Carbon fiber alloy automobile front cover and manufacturing process thereof

Abstract

The invention relates to the technical field of automobile part manufacturing, and particularly discloses a carbon fiber alloy automobile front cover and a manufacturing process thereof. A new thought for connecting the inner plate and the outer plate which are made of different materials is provided for the automobile front machine cover composed of the aluminum alloy inner plate and the carbon fiber outer plate, the new technology of riveting first and then forming is utilized, the problem that cured carbon fibers do not have plasticity is fundamentally solved, and the riveting quality is improved; moreover, the curing process of the carbon fiber prepreg tape and the curing process of the bonding of the inner plate and the outer plate are unified into one process step, and layering, gaps and the like generated in the riveting process are filled with flowing resin by utilizing the pressure during hot press molding; the problems that carbon fibers are prone to layering and tearing after riveting, carbon fiber plates around rivets are in a fragment shape and the like are solved, stress concentration is reduced, the connection strength is improved, the manufactured machine cover inner plate and the manufactured machine cover outer plate are good in connection integration effect and high in mechanical strength, and the appearance quality of an automobile is remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of automobile parts manufacturing, and in particular to a carbon fiber alloy automobile front hood and a manufacturing process thereof. Background Art

[0002] With the continuous and rapid development of the national economy, my country's automobile industry has developed rapidly in recent years, and my country's automobile production has leapt into the forefront of the world. While cars bring convenience to personal travel, they also bring some problems such as driving safety and energy consumption. Safety, energy saving and environmental protection are still the main directions of today's automobile technology development.

[0003] One of the effective ways to reduce energy consumption in the automotive industry is to optimize the design of the car body to reduce the weight of the car body. Therefore, in recent years, more and more lightweight materials have been used in automotive products, and carbon fiber composite materials have become the preferred material for lightweighting automobiles due to their excellent high specific modulus, high specific strength and designability. Compared with steel parts, the weight reduction is 40%-60%, and compared with aluminum alloy materials, the weight reduction is 20%-30%. The lightweight automobile front hood made of carbon fiber composite materials has high stiffness and strength, as well as excellent thermal stability and corrosion resistance, and has attracted the attention of more and more scientific researchers. However, due to the high brittleness and low plasticity of carbon fiber composite materials after curing, the self-piercing riveting technology is prone to delamination, tearing and other damage when connecting the inner and outer panels of the automobile hood made of carbon fiber composite materials, which reduces the connection strength. The connection method used between automotive carbon fiber parts has a significant impact on the structural integrity of carbon fiber cars. Therefore, it is necessary to find a suitable connection process to avoid defects such as delamination and local tearing in the thermosetting carbon fiber hood after connection. Summary of the invention

[0004] Aiming at the problems of delamination and tearing of the carbon fiber composite material front hood prepared by the traditional process in the prior art, and the carbon fiber plate around the rivets being in fragments, the present invention provides a carbon fiber alloy automobile front hood and a manufacturing process thereof.

[0005] In order to solve the above technical problems, the technical solution provided by the present invention is:

[0006] A manufacturing process of a carbon fiber alloy automobile front hood, the carbon fiber alloy automobile front hood comprising a carbon fiber outer plate and an aluminum alloy inner plate, the manufacturing process comprising the following steps;

[0007] S1, provides a single layer of carbon fiber prepreg tape;

[0008] S2, stacking and laying the single-layer carbon fiber prepreg tapes according to a preset method to form an uncured carbon fiber outer panel;

[0009] S3, applying a silane coupling agent to the surface of the pretreated aluminum alloy inner panel, then placing the uncured carbon fiber outer panel on the surface of the aluminum alloy inner panel, and riveting the arranged carbon fiber outer panel and the aluminum alloy inner panel to form a prefabricated part;

[0010] S4, performing hot pressing and curing on the preform in stages to obtain a fiber alloy automobile front hood.

