environment with a heating rate of 1~2℃, heat it to 120℃ and hold it for 1.5 hours, then demold it at a cooling rate of 1~2℃ to 60℃ to obtain a composite material thin-walled tube semi-finished product.

[0126] S6. Grind the wall of the first end of the composite thin-walled tube semi-finished product obtained in S5 to form a 45° chamfer, and cut or grind the second end flat to obtain the composite thin-walled tube. Example 4

[0127] Raw materials: finished fiber-reinforced epoxy resin unidirectional prepreg tape made from epoxy resin 618, TC35 carbon fiber filament, D-230 polyetheramine curing agent, 7901 epoxy resin, and TC35 carbon fiber.

[0128] The thin-walled tube is 6 ± 0.2 cm long, with a length-to-diameter ratio of approximately 1:1. The irregular cross-section 4 consists of diagonally connected regular hexagons, with a circle added at each diagonal and the midpoint connecting it to the center point. Specifically, the outer hexagonal vertices are composed of six first circles 43, and the inner hexagonal vertices are composed of six second circles 44. Figure 11 As shown. The side length of the outer hexagon is 32mm, and the ratio of the side length of the regular hexagon to the diameter of the circle is 4:1, that is, the diameters of the first circle 43 and the second circle 44 are 8mm.

[0129] The ratio of the load-bearing layer wall thickness to the side length of the regular hexagon is 1:40, and the wall thickness is 0.8 mm. The wall thickness of the binding layer is the same as that of the load-bearing layer. The fiber orientation of the load-bearing layer is 0±5°, and the thickness after curing is 0.8±0.1 mm (4 layers of carbon fiber prepreg tape). The fiber orientation of the outer binding layer is 90±5°, and the thickness after curing is 0.8±0.1 mm (4 layers of carbon fiber prepreg tape). The TC35 carbon fiber has a tensile strength of 4000 MPa, a thin-walled tube fiber volume ratio of 50±5%, and is prepared by pultrusion molding with a chamfer of 45°.

[0130] The preparation steps are as follows:

[0131] S1. Mix epoxy resin 618 and D-230 polyetheramine curing agent in a 5:1 ratio and stir evenly to prepare a colloid for later use;

[0132] S2. T35 carbon fiber filaments are etched using argon plasma etching.

[0133] S3. After the etched continuous long fibers are impregnated through the impregnation tank containing the colloid obtained in step S2, they are slowly passed through the binding port of the pultrusion molding device, and then enter the channel of the pultrusion molding device to be heated and cured to form the load-bearing layer of the thin-walled tube. The fiber orientation of the load-bearing layer is 0±5°.

[0134] S4. The outermost part of the load-bearing area obtained in step S3 is wrapped with 4 layers of etched carbon fiber to form a finished continuous fiber reinforced unidirectional prepreg tape as the outer binding area. The fiber orientation of the outer binding area is 90±5°, and a preform of composite thin-walled tube is obtained.

[0135] S5. Place the preform of the composite thin-walled tube into a vacuum bag and evacuate it. The vacuum pressure should reach 1MPa. Then seal the vacuum interface and maintain the vacuum state inside the bag.

[0136] S6. Place the sealed vacuum bag from S5 into a normal atmospheric pressure environment with a heating rate of 1~2℃, heat it to 120℃ and hold it for 1.5 hours, then demold it at a cooling rate of 1~2℃ to 60℃ to obtain a composite material thin-walled tube semi-finished product.

[0137] S7. Grind the wall of the first end of the composite thin-walled tube semi-finished product obtained in S6 to form a 45° chamfer, and cut or grind the second end flat to obtain the composite thin-walled tube. Example 5

[0138] Example 5 modified the resin matrix in Example 2 by replacing the thermosetting epoxy resin used in Example 2 with thermoplastic phenolic resin, heating and shaping, and cooling and demolding to obtain a composite material thin-walled tube.

[0139] Examples 6 / 7 / 8

[0140] Examples 6-8 respectively adjusted the fiber reinforcement in Example 2, replacing the carbon fiber in Example 2 with glass fiber, Kevlar fiber, and silicon carbide fiber, respectively, to obtain composite thin-walled tubes.

[0141] Example 9 / 10

[0142] Examples 9 and 10 respectively adjusted the fiber reinforcement in Example 2 by adding Kevlar fibers. Example 9 replaced the carbon fiber reinforced unidirectional prepreg tape used in the load-bearing area of ​​Example 2 with Kevlar fiber reinforced unidirectional prepreg tape, while keeping other areas unchanged, to obtain a composite thin-walled tube. Example 10 replaced the carbon fiber reinforced unidirectional prepreg tape used in the binding area of ​​Example 2 with Kevlar fiber reinforced unidirectional prepreg tape, while keeping other areas unchanged, to obtain a composite thin-walled tube.