[0011] Compared with the prior art, the present invention provides a new idea for connecting inner and outer panels of different materials for a car front hood composed of an aluminum alloy inner panel and a carbon fiber outer panel. The idea of ​​combining the self-piercing riveting process with the bonding process is adopted, and a new process of riveting first and then forming is used, which fundamentally avoids the problem of the lack of plasticity of the cured carbon fiber and improves the riveting quality; and the curing process of the carbon fiber prepreg tape and the curing process of the inner and outer panel bonding are unified into one process step, and the pressure during hot pressing is used to fill the flowing resin with the delamination and gaps generated in the riveting process, which solves the problems of delamination, tearing of the carbon fiber after riveting, and the carbon fiber plate being in fragments around the rivets, etc., which are easy to occur after riveting. It not only reduces stress concentration and improves the connection strength, but also simplifies the curing step and improves production efficiency. The prepared hood inner and outer panels have good connection integration effect and high mechanical strength, which significantly improves the appearance quality of the car and has high practical value.

[0012] Furthermore, in S1, the matrix of the single-layer carbon fiber prepreg tape is epoxy resin.

[0013] The single-layer carbon fiber prepreg tape described in the present invention can be directly a commercially available carbon fiber prepreg tape product, or can be prepared by itself. If a commercially available carbon fiber prepreg tape is used, when stacking and laying the layers in the subsequent step S2, it is necessary to coat the surface of each layer of the carbon fiber prepreg tape with epoxy resin emulsion, and then stack and lay the layers.

[0014] Exemplarily, the method for preparing the single-layer carbon fiber prepreg tape comprises the following steps:

[0015] The carbon fiber cloth is immersed in epoxy resin emulsion to obtain a single-layer carbon fiber prepreg tape.

[0016] The carbon fiber cloth can be made from continuous carbon fiber tows into braided carbon fiber cloth, or directly purchased from commercially available carbon fiber braided cloth.

[0017] Optionally, the epoxy resin emulsion can be commercially available DS1202 resin, and the carbon fiber can be commercially available Toray T700-12K.

[0018] Furthermore, in S1, the thickness of the single-layer carbon fiber prepreg tape is 0.08 mm-0.17 mm.

[0019] Preferably, in S1, the thickness of the single-layer carbon fiber prepreg tape is 0.15 mm.

[0020] Furthermore, in S1, the carbon fiber surface density of the single-layer carbon fiber prepreg tape is 65 g / m 2 -75g / m 2 , the resin content is 60%-70%, and the total surface density of resin and carbon fiber is 275g / m 2 -285g / m 2 , the volatility ratio is less than 0.1%.

[0021] Preferably, in S1, the carbon fiber surface density of the single-layer carbon fiber prepreg tape is 70 g / m 2 , the resin content is 65%, and the total surface density of resin and carbon fiber is 280g / m 2 , the volatility ratio is less than 0.1%.

[0022] Furthermore, in S2, the number of layers of the stacked layers is 8-16 layers.

[0023] The specific number of stacked layers can be determined based on the designed thickness of the car's front hood.

[0024] It should be noted that when stacking carbon fibers, the release paper on the bottom and top carbon fiber surfaces needs to be retained to ensure the cleanliness of the bottom surface of the carbon fiber prepreg tape. When the carbon fiber prepreg tape is placed on the aluminum alloy surface, the upper and lower layers of release paper can be removed.

[0025] Furthermore, in S2, the preset method is: taking the width direction of the single-layer carbon fiber prepreg tape as a reference line, the radial direction is sequentially stacked and laid in an orthogonal manner of 0 degrees and 90 degrees.

[0026] The orthogonal lamination method can minimize the performance difference between carbon fiber composite materials and aluminum alloy plates, making the aluminum alloy plates approximately isotropic, thereby giving the specimens better mechanical properties.

[0027] Furthermore, in S3, the pretreatment method of the aluminum alloy inner plate includes: using sandpaper with successively decreasing fineness to grind the surface of the aluminum alloy inner plate step by step.

[0028] Exemplarily, 6000#-1000# silicon carbide water-abrasive sandpaper is used to grind the surface of the aluminum alloy inner panel step by step.

[0029] The above-mentioned pretreatment of the surface of the aluminum alloy inner plate can improve the cleanliness of the aluminum alloy surface, and at the same time, change the roughness of the aluminum alloy surface so as to better combine with the resin on the surface of the carbon fiber prepreg tape.

[0030] Exemplarily, in S3, the silane coupling agent may be A-150, A-151, A-171 or A-172. Coating the silane coupling agent on the surface of the aluminum alloy inner plate can prevent potential corrosion between the carbon fiber outer plate and the aluminum alloy inner plate, improve the bonding strength between the aluminum alloy inner plate and the carbon fiber outer plate, and improve the accuracy of subsequent riveting.

[0031] Specifically, the coating amount of the silane coupling agent on the surface of the aluminum alloy inner plate can be conventionally adjusted to cover the surface of the aluminum alloy inner plate.

[0032] The riveting described in the present invention can be performed by conventional riveting processes in the art. For example, aluminum alloy rivets, such as semi-hollow rivets with a length of 8 mm and a diameter of 3.5 mm, can be used. The rivets must penetrate into but not penetrate the aluminum alloy inner plate when connecting the inner and outer plates.

[0033] Furthermore, in S4, the pressure of the staged hot pressing curing is 0.098MPa-0.1MPa.

[0034] Furthermore, in S4, the specific steps of the staged hot pressing curing are: firstly program heating to 80°C-90°C, keeping warm for a first preset time, and then continue heating to 140°C-160°C, keeping warm for a second preset time.

[0035] Preferably, in S4, the specific steps of the staged hot pressing curing are: firstly heating to 80°C-90°C at a rate of 10°C / min-20°C / min, keeping warm for 30min-40min, and then continuing to heat to 140°C-160°C, keeping warm for 90min-100min.

[0036] First, the curing temperature is raised to 80℃-90℃, which can make the resin in the carbon fiber inner panel in a viscous flow state, with certain fluidity and plasticity, and a certain fluidity under pressure, so as to fill the delamination, tearing and gaps generated by the riveting process. Then the temperature is raised to 140℃-160℃ for insulation to fully cure the carbon fiber inner panel, effectively solving the problems of delamination and tearing of carbon fiber composite panels after riveting, and fragmented carbon fiber panels around rivets, and significant progress has been made.

[0037] The present invention also provides a carbon fiber alloy automobile front hood, which is prepared by the manufacturing process of any of the above-mentioned carbon fiber alloy automobile front hoods.

[0038] The present invention solves the problem that the existing carbon fiber plate has no plasticity after curing and molding through a novel glue-riveting composite process, utilizes the uncured carbon fiber outer panel and the aluminum alloy inner panel to rivet, and in the hot pressing molding process, the resin is redistributed to compensate for various defects caused by riveting, thereby ensuring the integrity of the riveting and improving the overall quality of the glue-riveting composite connection test piece. The prepared fiber alloy automobile front hood has high connection strength, good integration effect and high reliability. At the same time, the existing step-by-step curing process is simplified, the production efficiency is improved, the energy consumption is reduced, and the invention has a high value of promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a structural schematic diagram of the carbon fiber outer plate of the present invention;

[0040] Figure 2 The schematic diagram of the structure of the aluminum alloy inner plate of the present invention, wherein 1, riveting position point, 2, weakened area, 3, stiffness reinforcement structure;

[0041] Figure 3 Schematic diagram of the riveting process of an embodiment of the present invention, wherein 11, carbon fiber outer plate, 12, aluminum alloy inner plate, 13, lower mold, 14, rivet, 15, upper mold;

[0042] Figure 4 The load-displacement curves of the front hoods prepared in the embodiments of the present invention and the comparative examples. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0044] The carbon fiber prepregs used in the embodiments of the present invention and the comparative examples are commercially available carbon fiber prepregs with epoxy resin as the matrix. The carbon fiber in the carbon fiber prepreg is Toray T700-12K, and the epoxy resin is DS1202 resin. The surface density of the carbon fiber is 70 g / m 2 , the resin content is 65%, and the total surface density of resin and carbon fiber is 280g / m 2 , the volatility ratio is less than 0.1%.