[0143] Example 11 / 12 / 13 / 14 / 15 / 16 / 17 / 18 / 19 / 20 / 21 / 22 / 23 / 24

[0144] Examples 11-24 adjusted some parameters of Examples 1 or 2, selecting parameters such as fiber orientation, wall thickness of the load-bearing layer / binding layer, diameter of the first / second circle, aspect ratio, and chamfer angle, and choosing one value while keeping the other parameters unchanged to obtain composite material thin-walled tubes. The specific parameter adjustments are shown in Table 1.

[0145] Table 1 Adjustment Indicators for Examples 11-22

[0146]

[0147] Comparative Example 1

[0148] The thin-walled tube is a round tube formed by vacuum bag thermoforming using continuous fiber-reinforced unidirectional prepreg tape made of unetched carbon fiber and epoxy resin as raw material. The round tube is 5cm long, with an aspect ratio of 1:1 and a wall thickness of 3.5mm. The end is provided with a 45° inner chamfer. The fiber orientation of the load-bearing layer of the thin-walled tube is 0±5°, the fiber orientation of the binding layer is 90±5°, and the fiber volume ratio is 67±2%. Comparative Example 2

[0149] Thin-walled tubes are irregularly shaped tubes formed by vacuum bag thermoforming using continuous fiber-reinforced unidirectional prepreg tape made of unetched carbon fiber and epoxy resin as raw material. The thin-walled tubes are 6cm long, with an aspect ratio of 1:1, a wall thickness of 1.5mm, no chamfer at the end, a fiber orientation of ±15°, and a fiber volume ratio of 65±2%. Comparative Example 3

[0150] Thin-walled tubes are irregularly shaped tubes formed by vacuum bag thermoforming using continuous fiber-reinforced unidirectional prepreg tape made of unetched carbon fiber and epoxy resin. The thin-walled tubes are 6cm long, with an aspect ratio of 1:1, a wall thickness of 1.5mm, and no chamfer at the ends. The fiber orientations are 0, ±15, ±30, and ±45°, and the fiber volume ratio is 65±2%. Comparative Example 4

[0151] Thin-walled tubes are round tubes made by winding and curing unetched glass fiber filaments, epoxy resin, and PVC. The thin-walled tubes are 12.5cm long, have an aspect ratio of 2:1, a wall thickness of 3mm, and a 45° chamfer at the end. The fiber orientation of the thin-walled tubes is 90±5°. Comparative Example 5

[0152] Thin-walled tubes are round tubes formed by pultrusion of etched carbon fiber filaments and epoxy resin, followed by vacuum bag compression curing. The tubes are 5cm long, with an aspect ratio of 1:1 and a wall thickness of 3.5mm. The ends are chamfered at 45°. The fiber orientation of the load-bearing layer is 0±5°, the fiber orientation of the binding layer is 90±5°, and the fiber volume ratio is 50±5%.

[0153] Comparative Example 6 / 7

[0154] Comparative Example 6 is an adjustment to the raw materials in Example 2, in which the TC35 carbon fiber in Example 2 was replaced with phenolic fiber (fiber breaking strength of 147.3 MPa) and T800 carbon fiber (fiber breaking strength of 5880 MPa).

[0155] Table 2 Performance test results of thin-walled tubes in the embodiments and comparative examples of the present invention

[0156]

[0157] As can be seen from the data of various parameters in Table 2 of the embodiments and comparative examples, the load-bearing capacity and energy absorption of thin-walled tubes without high-strength, high-modulus, high-performance fibers are significantly reduced; an excessively large aspect ratio of the thin-walled tube makes the crushing process unstable and energy absorption low; excessive wall thickness of the thin-walled tube will bring manufacturing difficulties and excessive crushing force. In terms of molding methods, there are significant differences in fiber-resin interface strength between thin-walled tubes produced by hot pressing and pultrusion molding, mainly because the fiber volume ratios of the thin-walled tubes produced by the two molding methods are different. Increasing the fiber volume ratio will improve the axial load-bearing capacity of the thin-walled tube to a certain extent, but at the same time, the constraint force between fiber bundles will be significantly reduced. The present invention adds a fiber transverse binding layer, which can effectively improve the energy absorption of the thin-walled tube.

[0158] The composite thin-walled tube of the present invention has a low density and light weight, which is much lower than that of a metal structure of the same volume. At the same time, it can be seen from the experimental data of each embodiment in Table 2 that the composite thin-walled tube of the present invention has high hardness and good impact resistance and energy absorption performance. The energy absorption efficiency is more efficient and stable, which solves the technical problem that composite tubes are difficult to have both small deformation and high energy absorption.