[0045] Example

[0046] The embodiment of the present invention provides a manufacturing process of a carbon fiber alloy automobile front hood, which specifically includes the following steps:

[0047] S1, the carbon fiber prepreg tapes are stacked in an orthogonal stacking manner of [0° / 90°]s (s represents symmetry), with a total of 16 layers. When stacking the layers, the release paper of the bottom layer and the top layer of the carbon fiber prepreg tapes are retained to ensure the surface cleanness of the carbon fiber plate. The carbon fiber plate is cut by a shearing machine to form an uncured carbon fiber outer plate, such as Figure 1 As shown;

[0048] Specifically, the thickness of the carbon fiber prepreg tape is 0.15 mm, which is convenient for controlling the total thickness and weight of the roof cover;

[0049] S2, choose cast aluminum alloy as the inner panel of the automobile hood, and set corresponding weakened areas and stiffness compensation structures on the aluminum alloy inner panel, such as Figure 2 As shown, the connection surface of the aluminum alloy inner panel is mechanically polished to remove impurities such as dust and oil on the surface of the aluminum alloy inner panel and change its surface roughness so as to better bond with the uncured carbon fiber outer panel;

[0050] Specifically, the aluminum alloy inner plate is polished using 600#-1000# silicon carbide water-abrasive sandpaper in order from small to large mesh numbers;

[0051] S3, coating the polished aluminum alloy inner plate with a silane coupling agent to prevent potential corrosion between the carbon fiber outer plate and the aluminum alloy inner plate;

[0052] Specifically, A-150, A-151, A-171 or A-172 silane coupling agent can be used; during coating, only a thin layer needs to be applied on the surface of the polished aluminum alloy inner plate to cover the aluminum alloy inner plate, and then the aluminum alloy inner plate coated with the silane coupling agent can be dried;

[0053] S4, use a rivet gun to rivet the overlapped carbon fiber outer panel and the aluminum alloy inner panel to form a prefabricated part. The riveting process diagram is shown in Figure 3 As shown;

[0054] Specifically, a semi-hollow rivet with a length of 8 mm and a diameter of 3.5 mm can be used. When connecting the carbon fiber outer panel and the aluminum alloy inner panel, the rivet penetrates but does not penetrate the aluminum alloy inner panel. Under the action of the lower mold, the rivet is plastically deformed to form a dovetail-shaped embedding.

[0055] S5, putting the preform into an autoclave, setting the vacuum pressure to 0.098MPa-0.1MPa, setting the heating rate of the autoclave to 10℃ / min-20℃ / min, heating from room temperature to 80℃-90℃, keeping the temperature for 30min-40min, then continuing to heat to 140℃-160℃, keeping the temperature for 90min-100min, keeping the pressure until the curing process is completed, waiting for the temperature of the autoclave to drop to room temperature, releasing the pressure and cooling, taking out the test piece, and obtaining a finished carbon fiber alloy automobile front hood.

[0056] Specifically, the vacuum pressure of the autoclave was set to 0.1 MPa, the heating rate of the autoclave was set to 10°C / min, the temperature was raised from room temperature to 85°C, kept for 30 min, and then continued to rise to 150°C, kept for 90 min;

[0057] In addition, the finished car hood can be subsequently painted as needed, or connected and fixed to the car body with adhesives.

[0058] Comparative Example

[0059] This comparative example provides a manufacturing process of a carbon fiber alloy automobile front hood, which specifically includes the following steps:

[0060] S1, the carbon fiber prepreg tape is stacked in an orthogonal stacking manner of [0° / 90°]s (s represents symmetry), with a total of 16 layers. When stacking the layers, the release paper of the bottom layer and the top layer of the carbon fiber prepreg tape is retained to ensure the surface cleanness of the carbon fiber board. After cutting with a shearing machine, it is placed in an autoclave, and the vacuum pressure is set to 0.098MPa-0.1MPa. The heating rate of the autoclave is set to 10℃ / min-20℃ / min, and the temperature is raised from room temperature to 80℃-90℃, and the temperature is kept for 30min-40min, and then the temperature is continued to rise to 140℃-160℃, and the temperature is kept for 90min-100min. The pressure is maintained until the curing process is completed. When the temperature of the autoclave drops to room temperature, the pressure is released and cooled to form a carbon fiber outer plate, such as Figure 1 As shown;

[0061] Specifically, the thickness of the carbon fiber prepreg tape is 0.15 mm, which is convenient for controlling the total thickness and weight of the roof cover;