[0159] The embodiments described above are merely illustrative of several implementations of the present invention, designed to facilitate a detailed understanding of the technical solutions of the present invention, but should not be construed as limiting the scope of protection of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided by the present invention through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this invention patent should be determined by the content of the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A composite material thin-walled tube, said thin-walled tube being made of a high-performance fiber-reinforced resin composite material, characterized in that: The high-performance fiber-reinforced resin composite material includes a fiber reinforcement and a resin matrix, wherein the fiber reinforcement is an etched high-performance fiber; the head end of the composite thin-walled tube is chamfered; the internal voids of the composite thin-walled tube have a thin-walled layer, and the cross-section formed by the thin-walled layer and the outer wall layer of the composite thin-walled tube is an irregular cross-section, which is structurally divided into a load-bearing zone and a restraining zone, which respectively constitute the load-bearing layer and the restraining layer of the composite thin-walled tube along the axial direction of the thin-walled tube; the fiber orientation of the load-bearing layer has an angle of 0~30° with the stress direction in space, and the fiber orientation of the restraining layer has an angle of 45~90° with the stress direction in space; the outermost layer of the planar geometry of the irregular cross-section is a regular hexagon. The vertices of the regular hexagon are replaced by six identical first circles, the ratio of the diameter of the first circle to the side length of the regular hexagon being 1:4 to 1:8; the regular hexagon contains six second circles of the same size as the first circles, and the second circles and the first circles are regularly connected; the composite material thin-walled tube has a length of 5-15 cm and an aspect ratio of 0.5:1 to 2:1, the aspect ratio being the ratio of the length of the composite material thin-walled tube to the length of the diagonal of the regular hexagon; the wall thickness of the load-bearing layer is 0.2-4.7 mm; the binding layer includes only an outer binding layer, or includes both an outer binding layer and an inner binding layer.

2. The composite material thin-walled tube according to claim 1, characterized in that: The chamfer angle is 15~75°; the composite material thin-walled tube is installed by slot connection or plug connection.

3. A composite material thin-walled tube according to claim 2, characterized in that: The high-performance fiber accounts for 50-65% of the volume of the composite material; the tensile breaking strength of the high-performance fiber is 1900-4500 MPa.

4. A composite material thin-walled tube according to claim 3, characterized in that: The high-performance fiber is a mixture of one or more of glass fiber, carbon fiber, Kevlar fiber, basalt fiber, and ultra-high molecular weight polyethylene fiber; the resin matrix is ​​a thermosetting resin or a thermoplastic resin; the resin matrix types used in the load-bearing layer and the binding layer are independent; the fiber types used in the load-bearing layer and the binding layer are independent.

5. The manufacturing process of a composite material thin-walled tube according to any one of claims 1 to 4, characterized in that: Includes the following steps: S1. Prepare the required high-performance fibers, resin matrix, and mold for later use; S2. The etched high-performance fibers and resin matrix are used to form a continuous fiber-reinforced unidirectional prepreg tape; S3. Using one or more of the resin matrix, the high-performance fiber, and the continuous fiber reinforced unidirectional prepreg tape as raw materials, the composite material thin-walled tube semi-finished product is prepared by overlay splicing method or pultrusion molding method. S4. Grind the chamfer at the head end of the composite material thin-walled tube semi-finished product, and cut and grind the tail end flat to obtain the composite material thin-walled tube.

6. The manufacturing process of a composite material thin-walled tube according to claim 5, characterized in that: The specific steps of the wrapping and splicing method are as follows: S31. The continuous fiber reinforced unidirectional prepreg tape is cut into strips of a preset width and heated at a preset temperature to obtain a softened prepreg tape; S32. Wrap the prepreg tape around the mold in layers according to the preset thickness and fiber orientation, and then splice all the wrapped molds together. S33. The outermost layer of the assembled mold is then covered with a predetermined number of layers to form the outer binding layer; S34. Place the coated mold into a vacuum bag, vacuum it, and seal it to maintain a vacuum inside the bag; S35. The vacuum bag is placed in a normal atmospheric pressure environment, cured, and demolded to obtain the composite material thin-walled tube semi-finished product.

7. The manufacturing process of a composite material thin-walled tube according to claim 5, characterized in that: The specific steps of the pultrusion molding method are as follows: S31'. Add the resin matrix to a curing agent or plasticizer, mix and stir evenly to form a colloid; S32'. After the etched continuous long fiber is impregnated through the impregnation tank containing the colloid, it is slowly passed through the restraint port of the pultrusion molding device, and then enters the heating and curing channel of the pultrusion molding device to form the thin-walled layer. S33'. The continuous fiber-reinforced unidirectional prepreg tape is wrapped around the outermost layer of the thin-walled layer to form the outer binding layer, thereby obtaining the preform of the composite material thin-walled tube; S34'. The preform can be heated and cured to obtain a composite material thin-walled tube semi-finished product.

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