[0062] S2, choose cast aluminum alloy as the inner panel of the automobile hood, and set corresponding weakened areas and stiffness compensation structures on the aluminum alloy inner panel, such as Figure 2 As shown, the aluminum alloy inner panel is polished using 600#-1000# silicon carbide water-abrasive sandpaper in order from small to large mesh numbers;

[0063] S3, coating the polished aluminum alloy inner plate with a silane coupling agent to prevent potential corrosion between the carbon fiber outer plate and the aluminum alloy inner plate;

[0064] Specifically, A-150, A-151, A-171 or A-172 silane coupling agent may be used;

[0065] S4, using a rivet gun to rivet the overlapped carbon fiber outer panel and the aluminum alloy inner panel to obtain a carbon fiber alloy automobile front hood finished product;

[0066] Specifically, a semi-hollow rivet with a length of 8 mm and a diameter of 3.5 mm can be used to form a dovetail embedding.

[0067] Performance Testing

[0068] 1. Tensile properties

[0069] The two automobile front hoods prepared in the embodiment and the comparative example were subjected to a tensile performance test according to the national standard GB / T 228.1-2021, and their performance under axial tensile load was measured using an electronic universal testing machine to obtain the tensile load-displacement curves of the front hoods prepared by the two processes. The results are as follows: Figure 4 As shown, the morphologies of the front hoods prepared by the two processes after tensile fracture are compared to obtain their failure form characteristics.

[0070] The results show that the connection strength of the front hood of the car prepared by the embodiment of the present invention is much greater than that of the comparative example, and the connection strength is increased by about 40.5% relative to the comparative example. The displacement used to reach the maximum value of the tensile curve 1 of the front hood prepared by the embodiment of the present invention is smaller than that of the comparative example. The load-displacement curve shows that the front hood prepared by the embodiment of the present invention can reach a loading tension of 2470N at a tensile displacement of about 5mm, while the comparative example needs to reach the maximum tensile load at a tensile displacement of about 9mm, and the loading tension is only 1760N. The front hood prepared by the embodiment can reach a load force of 1750N when stretched by 3mm. It proves that the combination between the various parts of the front hood prepared by the process of the embodiment of the present invention is tighter, with no or few defects such as gaps and holes. At the same time, by comparing the tensile failure forms of the front hood prepared by the two processes of the embodiment and the comparative example, it is found that the front hood of the comparative example is mainly a failure of the carbon fiber plate, and the front hood of the embodiment is mainly a failure of the aluminum alloy plate.

[0071] 2. Riveting quality

[0072] When the process of the embodiment of the present invention rivets the carbon fiber outer panel and the aluminum alloy inner panel, the resin contained in the carbon fiber inner panel is flowable and deformable and has a certain plasticity. During the riveting process, the carbon fiber panel is not damaged by the impact and extrusion of the rivets. Even if the carbon fiber outer panel is occasionally damaged during the riveting process, the flowing resin in the subsequent hot pressing and curing process will fill the gaps caused by the damage and wrap the torn fiber tissue, thereby compensating for the various defects caused by the riveting.

[0073] After testing, the residual bottom thickness of the rivet in the riveting process of the embodiment is 481.56μm, and the comparative example is 412.31μm, which shows that the penetration depth of the rivet in the embodiment of the present invention is within the safe range, and the appearance, sealing and anti-corrosion performance of the joint can be effectively guaranteed. The inner locking length of the rivet in the embodiment is 625.45μm, and the rivet opening is 648.77μm, which are both greater than the inner locking length of 417.47μm and the rivet opening of 429.64μm in the comparative example, indicating that the rivet legs have been fully opened and formed a stable inner embedded interlocking structure with the lower aluminum alloy plate. Although the rivet head height of the embodiment is larger than that of the comparative example carbon fiber plate after curing and riveting, it is still within a reasonable range, and the rivet height can be made close to 0 by mechanical grinding later, so it will not affect the connection strength of the front hood.

[0074] Therefore, the new glue-riveted composite process provided by the present invention not only solves the problem that the carbon fiber plate has no plasticity after being cured and formed by the existing process, but also utilizes the hot pressing curing process to complete the redistribution process of the flowing resin, thereby compensating for the absence caused by riveting, ensuring the integrity of the riveting points, and improving the connection strength of the glue-riveted composite connection specimens.

[0075] In summary, the present invention provides a new idea for connecting the carbon fiber outer panel and the aluminum alloy inner panel in the existing lightweight design of the automobile hood. It combines the existing self-piercing riveting process and the bonding process to improve the existing traditional process. The process of riveting first and then forming is adopted, which fundamentally avoids the problem that the solidified carbon fiber plate has no plasticity, and unifies the curing process of the carbon fiber outer panel and the bonding and curing process of the carbon fiber outer panel and the aluminum alloy inner panel into one process step. The temperature and pressure applied during the integrated curing and forming by hot pressing are used to promote the flowing resin to fill the delamination and gaps generated during the riveting process, which solves the problems of easy delamination and tearing of the carbon fiber outer panel after riveting, and the carbon fiber around the rivet being in fragments, etc., which not only reduces stress concentration and improves the connection strength, but also simplifies the curing step and improves production efficiency. The obtained hood inner and outer panels are connected together with good effect, high reliability and high mechanical strength, and have a high value of promotion and application.

[0076] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A manufacturing process of a carbon fiber alloy automobile front hood, the carbon fiber alloy automobile front hood comprising a carbon fiber outer panel and an aluminum alloy inner panel, characterized in that: The manufacturing process comprises the following steps: S1, provides a single layer of carbon fiber prepreg tape; S2, stacking and laying the single-layer carbon fiber prepreg tapes according to a preset method to form an uncured carbon fiber outer panel; S3, applying a silane coupling agent to the surface of the pretreated aluminum alloy inner panel, then placing the uncured carbon fiber outer panel on the surface of the aluminum alloy inner panel, and riveting the arranged carbon fiber outer panel and the aluminum alloy inner panel to form a prefabricated part; S4, performing hot pressing and curing on the preform in stages to obtain a fiber alloy automobile front hood.

2. The manufacturing process of the carbon fiber alloy automobile front hood according to claim 1, characterized in that: In S1, the matrix of the single-layer carbon fiber prepreg tape is epoxy resin; and / or In S1, the thickness of the single-layer carbon fiber prepreg tape is 0.08 mm-0.17 mm.

3. The manufacturing process of the carbon fiber alloy automobile front hood according to claim 1, characterized in that: In S1, the carbon fiber surface density of the single-layer carbon fiber prepreg tape is 65g / m 2 -75g / m 2 , the resin content is 60%-70%, and the total surface density of resin and carbon fiber is 275g / m 2 -285g / m 2 .

4. The manufacturing process of the carbon fiber alloy automobile front hood according to claim 1, characterized in that: In S2, the number of the stacked layers is 8-16 layers.

5. The manufacturing process of the carbon fiber alloy automobile front hood according to claim 1, characterized in that: In S2, the preset method is: taking the width direction of the single-layer carbon fiber prepreg tape as a reference line, the radial direction is sequentially stacked and laid in an orthogonal manner of 0 degrees and 90 degrees.

6. The manufacturing process of the carbon fiber alloy automobile front hood according to claim 1, characterized in that: In S3, the pretreatment method of the aluminum alloy inner plate includes: using sandpaper with decreasing fineness to grind the surface of the aluminum alloy inner plate step by step.

7. The manufacturing process of the carbon fiber alloy automobile front hood according to claim 1, characterized in that: In S4, the pressure of the staged hot pressing curing is 0.098 MPa-0.1 MPa.

8. The manufacturing process of the carbon fiber alloy automobile front hood according to claim 1 or 7, characterized in that: In S4, the specific steps of the staged hot pressing curing are: firstly program the temperature to 80°C-90°C, keep it warm for a first preset time, then continue to heat up to 140°C-160°C, keep it warm for a second preset time.

9. The manufacturing process of the carbon fiber alloy automobile front hood according to claim 8, characterized in that: In S4, the rate of the programmed temperature rise is 10°C / min-20°C / min, the first preset time is 30min-40min, and the second preset time is 90min-100min.

10. A carbon fiber alloy automobile front hood, characterized in that: The carbon fiber alloy automobile front hood is prepared by the manufacturing process of any one of claims 1 to 9.

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